JPH0959071A - Monolithic refractory containing graphite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of plasticizing water for a slurry and improve the thermal shock and slag resistnaces of a refractory by blending a prescribed amount of a specific graphitic powder in the refractory composition prepared by blending an aggregate with the graphitic powder and a fine powder as principal components. SOLUTION: This monolithic refractory containing graphite is obtained by blending 4-40wt.% one or more of a natural scaly graphite, a natural earthy graphite, anthracite and artificial graphite as a graphite powder, especially having >=0.8cc/g filling density, and using a mixture of one or more of alumina, magnesia, spinel, zircon, silica, zirconia, quartzite, agalmatolite, aluminous shale, chamotte and silicon carbide as an aggregate and a mixture of one or more of alumina, zircon, silica, zirconia and clay as a fine powder. The porosity is preferably regulated to <=22% without any regard to the amount of the added graphite in order to provide the refractory with the slag resistance of <=90 extent of slag corrosion. The amount of the plasticizing water needs to be <=8wt.% for that purpose and the filling density described above is required therefor.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a carbon-containing amorphous refractory having excellent thermal shock resistance, slag resistance and abrasion resistance.

[0002]

2. Description of the Related Art Refractory materials containing carbon raw materials such as graphite can be used to enhance their durability by utilizing the excellent high thermal conductivity of carbon and the excellent resistance to molten metal and molten slag. Widely used as various metal refractory materials. By the way, in recent years, the refractory materials for metallurgy have been severely used, so that the dependence on carbon is further increasing.

As a carbon material which can meet such demands, graphite is particularly well suited, and as described above, it largely depends on the characteristics such as high corrosion resistance and high thermal stability of graphite. However, since natural graphite having high crystallinity has a flaky shape, it has poor fluidity. Artificial graphite has a columnar shape, but also has many flake shaped cleavage planes, which also has poor fluidity. For this reason, when a refractory material containing graphite is made into a slurry state, the amount of water to be added (hereinafter referred to as “plastic water amount”) must be increased in order to improve the fluidity, and this results in There was a fatal flaw that hindered the construction of various structures. In this sense, the addition of graphite into an amorphous refractory has hitherto been
It was difficult to add a large amount.

On the other hand, conventionally, there have been proposed some techniques for overcoming the disadvantages of graphite and improving the properties of amorphous refractories. For example, there is a method of coating a surface of graphite with a surfactant in advance (see Japanese Patent Laid-Open No. 4-12064). However, in this method, in the coexistence with a metal oxide or the like, the surfactant is redissolved in water, so that the fluidity of the product cannot be remarkably superior. There is also a method of adhering fine particles such as metal oxides and metal carbides to the surface of graphite to make it hydrophilic (see Japanese Patent Laid-Open No. 5-194044). However, for this method, it is necessary to make the metal compound fixed to the graphite surface into ultrafine particles,
The production of such fine metal particles is extremely difficult and has a problem of being expensive.

[0005]

As described above, the conventional technique, in particular, the conventional surface-treated graphite using flake graphite or artificial graphite, is improved in hydrophobicity to some extent, but its shape is originally Because it is scaly,
As an unfixed refractory for casting, there is a problem that it is difficult to form a dense filling structure, and it is necessary to solve this problem. Therefore, an object of the present invention is to propose a graphite-containing amorphous refractory material that does not have the above-mentioned problems that the prior art has, and is particularly excellent in basic characteristics as graphite; thermal shock resistance and slag resistance. Of course, it is to obtain a graphite-containing amorphous refractory that is effectively used for obtaining a dense construction body.

[0006]

SUMMARY OF THE INVENTION The present invention exhibits hydrophilicity by controlling the graphite properties and the content thereof which are convenient for achieving the above objects, and exhibits the above-mentioned properties (heat shock resistance, Slag resistance, etc.) is used, and the ratio of the graphite in the amorphous refractory is 4 to 40.
By blending so as to be wt%, the above various characteristics,
In particular, it is a graphite-containing amorphous refractory which is convenient for obtaining a dense construction and has excellent durability.

