热输入对深海X70粗晶区组织和韧性的影响

刘治文 贾书君 杨浩 梁小凯 张亮 樊祎宁 韩鹏彪

摘 要：為解决深海X70管线钢在实际焊接中粗晶区（CGHAZ）的脆化问题，在不同热循环工艺下对X70管线钢进行了热模拟研究。采用Gleeble-3800热模拟机模拟X70管线钢CGHAZ，研究CGHAZ在10～60 kJ/cm不同热输入（HI）条件下组织和韧性的变化规律，并通过光学显微镜（OM）、扫描电镜（SEM）和夏比冲击试验等手段表征CGHAZ的组织和韧性。结果表明，不同热输入下试验钢的组织主要由粒状贝氏体（GB）、贝氏体铁素体（BF）和马-奥组元（M-A组元）组成;当HI不断增大时，BF比例减少，GB比例增加，M-A组元粗化，冲击吸收能先升高再降低;当HI为20 kJ/cm时，BF和GB可获得优异组合，断口为韧性断裂，冲击吸收能达到173.8 J;当HI大于20 kJ/cm时，断口解离断裂，冲击吸收能下降明显，最低为18.8 J。因此，较低的热输入可提高CGHAZ的韧性，使X70管线钢具有高强度、高韧性和良好的焊接性。研究结果可为优化焊接工艺提供理论依据。

关键词：焊接工艺与设备;X70管线钢;粗晶区;热输入;组织;韧性

中图分类号：TG406   文献标识码：A

doi：10.7535/hbkd.2021yx05010

收稿日期：2021-08-12;修回日期：2021-09-20;责任编辑：张士莹

基金项目：河北省重点研发项目（19211007D）

第一作者简介：刘治文（1997—），男，山东潍坊人，硕士研究生，主要从事金属材料成型及控制方面的研究。

通讯作者：韩鹏彪教授。E-mail：hpb68@163.com

贾书君高级工程师。E-mail：jiajsj504@126.com

Effect of heat input on microstructure and toughness of CGHAZ of deep-sea X70

LIU Zhiwen1，JIA Shujun2，YANG Hao3，LIANG Xiaokai2，ZHANG Liang1，4，FAN Yining1，HAN Pengbiao1，4

（1.School of Materials Science and Engineering，Hebei University of Science and Technology，Shijiazhuang，Hebei 050018，China;2.Institute of Structural Steels，Central Iron and Steel Research Institute，Beijing 100081，China;3.Research Institute of HBIS Group，Shijiazhuang，Hebei 050018，China;4.Hebei Key Laboratory of Material Near-Net Forming Technology，Shijiazhuang，Hebei 050018，China;）

Abstract：In order to solve the embrittlement problem of coarse grain zone （CGHAZ） of deep-sea X70 pipeline steel in actual welding，the thermal simulation study of X70 pipeline steel was carried out under different thermal cycle processes.X70 pipeline steel CGHAZ was simulated by Gleeble-3800 thermal simulator to study the microstructure and toughness of CGHAZ under different heat input （HI） conditions in the range of 10～60 kJ/cm.The microstructure and toughness of CGHAZ were characterized by means of optical microscope （OM），scanning electron microscope （SEM） and Charpy impact test.The results show that the microstructure of the test steel under different heat input is mainly composed of granular bainite （GB），bainite ferrite （BF） and martensite-austenite component（M-A component）.When HI increases continuously，the proportion of BF decreases，the proportion of GB increases，the M-A component coarsens，and the impact absorption energy first increases and then decreases.In the case of 20 kJ/cm，the excellent combination of BF and GB is obtained，the fracture is ductile fracture，and the impact absorption energy reaches 173.8 J;when HI is greater than 20 kJ/cm，the fracture is dissociated and fractured，and the impact absorption energy decreases obviously，with the lowest of 18.8 J.Therefore，lower heat input can improve the toughness of CGHAZ，make X70 pipeline steel have high strength，high toughness and good weldability，and provide some theoretical guidance for the optimization of welding process.

Keywords：

welding process and equipment;X70 pipeline steel;CGHAZ;heat input;microstructure;toughness

随着国民经济的快速增长，中国对石油等资源的需求急剧提高，人们在开采陆地资源的同时，也在着手开发海底资源[1]。管道输送是运送石油和天然气最为高效便捷的方式，在海底运输中占据重要地位[2]。管线钢作为输送管道的主要材料，不但要具有优异的力学性能，还需要拥有良好的可焊性[3]。……