Effect of niobium on the cold resistance of low-carbon and low-alloy steels

Niobium in low-carbon and low-alloy steels combines carbon in NbC. The carbon is completely combined when the niobium to carbon ratio is about 1.5∶1. A relationship was found between the carbon content of the solid solution and the niobium content of the steel: The greatest reduction in the carbon content of the solid solution occurs with the addition of 0.05–0.1% Nb. With larger niobium concentrations the amount of carbon dissolved in ferrite continues to decrease, but at a lower rate.