Efeito de magnésias com diferentes aditivos nas estruturas e propriedades de aço elétrico de grão orientado

Abstract

Grain oriented electrical steel has as their major characteristics the excellent magnetic properties, specially developed for reducing core losses and to increase the efficiency of electrical machines. During the manufacturing process of this steel occurs the formation of forsterite ceramic, obtained from the reaction of the silica present on the surface ofthe strip with magnesia and other additives. The present work aimed at obtaining forsterite coating on grain-oriented electrical steel using magnesium sludge mixed with TiO2, SrSO4 and Sr(OH)2 catalysers. Coating evaluation process was carried out using different characterisation techniques. We observed that the use of these addition agents promotes coating formation and the addition rate increase helps to increase coating thickness. The use of TiO2 addition agents decreases sulphur content on the coating, reduces the amount of particles near the coating and increases coating resistance, thusimproving electrical isolation and coating adherence properties. However, when this coating is applied in excess it jeopardises steel core loss because the Ti contained on the coating diffuses to the steel. In regard to the coatings produced with Sr addition agents, when SrSO4 is reduced it decreases sulphur content on the continuous coating surfaceand when this addition agent is replaced by Sr(OH)2 it triggers the deterioration of electrical isolation properties. The addition of SrSO4 to the magnesium sludge reduces core loss and the best results were presented by samples coated with 0.8% SrSO4 combined with 1.5% TiO2 material.