纯镍直缝焊管不同焊接方法的接头性能对比

Performance comparison of straight joint of pure nickel pipe welded with different welding methods

采用等离子与等离子+TIG 2种焊接方法获得尺寸为Φ112mm×3.5mm×6 500mm纯镍直缝焊管.分析了焊后接头宏观形貌、微观组织、力学性能及耐蚀性.结果表明:等离子+TIG较等离子接头各区域晶粒尺寸有所粗化;等离子+TIG接头抗拉强度达到母材的85.6%,满足了镍管接头力学性能要求;等离子+TIG焊缝耐蚀性优于等离子焊缝,较母材有所降低;TIG电弧对焊后等离子接头的二次加热使得等离子接头产生了二次重熔效果,消除了等离子接头产生的咬边、气孔等缺陷,提高了焊接速度,获得了均匀、美观的鱼鳞纹状焊缝表面形貌.综合可见,等离子+TIG焊接是纯镍N6直缝焊管焊接的理想方法.

Both plasma arc welding （PAW） and PAW＋TIG welding methods were used to obtain a pure nickel straight-seam pipe with dimensional specification of 4112 mm×3. 5 mm×6 500 mm for its test, and the macroscopic morphology, microscopic structure, mechanical performance and corrosive resistance of the welded joint were analyzed. The experimental result indicated that compared with PAW joint, the grains in＇ weld region of PAW＋TIG would be coarser, the tensile strength of the joint would reach 85. 6 % of that of the base metal, meeting the requirement of mechanical performance of nickel pipe, and the corrosive resistance would be better, but some what worse than that of base metal. The TIG arc behind the PAW arc would heat the joint secondarily, making the joint of PAW remelted secondarily, eliminate the defect of edge-biting and porosity of the joint, improve the welding speed, and obtain uniform, beautiful and ripple-like surface morphology. It could be found by summarization that the PAW＋TIG welding process would be an ideal welding method for implementing the welding of a pure nickel N6 straight-joint welded pipe.