Study On The Influence Factor And Improvement Measures Of X70 Welded Joints Toughness

Pipeline welding is one of the key factors affecting the quality and efficiency of pipeline construction, self-shielded flux-cored wire semi-automatic welding is widely used in pipeline construction. Girth weld joint is the weak link in the pipeline, as well as most parts of pipeline construction and safety. In recent years, with the increase of steel grade and welding raise the level of automation, high grade pipeline girth weld joint related failure incidents increased, high grade pipeline girth weld joint quality and safety issues are becoming increasingly prominent. Mainly for i MPact property of welded joints of great instability and discrete, difference on properties of welded joint of different manufacturers of welding consumables. Our girth weld joint fracture initiation toughness of control indexes of mostly standard adopted in API and ASME, typical defects in welded joint iMPact on pipeline safety is the lack of theoretical analysis and calculation.In this paper, based on existing project, select the X70 used as the object of study of pipeline steel and self-shielded flux-cored wire semi-automatic welding was studied factors influencing iMPact property of welded joints, to reasonably determine girth weld joint toughness, control welding process parameters, Improve the quality of construction to provide the theoretical foundation and reliable method. Through on different metallurgy system X70 pipeline steel and different wire of matching research, exploration of the parent metal and wire microalloy matching on self-shielded flux-cored wire welding joint performance iMPact, analysis welding heat input, and content of hydrogen diffused in welding joints, and welding joints metallographic structure and morphology and distribution of inclusions on welding joints performance of effects, targeted X70 pipeline steel is put forward from the protection of self-shielded flux-cored wire welding joint measures to boost the toughness of the optimal control, solved X70 self-shielded flux-cored wire welding joint properties of problems, provides theoretical foundation for revision and perfection of the existing X70 welding technical specification and essential data. X70 welding procedure specification and quality control of pipeline welding provides an important reference, ensures that the 2ed West-East Gas Pipeline Project and the Trans-Asia Gas Pipeline Project etc. successfully construction.