Formation process and analysis method of thermal stress in sand casting

During the solidification and cooling process of sand castings, the shrinkage capacity of each part is different due to the different cooling speed of each part of the sand castings, and the uneven cooling also leads to the uneven temperature distribution in the sand castings at the same time, which leads to the different material characteristic parameters in the sand castings, which leads to the thermal stress in the sand castings.

Thermal stress analysis is to use numerical simulation method to calculate the change of thermal stress of sand castings during solidification, so as to predict the possible residual stress and residual deformation in sand castings. Through the analysis of the simulation results, the internal structure or sand casting process of sand casting can be optimized to eliminate hot cracks and reduce the defects of sand casting. The numerical simulation of thermal stress field covers the plasticity and creep with temperature and stress, the interaction between casting molds, fluid flow and hot crack generation.

On the one hand, the generation of thermal stress in the solidification process of sand castings is related to the cooling process. On the other hand, the deformation of the casting / mold boundary will change the heat transfer state of the boundary and affect the heat transfer, while the thermal effect caused by the deformation caused by stress and strain can generally be ignored. Most of the previous research work only considered the influence of heat transfer on thermal stress of sand castings, but did not consider the influence of thermal stress on heat transfer. Thermal analysis and stress analysis were treated separately. In recent years, with the deepening of research, many researchers at home and abroad began to consider the influence of air gap between sand castings and molds due to deformation on heat transfer process.