JP3197681B2 - Method for producing unburned MgO-C brick - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an unburned MgO-C brick having excellent corrosion resistance and heat spalling resistance.

[0002]

2. Description of the Related Art Unburned MgO-C bricks have been used as lining materials in converters, ladles, mixed iron wheels, vacuum degassing furnaces and the like, and have achieved good results. However, with the recent severe operating conditions in each furnace, there is a strong demand for MgO-C non-fired bricks having better durability.
In order to improve the corrosion resistance of the unburned MgO-C brick, the proportion of magnesia may be increased. However, along with that, the amount of carbon decreases, and the heat-resistant spalling property decreases.

Hitherto, it has been known to add pitch powder for the purpose of preventing the heat spalling property from lowering. In these bricks, since the pitch powder was uniformly dispersed in the brick matrix, the entire brick matrix became porous, preventing the propagation of cracks and helping to improve the heat-resistant spalling property. However, the corrosion resistance of the brick is reduced because molten slag, molten metal, and gas easily enter the porous matrix.

As a solution to these problems, for example, as disclosed in Japanese Patent Application Laid-Open No. 1-275463,
A method of using secondary particles produced by adding a binder such as phenol or pitch to primary particles of magnesia and carbon is known.

[0005]

However, even in the above-mentioned method, if the amount of carbon is reduced in order to improve corrosion resistance, sufficient heat-resistant spalling properties cannot be obtained. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an unburned MgO-C brick in which heat resistance spalling property is improved while suppressing deterioration of corrosion resistance.

[0006]

Accordingly, the present inventors have conducted various studies. As a result, by using a specific ratio of granules composed of pitch and magnesia raw materials,
Knowing that the above conventional problems can be solved, the present invention has been completed. In the present invention, the pitch is 10 to 7
Production of unburned MgO-C brick characterized by molding 0 to 10 parts by weight of granulated particles composed of raw material of magnesia, 0 to 10 parts by weight, and a mixture of magnesia and carbon as a main material. Is the way.

The magnesia used in the present invention may be one selected from sintered magnesia, electrofused magnesia, natural magnesite, or a calcined product thereof, or a combination thereof. The particle size is adjusted to coarse, medium, and fine particles so as to obtain a densely packed structure, as in the case of the conventional unburned MgO-C brick.

Although there is no particular restriction on the production method and particle size of the granulated particles, for example, one or more of the above magnesia powders having a diameter of 1 mm or less and a pitch powder having a diameter of 0.2 mm or less are mixed in an appropriate amount as a binder. The liquid phenol resin is added, mixed with a high-speed stirring mixer, and granulated. And about 2
After drying with hot air at 50 ° C., a method of collecting those having a diameter of 3 mm or less with a sieve was used.

In the present invention, the pitch is concentrated in a specific portion of the brick matrix, that is, between the magnesia-containing particles and in the granulated particles, thereby preventing the entire matrix from being uniformly porous as in the prior art. ing.
Of course, voids are generated in the high temperature region in the portion occupied by the granulated particles. Therefore, the amount of voids in the entire matrix increases as the used amount of the granulated particles increases and as the pitch amount in the granulated particles increases.

According to the present invention, the gap prevents the propagation of cracks generated by thermal shock. That is, further propagation of the crack stops at this gap. Therefore, the higher the probability that cracks meet the granulated particles including voids, the better the heat-resistant spalling property. In other words, the effect of preventing crack propagation increases as the amount of particles used increases. However, if the amount used is too large, and if the amount of pitch in the granulated particles is too large, the voids will increase, leading to a decrease in the strength of the brick, and in the worst case, the rate of occurrence of cracks due to thermal shock will increase. That is, too much voids deteriorate the heat-resistant spalling property.

As described above, the inventors of the present invention have conducted various studies on the pitch content in the granulated particles and the amount of the granulated particles, and as a result, have found that crack propagation is prevented, the crack generation rate is low, and the corrosion resistance is further reduced. Not found areas. In this region, the cracks generated by the thermal shock do not easily grow to a size such that the brick will fall off.

