桥梁钢Q420qD焊接热影响区组织性能研究  

Study on Microstructure and Properties of Welding Heat Affected Zone of Q420qD Bridge Steel

作　　者：白斌 侯蕾[1] 刘凤新 郑文超 刘宝喜 Bai Bin;Hou Lei;Liu Fengxin;Zheng Wenchao;Liu Baoxi(Tangshan Medium and Heavy Plate Co.,Ltd.)

机构地区：[1]唐山中厚板材有限公司

出　　处：《宽厚板》2020年第4期7-11,共5页Wide and Heavy Plate

摘　　要：桥梁钢Q420q要求同时具有优异的强韧性和良好的可焊性,焊接热影响区(HAZ)的显微组织和性能直接影响构件焊接接头质量。20 mm厚度控轧控冷型Q420qD钢板在不进行焊前预热和焊后热处理条件下进行焊接试验,并针对其焊接热影响区的组织和性能展开分析研究。结果表明:当焊接线能量为15 kJ/cm时,焊接接头的力学性能达到国家标准;焊接接头各区域断口均由韧窝组成,呈现韧性断裂形貌;-20℃冲击功≥279 J,超过国家标准要求值;焊接接头区域未出现明显的软化、硬化现象;焊缝显微组织以针状铁素体为主,能有效阻碍裂纹扩展;熔合线显微组织包含粒状贝氏体、侧板条铁素体、针状铁素体和多边形铁素体;粗晶区的显微组织为粒状贝氏体、板条贝氏体、针状铁素体及少量多边形铁素体的混合组织;细晶区的显微组织为大量多边形铁素体、珠光体及少量渗碳体。Q420q bridge steel requires excellent strength-toughness and good weldability,but the microstructure and mechanical properties of welding HAZ directly affect the weld joint quality of welding structure.By means of welding test without preheating and post-weld heat treatment,the paper analyses and studies the microstructure and mechanical properties in welding HAZ of 20 mm thick controlled rolling and controlled cooling Q420qD steel plate.The results show that the mechanical properties of weld joint meet the requirements of national standard at the welding heat input of 15 kJ/cm.The fracture at each zone of weld joint is composed of dimples in the mode of toughness fracture.The impact energy at-20℃is equal to or greater than 279 J,which exceeds the required value in national standard.No evident softening or hardening phenomena occurs at the weld joint.The microstructure at weld seam is mainly composed of acicular ferrite,which can prevent the crack propagation more effectively.The microstructure at fusion line consists of granular bainite,side lath ferrite,acicular ferrite and polygonal ferrite.The microstructure at coarse grained region constitutes mixed structure of granular bainite,lath bainite,acicular ferrite and less polygonal ferrite.The microstructure at fine grained region consists of large amount of polygonal ferrite,pearlite and less cementite.

关 键 词：超快冷 桥梁钢 焊接热影响区 组织性能 

分 类 号：TG457.11[金属学及工艺—焊接]