JPH09100172A - Basic castable refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a basic castable refractory excellent in slag permeation resistance, digestion resistance and spalling resistance and not excessively sintered, by adding specific large coarse magnesia granules to the composition of a refractory aggregate and a magnesia-calcia clinker having a specific composition. SOLUTION: 5-50 outer wt.% of large coarse magnesia granules having granule diameters of 10-50mm and subjected to a surface treatment are added to a composition comprising 80-50wt.% of a refractory aggregate having a controlled granular size and 20-50wt.% of a magnesia-calcia clinker having the below-described characteristics. The magnesia-calcia clinker contains MgO, CaO and Fe2 O3 in a total amount of >=97wt.%, has a chemical composition comprising 30-90wt.% of MgO, 0.2-5wt.% of Fe2 O3 and 0.5-3wt.% of TiO2 , and is coated with a coating comprising calcium phosphate and magnesium phosphate. The surface-treating agent for the large coarse magnesia granules is preferably a phosphate salt, sodium silicate, a silane coupling agent, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a basic castable refractory having excellent digestion resistance, corrosion resistance, spalling resistance, and slag penetration resistance.

[0002]

2. Description of the Related Art The inner lining of a steelmaking furnace for steelmaking is shifting from a regular refractory to an irregular refractory for the purpose of labor saving, construction work, cost reduction, etc. And in recent years,
With the improvement of vacuum degassing method, continuous casting, ladle refining technology, the ratio of argon stirring, alloy addition vacuum treatment, etc. has increased, and steelmaking conditions tend to become severe due to high temperature tapping, extension of residence time, etc. In addition, the demand for clean steel is increasing. Amorphous refractories also need to meet these conditions, and as an irregular refractory that meets this requirement,
Castable refractories with basic properties are being considered. For example, JP-A-4-198064 discloses MgO 65.
_{~96wt%, ZrO 2 2.6~20wt%,} SiO 2
It has been proposed to use magnesia / zirconia / forsterite clinker having a composition of 1.3 to 10 wt%, which is believed to improve the slag penetration resistance and spalling resistance of a basic amorphous refractory material. There is.

However, when this amorphous refractory material is applied to a steelmaking furnace, a ladle, etc. where the temperature changes drastically, peeling wear occurs due to structural spalling due to thermal or slag infiltration, and the basic material has High corrosion resistance cannot be fully exhibited.

From this, expectations are high for a castable refractory having a basic property, which contains magnesia-calcia clinker excellent in slag penetration resistance and spalling resistance.

However, when magnesia-calcia clinker is used, the digestibility of the clinker itself is remarkable,
In practical application, it is necessary to take measures against this digestibility. For example, Japanese Patent Laid-Open No. 5-294713 discloses an attempt to improve digestion resistance by adding TiO ₂ or Fe ₂ O ₃ to a magnesia / calcia clinker and applying a sparingly soluble coating on the clinker surface. ing. However, in the case of amorphous refractories that use such magnesia / calcia clinker as they are, especially castable refractories, they usually react with alumina in alumina cement, which is used as a binder, to significantly reduce the refractory resistance and to improve corrosion resistance. Is deteriorated.

Further, in the case of using alumina cement as a binder, it is possible to obtain a refractory composition having a high strength by using a small amount of alumina cement by using a combination of ultrafine powder and a dispersant. 60-9983
No. 6,086,045. Furthermore, JP-A-5-2298
No. 76 publication, even if the alumina cement is not used,
It is disclosed that a high-strength refractory composition can be obtained by using active magnesia and fine siliceous powder together with a dispersant. The method of combining this dispersant and ultra-fine powder is carried in the powder material into the casting site, adding water, kneading, casting, curing, deframing and in the case of ordinary castable refractory used after drying, kneading It is based on the idea that it is possible to obtain a kneaded mixture that exhibits a fluidity that can be sufficiently constructed with a low amount of water at times, and a castable refractory construction body having a dense structure can be obtained. As the ultra-fine powder raw material used in this case, although ultra-fine powder of alumina or silica is generally effective, as described above, alumina reacts with magnesia / calcia clinker to reduce corrosion resistance, The fine powder itself has a drawback that it is a sintering agent and also reacts with magnesia / calcia clinker to become slightly oversintered, resulting in large shrinkage after firing.

