Pig iron
Pig iron is mainly used to increase the carbon content in the charge or steel, and can solve the problem of insufficient scrap steel or heavy material sources. Strictly speaking, pig iron used for electric furnace steelmaking should be divided into two types: batching pig iron and carbon-increasing pig iron.
Due to the high carbon and impurities in pig iron, the pig iron ratio in the electric furnace steel charge cannot be too high, usually 10%-25%, and the maximum is not more than 30%. If the ratio is higher, it will cause the total molten carbon to be too high, and the smelting time will be extended, which will not only increase power consumption, but also reduce the service life of the furnace lining.
In addition, pig iron can hardly be added to the simple induction furnace (IF) smelting because it has almost no refining capacity. In the IF+LOD+LRF process independently developed by Shanghai Metallurgy Equipment Group, up to ~25% of pig iron can be added.
Raw material pure iron
The content of C, P and other impurities in raw material pure iron is very low. In a sense, it is a special steel, so it is also called soft steel. The smelting of raw pure iron is difficult and the cost is high. In the production of electric furnace steel, it is mainly used in the ingredients of smelting low-carbon or ultra-low-carbon high-alloy steel by non-oxidation method or back-blowing method. It can also be used as a material for remelting alloys and powder metallurgy such as permanent magnet alloys, precision alloys, and electrical alloys. The melting point of raw pure iron is high and it is not easy to melt, so when using it, it requires not only accurate composition, clean surface and small block size.
Sponge iron
Sponge iron has a high content of metallic iron, low content of S and P, and less impurities. It has been proved that the direct use of sponge iron instead of scrap steel in electric furnace steelmaking can not only solve the practical difficulties of insufficient supply of scrap steel, but also greatly shorten the smelting time, thereby improving the productivity of electric furnace steel. In addition, using sponge iron as a charge can also reduce non-metallic inclusions and nitrogen content in steel. Sponge iron is light, loose and porous, and has a strong water absorption capacity in the air, so it should be kept dry or put into the furnace in a red-hot state before use.
Master alloy materials
Master alloy materials are high-quality special materials. They are obtained by remelting alloy elements. They are often used as furnace materials for smelting high-temperature alloys or precision alloys, and some can also be used for deoxidation of molten steel. For those elements that are easily oxidized or have a low density, it is difficult to add them directly to the molten steel when the smelting requires a high content. In addition, the inaccurate recovery rate affects the accurate control of the chemical composition. Therefore, the master alloy materials obtained by remelting the alloy ingredients are often used as furnace materials for smelting. Therefore, in the master alloy materials, the content of elements that are easily oxidized or have a low density (Al, Ti, Si, B, Mg, Ca, etc.) is high or there are many types. Special master alloy materials can be used for deoxidation of molten steel after being crushed. The remelting process of alloy elements is also a purification process of the alloy, so the impurities and gas content in the master alloy materials are relatively low. It is not difficult to see that the use of master alloy materials as furnace materials for smelting has stable chemical composition and high purity, but the cost is relatively expensive.
