Development and Industrial Testing of a Slag-Segregation System for Steel Casting

Abstract

Existing methods of determining the onset of slag flow in the discharge of liquid steel from the casting ladle to the tundish are analyzed. Two aspects are considered: (1) selection of the best method of generating a diagnostic signal in terms of cost and quality; (2) development of a method of signal processing so as to derive useful information. The proposed method is to obtain a vibrational-acceleration signal from a sensor on the protective-tube manipulator in the casting ladle. A prototype is developed for installing the sensor on the manipulator. This prototype protects the sensor from industrial disturbances. In signal analysis, the onset of slag flow is determined by calculating the entropy energy. The corresponding system is tested in an industrial casting system. To ensure effectiveness of the approach, a manual subsystem maintaining the steel level in the tundish in the last stage of casting must be introduced, so as to rule out perturbations associated with motion of the gate valve controlling the flow of steel melt. Industrial experiments indicate that the automatic system must be switched off when the ladle contains only around 18–19 t of steel. In tests, the operator has always been able to select the casting rate such that the steel level in the tundish is consistent with the regulations. As a result, the algorithm triggers slag segregation for each casting run before the operator does so. When using this method, the steel residue with the slag in the casting ladle differs by no more than 3.8 t from the value for slag segregation by the operator.