1, weld porosity tendency
Porosity in the weld is the most common defects in welded titanium alloys, the presence of hydrogen and oxygen in the arc zone of the welded metal is the main cause of porosity.TC4 titanium alloy electron beam welding, its weld porosity defects in the weld is rare. For this reason, focusing on the formation of pores in the laser welding weld process factors for research. From the test results can be seen, laser welding in the weld porosity and weld line energy has a close relationship, if the welding line energy is moderate, the weld only a very small number of pores, or even no pores, line energy is too large or too small will lead to serious porosity defects in the weld. In addition, whether the weld has porosity defects in the weld also has a certain relationship with the wall thickness of the weldment, comparative sample test results can be seen, with the increase in weld wall thickness, the probability of porosity in the weldment increases.
2, the internal quality of the weld
The use of flat plate butt specimens, the use of electron beam welding and laser welding to examine the internal quality of the weld, managerial testing, the internal quality of the weld by X-ray flaw detection, up to the GB3233-87 Grade II requirements, the weld surface and the internal are no cracks, the weld appearance of good molding, color and lustre is normal.
3,Welding depth and its fluctuation
Titanium alloy used as engineering components, the weld depth has certain requirements, otherwise it can not meet the requirements of component strength; and to realize the precision welding, the weld depth fluctuations must be controlled. To this end, the use of electron beam welding and laser welding methods were welded two pairs of butt test ring, welded on the test ring longitudinal and transverse anatomy, to examine the weld depth and weld depth fluctuations, the results show that the average weld depth of the electron beam welding weld up to 2. 70mm or more, weld depth fluctuations of -5. 2 ~ +6. 0%, not more than ± 10%; laser welding weld weld depth of about 2. 70mm, weld depth fluctuation of - 3. The average weld depth of laser welded seam is about 2.70mm, and the fluctuation of weld depth is - 3.8~+5.9%, not more than ±10%.
4, joint deformation analysis
The use of butt test ring to examine the joint welding deformation, detection of butt test ring radial and axial deformation, the results show that the electron beam welding and laser welding deformation are very small. The radial shrinkage deformation of electron beam welding is f {{0}}.05~f 0.09mm, and the axial shrinkage is {{10}}.06~0.14mm; the radial shrinkage deformation of laser welding is f 0.03~f 0.10mm, and the axial shrinkage deformation is 0.02~0.03mm.
5, weld organization analysis
Manager chemical detection, the weld organization for a + b, organizational morphology for columnar crystal + isometric crystals, there are a small number of slat martensite appears, grain size and matrix close to the heat affected zone is narrower, the organizational morphology and characteristics of the more desirable. It can be concluded that: for TC4 titanium alloy, whether it is laser welding or electron beam welding, as long as the process parameters are matched reasonably, the internal quality of the weld can reach the national standard GB3233-87 Ⅱ weld requirements to achieve the precision welding of TC4 titanium alloy; weld appearance of good shape, color and lustre; weld residual height is very small, no biting edges, depressions, surface cracks and other defects produced.
