Background of the Invention A taphole is a hole that extends through a refractory wall in a molten metal manufacturing furnace to allow molten metal within the furnace to exit the same. The taphole is conventionally defined by the refractory material forming the wall. A taphole in a cupola furnace connects the melting zone within the cupola furnace with a front slagger box located on the exterior of the cupola furnace. Molten metal and slag flows continuously from the melting zone into the slagger box. The continuous flow of molten metal and slag eventually erodes the refractory material defining the taphole to a point where the taphole must be reforme, i. e., rebuilt.

Typically, a taphole is reformed in a cupola furnace by first removing the refractory material in the vicinity of (i. e. surrounding) the taphole. A piece of steel pipe or tubing is then positioned relative to the melting zone and slagger box.

Refractory material is then placed around the pipe to refill the opening in the refractory wall. The refractory material may either be 1) packed or 2) cast around the pipe or tube to seal the opening in the refractory wall. Casting refractory material around the pipe or tube requires the use of forms or molds to hold the refractory castable material in position until the refractory castable material has set and hardened.

While the refractory castable sets and hardens, the pipe is held in place in the refractory wall. The packing process involves ramming a clay-like refractory material into the opening around the pipe. The refractory material used for this type of construction is pliable and has a clay-like consistency and is rammed into the opening between the pipe and the existing refractory wall until the entire opening around the

pipe is filled. During the first use of the re-built taphole, the metal pipe held in the refractory wall melts away, leaving the cast or rammed refractory material defining the opening that is the taphole.

A problem with the ramming process for reforming the taphole is that voids and interfaces may be formed between successive slabs or layers of the pliable refractory material, resulting in voids or irregularities being formed around the pipe.

When the pipe is melted away, a bore with irregularities or voids in its inner surface results. These voids or irregularities produce non-turbulent flow, and locations where the molten metal and slag may be captured. This irregular flow accelerates the erosion of the refractory material forming the bore.

The casting process for forming the taphole is generally superior to ramming in terms of avoiding erosion and voids. However, the casting process requires the building of forms and molds in or adjacent to the cupola furnace refractory wall and requires a longer setting and curing time. The construction of the building forms, and the curing and setting time of the castable refractory, extend the down time for the furnace. Still further, the density of both the rammed refractory or a cast refractory is limited.

The present invention overcomes these and other problems, and provides an assembly and method of forming a taphole wherein a taphole is formed of a much denser, compact, erosion-resistant refractory material and is formed having a smoother, contoured inner bore.

Summary of the Invention In accordance with the present invention, there is provided an assembly for forming a taphole in a molten metal furnace. The assembly is comprised of an elongated, isostatically pressed tubular member formed of a refractory material. The tubular member has a first end, a second end and an outer surface. An inner bore extends from the first end to the second end and defines the taphole to be formed. A block of refractory material is attached to the tubular member to form a base therefor.

The block engages, in mating fashion, the outer surface of the tubular member and has a planar, bottom surface dimensioned to rest upon a planar structural surface of the furnace so as to support the tubular member at a predetermined position and orientation relative to the furnace.

In accordance with another aspect of the present invention, there is provided an assembly for forming a taphole in a molten metal furnace. The assembly is comprised of an elongated, isostatically pressed tubular member formed of a refractory material.

The tubular member has a first end, a second end, an outer surface, and an inner bore that extends from the first end to the second end and that defines the taphole to be formed. A metal pipe is disposed within the inner bore of the tubular member. The pipe is fixedly mounted to the tubular sleeve and has a length such that the pipe extends beyond the first and the second ends of the tubular member.

In accordance with another aspect of the present invention, there is provided a method of forming a taphole in a furnace wall to communicate the interior of the furnace to a location exterior to the furnace. The method is comprised of the steps of : isostatically pressing refractory material into an elongated, tubular member having an inner bore extending therethrough, the bore dimensioned to form the taphole; casting a refractory material around at least a portion of the tubular member to form a support block having a planar bottom surface; forming an opening in a furnace wall where the taphole is to be formed, the opening having a planar support surface defining the bottom thereof ; positioning the tubular member and the support block in the opening in the furnace wall with the planar bottom surface of the block resting on the planar support surface of the opening; and ramming plastic refractory material around the tubular member and the support block to close the opening.

It is an object of the present invention to provide a pre-formed assembly for installing and repairing tapholes in molten metal furnaces.

Another object of the present invention is to provide a pre-formed assembly as described above for use in a cupola furnace.

Another object of the present invention is to provide a pre-formed assembly as described above that reduces furnace down time during repairs and installation.

