JPH07196362A - Highly durable magnesia-carbonaceous refractory - Google Patents

Abstract

PURPOSE:To eliminate problems of disintegration of a grain boundary and outflow due to impurities deposited in the crystal grain boundary in an electrofused magnesia clinker used as an aggregate raw material for conventional magnesia-graphitic refractory and improve the corrosion resistance and durability. CONSTITUTION:This highly durable magnesia-carbonaceous refractory is obtained by blending a magnesia clinker aggregate with a graphitic material and a binder. In the refractory, the magnesia clinker aggregate is prepared by electrofusing seawater magnesia having >=99.9% purity, providing an electrofused magnesia clinker composed of a single crystal having >=1000mum grain size, blending the resultant clinker in a polycrystalline magnesia clinker, pulverizing and controlling the size of the resultant magnesia clinker blend and using the magnesia clinker having the grain size controlled within the range of 0.074-3mm. Impurities are not deposited in the grain boundary and converted into a solid solution in the magnesia to promote the coarse-grain crystallization. Thereby, a single crystal having >=1000mum grain size is obtained and used as a constituent aggregate for a magnesia-graphitic refractory. As a result, an influence of permeation of a slag into the grain boundary in refining can be reduced to prevent the disintegration by thermal shock.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a Q-BOP furnace, a converter,
The present invention relates to a magnesia-graphite refractory having excellent spalling resistance and corrosion resistance used for lining steelmaking furnaces such as ladle, tundish, mixed pig furnace, and vacuum treatment furnace.

[0002]

2. Description of the Related Art This magnesia-graphite refractory material is disclosed, for example, in JP-A-57-11874 and JP-A-63-24.
As described in Japanese Patent No. 1109, a mixture of a magnesia clinker and a graphite material such as scaly graphite, soil graphite, pitch, and coke, and an organic binder such as coal tar pitch and phenol resin is molded, and then the temperature is 300 ° C. It was heat-treated at the following low temperature.

The magnesia clinker used as the magnesia raw material has a relatively high purity of about 95.0 to 99.5%, and since it has a high density, the electrofusion magnesia clinker has come to be widely used.

A magnesia-graphite refractory using this electrofused magnesia clinker is refractory 32.

[9] 486
(1980) As described in "Outline and Problems of Magnesia-Carbon Refractory Materials", silica, lime, iron oxide, boric oxide and the like as impurities are contained in the electromelted magnesia clinker as a raw material. It is contained in an amount of about 5 to 0.8%, and these impurities precipitate at the crystal grain boundaries to form a polycrystalline body having a crystal diameter of about 500 microns.

[0005]

Therefore, in the graphite-containing refractory using the electro-fused magnesia clinker, refining slag penetrates into the grain boundaries during use, collapse of the clinker occurs, and thermal shock is generated. When this happens, cracks are easily induced from the grain boundaries, and the grain function is lost to lose the aggregate function, and when the mechanical action such as molten steel flow acts, it easily flows out and the durability is lost. It has the drawback of

An object of the present invention is to solve the problems of grain boundary collapse and outflow due to impurities deposited at the crystal grain boundaries in the electro-melting magnesia clinker used as a raw material for aggregates of conventional magnesia-graphite refractories. Another object of the present invention is to provide a magnesia-graphite refractory having improved corrosion resistance and durability.

[0007]

The present invention has been solved by blending an electro-fused magnesia clinker having large crystal grains, and as a result of pursuing an optimum particle size range for use of the single-crystal electro-fused magnesia clinker, as a result of conventional It has been found that the problem can be achieved by blending a clinker having a single crystal of 1000 microns or more in an aggregate composition instead of the crystalline electrofused magnesia clinker.

That is, according to the present invention, a magnesia clinker aggregate, a graphite material and a binder are blended together.
In a carbon-based refractory, the magnesia clinker aggregate is mixed with a polycrystalline magnesia clinker by combining a magnesia clinker composed of a single crystal of 1000 microns or more,
This magnesia clinker compound was crushed and sized to give a particle size of 0.
It is characterized in that the particle size is adjusted in the particle size range of 074 to 3 mm.

The clinker having a single crystal of 1000 microns or more can be obtained by electromelting a magnesia raw material having a purity of 99.9% or more, such as seawater magnesia or a refined magnesite product.

The clinker having this single crystal is a normal polycrystal, and the magnesia-carbon refractory composition of the present invention is a compounding material for strengthening the base material such as Al, Al-Mg, etc. Additives can be added.

This magnesia single crystal clinker having a large particle size can be blended alone, but the polyclinic clinker can be blended to a total amount of 100 parts by weight in an amount of 10 parts by weight or more to achieve the desired purpose. Can be achieved.

The carbon material and the binder to be blended do not have to be special raw materials, and graphite materials such as scaly graphite, earthy graphite, pitch and coke, and organic materials such as coal tar pitch and phenol resin can be used as in the past. A binder or the like can be used, but the CaO content in the binder needs to be less than 4%.

