JPH07291748A - Irregular refractories construction method - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a method for constructing a refractory having an irregular shape, which has excellent durability, as a refractory lining for a molten metal container. [Composition] As an aggregate, MgO is 35 in terms of chemical composition.
˜95 wt%, Al ₂ O ₃ is 5 to 65 wt%, and the balance component is 5 wt% or less MgO—Al ₂ O ₃ based spinel clinker, or the chemical component ratio is 30 to 95 MgO.
wt%, CaO is 5 to 70 wt%, and the remaining component is 5 wt
An amorphous refractory material containing MgO-CaO clinker in an amount of not more than 10% is poured, and after curing, drying is performed under reduced pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of constructing a refractory lining having an irregular shape and excellent durability.

[0002]

2. Description of the Related Art As one of the molten steel processing equipment, RH type
Vacuum degassing furnaces such as the DH type are known.

Conventionally, the lining of this vacuum degassing furnace is
Mainly fired magnesia-chromic bricks are used. However, since it is brick, there are problems that the cost increases due to the firing process during manufacturing, that special skill and many man-hours are required for the furnace.

Further, since the magnesia-chromic brick contains chromium, it causes a problem in waste disposal after use from the viewpoint of environmental protection.

Therefore, in recent years, in the lining of the vacuum degassing furnace, there is a strong demand for dechromization and indeterminate shape.

However, the lining of the vacuum degassing furnace has a high basicity and a high F under vacuum conditions at a high temperature of 1600 ° C. or higher.
Due to the extremely harsh operating conditions of constant contact with slag containing eO component and physical wear due to molten steel flow, not only irregular refractory but also brick material other than magnesia-chrome brick The current situation is that the material cannot be used.

For example, magnesia brick has excellent corrosion resistance to slag and molten steel, but has a drawback that crack peeling easily progresses due to its large thermal expansion and that slag penetration resistance is poor. Actual use is difficult.

The use of magnesia-carbonaceous bricks has also been studied, but since carbonaceous materials are used as the raw material composition and binder, sufficient durability cannot be obtained due to deterioration of the structure due to oxidation. There is also concern about carbon pickup for molten steel.

Among them, a basic amorphous refractory material which can be easily poured, has a small thermal expansion, and has a relatively small slag penetration is disclosed in, for example, JP-A-64-
Magnesia as reported in Japanese Patent No. 83575
Spinel-containing materials such as spinel have been proposed.

[0010]

Since the spinel-containing material is an amorphous refractory material, it does not require furnace work,
Although it is preferable in terms of workability, it is still insufficient in corrosion resistance to slag as compared with magnesia-chromic bricks because a neutral spinel clinker is used.

The present invention provides a method for obtaining a cast refractory having a durability comparable to that of a magnesia-chromic brick, as to a method for applying a cast material which is dried under reduced pressure after being applied and cured.

[0012]

According to the present invention, in a refractory lining for molten metal, MgO is 35 to 9 in terms of chemical composition.
5 wt%, Al ₂ O ₃ is 5 to 65 wt%, and the balance component is 5
This is a method for constructing an amorphous refractory material, which comprises pouring an amorphous refractory material containing wt% or less of MgO-Al ₂ O ₃ -based spinel clinker, curing and then drying under reduced pressure.

Further, according to the present invention, an amorphous refractory material containing MgO-CaO clinker having a chemical composition ratio of MgO of 30 to 95 wt%, CaO of 5 to 70 wt% and a balance of 5 wt% or less is poured, After hardening, it is a method for constructing an irregular-shaped refractory, characterized by drying under reduced pressure.

[0014]

In the spinel clinker, the theoretical composition of MgO is 28 wt% and Al ₂ O ₃ is 72 wt%.
The MgO-excess spinel clinker having a higher MgO composition exhibits excellent durability in combination with the volume stability and slag penetration resistance of spinel and the corrosion resistance of MgO.

However, in the MgO-excess spinel clinker, hydration reaction easily occurs due to the presence of water.
Fine crystals of gO are present.

The crystal diameter of this MgO is about 1 to 10 μm, although it varies depending on the spinel manufacturing conditions.

Therefore, when this MgO-excess spinel clinker is used as an aggregate of an amorphous refractory by pouring construction, a slaking (digestion) phenomenon in which the MgO component in the clinker hydrates when the construction water is dried, It adversely affects the construction body, such as the occurrence of cracks due to volume expansion and the weakening of the structure.

Although MgO-CaO clinker is superior in volume stability and slag penetration resistance and is more excellent in corrosion resistance to slag having a higher basicity than MgO, MgO and Mg
Since it consists of a CaO component that is more easily hydrated than O, when used as an amorphous refractory, a slaking phenomenon easily occurs during drying.

As a method for preventing the slaking of a basic component such as MgO, the addition of amorphous SiO ₂ in JP-A-58-99177 and the addition of phosphate in JP-A-61-291465 are reported. Has been done.

