热输入对超高强钢焊接接头组织与性能的影响  

Influence of Heat Input on Microstructure and Properties ofUltra⁃high Strength Steel Welded Joints

作　　者：闫强军 巴凌志 梁川 邢萍 利成宁 刘丽华 邸新杰[1] YAN Qiangjun;BA Lingzhi;LIANG Chuan;XING Ping;LI Chengning;LIU Lihua;DI Xinjie(School of Materials and Science Engineering,Tianjin University,Tianjin 300350,China;Nanjing Iron and Steel Co.,Ltd.,Nanjing 210094,China)

机构地区：[1]天津大学材料与科学工程学院,天津300350 [2]南京钢铁股份有限公司,南京210094

出　　处：《焊管》2024年第11期34-38,共5页Welded Pipe and Tube

基　　金：国家自然科学基金项目“低碳含铜超高强钢可控相变焊接接头氢扩散及抗氢脆机理研究”(项目编号52274391)。

摘　　要：采用不同的热输入对1500 MPa级超高强钢进行熔化极气体保护焊,并通过硬度分布试验和DIC拉伸试验分析焊接接头硬化区,对比粗晶热影响区(CGHAZ)的冲击韧性,结合金相观察分析热输入对接头脆化行为的影响。结果表明:两种热输入的显微组织类型一致,焊缝区域主要为贝氏体、针状铁素体和准多边形铁素体,CGHAZ区域主要由板条马氏体构成,形成脆化区,硬度高达550HV_(10)。当焊接热输入由29 kJ/cm提高至47 kJ/cm后,焊缝和CGHAZ的组织发生显著粗化,CGHAZ的冲击韧性严重恶化,由47 J降至19 J。焊接接头的软化区位于熔合线焊缝侧,大小热输入焊接接头均在焊缝位置断裂,抗拉强度分别为704 MPa和628 MPa,区别在于大热输入下应变集中在根焊和第二层的交界,而小热输入应变集中在中层焊道的熔合线内侧。1500 MPa grade ultra⁃high strength steel was subjected to gas metal arc welding(GMAW)with different heat inputs.The hardening zone of the welded joints was analyzed through hardness distribution tests and digital image correlation(DIC)tensile tests.The impact toughness of the coarse⁃grained heat⁃affected zone(CGHAZ)was compared,and the effect of heat input on joint embrittlement behavior was examined using metallographic observations.Results show that the microstructure types for both heat inputs are consistent,with the weld region mainly composed of bainite,acicular ferrite,and quasi-polygonal ferrite,while the CGHAZ is predominantly composed of lath martensite,forming an embrittled zone with a hardness reaching 550HV_(10).When the welding heat input was increased from 29 kJ/cm to 47 kJ/cm,significant coarsening occurred in the weld and CGHAZ microstructures,severely degrading the impact toughness of the CGHAZ from 47 J to 19 J.The softening zone of the welded joints was located on the weld side of the fusion line,and both high and low heat input joints fractured at the weld location.The tensile strength of the joints was 704 MPa and 628 MPa for low and high heat inputs,respectively,with strain concentration occurring at the junction between the root weld and the second layer in high heat input welding,and at the inner side of the fusion line in the middle weld layer in low heat input welding.

关 键 词：超高强钢 热输入 焊接接头 微观组织 力学性能 

分 类 号：TG441[金属学及工艺—焊接]