Heat Treated High Strength Fasteners

Heat treated high strength fasteners are conditioned according to technical requirements. Heat treatment quenching and tempering is to improve the comprehensive mechanical properties of fasteners to meet the required tensile strength and yield strength ratio of products. Heat treatment process has a vital impact on the internal quality of high-strength fasteners, especially its internal quality. Therefore, in order to produce high-quality heat treated high-strength fasteners, it is necessary to have advanced heat treatment technology and equipment. Because of the large production capacity, low price and relatively fine and precise structure of high strength bolts, heat treatment equipment is required to have the ability of large production capacity, high automation and good heat treatment quality. The reaction produces some oxidizing gases. For example, the surface rust of steel wire, which is composed of iron carbonate and hydroxide, will be decomposed into CO2 and hydrogen peroxide after heating, thus aggravating decarburization.

The results show that the decarbonization degree of medium carbon alloy steel is more serious than that of carbon steel, and the fastest decarbonization temperature is between 700 and 800 degrees Celsius. Because the adhesion on the surface of steel wire decomposes rapidly to synthesize CO2 and H2O under certain conditions. Therefore, during quenching and heating, it is necessary to protect the top of thread from decarbonization, and to cover the decarbonized fasteners of raw materials appropriately. The advantage of protective atmosphere in mesh belt furnace should be adjusted to basically equal the original carbon content of the parts covered with carbon, so that the decarbonized fasteners can gradually recover to the original carbon content, and the carbon potential should be set at 0.42%. – 0.48% is suitable. Carbon coating temperature is the same as quenching heating. It can not be carried out at high temperature in order to avoid coarse grains and affect mechanical properties.