Welding Techniques and Processes

yes uh good morning guys to all of you please tell me am I properly Audible and visible to all of you or not and guys today we have a wonderful session on welding and we would be completing this welding within two to 2.5 hours okay and we are going to revise all the concepts quickly from the welding as you know every year one question for two Mark is coming from this topic so it is important so with this two hours of session if you can get two marks what else you need yes uh Gokul not sure Naveen uh I welcome you all and good morning guys so without wasting the time we are starting the session so guys this is some detail about me my name is jeera sardana and I am having around 10 plus years of experience and today&#39;s subject is today&#39;s topic is related to the production yes so guys we are starting and this is one more information those who are preparing for gate 2024 so guys uh I am going to take a mega workshop for the strategy to be in top one percent for gate 2024 exam tomorrow 12 30 PM will be the time so tomorrow is New Year also so on this new year you can take that pledge if you are talking about 2024 and I will be telling you how you can be in top one percent because top one percent are going to be either in iit&#39;s psus iises like that kind of institutes so guys that is what is the dream of the students okay so guys uh if you want to register for the workshop if you want to register for scholarship test if you want to download the ebook just go to the description of this session okay shubham Manas shreyas good morning to all of you guys so now we are starting the session so this I have already taken many times production versus manufacturing then we will be going for the welding so you already know when we are talking about production and Manufacturing manufacturing and production are same with reference to the mechanical engineering same with respect to the mechanical engineering but in general when we are talking about production is a very big field for which manufacturing is a small part okay so I already told you uh production word is used everywhere like whenever you see any movie so in the movie uh you are always saying the uh cast star cast there you see produced by you will never see manufactured by I told you we are the production of our parents not manufactured by our parents so likewise production is a term which can be used everywhere but for mechanical engineering both can be treated the same okay then my dear today our topic is going to be the welding so first of all you must understand what is welding when I was teaching you very good very good shubham so when I was teaching you casting at that time also I have shown you some kind of uh laboratory method what you are going to do in the casting here also I am showing you an animation which is showing you how you are going to perform the welding this will help us but first of all let us see what is welding welding is the process of joining two metals and when we are going to join those two materials that may be similar may be dissimilar and when you are joining them you may be using the effect of heat or effect of pressure you may be using some kind of filler material or not so it is the process of joining two material in such a way with the application of either heat or pressure or both with or without the application of filler material this is how the welding is defined Umar good morning dear so when we are talking about this in the college you have seen this kind of welding which is said to be the arc welding you must have taken two plates good morning Amir you must have taken two plates those plates were kept together like you will see and when those plates were kept together you can see here plates were kept together and after that you were having an electrode with the electrode holder and from that some flux amount was going on and the welding was taking place but you were not that much perfect in welding that is why when you were doing sometime you were having that electrode was sticking to the work piece sometimes you have seen welding was not initiated because of the Gap is more so that all the things we are going to discuss now this is just a process I have shown you you have seen in the welding lab in the manufacturing lab in the first year sir you will take forming same yes dear I am planning for the same and for that I have already planned I feel we can go for one topic tomorrow and one topic on Monday okay then from Wednesday onward uh Wednesday I&#39;m going to take strength of material for that so we will be revising entire mechanical engineering good morning so now we are starting the process okay so my dear now I will be teaching you everything from the basic like in the last time what we have done first of all I have shown you the lab what is going on so I have shown you that now we are talking about first of all weld beat Geometry so whenever you are going to weld after welding you are getting this kind of thing okay so my dear in this world beat Geometry there are three parts first part is this hatched part so this hatched part is given the name of weld bead this is the part which was initially not there initially you were having only the plates so this is said to be weld beat and this weld bead also have the two parts one part is which you can see below this red line which is uh you can see inside the plates this part is given the name of penetration and after that the above part is said to be the reinforcement and guys you have seen in the previous figure after welding is over in the reinforcement we are having a layer of slag which is removed after welding okay so my dear that is why some part of reinforcement is generally removed by the Machining process but this penetration is going to be the part of this Complete Welding so this is the penetration part and my dear as you are using when you are doing the welding process you are taking the use of heat or pressure or both so my dear some nearby region are also affected by that heat you must have seen that when you are talking about heat you are using the Heat or pressure or both for the welding so when you are using these things for the welding purpose obviously at the time of heating nearby region would be affected so the region which is affected by the heat of welding that region is given the name of heat affected Zone and this zone is very much near to the weld bead you can see after that this part which is not going to be affected by the heat of welding is said to be unaffected zone so my dear and if I go if I am going to make a tangent onto the reinforcement part I can make a tangent like this then this would be an angle this is said to be the angle of convexity it somewhere gives the idea about reinforcement how much it is so angle of angle of convexity okay so guys this is I have just defined the just Define the geometry weld geometry okay very good very good Amir so I would ask you that we have discussed here the three portions one is heat affected Zone unaffected Zone and wet bit geometry if I ask you out of these three which is having more strength which is having least strength that kind of discussion I have done many times in the classes on YouTube so I would like to ask you out of these three which do you feel is going to have more strength and which do you feel will be having the lesser strength yes please answer all of you very good guys so as per your answer you know weld bead is having the highest strength and my dear unaffected Journey heat affected Zone would be having the lowest strength I would also give you the reason for that also very good Deepak yadav sham sundariya Naveen Surendra Singh so guys out of these three I can say one thing weld bead is having the highest strength weld bead is having the highest strength and heat affected John is having the lowest strength okay and this is going to be intermediate strength okay intermediate strength now you would be interesting to know that why it is happening so you have seen when the welding is going to be formed you are joining the two plates and you are having the electrode due to heat electrode is melting and also plates are melting but on the electrode we are having some flux material on this electrode we would be having some flux material which is different than the metal so because of that when this electrode would be melting inside the groove for the weld bead it would be making an alloy and you already have studied that Alloys are stronger than pure material so that is why weld bead is having the highest strength then my dear why heat affected zone is having the lowest strength in the material science you must have studied about heat treatment heat treatment are the processes in which we heat the metal up to some temperature then we hold it for some particular time then we cool it with some specific cooling rate so when you are doing this heating holding and cooling your target is to improve the properties of the material so you are doing all this to improve the properties of the material but you know whenever you are taking medicine it is for the betterment of our body but if you do overdose of that it is going to affect badly so my dear when you take medicine it is always to be taken as per the prescription so when heat treatment is done then we know up to which temperature we have to go how we have to heat it up to which temperature we need to hold it and what should be the cooling rate if all these things are not controlled it is said to be uncontrolled heat treatment and uncontrolled heat treatment are not going to give the better results they are not improving the property actually so because of that when heat affected Zone we are going to see there we are not intentionally heating so heat is going on because of welding so sometimes whatever the temperature they are rising that is not in our control obviously we don&#39;t know up to which temperature it is going to be heat and up to which time it would be heat and we even don&#39;t know what would be the cooling rate so everything is not in control of ours for that zone so that is why uncontrolled heat treatment is going to happen and when the things are going to be uncontrolled definitely properties are going to be on the Poor Side so that is why heat affected zone is said to be the weakest part very good deeper so my dear when we are talking about the unaffected Zone there no effect of heat no alloy content so it is having in intermediate strength so I will be saying weld bead is having the highest strength then we will be having the unaffected Zone and then we will be having the heat affected Zone and I feel you are very well aware about one thing that if the welding speed will increase then my dear The Zone which is affected by the heat will also reduce this portion I&#39;ve already been asked in Gate examination that when we are talking about the welding speed if welding speed will increase then my dear heat affected Zone will reduce so there are many processes where we will see welding speed is very very high so because of that high welding speed we would be having very low heat affected Zone very good shubham so guys just like and share the session I read more and more people to join it and one more thing I would like to say that you know something is penetration something is reinforcement so we are going to define a term dilution dilution is defined as the area of penetration to the area of weld bead you can also write it as area of penetration but a area of penetration plus area of reinforcement and sometimes we are going to Define percentage dilution as well it is defined as a p by AP plus a r in 200 I also want to tell you one thing that from this dilution type of term you may also get numerical so be ready for that it would be a new type of numerical very good Uber very good shubham very good Deepak so guys now we are going to start the first type of welding that is shielded metal arc welding process so my dear it is a type of arc welding okay yes very good shares Umar shubham so in short form it is said to be s m a w so sometime in Gate also they are using this short term so you must be aware of that so my dear first of all we will see about the principle of this welding process so if you have this work piece to work which will be joined like this this is the electrode so what is going to happen whenever you are going to have this electrode and this work piece we are going to provide the power supply obviously this is our choice whether we are using DC or AC so there are different advantages disadvantages for DC and AC we will see them on the later stages okay this is in our hand whether we want to take work piece positive or electrode positive for the timing we are assuming work piece to be positive electrode to be negative so obviously we are using this polarity and let us assume this to be power source for the timing let us assume DC on the later stages we will see whether it is DC where it is AC so this is work piece this is electrode so what is going to happen my dear between the electrode and work piece there is a air there is a gap because of that there is air you know air is not a very good conductor of heat and very very good conductor air is the insulator so my dear because of that electrode and work piece between the Gap air is there so resistance is between them is very very high so my dear obviously you are providing some potential difference with the help of power source so my dear this potential difference or power source what you are applying is generally having the potential difference between the range of 40 to 80 volt I am giving you the general ranges so whenever you are going to have electrode and work piece you are going to take electrode towards the work piece then what will happen when electrode will be going towards work piece the gap between them will reduce and as the Gap will be reducing this potential difference will try to be enough will try to be enough to produce some kind of air ionization oxygen ionization so when this is going towards the workpiece when this potential difference is enough to ionize the air between the Gap in that case what will happen this is electron and this is work means between this Gap whatever the air is present that is going to start ionized you would be having some positive charge ions and negatively charged electron positive charge iron and negatively charged electron positive charge ions and negatively charged electrons so air ionization will happen and environment will become ionized so because of this ionized environment my dear in between this would be happening that electrodes would be attracting towards the work which because work piece is positive and work piece is positive it would be attracting electron and Electrode would be attracting the ions so my dear electrons will be moving towards work piece ions will be moving towards electrode and whatever this attraction is going on because of that obviously electrons have some kinetic energy ions have some kinetic energy High Ajay how are you so because of that what is going to happen because of this work piece would be absorbing the kinetic energy of electron and Electrode would be absorbing the kinetic energy of ions and it have been seen that the kinetic energy of electron divided by kinetic energy of ions is found to be in the ratio of such that you would be having this to be two third part and this to be one third part so if total hundred Joule is there 67 joules will be going to the work piece 33 joules would be going to the electrode you already know work piece is having thick thick plates so it need more heat also if you want to match them into good amount so my idea that is why when you are providing adding this positive electrode I am not saying always electrode is negative for this case I am talking about so work piece would be getting kinetic energy of electron electrode would be getting kinetic energy of of of ions and by getting that kinetic energy it would be converting into heat because of that first of all this electrode wire is going to melt because this electrode wire is going to have the lowest melting point and when it will start melting after that by taking the Heat this flux will also start melting so flux is such that its melting point temperature is above then that of the electrode wire electrode wire and parent metal is of same material so this and wire is of same material flux is of different material so my dear flux is different material because it is going to provide the alloy content second thing it should have high melting point temperature why it should be having high melting point temperature because if electrode wire is going to melt first you are melting will happen in such a way that electrode wire is melting before so because of that you will getting this type of shape and the advantage of this type of shape is the flame Arc or spark whatever you want to say that would be concentrated towards the workpiece and if by chance flux is going to melt first then you will be having this type of diagram if electrode wire is melting in the last then your R for spark will not be concentrated but diverse like that in that case it may not be able to do the welding so for concentrated Arc or spark yes malesh good morning for that convergent Flame or convergent spark or Arc we want electrode wire shell melt first so my dear we have discussed actually two functions of this flux flux have a very first function that it would be it would be providing the alloy content because of that weld bead is going to be strong as and that is why welded joints are said to have more stronger than the parent metal second function is as it is melting in the last that is why because of which you are going to get the convergent flame Oracle spark so my dear when this will happen now the mixture of electrode wire and flux will mix up and go inside the groove and you will be getting the weld to be produced so my dear you will be having this weld weld pool because when it is in liquid form we will call it pool after solidification we will call it as weld bead so my dear it would be having the combination of flux as well as flux as well as the molten wire material so my dear now what is going to happen you know that flux material is having high melting point temperature and also it have one more property it is lighter than the pure metal so as flux is lighter than the pure metal when you would be having this molten weld pool the flux metal will flux material will be going up because it is having lighter weight because of that flux will be going at the top and it would try to make a layer upward when it will be taking making a layer upward it is avoiding the avoiding the contact of this molten metal with the air you may be thinking sir why it is required to avoid the contact with the air of the metal so my dear metals have a bad habit and that bad habit of metal is like we also have some bad habits some peoples are not able to control themselves by looking at the fast food some may not control on some other things likewise metal cannot control when they see oxygen they are going to immediately react with oxygen and they will be making the metal oxides so when they will be making metal oxides metal oxides are found to be they are found to be generally brittle because they are of ceramic nature so if they are brittle in nature your entire weld will become brittle like you know glass is whenever glass is going to be like glass is a brittle material when you are going to have a glass and let us say by mistake when you are holding it it went down it will break into parts so likewise if weld will be brittle it will also break fast but we don&#39;t want to have that property we want that to be ductile in nature so that is why we want that oxide shall not form so this is the third function of the flux coating so flux coating perform this function it avoid air oxidation of metal it gives us alloy content and also gives the direction to the flame or arcore spark so this is how the things are going to happen so my dear the entire setup is going to be like this I would also like to tell you in this in this Zone which is said to be you can say uh this is the Zone where Arc is going to be produced their electrons and ions were moving when electrons were going towards workpiece ions were going towards electrode during that motion there were there was a collision between electrode and ions also so because of that collisions we are going to have a very high temperature of around 6000 to 12 000 degree Celsius in between the arc Gap and my dear in this Arc Gap some ultraviolet rays are also going to be produced so because of those Rays to be produced those rays are harmful for our eyes that is why it is never advised whenever you are going to do welding arc welding it is advised to have some glasses for that so we need to wear the glasses for that and that is why this type of glasses you have seen in the labs also you were provided and we were going to do welding with these glasses because otherwise our eyes may be affected if at some of the place arc welding is going on you look at it for longer duration you will feel some kind of uh you can say a pain in your eyes for next two three days you may not be able to sleep properly because of this so that kind of effects are coming if you are not wearing the glasses okay now my dear the point is sometime what is going to happen when these particles are moving up this is that flux vertical can make a layer over only if they are able to go up within time because at the same time solidification will also start so my dear that solidification of this molten weld pool shall happen only once the flux particle go up and make the layer otherwise flux particle will remain inside so my dear if flux particle are going to remain inside then my dear that actually after solidification we are calling them slag so after solidification we are calling them slag slag is to avoid the air oxidation if that slag is going to solidify in between the weld pool it will make defect that defect is said to be slang inclusion so why this defect will happen because if that plus particle is unable to move up before solidification which will be depending on the temperature of the weld pool which will be depending upon the current settings which will be depending upon the current settings so my dear if proper current is not provided in that case definitely it is going to happen you know the heat generation is going to be I Square RT so my dear heat generation is directly proportional to I Square if current setting is not proper heat generation will be not proper in that case you may not be having good temperature of weld pool because of which slag inclusion kind of defect can appear so my dear we need to avoid this slag inclusion for that we need to work over the current setting now my dear when we are talking about the current setting you know definitely it would be a part of Transformer so my dear when we are going to have the Transformer many times of Transformers are coming but first of all you must be knowing one thing that when this electrode is going towards work piece when this gap between them is reducing lesser Gap will require lesser voltage and more Gap will require More Voltage so if I am going to make a diagram between voltage and Arc Length it comes like this a straight line so we Define voltage to be a plus b so if Arc lens will be More Voltage required to produce the spark will also be more and guys if that is the case v is equals to A plus b l so my dear it means whenever we are having Electro towards work piece if that Gap is going to vary it will be definitely varying the voltage requirement and if the voltage requirement will vary definitely current will also vary which will definitely result into slag inclusion because if current settings are not proper yes uh guys mm am I Audible and visible to all of you actually some IPL Network issue happens fine fine fine okay so we are once again starting from here don&#39;t worry okay yes fine fine fine so guys I would like to say that when we were talking about electrode and work piece okay it is lagging let let me once again do this yes so guys now is it fine now is it fine I feel some Network issue is there now I feel it is fine okay guys now I feel it is fine now we are continuing so as I said that when we are going to talk about this a plus BL curve we have just are made I was telling you about voltage I was telling you about voltage with respect to our plane so I told you that if the gap between electrode and work piece just wait guys sorry for the disturbances foreign guys now shall we continue shall we continue yes yes yes yes Amir don&#39;t worry actually I have planned in such a way that both Theory and numericals would be covered okay both Theory and numericals would be covered okay so now we are going to continue once again so as I said let us say we have this work piece and this electrode and if the Gap is more more air More Voltage is required if Gap is less less voltage is required so we have seen that it is going to be a straight line V is equals to A Plus BL this is the equation between voltage and arc length Okay so I said if you are doing this welding manually you can see this is workpiece this is electrode so as the Gap is changing the voltage requirement will change and if voltage requirement will change my dear if voltage requirement will change my dear then what will happen because of change of voltage requirement obviously the current setting will also change and if current setting is going to change the heat generation will change because of that the temperature will also change so because of this the chances of slag inclusion are there so what we have seen there are two types of movement between electrode and work piece one is movement of electrode to wash the workpiece other is movement of electrode along the work piece so when we have two types of movement this movement which is electrode to wash the work piece is very very important because based on that we are going to have the defect like slag inclusion so that is why if both the movement we are doing manually it is said to be it is said to be it is said to be manual metal arc welding process if we are going to perform the critical movement with machine and non-critical movement manually we will call it as semi-automatic type of welding and if we are going to perform both the motion with the help of machine it is said to be automatic welding So based on that we have three types of welding so to wash the workpiece along the workpiece this is the critical movement because if this is not proper slag inclusion will happen this is non-critical movement okay this is non-critical movement So based on these we have three types of welding process if both are going to be done with the machine if both are going to be done manually then it is manual metal automatic and the best solution is semi-automatic where critical movement would be done with the machine non-critical movement will be done manually so my dear now if we are going to perform manual metal arc welding process then in case of manual it is damn sure that Arc Length will change because of Arc Length voltage requirement will change because of this current is going to change so we wanted some temporary solution also for that because under some situation we may not be able to go always for the automatic types of welding where maybe we want to save uh foreign are you facing any audio issues are you facing any audio issues I feel now everything is fine from my side yes so my dear if that kind of thing is going to happen we wanted some solution for this we wanted some solution for this so we thought let us make up now we thought that let us make a Transformer which will be providing us less change of current for more change of voltage so that Transformer was given the name of drooper so grouper is generally preferred with the manual metal arc welding process when we are going to have the movement between wall between this electrode and work piece which is done manually so for such cases we are going to have this type of characteristic which drooper is going to provide so grouper provide this type of characteristic so if you see we are going to have this voltage related to that current will be this so I am saying this is V1 this is i1 if voltage is this much current is this much so you can see my dear when voltage changes from this to this value current is changing very less so in the dropper the change of current with respect to change of voltage is very very less so my dear if that kind of thing is going to happen we can use it with the manual metal arc welding process and the chances of slag inclusion would be reduced but my dear if we are going to have semi-automatic type of welding for that case we need not to go for drooper for that case we are using this type of voltage arcline characteristic where we are defining it like previous one is said to be constant current Transformer constant current Transformer okay and similarly this one is said to be constant voltage Transformer constant voltage Transformer but my dear if I am going to show some linear voltage voltage current characteristic if I am going to show some linear voltage current characteristic there I can make the equation of this type of Transformer like you have seen it was linear so if I plot it like this then this voltage is said to be open circuit voltage and this current is said to be short circuit current so my dear I already told you if we have a circuit like this if we have a circuit like this okay like this and we are going to have we are going to have this is going to be the battery let us say okay we are going to have a battery like this we are going to show this so when we are going to have this circuit this is said to be open because there is nothing in between so in this circuit whatever the voltage you will be having across these two terminal that is said to be open circuit voltage or this is something you are calling it as EMF electromotive Force so you would be knowing that in the 12th class you were writing an equation that voltage can be written as pmf minus I times of internal resistance that internal resistance is defined as EMF divided by short circuit current so open circuit voltage is that maximum voltage when no current is flowing in the circuit because it is open and short circuit current is that maximum value of current when there is no when you will be having zero potential difference means there was a time when this electrode was stick to the workpiece at that time no spark was getting produced because the circuit was complete and direct flow of current was happening that condition is said to be short circuit they are welding was not happening so as this current welding will not happen at this voltage also welding will not happen but from this straight line if you want to write the equation you know we can write X by a plus y by B is equals to 1 so you can write X&#39;s having I so I by is plus V by V naught is equals to 1 whether you use this or you use this you will be