强度匹配对X80螺旋埋弧焊管环焊接头宽板拉伸性能的影响

Effect of Strength Matching on Wide Plate Tensile Properties of GMAW Girth Welded Joint of X80 Submerged⁃arc Welded Helical Pipe

为了研究不同强度匹配下X80螺旋埋弧焊管环焊接头的拉伸性能,采用等强匹配根焊+高强匹配填充盖面焊和低强匹配根焊+等强匹配填充盖面焊的两种不同强度匹配组合进行了熔化极气体保护自动焊(GMAW),测试了环焊接头的拉伸性能和夏比冲击韧性,并采用宽板拉伸试验研究了环焊接头的拉伸性能和失效行为。结果表明,两种强度匹配下的X80钢管GMAW环焊缝接头均具有较好的形变能力,二者的平均总应变均大于4.0%;最大载荷下,两种强度匹配组合的环焊接头全截面抗拉强度略低于环焊接头小尺寸试样的抗拉强度,但等强+高强匹配的环焊接头具有更高的平均总应变、平均远端应变和裂纹口张开量,失效模式为管体母材发生颈缩失效,而低强+等强匹配组合的GMAW环焊接头失效模式为根焊热影响区发生开裂失效。试验表明,对于X80螺旋埋弧焊管环焊接头,可选用具有一定韧性的等强度焊接材料进行根焊,从而避免焊缝根部产生应变集中而失效。

In order to study tensile properties of X80 submerged⁃arc welded helical pipe girth welded joint under different strength matching,two different strength matching combinations were used for automatic metal arc welding(GMAW).One matching combination was equal strength matching for root welding and high strength matching for filling and cap welding,and the other was low strength matching for root welding and equal strength matching for filling and cap welding.The tensile properties and Charpy impact toughness of girth welded joint were tested.The tensile properties and failure behavior of girth welded joint were studied by wide plate tensile tests.The results show that the GMAW girth welded joints of X80 steel pipes with two strength matching have good deformation,and their average total strain is greater than 4.0%.Under maximum load,the tensile strength of the whole section of the girth welded joint with the two kinds of strength matching combination are slightly lower than that of the conventional tensile strength of the small sample of the girth welded joint,but the average total strain,average distal strain and crack mouth opening displacement of the girth welded joint with the equal strength+high strength matching are higher,and the failure mode is that the pipe body has neck shrinkage failure.However,the failure mode of GMAW girth welding joint with low strength and equal strength matching combination is cracking failure in the heat affected zone of root welding.For X80 submerged⁃arc welded helical pipe girth joint,equal strength welding materials with certain toughness are recommended for root welding,which can effectively avoid the failure caused by strain concentration at the root of the weld.