[0013]

According to the present invention, when the purity of the electromelting raw material is set to 99.9% or more, impurities are not dissolved at the grain boundaries but are solid-solved in magnesia, and coarse crystallization is promoted to obtain a single crystal of 1000 μm or more. It becomes a crystal, and by using this as a constituent aggregate of magnesia-graphite refractory, it is possible to reduce the effect of slag penetration into grain boundaries during refining and reduce the effect of slag penetration into grain boundaries during refining. It is possible to prevent collapse due to thermal shock.

[0014]

EXAMPLE An electrode is set on a moving carriage whose surface is self-coated, and a cylindrical furnace whose inner surface is self-coated with a water-cooled double iron structure is set on the outer periphery thereof and a cooling pipe is connected. After that, 99.9% from the top of the cylindrical furnace in the furnace
Seawater magnesia clinker having the above-mentioned purity and dust collecting powder generated during the production of the magnesia clinker were loaded in a fixed amount at a mixing ratio of 80:20 in a weight ratio, a canopy was arranged, and an electrode was opened from the opening of the canopy. Insert and start energizing.

About 30 minutes after the start of energization, the charged raw material around the electrodes starts melting. At this point, a certain amount of raw material is further charged through the canopy opening. This step is repeated repeatedly, and after melting for about 8 hours, the energization is stopped and the cooling of water through the cylindrical furnace is carried out for about 8 to 12 hours. After that, the cylindrical furnace is pulled up from the movable carriage, the in-furnace electromelting ingot is left on the ball cooling plate, and further cooled for 12 hours or more. Then, a molten mass obtained by removing the unmelted portion on the outer peripheral portion of the ingot is collected. Then, by collecting only the core portion of the collected molten mass around the electrode, a coarse crystal magnesia clinker having a diameter of 100 mm or more was obtained.

Using this coarse crystal magnesia clinker, 3% by weight of a graphite material composed of flake graphite and Al fine powder for reinforcing the base material in the proportions shown in Table 1 were externally blended. Was mixed with a resin binder in a temperature-controllable kneader for 30 minutes, molded with a 2000 ton vacuum friction press, and baked at 250 ° C to obtain a refractory material for a rotary slag erosion test, which was obtained. After the test, the degree of clinker disintegration after testing the refractory was tested (1700 ° C, slag basicity 3.3, erosion time 4 hours)
The corrosion resistance of the above sample was examined by a reflection microscope, and the corrosion resistance was examined by the erosion index according to the wear size of the sample after the test. The results are shown in Table 1.

[0017]

[Table 1] For comparison, a 98% pure magnesia raw material was similarly processed to prepare a raw material clinker. The obtained magnesia was a polycrystal having a particle size of 500 microns or less.
Using this, a magnesia-graphite refractory material was obtained and a similar test was conducted. The results are also shown in Table 1.

The table shows the following.

(1) Corrosion resistance is improved by the addition of single crystal electro-fused magnesia.

(2) Addition of single crystal electrofused magnesia to 3 m
If the particle size is m or less, there is no clinker collapse.

(3) As for the effect of adding the single crystal electro-fused magnesia, the corrosion resistance is remarkably improved when the content is 1 mm or less and 10% or more.

[0022]

The present invention has the following effects.

(1) A carbon-containing magnesia refractory having excellent durability can be obtained without using a large-sized single crystal which can be easily produced by a conventional electro-melting process and without special treatment.

(2) By applying the above-mentioned single crystal magnesia, the collapse of magnesia due to the grain boundary can be prevented and the corrosion resistance can be improved.

(3) By applying the above-mentioned single crystal magnesia, the penetration of the slag component at the time of refining into the grain boundaries of magnesia can be prevented, and the corrosion resistance is improved.

(4) By adding 10% or more of the above-mentioned single crystal magnesia in a particle size range of 1 mm or less, it is possible to significantly improve the corrosion resistance.

Claims (4)

[Claims] 1. A magnesia-carbon-based refractory obtained by blending a magnesia clinker aggregate, a graphite material, and a binder, wherein the magnesia clinker aggregate is a crystalline magnesia clinker composed of a single crystal of 1000 μm or more. A highly durable magnesia-carbon refractory which is blended with a clinker, and this magnesia clinker blend is pulverized and sized to adjust the grain size within a grain size range of 0.074 to 3 mm. 2. The high durability magnesia according to claim 1, wherein the clinker having a single crystal of 1000 microns or more is an electrofused magnesia clinker obtained by electrofusing a magnesia raw material having a purity of 99.9% or more. -Carbon refractories. 3. The highly durable magnesia-carbon system according to claim 1, wherein the blending amount of the single crystal magnesia clinker in the blend with the polycrystalline magnesia clinker is 10 parts by weight or more out of 100 parts by weight in total. Refractory. 4. The highly durable magnesia-carbon refractory material according to claim 1, wherein the total content of CaO is less than 4%.