JPH04342457A - Carbon-containing unburned refractory - Google Patents

Abstract

PURPOSE:To further improve the oxidation resistance and the corrosion resistance of a carbon-containing unburned refractory. CONSTITUTION:The objective carbon-containing unburned refractory has a composition obtained by adding an Al-Zr alloy powder having an Al/Zr atomic ratio within a range of (9/1) to (1/3) in an amount of 0.5-10wt.% by outer percentage to a fire-resistant material composed of 5-30wt.% carbonaceous raw material and 70-95wt.% fire-resistant MgO-based material.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to refractories, and more particularly to carbon-containing unfired refractories.

0002

[Prior Art] Carbon-containing refractories have excellent spalling resistance and corrosion resistance against slag and molten metal, so their range of application has been rapidly expanding in recent years. Since unfired refractories using carbon as a binder meet the demand for energy conservation, carbon-containing refractories combined with various refractory raw materials are used in various molten metal containers and peripheral equipment. Among these carbon (C)-containing unfired refractories, MgO-C materials are made by blending a carbonaceous raw material such as scaly graphite with a magnesia (MgO) raw material such as sintered magnesia clinker or fused magnesia clinker. Refractories are often used in the walls of converters, electric furnaces, etc., and contribute to dramatically extending the life of the furnace.

0003

[Problems to be Solved by the Invention] However, the bonding parts in the structure of such MgO-C refractories depend on carbon bonds that essentially have no bonding properties with oxides, so the hot strength is low. It is also well known that it has the disadvantage that it is rapidly oxidized in a strongly oxidizing atmosphere, resulting in a marked increase in the rate of erosion.

[0004] In order to improve the oxidation resistance and hot strength characteristics, which are the drawbacks of this MgO-C refractory, Al, Si, Mg
Adding easily oxidizable metals such as B4C, carbides such as SiC, or silicon hexaboride (SiB6
) by adding B2 O3 -SiO during refractory operation.
A method has been proposed in which a carbonaceous raw material is coated with a film made of a highly viscous melt produced by the reaction between B2 O3 and refractory aggregate at high temperatures during operation.

[0005] However, although the above-mentioned method of adding easily oxidizable metals and carbides improves the oxidation prevention effect of carbonaceous raw materials to a certain extent, it is not fully satisfactory. Further, in the method of adding silicon hexaboride, it takes time to form a stable coating with the high viscosity melt, and depending on operating conditions, the refractory surface is often damaged by melting or abrasion.

The present invention was proposed in view of the above-mentioned conventional circumstances, and an object of the present invention is to provide a carbon-containing unfired refractory having even better oxidation resistance and corrosion resistance.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention employs the following means. That is, for a refractory material consisting of 5 to 30% by weight of carbon raw material and 70 to 95% by weight of MgO refractory material, the Al/Zr atomic ratio is 9/1.
Al-Zr alloy powder in the range of ~1/3 is applied externally to 0.
．． It is added in an amount of 5 to 10% by weight.

[0008]

[Function] As the carbonaceous raw material having the above structure, known materials such as scaly graphite, earthy graphite, petroleum coke, coal pitch coke, foundry coke, and carbon black can be used. Graphite is most preferred. Further, the particle size of the carbon raw material is not particularly limited and may be selected as appropriate, but a particle size of about 1 mm or less is usually used.

Next, any MgO raw material can be used as the refractory aggregate. As the MgO raw material, sintered magnesia clinker, fused magnesia clinker, natural magnesia clinker, etc. can be used. The blending amount of the carbon raw material varies depending on the object to which the refractory is applied, but is preferably 5 to 30% by weight based on the total amount of the refractory material. For example, when graphite scales are added as a carbonaceous raw material, if the scale graphite content is less than 5% by weight, the spalling resistance will decrease, and the advantages of carbon-containing unfired refractories cannot be fully demonstrated. If it exceeds 30% by weight, corrosion resistance decreases, which is not preferable.

