JPH03205348A - Magnesia-carbon brick - Google Patents

Abstract

PURPOSE:To improve coating properties and improve oxidation resistance, corrosion resistance and spalling resistance by adding magnesia-chrome clinker to a blend of magnesia raw material and carbon raw material. CONSTITUTION:5-50wt.% magnesia-chrome clinker containing 5-80wt.% MgO, 5-20wt.% Al2O3, 15-30wt.% Cr2O3, <=15wt.% Fe2O3 and <=3wt.% impurities and 1-10wt.% binder (coal tar pitch) are added to a blend magnesia raw material (e.g. sea water magnesia) and 3-60wt.% carbon raw material (e.g. coke) having >=3mm grain size and the mixture is kneaded, formed and dried at 100-500 deg.C and cured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a refractory material that improves the slag coating properties of magnesia carbon bricks and improves corrosion resistance and oxidation resistance.

[Conventional technology]

Magnesia (MgO) has a very high melting point of 2,800°C, and iron oxide is a solid solution that does not easily form low-melting point compounds, and when combined with carbon, it has excellent spalling resistance. Magnesia carbon (hereinafter referred to as rMgo-C) because of its remarkable improvement, etc.
It is widely used as a refractory lining for steelmaking furnaces.

[Problem to be solved by the invention]

However, in contrast to the above-mentioned advantages, the disadvantage of large-sized Mg○-C-based materials is that Mg○ has a high melting point and a high coefficient of thermal expansion, so the brick U weave tends to become brittle during use, making it difficult to operate. The problem is that low melting point compounds are difficult to produce, resulting in poor oxidation resistance. That is, when used in areas where there is significant air oxidation, the life of the furnace may be shortened because the oxidation loss of the refractory is large. To prevent oxidation of refractory bricks, Aj! Attempts have been made to add metal powders such as , Mg, and Si, and boron-containing compounds such as BN and B4C, but although these additions improve oxidation resistance, they also reduce corrosion resistance and reduce the coefficient of thermal expansion. As the refractory lining becomes larger, the spalling resistance decreases, and wear and tear on the refractory lining may even increase.

In addition, aluminum carbide (AE4C3), which is trapped in the reaction between added AA and carbon, causes a hydration reaction (so-called digestion reaction) seen in formula (1) at low temperatures, leading to the destruction of refractories. This is a serious problem in metallurgical furnaces that are forced to operate intermittently.

Ax4c. +1 2 H20→4Aβ(OH)l
+ 3 C H a (1) Therefore, in view of the conventional problems as described above, an object of the present invention is to provide a magnesia carbon brick having excellent oxidation resistance, corrosion resistance, and spalling resistance.

[Means to solve problems]

The present invention improves the formation of a slag adhesion layer (so-called slag coating layer) during use as a steelmaking furnace lining material by adding 3 to 50% by weight of magnesia/chromium raw materials to a certain compound made of magnesia raw materials and carbon raw materials. It has been developed based on the knowledge that the above objectives can be achieved by promoting productivity, and provides the following means to achieve the above objectives.

That is, it is a magnesia carbon brick made by adding 5 to 50% by weight of magnesia/chromium clinker to a blend of magnesia raw materials and carbon raw materials, and the above magnesia/chromium clinker contains 50 to 80% by weight of MgO, A
The composition is 12035 to 20% by weight, Cr203 15 to 30% by weight, FezOz 15% by weight or less, and M
g○, Aj! It is desirable that the amount of impurities other than z()+, Cr20s, and Fez○3 is 3% by weight or less.

[For production]

In general, when magnesia/chromium raw materials come into contact with iron oxides at high temperatures (approximately 1200°C or higher), they easily form a solid solution, but they are difficult to form low-melting compounds. Because of this property, magnesia-chromium refractories are widely used in the lining of steelmaking furnaces.

As mentioned earlier, when magnesia comes into contact with iron oxide, like magnesia/chromium raw materials, it forms a solid solution.
Although it does not easily produce low melting point compounds, the reaction temperature is 1
At over 300℃, it is higher than magnesia/chrome clinker.

