CA2050722A1 - Monolithic refractory lining - Google Patents

Abstract

ABSTRACT OF THE INVENTION
A method of making a high temperature monolithic conduit and the article made by the method. A mandrel or sacrificial member is used to define the interior passageway within the conduit. In one embodiment, the mandrel or sacrificial member is coated with a layer of predetermined thickness to form the conduit walls.
In another embodiment, the mandrel or sacrificial member is positioned within a larger form, and the space between the interior surface of the larger form and the mandrel or sacrificial member is packed with mix of predetermined refractory mate-rial to form the walls of the conduit. After the conduit walls are formed, they are cured. In the first embodiment, the sacrificial member is sacrificed or the mandrel is removed. In the sec-ond embodiment, the larger form and mandrel or sacrificial form are removed to expose the com-pleted conduit.

Description

2~07~

BACKGROUND OF THE INVENTION
This invention relates to monolithic refractory conduits and more particularly to such conduits beinq formed ln situ for use with molten metals such as steel for the "bottom pouring"
process of forming ingots.
Refractory shapes for containing molten metal are well known in the art and have been in use since the earliest days of molten metallurgy.
However, because of the extremely high tempera-tures of some molten metals (e.g., steel), such shapes have been liable to breakage because of severe thermal conditions imposed by such high temperatures. Moreover, the materials from which lS such shapes are made must be carefully selected in order to avoid entraining impurities and poisoning the molten metal through the formation of undesired ingredients such as slag. Also, steel breakout through the joints between these shapes is a major problem.
Clay type materials have been used extensively to provide refractory linings for high temperature molten metals. However, because of the particular characteristics of such materials, it has been conventional to form the refractories ,, ) `
2~a~ 72 --3~

in bricks, tiles or other discrete shapes and then piecing them together to form the desired refractory assembly. Thus, for example, it is cus-tomary to use refractory bric]cs for lining S furnaces and ladles, and discrete tubular shapes are pieced together in sections to form tubular conduits of the desired length.
Problems associated with the piecing together' of tubular shapes to form tubular conduits of needed length have been particul~rly acute in that branch of the steel making art that is known as "bottom pouring". As generally used in the steel making arts and as employed in this specification, the term "bottom pouring" connotes the conveying of molten steel into a mold from or through its bottom. Typically this has been accomplished to improve surface quality of certain grades of steel, although bottom pouring is also practiced in steel making facilities for which continuous casters are not economical. It is also attractive for use,in the maXing of special grades of steel.
In such instal~ces, the refractory shapes required for conductinq molten metal from its source to the bottom of the mold must be joined tightly to pre-vent leakage while the liquid steel is being con-ducted-from the conduit through holes in the ) 2~72~

! '. ....
bottom of the mold. Such conduits have heretofore been fabricated with individual shapes which are then joined together to create the completed structure. However, it has been found that despite care in fabrication and care in surround-ing the conduit with appropriate void-filling particulate materials, such conduits are normally vulnerable to fracture or joint leakage with the attendant loss of molten steel and/or other undesired consequences. Moreover, since it is not practicable to flush molten steel from the conduit and to recover it while it is in its molten state at the end of the pour, the steel still remaining in the conduit solidifies and the conduit must be removed for extraction of the steel, thereby requiring the reconstruction of the conduit each time a pour is made.

BRIEF_ SUMMARY OF T13E. INVENTION
In accordance with the instant invention, the disadvantages of the prior art are substantially overcome in that the aforementioned conduit is constructed in one monolithic piece which is substantially less expensive both to produce and install. According to the invention a discardable shape is employed as an internal form about which a monolithic refractory lining is produced by 203~72~

