A Model of Unsteady Bulging in Continuous Casting and Control of Periodical Mold Level Fluctuations

摘要

“Unsteady bulging” is one of the most serious disturbance to the mold level control of a continuous caster, since that makes worsen the performance of the caster. It is recognized from the characteristic periodical fluctuations of the mold level that their period agrees with the proportion of a particular interval of the support rollers in the caster to the casting speed. Nowadays, several groups have published reports on their model of the unsteady bulging. Yoon et al. 1) have reported that uneven solidification by the mold level fluctuation and the change of the casting speed caused the unsteady bulging. Kanai et al. have presented a model that the bulging of the solidified shell in plastic deformation is collapsed by adjoining support rollers2). However, these models have not clarified the reason of the growing of mold level fluctuations. In this paper, we will present a model of unsteady bulging that the size of the bulging periodically changes according to the relative position of the lateral depressions forming at the meniscus of the molten steel between the support rollers. In addition, we will propose placement conditions of the support rollers to inactivate the unsteady bulging.