getting a wonderful equation of Transformer and that equation is given as V is equals to V naught minus this is going to be I times of R we have written so it is V naught minus V naught by i s into I so we can also write it as open circuit voltage minus open circuit voltage by short circuit current into I this is the equation of the Transformer and from this a load of numericals are coming a note of numericals are coming as this session is related to the marathon I am going to take majorly Theory here only okay Mishra that&#39;s what for what only we are going to do this hard work okay yes very good guys so I have given you this equation and soon we will be having the practice session where we will solve some problems onto this now my dear there were some problem with the manual metal arc welding process because of which we are going to the second type of arc welding that is submerged arc welding you have seen if that manual metal arc welding annually the first issue which was occurring at that time was the problem with this motion yes if we were using dropper the problem was resolved but still that was a temporary solution so if my did this motion to be perfect we are going to include machine for that so submers our quilting process is a semi-automatic type of welding this is a semi-automatic type of welding this is the first Improvement we are getting okay hello teju so the first Improvement we are getting is submers arc welding is a semi-automatic type of welding then my dear we were also having some other issues we were also having some other issues like my dear what was going to happen ah previously we were using some electrode wire we were using some electrode wire which was having some flux material which was having some flux material so it was having some kind of flux material so because of this flux material you were having this electrode wire and it was having some size like 9 inches one feet so once one electrode wire is going to melt out you need to change the electrode so once you are going to change the electrode for that you need to stop the welding process and if we need to stop this welding process it will become a discontinuous process so my dear if we want to join two plates like that so after some time like this electrode is enough we will be have a joint then this electrode enough we will be having a joint so in that kind of process we will be having a number of joints present between that welding so if the joints are present at the Joint there are chances of leakages so if we are going to weld the LPG cylinder or ship in that case if that kind of joint will happen from where leakage will happen so in case of LPG cylinder shift building type of application we may get some kind of accidents So to avoid that we needed the continuous welding process so this process is going to be a continuous welding process so to make the process continuous We have replaced the electrode with the electrode wire so this time we are going to use this electrode wire which is going to move continuously because it is present in the wire spool so continuously electrode wire will be coming and my dear for that continuous input we are also going to provide the servo mechanism in This Server mechanism two rollers are there which are going to send the electrode wire at a constant rate because when it is going to be at constant rate the problem of the problem of this movement this Gap will also be resolved because of this constant rate my dear you would not be having slag inclusion kind of defect it is becoming semi-automatic type of welding but my dear if you are providing wire in this format if flux is also there on to the wire that flux may get erode from The Wire because of friction when it is coming again and again between the rollers So to avoid that we are not providing flux onto the wire this time flux is provided in the flux drum in the molten format okay so molten flux is separately provided which would be making a layer outside and Performing its function very nicely it will perform all the function it will avoid the air oxidation because air is not coming in contact and this Flame or spark is going to be concentrated because once again the convex type of shape is there so all the functions are going to be performed in the same way this process can be used for two wonderful applications like LPG cylinder and also the second application we have said is what after LPG cylinder that is the ship building so my dear as you know this is a continuous process it can be used for mass production and as here high speed of welding is possible so whenever welding is going to be with the highest speed the chances of heat affected Zone will be lesser so heat affected zone is going to be smaller for such case yes please tell me guys chili shreyas free arvinda and other students please tell me up to this everybody got it or not so I have revised this these are the application in short formal arc welding is also said to be s a w ramismon hi dear how are you sir ship building yes yes yes Amir that is correct that I will be telling you but if you are not having the option of Electro slag or Electro gas welding for such case you can tick this summer dark welding also okay so otherwise someone&#39;s arc welding is preferred for LPG and for ship building we are preferring Electro slag but if Electro slag is not in the option we can go for summer dark wedding and mass production is possible because of continuity of the process moving further guys so my guys these are the point we have already discussed so my dear as continuously welding process is happening and molten weld pool is protected under the environment of what the flux the flux molten flux so guys here chances of Specter are less why because my ideal that electrode wire is continuously within the environment of molten flux so there is no contact of air and this this Flame or this R cannot be deviated if it would be deviated it can also create some kind of molten droplets on the metal surface which is scattering off or scattering of molten metal which is not going on here because there is no contact of air with the flame or spark so my dear less chances of spatter is there Specter is the defect which is known as scattering of molten metal so that is also having less tendency here so guys uh this is scattering of molten metal have less tendency here so the defect of Specter will not be there the defect of slag inclusion will also not be there so now we are moving to the third type of welding process that is Di IG Mig arc welding process generally you know TIG is said to be tungsten inert gas arc welding tungsten inert gas arc welding then you also know that Mig is metal inert gas are coiling generally students are getting confused over this because the name is tungsten inert gas they are not using Arc word they feel it is tungsten inert gas welding so it is not a gas welding technique it is a arc welding technique so the name is t i g arc welding or migr welding this is the name of this welding process so my dear when we are using the tungsten electrode we call it as tungsten inert gas arc welding so my dear when you will be using tungsten electrode let us say this is the transitional electrode so tungsten electrode is going to be known uh consumable electrode it is not going to melt so my dear because of that we are not going to provide any flux over it and my dear at the same time when you will be using this electrode as it is not consumed so molten metal will not be coming from this tungsten so for that purpose we are going to use some filler Road in this type of process so that filler road is made up of the same material as that of the as that of the parent metal so they have same material so we will be using this consumable road separately so my dear what is the purpose of using such type of thing why we are using the tungsten tungsten is very very hard and brittle material so that is why if by chance its droplet will come inside the weld pool it will make entire weld brittle so we never want that kind of thing first thing is very very clear for from here second thing is my dear when we are using this tungsten what is the reason behind that till now we were using till now we were using the polarity with work piece was going to be positive an electrode was going to be negative but my dear this was fine and this type of polarity is said to be the straight polarity but my dear when we are going to have aluminum type of material it is very very difficult to weld the aluminum so weld ability for aluminum is very very poor so my dear why it is you already know Metals cannot control themselves when they see Oak season in the heated state but aluminum is that much reactive that even at room temperature it react with oxygen and make a layer of aluminum oxide al2o3 so this al2o3 is the kind of ceramic material which is very very hard and brittle we cannot weld it so for welding of aluminum we need to remove this layer so for that purpose we are going to reverse the polarity and when we are going to reverse the polarity this time work piece is going to be negative and Electrode is going to be positive what is the benefit of that when electrode when work piece is going to be negative polarity now due during the welding process electrons will be coming out from the surface of aluminum so when electrons will be coming out from the aluminum surface they will just peel off the layer of aluminum oxide so when they will be peeling off the layer of aluminum oxide that layer will be removed and fresh aluminum will be exposed for the welding purpose do we get a alloy composition in weld dear if you want alloy composition you would be providing separate powder for that purpose but actually TIG welding is generally done for aluminum very very thin plate of 5 to 8 mm so for that we need not to do all these kind of thing so my dear when these electrons are going to go out and peeling off this layer that process is said to be cathodic cleaning like Manas have written so you might be asking sir what is cathodic cleaning so my dear cathodic cleaning means we are going to make the work piece cathode means negative and then we are cleaning it so that cleaning is happening because of this cathode so that is why the name is cathodic cleaning but now the problem is you are making electrode positive so for that the melting temperature of work which electrode should be very high so we are using tungster or tungsten carbide because melting point temperature is more than 3500 for such cases so my dear no doubt if by chance even a single droplet of tungsten will be going into the pool weld will be very poor so we need to avoid that so we never make this type of electrode in reality when we make the tungsten electrode we make it of this shape means if here the diameter if here the diameter of this transitional electrode is D we will be keeping the diameter of the surface to be 1.2 to 1.5 times means 20 to 50 percent more diameter we are going to keep so my dear when we are doing this now the heat required to melt the tungsten electrode would be more so because of that the chances of melting will get reduced and my dear this thing is said to be electrode preparation and my dear whenever you are doing hair welding we can weld very thin plates of aluminum because work piece is getting less heat because negative was getting one third part of it T was getting two third part of it so that is a kind of limitation for this process also so my dear when we are using this TIG here we get to know about the term weld ability if we are going to talk about the weld ability of Steel I would like to say that weld ability is inversely proportional to the carbon content if carbon content is going to be more weld ability will be poor so that is why whenever we are going to have low carbon steel medium carbon steel and high carbon steel so weldability is going to be poor for high carbon steel then highest for low carbon steel weld ability is directly proportional to 1 bicarbon percentage or I will say weld ability is inversely proportional to the percentage of carbon content okay so my dear now the point is here you are not using the flux who will solve the purpose of flux we are not providing here molten flux we are providing the inert gas so this inert gas will be solved the purpose of flux inert gas will be solving the purpose of flux so inert gas will be solving the purpose of flux okay so when inert gas is provided inert gas will also helping us to make a flame which is going to be concentrated because from throughout the sides we are going to provide the inert gas it will also avoid the contact of air and inert gas is non-reactive so there would be no reaction between the Surface with the inert gas that is one more Advantage so inert gases you can use helium you can use neon you can use argon generally we are using argon for availability point of view so my dear we have studied TIG process here there are some problems one is you are using tungsten electrode which is non-consumable still chances of consumption is there if temperature increases beyond the range second problem is we are using we are using uh this non-consumable so filler road is required filler Road will be having a constant size once again you need to stop the welding and because of this uh you can say negative polarity reverse polarity you cannot weld the thick plates so for that purpose and Improvement come in the form of MiG process in Mig process We have replaced the tungsten electrode from the metal electrode which was consumable so filler road is not required here we were once again providing the servo mechanism so my dear continuous flow of electrode will be there once again you are using the inert gas for the purpose of flux that is why the name is metal inert gas arc welding and my dear when we are going to do this we have removed this is inert against in general inert gas is going to be very very costly if you are going to replace this inert gas by CO2 which can be done with the metal unit gas welding then this CO2 is not an inert gas so the name of the process will become active gas active gas metal arc welding process so my dear this is the process nowadays used in the industries it is similar to submers arc welding okay so this process is active gas metal arc welding and this is used in industry it have replaced TIG process okay I feel everybody is getting this OK everybody is getting this so this is said to be the Mig process so my dear now I am going to tell you something more about numericals there are three types of heat one is heat generated which is given as I Square RT second is heat supplied okay third one is heat required so my dear let us say we need some 700 joules of heat for welding or melting purpose then my dear for melting purpose if we require this we may be providing some 1400 joules so why we are providing more because during welding that entire setup is exposed to Atmosphere so there would be some losses of heat to the atmosphere okay so as some losses of heat are there to the atmosphere because of that we are providing extra heat so my dear if requirement is 700 you are supplying 1400 so this gap of 700 this is going to be the heat loss to the surroundings okay then my dear whenever we are going to have this heat supply for that we need to generate the heat heat generation takes place by this formula and let us say we are going to generate the heat of 2000 joules why heat generation is more than Supply because heat is generated at the tip of electrodes then that heat is distributed then also some kind of heat loss to surrounding happen so here also there would be a heat loss that is of 2000 minus 1400 600 joules and that is said to be heat loss one this is heat loss two so guys this total is the heat loss to the surrounding so heat generation is 2000 requirement was 700 so my dear based on these three types of heat we are having three types of efficiencies first is the efficiency of heat transfer which is defined as heat Supply by heat generated it can also be written as rate of heat Supply by rate of heat generation then thermal abuse efficiency OK or we can also call it as melting efficiency this is heat required but a heat Supply or we can have rate of heat required but a rate of heat Supply then we are going to have overall efficiency which is written as efficiency of heat transfer into melting efficiency if you are going to Define it it is the rate of heat Supply but a heat generated into heat required but a heat Supply so you would be having Supply Supply cancel heat required by heat generated so guys you may be thinking sir is going very fast but as I already said that this is the revision Marathon so here it should be like when you are reading your notes so you must feel like from the notes like you have seen in the movies whenever letters were exchanged from the letter always the actress was looking like and he was feeling actor is speaking so this marathon is of that type only like your notes are speaking okay or their process is welding so generally process efficiency will be said to be this melting efficiency only but in general they mention in the East terminology which we have discussed here okay I feel you got it okay Mishra don&#39;t worry so dear numerical whatever formula we are discussing they are going to be useful only and I am planning a practice session of welding and casting both on Tuesday so there you will see all the types of questions so don&#39;t worry about questions also here you revise Tuesday we will do the questions now you can see this is direct current straight polarity direct current reverse polarity and alternating current so this table is very important for exam sometime one mark question is coming from this okay so guys just like and share the session because still we have completed only one type of welding but you know after resistance welding the time required would be less if you see in the classes we have covered whatever we have covered in the four hours that we have covered in this one R because 10 to 15 minutes uh problems were also there in between now my dear we are talking about the polarity so in direct current straight polarity we are going to have work piece positive electrode negative we are going to have work piece negative electron positive direct current state direct current reverse here work piece will be positive negative alternately electrode would be negative positive alternately heat generation here work piece would be having 67 percent electrode would be having 33 percent here workpiece would be having 33 percent electrode would be having 67 percent here both workpiece and Electrode would be having 50 50 percent okay then penetration so here work piece is getting more heat so we would be having d penetration here we will be having shallow penetration here we will be having intermediate penetration wire feed rate means with what rate electrode wire is melting that would be less here because less heat or electrode more hair and more heat of electron here it would be intermediate because 50 50 heat is there thickness of plate you can weld here so in straight polarity you can weld thick plates because work piece getting more heat here thin plates because electrode getting less heat here intermediate because both get 50 50. so work piece uh here I would like to say work piece preparation we have already seen electrode preparation so if my work piece size is less than 5 mm then we are going to directly weld them for more than 5 mm we are going to provide some kind of preparation for more molten metal to come inside this thing is said to be the workpiece preparation so work piece preparation is done when plates are of more thickness so my dear work piece preparation is done in the dcsp do not done here here we will say it depends what is the thickness so if thickness is generally more than six to eight mm then only we are going for this work piece preparation kind of thing different book shows different value for that so moving further guys okay now numericals we are not going to do here so I am having these numericals but that we are not going to solve now we are moving to plus Mark welding for numerical we have session on Tuesday where we will take casting welding forming all plasma are welding this is one more type of arc welding you must be aware of plasma so my dear plasma is the fourth state of matter okay plasma when we are talking about is nothing but ionized gases so ionized gases is said to be the plasma so my dear generally we are going to use the nitrogen gas okay so here what we are going to put everything is same we would be having a tungsten electrode like that then we would be having some plasma cases like nitrogen okay we would be having plasma gases like nitrogen then my dear we are also having the inert gas to perform the function of flux that is ah let us say argon okay we are having this work piece now as this is tungsten electrode which is not going to melt we have to use some pillar out also so my dear in this process I would like to tell you when you are using this plasma you can get a temperature from 8000 degree Celsius to fifty thousand degree celsius that temperature can be produced but for welding we are restricting it to 20 000 degree celsius you may be thinking sir at that temperature plates will get melt out so I am noticing that temperature will be there with the plates that temperature would be there with the gases so whenever these plasma gases are going to react with The Arc because you are going to provide here some power supply so whenever these plasma gases are going to react with The Arc they will convert into ionized gases ionized gases are said to be these plasma will get a very very high temperature like whenever you are sitting in front of fire you are going to see that that fire is definitely having some very high temperature but when the air taking the heat from that will be coming to us then when it will be giving heat to us that heat will not be creating that temperature for our body okay why because our area is more so when that heat would be distributed our temperature will not reach to that much so that is going to happen when those plasma gases are going to come to this work piece a deep and deep penetration will be there and that is why when this kind of welding going to take place we will call it as Keyhole phenomena why Keyhole phenomena because when this plasma will be giving energy to the plate then my dear it is going to get cool off so because of that you will be getting the Keyhole type of weld bead here this type of weld bead you will see because when the plasma will be attacking that would be giving energy and it would be reaching to the deep but with the very less thickness so this type of weld bead you will be getting here so welding comparison okay dear for that uh I will provide you the actually tab you are asking about the temperature they are asking which welding process is having highest temperature ok so that kind of I will provide you a table where it would be mentioned that temperature ranges of different welding processes so that table will solve your purpose ok you might be thinking sir when we are restricting the temperature up to this where we use this temperature when you you would be going for plasma or cutting so in the metal cutting plasma cutting will be there so there we will be using more temperatures so here we are restricting our process to this and my dear all other things are going to be same here we need to ah cool the electrode also otherwise electrode may get that high temperature and melt out so for that purpose sometime we are going to provide some artificial cooling okay so water cooled nozzle are going to be provide all around the tungsten electrode to keep it cool for that welding process okay so that is said to be plasma arc welding process now the last type of arc welding process is Electro gas or Electro slag welding okay so my dear in this what we are going to have I am showing you with the simple diagram you are going to have this as workpiece one this as work piece too you can consider you can consider them to be the two plates of the ship and you want to join these two plates as wise so when you want to join them along the edges you need to pass your electrode wire from here so that this electrode wire can provide molten metal here for that my dear to start the welding we need some starting point otherwise molten metal will spill away so my dear for such type of welding process we need to provide a starting plate for the welding so we would be providing a starting plate this is the starting plate so initially the arc is going to be produced between the starting plate and the work piece and my dear we would be providing the power supply like this and once the welding is going to start this electrode wire after melting will be going up and weld will be moving ahead in the upward direction for that purpose you know that if molten metal is not going to be solidified soon then it will still spill away from the sideways okay you have provided starting plate but from the sideways it can still spill away so for that purpose we are going to provide some copper shoes we are going to provide some copper shoes the copper shoes are like this okay so in between electrode wire is there this is copper shoes when the melting helps when the melting take place copper shoes will take the Heat and solidify the molten metal and move in the upward Direction so my dear when this kind of thing is going to happen this will be moving in upward Direction so here you can see see these are the copper cooling shoes so they would be these copper pulling shoes are there so this will be moving in upward direction will the welding process this is the starting plate which is required initially okay so as the solidification will take place this will move ahead so here also flux is not there so four flux we are going to provide the molten flux so molten flux is provided in between my dear hair actually the lows of heat from the sideways or all around is not going that much so because of that my dear what is going to happen because of that sometimes the heat is going to be very very high so for such cases we can switch off the arc for such some time because of that very high temperature welding will continue without any r or spark so you can switch off the current and Welding will still take place so when you are switching off this for some time the temperature will go down and once again when the temperature go down Beyond a value you will once again switch on the arc okay is it clear thanks samin for your wonderful words so this is what is going on for Electro slag and Electro gas welding and my dear this is one type of arc welding only when we call it Electro slag and when we call it Electro gas when we are going to use the molten flux we call it as Electro slag and when we are going to use when we are going to use the CO2 we will call it as Electro gas bending guys on my telegram Channel we are also having some handwritten notes of this welding so whatever I am saying word to word is written there so after learning the process you just need to remember only the application of the processes nothing more than that and you need to practice the numerical so those nodes now will if you see if you go through this that will be very easy for you to understand okay those who are learning for the first time those who have already learned for them already this is the revision so guys Electro slag and Electro gas welding is a vertical welding process so it is used for what it is used for what for ship building we have already seen a previous process was good for LPG cylinder and this is good for shipper building with this we have completed the arc welding process now my dear we are moving to the other processes because arc welding is over you can see every theory is also written in the slides okay so my dear now we will move to the other processes Okay so moving to resistance welding so whatever I have told all theory is also written in the slides okay very good truth very good Naveen wonderful Army notes and this lecture yes yes I mean that was the exact word that I wanted to tell at that time that if you have that nose then this class is the audio book for that okay so these days there is a trend of audio books so you can get that Advantage moving to the second welding process that is the resistance welding so my dear in the arc welding voltage was playing a very very important role actually okay so if we are talking about the arc welding process that is said to be high voltage high voltage and low current welding process but when we are talking about the resistance welding it is low voltage and high current welding process when we are saying this many students are getting confused because they see in the question voltage is given in the range of 40 to 80 volts and current is generally they have seen that from 400 amperes to 1000 1200 1300 ampere likewise this is written so this is the current is more than voltage so guys comparison can never be done like voltage with the current comparison is done with the voltage with the voltage current with the current so here voltage may be up to 12 volt so 12 volt and 40 to 80 volt this is more and here the current if you are talking about it is more than 10 000 amperes so just compare this current and this compare so here current is more here voltage is more so in the resistance welding current is more than 10 000 ampere in general even sometime you will see the value of 1 lakh amperes 50 000 amperes 35 000 ampere so here as the current is very very high all of you are aware that heat generation is written as I Square RT so as current square is there so if current is very very high you need to reduce this time because you cannot have that high current for more time otherwise the entire plates will melt out so uh sagrika up to lack of very good very good sagrika so mighty refuse see the types of resistance weldings so first of all why we need it so my dear till now we were doing the arc welding and arc welding were performed in the form of butt welds okay like this plate and this plate are kept like that and you are welding it in the butt weld configuration we have not seen any process where we were doing lap joint configuration so resistance welding came for the purpose of lap joint configuration when for the first time you are going for this lab joint configuration the name of process is resistance welding so the types of resistance welding is spot welding projection welding flash butt welding high frequency resistance and induction welding and seam welding all these are the type of resistance welding and after this welding process other welding process will not take that much time as I said we are going to complete in 2.5 hours so this is the first type of resistance welding process spot welding so my dear what is going to happen this is work Piece One Work piece two this time you are going to keep two work pieces like this and I would like to tell you there is the lower die which is fixed upper die is movable so my idea this is the upper die or I I shall