Resistance Welding Electrodes

Resistance Welding Equipment - Electrodes

In addition to weld heads and power supplies, electrodes are an important part of the equipment and setup. Ultimately, it is through the electrodes that the welding current is transferred to the parts being welded. Electrodes have limited life since they are exposed to very high temperatures on the parts surface and are also likely to be contaminated from material transfer from the surface of the parts. In addition to supplying the welding energy, electrodes also have to supply the welding (or forging force) and often have to act as heat sinks to remove excess heat from the weld. The most common type of electrodes are discussed below:

Copper Alloy Electrodes
Most of the electrodes used for welding are made of copper. Depending on the alloy composition, you can have Class I, II, or III. Class I is the most conductive (and consequently softest) or the three. Class III is the most resistive but also has the ability to withstand high forces without deforming. Copper electrodes are commonly used for welding resistive parts such as steels.
Tungsten (W) and Molybdenum (Mo or Moly) Electrodes
Tungsten and Molybdenum are some of the highest melting metals and are quite resistive compared to copper. They are used for welding conductive components where they not only add heat to the weld but also heat loss from the weld.
Mixture electrodes - copper and Tungsten/Molybdenum/Tungsten Carbide
There are applications where copper electrodes are too conductive and tungsten/moly electrodes are too resistive. For such applications, a whole slew of mixture (powder metallurgy) electrodes are available under variety of trade names. The mixture ratio can be changed to suit.