US3343827A - Taphole for a metallurgical vessel - Google Patents

Description

Sept. 6, 1967 K. w. HANSEN 3,343,827

TAPHOLE FOR A METALLURGICAL VESSEL Filed April 29, 1965 Fig.2

//VV/V70A. KENNETH w. HANSEN United States Patent 3,343,827 TAPHOLE FOR A METALLURGICAL VESSEL Kenneth W. Hansen, Bethe] Park, Pa., assignor to Harbison-Walker Refractories Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 29, 1965, Ser. No. 451,803 6 Claims. (Cl. 266-33) ABSTRACT OF THE DISCLOSURE Taphole for a metallurgical vessel of ceramically bonded inverted U-shaped conduit segments in interlocking relationship nested in a surrounding layer of monolithic refractory material.

In the processing of molten steel, in furnaces such as the basic open hearth and the basic oxygen furnaces, refractories having a high degree of erosion resistance must be employed in the metal contact area. One such area of these vessels, which is vulnerable to erosion is the taphole of the vessel. The taphole of a metallurgical furnace may be disposed in various locations depending on furnace type. For example, in the basic open hearth, the taphole is located below the molten metal bath, while in the basic oxygen furnace, it is located above the metal bath and the furnace is tilted to allow gravity flow of the molten metal through the taphole.

In the formation of basic open hearth tapholes, by prior practice, a steel pipe, generally ranging from 2 to 6 in length was placed in the taphole area and an unconsolidated refractory mix was rammed or cast around the pipe to hold it in place. After the first tapping of a furnace heat, the steel pipe would melt out and a completely refractory taphole would result. However, these tapholes are physically unsatisfactory for various reasons. The ramming and casting mixes had to be, of course, placed in the furnace in an unburned state and thus could not attain the maximum density and strength necessary to develop suflicient erosion resistance necessary to satisfactorily survive a furnace heat. Further, the density and strength of the tapholes were nonuniform from end to end.

It has been suggested to prefabricate a combination of castable and metal pipe. There has also been some sug-' gestion to employ prefabricated refractory sleeves to form the tapholes. However, physically satisfactory refractory sleeves have not been fabricated economically with known forming apparatus, particularly long ones ranging up to 6 in length.

Another problem confronting prior workers, particularly in basic open hearth furnace operation, is the dissipation of molten metal and slag which has accumulated on the furnace bottom below the taphole in refractory areas that have eroded or worn away. Before the recharging of the furnace for another heat, the molten metal and slag must be removed, preferably through the taphole, so that the furnace bottom can be patched, where necessary, or relined. The general practice for removing the molten metal is to burn a passage with an oxygen lance along the lower perimeter of the taphole between the taphole opening and the furnace hearth to the depth of the accumulated molten metal so that the metal will flow through the taphole. The formation of a suitable passage was not too difiicult with completely rammed or cast tapholes because of their susceptibility to erosion. However, tapholes containing preformed, burned refractory sleeves presented a dilemma. The sleeves were designed to withstand erosion and thus were very difiicult to provide with a passage. Therefore, it was desirable to fabricate a taphole having the superior refractory properties of preformed, burned refractory sleeves, yet being amenable to enlargement in depth at the lower perimeter thereof to facilitate removal of accumulated molten metal below the taphole in the hearth.

Accordingly, it is an object of the present invention to provide a taphole for a metallurgical vessel composed of a preformed, prefired refractory sleeve and one that is readily amenable to enlargement at the lower perimeter thereof to facilitate removal of accumulations of molten metal below the taphole opening.

Another object of the present invention, is to provide a means for fabricating a taphole for a metallurgical vessel consisting of preformed, prefired refractory shapes.

Still another object of the invention is to provide tapholes for basic steelmaking furnaces that may be readily replaced between furnace heats.

Other objects of the invention, will in part, appear hereinafter.

In order to more fully understand the nature and scope of the invention, reference should be had to the following description and drawings in which:

FIG. 1 is a perspective view of a taphole conduit segment employed in fabricating a taphole according to the present invention; and

FIG. 2 is an elevation view, partly in cross section, illustrating the taphole area of a basic open hearth furnace.

Briefly, in accordance with one embodiment of the present invention, there is provided a metallurgical vessel having a molten metal containing chamber and a taphole. The taphole is lined with a composite, longitudinally joined refractory conduit nested in a surrounding layer of monolithic refractory material. The conduit is composed of a plurality of prefabricated, ceramically bonded, inverted U-shaped cylindrical conduit segments. Each segment includes a passage for molten metal between the end surfaces thereof. Further, the end surfaces of each segment are provided with complementary interlocking means, such as, tongues and grooves, for mating with an adjacent segment. The conduit segments are arranged in series and are complementarily mated to provide an integral taphole conduit having a continuous molten metal passage.

