JPH08198686A - Alumina-spinel casting material - Google Patents

Abstract

PURPOSE: To suppress a densifying due to oversintering resulted from the use of superfine powder and to prevent a structural spalling. CONSTITUTION: In an alumina-spinel casting material, 0.5-8 pts.wt., preferably 0.5-5 pts.wt., zirconia-containing clinker containing monoclinic zirconia and having <=125μm grain size is added to 100 pts.wt. refractory material consisting of 10-70wt.% aluminum material refractory containing superfine starting material, 10-70wt.% spinel material refractory and 2-15wt.% alumina cement. The clinker containing 5-60wt.% monoclinic zirconia in the clinker, preferably an alumina-zirconia material clinker containing 5-60wt.% monoclinic zirconia in the clinker, is preferably used as the zirconia-containing clinker.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alumina-spinel casting material suitable for linings such as ladle and RH used for various refining of molten steel.

[0002]

2. Description of the Related Art In recent steelmaking, basic materials such as magnesia, neutral materials such as alumina, and materials such as spinel are often used as materials for refractory materials used in ladles. Has become. The basic material is excellent in terms of corrosion resistance, but has a drawback of causing spalling due to slag penetration. On the other hand, neutral materials such as alumina are excellent materials that satisfy both corrosion resistance and spalling resistance.

However, the alumina-based refractory material has a drawback that its corrosion resistance is deteriorated with respect to slag containing a large amount of FeO component. Therefore, MgO that is strong against slag with a lot of FeO
Magnesia-alumina spinel (hereinafter simply referred to as spinel) has attracted attention as a refractory material containing, and an alumina-spinel refractory is used.

Further, from the aspect of furnace construction, due to the recent shortage of manpower, it has been gradually attempted to construct an unshaped material by pouring for the purpose of integral construction of a container, and an alumina-spinel pouring material. Has been developed (Japanese Patent Laid-Open No. 4-59665).

In pouring construction of irregular refractory materials, in order to obtain a denser construction body, ultrafine powder raw materials have been widely used for the purpose of reducing water content. However, since the ultrafine powder raw material is rich in sinterability, structural spalling due to oversintering easily occurs at high temperature. As a countermeasure against this, a method has been disclosed in which a magnesia material is added to an alumina-spinel material to impart residual expansivity to prevent oversintering. Further, in JP-A-5-512266, unstabilized zirconia having a particle diameter of 1 mm or less is added to an alumina-spinel-magnesia material in a range of 5 to 10% by weight to utilize the volume change due to the crystal transformation of zirconia. Then, attempts have been made to introduce microcracks into the material to prevent expansion of magnesia and prevent excessive sintering due to silica ultrafine powder.

[0006]

However, the addition of the magnesia material to the alumina-spinel amorphous material loses the sustainability of the residual expansion during repeated heat history of heating and cooling during long-term use. Finally, the problem of structural spalling due to oversintering occurs.

Further, according to the study by the present inventors regarding the addition of unstabilized zirconia, both the size and the amount of cracks introduced by the crystal transformation of zirconia are too large by the addition method described in JP-A-5-51266. Therefore, the effect on physical property deterioration is greater than the effect of preventing oversintering,
A decrease in corrosion resistance and an increase in slag penetration were observed.

The crystal transformation of zirconia that occurs at a temperature of 800 to 1200 ° C. is a reversible reaction, and a persistent oversintering prevention effect is expected, but it controls a volume change of about 7% that occurs during transformation. Therefore, the development of an addition method that does not deteriorate the physical properties of the construction body is desired.

[0009]

Means for Solving the Problems The present inventors have conducted various studies, and by using a fine powder of zirconia-containing clinker containing monoclinic zirconia within a prescribed range, the volume change due to crystal transformation is moderately performed. The present invention has been completed by succeeding in controlling and producing fine cracks in a well-balanced manner in a construction body. That is, the present invention is 10 to 70% by weight of alumina refractory material containing ultrafine powder material, 10 to 70% by weight of spinel refractory material, and alumina cement 2-1.
With respect to 100 parts by weight of the refractory material consisting of 5% by weight, 0.5 to 8 parts by weight, preferably 0.5 to 8 parts by weight, of a clinker containing zirconia containing monoclinic zirconia and having a particle diameter of 125 μm or less.
It is an alumina-spinel inflow material characterized by being added in an amount of up to 5 parts by weight. Further, in the present invention, the zirconia-containing clinker contains 5
Alumina-spinel castable material in which it is desirable to use a clinker containing ˜60 wt% monoclinic zirconia, preferably an alumina-zirconia clinker containing 5-60 wt% monoclinic zirconia in the clinker. Is.

The alumina refractory material used in the present invention is an alumina refractory material such as fused alumina or sintered alumina, which is generally used as a refractory material, and also includes ultrafine alumina powder. The spinel-based refractory material is various magnesia-alumina spinel, that is, a normal spinel, an alumina-rich spinel containing more Al ₂ O ₃ than the normal spinel, a magnesia-rich spinel containing more MgO, or a sintered product. Other refractory materials may be used in combination with these as the main components. The amount of alumina refractory material used is 10 to 70% by weight,
The spinel refractory material is used in the range of 10 to 70% by weight. If any of the values deviates from this range, the corrosion resistance and spalling resistance decrease.