That is, according to the present invention, in a refractory composition containing an aggregate, graphite powder and fine powder as main components, the graphite powder having a packing density of 0.8 g / cc or more is 4
It is a graphite-containing amorphous refractory characterized by being mixed in an amount of -40 wt%. In addition, in the above-mentioned amorphous refractory, the aggregate is selected from alumina, magnesia, spinel, zircon, silica, zirconia, silica, wax, van shale, chamotte, and silicon carbide.
Or a mixture of two or more kinds, the fine powder includes one or more kinds selected from alumina, zircon, silica, zirconia and clay, and the graphite powder includes natural flake graphite and natural soil. One type or two or more types selected from flake graphite, anthracite and artificial graphite are used.

In the present invention, in addition to the above main components, for example, as dispersants, sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, acidic sodium hexametaphosphate, sodium borate, sodium carbonate, etc. Inorganic salt, sodium citrate, tartrate,
One or more selected from organic salts such as sodium polyacrylate, sodium sulfonate, and sodium naphthalenesulfonate, and any one of alumina cement, silica sol, and alumina sol as a curing agent.
One kind or two or more kinds can be used.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors examined the relationship between the characteristics of graphite powder and the characteristics of refractory materials containing the same. As a result, the following phenomenon was discovered. When the flowability of a refractory slurry containing graphite was examined, it was found that there is a close correlation between the packing density of graphite and the amount of plastic water when the flow value of the slurry is 150 mm, as shown in FIG. I found out that there is. This means that the amount of plastic water can be controlled by the packing density.

As described above, the amount of plastic water in making a slurry is easily influenced by the packing density of graphite, and it is understood that the plastic water amount when the same weight of graphite is added can be reduced as the packing density becomes higher. It was. This was also considered to mean that the larger the bulk density, the smaller the void volume between the graphite particles represented by the following formula, and therefore the amount of water taken in the voids could be reduced.

[0011]

[Equation 1] Here, v is the void volume between graphite particles (cc / g), β and α of the graphite powder are packing density and true density (g / cc), w
Is the compounding ratio (%) of graphite. The above-mentioned packing density is a measured value tested according to the measuring method of "packing density" specified in 6.7 of JIS K 1464.

Next, according to the research conducted by the inventors, a relationship between the amount of plastic water, which is an index for forming a slurry of a refractory raw material, and the porosity of the refractory obtained after the slurry is dried and fired is shown in FIG. We also found that there is a relationship as shown in 2. In general, it is well known that the porosity of refractories affects durability.The higher the porosity, the greater the amount of slag infiltrated during use, and the reaction between infiltrated slag and refractory aggregates. It is considered that the outflow of aggregate, that is, the amount of slag erosion due to slag increases. FIG. 3 shows the relationship between the porosity of the refractory and the slag erosion amount. It is clear that the lower the porosity of the refractory, the higher the resistance to slag erosion, ie the durability. It is also known that the increase in porosity caused by the increase in the amount of plastic water reduces the strength of the refractory molded body. For example, if the porosity is
If it exceeds 25%, the molded product becomes brittle so that the strength test cannot be performed. For the reasons described above, it is desirable to reduce the amount of plastic water as much as possible, and for that purpose, it is desirable to increase the packing density of graphite.

The graphite must have a packing density of at least 0.8 g / cc or more. The reason will be described below. FIG. 3 shows the relationship between the slag erosion resistance of a refractory and the porosity.
To make it 90 or less, regardless of the amount of graphite added,
A porosity of 22% is preferably below. And FIG.
As shown in (1), in order to reduce the porosity to 22% or less, the amount of plastic water needs to be 8 wt% or less. Then, in order to reduce the amount of plastic water to 8 wt% or less, as shown in FIG. 1, the packing density is 0.8 g / cc even when the graphite addition amount is 5 wt%.
From the above, it is understood that when the addition amount is 10 wt%, the amount needs to be 1.0 g / cc or more. On the other hand, as described above, the amount of graphite added must be at least 4 wt% or more. That is, in the present invention, it is desirable that the packing density of graphite be 0.8 g / cc or more.