However, the addition of such a low-melting material source leads to a decrease in the hot strength of the refractory material and the formation of an oversintered layer,
It is feared that the corrosion resistance may be deteriorated or peeling may occur due to the spalling phenomenon.

Therefore, as a new countermeasure against slaking of irregular shaped refractory, it was found that it is effective to dry in a decompressed state after casting, and the present invention was derived.

That is, the hydration reaction rate of MgO and CaO greatly depends on the temperature, and the fact that the reaction rate becomes extremely small as the temperature lowers, so that low-temperature drying is carried out under reduced pressure to achieve slaking as much as possible. It was possible to suppress it.

Here, the term "drying under reduced pressure" refers to the method described in Japanese Patent Application No. 05-108819 filed by the inventors of the present invention. After the casting, the atmosphere is reduced to a reduced pressure during drying. By maintaining and lowering the boiling point of water (100 ° C at atmospheric pressure) and evaporating the water at a low temperature of 100 ° C or lower and above the boiling point in the atmosphere, both rapid drying and prevention of slaking of refractory construction can be realized. Is possible. Here, if the temperature is lower than the boiling point, the drying rate is extremely reduced.

The specific method of vacuum drying in the present invention is as follows.
A vacuum degassing furnace, or a molten metal container such as a ladle, a converter, and a hot metal car is poured into the container using a core, and the container is sealed. Warm.

The degree of pressure reduction at this time is 30 torr or more 2
It is preferably 50 torr or less.

If it is less than 30 torr, the microwave discharge phenomenon remarkably occurs, and if it exceeds 250 torr, it becomes difficult to dry at low temperature.

The drying time is determined according to the material of the construction body, the construction thickness, the construction volume, the temperature change on the back surface of the construction body, and the like.

By this low temperature drying under reduced pressure, Mg
Since the slaking of O and CaO is suppressed, it is possible to prevent the deterioration of the strength of the refractory and the occurrence of cracks.

The spinel clinker used in the present invention has a chemical composition of 35 to 95 wt% of MgO and Al.
₂ O ₃ is 5 to 65 wt%, and the balance component is 5 wt% or less.

As described above, since the MgO content is higher than the theoretical spinel composition, the corrosion resistance of MgO is exhibited in addition to the volume stability and slag penetration resistance of spinel. MgO is less than 35 wt% and Al ₂ O ₃ is 65w
If it is more than t%, the corrosion resistance is poor.

When MgO is more than 95 wt% and Al ₂ O ₃ is less than 5 wt%, the spinel mineral is reduced and the volume stability becomes poor. Further, when the balance component exceeds 5 wt%, the corrosion resistance is lowered.

The MgO-CaO clinker used in the present invention contains 30 to 95 wt% of MgO and C in terms of chemical composition.
The aO content is 5 to 70 wt% and the balance is 5 wt% or less.

When MgO content is less than 30 wt% and CaO content is more than 70 wt%, it is extremely rich in hydration and cannot be prevented from deterioration due to progress of slaking even by drying under reduced pressure.

More than 95 wt% MgO and 5 CaO
If it is less than wt%, the volume stability tends to be poor. Further, when the balance component exceeds 5 wt%, the corrosion resistance is lowered.

For the refractory aggregate in the amorphous refractory, MgO is used.
Besides both clinker of excess spinel clinker and MgO-CaO clinker, for example, magnesia, alumina,
Aggregates such as zircon, zirconia, and alumina-silica may be combined.

Further, spinel clinker having a ratio of MgO and Al ₂ O ₃ which is out of the present invention may be used in combination.

The particle size composition of the aggregate is, for example, 5 m.
MgO rich spinel clinker or MgO—CaO clinker is used for some or all of these particle size ranges, consisting of coarse particles in the range of m to 3 mm, medium particles in the range of 3 mm to 1 mm, and fine particles of 1 mm or less.

However, in order to fully exert the effects of the present invention, it is necessary to blend MgO-excess spinel clinker or MgO-CaO clinker having the chemical composition aimed at in the present invention in an amount of 30 wt% or more of the total refractory aggregate. desirable.

The addition of a dispersant, a binder and the like to the blended refractory aggregate is the same as in the conventional castable irregular refractory material.

Examples of the dispersant include inorganic salts such as sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, acidic sodium hexametaphosphate, sodium borate, sodium carbonate, sodium citrate, sodium tartrate, sodium polyacrylate, and the like. Examples thereof include organic salts such as sodium sulfonate.

The addition amount is preferably 0.001 to 1 wt% with respect to 100 wt% of the refractory aggregate. As the binder, for example, a cement having a hydraulic property such as alumina cement or light burned magnesia is added in an amount of 1 to 15 wt%.