The taphole conduit segments may be fabricated by methods well known in the refractories art. One method includes forming a stiff mud-like mixture of selected refractory material, vibration casting and then burning at a suitable temperature to impart maximum strength. However, the most economical and preferred method of fabrication is by mixing the selected refractory material with a tempering agent and ramming the mixture in a mold conforming to the contours of the conduit segments to obtain good densities in subsequent burning. In either method, the burning and ceramic bonding may be carried out after the segments are assembled into an integral unit, if the burning kiln can accommodate the complete unit. An advantage of firing the segments before assembly is that the segments may be shipped to the job site where they are assembled without great risk of damage.

The conduit segments may be composed of any basic refractory materials characterized by relatively good erosion resistance in contact with molten steels produced in the basic open hearth and basic oxygen furnaces. The preferred refractory materials for use in the furnaces mentioned are dead burned magnesite and dolomite and mixtures thereof. Other basic refractory materials hav- Patented Sept. 26, 1967 ing relatively good erosion resistance would also be satisfactory. These refractories may be tar bonded or tar impregnated and contain various other refractory ingredients known in the art to impart superior physical properties. A particularly useful refractory sleeve is composed of an extremely refractory dead burned magnesi-te material of high purity periclase having a magnesia content of at least about 90% by weight.

Referring to the drawings, in FIGURE 1, there is shown a taphole conduit segment 20 having a U-shaped cross section. The conduit segment contains a molten metal passage 22. At one end of the segment is located an inner peripheral projection or tongue 24 and at the other end is located an inner peripheral depression or groove 26.

Referring to FIGURE 2, there is shown a typical taphole area of a basic open hearth furnace 39. The furnace contains an outer metal shell 32 and a refractory lining therein. In the taphole area, the lining consists of a supporting layer or lining of burned basic brick 34 with a sufficient area left open for the taphole. An inverted U- shaped taphole conduit composed of prefabricated and fired conduit segments 40 is then inserted in the taphole area and is held in place with a ramming or casting mix 42. The conduit is formed by mating together the complementary tongues and grooves of a series of segments and securing them into a unit.

Generally, a refractory cement is not necessary at the tongue and groove joints, since at the operating temperatures of the vessel the conduit segments will expand slightly to provide a sufficient seal. However, refractory cement may be employed, if desired, as an added safety factor or to facilitate installation.

After the monolithic lining is built up in the taphole area to a sufficient height, the inverted U-shaped conduit is disposed on the lining immediately, before drying, so that the leading edges of the inverted U-shaped conduit will impale the monolith to provide a relatively tight molten metal seal therewith.

The monolithic refractory material is then rammed or cast around the conduit, filling all the voids between the conduit and brickwork. It is preferred that a suflicient volume of the monolithic refractory 42 be employed around the taphole conduit, so that when the conduit must be replaced, it can be readily scraped or burned out or the like and a new conduit inserted and secured in place in a similar manner. A taphole spout 44 may then be secured to the outer shell 32.

With the taphole construction of the invention, only the lower perimeter of the taphole, between the leading edges of the inverted U-shaped conduit will be subject to appreciable erosion. However, the eroded areas may be readily patched between furnace heats. This tendency to erode is exceeded in importance by the facility of providing a passage therein to allow the accumulated molten metal below the taphole to flow from the furnace.

The length and radius of the taphole conduits will vary according to the size of the furnace and the thickness of the supporting and working linings maintained therein. However, generally, for a basic open hearth furnace they are about in length and have an inner radius of about 3". Each of the prefabricated segments would measure about 12" to 14" in length.

As was pointed out previously, the completely rammed or cast tapholes had relatively nonuniform density and strength. Contrariwise, the prefabricated, ceramically bonded conduit of the present invention is characterized by substantially uniform and relatively high density and strength at substantially all points of contact with the molten metal and have proved to be satisfactory in service.

In addition to the other advantages discussed above for the present invention, it should be noted that our use of many separate burned units to form the taphole discharge advantageously serves to lessen the effects of thermal shock which might be expected if a single unit had been used. The many joints between the composite units serve to break the continuity of heat travel from one end of the tube to the other, thereby preventing disastrously steep thermal gradients from occurring. Yet further, should the thermal gradient in any given section be such as to cause cracking, stresses would-in some parttend to concentrate in the joints between sequential units. Cracking in this area would not allow escape of molten metal for two reasons. First, the tortuous flow path, because of the nesting cooperation between adjacent tubes, together with the inherent relatively high viscosity and surface tension of the molten metal, will tend to depress any runout of metal.

