JPH08246032A - Method for repairing bottom blowing porous plug - Google Patents

Abstract

PURPOSE: To provide a method for repairing a bottom blowing porous plug which is easily executable without requiring a large-scale equipment and less damages a ladle lining. CONSTITUTION: A patching material 13 contg. a small amt. of combustible fibers and essentially contg. alumina is adhered and packed into the worn part of the porous part 11 of the bottom blowing porous plug 10 mounted at the bottom part of a molten steel vessel 19 in this method for repairing the bottom blowing porous plug 110 which is mounted at the bottom of the molten steel vessel 19 and is provided with the air permeable porous part 11 for blowing gas into the molten steel 20 and a dense sleeve 12 formed to a tapered shape to fix and protect the porous part 11. The bottom blowing porous plug 10 is thereafter dried and heated up, by which the combustible fibers are burned away and the patching material 13 is made porous.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for repairing a bottom-blown porous plug in which gas is blown into a ladle holding molten steel melted in a converter, an electric furnace or the like to stir the molten steel.

[0002]

2. Description of the Related Art Generally, for refining molten steel with a bottom-blown porous plug, the bottom-blown porous plug is inserted into a bottom brick for the bottom-blown porous plug, which is provided at the bottom of the ladle.
Molten steel is stirred by receiving the molten steel in a ladle and blowing a gas such as argon into the ladle. Therefore, on the gas blowing surface of the bottom blowing porous plug, gas and molten steel move violently and wear of the bottom blowing porous plug is large. There is. Therefore, as a repair method for extending the life of such a bottom-blown porous plug, for example, in Japanese Patent Laid-Open No. 63-62816, the damaged portion of the plug is preheated and nitrogen is flowed from the gas introduction pipe to the plug. A method has been proposed in which the burner is preheated from the top surface and then thermal spraying is repaired. In addition, a method has been adopted in which a refractory, which serves as a marker for accurately grasping the amount of wear of the bottom-blown porous plug, is embedded in the plug and monitored, so that the porous plug is used up to the allowable limit. There is.

[0003]

However, the method described in Japanese Patent Laid-Open No. 63-62816 requires separate large-scale equipment such as a thermal spraying device and a preheating device, and the porous material to be repaired by thermal spraying. Since it is essential to flow nitrogen to secure the ventilation amount of the plug, the sprayed surface is cooled, the spraying efficiency is significantly reduced, and it is difficult to form a porous state with uniform ventilation characteristics. is there. Also, in the method of embedding a refractory to be a marker and monitoring it, the life itself of the bottom blown porous plug itself is not directly extended. The mechanical wear of the tuyere becomes large during replacement, causing the life of the ladle lining itself to be shortened. The present invention has been made in view of such circumstances, and can be easily executed without requiring large-scale equipment,
Moreover, it is an object of the present invention to provide a method for repairing a bottom-blown porous plug that does not damage the ladle lining.

[0004]

A method according to the above-mentioned object.
The bottom blown porous plug repair method described is a breathable porous part that is attached to the bottom of a molten steel container and blows gas into molten steel, and a dense sleeve formed in a taper shape to fix and protect the porous part. In a method of repairing a bottom-blowing porous plug comprising, a putting material containing a small amount of combustible fiber and containing alumina as a main component is attached to the bottom of the molten steel container as a wear part of the porous portion of the bottom-blowing porous plug. It is configured such that it is adhered and filled, and then the bottom blowing porous plug is dried and heated to burn and remove the combustible fibers to form the putting material into a porous body. The method for repairing a bottom blown porous plug according to claim 2 is
The method for repairing a bottom blown porous plug according to claim 1, wherein the combustible fiber is a carbonaceous fiber and has a length of 5 to 5.
0.25-0.6w for the putting material at 20mm
It is configured to contain t%. A method for repairing a bottom blow porous plug according to claim 3 is the method for repairing a bottom blow porous plug according to claim 1 or 2, wherein alumina and chromium oxide are 88 to 88 each in the putting material.
It is configured to contain 94 wt% and 0.1 to 1 wt%.

