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In the casting industry, melting speed has always been a key concern for casters. At the request of its customers, Kanda Electric Furnace has continuously improved its melting speed.
During the smelting process, proper equipment maintenance and good operating practices for medium-frequency furnaces not only significantly enhance equipment utilization rates but also greatly improve energy efficiency.
Compared with power-frequency furnaces, medium-frequency furnaces are generally used for producing alloy materials, whereas power-frequency furnaces are more commonly used for refining steel. Medium-frequency furnaces can reach capacities of several dozen tons, but typical medium-frequency furnaces are not usually this large—few exceed ten tons. Medium-frequency furnaces and electroslag remelting furnaces operate at different frequencies; the frequency of a medium-frequency furnace is higher than that of a power-frequency furnace.
　　The medium-frequency induction furnace uses this heat to heat and melt the metal, thereby achieving the purpose of melting.
　　Its main features are as follows:
　　1. The molten metal, subjected to electromagnetic forces, undergoes intense stirring. This is a key feature of medium-frequency induction furnaces. The movement (stirring) of the liquid metal begins from the center of the melt pool and progresses toward both ends of the coil. Due to the constraints imposed by the furnace bottom and walls, the metal ultimately moves upward, forming a hump at the top of the melt pool.
　　2. In the remelting process using a medium-frequency induction furnace, which is a batch melting process, the entire charge of metal to be melted consists of small pieces of furnace charge. Due to factors such as the feeding method, the packing density of the charge is only about one-third of the furnace’s capacity. At this stage, the charge presents a very poor electrical load. When power is fed into the furnace, arcs will occur between individual pieces of charge and weld them together. Once the pieces have welded together, the entire charge will coalesce into a single large mass, thereby significantly improving the furnace’s efficiency.
　　The cost of steel produced by medium-frequency induction furnaces is 800 to 1,000 yuan cheaper than that produced by refining furnaces. The main reason is that the equipment for medium-frequency induction furnaces is extremely inexpensive—typically costing only a few tens of thousands of yuan, and some used units are even cheaper. If favorable electricity rates can be secured, the cost of steelmaking will be even lower. However, as economies of scale take effect and government regulations tighten, we believe that in the near future, medium-frequency induction furnaces will gradually fade from the stage of history. Therefore, let’s use... Medium-frequency electric furnace Steelmaking has stringent requirements for raw materials, and their chemical composition is difficult to control—this is particularly evident in the control of carbon content. Since it’s impossible to achieve a vacuum environment like that in an AOD furnace, even if the raw materials are meticulously controlled, it remains extremely challenging to keep the carbon content in a medium-frequency induction furnace below 0.03%. Moreover, without dedicated desulfurization and dephosphorization processes, it’s generally impossible to completely remove harmful elements such as sulfur and phosphorus from the raw materials. Therefore, when selecting 304L or 316L grades, medium-frequency induction furnaces are typically ruled out—especially when producing export-quality products. Steel flats and rounds produced by medium-frequency induction furnaces often exhibit excessive levels of P and S, though the extent of this issue may be more obvious in some areas than in others. As the steel progresses through subsequent processing stages, these defects become even more apparent. For instance, ingots cast from the same batch of molten steel, after being forged and pickled, frequently reveal subtle differences in material properties in certain areas. This is hardly surprising, given that medium-frequency induction furnaces lack the ability to effectively remove slag. Consequently, when these products undergo surface treatments, such as polishing or finishing, any pre-existing flaws—such as pinholes, cracks, or peeling—become even more pronounced.
To further increase the melting speed, you need to use high-quality equipment.