US3549061A - Tundish nozzle for continuous casting - Google Patents

Description

United States Patent Inventor Kristian Piene Oslo, Norway Appl. No. 649,612

Filed June 28, 1967 Patented Dec. 22, 1970 Assignee Jones & Laughlin Steel Corporation Pittsburgh, Pa.

a corporation of Pennsylvania TUNDISH NOZZLE FOR CONTINUOUS CASTING 5 Claims, 2 Drawing Figs.

US. Cl 222/566 Int. Cl. 8651! 5/72 222/460,

Field of Search 462, 464, 564, 566, 572,575, 112, 322; l06/(lnquired); 266/(lnquired) References Cited UNITED STATES PATENTS 3/1968 Hase et al. 7/1909 Collier 12/1941 Debenham et al FOREIGN PATENTS 3/1959 Great Britain Primary Examiner-Samuel F. Coleman Attorney-G. R. l-larris ABSTRACT: The apparatus of this invention is a tundish provided with a heat insulating lining below its bottom working lining and a composite nozzle, the upper portion of which is made of refractory material of high thermal conductivity and projects above the tundish bottom working lining, and the lower portion of which is made of heat insulating refractory material.

PATENTED UEC22 I976 FIGJ.

R o T N E V m KRISTIAN PIENE his ATTORNEY This invention relatesto the art of continuously casting high T melting point metals; It'is particularly concerned with atundish and nozzleadapted for continuously casting steel. In the continuous casting of high met melting point metals,

: -i. such as steel, it is desirable to maintain ajuniform rate of flow 1; of molten metal into the mold. This is conventionally achieved by casting the steel from a tundish, to which hot metal is added from time'to time, was to, maintain a relatively constant ferrostatic head. The amount'of metal which the tundish holds is, of course, limited. In the continuous casting of billets and the like I of relatively small crosssec'tion, it is necessary to supply molten metal at'a relatively restricted rate, and this is achieved by using a'tundishnozzle of appropriate diameter. In such circumstances when conventional tundish nozzles are used, the molten steel has a: tendency ;to freezein the nozzle. Any significant impediment 'in the. nozzlereduces the rate of flow of the steel there through, which reduction is deleterious to the "f continuous casting process. :This tendency to freeze is more ii pronounced in aluminum killed steels than in steels deoxidized with other deoxidizers such as silicon. I

' In additio'nfmast experience with conventional tundish nozzles has shown that during casting of aluminum killed steel the tende'ncyof the steel'to freeze in the nozzle is accompanied by i a gradual buildup'of nonmetallic inclusions consistingmainly of ,alurnina'Depending on the aluminum concentration this I buildup canlead eventually to a complete blockage of the tundish nozzle. Again past experience has shown that in view of this reaction it is practically impossible to continuously cast aluminum killed-steel successfullythrough conventional tundish nozzles at aluminum concentrations which are typical for conventionally produced steel of this type (-0.015 percent Al. ,,5,; and higher).

It is an object of my invention invention, therefore, to pro- ";Zl'vide a tundish and nozzle so constructed as toreduce the tendenc'y of molten m'etaljto freeze in the nozzle. It is another ob- ..ject to provide a tundish'so constructed as to facilitate heat transfer from the molten metal in theltundish to the nozzle and retard heat transfer-from the nozzle to the tundish lining. Oth er objects of my invention'will'appearfrom the description thereof.which follows.

.j Anembodiment of my invention presently preferred by me is illustrated in the attached figures, to which reference is now made.

, FIGQI is an elevationin cross section of a tundish of my in- 'vention.

FIG. 2 is a detail view to-an enlarged scale showing a verti- -c'al section through the nozzle of FIG. 1. I j The tundish is provided with a steel bottom plate 2 and upright steel sides 3. and 4; which are provided with a refracto- Qry linings." The bottom plate 2 and lining 5 are formed to providea vertical cylindrical teeming channel 6, in which is posij tioned a nozzle 7. A ladle 8 is positioned above tundish 1, from which molten metal is teemed into the tundish as is required.

