JP3009060B2 - High corrosion resistant magnesia carbon brick using zirconia-containing magnesia clinker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high corrosion-resistant magnesia carbon brick applied to the lining of a high-temperature refining furnace such as a converter or a stainless steel smelting furnace having a high secondary combustion ratio.

[0002]

2. Description of the Related Art Magnesia-carbon brick containing MgO as a main component has excellent spall resistance and slag infiltration resistance, and has been widely used as a lining material in converters, stainless steel melting furnaces and the like. Have been.

[0003] However, the increase in the refining temperature and the increase in the secondary combustion ratio in converters, stainless steel smelting furnaces, etc., have severely severed the conditions of use of this type of magnesia-carbon brick. Under these conditions, magnesia-carbon bricks are subjected to slag attack at high temperatures, the magnesia clinker in the bricks elutes into the slag, and the bricks will be used with carbon such as graphite constantly exposed on the operating surface. The oxidation of carbon is accelerated, and the damage rate of magnesia-carbon brick is significantly increased.

As a measure for protecting the graphite in the magnesia carbon brick from oxidation, a method of adding an antioxidant such as an easily oxidizable metal or alloy to the brick composition has been adopted.

However, in refining furnaces such as converters and stainless steel smelting furnaces, the temperature in the furnace reaches 1700 ° C. or more, and at such high temperatures, measures such as simply increasing the amount of antioxidants such as metals and alloys are used. Then, it is difficult to expect the decarburization reaction layer to have the function of elution and oxidation prevention by suraguatack.

Therefore, in order to improve the corrosion resistance to slag under high temperature, for example, Japanese Patent Publication No. 54-8206 discloses that the aggregate is strengthened by using a high-purity electrofused magnesia clinker, It has been proposed to form a protective layer that is stable against slag attack on the surface, but no satisfactory results have yet been obtained.

Further, T.I. Japanese Patent Application Laid-Open No. 57-183360 discloses a method for improving the corrosion resistance of a slag with a high Fe content by dissolving a trace amount of ZrO ₂ into a solid solution in MgO particles.
It has been proposed to prevent oxidation at 0 ° C. or higher. However, this causes the clinker to collapse due to the intrusion of silicate or silicate containing iron oxide into the grain boundaries of the magnesia clinker.

As another countermeasure, the use of ZrO ₂ alone has been proposed. However, a reduction reaction of ZrO ₂ by a coexisting Al-based metal or the formation of ZrC at a high temperature destroys a brick structure. And good results cannot be obtained.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method which is stable against suraguatac even under high temperature and oxidizing atmosphere conditions. An object of the present invention is to obtain a magnesia-carbon brick having excellent corrosion resistance even for a slag having a high Fe content.

[0010]

The high corrosion-resistant magnesia-carbon brick of the present invention comprises 3 to 30% by weight of carbon powder.
If, Al, Mg, Ca, and 0.5-7% by weight of one or more or their these alloys in the Si, the ZrO ₂ 2-10% by weight as an aggregate of magnesia clinker
It achieved its objectives by using a blend of dispersed in the grain boundaries in periclase zirconia-containing Mug <br/> Indonesia clinker.

As the carbon powder, natural or artificial graphite, coke, mesophase carbon and carbon black can be used.

The magnesia clinker used as the aggregate used in the present invention is a high-purity MgO powder and a high-purity ZrO ₂
It is obtained by mixing powder and a predetermined ratio and firing at 1900 ° C. or higher or melting in an arc furnace.

The aggregate to be used is preferably as high as possible in purity. In the case of MgO, the magnesia clinker may be an electrofused product, a calcined product, or the like, but preferably has a large periclase crystal system. .

In order to improve the spall resistance, it is effective to add a pitch, a phenolic polymer resin powder or the like to the composition.

