Correlating welding reaction stresses and weld process conditions for high-strength steel S960QL

As a result of current trends towards lightweight design, a growing amount of high-strength steels with yield strengths above 690 MPa is applied. In comparison to the weld process of lower-strength steels, small working ranges have to be achieved with respect to a special microstructure and high yield ratio. However, the sustainable and economic application of these steels depends on the loading capacity and the safety of welds when designing weld constructions. For these demands, a precise knowledge of welding stress level and distribution is essential. Therefore, the present study is concerned with the interaction between heat control (interpass temperature and heat input) and local as well as global stresses in high-strength steel welds. Specimens were multirun welded under defined restraint conditions in a special test facility (controlled tensile weldability (CTW) test) to consider global restraint. For the comparison concerning local residual stresses, free shrinkage test welds were performed as well. The evaluation shows a significant influence of the interpass temperature on the global reaction forces. Furthermore, increased heat input and high interpass temperatures cause higher tensile residual stresses. This occurred in the weld area of both free shrinkage test specimen and CTW test specimen.