JP3276461B2 - MgO-C non-fired 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 structure to be provided in 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.
A large amount of magnesia particles is observed in the structure of the unburned MgO-C brick having improved corrosion resistance. However, bricks having such a structure have low heat-resistant spalling properties due to a small amount of carbon.

Heretofore, pitch has been found in the matrix of bricks in which a decrease in heat-resistant spalling properties has been prevented.
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 low because the molten slag, the molten metal, and the gas easily enter the porous matrix.

[0004] As a brick structure that solves these problems, for example, a structure in which a magnesia raw material and carbon are dispersed in a matrix in the form of a mixture of phenol, pitch, or the like, as seen in Japanese Patent Application Laid-Open No. 1-275463, is known. Are known. In addition, Japanese Patent Application Laid-Open No. 2-167855
In the method disclosed in Japanese Patent Application Laid-Open Publication No. H11-264, a structure in which a phenol resin is present on the surface of coarse-grained aggregate is proposed.

[0005]

However, even in the above-mentioned method, sufficient heat-resistant spalling property is not exhibited when a structure having a small amount of carbon is used in order to improve corrosion resistance. When the phenol resin is present on the surface of the coarse-grained aggregate, in addition to the above-mentioned disadvantages, the residual carbon is amorphous, so that the corrosion resistance is poor. An object of the present invention is to provide a structure that should be included in the MgO—C-based unfired brick, in which heat resistance spalling property is improved while suppressing a decrease in corrosion resistance.

[0006]

Accordingly, the present inventors have conducted various studies. As a result, the present inventors have found that the above-described conventional problem can be solved by the presence of a layer composed of pitches and voids (hereinafter, referred to as an edge layer) with a specific thickness around the magnesia particles. That is what led to it. That is, the present invention is an unburned MgO-C brick characterized by exhibiting a structure containing 10 to 50% by volume of magnesia particles having a layer having a thickness of 5 to 100 μm including voids and pitches.

[0007] The magnesia particles used in the brick of the present invention are one or more selected from sintered magnesia particles, electrofused magnesia particles, natural magnesite particles or calcined products thereof. The particle size of these magnesia is dispersed in the brick structure as coarse, medium and fine particles so as to obtain a tightly packed brick, similarly to the conventional unburned MgO-C brick.

The pitch constituting a part of the marginal layer existing around the magnesia particles includes powder pitch and tar, but the type is not limited.
Tar can also have the same effect as powder pitch.

Although there is no particular restriction on the method of causing the edge layer to be present around the magnesia particles, in the embodiment of the present invention, one or two of the above magnesia particles preheated at a temperature at which the powder pitch melts and flows sufficiently. A method was used in which powder pitch was applied to particles of more than one kind. The particle size of the magnesia particles having the edge layer is not particularly limited, but in order for the edge layer of the present invention to have a sufficient effect on the heat-resistant spalling property, the magnesia particles having a diameter of 1 mm or more and less than 6 mm are used. Is preferably a tissue having an edge layer.

[0010] In the present invention, by forming a structure in which the pitch exists only around the magnesia particles, uniform porosity of the entire matrix which is observed in the structure obtained by the prior art is prevented. In the brick structure of the present invention, since there is no pitch in the brick matrix portion, the portion is maintained in a dense and high-strength state. Due to the nature of this matrix, it is possible to maintain excellent corrosion resistance.

In the brick of the present invention, voids and graphite having low crystallinity exist around the magnesia particles. These voids and graphite prevent the propagation of cracks caused by thermal shock. Due to this blocking action, the crack does not develop into a crack large enough to spall.

Thus, as the proportion of magnesia particles having an edge layer increases, the chance of cracks encountering the edge layer increases, and the thermal spalling resistance of the brick improves accordingly. On the other hand, the corrosion resistance of the brick deteriorates when the amount of the magnesia particles having the edge layer is too large. This is because the increase in the marginal layer inevitably increases the voids contained therein. Specifically, if the amount of the magnesia particles having the edge layer is less than 10% by volume, the effect of improving the heat-resistant spalling property is small. Also,
50% by volume of magnesia particles having an edge layer
If it exceeds, the corrosion resistance deteriorates. For this reason, when the abundance of the magnesia particles having the edge layer is 10 to 50% by volume, the heat-resistant spalling property is the best, and the deterioration of the corrosion resistance is suppressed to a minimum.

The above-mentioned voids are filled by thermal expansion of magnesia particles in a high temperature range of 1500 ° C. or higher. Therefore, it is desirable that the thickness of the void existing around the magnesia particles is within a range that can be filled by thermal expansion of the magnesia particles at the temperature of the operating surface of the actual machine. The thickness of the edge layer around the magnesia particles is 5 to 10
0 μm. If it is less than the lower limit of this range, the propagation of cracks generated by thermal shock cannot be prevented, so that there is almost no effect of heat-resistant spalling. If the amount is larger than the upper limit of this range, the voids become too large around the magnesia particles, so that the corrosion resistance deteriorates.

The specific type of carbon used in the brick of the present invention is one or more selected from phosphorous graphite, earthy 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.

