ABSTRACT
As we discussed in the previous sections of this book, niobium (columbium) is a very effective strengthening agent for hot-rolled carbon steels. During conventional rolling niobium produces marked precipitation strengthening which is complemented with some strengthening due to refining the ferrite grain size [1]. Niobium carbide (Nb4C3) and niobium nitride (NbN) are mutually soluble. In combination with carbon and nitrogen, they form the compound known as niobium carbonitride Nb(C‚N). The usual range of niobium content in microalloyed steels is from 0.03wt% to 0.08wt%.
