| The purpose of this article is to study quenching and temperring transformationkinetics, microstructure and mechanical properties of high carbon steels containingabundant Si-Mo, denominated0.7Si,1.2Si and1.5Si (with different Si contents).Through the analysis on microstructure and mechanical property of the steels processed byaustempering, select the steel with the best mechanical properties.DIL402C type thermal expansion instrument has been applied to the determinationAc1sand Ac1fof three kinds high carbon steels containing abundant, and the determinationof0.7Si,1.2Si and1.5Si three kinds of high carbon steels containing abundant Mspointsand the kinetics of isothermal transformation curve of different austempering temperaturewas held on the thermalmechanical simulator model of Gleeble–3500. According to theMs points on different austenitic tenperature, the technics of heat treatment was set up.Mechanical properties, including hardness, tensile and impact toughness, were measuredfor different austempering process samples. In addition, phase composition andmicrostructure morphologies were examined by X ray diffractometry, transmissionelectron microscopy and optical microscopy.Experimental results show that the Msof0.7Si,1.2Si and1.5Si high carbon steelscontaining abundant Si-Mo were195,196and203oC, respectively; Ac1spoint is754,765and772oC, respectively; Ac1fpoint is784,795and803oC, respectively.The threedifferernt Si contents’ steels’s austenitic temperature were850,860,870,880and890oC,and they were tempered at165,180,195and210oC with different time in0.5,1,1.5,2,3and5h. The microstructures were admixture containing with tempering martensite,retained austenitic and grained carbonization. Form mechanical properties by testing,when tempering temperature was uniform on2h, with increasing tempering temperature,the hardness decreases, while tensile strength increasing, show that with increasing Sicontenting, the resistent of temper soften increased. |
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