The casting crack is a kind of defect which is harmful. It destroys the continuity of the metal structure. It can not be pressed in the process of subsequent extrusion or calendering, and the aluminum casting will also produce the crack. It will seriously affect the production efficiency and economic benefit of the enterprise.

The essential reasons for the production of casting cracks are as follows: at the end of solidification, most of the aluminum castings have solidified into solid state, but their strength and plasticity are low. When the shrinkage of the aluminum castings is hindered by the mould, core and pouring system, the casting stress will be produced inside the aluminum castings, and the size of the casting stress exceeds the cast in the casting. The strength limit at this temperature is the generation of hot cracks. The cold crack is caused by the local casting stress which is greater than the ultimate strength of the alloy when it is cooled to the elastic state after solidification. It is concluded that the essential reason for the production of aluminum casting cracks is that the internal stress of the tissue and the external mechanical stress are too large, and the plastic deformation ability of the material is more than that of the material, which causes the discontinuity of the metal structure to crack.