Process Characteristics Of Precision Casting

Stainless steel precision casting is full of mold capabilities. For thin and complex castings, high fluidity is required, otherwise, the entire mold cannot be filled. The casting becomes a waste product. The precise fluidity of stainless steel is mainly related to its chemical composition and pouring temperature. For example, alloys with eutectic components or close to eutectic components, as well as alloys with a narrow product temperature range, have good fluidity; phosphorus in cast iron can improve fluidity, while sulfur makes fluidity worse. Increasing pouring temperature can improve fluidity.

Since the shrinkage of stainless steel precision casting greatly exceeds that of cast iron, in order to prevent shrinkage cavities and shrinkage defects in castings, most of the casting processes adopt measures such as risers, cold iron, and subsidies to achieve sequential solidification.

In order to prevent the occurrence of shrinkage cavities, shrinkage porosity, pores and cracks in stainless steel castings, the wall thickness should be uniform, sharp corners and right-angle structures should be avoided, sawdust is added to the casting sand, coke is added to the core, and hollow type Cores and oil sand cores to improve the retreatability and air permeability of sand molds or cores.

Due to the poor fluidity of molten steel, in order to prevent cold barriers and insufficient pouring of steel castings, the wall thickness of steel castings should not be less than 8mm; use dry casting or hot casting; appropriately increase the pouring temperature, generally 1520°~1600°C , Because the pouring temperature is high, the molten steel has a high degree of overheating, and it stays liquid for a long time, and the fluidity can be improved. However, if the pouring temperature is too high, it will cause defects such as coarse grains, hot cracks, pores and sand sticking. Therefore, in general small, thin-walled and complex-shaped precision castings, the pouring temperature is about the melting point temperature of steel + 150℃; the structure of the pouring system is simple and the section size is larger than that of cast iron; the pouring temperature of large and thick-walled castings It is about 100°C higher than its melting point.