Ferrosilício de alta pureza para aços elétricos: uma abordagem sobre a influência da composição química e a importância do refino na produção do ferrosilício destinado a aços elétricos.

Abstract

Ferrosilicon (FeSi) is a widely used raw material in the steel industry, playing a key role as a deoxidizer during steel production. Electrical steels are a special type of steel capable of conducting and amplifying a magnetic field, while exhibiting low magnetic losses during their magnetization cycle. This material is extensively used in the manufacture of motor and transformer cores and may be classified as grain-oriented (GO) or non-oriented (NGO). To optimize the magnetic properties of electrical steel, the presence of silicon in amounts up to 3.5 wt.% is essential, as silicon reduces magnetic losses caused by eddy currents. Therefore, electrical steels are also known as silicon steels. In this context, it is crucial to control elements such as aluminum and carbon in the composition of silicon steel, since they influence the grain growth in the steel’s crystallographic structure, and grain size directly affects magnetic losses. For this reason, steel mills require a high-purity product from ferrosilicon producers, with silicon content of approximately 75% and aluminum and carbon contents lower than 0.02%. To meet these specifications, ferrosilicon undergoes a refining process, a stage in which an oxygen-rich gas stream permeates the FeSi metal bath and removes, through oxidation, metals with a higher affinity for oxygen, such as Al and Ca. Carbon, on the other hand, is removed at lower rates, since its removal mechanism differs from that of metallic elements.