POURING DEVICE OF MOLTEN-METAL-CONTAINING VESSEL

Abstract: Molten metal contained in a vessel (1) such as a Bessemer type converter is tapped or poured out or stoppered by a pouring device comprising a tubular refractory structure forming a fixed lining (2) of a hole through the bottom of the vessel and having therethrough a pouring orifice (12) having an upper opening (12a) open to the vessel interior and a lower opening (12b) openable to the outside, a cooling device (13) for cooling the upper opening (12a) and the neighboring region with a cooling medium, and a stopper mechanism (17) mounted on the outer side of the vessel (1) for opening and closing the lower opening (12b) of the pouring orifice (12) thereby to pour out molten metal and to stopper the same.

Description: BACKGROUND OF THE INVENTION This invention relates generally to vessels designed to contain molten metal at high temperatures, such as Bessemer converters, metal mixers, electric furnaces, ladles, and tundishes. More particularly, the invention relates to devices for tapping or pouring out molten metal through the bottoms of such vessels. A vessel of the above exemplified kind for containing molten metal (hereinafter referred to as vessel) is used to receive molten metal poured thereinto, to melt or smelt a metal therewithin, or to hold a molten metal therewithin for a specific time for refining or reserving and thereafter to pour out the molten metal for conveyance to a succeeding process. For this reason, a vessel of this character is required to have the functional capability, in addition to that of receiving and retaining molten metal, of appropriately pouring out the molten metal. In general, since the molten metal handled by these vessels are at high temperatures, ordinary metal valves cannot be used at the pouring out openings at the bottoms of these vessels. For this reason, one of the following principal methods has heretofore been used to tap or pour molten metal out of these vessels. (a) The method of tilting and inverting the vessel -- This method is used in the operation of a Bessemer-type converter, metal mixer, electric furnace, or the like and comprises tilting and inverting the vessel containing molten metal thereby pouring out the molten metal from the open top or through a pouring hole provided on the side of the vessel. (b) The method of mechanically opening/closing a pouring-out orifice in the vessel bottom -- This method is used in the operation of a ladle, tundish, or the like and comprises installing a mechanical stopper or valve mechanism such as a nozzle stopper or a sliding gate made of a refractory material at a pouring orifice formed through the bottom of the vessel and operating this mechanism to close the pouring orifice for receiving molten metal in the vessel and to open the pouring orifice for pouring the molten metal out of the vessel. With respect to a rotary furnace, a pouring orifice of a special form is formed in the furnace bottom and is provided with a pouring device of such a construction that, by varying the rotational angle and the inclination angle of the furnace, the molten metal within the furnace can be poured out, or its pouring out can be stopped as proposed in Japanese Laid-Open Patent Application No. 234915/1985. However, the above methods (a) and (b) have been accompanied by the following problems. In the case of tilting and inverting -- a-1. The inverting operation requires time, whereby the work time cycle becomes long. a-2. While the vessel is holding the molten metal, the upper part of the refractory material of the vessel above the molten metal and not in contact therewith is at a relatively low temperature. Then, when the molten metal is poured out, it contacts this upper part, and its temperature drops. a-3. When the vessel is tipped, the slag floating on the molten metal contacts the refractory material over a wide area thereof and erodes this material, whereby the serviceable life thereof is shortened. a-4. When the molten metal is being poured out, the slag readily becomes mixed therewith and tends to be discharged in a large quantity with the molten metal, whereby the work of slag removal in the succeeding process adds to the operational cost, and moreover the quality of the metal is apt to drop. a-5. Depending on the type and nature of the vessel, accessory equipment such as tilting devices and inverting cranes exclusively for pouring become necessary. In the case of mechanical opening/closing of the pouring orifice -- Since the nozzle plug or sliding gate directly shuts off the flow of molten metal when the pouring orifice is being closed, it is subjected to thermal and mechanical attrition and erosion due to the molten metal and becomes severely worn and damaged, whereby its serviceable life is extremely short. For this reason the frequency with which the nozzle plug or sliding gate must be replaced becomes high. Thus, time and labor for this part replacement work are required and moreover the operational cost increases. SUMMARY OF THE INVENTION In view of the difficulties encountered heretofore with respect to vessels of the above described character, it is an object of this invention to provide a pouring device of such vessels which is capable of pouring molten metal out through the bottom of the vessel, after it has held the molten metal, without the necessity of tipping the vessel and, moreover, is capable of performing this pouring function with long serviceable life of the