JPH06199575A - Alumina-spinel castable refractory - Google Patents

Abstract

PURPOSE:To suppress the reduction of the temp. of molten steel while retaining the characteristics of alumina-spinel castable refractories excellent in slag resistance by using Al2O3-MgO spinel clinker not contg. periclase crystals as a refractory material. CONSTITUTION:The objective alumina-spinel castable refractories consist of 100 pts.wt. refractory material contg. >=4 pts.wt. SiO2 and 2-25 pts.wt. binder. The refractory material consists of 10-70 pts.wt. Al2O3-MgO spinel clinker having 1.6-2.8 bulk specific gravity and not contg. periclase crystals and 30-90 pts.wt. alumina stock.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alumina-spinel castable refractory, and more particularly to an alumina-spinel castable refractory suitable for secondary refining furnaces, ladle ladle, tundish linings, linings and the like.

[0002]

2. Description of the Related Art Alumina-spinel castables are now widely used for molten steel refining vessels such as ladle. For example, in Japanese Patent Laid-Open No. 55-23004, there is a vacuum degassing device, etc. which is composed of "・ 10 to 85 wt% spinel clinker, ・ 5 to 30 wt% alumina, ・ 10 to 25 wt% high alumina cement, etc. Castable refractory to be used. "

In addition, JP-A-59-128271 (Japanese Patent Publication No.
No. 11906) discloses "a casting material for hot metal desiliconization, which is composed of a refractory raw material containing 50 to 95 wt% of spinel and the balance of alumina as a main component." Further, as a material for a molten steel refining vessel, application of a basic material such as a magnesia material or a magnesia-calcium material having excellent slag erosion resistance has been considered. In these castables, the corrosion resistance is emphasized more than ever before, and the main focus is on obtaining a compact construction body with a porosity as low as possible.

[0004]

Various types of spinel clinker are commercially available, and the bulk specific gravity thereof is usually 3.2 to 3.4. Since the bulk specific gravity of the clinker-grains has an influence on the corrosion resistance to slag,
Generally, for refractories, those with a high bulk specific gravity,
That is, a material having a high slag erosion resistance is preferred.
Therefore, clinker having high corrosion resistance, that is, high bulk specific gravity has been conventionally produced, and clinker having low bulk specific gravity has hardly been omitted.

However, since the refractory material containing magnesia as described above has a high thermal conductivity and a large specific heat of the material, for example, when it is used for the inner lining of a ladle, the amount of heat loss of molten steel in the ladle is lost. However, there was a problem that the temperature of the molten steel decreased, which hindered the satisfactory refining and casting operations. Therefore, in the case of using the castable made of such a magnesia-containing refractory material, in order to compensate the temperature of the molten steel, it is the actual situation that the above problems are avoided by setting the refining steel temperature high.

On the other hand, as a technique for lowering the thermal conductivity of refractory materials, (1) a method of adding a silica-containing lightweight aggregate into a castable material, (2) a fiber such as alumina-silica ceramic fiber or slag wool A method of adding a quality material is known.

However, any of these additions acts as an impurity component in the alumina-spinel castable, and significantly reduces the corrosion resistance.
Furthermore, the addition of the lightweight aggregate of the above (1) has a drawback that the bulk specific gravity is too different from that of alumina or spinel clinker, and thus it is easily separated and unevenly distributed. In addition, the addition of the fibrous material (2) has a drawback of impairing the castability as a castable.

The present inventors have earnestly studied to provide an alumina-spinel castable refractory capable of suppressing the temperature drop of molten steel while maintaining the characteristics of the alumina-spinel castable having excellent slag erosion resistance. As a result of the repetition, the present invention has been completed. That is, firstly, the object of the present invention is to eliminate the above-mentioned drawbacks of the conventional alumina-spinel castables, which have excellent corrosion resistance, but have the drawback of causing the temperature drop of the molten steel due to high thermal conductivity and high specific heat. Secondly, an alumina-spinel material that has practically sufficient corrosion resistance, does not cause problems such as digestion during curing and drying after pouring, and can minimize the temperature drop of molten steel. To provide castable refractories.

