正火工艺参数对轨道交通用20MnV弹簧钢显微组织与力学性能的影响

Effects of Normalizing Process Parameters on Microstructure and Mechanical Properties of 20MnV Spring Steel for Rail Transit

对轨道交通用20MnV弹簧钢进行了不同温度(780,830,880,930,980℃)和不同时间(0.5,0.75,1,1.25h)的正火处理,研究了正火温度和正火时间对试验钢显微组织和力学性能的影响。结果表明:随着正火温度升高,20MnV弹簧钢组织由不均匀铁素体和粒状贝氏体转变为等轴铁素体和块状铁素体;当正火温度低于830℃时,随着正火温度的升高,试验钢的屈服强度和抗拉强度降低,断后伸长率和低温冲击功增大;当正火温度高于830℃后,试验钢的屈服强度和抗拉强度均随着正火温度升高而增加;在不同正火时间下,试验钢的显微组织均为等轴铁素体和块状珠光体;随着正火时间的延长,试验钢的屈服强度、抗拉强度、断后伸长率、低温冲击功均先增后降;当正火温度为930℃、正火时间为1h时,试验钢的力学性能最佳。

20MnV spring steel for rail transit was normalized at different temperatures(780,830,880,930, 980℃)for different times(0.5,0.75,1,1.25h).The effects of normalizing temperature and normalizing time on microstructure and mechanical properties of the tested steel were studied.The results show that with normalizing temperature increasing,the microstructure of 20MnV spring steel transformed from inhomogeneous ferrite and granular bainite to equiaxed ferrite and massive ferrite.When the normalizing temperature was lower than 830℃, with normalizing temperature increasing,the yield strength and tensile strength of the tested steel decreased,and the elongation after fracture and impact energy at low temperature increased.When the normalizing temperature was higher than 830 ℃,the yield strength and? tensile strength of the tested steel increased with the increase of normalizing temperature.The microstructure of the tested steel were equiaxed ferrite and massive pearlite for different normalizing times.With the extension of normalizing time,the yield strength,tensile strength,elongation after fracture and impact energy at low temperature of tested steel increased first and then decreased.When the normalizing temperature was 930℃and the normalizing time was 1h,the mechanical properties of the tested steel were the best.