As the ultrafine alumina powder, either an electromelted product or a sintered product can be used, but 3 to 1 if the particle size is 10 μm or less.
It is preferably used in the range of 5% by weight. Particle size is 10μ
If it exceeds m, the effect as ultrafine powder cannot be exhibited. If the amount used is less than 3% by weight, the effect of lowering the water content during kneading is not sufficient and a dense work body cannot be obtained. On the other hand, if it exceeds 15% by weight, the amount of water for kneading increases and the risk of explosion during drying increases, which is not preferable.

As the zirconia-containing clinker which is a feature of the present invention, monoclinic zirconia having a particle size of 125 μm or less is used in the range of 0.5 to 8% by weight, preferably 0.5 to 5% by weight. . If the particle size exceeds 125 μm, the size of each crack generated due to the volume change accompanying the crystal transformation becomes large and the physical properties of the structure deteriorate, so that the corrosion resistance decreases. If the amount of the clinker used is less than 0.5% by weight, the effect of addition is not sufficiently exerted, and if it exceeds 8% by weight, the corrosion resistance decreases. Considering the balance between the effect of preventing excessive sintering due to the introduction of cracks and the effect on corrosion resistance, the amount of the clinker used is preferably in the range of 0.5 to 5% by weight.

As the zirconia-containing clinker, one containing monoclinic zirconia is used. Although tetragonal or cubic zirconia may coexist in addition to the monoclinic crystal, it is preferable to use a clinker containing 5 to 60% by weight of monoclinic zirconia in the clinker. Further, it is more preferred to use an alumina-zirconia clinker containing 5 to 60 wt% monoclinic zirconia in the clinker. The effect of oversintering can be obtained by the volume change accompanying the crystal transformation of monoclinic zirconia, but in order to obtain a sufficient effect, the amount of monoclinic zirconia in the clinker is preferably 5% by weight or more. Considering the influence on the physical properties of the body, it is more preferable not to exceed 60% by weight. Also, comparing with zirconia-containing clinker,
Since an alumina-zirconia-based material having a low porosity can be obtained as a clinker, the amount of water at the time of construction can be small, and the corrosion resistance tends to be excellent, which is advantageous.

Commercially available clinker containing monoclinic zirconia can be used. For example, a small amount of CaO, Mg
Zirconia clinker containing O, Y ₂ O _{3 and the} like, containing monoclinic zirconia, and the remainder being cubic or tetragonal zirconia, or an electric current obtained by coexisting monoclinic and tetragonal zirconia in an alumina raw material. Raw materials are available. The content ratio of monoclinic zirconia in these clinker is almost the same even after repeated heat treatment. Such clinker is conventionally used as an abrasive grain for grinding.

The casting material of the present invention is constructed according to a conventional method using alumina cement as a binder. The amount of alumina cement is 2 to 15% by weight. If it is less than 2% by weight, the strength of the work body upon curing is weak, and if it exceeds 15% by weight, the corrosion resistance is lowered.

[0016]

[Function] Monoclinic zirconia exhibits expansion behavior when heated, but at around 1100 ° C., it changes to contraction behavior due to the transition from the low temperature type to the high temperature type. In the cooling process, 1000 ° C
In the vicinity, a transition from a high temperature type to a low temperature type causes a transition from contraction to expansion behavior, expansion occurs up to around 800 ° C., and in a temperature range below that, it contracts again and shows a slight residual expansion property when cooled to room temperature. Zirconia causes a volume change of about 7% due to this crystal modification, which is an obstacle to its use in refractories. By defining the monoclinic zirconia content in the zirconia-containing clinker used in the present invention, it is possible to control the volume change due to the crystal modification within an appropriate range. It became possible to introduce cracks. Since the clinker is used as a fine powder having a particle size of 125 μm or less,
The individual cracks become extremely fine, and the physical properties of the construction body as a whole do not deteriorate, and the penetration of slag through these cracks hardly increases.

When a proper amount of ultrafine alumina powder is added to the alumina-spinel inflow material, the fluidity at the time of construction is increased, so that it is possible to construct with a low water content, and a compact construction body with low porosity can be obtained. Obtainable. Further, since the ultrafine alumina powder also has the effect of capturing the slag component near the operating surface and preventing the penetration of slag into the deep part, it is indispensable for improving the durability of the casting material. However, since the ultrafine powder raw material is rich in sinterability, the sintered body is likely to be oversintered at high temperature, and when cracks occur due to shrinkage during the cooling process, it promotes slag infiltration into the altered layer. Is thickened, increasing the risk of structural spalling. Further, although thermal stress is generated due to the temperature gradient generated inside the construction body during operation, the thermal stress is repeatedly generated by heating and cooling, which causes deterioration of the tissue.

