Welding residual stresses in 960 MPa grade QT and TMCP high-strength steels

High-strength steels with yield strengths >= 690 MPa are becoming increasingly significant for modern steel constructions. Both quenched and tempered (QT) high-strength steels and steels produced by the thermo-mechanically controlled process (TMCP) are currently available. TMCP-steels are usually provided with a typical mill scale. Apart from the manufacturing process these steels differ also in their chemical composition. The influence of these differences are investigated here with focus on the residual stresses formed during TIG welding. Bead on plate welds have shown characteristic residual stress distributions depending on the type of steel as well as on the heat input and preheat temperature. The following work demonstrates that the fluid flow, induced by the elements present in the mill scale, leads to a deeper penetration of the material. This can also lead to increased residual stresses in the surface of the weld and the HAZ. Furthermore, higher heat input and preheat temperature can induce higher tensile residual stresses - which are evident in the present study. (C) 2017 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.