The quality of aluminum alloy die castings includes appearance quality, inner quality, and use quality. Appearance quality refers to the surface roughness, surface quality, dimensional tolerance, shape tolerance, and quality deviation of the casting; inner quality refers to the chemical composition, physical and Mechanical properties, metallographic structure, and holes, inclusions, and cracks in the casting; service quality means that the casting can meet various service requirements and work performance, such as wear resistance, corrosion resistance, machinability, welding, etc. sex, etc.
During the operation of aluminum alloy die castings, most of them will be concentrated on the surface or inside, and pores and sand holes will appear in these two parts. Generally speaking, if the old-fashioned repair method is used, an electric welding machine is used. Repairing, this repairing method will make the hardness of the solder joints too high after welding, which will easily cause stress inside the aluminum alloy die-casting, and will easily cause deformation and cracks. After welding, annealing heat treatment is required to meet the requirements.
In addition, the primary oxide inclusions of aluminum alloy die castings can be divided into two types according to their shapes. One type is large inclusions with uneven distribution in the macrostructure. This type of inclusions makes the alloy structure discontinuous and reduces the atmosphere of the workpiece It becomes the source of corrosion, significantly reduces the strength and plasticity of aluminum alloy, and often becomes the source of cracks in parts. The second type of oxide inclusions refers to small and diffuse inclusions, which cannot be completely removed even after careful purification. Increase the viscosity of molten metal, reduce the feeding ability of molten aluminum during solidification, and easily cause shrinkage of castings.
Cause of deformation
The overall or partial geometry and design of aluminum alloy die castings do not match the finished product, which is called deformation. Deformation occurs for several reasons:
- Die-casting parts have sticky molds;
- The temperature of the die-casting mold is high, the hardness of the mold itself is not enough, and the cooling time is insufficient;
- The temperature difference between different parts of the cavity is large, and the cooling is not implemented uniformly.
- The structural design of aluminum alloy die castings is not good, and it is caused by uneven shrinkage;
- The mold setting position is incorrect and deflected;
The solution to deformation
The solution to the deformation of aluminum alloy die castings is as follows:
- Increase the cooling time and reduce the mold temperature;
- Clean up the sticky mold;
- Improve the structure of the workpiece to increase the thickness of the inner wall of the mold;
- The temperature control of the aluminum alloy die-casting mold is correct, and the overall temperature of the cavity is almost balanced;
- Adjust the position of the mold and balance the ejection.