Per: PEDRO HENRIQUE RESENDE VAZ DE MELO (Usiminas), Hélio Alexandre Alves (Usiminas), Marlon José dos Anjos Silva (Usiminas), Wagner Viana Bielefeldt (UFRGS), André Luiz Vasconcellos da Costa e Silva (UFF)
Abstract:
One of the calcium addition objectives in steels is to modify inclusions aiming for continuous casting process stability and product improvement. Despite the treatment benefits, there are challenges regarding the alloy yield optimization, the alloy amount to be added and the repeatability in the heats. Alloy addition at the ladle bottom is recommended since the higher metallostatic pressure inhibits calcium vaporization. Calcium alloy is injected in a wire form, surrounded by a metallic sheet, which protects the core. Several parameters may influence the alloy release instant in liquid steel, such as injection speed, bath temperature and wire characteristics. In this work, the release depth of calcium alloys in liquid steel was calculated and tests were carried out with injection speed variation in experimental heats, comparing their effects on yield. A numerical procedure was used to estimate the release depth, study trends and parameter influences on calcium treatment. To validate the calculations, 91 industrial heats were monitored, in which four injection speeds were tested for two wire types: calcium silicide (CaSi) and pure calcium. The speed variation did not result in calcium yield changes. In this way, the use of higher speeds may promote shorter addition times and, consequently, productivity gains. Furthermore, there was good agreement between the numerical procedure calculations and industrial test results.