Brian Rust

As the strength of steels increases, it becomes more and more difficult to produce welded connections whose mechanical-technological properties correspond to those of the base material. The choice of welding process, filler materials and temperature control are of great importance for the connection properties. This concerns not only the weld seam itself but also the heat-affected zone. Especially in the case of high-strength fine-grain steels with low carbon content, where the strength properties are specifically adjusted by a combination of alloying concepts and heat treatment, and if necessary, rolling at defined temperatures, the importance of softening the heat-affected zone (HAZ) increases. This article gives an overview about current manufacturing processes of high-strength fine-grained structural steels and summarizes normative and manufacturer-related specifications for their welding processing. The influence of the cooling time on the mechanical properties of the HAZ and the weld metal is clarified, and possible failure modes of welded connections with softening of the HAZ are described. Finally, the future European design rules for welded connections are explained and a newly developed design model is presented.