It can be seen from the characteristics of squeeze casting that the temperature distribution and stress distribution inside the casting are not independent of each other, but there is a complex coupling relationship in the solidification process of squeeze casting. On the one hand, because of the cooling of the casting, the metal not only has phase transformation, but also has cooling shrinkage. At the same time, because the mechanical properties of the metal are greatly affected by the change of temperature, the mechanical properties of the casting will also change greatly with the cooling of the casting, thus affecting the internal stress distribution of the casting; on the other hand, under the action of external force, the deformation and stress distribution of the casting will be reduced The change of temperature will directly affect the heat transfer at the interface between the casting and the die, and then affect the temperature distribution inside the casting. Therefore, the research on the law of pressure transfer and the heat transfer behavior of the casting die interface in the solidification process of squeeze casting is helpful to fully understand the thermal mechanical problems in the process of squeeze casting, to predict the defects related to shrinkage and gas, and to understand the influence of process parameters on the quality of castings.
Casting process simulation is an effective means to optimize process design, but the premise is that the simulation results are accurate and reliable, and one of the keys to obtain reliable simulation results is to correctly deal with the heat transfer boundary between the casting mold interface. For common casting processes such as sand mold, metal mold gravity casting and low pressure casting, computer simulation has entered the practical stage. However, due to metal solidification under pressure, the interaction mechanism between casting and die is complex (including mechanical and heat transfer), and there is still no effective model to deal with the heat transfer boundary between casting and die. Some researchers use the commonsimulation software and methods to simulate squeeze casting, without considering the influence of the contact pressure on the heat transfer. According to the known knowledge, the cooling rate of squeeze casting can reach 3-5 times of that of conventional metal mold casting due to the close fit between casting and die. Some researchers treat the interfacial heat transfer coefficient as a function of the process pressure (the process pressure refers to the pressure exerted on the casting by squeeze casting machine), which is related to but different from the contact pressure at the casting die interface. Some researchers try to associate the interfacial heat transfer coefficient with the interfacial pressure according to the characteristics of squeeze casting. Lee et al. And Zhu Wei et al. Have considered the characteristics of squeeze casting process. However, these models are based on experience. The relationship between the interfacial pressure and the interfacial heat transfer coefficient in these models is lack of experimental data support. Therefore, it is of great significance for the development of simulation of squeeze casting process to study the heat transfer behavior of casting die interface and establish a reliable model of heat transfer coefficient.
In fact, in the production cycle of a single part in squeeze casting, the heat transfer between casting and die is a complex and unsteady process. The heat transfer coefficient of the interface changes with time and is related to the contact pressure of different parts of the casting die interface. The contact pressure of the interface is affected by the internal pressure transfer law of the casting The internal pressure transfer law is very complex. Therefore, it is not only of great academic significance, but also of great application value to carry out in-depth research on the heat transfer and pressure transfer of squeeze casting die interface, to obtain a systematic understanding of the heat transfer mechanism of casting die interface and the internal pressure transfer law of castings, and to establish a quantitative model to describe the factors such as the heat transfer coefficient and the interface pressure.