Development on improving fatigue life of high strength steel welded joints

With the increasing application of high-strength steel in people's pursuit of equipment performance and environmental protectio, welding, as an important material joining method, is essential in the application of high-strength steel. However, the fatigue performance of welded joints does not improve with the increase of steel strength level. So how to improve the fatigue life of the welded joints is of great significance to the application of high-strength steel. Based on the relevant research results at home and abroad in recent years, this paper summarizes the factors affecting the fatigue performance of high-strength steel welded joints, including stress concentration, welding residual stress, welding method and welding material. A variety of methods to improve the fatigue life of high strength steel welded joints are reviewed, and they are classified according to the mechanism of improving the fatigue performance of joints. The first type of life improvement method is mainly based on the improvement of the geometric morphology of the joint, and the life is improved by reducing the stress concentration factor to slow down the initiation of fatigue cracks, such as TIG dressing, laser dressing, spray deposition, profiling and grinding methods. Some of these methods improve the weld morphology and lead-in residual compressive stress that is beneficial to fatigue life. The second type of life improvement method is mainly based on the adjustment of the residual stress of the joint. The crack growth rate is slowed down by reducing the residual tensile stress or introducing the residual compressive stress, such as post-weld heat treatment (PWHT), high frequency mechanical shock (HFMI), laser shock processing (LSP), rolling and friction stir. Some of which also improve the surface hardness and grain size of the joint to affect the fatigue crack initiation. Suggestions and prospects for the use of these methods are put forward.