Measurements of surface velocity and level fluctuation in an actual continuous wide slab casting mold

Abstract

In the current work, a kind of nailboard made of three rows of nails was designed to simultaneously measure the surface velocities and level fluctuations of the loose side, the center plane and the fixed side in an actual continuous wide slab casting mold. Seven nailboard dipping experiments were conducted to obtain both the transient and time-averaged behaviors near the meniscus. The distribution of disturbed oscillation marks (OMs) on the surface of corresponding slabs (in common with nailboard experiments strand) was systematically studied. In order to investigate the relationship between disturbed OMs and entrapment of inclusions or slag to the solidified shell, samples were taken at 10 locations on one relevant slab, and they were polished 2 mm each time. Inclusions larger than 10 µm were analyzed using the optical microscope. The level fluctuates with the continuous casting processing. The level positions on the fixed side and loose side may not be consistent. Surface level near the submerged entry nozzle (SEN) and the narrow face fluctuates on a higher position, while on the region between the SEN and the narrow face, the level fluctuates on a lower position. Time-history of the level fluctuation on the loose side and the centerline is synchronous, while the flow fluctuates in another pace on the fixed side. Root-mean-square (RMS) value of level fluctuation varies along the mold width. There are peak values at the locations near the SEN and narrow face, where slag entrapment may be induced. The OMs are more likely to be disturbed at the middle and 1/4 location in mold width. There is a big difference in entrapment of inclusions at the solidified shell between loose side and fixed side. On the fixed side, the distribution of number density of inclusions is in agreement with number distribution of disturbed OMs on meniscus, while more inclusions were entrapped at narrow faces on the loose side.