JPH07102987B2 - Carbon-containing refractory - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon-containing refractory material mainly used for hot metal pretreatment.

[0002]

2. Description of the Related Art Recent advances in steel technology have transformed Japan's refractory technology. Among them, the progress of composite blowing technology, hot metal pretreatment technology, secondary refining technology and continuous casting technology has a great influence on the improvement and development of refractories. Mg was developed along with the progress of these steel technologies.
O-C, is a carbon-containing refractories such as Al ₂ O ₃ -SiC-C.

Carbon-containing refractories are excellent in resistance to slag and have low cracking susceptibility. As is well known, these characteristics are brought about by carbon. Carbon does not easily wet the slag, and since the slag is prevented from penetrating into the structure of the brick, the carbon-containing refractory is less likely to cause structural spalling as compared with the conventional brick. Further, due to the high thermal conductivity of carbon, the carbon-containing refractory has excellent resistance to thermal spalling. However, carbon has a drawback that it becomes completely ineffective when it is lost by oxidation. Further, it has a drawback that it is difficult to increase the strength of the refractory because it does not bond with the oxide. Therefore, in carbon-containing refractories, suppression of carbon oxidation and enhancement of strength are the most important themes for improvement.

For example, a refractory for hot metal pretreatment is A
l ₂ O ₃ -SiC-C bricks are used. This type of refractory is added with tar, pitch, phenol resin, etc. as a binder, kneaded and molded, and the binder is carbonized by heat received during drying, firing, or during use to form a so-called carbon bond. However, the carbon bond is inferior in strength as compared with the conventional ceramic bond which is a refractory bonding mode, and there is a problem in oxidation resistance. Furthermore,
Carbon or silicon carbide is inferior in corrosion resistance to the soda system and lime-based flux, Al ₂ O ₃ -SiC-C brick is observed a tendency that the matrix is damaged prior to use. As a result, the Al ₂ O ₃ aggregate having high corrosion resistance may result in separation from the brick structure without utilizing its characteristics. Therefore, in order to overcome the drawbacks of the carbon-containing refractory material, it is necessary to improve the corrosion resistance and the oxidation resistance of the matrix portion.

Various studies have heretofore been made to improve the corrosion resistance of carbon-containing refractory materials. For example, as the aggregate, a high-purity product or an electromelted product is used when high corrosion resistance is required. Further, as a graphite raw material, a material having high purity and low ash content is often used. On the other hand, in order to improve the oxidation resistance, addition of various metals, borides such as B ₄ C, and glass powder have been tried. Although these measures have dramatically improved the performance of carbon-containing refractories, they have not reached a satisfactory level due to the severer operating conditions.

Further, various studies have been made on chromium-containing refractories. For example, JP- A- 1-320262 discloses that 3 to 50% by weight of graphite and an aluminum-containing metal are
The amount of 0.5 to 10% by weight and 0.7 to 16% by weight of one or more of chromium compounds such as metallic chromium and chromium carbide and chromium boride, and the balance being magnesia. An unfired magnesia carbon brick consisting of a clinker is disclosed. The brick of the present invention has high corrosion resistance by suppressing elution of low-basic slag of magnesia aggregate by adding metallic chromium and a chromium compound, and a converter, a stainless steel melting furnace, Fe-Cr
Smelting reduction furnace, iron and steel smelting reduction furnace, scrap melting furnace, F
Although suitable for e-Mn refining furnace, it exhibits high corrosion resistance as a hot metal pretreatment brick, but has a large coefficient of thermal expansion.
Since mechanical spalling is likely to occur, there is a problem in long-term use in a hot metal pretreatment container such as a kneading car.

Further, in Japanese Patent Laid-Open No. 3-90271, a carbonaceous fiber having a diameter of 0.2 mm or less and a length of 1 to 5 mm is added to a compound containing alumina as an aggregate and carbon and metal fine powder to 0.5. ~ 3 parts by weight, 0.5 to 3 parts by weight of boron carbide, 0.5 to 10 parts by weight of chromium carbide, phenolic resin or pitch as a binder, kneading, molding, and heat treatment at 700 ° C or lower. Unfired sliding nozzle plate bricks are disclosed. However, this product is suitable as a sliding nozzle plate brick for tundish, but it is difficult to disperse carbonaceous fibers uniformly, and the amount of carbon added is as small as 5% by weight, which is poor in spalling resistance and long. It is insufficient as a container for hot metal pretreatment used for a certain period.

Further, in JP-A-3-232765, 3 to 30% by weight of graphite, 0.5 to 10% by weight of metallic aluminum, and one of non-oxidizing chromium compounds such as metallic chromium and chromium carbide. Or 1 or more of 2 or more in terms of Cr ₂ O ₃
10 to 10% by weight, the balance is made of Al ₂ O _{3 2} to 15% by weight of a thermosetting resin to a refractory material, and after kneading and molding 8
A high corrosion resistance alumina-carbonaceous refractory heat-treated at 00 ° C or below is disclosed. Although this refractory is suitable as a lining material for molten metal furnaces such as hot metal trucks, it is difficult to say that it has sufficient oxidation resistance, and even now, the improvement theme of carbon-containing refractories is oxidation resistance, corrosion resistance and hot strength. Improvements are currently being addressed.

