Research On Welding Process And Corrsion Mechanism Of Electron Beam Welded Titanium To Steel Joint

With the gradual development of modern industry,the reliability of titanium and steel composite joints are more and more important and the requirement of joints are also rising.Due to the use of titanium and steel joints in complex marine environment,this paper studies microstructure and performance,reveals the difference of corrosion resistance of different titanium and steel joints and analyzes the corrosion mechanium of joints.Two welding methods were used to weld TA10 titanium alloy and Q345 low allow steel.Transition joints prepared by explosively welding method?abbreviated as EXW?were used during electron beam welding?abbreviated as EBXW?of TA10 to Q345.Structure evolutions of Ti/Fe interface,residual stress and tensile strengths of the joints with different distances between electron beam weld and explosive weld?abbreviated as DEW?of 1.5-6 mm were investigated.Finite element method including temperature and stress field was used to analyze the reason why the interface and joint strength has changed remarkably when DEW was different.When the DEW was 1.5 mm,the peak temperature of the Ti/Fe interface was up to 1345°C to have eutectic and eutectoid reactions which lead to the generation of FeTi and Fe₂Ti intermetallic compounds and cracks was produced under transversal stress.All the samples undergone tensile residual stresses except the sample obtained under the condition of DEW=6 mm,which was a key factor leading to the maximum tensile strength when DEW=6 mm.Cu/V composite layers was applied to joining TA10 and Q345 with electron beam welding?abbreviated as EBW?.The microstructure of joints was consisted of IMCs and solid solution.FeTi and Fe₂Ti intermetallic compounds were not observed from joints.Tensile strength of joints was312 MPa and the fracture mode of joint was the intergranular fracture.The corrosion resistance of EXW,EBXW and EBW Ti/Fe joints in artificial seawater was studied in the paper by immersion test,polarization test and electrochemical impendence spectroscopy?EIS?.According to the results of immersion test,corrosion products can not be seen from the surface of the titanium.The surface of steel has been corroded and corrosion products were stacked next to the Ti/Fe interface on the surface.Results of weight-loss test method showed that the corrosion resistance of EBXW joint was better than that of EXW joint.The corrosion resistance of EBW joint was worst.Results of polarization test revealed that average corrosion current density and self corrosion potential of EBW joints were lowest which meaned the corrosion resistance was worst.Results of EIS showed that the capacitive reactance radius of EBW joints was smallest in Nyquist diagram and impedance of EBW joints was lowest when the frequency was in low and medium frequency.Combing principle of electrochemical corrosion and dynamic analysis to analyze the corrosion mechanium of different welding joints.Due to the potential difference of titanium,iron,vanadium and copper,the corrosion resistance of EBW Ti/Fe joints was worst.The corrosion dynamic fitting result confirmed the corrosion mode was power function model.The corrosion rate of joints was from fast to slow and turned to be smooth eventually.