Study on microstructure and properties of laser welded thin-walled straight seam titanium pipes

The thin-walled Gr.1 pure titanium straight seam welded pipe was welded by laser, and the samples obtained from the experiment were analyzed for macroscopic morphology, microstructure and mechanical properties. The results show that the weld width of longitudinally welded thin-walled pipe is relatively narrow, with an outer weld width of 1.51 mm and an inner weld width of 0.98 mm. The microstructure of titanium welded pipe weld is mainly columnar α phase, serrated α phase and a small amount of needle shape α phase. The results of flaring, flattening, and reverse bending tests are all qualified. Finally, an expansion test was conducted on the sample tube, and the expansion amplitude reached 18.4%, with a relatively uniform deformation in appearance. From the microstructure after tube expansion, it can be seen that after tube expansion, most of the grains in the weld seam, heat affected zone, and base metal are significantly deformed and broken due to tensile action, and many needle shaped α phase grains are produced , but no cracks occurred.