not say die it is actually the copper electrode so this copper electrode generally this is said to be the fixed one and this is said to be the moving one in general okay so when we are going to apply the force from that some penetration will happen from both the sides because pressure is applied from both the side so this much penetration will happen electrode will get penetrated into the sheet now my dear this phase is said to be the penetration and in this phase if I show you two diagrams one for the pressure other for the current so this first time is said to be the squeeze time for that time we are going to increase the pressure and there is no current flowing for that phase okay now my dear what will happen after that after that my dear this squeezing time is over we are going to supply some current that very high current is going to pass like this so my dear when this current is passing obviously every surface will show some resistance there is resistance of this copper electrode is R1 R1 then there is an uh resistance of this surface a interface between copper electrode and work piece one so this resistance I will be giving the name of R4 R4 so here also R4 will be there then my dear there is some resistance provided by this mild steel plate this I am showing it by R3 R3 and my dear there is a resistance between the interface of two plate which is denoted by R2 so you can see R2 is one time R 3 2 times r four two times R1 two times so if you see this R2 is quite quite quite more than all other resistances which are already 2 times 2 r 1 plus R3 plus R4 summation of that is even lesser than this R2 so R2 resistance is very very high and because of that high resistance when the current will get passed here we will be having more generation of heat and because of that more resistance more heat Here My Dear weld is getting produced and when the melting will start from the center this weld bead this Zone Fusion Zone will start expanding this may expand in the shape of sphere in the shape of cylinder in the shape of any other geometry but here we have shown like a cylinder but this can be cylinder can be ellipse can be other shape but in general we will assume it either a cylinder or a sphere so as per our assumption it would be cylinder or Sphere for easy calculation otherwise it can take any shape and this Fusion Zone will be reaching up to the electrode and we will get this weld to be done okay so this is how the welding will be performed so my dear if that is the case this is the second time like already in the comment section we have this pressure remains same and for this time we are going to provide some current so my dear this time is said to be well the time now because of this melting obviously between this this where it is melt is going to take place but this time we will not call it as weld bead this time we are going to call it as weld nugget after solidification so my dear until this gets solidify we will maintain the pressure but no current will be supplied so for this time pressure remains same current is zero this is said to be the or this is said to be which time hold time after that we will relieve the pressure and as the pressure is relieved this weld is performed you would be getting these two plates to be joined with the joint and as the joint is like a spot we will call this process to be a sport welding so this is how the process is going to be over yes yes very good very good sagarika that&#39;s really great thanks for that and even you can get by handwritten notes from the telegram channel so that will also further help you okay sagrika so let us move further very good so this is the sport welding process so this is the squeeze time then we are going to have weld time then we are going to have hold time then we have relief time so this is what is going to happen so my dear these are the resistances defined like that so these are the curves we have already seen so my dear when we are talking about these resistance welding I would also like to tell you that when we are going to have this the heat generation we are going to have an i Square RT this is the heat generation going to take place so my dear if you are going to see that whatever the heat required for melting that would be like mCP delta T in general okay this is required for increasing the temperature to Melting Point temperature then we would be requiring M into latent heat okay so that would be required for the melting purpose so these are the two Heats generally required this is said to be sensible heating this is said to be then latent heat so with that the melting is going to take presently that is the heat required so my dear if you are going to say this heat required you must also understand that if we have some thickness if thickness is going to be more then my dear heat generation required is also going to be more because more thickness will require more heat to get melt out okay so my dear if that is the case we can also say that thickness is directly proportional to heat generation which is a it is directly proportional to I square and this thickness is also directly proportional to the melting point of the plate sorry I am going to correct it don&#39;t worry I would like to say that this uh this I I square is also directly proportional to this melting pointed melting point is going to be more then also the current requirement will be more so my dear why I am telling you these things sometimes the questions are coming that for this much thickness this much current is required so for that much thickness how much current would be required so if they say for th1 we need i1 for th2 what would be the current requirement so you can say that thickness is directly proportional to current Square so th1 by TS2 can be written as this is uh I square is there so it can be written as this is I 1 cos Square by I 2 cos Square similarly thickness are not given melting point are given then you can write melting point of one by melting point of 2 is is equals to I 1 square by I 2 square ok so in the using those relation you can find out the unknown if any unknown is there so from these formula till now there is no question asked so because of that in the practice session I will take these type of question so you all must attend that practice session there I would be taking all these things okay now we are talking about the projection welding the second type of resistance welding process this is more theoretical uh if you see my dear when we are looking for more number of sports like if we are joining the two plates in such a way that we require Sports at multiple point so for that purpose we are using projection welding so the second name of projection welding is nothing but multi-spot welding so my dear if you want sport at multiple places we will call it as multi-sport welding Here My Dear we will be having one plate on which the projections are going to be given and the projections are provided like this the places where you need the sport we provide the projection these projections are made by a process known as embossing which we are going to study at the time of metal forming and boasting and coining are the similar processes you must have seen there so embossing is the process which is going to be used for this and my dear what we are going to do once again similarly we would be having the copper electrode on both the sides so this time once again when you will do the squeezing then my dear add these at these projections what you have made those projections are going to be broken because of that because of why these are broken they are going to be broken because you are applying the pressure so some plastic deformation will happen so these projection would be broken so obviously wherever the projections are there the sheet which is having the projection that will be having more heat because of this plastic deformation so generally projections are provided on the sheet which have either good conductivity or have more thickness so that it can bear that kind of heat and transfer it to the surrounding so my dear whenever you are using this process all other things are going to be same projections are going to be there only at the places where you are providing the projections only that places will provide you the spots of the welding okay so when we are using this as it is a continuous continuous Sports you are getting so my dear in general sport welding is going to be used in the automobile sectors and when you are going to make so much Sports together then also the chances of leakages will be there because it is not a continuous type of welding okay so my dear when we are having this ah projections it is like that so these are the hot spot because whenever you would be providing them plastic deformation will happen there and if you are going to compare these two plates if they have different thicknesses then this would be having more thickness and this would be having less thickness if they have same thickness conductivity is different then this sheet will be having more conductivity this will be having less conductivity these are the point you need to take care in this type of welding process okay uh dear projection welding projection chili Mishra when we are going to make these projections then these projections are made by embossing process embossing is the metal forming process like when you will be making these projection in the sheet you would be putting this sheet normally at some place where you would be using this type of ah you would be using this type of dye you would be having a die of this type so when you would be having tie of this type when you will apply the pressure this sheet will be converting into this sheet where projections are there so these projections are made by this kind of process and this process is said to be the embossing we will be having more more clarity on embossing and coining when we will see the metal forming chapter means tomorrow or day after tomorrow we will see that okay now we are moving to the third type of resistance welding process which is The Flash but welding process my dear as we have already seen that this welding process came for the lab joint configuration so when this came for the left joint configuration some people think that we cannot use it for the butt joint configuration so it is not like that we can also make the butt joint from this type of welding for that what we are going to do we are going to place two rows which are going to be joined together now my dear this process is generally used for joining the railway tracks in the developed countries okay so railway tracks are joined by this process in the in the developed countries like America and all in developing countries we use thermite welding for the purpose so you would be keeping two railway tracks together like that and you would be taking them towards each other when they will be going to our each other there would be a time when they will just connect with each other so my dear you are going to provide this pressure at that time we are going to provide some current here as well and my dear that current is generally of the range of 1 lakh ampere so my dear initially as you know some oxide layer may be present on the metal surfaces so some flash is going to generate it initially that indicates the burning of oxide layer that is why the name is Flash but welding then after that because of this High current and this pressure the weld is going to take place in arc welding we were only using the heat for the welding process whereas in resistance welding we are using heat as well as pressure both for the welding process so I feel you are getting it so this is splashed but welding process the important Point here is 10 to the power 5 ampere of the current okay moving to the next that is seam welding this is not projection but the seam welding in the seam welding you would be having two plates like this these are two plates and you are providing some roller so for this roller they are also provided the power supply like this so whenever these rollers are moving continuously over the surface they are continuously providing some penetration okay so some continuous penetration is there and here current is also passing and as you know at the Joint of the sheet at the interface of the sheet we would be having the highest resistance so because of highest heat they are weld will take place this is the process which is continuous welding process so my dear if you see the sport welding if you see the projection welding they were discontinuous welding processes but this is going to be the continuous welding process so sometimes in numerical they are using six D ah yes root T and other times D is equals to T what should we use dear it depends on the thickness of the sheet when thickness is coming out to be less than 8 mm then we are going to use this what you have mentioned as D is equals to ah 6 root T okay so my dear that is actually coming from the data book in the gate question you will note get that kind of thing because that requires data so from the data book only when thickness is less than 8 mm then we are using this relation what you have mentioned okay so I also told at that time of welding when I was teaching you and my dear in this process as continuously current is Flowing so at this point when roller reached this place this much part is already welding so sometime it happens that when you are reaching to the new position some part of current also passes through the already welded portion that is the lows of current that is said to be shunting of current so my dear this is a continuous welding process it is used to make the Jolly like this you have seen in the kitchen that kind of jalis are there there also they are connected continuously so this kind of structures are made using this welding process it is a continuous welding process so obviously speed of welding will be more here and as I said shunting of current is the lows Mishra it would be mentioned in the question okay so my dear now we are moving now we are moving to the next process that is fifth one high frequency induction and resistance welding so they are not two different process actually one only so here what is going to have let us say you have this strip of Steel you want to make the pipe of it then what you will do you would be having this strip this would be having some width and some length so this width would be made as circumference you would be just bending it and you would be after bending it just giving input here here you are having some mandrel okay and along this mandrel you will be just bending it and providing it these are the concave rollers which will be applying some pressure onto this and they will give this the shape of exact pipe and when this shape would be provided like this the shape would be provided like this then my dear you need to join this and you will get a pipe so my dear steel pipes are made by this process and seamless pipes are made by centrifugal through centrifugal casting okay so if you are going to join this what is going to happen you would be having this sheet like this here you will provide some positive here you will provide some negative then my dear when this will be getting joined together by dear because of the current produce the weld is going to be happen Okay so my dear this will help you to make that kind of pipes and my dear generally they have a length of 20 feet which are available in the market like General Industry made that kind of pipes many others are also there so when you will get these types of pipe they are having generally a length of 20 feet so my dear now if you are going to provide the conductors and using the direct current we will call it as resistance welding if you are going to provide the inductor coils and using AC we will call it as induction welding generally we are going to provide high frequency of alternating current so is there any term ah repercussion welding okay dear I feel you have written the name note correctly percussion welding is there okay so that percussion welding is not a type actually actually uh that is depending on the process if the finishing is happen uh better then we are calling that okay if you want also I will share it to you okay percussion welding is the name which is used so my dear here if you are going to see we are using the copper conductor here here and here copper conductors are there this is the mandrel which is used to make the cylindricity of the pipe okay this is used to make the cylindricity of the pipe current used is 100 kilohertz to 500 kilohertz this is the frequency of the current we are using Okay seamless pipes are made using centrifugal casting we have already seen so Here My Dear we are making it and we have completed the resistance welding process now we are moving to the Solid State welding process in Solid State welding process the first process is explosive welding so as here I said the solid state welding it means here melting will not happen so my dear we would be having a work piece which would be treated as a Target plate and we would be having a flyer plate which is always thin than the target plate and this is something something I want to be valid over it always plier plate is thin then my dear here we are going to use explosion so we need to use some explosive material so we could provide this explosive onto this thin plate known as plantar plate but when explosion happen there are chances that the surface will get blackened So to avoid the blackening of the surface of plier plate we are providing a buffer plate in between this buffer plate generally is made up of rubber as we know rubber is having excellent damping capacity so my dear generally this buffer plate is provided in between now Detonator is required to start this explosion so when deteriorator is starting then explosion will happen because of that explosion a very high pressure wave energy wave is getting created you must have seen in the movies uh where these kind of scenes are shown where some blast are shown like there was a movie uh where Akshay Kumar was also there here I do not remember the name it was 26 special 26 whatever it is so in that movie when the blast happens then that actor or whatever the person near that blast is there they are shown like they are just moving in the air like that so they got some pressure wave because of that they got a very high kind of shock and because of that they go to a very far distance so my dear similarly that pressure wave will be given to this plier plate because of that this plier plate is becoming in the semi-solid form and going to connect on to this work piece you are providing this angle which will decide the direction of welding you are providing this initial distance known as standoff distance this is provided for initial impact numericals are coming from okay okay fine let&#39;s move further so my dear when we are talking about so in South movies they are happening more but in South movies this is not happening because of blast this even happens from the fightings but in Bollywood movie it happens only in the case of blast that is the difference Army so I would also like to tell you guys that whatever the numericals are coming they are basically from Arc and resistance welding from other topics we are not having numerical this is just application you need to remember so when we are having this welding here one very important point which is already asked in the gate paper the speed of this welding process is limited by the speed of sound the relation between them is because of this uh explosion okay so there it would be having a limit from speed of sound so my dear when we are talking about this type of process okay here generally diffusion is going to happen so one material is getting diffused into other whenever we are talking about the diffusion it is like you must be knowing that if we have two gases in this container a gas is here B gas is there if you remove this partition then both the gases will get diffused into each other so that kind of thing is said to be diffusion which is going to happen in this type of welding the second type of solid state welding is friction welding and my dear if you are going to see the application of this this is in whenever you are going for uh colliding of cylinders for cladding process we are going to use this for cladding process explosive welding is getting used friction welding is used whenever we are going to join drill bit drill bit with the stand this also have already been asked in the gate exam what is the application of friction welding so when drill bit is connected with the shank that process is said to be the friction welding process so my dear here also we would be having two things one is erode a other is a road B so my dear this road is rotating with some speed of Omega and this road B is going to be stationary okay this road B is stationary you are going to take this road B towards a so a is having some motion B stationary so when both of them will be connected initially a is rotating B is at rest so because of that at the interface there will be some relative motion relative motion means confirmation of friction so because of that obviously the friction what it does friction tries to convince both the bodies friction will try to stop a and try to rotate B so as you are over all all the time giving the speed to this definitely friction will not be able to convince this first body so friction will be able to convince the second body and after some time both will be rotating with the same speed so during the time when friction is there a lot of heat is getting produced between the surfaces and because of that heat diffusion welding will take place and here also melting will not happen so it is a kind of solid state welding process so my idea this is used for drill bit and shank so my dear if you have both the materials of same then my dear you will be having this type of weld bead if you have both sides same material but if the material is going to be different if same material are there this type of weld bead would be happen if you have different material then hard material will not be showing any kind of deformation soft will make a layer over it like this okay so this is going to happen so in case of drill bit and shank shank is going to be soft and drill bit is said to be hard material so we would be having this type of weld bead geometry so moving to the next process guys the third Solid State welding process is ultrasonic welding so as the name suggests we would be using the ultrasonic energy of vibration so here these are work piece one this is work piece two they are placed together and here we are having some HSS tooltip there is some clamping Arrangement which is going to provide solar road which transfers the vibration to the tooltip vibrations are produced in the transducer so in this transducer vibration will be produced those vibrations transfer to the HSS tooltip with the help of the sodot road and due to this vibration the weld is going to produce between the work piece pressure is applied from the Anvil side also Anvil is the kind of support which is stationary and my dear here as you are not using a lot of energy as I said here this kind of welding can join very very small or thin elements and it is used in electronics Industry if you want to join ICS if you want to join some kind of diodes some kind of transistors so those kind of elements so in the electronic industry in the electronic industry this process is used where we need to weld very small small electronic components like IC like trans transistors like or you can say ah that diodes okay so that is the application of ultrasonic welding so others we have already seen now we are reaching to the gas welding process gas welding process is a kind of chemical reaction type of welding it is the kind of chemical reaction type of welding and gas welding have a generalized name this is important for Theory point of view some ideas generalized name of this welding is oxy fuel welding here oxy indicates we have oxygen cylinder fuel indicates we have some fuel cylinder that fuel can be acetylene that fuel can be acetone that fuel can be methane fuel can be propane so whatever the fuel we are going to use the name will be changing based on that if you are using hydrogen it is oxyhydrogen welding if the fuel is ah methane oxymethane welding but in general what we study is we have acetylene so we will be calling it as oxy acetylene welding so my dear when we are talking about oxy acetylene welding c2h2 is acetylene so my dear when we are going to use this the principle of this value process is nothing but the combustion so in the combustion reaction whenever the fuel is reacted with oxygen it gets converted into CO2 and steam CO2 and steam are the byproduct of such reaction so my dear when this c2h2 which is acetylene this will be reacting with the oxygen it is getting converted into the CO2 and steam because water will not be in the liquid form and the large amount of heat is getting produced this heat is going to be used for the welding process then I feel you all are aware that this C2 S2 and react with oxygen you will get two CO2 plus s two plus heat you must be thinking of that sir how this reaction is happening one mole of acetylene require 2.5 mole of oxygen if you are going to provide 2.5 mole of oxygen you will not get any kind of flame or per spark because it would be a complete combustion which happens in the ice engine but we also require some kind of flame some kind of spark which can be used for the welding process so my dear for that purpose when we see this reaction this reaction is going to happen in the two stages so in the one stage C two h two when it is going to react with the oxygen it will be converting into carbon monoxide H2 plus heat then my dear this is two Co then my dl2co plus H2 when it is reacting with 3 by 202 it is going to give you CO2 t o two plus H2O plus heat so my dear you are getting heat two times in two stage reaction so my dear this heat one heat one and heat two when we are talking about so my dear these are the two kind of heat we have seen so these two reactions are denoted by two plane this first reaction requires one mole second reaction required one point five mole we never provide 2.5 mole of oxygen we always provide lesser amount of oxygens why because we are when you are not given the proper food at home you will search for the food from outside so my idea similarly we are going to have a torch so when we are going to have this torch in which in which acetylene and oxygen are provided from the cylinder so if oxygen is provided in insufficient amount then to take the extra oxygen for combustion purpose my dear fuel is coming outside so that fuel is coming outside in the form of the plane so my dear stage one reaction will give smaller play stage two reaction will give large flame because here more need of oxygens are there so these reactions are not going on separately they are going on simultaneously as fuel is coming continuously so when these reactions are happening here also note complete oxygen provided here also not so two two Flames are coming from two reactions inner flame is having lesser surface area outer is having more surface area so this heat and this heat when we compare any heat can be more for different different fuel but temperature of inner inner inner one is always more because of lesser surface area so when heat is getting distributed over a flame then its temperature is also going to increase so my dear for this smaller flame we are always having more temperature so due to more temperature of the smaller plane always the inner flame is going to be used for the welding purpose and outer flame is used for the preheating and post heating kind of work so my dear you can see here we have inner white cone and outer bluish cone outer bluish cone so two types of cones are there so this inner cone is traveling some distance n and my dear this outer cone will be traveling always the more distance okay so by dear now we are talking about this is first type of flame which we are actually there are three types of flames are there one is said to be neutral Flame other is said to be oxidizing Flame and third one is said to be the carburizing plate okay so when we have these three types of flame how we are deciding it so my dear you know one more required 2.5 mole of oxygen so we are never providing that much we are never providing that much thanks chili for your wonderful words but don&#39;t worry right now take the benefit of online so when we are talking about the neutral flame we are going to provide acetylene and oxygen in the ratio of one is to one means for one mole of acetylene we are providing one mole of oxygen from the cylinder then my dear when we are talking about oxidizing flame here we are providing more oxygen not from the requirement but more from the acetylene so we would be providing around 1.15 to 1.6 times of oxygen than the acetylene and here you would be providing 0.72.8 times of oxygen than that of acetylene so in all the Flames we are providing oxygen lesser than the ah fuel only so my dear if we are having the neutral plane this is the neutral plane for the neutral plane we are going to provide c2h2 but a O2 in the ratio of 1 is to one so my dear for that n is the distance traveled by this flame okay so my dear the temperature here we are getting three to six zero degree Celsius for the inner plane then my dear we are also going to have the second type of plane which is oxidizing flame where you are providing oxygen amount slightly more than the one then that of the acetylene here temperature is three three eight zero as you are providing more amount of oxygen from the cylinder this time the distance traveled by the flame is lesser it is around 0.52 or 0.332 0.5 times of the N if in the neutral flame it was traveling and distance here it is traveling 0.332.5 times of n okay so my idea if that is the case that is the traveling distance my dear 0.33 to 0.5 this time the temperature would be more because the flame size is surface is going to be less than Samir for your wonderful words so that is why the temperature would be more so my dear generally oxidizing Flames are used for the Alloys like brass bronze and all and neutral flame is used for the normal Paris materials what we have seen so my dear there is one more exception when we are talking about uh the brass here some zinc is present so whenever we are going to weld this brass with the neutral flame zinc is having very less vaporization temperature so it gets vaporized this and if you don&#39;t want it to vaporize we are going to weld it from oxidizing flame because here more oxygen is present so zinc will react with oxygen and will make zno vaporization temperature of jadeno is quite more than that of zinc so because of that zno will make a layer over the weld pool so because of that zinc will not be vaporized this and in that case you can save your zinc inside so brass is generally welding using the oxidizing flame then my dear