There are significant differences in performance between metal mold and sand mold, for example, sand mold has air permeability, while metal mold does not; Sand mold has poor thermal conductivity and metal mold has good thermal conductivity. The sand mold gave in, but the metal mold didn't. These characteristics of metal mold determine that it has its own laws in the process of casting formation.

Influence of gas state change in cavity on casting forming: When metal is filled, the gas in the cavity must be discharged quickly, but the metal has no air permeability. As long as the process is slightly negligent, the quality of castings will be adversely affected.

The characteristics of heat exchange during solidification of castings: once the molten metal enters the cavity, it transfers heat to the metal mold wall. Liquid metal dissipates heat through the mold wall and solidifies and contracts, while the mold wall gains heat while expanding, and the temperature rises, resulting in a "gap" between the casting and the mold wall. Before the "casting-gap-metal mold" system reaches the same temperature, the casting can be regarded as cooling in the "gap" and the metal mold wall is heated through the "gap".

Influence of metal mold on casting shrinkage: The metal mold or metal core did not give in during casting solidification, which hindered casting shrinkage, which is another feature.