The reason for the chemical composition of molten iron. It means that the chemical composition of the product exceeds the specified standard range, the conventional elements such as carbon and silicon are too low, and the comprehensive carbon equivalent is lower than the normal 0.25% (for example, the carbon content is less than 2.7%, and the primary silicon content is less than 0.25%). 1.4%, etc.); in addition, the manganese content is too high, and the manganese content is greater than 1.3%. The content of graphitization elements is low, and the content of anti-graphitization elements is high, resulting in low precipitation capacity of graphite, and a large amount of carburizing is formed during solidification and crystallization. body; thereby increasing the hardness of the casting.

The influence of molten iron smelting quality. During smelting, the air volume of the cupola is too large or too small, the hot air efficiency of the hot air cabinet is low, the tuyere is not smooth, the quality of coke is poor or the amount of coke added is too small, the lump of raw materials is too fine, and the oxidation is serious. It will cause the molten iron to have a low temperature and serious oxidation. It will cause a lot of burning of the alloying elements in the molten iron, the surface of the molten iron will be white, and the fluidity will be poor; the triangular test block is knocked out in front of the furnace, and the width of the white opening of the fracture is too large or even full white opening. During the composition test, due to the excessive burning of the elements, the carbon and silicon content is abnormally low; this molten iron is unqualified molten iron. If it is poured into a product, there will be defects such as high hardness, shrinkage cavities, and serious shrinkage porosity.

The reason for the heredity of raw materials. The heredity of cast iron means that when one metal charge is changed to another metal charge, although the chemical composition of molten iron remains unchanged, the organization of cast iron (such as graphite shape, degree of graphitization, white mouth tendency) etc.) will change; the relationship between the charge and the casting structure is called heredity. Here is to see whether the hardness of the pig iron, scrap steel, returned charge and alloy used in smelting is too large. Usually, under the condition of batching, qualified pig iron, scrap steel There will be no problem with alloys; it mainly depends on whether the returned material used has a large hardness defect.