JPH03141152A - Carbon-containing unburned refractory brick - Google Patents

Abstract

PURPOSE:To improve durability of carbon-containing unburned refractory brick by blending specific amounts of Al2O3 raw material, MgO raw material, C raw material, ZrO2 raw material, thermosetting resin and, if necessary, antioxidant and glass forming material, molding and heat-treating. CONSTITUTION:90-10wt.% total amounts of 3-50wt.% MgO raw material having 0.5-3mm particle diameter, such as calcined MgO having >=95% purity is blended with 3-50wt.% C raw material such as scaly graphite and the rest of Al2O3 having >=90wt.% purity, such as fused Al2O3 are blended with 10-90wt.% ZrO2 raw material having >=0.1mm particle diameter and containing partially stabilized ZrO2 and a thermosetting resin such as phenol resin. Further the blend is mixed with 3-30wt.% SiC as an antioxidant, 1-10wt.% (outer percentage) at least one or more of metallic powder such as Al, various kinds of carbonate, nitride and boride except SiC and 0.5-5wt.% (outer percentage) glass forming raw material such as refractory clay. Then the blend is molded, heat-treated in a nonoxidizing atmosphere at 150-600 deg.C to give carbon-containing unburned refractory brick.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to ladles, hot metal pretreatment containers, linings for various smelting furnaces,
Unfired refractories used especially in slag line parts [Conventional technology] In recent years, the use conditions for refractories have become extremely harsh in the steel manufacturing process due to higher quality steel, energy conservation, rationalization of manufacturing processes, etc. There is a demand for the development of refractories with excellent spalling resistance.

As a refractory that meets this demand, for example,
As seen in Publication No. 882, Alumina-3i attempts to improve impact resistance while maintaining wear resistance by adding silicon carbide, aluminum, and even silicon.
C-carbon brick, also JP-A-60-19104
No. 9 discloses bricks made of sintered alumina, synthetic mullite, scaly graphite, fireclay, and phenolic resin, each of which has increased hot strength by adding a low-melting point metal such as aluminum. However, during dephosphorization of hot metal, for example, the slag is exposed to highly basic slag in which the weight ratio of CaO and SiO The speed is high and the bricks do not have sufficient durability.

Furthermore, JP-A-60-191049 shows an example of using magnesia instead of synthetic mullite and sintered alumina, but when the basicity of slag is high, the amount dissolved in the slag is small; The corrosion resistance is better than that of the alumina-3iC-carbon brick described above.

However, since magnesia-carbon bricks contain almost no glass-forming components, they do not form a protective layer of glass, and when used in locations where the operating period is long or where heating and cooling are repeated. , Magnesia has a high coefficient of thermal expansion, so it may flake off due to spalling, or the brick structure will become brittle, gradually decreasing its oxidation resistance, resulting in greater structural deterioration, and its durability will be lower than that of alumina-5iC-carbon bricks. It may be lower.

[Problem to be solved by the invention]

As mentioned above, alumina-3iC-carbon bricks have poor corrosion resistance, and magnesia-carbon bricks have poor oxidation resistance and spalling resistance. The current situation is that they do not have sufficient durability for use as bricks for slag line parts such as containers.

Therefore, in view of the above circumstances, the present invention not only has excellent spalling resistance and corrosion resistance even when exposed to high basicity slag, but also has an excellent structure that is resistant to structural deterioration due to oxidation even after long-term operation. The purpose of the present invention is to provide a carbon-containing unfired refractory brick that exhibits excellent durability.

[Means for solving problems]

In order to achieve the above object, in the present invention, the content of the alumina raw material, magnesia raw material, and carbon raw material is 90 to 1.
The present invention provides a carbon-containing unfired refractory brick comprising 0% by weight, 10 to 90% by weight of a zirconia raw material, and a thermosetting resin.

Furthermore, if necessary, as an antioxidant, for example, A
Fine powder of metals such as n, Si, Mg, MgA/, SiC,
It is also possible to add low melting point inorganic materials such as carbides, nitrides, borides, frits, borosilicate glass, etc. such as Ba C, BN, Si, and N4, knead and shape, and heat-treat.

[Effect]

Zirconia used as refractory aggregate has a particle size of 0.
One or more fins of partially stabilized zirconia and unstabilized zirconia can be used. In terms of volumetric stability, it is preferable to use partially stabilized zirconia, but corrosion resistance tends to be slightly lowered. Unstabilized zirconia has good corrosion resistance, but tends to have poor volumetric stability.

Therefore, when increasing the amount of zirconia used, it is preferable to use partially stabilized zirconia and unstabilized zirconia together.

