Study of low flow rate ladle bottom gas stirring using triaxial vibration signals

Secondary steelmaking plays a great role in enhancing the quality of the final steel product. The metal quality is a function of metal bath stirring in ladles. The metal bath is often stirred by an inert gas to achieve maximum compositional and thermal uniformity throughout the melt. Ladle operators often observe the top surface phenomena, such as level of meniscus disturbance, to evaluate the status of stirring. However, this type of monitoring has significant limitations in assessing the process accurately especially at low gas flow rate bubbling. The present study investigates stirring phenomena using ladle wall triaxial vibration at a low flow rate on a steel-made laboratory model and plant scale for the case of the vacuum tank degasser. Cold model and plant data were successfully modeled by partial least-squares regression to predict the amount of stirring. In the cold model, it was found that the combined vibration signal could predict the stirring power and recirculation speed effectively in specific frequency ranges. Plant trials also revealed that there is a high structure in each data set and in the same frequency ranges at the water model. In the case of industrial data, the degree of linear relationship was strong for data taken from a single heat

Vibration analysis in ladle metallurgy

Gas stirring in ladles isdominated by manual control and plays an important role in enhancing steel quality.This reliance on manual control has considerable limitations in optimizingprocess parameters. Various researchers have used one dimensional vibration,sound and image signals measured from vessels to develop algorithms to predictthe degree of stirring inside the vessel. Commercial instruments have beendeveloped based on these principles. In the literature, there has only limitedtreatment detecting stirring at low flow rates and interpreting vibration signalsin three dimensions. This paper will critically review these studies andconsider the gaps in the knowledge and how these can be addressed. Somepreliminary results from a cold model study will be presented