JP2000203931A - Magnesia-carbon slide gate plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the bulk specific gravity of a molding by using earthy graphite as a raw material and to obtain a magnesia-carbon slide gate plate having high strength and excellent wear resistance. SOLUTION: A material composition consisting of 2-6 wt.% one or more of metal powders of Al, Si and Mg or alloy powders of these metals, 1.0-6.2 wt.% self-sintering pitch powder, 0.3-3.2 wt.% earthy graphite and the balance MgO-base aggregate is prepared, 3.0-10 outer wt.% thermosetting resin is added to the composition and the resultant mixture is kneaded, molded and fired in nonoxidizing atmosphere at 800-1,400 deg.C to obtain the objective magnesia- carbon slide gate plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnesia-carbon slide gate plate used for controlling the flow rate of molten metal.

[0002]

2. Description of the Related Art Conventionally, a slide gate plate mounted on a molten metal container and used for controlling the flow rate of the molten metal is:
Carbon-containing refractories represented by alumina-carbon refractories are widely used because of their excellent corrosion resistance and spalling resistance. This refractory has excellent corrosion resistance because carbon is hardly wetted by molten slag and the like, and is chemically stable and hardly reacts with slag. Further, the reason why the spalling resistance is excellent is that carbon has a high thermal conductivity and a low coefficient of thermal expansion.

[0003] However, on the other hand, there is a disadvantage that carbon is easily oxidized. When this oxidation occurs in the slide gate plate, the strength of the slide gate plate is reduced and the molten slag is infiltrated. There was a risk of lowering. Also, the addition of a large amount of carbon causes a reduction in the strength of the brick,
In the slide gate plate, the flow of molten steel and the wear resistance when sliding the plate were reduced. With these things,
For the carbon raw material, it was necessary to select an appropriate raw material and an appropriate addition amount.

On the other hand, as a refractory for refining molten metal, a carbon-containing refractory using a basic aggregate represented by magnesia has been used (JP-A-55-116559, JP-A-5-48661, Fairness 7-108805). Magnesia has a high melting point (2800 ° C.) and is excellent in corrosion resistance to basic slag and molten metal, but has a drawback of poor spalling resistance. For this reason, by combining magnesia with carbon such as flaky graphite, high thermal conductivity and low thermal expansion were imparted, and a magnesia-carbon brick excellent in spalling resistance and corrosion resistance was obtained. A magnesia-carbon brick developed as a refractory for refining molten metal contains 10 to 25% by weight of a carbon material such as scale graphite in order to improve spalling resistance.
However, when this material is used for the slide gate plate, there is a problem that the sliding surface is largely damaged due to insufficient strength, resulting in poor wear resistance.

[0005] The slide gate plate does not need the spalling resistance required for the immersion nozzle or the long nozzle, but is used by being restrained by a bolt or a cotter on a metal frame, so that the flow rate control of the molten metal can be performed safely. It is very important to provide abrasion resistance and high corrosion resistance so that it can be performed smoothly.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a magnesia-carbon slide gate plate having high strength and excellent wear resistance is obtained by improving the bulk specific gravity of a compact by using earth graphite as a raw material. It is to try.

[0007]

