US3396961A - Precast taphole assembly - Google Patents

Description

3, 1968 G. M. FARRINGTON 3,396,961

PRECAST TAPHOLE ASSEMBLY Filed Aug. 9, 1965 mvsn'roaz GRANT M. F ARRINGTON ATTYS.

United States Patent 3,396,961 PRECAST TAPHOLE ASSEMBLY Grant M. Farrington, Marlton, N.J., assignor to General Refractories Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Aug. 9, 1965, Ser. No. 478,047 2 Claims. (Cl. 266-42) ABSTRACT OF THE DISCLOSURE A precast taphole assembly for a vessel adapted for the containment and discharge of molten metal and having a metal shell, a refractory lining within the shell, and a taphole opening in the shell and lining. The invention comprises a replaceable taphole assembly for mounting in the vessel taphole opening and includes a precast refractory section adapted for mounting in closely fitting relation against the vessel metal shell, and a pipe extending through and projecting inwardly from the precast section. The pipe being adapted to extend interiorly through and in spaced relation to the refractory lining to permit the placement of refractory material between the pipe, precast section and the vessel lining.

The present invention relates generally to taphole arrangements for carrying a flow of molten metal through the wall of a refractory-lined vessel and relates more particularly to a precast replaceable taphole assembly which is especially adapted for use in a basic oxygen furnace.

The problem of wear and enlargement of the taphole through which molten metal is discharged from a vessel has long been a source of difliculty. Not only may enlargement of the taphole cause the flow of molten metal to become uncontrollable, but in addition may cause too rapid a flow which in many instances must be controlled for metallurgical reasons.

The present invention is directed particularly to tapholes in steel-shelled refractory-lined vessels which are tilted to tap the contained molten metal. In a basic oxygen furnace, for example, the original taphole is generally formed using one of three methods; forming the hole from arch or circle brick, using a precast block having a hole of the correct diameter, or ramming or vibrating a refractory mix around a thin-walled steel pipe. When the original taphole is no long-er serviceable due to erosion caused by outfiowing molten metal, only one method has proven satisfactory for renewing the taphole. This method, appropriately known as repiping consists of the insertion of a steel pipe into the eroded taphole from outside the vessel, the ramming or gunning of an air setting refractory material around the pipe at the outside and to position the pipe, the tilting of the vessel until the pipe is vertical, and the gunning of a refractory material around the pipe on the inside of the vessel. The gunned material is dried by the heat remaining in the vessel and sets to a hard mass to form the new taphole. The steel pipe melts out during tapping of the first heat.

Although this hot repiping method may be carried out quickly and provides a smooth walled and accurately dimensioned hole, the life of holes repiped in this manner is relatively short, and is only about one half the life of the original taphole. Frequent replacement of the taphole is thus required, resulting in additional downtime of the facilities plus added labor costs. In view of the fact that the refractory material used in the repiped taphole is the same as that of the original taphole, the difference in service life can be attributed to the difference in density of the two constructions, the brick, precast block, or rammed refractory having a substantially greater density and hence a longer life.

3,396,961 Patented Aug. 13, 1968 Until the present invention, it has not appeared feasible to employ a replacement taphole having the desirable greater density since the repiping must be accomplished While the furnace is hot, and ramming or vibrating of the refractory is not feasible under such conditions. Nor would it be feasible to attempt to insert a precast sleeve into the worn taphole since the shape and diameter of the worn holes are irregular and vary widely in diameter. This is particularly true when tunnelling occurs due to the forming of obstructions on the walls of the taphole or furnace lining causing an uncontrollable metal stream. In such circumstances, the hole must be repiped before the diameter has been enlarged appreciably, and the insertion of a sleeve would obviously not be possible.

In the present invention, the above difficulties have been surmounted by the use both in the original taphole installation and in subsequent replacements of a precast taphole section of high density which is preferably cylindrical in shape and adapted for mounting within the cylindrical neck protruding from the vessel shell. A concentric steel pipe extends through and inwardly of the precast section, and refractory material is gunned around the inwardly extending pipe to complete the assembly.

