JP2004107742A - Structure for constructing refractory in rh-degassing vessel bottom, rh-degassing vessel and method for manufacturing refractory block - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preventing breakage and float-up of a block from being caused in a comparatively simple structure by using monolithic refractory as a pre-cast block which is easily dried and a method for manufacturing the pre-cast block used for the same. <P>SOLUTION: This refractory constructing structure for RH-degassing vessel bottom, is provided with refractory blocks constituting a center block 2 held between two circulating-flow tubes 1, circulating-flow tube tuyeres 3 surrounding the circumference of respective circulating-flow tubes and the other bed parts 6, and the monolithic refractories filled up the gaps and/or the surrounds of these refractory blocks, and the refractory block constituting the central block held between two circulating-flow tubes, has a widening downward reverse jack structure. The vessel bottom central part is lower by ≥30 mm than the circumference and a gap with the block is filled up with the dry-type monolithic refractory. The block is manufactured by partitioning the inner part of a large molding flask with plates. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a refractory construction structure for a lower tank of an RH degassing facility used for steel refining.
[0002]
[Prior art]
The main part of the RH degassing equipment consists of a vertically long tank and two immersion tubes provided at the lower end thereof. When the inside of the tank is evacuated and the molten steel is sucked up, and argon gas is blown into the molten steel from the inner surface of one of the immersion tubes, the molten steel rises as the gas floats and flows down from the other immersion tube.
[0003]
The tank body can be divided into several parts, and the lowermost end to which the dip tube is connected is called a lower tank. At the bottom (also called floor) of the lower tank, there is a dip tube and two through holes.
[0004]
The refractory used for the lining of the lower tank not only has high stability under vacuum, but also has abrasion resistance to withstand erosion by flowing molten steel, corrosion resistance to slag entering from a ladle, and oxygen for molten steel. It is required to have corrosion resistance against high-temperature iron oxide generated at the time of spraying or blowing.
[0005]
Conventionally, magnesia-chrome brick has been used for the lower RH tank. However, in recent years, an RH lower tank in which a refractory lining is built by integrally pouring an irregular-shaped refractory kneaded with water is also used. Since irregular-shaped refractories can be added and constructed, there is an advantage that refractories are less wasted. In addition, amorphous refractories are advantageous in that manufacturing costs and prices are low because there are no steps such as molding and firing during production, and that delivery times are short.
[0006]
There is known a method of using a precast block and a brick that has been cast and dried in advance when using an amorphous refractory in an RH lower tank (see Patent Document 1).
[0007]
On the other hand, when building a refractory lining for a lower RH tank using a brick or a precast block, the brick or block may be deformed by thermal expansion, leading to chipping or floating. In order to suppress this, various furnace construction structures have been devised and proposed. For example, there is known an example in which a jack arch structure of a lower wide tapered brick is incorporated in a portion sandwiched between both reflux tube tuyeres (see Patent Document 2).
[0008]
In addition, a structure has been proposed in which a joint is provided between flow holes when an irregular-shaped refractory is poured into the construction to suppress deterioration of the refractory (see Patent Document 3).
[0009]
In addition, a structure has been proposed in which the floating tube tuyere brick has an upwardly spreading shape and the floating is prevented by the lining brick of Nakanoshima (see Patent Document 4).
[0010]
[Patent Document 1]
JP 07-233410 A [Patent Document 2]
Japanese Utility Model Publication No. 03-00249 [Patent Document 3]
JP-A-11-029816 [Patent Document 4]
Japanese Patent Application Laid-Open No. 2000-160231
[Problems to be solved by the invention]
When an amorphous refractory is used, a drying step for removing water used for kneading by evaporation is essential. The thickness of the refractory lining of the lower RH tank is often more than 400 mm. In addition, since the entire tank is a vacuum vessel, there is no hole in the steel shell to allow steam to escape, so the refractory is irregular. Drying is not easy. The use of precast blocks can solve this problem. However, as described in Patent Literature 1, even if a precast block or a brick is simply combined, it is not possible to suppress the loss or the floating.