when we are talking about the sound dogs in the neutral flame we are going to have hissing sound like you have seen one movie was also there kind of okay similarly oxidizing flame will give you roaring sound roaring sound is there but my dear carburizing flame is a silent plate there no sound will be coming so in carburizing flame my dear you are providing that much less oxygen that this time fuel itself comes outside to take down season because of that some acetylene feeders are going to form which is traveling the distance two times the neutral flame because of which temperature reduced to 3060 degree celsius carburizing flame is generally used for uh welding of cast iron or high carbon steel where carbon amounts are more otherwise if you would be welding low carbon steel using this flame then it may absorb carbon it may absorb carbon from acetylene feeder okay so we are using those element which are already saturated with the carbon so carbon Rising flame is used for cast iron for high carbon steel that kind of elements okay so guys just like and share the session we are already at the gas welding we have completed now we are reaching to the Allied processes some other welding process are pending that will be coming Electron Beam welding and all so this is Allied processes where we are talking about soldering brazing and Brace welding okay for this I am taking this table because questions are generally coming from this table so my dear when we are going to have the mechanism the mechanism used for soldering is adhesion here also attention here also addition if you are talking about the temperature here temperature is less than 427 degree Celsius here temperature is more than 427 degree Celsius here temperature is more than 427 degree Celsius here the filler material actually in this process what we are talking about Allied processes they are neither said to be solid state welding nor liquid State welding they are said to be actually solid liquid why it is said to be because here parent metals are not melted but filler metal is melted so you would be having two materials like let us say I want to join these two things they are in solid format but the filler material by which I am going to join them that would be liquid form so that is why solid liquid State welding it is some ideas that pillar material by which we are joining here we are using lead plus tin in soldering here we are using copper plus zinc which is brass in brazening and copper plastin which is said to be Bronze in the bridge welding brace welding is the kind of welding process only soldering and brazing are slightly different from the welding process generally brace welding using the gravity force for the filling of molten metal on the other hand soldering and brazing are using the capillary action for the filling of the Gap so that is the major difference so for capillary action the gap between them should be very very less then only capillary will happen uh hi sir I have to revise machine design yes through Marathon would be sufficient because eight hours marathons are definitely going to give you a quick revision the problem is only one that is the practice so for that also I have already planned for you on the same day when I will take the marathon I will take a practice session also and tonight also if you want you can join me for the practice session of machine design so I will be teaching from very basic everything and if you are going to join it it would be enough at least it will be enough for 80 percent of the marks in the gate exam three years uh shreyas we are going to complete it within next 20-25 minutes as per the promise 2.5 hour session it is going to be okay so let&#39;s move further so guys the application when we are talking about so for electrical and electronic circuits we use soldering for hydraulic circuits we are going to use brazing and my dear when we are talking about the brace welding here we are going to join the plates like welding only so my dear when we are having different types of welding technique first is said to be forehand welding technique when you are moving towards non-welding material known non-welding welding to non welding part so Here My Dear outer flame will reach first and inner flame will be reaching second so because of that here outer flame is going to do preheating so it would be removing any oxide layer if present preheating it would be increasing the temperature to some extent so that directly the temperature will not go to the welding temperature so cracking defect will reduce there would be no hot crack cold cracks would happen and there would be no oxide layers will also be present then my dear this is also said to be forehand welding technique and it is used for horizontal and vertical type of welding so my dear when we are using backhand technique in this case flame is going from welded to Flame is having ah this ah you can say flame is heading towards the bended part previously flame is headed towards the known welded part so Here My Dear you can see that first of all inner flame will reach then outer plane will reach so outer plane will be going for post hitting this time pose fitting will help us in relieving of thermal stresses after the welding process completed okay so once welding is over we need to remove the thermal stresses for that we would be having the outer flame inner flame is used for the welding purpose for horizontal and overhead joint we are using this backhand technique then my dear the angle made by the torch axis with the horizontal is said to be the torch angle and the storage angle is said to be 90 degree in the start of welding it is 0 degree at the end of welding during the welding it would be lying between 0 to 90 because in the starting we need more heat to be concentrated okay so I am going very fastly because they are not very important things my dear if you are not going to provide the oxygen from the cylinder then entire oxygen required for welding would be taken from the outside such processes are known as air acetylene welding and in such case we are reaching to this temperature only because flame length is increasing temperature would get reduced and my dear and when we are talking about this here for complete combustion entire oxygen is taken from the outside air that is why temperature is very very less it is used as the heat source for the for the soldering process then my dear we are talking about radiation okay radiation energy welding radiant energy welding okay radiant energy welding so my dear here we have Electron Beam welding first so as the name suggests welding would be happening with the beam of the electrons so Here My Dear phosphol you would be having a tungsten electrode or some kind of electron gun here which is cathode then my dear here we would be having a cup shape okay here a cup shape cathode okay I&#39;m making it separately if I make this figure so you would be having first of all a tungsten electrode which is said to be electron gun then we have a cup show cup shape cathode okay this is the cathode then we have an annular anode which is having some hole in between okay so what is going to happen as you are going to provide here the power source so electrons are coming from here out then electron are repelled by this cathode and attracted towards anode but when it is like in some of the ad have you seen some ad where it was uh it was a ad for like actress and actor are there actor is standing like this with Open Hands open arms and actresses coming towards him and when actress is coming towards him at the same time actor has to hold his pen so actress goes down that kind of AD once was there on the television so similar thing is happening this annular anode is calling the electrons but when electrons are coming it is having holes so those electrons are attracted very fastly towards the node and when they come they are going to pass through it because it is having some holes in between so my dear when these Electric electrons layers are going on going from this anode we are going to have some focusing lens which are going to help us to focus this electrons at the welding region now my dear these electrons if they are going to collide to the workpiece surface they will give their kinetic energy which would be used for the welding purpose so that is why we need to take care that these electron shall not collide with the oxygen otherwise they will lose their energy and Welding will not happen so that is why we are going to provide vacuum and when these electrons are going to collide over metal surface x-ray gets generated which are very harmful for human being which can create cancer So to avoid that kind of thing we need to make this setup lead lined lead is going to absorb the x-rays this is going to be used for welding of super Alloys and here the kind of weld produced they are very deep they are very deep and thin so my dear the width to depth ratio this is depth this is width so width to depth ratio is generally one is to three so whenever these welds are going to produce their width to depth ratio is very very high generally they are deep penetrated valves are produced so deep penetration and they are having very good quality so this is ebw process now my dear we are you can see the application of this process is joining tungsten titanium nickel cobite stainless steel beryllium in Aerospace application moving to the thermite welding thermite welding is the second type of chemical reaction welding and uh is it also used in space there it is not used in space but used for Aerospace applications okay for Aerospace application it is used so when we are talking about the thermite welding once again the second type of chemical reaction welding in the country like India which is not a developed one it is a developing country so in the developing country what is going to happen dear so in the developing countries my dear we are having the railway Network at the places where even jungles are there so we don&#39;t have the setup for Flash but welding we are one lakh ampere of current would be coming so they are what we are going to do actually for such cases we are using this process thermite welding for that we just need some basic thing which an engineer is always having one lighter is there we have one pudia is there where we have thermite mixture containers are available generally everywhere so what we are going to do we are going to have a container in this container we would be putting the thermite mixture thermite mixture and my dear we would be having the match box to start the reaction so this thermite mixture will be having al2 sorry aluminum and fe3o4 this is the thermite mixture so my dear when we will be having this thermite mixture fp304 and aluminum and generally if I see the ratio fp3 o4 and aluminum it is provided into three is to 8 ratio so we are going to have this mixture and when they are going to react with each other when they are going to react with each other then a l Plus fp304 these are three these are eight you will be getting nine iron plus plus al2o3 it would be four so this is what you are getting this is the molten Steel so this is the molten steel which turns to boil and this molten steel is heavier and this slag is lighter so we will be removing this ah lighter layer of slag which is coming at the top and rest molten steel would be poured inside the gap of the two rails and the weld will be getting produced is it clear hahaha dear I will share Amir I will share that sorry the deep penetration then heat affected zone 9 inch rear wind deep actually in Electron Beam welding process the speed of welding is more so that is why hair also heat affected zone is less because very large amount of Heats are coming if you want to know in the Electron Beam welding I would like to say that we are going to provide 80 000. uh 80 000 that much potential differences provided so 80 000 electron volt kind of potential difference is provided and it is restricted to 1.5 lakh 80 000 to 1.5 lakh we are providing for welding and it is going to 2 lakh for the cutting purpose so because of that it is a continuous process which is happening very fast so because of that Speed high heat effective Zone will be lesser okay so that in general already I told you that&#39;s why I didn&#39;t say that point so when we are going to have this process we just need to pour that molten steel into the gap of the rails and weld will be produced so that is the beauty of thermite welding process it is second type of chemical reaction welding process okay so my dear this is used to join Railway track on site where we do not have availability of very large and heavy equipments so all these welding process are shown in the table we have seen explosive ultrasonic friction ah submerged arc welding uh shielding metal arc welding t i g m IG plasma welding Electro gas everything we have seen so all these are shown in this table to show you the classification one is solid state welding other is liquid State welding other is solid or liquid then radiant energy welding okay so all these things we have already discussed so my dear thermate welding also we have already mentioned this so this is steel turned boil provided into the Gap and Welding will take place next is atomic hydrogen welding this is a special welding process which is a combination of two and this is not coming in any of the category in this we are providing this hydrogen gas and we are providing these electrodes so when hydrogen gas is going to provide with these electrons some Arc is provided that is getting broken into hydrogen positive and hydrogen negative ions ok so hydrogen gas is broken into the ions now my dear for that energy is provided by the spark now hydrogen ions are unstable so they will once again react with each other and provide H2 plus a large amount of energy is generated this energy is used for the welding purpose so my dear some peoples may be asking you one question like I always ask being an interviewer all the time this question that when it is happening why we are not directly use this energy for welding why we are using this one some people say this energy is more than that then I say wonderful why you are looking for any job just do this work at your home break hydrogen join hydrogen every time you will get some energy this is against the energy conservation how you are getting more energy this is not Fusion or fission happen in Fusion you get extra energy there it is not Fusion hydrogen is resulting into hydrogen only so no Fusion no Fusion is going to happen here in Fusion reason we get some other element so my dear the reason for this is something different and Amir the reason for that is they are in the heat transfer when you study heat transfer you must have seen a curve between activity and temperature and they are these three lines were provided this is for the air this is for hydrogen this is for helium helium is costly so we are not using it so if you see the hydrogen if you see the hydrogen you can feel the conductivity at some temperature is going to be more for hydrogen than that of air so if we are going to use hydrogen environment more heat would be supplied to the welding and efficiency of the process will be high because heat loss to the surrounding will reduce so that is the reason why we use this otherwise you are going to say whatever the energies difference is wrong energy is no different energy reaching to the surface is different okay so I feel Amir now you got it so the reason for that is this already at welding temperatures are higher so at high temperature hydrogen is more conducting than air so that is how we are using it okay that&#39;s why I mentioned also there is nothing like Fusion okay this is not going to happen exothermic reaction is the process this reaction is exothermic reaction so my dear moving to the next Atomic hydrogen welding we have completed okay so all these things we have already seen so my dear these are the file two things which are never going to come in the examination these are the symbols of weld so I will provide you these PDF now whatever I have these things they are not something which I will teach you because they are to remember that these are the notations of symbols okay how the words are shown like this okay fine so let us move to the next foreign so moving further guys now my dear we are talking about welding defect pattern we have already discussed pattern effect we have already discussed then my dear heat flow characteristics so my dear when we have heat flow during welding process there are two types of heat flow formulas are given this is for three dimensional this is for two dimension you know heat flow happened during the welding process no issues I know you guys are having some other classes also huh Amir don&#39;t worry today we have today we have that okay don&#39;t worry for that okay so just wait yes I&#39;m continuing just wait fine guys so these are the formulas for heat flow characteristic they are also not required for gate forget you can leave them still I am showing the formula never asked in Gate till now may come but till date it is not okay so my dear when we are talking about this if we are talking about this uh I would like to say that whenever we have the sport went so for the sport type of welding this is a kind of sphere so we are assuming this would be acting like a heat Source in three dimension so for the sport welding we would be using this formula for heat flow characteristic but in case of the butt weld like when we have butt weld so it is like a line so that would be considered as a two dimensional where heat is going to flow in two Dimension like this so for what weld we will use this for lab joint or sport weld we will be using this Here My Dear these parameters are explained like three time is the temperature difference okay then my dear you know VW is the weld below City Alpha is the thermal diffusivity so all these things are mentioned Q is the heat rate rate heat means what will be the limit Unit H is height of B weights of weed conductivity melting point then welding speed thermal diffusivity okay so these are the parameters now there is a term known as duty cycle which is very very important while solving welding problem I come across the designation standard of welding electrode uh dear actually that is in p and I syllabus not in mechanical so we are referring mechanical syllabus only okay so Pi syllabus it have so that question will be in pi you can check it okay that is from production Industrial Paper so my dear when we are talking about duty cycle as in the electro slag welding you also have seen that after some time we stop the arc and Welding was happening without any current because of already presence high temperature so duty cycle is defined in such a way that the time for which you are continuously ah switching on the arc it is also defined as Arc time by weld time generally a standard of 10 minutes of duty cycle is defined for Universal for India we defined it like five minutes okay so when I say 10 minutes as standard 10 minutes would be considered as 100 duty cycle so if someone say five minutes I will call it as 50 percent so the I square into D is going to be constant so duty cycle is nothing but the time for which you are continuously providing okay so my dear if that is the case I Square D is equals to constant will be used the question will be like for 1000 ampere current duty cycle is 40 percent then for 600 ampere current what would be duty cycle so what you would be doing you would say 1000 square I square into 14 is equals to 600 square into one so whatever you will get here this would be the value of duty cycle D2 this type of question can come in this so my dear next defect is Arc blue welding defect is Arc blue so my dear what is going to happen if you are going to weld this plate during the welding current is Flowing because of current magnetic field is generated across the electrode and work piece so my dear whenever you are going to start the weld there are chances of deflection of or deviation of Arc because of this magnetic field so because of this deviation we can have the defect likes better scattering of molten metal if you want to avoid that kind of defect we are going to provide some extra plates so that this deviation should not happen which is stabbing and timeout the chances of Arc blow are more with DC less with AC okay so that also you guys have studied duty cycle and Arc blow so my dear now we are moving to laser beam welding in the laser beam welding the principle is if we have atoms at some low energy when some energy is provided with the Xenon lamp these low energy atoms would be going to the high energy it doesn&#39;t mean that atoms are moving like that I want to say their energy will increase so when energy is more everybody wants to be at a lower energy State because they are he face more stability so when you are going to provide the energy they reach to high energy then they are feeling unstability they try to reach to some meta stable State and they release some energy in the form of photons that energy is used for the welding purpose so we are calling it as laser beam welding okay so my dear how it is happening this is the Xenon lamp here we are having the pumping zone so here we are providing some powder so because of the amount of heat coming from Xenon lamp it would be going to high energy region will leave some kind of proton and when those energy light will be coming this surface is 100 percent reflective which will hundred percent reflect the light this is 98 reflective which will allow two percent to come out which would be coming straight okay so when it would be coming straight it would be colliding with the mirror which will be directing it towards the lens which we convert it to the welding area so in laser beam welding we need not to go for any kind of uh vacuum pump so cost of this is less here no x-rays are produced it is lesser harmful so it is more preferred over Electron Beam welding and can be used for all those application of Electron Beam Welding which we have seen so laser beam welding can be used for all of them okay so my dear this is something known as laser beam welding for this you are using two types of laser one is ndyag here ND represent neodymium y for Atrium a for aluminum G for Garnet okay so my dear these are the numericals so we are not doing numerical in this session so that we have a separate practice session okay so my dear I feel we have completed this welding part so now I feel we have already completed a lot of time also uh I feel the session is going on from 11 so I will 2.5 hours are completed now you want me to cover casting defect today you want me to cover casting defect today because welding is almost completed I can complete casting defect today and then next session I am asking from you when you want metal forming tomorrow or day after tomorrow when you guys want metal forming tomorrow or day after tomorrow metal forming tomorrow or day after tomorrow yes so there are some theories which I am not covering here because that is something to remember that I cannot help in like there are some type of flux Coatings so flux Coatings are having some element which will help us to provide the weld bead they are having some elements which help us to provide their melting point temperature higher there are some element which will help us for flame stabilization which would be increasing their melting point temperature there are some elements which would be helping us to make them lighter so those elements are mentioned like there are some types of flux coating like acidic basic rutile so all these are mentioned in this you need to remember the elements in those Coatings so for that purpose like in acid coating we have fe3o4 mno2 quad silicates so that I cannot help into that you need to remember only okay so that&#39;s why I am giving you providing you these slides but that you need to remember yes that&#39;s why I was asking you my Sunday is I can dedicate it for you but the point is whether you can dedicate your Sunday for that or not okay fine guys so I am just quickly going through the casting defect otherwise that is also something you can mug up kind of thing so in gas defect first of all we are having the defects like blow holes open blows okay so you know my dear Sometimes some moistures are present when the casting is going to happen so because of that my dear we are going to have some some uh you can say holes inside okay like you can see here these are the holes inside why they are coming if you remember some gases were producing at the time of casting when molten metal was coming in contact with the facing sand and mouthwash so those gases were coming and those gases were remain inside if porosity of the mouth is not good so inside if it is present there were some gaps were there bubbles were there so because of that bubbles we will be having no molten metal going there so some blow holes would be present if inside these bubbles are there we are calling it blow holes if they are coming on the surface we call it as open blows okay then my dear we are going to have scan so my dear when we are talking about the scare if you are going to have on the surface a very big bubble in the blow holes it was smaller one this kind of thing is coming this kind of thing is coming when the size is bigger for this and in the blister it is one layer is covering this so when the layer is covering it it is said to be blister when layer is not covering it it is said to be square okay and my dear if some hydrogen gas is present then you will be having very small small hole inside the casting then that is said to be porosity or pin holes we want porosity in the mouth but not in the casting okay so now the reason is also mentioned that gas defect which forms inside of the casting are blow holes and surface or open blows scare is the shallow blow formed on the surface because of presence of bubble so if bubble is present on the surface it will create scare inside it will create blister okay and small size holes are created by hydrogen gas which is said to be pin holes okay next is remedies so remedies are you have to make good porosity of the mouth so that gases is go out second type of things are said to be molding defect okay so my dear if your mold is not having good properties like let us say you are going to have this as mold but my dear what is going to happen if at some of the place the sand is not having good strength and some particle of sand is going down from here and this would be reaching to the lower surface like this so your casting will also solidify in this shape now so your casting will also solidify this shape now so this thing is said to be drop because from here sand is getting dropped and this is said to be dirt because here you will not be having the metal so this would be the kind of casting you will get so this defect is coming because of the moldy mild defect if my dear Corners are not good and having less strength for such case your Corners may be broken and you may be having the casting to be of this shape so some Corners may get broken so my dear they are said to be curse and washes once again a molding defect okay so my dear for that what you can do you can convert greens and mold into dry sand mold it will increase the strength of the mouth as well it would be increasing the permeability of that as well okay you can improve permeability by additives also okay you can improve strength by additives also so we have seen the molding defects complete quickly now my dear you must have seen ryzen was doing some of the functions and you were having two types of solidification one was skin forming and other kind of solidification was a dendritic growth otherwise then treaty growth so in dendritic growth we were having the possibility of multiple risers because shrinkages were coming at many places and at all the places you cannot provide the risers so you were calling that defect as shrinkage cavity okay thanks for that so tomorrow we will not be having that session okay no problem but tonight tonight we have a practice session of machine design at 7 pm we have a practice session of machine design where I will solve 15 questions in the class and 15 questions would be given to you as homework okay so this is what we have completed okay sure value sure for that you will get some video on that so we have seen those defects okay so my dear if you have if you have some particle like you know that if you have some particle to be removed from this we have seen dirt and drop now my dear when molten metal is entering inside the cavity it is providing some hydrostatic forces so my dear because of these hydrostatic forces sometimes mold gets some kind of shift so this mounting sand will be shifting by this amount so my dear because of that here molten metal will enter so it is a kind of you can say extra part would be coming on the on the on the on the roof similarly sometimes this can happen in the side wall also so my dear this can happen in the side wall also so this shifting of mold will be happening because of hydrostatic forces so these defects are said to be scab and spell cab and swell they are happening because of Shifting of stand with the hydrostatic forces of molten metal here shifting is happening in drop and dirt mounting sand was eroded and coming down that is the difference okay then my dear fluidity defects are there sometimes your molten metal is having improper fluidity it is unable to fill the cavity completely so if my dear like you are having a cavity like this and it is unable to fill it completely and it is capable of filling up to this only then this defect is said to be misrun and if there are two molten Metals steam are coming like this one is reaching here other is reaching here so this much part remain empty that is said to be cold shut so this defect is said to be cold set both are going on because of improper fluidity so guys I feel we shall complete it here because likewise I have a lot of ah you can say things but these are I feel less important so I am providing you the handwritten notes for revision purpose if you still want otherwise this audio book is there for you all the time and I will also share this PDF with you so that you can revise it if you want so guys here I will say goodbye to all of you and I will also say thanks for your love and support so if any one of you is preparing for gate 24 you can register for the workshop tomorrow and one more thing guys marathons are starting from 3rd of January so you can revise them I will be sharing the schedule third January would be strength of material yes you welcome chili Mishra so goodbye guys for this session thanks for joining we will meet again so as per your request we will keep the next session on Monday only okay so goodbye guys for this session tonight machine design practice goodbye good night sorry note good night okay goodbye and happy New Year to all of you guys

