The quality of molten iron metallurgy is the decisive factor for improving the performance of cast iron parts. The main influencing factors are molten iron composition, alloying elements, eutectic graphitization and inoculation treatment.
1. Carbon equivalent: Carbon and silicon are strong graphitization elements, carbon and silicon content increase, graphitization degree increases, and the amount of graphite increases. However, if the carbon equivalent is too high, ferrite is liable to appear, the wear resistance is lowered, or the graphite is coarse and the graphite floats, resulting in a decrease in the mechanical properties of the casting; the carbon equivalent is too low and the supercooled graphite is easily formed, thereby reducing the wear resistance. The influence of silicon on the wear resistance of cast iron is mainly determined by its graphitization. Generally, it is more suitable to choose CE=3.6-3.8.
2. Mn: enables cast iron to have a fine grain structure and to refine graphite. There is also the role of stabilizing pearlite. When the manganese content is too high, the amount of cementite will increase and the Leysite will be formed. The manganese content is generally controlled at 0.8%-1.0%.
3.P: It has certain promotion of graphitization, which can improve hardness and improve wear resistance. It is helpful to obtain pearlite and refine the crystal grains, but the content is too high, and it is easy to make the P eutectic exceeding the standard, which is generally controlled at 0.15%-0.18%.
4.S: Element which is a harmful impurity to wear resistant castings S and strongly resists graphitization. However, the low S is not good for the inoculation effect, and the general control is preferably 0.03%-0.06%.
5. Ni, Cu: an element that promotes graphitization. Nickel also promotes pearlite sootization and has a good influence on wear resistance. Copper can strengthen pearlite and refine pearlite to improve wear resistance and corrosion resistance. However, high content will increase the cost of castings, generally controlled at Ni=0.2%-0.3%, Cu=0.2%-0.3%.
6.Cr: It can increase the stability of cementite, delay the graphitization process, and promote the formation of pearlite, so it can increase the wear resistance of castings. However, if the chromium content is too high, the casting will be white-mouthed, which will increase the hardness and brittleness and reduce the wear resistance. It should be strictly controlled within the range of 0.15%-0.20%.