If necessary, fibers, metal powder, hardening accelerator, hardening retarder, refractory ultrafine powder, silica sol, alumina sol, calcined alumina, etc. may be added within a range that does not impair the effects of the present invention. Good.

[0043]

EXAMPLES Examples of the present invention and comparative examples will be shown below.

Table 1 shows the chemical analysis values and mineral composition survey results of the clinker used in each example. Among the clinker described in the table, the clinker having the chemical composition limited in the present invention is A, B, C, D, E, F.

Table 2 shows examples of the non-standard refractory structure according to the present invention, comparative examples, and conventional non-standard refractory products.
This is a summary of the composition of the composition and the characteristics of the construction product after drying.

In the actual machine test, 5 to 7 wt% of the working water was added to the weight of the amorphous refractory, and after sufficient kneading, the core was placed inside the lower tank of the RH type vacuum degassing furnace. Was applied while applying vibration, and the applied product was dried in a predetermined manner.

Drying was carried out by irradiating with microwaves in an atmosphere kept at a predetermined reduced pressure.

Here, the average drying temperature is the average value of the surface temperature and the back surface of the construction body at the end of drying.

The surface properties, bulk specific gravity, porosity, spall resistance, corrosion resistance, and slag penetration resistance are the results of samples sampled in a specific shape after drying.

Regarding the anti-slaking property, the line change rate before and after the drying was measured for a sample which was separately constructed in a shape of 40 × 40 × 160 mm and subjected to predetermined drying.

For magnesia-chromic bricks,
The test results of 1800 ° C fired products are posted.

Each test method is as follows.

Surface properties: The presence or absence of cracks on the surface of the construction body after drying was examined by visual observation.

Slacking resistance: The rate of linear change immediately after pouring and after drying was determined. The larger the value, the larger the volume expansion due to hydration and the poorer the slaking resistance.

Porosity: According to JIS-R2205.

Spor resistance: After heating at 1500 ° C. for 20 minutes, air cooling in air was repeated, and the number of times until peeling was determined. The larger the value, the better the spall resistance.

Corrosion resistance: Steel piece by weight ratio: converter slag = 6
Using the erosion agent of 0:40, a rotary erosion test was performed at 1600 ° C. for 3 hours, and the melt loss dimension after the test was measured.

Slag penetration resistance; after the above-mentioned rotary erosion test,
The penetration size of the slag was measured.

Actual machine test: Part of the examples and comparative examples were actually used in the RH lower tank, and the durability was determined by the average amount of wear per channel mm / ch. The smaller the value, the better the durability.

As the test results show, Examples 1 to 1 of the present invention
No. 7 shows that the linear change rate after drying is smaller than that of Comparative Examples 8 to 12 and that it is excellent in slaking resistance, which is also reflected in the presence or absence of surface cracks in the post-drying construction body.

As a result, in the examples of the present invention, the compactness (low porosity) of the construction body is maintained and the corrosion resistance, the slag penetration resistance and the spall resistance are excellent.

As a result of evaluating the constructions shown in the examples of the present invention using an actual machine, in all cases, the durability was equal to or higher than that of the current magnesia-chromic brick (Example 13).

Comparative Example 8 is a composition of Mg limited by the present invention.
Since the amount of O-excess spinel clinker is small and the amount of neutral spinel clinker is almost theoretical, corrosion resistance is poor.

Comparative Examples 9 and 10 are MgO-rich spinel clinker, MgO-C, which is out of the composition defined by the present invention.
Since the aO clinker is contained in a large amount, it is inferior in slaking resistance.

In Comparative Examples 11 and 12, the degree of pressure reduction during drying was insufficient, and low-temperature drying could not be sufficiently carried out.
Inferior to resistance to slaking.

[0066]

[Table 1]

[0067]

[Table 2]

[0068]

As described above, the refractory aggregate having the specific chemical composition, the MgO-excess spinel clinker, and the amorphous refractory material containing the MgO-CaO clinker are poured, and after curing, they are dried at low temperature under reduced pressure. The obtained construction of the present invention has both volume stability and slag permeation resistance and corrosion resistance originally possessed by the clinker, since slaking during drying can be prevented.

The durability thereof is equal to or higher than that of the existing magnesia-chromic brick, and, for example, in the refractory lined in the vacuum degassing furnace, its amorphous form and dechrome form are possible.

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Claims (2)

[Claims] 1. The ratio of chemical components is 35 to 95 w of MgO.
t%, Al ₂ O ₃ is 5 to 65 wt%, and the remaining component is 5 wt
% Of MgO—Al ₂ O ₃ -based spinel clinker is poured, and after curing, drying is carried out under reduced pressure. 2. The chemical composition ratio of MgO is 30 to 95 w.
t%, CaO is 5 to 70 wt% and the balance is 5 wt%
A method for constructing an amorphous refractory, which comprises pouring the following amorphous refractory containing a MgO-CaO clinker, curing and then drying under reduced pressure.