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Aluminum castings need to be made in a way that prevents porosity. In the process of production, it is necessary to take effective measures to minimize the moisture of the raw material. In the process of aluminum casting, it is necessary to choose the casting process reasonably and strengthen the melting quality management effectively.
Under production conditions, aluminum alloy castings will form tiny cavities when solidifying, called pinholes.
Pinholes are usually distributed throughout the section, especially in the thick part of the casting where the solidification speed is slow. Pinholes reduce the actual force area of the component and may become a source of cracking, and destroy the continuity of the material, reducing the strength and plasticity of the casting, at the same time, pinholes also affect the corrosion resistance and anodic oxidation properties. Therefore, in aluminum castings, especially for the aerospace industry, aluminum alloy castings acceptance standards, are clearly proposed to limit the level of pinholes in the casting.
According to the "ISO-10049 Aluminum alloy castings pinhole degree visual assessment method", aluminum alloy castings pinhole degree rating is shown in Table 1. by assessing the pinhole degree, the quality of the metallurgical treatment of the material and its macro homogeneity can be judged. Only the number of holes on the surface and their average diameter are evaluated, and the depth of the holes is not measured. The evaluation was carried out according to Table 1. A sample frame with a 10 mm x 10 mm square hole was used. The number and size of the holes visible on the surface of the frame inside the square hole were measured.
All the raw materials and tools needed for melting in aluminum castings need to be carefully removed from the surface of the oil and rust, and the quality of the alloy and reheat material in the middle of the product also needs to be controlled in a timely manner, and the poor quality of the reheat material has broken metal chips.
In general, the surface of the metal in addition to the cohesion of its water, but also effectively and the role of the metal oxide film to form its crystalline water, and then at a certain temperature for low-temperature baking, so that it can effectively remove its dissolved water and part of the cohesion of water.
Aluminum castings can be at 500 degrees to remove most of its crystallization more easily. In the process of operation, it is necessary to shorten its melting time as much as possible, so as to effectively reduce the air absorption of its aluminum alloy, and the melting temperature of its products must not be too high.
Because the higher the temperature, the larger the air absorption will be, so in general the temperature will not exceed 800 degrees, and the melting process should be controlled by a temperature measuring device.
Aluminum castings of aluminum alloy liquid surface with the role of the protection of the oxide film can effectively prevent the metal liquid directly and atmospheric water moisture reaction, so that the melting and casting process should try to avoid the destruction of the oxide film and deterioration.
After the aluminum casting is cast out, it still needs certain processing technology, so that the surface precision is better, gloss and brightness are improved, and then applied to our life.