Properties of thermomechanically rolled Nb/Ti microalloyed steel sheets

Structure and mechanical properties of a Nb/Ti microalloyed steel, thermomechanically rolled on a strip-production facility, are evaluated. Small (0.02%) titanium addition to niobium-containing steel is found to increase precipitation while reducing grain-refining potential of niobium. This effect increases with increasing finish-rolling temperature, and is also reflected in an increased charpy energy transition temperature. A reduced tendency for precipitation in a nitrogen-free austenite together with the short interpass times in the finishing train, is assumed to reduce the tendency for pancaking, which is prerequisite for an effective grain refining.