US3038423A - Furnace roof and wall construction - Google Patents

Description

June 12, 1962 R. c. oswALD FURNACE ROOF AND WALL CONSTRUCTION 2 Sheets-Sheet l Filed Sept. 4, 1958 Flgqr 2 Raymond (I Oswahi &

INVENT'OR BY ATTORNEYS June 1962 R. c. OSWALD 3,038,423

FURNACE ROOF AND WALL CONSTRUCTION Filed Sept. 4, 1958 2 Sheets-Sheet 2 INVENT'OR Raymond C. Oswald ATTORNEYS United States Patent 3,038,423 FURNACE R98 AND WALL (ZQNSTRUCTIQN Raymond C. Oswald, Poland, @hio, assignor to Sharon Steei @orporation, Sharon, Pa, a corporation of Pennsyivania Fiied Sept. 4, 1958, Ser. No. 758,949 6 Claims. (til. ma as The invention relates to furnace roof and wall construction and pertains more particularly to open-hearth furnace roof construction.

Most steel refining furnaces, such as the basic openhearth furnace, include a hearth from which front and back walls extend upwardly supporting an arched roof formed of bricks, and end walls extending upwardly from the hearth closing the ends of the furnace.

The raw materials available for the production of the bricks from which the walls and roof are formed are classified into basic and acid or siliceous materials. The principal basic raw materials are magnesite (MgCO dolomite (CaCO MgCO and chrome ore (Cr O The principal acid or siliceous materials are silica (SiO or fire clay (Al O 2SiO 2H O).

The arched roof the furnace may be formed of either acid or basic bricks but is usually constructed of silica brick because of its substantially low cost as compared with basic brick and also because it is more resilient and lighter in weight than basic brick.

On the other hand, basic brick has the advantage of being more durable, owing to its ability to withstand higher temperatures than silica brick. A furnace having an all-basic brick roof can be operated at about 3100 F. while with an all-silica brick roof the furnace temperature must be maintained at not above 2950" F. to 3000 F.

The average life of an all-basic brick roof is 450 heats While an all-silica brick roof lasts for an average of only 110 heats. Notwithstanding the above-mentioned advantages of silica brick, basic brick would be used almost exclusively for such furnace roofs except for the considerable cost of a basic brick roof as compared with a silica brick roof which is about one-third the cost of a basic brick roof.

One of the inherent difficulties in the use of basic brick for furnace roof construction is that basic brick has a much greater degree of expansion and contraction than acid brick. A basic brick furnace roof is more subject to thermal shock and tends to crack and spall because of extreme expansion and contraction where furnaces are repeatedly cooled down and reheated. Thus, repeated cooling and reheating of the furnaces for shutdowns or repairs can result in complete disintegration of roof from such thermal shock.

In order to overcome this dificulty in the prior usual construction of an all-basic roof, a complete mechanical supporting structure has been provided which individually and collectively supports the brick. Such support structure also involves the requirement of special brick shapes for engaging the support members.

Furthermore, basic bricks used in furnace roof or wall construction usually are metal clad, being enveloped on four sides, but not the ends, with a sheet steel casing. The casing and brick fuse or bond together at furnace operating temperatures.

On the other hand, acid brick is less subject to thermal shock, because of its smaller degree of expansion and contraction so that less harm is done to an acid brick roof or wall on repeated cooling and reheating of a furnace for shutdowns or repairs. Furthermore, acid brick roofs do not require a separate support structure and the acid brick is not required to be metal clad. These considerations among others are the reasons for the great difference in comparative cost of all-basic and all-acid brick roofs.

I have discovered that a mosaic combination of silica or acid bricks and basic bricks provides a furnace roof which avoids the foregoing dirliculties and has a longer life than an all-silica brick roof. Such combined basic-acid brick roof has the advantages of resilient silica bricks with their relatively low degree of expansion and contraction and the more durable basic bricks from the standpoint of higher temperature operation, thus permitting furnaces to be operated at increased temperature.