[0012]
The structure described in Patent Document 2 has an effect of suppressing the floating of the portion sandwiched between the reflux tube tuyeres and the extension thereof, but cannot suppress the floating of the tuyere brick.
[0013]
The structure described in Patent Literature 3 is effective for relieving thermal stress generated inside a refractory construction body which is integrally cast and usually has no joint, but is already used for lining combining bricks and blocks. It has a lot of joints and is not a very useful technology.
[0014]
Further, the structure described in Patent Document 4 may be an effective method for suppressing the loss of the brick constituting the reflux tube tuyeres, but the structure is complicated and the furnace is not easy to build.
[0015]
The present invention provides a relatively simple and stable refractory building structure at the bottom of an RH degassing tank.
[0016]
[Means for Solving the Problems]
In order to solve these problems, the present inventors have made various efforts and obtained the present invention.
(1) Nakanoshima sandwiched between two reflux pipes, a refractory block constituting a reflux pipe tuyere surrounding the respective reflux pipes and other laying parts, a gap between the refractory blocks and / or In a refractory building structure at the bottom of an RH degassing tank having an amorphous refractory filled around, a refractory block constituting Nakanoshima has an inverted jack-arch structure extending downward, and a tuyere of a reflux tube tuyere. A refractory construction structure at the bottom of the RH degassing tank, which is partly constituted.
(2) The refractory building structure at the bottom of the RH degassing tank according to (1), wherein the surface of the refractory block is 30 mm or more lower than the periphery at the center of the tank bottom.
(3) The refractory building structure at the bottom of the RH degassing tank according to (1) or (2), wherein the refractory block is a block in which an amorphous refractory is formed in advance.
(4) An RH degassing tank having the refractory building structure according to any one of (1) to (3).
(5) A method for producing a refractory block according to any one of (1) to (3), wherein the refractory block corresponds to all or a part of a portion to be constructed and has a formwork larger than an individual block. A method of manufacturing a refractory block, comprising partitioning the inside with a board, pouring an irregular refractory into the partitioned portion, curing, and forming two or more blocks from one mold.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
The features of the furnace construction of the present invention will be described with reference to FIG.
[0018]
Referring to the plan view of the lower tank floor (tank bottom) of the RH degassing tank in FIG. 1, the refractory block constituting the reflux tube tuyere 3 surrounding the reflux tube 1 is divided substantially evenly in the circumferential direction. In FIG. 1, it is divided into six. A refractory block called Nakanoshima 2 sandwiched between two reflux pipes is also one of the refractory blocks constituting the tuyere of the reflux pipe. Referring to the RH lower tank cross-sectional view (FIG. 1 (b)) showing the AA cross-sectional view of FIG. 1 (a), the refractory block constituting Nakanoshima 2 has a trapezoidal cross section, and both sides thereof Has a structure in which the refractory 6 is covered from the left and right, that is, an inverted jack arch structure. That is, the refractory block of Nakanoshima 2 forms an inverted jack arch structure between both reflux pipes and constitutes a part of the tuyere of the reflux pipe as described in the invention according to the above (1).
[0019]
Thermal stress concentrates on Nakanoshima 2 and causes deficit or surfacing if no countermeasures are taken. However, by adopting the inverted jack arch structure, deficit and surfacing can be effectively suppressed, and By also serving as a part of the tuyere, it is possible to suppress loss and floating of the tuyere.
[0020]
When constructing a refractory lining using blocks, the gaps and / or the surroundings of those blocks are filled with irregular-shaped refractories in order to prevent hot water leakage. Mortar may be applied or filled with a pouring material, but it is not always easy to dry the water used for kneading. Therefore, it is particularly preferable to apply a dry amorphous refractory, such as a dry ramming material, because there is no need for drying. Immediately after the start of operation, the unsintered dry filler may be washed away and disappear, so the part close to the operation surface should be moistened by adding a little moisture, water glass, or other liquid binder. It is good to construct from.
