The furnace lining is divided into acid refractory and alkaline refractory. The acid lining is made of quartz sand containing more than 98% silicon dioxide. Because of its low melting point and poor stability, it is mainly used for smelting and heat preservation of non-ferrous metals and cast iron. The alkaline lining is made of magnesia containing more than 85% magnesia, which is used for smelting special steel and nickel-based alloy. Furnace lining is made of refractories with proper size ratio by dry or wet method, which need to be compact and non-stratified. The initial smelting should be heated slowly to avoid cracking.
In smelting, metals are heated by induction and then transmitted to the slag, so the slag temperature is lower and the interface between steel and slag is smaller because of the furnace structure, which is not conducive to the physical and chemical reaction between the molten pool and slag. Therefore, in smelting special steel or nickel-based alloy, better raw materials should be used to quickly heat and melt according to the burning loss of each element. When a large amount of burden has been melted, slag should be added to reduce oxidation. Slag should be compatible with furnace lining. After full melting, deoxidizers (ferrosilicon powder, calcium silicate powder, aluminium powder, etc.) are added in batches according to the composition of the finished product. Sampling and analysis are carried out when necessary to adjust the composition. When the composition is qualified and the deoxidation is good, the steel can be tapped. Cast iron is not oxidized seriously during melting and holding, and the requirement of metallurgical quality is low. It can give full play to the advantages of easy operation of induction heating.
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