Practical advantages of niobium and molybdenum alloying in the production and processing of forged engineering steels

Ever-increasing quality demands on forged engineering steels require specific modifications of the chemical composition of existing alloys or even necessitate the development of new steel grades. The current paper mainly focuses on the metallurgical principles of addition of niobium and molybdenum to forged case carburising and quenched and tempered steel grades. The influence of niobium alloying on the grain size stability after carburising at high process temperatures, in combination with further development of the typical chemistry of casehardening steels, has been worked out. An additional practical study shows the effects of microalloying on the grain size of heavy-duty forgings. (AU) © 2015 Companhia Brasileira de Metalurgia e Mineração (CBMM)