According to the present invention, Al, S
i, Mg powder or alloy powder of one or more of these metals, 2 to 6% by weight, pitch powder having self-sintering property, 1.0 to 6.2% by weight, earth graphite 3 ~
3.2 to 10% by weight of a thermosetting resin is added to a raw material composed of an aggregate mainly composed of MgO, and the remainder is kneaded and molded in a non-oxidizing atmosphere. 800-1
Magnesia-carbon slide gate plate fired at 400 ° C. (Claim 1), one or two of metal powders of Al, Si, Mg or alloy powders of these metals
At least one kind is Al metal powder or Si metal powder or Si
2. A magnesia-carbon slide gate plate according to claim 1, wherein said alloy powder is a mixed powder to which said alloy powder is added.
2. The magnesia-carbon slide gate plate according to claim 1, wherein the amount of the pitch powder is 3.0 to 5.0% by weight. The magnesia-carbon slide gate plate according to claim 3, wherein the pitch powder has a softening point of 300 to 450 ° C. (Claim 5) The amount of addition of the ground graphite is 0.5 to 3.0.
The magnesia-carbonaceous slide gate plate according to claim 1, wherein the slide gate plate is in weight%.
2. The magnesia-carbon slide gate plate (claim 7) according to claim 1, wherein the addition amount of the ground graphite is 1.0 to 2.0% by weight.
Magnesia-carbonaceous material comprising 84-91% by weight of O, 3.0-9.5% by weight of C, the balance being Al ₂ O ₃ and SiC, and having a compressive strength of 90 MPa or more and a bending strength at 1400 ° C. of 20 MPa or more. It is a slide gate plate (claim 8).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The magnesia-carbon slide gate plate of the present invention uses Al, Si, M
g of metal powder or alloy powder thereof, pitch powder, earth graphite, and the balance being an aggregate containing MgO as a main component. The major feature of the present invention is that earth graphite is used as graphite.

In conventional magnesia-carbon bricks, scaly graphite has been used exclusively. Although squamous graphite has a great effect on improving spalling resistance, it has a problem that the strength is greatly reduced and the abrasion resistance is poor when used for a slide gate plate. Therefore, in the present invention, a slide gate plate is formed by using earth graphite.
The use of earthy graphite has the effect of improving the bulk specific gravity in the case of forming a molded body, making the structure dense and improving the strength. In addition, since fine powder having an average particle size of about 2 μm is available for the ground graphite, deterioration in strength after oxidation can be suppressed. Since even small amounts of soil graphite are effective,
The lower limit of the addition amount is 0.5% by weight. Conversely, if a large amount of this is added, the strength decrease after oxidation is increased,
The upper limit of the addition amount is 3.0% by weight. A more preferable addition amount of the earth graphite is 1.0 to 2.0% by weight. Since carbon is easily oxidized, one or more of Al, Si, and Mg metal powders or alloy powders thereof are added in order to suppress carbon oxidation and prevent a decrease in strength. The addition amount of these metal powders is 2 to 6% by weight. If it is less than 2% by weight, the effect of preventing oxidation of carbon is not obtained, and if it exceeds 6% by weight, spalling resistance is reduced.

The pitch powder has the effect of lowering the dynamic elastic modulus and improving the spalling resistance. Pitch powder has less decrease in product strength than graphite due to its self-sintering properties. The finer the pitch powder is, the finer the particle is at 1 mm or less, the more easily it becomes compatible with the resin, the better the oxidation resistance, and the better the strength. The lower the softening point of the pitch powder, the more effective in improving the strength. However, if the softening point is too low, the brick structure becomes porous, which is not preferable. The preferred range of the softening point of the pitch powder is 300 to 45.
0 ° C. If the amount of the pitch powder is large, the brick becomes porous and the strength is reduced. The amount of pitch powder added is 1.0 to 6.2% by weight, preferably 2 to 6% by weight. A more preferred addition amount of the pitch powder is 3.5 to 5.0.
% By weight. Others are aggregates containing MgO as a main component.

A thermosetting resin such as phenolic resin is added as a binder to the above raw materials in an amount of 3.0 to 10% by weight, and the mixture is kneaded and molded. If the amount of the thermosetting resin is less than 3.0% by weight, the strength of the molded body is insufficient and handling is hindered. The firing temperature is 800 to 1400 ° C. If the firing temperature is lower than 800 ° C., the reaction of Al acting as a strength developing agent is small, and the product strength cannot be increased. Also,
If the firing temperature exceeds 1400 ° C., metal Al or metal Si
Becomes an oxide, and improvement in corrosion resistance cannot be expected. When metal Al is heated in the presence of carbon, Al ₄ C ₃ is generated, which is hygroscopic at room temperature and causes digestion. However, if metallic Si or Si alloy powder is present, a compound or solid solution of Al ₄ C ₃ and Si can be formed to prevent digestion. Therefore, metal Al is preferably used in combination with metal Si or a Si alloy.

