Formation of multi-axial welding stresses due to material behaviour during fabrication of high-strength steel components

Abstract

Today an expanding application of high-strength steels in modern welded constructions can be observed. The economical use of these steel grades largely depends on the strength and reliability of the weldments. Therefore the special microstructure and mechanical properties of these grades have to be taken into account by keener working ranges regarding the welding parameters. However, performance and safety of welded components are strongly affected by the stresses occurring during and after welding fabrication locally in the weld seam and globally in the whole component, especially if the shrinkage and distortion due to welding are restrained. Some extensive studies describe the optimization of the welding stresses and the metallurgical effects regarding an adapted welding heat control. In particular lower working temperatures revealed to be effective to significantly reduce the local and global welding induced residual stresses of the completed weld. However, decreased interpass temperatures cause concurrently higher stresses during welding fabrication. This work shows some strategies to reduce these in-process stresses. With help of multi-axial welding stress analyses in component-related weld tests using a special 2-MN-testing facility differences in stress build-up are described in detail for root welds, filler layers and subsequent cooling to ambient temperature.