点凸焊机 ）由电源、电极及其加压机构和控制系统构成。 The resistance welding machine ( spot welding machine ) is composed of power supply, electrode and its pressurizing mechanism and control system. The electrode is made of high-strength copper alloy, and the inside (or outside) is cooled by water. 。 The pressurizing mechanism can be a manual, pneumatic or hydraulic mechanism .
The complexity of the control system depends on the required welding quality. When using electronic or microprocessor control, it can automatically and accurately control the entire welding process and improve its stability. An AC resistance welding machine using a 50 Hz AC power supply generally uses a step-down transformer. The secondary no-load voltage is about 1 to 36 volts, the current is from several thousand to tens of thousands of amperes, and the electric power can reach more than 1,000 kilovolts.
Resistance welding machine is mainly used for welding steel materials. Welders that use lower frequency power sources are called low-frequency resistance welders and can weld steel materials and non-ferrous metals. Welding machines that use DC pulses, capacitor energy storage, and secondary rectifier power are called DC resistance welding machines and are used to weld non-ferrous metals and steel materials.
The method of applying pressure to the weldment through the electrode, while using the resistance heat generated by the current through the contact point, is also called contact welding. The form of resistance welding is point welding, projection welding, seam welding and butt welding. Resistance welding has high productivity and is easy to realize mechanization and automation, but the required welding machine is complicated and consumes large electric power, which is mainly used for mass production.