Aluminum Gravity Casting Process and Characteristics
Aluminum Gravity Casting Process
Aluminum gravity casting refers to the process of injecting aluminum liquid into a mold under the action of gravity, and gravity casting is divided into: sand casting, metal mold (steel mold) casting, and lost foam casting, etc.
Nowadays, steel mold casting is widely used in aluminum gravity casting. The mold of aluminum gravity casting is made of heat-resistant alloy steel. The strength, size, appearance, and other properties of the cast aluminum parts are higher than those of other casting processes.
The aluminum liquid for gravity casting is generally manually poured into the pouring port, relying on the weight of the metal liquid to fill the mold cavity, exhaust, cool, and then open the mold to obtain the sample. The process flow generally includes: aluminum liquid melting, casting filling, venting, cooling, demolding, cleaning, heat treatment, and processing.
Characteristics of Aluminum gravity casting Parts
The surface finish of the product is not high, and it is easy to produce pits after shot blasting.
There are few internal pores in the aluminum castings, which can be subjected to heat treatment.
The product has low density, slightly lower strength, but higher elongation.
The mold cost is relatively low and the mold life is long.
The production efficiency is low, thus increasing production costs.
The process is relatively simple and not suitable for producing thin-walled parts.
What should be paid attention to when using gravity casting?
The issues that need attention when using gravity casting include:
The aluminum alloy raw materials must be stirred evenly after melting. They cannot be in lumps.
Filter impurities in the raw materials.
The pouring temperature and cooling temperature should be appropriate.
The coating should also be uniform. Uneven coating can increase the wall thickness of the casting, causing inaccurate dimensions. A uniform coating can reduce the wall thickness, and cracks are less likely to occur in the product.
Evaluation of Gravity Casting
Gravity casting often uses its immersion testing and coloring testing. It wets or sprays colored liquid with high penetration ability on the surface of the casting, the penetrant enters the opening defect, quickly wipes the affected liquid layer on the surface, sprays an image-forming agent on the surface of the casting that is easy to dry, and after the residual penetrant in the opening defect is sucked out, the image-forming agent is colored, which can reflect The shape, size, and distribution of defects.
If there are defects on the surface of the casting, the electrical characteristics of eddy currents will be distorted, and the existence of defects can be detected. The main disadvantage of eddy current testing is that it cannot display the size and shape of the detected defects intuitively. It can only determine the surface orientation and depth of the defects. In addition, its sensitivity to small open defects on the surface of the workpiece is not as good as the immersion testing.