Q500qE桥梁钢焊接接头的低温断裂韧性  

Low-temperature Fracture Toughness of Welded Joint of Q500qE Bridge Steel

作　　者：武凤娟 程丙贵 曲锦波 WU Fengjuan;CHENG Binggui;QU Jinbo(Institute of Research of Iron and Steel Jiangsu Province(Shasteel),Zhangjiagang Jiangsu 215625,China)

机构地区：[1]江苏省(沙钢)钢铁研究院

出　　处：《上海金属》2019年第5期1-7,共7页Shanghai Metals

摘　　要：实验室试制了60 mm厚TMCP型Q500qE桥梁钢厚板;使用自动埋弧焊机对试验钢板进行双面多层多道次对接焊试验。采用裂纹尖端张开位移(CTOD)测试技术和显微组织分析,对母材、焊缝金属和热影响区(HAZ)进行了低温(20、-10、-40℃)断裂韧性测试研究,利用扫描电镜对各部位的CTOD试验断口特征进行了分析,进而比较了母材、焊缝金属和热影响区不同区域金属低温断裂韧性。结果表明:随着试验温度的降低,焊接接头不同部位的断裂韧性CTOD特征值明显降低,F-V曲线逐渐缩短,试样的裂纹稳定扩展区变窄,断裂时的塑性变形不断减小直至消失,两侧剪切区也越来越不明显,焊接接头的韧性降低。在同一试验温度下,母材试样的裂纹稳定扩展区较宽,纤维断裂区较明显,裂纹扩展缓慢;热影响区试样的裂纹稳定扩展区最窄,断口平整,纤维区不明显,主要为脆断区。焊接过程的大输入量热循环使得焊接热影响区中原奥氏体晶粒尺寸增大,从而恶化了热影响区的低温韧性。Thermomechanically controlled process(TMCP)type Q500qE bridge steel heavy plates 60 mm thick were trial-produced in laboratory.The test steel plates were double-sided multi-layer and multi-pass butt welded by automatic submerged arc welding(SAW)machine.The fracture toughness of base metal,weld metal and heat affected zone(HAZ)was studied at low temperature(20℃,-10℃,-40℃)by means of crack tip opening displacement(CTOD)and microstructure analysis.The fracture characteristics of CTOD test of different positions were analyzed by using scanning electron microscope,and then the low temperature fracture toughness of base metal,weld metal and HAZ was compared.The results showed that with the decrease of test temperature,the fracture toughness critical CTOD values at different positions of the welded joints decreased obviously,and the F-V curves shortened gradually,the stable crack growth zone became increasingly narrower,and the plastic deformation of the welded joints decreased until it disappeared,the shear zone on both sides became less and less obvious,and the toughness of welded joint decreased.At the same test temperature,the stable crack growth zone of base metal sample was wider,the fiber fracture zone was obvious,and the crack propagation was slow;the stable crack growth zone of the HAZ was the most narrow,the fracture surface was flat,the fiber zone was not obvious,and the brittle fracture zone was the main one.The increased prior austenite grain size in HAZ arised from the large heat input cycle during welding process,thus deteriorating the low temperature toughness of the HAZ.

关 键 词：Q500qE桥梁钢 焊接接头 裂纹尖端张开位移 低温断裂韧性 解理面 

分 类 号：TG1[金属学及工艺—金属学]