Pipeline And Properties Of Self-Cored Welding Protection Organization

X70, X80grade Pipeline Steels welded by self-shielded flux-cored wire (FCAW-S).The impact unstable performance and greatly reduce the active time of the Pipeline Steels.In this paper,Discrete micoscopic structure and mechanical property of welded joint of X70/X80pipeline steel was discussed under self shielded flux cored wire (FCAW-S). Found welded joints of X70/X80grade pipeline steel under self-shielded flux cored wire welded the impact toughness was affected by discrete the weld CGHAZ organization, the MA group, composition segregation influence. This paper uses the the United States G.Krauss scholars view,Isothermal transformation product is divided into two types of granular bainite and acicular ferrite, the lower temperature precipitation is called acicular ferrite and research.Microstructure of the different filling welded layer was observed and the M-A constituent content was quantitatively analyzed, and the influence of welding heat cycle on pipeline steel was discussed. The result shows that the microstructure of CGHAZ produced by multi-layer welding retains part of the original crystallographic orientation relationship, and M-A constituent in intracrystalline reduces significantly. After many welding heat cycle effect, the weld joint received extremely low Impact value. The nucleation of many of the orientation of acicular ferrite in filling layer coarse grain area and the content of Massive M-A constituent increased in intracrystalline and intercrystalline made impact toughness descend.Through Original position statistic distribution analysis(OPA) study the effects of C, Mn, Mo, Nb, found that:Statistic segregation can be used as a basis for judging the pros and cons of the Pipeline Weld impact properties.Through the control of welding heat with self-shielded flux cored wire of pipeline steel welding and reheat the simulation of pipeline steel welding specimen through Gleeble3500thermal simulation testing machine.Respectively use cooling rate of8s,13s,18s,then Study their microscopic structure and impact properties, Found t8/5cooling time and the welding heat affected Pipeline Weld mechanical properties.