JP2008202080A - Vacuum vessel structure and repairing method of vacuum-degassing facility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the vacuum vessel structure of a vacuum-degassing facility with which even in the case of needing the repair of a lining refractory layer in the upper vessel, the upper vessel can be replaced with the upper vessel having sound lining refractory layer in an extremely short operation stopping time. <P>SOLUTION: The structure of the vacuum vessel 5 of the vacuum-degassing facility 1 is provided with: the upper vessel 6 having a raw material charging port 14 and a duct 13 for exhaust gas; a lower vessel 9 having submerging tubes 10, 11 to be submerged into molten steel and to hold the molten steel 3; and intermediate vessels 7, 8 arranged in between the upper vessel and the lower vessel so as to be attachable to and detachable from the upper vessel and the lower vessel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a structure of a vacuum tank of a vacuum degassing equipment such as an RH vacuum degassing apparatus and a DH vacuum degassing apparatus used as a molten steel refining furnace, and a repair method of the vacuum degassing equipment.

  In recent years, with the upgrading of steel and the expansion of applications, the number of steel types that require vacuum degassing refining is increasing, and in the steelmaking refining process, RH vacuum degassing equipment, DH vacuum degassing equipment, etc. Vacuum degassing equipment is widely used. Among these vacuum degassing equipment, the vacuum tank of the RH vacuum degassing apparatus is composed of an upper tank having a canopy and a lower tank positioned below the upper tank, and the lower tank is for sucking molten steel and discharging molten steel These two dip tubes (an ascending side dip tube and a descending side dip tube) are provided. The inner surfaces of the upper and lower tanks are lined with refractory.

  In this RH vacuum degassing apparatus, the ascending-side dip tube and the descending-side dip tube are each immersed in the molten steel in the ladle, and an inert gas such as Ar gas is blown into the ascending-side dip tube, so that the molten steel Is raised into the vacuum chamber through the rising side dip tube, and the elevated molten steel is returned to the lower ladle through the lower side dip tube, and this is repeated to circulate the molten steel, and the molten steel is degassed in the vacuum vessel. Refining such as processing.

  By the way, when refining with this RH vacuum degassing apparatus, it is mainly the lower tank that comes into contact with the molten steel, and therefore the erosion rate of the refractory layer of the inner lining of the lower tank is large. Therefore, the lower tank is detachable, the lower tank is removed from the upper tank according to the state of melting, and another lower tank is attached to allow the operation to continue. In this case, the operation stop time of the RH vacuum degassing apparatus is a dozen hours, which is not so long.

  On the other hand, although the upper tank has less erosion of the lining refractory layer than the lower tub, the inner refractory layer at the lower end of the upper tub adheres to the molten steel splash and slag that are scattered during refining, The erosion progresses due to iron oxide generated when these deposits are dissolved. In addition, when a raw material input port for introducing a flux of alloy iron or quick lime for adjusting the molten steel composition is installed on the side wall of the upper tank, the raw material input port is caused by the collision of the introduced alloy iron or the like The opposite side wall refractories may be damaged. Therefore, although the frequency of the upper tank is less than that of the lower tank, it is periodically repaired.

  However, the repair of the lining refractory layer of the upper tub is done by installing a scaffold inside the upper tub while the upper tub is installed on the site, and when the worker enters the inside of the narrow upper tub, The material layer is dismantled and removed, and then the refractory bricks are manually stacked one by one in the upper tank. Because the worker enters the inside, it is necessary to cool the upper tank, and since the inside of the upper tank is a narrow space, it is difficult for multiple workers to enter and work at the same time. Repairing the upper tank takes a long time of about one week. In the meantime, the RH vacuum degassing apparatus had to be shut down, which was one of the major causes that hindered the manufacturing process.

  In the above description, the RH vacuum degassing apparatus has been described as an example. However, this problem also occurs in common with a DH vacuum degassing apparatus having a two-divided vacuum chamber.

  As a countermeasure, the RH vacuum degassing unit is configured as a Twin Vessel type with two upper tanks, one of which is operated, and the other is operated as an off-line refractory layer construction. Although there is a method of shortening the stop time, in this case, since a space for two upper tanks is required, there is a problem that it cannot be realized unless a new RH vacuum degassing apparatus is installed. Since two upper tanks are required, there is also a problem that the equipment cost becomes expensive.

