Casting impeller is a key component of large equipment in shipbuilding, electric power, pharmaceutical, pump valve, transportation and other industries, and plays a pivotal role in the comprehensive performance of the entire equipment. At present, there are some difficulties in the casting process of complex integral impeller, so the research on the casting process of impeller has always been a hot topic in the casting industry.

The precision casting mechanical properties of stainless steel are higher than those of cast iron, but the casting properties of cast iron are not as good. Because the melting point of stainless steel precision casting is high, the fluidity of molten steel is poor, the liquid steel is easy to oxidize, and the shrinkage is large, the linear shrinkage is about 1.8 ~ 2.5%, and the shrinkage rate is about 10 ~ 14%. In order to prevent defects such as cold isolation, insufficient pouring, shrinkage, shrinkage and sand and cracks in steel castings, more complex process measures must be taken than that of cast iron:

The structure of the casting system of stainless steel precision casting is simple, and the cross-section size is larger than that of cast iron, generally using dry casting or hot casting. Due to the poor fluidity of liquid steel, in order to prevent cold insulation and insufficient pouring of cast steel, the wall thickness of cast steel can not be less than 8mm; Appropriately increase the pouring temperature, because the pouring temperature is high, the superheat of the molten steel is large, and the liquid state is maintained for a long time, and the fluidity can be improved. However, high pouring temperature will cause defects such as hot cracking, coarse grain, sticky sand and porosity. Therefore, the pouring temperature of large and thick wall castings is about 100℃ higher than the melting point. For thin-walled, small and complex castings, the pouring temperature is about the melting point temperature of steel +150℃.

Dalian Precision Foundry tells you that because the shrinkage rate of stainless steel precision casting is much larger than that of cast iron precision casting, in order to prevent the shrinkage and shrinkage defects of castings, most of the measures such as cold iron, riser and subsidy are used in the casting process to achieve sequential solidification. In addition, in order to prevent the shrinkage of stainless steel castings, shrinkage holes, cracks and porosity defects, it should be avoided to avoid sharp and right Angle structure, uniform wall thickness, coke in the core, sawdust in the mold sand, and the use of oil sand core and hollow core to improve the permeability and yield of the core or sand.