A further object of the present invention is to provide a pre-formed assembly as described above that creates a taphole having a longer service life.

A further object of the present invention is to provide a pre-formed assembly as described above that is comprised of an isostatically-pressed refractory sleeve.

A still further object of the present invention is to provide a pre-formed assembly as described above wherein the pre-formed sleeve has a support block formed of a refractory material cast thereabout.

A still further object of the present invention is to provide a pre-formed assembly as described above having a handling fixture to allow handling of the assembly without damaging the refractory materials.

These and other objects and advantages will become apparent from the following description of a preferred embodiment of the invention, taken together with the accompanying drawings.

Brief Description of the Drawings The invention may take physical form in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail in the specification and illustrated in the accompanying drawings which form a part hereof, and wherein: FIG. 1 is a partially sectioned perspective view of a cupola furnace; FIG. 2 is an enlarged sectional view of area 2 of FIG. 1, showing a taphole assembly illustrating a preferred embodiment of the present invention; FIG. 3 is a perspective view of a taphole replacement assembly according to the present invention, showing the taphole assembly with a handling fixture attached thereto; FIG. 4 is a sectional view taken along lines 4-4 of FIG. 3; FIG. 5 is a sectional view taken along lines 5-5 of FIG. 3; and FIG. 6 is a sectional view of a taphole replacement assembly and handling fixture, illustrating another embodiment of the present invention.

Brief Description of Preferred Embodiment Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, FIG. 1 shows a cupola furnace 10 for manufacturing iron. Cupola furnace 10 is a vertical furnace for melting iron and broadly stated, is basically comprised of a cylindrical metal superstructure 12, the inner surface of which is lined with refractory materials, (such as bricks or refractory castables) to define an interior chamber 14. The lower end of inner chamber 14 comprises a melting zone 16. A taphole 20 is formed through the wall of furnace 10 to allow molten metal to continuously flow from melting zone 16 to a slagger box 22 outside of furnace 10.

Furnace 10 as heretofore described is conventionally known, and in and of itself forms no part of the present invention. Furnace 10 is shown to disclose the environment of the present invention and to better illustrate the same.

The present invention relates to a method for forming a taphole in furnace 10.

Referring now to FIGS. 2-5, an assembly 30 for forming a taphole in a furnace wall is shown. Assembly 30 is basically comprised of a tubular member 40 and a support block 60.

Tubular member 40, best seen in FIG. 4, is essentially an elongated tube having a planar first end 42, planar second end 44, an outer surface 46, and inner surface 48. Inner surface 48 defines an axially aligned bore 50 that extends through tubular member 40 from planar first end 42 to planar second end 44. Bore 50 basically defines the taphole or opening that ultimately will connect melting zone 16 with slagger box 22. Tubular member 40 is formed of a refractory material. In accordance with one aspect of the present invention, tubular member 40 is isostatically pressed into a tube shape by a conventionally known process.

The refractory composition of tubular member 40 is preferably chosen based upon the type of furnace in which it will be installed, and upon the type of molten metal to be conveyed therethrough. In the embodiment shown, refractory material is preferably chosen to have minimum reaction and wear to molten iron. In this respect, the slag associated with molten iron formed in a cupola furnace may have a basic or acidic composition. For more basic slag compositions, tubular member 40 is preferably comprised of a resin or pitch bonded magnesia-graphite refractory. Such refractory would typically be comprised of about 60% to about 98% sintered or fused magnesia, about 2% to about 20% graphite or carbon, about 2% to about 8% resin or pitch and about l % to about 10% by weight of a metal such as, by way of example but not limitation, aluminum, silicon, magnesium, boron-carbide and alloys of such metals.

For molten iron having an acidic slag composition, tubular member 40 is preferably comprised of a resin or pitch bonded alumina-silicon/carbide-graphite composition. The alumina-silicon/carbide-graphite refractory is preferably comprised of about 40% to about 85% by weight alumina, about 1% to about 20% by weight of graphite or carbon, about 5% to about 50% by weight silicon carbide and about 2% to about 8% by weight resin or pitch. As indicated above, based upon the refractory

material forming tubular member 40, such refractory material is preferably isostatically pressed into the tubular shape as heretofore described.

In the embodiment shown, tubular member 40 is cylindrical in shape and has a cylindrical outer surface 46 and a cylindrical inner surface 48 that defines bore 50. In the embodiment shown, bore 50 near first end 42 is preferably flared or tapered to define a funnel-shaped region 52, best seen in FIG. 4. As will be appreciated by those skilled in the art from a further reading of the specification, in some applications, it may be desirable that bore 50 be completely cylindrical in shape (i. e., without funnel- shaped region 52).

