New method to measure metallurgical length and application to improve computational models

Accurate knowledge of metallurgical length (ML), the distance where solidification is sufficiently complete, is important to control the positioning of soft reduction and containment rolls, in order to avoid centerline segregation, bulging, and whale formation during continuous casting of steel. Previous methods to measure ML are surveyed briefly, and typically involve expensive instrumentation of support rolls. In this work, a new "sensor-less" method infers the ML by observing when a particular roll first starts turning during small step increases in casting speed. This method was applied to the thin (90 mm) slab caster at Nucor Decatur and the trial results were used to calibrate a real-time computational heat-transfer model, which is currently in use at this caster. The calibrated model was then validated against published measurements, based on strain gauges installed on support rolls, at a conventional (260 mm) slab caster.