Effect of dimensionless numbers on vortexing during continuous casting processes

Abstract

Exogenous oxide inclusions in continuously cast steel are primarily caused by the entrapment of slag during the key stages of steelmaking processes, including in furnaces, ladles, and molds. To prevent contamination and maintain steel cleanliness, operators often halt the ladle and tundish processes before the onset of “slag vortexing,” as this phenomenon can significantly degrade product quality by entraining unwanted slag into the molten metal. To study the vortexing phenomenon, previous studies have used water model experiments to simulate the casting process. To ensure valid comparisons between the two, the dimensionless numbers in both the actual casting process and water models must be matched. Hence, it is significant to identify the critical non-dimensional numbers that influence the vortexing phenomenon (Rankine vortex formation). A thorough scrutiny of the current literature reveals that no studies have been made in this direction so far. To address this potential gap, the current study aims to identify the key dimensionless numbers that affect air-core vortexing in the liquid draining process and to determine their individual impact on this phenomenon. The study investigates how these dimensionless numbers influence the formation of air-core vortices during water drainage, simulating molten metal behavior. It specifically examines the Characteristic Volume of the Air Core, along with the dimensionless recession velocity, which is used exclusively in the pre-critical height regime. The results demonstrate that these dimensionless numbers significantly influence vortexing behavior, with the strength of the air core being controlled by both airborne and waterborne Taylor vortices. Additionally, the study reveals the effects of these dimensionless numbers in the pre-critical regime, an aspect not previously reported in the literature. These findings offer valuable insights for optimizing continuous casting processes in steel and other metals.