JPH09241067A - Mgo-cao based carbon-containing refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive high durability and longevity of a smelting vessel by lining a part of or full surface of the vessel with a molten MgO-CaO based carbon-containing refractory. SOLUTION: The MgO-CaO based carbon-containing refractory is obtained by kneading the raw materials of a blending composition composed of (1) 70-94wt.% MgO-CaO based refractory raw material, which contains >=96wt.% MgO, 1.3-2.7wt.% CaO and 0.1-0.3wt.% SiO2 and in which the CaO/SiO2 ratio is 6-20, CaO inters into a periclase of MgO and the periclase of MgO has 300mμ crystal dimeter, (2) 5-25wt.% carbon based refractory raw material and (3) 1-5wt.% metal Al or one or more kinds of Al-Mg alloys in total with a hinder, molding and drying.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a melting / refining vessel such as a smelting reduction furnace, a scrap melting furnace, a converter, etc., particularly one of the bottom or side wall of a melting / refining vessel used under slag conditions of low C / S. MgO-C that stretches over all parts
It relates to an aO carbon-containing refractory material.

[0002]

2. Description of the Related Art In the melting and refining vessels for molten metal such as smelting reduction furnaces, scrap melting furnaces, converters, etc., which are generally used in the pig steel process, in recent years, aiming at the same efficiency of melting and refining, the bottom blowing Since the stirring power has been strengthened and the secondary combustion ratio has been increased, the refractory linings used there are exposed to severe conditions. Conventionally, MgO-C bricks have been used as refractory linings for these melting and refining vessels.

Particularly in the case of a melting / refining vessel used under a low CaO / SiO ₂ (C / S) slag condition, JP-A-63-248753 or JP-A-63-27.
MgO-CaO- as disclosed in Japanese Patent No. 7557.
C bricks are used. This MgO-CaO-C brick has a function of suppressing the reaction between the slag and the brick because CaO eluted from the brick increases the C / S of the slag with respect to the low C / S slag.

On the other hand, CaO reacts with FeO in the slag and easily forms a low-melting material, which lowers the corrosion resistance of the brick. Therefore, while suppressing the reaction between FeO in the slag and CaO eluted from the brick, the C / S of low C / S slag is suppressed.
In order to take advantage of the advantage of MgO-CaO-C bricks to improve the temperature, JP-A-4-132655 proposes the use of MgO-CaO clinker having a low CaO content.

However, this clinker has CaO distributed in the MgO periclase grain boundaries, and as a result, MgO
O The crystal size of periclase has become smaller, and M has entered the slag.
The gO periclase flows out, and the corrosion resistance is limited. In addition, the finely powdered MgO-CaO clinker has a problem that the hydration reaction is quick and it cannot be stably used as a raw material.

On the other hand, in Japanese Unexamined Patent Publication No. 5-186258 or Japanese Unexamined Patent Publication No. 6-107453, C / S and S in the clinker as an electrofused magnesia clinker.
It is disclosed that the iO ₂ content and the periclase crystal diameter are regulated. However, both are stable MgO
In addition to the fact that the characteristics of -CaO clinker cannot be extracted, there are also problems such as high cost.

On the other hand, with the recent increase in the secondary combustion ratio,
The temperature rises from the slag bath to the atmosphere. as a result,
Oxidation of medium C bricks at high temperatures, wear due to molten steel flow, slag flow, dust, etc. at high temperatures, and heat spalls due to temperature rise of brick working surface have become remarkable. Therefore, with respect to these wear and tears, corrosion resistance, oxidation resistance, wear resistance, spall resistance, or hot strength is particularly required as a characteristic that a brick should have. Although the use of such MgO-C bricks or MgO-CaO-C in addition to bricks also MgO-Cr ₂ O ₃ brick, whereas been tried, no satisfactory results are obtained up to now.

Particularly in MgO-C bricks, the amount of metal added is increased for the purpose of improving oxidation resistance and hot strength. However, on the contrary, the spall resistance is lowered, which is a problem. Further, in order to improve the oxidation resistance, JP-A-3-208862 discloses that SiC is contained in an amount of 1 to 6% by weight.
Addition is described. However, this addition amount is insufficient for improving the oxidation resistance, and conversely, there is a problem that the corrosion resistance decreases.

