Induction heating power supply has the highest heating efficiency, the fastest speed, low consumption and environmental protection for metal materials. It has been widely used in hot processing, heat treatment, hot assembly, welding, smelting and other processes of metal materials in all walks of life. Induction heating power supply consists of two parts. One part is the AC power supply that provides energy, also known as variable frequency power supply; The other part is the induction coil that completes the conversion of electromagnetic induction energy, which is called inductor.  
The main advantages of induction heating equipment are:
① No overall heating is necessary, the workpiece deformation is small, and the power consumption is small.  
② Pollution free.  
③ The heating speed is fast, and the oxidation and decarburization of the workpiece surface is light. ④ the surface hardening layer can be adjusted as required and easy to control.  
⑤ Induction heating equipment can be installed on the machining production line, which is easy to realize mechanization and automation, easy to manage, reduce transportation, save manpower and improve production efficiency.  
⑥ The hardened layer has fine martensite structure and high hardness, strength and toughness.  
⑦ After surface quenching, there is a large compressive internal stress on the surface of the workpiece, and the fatigue breaking resistance of the workpiece is high. Induction heating heat treatment also has some disadvantages. Compared with flame quenching, induction heating equipment is more complex and has poor adaptability. It is difficult to ensure the quality of some workpieces with complex shapes.
Induction heating equipment is widely used for surface quenching of gears, shafts, crankshafts, cams, rolls and other workpieces in order to improve the wear resistance and fatigue breaking resistance of these workpieces. Induction heating surface quenching is adopted for the rear half axle of automobile, and the number of fatigue cycles under design load is about 10 times higher than that with quenching and tempering treatment. The workpiece material for induction heating surface quenching is generally medium carbon steel. In order to meet the special needs of some workpieces, a special low hardenability steel for induction heating surface quenching has been developed. Induction heating surface quenching can also be used for workpieces made of high carbon steel and cast iron. Quenching medium is usually water or polymer aqueous solution.  
Induction heating and heat treatment equipment is mainly composed of power supply equipment, quenching machine tool and inductor. The main function of power supply equipment is to output alternating current with appropriate frequency. There are two kinds of high-frequency current power supply equipment: electron tube high-frequency generator and thyristor frequency converter. The medium frequency current power supply equipment is a generator set. General power supply equipment can only output current of one frequency. Some equipment can change the current frequency or directly use power frequency current of 50 Hz for induction heating.  
The selection of high frequency induction heating power supply equipment is related to the required heating layer depth of the workpiece. For the workpiece with deep heating layer, the power supply equipment with low current frequency shall be used; For workpieces with shallow heating layer, power supply equipment with high current frequency shall be used.  
Another condition for selecting a power supply is the power of the device. As the heating surface area increases, the required power supply power increases accordingly. When the heating surface area is too large or the power supply power is insufficient, the continuous heating method can be adopted to make the workpiece and the sensor move relatively, heating in the front and cooling in the back. However, it is better to heat the whole heating surface at one time. In this way, the waste heat in the core of the workpiece can be used to temper the hardened surface, so as to simplify the process and save electric energy. The main function of induction heating quenching machine tool is to position and move the workpiece. In addition, a device for providing quenching medium shall be attached. Quenching machine tools can be divided into standard machine tools and special machine tools. The former is suitable for general workpieces and the latter is suitable for complex workpieces produced in large quantities.  
During induction heating heat treatment, in order to ensure the heat treatment quality and improve the thermal efficiency, the inductor with appropriate structure must be designed and manufactured according to the shape and requirements of the workpiece. Commonly used inductors include outer surface heating inductor, inner hole heating inductor, plane heating inductor, general heating inductor, special heating inductor, single heating inductor, composite heating inductor, smelting furnace, etc.