US2792214A - Furnace lining - Google Patents

Description

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May 14, 1957 G. R. EUSNER ETAL FURNACE LINING Filed Nov. 12, 1953 F I E 1 PRESS.

IN VE/V T0175,

GEORGE R. EUSNER and MICHAEL A. OREHOS/U,

f/zeir A flarney.

FURNACE LINING George R. Eusuer, McKeesport, and Michael A. Orehoski,

Duquesne, Pa., assignors to United States Steel Corporation, a corporation of New Jersey Application November 12, 1953, Serial No. 391,564

1 Claim. (Cl. 266-43) This invention relates to the brick used for lining metallurgical furnaces and, in particular, the basic brick used in open-hearth furnaces.

The rate of deterioration of basic brick in open-heart furnaces is principally a function of the porosity of the product and numerous attempts have accordingly been made by brick manufacturers to reduce the porosity of their product. Such eiforts have not, however, been successful in respect to basic brick. It is the object of our invention, therefore, to provide a method of treating brick which will materially reduce its porosity without impairing its desirable properties.

We have found that the porosity of basic brick may be materially reduced by impregnation with molten metal and subsequent oxidation thereof. The impregnation, however, must penetrate substantially uniformly throughout practically the entire mass as contrasted with the application of a thin superficial coating as by dipping or spraying. Preferably we heat brick which has been formed and fired, at least to the melting point of the metal used for impregnation. We then subject the brick to a vacuum and immerse it in the molten impregnating metal. On removal from the metal, the impregnated brick is then ready for use in furnace linings or may be fired at a temperature sufficient to oxidize the metal left in the pores thereof, before laying.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawing illustrating the present preferred embodiment. In the drawing,

Figure 1 is a diagrammatic sectional view of one form of apparatus which may be employed to carry out our method; and

Figure 2 is a perspective view in section showing a portion of a brick treated according to our invention.

Referring now in detail to the drawing and, for the present to Figure 1, a tank of any suitable construction adapted to hold molten impregnating metal, is provided with appropriate means for heating a charge of the metal to a temperature above its fusion point. An impregnating tank 11 also designed to hold molten impregnating metal is connected to tank 10 by a pipe 12 having a valve 13 therein. As shown, pipe 12 extends downwardly from the bottom of each tank and is below the level thereof. Tank 11 is provided with a removable cover 14 having suitable means to efiect an air-tight seal with the walls of the tank, and with heating means of any convenient type (not shown). Near the top of tank 11, an outlet pipe 15 communicates therewith, having a control valve 16 therein. Pipe 15 has two branches 17 and 18 with control valves 19 and 20 therein, respectively. Branch 17 leads to any convenient source of air pressure and branch 18 to a vacuum pump of any suitable type.

A charge of impregnating metal is placed in tank 10 and heated to a temperature somewhat above its melting point. Alternatively, the metal may be melted elsewhere and poured into tank 11 in which case only enough heat ice need by supplied to the latter to make up for losses by convection and conduction so as to keep the impregnating metal molten. Ordinarily, after starting operations, the

. tank 10 will be maintained full of impregnating metal in molten condition, make-up additions being made as needed, whereby successive batches of brick may be treated as now to be described, withoutthe delay incident to melting the whole charge of metal.

The metal used for impregnating the brick may be any suitable one the oxide of which is refractory. The metal may, for example, be any one of aluminum, magnesium, chromium, titanium or calcium or an alloy of two or more thereof. For example, it will be preferable to use an alloy of about magnesium and about 35% alu minum since the volume change thereof on oxidation is practically zero. H In carrying out our method with the aid of the apparatus described above, assuming allthe valves to be closed and cover 14 removed, a load of'brick is placed in tank 11 as shown at 21. 'While the brickare shown stacked, it is better if they are placed in helter-skelter arrangement to permit direct access of the impregnating metal to all surfaces thereof. The brick may be of any type used in lining furnaces but "the method is particularly advantageous for basic brick. Such brick, i. e., conventional chrome-magnesite brick, as made and fired in conventional practice, have a porosity indicated by a percentage of voids from 18 to 30%.

