JP2003301209A - Tap hole of blast furnace, and tap flume of blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend the lifetime of a tap hole and a tap flume of a blast furnace, in order to stabilize operation of the blast furnace and improve the working conditions. <P>SOLUTION: The tap hole and the tap flume are made of an SiC ceramic sintered compact which includes 96 mass% or more SiC and sintering auxiliaries of 4 mass% or less, with the total of 99 mass% or more, and has a porosity of 5% or less. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blast furnace taphole and a taphole gutter which are composed of a high-purity and highly-densified SiC ceramics sintered body for improving working conditions and stabilizing operation of the blast furnace. is there.

[0002]

2. Description of the Related Art The tapping operation for taking out hot metal from a blast furnace is carried out by using a mud material (for example, SiC-Al ₂ O ₃ ) which has a closed tap hole.
- are carried out pierced aperture in the carbonaceous material with SiO _2, Si ₃ N ₄ clayey castable refractory mixed quality material or the like) drill and opening machine such as a hammer. The opened tap hole is eroded mainly by chemical wear due to the components contained in the molten pig iron, the diameter gradually expands, the tapping rate increases to a level that greatly exceeds the pig iron production rate, and melting in the furnace The object level is lowered to a position lower than the taphole. At this time, the in-furnace gas protrudes from the tap hole with dust, and the melted material is scattered. Therefore, it is impossible to continue tapping from one taphole forever, and after a certain time has elapsed from the opening, the taphole is filled with mud material to close the taphole. The next tapping is performed by opening another closed tapping port. The time from the opening of one taphole to the blockage depends on the erosion rate of the taphole material.
Since one tapping time is about 2 to 4 hours, the tapping frequency of one blast furnace is about 7 to 10 times a day. That is, the opening and closing work of the taphole, which is a heavy work under high temperature, is performed 7 to 10 times a day. Further, there is also a problem that the molten metal level in the blast furnace also fluctuates due to the fluctuation of the tapping speed due to the enlargement of the tapping hole diameter, which causes unstable operation and quality. Also, the hot metal and molten slag from the tap hole are stored in the tap gutter such as large gutter, hot metal gutter, and slag gutter, separated from the slag, and discharged to a torpedo car, etc., but the lining of these tap gutters is For example, castable refractories such as Al ₂ O ₃ —SiC—C material are used. Castable refractories lined in the gutter are also eroded by the hot metal and slag, so they will be repaired when the damage becomes severe. Even the current cast iron lined castable refractories have insufficient service life due to the erosion caused by the molten pig iron, and the refurbishment work of the taphole gutter is performed once every 20 days. is the current situation.

Under these circumstances, in order to improve the working conditions and stabilize the operation of the blast furnace, the service life of the tap hole and tap gutter is extended, and the frequency of opening and closing work and the frequency of repairing the gutter are reduced. Technology has been developed.

For example, in Japanese Unexamined Patent Publication No. 7-316615, a sleeve-shaped refractory material of SiC-Si ₃ N ₄ -Al ₂ O ₃ is used to form the taphole, so that the taphole is not enlarged by the molten pig iron. A technique is disclosed in which the tapping can be performed for a long time and the number of times of opening and closing can be reduced. However, in the sleeve-shaped refractory mentioned above, SiC, which is the most important component for improving the corrosion resistance, is 85% by mass at the maximum.
And low. Si ₃ N ₄ is added in order to enhance the cohesive strength of the tissue, but at the expense of corrosion resistance. Further, according to the examples, the firing temperature is as low as 1550 ° C., which is not the temperature at which the sintered body is sufficiently densified. Therefore, the product of the present invention does not have a corrosion resistance that is significantly higher than the materials conventionally used in blast furnaces, and has a longer service life than mud materials, but is not a sufficient technique for the purpose of improving blast furnace operation. .

In JP-A-8-225814 and JP-A-8-225815, a cylindrical refractory material of silicon carbide material-alumina material or silicon carbide material-alumina material-mullite material is used. A technique is disclosed in which the number of openings and closings can be reduced by forming a taphole, but according to the examples, the porosity of this cylindrical refractory is as high as at least about 11%, The SiC content is as low as 90% by mass to 95% by mass at the highest. This invented product also does not have the property that it can be said that it is extremely superior to the materials used conventionally, and is not a satisfactory technique for improving the operation of the blast furnace.

[0006] In addition, in most cases, amorphous refractory is used for tapping gutter from the viewpoint of workability. In general, amorphous refractory has low raw material purity and is fired at a low temperature due to the heat of molten pig iron during operation, so high densification cannot be expected. Although much research has been conducted on irregularly shaped refractories for gutters, there is a limit to the improvement in properties for the reasons described above, and irregularly shaped refractories cannot sufficiently extend the useful life of the gutters. on the other hand,
Brick-stacked gutters have a longer life than amorphous refractories, but conventional refractory bricks do not have sufficient durability, so as long as conventional refractory bricks are used, gutter extension of service life is sufficient. It's not something.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and provide a taphole and a tappipe which enable continuous use for a long time, which has never been seen before, and to provide a blast furnace. To improve work conditions and operations.