When replacement is necessary, the vessel is inverted and the worn precast section dropped out, removal being aided by the use of a parting material which is not affected by high temperatures. A precast replacement may then be installed in the same manner as the original taphole except that refractory material is gunned rather than rammed or vibrated around the inwardly extending portion of the pipe. The high density precast portion prevents the funneling out of the outer end of the taphole and thus results in an appreciably longer taphole life.

In view of the above, it is an object of the present invention to provide a novel precast taphole for a vessel such as a basic oxygen furnace which may be quickly and easily replaced while the vessel is hot regardless of the condition of the previous taphole.

A further object of the invention is to provide a novel precast taphole as described which, due to the high density of the precast refractory material, results in a taphole life comparable to that of the original taphole, thus decreasing the high downtime and labor casts normally required for frequent repiping.

An additional object of the invention is to provide a novel precast taphole as described which is adapted for manufacture in quantity in standard diameters and lengths and which may be made from a variety of refractory mater-ials.

Additional objects and advantages of the invention will be more readily apparent from the following detailed description of an embodiment thereof when taken together with the accompanying darwings in which:

FIG. 1 is a side elevational View looking into the taphole of a basic oxygen furnace which is equipped with a novel precast taphole assembly in accordance with the present invention;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1 showing the construction details of the precast taphole assembly;

FIG. 3 is a sectional view of a taphole employing the present invention as it appears in the eroded state ready for replacement;

FIG. 4 is a view similar to FIG. 3 showing the eroded precast section removed and a new precast section in position for insertion;

FIG. 5 is a view similar to FIG. 4 showing the precast section secured in position; and

FIG. 6 is a view similar to FIG. 5 showing the gunned refractory material in place.

Referring to the drawings, FIGS. 1 and 2 show a portion of a basic oxygen furnace 16 having a steel shell 12, a refractory backup lining 14, and a refractory working lining 16. Since the inner face 18 of the lining 16 comes into direct contact with molten metal, a substantial amount of wear of the working lining occurs, and replacement of this lining is periodically necessary.

Extending outwardly from the vessel shell 12 is the usual cylindrical flanged steel neck 20 which forms an opening in the shell for the taphole. The cylindrical inner surface 22 of the steel neck 20 is inwardly continued following a relining of the vessel by the concentric cylindrical surfaces 24 and 26 respectively of the linings 14 and 16 to form a cylindrical chamber opening into the interior of the vessel.

A cylindrical precast refractory section 28 of a slightly smaller diameter than the surface 22 of the neck 20 is inserted into the outer end of this chamber and extends inwardly as far as the inner lining 16. The inner surface 30 and cylindrical surface 32 of the precast section 28 are coated with a refractory parting material 34 which is not affected by high temperatures. The precast section includes a circumferential groove 36 into which the bolts 38 threadedly engaged in the neck 20 are seated to prevent axial movement of the precast section.

Cast into the precast section and extending inwardly thereof slightly beyond the inner face 18 of the inner lining is a concentric steel pipe 40. An air setting refractory material 42 is rammed or vibrated in place around the pipe 40 to completely fill the space between the pipe and the cylindrical surface 26 of the lining 16. The pipe 40 should extend inwardly slightly beyond the material 42 to permit the placement of the material without danger of blocking the pipe passage. The material 42 is most readily placed in position when the vessel is tilted to the pouring position, at which time the pipe 40 is vertically disposed.

After repeated usage, the taphole shown in FIG. 2 becomes eroded by the flow of molten metal to such a degree that replacement is necessary. As shown in FIG. 3, this erosion causes a pronounced funnelling of the inner lining 16 as shown at 46, the pipe 40 and most of the rammed or vibrated refractory material 42 having been carried away. In addition, the precast section 28 is worn down to the irregular surface 48.

