US2711950A - Method of closing a tap-hole for an open hearth furnace or the like - Google Patents

Description

June 28, 1955 J. s. MATASY METHOD OF CLOSING A TAP-HOLE FOR AN OPEN HEARTI-I FURNACE, OR THE LIKE Filed May 16, 1952 IOA FIG. 2

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FIG.

INVENTOR. JOSEPH s. MATASY 6% 9 (OMZM ATTORNEYS METHOD (3F CLGSING A TAP-HOLE FOR AN UPEN HEARTH FURNAfIE OR THE LIKE .ioseph S. Matasy, Youngstown, Ghio Application May 16, 1952, Serial No. 288,201

3 Claims. (Cl. 75-05) This invention relates to improved methods for closing tap-holes or the like in open hearth furnaces or other refractory structures.

The tapping of open hearth furnaces has long presented complications. Usually the furnace is provided with a tap-hole when built which slopes backwardly from the fioor of the furnace adjacent one side or back wall thereof, this tap-hole being closed with refractory material prior to and during the preparation of a heat of steel in the furnace. Once the desired composition of the steel heat has been achieved, the furnace is tapped. This has been accomplished by scraping out the refractory material from the discharge end of the tap-hole in as far as possible. Thereafter, a steel pipe through which oxygen is passed is inserted into the tap-hole after the end of the pipe has been set afire, and the intense heat generated by the burning of the metal pipe under the influence of the oxygen is used to melt through the refractory material closing the remaining portion of the tap-hole. This refractory material has generally soliditied under the heat of the molten steel in the furnace and it is difficult to burn through. Moreover, often the molten steel has soaked into and around the refractory closing the inner end of the tap-hole and has solidified as a plurality of rivulets or fingers which further complicate the final breakthrough. it is often necessary to use a considerable number of these burning pipes which is expensive and time-consuming at a time when the composition of the heat of steel may be tending to change. When the burning pipe breaks with a relatively small hole through the last portion of refractory material closi ing the tap-hole, the burning pipe is quickly withdrawn and the molten steel which comes pouring out of the tap-hole is expected to complete the opening of the taphole by the corrosive action of the flow.

If the relatively small opening made by the burning pipe in the refractory material closing the tap-hole is not enlarged by the flow of steel then it becomes necessary for the remaining portion of the refractory wall closing the tap-hole to be battered through by introducing a bar or billet from the front of the furnace which is relatively long and of steel. This bar is manipulated by an operator who attempts to punch the bar down through the molten steel bath to break through the remainder of the refractory partially closing the furnace end of the tap-hole.

The expense, dangers, physical difliculty and hardship of successfully performing the tap-hole opening operation with the oxygen-burning pipes, with or Without the necessity for further operations with the steel bar or billet, and under the temperature conditions existing closely adjacent the furnace can be imagined. Also, it will be evident that known methods are usually characterized by lack of uniformity of tapping times, rate of flow, and the like.

it has been proposed heretofore in opening a tap-hole to first scrape out all loose refractory and to then' effect the final breakthrough of the body of refractory material ice closing the tap-hole by means of a blast of powder, usually in the form of a torpedo introduced into the tap-hole up to a position adjacent the wall of refractory closing the inner end of the tap-hole, followed by detonation of the torpedo to efiect the opening of the tap-hole. The use of torpedos or blasting charges of the type described, sometimes called jet-tap, is a definite item of expense, and they obviously must be carefully handled, there being attendant dangers of backfire, premature firings, or the like. Moreover, even with this method lack of uniform opening often results due to variations in resistance to the blast.

Known methods of opening a tap-hole in an open hearth furnace or the like also bring other problems and complications well known to the open hearth furnace opeator. Sometimes the opening of the tap-hole by a bar or billet causes a gouge or pocket down in the taphole near the furnace end of the tap-hole, and such an interruption in the smooth bore of the tap-hole is accentuated by the very corrosive action of the steel flowing through the tap-hole with a consequent deterioration of the tap-hole necessitating repair or re-piping of the taphole before another heat can be melted in the furnace. Sometimes a dam is created at the inner bottom end of the tap-hole which prevents the entire heat of the furnace from being tapped with the attendant waste. Sometimes in tapping a furnace with known methods a cavity or opening is created in the furnace wall down to the taphole near the furnace end thereof so that during tapping the steel will flow through this opening as well as or in place of flowing through the inner end of the tap-hole itself. Any condition of this type results in slag mixing improperly in the flow of the steel during the tapping operation with attendant highly objectionable results.