[0008]

[Means for Solving the Problems] In a blast furnace taphole and tappipe, an extremely severe environment for materials, such as hot metal at about 1500 ° C. Is.

In order to prolong the life of tapholes and tappipes, materials that are small in dimensional change due to melting loss even under these severe environments are required. Carbon refractories have high resistance to hot metal and high resistance to molten slag, but are damaged by oxidation. Oxides such as Al ₂ O ₃ have high hot metal resistance and high oxidation resistance, but are melted by the molten slag. Non-oxides such as Si ₃ N ₄ have a high slag resistance, but are eroded by the hot metal and have a low oxidation resistance. As a result of repeated experiments and studies for solving the above-mentioned problems, the present inventors have found that highly purified and highly densified SiC ceramics form a glass layer of SiO _{2 on} the surface of the ceramics against slag and oxidation. However, the reaction does not proceed any further, and although a reaction phase of Si-Fe intermetallic compound and graphite is formed on the ceramic surface for the hot metal, the reaction phase is not dissolved in the hot metal and the dimensional change due to melting loss. Found that it would not happen.

It has been known for a long time that SiC has high strength, abrasion resistance and corrosion resistance, and SiC is used as a raw material for refractories in the blast furnace and the peripheral portion of the blast furnace regardless of a fixed shape or an amorphous shape. However, it is difficult to densify high-purity SiC in the conventional refractory manufacturing process, and in the refractory field, when the SiC content in the material is 90 mass% or more, the cohesive force of the structure becomes weak and It has been said to cause a decline. When the purity of SiC and the relative density of the sintered body decrease, the strength, wear resistance and corrosion resistance of the material decrease significantly. The highest SiC content of a general SiC refractory is about 90% by mass, and the sintered body contains 10% or more pores. Therefore, in conventional refractory materials, Si
The characteristics originally possessed by C itself have not been fully exerted. For these reasons, there has been a problem in the use of SiC-based materials in a blast furnace, that is, 1) melting and melting in hot metal and 2) a limit in use in an oxidizing environment. However, as a result of repeated studies by the present inventors, the above-mentioned problem is not due to the characteristics of SiC itself.
This is due to the low raw material purity and the high porosity of the C-type refractory material.
It was found that it is extremely difficult to melt in any environment of molten slag, coexistence of molten pig iron, and oxidation.

The present invention has been made on the basis of the above findings, that is, it contains 96% by mass or more of SiC and 4% by mass or less of a sintering aid, and their total content is 99% by mass or more. And a blast furnace taphole characterized by being composed of a SiC ceramics sintered body having a porosity of 5% or less, and containing 96 mass% or more of SiC and 4 mass% or less of a sintering aid, Is a blast-furnace tapping gutter, which is composed of an SiC ceramics sintered body having a total of 99% by mass or more and a porosity of 5% or less.

A novel point of the present invention is that SiC ceramics having a high raw material purity and relative density, which were not in the conventional refractory field, are applied to tapholes and tappipes. , By using the tap iron gutter, the service life of them can be greatly extended, the working conditions of the blast furnace can be improved, and the operation can be stabilized.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be described below.

Regarding the sintering aid of SiC ceramics, B and B compounds, C and C compounds, Al, Si, S
Known substances such as ialon, AlN, Al ₂ O ₃ , Y ₂ O _{3 and the} like can be used as the sintering aid, and two or more types of substances may be contained. However, the total amount of sintering aids needs to be 4% by mass or less. When the second phase is generated at the grain boundary by the sintering aid, the corrosion resistance of the material is lowered, which becomes remarkable when the total amount of the sintering aid exceeds 4% by mass. For the same reason, the unavoidable impurities mixed in the raw material need to be 1% by mass or less depending on the kind. The porosity must be 5% or less, that is, the relative density must be 95% or more. Generally, when the relative density of the sintered body is 95% or more, the sintered body does not include open pores. When the material includes open pores, the durability is significantly reduced due to cracking during heating / cooling due to impregnation of the hot metal into the pores and deterioration of corrosion resistance due to increase in surface area.

