Notes on Resistance Welding

Overview

• Resistance Welding: Property of a conductor that resists the flow of electrons, generating heat through friction, which is then used to join metals.
• Key Types of Resistance Welding Processes:
  1. Spot Welding
  2. Seam Welding

Spot Welding

• Also known as Resistance Spot Welding (RSW).
• Used to weld thin sheets of metal together by applying pressure.
• Working Principle:
  • Electrodes made of copper generate heat through resistance during current flow.
  • Current passes through electrodes, causing resistance at metal contact points, generating heat.
  • Heat melts the interface of workpieces, and pressure fuses them to form a solid bond.

Equipment Required

• Spot welding machine
• Tongs (electrodes)

Working Process

1. Power activates transformer to supply low voltage, high current to electrodes.
2. Electrodes exert pressure against workpieces.
3. Current flows, experiencing resistance at metal interface, generating heat.
4. Molten metal fuses, forming a bond.

Applications

• Manufacturing fuel tanks
• Joining vehicle body parts
• Radiators
• Wire ends

Advantages

• Automated process
• Simple operation
• No filler metal required
• Low fume generation
• High welding rate possible

Limitations

• High initial cost
• Low strength due to discontinuous welds
• Limited to certain metal thicknesses

Seam Welding

• Continuous form of spot welding.
• Workpieces supported by roller electrodes.
• Working Principle: Similar to spot welding but uses roller electrodes for continuous welds.

Equipment Required

• Seam welding machine
• Roller electrodes

Working Process

1. Power supplies low voltage, high current to roller electrodes.
2. Roller electrodes contact workpieces, allowing current to flow.
3. High resistance at metal interface raises temperature to fusion point, generating weld nugget.

Applications

• Welding transformer paint containers
• Gasoline tanks
• Automobile mufflers
• Sheet metal tanks

Advantages

• Leak-proof welds
• High production rate
• Capability to weld dissimilar metals
• No filler metal or flux required
• Can be automated
• Effective for thin sheets

Limitations

• Suitable for thin sheets only (up to 3mm thickness)
• Electrode rollers limit welding to straight or well-curved paths
• Limited to lap joints

Conclusion

• Resistance welding is crucial for joining metals efficiently.
• Various applications span multiple industries, from automotive to manufacturing.
• Understanding advantages and limitations is essential for selecting the right welding process.