As described above, in the case of a basic castable refractory containing a cohesive bond in which the amount of alumina cement is reduced and ultrafine powder and a dispersant are used in combination and magnesia / calcia clinker, it is necessary to add a large amount of ultrafine powder. However, since the sintered body after sintering has a large degree of sintering and shrinkage, it has poor spalling resistance when used in an actual furnace,
Cracks and peeling will occur.

As a method of suppressing such oversintering, by using an aggregate that expands at a high temperature such as kyanite, loastone, and silica stone, fine cracks are generated in the matrix to disperse the cracks and burn. A method of suppressing the binding can be considered. However, since these methods contain a large amount of acidic oxides as an aggregate, they are exposed to a high basicity slag that a basic material is considered, and are subjected to severe operations with severe temperature fluctuations at high temperatures around 1600 ° C. In a steelmaking furnace in which No. 1 is performed, the fire resistance is significantly lowered and the corrosion resistance is lowered, which is not preferable.

In addition to the above, addition of brick scraps or granules is known, for example, in Japanese Patent Publication No. 3-2824.
It is disclosed in Japanese Patent Publication No. 183664. However, as in the former case, the surface of brick scraps coated with silicon oil, silica sol, alumina sol, etc. is a basic castable refractory that wants to eliminate insufficient filling due to water absorption during kneading and deterioration of workability during construction. This is not sufficient, and the latter granulated product having a smooth surface is also the same as the former, and a sufficient improvement effect on the spalling resistance due to oversintering during use in an actual furnace cannot be obtained.

[0010]

SUMMARY OF THE INVENTION From such a problem,
A basic castable refractory whose aggregate is magnesia or alumina-magnesia or magnesia-calcia.
Further, refractory materials such as those using brick scraps or granulated materials have the above-mentioned problems in practical use.

In the present invention, the problem to be solved is a castable refractory having basic properties which is excellent in slag penetration resistance and digestion resistance, suppresses oversintering, is excellent in spalling resistance and is highly practical. Is to get.

[0012]

The castable refractory having a basic property according to the present invention is a magnesia / calcia clinker-containing basic refractory having excellent digestion resistance. 5 times
It was completed based on the clarification that the addition of 50 wt% can suppress the oversintering due to the ultrafine powder in the composition and improve the spalling resistance of the castable refractory having basic properties. .

That is, the basic castable refractory material of the present invention comprises 80 to 50 wt% of a particle size-adjusted refractory aggregate.
A magnesia / calcia clinker of 20 to 50 wt% is added to the surface of a large coarse magnesia having a particle size of 10 to 50 mm in an amount of 5 to 50 wt%.

As the magnesia / calcia clinker, the total amount of MgO, CaO and Fe ₂ O ₃ is 97 wt% or more, and MgO is 30 to 90 wt%, Fe ₂ O ₃
It has a chemical composition of 0.2 to 5 wt% and TiO ₂ 0.5 to ₃ wt%, and its surface is coated with calcium phosphate and magnesium phosphate.

The coating on magnesia is for improving the digestion resistance, and the surface of the large coarse magnesia is surface-treated with one or more of phosphate, sodium silicate and silane coupling agent. do.

