Metallurgical apparatus – Process – Plugging or tapping
Patent
1997-07-10
1999-03-16
Kastler, Scott
Metallurgical apparatus
Process
Plugging or tapping
266229, 266275, B22D 4100
Patent
active
058825770
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a tundish and is particularly concerned to provide a means of improving flow of molten metal through a tundish.
In the continuous casting of steel molten steel is poured from a ladle into an intermediate vessel, a tundish, and from the tundish into one or more continuous casting moulds. For example, the tundish may feed two casting moulds, i.e. it is a two-strand tundish.
It is well known that unwanted non-metallic inclusions can be entrained in the steel in the tundish and a variety of means have been proposed to improve the steel quality by removing such inclusions before the steel passes from the tundish. Such means include the use of a layer of `active` flux on the surface of the molten steel in the tundish, which flux captures unwanted inclusions. Also, such means include a variety of baffles, dams and weirs positioned in the tundish. In this context. a baffle is an obstruction to steel flow extending from the floor of the tundish to above the uppermost level of the molten steel, a dam is an obstruction protruding upwardly from the floor of the tundish and over which the steel must flow and a weir is an obstruction protruding downwardly into the molten steel and under which the steel must flow.
Such baffles, dams and weirs may be made of, or include a surface layer of an active material, e.g. alumina, to capture inclusions from the steel. They may have holes to allow passage of a portion of the steel through and they may be dimensioned and positioned to urge upward flow of the steel into a better contact with a surface layer of flux material.
Furthermore, it is also known to position an erosion-resistant impact pad on the floor of the tundish to receive the incoming stream of molten steel from a ladle.
Baffles, darts, weirs and impact pads will herein be referred to collectively as tundish furniture.
Impact pads have also been designed to minimise surface turbulence in the tundish in addition to their primary erosion-resistance role. For example, in U.S. Pat. No. 5,169,591, an impact pad is disclosed which has a base to receive an incoming ladle stream and a sidewall extending upwardly alone the periphery of the base. The upwardly extending sidewall includes an inner surface having an undercut portion facing the incoming ladle stream, the undercut portion extending along the length of the inner surface and having a surface shaped to receive and reverse the direction of fluid flow generated by the incoming ladle stream. Molten metal flowing from the impact pad can pass through holes in a baffle located between the impact pad and the outlet from the tundish.
By reducing pour zone turbulence, the risk of the surface covering flux layer being broken and exposing the steel to air can be reduced, thereby reducing levels of steel reoxidation and heat loss.
The present invention aims to provide an improved arrangement of tundish furniture for a tundish that reduces risk of pour zone turbulence and improves flow patterns for steady state casting in the tundish so that inclusion removal can also be improved tundish so that inclusion removal can also be improved and the amount of slag/flux cover layer break up and entrainment at ladle changes can be reduced.
Accordingly, in one aspect the invention provides a tundish having an outlet in its base the outlet being spaced longitudinally of the tundish from a pour zone, the pour zone being positioned to receive a stream of molten steel from a ladle, an impact pad on the floor of the tundish in the pour zone, the impact pad comprising a base having an impact surface, an upwardly extending sidewall along the periphery of the base, the sidewall having an inner surface having an undercut portion to face the incoming steel stream and the undercut portion having a surface shaped to receive and reverse the direction of flow of the incoming stream, and a dam positioned between the impact pad and the outlet, the dam having one or more holes to allow through passage of a proportion of the steel whereby a proportion of the steel can pass through the d
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patent: 5133535 (1992-07-01), Soofi
patent: 5169591 (1992-12-01), Schmidt et al.
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patent: 5358551 (1994-10-01), Saylor
patent: 5518153 (1996-05-01), Zacharias et al.
patent: 5551672 (1996-09-01), Schmidt
Isenberg-O'Loughlin, "Dishing it Out" the latest in Tundish Utensils and High-Tech Tableware, Metalproducing, No. 33, Feb. 1996 .
Foseco International Limited
Kastler Scott
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