Stamping of Thick Sheets After Welding Process

Abstract

This paper focuses on the analysis of post-weld forming of 8 mm thick sheet metal, with particular reference to the influence of the weld zone, heat affected zone, and residual stresses on the course of the forming process and deformation characteristics. Experimental tests were carried out on steel specimens joined by active gas shielded welding. After the welds were made, the specimens were subjected to stamping tests. Observations revealed significant differences in the strain distribution in the weld regions compared to the parent material, which manifested itself as increased stress concentration and a tendency to initiate microcracks, especially in the heat affected zone. Variable hardness gradients and tensile stresses acting perpendicular to the weld line proved to be particularly significant. Successful post-weld pressing of thick plates requires not only optimisation of the parameters (forces, punch radius, process speed) of the forming process but also appropriate preparation of the weld itself — by controlling the heat affected zone structure, applying stress-relieving heat treatment, or preemptively removing the layer with microcracks in the future pressing area. Particularly for thicknesses above 6–8 mm, local differences in mechanical properties become crucial for maintaining material continuity and avoiding cracks. This article highlights the importance of an integrated approach to the design of post-weld sheet metal stamping technology, in which not only the geometry of the tool but also the previous stages of blank preparation, the quality of the welded joint and the structural characteristics of the material in the transition zones play an important role.