This paper reviews the current technology related to control of weld HAZ properties in high strength steels. The debate related to appropriate balance of Ti and N is addressed and it appears that a stoichiometric ratio provides optimum fracture toughness. The results are significant because despite the well established difficulties in controlling Ti/N ratio, this data now provides guidance in terms of alloy design to achieve optimum fracture toughness in the HAZ of welds.
The enhanced resistance to grain coarsening behaviour of high Nb steels has now provided another incremental improvement in the weldability of steels for critical applications such as high pressure gas transmission pipelines. The role of Mo in the alloy design of these new steels is a further activity to be undertaken in the design concepts to further improve the performance and safety of modern steel structures.