US3525506A

US3525506A - Tundish-tundish roof assembly

Info

Publication number: US3525506A
Application number: US757563A
Authority: US
Inventors: George Harry Jr; Robert A Carbaugh
Original assignee: Jones and Laughlin Steel Corp
Current assignee: Jones and Laughlin Steel Corp
Priority date: 1968-09-05
Filing date: 1968-09-05
Publication date: 1970-08-25
Anticipated expiration: 1987-08-25
Also published as: BE741896A

Description

l .2 LL

INVENTORS GEORGE HARRY,JR. ROBERTACARBAUGH ET AL 3,525,506

g- 1970 G. HARRY, JR.

TUNDISH-TUNDISH ROOF ASSEMBLY 2 Sheets-Sheet l Filed Sept. 5

11 mmarromvev Aug. 25, 1970 HARRY, JR" ET AL 3,525,506

TUNDISH-TUNDISI-I ROOF ASSEMBLY 2 Sheets-Sheet 2 Filed Sept.

' INVENTORS. GEORGE HARRY, JR. ROBERT A.CARBAUGH BY 4 A iheirATTORNEY United States Patent 3,525,506 TUNDISH-TUNDISH ROOF ASSEMBLY George Harry, In, Beaver, and Robert A. Carbaugh,

Pittsburgh, Pa., assignors to Jones & Laughlin Steel Corporation, Pittsburgh, Pa., a corporation of Pennsylvauia Filed Sept. 5, 1968, Ser. No. 757,563 Int. Cl. F27b 14/14 US. Cl. 26340 4 Claims ABSTRACT OF THE DISCLOSURE Apparatus comprising a tundish-tundish roof assembly and including gas burner means mounted in said roof for delivering hot combustion gases to the inside of the assembly both during preheating of the assembly and during casting, creating Within the assembly a high temperature protective atmosphere at a positive pressure.

This invention relates generally to apparatus for delivering molten metal at a controlled, uniform rate from one structure to another, and more particularly to a tundish-tundish roof assembly for receiving molten metal from a ladle and distributing the metal to a casting unit.

The tundish-tundish roof construction of the present invention comprises a tundish having nozzles in the bottom wall thereof for feeding molten metal to a casting unit and an associated tundish roof which fits tightly to the tundish, enabling a positive pressure to be maintained within the vessel. Gas burner means are mounted on the tundish roof and exhaust their burning gases into the vessel to maintain a positive pressure and controlled nonoxidizing atmosphere therein.

The gas burner means include a burner head for mixing air with combustible gases and a burner block means constructed to fan out the burning gases issuing from the burner head, thereby establishing short flame patterns of substantial areal extent. The entire face of the burner blocks are heated by the burning gases and this heat transmitted by radiation to the inner surface of the vessel generally, whereby the interior of the tundish is effectively heated both during preheating and casting operations.

An object of the invention is to provide a tundishtundish roof construction which results in a minimum of molten metal oxidation during casting. Another object of the invention is to provide a tundish-tundish roof construction which permits the use of molten metal having lower initial temperatures. A further object of the invention is to provide a tundish-tundish roof construction which limits temperature losses during casting, particularly at the start of casting when clogging of nozzles is prevalent. Yet another object of the invention is to provide a tundishtundish roof construction which can maintain uniform flow rates from all tundish nozzles during casting. Still another object of the invention is to provide a tundishtundish roof construction which results in producing metallurgically clean and uniform cast products. Another object of the invention is to provide a tundish construction which enables steels considered difficult to cast to be readily cast through small nozzles. Another object of the invention is to provide a tundish-tundish roof construction that will minimize the formation of oxide deposits in the tundish during casting and also make possible at the end of the casting cycle the drainage through the nozzles of any oxides that may be formed, thus eliminating costly and time-consuming cleaning of the nozzles.

These and other objects and advantages of the invention will be apparent from the following description of an embodiment thereof with reference to the accompanying drawings in which:

FIG. 1 is a top plan view of a tundish-tundish roof as sembly according to the present invention.

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FIG. 2 is a top plan view partly in section of a tundish according to the present invention illustrating certain internal details of the tundish.

FIG. 3 is a side elevation, largely in section, of the tundish-tundish roof assembly.

The tundish-tundish roof assembly generally comprises a tundish 1 and tundish roof 2. Tundish 1 includes a steel shell having a bottom wall 3, substantially vertical back wall 4 and end walls 5, 6 and an outwardly inclined front wall 7. A central portion of the front wall 7 juts out from the main body of the tundish to form a spout 8 through which molten metal from a ladle is delivered to the interior of the tundish. A top section of end wall 5 is cut out and a runner 11 attached thereto to provide an overflow opening for excess molten metal poured into the tundish.

The interior of the tundish shell is completely lined with conventional refractory material 9. Six nozzles 1010 are positioned along the bottom wall of the tundish in holes provided in shell bottom wall 3 for distributing molten metal from the interior of the tundish to a casting unit positioned beneath the nozzles.

Tundish roof 2 is constructed of an outer steel shell having sloping front and back walls 12-12, vertical end walls 1313, and a curved upper wall 14 overlying the tundish interior. The upper Wall is secured to the front, back and end walls as by welding. A plurality of arcuate strengthening webs 1515 are secured to the front and back wall and the upper Wall also as by welding. The interior of the roof is lined with a suitable refractory material 16.

