The interface heat flux and die surface temperature of each time step can be calculated by inverse algorithm. In order to calculate the interfacial heat transfer coefficient, it is necessary to obtain the temperature distribution inside the casting. Since the casting is a plate type casting and symmetrical along the thickness direction, the central position of the casting is an adiabatic boundary condition, which can be expressed as follows:

Where, L2 is the distance from the center of the casting to the surface of the casting, i.e. the thickness of the half casting. Because there is a phase transformation process in the internal heat transfer of casting, the source term related to the latent heat of solidification process should be added to the heat transfer equation,

Where l is the latent heat of the casting and FS is the solid fraction of the casting. This can be done by

The solidification path of the alloy was calculated by thermocalc software.

Based on the interface heat flux and the surface temperature of die and casting, the heat transfer coefficient of squeeze casting die interface can be calculated by the formula.