spraying/grouting of a monolithic refractory mate-rial preferably comprised of fire clay, magnesia, and/or high-alumina material. Steel tubing, hard cardboard tubing, or the like may be employed as the form about which the refractory material is applied Such a form is sacrificed and is liquified, vaporized or burned up during dry out or when molten steel is introduced to the interior of the refractory conduit. Moreover, sinCe the monolithic refractory material is applied in a viscous or slurry condition, a variety of shapes to fit required circumstances can readily be prepared, thus simplifying manufacture and reduc-ing time and expense.
OBJECTS AND FEATURES OF THE INVENTION
It is one general object of this invention to improve the fabrication of molten`metal conducting conduits.
I~ is another object of this invention to reduce costs and simplify construction or fabrication of such conduits. ~ -It is still another object of the invention to facilitate the on-site preparation of odd shaped refractory conduits.
It is yet one other object of the invention to reduce problems associated with the joining of refractory segments in refractory conduits.

`~
2~072 . Accordingly, in accordance with one feature of the invention, a sacrificial form is employed to define the desired internal shape of the conduit and a monolithic refractory material slurry or similar viscous mixture is applied to the exterior of the form, thereby facilitating the production of monolithic metal conducting conduits of substantial length.
In accordance with another feature of the invention, particular compositions of fireclay, magnesia, and/or high-alumina refractory materials are advantageously employed in slurry form, thereby imparting qualities of.dependability to the finished product.
These and other objects and features of the invention will be apparent from.the following detailed description of preferred embodiment of the invention, with reference to the drawings.
BRIEF SUMMARY OF THE DRAWINGS
Figure 1 illustrates a typical configuration which hçretofore been employed in the bottom casting of steel;
Figure 2 illustrates a typical installation of refractory conduit by which the molten steel is conducted from its source into the bottom interior of the ingot molds;

2 ~ 7 2 ~

Figure 3 is a partial plan and partial sectional view of a typical "spider" shape and conduit configuration of the prior art;
Figure 4 is a cross-section taken through a port of Fiyure 3; and Figure 5 is a view depicting the principal components of the equipment employed to practice the principles of the instant invention.

DETAILED DESCRIPTION
Now turning to the drawing, and more particularly to Figure 1 thereof it will be observed that it discloses a partially sectioned elevation view of conventional apparatus of the prior art employed to perform the bottom pouring of steel. Typically, such apparatus comprises a foundation for the e~uipment which is known in the art as a bottom plate. Such bottom plate is iden-tified with the designating symbol 10.
Within bottom plate 10, there is provided a recessed area 11, which may be partially filled with any suitable substance such as sand 12. This material forms a convenient leveling bed for the refractory shapes and in addition to providing some general thermal insulation qualities, more -importantly provides intimate contact with the , .

) 2~72~

"molten metal conducting conduit" and its associ-ated parts to ensure the shapes are held firmly in place and in compression during the pouring of molten steel.
The ingot mold 13 is seen to include side walls 14, and the entire ingot mold is typically fabricated of cast iron by known techniques.
Mold 13 is typically anchored on the bottom plate 10 by methods well known in the art for such purpose. In addition, mold 13 is seen to include a conventional hot top 16 which is positioned at the upper portion of the mold and is included so as to provide a suitable transition from the extreme heat of the mold interior to the outer ambient. Such hot top may also provide a con-trolled rate of cooling so as to prevent excessive heat loss from the upper surface of the molten metal prematurely and prevent undesired characteristics that may result from premature solidification. As will be observed from Figure 1, such hot top may be made of any suitable refractory material well known in the art and may be positioned atop the mold side walls 14, by any suitable means such as wood blocks 17.
At the right side of Figure 1 there ls dis-closed a conventional vertical member generally .