Reference has been previously made to the fact that delay in tapping may change the composition of the steel in the furnace, and it is also well known that slow taps or improperly flowing taps of steel from an open hearth furnace are highly undesirable making the steel too cool in the ladle, resulting in skulls in the ladle, freezing around the nozzle and stopper, and sometimes requiring the scrapping of parts or even all of the heat.

It is the general object of my invention to avoid and overcome a considerable portion of the difficulties of and objections to known methods for closing and opening a tap-hole in an open hearth furnace or the like by the provision of an improved method for closing the tap-hole which will notably simplify and render uniform the tapping of the furnace.

Another object of my invention is to provide a taphole closing method which will increase the life of the tap-hole in an open hearth furnace or the like, and which will provide noticeably improved tap-hole opening techniques, and in general make for easier, more uniform and better taps and at the same time largely eliminate cold or other bad taps.

Another object of my invention is the provision of a tap-hole closing method whereby tap-hole openings of a selected and desired size can be obtained to provide a tap of the required speed.

The foregoing objects of my invention, and others which will become evident as the description proceeds, are achieved by the provision of a tap-hole closing method which includes the steps of positioning a body of relatively soft, substantially non-hardening, semi-refractory material near the furnace end of the tap-hole, covering the body and the furnace end of the hole with a layer of highly refractory material, and plugging the remainder of the major portion of the tap-hole with refractory ma terial and in a substantially air-tight manner. The body of semi-refractory material is generally at least partly gassifiable under heat to create a pressure opposing the inward seepage of molten steel into the furnace end of the tap-hole. A typical material used is raw dolomite which possesses the gassifying characteristics. Conveniently the body of material is positioned in a suitable container which is usually made flexible and fireproof. as from asbestos cloth, and which is generally cylindrical and of a length not greatly different from its diameter. The size of the container can be altered to control the size of the tap-hole and the speed of withdrawal of the heat, and the bag can be adapted to be shaped or conformed to tap-holes of diflerent cross-sectional contour. all as hereinafter explained in greater detail.

For a better understanding of my invention reference should be had to the accompanying drawings wherein Figure 1 is a fragmentary vertical cross-sectional view through the tap-hole portion of an open hearth furnace, and illustrating one manner of performing the method of my invention; and

Figures 2, 3 and 4 are views similar to Figure 1 but illustrating other embodiments of my invention.

Although the principles of my invention are broadly applicable to closing temporarily holes in refractory structures of various kinds, I am primarily concerned with and my invention is particularly beneficial in the closing of tap-holes for open hearth furnaces, and my invention has been so illustrated and will be so described. It might be noted here that the exact tap-hole size, slopes, etc. in relation to the rest of the furnace have not always been shown in exact proportion but have sometimes been exaggerated to better illustrate the invention.

In Figure l the numeral indicates generally an open hearth furnace having a bed 12 of highly refractory material, such as chrome ore or magnesite, a built up side or back Wall 14 of similar material and a covering 16 for the wall of burnt dolomite or magnesite, all in accord with substantially known and conventional practices. A tap-hole 18 extends backwardly and slightly downwardly from the bed 12 of the furnace through the wall 14, again in accord with standard practice, the taphole being closed during the heating of the bath 20 of molten steel in the furnace, but being adapted to be opened to tap or withdraw the heat of steel when the desired steel composition has been reached.

In the practice of my invention, as illustrated in Figure l, the tap-hole 18 is adapted to be closed by moving a bag or a container 22 into the tap-hole 18 from the exit end thereof and up to a position in the tap-hole near the furnace end thereof, for example, to the position shown in Figure l. The bag 26 is generally made of a flexible fireproof material, for example, asbestos fabric, wire fabric, or the like, and the bag is usually substan tially cylindrical and of a length not much different from its diameter. it is theoretically possible to make the bag 28 of perforated clay or other materials which would be pervious, although not particularly flexible, but I preferably make the bag Zll of flexible material so that it will adapt itself to the contour of the tap-hole even though this contour might be other than substantially cylindrical, for example, elliptical, it being understood that the corrosive action of the molten steel flowing through the tap-hole often wears the tap-hole to other than a truly cylindrical cross-section.

