Roll load measurements on thin slab caster for liquid core detection

Measurements of roll loads with strain gauges implemented on roll girders were carried out on a thin slab caster. Numerical calculations and shop tests indicated the applicability of this measurement arrangement. It has to be considered under the specific aspect that, owing to the low design height of thin slab casters, the occurring loads are considerably smaller than in standard slab casters. The evaluation of the measurement data obtained during operation of the thin slab caster was done from two main viewpoints. First, it was of interest whether it is possible to measure the presence of a liquid core at a given distance from the meniscus. Second, the measurements were supposed to be used for verification of the liquid core position calculated on line by Dynacs®, VAl's dynamic cooling model. Essential difficulties in evaluating the data originated from the changing thermal and mechanical loads. The slowly changing thermal loads that are superimposed on the mechanical loads make it impossible to determine the presence of a liquid pool simply by checking the strain gauge signal and comparing it with results collected during the shop tests. Mechanical load changes at relatively high frequencies occurred owing to varying roll forces even with minor eccentricities of the rolls. Thus, checking for critical values of the load changes also seems impractical. For on line prediction of the liquid core position, a combination of numerical estimation of the liquid core position with on line thermal tracking as an approximate approach and measurements for exact prediction seems to be the most promising strategy. An interesting alternative to this strategy could be the on line evaluation of fast Fourier transformed (FFT) strain gauge signals.