After the pouring liquid metal, the shrinkage can be divided into three stages：
- liquid contraction since the pouring liquid metal into the shell to start before solidification is called liquid contraction. At this point, the metal is completely liquid metal reduced within a cavity volume shrinkage performance of the liquid surface. The higher the pouring temperature, the greater the liquid contraction. When the pouring temperature is constant, with the increase of carbon content in steel, solid liquidus temperature decreases and liquid shrinkage increases.
- the solidification shrinkage: from coagulation, beginning to end, namely by the liquidus temperature cooled to solidus temperature of metal by the volume of the liquid into a solid show contraction is called solidification shrinkage. For under a certain temperature crystallization of pure metal and crystal alloy, solidification shrinkage is only the change of the state, and has nothing to do with temperature. But the crystallization temperature range of alloy, its solidification shrinkage in addition to related to the state, also increases with the increase of the gap between crystallization.
- solid shrinkage: from after solidification to room temperature, the shrinkage under solid state.Before both contraction of volume reduction, and directly related to the formation of shrinkage cavity, its shrinkage is larger, the greater the volume of shrinkage cavity. Only after a contraction performance for casting outer profile dimension reduction, only with the precision of casting and the production of stress, deformation, cracks,