Crack sensitivity of X65 steel root welding process with copper liners

In this paper, crack sensitivity analysis was performed on the root welding process with copper liners in X65 pipeline by the pipeline girth weld sensitivity test method which is developed on the basis of finite element simulation. The welding process with copper liners was proved to be reasonable by comparing its test results with that of the process without copper liners. The lower cold crack sensitivity is mainly caused by the following two reasons. First, the designed welding parameters are rational with heat input as low as 0.56 kJ/mm and the heat input is less during the on-site welding, so it is difficult for the coppers to penetrate into the welding lines. And second, its cold cracking resistance is good when X65 steel is welded by CO₂ gas shielded welding process with ER70S-G solid wires. Besides, local corrosion test was performed at the roots. It is shown that X65 root welding with copper liners can fully meet construction specifications in terms of welded-joint mechanical properties by formulating welding parameters reasonably.