Heat is usually transmitted from one part to another through heat conduction, convection and radiation. In the process of sand casting, solidification refers to the transformation of high-temperature liquid metal from liquid phase to solid phase. In this process, the heat contained in the high-temperature liquid metal must be transferred to the sand casting mold and the surrounding environment through various ways, and gradually cooled until solidification. The heat transfer in this process includes: heat conduction inside the metal and sand casting mold, radiation heat transfer and convection heat transfer between the metal and the atmosphere.
Heat conduction is also called heat conduction. Heat conduction phenomenon is the process of heat transfer when each particle of an object or each object with different temperature is in direct contact. Convective heat transfer refers to the heat transfer process of fluid (liquid or gas) in motion. In this process, heat transfer is the result of convection and heat conduction. The most practical significance in engineering is the heat exchange process between the relatively moving fluid and the contacted solid wall, which is generally called convective heat transfer. Radiation is a phenomenon that electromagnetic waves transmit energy. The energy carried by radio waves is called radiant energy. Electromagnetic radiation caused by heat is called thermal radiation.
For sand mold casting, when simulating the temperature field, the energy exchange mode is mainly conducted by heat conduction. Considering the effect, the other two can be ignored. For the case of open riser in sand mold casting, thermal insulation sand is placed on the open riser, which greatly reduces the efficiency of radiation heat transfer, so it can be considered as heat conduction.
For the heat conduction problem of three-dimensional process, the overall basis is Fourier heat conduction equation. The general form of heat conduction differential equation derived from Fourier heat conduction law and energy conservation law is:
Where ρ— Is density; c – specific heat capacity; t – time; T – temperature; Q – heat source; λ— Thermal conductivity