Projection Welding

Questions and Answers

Class 3 material is a designation of the Resistannce Welding Manufacturers Alliance (RWMA).  It describes a group of copper alloys with excellent strength and good electrical conductibity.  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

The proper electrode material can be determined from published weld schedules based on the work pieces being spot welded. These weld schedules can be found in AWS Standard C1.1, Recommended Practices For Resistance Welding and RWMA The Resistance Welding Manual. Your electrode supplier is another source. Spot welding requires a few initial decisions to be made to set up a good welding process. Most of these evolve around pressure, current and time.

Cooling is possibly the most important factor in electrode life. Proper water tube location will insure water flow as close as possible to the working face with the proper flow and temperature water. In each resistance welding application after the weld schedule is determined and the proper pressure, current and time (PCT) are set another important factor for electrode life is water cooling. Even with the proper setting every electrode will see very high temperatures and forces on its face. Over time this creates the traditional mushrooming of the weld face. To slow this face wear down we must reduce the time at high temperature that the weld face sees. Proper water cooling of the electrode is critical.

Water for the electrode should always come directly from the water manifold and not be plumbed to use water from another weld machine component. Cooling water is the most important item to insure electrode life. Therefore the amount of water and its temperature are very critical.

Have a Question?

Do you have a question that is not covered in our knowledgebase? Do you have questions regarding the above article? Click here to ask the professor.