yes uh good morning guys to all of you please tell me am I properly Audible and visible to all of you or not and guys today we have a wonderful session on welding and we would be completing this welding within two to 2.5 hours okay and we are going to revise all the concepts quickly from the welding as you know every year one question for two Mark is coming from this topic so it is important so with this two hours of session if you can get two marks what else you need yes uh Gokul not sure Naveen uh I welcome you all and good morning guys so without wasting the time we are starting the session so guys this is some detail about me my name is jeera sardana and I am having around 10 plus years of experience and today&amp;#39;s subject is today&amp;#39;s topic is related to the production yes so guys we are starting and this is one more information those who are preparing for gate 2024 so guys uh I am going to take a mega workshop for the strategy to be in top one percent for gate 2024 exam tomorrow 12 30 PM will be the time so tomorrow is New Year also so on this new year you can take that pledge if you are talking about 2024 and I will be telling you how you can be in top one percent because top one percent are going to be either in iit&amp;#39;s psus iises like that kind of institutes so guys that is what is the dream of the students okay so guys uh if you want to register for the workshop if you want to register for scholarship test if you want to download the ebook just go to the description of this session okay shubham Manas shreyas good morning to all of you guys so now we are starting the session so this I have already taken many times production versus manufacturing then we will be going for the welding so you already know when we are talking about production and Manufacturing manufacturing and production are same with reference to the mechanical engineering same with respect to the mechanical engineering but in general when we are talking about production is a very big field for which manufacturing is a small part okay so I already told you uh production word is used everywhere like whenever you see any movie so in the movie uh you are always saying the uh cast star cast there you see produced by you will never see manufactured by I told you we are the production of our parents not manufactured by our parents so likewise production is a term which can be used everywhere but for mechanical engineering both can be treated the same okay then my dear today our topic is going to be the welding so first of all you must understand what is welding when I was teaching you very good very good shubham so when I was teaching you casting at that time also I have shown you some kind of uh laboratory method what you are going to do in the casting here also I am showing you an animation which is showing you how you are going to perform the welding this will help us but first of all let us see what is welding welding is the process of joining two metals and when we are going to join those two materials that may be similar may be dissimilar and when you are joining them you may be using the effect of heat or effect of pressure you may be using some kind of filler material or not so it is the process of joining two material in such a way with the application of either heat or pressure or both with or without the application of filler material this is how the welding is defined Umar good morning dear so when we are talking about this in the college you have seen this kind of welding which is said to be the arc welding you must have taken two plates good morning Amir you must have taken two plates those plates were kept together like you will see and when those plates were kept together you can see here plates were kept together and after that you were having an electrode with the electrode holder and from that some flux amount was going on and the welding was taking place but you were not that much perfect in welding that is why when you were doing sometime you were having that electrode was sticking to the work piece sometimes you have seen welding was not initiated because of the Gap is more so that all the things we are going to discuss now this is just a process I have shown you you have seen in the welding lab in the manufacturing lab in the first year sir you will take forming same yes dear I am planning for the same and for that I have already planned I feel we can go for one topic tomorrow and one topic on Monday okay then from Wednesday onward uh Wednesday I&amp;#39;m going to take strength of material for that so we will be revising entire mechanical engineering good morning so now we are starting the process okay so my dear now I will be teaching you everything from the basic like in the last time what we have done first of all I have shown you the lab what is going on so I have shown you that now we are talking about first of all weld beat Geometry so whenever you are going to weld after welding you are getting this kind of thing okay so my dear in this world beat Geometry there are three parts first part is this hatched part so this hatched part is given the name of weld bead this is the part which was initially not there initially you were having only the plates so this is said to be weld beat and this weld bead also have the two parts one part is which you can see below this red line which is uh you can see inside the plates this part is given the name of penetration and after that the above part is said to be the reinforcement and guys you have seen in the previous figure after welding is over in the reinforcement we are having a layer of slag which is removed after welding okay so my dear that is why some part of reinforcement is generally removed by the Machining process but this penetration is going to be the part of this Complete Welding so this is the penetration part and my dear as you are using when you are doing the welding process you are taking the use of heat or pressure or both so my dear some nearby region are also affected by that heat you must have seen that when you are talking about heat you are using the Heat or pressure or both for the welding so when you are using these things for the welding purpose obviously at the time of heating nearby region would be affected so the region which is affected by the heat of welding that region is given the name of heat affected Zone and this zone is very much near to the weld bead you can see after that this part which is not going to be affected by the heat of welding is said to be unaffected zone so my dear and if I go if I am going to make a tangent onto the reinforcement part I can make a tangent like this then this would be an angle this is said to be the angle of convexity it somewhere gives the idea about reinforcement how much it is so angle of angle of convexity okay so guys this is I have just defined the just Define the geometry weld geometry okay very good very good Amir so I would ask you that we have discussed here the three portions one is heat affected Zone unaffected Zone and wet bit geometry if I ask you out of these three which is having more strength which is having least strength that kind of discussion I have done many times in the classes on YouTube so I would like to ask you out of these three which do you feel is going to have more strength and which do you feel will be having the lesser strength yes please answer all of you very good guys so as per your answer you know weld bead is having the highest strength and my dear unaffected Journey heat affected Zone would be having the lowest strength I would also give you the reason for that also very good Deepak yadav sham sundariya Naveen Surendra Singh so guys out of these three I can say one thing weld bead is having the highest strength weld bead is having the highest strength and heat affected John is having the lowest strength okay and this is going to be intermediate strength okay intermediate strength now you would be interesting to know that why it is happening so you have seen when the welding is going to be formed you are joining the two plates and you are having the electrode due to heat electrode is melting and also plates are melting but on the electrode we are having some flux material on this electrode we would be having some flux material which is different than the metal so because of that when this electrode would be melting inside the groove for the weld bead it would be making an alloy and you already have studied that Alloys are stronger than pure material so that is why weld bead is having the highest strength then my dear why heat affected zone is having the lowest strength in the material science you must have studied about heat treatment heat treatment are the processes in which we heat the metal up to some temperature then we hold it for some particular time then we cool it with some specific cooling rate so when you are doing this heating holding and cooling your target is to improve the properties of the material so you are doing all this to improve the properties of the material but you know whenever you are taking medicine it is for the betterment of our body but if you do overdose of that it is going to affect badly so my dear when you take medicine it is always to be taken as per the prescription so when heat treatment is done then we know up to which temperature we have to go how we have to heat it up to which temperature we need to hold it and what should be the cooling rate if all these things are not controlled it is said to be uncontrolled heat treatment and uncontrolled heat treatment are not going to give the better results they are not improving the property actually so because of that when heat affected Zone we are going to see there we are not intentionally heating so heat is going on because of welding so sometimes whatever the temperature they are rising that is not in our control obviously we don&amp;#39;t know up to which temperature it is going to be heat and up to which time it would be heat and we even don&amp;#39;t know what would be the cooling rate so everything is not in control of ours for that zone so that is why uncontrolled heat treatment is going to happen and when the things are going to be uncontrolled definitely properties are going to be on the Poor Side so that is why heat affected zone is said to be the weakest part very good deeper so my dear when we are talking about the unaffected Zone there no effect of heat no alloy content so it is having in intermediate strength so I will be saying weld bead is having the highest strength then we will be having the unaffected Zone and then we will be having the heat affected Zone and I feel you are very well aware about one thing that if the welding speed will increase then my dear The Zone which is affected by the heat will also reduce this portion I&amp;#39;ve already been asked in Gate examination that when we are talking about the welding speed if welding speed will increase then my dear heat affected Zone will reduce so there are many processes where we will see welding speed is very very high so because of that high welding speed we would be having very low heat affected Zone very good shubham so guys just like and share the session I read more and more people to join it and one more thing I would like to say that you know something is penetration something is reinforcement so we are going to define a term dilution dilution is defined as the area of penetration to the area of weld bead you can also write it as area of penetration but a area of penetration plus area of reinforcement and sometimes we are going to Define percentage dilution as well it is defined as a p by AP plus a r in 200 I also want to tell you one thing that from this dilution type of term you may also get numerical so be ready for that it would be a new type of numerical very good Uber very good shubham very good Deepak so guys now we are going to start the first type of welding that is shielded metal arc welding process so my dear it is a type of arc welding okay yes very good shares Umar shubham so in short form it is said to be s m a w so sometime in Gate also they are using this short term so you must be aware of that so my dear first of all we will see about the principle of this welding process so if you have this work piece to work which will be joined like this this is the electrode so what is going to happen whenever you are going to have this electrode and this work piece we are going to provide the power supply obviously this is our choice whether we are using DC or AC so there are different advantages disadvantages for DC and AC we will see them on the later stages okay this is in our hand whether we want to take work piece positive or electrode positive for the timing we are assuming work piece to be positive electrode to be negative so obviously we are using this polarity and let us assume this to be power source for the timing let us assume DC on the later stages we will see whether it is DC where it is AC so this is work piece this is electrode so what is going to happen my dear between the electrode and work piece there is a air there is a gap because of that there is air you know air is not a very good conductor of heat and very very good conductor air is the insulator so my dear because of that electrode and work piece between the Gap air is there so resistance is between them is very very high so my dear obviously you are providing some potential difference with the help of power source so my dear this potential difference or power source what you are applying is generally having the potential difference between the range of 40 to 80 volt I am giving you the general ranges so whenever you are going to have electrode and work piece you are going to take electrode towards the work piece then what will happen when electrode will be going towards work piece the gap between them will reduce and as the Gap will be reducing this potential difference will try to be enough will try to be enough to produce some kind of air ionization oxygen ionization so when this is going towards the workpiece when this potential difference is enough to ionize the air between the Gap in that case what will happen this is electron and this is work means between this Gap whatever the air is present that is going to start ionized you would be having some positive charge ions and negatively charged electron positive charge iron and negatively charged electron positive charge ions and negatively charged electrons so air ionization will happen and environment will become ionized so because of this ionized environment my dear in between this would be happening that electrodes would be attracting towards the work which because work piece is positive and work piece is positive it would be attracting electron and Electrode would be attracting the ions so my dear electrons will be moving towards work piece ions will be moving towards electrode and whatever this attraction is going on because of that obviously electrons have some kinetic energy ions have some kinetic energy High Ajay how are you so because of that what is going to happen because of this work piece would be absorbing the kinetic energy of electron and Electrode would be absorbing the kinetic energy of ions and it have been seen that the kinetic energy of electron divided by kinetic energy of ions is found to be in the ratio of such that you would be having this to be two third part and this to be one third part so if total hundred Joule is there 67 joules will be going to the work piece 33 joules would be going to the electrode you already know work piece is having thick thick plates so it need more heat also if you want to match them into good amount so my idea that is why when you are providing adding this positive electrode I am not saying always electrode is negative for this case I am talking about so work piece would be getting kinetic energy of electron electrode would be getting kinetic energy of of of ions and by getting that kinetic energy it would be converting into heat because of that first of all this electrode wire is going to melt because this electrode wire is going to have the lowest melting point and when it will start melting after that by taking the Heat this flux will also start melting so flux is such that its melting point temperature is above then that of the electrode wire electrode wire and parent metal is of same material so this and wire is of same material flux is of different material so my dear flux is different material because it is going to provide the alloy content second thing it should have high melting point temperature why it should be having high melting point temperature because if electrode wire is going to melt first you are melting will happen in such a way that electrode wire is melting before so because of that you will getting this type of shape and the advantage of this type of shape is the flame Arc or spark whatever you want to say that would be concentrated towards the workpiece and if by chance flux is going to melt first then you will be having this type of diagram if electrode wire is melting in the last then your R for spark will not be concentrated but diverse like that in that case it may not be able to do the welding so for concentrated Arc or spark yes malesh good morning for that convergent Flame or convergent spark or Arc we want electrode wire shell melt first so my dear we have discussed actually two functions of this flux flux have a very first function that it would be it would be providing the alloy content because of that weld bead is going to be strong as and that is why welded joints are said to have more stronger than the parent metal second function is as it is melting in the last that is why because of which you are going to get the convergent flame Oracle spark so my dear when this will happen now the mixture of electrode wire and flux will mix up and go inside the groove and you will be getting the weld to be produced so my dear you will be having this weld weld pool because when it is in liquid form we will call it pool after solidification we will call it as weld bead so my dear it would be having the combination of flux as well as flux as well as the molten wire material so my dear now what is going to happen you know that flux material is having high melting point temperature and also it have one more property it is lighter than the pure metal so as flux is lighter than the pure metal when you would be having this molten weld pool the flux metal will flux material will be going up because it is having lighter weight because of that flux will be going at the top and it would try to make a layer upward when it will be taking making a layer upward it is avoiding the avoiding the contact of this molten metal with the air you may be thinking sir why it is required to avoid the contact with the air of the metal so my dear metals have a bad habit and that bad habit of metal is like we also have some bad habits some peoples are not able to control themselves by looking at the fast food some may not control on some other things likewise metal cannot control when they see oxygen they are going to immediately react with oxygen and they will be making the metal oxides so when they will be making metal oxides metal oxides are found to be they are found to be generally brittle because they are of ceramic nature so if they are brittle in nature your entire weld will become brittle like you know glass is whenever glass is going to be like glass is a brittle material when you are going to have a glass and let us say by mistake when you are holding it it went down it will break into parts so likewise if weld will be brittle it will also break fast but we don&amp;#39;t want to have that property we want that to be ductile in nature so that is why we want that oxide shall not form so this is the third function of the flux coating so flux coating perform this function it avoid air oxidation of metal it gives us alloy content and also gives the direction to the flame or arcore spark so this is how the things are going to happen so my dear the entire setup is going to be like this I would also like to tell you in this in this Zone which is said to be you can say uh this is the Zone where Arc is going to be produced their electrons and ions were moving when electrons were going towards workpiece ions were going towards electrode during that motion there were there was a collision between electrode and ions also so because of that collisions we are going to have a very high temperature of around 6000 to 12 000 degree Celsius in between the arc Gap and my dear in this Arc Gap some ultraviolet rays are also going to be produced so because of those Rays to be produced those rays are harmful for our eyes that is why it is never advised whenever you are going to do welding arc welding it is advised to have some glasses for that so we need to wear the glasses for that and that is why this type of glasses you have seen in the labs also you were provided and we were going to do welding with these glasses because otherwise our eyes may be affected if at some of the place arc welding is going on you look at it for longer duration you will feel some kind of uh you can say a pain in your eyes for next two three days you may not be able to sleep properly because of this so that kind of effects are coming if you are not wearing the glasses okay now my dear the point is sometime what is going to happen when these particles are moving up this is that flux vertical can make a layer over only if they are able to go up within time because at the same time solidification will also start so my dear that solidification of this molten weld pool shall happen only once the flux particle go up and make the layer otherwise flux particle will remain inside so my dear if flux particle are going to remain inside then my dear that actually after solidification we are calling them slag so after solidification we are calling them slag slag is to avoid the air oxidation if that slag is going to solidify in between the weld pool it will make defect that defect is said to be slang inclusion so why this defect will happen because if that plus particle is unable to move up before solidification which will be depending on the temperature of the weld pool which will be depending upon the current settings which will be depending upon the current settings so my dear if proper current is not provided in that case definitely it is going to happen you know the heat generation is going to be I Square RT so my dear heat generation is directly proportional to I Square if current setting is not proper heat generation will be not proper in that case you may not be having good temperature of weld pool because of which slag inclusion kind of defect can appear so my dear we need to avoid this slag inclusion for that we need to work over the current setting now my dear when we are talking about the current setting you know definitely it would be a part of Transformer so my dear when we are going to have the Transformer many times of Transformers are coming but first of all you must be knowing one thing that when this electrode is going towards work piece when this gap between them is reducing lesser Gap will require lesser voltage and more Gap will require More Voltage so if I am going to make a diagram between voltage and Arc Length it comes like this a straight line so we Define voltage to be a plus b so if Arc lens will be More Voltage required to produce the spark will also be more and guys if that is the case v is equals to A plus b l so my dear it means whenever we are having Electro towards work piece if that Gap is going to vary it will be definitely varying the voltage requirement and if the voltage requirement will vary definitely current will also vary which will definitely result into slag inclusion because if current settings are not proper yes uh guys mm am I Audible and visible to all of you actually some IPL Network issue happens fine fine fine okay so we are once again starting from here don&amp;#39;t worry okay yes fine fine fine so guys I would like to say that when we were talking about electrode and work piece okay it is lagging let let me once again do this yes so guys now is it fine now is it fine I feel some Network issue is there now I feel it is fine okay guys now I feel it is fine now we are continuing so as I said that when we are going to talk about this a plus BL curve we have just are made I was telling you about voltage I was telling you about voltage with respect to our plane so I told you that if the gap between electrode and work piece just wait guys sorry for the disturbances foreign guys now shall we continue shall we continue yes yes yes yes Amir don&amp;#39;t worry actually I have planned in such a way that both Theory and numericals would be covered okay both Theory and numericals would be covered okay so now we are going to continue once again so as I said let us say we have this work piece and this electrode and if the Gap is more more air More Voltage is required if Gap is less less voltage is required so we have seen that it is going to be a straight line V is equals to A Plus BL this is the equation between voltage and arc length Okay so I said if you are doing this welding manually you can see this is workpiece this is electrode so as the Gap is changing the voltage requirement will change and if voltage requirement will change my dear if voltage requirement will change my dear then what will happen because of change of voltage requirement obviously the current setting will also change and if current setting is going to change the heat generation will change because of that the temperature will also change so because of this the chances of slag inclusion are there so what we have seen there are two types of movement between electrode and work piece one is movement of electrode to wash the workpiece other is movement of electrode along the work piece so when we have two types of movement this movement which is electrode to wash the work piece is very very important because based on that we are going to have the defect like slag inclusion so that is why if both the movement we are doing manually it is said to be it is said to be it is said to be manual metal arc welding process if we are going to perform the critical movement with machine and non-critical movement manually we will call it as semi-automatic type of welding and if we are going to perform both the motion with the help of machine it is said to be automatic welding So based on that we have three types of welding so to wash the workpiece along the workpiece this is the critical movement because if this is not proper slag inclusion will happen this is non-critical movement okay this is non-critical movement So based on these we have three types of welding process if both are going to be done with the machine if both are going to be done manually then it is manual metal automatic and the best solution is semi-automatic where critical movement would be done with the machine non-critical movement will be done manually so my dear now if we are going to perform manual metal arc welding process then in case of manual it is damn sure that Arc Length will change because of Arc Length voltage requirement will change because of this current is going to change so we wanted some temporary solution also for that because under some situation we may not be able to go always for the automatic types of welding where maybe we want to save uh foreign are you facing any audio issues are you facing any audio issues I feel now everything is fine from my side yes so my dear if that kind of thing is going to happen we wanted some solution for this we wanted some solution for this so we thought let us make up now we thought that let us make a Transformer which will be providing us less change of current for more change of voltage so that Transformer was given the name of drooper so grouper is generally preferred with the manual metal arc welding process when we are going to have the movement between wall between this electrode and work piece which is done manually so for such cases we are going to have this type of characteristic which drooper is going to provide so grouper provide this type of characteristic so if you see we are going to have this voltage related to that current will be this so I am saying this is V1 this is i1 if voltage is this much current is this much so you can see my dear when voltage changes from this to this value current is changing very less so in the dropper the change of current with respect to change of voltage is very very less so my dear if that kind of thing is going to happen we can use it with the manual metal arc welding process and the chances of slag inclusion would be reduced but my dear if we are going to have semi-automatic type of welding for that case we need not to go for drooper for that case we are using this type of voltage arcline characteristic where we are defining it like previous one is said to be constant current Transformer constant current Transformer okay and similarly this one is said to be constant voltage Transformer constant voltage Transformer but my dear if I am going to show some linear voltage voltage current characteristic if I am going to show some linear voltage current characteristic there I can make the equation of this type of Transformer like you have seen it was linear so if I plot it like this then this voltage is said to be open circuit voltage and this current is said to be short circuit current so my dear I already told you if we have a circuit like this if we have a circuit like this okay like this and we are going to have we are going to have this is going to be the battery let us say okay we are going to have a battery like this we are going to show this so when we are going to have this circuit this is said to be open because there is nothing in between so in this circuit whatever the voltage you will be having across these two terminal that is said to be open circuit voltage or this is something you are calling it as EMF electromotive Force so you would be knowing that in the 12th class you were writing an equation that voltage can be written as pmf minus I times of internal resistance that internal resistance is defined as EMF divided by short circuit current so open circuit voltage is that maximum voltage when no current is flowing in the circuit because it is open and short circuit current is that maximum value of current when there is no when you will be having zero potential difference means there was a time when this electrode was stick to the workpiece at that time no spark was getting produced because the circuit was complete and direct flow of current was happening that condition is said to be short circuit they are welding was not happening so as this current welding will not happen at this voltage also welding will not happen but from this straight line if you want to write the equation you know we can write X by a plus y by B is equals to 1 so you can write X&amp;#39;s having I so I by is plus V by V naught is equals to 1 whether you use this or you use this you will be getting a wonderful equation of Transformer and that equation is given as V is equals to