The Study Of Microstructure And Property Of The Friction Welding Joint Of High Strength Pipeline Steel

As a kind of microalloyed high strength low alloy steel,welding of pipeline steel at the scene of the steel pipe forming and welding in the process of machining operations will be affected by a lot of,especially some special application line.For general fusion welding,the welding joint of inevitably produce welding defects such as inclusions and pores,these defects greatly reduces the welding strength of the welded joint.Among them,the effect of heat affected zone is the largest,as is known to all,organization of heat affected zone,grain is relatively bulky,the region will make the performance degradation is relatively serious,making the region far worse performance than the parent metal,based on these defects,can consider to other welding methods.Therefore,how to choose the welding method and improve welding process in order to improve the efficiency of welding and welding quality,has always been a hot research topic in the field of pipeline construction.Friction welding as a kind of solid phase welding method,because of its good welding quality,welding short construction time,high efficiency,high precision characteristics,in areas such as aerospace,automobile,petroleum drill pipe welding has been widely used.Based on X80 pipeline steel as the research object,this paper adopts the methods of microstructure analysis and mechanical property test,studied under different friction welding welding process,welding joint organization performance change rules,this paper discusses the friction welding was applied to the feasibility of the girth weld high grade pipeline steels.Using the method of orthogonal experiment combined with poor,obtained the high strength pipeline steel the optimal combination of the technological parameters of friction welding is: speed 1500 r·min-1,friction pressure 160 Mpa,upset forging pressure 320 Mpa,shorten the quantity to 4 mm.After butt welding heat treatment process for the design and optimization,and connecting with the hardness test,microstructure observation,SEM analysis,analysis the influence of different heat treatment process on the welding joint,determine the optimum process parameters of weld heat treatment is: heating temperature is 950 ?,heat preservation time 20 min,quenching medium is water,tempering temperature is 600 ?,tempering heat preservation time for 60 min.Corrosion testing results of welded joint show that the temperature of 50? environment,welding joint in two different corrosion solution immersion corrosion occurred after 288 h.Due to the alkaline soil simulation solution from the corrosion potential negative than 3.5%NaCl solution,extremely serious corrosion.Through SEM and EDS analysis was carried out on the corrosion products,can be welded joint for iron oxide corrosion products in both two solutions,and the corrosion products on the substrate without protection.