Appearance Film Thickness Test And Hanger Fixture Requirements
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- A. Hard oxide film thickness test: Micro hardness can be measured in the transverse direction with a micro hardness tester, and should not be less than 300kg / mm2. The film thickness is averaged to prevent uneven thickness caused by the alloy. Foreign specifications of hard oxidation: standard 50 ?, error ± 10 ?. When the film thickness is set to 100 Å, the error range does not change. Hard anodizing is a thick film anodizing method. A transverse test piece is taken from the tangent of a part or test piece and the thickness is measured under a full-phase microscope. The thickness of the oxide film can also be measured directly with an eddy current thickness gauge.
- B. Hard oxidation appearance: Except for the influence of the fixture, the entire surface of the part must not have a place without an oxide film, allowing small cracks on the oxide film of the entire aluminum clad plate. Scorched or agitated loose membranes are not allowed, nor are bright spots of oxidative corrosion due to local heating and shedding of edges and corners. Due to different aluminum materials and different processes, the color of the oxide film is also different. The film layer changes from brown, dark brown, gray to black; the lower the temperature of the electrolyte, the thicker the oxide film. The hard oxidation process is used to replace the traditional hard chromium plating. Compared with the hard chromium process, it has the advantages of low cost, firm film layer bonding, convenient plating solution, and convenient cleaning of waste liquid.
- C. Hard oxidation electrical equipment: The sulfuric acid hard film DC method anodizing process only requires a DC generator or rectifier. Among them, the use of a rectifier is more efficient and requires constant current control. An automatic device for voltage rise is required when the film grows. According to the above formula, a cooling device for cooling can be designed. The hard oxidizing heat must be quickly exchanged. If it is not cooled in time, the oxide film is not only chemically dissolved, but also electrochemically dissolved due to the addition of an electric field. In this way, the surface finish of the film layer is seriously affected, and the thickness is also reduced. Therefore, it is necessary to have mandatory cooling measures to keep the electrolyte at a low temperature in order to obtain a relatively hard oxide film. The calorific value can be calculated by the following formula: Joule heat Q1 = 0.864 × voltage × current (kcal / hour) Calorific value of the oxidation solution Q2 = 2.334 × current (kcal / hour) Anodizing oxidation reaction heat 2Al + 3 [O] → Al2O3 +375800 card total heat output Q = (Q1 + Q2) × 1.1 (kcal / hour). The problem of heat generation and redissolution of the hard oxide solution During oxidation, a large current is passed through the working surface. Since the oxide film has a large resistance, most of the heat is concentrated on the oxide film.
- D. Hard anodized hanger: Hard anodized hanger The hard anodized hanger and fixture should have sufficient mechanical strength and rigidity to prevent the parts from being washed down by the rapid solution when stirring the electrolyte. In addition, the hanger should have good contact conductivity, light weight, sturdy and durable, convenient loading and unloading of parts, and proper requirements for loading capacity and parts layout. Improve production efficiency, save metal materials and power consumption of the hanger. Hard anodized hangers and fixtures should have sufficient mechanical strength and rigidity to prevent the parts from being washed down by the rapid solution when the electrolyte is stirred. In addition, the hanger should have good contact conductivity, light weight, sturdy and durable, convenient loading and unloading of parts, and proper requirements for loading capacity and parts layout. All the contacts with the parts are made of aluminum, aluminum-magnesium alloy, and aluminum-silicon-magnesium alloy. Except for the conductive parts of the contact parts of the parts, the other parts must be insulated from the hanger to make them non-conductors. In this way, the anodizing process can be concentrated on the workpiece. There are two types of hard anodizing hangers: one is a clamp with a compression screw, and the other is a bolt or a clamp connected with a bolt.
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