What is gravity casting?
Answer: Gravity casting, in simple terms, can also be called gravity casting, which uses gravity to inject molten metal into a mold to form a casting. In a broad sense, sand casting, metal casting, investment casting, lost foam casting, etc. are all gravity casting, while the narrow definition refers to metal casting, which is different from non-ferrous casting as the two are not the same.
After understanding the definition of gravity casting, let's now explain the defects of aluminum alloy gravity casting.
Defect 1: Shrinkage
1. Causes
(1) During the crystallization process, the shrinkage of the casting is insufficient.
(2) The position of introducing the alloy liquid is incorrect.
(3) The temperature of each part is inappropriate, which violates the principle of solidification.
(4) The paint has peeled off.
(5) The pouring temperature is too high or the speed is too fast.
(6) The cooling speed of the casting is too slow, or the casting has burrs.
2. Preventive measures
(1) For parts of the casting that are relatively thick, a riser should be installed with a reasonable height.
(2) Pour evenly or supplement pouring.
(3) Choose the appropriate coating according to the actual situation, and if it falls off, it should be evenly replenished.
(4) Reduce the pouring temperature and slow down the pouring speed appropriately.
Defect 2: Cracks
1. Causes
(1) There are sharp corners and uneven thickness on the castings, sometimes with significant differences.
(2) The local temperature of the mold is too high, or the pouring temperature is too high.
(3) The cold iron is not placed correctly.
2. Preventive measures
(1) Remove sharp corners from the casting and ensure even transition of the casting wall thickness.
(2) The position of the sprue and runner should be selected correctly, and the pouring temperature should be controlled well.
(3) Cold iron should be placed correctly to increase the feeding capacity of the riser.