various parts of the vessel and the pouring device and at low operational cost. An important feature of this invention, which provides, in a vessel of the instant character, a pouring device having a mechanism for opening/closing the lower end of a pouring orifice formed in the vessel bottom, is the provision of a cooling system for cooling the upper end of the pouring orifice by using a cooling medium, which cooling system can be used for introducing other fluids such as argon gas, nitrogen gas, and oxygen into the vessel for various purposes, as will be described more fully hereinafter. One important function of this cooling system is to supply the cooling medium through tuyeres into the vessel in order to cool the upper opening of the pouring hole and surrounding parts when a cycle of pouring is nearing its conclusion and the slag floating on the molten steel is approaching the pouring orifice thereby to cause the molten steel or slag to coagulate and form a sealing mass over the upper opening of the pouring orifice, thus stopping the pouring. Then, with vessel in this state the above mentioned opening/closing mechanism is operated to fully close the pouring orifice. According to this invention, briefly summarized, there is provided a pouring device of a molten-metal-containing vessel said pouring device comprising: a refractory structure of substantially tubular shape which forms a lining fixed to the wall surface of a through hole formed through the bottom of the vessel, and which forms therethrough a pouring orifice having an upper opening to the interior of the vessel and a lower opening to the outside of the vessel, characterized by a cooling device operable to blow a cooling medium to the region of the upper opening and the vicinity thereof for cooling the upper opening and the region in the vicinity thereof, and an opening/closing mechanism installed outside of the vessel for mechanically opening and closing the lower opening thereby to permit pouring out of molten metal contained in the vessel and to stop this pouring out. A cooling device according to the precharacterizing clause is disclosed in JP-A-60 - 234 915. The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawings, briefly described below. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: FIG. 1 is a simplified elevation, in vertical section, showing a Bessemer type converter, as an example of a molten-metal-containing vessel, provided with a pouring device of this invention, and showing molten metal being poured out of the converter into a ladle; FIG. 2 is a partial elevation, in vertical section, showing the essential parts of one example of a pouring device according to the invention; FIG. 3 is a view similar to FIG. 2 of the same device indicating tentative stoppering of the pouring of molten metal by a mass of metal and slag coagulated by cooling at the upper opening of a pouring orifice of the pouring device; FIG. 4 is a similar view showing a nozzle plug in fully closed state in the lower opening of the pouring orifice; FIG. 5 is a similar view showing the vessel in tilted state and indicating one mode of use of the pouring device; and FIG. 6 is a view similar to FIG. 2 showing another example of the pouring device according to the invention. DETAILED DESCRIPTION OF THE INVENTION An example of a Bessemer converter provided with an example of the pouring device according to this invention as illustrated schematically in FIG. 1 comprises essentially a converter vessel 1 for containing molten steel 3 with a layer of slag 4 covering the upper surface of the molten steel 3, an overhead oxygen lance 21 insertable from above into the vessel through the upper furnace opening 1b thereof, and the pouring device 11 provided at the bottom of the vessel 1. A ladle 22 is positioned immediately below the pouring device 11 to receive molten steel tapped or poured therefrom and to transport this molten steel to a succeeding process. The pouring operation will be described more fully hereinafter. As shown in FIG. 2, the bottom of the converter vessel 1 comprises a furnace iron cladding 1a and an inner vessel refractory lining 2 comprising permanent bricks 2b in contact with the inner surface of the iron cladding 1a and consumable bricks 2a in contact with the inner surface of the permanent bricks 2b. This bottom of the vessel 1 is provided with the pouring device 11 of the invention, which is constructed and installed in the following manner. A pouring drain orifice 12 is formed through the center of the bottom of the vessel 1 and is provided around its inner peripheral surface with a cooling device 13 comprising tuyeres 13a opening at their upper ends into the interior of the vessel 1, tuyere pipes 13b connected to the lower ends of the tuyeres 13a, and piping 13c for supplying a cooling medium 19 to the tuyere pipes 13b. The tuyeres 13a comprises, for example, a plurality of nozzles formed from a heat-resistant metal material and opening into the interior of the vessel 1 around the inner or upper opening 12a of the pouring drain orifice 12. Around the tuyere pipes 13b is provided a refractory material 14a for protecting the interior surface, and refractory materials 14b and 14c are provided to fill the spaces between the furnace refractory structure 2 and the tuyeres 13a and the tuyere pipes 13b. These refractories are supported by a metal frame 15, which in turn is fixed by way of metal gusset stays 16 to the furnace iron cladding 1a. Thus, these