Open Access

Current efforts for lightweight design result in a growing application of high-strength fine-grained structural steel in modern steel constructions, e.g. mobile cranes, with yield strength from 960 MPa. The design of welded structures and the welding process become more challenging with increasing material strength due to higher elastic ratios. The formation of high residual stresses, which are able to diminish lifetime, load capacity and component safety, has to be avoided. Recent numerical and experimental analyses have shown a strong influence of the heat control and the rigidity of the weld on the welding stresses. Global reaction stresses due to an external shrinkage restraint superimpose with local residual stresses in the weld seam. Modern inverter technologies allowed the development of numerous modified spray arc processes driven by the power source manufactures with almost equal characteristics. They provide several well-known technical and economic benefits, like the possibility of welding narrower seam configurations. As a result a smaller weld volume, total heat input and, therefore, reduced welding stresses are achievable. This research focuses on the welding loads due to modified weld seams. The global reaction forces in welded components due to an external shrinkage restraint were investigated in a special in-house developed testing facility. Additionally, the superposition of the local residual stresses, global stresses and bending moments were analysed with the help of X-ray diffraction. The intensity of the restraint, the weld seam configuration and the weld process (transitional arc and modified spray arc) were varied for a statistical evaluation of the resulting welding loads. It was observed that under restraint a smaller weld seam volume affects reduced reaction stresses.