Accordingly, it is an object of the present invention to provide a carbon-containing refractory having excellent corrosion resistance and oxidation resistance of the matrix.

[0010]

The carbon-containing refractory material according to the present invention contains 5 to 25% by weight of carbonaceous raw material and 1 to 5% of silicon carbide.
It is characterized in that it contains 20% by weight and 1 to 10% by weight of chromium carbide, and the balance is made of a refractory aggregate other than carbon.

The carbon-containing refractory material according to the present invention contains 5 to 25% by weight of carbonaceous raw material, 1 to 20% by weight of silicon carbide, 1 to 10% by weight of chromium carbide, metal Al, metal Si, ferrosilicon, It is characterized in that it contains 0.5 to 8% by weight of one or more components selected from the group consisting of Al-Mg and boron carbide, with the balance being alumina.

[0012]

The carbon-containing refractory of the present invention is a carbon-containing refractory in which silicon carbide and chromium carbide are used together within the above-mentioned addition range, and the remainder is a refractory aggregate other than carbon. It has excellent corrosion resistance as well as excellent oxidation resistance due to the coexistence of chromium carbide and silicon carbide.

Further, in order to further improve the hot strength and oxidation resistance of the carbon-containing refractory, metals such as Al, Si, ferrosilicon and Al-Mg, alloy powder and boron carbide are added in an amount of 0.5 to 8 weight. % Is also an effective means.

The carbon-containing refractory material of the present invention comprises Cr ₇ C ₃ , C
Chromium carbide having the chemical formula of r ₃ C ₂ is CaO-CaF _2-.
The present invention focuses on the fact that it exhibits high corrosion resistance to FeO-based dephosphorization slag and blast furnace slag with a relatively low basicity, and that it significantly improves the oxidation resistance of carbon-containing refractories when used in combination with silicon carbide.

Regarding the addition of the chromium-based raw material, as described above, JP-A-1-320262, JP-A-3-232765,
Although proposed in Japanese Patent Laid-Open No. 3-90271 and the like, all of them are focused on the high corrosion resistance of the chromium-based raw material. On the other hand, the carbon-containing refractory of the present invention not only makes use of the high corrosion resistance characteristic of chromium carbide, but also uses silicon carbide in combination to suppress the oxidation of graphite, which is the greatest drawback of the carbon-containing refractory. It has a feature. That is, although the corrosion resistance is obviously improved in the laboratory by the addition of chromium carbide, there is a problem in the oxidation resistance of carbon in the refractory, so that high durability is not necessarily obtained in the actual furnace. The present inventors have found that the combined use of chromium carbide and silicon carbide makes it possible to remarkably improve the oxidation resistance without impairing the corrosion resistance of the carbon-containing refractory, and has achieved both the corrosion resistance and the oxidation resistance which have not been found in the past. A carbon-containing refractory has been completed.

The purpose of adding silicon carbide to Al ₂ O ₃ --SiC--C bricks is to prevent carbon oxidation. However, silicon carbide is basically inferior in corrosion resistance, and excessive addition is not preferable. In the present invention, it has been noted that the combined use of chromium carbide, which has high corrosion resistance and oxidation resistance similar to that of silicon carbide, complements the drawbacks of silicon carbide, and at the same time, the combined use with silicon carbide dramatically improves the oxidation resistance. It is a thing.

The composition of the carbon-containing refractory material of the present invention will be described in detail below. First, as the carbon to be added, natural scaly graphite, artificial graphite, earthy graphite, carbon black and the like are used, but basically, it is preferable to mainly use high-purity raw materials. The amount added is 5 to 25% by weight. If it is less than 5% by weight, the spalling resistance tends to be low and 25
If it exceeds 5% by weight, the corrosion resistance tends to decrease and the oxidation resistance tends to deteriorate.

Silicon carbide is effective in reducing the expansion of refractory and suppressing the oxidation of carbon. Addition amount is 1 to 20% by weight
Is preferable, and the characteristics cannot be utilized outside this range.
That is, if it is too small, it has no effect on oxidation resistance and low expansion,
If it is too much, the corrosion resistance will be reduced.

Next, the addition amount of chromium carbide is 1 to 1
A range of 0% by weight is preferred. If it is less than 1% by weight, the feature of high corrosion resistance is not recognized. The improvement of the corrosion resistance is remarkable in the range of 1 to 10% by weight, and the expected effect cannot be recognized even if it exceeds 10% by weight. Further, 10% by weight or less is appropriate in consideration of economy.

