Numerical Simulation And Experimental Investigation Of Micro Plasma Arc Welding Of Tantalum Tungsten Alloy Thin Sheets

Tantalum tungsten alloy,with its excellent mechanical properties,corrosion resistance,mechanical behavior under high temperature,low brittle transition temperature as well as the advantages of good machinability,is widely used in kinds of fields of modern industry.But in the process of the application of tantalum tungsten alloy sheet parts,often encountered precision welding problems.Precision micro plasma arc welding,as one of the high energy beam welding process,has many advantages such as narrow heat affected zone,small welding deformation,high welding speed,cheap equipment and so on,which make it valuable in the research and application of the welding of tantalum tungsten alloy sheet parts.The process and properties of the micro plasma arc welding of tantalum tungsten alloy thin sheets were studied,by numerical simulation combined with welding experiments,in this paper.Through the analysis of macroscopic quality,microstructure,mechanical properties and tensile fracture morphology,obtained the suitable welding process parameters.The process of numerical simulation of the tantalum tungsten alloy welding was accomplished by ANSYS,and the accuracy of the three dimensional model had been verified by experiments.Simulation results show that the heat affected zone of welding joint is narrow,the distribution of temperature and equivalent is uneven in the process of welding,the largest temperature and equivalent stress is located in the weld zone,the final residual stress is only about 70% of the tensile strength;The way of welding residual deformation is the upward Angle deformation,and within a certain range,with the increase of welding speed,residual deformation is reduced.The analysis results of welding joint microstructure and micro-hardness show that the grains organization,near the fusion line and weld,are thick.Away from the weld,grains become small quickly,and in the fusion line obvious epitaxial Growth occurred;The fusion line and weld zone’s micro-hardness is greater than other region.From the fusion line to recrystallization area,micro-hardness falls.But in the recrystallization zone,micro-hardness increases,after that,micro-hardness decreases until to the parent metal hardness.By the tensile mechanical properties and fracture morphology analysis of different weldments,the best welding process was obtained.The experimental results show that the mechanical strength of the weldment is good.The maximum tensile strength of Ta-2.5W is 434 MPa,and the maximum tensile strength of Ta-2.5W/Ta-10 W weldment is 364 MPa.But the elongation is small,the tensile fracture morphology presents the typical characteristics of brittle fracture: E1 and D2 weldment fracture has a small amount of dimple,the rest of the Ta-2.5W weldment fracture presents numerous rivers stripes.Ta-2.5W/Ta-10 W weldment fracture surface presents typical characteristics of intergranular fracture.Under the experimental conditions,the best welding process of Ta-2.5W is given priority to that: main arc current is 30 A,welding speed is 0.75 mm/s,nozzle distance from workpiece is 0.75 mm.The best welding process of Ta-2.5W/Ta-10 W is given priority to that: main arc current is 30 A,welding speed is 1.25 mm/s,nozzle distance from workpiece is 0.5 mm.In this paper,through comparative quality analysis of different welding process,the good welding process parameters are obtained,providing certain basis for the research and application of micro plasma arc welding of tantalum tungsten alloy thin sheets.