Rippled surface stopper rod system

#The present invention generally relates to an apparatus for regulating the rate of metal flow out of a vessel that contains liquid metal. More specifically, the present invention relates to an improved stopper rod system.

#In the processing of molten or liquid metals, for example, steel, the flow of liquid metal proceeds from a metallurgical container, such as a ladle, into a tundish. The liquid metal then proceeds through the tundish into a mold. At or near the bottom of the tundish, the flow of liquid metal out of the tundish and into the mold is controlled. Generally, the flow is controlled using a stopper rod system.

#The stopper rod system is comprised of a moveable stopper rod and a nozzle. The nozzle has a bore through which the liquid metal is allowed to flow. The flow of liquid metal out of the tundish through the nozzle bore is generated by the action of gravity. The stopper rod has an end or nose immersed in the liquid metal that mates with an entry portion of the nozzle bore, such that if the stopper nose is moved into contact with the nozzle, the nozzle bore is blocked and liquid metal flow is stopped. When the stopper rod nose is moved away from contact with the nozzle, an aperture between the stopper nose and the nozzle bore is formed, allowing liquid metal to flow from the vessel through the nozzle bore. Through precise movement of the stopper rod, the rate of liquid metal flow is regulated, while maintaining a close proximity between the stopper rod nose and the nozzle bore. In this way, adjusting the size of the aperture regulates the flow rate of the liquid metal. In particular, the present invention relates to the shape of the stopper rod nose and/or to the shape of the nozzle surface.

#FIG. 1 is a cross-sectional view of a typical tundish utilized in the processing of liquid metal.

#FIG. 2 is a cross-sectional view of traditional stopper rod systems.

#FIG. 3 is a cross-sectional view showing the localized flow patterns in a traditional stopper rod system.

#FIG. 1 illustrates a traditional tundish configuration. In the tundish 1, a stopper rod 2 having center axis 6 is aligned with the center axis 5 of the nozzle 3 and is used to regulate liquid metal flow through an aperture 4.

#FIG. 2 illustrates several alternative geometric configurations of the traditional stopper rod systems. Stopper rod 7 has a round or hemispherical nose which mates with the rounded entrance surface 8 of the nozzle bore. Alternatively, stopper rod 9 has a pointed or conical nose that mates with the tapered or conical nozzle bore entrance 10. Alternatively, stopper rod 11 has a multi-radius or bullet-shaped nose.

#FIG. 3 is a close-up view around the regulation area in a traditional configuration such as those illustrated in FIG. 2. Stopper rod nose 12 is positioned relative to a nozzle bore 13 so as to form an aperture 15 which regulates the liquid metal flow represented by streamlines 14. The aperture 15 lies along the line of closest proximity between the stopper nose 12 and the nozzle bore 13. Downstream of the aperture 15, the streamlines may detach from the surfaces of stopper rod nose 12 and nozzle bore 13 so as to cause uncontrolled turbulent eddies as represented by arrows 16. The turbulent eddies form in regions of the liquid flow downstream of the aperture 15 adjacent to the stopper nose surface 12 or the inner surface of nozzle bore 13. The turbulent eddies can appear and disappear in those two regions in an uncontrolled and unpredictable manner. The size or scale of the turbulent eddies is also time variant. Variations in the scale and location of the turbulent eddies generated in the flow downstream of the minimum aperture can affect the flow regulation so as to cause variation in the flow rate even when the stopper position, and thus the aperture size, is fixed.