There are three kinds of smelting methods of steel for general forgings.
First, Sheping method: Hearth and slope with alkaline refractories such as Magnesia bricks, aluminum magnesia bricks, magnesia and dolomite, such as the formation of the open hearth called Sheping. It uses alkaline slag to make steelmaking in an oxidizing atmosphere.
Sheping method has the following characteristics: Because the use of alkaline slag, can be a large number of sulfur and phosphorus removal. Therefore, the control of steel-making raw materials is not as strict as acidic open hearth, which is the advantage of this method; Slag is high in alkalinity and permeability, and the solubility and diffusion capacity of hydrogen in steel increases. Non-metallic inclusions in Sheping steels are mainly oxides and sulphides. The sulfide inclusions will cause thermal brittleness to the steel, and have a certain plasticity, which is shaped by the main deformation direction of the metal after forging. The transverse and tangential performance of forgings is reduced, and the anisotropy of forgings is increased.
Second, Alkaline electric furnace method: Alkaline electric furnace steelmaking, because the use of high-temperature arc heating, smelting process in the furnace gas can be controlled. When smelting with the double slag oxidation process, after the melting period, there is an iron ore to make the molten pool oxidation boiling oxidation period. When smelting with the return method, the oxidation period of the ore is not added in order to prevent the alloying elements from burning in the molten steel. After melting, you can go directly to the restoration period.
Third, acidic open hearth method: Furnace bottom and slope with acidic refractories such as silica brick, quartz sand masonry, such as the open hearth known as acidic open hearth.
The smelting of forgings is operated with acidic slag. Has the following characteristics: Smelting can not remove sulfur, phosphorus. Therefore, it must be selected in the finished steel containing sulfur, the amount of phosphorus is lower than the required raw materials, which will make the cost of steel increase; the molten steel is automatically deoxidation due to the reduction of silicon in smelting, so the end of refining can be deoxidation with Ferrosilicon, Ferromanganese and aluminum, and the resulting deoxidation products are few. Therefore, there are few non-metallic inclusions in acidic open hearth steel, and the purity of molten steel is high.