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United States Patent  Inventor GrantM.Farrington.Jr.
211 AppLNo. 789,896
 Filed Jan.8,l969
 Patented Au|.l0,197l
 Assignee General Refractories Company Philadelphia, Pa.
 REFRACTORY BRICK FOREIGN PATENTS 3/1956 Austria Primary Examiner-Henry C. Sutherland Au0rney-Fidelman, Wolffe & Leitner ABSTRACT: A refractory brick adapted for use in furnace roof construction and having bonding faces and nonbonding faces and a casing sheet of oxidizable metal carried on at least one of the bonding faces, the casing including a sheet characterized by at least one spacing rib projecting from at least one surface, the rib or ribs being disposed longitudinally along the longest dimension of the bonding faces of the brick and along a line or lines to one side of the centerline and at least one-half the distance from the centeriine to one edge of the bonding faces. Preferably, the spacing ribs are disposed in surface engagement with the brick side face and function to space the one surface of the sheet therefrom. The relative size, configuration and positioning of the spacing ribs of the sheet permits substantially complete oxidation of the steel during use without resulting in growth in overall sheet thickness, and maintains uniform bearing stress conditions in furnace roof brick joints.
Patented Aug. 10, 1971 2 Sheets-Sheet 1 INVENTOR GRANT M. FARRINGTON, JR.
ATTORNEYS Patented Aug. 10, 1971 2 Sheets-Sheet 2 Ja j? ATTORNEYS REFRACTORY BRICK Recently there has been developed high-fired basic brick having high hot strength which is particularly adapted for use infurnace roof and arch construction. However, while highfired basic brick has been proven to give betterroof service than conventional chemically bonded basic brick, difficulties have been encountered in use due to expansion problems developed because of oxidation of the steel casing conventionally provided on furnace brick. Unlike chemically bonded basic brick, little of the oxidized casing is found to be absorbed by high-fired basic brick and there is less of a tendency for a high-fired basic brick to crush or undergo plastic deformation adjacent the hot surface of the roof and thus relieve ings have been found to result in roof failure unless compensation is provided therefor.
Various solutions have been proposed to relieve or minimize expansion stress resulting from oxidation of brick casings. In this respect it has been proposed to include a compressible asbestos sheet in the joints between bricks for the purpose of compensating for both expansion of brick casings due to oxidation and thermal expansion of the bricks. However, the provision of asbestos sheets complicates brick installation,'increases construction costs, interferes with desired bonding of casing to brick, and has been found to result in a higher oxidation rate of the casing. Also, it has been proposed 'to reduce the degree of expansion in a furnace roof by decreasing casing thickness and by increasing the dimensions of the bricks. However, these proposals fail to completely solve the oxidation problem or bring overall roof expansion I within desired limits.
Also, it has been proposed to compensate for thermal expansion of the individual bricks forming a furnace roof by providing brick casings or spacers with dimples, embossments or corrugations which permit the casing to collapse under high stress conditions. For instance, in U.S. Reissue Pat No. 25.,755, there is disclosed a spacer, wherein one of a pair of facing plates is provided adjacent the lower or hot end portion of the brick with a pair of embossments which project from the surface of such plate into engagement with a plate carried on an adjacent brick. While this construction compensates in part for thermal expansion of the bricks, it does not compensate for expansion due to oxidation of the spacer plates themselves. Further, when employing this type of structure, difficulty has been encountered in achieving proper alignment of the embossments across any given transverse element or ring of the roof, thereby resulting in improper alignment of the forces which are set up due to thermal expansion of bricks and oxidation growth of the spacer plates. Misalignment of forces 3 has been found to cause snaking or curvature ofthe individualbricks along the roof element or ring which may result in complete failure of the roof. Simple spacers or pairs of dimples in thin steel sheet casings do not possess adequate strength to resist the load between brick in large sprung arches and have been known to collapse in constructed arches and,
bricks are forced to slide into place. In this type of structure the bearing stress which individual joints will sustain will vary substantially depending upon the alignment or the relative misalignment of the casing plate crests, and there exists a tendency for. the plate corrugation to collapse when forces present in the roof structure during use tend to force an adjacent brick or bricks to move in a direction transversely of the corrugations.