The porous portion is a refractory material having a high air permeability, which is obtained by adding a small amount of a sintering material or the like to an aggregate having a controlled grain size and firing the aggregate. What is a dense sleeve formed in a taper shape?
It consists of a fired or unfired refractory material that has a lower air permeability than the refractory material of the porous portion and has improved erosion resistance and wear resistance, and the porous portion provided inside the taper by the reverse taper and repair. It is configured to prevent the putting material from falling off. What is putting material?
It is a material for repair that is made by adding plasticity to organic materials such as organic or inorganic binder and water, etc. to refractory aggregates. It is a material for repair that can be cured after drying to cover the surface to be repaired. It is a refractory material. The combustible fiber means an organic or inorganic fiber containing a large amount of carbon as a main component. The worn portion of the porous portion means a portion where the porous portion is worn as a result of gas blowing into the molten steel and its periphery.

[0006]

According to the method for repairing a bottom blow porous plug according to any one of claims 1 to 3, in the method for repairing a bottom blow porous plug having a tapered dense sleeve, a small amount of combustible fiber is contained, A putting material containing alumina as a main component is adhered and filled in the wear part of the porous part, and then the bottom blown porous plug is heated to dryness to burn off the combustible fibers to form the putting material into a porous body. , The putting material filled in the wear part of the porous part is securely fixed by the taper part of the sleeve, and
A gas passage can be formed by burning and removing the combustible fibers in the putting material.

According to a second aspect of the present invention, in the method for repairing a bottom blown porous plug, the combustible fiber is a carbonaceous fiber, the length is 5 to 20 mm, and the putting material has a thickness of 0.
Since it is contained in an amount of 25 to 0.6 wt%, it is possible to further maintain the ventilation characteristics and mechanical strength of the putting material after heating, in an appropriate range. By using the carbonaceous fiber as the combustible fiber, the carbon content is completely removed as CO in the process of combustion, so that a gas path is secured.
Further, when the length of the carbonaceous fiber is shorter than 5 mm, the degree of entanglement of the fibers for forming the gas passage is small, and it is not possible to secure an appropriate ventilation amount. On the contrary, if the length of the combustible fiber is longer than 20 mm, the mechanical strength of the putting material itself is lowered, which is not preferable. Further, if the amount of the carbonaceous fiber added to the putting material is less than 0.25 wt%, the effect of forming the gas passage is small, and if it exceeds 0.6 wt%, the mechanical properties of the porous body obtained by burning the carbon content are reduced. The strength is drastically reduced.

In a method for repairing a bottom blown porous plug according to a third aspect, alumina and chromium oxide are contained in the putting material at 88 to 94 wt% and 0.1 to 1 w, respectively.
Since it is configured to contain t%, the wear resistance and melt damage resistance of the putting material are enhanced. If the alumina component is less than 88 wt%, the wear resistance of the putting material cannot be maintained, and if it is more than 94 wt%, the spalling resistance is reduced, which causes cracking due to thermal shock. Further, when the content of chromium oxide is less than 0.1 wt%, the wettability with molten steel is increased and the melt damage resistance is deteriorated. The impact on problems will increase.

[0009]

Embodiments of the present invention will now be described with reference to the accompanying drawings to provide an understanding of the present invention. 1 is a cross-sectional view of a bottom-blowing porous plug to which a method of repairing a bottom-blowing porous plug according to an embodiment of the present invention is applied, FIG. 2 is an explanatory view of an apparatus to which the method is applied, and FIG. 3 is a carbonaceous fiber. It is a graph which shows the relationship between content rate and aeration index.