) known in the industry as a "down-fountain" or "center runner" 18. Such down-fountain provides for the introduction of moltenl steel from any suitable means such as a ladle into refractory funnel 19 and thence downwardly through vertical interior conduit 20 formed by re~ractory shapes 21. The supporting structure 2a for these refractory shapes is cast iron.
The funnel 19 and its associated vertical section is supported in known fashion by anchoring flange 23 to the bottom plate 10, thus imparting structural stability.
The inte;rior of conduit 20iis connected to a horizontal mating conduit 24 which includes 15 refractory walls 25 and interior channel 26. -Thus, when molten steel is introduced to the pour-ing funnel 19 at the top thereof, it can be con-ducted vertically down channel 20 and thence horizontally through channel 26 to the bottom of mold 13.
~ -will be observed from further reference to the ~igure, horizontal unit 24 is comprised of discrete segments such as segments which are con-nected together by abutting or adjoining sections te.g., 30, 31). As mentioned above it is the segmentation of the vertical conduit 21 and the 7 2 ~

horizontal conduit 24 that is at least partially responsible for the high costs of installation and the vulnerability to conduit rupture.
Within the upper portions of the sections of conduit 24 which underlie mold 13, (e.g., sections 27, 28, and 29) are located outlets 40, 41, 42 ~nd 43. These outlets communicate from the interior opening 26 of horizontal conduit 24 to the inte-rior 44 of ~old 13. Accordingly, molten steel introduced into the pouring funnel 19 is conducted through channels 20 and 26 and thence through apertures 40 - 43 to the interior 44 of mold 13, thus providing for conventionaL bottom introduc-tion of molten steel for bottom pouring.
Now turning to Figure 2, there is therein depicted a dual mold figuration wherein molds 50 and 51 are provided with bottom entry ports 52 and 53 through which molten steel is conducted to the interior of the molds from horizontal metal-conducting conduit 54. Thus, Figure 2 illustrates a configuration for simultaneous filling of a plurality of molds, a feature which is conventional of the prior art. However, Figure 2 ;
illustrates monolithic walls 55 and 56 which are illustrative of one form of the instant invention in which the conduit walls have been 2 ~ P5 ~

advantageo~sly fabricated in accordance with the principle~ hereof. Although the .~upporting mate-rials 57 and 58 are conventional ~e.g., cast iron) and well known in the art; and although the walls 59, 60, 61 and 62 of molds 50 and 51 are also conventional (e.g, cast iron~ it will be under-stood by those skilled in the art that they may be constructed of other conventional materials.
Figure 3 illustrates another form of molten metal-conducting conduit construction known in the steel making arts as a "spider". ~ere, the molten metal is conducted downwardly within circular conduit 65 and exists at the bottom thereof through conventional ports into the interior con-ducting channel 66, 67, 68 and 69 whence it is conducted laterally to positions beneath molds (not shown) and introduced thereto through verti-cal orfiices similar to 52 and 53 of Figure 2.
Figure 3 is included to illustrate the some-what irregular shapes that moltel~ metal conducting conduits sometimes take. Thus, for examplej mem-ber 70 which includes interior conducting channel 66, includes one right angle bend 71 and an acute angle bend 72. Other irregular shapes are com-monly encountered in the art, and it will beevident to one skilled in such art that require-.

., : , . ~: .. .. ., , - . -.: . .

2~72~

ments of bottom pouring often times require diffi-cult to fabricate geometries.
Figure 4 is a section ta~;en alon~ the lines 4-4 of Figure 3 and illustrates the preferred form for the molten metal conduction through conduit formed in accordance with the principles of the invention. Vertically standing circular conduit 65 is defined by refractory walls 73 formed by any suitable refractory material well known in the :
art. Moreover, in isome instances, such refractory may be formed in accordance with the principles o the instant invention. In such case, the interior form which as described above -is made of any suit-able material such as steel or cardboard-like material, disappears when dried out or when the first flow of molten metal is introduced thereto and consequently such form is not shown in Figures 3 or 4. .
As with conventional down-fountains, the refractory support is cast iron casing 74 which is anchore~ by conventional methods to base plate 76.
It is now evident that in order to efficiently practice known methods of bottom pour-ing for high temperature molten metals, there is a need for a way to fabricate the liquid metal con-ducting conduits so as to provide such conduits . , ., . . ~ . .

