JPH0747465A - Zirconia quality sliding nozzle plate - Google Patents

Abstract

PURPOSE:To provide a plate refractory for a sliding nozzle showing high durability even in the case it is used for casting steel of high erosion property such as Ca alloy treated steel. CONSTITUTION:At least the part in contact directly with molten steel in the course of casting of steel is made of zirconia quality containing monoclinic zirconia and cubic zirconia, and it is preferably constituted of a refractory raw material constituting of partially stabilized zirconia of <50% stability and/or 3-40weight% unstable zirconia, or partially stabilized zirconia of >=50% stability and/or 60-97% stabilized zirconia.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate of a sliding nozzle device used for controlling a flow rate during molten metal casting.

[0002]

2. Description of the Related Art A refractory portion constituting a sliding nozzle device usually comprises an upper nozzle, a fixed and sliding plate, and a lower nozzle. Among them, the plate refractory is the most important thing that directly controls the flow rate of molten steel.It is resistant to corrosion by molten steel and slag, that is, corrosion resistance, resistance to thermal shock by molten steel, that is, spalling resistance and wear and sliding due to molten steel flow. It is required that the plates have resistance to wear, that is, wear resistance. Furthermore, in the plate, the metal or slag infiltrates the part in contact with the molten steel, and sliding in the infiltrated state causes the sliding surface to be worn and damaged, and also the infiltration resistance and mechanical strength. Will be needed.

Conventionally, an alumina carbon material obtained by reduction firing has been widely used as the plate refractory material. Further, JP-A-60-180950 discloses that alumina is used as a main raw material and alumina zirconia raw material is added to the main raw material to achieve both corrosion resistance and spalling resistance. In addition, Japanese Examined Japanese Sho
-29664 (Patent No. 1343010),
Disclosed is a plate refractory having a certain amount of spalling resistance which is improved in corrosion resistance and wear resistance by blending a metal and a thermosetting resin in a refractory aggregate.

On the other hand, due to the adoption of a steelmaking method aimed at improving the quality of steel, the service conditions required for sliding nozzle plates are becoming severe. For example, in order to control the morphology of inclusions in the steel, when performing a so-called molten steel flow rate control at the time of casting of so-called Ca-treated steel in which a Ca alloy is added to the molten steel in the ladle, when the sliding nozzle is used, Melting loss becomes remarkable. As a countermeasure, JP-A-6
Japanese Patent Application Laid-Open No. 4-24069 proposes the use of a zirconia carbon-based material, and it is said that it is possible to reduce the melting loss at the time of injecting Ca-treated steel. However, this type of carbon bond material has low oxidation resistance and its structure deteriorates due to the thermal history of the operating surface, so when it is applied to an actual furnace, it lacks abrasion resistance and achieves sufficient durability. You cannot do it. In order to improve the oxidation resistance of this carbon bond material, it has been attempted to add an antioxidant such as a metal, but the addition of this antioxidant leads to a decrease in the zirconia content, resulting in a corrosion resistance Cause decline. Furthermore, in order to improve the oxidation resistance of the carbon bond material, it is possible to lower the carbon content, but lowering the carbon content impairs spalling resistance, and as with sliding nozzle plates, It is not preferable as a refractory material that requires spalling resistance.

[0005]

The object of the present invention is to provide Ca
Corrosion resistance, spalling resistance, wear resistance, and infiltration resistance required for sliding nozzle plates without any loss of zirconia properties due to Ca components in treated steel and CaO in slag. The purpose of the present invention is to provide a zirconia-based sliding nozzle plate that is properly balanced in terms of all required properties such as the mechanical properties and the mechanical strength.

[0006]

The zirconia-based sliding nozzle plate of the present invention is characterized in that the main mineral phase is composed of monoclinic zirconia and cubic zirconia, and contains 90% by weight or more of ZrO ₂ as a chemical component. To do.

In order to allow both monoclinic zirconia and cubic zirconia to exist as mineral phases in the zirconia refractory forming the sliding nozzle plate, both monoclinic zirconia and cubic zirconia should be included as zirconia raw materials. There are two possibilities, one is to use one and the other is to combine raw materials containing at least one of monoclinic zirconia and cubic zirconia.

