No abstract

ResumoAs inclusões são partículas que, em sua maioria, afetam negativamente as propriedades dos aços. O presente trabalho teve o objetivo de avaliar algumas variáveis no tratamento de borbulhamento de gás para remoção de inclusões na panela durante a sua drenagem na torre de lingotamento. Usou-se um modelo físico em escala 1:5 de uma panela real de aciaria de 180 toneladas de aço. Para contagem das partículas, simulando as inclusões, foi usada a sonda APS. Esta sonda conta as partículas e determina a sua distribuição de tamanhos. Os resultados indicaram que existe um tempo ótimo de tratamento para cada vazão de gás e quanto maior a vazão, menor é esse tempo. Além disso, o trabalho também mostrou que em baixas vazões foram obtidos melhores resultados para o tratamento. Essas conclusões podem ser explicadas pelos fenômenos de reversão e de remoção das inclusões no aço durante o tratamento. Palavras-chave: Remoção de inclusões; Metalurgia secundária; Aciaria; Modelamento físico. STUDY OF INCLUSION REMOVAL IN THE LADLE BY INNERT GAS INJECTION BY PHYSICAL MODELING AbstractInclusions are particles that usually have deleterious effects on steel quality. The present work had the objective of evaluating the effects of different variables on the efficiency of the gas bubbling treatment during the drainage of the ladle in the continuous casting process. A physical model in a 1:5 scale of a 180 metric tons ladle was used in the experiments. The APS sensor was used to count and determine the size distribution of the particles used to simulate the inclusions. The results indicated that there is an optimum treatment time for each gas flow rate and that lower gas flow rates gave better results. These conclusions could be explained by the reversion and floatation phenomena.

No abstract

The RH process is a secondary refining process that can simultaneously attain significant levels of removal of interstitial elements, such as carbon, nitrogen and hydrogen, from liquid steel. In the RH process, the decarburization rate plays a very important role in determining the productivity of the equipment. The kinetics of this reaction is controlled by mass transfer in the liquid phase. In the present work, a physical model of a RH degasser has been built and used in the study of the kinetics of decarburization. The effects of the gas flow rate and of the configurations of the nozzles used in the injection of the gas have been analyzed. The decarburization reaction of liquid steel was simulated using a reaction involving CO2 and caustic solutions. The concentration of CO2 in the solution was evaluated using pH measurements. Based on the experimental results, it was possible to estimate the reaction rate constant. A volumetric mass transfer coefficient was then calculated based on these rate constants and on the circulation rate of the liquid. The logarithm of the mass transfer coefficient showed a linear relationship with the logarithm of the gas flow rate. The slope of the line was found to vary according to the relevance of the reaction at the free surface in the vacuum chamber. A linear relationship between the volumetric mass transfer coefficient and the nozzle Reynolds number was also observed. The slopes of the lines changed according to the relative importance of the two reaction sites, gas-liquid interface in the upleg snorkel and in the vacuum. At higher Reynolds number, the reaction in the vacuum chamber tends to be more significant.

No abstract