The most prominent feature of induction heating is that it heats the workpiece directly. Its core advantages include fast heating speed, uniform thermal field, easy temperature control, no mixing of metal impurities during heating, low metal burning loss of workpieces and good working conditions for workers, so it is widely used in industrial production. At present, in the machinery manufacturing and equipment industry, especially the metallurgical industry, induction heating is mainly used for casting smelting, through heating, quenching, sintering, brazing and other processes. According to the operating frequency of induction melting furnaces, induction melting furnaces for the foundry industry are divided into power-frequency induction furnaces, medium-frequency induction furnaces and high-frequency induction furnaces. With high efficiency, fast melting speed, easy temperature control of molten metal, low burning loss of alloy elements and uniform chemical composition, medium-frequency induction furnaces deliver high product quality, are especially suitable for smelting various high-grade alloy steels. With mature technology, they are gradually adopted by many foundry enterprises and have a wide range of applications. Induction heating for through heating is mainly applied to heating and annealing in forging, hot stamping, hot rolling, extrusion and pipe bending. Induction heating can equalize the temperature across the whole surface and interior of the workpiece. With the advantages of high heating efficiency, fast speed, reduced metal burning loss, convenient temperature control, guaranteed heating quality and easy integration into automatic production lines, it has been applied more and more widely.
Quenching, a technology in heat treatment, is a process that heats the workpiece to a certain temperature and then cools it rapidly to change the metallographic structure of the workpiece correspondingly, so as to increase the hardness and wear resistance of the workpiece. However, restricted by heating methods in the past, the fatigue resistance of quenched workpieces deteriorated and the brittleness of workpieces increased. To solve this problem, a method of heating only the surface of the workpiece (without heating the interior) and then cooling rapidly is adopted. In this way, the metal surface is quenched, which increases the hardness and wear resistance of the workpiece, while the interior of the workpiece is not quenched and still retains its original strength. Induction heating has become the most ideal heating method for surface quenching.
However, the application of induction heating technology with the best performance and most remarkable benefits still remains in the smelting sector of the foundry industry. In the past decade, with the gradual improvement of power supply in China, more and more domestic foundry enterprises have adopted induction furnaces for metal smelting and heat preservation. This is mainly because compared with other metal smelting equipment, induction furnaces have the advantages of low smelting energy consumption, small metal burning loss, easy control of chemical composition, and flexible and convenient operation. In addition, induction furnaces boast better working environment, less environmental pollution, and more convenient production organization and management.
Nowadays, induction furnaces have become the preferred melting furnace equipment for the design of new foundry workshops and technical transformation. Especially with the increasingly improved and expanded application of computers in induction furnaces, covering furnace condition monitoring, fault diagnosis, furnace leakage alarm devices, and even process control of smelting and pouring operations, the advancement of induction heating technology has become more prominent. To meet the demand of high and new technology for ultra-precise alloys, new types of induction furnaces have been continuously developed for medium-frequency applications, such as plasma induction furnaces, vacuum induction furnaces, liningless water-cooled copper crucible induction furnaces, magnetic levitation induction furnaces and other new technologies and equipment, which will play a more important role in cutting-edge industrial fields.
