Mirror Treatment On Die-cast Aluminium
The processing technology of aluminum alloy die-casting mirror glass should meet two requirements: the plate itself should achieve the actual effect of mirror glass; The air oxide film on the surface of the casting piece is sweet and transparent in aspect ratio. The key here is to introduce in detail the way to make the air oxide film on the surface of the casting piece sweet and transparent in aspect ratio.
Among all kinds of air oxide films, hydrochloric acid air oxide film is the key factor that endangers the sweetness and transparency of the air oxide film of the casting. The thickness of the air oxide film of hydrochloric acid air oxide film, the porosity of the air oxide film, the purity of the air oxide film, and the quality of grouting reinforcement can all harm the actual effect of the mirror glass.
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 definition will be reduced. The basic principle depends on the fact that although the air oxide film is transparent, some light transmission damage may occur. When the thickness of air oxide film is increased, the definition will also be reduced. The pinhole of air oxide film is the key root cause of light transmission, and the more the porosity is, the greater the transmission is. Especially when the needle eye is triangular, the light transmission will be greatly improved, and the definition will be rapidly reduced.
The chemical substance for grouting reinforcement is boehmite. At normal temperature, nickel hydroxide and fluoroaluminate are also used for grouting reinforcement. They are all transparent. Therefore, most normal grouting reinforcement is not easy to reduce the clarity of the air oxide film. However, if the pores are sealed, the resulting powder will all become light transmission particles, which will greatly reduce the definition of the air oxide film. For grouting reinforcement, it is mainly to control the temperature and time to prevent over-sealing. In case of grouting reinforcement at normal temperature, the nickel/fluorine composition and proportion should also be adjusted, especially the fluorine ion composition should not be too high. In case of over-grouting reinforcement, the die casting can be infiltrated into dilute nitric acid to remove the frost.
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 solution. Therefore, the purity of air oxide film can be improved by moderately reducing the composition of aluminum alloy elements in die castings, reducing the residual composition of die castings as much as possible, and even using high-purity aluminum. The purity of the air oxide film can also be improved by reducing the impurities in the bath solution and maintaining the freshness of the bath solution. The thickness of air oxide film should be controlled at 10-12um. If the product executive standard does not specify that the thickness of air oxide film is>=10um, the thickness of air oxide film should be controlled at 6-8um. The key to the porosity of air oxide film is the dissolution rate. The faster the dissolution rate is, the larger the porosity is. The hydrochloric acid concentration value of the dissolution rate, the temperature of the bath solution, and the current intensity are positively correlated. Therefore, moderately reducing the hydrochloric acid concentration value, the stability of the bath solution, and the current intensity are all to reduce the porosity of the air oxide film.
Therefore, in order to obtain the actual effect of the air oxidation mirror glass casting, it is necessary to improve the clarity of the air oxidation film, and start from controlling the thickness of the air oxidation film, reducing the porosity of the air oxidation film, improving the purity of the air oxidation film, and ensuring proper grouting reinforcement.
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