Material and residual stress improvement in S355 welded structural steel using mechanical and thermal post-weld treatment methods

Welding is by far the most widely used metal joining method. High-Frequency Mechanical Impact (HFMI) treatment and Tungsten Inert Gas (TIG) remelting are two post-weld treatment methods that aim to enhance the strength of the steel. In this paper, the improvement in residual stress and material characteristic obtained with these methods are studied by conducting several experimental investigations such as hole drilling, hardness testing and microscopy. Hole drilling shows that HFMI treatment improves the status of residual stress at the weld toe in the first 1 mm from the surface. Furthermore, Vickers testing shows a remarkable improvement in the hardness values at the weld toe in the first 2 mm. This can be attributed to the reduction in grain size after treatment. Moreover, acicular ferrite and tempered bainite are found to be the main constituents in the fusion and heat-affected zones after TIG-remelting.