长输管道外自动根焊采用铜衬垫焊接接头组织与性能分析  

Microstructure and mechanical properties of long-distance pipeline joint by external automatic root welding with copper backing

作　　者：罗智超 汪宏辉 路焰 文学 戚国顺 刘兴邦 雷正龙 

机构地区：[1]中石化江苏油建工程有限公司,扬州市225009 [2]哈尔滨工业大学先进焊接与连接国家重点实验室,150001

出　　处：《焊接》2014年第12期42-47,66-67,共6页Welding & Joining

摘　　要：采用熔化极活性气体保护焊（MAG）对壁厚15.88 mm的X70钢管道多层焊接过程中,外自动根焊采用带铜衬垫的内对口器强制成形时,由于焊接能量输入较大,导致焊缝背面出现了渗铜或熔铜现象.文中采用EDS对焊缝中的渗铜量进行了测量,并分析了渗铜对焊接接头硬度、拉伸、冲击、弯曲等力学性能的影响.试验结果表明：焊缝背面出现渗铜的几率较小,铜含量介于0.11％ ～0.42％之间;焊接接头热影响区硬度最高,达到237 HV,母材硬度最低;拉伸试样全部断裂在母材,平均抗拉强度达到751 MPa,断后伸长率达到11.2％,为塑性断裂,断口呈韧窝状;-20℃时,焊缝冲击吸收能量为153.1 J,熔合区冲击吸收能量为227.6 J.焊缝组织为针状铁素体和少量先共析铁索体;正火区组织主要是细晶铁素体,过热区组织为马氏体和部分贝氏体.In multi-layer MAG welding process of X70 pipe of with 15.88 mm in thickness,the high input energy induces copper infiltration or copper fusion on the back of the weld seam during the enclosed-welding of the internal clamp with a copper backing.In this paper,the amount of the copper infiltration was measured by EDS and the influence of the copper infiltration on the mechanical properties such as the joint hardness,the tensile strength,the impact property and the bending property were analyzed.The experimental results indicate that there hardly appears copper infiltration on the back side of the weld seam with copper content ranging from 0.11%to 0.42%.The HAZ of the welded joint has the maxi mumhardness,which reaches 237 HV.while the base metal has the minimumhardness.The fractures of all tensile samples appear on the base metal with the ductile mode,the average tensile strength and elongation are 751 MPa and 11.2%,respectively.The impact energy of the weld seam and the fusion zone are 153.1 J and 227.6 J at the temperature of-20℃,respectively.The microstructures of the weld seam,the normalized zone and the overheated zone are acicular ferrite and a small amount of proeutectoid ferrite,ultrafi Be ferrite,and martensite with some bainite,respectively.

关 键 词：X70钢管道 渗铜 力学性能 组织 MAG电弧焊 

分 类 号：TG442[金属学及工艺—焊接]