复合型高铌耐火钢热影响区粗晶区的低温冲击韧性  

Low temperature impact toughness in the CGHAZ of high Nb fire-resistant steel

作　　者：陈林恒 刘攀 崔强 范益 孟令明 王红鸿[2] Chen Linheng;Liu Pan;Cui Qiang;Fan Yi;Meng Lingming;Wang Honghong(Nanjing Iron and Steel Group Co.,Ltd.,Nanjing 210035,China;Wuhan University of Science and Technology,Collaborative Innovation Center for Advanced Steels,Wuhan 430081,China)

机构地区：[1]南京钢铁有限公司,南京210035 [2]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,武汉430081

出　　处：《焊接》2020年第9期19-23,26,62,共7页Welding & Joining

基　　金：国家自然科学基金资助项目(51971165)。

摘　　要：采用热模拟方法及激光共聚焦高温显微分析方法研究了高铌耐火钢的逆转变奥氏体长大机制及其热影响区粗晶区的低温冲击韧性。以低锰、高铌、超低碳的化学成分体系设计,提高了加热过程中奥氏体逆转变温度,缩短了逆转变奥氏体长大时间。激光共聚焦高温显微方法表明,形成逆转变奥氏体后,在加热过程中,奥氏体初期以晶界迁移长大,长大速度小,之后结合晶粒合并的方式,没有发现吞并长大的方式,且在冷却过程中没有晶粒长大。因而,在焊接热循环作用下,奥氏体晶粒长大较小。15 kJ/cm,50 kJ/cm,75 kJ/cm埋弧焊焊接热影响粗晶区的晶粒在24~41μm之间,细小的晶粒提高了-40℃的冲击韧性,冲击吸收能量均大于240 J。The reversed austenite growth mechanism and low temperature impact toughness of coarsen-grain heat-affected zone(CGHAZ)were studied through methods of welding thermal simulation and high-temperature laser scanning con-focal microscopy(LSCM)for high-Nb fire-resistant steel.The chemical composition system that was designed with low-Mn,high-Nb and super low-C increased the reverse austenite transformation temperature and shortened the austenite growth time on heating of welding thermal cycle.LSCM showed that the reversed austenite grew in the mode of grain boundary migration with the low growth rate at the first growth stage on heating of welding thermal cycle.Then it grew in the mode of grain merging without growth mode of swallowing up,and the austenite grains did not grow up on cooling of welding thermal cycle.Thus,austenite grains were not coarsened largely in the investigated steel.The grain size was around 24~41μm in submerged arc welding CGHAZ under heat input of 15 kJ/cm,50 kJ/cm,75 kJ/cm.The fine grains increased the impact toughness at-40℃ and the impact absorption energy was greater than 240 J.

关 键 词：复合型耐火钢 逆转变奥氏体 热影响区粗晶区 晶粒长大 冲击韧性 

分 类 号：TG401[金属学及工艺—焊接]