V naught minus this is going to be I times of R we have written so it is V naught minus V naught by i s into I so we can also write it as open circuit voltage minus open circuit voltage by short circuit current into I this is the equation of the Transformer and from this a load of numericals are coming a note of numericals are coming as this session is related to the marathon I am going to take majorly Theory here only okay Mishra that&amp;#39;s what for what only we are going to do this hard work okay yes very good guys so I have given you this equation and soon we will be having the practice session where we will solve some problems onto this now my dear there were some problem with the manual metal arc welding process because of which we are going to the second type of arc welding that is submerged arc welding you have seen if that manual metal arc welding annually the first issue which was occurring at that time was the problem with this motion yes if we were using dropper the problem was resolved but still that was a temporary solution so if my did this motion to be perfect we are going to include machine for that so submers our quilting process is a semi-automatic type of welding this is a semi-automatic type of welding this is the first Improvement we are getting okay hello teju so the first Improvement we are getting is submers arc welding is a semi-automatic type of welding then my dear we were also having some other issues we were also having some other issues like my dear what was going to happen ah previously we were using some electrode wire we were using some electrode wire which was having some flux material which was having some flux material so it was having some kind of flux material so because of this flux material you were having this electrode wire and it was having some size like 9 inches one feet so once one electrode wire is going to melt out you need to change the electrode so once you are going to change the electrode for that you need to stop the welding process and if we need to stop this welding process it will become a discontinuous process so my dear if we want to join two plates like that so after some time like this electrode is enough we will be have a joint then this electrode enough we will be having a joint so in that kind of process we will be having a number of joints present between that welding so if the joints are present at the Joint there are chances of leakages so if we are going to weld the LPG cylinder or ship in that case if that kind of joint will happen from where leakage will happen so in case of LPG cylinder shift building type of application we may get some kind of accidents So to avoid that we needed the continuous welding process so this process is going to be a continuous welding process so to make the process continuous We have replaced the electrode with the electrode wire so this time we are going to use this electrode wire which is going to move continuously because it is present in the wire spool so continuously electrode wire will be coming and my dear for that continuous input we are also going to provide the servo mechanism in This Server mechanism two rollers are there which are going to send the electrode wire at a constant rate because when it is going to be at constant rate the problem of the problem of this movement this Gap will also be resolved because of this constant rate my dear you would not be having slag inclusion kind of defect it is becoming semi-automatic type of welding but my dear if you are providing wire in this format if flux is also there on to the wire that flux may get erode from The Wire because of friction when it is coming again and again between the rollers So to avoid that we are not providing flux onto the wire this time flux is provided in the flux drum in the molten format okay so molten flux is separately provided which would be making a layer outside and Performing its function very nicely it will perform all the function it will avoid the air oxidation because air is not coming in contact and this Flame or spark is going to be concentrated because once again the convex type of shape is there so all the functions are going to be performed in the same way this process can be used for two wonderful applications like LPG cylinder and also the second application we have said is what after LPG cylinder that is the ship building so my dear as you know this is a continuous process it can be used for mass production and as here high speed of welding is possible so whenever welding is going to be with the highest speed the chances of heat affected Zone will be lesser so heat affected zone is going to be smaller for such case yes please tell me guys chili shreyas free arvinda and other students please tell me up to this everybody got it or not so I have revised this these are the application in short formal arc welding is also said to be s a w ramismon hi dear how are you sir ship building yes yes yes Amir that is correct that I will be telling you but if you are not having the option of Electro slag or Electro gas welding for such case you can tick this summer dark welding also okay so otherwise someone&amp;#39;s arc welding is preferred for LPG and for ship building we are preferring Electro slag but if Electro slag is not in the option we can go for summer dark wedding and mass production is possible because of continuity of the process moving further guys so my guys these are the point we have already discussed so my dear as continuously welding process is happening and molten weld pool is protected under the environment of what the flux the flux molten flux so guys here chances of Specter are less why because my ideal that electrode wire is continuously within the environment of molten flux so there is no contact of air and this this Flame or this R cannot be deviated if it would be deviated it can also create some kind of molten droplets on the metal surface which is scattering off or scattering of molten metal which is not going on here because there is no contact of air with the flame or spark so my dear less chances of spatter is there Specter is the defect which is known as scattering of molten metal so that is also having less tendency here so guys uh this is scattering of molten metal have less tendency here so the defect of Specter will not be there the defect of slag inclusion will also not be there so now we are moving to the third type of welding process that is Di IG Mig arc welding process generally you know TIG is said to be tungsten inert gas arc welding tungsten inert gas arc welding then you also know that Mig is metal inert gas are coiling generally students are getting confused over this because the name is tungsten inert gas they are not using Arc word they feel it is tungsten inert gas welding so it is not a gas welding technique it is a arc welding technique so the name is t i g arc welding or migr welding this is the name of this welding process so my dear when we are using the tungsten electrode we call it as tungsten inert gas arc welding so my dear when you will be using tungsten electrode let us say this is the transitional electrode so tungsten electrode is going to be known uh consumable electrode it is not going to melt so my dear because of that we are not going to provide any flux over it and my dear at the same time when you will be using this electrode as it is not consumed so molten metal will not be coming from this tungsten so for that purpose we are going to use some filler Road in this type of process so that filler road is made up of the same material as that of the as that of the parent metal so they have same material so we will be using this consumable road separately so my dear what is the purpose of using such type of thing why we are using the tungsten tungsten is very very hard and brittle material so that is why if by chance its droplet will come inside the weld pool it will make entire weld brittle so we never want that kind of thing first thing is very very clear for from here second thing is my dear when we are using this tungsten what is the reason behind that till now we were using till now we were using the polarity with work piece was going to be positive an electrode was going to be negative but my dear this was fine and this type of polarity is said to be the straight polarity but my dear when we are going to have aluminum type of material it is very very difficult to weld the aluminum so weld ability for aluminum is very very poor so my dear why it is you already know Metals cannot control themselves when they see Oak season in the heated state but aluminum is that much reactive that even at room temperature it react with oxygen and make a layer of aluminum oxide al2o3 so this al2o3 is the kind of ceramic material which is very very hard and brittle we cannot weld it so for welding of aluminum we need to remove this layer so for that purpose we are going to reverse the polarity and when we are going to reverse the polarity this time work piece is going to be negative and Electrode is going to be positive what is the benefit of that when electrode when work piece is going to be negative polarity now due during the welding process electrons will be coming out from the surface of aluminum so when electrons will be coming out from the aluminum surface they will just peel off the layer of aluminum oxide so when they will be peeling off the layer of aluminum oxide that layer will be removed and fresh aluminum will be exposed for the welding purpose do we get a alloy composition in weld dear if you want alloy composition you would be providing separate powder for that purpose but actually TIG welding is generally done for aluminum very very thin plate of 5 to 8 mm so for that we need not to do all these kind of thing so my dear when these electrons are going to go out and peeling off this layer that process is said to be cathodic cleaning like Manas have written so you might be asking sir what is cathodic cleaning so my dear cathodic cleaning means we are going to make the work piece cathode means negative and then we are cleaning it so that cleaning is happening because of this cathode so that is why the name is cathodic cleaning but now the problem is you are making electrode positive so for that the melting temperature of work which electrode should be very high so we are using tungster or tungsten carbide because melting point temperature is more than 3500 for such cases so my dear no doubt if by chance even a single droplet of tungsten will be going into the pool weld will be very poor so we need to avoid that so we never make this type of electrode in reality when we make the tungsten electrode we make it of this shape means if here the diameter if here the diameter of this transitional electrode is D we will be keeping the diameter of the surface to be 1.2 to 1.5 times means 20 to 50 percent more diameter we are going to keep so my dear when we are doing this now the heat required to melt the tungsten electrode would be more so because of that the chances of melting will get reduced and my dear this thing is said to be electrode preparation and my dear whenever you are doing hair welding we can weld very thin plates of aluminum because work piece is getting less heat because negative was getting one third part of it T was getting two third part of it so that is a kind of limitation for this process also so my dear when we are using this TIG here we get to know about the term weld ability if we are going to talk about the weld ability of Steel I would like to say that weld ability is inversely proportional to the carbon content if carbon content is going to be more weld ability will be poor so that is why whenever we are going to have low carbon steel medium carbon steel and high carbon steel so weldability is going to be poor for high carbon steel then highest for low carbon steel weld ability is directly proportional to 1 bicarbon percentage or I will say weld ability is inversely proportional to the percentage of carbon content okay so my dear now the point is here you are not using the flux who will solve the purpose of flux we are not providing here molten flux we are providing the inert gas so this inert gas will be solved the purpose of flux inert gas will be solving the purpose of flux so inert gas will be solving the purpose of flux okay so when inert gas is provided inert gas will also helping us to make a flame which is going to be concentrated because from throughout the sides we are going to provide the inert gas it will also avoid the contact of air and inert gas is non-reactive so there would be no reaction between the Surface with the inert gas that is one more Advantage so inert gases you can use helium you can use neon you can use argon generally we are using argon for availability point of view so my dear we have studied TIG process here there are some problems one is you are using tungsten electrode which is non-consumable still chances of consumption is there if temperature increases beyond the range second problem is we are using we are using uh this non-consumable so filler road is required filler Road will be having a constant size once again you need to stop the welding and because of this uh you can say negative polarity reverse polarity you cannot weld the thick plates so for that purpose and Improvement come in the form of MiG process in Mig process We have replaced the tungsten electrode from the metal electrode which was consumable so filler road is not required here we were once again providing the servo mechanism so my dear continuous flow of electrode will be there once again you are using the inert gas for the purpose of flux that is why the name is metal inert gas arc welding and my dear when we are going to do this we have removed this is inert against in general inert gas is going to be very very costly if you are going to replace this inert gas by CO2 which can be done with the metal unit gas welding then this CO2 is not an inert gas so the name of the process will become active gas active gas metal arc welding process so my dear this is the process nowadays used in the industries it is similar to submers arc welding okay so this process is active gas metal arc welding and this is used in industry it have replaced TIG process okay I feel everybody is getting this OK everybody is getting this so this is said to be the Mig process so my dear now I am going to tell you something more about numericals there are three types of heat one is heat generated which is given as I Square RT second is heat supplied okay third one is heat required so my dear let us say we need some 700 joules of heat for welding or melting purpose then my dear for melting purpose if we require this we may be providing some 1400 joules so why we are providing more because during welding that entire setup is exposed to Atmosphere so there would be some losses of heat to the atmosphere okay so as some losses of heat are there to the atmosphere because of that we are providing extra heat so my dear if requirement is 700 you are supplying 1400 so this gap of 700 this is going to be the heat loss to the surroundings okay then my dear whenever we are going to have this heat supply for that we need to generate the heat heat generation takes place by this formula and let us say we are going to generate the heat of 2000 joules why heat generation is more than Supply because heat is generated at the tip of electrodes then that heat is distributed then also some kind of heat loss to surrounding happen so here also there would be a heat loss that is of 2000 minus 1400 600 joules and that is said to be heat loss one this is heat loss two so guys this total is the heat loss to the surrounding so heat generation is 2000 requirement was 700 so my dear based on these three types of heat we are having three types of efficiencies first is the efficiency of heat transfer which is defined as heat Supply by heat generated it can also be written as rate of heat Supply by rate of heat generation then thermal abuse efficiency OK or we can also call it as melting efficiency this is heat required but a heat Supply or we can have rate of heat required but a rate of heat Supply then we are going to have overall efficiency which is written as efficiency of heat transfer into melting efficiency if you are going to Define it it is the rate of heat Supply but a heat generated into heat required but a heat Supply so you would be having Supply Supply cancel heat required by heat generated so guys you may be thinking sir is going very fast but as I already said that this is the revision Marathon so here it should be like when you are reading your notes so you must feel like from the notes like you have seen in the movies whenever letters were exchanged from the letter always the actress was looking like and he was feeling actor is speaking so this marathon is of that type only like your notes are speaking okay or their process is welding so generally process efficiency will be said to be this melting efficiency only but in general they mention in the East terminology which we have discussed here okay I feel you got it okay Mishra don&amp;#39;t worry so dear numerical whatever formula we are discussing they are going to be useful only and I am planning a practice session of welding and casting both on Tuesday so there you will see all the types of questions so don&amp;#39;t worry about questions also here you revise Tuesday we will do the questions now you can see this is direct current straight polarity direct current reverse polarity and alternating current so this table is very important for exam sometime one mark question is coming from this okay so guys just like and share the session because still we have completed only one type of welding but you know after resistance welding the time required would be less if you see in the classes we have covered whatever we have covered in the four hours that we have covered in this one R because 10 to 15 minutes uh problems were also there in between now my dear we are talking about the polarity so in direct current straight polarity we are going to have work piece positive electrode negative we are going to have work piece negative electron positive direct current state direct current reverse here work piece will be positive negative alternately electrode would be negative positive alternately heat generation here work piece would be having 67 percent electrode would be having 33 percent here workpiece would be having 33 percent electrode would be having 67 percent here both workpiece and Electrode would be having 50 50 percent okay then penetration so here work piece is getting more heat so we would be having d penetration here we will be having shallow penetration here we will be having intermediate penetration wire feed rate means with what rate electrode wire is melting that would be less here because less heat or electrode more hair and more heat of electron here it would be intermediate because 50 50 heat is there thickness of plate you can weld here so in straight polarity you can weld thick plates because work piece getting more heat here thin plates because electrode getting less heat here intermediate because both get 50 50. so work piece uh here I would like to say work piece preparation we have already seen electrode preparation so if my work piece size is less than 5 mm then we are going to directly weld them for more than 5 mm we are going to provide some kind of preparation for more molten metal to come inside this thing is said to be the workpiece preparation so work piece preparation is done when plates are of more thickness so my dear work piece preparation is done in the dcsp do not done here here we will say it depends what is the thickness so if thickness is generally more than six to eight mm then only we are going for this work piece preparation kind of thing different book shows different value for that so moving further guys okay now numericals we are not going to do here so I am having these numericals but that we are not going to solve now we are moving to plus Mark welding for numerical we have session on Tuesday where we will take casting welding forming all plasma are welding this is one more type of arc welding you must be aware of plasma so my dear plasma is the fourth state of matter okay plasma when we are talking about is nothing but ionized gases so ionized gases is said to be the plasma so my dear generally we are going to use the nitrogen gas okay so here what we are going to put everything is same we would be having a tungsten electrode like that then we would be having some plasma cases like nitrogen okay we would be having plasma gases like nitrogen then my dear we are also having the inert gas to perform the function of flux that is ah let us say argon okay we are having this work piece now as this is tungsten electrode which is not going to melt we have to use some pillar out also so my dear in this process I would like to tell you when you are using this plasma you can get a temperature from 8000 degree Celsius to fifty thousand degree celsius that temperature can be produced but for welding we are restricting it to 20 000 degree celsius you may be thinking sir at that temperature plates will get melt out so I am noticing that temperature will be there with the plates that temperature would be there with the gases so whenever these plasma gases are going to react with The Arc because you are going to provide here some power supply so whenever these plasma gases are going to react with The Arc they will convert into ionized gases ionized gases are said to be these plasma will get a very very high temperature like whenever you are sitting in front of fire you are going to see that that fire is definitely having some very high temperature but when the air taking the heat from that will be coming to us then when it will be giving heat to us that heat will not be creating that temperature for our body okay why because our area is more so when that heat would be distributed our temperature will not reach to that much so that is going to happen when those plasma gases are going to come to this work piece a deep and deep penetration will be there and that is why when this kind of welding going to take place we will call it as Keyhole phenomena why Keyhole phenomena because when this plasma will be giving energy to the plate then my dear it is going to get cool off so because of that you will be getting the Keyhole type of weld bead here this type of weld bead you will see because when the plasma will be attacking that would be giving energy and it would be reaching to the deep but with the very less thickness so this type of weld bead you will be getting here so welding comparison okay dear for that uh I will provide you the actually tab you are asking about the temperature they are asking which welding process is having highest temperature ok so that kind of I will provide you a table where it would be mentioned that temperature ranges of different welding processes so that table will solve your purpose ok you might be thinking sir when we are restricting the temperature up to this where we use this temperature when you you would be going for plasma or cutting so in the metal cutting plasma cutting will be there so there we will be using more temperatures so here we are restricting our process to this and my dear all other things are going to be same here we need to ah cool the electrode also otherwise electrode may get that high temperature and melt out so for that purpose sometime we are going to provide some artificial cooling okay so water cooled nozzle are going to be provide all around the tungsten electrode to keep it cool for that welding process okay so that is said to be plasma arc welding process now the last type of arc welding process is Electro gas or Electro slag welding okay so my dear in this what we are going to have I am showing you with the simple diagram you are going to have this as workpiece one this as work piece too you can consider you can consider them to be the two plates of the ship and you want to join these two plates as wise so when you want to join them along the edges you need to pass your electrode wire from here so that this electrode wire can provide molten metal here for that my dear to start the welding we need some starting point otherwise molten metal will spill away so my dear for such type of welding process we need to provide a starting plate for the welding so we would be providing a starting plate this is the starting plate so initially the arc is going to be produced between the starting plate and the work piece and my dear we would be providing the power supply like this and once the welding is going to start this electrode wire after melting will be going up and weld will be moving ahead in the upward direction for that purpose you know that if molten metal is not going to be solidified soon then it will still spill away from the sideways okay you have provided starting plate but from the sideways it can still spill away so for that purpose we are going to provide some copper shoes we are going to provide some copper shoes the copper shoes are like this okay so in between electrode wire is there this is copper shoes when the melting helps when the melting take place copper shoes will take the Heat and solidify the molten metal and move in the upward Direction so my dear when this kind of thing is going to happen this will be moving in upward Direction so here you can see see these are the copper cooling shoes so they would be these copper pulling shoes are there so this will be moving in upward direction will the welding process this is the starting plate which is required initially okay so as the solidification will take place this will move ahead so here also flux is not there so four flux we are going to provide the molten flux so molten flux is provided in between my dear hair actually the lows of heat from the sideways or all around is not going that much so because of that my dear what is going to happen because of that sometimes the heat is going to be very very high so for such cases we can switch off the arc for such some time because of that very high temperature welding will continue without any r or spark so you can switch off the current and Welding will still take place so when you are switching off this for some time the temperature will go down and once again when the temperature go down Beyond a value you will once again switch on the arc okay is it clear thanks samin for your wonderful words so this is what is going on for Electro slag and Electro gas welding and my dear this is one type of arc welding only when we call it Electro slag and when we call it Electro gas when we are going to use the molten flux we call it as Electro slag and when we are going to use when we are going to use the CO2 we will call it as Electro gas bending guys on my telegram Channel we are also having some handwritten notes of this welding so whatever I am saying word to word is written there so after learning the process you just need to remember only the application of the processes nothing more than that and you need to practice the numerical so those nodes now will if you see if you go through this that will be very easy for you to understand okay those who are learning for the first time those who have already learned for them already this is the revision so guys Electro slag and Electro gas welding is a vertical welding process so it is used for what it is used for what for ship building we have already seen a previous process was good for LPG cylinder and this is good for shipper building with this we have completed the arc welding process now my dear we are moving to the other processes because arc welding is over you can see every theory is also written in the slides okay so my dear now we will move to the other processes Okay so moving to resistance welding so whatever I have told all theory is also written in the slides okay very good truth very good Naveen wonderful Army notes and this lecture yes yes I mean that was the exact word that I wanted to tell at that time that if you have that nose then this class is the audio book for that okay so these days there is a trend of audio books so you can get that Advantage moving to the second welding process that is the resistance welding so my dear in the arc welding voltage was playing a very very important role actually okay so if we are talking about the arc welding process that is said to be high voltage high voltage and low current welding process but when we are talking about the resistance welding it is low voltage and high current welding process when we are saying this many students are getting confused because they see in the question voltage is given in the range of 40 to 80 volts and current is generally they have seen that from 400 amperes to 1000 1200 1300 ampere likewise this is written so this is the current is more than voltage so guys comparison can never be done like voltage with the current comparison is done with the voltage with the voltage current with the current so here voltage may be up to 12 volt so 12 volt and 40 to 80 volt this is more and here the current if you are talking about it is more than 10 000 amperes so just compare this current and this compare so here current is more here voltage is more so in the resistance welding current is more than 10 000 ampere in general even sometime you will see the value of 1 lakh amperes 50 000 amperes 35 000 ampere so here as the current is very very high all of you are aware that heat generation is written as I Square RT so as current square is there so if current is very very high you need to reduce this time because you cannot have that high current for more time otherwise the entire plates will melt out so uh sagrika up to lack of very good very good sagrika so mighty refuse see the types of resistance weldings so first of all why we need it so my dear till now we were doing the arc welding and arc welding were performed in the form of butt welds okay like this plate and this plate are kept like that and you are welding it in the butt weld configuration we have not seen any process where we were doing lap joint configuration so resistance welding came for the purpose of lap joint configuration when for the first time you are going for this lab joint configuration the name of process is resistance welding so the types of resistance welding is spot welding projection welding flash butt welding high frequency resistance and induction welding and seam welding all these are the type of resistance welding and after this welding process other welding process will not take that much time as I said we are going to complete in 2.5 hours so this is the first type of resistance welding process spot welding so my dear what is going to happen this is work Piece One Work piece two this time you are going to keep two work pieces like this and I would like to tell you there is the lower die which is fixed upper die is movable so my idea this is the upper die or I I shall not say die it is actually the copper electrode so this copper