Spot welding

The operating principle of spot welding is based on the thermal effect of electric current. During spot welding, the two workpieces are first clamped between upper and lower electrodes under the action of the welding clamp or the welding gun’s pneumatic cylinder. A welding current—typically ranging from several thousand to tens of thousands of amperes—is then passed through the joint. According to Joule’s law, Q = 0.24I²Rt, the metal at the weld interface melts; once the required welding temperature is reached, the current is interrupted. Under the pressure exerted by the electrodes, the molten metal cools and solidifies, forming a weld nugget.