The bag 29 is filled, or substantially filled with a material or a mixture of materials which can best be described as being semi-refractory in nature, relatively soft, and substantially non-hardening. Also, the material or materials in the bag 2t preferably possess gassifying characteristics when subjected to the temperature of the furnace. One particular material which I have found to perform very satisfactorily in the ba g 20 is raw dolomite which possesses all of the characteristics described. I may also employ mixtures of burnt and raw dolomite, mixtures of crushed burnt dolomite, magnesite, chrome ore, or other refractory with coal. It will be recognized that still other materials can be selected possessing the characteristics set forth which will perform in the manner to be described.

The bag 20 with the described material therein may be moved into the tap-hole 18 to the point shown closely adjacent the end of the tap-hole by means of a curved sheet metal cradle carried upon a long bar which can be jerked out from under the bag once the bag is in proper position. As shown in Figure 1, the innermost end of the bag 20 is generally positioned some 2 to 10 inches from the boundaries of the innermost end of the tap-hole, as defined by a continuation of the inclined surface of the material 16 forming the sidewall of the furnace. Then a highly refractory material, for example burnt dolomite is shoveled in from the front of the furnace to deposit a cover or layer 24 over the innermost end of the bag 22 to effect a closing of the innermost end of the tap-hole. Also, a highly refractory material, for example burnt dolomite is shoveled and tamped into substantially the remainder of the tap-hole 18 and from the exit end of the tap-hole to substantially close the tap-hole in an air-tight manner, this material being indicated by the numeral 26. Tamping the refractory material 26 into the tap-hole and up against the bag 22 causes the bag 22 and the material therein to expand outwardly into tight contact with the tap-hole. The discharge end of the tap-hole is thereafter generally closed with a plug of clay in accordance with known practice.

The furnace 1G is now ready for a heat which is performed in the conventional manner. During the heat the burnt dolomite 24 hardens and solidifies over the innermost end of the bag 22, but heat will naturally penetrate into the material in the bag 22 which at least partially gassifies to create pressure toward the furnace end of the tap-hole which functions to prevent the molten steel from penetrating any appreciable distance down through the refractory layer 24. These fingers or rivulets of steel which normally penetrate down through the refractory adjacent a conventionally closed tap-hole cool and solidify after getting some distance from the bath of molten steel, and in the past with conventional taphole closing and opening methods the solidified fingers or rivulets of steel have greatly resisted the opening of the tap-hole. I believe that I am able to confine the inwardly flowing fingers or rivulets of steel to a relatively narrow or thin layer by the opposing gas pressure and that the opening of the tap-hole is greatly facilitated. The gas pressure generated by the material in the bag 22 cannot escape out the discharge end of the tap-hole because this is sealed against the pressure.

Now in the opening of the tap-hole illustrated in Figure 1 an operator removes the clay plug at the discharge end of the tap-hole and then scrapes all of the refractory material 26 out of the tap-hole by a rake, this being readily accomplished up until the bag 22 is reached. The reaching of the bag 22 warns the operator that he is getting near the furnace end of the tap-hole, and then the operator carefully removes the relatively soft and non-hardening material contained in the bag 22, the bag either being broken to facilitate this operation or being hooked and pulled out by a suitable rod wielded by the operator. There now remains only a relatively thin wall of highly refractable and hardened material closing the tap-hole. This can be broken through in any of the conventional manners, but with the operator knowing that only this relatively thin wall remains to be pierced. For example, an oxygen burning pipe may be utilized. Again, the jet or torpedo can be employed to break through the final wall, but because the position and extent of the final sealing wall is better known a smaller blasting charge and a more accurately directed one can be used for this operation. The result is a definite improvement in the uniformity of the tap.

