The influence of welding on the hardness and weldability of thermally hardened S620Q steel sheets

The thermally hardened 12 mm sheets of S620Q steel underwent research. The sheets weldability was examined during semi-automatic welding by MAG method, at the welding conditions usually applied in industry for welding normalized sheets of this steel. The technology of welding was presented. The achievement of metallically continuous joints was confirmed by X-ray examination. For the purpose of usefulness assessment, samples were taken from test joints then the joints hardness distribution measurements were performed. The microstructure was examined and the static tensile tests as well as technological bend tests were carried out. Hardness measurements were performed in three measurement lines for each joint according to PN-EN 1043-1:2000 requirements. Joints microstructures were examined in the joints axis, in SWC and in native materials. Steel microstructures were classified as low carbon tempered martensite of layered construction. Mean values of the selected joints strengths were also presented. The tensile tests values of native materials of metallurgic certificates were given for the sake of comparison. The research results presented in the paper made it possible to determine the weldability of S620Q steel.