LNG工程用节镍型7Ni钢焊接接头组织与力学性能  

Microstructure and Mechanical Properties of Welded Joint of Nickel Saving 7Ni Steel for LNG Engineering

作　　者：蔡啸涛 齐彦昌[1] 魏金山[1] 马成勇[1] CAI Xiaotao;QI Yanchang;WEI Jinshan;MA Chengyong(Department of Welding,Central Iron and St eel Research Institute,Bejing 100081,China;Suzhou Institute of Technology,Jiangsu University of Science and Technology,Zhangjiagang 215600,China)

机构地区：[1]钢铁研究总院焊接研究所,北京100081 [2]江苏科技大学苏州理工学院,江苏张家港215600

出　　处：《热加工工艺》2023年第13期47-51,56,共6页Hot Working Technology

基　　金：国家重点研发计划项目(2017YFB0305005)。

摘　　要：采用国产ENiCrMo-6焊条对节镍型7Ni低温钢进行了焊接,使用OM、SEM、EDS等手段观察分析了焊接接头的显微组织和冲击断口,并对焊接接头的拉伸、低温冲击、弯曲、硬度进行了研究。结果表明:焊材与母材匹配良好,焊接接头中未发现焊接缺陷,综合力学性能满足LNG工程使用要求。焊缝金属由富Ni奥氏体枝晶和析出相组成,平均硬度为196.6 HV;熔合线界面上存在硬度较高的稀释层,最高硬度达405.2 HV;热影响区分为明显的粗晶区、细晶区和临界区,主要组织均为马氏体+少量残余奥氏体,平均硬度为319.8 HV,高于母材平均硬度(233.1 HV)。接头的平均抗拉强度为726 MPa,均断于母材;焊缝中心、熔合线和热影响区的-196℃平均冲击功分别为82、64、120 J;侧弯试样在熔合线处存在轻微开裂。熔合线附近的硬脆组织是影响接头低温冲击韧性和弯曲性能的主要因素。Nickel saving 7Ni cryogenic steel was welded by using Chinese ENiCrMo-6 electrode.The microstructure and impact fracture of the welded joint were observed and analyzed by applying OM,SEM and EDS methods.The tensile,cryogenic impact,bending and hardness of the welded joint were studied.The results show that the welding material matches well with the base metal,no welding defects are found in the welded joint,and the comprehensive mechanical properties of the joint meet the requirements of LNG engineering.The weld metal consists of Ni-rich austenite dendrites and precipitates,and the average hardness is 196.6 HV.There are some hard dilution layers at the interface of the fusion line,and the highest hardness is 405.2 HV.The heat affected zone is clearly composed of CGHAZ,FGHAZ and ICHAZ,and all the microstructure is martensite and a small amount of retained austenite.The average hardness of HAZ is 319.8 HV,which is higher than that of the base metal(233.1 HV).The average tensile strength of the joint is 726 MPa,and the fracture is located in the base metal.The average impact energy of the weld center,fusion line and HAZ is 82,64 and 120 J at-196℃respectively.There are microcracks at the fusion line zone in side bending specimens.The hard and brittle microstructure near the fusion line is the main factor affecting the cryogenic impact toughness and bending performance of the joint.

关 键 词：7Ni钢 ENiCrMo-6焊条 焊接接头 显微组织 力学性能 

分 类 号：TG444.1[金属学及工艺—焊接] TG457.11