Research On Amorphous Brazing Fillers For Brazing Titanium TA2 And Q235 Steel

Titanium alloys have good thermostability,corrosion resistance but high price.Composite structure is of excellent performance of Ti and Steel but reasonable price.Because there is big difference in the physical and chemical properties of titanium and steel,it is hard to weld these two dissimilar metals.And brazing is one of the better methods of connecting them.Ti-Zr-Cu-Ni brazing fillers with good performance are mostly applied to the connection of TC and TB titanium alloys.But the brazing temperature of brazing TA titanium alloys with these brazing fillers is much higher than 882.5 ?,the ??? phase transition temperature of TA2,which reduces the ductility of the base metal titanium near the brazing seam.Accordingly,to solve this problem that the brazing temperature is too high to be appropriate for brazing Ti and Steel,the thinking that the brazing temperature can be reduced by reducing the melting temperature of the brazing fillers was proposed.Two methods to reduce the melting temperature of the brazing fillers were used in this paper.On one hand,the components of the brazing fillers was redesigned and optimized.On the other hand,element Sn was added into the fillers.These two designed sets of brazing filler foils were prepared by using a single roller rapid solidification apparatus,the phase composition,melting temperature and tensile strength of the fillers were tested,the better fillers in each set were applied to the brazing of dissimilar metals TA2 and Q235,the microstructure of the joints was observed and the shear strength was tested.After getting the appropriate welding process,TA2 and Q235 were brazed again to ultimately obtain brazing fillers with lower melting temperature adapted to brazing TA2 and Q235.The results show that,two new sets of Ti-Zr base amorphous brazing fillers were designed.Both of Zr-Ti-Ni-Cu and Ti-Zr-Cu-Ni-Sn brazing fillers have amorphous structure,good shaping properties,thickness of 40?m?60?m,width of 4mm and melting temperature lower than the phase transition temperature 882.5 ? which meets the requirements for brazing.Titanium TA2 and Q235 steel were brazed with Zr52Ti22Ni18Cu8,Zr52Ti24Ni16Cu8,Zr52Ti24Ni13Cu11,Ti33.95Zr33.95Cu14.55Ni14.55Sn3,Ti33.25Zr33.25Cu14.25Ni14.25Sn5,Ti32.55Zr32.55Cu13.95Ni13.95Sn7 and Ti31.85Zr31.85Cu13.65Ni13.65Sn9 amorphous brazing fillers.The alloys have good flowability and the brazing seams are dense,fully filled and closely combined with the base metals without any obvious weld defect.A lot transition of the base metal titanium TA2 near the seam did not come into being and the good ductility of the base metal was remained.But there are some intermetallic compounds in the seam,when its content gets high,the performance of the joints will be affected,then the guarantee of the ductility of the base metal by restraining ??? transition will not make up the damage caused by intermetallic.When the technical parameters are:heating current 25A,heating time 10s and heat-retaining time 15s,the shear strength of joint TA2/Zr52Ti22Ni18Cu8/Q235 is 117.12MPa.