1300MPa级超高强钢临界粗晶热影响区组织和韧性  

Microstructure and toughness of intercritically reheated coarse-grained heat affected zone in a 1300MPa grade ultra-high strength steel

作　　者：温长飞[1] 邓想涛[1] 王昭东[1] 王国栋[1] WEN Chang-fei;DENG Xiang-tao;WANG Zhao-dong;WANG Guo-dong(State Key Laboratory of Rolling Technology and Automation,Northeastern University,Shenyang 110819,Liaoning,China)

机构地区：[1]东北大学轧制技术及连轧自动化国家重点实验室

出　　处：《钢铁研究学报》2018年第8期650-656,共7页Journal of Iron and Steel Research

基　　金：国家自然科学基金资助项目(51234002,51504064,51474064)

摘　　要：通过焊接热模拟试验、冲击试验和显微组织观察分析,研究了二次热循环峰值温度（θp2）对1 300MPa级低合金超高强钢临界粗晶热影响区（ICCGHAZ）的组织和冲击韧性的影响。结果表明,当θp2由720℃增加至800℃时,ICCGHAZ的-20℃冲击吸收功由21.47J增加到76.05J,裂纹形核功和扩展功均得到较大提高;θp2低于760℃时在原奥氏体晶界处形成的粗大的链状M-A组元,不但弱化晶界而且作为裂纹形核源是降低韧性的主要原因;θp2增加到800℃时所形成的M-A组元其内部结构呈板条状,晶内的板条马氏体回复程度增加,位错密度降低,碳化物尺寸减小,有利于提高韧性。It was generally recognized that intercritically reheated coarse-grained heat affected zone（ICCGHAZ）was the poorest toughness zone in the welded joint.Welding thermal cycles of ICCGHAZ with different intercritical peak temperatures for 1 300 MPa grade ultra-high strength steel were carried out on the thermomechanical simulator.The influence of peak temperature on microstructure and impact toughness of ICCGHAZ was discussed on the basis of impact test results and microstructural observation.The results show that the impact absorbed energy tested at-20℃increases from 21.47 Jto 76.05 Jwhen the peak temperature improves from 720℃to 800℃,and the crack initiation energy and crack propagation energy have both been greatly increased.When the peak temperature is below 760℃,the near-connected coarse M-A constituents form along the prior austenite grain boundary not only weaken the grain boundary but also serve as crack initiation position,which is the main reason for the decrease of toughness.The best toughness will be obtained in this study when the peak temperature reaches up to 800℃.That＇s because of the disappearance of near-connected coarse M-A constituents,the decrease of dislocation density and the reduction of carbide size in the microstructure.

关 键 词：超高强钢 临界粗晶热影响区 组织 冲击韧性 M-A组元 

分 类 号：TG142.1[一般工业技术—材料科学与工程]