The structure of the:- nozzle 7 and refractory lining 5 on the .,.,bottom of tundish l is more clearly shown in FIG. 2. Immediately adjacentbottorn plate 2 is positioned a layer 10 of thermal. insulatingbrick. Ontopofthis layer is positioned a layerl l. of conventional refractory brick. This layer 11 constitutes the workinglining. Layers '10 and 1.1 together make up the tundish linings. Around cylindrical channel 6, layer 11 is stepped back fromlayerI10, so as to provide an annular ledge 12,- which supports nozzle 7.

Nozzle 7 comprises an annular base portion 13 which sup- -port s a frustoconical nozzle block 16. Base portion 13 is made of thermal insulating brick and is dimensioned to be supported onxledgell. -The*top surface-l4 of base 13 is aportion of a sphere and does not extend above the upper face of layer 11 of lining 5. The central opening 15 in base 13 has a bottom diameter,- somewhat less than that of channel 6 and tapers to a still smaller diameter at'its upper end.

Frustoconical nozzle block 16 has a central bore 17 of the desired nozzle diameter; This diameter is smaller than that of -the:,upper-end of central opening 15. The lower surface of block 16 matches the spherical upper surface 14 of base portion-13f Nozzle block 16 projects well above the upper surface of refractory layer 11, so that most of its external surface is in contactwith the molten metal in the tundish l. The gap between its lower outer edge or skirt l8 and layer 11 is filled with a plastic refractorycement l9. Nozzle block 16 is made of arefractory material having a high thermal conductivity.

. In operation tundish 1 is filled to the desired height with molten metal, such as steel, from ladle 8. The steel immediately begins to flow outof tundish lthroug h bore 17 of nozzle block 316 at a rate determined by the diameter of that bore and at aiheiglit of the steel in the tundish. As the molten steel is in contact bothewithithe inside and outside surfaces of nozzle block 16, which is made of high thermal conductivity refractory material, the temperature of block 16 tends to approach that of the-molten steel. While momentary chilling of steel may occur around the outside of the relatively small volume of steel passing throughbor 17, it does not occur around the outside surface of block 16, which is in contact with a much larger volume of steel, but on the contrary, heat will flow from themolten steel through the outside surface of the high thermal conductivity nozzle block 16 toward the bore 17, so as to raise the temperature around the inside of that bore. As the base portion 13 is made of thermal insulating refractory material, heat flow away from bore 17 through the base of nozzle block 16 will be retarded.

' The fire clay compositions, which are conventionally used for the refractories of layer 11 of the tundish lining, have a thermal conductivity range from about 8 to 12 B.t.u.s per hour per square foot per degree F. per inch at temperatures in the neighborhood of 2000 F. For nozzle block 16 I prefer to use a refractory having a thermal conductivity at that temperature not less than that of zircon, which has a thermal conductivity of about 17 in the units above mentioned. I have used materials having a thermal conductivity as high as 2 0 area within the working lining, and supports the high heat con- 1 ductivity nozzle block.

I claimi 1. In a tundish for teeming molten steel including a refractory working lining and a teeming nozzle, the improvement comprising alining of heat insulating material positioned below the refractory working lining at least in the area surrounding the teeming nozzle and extending up into the refractory work ing lining'in the area of the teeming nozzle, a nozzle block of heat conductive refractory material having a bore which defines the cross section of the stream of molten steel teemed therefrom, and being positioned so that at least the major portion of the bore is a'bovethe upper surface of the refractory working lining,whereby,heat is transferred to the nozzle block from the molten steel sufficient to retard solidification of mo]- ten steel in the bore, the nozzle block being spaced from the refractory working lining by the heat insulating lining extending up into the refractory working lining.

2. The apparatus of claim 1 in which the heat insulating lining extends up into the refractory working lining to aboutrthe upper surface thereof.

3. The apparatus of claim 1 in which the heat insulating lin ing extending up into the refractory working lining is of subbeing not higherqthan the upper surface of the" refractory lin' ing, and the nozzle block has a bottom surface complementary to that hemispherical shape.

material extending up into the refractory working lining in the area of the teeming nozzle and the nozzle block are formed as a unit which fits into the tundish bottom.

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