Mold Level Fluctuation and Its Control for Slab Casting of Hypo-Peritectic Steels

The mechanism of the mold level fluctuation, especially for the hypo-peritectic steels, was investigated along with production tests. It is pointed out that the standing waves and unsteady bulging during slab casting are the dominant factors which contribute to the formation of mold level fluctuation. The popular mold level fluctuation of HP steels can be effectively depressed through the modification of the chemical composition together with the increasing cooling intensity for the earlier stage of the secondary cooling period, in which the carbon content should be given closest to the actual calculated peritectic point within the allowance of production composition control. The severe durative fluctuation during HP steels casting, however, is mainly attributed to the unsteady bulging from its uneven shell growth. The nearer of the actual carbon content of HP steels to the actual peritectic point, the weaker of the phase transformation contraction from the peritectic reaction, which will beneficial to the decrease of mold level fluctuation thanks to the more homogeneous shell thickness and the following smaller unsteady bulging.