In order to produce the above ceramics, SiC powder and a sintering aid are weighed so as to have a target composition, kneaded in a ball mill or the like, and then dried by a method such as spray drying and mixed. Get a powder. Then, the powder is molded by a method such as uniaxial pressing or hydrostatic pressing (CIP), and the temperature is 2000 ° C to 2300 ° C, preferably 2100 ° C.
Firing is performed in an inert atmosphere or vacuum in the range of 2200 ° C. to obtain a desired sintered body. The manufacturing method is not particularly limited, and a known method can be used. However, it is desirable that the manufacturing apparatus be as clean as possible in order to avoid mixing of impurities. Further, it is desirable that the porosity of the sintered body be as low as possible. Therefore, it is effective to use a pressure sintering method such as hot pressing or hot isostatic pressing (HIP).

The taphole of the present invention is composed of the above-mentioned SiC ceramics, and its form is SiC.
We manufacture pipes, rings, and plate-shaped members from ceramics,
There is a method of forming a taphole by combining them, or a method of manufacturing a block and then opening it. As a method of mounting the blast furnace, there is a method of embedding the taphole in the closed state and fixing it with an irregular refractory material, or a method of forming the taphole in advance at the time of repair, but it is not particularly limited.

Similarly, for the tappipe of the present invention, there are a method of forming a gutter using a combination of plate-like members, a method of forming a single piece, a method of manufacturing a block and performing the same construction as a brick. However, the present invention is not limited to the embodiments.

In order to maximize the effects of the invention, it is desirable that the seam is as small as possible and the adhesion of the seam is as high as possible so that the molten pig iron does not penetrate from the seam of the members. Preheating is also effective in order to prevent cracking due to thermal shock.
The method of opening / closing may be a method using an opening machine and a mud material as in the conventional method, but a method such as a sliding nozzle, a control method using a stopper, or a laser opening method is also possible and is not particularly limited.

[0019]

EXAMPLES The present invention will now be described in more detail with reference to Examples.

Commercially available SiC powder (average particle size: 0.7 μ
m, SiC purity: 98.7%, α phase: about 100%),
Sintering agent B ₄ C powder and carbon black were mixed with S
iC powder 97.70% by mass, B ₄ C powder 0.38% by mass, and carbon black 1.92% by mass were weighed, and these powders were ball milled with a SiC liner,
Using a SiC ball, kneading was performed for 24 hours using water as a solvent. Then, the obtained slurry was spray-dried in N ₂ gas at 120 ° C. to obtain a dry mixed powder. This dry mixed powder was filled in a rubber mold and subjected to CIP molding, and the molded body taken out was fired at 2150 ° C. in Ar gas (Example 1).

B ₄ which is a sintering aid is added to the above-mentioned SiC powder.
C powder, AlN powder, and carbon black
Powder 96.30% by mass, B ₄ C powder 0.37% by mass, A
1N powder was weighed to 0.90% by mass and carbon black 2.43% by mass, and after the same powder preparation and molding process as in Example 1, the molded body was fired in Ar gas at 2100 ° C. Example 2).

In the firing process of these examples, B_Four
C decomposes into B and C, B is SiC volume diffusion, grain boundary diffusion
Contribute to the promotion of_FourC decomposed from C and added
Contained as an impurity in carbon black and SiC powder
Is C on the surface of SiC ₂Included as phases and impurities
SiO₂In addition to reducing and removing
Contribute to promotion. C contained in the raw material powder is
Mostly SiO during the firing process₂It is lost in the reduction reaction. This
TEM observation of the SiC ceramics sintered body thus obtained
As a result, segregation of B compound and graphite was observed at the grain boundaries.
However, the amount is small, and the area ratio of the TEM image is
As a result of the calculation, the SiC content of the sintered body is
99.0 mass% (Example 1), 97.9 mass% (Example)
It was 2).

Table 1 shows the chemical components of the materials of the above-mentioned Examples and Comparative Examples, and the results of the immersion test. Comparative Examples 1 and 2
Are high-purity, low-porosity alumina and silicon nitride ceramics. Comparative Examples 3 and 4 are refractory materials generally used as furnace materials around the blast furnace and the like, and the burned mud material of Comparative Example 4 is the mud material which is the current taphole material.
It was fired in Ar at 550 ° C. for 8 hours. The chemical component value is a value calculated from the TEM observation image of the sintered body and the EDX analysis result.

From each material in Table 1, 10 mm × 10 mm × 3
Three 0 mm test pieces were manufactured, and one test piece was placed in one carbon crucible. Insert appropriate amounts of (a) pig iron, (b) slag, and (c) pig iron + slag into this carbon crucible, press down from above with a carbon rod so that the test piece does not come up during the test, and cover the crucible. Did. This crucible was placed in an atmosphere furnace and the temperature was 1550 ° C for 3 hours.
The immersion test was performed in Ar atmosphere. In this test method (i)
It is possible to independently evaluate the corrosion resistance under the three conditions of hot metal, (ii) molten slag, (iii) molten pig, and coexistence of molten slag. After the test, the test piece was vertically cut together with the crucible, and the dimensional change (one side) of the test piece before and after the immersion was taken as the amount of melting loss.

