OPTIMUM MICROALLOYING OF NIOBIUM AND BORON IN HSLA STEEL FOR THERMOMECHANICAL PROCESSING.

Abstract

In thermomechanical processing with water cooling, it is possible to utilize transformation strengthening with bainite by accelerated cooling and precipitation-hardening with niobium by direct quenching. The effect of a combined addition of boron and a grain refining element such as niobium, titanium or vanadium on mechanical properties and microstructures of plate was examined. In addition, the strengthening and toughening mechanism of Nb-B steel was clarified by examining the effect of alloying elements on the minimum recrystallization temperature of gamma , gamma - alpha transformation and distribution of boron.