The TIG Butt Welding Technique Of Titanium-Steel Clad Plates

Titanium-steel clad plates is widely used in petroleum,chemical,seawater desalination and ship building as well as other industries.Owing to a great difference of the linear expansion coefficient between titanium and steel,the residual stress produced by welding is liable to cause cracking of the joint.A large number of brittle intermetallic are easily produced and weaken the mechanical properties of the joint,which makes fusion welding become more difficulty.In this paper,according to high entropy alloying of transition weld metal,the groove type and size of butt-welded TA2-Q345 clad plates are designed.The welding process parameters were determined through numerical simulation of the fusion process of clad plate.Then TIG butt-welded TA2-Q345 clad plates.Analyzed the joint microstructure and researched the welding process that influence on the microstructure and mechanical properties of joint.The results show that:TIG butt-welded TA2-Q345 clad plate which thickness is（3+20）mm.degined as double V groove shaped,steel base slope depth of 17mm,angle of 45°,Cladding titanium groove angle of 60°,blunt side of 1.5mm,assembly gap of 2.0mm.Welding order for the steel substrate were butt welding,transition layer welding,and titanium plate welded together.The numerical simulation results of fusion welding process in the TA2-Q345 clad plates showed that the temperature field of the welding was elliptical and the temperature of the heat source was the highest,and the temperature gradient and the heat affected zone increased with the increasing of the welding current.The longitudinal residual stress was symmetrical and the maximum was 325MPa.The-transverse residual stress was similar to parabola distribution and the tensile stress was mainly distributed in the weld and the compressive stress was far away from the weld.The junction of the titanium-steel composite plate and the joint in the transition zone were the stress concentration zone of the welded joint,the junction of the three zones（fusion line）and the tensile zone of the heat affected zone were 80-175MPa.Welding voltage of 20V,welding current of 130A,welding speed of 5mm/s could be achieved when the TA2-Q345 composite plate direct melting welding,and the residual stress after welding the minimum value of 275MPa.The welding material H08Mn2SiA was chosen for base plate metal butt welding,the number of welding layers was six and the interlayer temperature is controlled at 150±10℃.The welding parameters are:I=110～150A,V=1.5～2.5mm/s,Q=17L/min.Ti₅Fe₁₅Ni₂₆Cu₂₈V₂₆ alloy welding material for transitional welding.which welding parameters are:I=130A,V=5mm/s,Q=17L/min.Cladding titanium welding material chose STA2R,welding parameters are:I=102A,V=4mm/s.The joint welded under the conditions above have high welding efficiency,low welding material consumption,and the strong weldable,so there had no defects for some unreasonable groove coefficient such as lack of penetration.The joint of GTAW of titanium-steel clad plates with Ti₅Fe₁₅Ni₂₆Cu₂₈V₂₆ welding material has a good formation,being full and uniformly continuous without obviously oxidized;Weld metal and base metal,weld metal between each layer are fusion better.The microstructure of the transition zone weld is made up of plenty of dendrites and a small amount of equiaxed crystals,which is FCC+BCC simple solid solution structure and effec（Ti,V）ely inhibit the production of brittle intermetallic compounds;The hardness value was in 150～550HV from the steel base weld to the cladding weld shows an increasing trend.The hardness of transition zone weld is 250HV～325HV,which plays an excellent transitional role between the base steel weld and cladding titanium weld,which improves the performance of the GTAW joint.Under the condition of welding current I=150A,welding speed V=7mm/s,argon gas flow rate Q=17L/min,GTAW the bonding layer of TA2-Q345 clad plates with Ti₅Fe₁₁Ni₂₆Cu₂₈V₃₀、Ti₅Fe₁₅Ni₂₆Cu₂₈V₂₆、Ti₅Fe₇Ni₂₆Cu₃₀V₃₂ welding fillers.which all obtained favorable joints.The joint shows best corrosion resistance when using the Ti₅Fe₇Ni₂₆Cu₃₀V₃₂ bonding layer welding material.