Potential methods of measuring the stirring intensity during secondary steel making in the ladle furnace

Sammanfattning: The main objectives of this research were to find a measuring technique for the gas stirring intensity and relate this to the argon gas stirring in the ladle furnace. However, the investigation mainly focused on methods of measuring the true amount of argon gas entering the ladle furnace, since this was needed to further determine the gas stirring intensity. The as stirring intensity is of importance because steel plants want to relate the quality and composition of the steel to the effect of the stirring. The methods for executing this research have been based on a literature study and a field trip, where five Swedish steel plants have been investigated. The steel companies included  SSAB, Uddeholms AB, Sandvik, Ovako and Outokumpu. The literature study focused on previous experiments with similar objectives that have been carried out, and other processing industries where measurements of gas flow are used. Since the physical conditions at steel plants are rather extreme (with respect to temperature and noise) compared to most other industries, those researches were not applicable for this implementation. The literature study also showed that previous studies with the same aim only exist to a very limited extent. The measuring techniques found to have a certain level of relevance were camera and vibrational measuring techniques. The field trip focused on collecting information about the present physical conditions at each steel plant and understanding the practical problems if a measuring method were to be implemented. In addition to this, the field trip investigation also included interviews and discussions with experienced operators and engineers. From the field trip it can be concluded that the most severe limitations for implementing are the physical conditions at the steel plant, such as temperature, loudness and vibrations, and not the research and simulations being available of what they would show. The results of the field trip indicated that all steel plants need an individual solution. However, most investigated companies face problems such as clogging of porous plug and inaccuracy of the measurement of the argon gas entering the ladle furnace. The latter can be partially removed by placing the flowmeter closer to the porous plug. The major conclusion of this study indicates that improvements of the porous plugs needs to be further studied to avoid clogging of the porous plugs and assure that no argon gas escapes. Furthermore, a relocation of the flowmeter needs to be made at all of the steel plants to improve the accuracy of the gas flow.