Level meter for the electromagnetic continuous casting of steel billet

A level measuring system has been investigated to work with the electromagnetic continuous casting of steel billet, based on the principle of electromagnetic induction. The basic idea of the development is the distinction of the magnetic field measured in the mold into the effect of the applied one and the effect of the level variation. Several candidates of induction type magnetic probes were devised and examined. It was seen that the so-called global sensor was the proper one from the viewpoint of sensing range, resolution of the signal, and robustness to the external perturbation. The level of the melt was successfully calculated from the sensor output by employing the reference voltage for the set current in the power supply as a measure of the applied magnetic field. The use of the global sensor associated with the electronic device and the program showed that the resolution of the measurement was within +/-0.2 mm, the dynamic range of sensing the level was 0-300 mm below the top of the mold under the electromagnetic field at 20 kHz. In its application to commercial scale electromagnetic continuous casting at a billet caster of POSCO works, it worked well with the existing control device in supplying the molten steel to the mold. Particularly, its accuracy and promptness was sufficient to control the level at the initial stage of casting.