回火温度对MC3钢碳化物析出及力学性能的影响

Effect of tempering temperature on carbide precipitation and mechanical properties of MC3 steel

由于工作环境的恶劣性,冷轧辊在工作过程中常会发生断辊。为使冷轧辊用MC3钢获得良好的强韧性匹配,避免断辊的发生,本文采用扫描电子显微镜、X射线衍射仪、能谱分析仪等研究了不同回火温度对冷轧辊用MC3钢显微组织和力学性能的影响。研究表明:经550~750℃回火处理的MC3钢组织均为回火索氏体组织,随着回火温度的升高,析出的碳化物由细片状逐渐向球状转变,且球化程度逐渐提高;回火温度达到700℃时,碳化物已完全球化,并均匀弥散分布在铁素体基体上,而当回火温度升高到700℃后,颗粒状碳化物粗化明显。随着回火温度的升高,MC3钢的塑性和韧性呈上升趋势,而硬度和强度则呈逐渐下降的趋势,合金的强韧性与其碳化物的形貌和分布有着密切的关系。在700℃回火时,MC3钢的硬度、抗拉强度、屈服强度、延伸率和冲击功分别为39.2HRC、902 MPa、803 MPa、11.9%、9.8 J,综合力学性能最优。

Due to the harsh working environment,roll breakage often occurs during the working process.In order to obtain a good match between the strength and toughness of MC3 steel for cold rolls and avoid the occurrence of roll breakage,the effects of different tempering temperatures on the microstructure and mechanical properties of MC3 steel for cold rolls were studied by Scanning Electron Microscope(SEM),X-ray Diffractometer(XRD),Energy Dispersive Spectroscopy(EDS),and so on.Results show that the structure of MC3 steel tempered at 550~750℃was tempered sorbite structure.As the tempering temperature increased,the structures of precipitated carbides gradually transformed from flakes to spherical shapes,and the degree of spheroidization gradually increased.When the tempering temperature reached 700℃,the carbides were basically spheroidized and evenly dispersed on the ferrite matrix.When the tempering temperature was above 700℃,the granular carbides were coarsened obviously.As the tempering temperature increased,the ductility and toughness of MC3 steel showed an upward trend,while the hardness and strength gradually declined.The strength and toughness of the alloy were closely related to the morphology and distribution of its carbides.When tempered at 700℃,the hardness,tensile strength,yield strength,elongation,and impact energy of MC3 steel were 39.2 HRC,902 MPa,803 MPa,11.9%,and 9.8 J,respectively,and the overall mechanical properties were the best.