If the oxygen burning pipe is employed for the final breakthrough and if this breakthrough and the resultant flow out of the tap-hole of molten steel is not satisfactory it is still possible to increase the flow by enlarging the tap-hole opening by a long bar or billet wielded from the front of the furnace, but such a bar or billet can be operated in a definitely more successful fashion than under previous practices for the reason that the position and extent of the material 24 is much more sharply defined and is notably thinner and less reinforced and compacted with frozen metals than heretofore.

In the embodiment of my invention illustrated in Figure 2, like parts of the furnace have been indicated by identical numerals, except that the suffix a has been added. In this form of my invention a flexible bag 22a is employed containing highly refractory material, such as burnt dolomite, this being positioned in the taphole 18a a somewhat greater distance from the furnace end of the tap-hole than the bag 22 of Figure 1. This leaves a space in the furnace tap-hole in front of the bag 22a, this space being filled with a semi-refractory, non-hardening material 30 similar to that used to fill the bag 22. This material 30 may be thrown in with a shovel from the front of the furnace 1011. Thereafter, a final layer of highly refractory material, such as burnt dolomite, and similar to the material 24, is positioned at 24a, this material being thrown in from the front end of the furnace ltia. The remainder of the tap-hole 18 is closed with highly refractory material 26a, and the closing of the discharge end of the tap-hole is completed in a manner identical to that heretofore described in conjunction with the form of the invention shown in Figure 1. This embodiment of my invention is definitely not as preferable as that of Figure l, but does give some of the advantages of my invention.

The opening of the tap-hole of Figure 2 is substantially the same as that described in detail in conjunction with Figure l, the material 26a being first removed up to the bag 22a which warns the operator that he is nearing the inner end of the tap-hole, the bag 22a is then removed, as is the material 30. Thereafter the tap-hole is finally opened by breaking through the material 24a in any of the several known methods. The gassifying of the material 30 during the production of the molten.

steel 29a of the heat prevents excessive penetration of the molten steel into the material 36, and the relatively soft character of the material 30 allows the tap-hole to be cleaned out nicely up to the closure provided by 1 the material 24a.

The form of my invention shown in Figure 3 illustrates several additional characteristics of the invention. In this figure of the drawing like numerals have been employed to illustrate parts identical to Figures 1 and 2,

of the tap in the manner shown in Figure 3 by employing a bag 22b of a selected diameter, namely, a relatively small diameter bag for a slow tap, a medium diameter bag for a medium speed tap, and a large diameter bag completely filling the tap-hole 18b for a fast tap. In Figure 3 I have illustrated a medium diameter bag 22b for providing a medium speed tap. The packing of the highly refractory material 24b around the outer end of the bag 22b and the end of the tap-hole creates a tap-hole opening of substantially the diameter of the bag when the tap-hole is opened, as previously described. It is most advantageous in using bags 22b of different diameter to use them in association with a tap-hole 181) which has been considerably corroded around the furnace end of the tap-hole. In fact, Figure 3 illustrates that the principle of my invention can be employed to rather effectively repair the tap-hole without necessitating repiping thereof when the tap-hole is very considerably increased in size adjacent the furnace end thereof. This feature of effecting repair, of course, can be used whether or not I employ the feature of a selected size bag 22b.

(iii

6 The balance of the tap-hole 18b is filled with refractory material 26b, and the materials used to fill the bag 22b and the materials 24b and 2612 are substantially like the materials in the bag 22 and the materials 24 and 26. The technique for opening of the tap-hole of Figure 3 is substantially the same as that previously described in conjunction with Figure 1.

In Figure 4 I have illustrated a substantially identical furnace, as heretofore illustrated, the parts being given the same numerals as before, but with the sufiix 0 being added. In this form of the invention I employ a bag 220 having an inclined inner edge substantially parallel to the surface of the sidewall 16b, the bag 22c being positioned in the tap-hole 180 near the furnace end thereof, and with the inner end of the bag being covered with highly refractory material, such as burnt dolomite, and indicated by the numeral 240, this material being shoveled into position from the front of the furnace. The remainder of the tap-hole 180 is closed with material 260. The material filling the bag 22c and comprising the materials 240 and 260 being similar to the materials contained in bag 22 and employed at 24 and 26, respectively, in Figure l. The manner of opening the tap-hole in Figure 4 is substantially the same as that described in conjunction with Figure 1.