The mechanism by which the corrosion resistance against slag is improved by adding zirconia is that zirconia has a high melting point of 2,600°C, and zirconia eluted from bricks forms a solid solution of ZrO□ and CaO in the highly basic slag. Since the solid solution has a high melting point, the suspension of particles with a high melting point in the slag significantly increases the apparent viscosity of the slag, suppressing the movement of the slag at the slag-metal interface, and resulting in the formation of bricks. This is thought to be due to a decrease in the amount of erosion.

If the amount of zirconia is less than 10% by weight, the effect of improving corrosion resistance will be small, and if it exceeds 90% by weight, not only will the spalling resistance decrease, but the ratio of cost to improvement in corrosion resistance will increase. Therefore, the amount of zirconia blended is preferably 10 to 90% by weight, more preferably 20 to 50% by weight.

Further, the particle size is preferably 0.1 ms or more in diameter, and if it is 0.1 ms or less, the reaction with CaO, which is the main component of slag, is accelerated and it becomes easy to become slag, which is not preferable.

Magnesia has a high melting point of 2800° C. and is a basic material, so it has excellent corrosion resistance against high basicity slags such as converter slags and dephosphorization slags in which the weight ratio of CaO to Sin is 2 or more. Also, during use of refractory materials, it reacts with alumina to produce spinel (MgA, /z Oa),
Adding residual expansion to refractory materials to increase volumetric stability,
Suppresses increased wear and tear due to joint opening and crack formation. Furthermore, it reacts with ZrO□, which is the third component, and forms a solid solution in ZrO□, thereby suppressing destabilization of zirconia and contributing to the stabilization of unstabilized or partially stabilized zirconia. Therefore, magnesia is an essential component in order to fully exhibit the volumetric stability and high corrosion resistance of zirconia.

As the magnesia raw material, any of sintered magnesia, natural magnesia, and fused magnesia with a purity of 95% or more can be used. In addition, the particle size is 0.5 to 3 ml in diameter.
It is preferable to use medium to coarse particles. The appropriate amount of addition is 3 to 50% by weight. If it is less than 3% by weight, the volume stabilizing effect is insufficient because the amount of spinel produced or the amount of solid solution in zirconia is small, and if it is more than 50% by weight, the characteristic of magnesia, which has a large coefficient of thermal expansion, becomes obvious. Spalling resistance decreases. Furthermore, as the amount of spinel produced increases, the residual expansion coefficient also increases, causing crushing or peeling damage due to contact between bricks.

Scale graphite is used as a carbonaceous raw material because it has excellent oxidation resistance and spalling resistance, but in some cases,
A carbon blank or pitch having good reactivity with aluminum or silicon can also be used. If the carbon content is less than 5% by weight, the spalling resistance will be low, and if it exceeds 50% by weight, the deterioration of the Mi fabric due to oxidation will increase, so a range of 3 to 50% by weight is best, and a carbon content of 10 to 30% by weight is good. Particularly preferred are formulations.

The alumina raw material may be used in the form of coarse particles or fine powder, but in order to form a strong brick structure, it is desirable to use zirconia in the form of coarse particles with a diameter of 0.5 to 511 mm.
To achieve this, it is necessary to add alumina of various particle sizes ranging from coarse to fine to bricks with a small amount of zirconia added, but with bricks with a large amount of zirconia added, it is necessary to add alumina of medium to fine particles with a diameter of less than 1. You can also use only As the alumina, a raw material having a purity of 90% or more is preferable, and from this point of view, high-purity fused alumina is particularly preferable. The amount of alumina blended is the balance excluding magnesia, carbon, and zirconia.

In the present invention, StC can be added as necessary. Generally, as bricks are used, oxidation progresses gradually due to CO gas, but SiC in the bricks has the function of preventing oxidation.

If the blending amount of SiC is less than 3% by weight, oxidation resistance during long-term operation will be insufficient, and if it exceeds 30% by weight, there will be no problem in terms of oxidation resistance of the brick, but SiC + 2CO = S
Since the amount of 5inZ produced by the iOi +3C reaction increases, corrosion resistance decreases, and the brick structure becomes denser, making it more likely to cause peeling damage. Therefore, the blending amount is 3~
Most preferred is a range of 30% by weight, especially from 5 to 15% by weight.