[0009]

The alumina-spinel castable refractory material of the present invention comprises, as a refractory material part, an Al ₂ O ₃ -MgO-based material which does not contain periclase crystals having a bulk specific gravity of 1.6 to 2.8. Characterized by using a spinel clinker, further characterized in that the SiO ₂ content in the refractory material part is 4 parts by weight or less, thereby providing the above-mentioned objective alumina-spinel castable refractory Is.

That is, the present invention is a "castable comprising a refractory material portion and a binder portion, and the refractory material portion has a bulk specific gravity.
Al ₂ O ₃ -MgO without periclase crystals of 1.6-2.8
System spinel clinker 10-70 parts by weight and alumina raw material 30-
Alumina-spinel castable refractory material, which comprises 90 parts by weight, and 2 to 25 parts by weight of a binder is added to 100 parts by weight of the refractory material. ], And further, "alumina-spinel castable refractory characterized in that the SiO ₂ content in the refractory material part is 4 parts by weight or less."

The present invention will be described in detail below. The present inventors conducted various studies on spinel clinker having a low bulk specific gravity in order to solve the problem of heat loss of molten steel when used in an actual furnace. It can be easily conceived that the thermal conductivity could be lowered by lowering the bulk specific gravity of the clinker, but from the experimental results of the present inventors, the bulk specific gravity was simply lowered. The slag resistance deteriorates only by using the clinker, and free MgO (i.e., periclase) is used during curing and drying after pouring, which is not a problem when using the conventional high bulk density clinker. crystal)
It was found that the digestive phenomenon caused by the hydration phenomenon of is likely to occur.

In order to find out what the bulk specific gravity of the spinel clinker used in the present invention should be, spinel clinker having different bulk specific gravity was prepared and the change in corrosion resistance was investigated. (Preparation of test compound and test construction body) Spinel clinker-40%, Sintered alumina 60%, Spinel clinker-55%, Sintered alumina 45% Two types of spinel clinker-containing refractory material parts 10
20% of high-alumina cement containing 80% of alumina as a binder was added to and mixed with 0 to prepare a test compound of alumina-spinel castable. Water was added and kneaded to obtain a suitable fluidity in each of the test compounds, and the mixture was poured into a mold at room temperature for construction, and after 24 hours of natural curing, deframed, 105
It was dried at ℃ for 24 hours to obtain a test construction body.

(Erosion test and test results) An erosion test was carried out at 1600 to 1650 ° C. by the rotating drum method on each of the above test construction bodies. The test results are shown in FIG. As is apparent from FIG. 1, the bulk specific gravity of the spinel clinker decreases and the erosion depth increases. The increase ratio is bulk specific gravity
Although it is not so large up to about 1.6, it is not preferable since the erosion depth sharply increases when the bulk specific gravity becomes lower than 1.6.
It should be noted that although the slope is slightly different depending on the difference in the content of the spinel clinker, the same tendency is shown as a whole. From the above results, at least in terms of corrosion resistance, the bulk specific gravity of the spinel clinker is preferably 1.6 or more,
Further, by adjusting the clinker content and the like, it is possible to suppress the change in corrosion resistance to the extent that there is no problem in actual use.

On the other hand, the upper limit of the bulk specific gravity of spinel clinker is limited by the thermal properties of castables. That is, the bulk specific gravity of the spinel clinker is preferably 2.8 or less in terms of both the thermal conductivity of the castable construction body and the heat absorption into the castable body. When it exceeds 2.8, the thermal conductivity of the castable is almost insignificant and is meaningless. Since the heat absorption into the castable correlates with the specific gravity of the castable construction body, there is an effect only by the decrease in bulk specific gravity of the spinel clinker, but when it exceeds 2.8, the temperature decrease of the molten steel which is the object of the present invention is suppressed. This is not preferable because it is insufficient. From the above facts, the spinel clinker used in the present invention preferably has a bulk specific gravity of 1.6 to 2.8, and this is one of the important features of the present invention.