The zirconia-containing clinker containing monoclinic zirconia used in the present invention effectively acts on such a factor that reduces the durability and prevents the deterioration of the structure. That is, it is possible to prevent excessive densification due to sintering of the construction body by causing fine cracks around the clinker due to the volume change of zirconia. However, during long-term operation, sintering of the construction gradually progresses, so that the shrinkage tendency on the operation surface side gradually increases during the cooling process, and the risk of crack formation increases. In the process of the contracted body, the zirconia-containing clinker acts to cause a high temperature → low temperature type crystal transformation to cause volume expansion. As a result, the shrinkage of the entire construction body is reduced, and thus the generation of cracks on the working surface is suppressed.
In the cooling process after the completion of crystal transformation, the zirconia-containing clinker gradually shrinks, but the degree is
Since it is slower than spinel materials, it also acts to reduce shrinkage in that process. The fine cracks introduced around the clinker also have the function of absorbing and relaxing the thermal stress generated in the construction body during operation. Due to the effect of the clinker as described above, permeation of slag and deterioration of tissue are suppressed and structural spalling is prevented. In the temperature range used as the lining material of a ladle, the crystal transformation of zirconia is a reaction that occurs repeatedly with each heating and cooling, so the structural spalling preventing effect of the clinker is maintained for a long period of time.

Further, the zirconia component existing in the vicinity of the operating surface reacts with the CaO component in the slag to produce CaZrO ₃ mineral, but the volume expansion at that time blocks the pores in the construction body and prevents the penetration of slag. Will also contribute.

[0020]

EXAMPLES Samples were prepared by pouring the materials having the formulations shown in Table 1 into a mold. The comparative examples shown in Table 2 were also manufactured in the same manner. The characteristics of the zirconia-containing clinker in the table are shown in Table 3. Table 3
Where A is a monoclinic zirconia clinker, B is a clinker containing a small amount of CaO and coexisting with monoclinic, tetragonal and cubic zirconia, C and D are monoclinic and tetragonal zirconia-containing alumina- Zirconia clinker, E is a tetragonal zirconia clinker containing no monoclinic zirconia. In both Examples and Comparative Examples, the fluidity and curability during sample preparation were good and there were no problems. The results of each test performed using the sample are also shown in Tables 1 and 2.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

The residual line change rate was measured after repeating a heat treatment in which a sample having a shape of 160 × 40 × 40 mm was held at 1500 ° C. for 3 hours in an electric furnace three times. In each of the examples, the residual shrinkage after the heat treatment is reduced, and particularly, in the example 2,
3, 4, 6 show good volume stability.

In the spalling test, a rotary erosion test apparatus was used, slag having C / S = 1 and Fe ₂ O ₃ content of 10% was charged, heated at 1650 ° C. for 30 minutes, and forcedly cooled for 30 minutes after discharging the slag. The cycle was repeated 5 times, and the state of the cut surface of the sample was observed after the test. In the comparative sample, cracks in the vertical direction on the working surface due to shrinkage during cooling and parallel cracks on the working surface due to the altered layer generated by slag permeation were observed, but the example samples were thin. Although the generation of the altered layer was observed, no crack was generated or it was stopped to a small extent, and particularly Examples 2, 3, 4, and 6 maintained a good microstructure.

For the corrosion resistance test, the same slag as in the spalling test was used, and the rotation erosion test apparatus was used to measure 10 at 10 °
The results of Comparative Example 1 in which a zirconia-containing clinker was not used were 100 for the amount of dissolution loss and the amount of slag permeation.
It was shown by the index. It is apparent that the examples have a better slag penetration resistance than the comparative examples, and the examples 2, 3, 4, and 6 are particularly excellent.

[0027]

The alumina-spinel flow-in material of the present invention can prevent densification due to oversintering and prevent structural spalling by adding a proper amount of clinker containing zirconia containing monoclinic zirconia. It is what
When this pouring material is used for a general wall of a ladle, a floor, etc., it can be expected that the life of the furnace will be greatly extended.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

Claims (4)

[Claims] 1. Alumina refractory material 10 containing ultrafine powder raw material.
~ 70 wt%, spinel refractory material 10-70 wt%,
Refractory material consisting of 2 to 15% by weight of alumina cement 10
Particle size 12 containing monoclinic zirconia to 0 parts by weight
An alumina-spinel inflow material, wherein 0.5 to 8 parts by weight of a zirconia-containing clinker having a size of 5 μm or less is added. 2. Alumina refractory material 10 containing ultrafine powder raw material.
~ 70 wt%, spinel refractory material 10-70 wt%,
Refractory material consisting of 2 to 15% by weight of alumina cement 10
Particle size 12 containing monoclinic zirconia to 0 parts by weight
An alumina-spinel inflow material, characterized in that 0.5 to 5 parts by weight of a zirconia-containing clinker of 5 μm or less is added. 3. Alumina-spinel casting material according to claim 1, wherein the zirconia-containing clinker is a clinker containing 5 to 60% by weight of monoclinic zirconia in the clinker. 4. The zirconia-containing clinker is an alumina-zirconia clinker.
The described alumina-spinel casting material.