Steel Casting Of The Technical Measures
Cast steel has higher mechanical properties than cast iron, Steel Casting but its casting performance is worse than cast iron. Because the melting point of cast steel is high, the molten steel is easy to oxidize, the flowability of molten steel is poor, the shrinkage is large, Steel Casting the shrinkage rate is 10% ~ 14% and the line shrinkage is 1.8% ~ 2.5% .To prevent the cast steel, Cold separation, shrinkage and shrinkage, cracks and sticky sand and other defects, must take more complex than the cast iron process measures:
1, due to the poor fluidity of molten steel, Steel Casting in order to prevent the cast steel produced cold and pouring, cast steel wall thickness can not be less than 8mm; pouring system structure is simple, and cross-sectional size than cast iron; Or hot mold; appropriate to improve the pouring temperature, generally 1520 ~ 1600 ℃, because the pouring temperature is high, the superheat of molten steel, to maintain a long liquid, liquidity can be improved. But the pouring temperature is too high, will cause coarse grain, Steel Casting hot cracking, pores and sticky sand and other defects. So the general small, thin-walled and complex shape of the casting, the pouring temperature is about the melting point of steel temperature + 150 ℃; large, thick castings casting temperature than its melting point of about 100 ℃ or so.
2, due to the shrinkage of cast steel much more than cast iron, in order to prevent castings shrinkage, shrink loose defects, in the casting process mostly use riser, Steel Casting cold iron and subsidies and other measures to achieve the order of solidification.
In addition, in order to prevent the steel castings from shrinkage, shrinkage, pores and cracks, the wall thickness should be uniform, to avoid sharp and right angle structure, in the molding sand with sawdust, in the core plus coke, and The use of hollow core and oil core, etc. Steel Casting to improve the sand or the core of the concession and permeability.
Cast steel has a high melting point and a corresponding pouring temperature is also high. High temperature molten steel and mold material interaction, easy to produce sticky sand defects. Therefore, Steel Casting the use of refractory high artificial quartz sand to do the mold, and in the casting surface brush by the quartz powder or zirconia powder made of paint. Steel Casting In order to reduce the gas source, improve the flow of molten steel and casting strength, most of the cast steel with dry or quick-drying type to cast, such as the use of CO2 hardened water glass sand.