[0025]

[Table 1]

The Si ₃ N ₄ ceramics of Comparative Example 1 exhibit high resistance to molten slag, but are eroded by the hot metal and undergo severe erosion damage in the presence of the molten slag. The Al ₂ O ₃ ceramic of Comparative Example 2 is
On the contrary, it shows a high resistance to hot metal, but it is eroded by the molten slag, and in the coexistence, it is still severely melted. The SiC refractory material of Comparative Example 3 was eroded by both the hot metal and the slag, and the melting loss was remarkable when coexisting. The baked mud of Comparative Example 4 has the best result in Comparative Examples, but it has melting loss under any of the conditions. On the other hand, in the SiC ceramics of the examples, although the reaction phase is formed with respect to the hot metal, there is no dimensional change and the slag is not corroded at all. No dimensional change occurs even in the presence of molten pig iron, which is the most severe melting environment.

From the above, SiC ceramics are extremely superior in corrosion resistance in the presence of hot metal / slag coexisting as compared with conventional refractory materials and ceramics such as Al ₂ O ₃ and Si ₃ N _4. understood.

Next, an actual machine test was conducted using the material of Example 1.

FIG. 1 is a schematic view of an actual machine test of the taphole of the present invention. A cylindrical member having an inner diameter of 70 mm, an outer diameter of 150 mm, and an axial length of 650 mm was made from the material of Example 1, the blast furnace tap hole portion that had been closed was processed, and this cylindrical member was inserted to a depth of 650 mm from the outer wall, and the mud was inserted. It was attached to the tap hole using wood. Next, the opening bit was inserted into the cylinder, and the mud at the inner side of the cylindrical member was opened and tapped. On this occasion,
The cylindrical member and the peripheral mud were firmly adhered to each other, and all the pig iron waste was discharged from the opening of the cylindrical member without leaking from the gap between the cylindrical member and the mud. The test results are shown in FIG. The change in tapping speed was evaluated in comparison with the case of tapping tap of mud material. As shown in Fig. 2, in the case of mud material,
The tapping speed increased due to the expansion of the diameter after the opening, and gas was generated 4 hours after the opening, so that the tapping was cut off and closed. On the other hand, in the taphole of the present invention, no change was observed in the tapping rate even 10 hours after the opening. After a lapse of 10 hours from the opening, the mud material was filled from the cylindrical member and closed. After blockage, the cylindrical member of the present invention was taken out, the member was observed after removing the mud material, and although the reaction phase was formed on the inner surface of the cylinder, there was almost no change in the inner diameter compared to before tapping, It was found to be sufficiently durable.

Next, using the same material, 200 mm × 200 mm
B. A plate material having a thickness of 40 mm was prepared, and this was embedded in an unshaped refractory material at a position corresponding to the metal / slag line of the Ohi skinmer part. This position makes contact with the hot metal / slag at high temperature, and when it is closed, it also contacts the atmosphere, which is a very severe melting environment. In this state, normal operation was carried out for 24 hours (of which, the running time was about 12 hours and the running amount was about 5000t.
on). Then, the deposit was peeled off and the amount of erosion was measured.
Table 2 shows the results of the actual test of the gutter. It has been found that the product of the present invention has much less melting loss than the conventional material and can extend the service life.

[0031]

[Table 2]

[0032]

As described above, by using the taphole and tappipe of the present invention, the service life of the taphole and tappipe can be extended, and the operation stability of the blast furnace and the improvement of working conditions can be achieved. Becomes

[Brief description of drawings]

FIG. 1 is a schematic view (cross-sectional view) of an actual machine test of a taphole.

FIG. 2 is a diagram showing the relationship between the elapsed time from the opening and the tapping speed in the actual machine test result.

[Explanation of symbols]

1 ... Blast furnace wall 2 ... hot metal slag 3 ... The taphole of the present invention 4 mud material

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yutaka Fujiwara             20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel shares             Company Technology Development Division F-term (reference) 4G001 BA22 BA23 BA36 BA60 BB22                       BB23 BB36 BB60 BC01 BC23                       BC52 BC54                 4K015 EB00 EC00                 4K051 AA01 BE01 BE03

Claims (2)

[Claims] 1. SiC in an amount of 96% by mass or more and a sintering aid of 4
A blast furnace taphole characterized by being contained in a SiC ceramics sintered body having a total content of 99% by mass or more and a porosity of 5% or less. 2. SiC in an amount of 96% by mass or more and a sintering aid of 4% or more.
A blast furnace tappipe which is contained in an amount of not more than 100% by mass, a total amount of which is not less than 99% by mass, and which is made of a SiC ceramics sintered body having a porosity of not more than 5%.