Otimização da escória no refino secundário do aço silício de grão orientado

Abstract

Oriented Grain Steel production has been a challenge in Melt Shops due to narrow chemical composition control that affects the magnetic properties with impact on the electrical machines efficiency. This work has great importance from Aperam South America because the replacement of the production of Oriented Grain Steel with high re-heating slab temperature (OGHT) by the Oriented Grain Steel with low re-heating slab temperature (OGLT). OGHT steel has Manganese Sulfide (MnS) to avoid the grain increasing and OGLT has Aluminum Nitrite (AlN) to avoid it. This replacement brings some changes in the steps for production of the Oriented Grain Steel on Second Metallurgy process. Mainly in the slag forming in the ladle. Before, slag had the function to stabilize the sulfur content in the molten steel, now the slag has to keep the dissolved Aluminum in the molten steel necessary to form the Aluminum Nitrite (AlN) in the next process. This work focused in the study of the behavior of the soluble Aluminum in the molten steel according to the chemical composition of the slag, to evaluate the effect of the slag chemical composition on the oxygen content in the molten steel, on slag physical characteristics and continuous casting performance in terms of clogging in the nozzle. Thermodynamics software for calculations (Thermo-Calc e Fact sage) helped in the work development. Some equilibrium calculations were performed to produce the experimental heats in the Melt Shop from Aperam South America. The results showed that the chemical composition of the slag affect strongly the aluminum yield in the Ladle Furnace process, the slag physical characteristics and the performance of the continuous casting. In the tests results, significant difference was observed between in the dissolved aluminum level and in the molten steel in function of the chemical composition of the slag.