Mold Thermocouple Locations and their Impact on Prevention of Caster Breakouts

Abstract

With advances in mold instrumentation, high performance mold fluxes, better reliability maintenance procedures, and improved operating practices, there has been a significant decline in the number of unplanned caster breakouts experienced at various production facilities. The typical breakouts of stickers and flux entrapments that were frequently observed in the past is often detected using embedded thermocouples in the mold and automatic slowdowns are initiated which inhibit excessive tearing of the partially solidified shell and prevent subsequent breakouts. However, in-mold events still occur resulting in caster downtime. Many of these occasional events have been linked to bleeders along the corners of the slabs, slab joint defects during tundish changes, and longitudinal face cracking. Considering the potential costs associated with unplanned caster breakouts, improvements have been made in the existing breakout prevention system. Major modifications of this existing breakout prevention system included, in particular, the addition of bleeder thermocouples or edge thermocouples which made possible the detection of shell containment loss near the corners of the slab. These bleeder thermocouples can also be utilized in detecting bad tundish joints related to excessive cooling and corner contraction that lead to tundish change joint defect type breakouts. In addition, changes in the location of the existing embedded thermocouples to a staggered-design extended the detection range of the breakout prevention system without increasing the total number of thermocouples.