How titanium alloys are welded
At present, TC4 titanium alloys are mostly welded by argon arc welding or plasma arc welding. However, both of these methods need to be filled with welding materials. Oxygen content of joints increases and strength decreases due to restrictions on the protection atmosphere, purity, and effects. , And after welding deformation. Using electron beam welding and laser beam welding, the welding process of TC4 titanium alloy was studied to realize the precision welding of the material.
(1) Porosity tendency of welds. The pores in the weld are the most common defects in the welded titanium alloy. Hydrogen and oxygen that are present in the arc region of the weld metal are the main cause of pore generation. The electron beam welding of TC4 titanium alloy has few porosity defects in the weld. For this reason, the research focuses on the process factors for the formation of pores in laser welds. It can be seen from the test results that there is a close relationship between the porosity of the weld and the weld line energy during laser welding. If the energy of the weld line is moderate, there is only a small amount of pores or even no pores in the weld, and the energy of the line is too large or too small. Both can cause serious porosity defects in the weld. In addition, whether there are pore defects in the weld is also related to the wall thickness of the weldment. Compared with the test results of the sample, it can be seen that as the thickness of the weld increases, the probability of occurrence of pores in the weld increases. (2) Internal weld quality. Using flat butt joint specimens, electron beam welding and laser welding were used to examine the internal quality of the welds. The internal quality of the welds was examined by X-ray inspection to meet GB3233-87 Level II requirements. No cracks appeared on the surface and inside of the welds. The weld appearance is well formed and the color is normal. (3) Weld depth and its fluctuations. Titanium alloy used as an engineering component has certain requirements for welding depth, otherwise it can not meet the requirements of component strength; and to achieve precision welding, we must control the welding depth fluctuation. For this purpose, two pairs of docking test rings were respectively welded by electron beam welding and laser welding. After the welding, the test rings were dissected longitudinally and transversely to investigate the depth of weld and fluctuations in weld depth. The results showed that electron beam welding was performed. The average weld depth can reach more than 2.70mm, the welding depth fluctuation range is -5.2% to +6.0% and does not exceed ±10%; the average welding depth of laser welding weld is about 2.70mm, and the welding depth fluctuation range is -3.8~+5.9% , not more than ±10%