US3540467A - Gas-cooled stopper rod assembly - Google Patents

Description

United States Patent lnventor Philip I). Stelts Center Valley, Pennsylvania Appl. No. 737,784 Filed June 17, 1968 Patented Nov. 17, 1970 Assignee Bethlehem Steel Corporation a corporation of Delaware GAS-COOLED STOPPER ROD ASSEMBLY 3 Claims, 3 Drawing Figs.

U.S. Cl 137/340 Int. Cl Fl6k 49/00 Field of Search 137/340;

251/118 in part; 181/60 in part, 55

Primary Examiner-Samuel Scott Attorney-John 1. lverson ABSTRACT: A gas-cooled stopper rod assembly for bottom pour molten metal ladies. The stopper rod is provided with a sound muffling device designed to prevent objectionable noise levels caused by the high velocity coolant gas circulated within the stopper rod.

1 GAS-COOLED STOPPER ROD ASSEMBLY BACKGROUND OF THE INVENTION This invention relates to stopper rods and stopper rod assemblies for use in bottom pour ladles used to transfer molten metals and more particularly to stopper rods which are gascooled.

The flow of molten metal through the nozzle in-the bottom of a bottom pour molten metal ladle is usually controlled by an internal stopper rod. Theserods normally are comprised of a 1 steel rod core encased in refractory sleeve bricks and a refractory stopper head designed to fit in a well in the upper portion of the ladle nozzle.

In most molten metal transfer operations, the molten metal does not usually remain in the ladle long enough for the high metal temperatures to seriously damage the stopper rods. However, recently several modern metallurgical practices, such as continuous casting and vacuum degassing. require the molten metal to be held in the ladle for extended periods of time. With these practices, stopper rod failures due to excessive heating of the rods, have been common.

.In order to prevent such failures, gas-cooled stopper rods have been developed in which air or another cooling gas is circulated inside the stopper rod to remove excessive accumulation of heatv While such air-cooled stopper rods have extended the length of time molten metal can be retained in the ladle, such rods are still subject to occasional failure from overheating due to the fact that they were designed to use inefficient low velocity gas cooling in order to prevent objectionable noises caused by the exiting gas.

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide a stopper rod assembly which will be able to stand high temperatures for, extended periods of time without failure.

It is a further object of this invention to provide a gas-cooled stopper rod assembly in which the cooling gas is circulated within the stopper rod at a high velocity for very efficient cool- It is a still further object of this invention to provide a gascooled stopper rod assembly which.is free of objectionable noises.

Other and further objects of the invention will become apparent. from the following description and the accompanying drawings and claims.

It has been discovered that the foregoing objects can be obtained by a hollow gas-cooled stopper rod assembly in which the cooling gas passages within the hollow rod are such that the cooling gas is circulated within the hollow rod at a very high velocity. A sound muffling device connecting the hollow interior of the rod with the atmosphere prevents objectionable noises caused by the high velocity cooling gas.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional elevation of the gas-cooled stopper rod of this invention shown attached to a conventional bottom pour ladle for molten metal.

FIG. 2 is an enlarged sectional elevation of portions of the gas-cooled stopper rod of this invention.

FIG. 3 is a graph illustrating stopper head temperature measurements of two conventional stopper rods and a gas-cooled stopper rod according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the FIGS., ladle 1 is fabricated from a steel shell 2 and a refractory lining 3. A refractory nozzle 4 in the bottom of ladle l is used to discharge molten metal from ladle l. A stopper rod 5 is used to control the flow of molten metal through nozzle 4.

Stopper rod 5 is comprised of a hollow rigid steel rod 6 closed at its lower end and encased in a plurality of refractory sleeve bricks 7 and a refractory stopper head 8 attached to the gas is temporarily shut off, such as when ladle 1 is being transported. A coolant gas supply tube 9 is spaced within and extends substantially thefull length of the hollow interior of rod 6-so that theexit end 11' thereof. is spaced above the bottom of the hollow steel rod 6 by a distance substantially equal to or less'than the'inside diameter of the hollow steel rod 6. Spacers I0 insure the proper spacing ofgassupply tube 9 within the hollow rigid steel rod 6. A fitting 12 connects the upper end of gas supply tube 9 with a conduit 13 leading to a high pressure source of coolant gas. While high pressure air would normally be used because of its availability in most shops, other gases, such as steam, have the capability of absorbing more heat.