refractories 14a, 14b and 14c may be considered collectively as constituting a tubular refractory structure containing the cooling device 13 and forming a lining fixed to the wall surface of a through hole formed through the bottom of the vessel. The outer or lower opening 12b of the pouring drain orifice 12, and therefore the entire drain orifice 12, can be closed by a nozzle stopper 17 comprising a swingable arm 17b pivotally supported at its proximal end by way of a pivot shaft 17a on a fixed part (not shown) of the converter vessel structure, a nozzle plug 17c made of a refractory material and fixed to the distal end of the arm 17b, and a driving device 18 for driving the arm 17b in closing and opening movements to bring the plug 17c into closed state in and against the rim of the lower opening 12b and into an opened state as shown in FIG. 2. In the state of the converter 1 shown in FIG. 1, the nozzle stopper 17 is in its opened state, and the molten steel 3 of one heat is being poured through the pouring orifice 12 into the ladle 22 positioned directly below the converter vessel 1. Then, as this pouring continues, the quantity of the molten steel 3 in the vessel 1 becomes small, and the slag 4 is about to be discharged. At this point, immediately before the slag 4 is discharged, the tapping or pouring operation is stopped by the following procedural steps (1) through (4). (1) The fact that the slag 4 has descended to the vicinity of the upper opening 12a of the pouring orifice 12 is detected. For this purpose, the molten steel 3 and the slag 4 may be distinguished by visual observation, but automatic detection can be carried out by any of various known sensors. (2) The aforementioned cooling medium 19 is thereupon supplied through the piping 13c and the tuyere pipes 13b and blown through the tuyeres 13a into the converter interior. For this cooling medium 19, for example, a hydrocarbon gas which decomposes at high temperatures and, while thus decomposing, absorbs a great quantity of heat thereby having a high cooling capacity is optimal. (3) As a consequence of this cooling action of the cooling medium 19, the slag 4 (or the molten steel 3) in the vicinity of the tuyeres 13a is cooled and coagulates. Thus, as indicated in FIG. 3, a coagulated region 4a is formed around the tuyeres 13a and across the upper opening 12a of the pouring orifice 12, whereby the upper opening 12a is closed, and outward flow of the molten steel 3 and slag 4 is stopped. (4) When the outflow of the molten steel 3 and slag 4 through the pouring orifice 12 has been completely stopped in the above manner, the nozzle stopper 17 is rotated through approximately 180 degrees of angle in the closing direction by the driving device 18 thereby to fit the nozzle plug 17c into the lower opening 12b and positively close the pouring orifice 12. Further, the injection of the cooling medium 19 into the converter 1 is stopped. An important feature of this pouring device 11 is that, since the flow of the molten steel 3 into the pouring orifice 12 is initially stopped by the closure of the upper opening 12a of the pouring orifice 12 by the cooling and coagulation of the slag 4 (or the molten steel 3) due to the injection of the cooling medium 19, the nozzle plug 17 itself is not required to shut off the outflow of the molten steel 3 or the slag 4 by direct contact. For this reason, damage to the nozzle plug 17c is very rare and slight. After the molten steel 3 processed in the converter 1 has been poured out, and the pouring device 11 has been operated to stop the outflow, the ladle 22, into which the molten steel has been poured, is transported away to the succeeding process, and the converter 1 is inverted to discharge the slag 4 within the converter 1 through its throat or upper opening 1b. Then the converter 1 is returned to its upright state, and the next batch of molten iron 3b for refining is received in the converter 1. The operational steps of refining the molten iron 3b thus received in the converter 1 to the pouring out therefrom are as follows. a. From an instant immediately before the molten iron 3b is received into the converter 1, an inert (inactive) gas 20 is blown in through the piping 13c, the tuyere pipes 13b, and the tuyeres 13a into the converter 1. The purpose of this is to prevent melting and damaging of the tuyeres 13a and the flowing of molten iron 3b (or molten steel 3) into the tuyeres 13a and to agitate the molten iron 3b within the converter 1 by means of the inert gas and thereby to promote the refining. It is desirable that this blowing-in of this gas be carried out continuously from immediately before the supplying of the molten iron 3b into the converter 1 to the conclusion of the pouring out of the refined molten steel 3. For this inert gas 20, argon gas is ordinarily used, but, depending on the kind of steel to be refined, nitrogen gas may also be used, or the aforementioned hydrocarbon gas for cooling may be blown in at a low rate. b. After the molten iron 3b has been charged into the converter 1, refining is carried out with a known overhead oxgen lance 21. Meanwhile, the following changes are occurring in the vicinity of the pouring hole 12. The coagulated region formed in the aforedescribed work step (3) around and over the upper opening 12a of the pouring orifice 12 is melted by the residual heat of the molten iron 3b during the charging thereof into the converter 1 and assumes a molten state. The upper opening 12a