Effect of Stopper-Rod Misalignment on Fluid Flow in Continuous Casting of Steel

Misalignment of metal-delivery systems can cause asymmetric fluid flow in the mold region of continuous casters, leading to abnormal surface turbulence, insufficient superheat transport to the meniscus, slag entrainment, inclusion entrapment, and other quality problems. This work investigates the effect of stopper-rod misalignment on nozzle and mold flow velocities in a conventional continuous casting process using both a water model and a computational model. Three stopper-rod configurations are studied (aligned, front misaligned by 2 mm, and left misaligned by 2 mm). The 3-D steady k-epsilon finite-volume model matched well with impeller probe measurements of both velocity and its fluctuations. Negligible asymmetry was found near the narrow faces. Asymmetry close to submerged entry nozzle is the main cause of vortex formation observed in all cases. The left-misaligned stopper-rod produces a shallower jet with a higher flow rate from the right port, leading to higher surface velocities on the right surface. This produced substantially more large vortices on the left side. The asymmetry produced by the nozzle length bore diameter ratio of similar to 21 in this work is consistent with the theoretical critical entrance length of similar to 24 for turbulent pipe flow. DOI: 10.1007/s11663-011-9478-5 (C) The Minerals, Metals & Materials Society and ASM International 2011