Therefore, means for reducing the repair time of the upper tank has been proposed. For example, in Patent Document 1, a brick block that forms the lining refractory layer of the upper tank is formed in advance outside the furnace by combining a plurality of refractory bricks, and the old lining refractory layer to be repaired is dismantled and removed. Thereafter, a method of forming a new lining refractory layer by connecting the brick blocks in the circumferential direction of the upper tub has been proposed. Further, Patent Document 2 discloses the removal or lining of metal bullion or lining adhering to the surface of the lining refractory layer, which can be inserted into the upper tank from above, and is provided with a breaker that can be swung, swung, and retreated. A dismantling device that can break down the refractory layer itself has been proposed.
JP 2005-48240 A JP 2005-146356 A

  According to Patent Document 1 and Patent Document 2, although the repair time of the upper tank in the RH vacuum degassing apparatus having only one upper tank has been shortened, both Patent Document 1 and Patent Document 2 have the upper tank to be repaired in the field. Since the lining refractory layer is repaired in the state where it is installed, it still requires a long time as compared with the lower tank to be replaced at once, which has been the main cause of lowering the operating rate of the RH vacuum degassing apparatus.

  The present invention has been made in view of the above circumstances, and the purpose thereof is to provide a sound lining refractory during a very short operation stoppage time even if the lining refractory layer of the upper tank is required to be repaired. The object is to provide a vacuum tank structure and a repair method for a vacuum degassing facility that can be replaced with an upper tank having a layer.

  The present inventors have intensively studied and studied to solve the above problems. As a result, in the lining refractory layer of the upper tank, the place where repair is necessary is about 600 to 1000 mm from the lower end part of the upper tank where the splash of molten steel flowing into the lower tank scatters, specifically, the joint with the lower tank The upper part and the side wall part facing the raw material inlet, approximately 1500 mm below the raw material inlet, where the iron alloy and the like introduced from the raw material inlet installed on the side wall of the upper tank collide, It was found that other parts do not need periodic repairs.

  Therefore, the vacuum tank is configured so that the severely damaged area of the lining refractory layer can be divided from the upper tank, and the part is left in a hot state and replaced with a previously constructed off-line refractory layer. As a result, it was found that the cooling time of the upper tank, the dismantling and construction work of the lining refractory layer in the upper tank became unnecessary, and the operation stop time could be greatly shortened.

  The present invention has been made on the basis of the above knowledge, and the vacuum tank structure of the vacuum degassing equipment according to the first invention includes an upper tank having a raw material inlet and an exhaust duct, and an immersion immersed in molten steel. A lower tank for holding molten steel, and an intermediate tank that is provided between the upper tank and the lower tank and is detachable from the upper tank and the lower tank. It is what.

  The vacuum tank structure of the vacuum degassing equipment according to the second invention is the vacuum tank structure according to the first invention, wherein the intermediate tank is divided into upper and lower two stages of a lower first intermediate tank and an upper second intermediate tank. The first intermediate tank and the second intermediate tank are detachable.

  The vacuum tank structure of the vacuum degassing facility according to the third invention is characterized in that, in the second invention, the vertical height of the first intermediate tank is 600 to 1000 mm.

  The vacuum tank structure of the vacuum degassing equipment according to the fourth invention is characterized in that, in the second or third invention, the vertical height of the second intermediate tank is 1200 to 1800 mm. .

  A vacuum degassing equipment repair method according to a fifth aspect of the present invention is the vacuum degassing equipment having the vacuum tank structure according to any one of the first to fourth inventions, wherein the vacuum tank portion requiring repair Is exchanged in a hot state.

  According to the present invention, in the vacuum tank of the vacuum degassing equipment such as the RH vacuum degassing apparatus, the lower tank is, of course, the portion of the conventional upper tank where the lining refractory layer is severely damaged. It is possible to replace the part with a refractory tank that has been lined off-line in advance while maintaining that part in a hot state. This eliminates the need for dismantling and construction work for the lining refractory layer, and for the repair of the lining refractory layer in the vacuum chamber, it is possible to significantly reduce the operation stop time compared to the conventional case.

  Hereinafter, the present invention will be specifically described with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view of an RH vacuum degassing apparatus equipped with a vacuum chamber according to the present invention.