For replacement, the first step is the withdrawing of the bolts 38 to the position shown in FIG. 3 after which upon inversion of the furnace the remainder of the precast section may be knocked out. The parting material 34 allows a clean release of this section from both the neck 20 and the remainder of the refractory material 42 as may be seen in FIG. 4.

With the old precast section removed, a new precast section 28' with pipe 40 and covered with parting material 34 is inserted as shown in FIGS. 4 and and the bolts 38 are tightened to secure the unit in place. With the vessel inverted, refractory material 50 is gunned around the pipe 40' as shown in FIG. 6 and the heat remaining in the vessel rapidly hardens the material. Although the original refractory material 42 was rammed or vibrated about the original pipe 40, this technique can not be employed with the hot vessel and the gunning method must be employed although the gunned refractory is less dense than the rammed or vibrated material. However, this fact does not affect the life of the replaced taphole, since the precast section controls the rate of erosion of the outer portion of the taphole and prevents an undue funnelling of the gunned material 50. Since the precast section replaces the entire outer portion of the taphole, the size of the eroded taphole is of no consequence and the replacement may be simply and efiiciently carried out regardless of the amount of taphole wear.

Subsequent hot replacements of the taphole may be 4 made in the manner described and it can thus be under stood that cooling of the vessel is not necessary until replacement of the working lining is required.

The precast refractory section should, as illustrated, extend up to the working lining to prevent the funnelling of the backup lining. However, the precast section could be somewhat shorter or longer than that illustrated and still provide an effective taphole.

Different arrangements can, of course, be employed to secure the precast section in place other than the bolt and groove arrangement illustrated. For example, a ring shaped plate could be bolted to the outer face of the neck flange, engaging a portion of the outer face of the precast section and preventing outward movement thereof.

The inner face 30 of the precast section may be grooved or recessed in a well known manner to prevent metal penetration along this joint.

Similar changes in' details of construction can be effected by those skilled in the art without departing from the spirit and the scope of the invention as defined in and limited solely by the appended claims.

I claim:

1. In a vessel adapted for the containment and discharge of molten metal and having a metal shell, a

refractory lining within said shell, and a taphole opening in said shell and lining, the improvement comprising a replaceable taphole assembly for mounting in said taphole opening comprising a precast refractory section adapted for mounting in closely fitting relation adjacent said metal shell, a refractory parting material on the surfaces of said refractory section, and a pipe extending through and projecting inwardly from said precast section, said pipe adapted to extend interiorly through and in spaced relation to the refractory lining, said assembly being adapted for the placement of refractory material between said pipe, precast section and the vessel lining whereby said pipe forms an accurately sized taphole within said taphole opening.

2. In a basic oxygen furnace comprising a metal shell, a refractory lining within said shell, a taphole opening in a wall of the furnace including a cylindrical neck extending outwardly from said shell and a cylindrical chamber extending through said lining aligned with and having the same diameter as said neck, the improvement comprising a replaceable taphole assembly for mounting in said taphole opening comprising a cylindrical precast refractory section adapted to fit within said cylindrical neck and extend partially into the chamber in said lining, a pipe extending concentrically through said precast section and projecting inwardly thereof through the lining chamber, means on said neck for securing said precast section in place, a refractory parting material on the peripheral and inner surfaces of the precast section to facilitate the replacement thereof, said assembly being adapted for the placement of rammed, vibrated or gunned refractory material in the annular cavity of the lining chamber between the pipe, precast section and lining whereby said pipe forms an accurately sized taphole within said taphole opening.

References Cited UNITED STATES PATENTS 940,561 11/1909 Seward 26642 1,565,084 12/1925 Frerichs 26642 1,797,566 3/1931 Brown 266-42 FOREIGN PATENTS 557,354 5/1958 Canada.

I. SPENCER OVERHOLSER, Primary Examiner.

E. MAR, Assistant Examiner.

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