Study On The Weldability And Corrosion Resistance Of Pure Titanium TA2

Because of its good corrosion resistance,high specific strength,non magnetic,impact resistance and weldability,the pure titanium TA2 has been widely used in ship and ocean fields.However,because of its high melting point,low thermal conductivity and small heat capacity,welding parameters will seriously affect the joint performance,and the deformation and burning of TA2 thin plate are easy to occur.At the same time inhomogeneous region near the weld affected by welding thermal cycle caused by the organization,leading to easy to produce electrochemical corrosion,and the weld area near the sharp changes in temperature caused after welding has great welding residual stress of the joint stress corrosion cracking significantly increased.Therefore,it is of great theoretical significance and practical value to successfully solve the welding of TA2 thin plate and to study the corrosion resistance of the joint.Using self-designed welding semi-automatic equipment and welding fixture,the TA2 board with 0.6mm thickness is welded by micro beam plasma arc welding,and the TA2 plate with 0.6mm and 2mm thickness is welded by TIG welding.The influence of welding parameters on the formability and mechanical properties of welds was investigated.The microstructure of the joint was observed,salt fog corrosion,electrochemical test and fracture surface analysis.The TA2 plates with a thickness of 2mm were welded with filler wire and non filling wire TIG respectively,and the SCC sensitivity of the TIG welded joint was investigated.When welding micro beam plasma arc welding,the welding current,ion gas flow rate and welding speed have different influence on the width of the weld joint's back and back.The process parameters are not appropriate,the martensite and coarse widmanstatten.The weld microstructure,decrease the mechanical properties of the joints;when the acicular martensite and lath martensite and less dense reticular small serrated alpha cross distribution,the optimal mechanical properties of the joints,the tensile strength is 455 MPa,tensile close to the base metal strength.The corrosion resistance of the welding seam is better than that of the base metal under this process.When the thickness of TA2 plate is TIG,the tensile strength of the joint can reach 405 MPa at 0.6mm.At this point,the corrosion resistance of base metal is the best,the weld is second,and the heat affected zone is the worst.It is found that the high quality welded joint can be obtained by micro plasma arc welding and TIG welding,and the uniform corrosion occurs in the joint area,while the corrosion resistance of TIG welding seam is slightly worse than that of micro beam plasma welding.The weld quality of the micro beam plasma is higher than that of TIG welding.The thickness of TA2 plate 2mm TIG welding without filler wire,the tensile strength is up to 295 MPa,the microstructure in the joint weld zone caused by coarse grain serious tensile brittle fracture fracture obviously in the weld zone and the fracture,corrosion resistance of this process under the parent material best,weld,heat affected zone is the worst.When TIG is filled,acicular martensite appears in the joint structure,and the tensile strength of the joint reaches 395 MPa.The corrosion resistance of the base metal is the best under this process,the weld is second,and the heat affected zone is the worst.It is found that the corrosion resistance of filler wire TIG welding seam is better than that of non filling wire TIG welding seam.Slow strain rate tensile tests show that when the strain rate is 0.018~0.18mm/min,in the 3.5% NaCl solution showed a certain degree of stress corrosion sensitivity,when the strain rate is 0.018mm/min stress corrosion sensitive location close to near the heat affected zone.