Seam Welding

Questions and Answers

Class 3 material is a designation of the Resistance Welding Manufacturers Alliance (RWMA).  It describes a group of copper alloys with excellent strength and good electrical conductivity.  Class 3 is often used to weld stainless steel, nickel alloys and other highly resistive - strong materials that require high weld forces.

bar stock

Class 3 Bar Stock

Class 2 material is a designation of the Resistance Welding Manufacturers Alliance (RWMA).  This is a group of copper alloys with high strength and electrical conductivity.  Class 2 is the most used material in the resistance welding industry.  As electrodes it is used for welding bare and coated steels.

bar stock

Class 2 Bar Stock

During the resistance welding process the electrode face is subjected to extreme temperatures for short periods of time. To prevent premature wear, water cooling is necessary for the resistance welding electrodes. The technical term for this wear and resultant deformation is annealing. In the case of spot welding the face will begin to take on the shape of a mushroom. As this face grows the weld quality suffers and eventually weld quality failure occurs. Prevention or retarding this mushrooming is very important. One of the most important items to control is the time at temperature that the electrode weld face sees. One method of control is by cooling the electrode. The second benefit of this is that it will also cool and solidify the weld nugget during the hold period of the weld cycle.

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