Study On Construction Process Of Semi-autometic Welding And Low-temperature Welding Of X80 Pipeline Steel

X80 pipeline steel is commonly used in the oil and gas pipelines in the construction longpipeline. In order to fulfil the request of strength and impact ductility of the X80 steelpipelines' weld joints, it is usually necessary of preheating the welding area and controllinginterpass-temperature, which would prolong the construction time, slow down theconstruction progress and raise the construction cost greatly.In order to solve this universal problem in the construction of X80 steel pipelines,technics of X80 steel pipelines' semiautomatic welding and low temperature welding areinvestigated systematically in this thesis. Semiautomatic welding process of combining RMDroot welding and padding, capping by using Self-shielded flux cored wire are studiedmassively, via combining the laboratory investigation and site operation, and have gotsatisfactory application in the second stage of the West-East natural gas transmission project.By using the new semiautomatic welding process, Daqing Oilfield Construction Group haveprocessed some of the X80 steel pipelines' weld joints, which completely corresponded to thecorrelative technique, construction and acceptance specification, increased the progress andmade good economical benefits.Along with the comprehensive construction of pipeline web around the whole nation anddevelopment of old industrial areas in East China, the pipeline construction in East China willbe more and more. When the environmental temperature goes below -5℃, it is forbidden toundertake welding. In this thesis, low temperature welding technique and construction methodwere systematically investigated, and then have been used in practical construction, whichhave got significant project benefits.