The effect of the carbon-containing refractory material of the present invention can be obtained by using carbon silicon and carbon chromium in combination. As shown in FIG. 1, in the Al ₂ O ₃ -C type brick, the addition of chromium carbide significantly improves the corrosion resistance. Further, as shown in FIG. 2, high corrosion resistance can be obtained even in a system in which chromium carbide and silicon carbide are used in combination with an Al ₂ O ₃ —C type brick. However,
As is clear from FIG. 2, when the amount of silicon carbide added exceeds 20% by weight, the corrosion resistance decreases and the characteristics of chromium carbide are impaired. FIG. 3 shows the effect of chromium carbide and silicon carbide in an Al ₂ O ₃ —C brick on the oxidation resistance (the thickness of the oxide layer after firing at 1400 ° C. in the air for 3 hours). Oxidation resistance is improved by the combined use of silicon carbide and chromium carbide.
From these experimental results, it was found that the combined use of silicon carbide and chromium carbide makes it possible to improve the oxidation resistance without impairing the corrosion resistance.

The carbon-containing refractory material of the present invention uses, for example, alumina as an aggregate. Examples of the alumina aggregate include fused alumina, sintered alumina, bauxite, and shale shale. Also, depending on the conditions of use, the aggregate is electrofused magnesia,
Select and use from sintered seawater magnesia clinker, electrofused spinel, etc. The amount of these aggregate raw materials used is 40 to 90
Weight percent is preferred. If it is less than 40% by weight, the corrosion resistance is poor, and if it exceeds 90% by weight, the spalling resistance is lowered.

In the carbon-containing refractory of the present invention, in addition to the above raw materials, metallic aluminum, metallic silicon, ferrosilicon,
It is also possible to improve the hot strength and the oxidation resistance by adding 0.5 to 8% by weight of one or more metals such as Al-Mg, alloys and borides such as B ₄ C. . If the amount of these additives is less than 0.5% by weight, the effect is insufficient. If the amount of these additives exceeds 8% by weight, spalling resistance and corrosion resistance are deteriorated, so the addition amount is 0.5 to 8% by weight. Is preferred.

As the binder used in the carbon-containing refractory material of the present invention, phenol resin, pitch-modified phenol,
Furan resin, urea resin, pitch, etc., which can be kneaded and molded and then heated at a temperature of 150 to 300 ° C. to obtain an unfired refractory material, or can be fired in a reducing atmosphere to obtain a fired brick.

[0024]

EXAMPLES Examples 1 to 7 of the present invention, 8 to 9 of comparative inventions 3 to 4% by weight of a phenol resin as a binder was added externally to the formulations shown in Table 1 and kneaded, and after molding, at 200 ° C. for 10 hours. Heat treatment is applied to the products of the present invention 1 to 7 and the comparative product 8 to
An unfired refractory material shown in No. 9 was prepared. The results of characteristics of the obtained refractories are also shown in Table 1.

[0025]

[Table 1]

Test method Corrosion resistance test: Rotating drum method, oxygen / propane burner used, 1400 ° C./5 hours, hot metal pretreatment slag (C
aO.CaF ₂ .Fe ₂ O ₃ ) and the evaluation is shown by an index with the corrosion resistance of the comparative product (8) being 1.00. Oxidation resistance test: burning in a heavy oil furnace, air atmosphere 1400 ° C / 3
Measure time and oxide layer thickness. The evaluation is based on the thickness of the oxide layer of the comparative product 1, and when the value is smaller than that, it is "good", and when it is larger, it is "bad".

Actual furnace test In the mixed pig car slag line, the product 8 of the comparative product 8 had a tonnage of 280,000 tons, but when the product 4 of the present invention was used, the result was 310,000 tons.

[0028]

As described above, according to the carbon-containing refractory of the present invention, the damage pattern due to the preceding dissolution of the matrix portion is almost avoided, the oxidation resistance is obtained, and the life can be extended. . Further, the corrosion resistance to the hot metal pretreatment slag can be improved by about 10 to 40%.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of chromium carbide added and the corrosion resistance (index) in an Al ₂ O ₃ —C brick.

FIG. 2 is a graph showing the relationship between the amount of silicon carbide added and the corrosion resistance (index) in an Al ₂ O ₃ —C-based brick containing chromium carbide or containing 7.5% of chromium carbide.

FIG. 3 is a graph showing the relationship between the added amounts of chromium carbide and silicon carbide and the oxide layer thickness (index) in an Al ₂ O ₃ —C-based brick.

Claims (2)

[Claims] 1. A carbonaceous raw material is contained in an amount of 5 to 25% by weight, silicon carbide is included in an amount of 1 to 20% by weight, and chromium carbide is included in an amount of 1 to 10% by weight, and the balance is made of a refractory aggregate other than carbon. Characteristic carbon-containing refractory. 2. A carbonaceous raw material in an amount of 5 to 25% by weight, silicon carbide in an amount of 1 to 20% by weight, chromium carbide in an amount of 1 to 10% by weight, metal Al, metal Si, ferrosilicon, Al-Mg, and boron carbide. A carbon-containing refractory material comprising 0.5 to 8% by weight of one or more components selected from the group, and the balance being alumina.