The magnesia / calcia clinker-containing basic refractory has a slag permeation suppression effect because the calcia in the clinker reacts with the silicate in the slag to increase the basicity and raise the melting point to suppress the permeation of the silicate. . However, as mentioned above, since the amount of alumina cement added is small, cohesive bonding using a combination of ultrafine powder and a dispersant results in the addition of a large amount of ultrafine powder. For this reason, the fired construction body has a problem that the sintering progresses and the shrinkage increases, so that cracks and peeling occur during use in an actual furnace and a sufficient effect cannot be obtained. As a result of various studies, the inventors of the present invention added 5 to 50 wt% of a surface-treated large coarse-grained magnesia of 10 to 50 mm, thereby suppressing the slag permeation by adding magnesia / calcia clinker in the formulation. It has been found that the spalling resistance of the construction body is improved without impairing the

That is, according to the present invention, the surface-treated large coarse-grained magnesia is added to the basic castable refractory containing magnesia / calcia clinker to prevent spalling resistance of castable refractory without impairing slag penetration resistance and corrosion resistance. There is a characteristic that the property is improved, and by this, the durability can be improved when the actual furnace is used.

Explaining in detail below, among the refractory raw materials, magnesia has a large coefficient of thermal expansion, and when large coarse particles are added to ordinary aggregate, the matrix part has a low expansion rather than magnesia. If the construction body is repeatedly heated up to 1500 ° C during use of an actual furnace due to the progress of sintering due to or other additives, the thermal expansion difference becomes large, and the spalling resistance does not improve, resulting in large coarse particles. Magnesia destroys the matrix and weakens the organization.

However, in the composition of the present invention, in which the magnesia-calcia clinker is added in an amount of 20 to 50% by weight, the large-grain magnesia linker does not destroy the matrix, but the crack deflection effect, that is,
It is assumed that the spalling resistance is improved by exerting an effect on the generation and propagation of cracks when using an actual furnace.

As the large coarse-grained magnesia, one or more of electro-melted magnesia, seawater magnesia (or synthetic magnesia) and natural magnesia can be applied. However, from the viewpoint of corrosion resistance, electrofused magnesia having a purity of 95 wt% or more, or seawater magnesia or synthetic magnesia is suitable. As the properties of the large coarse magnesia, crushed particles, granulated materials and brick scraps are considered, but crushed particles are preferable. This is seawater magnesia (or synthetic magnesia)
When spherical particles, pellet particles, or briquette particles are added to the castable composition as they are without crushing, the adhesiveness with the matrix is poor, and the effect of suppressing cracking by spalling becomes small.

The particle size of the large coarse magnesia is preferably 10 to 50 mm. That is, if the particle diameter is less than 10 mm, the effect of suppressing cracking by spalling is small, and if it exceeds 50 mm, the workability is deteriorated.

The amount of large coarse-grained magnesia added is preferably 5 to 50 wt% on the outside. That is, if it is less than 5 wt%, the crack suppressing effect by spalling is small,
If it exceeds t%, the workability is deteriorated.

The particle size used in the present invention is 10 to 50.
The surface treatment is applied to the large-grained magnesia of mm.
That is, when the amount of magnesia / calcia clinker added increases, the pH of the kneaded product excluding the large-grain magnesia increases.

Embedded image The reaction speed increases to the right in the above equation. For this reason, MgO
, The equilibrium shifts further to the right to compensate for Mg ²⁺ and becomes easier to digest. Therefore, it is necessary to prevent the surface of the large-grain magnesia from being digested. As the digestion prevention method used here, it is desirable to perform surface treatment with one or more of phosphate, sodium silicate, and silane coupling agent. Regarding the phosphate, calcium phosphate and magnesium phosphate are preferable, and they form a sparingly soluble phosphate on the surface of large-grain magnesia to suppress the hydration reaction with water. Examples of the coupling agent include silane-based, titanate-based, aluminate-based, and zirconialuminate-based coupling agents, and the silane coupling treatment agent-based agent is effective in terms of its effect and cost. The sodium silicate may be either powder or liquid.