First, an apparatus to which a bottom blowing porous plug repairing method according to an embodiment of the present invention is applied and a configuration of the bottom blowing porous plug will be described. As shown in FIG. 2 (a), a ladle 19 which is an example of a molten steel container has a substantially cylindrical shape with an inner diameter of 3,000 mm and a height of 3,700 mm, and the inner side surface and the bottom portion are lined with a refractory material, and the molten steel capacity is 175 t. Steel container having a bottom blowing porous plug 10 at the bottom. As shown in FIG. 1, the bottom-blown porous plug 10 has a sleeve 12 which is tapered and holds and holds the porous portion 11 therein, and a supporting refractory material 15 disposed below the porous portion 11. It comprises a metal case 16 which surrounds the outer periphery of the sleeve 12 and the supporting refractory material 15 and is arranged so as to seal the gas for blowing the bottom, and a pipe 17 for supplying argon gas. The sleeve 12 is made of a dense refractory material having a low air permeability, whose main component is alumina, which has high resistance to wear of molten steel due to gas bubbling. The porous portion 11 is a fired refractory material having a high air permeability, which is formed by adjusting the particle size of alumina spinel or alumina silica-based aggregate, molding and firing. Supporting refractory 1
Reference numeral 5 is made of a refractory material such as alumina-silica having a lower air permeability than that of the porous portion 11, and a supporting portion 15 has a marker portion 14 projecting toward the porous portion 11 and showing the remaining portion above the supporting refractory material 15. . The bottom blown porous plug 10 configured as described above is inserted through the mortar into the tuyere 18 which is a part of the refractory lining at the bottom of the ladle 19.

Next, a method of repairing a bottom blown porous plug according to an embodiment of the present invention will be described. First, FIG.
As shown in (a), the bottom-blown porous plug 1 is placed in a ladle 19 that holds 175 tons of molten steel 20 having a molten steel temperature of 1650 ° C.
Argon gas from 0 to 800 Nl / min (back pressure: 7 k
The refining treatment was performed by blowing at a flow rate of gf / cm ² ) for about 27 minutes. Then, after the treated molten steel 20 is discharged from the ladle 19, the ladle 19 is turned over as shown in FIG. Oxygen was blown onto the slag etc. to clean the ejection surface by dissolving and removing the metal.

Observation of the gas discharge surface of the bottom blown porous plug 10 revealed that the porous portion 11 was mainly worn due to the damage caused by the above-mentioned cleaning work by oxygen and the wear of molten steel during the gas blowing. Was in a state of protruding from the porous portion 11, but the marker portion 1 provided so as to protrude from the supporting refractory material 15 of the bottom blown porous plug 10.
No. 4 was not observed, the bottom-blown porous plug 10 remained sufficiently, and it was judged that the repair was within the safe use limit.

Therefore, the putting material 13 containing carbonaceous fibers, which is an example of combustible fibers, is adjusted, and the porous portion 11 is prepared by using a putting repair jig 21 or the like.
The temperature inside the ladle is 130
Hot repair was performed at 0 ° C. At this time, since the sleeve 12 is a tapered portion that expands inward in the wear direction, the putting material 13 can be easily compacted and filled, and the filled putting material 13 is held without flowing down. Here, the putting material 13 contains 0.4 wt% of carbonaceous fibers having a length of 10 mm and a fiber diameter of 0.3 mm, and alumina, silica, and chromium oxide are 90 wt% and 6 w, respectively.
It was obtained by adding an appropriate amount of a binder containing water and the like so as to be t% and 0.5 wt% and kneading. The combustible fiber is for the purpose of generating CO gas or the like in the subsequent heating process to vaporize and burn to form a passage for the gas, and the content and form of the combustible fiber depend on repair conditions and refining conditions. It can be specified in an appropriate range by considering the gas blowing conditions and the like. FIG. 3 is a graph showing a relationship between a carbonaceous fiber content rate and an air permeability index which are experimentally obtained, and the air permeability index is a putting material containing a predetermined amount of fibers under a predetermined temperature at which combustible fibers burn. It is a relative index that is measured by holding it in and taking it out. As shown in the figure, it can be seen that the air permeability index can be greatly increased by adding the carbonaceous fiber content of 0.25 wt% or more.