The improved basic-acid brick roof construction does not require any support structure or other mechanical aid for supporting either the basic or acid bricks and, thus, the mosaic combination of acid and brick roof provides for an increased roof life and lower costs.

It is, therefore, a general object of the invention to provide a more durable, low-cost furnace roof construction with which the tonnage produced in a furnace equipped with such roof may be more than doubled before the roof must be rebuilt as compared with an acidbrick roof.

Another object of the invention is to provide a furnace roof having a mosaic pattern of acid and basic bricks.

A further object of the invention is to provide a furnace roof that combines the properties of resilient silica brick and high temperature resisting basic brick while eliminating the necessity of a support structure for the brick, thus providing increased roof life at low cost and providing for high temperature furnace operation.

A still further object of the invention is to provide an improved open-hearth furnace roof which accomplishes the foregoing objects and desiderata in a simple, effective and inexpensive manner.

The above and other objects, apparent from the drawings and following description, may be attained, the above described difficulties overcome and the advantages and results obtained, by the apparatus, construction, arrangement and combinations, subcombinations and parts which comprise the present invention, preferred embodiments of which, illustrative of the best modes in which applicant has contemplated applying the principle, being set forth in detail in the following description and illustrated in the accompanying drawings.

The invention may be briefly stated in general terms as comprising an arched roof for open-hearth furnaces and the like, formed of a plurality of arched courses of bricks, each course being composed of a combination of acid bricks aind basic bricks.

The bricks in each course may be staggered relative to the bricks in adjacent courses and the ratio may be 1, 2, 3 or 4 acid bricks to one basic brick.

In cases where the ratio is 2, 3 or 4 acid bricks to each basic brick, the bricks in adjacent courses may be so arranged that various patterns of basic and acid bricks may be produced. Standard shapes of bricks are used and no expensive suspension is required.

In accordance with the invention, the basic bricks used are typical metal clad basic bricks provided on four sides with a sheet steel casing. It is preferred that the staggered basic brick in each course should be in contact with a basic brick in one or more of the adjacent courses so that in operation the metal clad basic brick fuse together and bridge across the adjacent brick courses to assist in supporting the basic brick without external support means.

Referring to the drawings, preferred embodiments of the invention are shown by way of example, wherein:

FIG. 1 is a perspective view of a portion of an arched roof of an open-hearth or similar furnace;

FIG. 2 is a bottom plan view of the arched roof of FIG. 1, showing silica bricks and basic bricks alternating in each course;

FIG. 3 is an enlarged, fragmentary plan view of another embodiment in which the ratio is two silica bricks to one basic brick in each course;

FIG. 4 is a view similar to FIG. 3 showing another mosaic pattern of silica bricks and basic bricks in a ratio of two silica bricks to one basic brick;

FIG. 5 is a similar view showing still another pattern of a ratio of two silica bricks to one basic brick;

FIG. 6 is a view similar to FIG. 3, showing a ratio of three silica bricks to one basic brick in each course;

FIG. 7 is a view similar to FIG. 4, showing a ratio of three silica bricks to one basic brick;

FIG. 8 is a view similar to FIG. 5, showing a ratio of three silica bricks to one basic brick;

FIG. 9 is a view similar toFIGS. 3 and 6, showing a ratio of four silica bricks to one basic brick in each course;

FIG. 10 is a view similar to FIGS. 4 and 7, showing a ratio of four silica bricks to one basic brick;

FIG. 11 is a view similar to FIGS. 5 and 8, showing a ratio of four silica bricks to one basic brick; and

FIG. 12 is a diagrammatic perspective view with parts broken away of a typical metal-clad basic brick.

Reference is now made to the embodiments illustrated in the drawings in which similar numerals refer to similar parts throughout.

Although the invention is illustrated as applied to an arched roof for an open-hearth furnace, it is not the intention to limit the invention to furnace roofs, or to openhearth furnaces, as the improved construction may be used in any melting furnace wall and in electric furnace roofs or walls, as well as in the roof or walls of an openhearth furnace.