Support flanges 17--17 are Welded to the front, back and side walls of the roof and When the roof is in position over the tundish rest on similar flanges 1818', welded on the front, back and end walls of the tundish. The engagement of the flanges provides a tight fit between the tundish and tundish roof so that the only openings from their interior are the spout 8 and the overflow opening in end wall 5 where runner 11 is attached. To further effect a seal between the tundish and tundish roof prior to placement of the roof onto the tundish, refractory mud is placed around the top of the tundish where it engages the tundish roof. Extensions or ears 19-19 are provided along flanges 1717 in line with extensions or ears 1919' provided along the tops of the walls of the tundish shell. Fastening bolts are positioned in cooperating holes in the extensions so as to securely maintain the tundish and tundish roof in tight engagement.

A series of six openings are provided in the upper wall 14, and a burner block 20 constructed of a refractory material and having a central passageway 21 opening down Wardly towards the interior of the tundish is positioned in each of the openings. The upper portion 22 of the burner block is of a square cross-section and extends outside of wall 14. The lower portion 23 of the burner block has the configuration of a truncated tetrahedron and fits in an opening in brickwork 16 and is seated thereat.

Burner heads 24-24 are mounted on the burner blocks by means of base plates 2525. The burner heads are supplied with combustible gases through conduits 26-26 which feed from gas line 27 and with air through conduits 28-28 which feed from air line 29. Suitable valves 30-30 and 3131 are provided in conduits 26-26 and 28-48, respectively, to control the flow of gas and air to the burners.

The combustible gases and air mix in the burner heads and the mixtures expelled therefrom through openings 21 in the burner blocks into the interior of the tundish-tundish roof assembly. Openings 21 include a throat portion 32 and diverging portion 33. Consequently, as the gas-air mixture ignites and exits from the throat area, the burning gases tend to diverge or fan out along the diverging portion of opening 21 and along the face of the burner block to produce a short flame pattern of substantial areal extent.

The burning gases, as they fan out along the face of the burner block, heat the burner block, and the heat therefrom is transmitted by radiation to the interior of the tundish construction. The combination of the hot burner blocks and arrangement of tightly fitting roof and tundish provides a highly efi'lcient heating system so that little heat is lost from the tundish construction either during preheating or casting. As a result, it is not necessary to supply excessively hot molten metal to the tundish to assure a proper metal casting temperature. Nozzle stoppage because of chilled metal at the beginning of casting is also minimized.

The use of a short flame, radiation-type burner is necessary as a means of developing a very high heat input while avoiding any turbulence of the metal bath in the tundish that could occur with long flame burners.

The tundish-tundish roof construction of the present invention also minimizes oxidation of the molten bath. By controlling the rate of gas and air supply to the burners, a non-oxidizing atmosphere is provided above the molten metal pool, and the tundish roof confines the buming gases to the interior of the tundish construction. This confinement of gases within the tundish with the tightly fitting roof enables a positive pressure to be maintained within the tundish and prevents the ingress of air therein. The low rate of oxide formation and the minimization of heat losses during casting enable uniform fiow rates to be maintained from all nozzles during casting.

We have found that with the tundish-tundish roof assembly according to the present invention, steels considered difficult to cast can be readily cast even where small nozzles are used. For example, Bessemer steels with acid soluble aluminum contents as high as .050% are satisfactorily cast through nozzles of five-eighths inch diameter.

The tundish construction of the invention has the further advantages that following casting it can be drained clean through the nozzles and thus does not require oxygen lance cleaning. This results in less handling of tundishes, longer refractory life, fewer tundish skulls and a more economical operation generally.

We claim:

1. Apparatus comprising a tundish having a bottom wall, a tundish roof closing over the open top of the tundish in tight engagement therewith so as to enable a positive pressure to be maintained within the confines of the tundish and tundish roof, said tundish roof having an upper wall overlying the tundish interior, at least one nozzle in said bottom wall for distributing molten metal to a casting unit, at least one burner head mounted on the upper wall of the tundish roof for delivering a combustible gas-air mixture to within the tundish construction and burner block means having a central passageway opening downwardly towards the tundish interior associated with said burner head for fanning out along the face of the burner block means the burning gases issuing from the burner means and for establishing a short flame pattern, thereby preventing significant contact of the burning gases with the molten metal in the tundish.

2. The apparatus of claim 1 wherein a plurality of said nozzles are provided in said bottom Wall along with a corresponding number of burner heads and burner block means in said roof, located substantially directly above said nozzles.

3. The apparatus of claim 2 wherein each burner head is connected to a combustible gas conduit and air conduit, all of said gas conduits being connected to a common gas feed line and all of said air conduits being connected to a common air feed line.

4. The apparatus of claim 1 including spout means associated with said tundish through Which molten metal is delivered to the interior of the tundish.

References Cited UNITED STATES PATENTS 3,099,437 7/1963 Bloom 263-43 3,336,020 8/1967 Palsak 266-24 3,374,995 3/1968 Cook 263-40 JOHN J. CAMBY, Primary Examiner US. Cl. X.R.