In the present invention, the amount of graphite blended in the amorphous refractory is in the range of 4 to 40 wt% in the refractory. The reason for this is that if the amount of graphite added is less than 4 wt%, the high thermal conductivity and slag resistance of graphite cannot be fully obtained, and if it exceeds 40 wt%, fluidity during construction will be secured. This is because the amount of plastic water increases and the porosity increases, leading to a decrease in oxidation resistance and corrosion resistance and a decrease in the strength of the refractory. The more preferable amount of graphite added is 4 to 20 wt%.

The graphite particles used in the present invention preferably have an average particle size of 1 to 50 μm.
If the average particle diameter is less than 1 μm, the strength of the refractory material is lowered, and it becomes extremely difficult to obtain particles having a high packing density as described below. On the other hand, if the average particle size exceeds 50 μm, the corrosion resistance of the refractory material decreases, which is not preferable.

As the graphite particles used in the present invention, any commonly available graphite such as natural flake graphite, natural earth graphite, anthracite, and artificial graphite may be used alone or in combination of several kinds. You can If any of these raw graphites satisfying the above-mentioned characteristics of the graphite used in the present invention in a commercially available state, they may be used as they are. However, in the case of natural phosphorus-like graphite or scaly graphite or artificial graphite, which has the most excellent properties for refractories with a well-developed graphite crystal structure, the packing density as described above is obtained in the state of commercial products.
Particles exceeding 0.8 g / cc cannot be obtained. In such a case, it is desirable to treat commercially available graphite by the method described below to obtain high packing density graphite.

As the raw material graphite before the treatment, any graphite which is usually available can be used, but it is desirable to use one having a packing density as high as possible. If the packing density of the raw material graphite is too low, the packing density may not fall within the desirable range for the present invention even by the high packing density treatment described below. Required packing density is 0.5g / cc
That is all.

The above-mentioned high packing density treatment for ensuring the packing density enables fine pulverization to an average particle size of about several μm, and the pulverized particles are aggregated and granulated. It is important to. By granulating the finely pulverized fine particles, it is possible to produce graphite fine powder having rounded corners and a higher packing density than conventional graphite pulverized products. As an apparatus used for this treatment, an ordinary fine crusher (Super Micron Mill manufactured by Hosokawa Micron Co., Ltd.,
The company's ACM pulsarizer, Chuo Kakoki's vibrating ball mill, etc.) can be used. Further, by combining these pulverizers and classifiers to form a closed circuit, and by adopting a form in which fine graphite powder circulates in the apparatus, finely pulverized graphite circulates in these apparatuses. A device that allows granulation in between is preferred. A powder surface modification device (hybridization system manufactured by Nara Machinery Co., Ltd.) is also a device well suited to the present invention.

As the dispersant used in the present invention, those having an effect of improving the dispersibility of the above aggregate, graphite powder and fine powder can be used. For example, inorganic salts such as sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, acidic sodium hexametaphosphate, sodium borate and sodium carbonate, sodium citrate, tartrates, sodium polyacrylate, sodium sulfonate, naphthalene sulfonic acid. One or a mixture of two or more selected from organic salts such as soda. Then, these aggregates are preferably mixed separately into coarse particles, medium particles, and fine particles so that a densely packed structure can be obtained.

The hardener used in the present invention includes general alumina cement, silica sol, alumina sol and the like used for castables.

In addition, in the present invention, organic / inorganic fibers, metal powders, ceramics, antioxidants, binders, etc. may be added in addition to the above-mentioned compounds unless the effects of the present invention are impaired. Good.

