机构地区:[1]武汉科技大学高性能钢铁材料及其应用省部共建协同创新中心,湖北武汉430081 [2]武汉科技大学冶金工业过程系统科学湖北省重点实验室,湖北武汉430081 [3]材谷金带(佛山)金属复合材料有限公司,广东佛山528000 [4]大冶特殊钢有限公司高品质特殊钢湖北省重点实验室,湖北黄石435001
出 处:《钢铁》2023年第2期113-125,共13页Iron and Steel
基 金:国家自然科学基金资助项目(U20A20279,52071238);湖北省双创战略团队资助项目;省高新技术重大资助项目(2021BAA057);泰山产业领军人才工程专项经费资助项目;高等学校学科创新引智计划资助项目(111计划)(D18018);武汉科技大学国防预研基金资助项目(GF202016)。
摘 要:为探索锰含量的变化(锰质量分数为0.1%(0.1Mn钢)和1.5%(1.5Mn钢))对无碳化物贝氏体钢中残余奥氏体(RA)回火稳定性的影响,利用扫描电镜(SEM)、电子背散射衍射(EBSD)及透射电镜(TEM)等试验方法对残余奥氏体稳定性和力学性能的变化规律进行研究。结果表明,0.1Mn钢的热轧态组织主要是由粒状贝氏体(GB)+板条贝氏体(LB)组成,而1.5Mn钢的热轧态组织主要以板条贝氏体为主,且1.5Mn钢中残余奥氏体含量较高,屈服强度和抗拉强度均优于0.1Mn钢。在经过300~500℃回火后,残余奥氏体体积分数逐渐下降至完全分解,屈服强度和抗拉强度均表现为先升高后降低,但伸长率逐步增加。300℃回火性能最佳,原因主要是由于残余奥氏体在300℃回火中,块状残余奥氏体分解为过饱和马氏体/贝氏体,碳从过饱和马氏体/贝氏体中扩散至邻近残余奥氏体中使其含量增加,热稳定性得到提高,在拉伸的过程中产生了TRIP效应,从而使试验钢的强塑性得到提升。1.5Mn钢的性能明显优于0.1Mn钢,因为锰可以与碳产生协同作用共同促进奥氏体的稳定,提高伸长率,另外锰含量的增加使碳当量也提高,强度增强。基于修正C-J模型对两试验钢在拉伸过程中的加工硬化行为进行表征,发现1.5Mn钢的应变硬化指数始终大于0.1Mn钢的应变硬化指数,且试验钢均表现3个阶段的应变硬化特性。In order to study the effect of Mn mass percent(0.1%and 1.5%)on the tempering stability of retained austenite(RA)in carbide-free bainite steel,scanning electron microscopy(SEM),electron backscatter diffraction(EBSD)and transmission electron microscopy(TEM)were used to study the stability and mechanical properties of retained austenite.The results show that the hot-rolled microstructure of 0.1Mn steel is mainly composed of granular bainite(GB)+lath bainite(LB),while the hot-rolled microstructure of 1.5Mn steel is mainly lath bainite,and the content of retained austenite in 1.5Mn steel is higher,and the yield strength and tensile strength are better than 0.1Mn steel.After tempering at 300-500℃,the volume fraction of RA gradually decreases to complete decomposition,and the yield strength and tensile strength increase first and then decrease,but the elongation increases gradually.The best tempering performance is obtained at 300℃.The main reason is that during the tempering of retained austenite at 300℃,the block retained austenite decomposes into supersaturated martensite/bainite,and the carbon diffuses from the supersaturated martensite/bainite to the adjacent retained austenite to increase its content,so that the thermal stability is improved,and TRIP effect is produced in the process of stretching,so that the strength and plasticity of the test steel is improved.The mechanical properties of 1.5Mn steel is obviously better than that of the 0.1Mn steel,mainly because Mn and C can have synergistic effect to promote the stability of austenite and improve the elongation.In addition,the increase of Mn content increases the carbon equivalent,so that the strength of the test steel is enhanced.Based on the modified C-J model,the work hardening behavior of two test steels during tensile process is characterized.It was found that the strain hardening index of the 1.5Mn steel is always greater than that of the 0.1Mn steel,and the test steels showed three-stage strain hardening characteristics.
关 键 词:贝氏体钢 残余奥氏体 回火 力学性能 修正C-J模型
分 类 号:TG142.1[一般工业技术—材料科学与工程]
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