OEM Prototype Cnc Metal Machining Aluminum Computer Back Cover

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Shenzhen pride Industrial Co., Ltd.

Tel:+8618666663894

Fax:+86-917-3387002

Mob:+86-755-23699351

E-mail: crush@pride-cnc.com

Add: Block D, Dianlian Science Park, Matian St., Guangming District, Shenzhen 518106, China

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Aluminum-silicon die-casting alloy parts are prone to pitting corrosion in a humid environment, especially in the rainy season, so the surface of the processed parts needs to be treated. The selected process is mostly colorless chemical oxidation. The thickness of the conversion film is generally 053.0, which has certain corrosion resistance and decorative effect. Since the parts have non-machined surfaces, the oxide scale, putty, stains, etc. produced during die-casting still exist, and the mechanically processed surfaces are in good condition. It is difficult to ensure uniform surface quality after degreasing and corrosion of the surface. For cast aluminum alloys, especially cast aluminum alloy parts with a high content of silicon and copper, although the addition of silicon and copper greatly improves the strength of the aluminum alloy, it also makes the finishing process more difficult. Some cast aluminum alloys cannot be directly electroplated or For anodized products such as high copper and high silicon cast aluminum alloy containing 20% 25% copper and 7% 12% silicon, a special pre-treatment process is required before electroplating or anodization to ensure product quality. Some box and frame parts are mostly made of silicon-containing copper die-cast aluminum alloy after machining. According to technical quality requirements, the surface needs to be protected and finished and the surface layer hardened. The process test proves that the following colorless chemical hydrogenation film forming process products are of good quality and high production efficiency is a more suitable process method.

1 Chemical oxidation treatment process flow The chemical oxidation treatment process flow of cast aluminum alloy parts is as follows:

(1) Acceptance before surface treatment

(2) Shot peening;

(3) Activation treatment;

(4) Washing with flowing cold water;

(5) Colorless chemical film formation

(6) Washing with flowing water:

(7) Blow dry;

(8) Check the income database.

2 main process analysis

2.1 Shot peening purification strengthening treatment Shot peening purification strengthening is the pre-treatment preparation for the chemical film formation of parts, and it also plays a role in surface strengthening. Shot peening generally uses glass pellets whose function is not only to remove the oxide scale and stains on the surface of the parts, but also to form many tiny semicircular surfaces with metallic luster after the glass pellets are sprayed on the surface of the parts. In addition, because shot peening produces compressive stress on the surface of the part, the fatigue life of the surface is increased, the sensitivity of the part to stress erosion, and the surface strength of the part are increased. The compressed air with a glass pellet diameter of 150250 should be filtered and purified by an oil-water separator. Its pressure is controlled at about 4.9105. The spray angle is 6070. The distance between the nozzle and the workpiece is 250350. It should be sprayed evenly and sequentially to avoid staying in local areas for a long time. This is a defect such as overheating or deformation of the surface of the part. The glass pellets can be recycled many times, but the crushed powder must be removed before use to ensure the quality of shot peening purification and strengthening.

2.2 Activation treatment In order to maintain the strengthened layer on the surface of cast aluminum parts, it is conducive to the smooth progress of chemical oxidation and film formation. It is necessary to activate the parts after shot peening purification and strengthening treatment. Activation treatment solution and process parameters:

(1) 330% 50% (volume percentage) temperature: room temperature: %5% (volume percentage), dipping Lang: 15.

(2) 3300/temperature and room temperature; 100/immersion time: 510. Adding can effectively activate the surface of high-silicon cast aluminum is the pre-treatment preparation for colorless chemical hydrogenation film formation.

2.3 Chemical oxidation treatment The high silicon cast aluminum parts that have been strengthened by shot peening and activation treatment should be put into the chemical oxidation treatment solution in time. The chemical oxidation film formation reaction is generally carried out under the condition of choking temperature, and the treatment time varies with different solutions. In the chemical oxidation treatment solution, the surface of the cast aluminum alloy can quickly form a uniform, transparent and colorless oxide film, which fully meets the technical quality requirements of the product. The colorless chemical oxidation treatment can usually choose one of the following process methods.

(1) 227335/3350.50.8/value 3.50.2 35 at room temperature

(2) 227041.0/ (grade) 0.250.5/ ionic surface active agent appropriate value 2.735 temperature 20403090 Sodium dichromate, chromic acid, potassium dichromate are the oxidants in the chemical oxidation solution and are the main components that promote the formation of oxide film. The fluoride ion in hydrofluoric acid or sodium fluoride acts as an activation in the solution. It works together with dichromate ions to produce a dense oxide film, but their content and ratio must be strictly controlled. The value of the chemical oxidation solution should be controlled within the specified range.

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