[0012]

Examples (Examples 1 to 3 and Comparative Examples 1 to 4) Novolak-type phenolic resins were added to the various raw material compositions shown in Table 1 in the amounts shown in the same table and kneaded. The magnesia clinker used was sintered magnesia. The kneaded material was formed by a hydraulic press, and then heated to 200 ° C. and dried. The dried compact was fired at 1200 ° C. in a reducing atmosphere filled with carbon breathe to obtain magnesia-carbon brick. Table 1 also shows those outside the scope of the present invention as comparative examples.

That is, Comparative Example 1 does not use earth graphite, Comparative Example 2 uses scale graphite together with earth graphite, and Comparative Example 3 uses earth graphite beyond the range specified in the present invention. In addition, those using scaly graphite and Comparative Example 4 are those using earthy graphite exceeding the range specified in the present invention. Apparent porosity (%), bulk specific gravity, compressive strength (MPa), bending strength (M) of bricks using the raw materials shown in Table 1
Pa) Compressive strength after heat treatment at 1200 ° C for 3 hours (M
Pa), abrasion resistance and spalling resistance were examined. The results are shown in Table 2. Further, Table 2 shows the results of similar tests performed on the bricks of Comparative Examples 1 to 4.
The compressive strengths of the bricks of Examples 1 to 3 and Comparative Examples 1 to 4 are shown in FIG. 1 and compared.

[0014]

[Table 1]

[0015]

[Table 2]

As shown in Table 2, Examples 1 to 3
It can be seen that all of them have excellent compressive strength and abrasion resistance, whereas Comparative Examples 1 to 4 are inferior in compressive strength and abrasion resistance. (Examples 4 to 7, Comparative Examples 5 and 6) Examples 4 to 7
Magnesia-carbon brick was prepared in the same manner as in Examples 1 to 3 using the raw materials shown in Table 3 with the addition amount of the pitch powder kept constant and the addition amount of the earth graphite changed. The firing temperature was 1200 ° C. Table 3 shows Comparative Examples 5 and 6. Comparative Example 5 uses no graphite, and Comparative Example 6 uses earth graphite beyond the range specified in the present invention.

For the bricks using the raw materials shown in Table 3, apparent porosity (%), bulk specific gravity, compressive strength (MP
a), the bending strength (MPa), and the compressive strength (MPa) after heat treatment at 1200 ° C. for 3 hours were examined. Further, Table 4 shows the same test results for the bricks of Comparative Examples 5 and 6. Further, the relations of the compressive strength and the specific gravity of each of the bricks of Examples 4 to 6 and Comparative Examples 5 and 6 with respect to the amount of earth graphite added are shown in FIG.

[0018]

[Table 3]

[0019]

[Table 4]

As shown in Table 4, Examples 4 to 7 are all excellent in compressive strength, while Comparative Examples 5 and 6 are inferior in compressive strength. FIG. 2 shows the compressive strength and the specific gravity of the bulk with respect to the addition ratio of earth graphite corresponding to the examples and the comparative examples. According to this, it can be seen that the compressive strength and the bulk specific gravity increase when the amount of addition of the ground graphite is 0.3 to 3.2% by weight. (Examples 8 to 10 and Comparative Examples 7 to 9)
Magnesia-carbon bricks were obtained in the same manner as in Examples 1 to 3 using the raw materials shown in Table 5 while mainly changing the amount of pitch powder while keeping earth graphite constant. The firing temperature was 1200 ° C. Table 5 shows Comparative Examples 7 to 9. Comparative Example 7 does not use pitch powder, Comparative Examples 8 and 9
Is the one in which pitch powder is used beyond the range specified in the present invention. For bricks using the raw materials shown in Table 5,
Apparent porosity (%), bulk specific gravity, compressive strength (MPa),
The flexural strength (MPa) and the compressive strength (MPa) after the heat treatment at 1200 ° C. for 3 hours were examined, and the results are shown in Table 6. Further, Table 6 shows the results of similar tests performed on the bricks of Comparative Examples 7 to 9. Examples 8 to 1
FIG. 3 shows the relationship between the compressive strength and the apparent porosity of each of the bricks of Comparative Examples 7 to 9 with respect to the amount of pitch powder added.