The present inventors focused on the difference in the reaction of magnesia chromium clinker and magnesia to iron oxide, and as a result of repeated research, we found that a specific composition of magnesia chromium clinker and magnesia
It has been found that the addition of chromium clinker promotes the formation of a slag coating layer on the working surface during use, resulting in a significant improvement in durability.

In addition, 5% by weight of the above magnesia/chromium tarinka
If it is less than 50% by weight, the fire resistance of the working surface is too high and a good (dense) slag coating layer cannot be formed, and if the magnesia/chromium clinker exceeds 50% by weight, a dense reaction layer will be formed on the working surface. However, since the melting point of the reaction layer is somewhat low, it becomes soft and easily flows down at high temperatures of about 1700° C. or higher, and sufficient corrosion resistance and antioxidation ability cannot be obtained, resulting in increased wear.

The amount of Fez03 in magnesia chrome clinker is 15
Weight% or less, MgO, An203, Cr203, Fe2
The amount of impurities excluding 03 is set to 3% by weight or less because if the amount of these impurities increases, the fire resistance of the magnesia/chromium clinker will decrease, the amount of erosion will increase, and a strong slag coating layer will not be obtained. It is.

The manufacturing method for magnesia chromium clinker is not special; it involves mixing raw material powders such as Mg○, A1203, and Cr203, or adding MgO and Cr to naturally produced chromite.
It can be obtained by adding zO 3 and adjusting the temperature as disclosed in claim 2, and shaping, firing or electromelting.

In addition, the particle size is not particularly limited, but the particle size is 1
The use of grains of m or more works more effectively because chemical adhesion due to reaction with slag on the working surface and so-called wedge effect (anchor effect) due to magnesia/chromium particles protruding onto the working surface are obtained.

As the magnesia raw material, for example, seawater magnesia, fused magnesia, and natural magnesia can be used. As the carbon raw material used in the present invention, the known Mg〇1C
There is no difference from those used in bricks, but more preferred are scale graphite, earthy graphite, coke, carbon fiber, artificial graphite, xoxographite,
A high density carbon material such as calcined anthracite is used. Although the particle size is not particularly limited, it is usually about 3fi or less. Further, the amount used is 3 to 60% by weight, more preferably 5 to 40% by weight.

The Mg○1C brick of the present invention contains a binder in addition to a magnesia carbon raw material and a magnesia/chromium raw material.

As the binder, an organic binder with residual carbon properties is used, and specific examples thereof include phenol resins and furan resins using coal tar pitch, petroleum pinch, hexamethylenetetrane, etc. as hardening agents. The blending amount of the binder is also not particularly limited, but is about 1 to 20% by weight of the blend of magnesia, a certain aggregate from the magnesia/chromium raw material, and a carbon raw material.

In addition, the MgO-C brick of the present invention may contain metals such as AN, Mg, and Si, alloys of these metals, and one type of B4C and BN to prevent oxidation of carbon, if necessary. Or two or more types can be blended. The blending amount is not particularly limited, but is usually about 1 to 10% by weight.

The Mg◯-C type unburnt brick according to the present invention is produced by kneading each raw material according to a conventional method, shaping it, and drying and hardening it at a temperature of usually about 100 to 500°C.

Further, the Mg○-C based fired refractory brick according to the present invention can be obtained by kneading each raw material according to a conventional method, shaping it, and baking it, for example, at a temperature of usually about 1000° C. in a coke breeze.

[Example 1]

Hereinafter, the usefulness of the present invention will be clarified through Examples.

(Effect of adding magnesia/chromium clinker) Magnesia/chromium clinker A (electro-fused magnesia/chromium grains)
Examples IIkL1 to 5 of the present invention in which 5 to 50% by weight of magnesia clinker B (sintered magnesia chromium particles) are added, and Example 6 of the present invention in which 20% by weight of magnesia chromium clinker B (sintered magnesia chromium particles) are added are comparative examples in which no magnesia clinker is added. It has less oxidation wear and erosion than Aim 1, and has excellent oxidation and corrosion resistance.

Furthermore, the amount of slag adhesion was greater than that of the comparative example.

Comparative example grade 2 has oxidation resistance and slag adhesion amount equivalent to that of the inventive example, but is inferior in corrosion resistance.

