Method description

Resistance welding is a method for joining materials by using heat and pressure. The work piece is heated by electrical current using conductive electrodes. The welding arrangement consists of individual series-connected contact and material resistances, which convert electrical power into heat in proportion to their size.

Contact resistances occur at the points of interface between the electrode and work piece, or between the work pieces. They are determined by temperature, pressure, contamination, oxide layers, coatings, alloying, the electrode caps and component fit. The material resistances result from the specific material resistances and temperature. Welded joints are made using a compatible resistance, heat distribution and sufficient energy supply, typically in the form of welding lenses. To reduce losses and provide targeted energy input into the weld zone, electrode materials with specific properties are used. These properties include high conductivity, high melting points, and low contact resistance. In order to achieve consistent contact resistance and welding results, the electrodes must be dimensionally stable. For this reason, electrode materials with high hardness and strength are used. It is important that these material properties are maintained during the welding process after long exposures to heat. Therefore, the materials generally are characterized by high softening temperature, and high tempering resistance.

When choosing the electrode, the lowering of the melting point due to the formation of mixed crystals of the electrode materials and work piece must be considered. Accordingly, the electrode material should be quite similar to the work piece material or have a higher melting point.