MgO-C non-fired bricks may be used in addition to the above-mentioned blends, as long as the effects of the present invention are not impaired, in the form of various metal powders, metal oxides, carbides, borides, nitrides, fibers and the like. It may have a tissue containing an appropriate amount of one or more selected from the above. Examples of metal oxides include alumina, spinel, chromia, and the like.

[0016]

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.

[0017]

[Table 1]

Using bricks having the structures shown in the table, tests were conducted for heat resistance spalling resistance and corrosion resistance. Heat resistant spalling; 40 mm x 40 mm x 114 mm
Approximately 50 mm from one end of the prismatic sample brick in the length direction
Immersion in hot metal at 1650 ° C. for 5 minutes, and then forcedly cooled to room temperature by air. The number of repetitions up to the peeling is defined as a heat-resistant spalling peeling generation cycle. Those having a large number of heat-spalling spallation occurrence cycles were judged to be good, and all of the examples of the present invention obtained good results.

Corrosion resistance: The erosion ratio was calculated using the rotational erosion method, with the corrosion resistance of Comparative Example 1 set 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, the thickness of the edge layer was 6
In the case where magnesia particles having a size of about 90 μm are present in an amount of 10 to 50% by volume, the magnesia particles having no marginal layer are present in comparison with the heat-resistant spalling spalling occurrence cycle of Comparative Example 1 in which only magnesia particles are present. The number of times is excellent.

In Comparative Examples 2 and 4, the amount of magnesia particles having an edge layer is less than 10% by volume. The thickness of the edge layer was 3 μm and 150 μm, respectively, and the number of cycles of the heat-resistant spalling spalling was 11 times,
Two times inferior.

Further, in Comparative Example 3, the abundance of the magnesia particles having the edge layer exceeds 50% by volume. The thickness of the edge layer is also less than 5 μm, and also in this case, the heat-resistant spalling peeling cycle is inferior to 13 times.

On the other hand, in Comparative Example 5, the abundance of the magnesia particles having the edge layer was more than 50% by volume, the thickness of the edge layer exceeded 100 μm, and the heat-resistant spalling peeling cycle was 20 times. Although the above is excellent, the erosion ratio is 250 and the corrosion resistance is poor.

In Comparative Example 6, the conventional method (Japanese Patent Laid-Open No.
No. 55), as an example, around the magnesia particles,
This is an example where the phenolic resin is present at a thickness of 50 μm.
In this example, the residual carbon amount around the magnesia particles is small, and the residual carbon is amorphous. Accordingly, cracks are more likely to propagate around the magnesia particles than when there is a pitch. For these reasons, in Comparative Example 6, the ability to prevent the propagation of cracks was low, the heat-resistant spalling property was not improved, and the corrosion resistance was poor.

In Comparative Example 7, the thickness of the peripheral layer around the magnesia particles was 50 μm, but the abundance was 60% by volume.
It has become. In this case, although the heat-resistant spalling peeling cycle was slightly improved, the erosion ratio was 170, and the corrosion resistance was considerably poor.

In the examples, 3% by volume of metallic aluminum is present in all examples, but the presence / absence and the presence ratio do not affect the effects of the present invention.

Regarding magnesia particles, in the embodiment,
The structure containing sintered magnesia particles was taken as an example, but the same effect was obtained even in the presence of electrofused magnesia particles, natural magnesite particles or this calcined product.

As for carbon, in the examples, 10% by volume of phosphorous graphite was present, but the proportion of carbon is not limited, and there are also carbonaceous graphite, artificial graphite, pitch coke, anthracite, and carbon black. The same effect was obtained.

Actual machine test; Examples 2, 4 and Comparative Example 1
An unburned MgO-C brick having the structure shown in Comparative Example 3 was actually built and operated under the inclined portion of the 330 t 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.

[0031]

The Mg having the structure shown by the present invention
The non-fired OC-brick has a marginal layer around the magnesia particles, and the heat-resistant spalling and corrosion resistance inherent in the MgO-C refractory inherently causes the molten metal treatment. As the lining material for the device, the durability is improved by 20 to 25% compared to the conventional product, and the economic effect is large.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Ishimatsu 1-1, Hibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Inside Yawata Works (72) Inventor Kiyoshi Okawa 20-Shintomi, Futtsu-shi, Chiba 1 Nippon Steel Corporation Technology Development Division (72) Inventor Takeki Yoshitomi 1-1 Higashihama-machi, Yawatanishi-ku, Kitakyushu-shi, Fukuoka Inside Kurosaki Ceramics Co., Ltd. (72) Inventor Kazuhiko Kawasaki Higashi-Hachimanishi-ku, Kitakyushu-shi, Fukuoka 1-1 Hamacho Kurosaki Ceramics Co., Ltd. (56) References JP-A-2-311358 (JP, A) JP-A-2-167855 (JP, A) JP-A 64-42361 (JP, A) JP-A Sho 61-127672 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/00-35/22 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] A thickness of 5 to 1 including a gap and a pitch;
10 to 5 magnesia particles having a layer of
An unburned MgO-C brick characterized by exhibiting a structure containing 0% by volume.