  As shown in FIG. 1, the vacuum tank 5 of the RH vacuum degassing apparatus 1 includes four parts of an upper tank 6, a second intermediate tank 7, a first intermediate tank 8, and a lower tank 9 in order from the upper side in the vertical direction. It is configured. The upper tank 6, the second intermediate tank 7, the first intermediate tank 8, and the lower tank 9 have a shell 15 as an outer shell, and a refractory layer 16 lining a refractory brick in which a refractory brick is constructed. Is formed. There is only one upper tank 6 that is fixed and cannot move, but the joint between the upper tank 6 and the second intermediate tank 7, the joint between the second intermediate tank 7 and the first intermediate tank 8, and the first The joint portion between the one intermediate tank 8 and the lower tank 9 has a flange structure, and is structured to be removable at these arbitrary positions. That is, removing only the lower tank 9 from the vacuum tank 5, or removing the lower tank 9 and the first intermediate tank 8 in a connected state, the lower tank 9, the first intermediate tank 8, and the second intermediate tank 7. Both of them can be removed in a connected state. Of course, it is possible to remove the lower tank 9, the first intermediate tank 8, and the second intermediate tank 7 one by one.

  The upper tank 6 is provided with an exhaust duct 13 connected to an exhaust device (not shown), and a raw material inlet 14 for introducing the component adjusting alloy iron into the vacuum tank 5. A lower side dip tube 10 and a lower side dip tube 11 are provided below the lower tank 9. The ascending-side dip tube 10 is provided with a circulating gas blowing nozzle 12 for blowing the circulating gas. From the recirculation gas blowing nozzle 12, an inert gas such as Ar gas is blown into the ascending-side dip tube 10 as a recirculation gas. Although only one recirculation gas blowing nozzle 12 is shown in FIG. 1, a plurality of recirculation gas blowing nozzles 12 branched from one supply pipe in the circumferential direction of the ascending-side dip pipe 10. However, the discharge direction is set as a horizontal direction toward the center of the ascending-side dip tube 10. Further, in FIG. 1, the discharge direction of the circulating gas blowing nozzle 12 is the horizontal direction toward the center of the ascending-side dip tube 10, but it is upward or downward or inclined from the direction toward the center to the horizontal direction. It is good also as a direction.

  In the RH vacuum degassing apparatus 1 having such a configuration, the ladle 2 containing the molten steel 3 refined in a converter or an electric furnace is transported directly under the vacuum tank 5 and is taken up by a lifting device (not shown). 2 is raised, and the ascending-side dip tube 10 and the descending-side dip tube 11 are immersed in the molten steel 3 accommodated in the pan 2. The ladle 2 is partially mixed with slag 4 generated by refining in a converter or an electric furnace, and covers the molten steel 3 surface. Then, an inert gas such as Ar gas is blown into the ascending-side dip tube 10 from the reflux gas blowing nozzle 12 as the reflux gas. Before and after the introduction of the reflux gas, the inside of the vacuum chamber 5 is evacuated by the exhaust device through the duct 13 to reduce the pressure inside the vacuum chamber 5. When the inside of the vacuum chamber 5 is depressurized, the molten steel 3 accommodated in the ladle 2 ascends the ascending-side dip tube 10 by the principle of the gas lift pump together with the bubbles 17 of the circulating gas blown from the circulating gas blowing nozzle 12. Flow into the vacuum chamber 5 and then return to the ladle 2 via the descending side dip tube 11, forming a so-called recirculation flow, and RH vacuum degassing such as dehydrogenation, denitrogenation, and decarburization. Refined. At the end of the RH vacuum degassing refining, alloy iron such as metal Al or Fe-Si is introduced from the raw material inlet 14 into the molten steel 3 circulating in the vacuum tank 5, the components of the molten steel 3 are adjusted, and the RH vacuum degassing is performed. Gas refining ends.

  Based on the RH vacuum degassing performed in this way, the optimum dimensions in the height direction of each part of the vacuum chamber 5 according to the present invention are set as follows.

  The lower tank 9 is a part that is in direct contact with the molten steel 3 circulating inside the vacuum tank 5, and therefore, the upper end position in the vertical direction of the lower tank 9 is the joint between the lower tank 9 and the first intermediate tank 8. In order to prevent the molten steel 3 from entering the steel, it is slightly higher (several tens mm to several hundred mm) than the molten metal surface of the molten steel 3 to be circulated. In this case, the surface position of the molten steel 3 is not the height of the portion raised by the bubbles 17 but the highest position where the molten steel 3 comes into contact with the lower tank 9.

