峰值温度对780HE复相钢粗晶区组织与性能的影响  

Effects of peak temperature on microstructure and mechanical properties of coarse grain zone of 780HE complex phase steel

作　　者：王月 董现春 牟淑坤 张大伟 陈树海[2] Wang Yue;Dong Xianchun;Mu Shukun;Zhang Dawei;Chen Shuhai(Shougang Group Co.,Ltd.,Beijing 100043,China;University of Science and Technology Beijing,Beijing 100083,China)

机构地区：[1]首钢集团有限公司,北京100043 [2]北京科技大学,北京100083

出　　处：《焊接》2024年第7期15-22,共8页Welding & Joining

基　　金：国家自然科学基金资助项目(52275306)。

摘　　要：【目的】该文旨在系统地研究峰值温度对780HE复相钢粗晶区组织、析出相及力学性能的影响。【方法】利用热模拟试验机模拟焊接过程中不同热输入下780HE复相钢粗晶区经历的焊接热循环。【结果】在不同峰值温度下,粗晶区组织均由贝氏体组成,峰值温度由1140℃提升至1320℃时,奥氏体初始转变温度降低,板条贝氏体含量由10%提升至95%,位错密度由0.96×10^(6) mm^(−2)增加至1.12×106 mm^(−2)。粗晶区析出相均以近圆形复合型析出相(Ti,Nb)C为主,伴随微量方形(Ti,Nb)(C,N)。峰值温度在1210℃及以上时,2~10 nm的(Ti,Nb)C消失,大尺寸的(Ti,Nb)C密度降低至7μm^(−2)以下。峰值温度由1140℃提升至1210℃及1320℃后,抗拉强度分别为750 MPa,744 MPa及789 MPa,屈服强度分别为661 MPa,652 MPa及705 MPa,断后伸长率分别为12.2%,12.4%及10.4%,冲击吸收能量分别为64.17 J,18.55 J及5.64 J,冲击断口由韧性断裂向脆性断裂转变。【结论】峰值温度对粗晶区组织、析出相种类无明显影响。随着峰值温度的增加,板条贝氏体含量增加,位错密度增加,同时析出相尺寸增大,屈服强度先略微下降再显著提升,与断后伸长率变化趋势相反,而冲击韧性显著降低。[Objective]The purpose of this paper was to systematically study effects of peak temperature on microstructure,precipitates,and mechanical properties of coarse grain zone of 780HE complex phase steel.[Methods]A thermomechanical simulator Gleeble-3800 was used to simulate thermal cycles experienced by 800 MPa-grade complex phase steel 780HE under different welding heat inputs during welding process.[Results]The coarse grain zones were composed of bainite under different peak temperatures.When peak temperature rose from 1140℃to 1320℃,initial transformation temperature of austenite decreased,making content of lath bainite increase from 10%to 95%,and dislocation density increase from 0.96×106 mm^(−2) to 1.12×10^(6) mm^(−2).Precipitates of coarse grain zones were mainly composed of nearly circular composite precipitates(Ti,Nb)C,accompanied by several square precipitates(Ti,Nb)(C,N).When peak temperature was 1210℃or above,(Ti,Nb)C with size of 2~10 nm disappeared,and density of(Ti,Nb)C with large size decreased to below 7μm^(−2).As peak temperature increased from 1140℃to 1210℃and 1320℃,tensile strength were 750 MPa,744 MPa and 789 MPa,yield strength were 661 MPa,652 MPa and 705 MPa,and percentage elongation after fracture was 12.2%,12.4%and 10.4%,respectively.Impact energy absorption were 64.17 J,18.55 J and 5.64 J,respectively,and impact fracture surface transformed from ductile fracture to brittle fracture.[Conclusion]Peak temperature had no significant effect on microstructure and types of precipitates in coarse grain zone.As peak temperature increased,content of lath bainite increased,dislocation density increased,and size of precipitates increased.Yield strength first slightly decreased and then significantly increased,opposite to the trend of percentage elongation after fracture,while impact toughness significantly decreased.

关 键 词：粗晶区 峰值温度 780HE 组织演变 力学性能 

分 类 号：TG442[金属学及工艺—焊接] TG457.1