In the present invention, it is possible to add various carbides, borides, nitrides, metal fine powders, and glass forming raw materials in addition to SiC as antioxidants for the carbonaceous raw material. As the metal powder, one or a mixture of two or more of aluminum, silicon, magnesium, calcium, chromium, etc., or an alloy thereof can be used. Metal powder has the effect of increasing hot strength by reducing the oxygen partial pressure in the refractory brick and suppressing carbon oxidation, as well as reacting with carbon to generate carbide and strengthening carbon bonds. If the amount of metal powder added is less than 1% by weight with respect to the above aggregate mixture, the effect will be small, and if it exceeds 10% by weight, the thermal expansion will become too large and the spalling resistance will decrease, or oxidation will occur. Corrosion resistance decreases depending on the composition of the oxide after oxidation. Therefore, the amount added is 1 to 10% by weight, especially 2 to 10% by weight.
The amount added is preferably in the range of 5%, and the smaller the particle size of the metal powder, the more effective it is.

As the glass forming raw material, one or more of raw materials mainly composed of silica or boron oxide, such as fireclay, sericite, feldspar, silica flour, water glass powder, borax, borosilicate glass, and frit, can be used.

Since the glass-forming raw material generates a liquid phase in a high temperature range, it can significantly suppress the diffusion of oxygen from the brick surface. However, if the amount of the glass-forming raw material added is too large, the aggregate will be suspended in the liquid phase, resulting in a significant decrease in hot strength and corrosion resistance. If the amount of the glass forming raw material added is less than 0.5% by weight based on the aggregate mixture, oxidation resistance will be insufficient, and if it exceeds 5% by weight, hot strength and corrosion resistance will decrease. Therefore, 0.5-5% by weight
A particularly preferable addition amount is 1 to 3% by weight.

Although each of the metal powder and glass forming raw material described above is effective when used alone, a combination of the two is more effective in improving oxidation resistance.

Further, as the thermosetting resin, phenol resin, furan resin, epoxy resin, modified phenol resin, melamine resin, urea resin, etc. can be used, but phenol resin or phenol-modified resin is particularly preferred in terms of residual carbon content and price. .

The carbon-containing unfired refractory brick of the present invention is obtained by kneading and molding the above-mentioned raw material composition by a conventional method and then heat-treating (i.e., hardening treatment) in a non-oxidizing atmosphere at 150 to 600°C.

〔Example〕

Examples of the present invention will be described below based on Tables 1 to 4.

In addition, in the following examples, molding and curing treatment conditions are as follows.

・Forming: Hydraulic press ・Shape: 114X115X65mm ・Forming pressure:
1500kgf/cnl・Curing treatment: 200℃×24
Knead, mold, and harden at the mixing ratio shown in Table 1 on one plate for an hour.
An unfired A1z O:I MgOZr0zC brick was obtained. In this example, measurements of various physical properties were carried out by changing the blending amount of ZrO□ of various particle sizes and alumina. Zr
Comparative Example 1 is a conventional product in which O□ is not added, and Comparative Example 9 is a product in which an excessive amount of ZrO is added and no alumina is added.

Compared to the conventional product (comparative example product No. 1), the products No. 2 to No. 8 of the present invention to which magnesia and zirconia are added have excellent corrosion resistance and a large residual expansion rate.

Although Comparative Height Measurement 1b9 has excellent corrosion resistance, it is inferior in durable poling property, and contains 95% by weight of expensive zirconia raw material, so the ratio of cost to improvement in corrosion resistance is large.

〈Left below〉 Knead, mold, and harden the mixture according to the proportions shown in Table 2.
An unfired AlzO:I-MgOZr0zC brick was obtained. In this example, various physical property measurement tests similar to those described above were conducted by changing the blending amount of magnesia having various particle sizes. A conventional product to which no magnesia was added was Comparative Example m1, and a product to which an excessive amount of magnesia was added was shown as Comparative Example 11h17.

In the products of the present invention N11i1 to N11i16, the residual expansion coefficient increases and the amount of erosion decreases due to the addition of magnesia.

Compared to products 1'hl to 16 of the present invention, Comparative Example Product 10 has a slightly smaller residual expansion coefficient, and Comparative Height Measurement 11h17 has inferior spalling resistance, so none of them are suitable.

〈Left below〉 271-Removed property I Knead, mold, and harden at the mixing ratio shown in Table 3,
Unfired A (2203Mg OZ r 02-C brick was obtained) In this example, the amount of graphite blended was changed and various physical property measurement tests were conducted in the same manner as above.A conventional product without graphite added was used as a comparative example. Comparative Example No. 23 was obtained by adding an excessive amount of graphite to m18.

Comparative example Takasho 18, which does not contain graphite, has poor spalling resistance, and comparative example Takasho 23, in which the amount of graphite added exceeds 50% by weight.
In this case, the oxidation resistance is significantly reduced, and the residual expansion coefficient is also reduced.

