Applications of niobium microalloyed ferrite pearlite steels to line pipe and plate

A variety of advanced controlled rolling techniques have been developed to improve toughness, strength and weldability of niobium-steels. To achieve optimum properties, control of prior stage rolling conditions and accelerated cooling are needed. In low carbon steel , the addition of niobium results in a greater increase in tensile strength than that of vanadium without a loss of toughness. A t the same strength level, niobium-steel has less susceptibility to weld cracking and good toughness in the HAZ of its weldments than similar vanadium steels. Separation and formability of niobium steels are also discussed. (AU)