Induction melting furnace is an advanced melting equipment. Applying the principle of electromagnetic induction, it generates heat inside the charge to be melted to melt the material, thus featuring high thermal efficiency and low burning loss of alloy elements. Due to the electromagnetic stirring effect, the composition of molten metal is uniform without segregation. Without using coke as heat source, it can produce special high-quality cast iron that cannot be produced by cupolas. Induction furnace melting is easy to control, with good operating conditions, low environmental pollution and low noise. It allows convenient and economical reuse of metallic charge (ranging from small iron scraps to large charges that can fit in the furnace hearth), so melting cast iron with induction furnace is widely used, and the application of induction furnaces for melting various cast irons shows an expanding trend.
At present, all types of induction melting furnaces are produced by professional manufacturers in China, with a relatively complete range of products that can basically meet production requirements.
Induction furnaces are divided into two categories: cored induction furnace and coreless induction furnace. Currently, the most widely used is coreless induction furnace (namely medium frequency induction furnace).
Classified by operating current frequency, they are divided into: ① Power frequency coreless induction furnace - 50Hz; ② Medium frequency coreless induction furnace > 50 ~ 10000Hz; ③ High frequency coreless induction furnace > 10000Hz.
The following mainly introduces the heating principle of the medium frequency coreless induction furnace produced by Luoyang Wanle Electric Power Equipment Factory: The coreless induction furnace operates based on the principle of electromagnetic induction. The spiral induction coil around the crucible is equivalent to the primary winding of a transformer, and the metallic charge inside the crucible is equivalent to the secondary winding of the transformer. When alternating current passes through the induction coil, the alternating magnetic field induces strong induction current in the short-circuited metallic charge inside the crucible. The current generates heat by overcoming the resistance of the surface layer of the metallic charge, thus melting the metal. This furnace features two characteristics: surface effect and stirring effect of electromagnetic force. The former depends on the frequency of induction current: the higher the current frequency, the more significant the surface effect, and the shallower the heat penetration depth on the metallic charge. This determines that the diameter of the metallic charge should not be too large, otherwise it will reduce electrical efficiency, which is the fundamental reason why there are no large-sized high frequency induction furnaces. The latter is reflected in that after the metallic charge melts and forms a molten pool, the liquid metal is strongly disturbed under the action of electromagnetic force, forming a stirring effect and a hump along the movement direction.
During melting, this stirring effect promotes rapid melting of metal, makes the temperature and composition in the molten pool more uniform, and facilitates the operations of deoxidation, degassing and inclusion removal.
Structure of coreless induction furnace: A coreless induction furnace is composed of furnace body, furnace frame, tilting mechanism, water cooling system and electrical equipment, etc.