In FIG. 1, an arched roof for an open-hearth furnace is generally indicated at 1. It is composed of a plurality of spaced ribs 2 and 3 with adjacent arched courses 4 dis posed therebetween. The ribs 2 and 3 differ from the courses 4 in that the bricks forming the ribs are longer than those forming the courses 4.

Opposite sides of the arched roof are supported upon skews 5 and 6 which are situated at the top of a furnace front wall 7 and a rear wall 8 respectively. The front wall 7 is shown as composed of a plurality of courses of brick having aligned edges, while the rear Wall 8 is composed of courses of bricks which are preferably staggered.

As shown in FIG. 2, the bricks in the entire width from front wall 7 to rear wall 8 of the roof and the entire length from end to end of the roof 1 are composed of silica and basic bricks disposed alternately in each arched course 4, as well as in the ribs 2 and 3. Each silica brick is identified by the letter A and each basic brick is indicated by the letter B, the basic brick being metal clad with a sheet metal casing on four sides, but not the ends, as illustrated in FIG. 12.

In FIG. 2 a plurality of courses collectively indicated at 9 are disposed at the front wall edge of the roof 1 adjacent the skew 5. Likewise, a similar number of courses 10 of basic brick are disposed adjacent the skew 6 above the rear wall 8 of the furnace. Otherwise, all other bricks in the entire roof 1 are disposed in the alternate pattern of silica and basic bricks with the basic brick in each course staggered but in contact with the one basic brick in each adjacent course.

In this manner, as shown and described with reference to FIG. 2, each arched course of brick consists of metal clad basic brick B spaced from one another repeatedly throughout the arched course, with an acid brick A between each two spaced basic brick B. The acid brick A between the spaced basic brick B in each course thus contacts the adjacent metal clad surfaces of the basic brick B.

In FIGS. 3, 4 and 5 other embodiments of the invention are shown in which the bricks are arranged in a ratio of two silica bricks to one basic brick in each course. The pattern of silica and basic bricks is varied from one arched course 4, or ribs 2 and 3, to another.

For instance, in FIG. 3 the basic bricks and silica bricks in each course are so arranged that either the basic bricks or the silica bricks form diagonal rows disposed upwardly from left to right across the .courses 4, while the corresponding basic or silica bricks in the rib 2 are located above the corresponding bricks and in the rib 3 are located below the adjacent ends of these diagonal lines. Thus the basic brick, which become fused together where in contact, bridge across courses 24-4-4-3.

In FIG. 4 the bricks are so arranged in the three courses that corresponding rows of basic or silica bricks are staggered horizontally as viewed in this figure, from the rib 2 across the courses 4 to the rib 3, with the basic brick bridging across the courses. In FIG. 5 a diamond pattern is provided throughout the courses 4 with the basic brick in courses 2 and 3 in contact with basic brick in adjacent courses 4.

In FIGS. 6, 7 and 8 are shown other embodiments of the invention in which a ratio of three silica bricks to one basic brick is provided in each course, The patterns in FIGS. 6, 7 and 8 correspond to the patterns of FIGS. 3, 4 and 5 respectively.

In FIGS. 9, 10 and 11 are shown other embodiments of the invention in which a ratio of four silica bricks to one basic brick is provided in each course. The patterns in FIGS. 9, l0 and 11 correspond to the patterns in FIGS. 3, 4 and 5 or FIGS. 6, 7 and 8 respectively. In each of FIGS. 2 to 11 the basic bricks have been shaded so as to more clearly show the various mosaic patterns,

Thus, there may be 2, 3 or 4 silica bricks to each basic brick in each arched course or rib so that the varying patterns of FIGS. 3 to 11 may result.

The basic brick for use in the construction of openhearth furnace walls and roofs may be composed of either chrome or magnesite refractories clad with sheet metal on the four brick sides. A typical analysis of basic brick is as follows:

Percent SiO 5.4 F6203 FeO 8.6 A1 0 20.6 CaO 1.2 MgO 43 .0 Cr 03 100.0

Silica brick is the predominate acid brick used in most The improved arched roof construction provides a mosaic pattern of silica and basic bricks which is highly resistant at high temperature melting operations, such as required for basic open-hearth steel refining. The use of silica and basic bricks in the furnace roof provides a roof structure having durability considerably longer than that of an all-silica brick roof, though somewhat shorter than an all-basic brick roof and at considerably less cost than the latter.