Further, it has been proposed to employ casings formed from metals which are less subject to oxidation than conventionally employed low-carbon steel. However, use of such metal both increases the cost of construction and may require modification of presently available casing applying equipment.
in accordance with the present invention there is provided a novel furnace brick casing design, which permits the utilization of conventional steel-casing material with high-fired basic brick, while avoiding the disadvantages of the prior art. The casing is preferably formed by stamping a flat sheet, usually from a coil, of oxidizable metal, such as conventionally employed cold-rolled low-carbon steel, to provide at least one rib on the casing sheet. The extent to which the sheet is deformed, i.e. the height of the projections, depends on the type of metal employed and is preferably at least equal to the growth in thickness of the nonembossed sheet due to oxidation expected to be encountered during use. The projecting ribs, which serve to space the nonribbed portions of the casing sheet from a casing carried on an adjoining brick when installed in a roof structure, define cavities or voids adapted to receive the 0xidized layer formed on the casing sheet while permitting gradual deformation of the projections upon oxidation thereof. The thus formed casing, even though completely oxidized during use, has been found to undergo little or no increase in overall thickness.
Also, the casing is additionally employed to compensate for thermal expansion of the bricks by increasing the height of the projections over that required to compensate for oxidation growth. ln this case the bearing strength of such projection may be accurately controlled to permit collapse thereof during use.
in the present invention the casing is formed, preferably from a single metal sheet, having a plurality of ribs arranged to provide a particular conformation when formed into a casing around a brick. The sheet is adapted to be wound around the bonding faces of the brick to form a casing structure of generally rectangular cross section, wherein the ribs project outwardly from the faces of the brick. The ribs are disposed on the sheet in a pattern such that when the sheet is conformed to the bonding faces of the brick, there are one or more ribs, on
' oneor more bonding faces, positioned along a line or lines therefore, do not satisfactorily provide expansion relief for plate oxidation or thermal expansion during service.
Further, in Austrian Pat. No. 238,621, there is disclosed a brick casing wherein an oxidizable metal sheet is provided with corrugations extending either longitudinally or transversely of a brick so as to form a yieldable joint between adjacent bricks. The projecting crests of the corrugations tend to promote interlocking between mating casing surfaces when running along the longest dimension of the brick and at not less than half the distance from the center line to one edge of the face. Alternatively, the casing may be applied to the brick by gluing. This can be accomplished by using the casing as single, double or more sections, as desired.
When two or more ribs are provided for each face it is necessary that each rib be positioned along a line which is at least one half the distance from the centerline to one edge of the face. The rib can actually be at the outside edge but such a location creates difficulties of manufacture. Also, the rib can occupy the total space involved, beginning at one half the distance from the centerline to the edge, and extending all the way to the edge. If, however, such a large area of ribwere contemplated, then more than one rib of narrower width could be employed, so long as each was located farther than one half the distance from the centerline to only one edge of the face, and thus, all ribs on each face one to the same side of the centerline. While any number of ribs may be employed, it is important to note that any or all located on one face of the brick are disposed to only one side of the centerline, and it is intended that the expression at least one half the distance from the centerline to one edge of said face be read to indicate that the ribs are positioned so that any or all on a given face are disposed to only one side of the centerline and at a certain minimum distance therefrom.
The dimensions of the ribs are not critical. It is, however, advantageous if the same percentage of brick expansion can be accommodated in all directions. This may be readily accomplished by providing the thickness of the ribs in proportion to the thickness of the brick. In other words, the extension of the rib above the plane of a given face will be in direct proportion to the thickness of the brick from the face on which the rib is located to the opposite face. But in no event will the extension be less than that required to accommodate the oxidation growth of the casing plate in use. Ordinarily, the ribs will project outwardly from the face of the brick by an amount at least equal to the thickness of the casing.
