EDDY CURRENT MOLD LEVEL SENSOR UNDER CONTINUOUS CASTING OF STEEL USING MOLD FLUX

The paper deals with the industrial test of eddy current device for direct metal level control under continuous casting of steel using mold flux. The new algorithm of detection meniscus level has been proposed. The algorithm consists of selecting of a signal variable component caused by oscillation of steel meniscus. The way of filtering the noise from electromagnetic stirrer based on the comb filter application has been developed. The paper deals with the industrial test of eddy current sensor for molten metal level detecting under continuous casting of steel using mold flux. The new algorithm of detection meniscus level has been proposed. The algorithm consists of extracting the signal variable component caused by oscillations of steel meniscus which are intended to reduce friction on the strand surface. The way of filtering the noise from electromagnetic stirrer based on the comb filter application has been developed. It has been proven that the developed algorithm can completely remove the influence of the electromagnetic stirrer field. The industrial test results show that the readings of eddy current and radioactive isotope sensor are synchronous both in a stationary casting mode and in case of fast metal level change. Moreover the eddy current steel level sensor has high precision of steel level measurement, quick response time and low noise level free from the influence of mold flux.

Modification of tundish design to improve quality of slabs, casted at CCM No. 4 of EVRAZ NTMK

A technology of continuous casting of steel has a large effect on its contamination. In particular, proper organization of metal flows in tundish and mold is very important. After completion a series of casting through a tundish and drop of metal level in it, it possible, that the slag flows from the surface layers of the tundish to capture the metal. An analysis of results of ultrasonic control of finished strip showed, that the basic number of the revealed defects was obtained during strip rolling out of the last slabs of the last heat in a series for a tundish. Metallographic studies determined, that the defects were located in the slab axis zone and filled by macro-inclusions of complex composition. To determine the actual distribution of metal flows, a water simulation of them was accomplished for the existing design of the EVRAZ NTMK tundish. It was determined, that at the drop of metal level in a tundish, a capture of slag from the metal reservoir and its transfer into the main bath of the tundish takes place due to whirligig flows. Following the weight metal consumption, the zone of slag inclusions distribution enlarges. Besides, denudation of the metal mirror in the metal reservoir takes place, resulted in metal secondary oxidation. Based on the results of the simulation, it was proposed to modify the design of the “turbostop”, which is installed in the metal reservoir of the tundish. Besides, it was proposed to remove the dividers installation in the tundish. It was noted, that the proposed steps enable to ensure a minimal level of rejections.