In the present invention, the Al-Zr alloy powder added to the refractory material as described above exhibits a greater affinity for oxygen than carbon at high temperatures, and is oxidized near the surface of the refractory material.
Al2O3 (alumina) and ZrO2 respectively
(zirconia) and improves corrosion resistance. moreover,
Due to the volume expansion accompanying the formation of Al2O3 -ZrO2, the particle gaps near the surface created during the formation of the refractory are almost completely closed and densified, thereby increasing mechanical strength and further improving oxidation resistance. Can be done. Also, Al2O3 reacts with MgO, forming MgO-Al2
O3 Forms spinel and improves strength.

Furthermore, the Al-Zr alloy reacts with carbon inside the refractory to form aluminum carbide and zirconium carbide, thereby strengthening the structure. In the present invention, Al-Zr
The composition of the alloy is limited to an Al/Zr atomic ratio of 9/1 to 1/3. This is because if the composition is outside the above range, Al2O3-ZrO2, which is oxidized and generated during use, is
An amount corresponding to the amount of l-Zr alloy added is not produced, and the desired effect cannot be exhibited.

Further, the particle size of the Al-Zr alloy powder is preferably 250 μm or less, more preferably 44 μm or less, from the viewpoint of reactivity, uniformity, dispersibility, reaction activity, etc. The amount of Al-Zr alloy powder added is 0.5 to 10% by weight, based on the refractory material containing the carbonaceous raw material, and if the amount added is less than 0.5% by weight, the desired effect cannot be obtained. On the other hand, if it exceeds 10% by weight, there is no problem in terms of oxidation resistance, but corrosion resistance decreases, which is not preferable.

[0013] The above-mentioned carbon-containing unfired refractory should be blended with a binder such as tar pitch or phenol resin, which has a large amount of residual carbon, that is, a high carbonization yield, and has excellent workability during molding. However, from the viewpoint of workability and cost, it is preferable to use phenol resin.

[0014]

EXAMPLES Examples according to the present invention and comparative examples according to the prior art will be shown below to further clarify the characteristics of the present invention. Each of the samples shown in Examples 1 to 6 and Comparative Examples 1 to 7 above includes: sintered magnesia 62% by weight fused magnesia 20% by weight scaly graphite
As shown in the upper column of Table 1, A with different Al/Zr atomic ratios was added to the refractory material raw material with a composition of 18% by weight phenol resin and 3% by weight.
After adding a predetermined amount of l-Zr alloy, metal aluminum, metal silicon, and boron carbide, kneading at room temperature for 20 minutes, 95%
It was obtained by pressure molding into a shape of 40 x 40 x 160 mm at a pressure of 0 kgf/cm 2 and heat-treating at 180° C. for 18 hours.

The physical properties of each of the above samples are shown in the lower column of Table 1. In Table 1, the weight loss rate and thickness of the decarburized layer after oxidation firing at 1500°C for 3 hours are relative to Examples 1 to 6.
showed a high value, indicating that the oxidation resistance was improved. Note that Comparative Examples 4 and 5 based on the prior art have larger values than Examples 3 and 6, but are inferior in hot bending strength.

[0016] Next, the obtained refractory was adjusted to basicity, that is, Ca
With a slag with an O/SiO2 weight ratio of 2.0, 165
The erosion amount of each sample was measured by subjecting it to a rotary slag test at 0°C for 3 hours, setting the erosion amount of Comparative Example 1 as 100, and calculating the erosion index shown in the bottom column of Table 1. All of the products showed a low corrosion index, and it can be seen that the present example has extremely superior corrosion resistance against slag compared to the comparative example.

It goes without saying that the present invention is not limited to the above-mentioned embodiments, and that various applications are possible without departing from the spirit of the present invention.

[0018]

[Table 1]

[0019]

[Effect of the invention] As can be seen from the results of the above examples,
The carbon-containing unfired refractory according to the present invention, which is made by adding an Al-Zr alloy to a refractory material containing a carbonaceous raw material, has good strength and oxidation resistance in addition to the excellent spalling resistance characteristic of conventional materials. It also has excellent sex. Therefore, according to the present invention, a carbon-containing unfired refractory having superior durability than conventional products can be obtained, contributing to further extension of furnace life.

Claims (1)

[Claims] Claim 1: A
Al-Z with l/Zr atomic ratio in the range of 9/1 to 1/3
A carbon-containing unfired refractory, characterized in that 0.5 to 10% by weight of r-alloy powder is added thereto.