Solution to blackening and deformation of precision castings
Under normal circumstances, the color of the finished precision castings is silver-white or silver-gray, but after a period of use, some castings will appear black, and the whole or part of the castings are processed products and designs. If the concept does not match, it will be deformed. What are the reasons and solutions for blackening and deformation?
Blackening causes and solutions:
1. Surface oxidation. During the production of precision castings, if there are substances such as mold release agents on the surface, it will continuously corrode the surface of the castings, resulting in blackening of the castings. Therefore, when the foundry workers complete the production, they should be cleaned as a whole to eliminate the external factors of oxidation of the castings.
2. Improper process operation. During the production of precision castings, the metal content is not properly matched, and the alloy composition does not meet the standard, which will lead to the hidden danger of oxidation of the castings. At the same time, insufficient compaction during die casting will also lead to the existence of capillary pores in the casting. Oxidative blackening of these pores also occurs after water absorption. Therefore, foundries should strictly control the ratio of metal chemical components, and control the speed and strength of die casting.
3. Artificial factors. When casting workers are producing, if there are water stains on their hands, they will leave the water stains on the surface of the casting when they touch the casting, which will accelerate the oxidation of the casting. To avoid this, foundry workers should wear gloves and keep their hands dry during production.
4. Poor storage environment. If precision castings are stored in a dark place, a humid environment is more prone to the production of oxidizing substances. Therefore, the storage environment of castings should be as ventilated as possible, and moisture-proof agents should be placed in the casting packaging if necessary.
Reasons for casting deformation:
1. The design concept of castings is not very sophisticated, caused by uneven shrinkage.
2. The mold temperature is high, but the hardness is insufficient, and the cooling time is not very long.
3. The design concept of the mold shell is not very reasonable.
4. There is a mucous membrane on the casting product.
5. The temperature difference between different parts of the cavity is relatively large, and the cooling operation is not very uniform.
Solution to casting deformation:
1. It can improve the structure of the casting, so that the thickness of the inner wall of the mold shell can be appropriately increased.
2. Increase the cooling time and reduce the temperature of the mold shell.
3. The parts of the mold shell can be adjusted appropriately, and the top should be balanced.
4. To remove the casting mucosa.
5. The temperature of the casting should be properly controlled to ensure that the overall temperature in the cavity reaches a balance.