One function of the ribs in addition to the provision of expansion in the refractory structure, appears in the construction of open hearth roofs, where the shape ofthe bricks is such that one end is slightly smaller than the opposite end. Such bricks are known as keys. Unless the brick is very carefully marked to designate one end from the other, it is very easy for the workmen on the job to reverse the keys so that the large end of the brick is toward the inner circumference of the arch, which, if not noticed before the furnace is put into service, can result in premature failure. The provision of the ribs in the present invention provides an automatic identification since if the brick is reversed the ribs will fall on top of other ribs of adjacent bricks rather than falling on the flat ,plate surface as they should. The provision of the alignment of the ribs along the longest dimension of the brick is significant in that the arrangement facilitates driving of keys during construction. If this were not so, i.e. if horizontal ribs were provided, one horizontal rib would be forece to ride over a horizontal rib on an adjacent brick during construction.
The ribs may be formed with tapered side wall surfaces to permit controlled collapse or deformation of the projections due to the growth of an oxide layer thereon and to make the individual projections more resistant to deformation or collapse should forces present in a roof structure cause adjacent bricks to slide with respect to one another. Alternatively, the ribs may be formed with relatively straight side wall surfaces in order to increase the bearing strength of relatively high gage casing sheet material.
Alternative casing embodiments are also anticipated, wherein ribs on two or even three side faces of the brick may be omitted, and wherein the projection and recess design and arrangement on the casing sheet permits the projections to space nonembossed portions of the sheet from a casing sheet of either like or flat surface configuration carried on a joining brick ofa roof structure.
The nature of the present invention will be more fully understood by reference to the following description, taken with the accompanying drawings, wherein:
FIG. 1 is a perspective view of the preferred embodiment of the present invention, a refractory brick having an oxidizable metal casing thereon;
FIG. 2 is a perspective view ofa second configuration showing certain optional variations;
FIG. 3 is a detail view ofa method ofjoining the edges of the metal casing;
FIG. 4 is a detail view ofa method for securing the casing in place on the brick;
FIG. 5 is a schematic view of the arrangement of the brick of FIG. 2 incorporated into a monolithic refractory structure;
FIG. 6 is a schematic view of an alternative configuration of the ribs wherein two ribs are provided on each bonding face of the brick;
FIG. 7 is a schematic view of still another configuration of the ribs;
FIGS. 8 and 9 show yet other configurations, again in a schematic view;
FIGS. 10, ll, 12 and 13 show in sequence the method of providing the brick ofthe present invention.
Referring now to FIG. 1, there is shown a refractory brick according to the present invention comprising brick l and metal casing 2. Metal casing 2 is carried on the four bonding faces of the brick. The respective faces of the brick may be rectilinear, trapezoidal or any other shape known in the manufacture of refractory brick. Disposed longitudinally along the longest dimension of each face of the metal casing, are ribs 3. In the embodiment of FIG. 1, there is one rib per bonding face, although as will be seen there may be two or even more ribs per face. The ribs are disposed longitudinally along the longest dimension of the bonding faces of the brick, along a line which is at least one half the distance from the centerline of the face 2, to the edge of the face of the brick. That is, the distance A from the centerline 5 to the rib 3 must be at least one half of distance B from the centerline to the edge of the face. The ribs 3 project from the surface of the brick l in such a manner that there remain voids 4 between the inner surface of the rib 3 and the face of the brick I. In the embodiment of FIG. 1, the ribs 3 are shown having tapered sidewalls, which serve to make the projections more resistant to deformation or collapse in service.
