Research progress on the role of ladle shroud in protecting molten steel during teeming in continuous-casting tundishes

The global steel yield heavily relies on the continuous-casting process in the modern steel industry. Thus, the implementation of protected teeming in continuous-casting tundish for high-quality clean steel production is essential. Ladle shroud is a refractory device that contains the teeming stream between ladle and tundish. The invention and application of the ladle shroud play a significant role in the development of continuous-casting technology and considerably influence the performance of protected teeming, including protecting molten steel from reoxidation and contamination from air/slag/refractory/ladle filler sand during both steady-state and transient casting periods (i.e., first-heat filling, ladle change, and tundish emptying). In this review, the sources and forms of atmospheric contamination of molten steel in the tundish were addressed and the possible solutions to the problems encountered during the use of the ladle shroud were proposed by considering the invention, industrial trials, and progressive optimization in the early stage of the development of continuous casting. The ladle shroud has been proven to effectively protect the teeming stream, which, however, is closely associated with the structural design and operating practice. Thus, the effect of the structural design of the ladle shroud, including two types of industrialized ladle shroud and several new designs, on protected teeming was analyzed and the advantage of the trumpet-shaped ladle shroud over the conventional ladle shroud in terms of production efficiency and molten steel cleanness was emphasized. The materials of the ladle shroud have also been progressively enhanced to prolong its service life and achieve a stable service performance. The influence of operational parameters, including the immersion depth of the ladle shroud in tundish and misalignment, was also discussed. On the basis of current research and development work in the steelmaking continuous-casting field, the future development direction of the ladle shroud was identified to be structure–function integration, characterized by long service life, lightweight, multifunction, and eco-friendly manufacturing.