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Resistance Spot Welding (RSW), Resistance Seam Welding (RSEW), and Projection Welding (PW) are commonly used resistance welding processes. Resistance welding uses the application of electric current and mechanical pressure to create a weld between two pieces of metal. Weld electrodes conduct the electric current to the two pieces of metal as they are forged together.
The welding cycle must first develop sufficient heat to raise a small volume of metal to the molten state. This metal then cools while under pressure until it has adequate strength to hold the parts together. The current density and pressure must be sufficient to produce a weld nugget, but not so high as to expel molten metal from the weld zone.
Resistance Welding Benefits
* High speed welding
* Easily automated
* Suitable for high rate production
Resistance Welding Limitations
* Initial equipment costs
* Lower tensile and fatigue strengths
* Lap joints add weight and material
Resistance Welding Problems and Discontinuities
*Electrode deposit on work
*Porosity or cavities
*Deep electrode indentation
*Improper weld penetration
*Irregular shaped welds