[0009]

As described above, the conventional Mg
For OC bricks and MgO-CaO-C bricks,
Although there are means for improving the oxidation resistance and hot strength, there is a problem that the corrosion resistance and spall resistance are deteriorated, and there is no means for simultaneously satisfying the above five characteristics.
The present invention has been developed in view of such problems, and MgO- that can improve corrosion resistance, wear resistance, spall resistance, and hot strength without impairing oxidation resistance.
It is intended to provide a refractory material containing CaO-based carbon.

[0010]

In order to achieve the above object, according to the present invention, (1) MgO content is 96% by weight or more, CaO content is 1.3 to 2.7% by weight, and SiO _{2 is} contained. 0.1 to 0.3% by weight, CaO / SiO ₂ ratio (C
/ S) is 6 to 20, CaO is solid-dissolved in MgO periclase, and the MgO periclase has a crystal diameter of 300 μm or more.
~ 94% by weight, (2) C-type refractory raw material such as scaly graphite 5-2
5% by weight, and (3) 1 to 5% by weight of one or more of metallic Al or Al-Mg alloys in total, 1 to 5% by weight (1), (2), and (3). A refractory material containing MgO-CaO-based carbon, which is obtained by kneading and molding a raw material having a composition with a binder such as phenol resin, and then drying the kneaded material is provided.

Further, with respect to 100 parts by weight of the raw material having the compounding composition composed of (1), (2), and (3), the maximum particle size [X] (μ) and the external weight Si that satisfies the relationship of the following expression (1) with the addition amount [Y] (parts by weight)
A MgO-CaO-based carbon-containing refractory obtained by adding a C raw material, kneading and molding with a binder, and then drying is also useful. [Y] ≦ 3log [X] ………… (1)

In particular, to 100 parts by weight of the raw material having the compounding composition composed of (1), (2), and (3) above, 8 parts by weight of a SiC raw material having a particle diameter of 0.1 to 0.5 mm is applied. Parts or less, or by adding 10 parts by weight or less of a SiC raw material having a particle size of 0.5 to 1.0 mm, the spall resistance is significantly improved. Also, the above (1), (2), and (3)
By adding 3 parts by weight or less of an SiC ultrafine powder material having a particle size of 10 μm or less to 100 parts by weight of a raw material having a compounding composition composed of, the hot strength and wear resistance are significantly improved.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION MgO used in the present invention
-The reason for defining the CaO content of the CaO refractory raw material is as follows. When CaO exceeds 2.7% by weight, M
gO Periclase could not be completely dissolved in C
aO is distributed, and as a result, the crystal size of MgO periclase is reduced. This causes the clinker to flow out after the CaO component distributed at the grain boundaries is eluted into the slag, and the corrosion resistance is limited. Further, when the amount of CaO distributed at the grain boundaries is large, the MgO-CaO quality refractory raw material becomes fine powder, so that the activity thereof increases and the hydration reactivity increases, so that it cannot be stably used as a raw material for bricks.

On the other hand, when the content of CaO is less than 1.3% by weight, the high C / S ratio of the low C / S slag cannot be achieved, and there is no great difference from the fused magnesia clinker. Therefore,
The CaO content is 1.3 to 2.7% by weight. Further, M
Regarding the SiO ₂ content of the gO-CaO refractory raw material,
If it exceeds 0.3% by weight, it becomes easy to form a CS-based compound and the corrosion resistance decreases. On the other hand, if the content is less than 0.1% by weight, CS-based compounds are difficult to form, but CaO that could not be completely dissolved in MgO periclese will be present in a free state, causing problems of hydration and price increase. Will occur.

