A low-cost non-invasive slag detection system for continuous casting

The majority of steel produced today is made by the technology known in the steel making industry as continuous casting. Deciding when to stop the flow of molten steel from the ladle is not trivial, since terminating the process too early affects yield negatively, while closing the outflow valve too late lets slag enter the casting process. There is a variety of automatic slag detection systems available now, but numerous casting operations still rely on the decision of a human operator. In this paper, we propose a cost-effective non-invasive slag detection system that is based on the vibration signal measured during the casting procedure. In this method, the vibration acceleration data is analyzed by a cumulative sum (CUSUM) control chart in real time, providing a violation signal that can be used to close the ladle outflow valve. The proposed algorithm is implemented in an embedded microcontroller unit and is verified through a simulation study and laboratory experiments. These trials suggest that the technique may perform similarly to the human operator, however, just as in the case of the human operator, the disadvantage is that it only identifies the change when a small amount of slag already enters the tundish. Its advantage lies in its simplicity, low-cost, portable and non-invasive nature; possibly aiding the decision of the operator or, it may be used to create a completely automated ladle outflow valve closing system.