In has been noted elsewhere that castable tends to shrink in service, and fire shaped of the type herein discussed tend to expand. True, the degree of expansion and shrinkage is quite minor. However, if too rigid a composite structure exists, cracking, spalling, or like destructive phenomena could occur. In the present construction, the shrinkage of the castable and expansion of the preformed, burned, conduit sections together cooperate to dampen or at least compensate to some extent their respective shrinkage and expansion.

It is intended that the foregoing description and drawings be construed as illustrative and not limiting.

Having thus described the invention in detail and with suflicient particularity as to enable those skilled in the art to practice it, what is desired to have rotected by Letters Patent is set forth in the following claims.

I claim:

1. The combination with a metallurgical vessel having a molten metal containing chamber and a taphole, said taphole being lined with a composite, longitudinally joined refractory conduit nested in a surrounding layer of monolithic refractory material, composed of a plurality of prefabricated, ceramically bonded, inverted U-shaped couduit segments having opposite ends provided with interlocking means for mating with an adjacent segment in molten metal sealed relation, said conduit segments being complementarily mated to provide a continuous molten metal passage.

2. The vessel of claim 1, in which the conduit segments are composed of at least one material selected from the group consisting of dead burned magnesite and dead burned dolomite.

3. The vessel of claim 1, in which the conduit segments are composed of an extremely refractory dead burned magnesite material of high purity periclase having a magnesia content of at least by Weight.

4. The vessel of claim 1, in which the complementary interlocking means of the conduit segments consist of tongues and grooves.

5. The combination with a basic open hearth furnace having a molten metal containing chamber and a taphole, said taphole being lined with a composite, longitudinally joined refractory conduit nested in a surrounding layer of monolithic refractory, said monolithic refractory forming a portion of the taphole lining in a longitudinal direction at the lower perimeter thereof, said conduit being composed of a plurality of prefabricated, ceramically bonded, conduit segments, each segment including a passage for molten metal between end surfaces thereof, the end surfaces of each segment being provided with interlocking means for mating with an adjacent segment in molten metal sealed relation, said conduit segments being complementarily mated to provide a continuous molten metal passage.

6. The combination with a basic open hearth furnace having a molten metal containing chamber and a taphole, said taphole being lined with a composite, longitudinally joined refractory conduit nested in a surrounding layer of monolithic refractory, said conduit being composed of a plurality of prefabricated, ceramically bonded, conduit segments, each segment including a passage for molten metal between end surfaces thereof, the end surfaces of each segment being provided with interlocking means for mating with an adjacent segment in molten metal sealed relation, said conduit segments being complementarily mated to provide a continuous molten metal passage, said taphole being amenable to enlargement in the longitudinal direction only at the lower perimeter thereof, without deleteriously affecting said taphole conduit, so as to provide a means of egress References Cited UNITED STATES PATENTS 1,184,634 5/1916 Duerrwachter 26346 X 1,565,084 12/1925 Frerichs 266-42 2,839,825 6/1958 Edwards et a1 264-30 X 2,845,261 7/1958 Furczyk 266-33 J. SPENCER OVERHOLSER, Primary Examiner.

for molten metal present in the furnace below the taphole. 10 E. MAR, Assistant Examiner.

Claims (1)

1. THE COMBINATION WITH A METALLURGICAL VESSEL HAVING A MOLTEN METAL CONTAINING CHAMBER AND A TAPHOLE, SAID TAPHOLE BEING LINED WITH A COMPOSITE, LONGITUDINALLY JOINED REFRACTORY CONDUIT NESTED IN A SURROUNDING LAYER OF MONOLITHIC REFRACTORY MATERIAL, COMPOSED OF A PLURALITY OF PREFABRICATED, CERAMICALLY BONDED, INVERTED U-SHAPED CONDUIT SEGMENTS HAVING OPPOSITE ENDS PROVIDED WITH INTERLOCKING MEANS FOR MATING WITH AN ADJACENT SEGMENT IN MOLTEN METAL SEALED RELATION, SAID CONDUIT SEGMENTS BEING COMPLEMENTARILY MATED TO PROVIDE A CONTINUOUS MOLTEN METAL PASSAGE.

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