In the MgO-CaO quality refractory raw material used in the present invention, CaO is not distributed at grain boundaries, and CaO is M
It is preferable that the gO periclase completely exists as a solid solution and stably exists. Therefore, the SiO ₂ content is 0.1
It needs to be 0.3% by weight. At the same time,
C / S in the MgO-CaO refractory raw material is in the range of 6 to 20, and further, from the viewpoint of the corrosion resistance, MgO.
It is also necessary that the crystal size of periclase is 300 μm or more. The MgO-CaO refractory raw material having such a component composition may be produced by either electrofusion or sintering, but from the viewpoint of CaO forming a solid solution, an electromelted product is preferable. Think

Next, in the present invention, in order to suppress deterioration of corrosion resistance, the amount of SiC added is limited by its maximum particle size. That is, SiC is C existing in the brick.
S reacts with O gas and reacts with S as shown by the following equation.
Generate iO ₂ . SiO + CO → SiO + C ... (2) SiO + CO → SiO ₂ + C ... (3)

The SiO ₂ thus produced forms a glass film and serves to prevent the oxidation of C. However, Mg
In the O-C system, since the viscosity of this glass film is high, Si
Unless C is added in a large amount, the antioxidant effect on C cannot be fully exhibited. In addition, SiC itself has a high hardness, and when a small amount of SiO ₂ is produced, it fills the voids of the structure, and therefore has the effect of improving wear resistance. However,
On the contrary, when a large amount of SiO ₂ is produced, the corrosion resistance decreases.

As described above, SiC has a side surface that improves the wear resistance of bricks, but has a side surface that deteriorates corrosion resistance. Therefore, sufficient consideration must be taken when adding to bricks. Generally, as the solid becomes finer, the activity of the surface of the particle increases, so that the reactions of the above formulas (2) and (3) proceed faster, and a large amount of SiO ₂ is produced, resulting in a decrease in corrosion resistance. To do. On the other hand, when the solid particles become large, the reactions of the above formulas (2) and (3) are limited only to the particle surface, and the amount of SiO ₂ produced is suppressed. As a result, the decrease in corrosion resistance is small.

Therefore, when adding SiC in the form of fine powder,
It is possible to reduce the amount used, and therefore to increase the amount used in the case of adding medium particles to coarse particles. In the present invention, as a result of various experimental investigations, SiC that can improve wear resistance without impairing corrosion resistance
It has been found that the relationship between the maximum particle size [X] (μ) and the added (used) amount [Y] (wt%) is [Y] ≦ 3 log [X].

On the other hand, SiC has a smaller coefficient of thermal expansion than MgO, and when heated, it forms microcracks due to the difference in expansion from MgO, lowers the elastic modulus of the brick, and improves spall resistance. In forming the microcracks, it is preferable to add as much medium- to coarse-grained SiC as possible so that only the surface layer of SiC reacts and the inside remains unreacted. Therefore, the particle size is 0.1
~ 0.5 mm SiC raw material is 8 parts by weight or less on the outside,
For SiC raw material with a particle size of 0.5 to 1.0 mm, it is 10
It is best to add less than 100 parts by weight to 100 parts by weight of the MgO-CaO refractory raw material.

Even if a SiC raw material having a particle size smaller than the above is added, the elastic modulus is less decreased, and the corrosion resistance is rather decreased, which is not preferable. Further, addition of a SiC raw material having a particle size larger than this causes a large decrease in elastic modulus but causes a decrease in structure strength and an increase in cost, which is not preferable.

Next, in order to improve the hot strength, it has been general practice to increase the content of metallic Al or Al-Mg alloy. However, since these Al-based metals once become oxides via Al ₄ C ₃ which is a carbide, they are accompanied by volume expansion, and at the same time, there arises a problem that the elastic modulus increases and the spall resistance decreases. There were also problems such as easy sublimation.

On the other hand, as in the present invention, MgO--
When SiC is used together with the CaO-based refractory raw material, SiO ₂ produced by oxidation of SiC and CaO, MgO
Reacts with each other to produce a CMS-based compound, so that the hot strength is improved. This reaction occurs around the MgO—CaO refractory raw material dispersed in the matrix without volume change, and therefore has a large bonding effect and is also useful for strengthening the structure (improving wear resistance). This effect is particularly great when using SiC ultra-fine powder, and when adding SiC ultra-fine powder with a particle size of 10 μm or less to 100 parts by weight of MgO—CaO refractory raw material, the external addition amount is 3 parts by weight or less. If so, there is little deterioration in corrosion resistance.

