Normal defects on aluminum casting

Same as investment casting, there're casting defects during aluminum parts casting. Normally happened defects are pores, cracks, shrinkage, cold shuts, etc. 

1)Pores/porosities

Amont all casting defects, pores are the most defects during aluminum casting process. There're mainly five kinds of pores defects,such as Intrusive porosities, Wrapped with porosities, Precipitating porosities, Endogenous reaction porosities, Exogenous reaction porosities. These porosities defects can be avoided by modifying pouring systems.

2)Cracks

Cracks on aluminum castings are mainly caused by two factors. One is solidification mode of aluminum casting and the other is casting stress caused during casting process. Solidification temperature range of aluminum casting is big. 

Factors below caused the cracks defects during aluminum casting.

*Percentage of Fe is too high or Silicon(S) is too low.
*Percentage of impurities is too much, which reduced the plasticity of the alloys.
*For aluminum-silicon alloy, the high percentage of zinc or Cu is too high will caused the defects.
*For aluminum-magnesium alloy, the high percentage of Mg will caused the defects during casting.
*If the temperature of molds, especially the sand cores, is too low, cracks will be caused during aluminum casting.
*Wall thickness of the castings also affects, especially at the area where the wall thickness changed much.
*The mold saving time is too long. This will also cause the crack defects.
*Stress imbalance when push-out the products from molds will also cause crack defects on aluminum castings.

3)Shrinkages

Shrinkages caused the uneven and very rough surfaces.Shrinkages usually appear at final solidification position and places with hot tears. Castings made in aluminum alloys with wide range of crystallization temperature are with more such shrikakges defects.

4)Cold shuts

Cold shuts are crackle gaps with radius edges. Cold shuts defects are mostly caused by blocks of aluminum alloy fluid head. The best way to solve the cold shuts of aluminum castings is to raise the pouring temperature, mold temperature, modify the exhausting system and better the pouring system.

Besides the above casting defects, there might more defects of aluminum casting. We can discuss and talk more of them soon. If you have inquiries for aluminum castings, please contacting us. We can work together to solve all casting defects to control quality of castings.