electrode generally this is said to be the fixed one and this is said to be the moving one in general okay so when we are going to apply the force from that some penetration will happen from both the sides because pressure is applied from both the side so this much penetration will happen electrode will get penetrated into the sheet now my dear this phase is said to be the penetration and in this phase if I show you two diagrams one for the pressure other for the current so this first time is said to be the squeeze time for that time we are going to increase the pressure and there is no current flowing for that phase okay now my dear what will happen after that after that my dear this squeezing time is over we are going to supply some current that very high current is going to pass like this so my dear when this current is passing obviously every surface will show some resistance there is resistance of this copper electrode is R1 R1 then there is an uh resistance of this surface a interface between copper electrode and work piece one so this resistance I will be giving the name of R4 R4 so here also R4 will be there then my dear there is some resistance provided by this mild steel plate this I am showing it by R3 R3 and my dear there is a resistance between the interface of two plate which is denoted by R2 so you can see R2 is one time R 3 2 times r four two times R1 two times so if you see this R2 is quite quite quite more than all other resistances which are already 2 times 2 r 1 plus R3 plus R4 summation of that is even lesser than this R2 so R2 resistance is very very high and because of that high resistance when the current will get passed here we will be having more generation of heat and because of that more resistance more heat Here My Dear weld is getting produced and when the melting will start from the center this weld bead this Zone Fusion Zone will start expanding this may expand in the shape of sphere in the shape of cylinder in the shape of any other geometry but here we have shown like a cylinder but this can be cylinder can be ellipse can be other shape but in general we will assume it either a cylinder or a sphere so as per our assumption it would be cylinder or Sphere for easy calculation otherwise it can take any shape and this Fusion Zone will be reaching up to the electrode and we will get this weld to be done okay so this is how the welding will be performed so my dear if that is the case this is the second time like already in the comment section we have this pressure remains same and for this time we are going to provide some current so my dear this time is said to be well the time now because of this melting obviously between this this where it is melt is going to take place but this time we will not call it as weld bead this time we are going to call it as weld nugget after solidification so my dear until this gets solidify we will maintain the pressure but no current will be supplied so for this time pressure remains same current is zero this is said to be the or this is said to be which time hold time after that we will relieve the pressure and as the pressure is relieved this weld is performed you would be getting these two plates to be joined with the joint and as the joint is like a spot we will call this process to be a sport welding so this is how the process is going to be over yes yes very good very good sagarika that&amp;#39;s really great thanks for that and even you can get by handwritten notes from the telegram channel so that will also further help you okay sagrika so let us move further very good so this is the sport welding process so this is the squeeze time then we are going to have weld time then we are going to have hold time then we have relief time so this is what is going to happen so my dear these are the resistances defined like that so these are the curves we have already seen so my dear when we are talking about these resistance welding I would also like to tell you that when we are going to have this the heat generation we are going to have an i Square RT this is the heat generation going to take place so my dear if you are going to see that whatever the heat required for melting that would be like mCP delta T in general okay this is required for increasing the temperature to Melting Point temperature then we would be requiring M into latent heat okay so that would be required for the melting purpose so these are the two Heats generally required this is said to be sensible heating this is said to be then latent heat so with that the melting is going to take presently that is the heat required so my dear if you are going to say this heat required you must also understand that if we have some thickness if thickness is going to be more then my dear heat generation required is also going to be more because more thickness will require more heat to get melt out okay so my dear if that is the case we can also say that thickness is directly proportional to heat generation which is a it is directly proportional to I square and this thickness is also directly proportional to the melting point of the plate sorry I am going to correct it don&amp;#39;t worry I would like to say that this uh this I I square is also directly proportional to this melting pointed melting point is going to be more then also the current requirement will be more so my dear why I am telling you these things sometimes the questions are coming that for this much thickness this much current is required so for that much thickness how much current would be required so if they say for th1 we need i1 for th2 what would be the current requirement so you can say that thickness is directly proportional to current Square so th1 by TS2 can be written as this is uh I square is there so it can be written as this is I 1 cos Square by I 2 cos Square similarly thickness are not given melting point are given then you can write melting point of one by melting point of 2 is is equals to I 1 square by I 2 square ok so in the using those relation you can find out the unknown if any unknown is there so from these formula till now there is no question asked so because of that in the practice session I will take these type of question so you all must attend that practice session there I would be taking all these things okay now we are talking about the projection welding the second type of resistance welding process this is more theoretical uh if you see my dear when we are looking for more number of sports like if we are joining the two plates in such a way that we require Sports at multiple point so for that purpose we are using projection welding so the second name of projection welding is nothing but multi-spot welding so my dear if you want sport at multiple places we will call it as multi-sport welding Here My Dear we will be having one plate on which the projections are going to be given and the projections are provided like this the places where you need the sport we provide the projection these projections are made by a process known as embossing which we are going to study at the time of metal forming and boasting and coining are the similar processes you must have seen there so embossing is the process which is going to be used for this and my dear what we are going to do once again similarly we would be having the copper electrode on both the sides so this time once again when you will do the squeezing then my dear add these at these projections what you have made those projections are going to be broken because of that because of why these are broken they are going to be broken because you are applying the pressure so some plastic deformation will happen so these projection would be broken so obviously wherever the projections are there the sheet which is having the projection that will be having more heat because of this plastic deformation so generally projections are provided on the sheet which have either good conductivity or have more thickness so that it can bear that kind of heat and transfer it to the surrounding so my dear whenever you are using this process all other things are going to be same projections are going to be there only at the places where you are providing the projections only that places will provide you the spots of the welding okay so when we are using this as it is a continuous continuous Sports you are getting so my dear in general sport welding is going to be used in the automobile sectors and when you are going to make so much Sports together then also the chances of leakages will be there because it is not a continuous type of welding okay so my dear when we are having this ah projections it is like that so these are the hot spot because whenever you would be providing them plastic deformation will happen there and if you are going to compare these two plates if they have different thicknesses then this would be having more thickness and this would be having less thickness if they have same thickness conductivity is different then this sheet will be having more conductivity this will be having less conductivity these are the point you need to take care in this type of welding process okay uh dear projection welding projection chili Mishra when we are going to make these projections then these projections are made by embossing process embossing is the metal forming process like when you will be making these projection in the sheet you would be putting this sheet normally at some place where you would be using this type of ah you would be using this type of dye you would be having a die of this type so when you would be having tie of this type when you will apply the pressure this sheet will be converting into this sheet where projections are there so these projections are made by this kind of process and this process is said to be the embossing we will be having more more clarity on embossing and coining when we will see the metal forming chapter means tomorrow or day after tomorrow we will see that okay now we are moving to the third type of resistance welding process which is The Flash but welding process my dear as we have already seen that this welding process came for the lab joint configuration so when this came for the left joint configuration some people think that we cannot use it for the butt joint configuration so it is not like that we can also make the butt joint from this type of welding for that what we are going to do we are going to place two rows which are going to be joined together now my dear this process is generally used for joining the railway tracks in the developed countries okay so railway tracks are joined by this process in the in the developed countries like America and all in developing countries we use thermite welding for the purpose so you would be keeping two railway tracks together like that and you would be taking them towards each other when they will be going to our each other there would be a time when they will just connect with each other so my dear you are going to provide this pressure at that time we are going to provide some current here as well and my dear that current is generally of the range of 1 lakh ampere so my dear initially as you know some oxide layer may be present on the metal surfaces so some flash is going to generate it initially that indicates the burning of oxide layer that is why the name is Flash but welding then after that because of this High current and this pressure the weld is going to take place in arc welding we were only using the heat for the welding process whereas in resistance welding we are using heat as well as pressure both for the welding process so I feel you are getting it so this is splashed but welding process the important Point here is 10 to the power 5 ampere of the current okay moving to the next that is seam welding this is not projection but the seam welding in the seam welding you would be having two plates like this these are two plates and you are providing some roller so for this roller they are also provided the power supply like this so whenever these rollers are moving continuously over the surface they are continuously providing some penetration okay so some continuous penetration is there and here current is also passing and as you know at the Joint of the sheet at the interface of the sheet we would be having the highest resistance so because of highest heat they are weld will take place this is the process which is continuous welding process so my dear if you see the sport welding if you see the projection welding they were discontinuous welding processes but this is going to be the continuous welding process so sometimes in numerical they are using six D ah yes root T and other times D is equals to T what should we use dear it depends on the thickness of the sheet when thickness is coming out to be less than 8 mm then we are going to use this what you have mentioned as D is equals to ah 6 root T okay so my dear that is actually coming from the data book in the gate question you will note get that kind of thing because that requires data so from the data book only when thickness is less than 8 mm then we are using this relation what you have mentioned okay so I also told at that time of welding when I was teaching you and my dear in this process as continuously current is Flowing so at this point when roller reached this place this much part is already welding so sometime it happens that when you are reaching to the new position some part of current also passes through the already welded portion that is the lows of current that is said to be shunting of current so my dear this is a continuous welding process it is used to make the Jolly like this you have seen in the kitchen that kind of jalis are there there also they are connected continuously so this kind of structures are made using this welding process it is a continuous welding process so obviously speed of welding will be more here and as I said shunting of current is the lows Mishra it would be mentioned in the question okay so my dear now we are moving now we are moving to the next process that is fifth one high frequency induction and resistance welding so they are not two different process actually one only so here what is going to have let us say you have this strip of Steel you want to make the pipe of it then what you will do you would be having this strip this would be having some width and some length so this width would be made as circumference you would be just bending it and you would be after bending it just giving input here here you are having some mandrel okay and along this mandrel you will be just bending it and providing it these are the concave rollers which will be applying some pressure onto this and they will give this the shape of exact pipe and when this shape would be provided like this the shape would be provided like this then my dear you need to join this and you will get a pipe so my dear steel pipes are made by this process and seamless pipes are made by centrifugal through centrifugal casting okay so if you are going to join this what is going to happen you would be having this sheet like this here you will provide some positive here you will provide some negative then my dear when this will be getting joined together by dear because of the current produce the weld is going to be happen Okay so my dear this will help you to make that kind of pipes and my dear generally they have a length of 20 feet which are available in the market like General Industry made that kind of pipes many others are also there so when you will get these types of pipe they are having generally a length of 20 feet so my dear now if you are going to provide the conductors and using the direct current we will call it as resistance welding if you are going to provide the inductor coils and using AC we will call it as induction welding generally we are going to provide high frequency of alternating current so is there any term ah repercussion welding okay dear I feel you have written the name note correctly percussion welding is there okay so that percussion welding is not a type actually actually uh that is depending on the process if the finishing is happen uh better then we are calling that okay if you want also I will share it to you okay percussion welding is the name which is used so my dear here if you are going to see we are using the copper conductor here here and here copper conductors are there this is the mandrel which is used to make the cylindricity of the pipe okay this is used to make the cylindricity of the pipe current used is 100 kilohertz to 500 kilohertz this is the frequency of the current we are using Okay seamless pipes are made using centrifugal casting we have already seen so Here My Dear we are making it and we have completed the resistance welding process now we are moving to the Solid State welding process in Solid State welding process the first process is explosive welding so as here I said the solid state welding it means here melting will not happen so my dear we would be having a work piece which would be treated as a Target plate and we would be having a flyer plate which is always thin than the target plate and this is something something I want to be valid over it always plier plate is thin then my dear here we are going to use explosion so we need to use some explosive material so we could provide this explosive onto this thin plate known as plantar plate but when explosion happen there are chances that the surface will get blackened So to avoid the blackening of the surface of plier plate we are providing a buffer plate in between this buffer plate generally is made up of rubber as we know rubber is having excellent damping capacity so my dear generally this buffer plate is provided in between now Detonator is required to start this explosion so when deteriorator is starting then explosion will happen because of that explosion a very high pressure wave energy wave is getting created you must have seen in the movies uh where these kind of scenes are shown where some blast are shown like there was a movie uh where Akshay Kumar was also there here I do not remember the name it was 26 special 26 whatever it is so in that movie when the blast happens then that actor or whatever the person near that blast is there they are shown like they are just moving in the air like that so they got some pressure wave because of that they got a very high kind of shock and because of that they go to a very far distance so my dear similarly that pressure wave will be given to this plier plate because of that this plier plate is becoming in the semi-solid form and going to connect on to this work piece you are providing this angle which will decide the direction of welding you are providing this initial distance known as standoff distance this is provided for initial impact numericals are coming from okay okay fine let&amp;#39;s move further so my dear when we are talking about so in South movies they are happening more but in South movies this is not happening because of blast this even happens from the fightings but in Bollywood movie it happens only in the case of blast that is the difference Army so I would also like to tell you guys that whatever the numericals are coming they are basically from Arc and resistance welding from other topics we are not having numerical this is just application you need to remember so when we are having this welding here one very important point which is already asked in the gate paper the speed of this welding process is limited by the speed of sound the relation between them is because of this uh explosion okay so there it would be having a limit from speed of sound so my dear when we are talking about this type of process okay here generally diffusion is going to happen so one material is getting diffused into other whenever we are talking about the diffusion it is like you must be knowing that if we have two gases in this container a gas is here B gas is there if you remove this partition then both the gases will get diffused into each other so that kind of thing is said to be diffusion which is going to happen in this type of welding the second type of solid state welding is friction welding and my dear if you are going to see the application of this this is in whenever you are going for uh colliding of cylinders for cladding process we are going to use this for cladding process explosive welding is getting used friction welding is used whenever we are going to join drill bit drill bit with the stand this also have already been asked in the gate exam what is the application of friction welding so when drill bit is connected with the shank that process is said to be the friction welding process so my dear here also we would be having two things one is erode a other is a road B so my dear this road is rotating with some speed of Omega and this road B is going to be stationary okay this road B is stationary you are going to take this road B towards a so a is having some motion B stationary so when both of them will be connected initially a is rotating B is at rest so because of that at the interface there will be some relative motion relative motion means confirmation of friction so because of that obviously the friction what it does friction tries to convince both the bodies friction will try to stop a and try to rotate B so as you are over all all the time giving the speed to this definitely friction will not be able to convince this first body so friction will be able to convince the second body and after some time both will be rotating with the same speed so during the time when friction is there a lot of heat is getting produced between the surfaces and because of that heat diffusion welding will take place and here also melting will not happen so it is a kind of solid state welding process so my idea this is used for drill bit and shank so my dear if you have both the materials of same then my dear you will be having this type of weld bead if you have both sides same material but if the material is going to be different if same material are there this type of weld bead would be happen if you have different material then hard material will not be showing any kind of deformation soft will make a layer over it like this okay so this is going to happen so in case of drill bit and shank shank is going to be soft and drill bit is said to be hard material so we would be having this type of weld bead geometry so moving to the next process guys the third Solid State welding process is ultrasonic welding so as the name suggests we would be using the ultrasonic energy of vibration so here these are work piece one this is work piece two they are placed together and here we are having some HSS tooltip there is some clamping Arrangement which is going to provide solar road which transfers the vibration to the tooltip vibrations are produced in the transducer so in this transducer vibration will be produced those vibrations transfer to the HSS tooltip with the help of the sodot road and due to this vibration the weld is going to produce between the work piece pressure is applied from the Anvil side also Anvil is the kind of support which is stationary and my dear here as you are not using a lot of energy as I said here this kind of welding can join very very small or thin elements and it is used in electronics Industry if you want to join ICS if you want to join some kind of diodes some kind of transistors so those kind of elements so in the electronic industry in the electronic industry this process is used where we need to weld very small small electronic components like IC like trans transistors like or you can say ah that diodes okay so that is the application of ultrasonic welding so others we have already seen now we are reaching to the gas welding process gas welding process is a kind of chemical reaction type of welding it is the kind of chemical reaction type of welding and gas welding have a generalized name this is important for Theory point of view some ideas generalized name of this welding is oxy fuel welding here oxy indicates we have oxygen cylinder fuel indicates we have some fuel cylinder that fuel can be acetylene that fuel can be acetone that fuel can be methane fuel can be propane so whatever the fuel we are going to use the name will be changing based on that if you are using hydrogen it is oxyhydrogen welding if the fuel is ah methane oxymethane welding but in general what we study is we have acetylene so we will be calling it as oxy acetylene welding so my dear when we are talking about oxy acetylene welding c2h2 is acetylene so my dear when we are going to use this the principle of this value process is nothing but the combustion so in the combustion reaction whenever the fuel is reacted with oxygen it gets converted into CO2 and steam CO2 and steam are the byproduct of such reaction so my dear when this c2h2 which is acetylene this will be reacting with the oxygen it is getting converted into the CO2 and steam because water will not be in the liquid form and the large amount of heat is getting produced this heat is going to be used for the welding process then I feel you all are aware that this C2 S2 and react with oxygen you will get two CO2 plus s two plus heat you must be thinking of that sir how this reaction is happening one mole of acetylene require 2.5 mole of oxygen if you are going to provide 2.5 mole of oxygen you will not get any kind of flame or per spark because it would be a complete combustion which happens in the ice engine but we also require some kind of flame some kind of spark which can be used for the welding process so my dear for that purpose when we see this reaction this reaction is going to happen in the two stages so in the one stage C two h two when it is going to react with the oxygen it will be converting into carbon monoxide H2 plus heat then my dear this is two Co then my dl2co plus H2 when it is reacting with 3 by 202 it is going to give you CO2 t o two plus H2O plus heat so my dear you are getting heat two times in two stage reaction so my dear this heat one heat one and heat two when we are talking about so my dear these are the two kind of heat we have seen so these two reactions are denoted by two plane this first reaction requires one mole second reaction required one point five mole we never provide 2.5 mole of oxygen we always provide lesser amount of oxygens why because we are when you are not given the proper food at home you will search for the food from outside so my idea similarly we are going to have a torch so when we are going to have this torch in which in which acetylene and oxygen are provided from the cylinder so if oxygen is provided in insufficient amount then to take the extra oxygen for combustion purpose my dear fuel is coming outside so that fuel is coming outside in the form of the plane so my dear stage one reaction will give smaller play stage two reaction will give large flame because here more need of oxygens are there so these reactions are not going on separately they are going on simultaneously as fuel is coming continuously so when these reactions are happening here also note complete oxygen provided here also not so two two Flames are coming from two reactions inner flame is having lesser surface area outer is having more surface area so this heat and this heat when we compare any heat can be more for different different fuel but temperature of inner inner inner one is always more because of lesser surface area so when heat is getting distributed over a flame then its temperature is also going to increase so my dear for this smaller flame we are always having more temperature so due to more temperature of the smaller plane always the inner flame is going to be used for the welding purpose and outer flame is used for the preheating and post heating kind of work so my dear you can see here we have inner white cone and outer bluish cone outer bluish cone so two types of cones are there so this inner cone is traveling some distance n and my dear this outer cone will be traveling always the more distance okay so by dear now we are talking about this is first type of flame which we are actually there are three types of flames are there one is said to be neutral Flame other is said to be oxidizing Flame and third one is said to be the carburizing plate okay so when we have these three types of flame how we are deciding it so my dear you know one more required 2.5 mole of oxygen so we are never providing that much we are never providing that much thanks chili for your wonderful words but don&amp;#39;t worry right now take the benefit of online so when we are talking about the neutral flame we are going to provide acetylene and oxygen in the ratio of one is to one means for one mole of acetylene we are providing one mole of oxygen from the cylinder then my dear when we are talking about oxidizing flame here we are providing more oxygen not from the requirement but more from the acetylene so we would be providing around 1.15 to 1.6 times of oxygen than the acetylene and here you would be providing 0.72.8 times of oxygen than that of acetylene so in all the Flames we are providing oxygen lesser than the ah fuel only so my dear if we are having the neutral plane this is the neutral plane for the neutral plane we are going to provide c2h2 but a O2 in the ratio of 1 is to one so my dear for that n is the distance traveled by this flame okay so my dear the temperature here we are getting three to six zero degree Celsius for the inner plane then my dear we are also going to have the second type of plane which is oxidizing flame where you are providing oxygen amount slightly more than the one then that of the acetylene here temperature is three three eight zero as you are providing more amount of oxygen from the cylinder this time the distance traveled by the flame is lesser it is around 0.52 or 0.332 0.5 times of the N if in the neutral flame it was traveling and distance here it is traveling 0.332.5 times of n okay so my idea if that is the case that is the traveling distance my dear 0.33 to 0.5 this time the temperature would be more because the flame size is surface is going to be less than Samir for your wonderful words so that is why the temperature would be more so my dear generally oxidizing Flames are used for the Alloys like brass bronze and all and neutral flame is used for the normal Paris materials what we have seen so my dear there is one more exception when we are talking about uh the brass here some zinc is present so whenever we are going to weld this brass with the neutral flame zinc is having very less vaporization temperature so it gets vaporized this and if you don&amp;#39;t want it to vaporize we are going to weld it from oxidizing flame because here more oxygen is present so zinc will react with oxygen and will make zno vaporization temperature of jadeno is quite more than that of zinc so because of that zno will make a layer over the weld pool so because of that zinc will not be vaporized this and in that case you can save your zinc inside so brass is generally welding using the oxidizing flame then my dear when we are talking about the sound dogs in the