In the solidification process of sand casting, due to the solidification shrinkage of sand casting itself and the expansion of metal mold, the boundary of metal mold will be formed between sand casting and metal mold, and the contact between them is basically incomplete, and the contact situation will change constantly It has something to do with temperature.
Due to the shrinkage of the metal, a gap will be formed between it and the metal mold. Therefore, the heat transfer between sand castings and molds is a very complex phenomenon. The heat transfer between them includes the contact heat conduction of metal mold interface, the heat conduction of gas in the gap between metal and mold, and the heat radiation between surfaces. In the numerical simulation of solidification process, this heat transfer condition is mainly treated by introducing the metal mold interface heat transfer coefficient. The expression of the boundary condition is:
Where: λ1 is the thermal conductivity of sand casting material, W1 and W2 represent sand casting and mold surface respectively, TW1 and TW2 represent sand casting and mold surface temperature respectively.
The heat transfer coefficient of metal mold interface can be accurately solved by inverse heat conduction algorithm. In general, hi can be processed by empirical values or assuming a certain distribution function.
The simplest treatment is to assume that the metal mold interface is in an ideal contact state, and the expression of its boundary condition is:
Where, λ2 is the thermal conductivity of the mold material.