With the increase of steel production, a large number of scrap steel has been produced in society, which provides conditions for EAF steelmaking in cast steel production. As the electric furnace with electricity as heat energy, it can be divided into two types, one is electric arc furnace, which uses the heat generated by electric arc to melt scrap, the other is induction furnace, which uses the heat generated by electromagnetic induction to melt scrap, especially the medium frequency induction furnace. Before the 1990s, electric arc furnace was widely used. At that time, there were few high-quality scrap, most of which were mixed with good and bad, and it was not easy to sort. The development of EAF technology is earlier and has large capacity, but the development of induction melting furnace technology is not mature. Since 1990s, medium frequency electric furnace has been widely used in steel casting plants, especially in developed capitalist countries. With the improvement of energy saving and environmental protection requirements, medium frequency technology has been greatly developed. From the previous maximum of several hundred kilograms to the current maximum of 50 tons, the largest induction furnace of 100 tons has been developed in foreign countries, with German technology as the best.
Analysis of advantages and disadvantages of EAF and EAF steelmaking.
1、 Induction furnace heating faster, high thermal efficiency, its heat is generated in the furnace charge (liquid steel), so heating faster. The heat of electric arc furnace must be transferred to molten steel through slag after the charge is cleared, which is indirect heating. The thermal efficiency is poor. The furnace is basin shaped, and a large part of the heat of the arc is lost through the furnace cover and wall.
2、 The oxidation loss of elements in induction furnace steelmaking is less. Because there is no ultra-high temperature effect of arc in induction furnace steelmaking, the burning loss rate of elements in steel is low.
3、 The composition and temperature of molten steel in induction furnace steelmaking are relatively uniform. Because it is the effect of electromagnetic force, the inductor and molten steel repel each other, so that the molten steel in the center part of the crucible rises and the molten steel in the edge part of the crucible falls, resulting in the circulation of molten steel. The effect of electromagnetic stirring makes the chemical composition and temperature of molten steel tend to be uniform, and is conducive to the floating of non-metallic inclusions in molten steel.
4、 The ability of slag to participate in metallurgical reaction is poor in induction furnace steelmaking. In EAF steelmaking, the temperature of slag is higher than that of liquid steel, and slag has strong ability to participate in metallurgical reaction. In the induction furnace, the slag is heated by molten steel and its temperature is low, so its ability to participate in metallurgical reaction is weak. Therefore, the effect of desulfurization, dephosphorization and diffusion deoxidization in the induction furnace steelmaking is worse than that in the electric arc furnace steelmaking.
5、 The charge (scrap) of induction furnace steelmaking is required to be high. Due to the weak metallurgical reaction ability of EAF steelmaking and its emphasis on remelting, better burden (good material, less rust and oil stain) and larger lump are required.
6、 Induction furnace steelmaking is more in line with the requirements of environmental protection, while electric arc furnace steelmaking produces a lot of waste gas, slag and noise, resulting in higher energy consumption.
As a result, some of the larger foundries have also replaced the EAF with the induction furnace. For example, the foundry of Dongfeng Motor Company replaced the two EAFs with the induction furnace in 2004. With the emergence of a large number of high-quality scrap in the market, such as the scrap of cold-rolled stamping parts and the trimming of marine steel plate, small and medium-sized steel casting plants have replaced electric arc furnace with induction furnace. According to Zhejiang Foundry Association, only about one percent of the steel casting plants in Zhejiang Province use EAF.
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