Overview of solidification characteristics of lost foam casting

In the process of lost foam casting molding, solidification is the process of metal liquid gradually cooling from liquid phase to solid phase. There are three different heat transfer modes in nature (heat conduction, heat convection and heat radiation), which are reflected in the heat transfer in the solidification process. The biggest characteristic of lost foam casting solidification is that the metal liquid needs to transfer heat with the outside world through the coating layer during solidification, and the solidification speed is slow, which makes the casting grains produced by lost foam casting generally coarse. There are many reasons for the slow solidification process in lost foam casting process:

(1) The dry sand in the sand mold does not contain water, and the heat taken away by the gasification of water in the mold is less;

(2) On the other hand, it makes the sand filling process more stable, which has an impact on the heat transfer of the sand filling process;

(3) The properties of the refractory coating are also different from the traditional cavity gravity casting. The refractory coating hinders the outward diffusion of heat in the cavity.

The fast and slow solidification of lost foam casting products directly affects the microstructure and properties of castings. Therefore, the control of the solidification process of lost foam castings can effectively control the internal quality of products. The heat transfer in the cooling and solidification process of lost foam castings is modeled, and the heat transfer equation is solved to obtain the law of cooling and solidification, and effectively predict the possible defects of lost foam castings.