回火温度对2%Mn高强钢组织和性能的影响

Influence of Tempering Temperature on the Microstructure and Mechanical Properties of 2%Mn High Strength Steel

高强度高塑性是先进高强钢发展的方向,本工作以2%Mn钢为研究对象,通过控制回火温度实现高强度高塑性最佳匹配,并采用SEM、TEM、XRD等技术分析影响2%Mn高强钢组织和力学性能的机制。结果表明:2%Mn高强钢经珠光体区等温退火后组织为铁素体、珠光体、低碳马氏体和残余奥氏体;随着回火温度升高,残余奥氏体体积分数由退火态的6.78%持续降低至425℃回火态的2.55%,回火温度继续升高,残余奥氏体体积分数基本不变,维持在稳定水平;随着回火温度升高,铁素体含量持续增加,位错密度、抗拉强度、屈服强度、硬度持续降低,延伸率先增加后降低;2%Mn钢经425℃回火后,铁素体平均板条宽度为95.1 nm,位错密度为2.6×10^(14)m^(-2),碳化物平均直径为13.9 nm,抗拉强度为1770 MPa,屈服强度为1450 MPa,伸长率为9.84%,强塑积达到最大值17.4 GPa·%。

Development direction of advanced high-strength steel is high strength and high plasticity.In this work,the 2%Mn steel as the research subject,and the best matching of high strength and high plasticity was achieved by controlling the tempering temperature,the SEM,TEM and XRD were used to analyze the influence mechanism of microstructure and mechanical properties.the results show that:The steel was organized as ferrite,pearlite,low carbon martensite and residual austenite after isothermal annealing in the pearllet region;the residual austenite volume fraction continuously decreased from 6.78%of the annealed state to 2.55%of the 425℃tempering state,then the residual austenite volume fraction was basically unchanged and maintained at a stable level as the tempering temperature increases further;with the increase of tempering temperature,ferrite content continues to increase,dislocation density,tensile strength,yield strength and hardness continuous to decrease,and extension increases first then decreasing;after 425℃tempering,the average batten width of ferrite was 95.1 nm,dislocation density was 2.6×10^(14)m^(-2),average diameter of carbide was 13.9 nm,tensile strength was 1770 MPa,yield strength was 1450 MPa,elongation was 9.84%,and the strong plastic product reached maximum of 17.4 GPa·%.