In the present invention, the content of the spinel clinker in the castable refractory material part is preferably 10 to 70%. In the actual formulation determination, by the combination of the bulk specific gravity of the spinel clinker and the content of the spinel clinker, it is determined by the balance between the effect of suppressing the temperature decrease of the molten steel, the corrosion resistance to slag, and the infiltration resistance. If it is less than 10%, the effect of improving the corrosion resistance and suppressing the slag infiltration, which is the original purpose of the spinel clinker, is not sufficient, and the effect of suppressing the temperature decrease of the molten steel is small, which is not preferable. On the other hand, when it exceeds 70%, the bulk specific gravity of the entire castable is greatly reduced, and the effect on heat absorption and dissipation is good, but the corrosion resistance is reduced.
Further, the slag infiltration property is also increased, which is not preferable.

Another important characteristic feature of the spinel clinker used in the present invention is that it does not contain free periclase crystals. The theoretical magnesia-alumina spinel is about 28.3% magnesia,
Although it has a composition of 71.7% alumina, it is a clinker.
Depending on the production conditions, all of them do not completely react to form spinel crystals, and many of them partially include periclase which is free magnesia and corundum which is a crystal of alumina.

By the way, the present invention is characterized by using a spinel clinker having a low bulk specific gravity of 1.6 to 2.8 as described above. If the magnesia, that is, the periclase crystal remains, the periclase crystal hydrates during curing and drying after casting as compared with the case of using a conventional spinel clinker having a high bulk specific gravity. It has been found that the castable construction body easily collapses because of the possibility of causing the above. Therefore, in the castable of the present invention, in order to prevent the disintegration due to such a hydration phenomenon,
Free pericle in spinel clinker with low bulk density
This is an important feature point in the present invention.

In the commercially available high bulk density spinel clinker,
There is a magnesia content of about 50% to about 10%, and naturally there is a free periclase in the spinel clinker with a higher magnesia content than the theoretical composition.
Up to now, no particular problems have been raised regarding curing when used in castables and hydration reaction when dried. It is considered that this is because the conventional spinel clinker with a high bulk specific gravity for densification does not easily diffuse water or water vapor into the particles and there is no influence of hydration phenomenon to the extent that the castable collapses. To be

On the other hand, the spinel clinker used in the present invention is a clinker having a low bulk specific gravity, and it is easy to infiltrate water or water vapor into particles during curing and drying, so that it is a free pericle. It is considered that the hydration of the sea squirrels occurs continuously, leading to the collapse of the entire castables. Therefore, in the present invention, in order to eliminate the presence of free periclase crystals and maintain the characteristics of the spinel clinker's corrosion resistance and slag infiltration resistance, the magnesia content as the composition of the low bulk density spinel clinker Is preferably about 28 to 5%. If the magnesia content exceeds 28%, a clinker with a low bulk density will be produced during production of the clinker with a low bulk density.
It is difficult to completely crystallize the spinel while manufacturing the above, and residual pellicle is likely to be mixed. On the other hand, if the magnesia content is less than 5%, the characteristics of the spinel become unclear, which is not preferable. The free corundum crystal is stable and does not cause hydration, so its existence does not cause any problem.

As the alumina raw material used in the refractory material portion of the present invention, in addition to sintered alumina and fused alumina, calcined clinker of natural high alumina raw material such as calcined bauxite can be used, and low alumina such as hollow alumina can be used. It is also possible to adjust the bulk specific gravity of the entire castable by using one having a bulk specific gravity. These alumina raw materials are necessary for adjusting the thermal expansion and heat shrinkage characteristics of the alumina-spinel castable refractory. The content of this alumina raw material is 10%
The balance of the content of spinel clinker out of 0, that is, 30 to 9
It is 0%. In addition, in order to enhance slag erosion resistance, the "low bulk density spinel clinker and alumina raw material" of the present invention
A conventional high bulk density spinel clinker may be added and used within a range of less than 60%.