neutral flame we are going to have hissing sound like you have seen one movie was also there kind of okay similarly oxidizing flame will give you roaring sound roaring sound is there but my dear carburizing flame is a silent plate there no sound will be coming so in carburizing flame my dear you are providing that much less oxygen that this time fuel itself comes outside to take down season because of that some acetylene feeders are going to form which is traveling the distance two times the neutral flame because of which temperature reduced to 3060 degree celsius carburizing flame is generally used for uh welding of cast iron or high carbon steel where carbon amounts are more otherwise if you would be welding low carbon steel using this flame then it may absorb carbon it may absorb carbon from acetylene feeder okay so we are using those element which are already saturated with the carbon so carbon Rising flame is used for cast iron for high carbon steel that kind of elements okay so guys just like and share the session we are already at the gas welding we have completed now we are reaching to the Allied processes some other welding process are pending that will be coming Electron Beam welding and all so this is Allied processes where we are talking about soldering brazing and Brace welding okay for this I am taking this table because questions are generally coming from this table so my dear when we are going to have the mechanism the mechanism used for soldering is adhesion here also attention here also addition if you are talking about the temperature here temperature is less than 427 degree Celsius here temperature is more than 427 degree Celsius here temperature is more than 427 degree Celsius here the filler material actually in this process what we are talking about Allied processes they are neither said to be solid state welding nor liquid State welding they are said to be actually solid liquid why it is said to be because here parent metals are not melted but filler metal is melted so you would be having two materials like let us say I want to join these two things they are in solid format but the filler material by which I am going to join them that would be liquid form so that is why solid liquid State welding it is some ideas that pillar material by which we are joining here we are using lead plus tin in soldering here we are using copper plus zinc which is brass in brazening and copper plastin which is said to be Bronze in the bridge welding brace welding is the kind of welding process only soldering and brazing are slightly different from the welding process generally brace welding using the gravity force for the filling of molten metal on the other hand soldering and brazing are using the capillary action for the filling of the Gap so that is the major difference so for capillary action the gap between them should be very very less then only capillary will happen uh hi sir I have to revise machine design yes through Marathon would be sufficient because eight hours marathons are definitely going to give you a quick revision the problem is only one that is the practice so for that also I have already planned for you on the same day when I will take the marathon I will take a practice session also and tonight also if you want you can join me for the practice session of machine design so I will be teaching from very basic everything and if you are going to join it it would be enough at least it will be enough for 80 percent of the marks in the gate exam three years uh shreyas we are going to complete it within next 20-25 minutes as per the promise 2.5 hour session it is going to be okay so let&amp;#39;s move further so guys the application when we are talking about so for electrical and electronic circuits we use soldering for hydraulic circuits we are going to use brazing and my dear when we are talking about the brace welding here we are going to join the plates like welding only so my dear when we are having different types of welding technique first is said to be forehand welding technique when you are moving towards non-welding material known non-welding welding to non welding part so Here My Dear outer flame will reach first and inner flame will be reaching second so because of that here outer flame is going to do preheating so it would be removing any oxide layer if present preheating it would be increasing the temperature to some extent so that directly the temperature will not go to the welding temperature so cracking defect will reduce there would be no hot crack cold cracks would happen and there would be no oxide layers will also be present then my dear this is also said to be forehand welding technique and it is used for horizontal and vertical type of welding so my dear when we are using backhand technique in this case flame is going from welded to Flame is having ah this ah you can say flame is heading towards the bended part previously flame is headed towards the known welded part so Here My Dear you can see that first of all inner flame will reach then outer plane will reach so outer plane will be going for post hitting this time pose fitting will help us in relieving of thermal stresses after the welding process completed okay so once welding is over we need to remove the thermal stresses for that we would be having the outer flame inner flame is used for the welding purpose for horizontal and overhead joint we are using this backhand technique then my dear the angle made by the torch axis with the horizontal is said to be the torch angle and the storage angle is said to be 90 degree in the start of welding it is 0 degree at the end of welding during the welding it would be lying between 0 to 90 because in the starting we need more heat to be concentrated okay so I am going very fastly because they are not very important things my dear if you are not going to provide the oxygen from the cylinder then entire oxygen required for welding would be taken from the outside such processes are known as air acetylene welding and in such case we are reaching to this temperature only because flame length is increasing temperature would get reduced and my dear and when we are talking about this here for complete combustion entire oxygen is taken from the outside air that is why temperature is very very less it is used as the heat source for the for the soldering process then my dear we are talking about radiation okay radiation energy welding radiant energy welding okay radiant energy welding so my dear here we have Electron Beam welding first so as the name suggests welding would be happening with the beam of the electrons so Here My Dear phosphol you would be having a tungsten electrode or some kind of electron gun here which is cathode then my dear here we would be having a cup shape okay here a cup shape cathode okay I&amp;#39;m making it separately if I make this figure so you would be having first of all a tungsten electrode which is said to be electron gun then we have a cup show cup shape cathode okay this is the cathode then we have an annular anode which is having some hole in between okay so what is going to happen as you are going to provide here the power source so electrons are coming from here out then electron are repelled by this cathode and attracted towards anode but when it is like in some of the ad have you seen some ad where it was uh it was a ad for like actress and actor are there actor is standing like this with Open Hands open arms and actresses coming towards him and when actress is coming towards him at the same time actor has to hold his pen so actress goes down that kind of AD once was there on the television so similar thing is happening this annular anode is calling the electrons but when electrons are coming it is having holes so those electrons are attracted very fastly towards the node and when they come they are going to pass through it because it is having some holes in between so my dear when these Electric electrons layers are going on going from this anode we are going to have some focusing lens which are going to help us to focus this electrons at the welding region now my dear these electrons if they are going to collide to the workpiece surface they will give their kinetic energy which would be used for the welding purpose so that is why we need to take care that these electron shall not collide with the oxygen otherwise they will lose their energy and Welding will not happen so that is why we are going to provide vacuum and when these electrons are going to collide over metal surface x-ray gets generated which are very harmful for human being which can create cancer So to avoid that kind of thing we need to make this setup lead lined lead is going to absorb the x-rays this is going to be used for welding of super Alloys and here the kind of weld produced they are very deep they are very deep and thin so my dear the width to depth ratio this is depth this is width so width to depth ratio is generally one is to three so whenever these welds are going to produce their width to depth ratio is very very high generally they are deep penetrated valves are produced so deep penetration and they are having very good quality so this is ebw process now my dear we are you can see the application of this process is joining tungsten titanium nickel cobite stainless steel beryllium in Aerospace application moving to the thermite welding thermite welding is the second type of chemical reaction welding and uh is it also used in space there it is not used in space but used for Aerospace applications okay for Aerospace application it is used so when we are talking about the thermite welding once again the second type of chemical reaction welding in the country like India which is not a developed one it is a developing country so in the developing country what is going to happen dear so in the developing countries my dear we are having the railway Network at the places where even jungles are there so we don&amp;#39;t have the setup for Flash but welding we are one lakh ampere of current would be coming so they are what we are going to do actually for such cases we are using this process thermite welding for that we just need some basic thing which an engineer is always having one lighter is there we have one pudia is there where we have thermite mixture containers are available generally everywhere so what we are going to do we are going to have a container in this container we would be putting the thermite mixture thermite mixture and my dear we would be having the match box to start the reaction so this thermite mixture will be having al2 sorry aluminum and fe3o4 this is the thermite mixture so my dear when we will be having this thermite mixture fp304 and aluminum and generally if I see the ratio fp3 o4 and aluminum it is provided into three is to 8 ratio so we are going to have this mixture and when they are going to react with each other when they are going to react with each other then a l Plus fp304 these are three these are eight you will be getting nine iron plus plus al2o3 it would be four so this is what you are getting this is the molten Steel so this is the molten steel which turns to boil and this molten steel is heavier and this slag is lighter so we will be removing this ah lighter layer of slag which is coming at the top and rest molten steel would be poured inside the gap of the two rails and the weld will be getting produced is it clear hahaha dear I will share Amir I will share that sorry the deep penetration then heat affected zone 9 inch rear wind deep actually in Electron Beam welding process the speed of welding is more so that is why hair also heat affected zone is less because very large amount of Heats are coming if you want to know in the Electron Beam welding I would like to say that we are going to provide 80 000. uh 80 000 that much potential differences provided so 80 000 electron volt kind of potential difference is provided and it is restricted to 1.5 lakh 80 000 to 1.5 lakh we are providing for welding and it is going to 2 lakh for the cutting purpose so because of that it is a continuous process which is happening very fast so because of that Speed high heat effective Zone will be lesser okay so that in general already I told you that&amp;#39;s why I didn&amp;#39;t say that point so when we are going to have this process we just need to pour that molten steel into the gap of the rails and weld will be produced so that is the beauty of thermite welding process it is second type of chemical reaction welding process okay so my dear this is used to join Railway track on site where we do not have availability of very large and heavy equipments so all these welding process are shown in the table we have seen explosive ultrasonic friction ah submerged arc welding uh shielding metal arc welding t i g m IG plasma welding Electro gas everything we have seen so all these are shown in this table to show you the classification one is solid state welding other is liquid State welding other is solid or liquid then radiant energy welding okay so all these things we have already discussed so my dear thermate welding also we have already mentioned this so this is steel turned boil provided into the Gap and Welding will take place next is atomic hydrogen welding this is a special welding process which is a combination of two and this is not coming in any of the category in this we are providing this hydrogen gas and we are providing these electrodes so when hydrogen gas is going to provide with these electrons some Arc is provided that is getting broken into hydrogen positive and hydrogen negative ions ok so hydrogen gas is broken into the ions now my dear for that energy is provided by the spark now hydrogen ions are unstable so they will once again react with each other and provide H2 plus a large amount of energy is generated this energy is used for the welding purpose so my dear some peoples may be asking you one question like I always ask being an interviewer all the time this question that when it is happening why we are not directly use this energy for welding why we are using this one some people say this energy is more than that then I say wonderful why you are looking for any job just do this work at your home break hydrogen join hydrogen every time you will get some energy this is against the energy conservation how you are getting more energy this is not Fusion or fission happen in Fusion you get extra energy there it is not Fusion hydrogen is resulting into hydrogen only so no Fusion no Fusion is going to happen here in Fusion reason we get some other element so my dear the reason for this is something different and Amir the reason for that is they are in the heat transfer when you study heat transfer you must have seen a curve between activity and temperature and they are these three lines were provided this is for the air this is for hydrogen this is for helium helium is costly so we are not using it so if you see the hydrogen if you see the hydrogen you can feel the conductivity at some temperature is going to be more for hydrogen than that of air so if we are going to use hydrogen environment more heat would be supplied to the welding and efficiency of the process will be high because heat loss to the surrounding will reduce so that is the reason why we use this otherwise you are going to say whatever the energies difference is wrong energy is no different energy reaching to the surface is different okay so I feel Amir now you got it so the reason for that is this already at welding temperatures are higher so at high temperature hydrogen is more conducting than air so that is how we are using it okay that&amp;#39;s why I mentioned also there is nothing like Fusion okay this is not going to happen exothermic reaction is the process this reaction is exothermic reaction so my dear moving to the next Atomic hydrogen welding we have completed okay so all these things we have already seen so my dear these are the file two things which are never going to come in the examination these are the symbols of weld so I will provide you these PDF now whatever I have these things they are not something which I will teach you because they are to remember that these are the notations of symbols okay how the words are shown like this okay fine so let us move to the next foreign so moving further guys now my dear we are talking about welding defect pattern we have already discussed pattern effect we have already discussed then my dear heat flow characteristics so my dear when we have heat flow during welding process there are two types of heat flow formulas are given this is for three dimensional this is for two dimension you know heat flow happened during the welding process no issues I know you guys are having some other classes also huh Amir don&amp;#39;t worry today we have today we have that okay don&amp;#39;t worry for that okay so just wait yes I&amp;#39;m continuing just wait fine guys so these are the formulas for heat flow characteristic they are also not required for gate forget you can leave them still I am showing the formula never asked in Gate till now may come but till date it is not okay so my dear when we are talking about this if we are talking about this uh I would like to say that whenever we have the sport went so for the sport type of welding this is a kind of sphere so we are assuming this would be acting like a heat Source in three dimension so for the sport welding we would be using this formula for heat flow characteristic but in case of the butt weld like when we have butt weld so it is like a line so that would be considered as a two dimensional where heat is going to flow in two Dimension like this so for what weld we will use this for lab joint or sport weld we will be using this Here My Dear these parameters are explained like three time is the temperature difference okay then my dear you know VW is the weld below City Alpha is the thermal diffusivity so all these things are mentioned Q is the heat rate rate heat means what will be the limit Unit H is height of B weights of weed conductivity melting point then welding speed thermal diffusivity okay so these are the parameters now there is a term known as duty cycle which is very very important while solving welding problem I come across the designation standard of welding electrode uh dear actually that is in p and I syllabus not in mechanical so we are referring mechanical syllabus only okay so Pi syllabus it have so that question will be in pi you can check it okay that is from production Industrial Paper so my dear when we are talking about duty cycle as in the electro slag welding you also have seen that after some time we stop the arc and Welding was happening without any current because of already presence high temperature so duty cycle is defined in such a way that the time for which you are continuously ah switching on the arc it is also defined as Arc time by weld time generally a standard of 10 minutes of duty cycle is defined for Universal for India we defined it like five minutes okay so when I say 10 minutes as standard 10 minutes would be considered as 100 duty cycle so if someone say five minutes I will call it as 50 percent so the I square into D is going to be constant so duty cycle is nothing but the time for which you are continuously providing okay so my dear if that is the case I Square D is equals to constant will be used the question will be like for 1000 ampere current duty cycle is 40 percent then for 600 ampere current what would be duty cycle so what you would be doing you would say 1000 square I square into 14 is equals to 600 square into one so whatever you will get here this would be the value of duty cycle D2 this type of question can come in this so my dear next defect is Arc blue welding defect is Arc blue so my dear what is going to happen if you are going to weld this plate during the welding current is Flowing because of current magnetic field is generated across the electrode and work piece so my dear whenever you are going to start the weld there are chances of deflection of or deviation of Arc because of this magnetic field so because of this deviation we can have the defect likes better scattering of molten metal if you want to avoid that kind of defect we are going to provide some extra plates so that this deviation should not happen which is stabbing and timeout the chances of Arc blow are more with DC less with AC okay so that also you guys have studied duty cycle and Arc blow so my dear now we are moving to laser beam welding in the laser beam welding the principle is if we have atoms at some low energy when some energy is provided with the Xenon lamp these low energy atoms would be going to the high energy it doesn&amp;#39;t mean that atoms are moving like that I want to say their energy will increase so when energy is more everybody wants to be at a lower energy State because they are he face more stability so when you are going to provide the energy they reach to high energy then they are feeling unstability they try to reach to some meta stable State and they release some energy in the form of photons that energy is used for the welding purpose so we are calling it as laser beam welding okay so my dear how it is happening this is the Xenon lamp here we are having the pumping zone so here we are providing some powder so because of the amount of heat coming from Xenon lamp it would be going to high energy region will leave some kind of proton and when those energy light will be coming this surface is 100 percent reflective which will hundred percent reflect the light this is 98 reflective which will allow two percent to come out which would be coming straight okay so when it would be coming straight it would be colliding with the mirror which will be directing it towards the lens which we convert it to the welding area so in laser beam welding we need not to go for any kind of uh vacuum pump so cost of this is less here no x-rays are produced it is lesser harmful so it is more preferred over Electron Beam welding and can be used for all those application of Electron Beam Welding which we have seen so laser beam welding can be used for all of them okay so my dear this is something known as laser beam welding for this you are using two types of laser one is ndyag here ND represent neodymium y for Atrium a for aluminum G for Garnet okay so my dear these are the numericals so we are not doing numerical in this session so that we have a separate practice session okay so my dear I feel we have completed this welding part so now I feel we have already completed a lot of time also uh I feel the session is going on from 11 so I will 2.5 hours are completed now you want me to cover casting defect today you want me to cover casting defect today because welding is almost completed I can complete casting defect today and then next session I am asking from you when you want metal forming tomorrow or day after tomorrow when you guys want metal forming tomorrow or day after tomorrow metal forming tomorrow or day after tomorrow yes so there are some theories which I am not covering here because that is something to remember that I cannot help in like there are some type of flux Coatings so flux Coatings are having some element which will help us to provide the weld bead they are having some elements which help us to provide their melting point temperature higher there are some element which will help us for flame stabilization which would be increasing their melting point temperature there are some elements which would be helping us to make them lighter so those elements are mentioned like there are some types of flux coating like acidic basic rutile so all these are mentioned in this you need to remember the elements in those Coatings so for that purpose like in acid coating we have fe3o4 mno2 quad silicates so that I cannot help into that you need to remember only okay so that&amp;#39;s why I am giving you providing you these slides but that you need to remember yes that&amp;#39;s why I was asking you my Sunday is I can dedicate it for you but the point is whether you can dedicate your Sunday for that or not okay fine guys so I am just quickly going through the casting defect otherwise that is also something you can mug up kind of thing so in gas defect first of all we are having the defects like blow holes open blows okay so you know my dear Sometimes some moistures are present when the casting is going to happen so because of that my dear we are going to have some some uh you can say holes inside okay like you can see here these are the holes inside why they are coming if you remember some gases were producing at the time of casting when molten metal was coming in contact with the facing sand and mouthwash so those gases were coming and those gases were remain inside if porosity of the mouth is not good so inside if it is present there were some gaps were there bubbles were there so because of that bubbles we will be having no molten metal going there so some blow holes would be present if inside these bubbles are there we are calling it blow holes if they are coming on the surface we call it as open blows okay then my dear we are going to have scan so my dear when we are talking about the scare if you are going to have on the surface a very big bubble in the blow holes it was smaller one this kind of thing is coming this kind of thing is coming when the size is bigger for this and in the blister it is one layer is covering this so when the layer is covering it it is said to be blister when layer is not covering it it is said to be square okay and my dear if some hydrogen gas is present then you will be having very small small hole inside the casting then that is said to be porosity or pin holes we want porosity in the mouth but not in the casting okay so now the reason is also mentioned that gas defect which forms inside of the casting are blow holes and surface or open blows scare is the shallow blow formed on the surface because of presence of bubble so if bubble is present on the surface it will create scare inside it will create blister okay and small size holes are created by hydrogen gas which is said to be pin holes okay next is remedies so remedies are you have to make good porosity of the mouth so that gases is go out second type of things are said to be molding defect okay so my dear if your mold is not having good properties like let us say you are going to have this as mold but my dear what is going to happen if at some of the place the sand is not having good strength and some particle of sand is going down from here and this would be reaching to the lower surface like this so your casting will also solidify in this shape now so your casting will also solidify this shape now so this thing is said to be drop because from here sand is getting dropped and this is said to be dirt because here you will not be having the metal so this would be the kind of casting you will get so this defect is coming because of the moldy mild defect if my dear Corners are not good and having less strength for such case your Corners may be broken and you may be having the casting to be of this shape so some Corners may get broken so my dear they are said to be curse and washes once again a molding defect okay so my dear for that what you can do you can convert greens and mold into dry sand mold it will increase the strength of the mouth as well it would be increasing the permeability of that as well okay you can improve permeability by additives also okay you can improve strength by additives also so we have seen the molding defects complete quickly now my dear you must have seen ryzen was doing some of the functions and you were having two types of solidification one was skin forming and other kind of solidification was a dendritic growth otherwise then treaty growth so in dendritic growth we were having the possibility of multiple risers because shrinkages were coming at many places and at all the places you cannot provide the risers so you were calling that defect as shrinkage cavity okay thanks for that so tomorrow we will not be having that session okay no problem but tonight tonight we have a practice session of machine design at 7 pm we have a practice session of machine design where I will solve 15 questions in the class and 15 questions would be given to you as homework okay so this is what we have completed okay sure value sure for that you will get some video on that so we have seen those defects okay so my dear if you have if you have some particle like you know that if you have some particle to be removed from this we have seen dirt and drop now my dear when molten metal is entering inside the cavity it is providing some hydrostatic forces so my dear because of these hydrostatic forces sometimes mold gets some kind of shift so this mounting sand will be shifting by this amount so my dear because of that here molten metal will enter so it is a kind of you can say extra part would be coming on the on the on the on the roof similarly sometimes this can happen in the side wall also so my dear this can happen in the side wall also so this shifting of mold will be happening because of hydrostatic forces so these defects are said to be scab and spell cab and swell they are happening because of Shifting of stand with the hydrostatic forces of molten metal here shifting is happening in drop and dirt mounting sand was eroded and coming down that is the difference okay then my dear fluidity defects are there sometimes your molten metal is having improper fluidity it is unable to fill the cavity completely so if my dear like you are having a cavity like this and it is unable to fill it completely and it is capable of filling up to this only then this defect is said to be misrun and if there are two molten Metals steam are coming like this one is reaching here other is reaching here so this much part remain empty that is said to be cold shut so this defect is said to be cold set both are going on because of improper fluidity so guys I feel we shall complete it here because likewise I have a lot of ah you can say things but these are I feel less important so I am providing you the handwritten notes for revision purpose if you still want otherwise this audio book is there for you all the time and I will also share this PDF with you so that you can revise it if you want so guys here I will say goodbye to all of you and I will also say thanks for your love and support so if any one of you is preparing for gate 24 you can register for the workshop tomorrow and one more thing guys marathons are starting from 3rd of January so you can revise them I will be sharing the schedule third January would be strength of material yes you welcome chili Mishra so goodbye guys for this session thanks for joining we will meet again so as per your request we will keep the next session on Monday only okay so goodbye guys for this session tonight machine design practice goodbye good night sorry note good night okay goodbye and happy New Year to all of you guys

Transcript for:Welding Techniques and Processes

Transcript for:
Welding Techniques and Processes