[0021]

[Table 5]

[0022]

[Table 6]

As shown in Table 6, Examples 8 to 10 are all excellent in compressive strength. On the other hand, Comparative Examples 7 to
No. 9 has small compressive strength and bending strength. FIG. 3 shows the compressive strength and the apparent porosity with respect to the added amount of the pitch powder corresponding to the examples and the comparative examples. According to this, it is understood that the preferable addition amount of the pitch powder is 2 to 8%. (Example 11 and Comparative Example 10) A slide gate plate was manufactured in the same manner as in Example 2 using the raw materials of Example 2 and Comparative Example 1 in Table 1 and used in an actual machine. Table 7 shows the results.
It was shown to. As shown in Table 7, in Example 11, damage to the sliding surface was reduced and the number of times of use was improved. There were no cracks and no problems. In contrast, Comparative Example 10 was used twice.

[0024]

[Table 7]

[0025]

As described above, according to the present invention, a material having high strength and excellent wear resistance can be obtained as compared with magnesia-carbon brick using scale graphite.
A slide gate plate using this can safely and smoothly control the flow rate of the molten metal with high corrosion resistance and wear resistance.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the compressive strength (MPa) of magnesia-carbon in Examples 1 to 3 and Comparative Examples 1 to 4.

Fig. 2 Addition amount (%) of earth graphite and compressive strength (MPa)
FIG. 3 is a diagram showing the relationship between the bulk density and the specific gravity.

FIG. 3 Pitch powder addition amount (%) and compressive strength (MPa)
FIG. 3 is a diagram showing a relationship between the porosity and the apparent porosity.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuo Ito 1 Minami Fuji, Ogakie-cho, Kariya City, Aichi Prefecture Toshiba Cellular Co., Ltd. (72) Inventor Isao Watanabe 1 Minami Fuji, Ogakie-cho, Kariya City, Aichi Prefecture F-term (reference) in Lamix Corporation Kariya Works 4E014 MA12 4G030 AA07 AA36 AA47 AA60 AA61 BA19 BA29 BA33 GA14 PA14

Claims (8)

[Claims] 1. A powdered powder having a self-sintering property of 2 to 6% by weight of one or more of Al, Si and Mg metal powders or alloy powders of these metals, and 1.0 to 6.2% by weight. %, 0.3 to 3.2% by weight of ground graphite, and the balance of 3.0 to 10% by weight of a thermosetting resin is added to a raw material composed of an aggregate containing MgO as a main component. A magnesia-carbon slide gate plate formed by kneading, molding and firing at 800 to 1400 ° C. in a non-oxidizing atmosphere. 2. One or more of Al, Si and Mg metal powders or alloy powders of these metals are mixed powders obtained by adding Si metal powder or Si alloy powder to Al metal powder. The magnesia-carbon slide gate plate according to claim 1, wherein: 3. The magnesia-carbon slide gate plate according to claim 1, wherein the amount of the pitch powder added is 2.0 to 6.0% by weight. 4. The magnesia-carbon slide gate plate according to claim 3, wherein the amount of the pitch powder added is 3.0 to 5.0% by weight. 5. The magnesia-carbon slide gate plate according to claim 1, wherein the softening point of the pitch powder is 300 to 450 ° C. 6. The magnesia according to claim 1, wherein the addition amount of the earth graphite is 0.5 to 3.0% by weight.
Carbon slide gate plate. 7. The magnesia according to claim 1, wherein the addition amount of the ground graphite is 1.0 to 2.0% by weight.
Carbon slide gate plate. 8. The chemical composition is 84 to 91% by weight of MgO, 3.0 to 9.5% by weight of C, and the balance is Al ₂ O ₃
And SiC having a compressive strength of 90 MPa or more, 1
A magnesia-carbon slide gate plate having a bending strength at 400 ° C. of 20 MPa or more.