As the C-type refractory raw material used in the present invention, any graphite can be used regardless of its purity, and amorphous graphite, carbon black, mesophase carbon and the like can also be applied. Further, as the Al-based metal, Al, Al-Mg alloy can be applied. However, if the addition amount exceeds 5% by weight, the spall resistance decreases, and if it is less than 1%, it is not effective in improving the oxidation resistance and the hot strength. Metals other than Al and Al-Mg alloys can be appropriately used as needed. On the other hand, as the SiC raw material, a material having a purity of 97% or more is preferable, but a low purity material is also applicable.

Brick can be provided as a non-fired product by kneading and molding with a binder such as phenol resin, tar and pitch, and then drying. Further reduction firing and tar impregnation treatment improve the characteristics. These bricks can be applied to the bottom of smelting and refining vessels such as smelting reduction furnaces, scrap smelting furnaces, converters, and the entire lining of side walls. In particular, it is even more effective when applied to a site with large wear.

[0026]

EXAMPLES Examples will be described below with reference to the drawings and tables. Each sample in Table 1 and Table 2 is a fused 99% pure Mg
O clinker, 99% pure scaly graphite, 99% pure S
After using the iC raw material and kneading and molding with phenol resin as a binder with the composition shown in the table, 20
It was dried under the condition of 0 ° C. × 24 Hrs and subjected to the evaluation test.
Corrosion resistance was 1700 ° C. × 3 Hrs, C / S = 1.
The slag of No. 2 was used to display the size of the melt-damaged by the rotary erosion method as an index, and It was shown as a melt loss index with 1 being 100. The abrasion resistance was measured by measuring the amount of reduction when MgO powder was sprayed by a thermal spray burner under the condition of 1600 ° C. × 1 Hr. It was shown as a wear index with 7 being 100. The elastic modulus was measured by measuring the kinetic elastic modulus after reduction firing under the condition of 1400 ° C. × 3 Hrs. The hot strength was measured by a 3-point bending method in a reducing atmosphere at 1400 ° C. In addition, the spall resistance was measured by the air-cooling heat spall test at 1500 ° C., and the number of times until the sample was broken was measured.

First, Table 1 shows the evaluation test results of various MgO-CaO quality refractory raw materials. Here, when the CaO content is 2.9% or more (No. 1, 2, 3), 0.8%
At this time (No. 12), the MgO—CaO quality refractory raw material has a large melt loss index of 88 or more. Even if the CaO content is in the range of 2.7 to 1.3%, the C in the clinker is
Those having a / S of less than 6 (Nos. 5 and 6) have a periclase crystal diameter of less than 300 μ and are not so good in corrosion resistance.
Moreover, C / S exceeds 20 (No. 10)
Since it is difficult to use the MgO-CaO refractory raw material in the fine powder portion, it is necessary to use electrofused MgO, and therefore the corrosion resistance is also deteriorated.

Next, Table 2 shows the evaluation test results of various SiC raw materials and Al-based metals. Here, Al and Al-Mg
The total alloy content exceeds 5% by weight (No. 13, 2)
2), the spall resistance is reduced. On the other hand, No. 1 containing medium-sized (particle size 0.1 to 1.0 mm) SiC was added. 1
Nos. 5 and 16 are No. Although the corrosion resistance is almost the same as that of No. 7, the dynamic elastic modulus is significantly reduced, and the hot strength and wear resistance are slightly improved. Further, addition of SiC ultrafine powder is extremely effective in improving hot strength and wear resistance (No. 17).
~ 20), the addition amount exceeds 3% by weight (No. 17)
And, the corrosion resistance is significantly reduced.

FIG. 1 shows the relationship between the maximum grain size of SiC and the addition amount with respect to corrosion resistance. Corrosion resistance was significantly deteriorated in the region above the straight line in the figure. Further, from Table 2, the wear resistance is improved in all the samples to which SiC is added, and the wear resistance is improved as the particle size of the added SiC is smaller and the amount thereof is larger. On the other hand, the dynamic elastic modulus is such that the particle size of the added SiC is 144
It did not change so much at μ or less, and tended to decrease as the addition amount increased at 200 to 500 μ,
Not very noticeable.