As shown in FIG. 1, a bottom blow porous plug 1
After filling the wear part of the porous portion 11 of 0 and its periphery with the putting material 13, the ladle 19 on which the bottom blown porous plug 10 is arranged is placed in the lining of the ladle 19 by a ladle preheating device such as a burner not shown. Heating the temperature to 600
By holding at 30 ° C. for 30 minutes, the putting material 13 was dried and hardened, and the carbonaceous fibers were burned and removed. And
Gas is supplied to the bottom-blown porous plug 10 through the pipe 17 to confirm that the proper ventilation amount is obtained, and then, again, as shown in FIG.
As shown in (a), a new gas-blown refining process for molten steel was performed.

After that, when the refining process including the above-mentioned repair process was repeated thereafter, the putting material 13 thus constructed was restrained by the sleeve 12 formed in the reverse taper, and the floating of the putting material 13 during ventilation was prevented. Then
It has been found that the service life of the bottom-blowing porous plug 10 is extended from 6 times to 11 times as compared with the case where it is not repaired, and the durability around the tuyere 18 of the bottom-blowing porous plug 10 is also improved. This is because the putting material 13 covers not only the discharge port of the argon gas as shown in FIG. 1 but also the periphery thereof, and thus the discharge area of the argon gas discharged through the putting material 13 becomes large, so that it is constant. It is considered that when a large amount of gas is flowed, local molten steel agitation given to the refractories around the tuyere 18 and the like is alleviated. Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and changes in conditions and the like without departing from the gist are all within the scope of the present invention.

[0016]

According to the method for repairing a bottom blown porous plug of claims 1 to 3, a putting material containing a combustible fiber and containing alumina as a main component is adhered and filled into the wear portion of the porous portion, and thereafter, Since the bottom blowing porous plug is heated to dryness by burning and removing the combustible fibers to form the putting material into a porous body, the putting material filled in the wear portion of the porous portion may fall off at the taper portion of the sleeve. In addition to being securely fixed, the combustible fibers in the putting material can be burned and removed to form a gas passage, and further, the putting material attached around the discharge port of the bottom blow porous plug fills the gas. The discharge area is expanded and maintained without shrinking after each repair, which makes it easy to control the gas discharge rate. Since the flow velocity is kept low improvement in tolerability including up refractories around the tuyere furnace material can be achieved.

In particular, in the method for repairing a bottom-blown porous plug according to claim 2, since the combustible fiber is a carbonaceous fiber and the length and the addition amount thereof are specified, the heating of the putting material is further increased. The subsequent ventilation characteristics and mechanical strength can be maintained in an appropriate range.

In the bottom blown porous plug repairing method according to the third aspect of the present invention, since the amount of alumina component and chromium oxide of the putting material is defined in a specific range, wear resistance and melt damage resistance of the putting material. Can be controlled to further improve durability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a bottom blowing porous plug to which a bottom blowing porous plug repairing method according to an embodiment of the present invention is applied.

FIG. 2 is an explanatory diagram of an apparatus to which the method is applied.

FIG. 3 is a graph showing a relationship between a carbonaceous fiber content rate and an air permeability index.

[Explanation of symbols]

 10 Bottom Blowing Porous Plug 11 Porous Part 12 Sleeve 13 Putting Material 14 Marking Part 15 Supporting Refractories 16 Metal Case 17 Pipe 18 Tuyere 19 Ladle 20 Molten Steel 21 Putting Repair Jig

Claims (3)

[Claims] 1. A bottom blower which is attached to the bottom of a molten steel container and has a gas permeable porous portion for blowing gas into the molten steel, and a tapered dense sleeve for fixing and protecting the porous portion. In a method for repairing a porous plug, a small amount of combustible fiber is contained, and a putting material containing alumina as a main component is attached to the wear part of the porous part of the bottom blown porous plug attached to the bottom of the molten steel container, After that, the bottom blowing porous plug is heated to dryness, the combustible fibers are burned and removed, and the putting material is made into a porous body. 2. The flammable fiber is a carbonaceous fiber,
The length is 5 to 20 mm and the putting material is 0.25
The repair method for the bottom blown porous plug according to claim 1, wherein the repaired amount is 0.6 wt%. 3. The putting material is alumina and
Chromium oxide is 88-94wt%, 0.1-1w
The method for repairing a bottom-blown porous plug according to claim 1 or 2, wherein the content is t%.