When the workpiece and electrode are constant, the resistance of the workpiece depends on its resistivity Therefore, resistivity is an important performance of the welded material Metals with high resistivity have poor conductivity, while metals with low resistivity have good conductivity. Therefore, when spot welding stainless steel, heat generation is easy but heat dissipation is difficult, and when spot welding aluminum alloy, heat generation is difficult but heat dissipation is easy When spot welding, the former can use a smaller current (several thousand amperes), while the latter must use a larger current (tens of thousands of amperes). The resistivity not only depends on the type of metal, but also on the state, processing method, and temperature of the metal.

1. If there is a high resistance oxide or dirt layer on the surface of the workpiece and electrode, it will greatly hinder the current. Excessive oxide and dirt layers can even prevent current from conducting.

2. Under very clean surface conditions, due to the micro roughness of the surface, the workpiece can only form contact points locally on the rough surface. The convergence of current lines at the contact point. Due to the reduction of the current path, the resistance at the contact point has increased.

Due to the generally lower electrical resistivity and hardness of copper alloys compared to workpieces, their impact on the formation of fusion nuclei is less significant, and we rarely consider their influence.