Regarding the magnesia-calcia clinker used in the present invention, the total amount of MgO, CaO and Fe ₂ O ₃ is 97 wt% or more, and MgO 30-90.
wt%, Fe ₂ O ₃ 0.2-5 wt%, TiO ₂ 0.
It is a magnesia calcia clinker having a chemical composition of 5 to 3 wt% and having a coating composed of calcium phosphate and magnesium phosphate on its surface.

The total amount of MgO, CaO and Fe ₂ O ₃ is 97.
If it is less than wt%, the density of the magnesia-calcia clinker decreases, the digestion resistance deteriorates, and at the same time, the amount of impurities increases, and the corrosion resistance of the magnesia-calcia clinker and the refractory material decreases, which is not preferable. Mg
When the O content is less than 30 wt%, the surface of magnesia / calcia clinker becomes mostly calcia crystals, and even if Fe ₂ O ₃ and TiO ₂ are added and further phosphate is coated, the digestion resistance is sufficient. None, and the MgO content is 9
If it exceeds 0 wt%, the amount of free CaO in the magnesia / calcia clinker becomes too small, and it becomes difficult to exhibit the properties of calcia in the refractory, which is not suitable. Regarding the amounts of Fe ₂ O ₃ and TiO ₂ , the former is 0.2 to
5 wt% and the latter is regulated to 0.5 to 3 wt%, but adding an appropriate amount of these oxides produces CaO and a compound,
Although the digestion resistance is improved, excessive addition reduces the density of magnesia-calcia clinker and deteriorates the digestion resistance.

In the magnesia calcia clinker used in the present invention, the surface of the clinker is coated with calcium phosphate and magnesium phosphate by a secondary treatment because the reason for this is that the clinker surface is coated with a sparingly soluble phosphate. This is because the covering film is formed and the hydration reaction between water and the clinker is suppressed.

The rate of increase in weight of the magnesia-calcia clinker, which indicates the resistance to digestion, varies depending on the CaO content of the clinker, but if it is in the range of 0.05 to 0.3 wt%, general dolomite clinker and magnesia-calcia It is far superior to clinker and can be used for amorphous refractories that use water.

In the present invention, the magnesia / calcia clinker having the above properties is used as the main raw material, but the addition amount is 2
0 to 50 wt% means that if the added amount is less than 20 wt%, the refractory material has poor spalling resistance and slag penetration resistance,
You cannot get enough effect. 50 wt% addition amount
If it exceeds, the workability at the time of kneading remarkably deteriorates, probably because a large amount of aggregated ions are dissolved during kneading.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION As the refractory aggregate used in the present invention, raw materials other than alumina and alumina-silica can be used in combination. For example, as a raw material containing oxides, silica stone, silica sand,
Fused silica, hydrous amorphous silica, anhydrous amorphous silica and other siliceous substances, zircon, zirconia and other zirconia substances, fused magnesia, seawater magnesia, synthetic magnesia, natural magnesia, basic properties such as calcium oxide, spinel, oxidation Chromium such as chromium and chromite, carbides such as silicon carbide, aluminum carbide and zirconium carbide, and nitrides such as zirconium nitride, silicon nitride, silicon iron iron, boron nitride, aluminum nitride, etc. Is a carbonaceous material such as coke, scaly graphite, scaly graphite, natural graphite such as earthy graphite, artificial graphite, calcined anthracite, bitch powder, carbon black, coal powder, carbon bricks and electrode scraps, and others. A group of all refractory raw materials such as boride such as boron, silicon, silicide such as ferrosilicon, etc. Selected, it can be solely or in combination as required.

For the casting material of the present invention, a dispersant used for ordinary castable refractories can be used.
Examples of the dispersant include alkali metal phosphates, alkali metal carboxylates, alkali metal humates, sodium polycarboxylates, sodium alkylsulfonates,
Alkali metal silicates such as sodium aromatic sulfonate,
Alkali metal carbonate, sodium lignin sulfonate, sodium salt of maleic anhydride-isobutylene copolymer and ammonium salt thereof, and one or more selected from substances having similar effects it can. The amount of these dispersants used is within a commonly used range, for example, 0.0 per 100 parts by weight of the refractory aggregate.
It is about 05 to 1.000% by weight.

