Por: JEAN VIANA BAHIA (USINAS SIDERURGICAS DE MINAS GERAIS SA), Fabio Dian Murari (Usiminas), Tadeu Messias Donizete borba (Usiminas)
Resumo:
Usiminas has dedicated research and development efforts to improve its production processes, focusing especially on cost reduction, superior product quality, and compliance with environmental requirements. Thus, high-quality flat steels applied to structural components are continually improved aiming for high performance in service. Structural steels can reach a yield strength of up to 450 MPa by varying only carbon and manganese contents. Manganese is traditionally added to these steels aiming to solid solution strengthening. However, due to the wide application of manganese in more advanced steels, its availability has become more restricted. In this context, in search of an alternative to this alloying element, this study evaluated, on a laboratory scale, the effect of replacing up to 0.7 percentage points of manganese by adding up to 150 ppm of niobium. As a result, it was observed that there is a potential for replacing 0.4 percentage points of manganese by niobium microadditions between 50 and 100 ppm without affecting the mechanical strength of the steels. Such substitution resulted in a less banded microstructure and a reduction in carbon equivalent. It is also worth mentioning the possibility of an indirect reduction in greenhouse gas emissions with this substitution.