| With the growing of energy demand,long distance transportation of oil and gas becomes more and more important,but the frequently occurrence of oil and gas leakage and pipeline explosion accident,makes the safety of oil and gas pipeline more attracted the attention of people.Corrosion cracking is the main cause of oil and gas pipelines accidents,In order to improve the pipeline corrosion resistance,people have tried to use pure stainless steel and titanium alloy in preparation of oil and gas pipelines,but the high cost makes people have to find another way.Titanium-steel bimetal composite plate is integrating the corrosion resistance of titanium and high strength and toughness of steel and good to solve the problem.But the large difference of physical and chemical characteristics for titanium and steel,making it too difficult to fusion weld joint.At present,lap welding method used on titanium-steel bimetal composite plate weld both at home and abroad,and has yet to see the butt fusion welding reports,however,the particularity structure of oil and gas pipelines makes lap welding hard for composite plate weld.In this study,the fusion weld butt joint of titanium-steel is studied from two aspects.On the one hand,by using the software ANSYS,it carried out the residual stress and deformation calculation analysis of the butt weld seam of TA1-X80 composite plate whose weld seam is divided into double to four layer.On the other hand,the TA1-Q235 composite plates are used as the base metals,which are welded with different combinations if welding materials and different welding processes.Then the deficiencies mechanism is researched further by the analysis of the microstructure and mechanical properties tests.Finally it will supply a strong theoretical basis to form the excellent titanium-sleel composite plate welding butt joint.Through ANSYS finite element analysis,it shows that the titanium and steel could not be directly fusion welding and the transition layer stress is larger when titanium alloy as single transition or titanium alloy/nickel base alloy as two transitions,so need to optimize welding materials.Analyzing the defects,it can obtained that the weld area on the both sides of titanium and steel have better fusion while using TC4/TA15/Ni60/YC-GX80 butt weld,nearly titanium transition zone exists inclusions,voids,and transition layer has poorer fusion with the base metal,and also the weld tip will remelt for many times and the thermal stress impact is obvious.So it should choose the groove form which has less stress.When single V element used as transition layer for butt weld,the interface in V/YC-GX80 can not achieve good metallurgical fusion due to V easily forms vanadium carbides with C element in steel as to increase the interface brittleness.As on the steel plate welding ERCuSi/YC-GX80,the interface fusion is good,so ERCuSi can be choosed as the welding materials nearly steel layer.When welding by using ERCuSi as nearly steel layer and V as nearly titanium layer of YC-GX80/ERCuSi/V/Ti,the Ti/V interface appears the V-rich phenomenon,so it cannot be infinite solid solution with titanium.Also the hardness differs greatly with Ti/V interface.Then the Cu and Ti intermetallic compound exists in the molten pool,eventually forming the crack defects. |
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