Nb微合金低碳钢表层超细晶中厚板的研制  

Development of Nb Microalloyed Low Carbon Steel Plate with Ultra-fine Grains in Surface Layer

作　　者：杜海军[1] 栗春[1] 赵德文[1] 王国栋[1] 

机构地区：[1]f东北大学轧制技术及连轧自动化国家重点实验室,沈阳110004

出　　处：《机械工程学报》2011年第2期58-64,共7页Journal of Mechanical Engineering

基　　金：国家自然科学基金资助项目(51074052)

摘　　要：应用中间坯加速冷却―轧制―轧后加速冷却工艺轧制的10 mm表层超细晶(1～5μm)Nb微合金高强度钢板,超细晶层厚度为0.5～2.0 mm,其屈服强度达到640 MPa,抗拉强度740 MPa,伸长率达到27%,–40℃冲击吸收功大于130 J。利用光学电镜、扫描电镜和透射电镜观察分析组织,得到如下结论:铁素体晶粒超细化的机制是过冷奥氏体应变诱导铁素体相变,先共析和应变诱导的铁素体动态再结晶;强化机制为细晶强化,Nb析出物的弥散析出强化,位错及亚结构强化;在实施中间坯加速冷却前通过再结晶区轧制得到细化的奥氏体晶粒,或未再结晶区轧制获得形变奥氏体晶粒,或在中间坯加速冷却后增大轧制压缩比,和降低轧后加速冷却的终冷温度均有利于获得表层超细晶粒,同时增大整个厚向超细晶粒比例。A 10 mm thick Nb microalloyed high strength steel with ultra-fine grains（1～5 μm） in surface layer is obtained by applying the accelerated cooling intermediate slab-rolling-post rolling accelerated cooling process,the thickness of ultra-fine grains layer lies between 0.5 and 2.0 mm.It has 640 MPa yield strength,740 MPa tensile strength,27% elongation and more than 130 J impact absorbing energy at –40 ℃.Microstructure investigation is done by using optical microscopy,scanning electron microscopy and transmission electron microscopy.The results show the mechanism of ultra-fined ferrite is deformation induced undercooling austenite to ferrite transformation（DIT）,and conjunction with dynamic recrystallization（DRX） of proeutectoid ferrite and DIF ferrite.The strengthening mechanism is fine grain strengthening,Nb precipitation strengthening,dislocation and substructure strengthening.Before accelerated cooling of intermediate slab,to obtain refined austenite grains through recrystallization region rolling or deformed ones through non-recrystallization region rolling,or to increase the rolling compression ratio after accelerated cooling of intermediate slab,and to decrease the final cooling temperature of post-rolling accelerated cooling,all help obtain ultra-fine grains in surface and increase the proportion of ultra-fine grains over the whole plate thickness.

关 键 词：应变诱导相变 铁素体动态再结晶 表层 超细晶 NB 微合金低碳钢 加速冷却 

分 类 号：TG142.1[一般工业技术—材料科学与工程]