What is the composition and working principle of resistance welding?

Resistance welding machine (spot welding machine) consists of power supply, electrode and its pressurizing mechanism and control system. The electrode is made of high-strength copper alloy and is cooled by water inside (or outside). The pressurizing mechanism can be manual, air pressure or Hydraulic mechanism.

The complexity of the control system depends on the required welding quality. When controlled by electronic or microprocessor, it can automatically and accurately control the entire welding process and improve its stability. AC resistance welding machines using 50 Hz AC power supply generally use step-down The secondary no-load voltage of the transformer is about 1 to 36 volts, the current ranges from several thousand to tens of thousands of amperes, and the electric power can reach more than 1,000 kVA.

Resistance welding machines are mainly used to weld steel materials. Welding machines that use lower frequency power sources are called low-frequency resistance welders, which can weld steel materials and non-ferrous metals. Welding machines that use DC pulses, capacitor energy storage and secondary rectified power sources are called DC resistance welding machine for welding non-ferrous metals and steel materials.

The method of welding by applying pressure to the weldment through electrodes and using resistance heat generated by current passing through the contact points is also called contact welding. The forms of resistance welding include spot welding, projection welding, seam welding and butt welding. Resistance welding has high productivity and is easy to Mechanization and automation are achieved, but the required welding machines are complex and consume large amounts of power, and are mainly used for mass production.