Spot Welding

Questions and Answers

Excessive weld indentation can cause rejected product. It is a condition that is specified is some quality plans, AWS D8.7 Recommended Practices for Automotive Weld Quality- Resistance Spot Welding. To reduce indentation one must reduce excessive forces and heat at the surface.

Electrode sticking to the work piece generally is caused by excessive heating between the electrode and the work piece. In the Relative Resistivity Diagram RC has become too large. Any factor which would cause this is an issue that must be addressed to prevent this manufacturing problem. In many cases this condition is accompanied with excessive surface expulsion.

Electrode Sticking

Electrode face mushrooming is the normal wear mechanism of a spot welding electrode. To slow this process or prevent excessive mushrooming one must control several factors in the welding process.

 Mushroomed electrode

EXTREME MUSHROOMING

Surface expulsion is caused when the part surface heats up. So anything which would cause this, could be a reason. The appearance is similar to interface expulsion. In this case we are looking for conditions which cause the contact surface heat to be high.

Expulsion of molten particles from between the two sheets of metal being welded can be caused by several items. All are related to causing excessive heat between the two work pieces or not containing the weld nugget during welding.

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