[0015]

In general, alteration of magnesia clinker in carbon bricks is caused by alteration of magnesia clinker grain boundaries. That is, when a silicate or a silicate containing iron oxide penetrates into the magnesia grain boundary, foreign components penetrate into the brick, and the following reaction with magnesia progresses, and MgO + SiO ₂ → M ₂ S, MgO + F
eO → (Mg, Fe) O A low melt is formed and collapsed.

The magnesia clinker in which ZrO ₂ is present at the grain boundaries according to the present invention captures such foreign components at the grain boundaries and suppresses invasion into the clinker by causing it to exist as ZrO ₂ · SiO ₂ or the like.

Further, the ZrO ₂ component in the clinker remains near the operating surface of the brick even after the magnesia is eluted by a foreign component, and has a function of protecting the magnesia clinker.

When the content of ZrO ₂ in the clinker is less than 2% by weight, ZrO ₂ is almost present as a solid solution in magnesia or precipitated in periclase grains, and precipitation at grain boundaries is small. The function of retaining foreign components at grain boundaries cannot be expected greatly. On the other hand, if the content exceeds 10% by weight, ZrO ₂ precipitates on the surface of the clinker, and a reduction reaction occurs with the carbon or Al-based metal in the brick, resulting in structural deterioration.

If the carbon powder is less than 3% by weight, the spall resistance and the slag infiltration resistance are inferior, and if it is more than 30% by weight, the workability in production is inferior.

If the amount of the added metal such as Al is less than 0.5% by weight, the strength is poor, and if it is more than 7% by weight, the spall resistance is particularly poor.

[0021]

EXAMPLES Table 1 is a table showing the blending ratio of simple bricks and the evaluation results of physical properties.

Table 2 and below show M containing 6% by weight of ZrO _2.
It is a table | surface which shows the physical-property evaluation result which changed the ratio of gO clinker and electrofused MgO.

An appropriate amount of a liquid phenolic binder is added to each of the raw material compositions shown in Table 1, and kneading, friction molding, drying (90 ° C. × 24 hours), and curing treatment (250
C. × 10 hours) to obtain magnesia-carbon brick. As shown in Comparative Examples 4 to 6 in Table 1, when the content of ZrO ₂ in the magnesia clinker is out of the range of the claims, the corrosion resistance is inferior to the examples.

Next, the 6% by weight ZrO ₂ -containing magnesia clinker having the best corrosion resistance was selected from the results shown in Table 1, and an appropriate amount of a liquid phenolic binder was added to each of the raw material compositions shown in Tables 2 to 7. After addition, kneading, friction molding, drying (90 ° C. × 24 hours), curing treatment (2
(50 ° C. × 10 hr) to obtain magnesia-carbon brick.

As shown in Comparative Examples 6 to 10 in Tables 2 to 7, when the amount of graphite or metal added is out of the predetermined range, the corrosion resistance is inferior to the examples.

As described above, the magnesia-carbon bricks shown in the examples of Tables 1 to 7 can obtain the result that the corrosion resistance is generally improved, and the magnesia-carbon brick using the zirconia-containing magnesia clinker according to the present invention is obtained. ,
Compared to conventional magnesia carbon brick, it is understood that it has high corrosion resistance.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5]

[0032]

[Table 6]

[0033]

[Table 7]

[0034]

According to the present invention, the following effects can be obtained.

(1) The ZrO ₂ component is stably present in the magnesia carbon brick up to a high temperature range, and a high corrosion resistant magnesia carbon brick can be obtained.

(2) Therefore, it can be suitably used as a lining brick of a high-temperature refining furnace such as a converter or a stainless steel smelting furnace having a high secondary combustion ratio.

────────────────────────────────────────────────── (5) References JP-A-58-99161 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/043

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein 3 to 30% by weight of carbon powder and Al,
0.5 to 7% by weight of one or more of Mg, Ca and Si or an alloy thereof, and 2 to 10% as an aggregate.
Weight percent ZrO ₂ with magnesia clinker periclé
High corrosion-resistant magnesia-carbon brick consisting of a mixture with zirconia-containing magnesia clinker dispersed in the grain boundaries of steel.