[Example 2] (Amount of graphite, carbon source, amount of metal additive, addition of carbide) Examples 7 to 12 of the present invention are examples in which 3 to 60% by weight of graphite is added, but the product of the present invention does not contain graphite. Comparative example N [L3
Excellent spalling resistance and corrosion resistance.

Comparative Example 4, in which 80% by weight of graphite was added, had better spalling resistance than the product of the present invention, but was inferior in oxidation resistance and corrosion resistance.

[Example 3] Examples Na13 to 17 of the present invention had a change in the magnesia raw material (N[
L14), combined use of 11+ graphite and carbon fiber (
lIkLl5), an increase in the amount of metal fine powder (16), and the combination with carbide (t'hl7), but these have better oxidation resistance and corrosion resistance than Comparative Example Fish 5 without the addition of metal fine powder. Furthermore, the spalling resistance is better than that of Comparative Example No. 6 in which 15% by weight of metal fine powder is added.

The physical property tests for each of the above Examples and Comparative Examples are as follows. This was done using the method shown below.

1) Physical test: According to JIS R2205-74.

2) Compression test: According to JIS R2206-77.

3) Oxidative wear test: Figure 1 shows an outline of the oxidative wear test apparatus. Ten 40 m square cube-shaped specimens C were placed in a horizontal cylindrical furnace 2 that had been heated to 1000°C in advance in an oxygen-proven burner 1.
~15 bricks were put in, rotated at 17 rpm for 30 minutes, and then taken out.The weight loss rate (of the specimen) before and after the test was determined and compared between the test bricks.

4) Slag adhesion index and erosion index Remaining thickness of slag line portion 4 of each specimen C when tested by the immersion rotation method using the high frequency furnace 3 schematically shown in Figure 2 11 Adhering slag thickness It is expressed as a ratio when T+-Tz is used as an index and the standard sample is set as 100.

Slag adhesion thickness (wm) = ('r+ + Tz)
/ 21 1 The above test conditions are: temperature 1650°C, time 30 minutes, rotation speed 6 Orpm, slag is converter slag, and C/S =
3.1, T. Fe=2.

5) Spalling test A test piece of 30 x 30 x 150 pieces was immersed in molten steel held at 1600°C for 3 minutes, and then cooled in water.
Judgment was made by the cracks observed on the surface of the sample when the test was repeated several times.

Q: No cracks ○: Microcracks are observed Δ: Small cracks are observed ×; Many large or small cracks are observed (margins below) 12 Table 1 Maguro Clinker-A-B Shinaga No. 2 Table 3: Amount of magkuro in Mg○-Magkuro-C system and physical properties l5 l6 [Effects of the present invention] By carrying out the present invention, special The oxidation resistance and corrosion resistance of the lining are improved by promoting the growth of the slag coating layer without using equipment, equipment, or raw materials, and the life of the furnace is extended. Specifically, the following products are used: ■ Linings for converters and throttle areas, ■ Roof bricks for pig iron mixers, and ■ Upper linings for hot metal pretreatment tanks.

It is suitable for lining metallurgical furnaces that are temporarily exposed to an oxidizing atmosphere during operation.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an oxidative wear test device, FIG. 2 is a schematic diagram of a slag adhesion index and erosion index measuring device, and FIG. 3 is a cross-sectional view of a sample after a slag attachment index and erosion index measurement test. ] 1 7 Aya Ijisho' 15 Sanskrit 4 Minato J.
Figure 1 JP-A-3 205348 (6)

Claims (2)

[Claims] (1) A magnesia carbon brick characterized by adding 5 to 50% by weight of magnesia chromium clinker to a blend of magnesia raw materials and carbon raw materials. (2) The above magnesia chromium clinker is MgO5
0-80% by weight, Al_2O_35-20% by weight, Cr
The composition is _2O_315 to 30% by weight, Fe_2O_315% by weight or less, and MgO, Al_2O_3,
Components other than Cr_2O_3 and Fe_2O_3 (impurities)
The magnesia carbon brick according to claim 1, characterized in that the amount thereof is 3% by weight or less.