  The first intermediate tank 8 is a part to which a splash of the molten steel 3 scattered during the RH vacuum degassing refining or a CaO-based desulfurizing agent charged from the raw material charging port 14 during desulfurization treatment adheres. If the attached metal melts down during RH vacuum degassing and enters the molten steel 3, it causes problems such as detachment of the components of the molten steel 3. To prevent this problem, oxygen or oxygen from a lance or burner (not shown) is used. The metal is melted by supplying gas or irradiating a burner flame. The lining refractory layer 16 is damaged by the iron oxide produced in this metal melting process. Although the range to which this metal adheres changes also with the distance of the upper end position of the lower tank 9, and the molten steel surface position in a lower tank, it is 600-1000 mm from the junction part with the lower tank 9, Preferably it is 700-900 mm. This is sufficient, and this range is preferably the first intermediate tank 8.

  The second intermediate tank 7 is a part where the lining refractory layer 16 is damaged by the collision of metal Al or alloy iron introduced from the raw material introduction port 14 for adjusting the components of the molten steel 3. The position where the metal Al or the alloyed iron charged from the raw material inlet 14 collides is a portion on the opposite side of the raw material inlet 14 from a position lower than the lower end of the raw material inlet 14 by about 1500 mm. Therefore, it is preferable that the position lowering about 1500 mm from the lower end of the raw material inlet 14 is the upper end position of the second intermediate tank 7.

  In the RH vacuum degassing apparatus 1 in which the raw material charging port 14 is installed on the side wall of the upper tank 6, a position lowered by about 1500 mm from the lower end of the raw material charging port 14 is obtained as a distance from the upper end position of the lower tank 9. It is about ~ 2400mm. Since the height of the first intermediate tank 8 is 600 to 1000 mm, the height of the second intermediate tank 7 is preferably 1200 to 1800 mm, and more preferably 1300 to 1700 mm. However, since the size of the RH vacuum degassing device 1 varies depending on the processing capacity of the RH vacuum degassing device 1, the above positional relationship does not apply to all RH vacuum degassing devices, but molten steel of 200 tons or more. In the RH vacuum degassing apparatus that processes the above, there is no problem in the above positional relationship.

  The second intermediate tank 7 is a measure against damage to the lining refractory layer 16 that occurs when the raw material inlet 14 is installed on the side wall of the upper tank 6, and the raw material inlet 14 is a canopy of the upper tank 6. This is a measure that is not necessary when the alloy iron or the like is introduced in the vertical direction. In this case, the second intermediate tank 7 is not necessary, and only the first intermediate tank 8 is used. It is enough.

  In repairing the lining refractory layer 16 of the vacuum chamber 5 in the RH vacuum degassing apparatus 1 including the vacuum chamber 5 having this configuration, the following method can be employed.

  For example, the lower tank 9 is periodically replaced according to the number of treatments, the first intermediate tank 8 is replaced every time the lower tank 9 is replaced twice, and the second intermediate tank is replaced every time the lower tank 9 is replaced four times. A method of exchanging 7 can be employed. Exchange of each part is performed in a hot state. In this case, assuming that all of the lower tank 9, the first intermediate tank 8 and the second intermediate tank 7 have started operation with the new lining refractory layer 16, after performing a predetermined number of treatments, the first time In the repair, only the lower tank 9 is removed and replaced with another lower tank 9 in which the lining refractory layer 16 has been previously constructed offline. In the second repair, the lower tank 9 and the first intermediate tank 8 are connected and removed at the joining surface of the first intermediate tank 8 and the second intermediate tank 7, and the lining refractory layer 16 is preliminarily constructed offline. The assembled lower tank 9 and first intermediate tank 8 are collectively replaced. In the third repair, only the lower tank 9 is removed and replaced with another lower tank 9 in which the lining refractory layer 16 has been previously constructed offline. In the fourth repair, the lower tank 9, the first intermediate tank 8 and the second intermediate tank 7 are connected and removed at the joint surface between the second intermediate tank 7 and the upper tank 6, and the lining refractory layer is offline beforehand. 16 is constructed, and the assembled lower tank 9, first intermediate tank 8, and second intermediate tank 7 are collectively replaced. Thereafter, replacement is performed according to the above. A lining refractory layer 16 is appropriately applied to the removed lower tank 9, first intermediate tank 8, and second intermediate tank 7 offline.

