Role of microalloying elements in the microstructure of hot rolled steels

摘要

A comparative study of some of the most important effects of the diverse microalloying elements on austenite and ferrite microstructure of hot rolled microalloyed steels is carried out. The values of different aspects such as pinning and driving forces, size of precipitates, activation energies or diffusion coefficients are discussed. Titanium is the most effective element to control grain growth at high reheating temperatures and a weight Ti/N ratio close to 2 is recommended. Aluminum can help to control grain growth at medium temperatures, but its addition to Ti steels can promote abnormal grain growth. Niobium is the most effective element to inhibit static recrystallization of austenite, due to the adequate precipitation temperature range at deformation temperatures and the strong pinning effect of Nb carbonitrides. Finally, the preferential nucleation of intragranular ferrite on particles such as vanadium carbonitrides enhances the ferrite grain refinement.