The blackening treatment of U-shaped bolts has the following detailed requirements for appearance:
1. The appearance of black treatment is blue, black or dark black.
2. The film crystal is dense and uniform, the product has no bottom dew, no obvious color difference, no whitening and other abnormal phenomena.
If the blackening is abnormal, the following will happen:
1. Vitiligo, flowers. This phenomenon is mainly manifested in the different colors of the oxide film, showing white spots and different colors;
2. The color is wrong. After darkening, the product will be blue or red.
3. The oxide film is not strong, due to the product degreasing and cleaning is not thorough, the blackening treatment time is too long, the blackening layer is too thick, the black floating layer is formed, the adhesion is poor, the clean water after the product is pickled is not clean, and the residual acid is carried Into the black liquor, the local reaction is too large, and the surface of the workpiece appears floating rust.
4. Rust spots. The reason for changing the color of the product is the oxidation reaction, so the blackened product needs to be dehydrated and sealed in time. If the darkened product is not immersed in the oil in time to shut down, the activated elements and air will continue to reverberate, sometimes discoloring.
U-shaped wire surface protection treatment
For a specific design, each designer must choose the surface treatment to be processed. There are many kinds of surface treatments, from ordinary oil to gold. But the designer should choose a surface treatment that can achieve the goal economically.
Since almost all commercial fasteners are made of carbon steel and alloy steel, some fasteners hope to prevent corrosion. Even if the fasteners of anti-corrosion materials are used, surface treatment is required to prevent corrosion of different materials.
In addition, the surface-treated coating must be firmly attached together and cannot fall off during installation and uninstallation. For threaded fasteners, the coating should be thin enough so that the threads can still be rotated after plating.
Generally, the temperature limit of the coating is lower than the temperature limit of the fastener material, so it is also necessary to consider the operating temperature requirements of the fastener. For surface treatment, people generally pay attention to beauty and anti-corrosion. The main function of fasteners is fasteners. Surface treatment also has a great influence on the fastening performance of fasteners. Therefore, when selecting the surface treatment, the factor of fastening performance should also be considered, that is, the consistency of installation torque and pre-tightening force. Senior designers must not only consider design, but also pay attention to the assembly process and even environmental requirements.