[0021]
FIG. 1C is a cross-sectional view taken along the line BB of FIG. The refractory block constituting Nakanoshima 2 has a vertical sectional structure in the BB section.
[0022]
According to the sectional view of FIG. 1B, Nakanoshima 2 is lower than the surroundings, and this corresponds to the invention according to the above (2). With such a lowering, the stress due to the thermal expansion generated on the surface of the refractory can be changed downward, so that the refractory blocks constituting the Nakanoshima and the recirculation tuyere can be effectively prevented from floating or deficient. The difference in height from the surroundings is 30 mm or more. If the thickness is less than 30 mm, the effect of suppressing the floating or breakage of the refractory block is poor. However, if the height difference is too large, the thickness of the Nakanoshima 2 becomes insufficient and the life is shortened. Therefore, it is preferable to set the height to 150 mm or less.
[0023]
The refractory block used in the present invention may be a precast block in which an amorphous refractory is previously cast, molded and dried. Amorphous refractories have a number of advantages, such as being relatively inexpensive and have a short delivery time, can be refilled, and can be easily dried by being made into a precast block. This is where the invention according to the above (3) is intended. is there. However, refractory blocks other than precast blocks, such as unfired or fired bricks, can be used.
[0024]
When manufacturing a precast block, it may be individually poured into a mold and molded. However, it is costly because many types of molds are required. Also, when you change the shape of a block, you have to remake many types. Therefore, as described in the invention according to the above (5), a mold frame larger than an individual block, which corresponds to all or a part of the tank bottom, is prepared, and the inside thereof is partitioned by a plate, and the partitioned portion is irregularly shaped. Refractory logistics are incorporated, cured, and molded into two or more blocks. In this way, the number or types of molds can be greatly reduced, and when a large mold corresponding to the entire bottom of the tank is used, only one is required per tank. By changing the partitioning method, the furnace construction and block shape can be changed as desired. By adjusting the thickness of the plate, the thickness of the gap 5 (joint) can be freely set. The plate may be either flat or curved. In order to adjust the shape of the block, a spacer can be installed inside the formwork.
[0025]
This block manufacturing method can be applied to all types of kilns, such as hot metal transport containers, converters, ladles, tundishes, and the like, which are used only for refractories for RH degassing tank bottoms.
[0026]
The material of the refractory is preferably alumina-spinel, alumina-magnesia, or basic as long as it is an amorphous refractory for an RH degassing tank. During kneading or molding, refractory coarse particles such as alumina, mullite, and magnesia and various refractory blocks may be mixed. Organic fibers or metal fibers may be added. The method of kneading and pouring is as usual, and a kneading liquid such as water is added, kneaded with a mixer, and poured into a mold. After pouring, a vibrator is used to produce a high-quality construction. Alternatively, the blocks may be formed by dry-type such as ramming or stamping or semi-dry-type construction to which a slight amount of moisture is added. The refractory may be brick or the like as described above.
[0027]
2A to 2C are examples in which the method of dividing the refractory block is changed. Also in this case, as in the case of FIG. 1, Nakanoshima sandwiched between the reflux pipes has an inverted jack arch structure, and Nakanoshima is a part of the tuyere of the reflux pipe, and the center of the tank bottom is lower than the surroundings. And other features of the present invention.
[0028]
【Example】
The tank bottom of the 300 tRH degassing tank was lined with the structure of FIG.
