몰드 레벨 안정화를 위한 비정상 벌징 메커니즘 연구

Abstract

A finite element thermal stress model to investigate the bulging behavior during thin slab continuous casting of steel has been applied. The mold level hunting caused by unsteady bulging comes from the uneven solidified shell, mostly made in the mold. To identify the effect of uneven solidified shell, the several factors such as uneven solidified shell, and casting speed variation were computed. To verify the model, steady bulging that the boundary conditions were same roll pitch, equal ferrostatic pressure and even solidified shell was computed. For the steady bulging case, one position of slab surface between the rolls was almost same with the casting time even though considering the creep effect, which means the bulging is steady state. When the uneven solidified shell was imposed to the model, the bulging displacement and the internal volume of the shell were fluctuated with casting time, which meaned the unsteady characteristic behavior. The frequency of the unsteady bulging was dominated by the roll pitch and the frequency of uneven solidifying shells only for shorter frequency of uneven shell than the roll pitch. In the case of the variation of casting speed, the unsteady behavior of bulging amount and volume change was also occurred. But the contribution to the unsteady bulging was smaller than uneven solidified shell effect. So, the uneven solidified shell could be a main cause of the unsteady bulging. The unsteady bulging mechanism was proposed based on the computed results.