Significant production of niobium steels began about 15 years ago.The early steels contained up to 0.03% Nb and permitted higher yield strengths to be obtained in steels having greatly reduced carbon equivalents.Thus the heat-affected zone properties of these steels were excellent and they were widely adopted for welded construction of ships, bridges, pipelines and the like.More recent development has extended the use of niobium strengthening to higher yield strengths, more complex base plate composition, greater thicknesses and to more severe climatic regions such as the Arctic. In addition niobium contents have been increased (in some cases to above 0.10%) steel rolling and heat treating practices have become more sophisticated and welding evaluations are now concerned with all regions of the weld and adjacent base plate.