Referring now to FIG. 3, support block 60 is best seen. Block 60 is preferably comprised of a refractory castable material and is preferably cast around tubular member 40. Block 60 has a planar bottom surface 62 adapted to rest upon a planar structural surface of furnace 10, as shall be described in greater detail below. In the embodiment shown, block 60 includes parallel, planar side walls 64,66 that are perpendicular to bottom surface 62. Block 60 may be dimensioned to totally encase outer surface 46 of tubular member 40 (see FIG. 5), but in the embodiment shown, is cast to enclose a little more than half of the periphery of outer surface 46. By casting block 60 around tubular member 40, the refractory material adheres to outer surface 46 of tubular member 40 leaving no space or gap therebetween. The refractory material used to form block 60 is preferably a high-temperature castable that is compatible with molten iron (or with other molten metals if assembly 30 is used in a different furnace with a different type of metal). To insure that block 60 does not separate from tubular member 40 during handling and installation, in accordance with another aspect of the present invention, metal fastening straps 72 surround block 60 and tubular member 40. Straps 72 are preferably metal bands that tightly wrap around tubular member 40 and support block 60.

In accordance with another aspect of the present invention, assembly 30 may include a handling fixture 80 (see FIGS. 3 and 4) to facilitate handling of assembly 30, and more importantly to prevent damage to tubular member 40, and particularly to prevent damage to inner surface 48 that defines bore 50. In the embodiment shown, handling fixture 80 is comprised of an elongated metal pipe 82 and metal end plates 84,86. Pipe 82 is dimensioned to be disposed within bore 50 of tubular member 40.

Pipe 82 preferably has an outer surface profile dimensioned to match the profile of

inner surface 48. In the embodiment shown, pipe 50 is cylindrical in shape having an outer diameter that closely matches the diameter of cylindrical inner surface 48.

Preferably, the outer diameter of pipe 82 is as near as possible to the diameter of inner surface 48 yet still allows easy insertion of pipe 82 into bore 50. As shown in FIG. l, pipe 82 has a lengthwise dimension wherein portions 92,94 of pipe 82 extend beyond each end of tubular member 40. End plates 84,86 are flat, metallic plates having centrally located holes (not illustrated) therethrough. The holes in end plates 84,86 are dimensioned to allow the plates to slide onto the ends of pipe 82. As best seen in FIG. 4, end plates 84,86 are positioned on pipe 82 to be in contact with the planar first and second ends 42,44 of tubular member 40. In this position, end plates 84,86 are secured to pipe 82 (preferably by welding) such that end plates 84,86 essentially secure pipe 82 within tubular member 40 with extension portions 92,94 extending therefrom. Pipe 82 and end plates 84,86 are preferably formed of conventional carbon steel when used in an assembly 30 for application in a cupola furnace 10 for forming molten iron. (Pipe 82 and end plates 84,86 could also be formed of aluminum if assembly 30 is to be used in a molten aluminum furnace). It will also be appreciated that bore 50 through tubular member 40 may have a cross-section defined by another geometric shape, such as a square or rectangle, and that pipe 82 may be formed of conventional square or rectangular pipe to match the cross-sectional configuration of inner surface 48 that defines bore 50.

Referring now to the operation of assembly 30, when a taphole needs to be built or replaced in a furnace wall, an opening is formed in the furnace wall. The opening circumscribes the location where a taphole is to be formed. In most instances, replacement of an existing taphole is required, which requires removal of the refractory material surrounding the existing taphole. The existing refractory material below the taphole is removed until a planar support surface, such as a layer of lining brick or a planar metal layer of the superstructure 12 is exposed. The planar support surface of furnace 10 provides a resting or mounting surface for support block 60. In this respect, planar bottom surface 62 of support block 60 is adapted to rest upon the planar support surface defined by the opening. The opening in the furnace wall is preferably only slightly larger than necessary to accommodate (i. e., receive) assembly 30.

