Gravity casting of aluminum alloy sometimes causes shrinkage, what’s the matter? How to avoid shrinkage?

Gravity casting refers to the process of introducing metal material liquid into metal mold casting under the force of the earth, which is also called metal casting. The equipment used for gravity foundry is called a gravity casting machine. Theoretical gravity casting includes sand gravity casting, metal material gravity casting, investment casting, lost foam casting, mud mold casting, etc. The key to narrow gravity casting refers to metal material gravity foundry.

Aluminum alloy has a low melting point and good casting characteristics. Gravity casting and low-pressure casting products are used in many fields such as small cars, motorcycles, electric motors, communications, and power tool accessories; very large-wall products are widely used. It can also prevent the re-production and processing of porosity as soon as possible. After T6 quenching and tempering treatment, the sealing performance reaches about 50kg/cm2.

Reasons and prevention methods of shrinkage cavity during gravity casting of the gravity casting machine

Shortcomings such as shrinkage are often produced in the thick part of the casting, or at the junction of thin and thick parts. Sometimes the surface of the casting is white, which is actually a casting defect.

Cause:
1. Insufficient feeding of castings during the whole process of crystal;
2. The place where manganese molten steel is added is wrong;
3. The temperature at each position of the metal material type is not appropriate and does not meet the standard of sequential condensation;
4. Poor architectural paint or falling of architectural paint;
5. The pouring temperature is too high;
6. The pouring rate is too fast;
7. Water cooling of castings is very slow;
8. The broken edges of castings are large.

Avoid method:
1. Set the riser at the thick position of the casting. The size and aspect ratio of the riser should be suitable to achieve the final condensation and improve the feeding effect of the riser;
2. Jointly distribute the inner runners around the castings, or set up filling runners from the root of the riser to carry out filling pouring;
3. Adjust the temperature standard of each part of the metal material type, which is beneficial to the sequential condensation of castings;
4. According to the different parts of the casting work and the position of the pouring riser, different architectural coating components and thickness of the architectural coating should be used, and the stripping should be evenly compensated;
5. Moderately reduce pouring temperature;
6. Slow down the pouring rate;
7. In places where casting defects are very easy to cause, insert copper chilled iron or ventilation plugs to speed up water cooling.

Delin Machinery specializes in the production of the automatic casting machine. It is a machinery manufacturing enterprise integrating scientific research, design, manufacturing, installation, debugging and consulting services.

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