[0012] The voids that contribute to the prevention of crack propagation are 15
It exists even in the high temperature range of 00 ° C or higher. Therefore, the diameter of the particles, the amount of pitch in the particles, and the amount of the particles used affect not only the heat-resistant spalling property but also the corrosion resistance. That is, among the diameter, the pitch amount, and the used amount of the granulated particles, particularly when the pitch amount and the used amount are too large, not only the heat-resistant spalling property is not improved but also the corrosion resistance is deteriorated.

[0013] For this reason, the heat-resistant spalling properties are best when the used amount of the particles is 1 to 10% by weight. The pitch amount in the granulated particles is 10 to 7 with respect to 100 parts by weight of the granulated particles.
0 parts by weight is desirable.

Specific types of carbon include phosphorous graphite,
One or more selected from earth graphite, artificial graphite, pitch coke, anthracite, carbon black and the like. The particle size is not particularly limited, but is preferably 0.5 mm or less.

The unburned MgO-C brick may be any of the above-mentioned blends, as well as various metal powders, metal oxides, carbides, borides, nitrides, fibers and the like as long as the effects of the present invention are not impaired. One or two or more selected from the above may be added in an appropriate amount.

Examples of the metal oxide include alumina, spinel, chromia and the like. In the method for producing an unburned MgO-C brick, a compound containing the above-described granulated particles is kneaded and molded.

For kneading, a phenol resin, a furan resin,
The pitch etc. is 2 to 5 by externally applying to the entire refractory composition.
% By weight. The molding is preferably performed using a rubber press so as to obtain a homogeneous structure, but can also be performed by a uniaxial molding method using an oil press or a friction press.
Furthermore, it is also possible to use both rubber press and uniaxial molding. After molding, for example, heat treatment is performed at 100 to 800 ° C. to harden the binder, thereby imparting strength to the molded body.

[0018]

Examples Examples of the present invention and comparative examples are shown below. Table 1 shows Examples of the present invention, Comparative Examples, and test results thereof.

[0019]

[Table 1]

A phenol resin as a binder was added to the formulations shown in the table at a ratio of 4% by weight, and the mixture was kneaded with an Erich mixer, and then 1000 kg / c using a friction press.
It was molded in a regular shape with a pressing force of m ² . Thereafter, the sample was heated at 200 ° C. and cooled to obtain a test brick. Using the test brick thus obtained, tests were conducted for heat resistance spalling resistance and corrosion resistance.

Heat-resistant spalling property: A square pillar-shaped test brick of 40 mm × 40 mm × 114 mm obtained from the above-mentioned normal brick has a length of about 50 mm from one end in the longitudinal direction.
After immersion in hot metal at 00 ° C. for 90 seconds, the operation of forcibly air-cooling to room temperature was repeated. The number of repetitions until peeling is defined as a heat-resistant spalling peeling generation cycle. Those having a large number of cycles of occurrence of heat-resistant spalling spalling were judged to be good, and all of the examples of the present invention obtained good results.

Corrosion resistance: The erosion ratio was calculated by using the rotational erosion method and setting the corrosion resistance of Comparative Example 1 to 100. The corrosion resistance test was performed under the following conditions. Temperature: 1700 ° C, Erosive: 60% steel + slag (CaO / SiO ₂ = 3.0, Total ・ Fe
= 15%) 40%, tap time and number of times: 10 minutes x 20 times

As shown in Table 1, when 10 to 70 parts by weight of the granulated particles is used in an amount of 1 to 10% by weight with respect to 100 parts by weight of the granulated particles, a comparison is made using no granulated particles. In comparison with the heat-resistant spalling spallation occurrence cycle of Example 1 which was four times, each of the samples showed an excellent number of ten times or more.

