The induction heating power supply has the highest heating efficiency, fastest speed, and low consumption and environmental protection for metal materials. It has been widely used in hot processing, heat treatment, hot assembly and welding, smelting and other processes of metal materials in all walks of life. The induction heating power supply consists of two parts, one part is the AC power supply that provides energy, also known as the variable frequency power supply; the other part is the induction coil that completes the electromagnetic induction energy conversion, called the inductor.
The main advantages of induction heating equipment are:
① It is not necessary to heat the whole, the deformation of the workpiece is small, and the power consumption is small.
③ The heating speed is fast, and the surface oxidation and decarburization of the workpiece is lighter. ④Surface hardening layer can be adjusted according to need, easy to control.
⑤The induction heating equipment can be installed on the machining production line, which is easy to realize mechanization and automation, easy to manage, and can reduce transportation, save manpower and improve production efficiency.
⑥ The martensite structure of the hardened layer is finer, and the hardness, strength and toughness are higher.
⑦After surface quenching, the surface layer of the workpiece has a large compressive internal stress, and the fatigue resistance of the workpiece is relatively high. Induction heat treatment also has some disadvantages. Compared with flame quenching, induction heating equipment is more complex and less adaptable, making it difficult to guarantee 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 resistance of these workpieces. The rear half shaft of the automobile adopts induction heating surface quenching, and the number of fatigue cycles under the design load is about 10 times higher than that of the 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, low hardenability steels for induction heating surface quenching have been developed. Workpieces made of high carbon steel and cast iron can also be surface hardened by induction heating. The quenching medium is usually water or high molecular polymer aqueous solution.
The equipment for induction heating and heat treatment is mainly composed of power supply equipment, quenching machine tools and inductors. The main function of the power supply equipment is to output alternating current with a suitable frequency. There are two types of high-frequency current power supply equipment: tube high-frequency generator and thyristor inverter. 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, and can also directly use 50 Hz power frequency current for induction heating.
The selection of high-frequency induction heating power equipment is related to the depth of the heating layer required by the workpiece. For workpieces with a deep heating layer, a power supply device with a lower current frequency should be used; for a workpiece with a shallow heating layer, a power supply device with a higher current frequency should be used.
Another criterion for selecting a power supply device is the device power. The heating surface area increases, and the required power supply increases accordingly. When the heating surface area is too large or the power supply is insufficient, the continuous heating method can be used to make the workpiece and the inductor move relatively, heating at the front and cooling at the back. However, it is better to heat the entire heating surface at once. In this way, the hardened surface layer can be tempered by using the residual heat of the workpiece core, thereby simplifying the process and saving electric energy. The main function of the induction hardening machine is to position the workpiece and perform the necessary movements. 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.
In induction heating heat treatment, in order to ensure the heat treatment quality and improve the thermal efficiency, it is necessary to design and manufacture an inductor with an appropriate structure according to the shape and requirements of the workpiece. Commonly used sensors include outer surface heating sensor, inner hole heating sensor, flat heating sensor, general heating sensor, special heating sensor, single heating sensor, composite heating sensor, melting furnace, etc. .