Further, in the alumina-spinel castable using the low bulk specific gravity spinel clinker of the present invention, it is possible to further add calcined alumina fine powder composed of particles of 20 μm or less to the refractory material part. The addition of this calcined alumina fine powder can strengthen the matrix portion, which is preferable from the viewpoint of improving slag resistance, and the addition amount is preferably about 2 to 15%. If it is less than 2%, its effect is insufficient, while if it exceeds 15%, it is meaningless in terms of economy.

As the castable binder in the present invention, an alumina cement-based binder or a phosphoric acid-based, silicic acid-based or organic-based binder or the like can be used, and the compounding amount thereof is 2 with respect to 100 parts of the refractory material. ~ 25% is preferred. A proper amount of the binder is selected depending on the kind, but in the case of the alumina cement binder, up to 25% can be added. If it exceeds 25%, Ca in the cement
Corrosion resistance is reduced due to the influence of the O component, etc.
On the other hand, in the case of a phosphoric acid-based or silicic acid-based or organic binder,
The binding effect is obtained with a very small amount, and addition of 2% or more is sufficient.

Further, in the present invention, alumina sol or ρ
A fine powder of alumina or amorphous alumina having a particle size of 10 μm or less may be added as a binder or a binding aid. Furthermore, the binder does not necessarily have to be a powder and can be used as a liquid binder, but in consideration of actual use, if it is a powder, it can be mixed with the refractory material portion in advance,
It is preferable because only water is added and kneaded at the site of use.

In the castable material of the present invention, the amount of SiO ₂ contained in the refractory material portion tends to affect the corrosion resistance. When the SiO ₂ content exceeds 4%, the slag wettability is not so affected, but the erosion is increased. Particularly, when SiO ₂ is added to the fine powder portion, the amount of erosion increases remarkably. Since the castable of the present invention uses a low bulk density spinel clinker, the erosion resistance originally tends to be slightly inferior to the conventional castable using a high bulk density spinel clinker.

In addition to this, if silica is further contained, this silica reacts with magnesia and alumina to form a low-melting point compound, and this low-melting point compound further reduces the erosion resistance of the castable to a greater extent. To be Therefore, in the castable using the low bulk specific gravity spinel clinker of the present invention, the SiO ₂ content in the refractory material portion needs to be 4% or less from the viewpoint of corrosion resistance.

In the castable material of the present invention, it is possible to use a small amount of a dispersant containing a phosphate or a surfactant, and a curing modifier such as a lithium carbonate salt, a calcium compound, an organic acid or a salt thereof. In addition, a small amount of a metal powder, an organic gas generating agent, an explosion proof agent such as an organic fiber can be added.

[0027]

The alumina-spinel castable refractory material of the present invention comprises, as a refractory material part, Al containing no periclase crystals having a bulk specific gravity of 1.6 to 2.8.
₂ O ₃ -MgO-based spinel clinker 10 to 70 parts by weight ・ Alumina raw material 30 to 90 parts by weight ・ Furthermore, SiO ₂ content in the refractory material part is 4 parts by weight or less As described above, this has the effect of suppressing the temperature decrease of the molten steel while maintaining the characteristics of the alumina-spinel castable having excellent slag resistance.

[0028]

EXAMPLES Next, the present invention will be described in more detail by giving examples of the present invention together with conventional examples and comparative examples. Mg shown in Table 1
Five types of spinel clinker with different O content and bulk specific gravity
Was used to add and knead water such that appropriate fluidity was obtained, and the mixture was cast to prepare a sample. These samples were subjected to comparative evaluation on the appearance of the samples after curing and drying, the bending strength after drying, the heat absorption / dissipation property, and the slag resistance, and the results are summarized in Table 2.