that have a high degree of rellability and protec-tion against rupture while at the same time being susceptible of being readily formed in any of a variety of shapes. Accordingly, in accordance with the principles of the instant invention, such molten metal conducting conduits can readily be fabricated in a simple and cost effective way.
Figure 5 illustrates the preferred method of forming the aforementioned molten metal conducting conduits. In this Figure is shown a store of refractory ~aterial ~0, a hopper 81 for receiving such material, a vertical passageway 82 havin~ a material controlling gate 83, a metering chamber 84, a mixing chamber 85 for mixing the material with a fluid such as water, mixed material hopper 86, pump 87 and flexible hose 88 leading from pump 87 to nozzle ~9.
Also depicted in Figure 5 are controls 90 which are provided in the conventional way to con-trol the flow of materials and the output of pump87. Such controls are well known in the art and provide for remote control by an operator (not shown) positioned near nozzle 89 by which he can control the flow rate of the mixture of refractory materials (e.g., slurry) exiting from nozzle 89.

~3~7~2 Figure 5 also depicts a platform cart 91 ha~-ing conventional wheels, 92 which support cart bed 93 on which there is supported a bottom plate 94 such as that described above ~hich is in place and ready for forming the runner refractory in situ.
As mentioned above, suitable examples of preferred materials are steel tubing and cardboard. Of course, as mentioned above, other corresponding or equivalent materials may be readily employed while practicing the invention.
In practicing the principles of the invention, the aforementioned refractory mix is expelled from nozzle 89 and is shown as grout or spray pattern 95. The grouted or sprayed material 95 surrounds the exterior of form 94 and fills the space within the channel of the~bottom plate 94.
Excess material above the top of the channel is trowelled to produce a level surface even with the top of the plate. The plate i5 then heated to dry out the monolithic refractory.
It-has been found that a preferred refractory material for practicing the inventive concepts hereof is a material generally known in the steel making arts of DOSSOLITE 1400-72. As is known to 2~ those skilled in the art, the composition of DOSSOLITE 1400-72 is approximately:

2 ~ 2 ~

Silica (Si~2) 16.0%

Alumina (A123) 1.5 Iron Oxide (Fe23) Lime ~CaO) ~.0 5 Magnesia ~MgO~ 75.0 Other oxides 3.5 TOTAL10 0 %
Refractory conduits in ac~cordance with the aforementioned described procedures can be formed using such material as described in the following example. However, other types of refractories which are compatible with clean steelmaking also can be used.
The invention will be further described in connection with the following example which is set forth for purposes of illustration only.

EXAMPLE
A monolithic ref~actory lining for the down-fountain or center runner is formed separately from the horizontal runners in the bottom plate.
Down-Fountain . . .

The iron casting has a series of 1/8" diame-ter weep holes spaced evenly around its perimeter and over its entire length. These will allow steam escape during dryout. "Ceramic paper" at lJ16" thickness is placed around the inside wall of the iron casing to act as a wick to facilitate 2 ~

dryout and then removal of the refractory monolithic lining after use. Next, a light gauge steel or cardboard mandrel at 4-1/2" O.D~ is cen-tered and supported within the casting by means of end members. Vsing the equipment shown in Figure 5, DOSSOLITE 1400-72 is pumped into the cavity between the mandrel and walls of the casting until this void is filled completely with DOSSOLITE.
The entire down-fountain is then placed in an oven to thoroughly dry out the DOSSOLITE slurry. If cardboard is used for the mandrel, it must be burned out or charred during dryout to eliminate any hydrogen pickup in the liquid steel. A number of down-fountains can be prepared in this manner at one time. After use, the DOSSOLITE will shrink upon cooling for easily removal and reuse of the iron casting.
Horizontal Runners A conventional "spider" shape is first set into the appropriate cavity in the bottom plate.
A 2-15/i6" O.D. mandrel of thin gauge steel pipe or cardboard is set in each of the channels. One end of the mandrel is placed into the outlet of the "spider" shape, and the other end is centered and supported by means of a jig set into the channel. ~sing the equipment shown in Figure 5, . . .

