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Screw surface treatment process, you mastered it?

Time:2017-04-20Hit:1426

In the process of processing and processing, especially in the process of acid washing and alkali washing before plating and subsequent electroplating, hydrogen atoms are absorbed on the surface, and the deposited metal layer is then captured by hydrogen. When the fastener is tightened, the hydrogen transfer toward the most stress concentrated part, caused by increased pressure to exceed the strength of the base metal and tiny surface crack. The hydrogen is particularly active and quickly enters the newly formed fissures. This pressure rupture penetration cycle continues until the fastener breaks. Usually occurs within a few hours after the first stress application.

In order to eliminate the threat of hydrogen embrittlement, the fasteners should be baked as quickly as possible after plating to make hydrogen from the coating in the exudation, baking is usually 375-4000F (176-190 C) for 3-24 hours.

Due to the fact that the mechanical zinc plating is non electrolyte, it eliminates the threat of hydrogen embrittlement. Because of engineering standards prohibit the hardness of more than HRC35 fasteners (British Gr8, metric 10.9 or more) hot dip galvanized. Therefore, hot dipped fasteners rarely occur hydrogen embrittlement.

Surface treatment type:

Surface treatment is a process of covering layer formed on the surface of the workpiece through a certain method, its purpose is assigned to the product surface appearance, corrosion effect, surface treatment methods are attributed to the following methods:

1, plating: plating parts will be immersed in the metal containing compounds containing aqueous solution to the current through the plating solution, so that the electroplating metal precipitation and deposition on the part. General plating zinc, copper, nickel, chromium, nickel and copper alloy, sometimes cook (black phosphating and Bluing) including.

2, hot dip galvanizing: through the carbon steel parts immersed in the temperature of about 510 degrees Celsius in the zinc bath. As a result, the alloy of iron and zinc on the surface of the steel becomes the passive zinc on the outer surface of the product. Hot dip aluminizing is a similar process.

3, mechanical plating: coating metal particles by the impact of the product surface, and the surface coating to the cold welding products.


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