Resistance welding is the process of heating the welded metal to local melting or high temperature plasticity by using electric current passing through the contact surface of the welded joint and adjacent area, and forming a firm welded joint under external force. Compared with arc welding, resistance welding has the following two characteristics:


(1) High thermal efficiency. In arc welding, the external concentrated heat source is used to transfer heat energy from the outside to the welding parts, while resistance welding is the resistance heat transfer from the high temperature zone to the low temperature zone, and the low temperature zone is the internal heat source. Therefore, the thermal energy loss is relatively small and the thermal efficiency is relatively high.


(2) The welds are dense. Usually, arc welding solidifies and crystallizes under normal pressure, while resistance welding solidifies and crystallizes under external pressure. It has the characteristics of forging and belongs to the category of pressure welding, so it is easy to avoid shrinkage cavity. Defects such as loosening and cracks lead to tight welding.


The forms of welded joints used for resistance welding are limited, but the parts used for resistance welding are still very wide, such as airplane body, car body, bicycle rim, various anchors, washing machine, refrigerator shell, etc. The material used for resistance welding is also very wide. It can not only weld low alloy steel, low carbon steel, but also other kinds of alloy steel and non-ferrous metal, as well as aluminum and copper alloys.