FIG. 2 shows the relationship between the particle size and amount of SiC added and the dynamic elastic modulus. When medium-sized SiC is added (0.1
.About.0.5 mm and 0.5 to 1 mm), the dynamic elastic modulus significantly decreases as the addition amount increases, and the corrosion resistance does not deteriorate,
Abrasion resistance is also improved. However, SiC less than 0.5 mm
In the case of adding, the change in the dynamic elastic modulus was slight even when the addition amount was increased, while the wear resistance was improved. However, if the addition amount is 8% by weight or more, the corrosion resistance deteriorates. Therefore, in order to improve the corrosion resistance and wear resistance,
The area near or below the straight line is most suitable. To further improve spall resistance, medium-grained S
Addition of iC (8% by weight or less if the particle size is 0.1 to 0.5 mm, 10% by weight or less if the particle size is 0.5 to 1 mm) is effective.

[0031]

[Table 1A] * 1) Electro-fused MgO was used as a substitute because MgO-CaO cannot be used for all amounts due to the grain size composition.

[0032]

[Table 1B] * 1) Electro-fused MgO was used as a substitute because MgO-CaO cannot be used for all amounts due to the grain size composition.

[0033]

[Table 2A] * 2) Table 1. Uses No.8 MgO-CaO clinker * 3) External hanging

[0034]

[Table 2B] * 2) Table 1. Uses No.8 MgO-CaO clinker * 3) External hanging

[0035]

INDUSTRIAL APPLICABILITY According to the present invention, not only the wear resistance and spall resistance of a refractory material containing MgO-CaO-based carbon can be improved but also the hot strength can be improved, and a smelting reduction furnace, a scrap melting furnace, a converter, etc. It is possible to significantly improve the durability of the refractory lining on the bottom and side walls of the melting and refining vessel. This not only reduces the cost of furnace materials and repairs, but also stabilizes production.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the maximum grain size of SiC and the addition amount with respect to corrosion resistance.

FIG. 2 is a diagram showing the relationship between the particle size and amount of SiC to be added and the dynamic elastic modulus.

Front Page Continuation (72) Inventor Yasuhiro Yamada 5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Co., Ltd. Nagoya Steel Works

Claims (4)

[Claims] 1. A MgO content of 96% by weight or more,
CaO content is 1.3 to 2.7% by weight, SiO ₂ content is 0.1 to 0.3% by weight, CaO / SiO ₂ ratio (C /
S) is 6 to 20 and CaO is solid-dissolved in MgO periclase, and the MgO periclase has a crystal diameter of 300 μm or more.
(2) 5 to 25 wt% of C-type refractory raw material, and (3) metal A
1 or 2 or more of Al or Al-Mg alloys in a total amount of 1 to 5% by weight, and kneading the raw materials of the compounding composition composed of (1), (2), and (3) together with a binder.
A MgO-CaO-based carbon-containing refractory material obtained by molding and then drying. 2. The maximum particle size [X] is further added to 100 parts by weight of the raw material having the compounding composition shown in claim 1.
MgO-CaO obtained by adding a SiC raw material in which (μ) and the added amount [Y] (parts by weight) in the external coating satisfy the relationship of the following equation, kneading and molding with a binder, and then drying.
Refractory containing high quality carbon. [Y] ≦ 3 log [X] 3. A particle size of 0.1 to 100 parts by weight of the raw material having the compounding composition shown in claim 1 is further added.
8 parts by weight or less of 0.5 mm of SiC raw material or 1 of externally applied SiC raw material of particle size 0.5 to 1.0 mm
A MgO-CaO-based carbon-containing refractory obtained by adding 0 parts by weight or less, kneading and molding with a binder, and then drying. 4. To 100 parts by weight of the raw material having the composition shown in claim 1, 3 parts by weight or less of SiC ultrafine powder having a particle size of 10 μ or less is externally added and kneaded with a binder. , M obtained by molding and then drying
Refractory containing gO-CaO carbon.