(Curing, state after drying, bending strength) After the casting, it was left to stand at room temperature for 24 hours for curing, followed by drying at 110 ° C. for 24 hours. The change in appearance of the sample at this time was observed and shown in Table 2 as "state after curing and drying". Also, the bending strength was measured after drying, and is also shown in Table 2. (Heat Absorption / Dissipation) Each sample cast into a crucible shape having an inner diameter of about 120 mm, a thickness of about 60 mm and a height of about 180 mm was cured and dried in the same manner as above, and then heated to 1000 ° C. in a furnace. This was taken out of the furnace, and when the temperature reached 800 ° C., iron melted at 1650 ° C. was injected, and the temperature drop of iron after 1 minute was measured. This is an experiment assuming the absorption and dissipation of heat into the castable when molten steel is poured into an actual ladle, tundish, etc., simply by looking at the temperature gradient in the steady state due to the difference in thermal conductivity. Not only that, it is a method that can also evaluate the heat absorption due to the temperature rise of the castable itself. The results at this time are shown in Table 2 as "heat absorption / dissipation". (Slag resistance) For each sample, a slag erosion test was performed using the rotating drum method, the erosion depth of the sample was measured after the test, and the value of Conventional Example 6 was set to 10.0. It was shown to.

[0030]

[Table 1]

[0031]

[Table 2]

Conventional Example 6 in Table 2 is an example using a widely used high bulk specific gravity spinel clinker (conventional clinker: bulk specific gravity 3.26, clinker of Table 1 No. 4). In Conventional Example 6, it was confirmed that the appearance, strength and slag resistance were good, but the heat absorption / dissipation was high and the temperature drop of molten iron was large.

Comparative Example 7 is an example using a spinel clinker containing periclase crystals (clinker of No. 5 in Table 1). In Comparative Example 7, large cracks were observed in the sample after curing and drying. This is considered to be due to the influence of free pericle crystals in the spinel clinker. Therefore, in Comparative Example 7, the flexural strength of the other samples was as low as about 1/4.

Comparative Example 8 is a castable caster using the low bulk specific gravity spinel clinker shown in Table 1 No. 3, but 70% of calcined bauxite having a SiO ₂ content of about 7% was blended as an alumina raw material. Here is an example. Therefore, in this comparative example 8,
The castable content of SiO ₂ was close to 5%, the slag resistance was poor, and the erosion depth was larger than in Examples 1 to 5 of the present invention.

In each of Examples 1 to 5, a product having a good appearance was obtained after curing and drying. In addition, the heat absorption / dissipation property was about 15 to 20% better than that of Conventional Example 6. Further, the bending strength is the same as that of Conventional Example 6, and the slag resistance is almost the same as that of Conventional Example 6 using a spinel clinker having a high bulk specific gravity.

[0036]

INDUSTRIAL APPLICABILITY As described above in detail, the present invention does not include a periclase crystal having a bulk specific gravity of 1.6 to 2.8 and containing no Al ₂ O _3-.
It is characterized by using MgO spinel clinker, which can suppress the temperature drop of molten steel while maintaining the characteristics of alumina-spinel castable, which has excellent slag resistance, and practically has a high bulk specific gravity. It has the same slag erosion resistance as castable using spinel clinker, and can reduce heat absorption and dissipation by about 15 to 20%. Then, by applying the alumina-spinel castable refractory of the present invention, it is not necessary to adjust the tapping temperature in consideration of the heat loss of the molten steel in advance, not only contribute greatly to the reduction of energy-intensity The effect that the complexity of the adjustment work can be reduced occurs.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the bulk specific gravity of spinel clinker and slag resistance.

Claims (2)

[Claims] 1. A castable comprising a refractory material part and a binder part, wherein the refractory material part has a bulk specific gravity of 1.6 to 2.8 and does not contain periclase crystals Al ₂ O ₃ -MgO spinel clinker 10 to Alumina-spinel castable refractory, which is composed of 70 parts by weight and 30 to 90 parts by weight of alumina raw material, and 2 to 25 parts by weight of binder is added to 100 parts by weight of this refractory material. . 2. The alumina according to claim 1, wherein the content of SiO ₂ in the refractory material part is 4 parts by weight or less.
Spinel castable refractory.