Aluminum alloy die-casting mirror glass processing technology generally needs to meet two requirements: the plate itself achieves the actual effect of mirror glass; the air oxide film on the surface of the casting can achieve a sweet and transparent aspect ratio.

Among all kinds of air oxide films, the hydrochloric acid air oxide film is the key factor that endangers the sweetness and full transparency of the casting air oxide film. Degree and grouting reinforcement quality can harm the actual effect of mirror glass.

How to carry out mirror treatment process for aluminum alloy die castings

If there are too many residual positive ions (or molecules) such as silicon, manganese, iron, copper, and chromium in the air oxide film, the purity of the air oxide film will be low, and the clarity will be reduced. The basic principle depends on the air oxide film, although it is light transmissive, there will be some light transmission damage. When the thickness of the air oxide film increases, the clarity will also decrease. The pinhole of the air oxide film is the key root cause of light transmission, and the higher the porosity, the greater the transmission. Especially when the eye of the needle is triangular, the light transmission will be greatly improved, and the clarity will be rapidly reduced.

The chemical substance for grouting reinforcement is boehmite. There are also nickel hydroxide and fluoroaluminate in grouting reinforcement at room temperature. They are all completely transparent, so most of the normal grouting reinforcement is not easy to reduce the clarity of the air oxide film. Spend. However, if over-sealing occurs, the resulting powder will all become light-transmitting particles, which will greatly reduce the clarity of the air oxide film. Pay attention to the reinforcement of the slurry, mainly to control the temperature and time to prevent over-sealing. If it is grouting reinforcement at room temperature, the nickel/fluorine composition and ratio should also be adjusted, and the fluoride ion composition should not be too high. If there is over-grouting reinforcement, the die casting can be infiltrated into dilute nitric acid to remove the powder.

The residue in the air oxidation film mainly comes from the die casting itself, and the primary and secondary sources are the air oxidation bath. Therefore, moderately reducing the composition of aluminum alloy elements in die castings, reducing the residue composition of die castings as much as possible, and even using high-purity aluminum can improve the purity of the air oxide film. Reducing the miscellaneous positive ions in the tank liquid and maintaining the freshness of the tank liquid can also improve the purity of the air oxide film. The thickness of the air oxide film should be controlled at 10-12um. If the product implementation standard does not specify the thickness of the air oxide film >=10um, it is better to control the thickness of the air oxide film at 6-8um. The key to the porosity of the air oxide film is the dissolution rate. The faster the dissolution rate, the greater the porosity. The dissolution rate of hydrochloric acid concentration, bath temperature, and current intensity are positively correlated. Therefore, moderately reducing the concentration of hydrochloric acid, bath stability, and current intensity can reduce the porosity of the air oxide film.

Therefore, in order to obtain the actual effect of air oxidation mirror glass castings, it is necessary to improve the clarity of the air oxidation film, and, from the control of the thickness of the air oxidation film, reduce the porosity of the air oxidation film, improve the purity of the air oxidation film, and ensure grouting reinforcement. Appropriate to start with these four levels.

Conclusion

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