There are two kinds of arc heating: direct arc heating and indirect arc heating. The arc current heated by direct arc directly passes through the heated object, which must be an electrode or medium of the arc. The arc current heated by indirect arc does not pass through the heated object, but mainly depends on the heat radiated by the arc. The characteristics of arc heating are high arc temperature and concentrated energy. The surface power of arc furnace melting pool can reach 560-1200 kW/m2. However, the noise of arc is large, and the voltage-ampere characteristic of the former manufacturer of cast aluminium heating coil is negative resistance characteristic (descending characteristic). In order to maintain the stability of the arc during arc heating, the instantaneous value of the circuit voltage is greater than that of the arc starting voltage when the arc current is instantaneous zero-crossing, and to limit the short-circuit current, a certain number of resistors must be connected in series in the power supply circuit. The surface of an object is bombarded and heated by electrons moving at high speed under electric field. The main component of electron beam heating is the electron beam generator, also known as the electron gun. The electron gun is mainly composed of cathode, bunching electrode, anode, electromagnetic lens and deflection coil. Anode grounding, cathode negative high position, focusing beam and cathode usually the same potential, between the cathode and the anode to form an accelerated electric field. Electrons emitted from cathode are accelerated to a high speed under the action of accelerated electric field. They are focused by electromagnetic lens and controlled by deflection coil, so that the electron beam is directed towards the heated object in a certain direction.

The advantages of electron beam heating are: (1) controlling the current value Ie of the electron beam can change the heating power conveniently and rapidly; (2) using the electromagnetic lens, the heating part can be changed freely or the area of the bombarded part can be adjusted freely; (3) the power density can be increased so that the material at the bombarded point can evaporate instantaneously.