[0022]

EXAMPLES In order to verify the effect of the present invention, the amount of plastic water,
For spalling resistance and slag resistance, porosity, bending strength, and digestion resistance tests were conducted. Table 1 shows the results.
The composition of a typical example of the present invention is shown in FIG. As a refractory raw material of the composition (excluding water) in the example, JIS R52
According to 01, add water so that the flow value by the flow test is 150 mm, and according to JIS R2553 40 mm × 40 mm × 160 mm
As a molded body of 1., it is fired at 1400 ° C in an inert atmosphere.
After cooling the molded body after firing, JIS R2205 and JIS R2553
Apparent porosity and flexural strength are measured according to. For the corrosion resistance test, a high frequency furnace was used, pig iron 15kg, blast furnace slag 0.2
kg was melted at 1580 ° C., the molded body after the above firing and cooling was immersed for 5 hours, and the wear of the molded body at the interface between pig iron and slag (= slag erosion amount) was compared to Comparative Example 1 in which no graphite was contained. To
It is indexed as 100, and the larger the number, the greater the wear. In addition, in the table, Invention Examples 1 and 2 are obtained by treating scaly graphite with a hybridization system (NHS-3, Nara Machinery Co., Ltd.). / Sec, processing time 3
Inventive Example 2 has a peripheral speed of 60 m / sec and a processing time of 1.5 minutes.

As is clear from the results shown in Table 1, Comparative Examples 2 and 3 each having a small packing density require a large amount of plastic water because of their high porosity, and the bending strength showing the influence on the refractory construction body. It was revealed that neither slag erosion amount could be measured, and so-called thermal shock resistance and slag resistance were poor.
On the other hand, the invention examples 1 to 5 all showed good results in each characteristic.

[0024]

[Table 1]

[0025]

As described above, according to the present invention, the plastic density of the amorphous refractory slurry is reduced by setting the packing density of graphite added to the amorphous refractory to 0.8 g / cc or more. It is possible to have thermal shock resistance of unshaped refractories,
Improved slag resistance can be expected.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a packing density of a graphite material and an amount of plastic water.

FIG. 2 is a diagram showing the relationship between the amount of plastic water and the apparent porosity of a molded body after firing at 1400 ° C. in Examples.

FIG. 3 is a diagram showing the relationship between the apparent porosity of a molded body after firing at 1400 ° C. and the slag erosion amount in a corrosion resistance test in Examples.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masato Takagi 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba In the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Keiichiro Isomura 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba (72) Inventor Masato Kumagai 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture, Japan (72) Inventor Yasunobu Toritani, Yasunobu Toriya 1576 Nakahiro, Higashi-oki, Ako-shi, Hyogo No. 2 in Kawasaki Furnace Materials Co., Ltd. (72) Inventor Katsufumi Jono 1576 Nakahiro, Aki-shi, Hyogo Higashi-oki 1576 Kawasaki Furnace Materials Co., Ltd. (72) Inventor Junichiro Mori Nakahiro, Ako City, Hyogo Prefecture 2 Kawasaki Reactor Co., Ltd. at 1576 Higashi-oki

Claims (2)

[Claims] 1. A refractory composition comprising an aggregate, a graphite powder and a fine powder as a main component, wherein the graphite powder having a packing density of 0.8 g / cc or more is blended in an amount of 4 to 40 wt%. Characteristic graphite-containing amorphous refractory. 2. The aggregate is any one or two selected from alumina, magnesia, spinel, zircon, silica, zirconia, silica stone, pyrophyllite, shale shale, chamotte, and silicon carbide. The above mixture is used, and as the fine powder, any one kind or a mixture of two or more kinds selected from alumina, zircon, silica, zirconia and clay is used. As the graphite powder, natural flaky graphite and natural graphite are used. Clay graphite,
The amorphous refractory material according to claim 1, wherein any one kind or two or more kinds of mixed graphite powder selected from anthracite and artificial graphite is used.