The Process Optimization Of Electron Beam Welding Of Titanium Alloy To Stainless Steel

Electron beam welding of TA15and304SS were carried out. It was studiedthat different filler metals, different joint forms and process parameters affectedon the microstructure and property of joints. Based on the calculated result oftemperature and stress fields of the joints, the formations of bubbles and crackswere discussed. In the end, good joints were obtained whose Tensile strength washigh and plastic property was improved.In order to add Cu and V elements to the weld, two joint forms weredesigned which were optimized Cu/V filler metals and adding a length of QCr0.8.If the filler metals were optimized Cu/V layers, the unmelted V filler metals atthe bottom of the joint were eliminated. However, the microstructure was σ-FeVand some unmelted V filler metals in the interface of two welds where it was theweakest part of the joint. Tensile strength of the joint was298.9MPa. Adding alength of QCr0.8, the fracture molds were brittleness crack and ductile fracture.When the length of QCr0.8was1.5mm and304SS/QCr0.8were welded at first,Tensile strength of the joint was338MPa.In order to improve the tensile strength of the joint and reduce the numberof bubble, Cu, V and Cr elements were added into the weld. When adding Cuand V elements into the weld, TiFe and TiCr2formed near titanium alloy, and thetensile strength of the joint was very low. When the filler metals were Cu-Cr/Vcomposite layers, the microstructure of the joint was304SS/ss(Fe,Cr)/Cu(s,s)/V(s,s)/Cu(s,s)/ss(Ti,V). Tensile strength of the joint was419MPa, reached77.6%of the stainless steel.Based on the calculated result of temperature and stress fields of the joints,it was found that the formation of bubble in the joint was due to the existence ofgaps between base metals and filler metals and a extreme cooling velocity. theformation of cracks was due to the existence of residual stress. By reducing thegap and adding process of postheat, a joint, which was free of bubbles andcracks, was obtained. When the filler metals were Cu9Cr/V composite layers andthe process was three-pass welding, tensile strength of the joint reached459MPa,and plastic property was improved a lot.