(Left below) Knead, mold and harden the clay according to the proportions shown in Table 4.
An unfired Alz Os MgOZr0zC brick was obtained. In this example, various physical property measurement tests similar to those described above were conducted by changing the blending amounts of S I Cs 84 C1 borosilicate glass and metal powder (1, MgA1 alloy, metal silicon). Comparative Example 11h32 was shown as Comparative Example 11h32 in which B, C and borosilicate glass were not added.

Comparative measurement N1132 has the SiC content increased from 5% by weight of the present invention product 25 to 40% by weight, and its erosion index has increased from 74 to 120, indicating a significant decrease in corrosion resistance. I understand.

The products of the present invention, 11kL26 and 11h27, have /
1 and added MgA1, resulting in corrosion resistance,
It has the effect of improving oxidation resistance and increasing hot bending strength.

<Alorary margin> 273-3- "1 Life 1 II & 14 shown in Table 1 250 t? The slag line part of the R pig iron car was lined with Comparative Example Product No. 1 (conventional product). When I inspected it for the 187th time I used it,
The brick-lined area of the high-bulk 4 of the present invention is prominent, and its wear rate is 0.18 n+/ch, whereas that of the conventional high-bulk 1 was 0.30+u/ch. That is, the product No. 4 of the present invention had a wear rate about 40% slower than the conventional product No. 1, and had excellent durability.

The methods for measuring the various physical properties listed in Tables 1 to 4 above are listed below.

i. Physical test: According to JIS R2205-74.

ii. Compression test: JIS R2206-77
by.

iii. Bending test: JIS R2213-7
According to 8.

iv. Measurement of residual expansion/shrinkage rate: 25 x 25 x 114 crane specimens were packed in a SiC sagger with coke please, and the rate of change in the length direction of the specimens was measured when treated at 1400°C for 2 hours (repeated 3 times).

■Corrosion resistance (measurement of the amount of erosion): High frequency furnace lining method.

As a treatment agent, a dephosphorizing agent (compounding ratio: iron dioxide 50%, 9 lime (
Using fluorite (CaFz) 30%, fluorite (CaFz) 20%] and soda ash, the process was repeated 4 times in total at 1450° C. by alternately charging and draining every hour.

After the test (processing) is completed, measure the erosion area of the longitudinal cross section of the specimen.

vi. Oxidation wear test: 10 to 15 40U square cube specimens were placed in a horizontal cylindrical furnace previously maintained at 1200°C with an oxygen-propane burner, rotated at 17 rpm for 30 minutes, and then taken out. The weight loss rate of the specimens was determined and compared between the test bricks.

vi. Hot bending test: A 25x25x150 specimen was buried in coke pleat,
After holding at 1400℃ for 30 minutes, the span length was 120℃.
Measured by point method.

vii, Spalling test; 30X30X 150 into molten steel kept at 1500℃
Judgment is made by the cracks found on the sample surface when a 3-minute immersion-air cooling cycle is performed on a 3-mm sample.

〔Effect of the invention〕

As mentioned above, since zirconia is used in the present invention, the zirconia eluted into the slag forms a solid solution of ZrO□ and CaO, which apparently significantly increases the viscosity of the upper slag. By suppressing the movement of slag at the slag-metal interface, the corrosion resistance of bricks can be significantly improved. Since magnesia is used, joint opening is suppressed, and since carbon is used, durability against poling is improved. Furthermore, by using SiC, the antioxidant effect can be maintained for a long period of time, and by adding antioxidants such as various carbides, borides, nitrides, metal fine powders, and glass forming raw materials, Due to improved oxidation resistance, it has become possible to obtain durability that was not possible with conventional bricks.

By lining the slag line with carbon-containing unfired bricks according to the present invention, the service life can be greatly improved, the balance of erosion and damage can be improved, the repair cycle can be extended, and the lining brick can be
This provides benefits such as winding, lighter weight of the kiln, and increased metal capacity. In addition, its uses include converters,
Its effects can be demonstrated in slag line parts such as refining furnaces such as electric furnaces, pig iron mixing cars, hot metal and molten steel ladle, and gutters.

Claims (1)

[Scope of Claims] [1] Total amount of alumina raw material, magnesia raw material, and carbon raw material 90 to 10% by weight, and 10% by weight of zirconia raw material
90% by weight of a carbon-containing unfired refractory brick, and a thermosetting resin. [2] The carbon-containing unfired refractory brick according to claim 1, further comprising 1 to 10% by weight of at least one of carbides, borides, nitrides, and fine metal powders. [3] The carbon-containing unfired refractory brick according to any one of claims 1 to 2, wherein the glass-forming raw material is added in an amount of 0.5 to 5% by weight.