Flow Transport and Inclusion Motion in Steel Continuous-Casting Mold under Submerged Entry Nozzle Clogging Condition

Abstract

Clogging of the submerged entry nozzle (SEN) is a serious problem during the continuous casting of steel, due to its influence on the casting operations and product quality. Fluid-flow-related phenomena in the continuous casting mold region with the SEN clogging are investigated in the current article, including the quantitative evaluation of inclusion removal, slag entrainment, heat transfer, and the prediction of breakouts. The calculations indicate that, in order to accurately simulate the fluid flow in the mold region, the SEN should be connected with the mold region and the two should be calculated together. In addition, the whole mold region has to be calculated. Clogging at the SEN at one side induces asymmetrical jets from the two outports; thus, the fluid flow in the mold is asymmetrical. In addition, more inclusions are carried by the flow to the top surface of the nonclogged side, and the slab at the nonclogged side has a lower quality. With SEN one-sided clogging, inclusions travel a much larger distance, on average, before they escape from the top or move to the bottom. The overall inclusion entrainment fraction from the entire top surface for inclusions of any size is less than 10 pct. A higher turbulence energy and a larger surface velocity induce more inclusion entrainment from the top surface. Smaller inclusions are more easily entrained into the steel than are larger ones. More >200-μm inclusions can be entrained into the molten steel from the top slag with SEN clogging than without clogging. The SEN one-sided clogging generates an asymmetrical temperature distribution in the mold; it also generates temperatures higher than the liquidus temperature at some locations of the solidified shell, which increases the risk of breakouts. The SEN clogging should be minimized in order to achieve a uniform steel cleanliness, a cleaner steel, and a safe continuous casting operation.