From the foregoing it will be recognized that the various objects of my invention have been achieved by the provision of improved simplified methods for closing the tap-hole in open hearth furnaces or the like, the tap-hole closing methods facilitating the opening of the tap-hole to effect the tapping of the molten steel in the furnace. I am able with my improved methods to effect fast, medium, or slow taps, and to eliminate many of the headaches, physical hazards, and hard work associated with previous tapping methods. Also, I prolong the life of the furnace tap-hole and reduce the frequency of re-piping the hole. Other advantages are likewise achieved, as previously pointed out, and in general better taps are effected, less scrap is produced, and operating costs are lowered.

While in accord with the patent statutes I have specifically illustrated and described certain best known embodiments of my invention, it is to be particularly understood that I am not to be limited thereto or thereby, but that the scope of my invention is defined in the appended claims.

I claim:

1. That method of closing a tap-hole in an open hearth furnace or the like which includes the steps of positioning a packaged body of relatively soft, substantially nonhardening gassifiable semi-refractory material near the furnace end of the hole, covering the body and the furnace end of the hole with a relatively thin layer of highly refractory material which is hardenable under heat, and plugging the remainder of the tap hole with highly refractory material.

2. That method of closing a tap-hole in an open hearth furnace or the like which includes the steps of enclosing a body comprising essentially raw dolomite in a substantially fireproof flexible bag of a substantially c lindricai shape and having a length not much different from its diameter, positioning the bag in the tap-hole near the furnace end thereof, covering the bag and the furnace end of the tap-hole with a layer of burnt dolomite, and filling substantially the remainder of the tap-hole with burnt dolomite in substantially an air-tight manner.

3. That method of closing a tap-hole, or the like, in an open hearth or other similar structure which includes the steps of selecting a flexible substantially fireproof bag of cylindrical shape and having a diameter substantially corresponding to the size and shape of the furnace end of the tap-hole and of a length not much different from the diameter, filling the bag with a gassifiable at least partially refractory material including coal and in an amount to allow the bag to substantially fill the taphole, moving the bag into the tap-hole to a position adjacent the furnace end thereof, packing refractory material into the outlet end of the tap-hole and up against the bag to expand the bag into firm engagement with the sides of the tap-hole, sealing the outlet end of the tap-hole against loss of gas pressure, and covering the bag and the furnace end of the tap-hole with a layer of highly refractory material.

References Cited in the file of this patent Basic Open Hearth Steel Making: Physical Chemistry of Steel Making Committee; second edition, page 40.

The Making, Shaping and Treating of Steel, 6th edition (1951), pages 418, 419, 456 and 457 are considered pertinent.

Published by U. S. Steel Co., Pittsburgh, Pa,

Claims (1)

1. 3. THAT METHOD OF CLOSING A TAP-HOLE, OR THE LIKE, IN AN OPEN HEARTH OR OTHER SIMILAR STRUCTURE WHICH INCLUDES THE STEPS OF SELECTING A FLEXIBLE SUBSTANTIALLY FIREPROOF BAG OF CYLINDRICAL SHAPE AND HAVING A DIAMETER SUBSTANTIALLY CORRESPONDING TO THE SIZE AND SHAPE OF THE FURNACE END OF THE TAP-HOLE AND OF A LENGTH NOT MUCH DIFFERENT FROM THE DIAMETER, FILLING THE BAG WITH A GASSIFIABLE AT LEAST PARTIALLY REFRACTORY MATERIAL INCLUDING COAL AND IN AN AMOUNT TO ALLOW THE BAG TO SUBSTANTIALLY FILL THE TAPHOLE, MOVING THE BAG INTO THE TAP-HOLE TO A POSITION ADJACENT THE FURNACE END THEREOF, PACKING REFRACTORY MATERIAL INTO THE OUTLET END OF THE TAP-HOLE AND UP AGAINST THE BAG TO EXPAND THE BAG INTO FIRM ENGAGEMENT WITH THE SIDES OF THE TAP-HOLE, SEALING THE OUTLET END OF THE TAP-HOLE AGANIST LOSS OF GAS PRESSURE, AND COVERING THE BAG AND THE FURNACE END OF THE TAP-HOLE WITH A LAYER OF HIGHLY REFRACTORY MATERIAL.

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