| Currently, Welded structures became more and more important; however the welded structures fracture accidents often occur. Statistical data shows that 90% of the fracture accidents are caused by fatigue failure of welded joints. Therefore, the fatigue strength improvement of welded joints is significant to social benefits and economic benefits. In this paper, low transformation temperature welding wire and the fatigue strength improvement of 304L welded joints are systematically researched.Based on the Martensite transformation principle, low transformation temperature welding wire (LTTW) is developed. Firstly, the residual stress of single channel welding LTTW is measured; the results show that compression stress exists. Then the impact toughness, microstructure, phase structure and hardness of welded metal are analyzed.ANSYS are used to simulate the welding temperature and the distribution of residual stress after welding of the no-load cruciform welded joints, which are divided into three groups: as-welded, 308L-dressing and LTTW-dressing. The welding temperature results simulate the actual situation of welding. The residual stress results show that, compared with the as-welded joints, 308L-dressing improves the residual tensile stress of weld toes, and LTTW-dressing change the residual tensile stress to residual compression stress duing to the Martensite transformation.The fatigue tests of no-load cruciform welded joints are conducted, and the results show that compared to the as-welded joints, the fatigue strength of LTTW-dressing joints increased by 7.87%.Compared to the 308 L-dressing joints, the fatigue strength of LTTW-dressing joints increased by 5.84%. The fatigue life of LTTW-dressing joints improved from several times to more than 20 times under three different loads. And the statistics analysis of fatigue data show that even consider the effect of dispersion, LTTW-dressing can significantly improve the fatigue strength of welded joints. |
PDF Full Text Request