Liquidity (fluidity,liquidity) refers to the ability of liquid alloys to fill the mould. The fluidity of the alloy liquid is good, easy to pour the full cavity, obtains the contour clear, the dimensional complete castings, the opposite alloy fluidity is not good, then is prone to produce the shortage of pouring, cold insulation, porosity and slag. In the commonly used alloys, the fluidity of gray cast iron, silicon brass is the best, and the steel casting is the worst fluidity. There are many factors influencing liquidity, which is mainly the chemical composition, pouring temperature and filling conditions of the mould. Shrinkage: the decreasing volume and size of liquid alloys during cooling and solidification is called shrinkage (contraction,shrinkage). Shrinkage is the physical properties of cast alloys, which are the basic reasons for many defects in castings (shrinkage cavity, shrinkage, internal stress, deformation and cracks). The alloy liquid cools from the pouring cavity to the room temperature to undergo three phases: 1. Liquid contraction (liquidcontraction): The shrinkage of the temperature of the liquid phase from the pouring temperature to the start crystallization. 2. Solidification Shrinkage (solidificationcontraction): From the beginning of the crystallization temperature cooling to the crystallization of the solid line temperature contraction. 3. Solid-State contraction (solidcontraction): From the crystallization of the temperature cooled to the contraction between room temperature.