Per: DANILO DI NAPOLI GUZELA (COMPANHIA BRASILEIRA DE METALURGIA E MINERACAO), marcos a. stuart nogueira (autônomo), antonio augusto gorni (autônomo), marcos arantes rebellato (rms - rolling mill solutions)
Abstract:
Recent developments proved that it is possible to reduce manganese content by adding small amounts of niobium, keeping the same mechanical properties of structural steels. For low yield strength around 350 MPa, small additions of niobium like 0.010% are enough to maintain the same mechanical properties of the original material, even reducing 0.50% of manganese content. This results in reduction of the costs of alloying design, that must be analysed based on updated ferroalloy prices. This paper points the benefits that reductions of manganese content can bring to the steelmaker and to the quality of product. The reduction of manganese content results in less additions of FeMn to the liquid steel, allowing to decrease the tapping temperature. This brings many benefits, e.g., regarding the consumption of refractories of LD furnace and ladle, the increase of metallic yield, the reduction of amount of aluminum as deoxidizer, of absorbed hydrogen and nitrogen, and of macro-segregation in the semi-products. This paper presents a simulation that considered the reduction of Mn contents from 1.40% to 0.90% associated with the addition of 0.010% Nb, resulting in the reduction of 15ºC in tapping temperature, which brings savings of 8.6 kg/t of FeSiMn; 0.050 kg of ladle lining/t of liquid steel; increase of 0.75% in metallic yield; savings of 0.135 kg/t of aluminum as deoxidizer; reduction of 13 ppm of phosphorous, 1.6 ppm of hydrogen and 8.7 ppm of nitrogen contents.