(p541) A Novel Ultrasonic Sensor for Mold Powder Thickness Control

摘要

The use of mold powders introduces key benefits in submerged steel casting: flux powders protect the liquid steelsurface from oxidation, lubricate the strand and provide uniform heat transfer, thus contributing to a homogeneousgrowth of the solid shell and reducing the risk of breakouts. It is therefore crucial to keep a constant powderthickness on top of the liquid bath. Powder feeding is usually performed manually, with the consequent risk ofpowder inhalation by the operators and the inevitable lack of process repeatability related to direct humanintervention. Safe and reliable automated powder control can be performed by coupling a radioactive and anelectromagnetic sensor: while the former measures the overall level of liquid steel and powder, the latter detectsthe meniscus position; dedicated inversion algorithms enable to determine the instantaneous value of powderthickness, which is in turn used to drive an automated powder feeder in a closed loop configuration. This solutionnevertheless presents some limitations: in fact, due to shielding effects, the inductive sensor can only operate on alimited range of copper thickness and cannot be applied to slab casting. In order to overcome this limit, Ergolinesdeveloped and patented a new ultrasonic technology aimed at replacing the inductive sensor in powder thicknesscontrol. As a unique feature, the new ultrasonic sensor measures the meniscus position independently of copperthickness. Dedicated field-testing demonstrated the improved performance of this novel ultrasonic technology overthe inductive method. By coupling the ultrasonic sensor with a radioactive sensor to drive a powder feedingmachine, Ergolines will develop new generation powder control systems, applicable to the whole range of castingformats, including slab casting. The introduction of this new ultrasonic technology sets the stage for furthertechnological developments, including ultrasound-based mold thermal monitoring and breakout prevention for slabcasting.