高硅铸钢的连冷组织及回火后性能

The microstructures of high silicon cast steel after continuous cooling and its tempered mechanical properties

采用膨胀法和显微组织分析结合方法测定了高硅铸钢在不同冷速下的转变组织,依据测定的临界点和CCT制定了高硅铸钢的淬火和回火工艺,并研究了回火温度对组织和性能的影响.试验结果表明:连冷组织中无碳化物析出,当冷却速度小于0.15℃/s时,组织为铁素体和贝氏体混合组织;当冷却速度在0.15和2℃/s之间时,组织为贝氏体与马氏体混合组织;当冷却速度大于2℃/s时,转变为马氏体组织.马氏体回火后,其抗拉强度达到1830 MPa,延伸率达到13%.回火组织为极细的回火马氏体与低温贝氏体组织.

The transformation microstructures of the high silicon cast steel at different cooling rates were obtained by means of dilatometric analysis and microstructure detection,and the quenching and tempering procedures were drawn up according to the measured Ms temperature and CCT curves.The effect of tempering temperature on its microstructures and mechanical properties were studied.The results show that the microstructures consisted of ferrite and bainite without carbides precipitation while the cooling rate was below 0.1℃/s.The microstructures were composed of bainite and martensite while the cooling rate was between 0.1℃/s and 2℃/s.It transformed into martensite while the cooling rate was above 2℃/s.Its tensile strength reached 1830 MPa and elongation reached 13%after martensite tempering.The microstructures of the sample transformed into a very fine tempered martensite and low-temperature bainite due to the low tempering temperature.