2205/X65复合管焊接工艺及焊接接头组织性能研究

Study on Welding Technology and Weld Joint Micro-structural Properties of 2205/X65 Clad Pipe

针对2205双相不锈钢与X65管线钢在化学成分、物理性能和组织性能差异很大,造成复合管焊接接头力学性能与腐蚀性能降低的问题,进行2205/X65复合管自动焊研究,决定采用多层焊技术:覆层和过渡层采用TIG焊,基层采用MIG焊。观察2205/X65复合管焊接接头的金相组织后发现:过渡层焊缝组织主要是奥氏体+鱼刺状和蠕虫状铁素体;覆层焊缝组织是铁素体+针状、块状的奥氏体;母材、焊缝和HAZ中的铁素体含量控制在40%～55%。基层与覆层焊缝过渡区域有一个宽度约为20μm的过渡层。焊接接头具有良好的拉伸和冲击等力学性能,其晶间腐蚀性能也满足标准和工程实际要求。

Obvious differences exist between the 2205 duplex stainless steel and the X65 linepipe steel in terms of chemical composition, physical properties and micro-structural properties, resulting in reduction of the mechanical properties and the corrosion resistance of the welded joint of the clad pipe. Accordingly, research on the automatic welding technology for the 2205/X65 clad pipe is conducted. As a result, it is determined to employ the multi-layer welding technology, i.e., using the TIG （tungsten inert gas） welding process for both the clad metal and the transition metal, and the MIG （metal inert gas） process for the base metal. Examination of the metallographic structure of welded joint illustrates that the microstructure of weld transition metal is mainly composed of austenite and fishbone and vermicular-shaped ferrites, while the microstructure of weld clad metal is composed of ferrite and acicular and blocky austenite. The contents of the ferrite are controlled within the range of 40%-55% in the base metal, weld and the HAZ, and a transition section wide as about 20 p^m is formed at interface between the base metal and weld metal. As a result it is ensured that the welded joint has excellent mechanical properties like tensile property and impact property, while its intergranular corrosion-resistance is also up to applicable specification as well relevant requirements by related projects.