[Music] what is MIG welding MIG stands for metal inert gas welding the American Welding Society calls this process gas metal arc welding or gmaw you might also hear it called wire welding an MIG welding a thin wire acts as the electrode this wire is fed from a spool mounted on a gun or inside the welding machine through a flexible tube and out of the nozzle on the welding gun or torch the wire is fed continuously when the trigger on the welding gun is pulled when this trigger is pulled it also switches on the welding current and a shielding gas an electric arc forms between this wire electrode in the workpiece and heats both metals above their melting point these metals mix together or coalesce and solidify to join the work pieces into a single piece the metal in these parts to be joined is called the base metal and the metal that comes from the melting wire electrode is called filler metal mig welding always adds filler metal to the joint because the wire electrode melts as it's being used mig is called a consumable electrode process here's the mcguire going through the wire feeder into a flexible tube or conduit liner the liner goes through the hose or welding lead all the way to the torch nozzle at the nozzle the wire is fed through a contact tip and comes out at the point of the well shielding gas is also fed through the welding lead it goes through a gas diffuser and flows out of the nozzle this shielding gas which is often a mix of argon and co2 protects the molten metal from reacting with oxygen water vapor and other things in the atmosphere the shielding gas is stored in high pressure cylinders like these the pressure is reduced to a usable level by a device called a regulator an MIG welding all the Machine controls are set on the machine itself most important of these are polarity wire speed and voltage the trigger on the gun is just an on-off switch for most MIG welding the current is direct current or DC DC is like the current flowing from a car battery one wire is always the negative and one is always positive in DC MIG welding the electrode is usually positive and the workpiece is negative the term dcep is used in that the current is direct current and the electrode is positive this is also called reverse polarity but dcep is a more descriptive term in an electric circuit the current flows in a loop in MIG welding the current has to flow in a complete circle from the machine to the torch into the work and back to the machine work lead is clamped to the work to complete the circuit from the workpiece back to the machine so in summary MIG welding is an electric arc welding process it uses a consumable wire electrode filler metal is added automatically and the shielding gas comes from a high pressure cylinder