How to perform mirror surface treatment process for aluminum alloy die castings
The processing technology of aluminum alloy die-casting mirror glass generally requires two requirements: the plate itself must achieve the mirror glass effect;the surface air oxide film of the casting must achieve a high aspect ratio and be completely transparent.Here, we will focus on detailing the method of achieving a high aspect ratio and completely transparent surface air oxide film on the casting.
Among various air oxidation films, hydrochloric acid air oxidation film is the key factor that affects the high-aspect-ratio, translucent appearance of castings. The thickness, porosity, purity, and grouting quality of the hydrochloric acid air oxidation film can affect the mirror-like glass effect.
If there are too many residual positive ions (or molecules) such as silicon, manganese, iron, copper, chromium, etc. in the air oxidation film, the purity and clarity of the air oxidation film will be reduced.The basic principle depends on the fact that although the air oxidation film is transparent, some light transmission damage may occur.When the thickness of the air oxidation film increases, the clarity will also decrease.The pin hole of the air oxidation film is the key reason for light transmission, and the higher the porosity, the greater the transmission.Especially when the pin hole is triangular, the light transmission will be greatly improved, and the clarity will be rapidly reduced.
The chemical substance used for grouting reinforcement is boehmite. In the case of grouting reinforcement at room temperature, nickel hydroxide and fluoroaluminate are also used. They are all completely transparent, so the clarity of the air oxide film is not easily reduced in most normal grouting reinforcement.However, if there is a sealing hole, the resulting powder frost becomes a light transmission particle, which greatly reduces the clarity of the air oxide film.Regarding grouting reinforcement, it is mainly to control the temperature and time to prevent the occurrence of sealing holes.If grouting reinforcement is carried out at room temperature, the nickel/fluoride composition and proportion should be well adjusted, especially the fluoride ion content should not be too high.If there is over-grouting reinforcement, the die-casting parts can be immersed in dilute nitric acid to remove the powder frost.
The residue in the air oxidation film mainly comes from the die-casting itself, and the main source is the air oxidation tank solution.Therefore, appropriately reducing the composition of aluminum alloy elements in the die-casting, minimizing the residue composition of the die-casting, and even using high-purity aluminum can improve the purity of the air oxidation film.Reducing the impurity cations in the tank solution and maintaining the freshness of the tank solution can also improve the purity of the air oxidation film.The thickness of the air oxidation film should be controlled at 10-12um. If the product implementation standard does not specify that the thickness of the air oxidation film is >=10um, it is better to control the thickness of the air oxidation film at 6-8um.The porosity of the air oxidation film mainly depends on the film dissolution rate, and the faster the film dissolution rate, the higher the porosity.The dissolution rate of the film is positively correlated with the hydrochloric acid concentration, the tank solution temperature, and the current intensity. Therefore, appropriately reducing the hydrochloric acid concentration, the tank solution stability, and the current intensity are all ways to reduce the porosity of the air oxidation film.
Therefore, to obtain the actual effect of air-oxidation mirror glass castings, it is necessary to improve the clarity of the air-oxidation film, and to start from the four aspects of 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.
The key manufacturing step model can immediately identify the impact of casting quality and production volume.Forging porosity, slag inclusion, scar, catalytic cracking, process performance, and dimensional accuracy are well correlated with the characteristics of sand selection.The application of models and new manufacturing technologies is the key to PEPSET, which uses epoxy resin as a binder to create a single, non-hardened chemical reaction system from hard sand, the kind of self-hardening sand system that is difficult to produce. Now is the time to start hardening, and the dry-cure reaction will start quickly once it begins.Therefore, the trainer bag, due to its excellent properties in a difficult, high toughness, and fat gas collapse environment, has excellent characteristics of aluminum alloy die-casting surface diversity, ensuring quality and reliability of dimensional accuracy.
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