The main factors affecting the mechanical properties of gray cast iron

Process, metallurgical factors: the main cooling rate, liquid iron overheating treatment, inoculation treatment, charge characteristics, etc. (1) On the effect of cooling rate Cast iron is a kind of material sensitive to cooling rate, the same casting thick wall and thin wall part, internal and external may obtain a wide difference in organization, commonly known as the organization of non-uniformity. Because the graphitization process depends largely on the rate of cooling. There are many factors that affect the cooling speed of castings: wall thickness and weight of castings, type of casting materials, pouring and weight, and so on. Since the wall thickness, weight and structure of the castings depend on the working conditions and cannot be changed at will, their effects on the organization should be taken into account when selecting the chemical composition. (2) The effect of inoculation treatment on liquid iron inoculation treatment is to add inoculant to liquid iron before the liquid iron enters the mold cavity to change the metallurgical state of the liquid iron, so as to improve the microstructure and properties of cast iron. For gray cast iron, inoculation treatment is to obtain A-type graphite, pearlite matrix, fine eutectic group structure, and reduce the tendency of white hole in the thin wall or corner of the casting and the sensitivity to the casting wall thickness. For malleable cast iron, it is to shorten the short annealing period, increase the allowable wall thickness of the casting and improve the structure of the structure. For nodular cast iron, it is to reduce the white casting tendency, improve the nodulation rate and improve the roundness of graphite. (3) The effect of superheat treatment on liquid iron. Increasing the superheat temperature of liquid iron can: (1) increase the combined carbon content and correspondingly reduce the carbon content of graphite (2) refine the graphite, and make the formation of dendrite ink (3) eliminate the "heritability" of cast iron (4) improve the uniformity of the structure on the section of casting (5) is conducive to the feeding of casting. Similarly, liquid iron insulation also has a similar effect of liquid iron overheating.

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