Technological characteristics of stainless steel precision casting
The mechanical property of stainless steel precision casting is higher than that of cast iron, but its casting property is worse than that of cast iron. Because of the high melting point of stainless steel precision casting, the steel liquid is easy to oxidize, molten steel flow is poor, the shrinkage is big, its body shrinkage rate is 10 ~ 14%, the line shrinkage is 1.8 ~ 2.5%. In order to prevent the casting defects such as casting defects, cold insulation, shrinkage cavity, shrinkage porosity, crack and sand sticking, etc., the complex technological measures of cast iron must be taken:
1, due to the contraction of the stainless steel precision casting greatly more than cast iron, in order to prevent casting defects of shrinkage cavity and porosity, in the casting process, most of the riser and chill and subsidies measures, in order to realize the solidification sequence.
2, due to poor mobility of the liquid steel, in order to prevent steel casting cold insulation and misrun, casting wall thickness can not less than 8mm; gating system structure strive to is simple and section size than cast iron. The dry cast or hot mould; proper increase of pouring temperature, generally 15-20 DEG to 1600 DEG C, because of the high pouring temperature, molten steel overheating degree and keep the liquid for a long time, the flow can be improved. But the high temperature, can cause the grain coarse, hot cracking, porosity and sand and other defects. Therefore, the general small, thin wall and complex shape of the casting, the casting temperature is about the melting point of the steel temperature +150 degrees Celsius, large, thick wall castings pouring temperature than the melting point of about 100.
In addition, in order to prevent the shrinkage hole, shrinkage porosity, pore and crack, should make the wall thickness uniform, avoid sharp corners and a right angle structure, in the mould with sand and sawdust, in the core and coke, and the empty heart core and oil core to improve the sand mold or core of concession and permeability caused by stainless steel castings.