In FIG. 2, there is shown a refractory brick of the present invention with details of the construction techniques utilized. The brick of FIG. 2 is the same as that of FIG. I, with the exception that the ribs are differently disposed on the casing, and therefore, have a different disposition on the faces of the brick. The reference numerals of FIG. 2 indicate the same features as those of FIG. 1. In addition, FIG. 2 shows at reference numeral 6 the overlapping joint, resulting from the formation of the casing by the preferred technique ofwrapping" a sheet metal casing about the brick with a small overlap 6 and spot welding. Permanent positioning of the casing 2 on the body of brick 1 is effected in FIG. 2 by the provision of the recess and case key projection 11. The overlapping joint and the key lock are further shown in detail in FIGS. 3 and 4. While other techniques of manufacture are contemplated within the scope of the present invention the techniques embodied in FIG. 2 are preferred for convenience.
In FIG. 3 the overlapping joint of the brick of FIG. 2 is shown in detail. Brick l is provided on one of its faces with recessed groove 9, adapted to receive flange 7, which is formed in the sheet metal of the casing 2. The thickness of the recess 9 is preferably the same as one thickness of the sheet metal of the casing. The joints formed between flange 7 and the opposite end of the sheet, shown at 8, are fastened preferably by spot welding. This describes a preferred method of applying the casing.
In FIG. 4 the positioning key 11 is shown in further detail. The brick l is provided, on one of its faces, with recess 10. The sheet casing is provided with key projection 11, which may be impressed in the casing after it has been formed on the brick, or it may be preformed in a unified step with the provision of ribs 3 and flange 7. The key projection 11 engages with the recess in the brick 10 to prevent the casing from sliding relative to the brick, and thus providing a permanent positioning of the casing on the brick body.
FIG. 5 illustrates the arrangement of the brick of the present invention in a finished bonded monolithic structure, where bonding faces 2 are shown to be spaced apart by the action of ribs 3. FIG. 5 is shown in schematic form.
In FIG. 6, the schematic view of another embodiment of the present invention is shown. In this embodiment two ribs are provided on each bonding face, and on the narrower bonding face the outermost rib is provided at the edge of the face. Each of the ribs on each of the faces is disposed at least one half the distance from the centerline to the edge of the face. The embodiment of FIG. 6 illustrates quite clearly that where a plurality of ribs are provided on a given face, all the ribs on that face must be disposed to only one side of the centerline.
In FIG. 7, still another embodiment of the present invention is shown, having still another disposition of the ribs on the face of the brick. In the embodiment of FIG. 7 the narrower faces of the brick have only one rib while the wider bonding faces have two ribs each.
. The provision of a plurality of ribs on a given face as shown in FIGS. 6 and 7, might be highly desirable where the structural loads to be placed on the brick, i.e. on the ribs, would exceed the bearing capacity of the particular gage of metal utilized, were only one rib provided. By providing a plurality of ribs the bearing capacity is substantially increased.
In FIG. 8, an embodiment of the present invention is shown, in schematic form, having one rib on each bonding face, disposed at the very edge of the face.
In FIG. 9, an embodiment is shown having ribs provided on only two of the bonding faces.
FIGS. 10, ll, l2, l3 and 14 illustrate the sequence of steps involved in the preferred method of manufacture of the brick of the present invention.
In FIG; 10 there is shown a sheet 'or web of conventional readily oxidizable, metal casing material, such as mild coldrolled steel. The length of sheet material is sufficient to permit it to be wrapped completely around the brick at its side faces and with further additional amounts to accommodate the material required for the ribs and for the marginal overlapping flange area. The sheet is then formed, as shown in FIG. 11, to provide the ribs and overlapping flange. The ribs are shown as recesses 3 and the overlapping flange is shown as 7. The technique whereby the sheet is formed into the appropriate shape is not significant to the present invention, however, it is preferred to utilize stamping techniques which are well known in the art, and which appear to provide the greatest economy and ease of processing. Projection 11 which is adapted to fit into a keyed recess in the brick may be provided as a part of the original stamping process, although it is also contemplated that the sheet may be formed around a brick and projection 11 may be subsequently impressed in the sheet to engage with the recess in the brick.
