Due to the significant reduction in shrinkage for precision casting compared to cast iron, measures such as risers, chillers, and auxiliary methods are commonly employed in the casting process to effectively prevent defects like shrink holes and shrink porosity, thereby ensuring proper solidification sequence.
To effectively prevent defects such as shrinkage holes, shrinkage porosity, gas holes, and cracks in thick-walled steel pipes, it is essential to ensure uniform wall thickness and avoid sharp and right-angle structures. Add sawdust to the molding sand used in casting molds and coke in the mold cores. Opt for hollow mold cores and oil sand cores to effectively improve the permeability of the sand molds and mold cores.
Due to poor molten metal fluidity, to avoid cold segregation in thick-walled steel pipe castings, the wall thickness of cast steel parts should be ≥8mm. Dry casting and hot casting molds are chosen. Increase the pouring temperature within the appropriate time frame, usually between 1520°C to 1600°C. The higher pouring temperature results in greater superheat of the molten steel and extended liquid time, which improves fluidity. However, excessively high pouring temperatures can lead to coarse grain structure, hot cracks, blow holes, and sand adhesion in thick-walled steel pipes. Therefore, for small, thin-walled, and irregularly shaped precision castings, the pouring temperature is typically around the melting point temperature of steel +150°C.