thereby is opened, and some of the molten iron 3b flows into the upper opening 12a and reaches the nozzle plug 17c at the bottom of the pouring orifice 12. However, since this molten iron 3b in the vicinity of the lower end 12b of the pouring orifice 12 is surrounded therearound by refractory material and becomes cooled by the nozzle plug 17c, it is immediately cooled and coagulates, whereby a coagulated layer 3a as indicated in FIG. 4 is formed. As a consequence, the nozzle plug 17c becomes covered by this coagulated layer 3a and is thus prevented from directly contacting the molten iron 3b (or molten steel 3) in molten state (at a high temperature). As a result, heat damage of the nozzle plug 17c is held to a minimum. c. Upon completion of refining within the converter 1, the nozzle stopper 17 is actuated by the driving device 18 to swing through approximately 180 degrees in the opening direction. Consequently, the coagulated layer 3a formed in the above desired step b loses its principal support and is forced out readily by the pressure of the molten steel 3 within the converter 1, whereupon the molten steel 3 follows and flows out through the pouring orifice 12 into the ladle 22. The pouring step is thus started. In one mode of operation in this pouring step, at a time when a large quantity of the molten steel 3 is remaining in the converter 1, the cooling medium 19 is injected into the converter through the tuyeres 13a thereby to close the upper opening 12a of the pouring orifice 12 and stop the pouring of the molten steel 3. By this procedure, molten steel 3 in a state wherein it contains no slag 4 whatsoever can be poured into the ladle 22. Furthermore, the molten steel can be divided into lots which are respectively poured into a plurality of ladles 22. In the event that, as a supposition, molten steel 3 which has flowed into the pouring orifice 12 coagulates and grows, whereby the molten steel cannot be poured out even when the nozzle plug 17c is opened, measures such as those described below can be carried out. 1) Oxygen gas is blown into the converter 1 through the tuyeres 13a or the overhead oxygen lance 21 to cause a reaction with the molten steel, and the resulting heat of reaction is utilized to raise the temperature of the molten steel in the vicinity of the upper opening 12a of the pouring orifice 12 thereby to melt a portion of the coagulated layer 3a. Then the pressure of the molten steel 3 thrusts out the coagulated layer 3a within the pouring orifice 12. 2) From the side of the lower opening 12b of the pouring orifice 12, that is, from the outside, the coagulated layer 3a within the pouring orifice 12 is pierced by means of a piercer device comprising mechanical means such as a drill, or a piercer device is mounted on the tip of the aforementioned lance 21, which is then lowered, and the coagulated layer 3a within the pouring orifice 12 is pierced by this piercer device to open up the pouring orifice 12 and thereby to cause the molten steel 3 to pour out.. When the converter 1 is inverted to discharge the slag remaining therein as described hereinbefore, the nozzle stopper 17 is opened to pack a material such as sand 25 into the pouring hole 12 beforehand, and then, if the nozzle stopper 17 is left closed as indicated in FIG. 5, a coagulated layer 3a will not be able to form deeply into the pouring orifice 12, whereby when the nozzle stopper 17 is thereafter opened, the molten steel 3 can be poured smoothly. In another example of the pouring device of this invention, as shown in FIG. 6, a sliding gate 31 is slidably installed at the lower opening 12b of the pouring orifice 12 in place of the nozzle stopper 17 of the preceding example. This sliding gate 31 is actuated in opening/closing movements by an actuating device 32. In this case also, a refractory member 31a constituting the greater part of the sliding gate 31 does not directly shut off the flow of the molten steel 3, whereby this sliding gate 31 can withstand a long period of use. In FIG. 6, those parts which are the same as or equivalent to corresponding parts in the preceding example are designated by the same reference numerals. In the two examples of the invention described above, a cooling mechanism 13 is provided at the bottom of the converter 1 in order to blow a cooling medium 19 thereinto. As an alternative measure, it is also possible to lower the aforementioned overhead lance 21 into the converter 1 and to use the same to blow the cooling medium 19 against the molten steel 3 or the slag 4 in the vicinity of the upper opening 12a of the pouring orifice 12 to cause coagulation thereof and thereby to close the pouring orifice 12 and stop the pouring. The pouring device of this invention is not limited to its use in a converter of the overhead oxygen blowing type as described above but can be applied also to Bessemer converters of the bottom blowing type wherein oxygen is blown into the interior through the converter bottom. Furthermore, the pouring device is similarly applicable also to a wide range of vessels for containing molten metals such as metal mixers, electric furnaces, tundishes, and various ladles. The pouring device of the above described construction and operation according to this invention affords the following advantageous features. (a) In comparison with conventional vessels for containing molten metals such as Bessemer converters, metal mixers, and electric furnaces which are inverted for pouring molten metal from