Research On Welding Process For Fusion Butt Joint Of TA1/X65 Layered-composite Plate

With the growing of energy demand,it has become inevitable for long distance transportation of oil and gas.But it at'tracts to the people's attention on the corrosion resistance of oil and gas pipeline because of the frequent occurrence of oil and gas leakage and pipeline explosion accidents.Corrosion cracking is the main reason about that cause the oil and gas pipelines leak.In order to improve the pipelines corrosion resistance,people have tried to use pure stainless steel and titanium alloy to manufacture oil and gas pipelines,but the high cost makes people have to find another way.Titanium-steel composite pipe integrates the corrosion resistance of titanium and high strength and toughness of steel and solves this problem very wellIn the paper,the research target was TA1/X65 layered-composite plate.Based on the particularity and suitability of melting welding non-uniform temperature field and the layers of weld metal solidification of titanium-steel composite plate,it analyzes the differences of strength and toughness and transition layer interface adapter and other issues of titaniurm-steel welding.Welding materials of TA1/X65 layered-composite plate in each layer had been respectively designed according to the strong and thinning properties of weld seam in welding process and the phase formation mechanism.At the same time,combining with the working condition of the base metal and molding technology characteristics of pipe welding,the welding processe had been developed.The study results show that it can be well for titanium and steel metallurgical connection by fusion welding with ERTA1 as the welding materials for titanium layer,flux-cored wire as the welding material for transition layer and ER50-6 as welding material for steel layer.But it can produce coarse microstructure and poor toughness.When Cu-Ag-Mo-Nb flux-cored wire is a single transition welding material,the interface micro structure of welded joint connected with each layer well.And it eliminates the element enrichment or partial poly and defects such as cracks due to mutual diffusion of elements with each other.The tensile strength reaches to expected target eventually,yet the toughness is slightly insufficient.On the other hand,it welds titanium-steel composite plate using to enchase 20 mm width pre-bending titanium covered plate by manual TIG welding.The welding current is 100 A and 110 A,respectively.Ar gas is chosed as gas protection on the back of covered plate.These can guarantee to get ideal titanium welding penetration and good bending performance.The test results of adding covered plate welding process show that the welding process can realize welding of titanium-steel composite plate.Based on the above reseach,TA1/X65 composite pipes are welded by using covered plate welding process.The automatic MAG is to weld steel layer,and manual TIG welding is to titanium layer.And the current is 100 A-110 A.Finally,the mechnical properties of welded joint are ideal,and it reaches to the using requirement.This provides reference for engineering application of TA1/X65 composite pipes.