Common five kinds of metal casting defects preventive measures

There are five common defects and prevention methods for metal castings:

1, pinhole

Measures to prevent pinholes: It is strictly forbidden to use contaminated cast aluminum alloy materials, organic compounds and materials that are severely oxidized and corroded. Control the smelting process and strengthen the degassing refining. Control the thickness of the metal coating, too thick and easy to produce pinholes. The mold temperature should not be too high, and chilling measures such as copper block or watering should be applied to the thick part of the casting. Strictly control the moisture when using the sand type, and use the dry core as much as possible.

2, stomata

Measures to prevent the generation of stomata: Modify the unreasonable pouring riser system to make the flow smooth and avoid gas entrapment. The mold and core should be preheated beforehand, and then applied to the coating. After the end, it must be dried before use. Designing molds and cores should consider adequate exhaust measures.

3. Oxidation slag

Measures to prevent oxidation slag: strictly control the smelting process, rapid smelting, reduce oxidation, and thoroughly remove slag. The Al-Mg alloy must be smelted under a covering agent. Furnace and tools should be cleaned, no oxides, and should be preheated. The paint should be dried after application. The designed gating system must have steady flow, cushioning, and slag removal capabilities. The inclined casting system is used to stabilize the liquid flow without secondary oxidation. The selected coating has strong adhesion, and does not peel off during the casting process and enters the casting to form slag inclusions.

4, hot cracking

Measures to prevent hot cracking: Local overheating should be avoided and internal stress should be reduced when actually pouring the system. The mold and core slope must be guaranteed to be above 2°. Once the pouring riser is solidified, the core can be opened and the core can be replaced by a sand core if necessary. Control the thickness of the coating so that the cooling rate of each part of the casting is consistent. Select the appropriate mold temperature according to the thickness of the casting. Refine the alloy structure and improve the thermal cracking ability. Improve the structure of the casting, eliminate sudden changes in corners and wall thickness, and reduce the tendency of hot cracking.

5, loose

Measures to prevent loosening: Reasonable riser setting to ensure its solidification and ability to supplement. Appropriately reduce the working temperature of the metal mold. Control the thickness of the coating and reduce the thickness at the thick wall. Adjust the cooling speed of each part of the metal type to make the casting wall have a large chilling capacity. Properly reduce the metal casting temperature.

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Label: Common five metal casting defects preventive measures

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