2 ~ 7 2 2 DOSSOLITE ls sprayed or pumped into the channel starting at the end next to the "spider" shape.
After the mandrel is sufficiently anchored into place with DOSSOLITE, the jig can be removed so that the entire channel can be filled with DOSSOLITE. The DOSSO~ITE is then trowelled to even it with the top of the bottom plate. Th~
slurry is then dried out by placing a burner into the inlet of the "spider" shape so that the hot gases exhaust through the runners and out the risers. Because the cast iron bottom plate is thermally conductive, it can also be heated using gas torches to facilitate dryout. If a cardboard mandrel is used, it must be heat treated as it was for the down~fountain. After this arrangement has been used, the DOSSOLITE will shrink in the chan-nel upon cooling. The solidified steel and used refractory conduit are removed from the bottom plate in the conventional manner.
It will now be evident that there has been described herein an improved refractory conduit and the methods of fabricating the same, which product and method exhibit significant advantages over the corresponding art. Although the inventive concepts hereof have;been illustrated by way of a preferred embodiment, it will be evident , to those s~illed in the art that adaptations and modifications may be employed without departing from the spirit and scope of the invention. :
The terms and expressions used herein are employed as terms of description and not of limitation; and there is no .intent in the use thereof to exclude equivalents, but on the contrary, it is intended to include all e~uivalents, adaptations and modifications that may be employed without departing from the spirit and scope of the invention as defined in the claims.

`" : ''. : :; .. ' , : :: . .. ; , , ' ,' , ': ' ,.; " , ,' .~ . ., . : , ,

Claims (11)

1. The method of making a high temperature monolithic conduit comprising selecting a sacrificial form having a predetermined exterior surface geometry to define an interior channel for said conduit, supporting said form to expose said exterior surface, coating said exterior surface with a layer of refractory material, curing said layer of refractory material thereby to solidify said layer, and removing said sacrificial form thereby retaining only the solidified layer.

2. The method of making a high temperature monolithic conduit comprising selecting a sacrificial form having a predetermined exterior surface geometry to define an interior channel for said conduit, supporting said form to expose said exterior surface, coating said exterior surface with a monolithic layer of refractory material of predetermined thickness, said thickness being substantially the desired thickness for the walls of said monolithic conduit, curing said layer thereby to solidify said layer, and removing said sacrificial form thereby retaining only the solidified layer as a completed conduit.

3. The method of making a high temperature monolithic conduit comprising selecting a mandrel having outside dimensions defining the interior dimensions of said conduit, selecting a form hav-ing walls defining the exterior geometry of said conduit, lining the interior surface geometry of said form with an insulating wick-like material adapted to attract liquid-gaseous products that may be emitted in producing said conduit, sup-porting said mandrel within said form to define an interior passageway of said interior dimensions within said conduit, positioning said mandrel within said form to provide a predetermined space therebetween and about said mandrel to define the walls of said conduit, introducing a preselected refractory material into said predetermined space to substantially fill said space, curing said preselected refractory material to harden said material and form said conduit, and removing said form and said mandrel thereby to expose said conduit.

4. A method according to claim 1 in which the step of curing said layer further includes the step of heating said layer to a predetermined ele-vated temperature for a predetermined period of time.

5. The method according to claim 2 in which the step of curing said layer further includes the step of heating said layer to a predetermined ele-vated temperature for a predetermined period of time.

6. A method according to claim 3 in which the step of curing said layer further includes the step of heating said layer to be a predetermined elevated temperature for a predetermined period of time.

7. A method according to claim 3 in which the step of positioning said mandrel within said form includes the step of aligning the axis of said mandrel with the axis of said form thereby to position said mandrel and said form coaxially.

8. A high temperature monolithic conduit made by the process of claim 1.

9. A high temperature monolithic conduit made by the process of claim 2.

10. A high temperature monolithic conduit made by the process of claim 3.

11. A high temperature monolithic conduit made by the process of claim 7.