their upper throat openings, such vessels provided with the pouring device of this invention are advantageous in that: (a-1) they do not need to be inverted for pouring out molten metal therefrom, whereby it is not necessary to expend time for inverting the vessel, and the operational time cycle is shortened; (a-2) it is not necessary to lower the temperature of the molten metal since the molten metal does not contact the low-temperature parts of the vessel refractory materials at the upper part of the vessel at the time the molten metal is poured out of the vessel; (a-3) the scope of erosion of the refractory material due to the slag is small because the area of contact of the slag floating on the molten metal with the refractory material does not spread, whereby the serviceable life of the vessel refractories is prolonged; (a-4) the work of removing the slag in a subsequent process is reduced, and moreover the quantity of the metal is not lowered since, during pouring there is almost no mixing of slag into the molten metal; (a-5) special equipment exclusively for pouring such as vessel inverting devices and inverting cranes, as required for metal mixers and some ladles, are unnecessary, whereby the construction is simplified; and (a-6) the vessel is constructed with a shape which is symmetrical about its axis since the pouring out orifice of the invention is formed at the center of the vessel bottom, whereby various parts of stress concentration otherwise occurring in the vessel skin (shell) and like parts during the use of the vessel do not occur, whereby the serviceable life of the vessel is prolonged. (b) In comparison with conventional melt pouring devices in which mechanical stoppers such as a nozzle plug and a sliding gate are provided at the pouring hole in the bottom of the vessel such as a ladle or a tundish, and which perform pouring of molten metal only by the opening and closing of these stoppers, the pouring device of this invention is advantageous in that, since the refractory material constituting the greater part of the opening/closing valve member such as the nozzle plug or the sliding gate does not shut off the outflow of the molten metal directly when the pouring is to be stopped, damage and wear of the opening/closing valve member are greatly reduced, whereby the serviceable life of the pouring device is extremely long. For this reason the frequency with which the opening/closing valve member and its refractory material are replaced is reduced, and the operational cost is thereby also lowered.

Claims: A pouring device of a molten-metal-containing vessel (1); said pouring device comprising: a refractory structure of substantially tubular shape which forms a lining (2) fixed to the wall surface of a through hole formed through the bottom of said vessel, and which forms therethrough a pouring orifice (12) having an upper opening (12a) to the interior of the vessel and a lower opening (12b) to the outside of the vessel, characterized by a cooling device (13, 21) operable to blow a cooling medium to the region of the upper opening (12a) and the vicinity thereof for cooling said upper opening (12a) and the region in the vicinity thereof, and an opening/closing mechanism (17) installed outside of the vessel for mechanically opening and closing said lower opening (12b) thereby to permit pouring out of molten metal contained in the vessel and to stop said pouring out. A pouring device according to claim 1 in which said cooling device (13) comprises tuyere means (13a) installed within said refractory structure and opening into the interior of the vessel around said upper opening (12a), tuyere conduits (13b) connected to the lower ends of the tuyere means (13a) for conducting said cooling medium thereinto from the lower part of said refractory structure (2), and piping connected to the lower part of the tuyere conduits (13b) for supplying the cooling medium thereinto from a cooling medium supply means (13c) outside of the vessel. A pouring device according to claim 1 or 2 in which said opening/closing mechanism (17) comprises an arm member (17b) pivotally supported at a proximal end thereof by an exterior part of the vessel (1) in the vicinity of said lower opening (12b) and adapted to swing pivotally through substantially 180 degrees of angle between a closing position and an opening position, a nozzle plug (17c) fixed to the other free end of the arm member (17b) at a position thereon to fit into and close said lower opening (12b) of the pouring orifice (12) when the arm member (17b) is in said closing position, and a driving device for actuating the arm member (17b) in swinging movement between said closing position and said opening position. A pouring device according to claim 1 or 2 in which said opening/closing mechanism comprises a sliding gate (31) made of a refractory material and slidably supported outside of the vessel (1) so as to be slidable between a closing position for closing said lower opening (12b) of the pouring orifice (12) and an opening position for permitting said pouring out, a supporting structure supported outside of and by a part of the vessel (1) and functioning to thus slidably support said sliding gate (31), and a driving device for actuating the sliding gate between said closing and opening positions.

Inventors: KOZA, YUKIHIKO, SATO, SATOSI
Applicants: KAWASAKI JUKOGYO KABUSHIKI KAISHA
Application year: 1988
Main classification: B22D35
IPC codes: C21C5, F27D3, B22D41, C21C1