The amorphous refractory material of the present invention further comprises various metal fibers known as additives for such refractory materials for casting, such as metal fibers such as SUS fiber and steel fiber, metal particles, metal powder, and glass. You may add antioxidants, such as a coagulant | flocculant, a thickener, a coagulation regulator, and a defoaming agent, in the range which does not impair various physical properties.

Further, the amorphous refractory material of the present invention includes animal natural fibers such as silk and wool, plant natural fibers such as hemp, cotton, cotton and straw, regenerated fibers such as viscose, acetate and the like. Organic fibers that disappear with heat such as semi-synthetic fibers, polyamide-based, polyester-based, polyurethane-based, polyolefin-based, polyvinyl chloride-based, polyvinylidene chloride-based, polyfluorethylene-based, polyacrylic-based, PVA-based, and other synthetic fibers Can also be added. And these organic fibers are about 0.001-1.0 weight%.

[0033]

EXAMPLES Table 1 shows the composition and properties of the large coarse magnesia and magnesia calcia clinker used. Table 2,
Table 3 shows examples of the present invention and comparative examples thereof. At the same time, the test results are shown.

[0034]

[Table 1]

[Table 2]

[Table 3] The magnesia / calcia clinker A has a composition within the range specified in the present invention, and TiO ₂ was added at the time of manufacturing the clinker in order to improve digestion resistance, and calcium phosphate and magnesium phosphate were coated. Has been done. On the other hand, magnesia / calcia clinker B
Has not been treated to improve such digestion resistance. Magnesia calcia clinker C exhibits a composition outside the scope of the present invention.

Further, the large-coarse-grain magnesia D to H have the same composition, and all are crushed large-coarse grains by a jaw crusher. However, the large-coarse-grain magnesia D contains phosphates (calcium phosphate, magnesium phosphate). Coating, large coarse magnesia E, surface treatment by silane coupling,
Large coarse magnesia F is coated with sodium silicate, large coarse magnesia G is coated with phosphate and surface-treated by silane coupling, and large coarse magnesia H is subjected to such treatment. Not done.

Silicic powder, hydraulic cement, and dispersant were added to these compounded raw materials to adjust coarse particles, medium particles, and fine particles so that close packing was obtained. After that, JIS R255
Water was added so that the standard softness state shown in 3 was obtained, and kneading, casting, curing and deframing were performed at room temperature, followed by drying at 110 ° C for 24 hours, and a comparative evaluation by the following test method. Was done.

<Slag erosion resistance> CaO / SiO ₂ molar ratio = 3.2, Al ₂ O ₃ = 10 wt%, T-Fe = 10 w
The slag of t% was used as the erosion agent. After heating and melting SS41 steel at 1600 ° C in a high-frequency induction furnace lined with test pieces,
The operation of charging the erosion agent and holding it for 30 minutes was performed for 10 cycles, and then the erosion dimension of the test piece was measured.

The numerical value is 100 for the erosion size of Example 1.
The smaller the value, the better the slag resistance.

<Slag Penetration Resistance> The penetration thickness of the slag was measured from the cut surface of the test piece whose melt loss dimension was measured.
In addition, this numerical value is shown as an index with the slag permeation thickness of Example 1 as 100, and the smaller this numerical value is, the better the slag permeation resistance is.

<Spalling resistance> One side of the sample was heated in an electric furnace, the test piece was rapidly heated to 1200 ° C., held for 30 minutes, and then rapidly cooled to 800 ° C. Repeatedly, the number of peeling was evaluated.

Examples 1 to 14 of the present invention have slag erosion resistance. Excellent balance between slag penetration resistance and spalling resistance.

