JPS62100484A - Expansion graphite-containing refractories - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an expanded graphite-containing refractory that has excellent thermal shock resistance, oxidation resistance, and corrosion resistance.

[Prior Art] In the production of acidic, neutral or basic refractories, it has been common practice to include natural graphite for the purpose of improving thermal shock resistance. Containing natural graphite not only provides excellent thermal shock resistance, but also has the advantage of improving corrosion resistance because natural graphite does not easily react with molten metal or slag. However, natural graphite has the fatal defect that it oxidizes when exposed to air at high temperatures, so the higher the content of natural graphite, the worse the oxidation resistance becomes. Furthermore, when the content of natural graphite increases, the strength of the refractory decreases.

Therefore, various studies have been made to improve the oxidation resistance and strength of natural graphite-containing refractories. That is, in order to improve oxidation resistance, the refractory A-weave is densified by high-pressure molding, and oxidation inhibitors such as glass materials are added. However, even with these efforts, from a microscopic perspective, in terms of refractory operation, [graphite oxidation] - [
There are repeated cycles of "penetration of slag into the oxidized layer" and "oxidation of J-r graphite due to damage to the refractory surface due to structural spalls", and it cannot be said that the iJ oxidation property is sufficient.
This method is not always satisfactory, as it requires equipment for high-pressure molding, which increases production costs, and the oxidation inhibitor has a negative effect on the corrosion resistance of the refractory at high temperatures.

Another problem that requires improvement is that the strength of refractories generally decreases due to graphite content. When refractories are used under single-sided heating, cranking occurs when the strain stress caused by thermal strain reaches -L for the tensile strength of bricks.
High strength is also an important property of bricks.

The acid content of natural graphite is manufactured by changing it in various ways depending on the other refractory substances it contains and the conditions under which the refractory material is used.

For example, the graphite-containing acid in the magnesia-graphite system and the alumina-graphite system is centered around 80% magnesia and 20% graphite in the case of the magnesia-graphite system, and alumina and 90% graphite in the alumina-graphite system. It is centered on lO%. The reason why the appropriate amount of graphite differs depending on the raw material to which graphite is used is due to the difference in thermal shock resistance of the raw material.

[Means for solving problems]

The present inventors conducted various studies on graphite raw materials in order to improve oxidation resistance, and as a result, they found that expanded graphite was suitable for this purpose, and were able to accomplish the present invention. The present invention is an expanded graphite-containing refractory characterized by comprising 0.5 to 5% by weight of fibrous expanded graphite and the balance being other refractory materials.

When commercially available expanded graphite is heated, it expands approximately 50 to 100 times its original volume. Volume expansion is 1ffi, which is about 7 to 1
It is fibrous with a length of 0+n. By crushing this fibrous material, ultrathin pieces with a thickness of about 10 μm or less can be obtained. The thickness of natural flaky graphite flakes currently used in refractories in Japan is approximately 20 to 80 μm in culm, and compared to this, ultrathin flakes of expanded graphite are significantly thinner. When this ultra-thin graphite is used in a refractory, a refractory having thermal shock resistance comparable to that of conventional products can be obtained even if the amount used is smaller than that of general natural flaky graphite. When using it, it is preferable to use it by crushing the expanded graphite into individual pieces, but it is also preferable to mix it with other refractory layers in its fibrous form and knead it using a mixer in a prescribed manner. I don't mind.

Also within the scope of the present invention is a method in which expanded graphite is blended before expansion, and the graphite is heated and expanded in the subsequent manufacturing process to form ultra-thin flakes or fibers. Since the refractory of the present invention contains significantly less graphite than conventional refractories, wear of the refractory due to oxidation can be reduced.

Examples Table 1 shows formulation examples and physical properties of the products of the present invention in comparison with conventional products. The compound was molded at about 400 kg/aJ, 1350℃ for floors 1 to 14 and 120℃ for positive 5 to floor 6.
Reduction firing was carried out at 0°C, and at 1050°C for holes 7 to 1lh8. Physical properties were measured after firing. Thermal shock resistance is 50
A specimen of 50 x 5 (bm) was heated to 1300°C for XIO minutes and immersed in cold water. This was repeated and the number of repetitions was expressed as the number of times a crack occurred in the specimen. Oxidation resistance was 40 x 40 x 40 dragon specimens in air 1
After holding at 300° C. for 5 hrs (50° C./hr temperature increase), heavy MN was compared with the thickness of the oxide layer measured by cutting it at the center.

[Effects of the present invention]

In Table 1, in the alumina-carbide TI elemental graphite refractory of the present invention N[11 and Nn2, natural scaly graphite was used as comparative example M4.
Thermal shock resistance was improved despite being almost the same. Room 3
In this case, natural flaky graphite is not used at all, and in this case as well, the thermal shock resistance is improved by 1-1, and the oxidation resistance is also significantly improved.

In the case of magnesia-graphite refractories and zirconia-graphite refractories, the present invention's problem 5 and floor 7 are comparative examples positive 6 and Il.
Thermal shock resistance and oxidation resistance are significantly improved compared to &18.

−6= Procedural amendment (voluntary) April 8, 1986

Claims (1)

[Claims] (1) An expanded graphite-containing refractory comprising 0.5 to 5% by weight of fibrous expanded graphite and the remainder of other refractory materials.