In accordance with one aspect of the present invention, assembly 30 is fabricated based upon the known relationship between the desired location of the taphole relative to the planar support surface in the furnace wall. In other words, assembly 30 is formed to rest upon the planar support surface of the furnace wall with tubular member 40 being positioned at a desired level so as to define an opening communicating melting zone 16 with slagger box 22. Assembly 30 is moved from its location of fabrication to the furnace wall using handling fixture 80. In this respect, chains or straps may be attached to pipe extensions 92,94 for movement of assembly 30 by overhead cranes or fork trucks. For installation of assembly 30 into the opening of the furnace wall, a conventional fork truck may be used. One fork of the fork truck (or a special pin mounted to a fork truck) is inserted into the opening in pipe 82 of handling fixture 80. Assembly 30 may then be lifted by the fork truck and driven and positioned into the opening in the furnace wall. The pin or fork of the fork truck is then lowered until planar bottom surface 62 of support block 60 comes to rest upon a planar support surface 102 (best seen in FIG. 2) of the refractory wall. The pin or fork of the fork truck is lowered further until the weight of assembly 30 is removed therefrom. The pin or fork is then backed out of pipe 82, leaving assembly 30 in position in the furnace wall, as illustrated in FIG. 4. As illustrated in FIG. 4, second end 44 of tubular member 40 is positioned facing melting zone 16, wherein flared portion 52 of bore 50 is disposed within the furnace in communication with melting zone 16.

During transport and handling of assembly 30, metal straps 72 insure that tubular member 40 and block 60 remain as an integral unit. Further, pipe 82 of handling fixture 80 prevents the fork or pin used to position assembly 30 from scratching, chipping or scouring inner surface 48 of tubular member 40.

With assembly 30 set in place in the opening of the furnace wall, a gap will still exist between the existing furnace wall and the outer surfaces of tubular member 40 and block 60. This gap is filled with conventionally known plastic refractory material 104 (best seen in FIG. 2) that is rammed into the gap in a conventionally known manner until the gap is completely filled to recreate the furnace wall around assembly 30.

The present invention thus provides an assembly and method for quickly forming or repairing a taphole in a molten metal furnace. By pre-forming the tubular

member 40 and block 60 for a particular furnace, the tear-out of the old refractory material defining a taphole and the recreation of a new taphole can be performed quickly, thereby avoiding the costly and time-consuming processes known heretofore.

It will be appreciated that the taphole defined by tubular member 40 is denser than could be obtained by the aforementioned conventional methods of forming the taphole, i. e., ramming or casting. The isostatic tubular member 40 defining the taphole is resistant to breakdown and wear for molten iron and slag flowing therethrough. (As will be appreciated, during the initial start-up or restart of the furnace operation, the molten iron in the furnace will melt away metal pipe 82 and end plate 84 leaving only the smooth inner surface 48 and flared opening 52 that defines bore 50). On information and belief, contoured end 52 of bore 50 facilitates uniform and laminar flow of molten metal through the taphole thereby reducing erosion and <BR> <BR> <BR> <BR> deterioration of inner surface 48 of bore 50. The dense refractory material forming bore 50 together with the contoured funnel-shape thereof extends the useful life of tubular member 40. By extending the life of tubular member 40, fewer replacements of the taphole are required, thus reducing downtime of the furnace as well as the cost of repairs.

Assembly 30, as heretofore described, contemplates the use of a support block 60 to position tubular member 40 within the wall of the furnace. In accordance with another aspect of the present invention, it is envisioned that an isopressed tubular member 40 may be positioned within an opening in the refractory of a furnace wall and that conventional plastic material may be packed completely around the isopressed tubular member 40. On information and belief, the positioning and packing of the refractory material completely around isostatically pressed tubular member 40 would be more time-consuming because of the fixtures necessary to locate position of tubular member 40. It is believed, however, that in its broadest concept, a tubular member 40 together with a handling fixture 80 may be used to position and locate tubular member 40 within an opening of a furnace wall and that the opening surrounding tubular member 40 may be completely filled in with conventionally known plastic refractory material by a conventionally known ramming procedures.

Handling fixture 80 would protect inner surface 48 that defines bore 50 during the handling and installation process, and would insure a smooth, dense refractory surface to define the taphole during operation.

The invention has been described with reference to preferred embodiments.

Modifications and alterations will occur to others upon reading and understanding of the specification. For example, FIG. 6 shows an alternate embodiment of assembly 30, wherein tubular member 40 is formed from three segments designated 40a, 40b and 40c. Segments 40a, 40b and 40c are formed to define the same inner bore 50, and to have the same outer profile as the single piece tubular member 40. Segments 40a, 40b and 40c are initially held together by handling fixture 80. Block 60, when caste around segments 40a, 40b and 40c, and metal straps 72, also helps hold the segments in position. Once in position with a wall of a furnace, the packing refractory surrounding segments 40a, 40b and 40c further maintains them in position. It is intended that all such modifications and alterations be included insofar as to come within the scope of the invention as claimed or the equivalents thereof.