JP3079296B2 - Method for producing fired brick for lining molten metal containers - 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 a fired brick having excellent structural stability and durability for lining a molten metal container.

[0002]

2. Description of the Related Art Conventionally, waxy brick has been used as a lining material for molten metal containers such as hot metal and molten steel.
However, in recent years, hot metal pretreatment such as desiliconization, dephosphorization, and desulfurization in a hot metal ladle, or secondary refining such as degassing and slag refining in a molten steel ladle have been carried out.
As a result, the operating conditions became severe and it was no longer possible to obtain sufficient durability with waxy bricks. Therefore, for example, Japanese Patent Application Laid-Open No. 22167/1990 discloses that
Unfired bricks combining carbon and silicon carbide have been proposed. This unfired brick exhibits excellent effects of preventing slag penetration and thermal shock resistance by containing carbon.

[0003]

However, carbon-containing bricks have a problem in that their life is shortened due to oxidative deterioration. The oxidation is considerably improved by adding metal powder or glass powder, but it is not sufficient. Carbon has the effect of absorbing the thermal expansion stress of the brick. For example, unburned brick of carbonite-free pyroxene-silicon carbide does not have the problem of oxidation, but cannot absorb the thermal expansion of pyroxene, resulting in cracks during use. An object of the present invention is to provide a brick for lining a molten metal container free of the above-mentioned conventional problems.

[0004]

As a result of various studies, the present inventors have found that a fired brick obtained by combining pyroxene with a specific ratio of silicon carbide can solve the problems of oxidation and cracking at once. And completed the present invention. That is, the present invention is a method for producing a fired brick for lining a molten metal container, which comprises kneading, shaping and then firing a compound mainly composed of 3 to 40% by weight of silicon carbide and the balance being a raw material of pyroxene. . In the present invention, silicon carbide has an effect of preventing slag penetration. The particle size of silicon carbide is, for example, 1
Fine powder of not more than 00 mesh, preferably not more than 325 mesh is preferred. In order to prevent oxidation, the content of carbon contained in silicon carbide is preferably as small as possible, for example, 10% by weight or less. If the compounding ratio of silicon carbide is less than 3% by weight, the effect of preventing slag penetration cannot be obtained, and if it exceeds 40% by weight, silicon carbide expands by oxidation during firing,
Cracks occur in the brick structure.

[0005] As a raw material for the limestone, a natural product or a calcined product previously heat-treated at 600 ° C or higher can be used. The particle size is adjusted to coarse particles and fine particles so as to obtain a tightly packed brick structure. The binder may be inorganic or organic, but an inorganic binder is preferable in order not to leave even a small amount of a carbon component that causes oxidation. As the inorganic binder,
For example, sodium silicate, potassium silicate, aluminum phosphate and the like. In addition to the above, metal powder, glass powder, clay, deflocculant and the like may be added as long as the effects of the present invention are not impaired. In the present invention, the above-mentioned compound is kneaded, subjected to high pressure molding by a friction press or an oil press, and then fired. The firing temperature is preferably from 600 to 1200 ° C.

[0006]

[Effect] Quartz is included in the raw material of the limestone. Quartz is about 5
Transforms from α-quartz to β-quartz at 73 ° C., at which time it expands rapidly and largely. In a material that does not contain carbon, an approach crack during use is caused by this rapid thermal expansion. In the case of carbon-containing materials, the thermal expansion of pyroxene is absorbed and mitigated by carbon, but there is a problem of structural deterioration due to oxidation of carbon. On the other hand, the calcined brick obtained by the present invention does not contain carbon and thus does not deteriorate by oxidation, and since it is calcined in advance, there is no problem of cracking due to rapid thermal expansion. In the present invention, the firing temperature is preferably from 600 to 1200 ° C. If the temperature is lower than 600 ° C., the quartz in the raw material of stone will be α
-The transition from quartz to β-quartz is not complete, and thermal expansion occurs during use, causing close cracking, making it difficult to obtain the effects of the present invention. If the temperature exceeds 1200 ° C., a problem such as deformation of the brick tends to occur due to the formation of the glass layer by the raw material of the stone.

[0007]

EXAMPLES Examples of the present invention and comparative examples will be described below. Table 1 shows the test results of the composition and the brick used in each example.

[0008]

[Table 1]

In each of the examples, the compounded compositions shown in Table 1 were kneaded, and then formed into regular shapes by a friction press. The unfired product was dried by heating at 200 ° C. for 24 hours. The baked product is 1
After drying at 50 ° C. for 24 hours, firing was performed at each temperature shown in the table.
The test method is as follows. The coefficient of linear thermal expansion was measured according to JIS-R2207. Corrosion resistance: An erosion test was performed at 1450 ° C. for 5 hours by a rotary erosion method, and the erosion dimension was measured. The test results of Comparative Example 1 are shown as a erosion index with 100 being set. The smaller the numerical value, the less the erosion. Oxidation resistance: A sample cut into a cube having a side of 50 mm was placed in an electric furnace, heated from normal temperature to 1000 ° C., heated for 16 hours, and then the thickness of the oxide layer of the sample was measured. Using an actual machine: For Example 2, Comparative Example 1, Comparative Example 4, and Comparative Example 5 of the present invention, they were lined with a 100-ton hot metal ladle to measure the state of occurrence of near cracks and the number of service life.

[0010] The brick obtained from the embodiment of the present invention has a low coefficient of linear thermal expansion which causes an approach crack. Excellent corrosion resistance. Also, since it does not contain carbon, there is no oxidation at all. Comparative Example 1 is an unfired product, has a large coefficient of linear thermal expansion, and is inferior in corrosion resistance. In Comparative Example 2, the proportion of silicon carbide was higher than the range of the present invention, and the corrosion resistance was poor. Comparative Example 3
Is an unsintered product containing carbon, which has a high coefficient of linear thermal expansion and is inferior in oxidation resistance. The unsintered carbon-containing product of Comparative Example 4 is equivalent to a conventional material, and is inferior to the present invention in the coefficient of linear thermal expansion and oxidation resistance. Comparative Example 5 is a material which was mainly used before Comparative Example 4 was used, and was a fired product. However, since it does not contain silicon carbide as in the present invention, it has poor corrosion resistance. In actual use, the examples of the present invention did not peel or oxidize, and excellent durability was obtained as compared with Comparative Examples 1, 4 and 5.

[0011]

The fired brick produced according to the present invention is
There were no problems such as oxidation and cracking, and as is clear from the results of the examples, the service life was improved by 50% or more as compared with the conventional material. In recent years, hot metal pretreatment, secondary refining, and the like have been actively performed, and the use conditions of lining materials for molten metal containers have become increasingly severe. The present invention has a great industrial value as a brick material that can cope with this. Further, since the calcined brick produced by the present invention does not contain carbon, it can be calcined in an oxidizing atmosphere in the air, and has an advantage that the production cost is low.

Claims (2)

(57) [Claims] 1. A method for producing a fired brick for lining a molten metal container, comprising kneading a compound containing 3 to 40% by weight of silicon carbide and a balance mainly composed of a raw material of rock, kneading, molding and firing. 2. The method according to claim 1, wherein the firing temperature is 600 to 1200 ° C.