[0029]
A mold (approximately 3 m in diameter) corresponding to the size of the entire floor is prepared, a spacer is placed on a portion to be a reflux tube, and a portion serving as a gap (a thick line in FIG. 1 (indicated by reference numeral “5”)) ) And a plate having a thickness of 2 mm was installed in a portion (the thin line portion in FIG. 1) serving as a joint to be joined by mortar without providing a gap. The material was made so that the lower surface at the time of construction was the upper surface at the time of material pouring, and a spacer was placed at a portion corresponding to the recess at the center of the tank bottom at the time of construction. The thickness of the block was about 400 mm, and the center of the tank bottom was 75 mm lower than the surrounding area. The block of Nakanoshima had a trapezoidal shape when viewed in the cross section of FIG. 1B, and had a height of 325 mm, a lower base of 800 mm, and an upper base of 600 mm.
[0030]
The material was an alumina-spinel pouring material containing about 20% by mass of spinel, kneaded by adding water, poured into a plate-partitioned mold, and vibrated by a rod-shaped vibrator.
[0031]
After curing, the mold was removed, and the removed block was dried in a dryer.
[0032]
The dried block was built in the lower tank of the RH degassing tank. First, a small amount of mortar kneaded with water was poured, and the block was placed at a predetermined position. Mortar was applied to portions where no gap was left, and the blocks were joined. The gap was filled with a magnesia-spinel dry ramming material containing about 20% by mass of spinel with an air rammer. The working surface side 50 mm was filled with the same ramming material to which a small amount of water glass was added, and the construction was completed. Thereafter, magnesia-chrome brick was built on the side wall, and the construction of the refractory lining the lower tank was completed.
[0033]
The tank was dried at 400 ° C., fastened to the upper tank, and started to be used after preheating. After being used about 500 times, it was removed from the upper tank and the state of the tank bottom was observed. No block defect was found.
[0034]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a refractory lining that is easy to dry and has a relatively simple and stable structure, and that an inexpensive amorphous refractory can be easily formed in an RH degassing tank. Can be used stably. As a result, the cost of refractories can be reduced, the degassing process can be stabilized, and as a result, the cost of steel production can be reduced.
[0035]
It is possible to provide a method of using an amorphous refractory as a precast block that is easy to dry, a relatively simple structure that does not cause block breakage or floating, and a method of manufacturing a precast block used therefor.
[Brief description of the drawings]
FIG. 1A is a plan view showing a lower tank bed (tank bottom) of an RH degassing tank, FIG. 1B is a cross-sectional view taken along line AA of FIG. 1A, and FIG. 1) is a sectional view taken along line BB of FIG.
2 (a) is a plan view showing another tank bottom (tank bottom) of another RH degassing tank, FIG. 2 (b) is a sectional view taken along line AA of FIG. 2 (a), and FIG. FIG. 2C is a sectional view taken along line BB of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Reflux pipe 2 ... Nakanoshima 3 ... Reflux pipe tuyere 4 ... Side wall refractory 5 ... Gap 6 ... laying part (other laying part)

Claims (5)

Nakanoshima sandwiched between two reflux pipes, a refractory block forming a tuyere and other laying parts surrounding the circumference of each of the reflux pipes, and filling a gap and / or a periphery of the refractory block. In the refractory construction structure at the bottom of the RH degassing tank provided with the shaped amorphous refractory,
The refractory building structure at the bottom of the RH degassing tank, wherein the refractory block constituting the Nakanoshima has an inverted jack arch structure extending downward and forms a part of a tuyere of the reflux pipe. 2. The refractory building structure according to claim 1, wherein a surface of the refractory block is lower by 30 mm or more than a circumference at a center of the tank bottom. 3. 3. The refractory building structure according to claim 1, wherein the refractory block is a block in which an amorphous refractory is formed in advance. 4. An RH degassing tank having the refractory construction structure according to claim 1. It is a method of manufacturing the refractory block according to any one of claims 1 to 3, which corresponds to all or a part of a part to be constructed and partitions the inside of a formwork larger than an individual block with a plate. A method for producing a refractory block, comprising: casting an irregular-shaped refractory into a partitioned portion; curing the refractory; and forming two or more blocks from one mold.

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