Projection welding is a variation of spot welding. Small projections are embossed at the plate where welds are desired as shown in Figure 20.44. The workpieces are then placed between large-area electrodes and current is switched on. High temperatures are generated at the projections. During the process, the projections collapse, owing to heat and pressure, and workpieces are brought in close contact. The shape of projection may be circular or oval depending on the design.
Figure 20.44 Resistance Projection Welding
Advantages
- This is faster process as the number of welds is made simultaneously.
- Small amount of current is required due to large density of current at the projection only.
- The pressure required on the electrode is low.
- Thermal shrinkage and distortion are less.
Limitations
- Correct application of pressure and current are very important.
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