When the brick have been loaded into tank 11, cover 14 is set in place and sealed thereon. Valves 16 and 20 are opened to evacuate the tank. The vacuum pump is left on until a vacuum of about .1 mm. of mercury is obtained. During the period of evacuation, the brick are heated by the heating means of tank 11 to help drive on the air entrapped in the pores and interstices thereof. After the vacuum has been applied for a suitable period, say 15 minutes, valve 20 is closed and valve 13 is opened slightly. Molten metal is thereupon forced by hydrostatic and atmospheric pressure from tank 10 through connection 12 and into tank 11. When the metal in tank 11 has risen to a level such as to immerse the brick, which may be determined by observing the fall of the level in tank 10 or other suitable means, valve 13 is closed and valve 19 is opened to admit air under at least one atmosphere pressure into the space above the level of the molten'metal in tank 11. After a suitable time, say 10 minutes, valve v13 is opened slightly and the molten metal is thus forced back from tank 11 to tank 10 under the pressure of the air above it which may be increased, if necessary, to do this. When all the metal has been returned to tank 10, which may be determined by the rising of air bubbles from the metal therein, valve 13 is closed and cover 14 is removed. The impregnated brick are then taken from tank 11, a fresh load placed therein and the treatment repeated.

The impregnated brick may be use-d immediately in laying up a furnace lining or they may be heated in an oxidizing atmosphere to a temperature and for a period such as to oxide fully the metal left in the pores of the brick after impregnation. The temperature and time required may easily be determined for any impregnating metal by experiment and observation of test specimens after various times at various temperatures. When the impregnating metal has been oxidized either throughout the minute masses thereof or at least on the surface of such masses, the brick are cooled to atmospheric temperature and are then ready for laying in a furnace lining. When the brick are laid without the oxidation treatment, the impregnating metal is oxidized in subsequent operation of the furnace. The porosity having been materially reduced by our treatment, the life of the brick when installed will be correspondingly increased. The reduction in porosity is evidenced by the fact that the percentage of voids after our treatment is less than 15% and may be as low as 3%. This is a measure of the degree of impregnation, indicating that a substantial portion of the entire mass of the brick has been penetrated.

Figure 2 shows clearly how thoroughly the brick is penetrated by the metal when treated by our process. The network of light areas shows in section the masses of metal left in the pores of the brick and are later oxidized. As shown, substantially complete impregnation was achieved, even at the center of the brick. It will thus be apparent that a brick treated by our invention is characterizc-d by having its voids substantially fully filled with the oxide of a metal or metals which is refractory.

The preheating of the brick materially aids thorough penetration of the voids by the impregnating metal. The size, shape and strength of the brick are not altered by the treatment. Brick treated by our invention show increased resistance to slag penetration, peeling and erosion by contact with hot gases or metals, when compared with untreated brick subjected to the same conditions. Such properties appear to result from the fact that the product of our method has a porosity much lower than that of conventional basic brick.

Although we have disclosed herein a preferred embodiment and practice of our invention, we intend to cover as well any change or modification therein which may be made without departing from the spirit and scope of the invention.

We claim:

In an open-hearth furnace, a lining comprising a plurality of bricks in which each brick comprises a fired shaped mass of basic refractory material such as a chrome-magnesite mixture, having the voids resulting from shaping and firing thereof filled with a material selected from the group consisting of aluminum, chromium, magnesium, titanium and alloys and oxides thereof, substantially uniformly throughout the entire extent of the brick, said brick having a volume percentage of remaining voids of from 3 to 15% and exhibiting improved resistance to penetration by molten slag such as that formed in an open-hearth furnace.

References Cited in the file of this patent UNITED STATES PATENTS 1,576,021 Aram Mar. 9, 1926 1,809,359 Schutte June 9, 1931 2,336,366 Mudge Dec. 7, 1943 2,364,713 Hensel Dec. I2, 1944 FOREIGN PATENTS 602,895 Great Britain June 4, 1948

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