Problems encountered when spot welding machines are welding copper and aluminum plates:
When the workpiece and the electrode are constant, the resistance of the workpiece depends on its resistivity. Therefore, resistivity is an important property of the material being welded. Metals with high resistivity have poor conductivity and metals with low resistivity have good conductivity. Therefore, it is difficult to produce heat when spot welding stainless steel, and it is difficult to dissipate heat. It is difficult to produce heat when spot welding aluminum alloy. Million amps). Resistivity depends not only on the type of metal, but also on the state of the metal, processing method, and temperature.
1) The surface of the workpiece and electrode has a high-resistance oxide or dirty material layer, which will greatly hinder the current. Excessive layers of oxides and dirt can even prevent current flow.
2) Under the condition that the surface is very clean, due to the micro unevenness of the surface, the workpiece can only form contact points on the rough surface. Collapse of current lines is formed at the contact points. The resistance at the contact is increased due to the narrowing of the current path.
Since the resistivity and hardness of copper alloys are generally lower than those of workpieces, they rarely have a smaller effect on nugget formation, and we rarely consider its effects.