The heat transfer coefficient model of squeeze casting interface is not affected by various experimental conditions theoretically. However, in the part of micro heat transfer analysis, the coefficient function is difficult to be obtained by theoretical analysis, and can only be obtained by fitting the experimental data. The relationship between the interface heat transfer coefficient and the interface spacing is bound to be affected by the experimental conditions. Therefore, a large number of squeeze casting experiments can be carried out to obtain the experimental data under various working conditions, and then through the fitting coefficient function φ (d) The relationship between the interface heat transfer coefficient and the interface spacing under different working conditions can be obtained. By averaging the relationship between the interface heat transfer coefficient and the interface spacing under different working conditions, the relationship between the interface heat transfer coefficient and the interface spacing required by the squeeze casting interface heat transfer coefficient model can be obtained, and its error range can also be obtained.

It can be seen from the research that the pouring temperature has little effect on the interface heat transfer after the external pressure is applied in the squeeze casting process. Therefore, the influence of pouring temperature on the relationship between the interface heat transfer coefficient, the interface pressure and the interface temperature is not considered in this chapter.

It can be seen from the research that the initial temperature of the die has a great influence on the interface heat transfer after the external pressure is applied in the squeeze casting process. With the increase of the initial temperature of the die, the peak value and average value of the interface heat transfer coefficient after the pressure is applied increase, and the peak value and action time of the pressure also increase significantly. In squeeze casting process, the initial temperature of die is usually about 250 ℃. Too low initial temperature of the mold will make the high-temperature metal melt be cooled, and a hard solidified shell will be formed soon. Due to the deformation resistance of the solidified shell, it is difficult for the casting to compensate the volume shrinkage caused by solidification shrinkage by plastic deformation under the action of external pressure, which leads to shrinkage defects in the casting. The high initial temperature of the mold slows down the solidification of the high temperature melt, and the high temperature melt is easy to enter the mold gap under the action of external pressure, which leads to the difficulty of casting demoulding. Therefore, it is necessary to set the appropriate initial temperature of the mold. In the experiment of squeeze casting in this chapter, under the premise of ensuring the casting quality and avoiding the difficulty of demoulding, the minimum initial temperature of the die is 190 ℃ and the maximum is 300 ℃. Therefore, based on the experimental data under three working conditions of mold initial temperature of 190 ℃, 250 ℃ and 300 ℃, the parameters of coefficient function (d) and coefficient function (d) are fitted respectively, and then the relationship between interface heat transfer coefficient and interface spacing under various working conditions is established, as shown in Figure 1. The relationship between the interface heat transfer coefficient and the interface spacing under different working conditions is averaged, and the relationship between the interface heat transfer coefficient and the interface spacing required by the squeeze casting interface heat transfer coefficient model as shown in Fig. 2 is obtained, and the maximum error is 8.7%.

With the relationship between the interfacial heat transfer coefficient and the interfacial spacing determined, the quantitative relationship between the interfacial heat transfer coefficient and the interfacial pressure and temperature can also be established. When the interface pressure and temperature are known, the interface spacing can be calculated, and then the corresponding interface heat transfer coefficient can be obtained according to the determined interface spacing. In this paper, the pressure of squeeze casting die interface can be obtained by Kistler pressure sensor, and the interface temperature can be obtained by inverse algorithm. Therefore, based on the above model, the interfacial heat transfer coefficient can be calculated. The calculated and experimental interface heat transfer coefficients are shown in Fig. 3, and they are in good agreement, which means that the model can calculate the interface heat transfer coefficient well.

In addition, the error of the interface heat transfer coefficient obtained by experiment and calculation is large at the peak value, which is due to the great impact at the moment when the applied pressure is applied, resulting in the large error of the interface heat transfer coefficient. However, the peak value of the interface heat transfer coefficient is only a transient value, which only describes the instantaneous heat transfer intensity at the interface and has little effect on the overall heat transfer.