  Moreover, the method of replacing | exchanging the 2nd intermediate tank 7 whenever the lower tank 9 is replaced | exchanged regularly according to the number of processes, the 1st intermediate tank 8 is replaced simultaneously with the lower tank 9, and the lower tank 9 is replaced twice. Can also be adopted. In this case, assuming that all of the lower tank 9, the first intermediate tank 8 and the second intermediate tank 7 have started operation with the new lining refractory layer 16, after performing a predetermined number of treatments, the first time In the repair, the lower tank 9 and the first intermediate tank 8 are connected and removed at the joint surface between the first intermediate tank 8 and the second intermediate tank 7, and the lining refractory layer 16 is preliminarily constructed and assembled offline. The lower tank 9 and the first intermediate tank 8 are collectively replaced. In the second repair, the lower tank 9, the first intermediate tank 8 and the second intermediate tank 7 are connected and removed at the joint surface between the second intermediate tank 7 and the upper tank 6, and the lining refractory layer is offline beforehand. 16 is constructed, and the assembled lower tank 9, first intermediate tank 8, and second intermediate tank 7 are collectively replaced. Thereafter, replacement is performed according to the above. If the refractory layer 16 of the first intermediate tank 8 is severely damaged and the lower tank 9 and the first intermediate tank 8 need to be exchanged all at once, the lower tank 9 and the first intermediate tank 8 are integrated. The upper tank 6, the second intermediate tank 7, and the integrally formed lower tank may be divided into three.

  In addition, the lining refractory layer 16 can be repaired by various combinations without being limited to the above.

  As described above, according to the present invention, in the vacuum chamber 5 of the RH vacuum degassing apparatus 1, the severely damaged part of the lining refractory layer 16 is divided so that the part remains in a hot state. It is possible to replace the refractory layer 16 that has been lined in advance offline, and as a result, there is no need to cool the upper tub 6, and the dismantling and construction work of the refractory lining layer 16 in the upper tub. Is no longer necessary, and when the lining refractory layer 16 of the vacuum chamber 5 is repaired, the operation stop time can be greatly shortened compared to the conventional case.

  In addition, although the said description demonstrated the vacuum tank 5 of the RH vacuum degassing apparatus 1, this invention is not applied only to the vacuum tank 5 of the RH vacuum degassing apparatus 1, but the vacuum tank of a DH vacuum degassing apparatus. The present invention can be applied along the above.

  An example in which the present invention is applied to the RH vacuum degassing apparatus shown in FIG. 1 that processes 250 tons of molten steel will be described.

  A first intermediate tank having a vertical height of 800 mm was provided above the lower tank, and a second intermediate tank having a vertical height of 1500 mm was provided above the first intermediate tank. In this case, the upper end position of the second intermediate tank corresponds to a position of 1500 mm from the lower end of the raw material charging port provided on the side wall of the upper tank.

  The lower tank was replaced every time 1500 heat treatment was performed, and the first intermediate tank was replaced at the same time as the lower tank was replaced. In addition, every time the lower tank was replaced, up to the second intermediate tank was replaced at once.

  In the conventional RH vacuum degassing apparatus composed of the upper tank and the lower tank, approximately 7.5 days (180 hours) were spent on repairing the lining refractory layer of the upper tank, but the present invention is applied. As a result, the replacement work was completed in 15 hours, and the operation stop time could be greatly shortened.

It is a schematic longitudinal cross-section of the RH vacuum degassing apparatus provided with the vacuum chamber which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 RH vacuum degassing apparatus 2 Ladle 3 Molten steel 4 Slag 5 Vacuum tank 6 Upper tank 7 Second intermediate tank 8 First intermediate tank 9 Lower tank 10 Ascending side dip pipe 11 Descending side dip pipe 12 Gas flow nozzle for recirculation 13 Duct 14 Raw material inlet 15 Iron skin 16 Lined refractory layer 17 Air bubbles

Claims (5)

  An upper tank having a raw material inlet and an exhaust duct, a dip pipe immersed in molten steel, a lower tank for holding molten steel, and an upper part provided between the upper tank and the lower tank A vacuum tank structure for vacuum degassing equipment, comprising: an intermediate tank detachable from the tank and the lower tank.   The intermediate tank is divided into upper and lower two stages of a lower first intermediate tank and an upper second intermediate tank, and the first intermediate tank and the second intermediate tank are detachable, The vacuum tank structure of the vacuum degassing equipment according to claim 1.   The vacuum tank structure for vacuum degassing equipment according to claim 2, wherein the vertical height of the first intermediate tank is 600 to 1000 mm.   The vacuum tank structure of the vacuum degassing equipment according to claim 2 or 3, wherein the vertical height of the second intermediate tank is 1200 to 1800 mm.   The vacuum degassing equipment having the vacuum chamber structure according to any one of claims 1 to 4, wherein a vacuum chamber portion requiring repair is exchanged in a hot state. How to repair gas equipment.

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