The upper portion of rod 6 is externally threaded to accommodate a refractory retaining washer l4 and lock nut 15 and also a yoke 16 and associated lock nuts 17 attached to the mechanism (not shown) used to raise and lower stopper rod 5. A forged steel tee member 18 is also attached to the threaded exterior of rod 6 above yoke 16. One outlet of tee 18 is provided with a bushing 19 which retains and spaces gas supply tube 9 centrally in the hollow interior of rod 6. A cylindrical sound muffling device 21 is screwed into the threaded side outlet of the tee member 18 and communicates with the hollow interior of rod 6. A cylindrical steel protective cover 22 encloses the sound muffling device 21 to protect it from the heat and splash of the molten metal. Cover 22 is welded or otherwise attached to the side outlet of the member 18.

In operation, high pressure air or other suitable gas is circulated down the bore of the gas supply tube 9 to the exit end 11 and up the space between the outer wall of the gas supply tube 9 and inner wall of the hollow rigid rod 6. By making the crosssectional area of this intervening space substantially equal to or less than the cross-sectional area of the bore of the gas supply tube 9 and by positioning the exit end 11 of the gas supply tube above the bottom of the hollow rod 6 by a distance substantially equal to or less than the inside diameter of the hollow steel rod 6, one achieves a very high degree of heat transfer from the hollow rod to the gas due to the fact that the gas is forced to travel at a very high velocity. Since under these conditions the high velocity gas will produce intolerable noise as the heated gas leaves the hollow interior of rod 6, the exiting gas is directed through sound muffling device 21 before being discharged to the atmosphere through apertures 23 in the bottom of protective cover 22.

One embodiment of this invention consisted of a 2 inch O.D. X l inch I.D. rigid rod 6 and a 9 1 inch O.D. X .049 wall stainless steel gas supply tube 9 with the exit end 11 thereof spaced I inch above the bottom ofthe hollow rigid rod 6. The rod 6 was encased with 8 inch O.D. fireclay sleeve bricks and a 7 inch O.D. clay-graphite stopper head. Air at a line pressure of 75-80 p.s.i.g. was fed into gas supply tube 6. FIG. 3 shows temperature measurements taken at the bottom end of rigid rod 6 for the aircooled rod of this invention as compared with a conventional solid stopper rod and a conventional low velocity air cooled stopper rod. As shown on FIG. 3, the tern perature of the rod of this invention did not exceed 1,200F.

whereas the prior art rods reached a temperature as high as 2,200F. During these tests the air flow was at times shut off to determine the effect of the air cooling. Such times are noted on the curves of the FIG. 3.

The sound muffling device used for this embodiment was an Atomuffler" manufactured by Allied Witan Company, Inc., Cleveland,Ohio.

The use of the gas-cooled stopper rod has permitted molten steel to be retained safely in the ladle for extended periods of time without any deleterious effects on the stopper rod and with noise levels acceptable for industrial working conditions.

I claim:

I. In a stopper rod assembly for molten metal bottom pour ladies or the like comprising in combination a hollow rigid rod, a refractory covering on the outsideof said rod, a refractory stoppernhead attached to the lower end of said rod, a coolant gas supply tube spaced within'and extending substantially the full length of the hollow interior of said rod a source of high pressure coolant gasconnected to the upper end of said coolant gas supply tube, theimprovement comprisingasize and spatial relationship between saidcoolant gas supply tube, and said hollow rigid rod such that the ;cross-sectional -area oil the space between the outer wall of said'gas supply tubeand the inner wall of said hollow rigid rod is substantially equal to v or less than the cross-sectional area of theibore of saidgas supply tube and the exit end of said gas supply tube is spaced,

above .the bottom of said hollow rigidrod. by a distance subhalf its outside diameter.

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