Tundish control

Abstract

Microwave transmission and reception, and analysis thereof, are used to monitor the level of molten metal, paradigmatically steel, in a tundish receiving molten metal (steel) from a ladle or other vessel and passing it to the head of a continuous caster, while the steel in the tundish is covered with slag. The control factors may include level, weight or volume limits in the tundish derived from historical or real-time data, including data representing a predictable or developing vortex in the well feeding the continuous caster. The system is particularly useful in minimizing transition mix during change from one metal specification or grade to another.

Description

RELATED APPLICATION [0001] This application claims the full benefit under 35USC119 of Provisional Application No. 60 / 531,959 filed Dec. 23, 2003.TECHNICAL FIELD [0002] In the continuous casting of steel and other metals, the level of metal in a tundish is controlled to inhibit vortexing and consequent entrainment of slag into the cast metal. Control is effected with the aid of microwave transmissions directed toward the molten material in the tundish, advantageously toward the well or tap hole in the tundish, optionally combined with other factors and data representing optimum levels of steel and slag in the tundish, product specifications, or disturbances in the mold. The process is particularly useful for transitioning between products of different specifications; the formation of intermix can be minimized. BACKGROUND OF THE INVENTION [0003] Good control of the continuous casting of steel requires good control of the level of steel in the mold. See the early Pat. No. 3,537,505 to ...

AI Technical Summary

Benefits of technology

[0025] An object of the present invention is to facilitate low-level tundish operation for application to ladle exchange, transition control, tundish exchange, and termination of a cast strand. A further object of this invention is to improve yield and quality in steel strand casting by accurate prediction of the optimum level to which a tundish should be drained during the above mentioned low-level operations, and to control the tundish level to the optimum level.

[0026] Our invention includes a method of managing a tundish to control the transition between a first grade of molten steel and a second grade of molten steel to be solidified sequentially in a continuous caster by draining the molten steel through a well in the tundish to a mold at the head of the continuous caster, wherein the first grade of molten steel is covered by a layer of slag in the tundish, comprising draining the first grade of steel to a level in the tundish slightly higher than the level at which a vortex is expected to form above the well, the level of the first grade of steel being determined by directing microwave radiation into the tundish from above the layer of slag and analyzing reflections of the microwave radiation from the slag and the steel, and adding the second grade of molten steel to the tundish at a rate at least that of the rate of draining the first grade of steel. Slag inclusions in the steel fed to the continuous caster are not only reduced because the steel level is not allowed to become too low, but also because the more or less continuously held level of steel provides time for any emulsified slag to become de-emulsified.

Problems solved by technology

By way of example, in some tundishes, a vortex is considered to be a danger when the level of steel is less than 10 inches, in practice typically less than 12 inches.

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