Vision-based detection system of slag flow from ladle to tundish with the help of the detection of undulation of slag layer of the tundish using an image analysis technique

Abstract

It is very important to have a slag detection system (SDS) in steelmaking to detect slag and prevent its flow for improving the quality of steel produced. Slag raking is used for removing slag from liquid iron. Detection and control of slag may be carried out with the help of refractory dart or infrared imaging in the steel making zone such as in a Basic Oxygen Furnace (BOF). Each method has its advantages and limitations. Detection and control of slag flow from ladle to tundish in a casting operation is an important step towards cleanliness of the steel production. Various techniques such as ultrasonic level sensor, conductivity measurement using magnetic field, use of microphone to monitor the sound of steel flow through shroud, monitoring the radiation intensity of the stream of steel flow through a lateral side duct of the ladle shroud and monitoring of the shroud vibration have been explored to minimize the slag flow from ladle to tundish. It is obvious from literatures that non-contact based SDS is much more preferred using advanced instrumentation techniques. The problem with the vibration-based system is reduced metal level in the tundish due to setting up of slide gate of the ladle at low flow level as well as non-detection of the slag flow where vortex did not form prior to slag flow. Research showed improved performance with the vision-based caster SDS. Monitoring the sudden brightening of the slag surface around the pouring tube with the help of a CCD camera and image processing technique is also an effective way to detect slag transfer from ladle to tundish. The major limitation of this method is that a significant amount of slag already enters the tundish due to increased flow rate at the end of the tapping before splashing takes place. This work attempts to overcome this problem. There is an increased trend in the amplitude of the undulation of the slag surface of the tundish before the sudden brightening of the slag surface. If such undulations are identified by image analysis technique, signal can be generated to move the ladle slide gate to limit a significant amount of slag flow into the tundish. This would help to improve the quality of the steel that is produced.