The main part of the welding machine is a step-down transformer, the secondary coil is welded at both ends of the workpiece and the electrode, the work of ignition arc, welding the electrode in the high temperature arc welding workpiece gap. As the core of the welding transformer has its own characteristics, it has the characteristics of a sharp drop in voltage, that is, the voltage drop after ignition of the electrode; the electrode is sticky short circuit, the voltage is a sharp decline. In the welding operation, although the current in the circuit is the same everywhere, but due to the resistance is not the same everywhere in the unfixed contact resistance (this resistance is called the contact resistance), according to the law of thermal effects of current (also known as Joule's law) , That is Q = IR. t know: in the current is equal, the greater the resistance of the higher heat, so the welding, the contact of the electrode is the contact of the metal body contact resistance maximum, the electric heat generated in this part of the natural That is up to, in addition to the electrode is a lower melting point alloy, naturally easy to melt. The melted alloy core is bonded to the object to be welded, and the object to be welded is bonded together after cooling.