To establish the technique for producing very high temperature steel slabs required in a continuous casting-direct rolling process, the measurement method for the solidification shell thickness of a continuous casting steel slab has been developed using the electromagnetic ultrasonic technique, and industrialized at Sakai Works, Nippon Steel Corporation. The main features of this method are as follows:
(1) On-line, real time, non-contact and continuous measurement is done at every 15 seconds.
(2) Sensors are transversally scanned and the measurement is done at any desired points.
The measurement error was determined to be 1.2 mm (standard deviation) by comparing the measured results with the destructive method, driving a special aluminum plated rivet into a slab of 250 mm in thickness.
Combining the shell thickness measurement with the two dimensional solidification simulation, the estimation method for the location and the shape of the crater-end (solidification completion end) was also developed.
In the real operation of the continuous casting machine, the shell thickness variation due to the casting speed change was clearly measured and moreover, the interesting shape of the W-figure type craterend was obtained. This measurement system has become very useful for the stable operation of the continuous casting machine and is now working very well.
