Compared with aluminum alloy, copper alloy has slightly higher resistivity and lower thermal conductivity, so spot welding of nut spot welder is not too difficult. Copper alloys with a thickness of less than 1.5 mm, especially copper alloys with low electrical conductivity, are widely used in production. Pure copper has extremely high electrical conductivity, making spot welding difficult.
It is usually necessary to add a gasket between the electrode and the workpiece, or use a composite electrode with tungsten embedded in the electrode tip to reduce heat dissipation to the electrode. The diameter of the tungsten electrode is usually 3-4 mm.
When welding copper and high conductivity brass and bronze, a type 1 electrode alloy is generally used as the electrode, and when welding low conductivity brass, bronze and copper-nickel alloy, a type 2 electrode alloy is used. Copper alloys can also be welded with composite electrodes embedded with tungsten electrodes. Due to the poor thermal conductivity of tungsten, spot welding can be performed on a commonly used medium power welding machine using a much smaller welding current, but the tungsten electrode easily adheres to the workpiece and affects the appearance of the workpiece.
Due to the serious adhesion of electrodes, copper and high-conductivity copper alloys are rarely used for spot welding. Even the use of composite electrodes is limited to spot welding of thin copper plates.