The roof having the basic and silica brick pattern combines the advantages of high resiliency and thermal shock resistance of a silica brick and the high temperature resistance of the basic brick. The mosaic pattern of silica and basic bricks is included in the rib courses as well as the arched courses therebetween.

The resulting roof permits. increased temperatures of operation without substantially reducing the total number of heats for which the given roof may be used.

Thus, the improved basic-acid brick wall construction provides a roof which may have an average life of 200 or more heats operating at temperatures in excess of the maximum allowable operating temperature for an all-acid brick roof. That is, the improved wall construction may have an average life of about twice the number of heats as compared with the average 110 heat life of an all-acid brick roof. Furthermore, open-hearth furnaces with the improved basic-acid brick wall construction may be operated at temperatures between 3000 F. and 3100 P. which is in excess of the maximum 2950 F. to 3000 F. allowable operating temperature for an all-acid brick roof.

For example, in one open-hearth furnace provided with a roof as shown in FIGS. 1 and 2, the improved roof construction had a life of 232 heats as compared with a 90-heat life of all-acid brick roofs previously used on the same furnace. Accordingly, on this particular furnace the tonnage produced by the furnace with the new roof construction before the roof had to be rebuilt was more than doubled over that produced previously in the furnace with an all-acid brick roof.

In the foregoing description, certain terms have been used for brevity, clearness and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such words are used for descriptive purposes herein and are intended to be broadly construed.

Moreover, the embodiments of the improved construction iliustrated and described herein are by way of example, and the scope of the present invention is not limited to the exact details of construction.

Having now described the invention or discovery, the construction, the operation, and use of preferred embodiments thereof, and the advantageous, new and useful results obtained thereby; the new and useful construction, and reasonable mechanical equivalents thereof obvious to those skilled in the art, are set forth in the appended claims.

I claim:

1. A furnace roof comprising a sprung arched roof formed of a plurality of adjacent arched courses of bricks, each course consisting of metal clad basic brick spaced from one another repeatedly throughout the arched course and at least one acid brick between each two spaced basic brick, the acid brick between the spaced basic brick in each course contacting adjacent metal clad surfaces of said basic brick, each basic brick in any course being in substantial surface contact with a basic brick in each adjacent course, and the contacting metal clad basic brick in adjacent courses being fused together at furnace operating temperatures and bridged across the adjacent courses to assist in supporting the arched-course-located basic roof brick throughout the entire width and length of the roof free of external support means.

2. The construction defined in claim 1 in which there are alternate basic and acid brick in each course.

3. The construction defined in claim 1 in which there are two acid brick between each two spaced basic brick in each course.

4. The construction defined in claim 1 in which there are three acid brick between each two spaced basic brick in each course.

5. T he construction defined in claim 1 in which there are four acid brick between each two spaced basic brick in each course.

6. A furnace roof comprising a sprung arched roof formed of a plurality of adjacent arched courses of bricks, each course consisting of metal clad basic brick spaced from one another repeatedly throughout the arched course and at least one acid brick between each two spaced basic brick, the acid brick between the spaced. basic brick in each course contacting adjacent metal clad surfaces of said basic brick, the bricks in each course being staggered with respect to the bricks in adjacent courses, each basic brick in any course being in substantial surface contact with a basic brick in each adjacent course, each basic brick in each course also being in contact with an acid brick in each adjacent course, and the contacting metal clad basic brick in adjacent courses being fused together at furnace operating temperatures and bridged across adjacent courses to assist in supporting the arched-courselocated basic roof brick throughout the entire width and length of the roof free of external support means.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Poth: CG Combination Basic and Silica Bricks in Openhearth Roof Construction.

Open Hearth Proceeding, AIME (1951),

vol. 34, pp. 1942-1956. (Copy in Div. 3.)

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