On the other hand, in Comparative Example 1, since the magnesia-calcia clinker which is out of the range of the present invention is used, the digestion resistance is remarkably lowered, and the digestion cracks are generated during the drying of the test piece, which cannot be evaluated. there were.

In Comparative Example 2, the magnesia-calcia clinker having the composition and particle size range of the present invention was used. However, since TiO _{2 was} not added and calcium phosphate and magnesium phosphate were not coated, It was inferior in digestion resistance and could not be evaluated because digestive cracks occurred when the test piece was dried.

In Comparative Example 3, the spalling resistance was lowered because the large coarse magnesia was not added.

Comparative Example 4 uses the magnesia-calcia clinker in the composition range of the present invention, but it is inferior in slag penetration resistance and spalling resistance because the addition amount is small.

In Comparative Example 5, magnesia-calcia clinker having a composition within the range of the present invention was used. However, since the amount of addition was large, the workability at the time of kneading was remarkably reduced, and excessive addition of added water was used. Since the mixture had to be kneaded, the structure was fragile, resulting in poor slag penetration resistance and spalling resistance.

In Comparative Example 6, since the large coarse-grained magnesia was not surface-treated, the digestion resistance was remarkably reduced, and digestive cracks were generated when the test piece was dried, and evaluation was not possible.

In Comparative Example 7, large coarse magnesia was 80 to 5
Since it is used with a particle size of 0 mm, workability during kneading is significantly reduced, and it is unavoidable to knead by adding excessively added water, resulting in weakening of the structure, slag permeation resistance and The spalling resistance was inferior.

In Comparative Example 8, although large coarse-grained magnesia was added, the spalling resistance was lowered because the addition amount was small.

In Comparative Example 9, magnesia with a large grain size of 10 to 5 was used.
Since it is used with a grain size of mm, the spalling resistance is lowered.

In Comparative Example 10, the amount of large coarse-grained magnesia added was too large and the workability was remarkably deteriorated during kneading. Even when water was added in excess and vibration was applied, it did not flow, and casting was impossible. When the amorphous refractory material according to Example 1 was used in the slag line portion of a 250-ton ladle, it was confirmed that the durability was equivalent to that of magrophilic brick and that it could be used as a castable refractory material in an actual furnace.

[0052]

Industrial Applicability According to the present invention, conventional basic bricks have equivalent durability, excellent slag erosion resistance, slag permeation resistance, digestion resistance and spalling resistance, and oversintering is suppressed. A basic amorphous refractory can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Jun Egami 7-1 Tsukiji, Kisarazu-shi, Chiba Kurosaki Ceramics Co., Ltd. Kisarazu Irregular Factory (72) Inventor Masahiko Amano 5-Tokai-cho, Tokai-shi, Aichi 3 Nippon Steel Co., Ltd. Nagoya Steel Works (72) Inventor Koshi Nakamura 5-3 Tokai-cho, Tokai City, Aichi Prefecture Nippon Steel Co., Ltd. Nagoya Works

Claims (2)

[Claims] 1. A refractory aggregate of which particle size is adjusted 80 to 50% by weight
And magnesia / calcia clinker 20-50 wt
% Of the formulation, the magnesia-calcia clinker being MgO and CaO
And Fe ₂ O ₃ in a total amount of 97 wt% or more, MgO of 30 to 90 wt%, Fe ₂ O ₃ of 0.2 to 5 wt%, Ti
O ₂ has a chemical composition of 0.5 to 3 wt%, the surface of which is coated with calcium phosphate and magnesium phosphate, and the surface-treated particles are added to the mixture of the refractory aggregate magnesia / calcia clinker. A basic refractory castable refractory to which 5 to 50 wt% of large coarse magnesia with a diameter of 10 to 50 mm is added. 2. The castable refractory having basic properties according to claim 1, wherein one or more of phosphate, sodium silicate and silane coupling agent is applied as a surface treatment agent for large coarse magnesia.