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High-strength bolt quality

Update:16-01-2021
Summary:

Today, advanced manufacturing represented by large airc […]

Today, advanced manufacturing represented by large aircraft, large power generation equipment, automobiles, high-speed trains, large ships, and large complete sets of equipment has entered an important development direction. As a result, fasteners will enter an important stage of development. High-strength bolts are used for the connection of important machinery. Repeated disassembly or various installation torque methods require extremely high-strength bolts. Therefore, the surface condition and thread accuracy will directly affect the service life and safety of the host. In order to improve the coefficient of friction and avoid corrosion, seizure or jamming during use, the technical requirements stipulate that the surface should be treated with nickel-phosphorus plating. The thickness of the coating is guaranteed to be in the range of 0.02~0.03mm, and the coating is uniform, dense and free of pinholes.

Bolt material: 18Cr2Ni4W, 25Cr2MoV steel; bolt specification: M27~M48. Since this type of steel is easy to form a passivation film on the surface, and this passivation film will prevent the bolt from obtaining a chemical nickel-phosphorus layer with good adhesion, special pretreatment measures must be taken to remove the film first, and measures should be taken To prevent it from regenerating, it is possible to ensure a good bonding force between the plated layer and the substrate after plating. At the same time, due to the large geometric size of the bolt, the quality inspection of the nickel-phosphorus plating treatment and process has increased the difficulty.

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