Steel Casting Process Measures
Cast steel has higher mechanical properties than cast iron, but its casting performance is worse than cast iron. Because the melting point of cast steel is higher, the molten steel is easy to oxidize, Steel Casting the flowability of molten steel is poor, the shrinkage is big, the shrinkage rate is 10 ~ 14%, and the line shrinkage is 1.8 ~ 2.5%. In order to prevent the cast steel produced insufficient pouring, Steel Casting 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, in order to prevent the cast steel produced cold and pouring, cast steel wall thickness can not be less than 8mm; Steel Casting pouring system structure is simple, and cross-sectional size than cast iron; Or hot cast; 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,Steel Casting will cause coarse grain, 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 higher than its melting point of about 100 ℃.
2, due to the shrinkage of cast steel much more than cast iron, Steel Casting in order to prevent castings shrinkage, shrink loose defects in the casting process mostly use riser, 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 mold with sand in the sawdust, in the core plus coke, and Using hollow core and oil core, etc. to improve the sand or the core of the concession and permeability.
(1) the melting point of cast steel is high, Steel Casting the corresponding pouring temperature is also high. High temperature molten steel and mold material interaction, easy to produce sticky sand defects. Therefore, 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. In order to reduce the gas source, Steel Casting 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 type.
Cast steel smelting generally use flat furnace, Steel Casting electric arc furnace and induction furnace. The furnace is characterized by large capacity, can use scrap as raw material, can accurately control the composition of steel and can melt high-quality steel and low alloy steel, Steel Casting used for smelting high quality, large steel castings with molten steel.
Three-phase electric arc furnace opening and shutdown operation is convenient, to ensure that the composition and quality of molten steel, the requirements of the furnace is not very strict, easy to heat up, Steel Casting it can refining high-quality steel, high-grade alloy steel and special steel, Common equipment for steel castings.