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Five commonly used aluminum alloy die-casting surface treatment process
- Jan 02, 2018 -

Aluminum die-casting products are mainly used in electronics, automobiles, motors, home appliances and some communications industries, some high-performance, high precision, high toughness and high quality products are also used in large aircraft, ships and other demanding industries, the general Five processes are used for the surface treatment of aluminum alloy die-castings.

 

1, aluminum phosphating

The influence of accelerant, fluoride, Mn2 +, Ni2 +, Zn2 +, PO4 and Fe2 + on the phosphating of aluminum was studied in detail by using SEM, XRD, potential-time curve and film weight change. The results showed that guanidine nitrate has the characteristics of good water solubility, low dosage and rapid film formation. It is an effective accelerator for aluminum phosphating: fluoride can promote the formation of film, increase the weight of film and refine the grain; Mn2 +, Ni2 + Thinning the grain so that the phosphating film is uniform and dense and can improve the appearance of the phosphating film. When the concentration of Zn2 + is low, the film can not be formed or the film is poorly formed. As the concentration of Zn2 + increases, the weight of the aluminum alloy profile increases; Phosphate film heavier impact, improve PO4. Phosphate content of the film to increase.

 

2, Al alkaline electrolytic polishing process

Alkaline polishing solution system was studied, compared with the corrosion inhibitor, viscosity agent, etc. on the polishing effect, successfully obtained a good polishing effect of alkaline solution system, and for the first time been able to reduce the operating temperature and prolonged use of the solution Life expectancy, but also improve the polishing effect of additives. The experimental results show that adding appropriate additives in NaOH solution can produce good polishing effect. Exploratory experiments also found that the surface reflectivity of aluminum can reach 90% after DC constant voltage electrolysis polishing under some conditions using glucose NaOH solution, but due to the instability factors still need further study. The feasibility of using DC pulsed electrolytic polishing method to polish aluminum in alkaline condition was explored. The results show that the pulse electropolishing method can achieve the leveling effect of DC constant voltage electrolytic polishing, but the flattening speed is slower.

 

3, aluminum and aluminum alloy environmentally friendly chemical polishing

It is determined to develop a new environmentally friendly chemical polishing technology based on phosphoric monosulfate. This technology should achieve zero emissions of NOx and overcome the quality defects of the similar technology in the past. The key to the new technology is to add nitric acid instead of nitric acid by adding some special compounds to the base fluid. To do this, we first need to analyze the three-acid chemical polishing process of aluminum, with particular emphasis on the role of nitric acid. The main role of nitric acid in aluminum chemical polishing is to inhibit point corrosion and improve polishing brightness. Combined with a simple phosphoric acid in a chemical polishing test, that the phosphoric acid in a particular substance added to the phosphoric acid should be able to inhibit pitting corrosion, slow down the overall corrosion, at the same time must have good leveling and light effects.

 

4, aluminum and its alloy electrochemical surface hardening

The process, properties, morphology, composition and structure of the ceramic-like amorphous composite film were formed by anodic oxidation of aluminum and its alloys in a neutral system. The film formation process and mechanism were preliminarily discussed. The results show that the concentration of the film-forming agent is 2.5-3.0g / l, the concentration of the complexing agent is 1.5-3.0g / l, the concentration of Na_2WO_4 is 0.5-0.8g / l in the Na_2WO_4 neutral mixed system , The peak current density of 6 ~ 12A / dm ~ 2, weak mixing, you can get a complete uniform, good gloss gray series of inorganic non-metallic film. The thickness of the film is 5 to 10 μm, the micro hardness is 300 to 540 HV, and the corrosion resistance is excellent. The neutral system has good adaptability to aluminum alloy profiles, rust-proof aluminum, forged aluminum and other series of aluminum alloy profiles are better film.

 

5, aluminum alloy casting surface treatment technology

Aluminum alloy castings are widely used in the structural parts of automobiles and motorcycles. The material needs to be surface treated prior to use to improve its corrosion resistance and to form a surface layer that easily bonds with the organic coating to facilitate subsequent surfaces.

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