Defects of cast aluminium parts
Cast aluminium is a process that uses molten aluminum to be poured into a mold and cooled to form a desired aluminum component. The castings obtained from cast aluminium are called cast aluminium parts.
The casting in casting forming process, prone to internal porosity, shrinkage, porosity and other defects, these defective castings in machined parts, the surface dense layer was removed and the organization internal defects exposed.
A representation of defects:
1. casting cracks: a crack formed at a higher temperature. It is easy to appear when the volume shrinkage of castings is larger and the thermal expansion coefficient is larger.
2. heat treatment crack: as a result of heat treatment, overheating or overheating caused by often transgranular cracks.
Causes of cracks:
1., the casting structure design is unreasonable, there are sharp corners, wall thickness change is too wide. If cracks occur in this case, the structural design of the casting shall be improved to avoid sharp corners, and the wall thickness shall be uniform and smooth.
2., sand (core) poor yield will also produce cracks. Measures to increase the yield of sand mould (core) shall be taken.
3. the local overheating of the mold will lead to cracks, should ensure that the casting parts at the same time solidified or sequentially solidified, improve the design of the gating system.
4., pouring temperature is too high will also produce cracks, should be appropriate to reduce the pouring temperature.
5. when the casting is removed from the mold, the die cooling time should be controlled by the heat check method when the casting deformation is premature
6. heat treatment overheating, excessive cooling rate cracks, casting deformation when the use of heat correction method. Correctly control the heat treatment temperature and reduce the quenching cooling speed.