Pig iron is a kind of iron carbon alloy with more than 2.11% carbon content. The carbon content of industrial pig iron is generally 2.11% - 4.3%, and contains C, Si, Mn, s, P and other elements. It is a product smelted by iron ore in blast furnace. According to the different forms of carbon in pig iron, it can be divided into steelmaking pig iron and casting pig iron.
Pig iron performance: pig iron is hard, wear-resistant and good castability, but pig iron is brittle and cannot be forged.
Besides iron, pig iron also contains carbon, silicon, manganese, phosphorus and sulfur. These elements have certain influence on the properties of pig iron.
Carbon (c): it exists in pig iron in two forms, one is free carbon (graphite), which mainly exists in cast pig iron, the other is combined carbon (iron carbide), which mainly exists in steel-making pig iron. Iron carbide is hard and brittle with low plasticity. Appropriate content can improve the strength and hardness of pig iron. Excessive content makes it difficult to cut pig iron, This is the reason of poor machinability of steel-making pig iron. Graphite is very soft and has low strength. Its existence can increase the castability of pig iron.
Silicon (SI): can promote the carbon contained in pig iron to separate into graphite, can deoxidize, can reduce the gas hole of casting, can improve the fluidity of molten pig iron, reduce the shrinkage of casting, but too much silicon will also make pig iron hard and brittle.
Manganese (MN): soluble in ferrite and cementite. When making pig iron in blast furnace, appropriate manganese content can improve the castability and cutting performance of pig iron. In blast furnace, manganese can also form manganese sulfide with harmful impurity sulfur and enter slag.
Phosphorus (P): it is a harmful element, but phosphorus can increase the fluidity of molten iron. This is because phosphorus reduces the melting point of pig iron, so it is often higher in some products. However, the presence of phosphorus increases the hardness and brittleness of iron. The phosphorus content of fine pig iron should be less. Sometimes, in order to increase the fluidity, the phosphorus content can reach 1.2%.
Sulfur (s): it is a harmful element in pig iron. It promotes the combination of iron and carbon, makes iron hard and brittle, and combines with iron to form low melting point iron sulfide, which makes pig iron hot brittle and reduces the fluidity of molten iron. Therefore, pig iron with high sulfur content is not suitable for casting fine parts. The sulphur content in cast pig iron shall not exceed 0.06% at most (except wheel pig iron).
(1) The higher the carbon content is, the higher the graphite precipitates. Silicon is an element that strongly promotes graphitization, and has strong binding force with iron atoms. Carbon exists in the form of graphite. The adjustment of carbon and silicon content can change the internal metal structure of metal casting. The strength and hardness of cast phosphorus cast iron ring should be moderate.
(2) As the name suggests, phosphorus is the key element in the anode assembly pouring of phosphorus pig iron. Because the anode assembly pouring adopts intermittent mode, the fluidity of molten iron is required to be better. The existence of phosphorus can reduce the viscosity of molten iron. The melting point temperature of crystal formed by the combination of phosphorus and iron is 1050 ℃, which can obviously improve the fluidity of molten iron, with high hardness and strong brittleness, Fragile, etc. Excessive phosphorus content can lead to the increase of cold brittleness of phosphorus cast iron ring, crack of cast iron ring, and even falling off. Therefore, the suitable content of phosphorus in pig iron should be controlled in the range of 0.6-1.5%.303 440c stainless steel sheets
(3) Sulfur: sulfur is recognized as a harmful element, and also exists in metal substances. Because sulfur is infinitely dissolved in molten iron, but it is very small in solid iron, when sulfur-containing molten iron condenses, iron sulfide will be formed. This kind of low melting point crystal, namely iron rust, will gather among the grains, causing cracks and fracture of cast iron, At the same time, the existence of sulfur also hinders the graphitization process and increases the shrinkage of the iron ring.china wholesale length 304 stainless steel pipe
(4) Manganese: in phosphorus pig iron, the sulfur element dissolved in molten iron forms manganese sulfide MNS. The solubility of manganese sulfide MNS is lower than that of iron sulfide FES in molten iron, which ensures the transfer of sulfur to non molten material (slag). According to thermodynamic analysis, the chemical affinity between manganese Mn and sulfur s is far greater than that between iron Fe and sulfur s (for example, It is known that the rust on the surface of pig iron is more obvious than that on the surface of ferromanganese, but the sulfur content in pig iron is not necessarily higher than that in iron, At the same time, manganese can form stable westernized pearlite in the chemical composition range of phosphorus pig iron, which can make the strength and hardness of phosphorus pig iron ring moderate.
(5) The change of elements in the process of using phosphorus pig iron and phosphorus pig iron ring.
The burning loss of each element of phosphorus pig iron and phosphorus pig iron ring is different at the high temperature of 1300 ° C. the burning loss of carbon and silicon is generally 0.4-0.7%, and that of phosphorus and manganese is generally 0.1-0.3%. The change of sulfur is uncertain. If the sulfur removal method is controlled, the sulfur can be controlled in the range, otherwise it will play the opposite role, and the sulfur rise standard will exceed the limit, which will cause adverse factors.DIN1028 V Shaped Angle Steels Bar Line Structural