Self - tapping screws or quick - set screws are quick - set fasteners made of steel, galvanized and passivated. Tapping screws are used to connect thin metal plates (steel plates, saw plates, etc.). When connecting, first make the threaded bottom hole of the connecting piece, and then screw the tapping screw into the threaded bottom hole of the connecting piece.
Carburizing is a process of ordering carbon atoms into the steel surface, make steel surface chemical composition close to the high carbon steel, for low carbon steel with high carbon steel hardness, wear resistance and fatigue strength of carburized materials for low carbon steel or low carbon commonly the traditional gas carburizing technology, general component is the carburizing process decomposition, adsorption and diffusion stages.
The carburizing process of tapping screw is different from that of medium and deep carburizing process. For the workpiece with the depth of the infiltration layer greater than 1.0mm, such as automobile gear, the depth of the carburizing layer and the distribution of the carbon concentration of the infiltration layer, and even the depth of the over-eutectomized layer and the eutectomized layer of the infiltration layer may have certain requirements.
In order to ensure a high carburizing speed, this kind of parts often use high carbon potential carburizing carbon potential of 0.7%-0.8%C atmosphere for diffusion. In order to reduce the distortion caused by direct quenching after carburizing and reduce the level of martensite and residual austenite, it is required that after the diffusion stage, the furnace is cooled to 820-860℃ isothermal and then quench, so as to ensure that the infiltration layer and the heart have qualified hardness and good microstructure. This carburizing process has different requirements for carrier gas and enriched gas compared with tapping screw carburizing.