In Comparative Example 2, the used amount of the particles was 2% by weight, but the pitch content of the particles was less than 10 parts by weight based on 100 parts by weight of the particles. Conversely, in Comparative Example 3, the pitch content of the particles was 10 parts by weight with respect to 100 parts by weight of the particles, but the amount of the particles used was less than 1% by weight. For this reason, both Comparative Examples 2 and 3 are inferior in the number of cycles of the heat-resistant spalling spalling occurrence to four and five.

On the other hand, in Comparative Example 4, the use amount of the granulated particles is 8% by weight, but the pitch content of the granulated particles exceeds 70 parts by weight based on 100 parts by weight of the formed particles. Conversely, Comparative Example 5
Is 70 parts by weight with respect to 100 parts by weight of the granulated particles, but the used amount of the granulated particles is 10% by weight.
Is over. For this reason, in each of Comparative Examples 4 and 5, the number of cycles in which heat-resistant spalling spallation occurred was inferior to five, and the corrosion resistance was also deteriorated.

In Comparative Example 6, the conventional method (Japanese Patent Laid-Open No. 1-2754)
No. 63), the pitch is 5 parts by weight, and the phosphorous graphite is 10 parts by weight as carbon with respect to 100 parts by weight of the granulated particles. In this example, the ability to prevent the propagation of cracks was low because the amount of pitch in the granulated particles was small, and the heat-resistant spalling spalling generation cycle was inferior to four.

In all of the examples, 3% by weight of metallic aluminum is used in the outer case in all cases. However, the use / non-use and the use ratio do not affect the effect of the present invention.

As for magnesia, sintered magnesia was used in the embodiment, but the same effect was obtained by using electrofused magnesia, natural magnesite or a calcined product thereof.

As for carbon, phosphorous graphite was used at 10% by weight in the examples, but the use ratio is not limited, and earth graphite, artificial graphite, pitch coke, anthracite, and carbon black are used. The same effect was obtained.

Actual machine test: Of the unburned MgO-C bricks manufactured in the actual machine shape in substantially the same manner as described in the above-mentioned embodiment, Examples 2, 4, Comparative Example 1 and Comparative Example About No. 3, it was actually constructed and operated under the inclined portion of the 330t converter. The durability was calculated assuming the number of times of use of Comparative Example 1 as 100. In comparison with Comparative Example 1 and Comparative Example 3, 100% or less, Examples 2 and 4 each provided a durability of 120% or more.

The construction site is a site where the temperature fluctuates greatly even inside the converter. As is clear from these results, the unburned MgO-C brick obtained from the example of the present invention exhibited a sufficient effect even in an actual machine. Although the actual machine test was used below the inclined part of the converter, the same effect was obtained in a ladle, a mixed iron wheel, a vacuum degassing furnace, and the like.

[0032]

The unburned MgO-C brick produced according to the present invention has a heat-resistant spalling property and a corrosion resistance inherent in MgO-C refractories by incorporating granulated particles into the blend. As a result, the durability as a lining material for a molten metal processing apparatus is improved by 20 to 25% as compared with the conventional product, and the economic effect is large.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kosuke Kurata 1-1, Hibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Prefecture Nippon Steel Corporation Yawata Works (72) Inventor Hirofumi Inoue Toyohata, Tobata-ku, Kitakyushu-shi, Fukuoka No. 1-1, Nippon Steel Corporation Yawata Works (72) Inventor Kazuhiko Kawasaki 1-1, Higashihama-cho, Yawata-nishi-ku, Kitakyushu-shi, Fukuoka Inside Kurosaki Ceramics Co., Ltd. (72) Toshihiro Suruga Inventor Toshihiro, Fukuoka Prefecture Higashihama-cho, Nishi-ku 1-1 Kurosaki Ceramics Co., Ltd. (56) Reference JP-A-2-311358 (JP, A) JP-A 1-275463 (JP, A) JP-A-61-127672 (JP, A) 57-3762 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/00-35/22

Claims (1)

(57) [Claims] 1. A composition comprising 10 to 70 parts by weight of a pitch, 1 to 10% by weight of granulated particles composed of a magnesia raw material, and magnesia and carbon as a main material. A method for producing unburned MgO-C brick.