In view of the defects in the trial production of the original process castings, the existing parts of the castings were dissected and analyzed. The casting defects had smooth curved surface or obvious shrinkage porosity. The causes of the two casting defects were analyzed.
1. Shrinkage casting defects
There are thick and large hot spots in the middle of the upper and lower water cavities of the cylinder head casting. Due to the difficulty of arranging cold iron in the water cavity and the air channel core, the solidification cooling rate in the injector hole of the casting is slow, resulting in the coarse solidification structure of the casting, resulting in loose casting defects in the casting.
2. Blowhole casting defect
The blowhole in the top plane of the cylinder head casting is due to the particularity of the casting structure. The water cavity and the air channel core are completely wrapped by molten aluminum, which makes the local gas pressure of the water cavity and the sand core of the air inlet and exhaust channel exceed the pressure of the liquid metal. At the same time, because the traditional core making method is difficult to inhibit the gas discharge of the water cavity and the air channel core, the blowhole casting defects on the casting surface and the sub-surface are formed.