Hydrogen Embrittlement Quality Problems Of Hinge Screws.
Hydrogen embrittlement is a significant quality hazard for hinge screws. The problem of hydrogen embrittlement is much more pronounced in hydrocarburized direct quenched screws than in carburized parts. Hydrogen generated during pickling and electroplating and hydrogen in the surrounding medium during carbonitriding (usually as high as 60%-70%) can dissolve a part of the steel in the steel. When the cathodic current efficiency of electroplating and phosphating processes does not reach 100%, A large number of hydrogen atoms will be attached to the surface of the screw, resulting in hydrogen permeation. This behavior of hydrogen has an important impact on the hydrogen embrittlement damage of steel.
The hinge screw driving time for hydrogen is 6-8h, because the temperature can improve the diffusion coefficient of hydrogen in the steel, so the heat preservation of 20-20 °C can eliminate hydrogen embrittlement, but the temperature is too high, such as above 40 °C, hydrogen is dissolved in the steel and added , hydrogen will no longer automatically escape from the steel, and the intention of removing hydrogen cannot be achieved. The hydrogen driving temperature is selected at 140-170 ℃ (phosphating), 200-240 ℃ (electroplating), but the production should be based on the core hardness, surface roughness, plating time, coating thickness, pickling time, acid concentration and other production conditions. Determining the moment of hydrogen flooding should be carried out before passivation treatment and just after electroplating (within 4 hours).
The research on hinge screws is at a relatively primary stage, and there are very few scientific and technological workers engaged in theoretical research on small screws, especially the theoretical research on hinge screws. Even, there is no published monograph on the design and production of small screws at all. This has formed a great restriction on improving the overall planning level of small screws in my country. Domestic manufacturers of hinge screws basically process according to standards and drawings. Although they have rich production experience, they have not sorted out and theorized their production experience at all, and are in the primary production mode of masters. This has greatly restricted the production level of hinge screws in our country. There are relatively few studies on hinge screws in the world. Like domestic ones, the relevant parameters of some hinge screws that are widely used in the industry have not yet been selected by the relevant national industry standards.