In FIG. 12 there is shown a brick adapted to receive the casing of the present invention, having recessed channel 9, and depression 10, adapted to receive the key projection 11 of the sheet. While the casing of the present invention possess particular utility when used with brick bodies of the high-strength type, known as high-fired basic brick, having a content of at least about 50 percent magnesium oxide and varying amounts of other oxides, including oxides of chromium, silica, iron, and aluminum, it will be clearly understood that it may be employed with improved results in combination with the more conventional chemically bonded basic bricks. The sheet of FIG. 11 and the brick of FIG. 12 are engaged and the sheet is folded about the brick as shown in FIG. 13. Marginal flange 7 is engaged in recess 9 as shown. Then, as shown in FIG. 14, the flange 7 and the opposed end of the sheet are engaged in overlapping joint 8 and spot welded.
By providing a wrap around casing structure, wherein a casing sheet is disposed on each bonding face of the brick body, there can be created a monolithic roof structure wherein all of the individual bricks are physically locked with respect to all adjacent bricks due to bonding of adjacent brick casings under high temperature furnace operating conditions. This permits subsequent repair of bricks within individual furnace roof rings, without danger that the remaining bricks forming such a ring will fall into the furnace.
In each of the foregoing embodiments of the present invention, the projection of the rib spacing portions with respect to the casing sheet surface 2 is-at least that necessary to accommodate oxide layer growths and, preferably, and additional amount to accommodate thermal expansion of the individual bricks. It will be apparent that when modifying the heights of the spacing portions, particular care must be taken in choosing the gage of the sheet metal employed in forming the casing and the dimensions in relative placement of the casing ribs so as to insure controlled uniform collapse of the side walls of the spacing portions to accommodate brick growth due to thermal effects.
Casing design requirements, i.e. the number, size and spacing of the ribs, vary depending upon such factors as brick composition and dimension, and operating conditions encountered in any given furnace roof construction. The casings are generally formed from 22 to 26 gage, preferably from 25 to 26 gage, cold-rolled low-carbon steel sheet which is stamped to provide the spacing ribs. The projection of the ribs above the surface of the steel sheet will generally range between about 0.020 and 0.060 inches, preferably about 0.030 to 0.045 inches, depending upon the degree of brick expansion clue to thermal effects for which it is desired to compensate.
While it has been shown and described preferred embodiment of the invention, and certain other embodiments thereof, still other modifications will readily occur to those skilled in the art. For example, the utilization of particular refractory materials in the forming of the brick, or the accommodation of unusual shapes thereof, could require certain adaptations of the present invention. It is therefore intended that the invention be limited only by the appended claims.
l. A refractory brick for use in furnace construction, said brick having four bonding faces and two nonbonding faces, and a unitary casing of a single thickness of oxidizable metal sheet secured on each of said bonding faces, said casing being of substantially uninterrupted planar surfaces except for at least one rib and no more than two ribs disposed longitudinally and extending fully along the longest dimension of at least two opposing bonding faces, each rib on each bonding face being along a line at least one half the distance from the centerline of each bonding face to one edge of each bonding face, each rib on each bonding face further being located on opposite sides of a plane passing through the centerlines of said opposing bonding faces, said ribs on said opposing bonding faces being adapted to cooperate with ribs of a like casing secured on bonding faces of an adjacent brick installed in a furnace construction thereby providing for proper orientation and spacing of adjacent bricks during furnace construction whereby sufficient space between adjacent bricks is produced to allow for expansion of each refractory brick casing.
2. The refractory brick structure of claim 1 wherein both pairs of opposing bonding faces have at least one rib disposed longitudinally along the longest dimension of said bonding faces.
3. The refractory brick of claim 2 wherein each pair of opposing bonding faces are different widths with the wider of said bonding faces being provided with two of said ribs and the narrower of said faces being provided with one of said ribs.
4. The refractory brick of claim 2 wherein there are two of said ribs on each bonding face.
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