r-W-Mo-V高合金高碳钢的二次硬化特性及回火硬度计算

wo forms of secondary hardening at high tempering temperature in the Cr-W-Mo-V high alloy high carbon steels are investigated. Firstly, the highest tempering hardness value may correspond to a certain quenching and tempering temperature, and the tempering temperature may increase with the quenching temperature; Secondly, the highest tempering hardness value increase with quenching temperature and the tempering temperature is invariable. The tempering temperature and the highest hardness value are related not only to the thermodynamic conditions of all types of carbides, but also to the progress of the residual austenite transformation. In the final analysis, these are determined by the composition of the austenite matrix. According to the austenite matrix composition at austenitizing temperature, two formula Cp＝0.011W＋0.02Mo＋0.057Cr＋0.19V and Hc= a（1+b）/(0.0127a＋0.00267) are brought forward, in which a is carbon saturation in the matrix, b is modifying factor of the amount of carbides precipitation.