The raw material containing both monoclinic zirconia and cubic zirconia is so-called partially stabilized zirconia, and the degree of stabilization is expressed by the weight percentage of cubic zirconia.

Generally, the degree of stabilization of zirconia is determined by powder X-ray diffraction, and is described in J. Amer. Ceram. So
c. , Vol. 55, No. In 6, Ronald
As shown by Garvie et al., The procedure for the mixing is as follows.

First, a raw material powder consisting only of monoclinic zirconia and a raw material powder consisting only of cubic zirconia are mixed in a predetermined ratio. This was used as a sample for powder X-ray diffraction, and (111) of monoclinic zirconia and

[Chemical 1] Integrated intensity of the diffraction peak Imlll,

[Chemical 2] Then, the integrated intensity Icllll of the (111) diffraction peak of cubic zirconia is measured. The same measurement is performed by changing the ratios of monoclinic zirconia and cubic zirconia, and a calibration curve of cubic zirconia content is prepared from the results.

Second, powder X-ray diffraction is performed on an unknown sample, and the integrated intensity of each diffraction peak described above is measured. From this integrated intensity and the calibration curve created earlier, the cubic zirconia content of the unknown sample,
That is, the degree of stabilization can be obtained.

The SN plate made of partially stabilized zirconia has a relatively small coefficient of thermal expansion and is also excellent in volume stability during heating and cooling. In addition, the high corrosion resistance inherent in zirconia is not impaired. Therefore, an SN plate having excellent yield, spalling resistance, and corrosion resistance can be obtained. As the partially stabilized zirconia, it is possible to use raw materials having the same degree of stabilization in all particle sizes, or it is possible to use two or more kinds of raw materials having different degrees of stabilization in combination. . At that time, if necessary, stabilized zirconia consisting only of cubic zirconia and unstable zirconia consisting of monoclinic zirconia are used as raw materials, and the whole SN plate contains both monoclinic zirconia and cubic zirconia. It is also possible to do so.

Further, two zirconia having different degrees of stabilization are used.
When using more than one kind, partially stabilized zirconia and / or unstable zirconia with a degree of stabilization of less than 50% 3-40
By mixing and using 60% by weight to 60% to 97% by weight of partially stabilized zirconia having a degree of stabilization of 50% or more and 60% to 97% by weight of stabilized zirconia, it becomes possible to further enhance the volume stability and spalling resistance.

The amount of partially stabilized zirconia and / or unstable zirconia having a degree of stabilization of less than 50% is 3-40.
Weight percent is suitable. If it is less than 3% by weight, the expansion is low and the formation of voids in the structure is insufficient, so that high spalling resistance cannot be achieved. If it exceeds 40% by weight, the expansion and contraction due to the phase transition of zirconia due to the heat effect during firing will increase, and the defects of the fired body such as cracks and deformation will increase.

The zirconia raw material used has a stabilization degree of 50.
One of less than 1% may be used, or two or more of those having different degrees of stabilization may be used. The same applies to those having a stabilization degree of 50% or more, and one kind may be used, or two kinds or more having different stabilization degrees may be used.

Partially stabilized zirconia or unstable zirconia having a degree of stabilization of less than 50% can be applied as fine powder,
Even if it is applied as coarse particles, the effect on improving spalling resistance is the same.

The degree of stabilization of zirconia can be changed by adding various stabilizers. Typical stabilizing agents are CaO, MgO, Y ₂ O _{3 and the} like. For the zirconia-based sliding nozzle plate, any stabilizer-added zirconia raw material can be used.

If the zirconia-based sliding nozzle plate contains monoclinic zirconia and cubic zirconia, the yield and spalling resistance can be secured to some extent, but in order to exert its effect, the sliding nozzle Stability of the plate as a whole is 40-9
It is preferably 5%.

Further, a metal such as Si, Zr, Al or an alloy thereof can be added to the material for the purpose of imparting strength.

When kneading the material, either an organic binder or an inorganic binder can be used, but phenol resin is most suitable because it is necessary to give sufficient green strength.

Regarding the firing temperature of this material, it is generally necessary to fire at a high temperature of 1500 ° C. or higher in order to develop the strength by sintering the zirconia raw material. However, in the case of promoting strength development by adding a metal,
Firing at a lower temperature is also possible. The firing atmosphere may be either an oxidizing atmosphere or a reducing atmosphere. However, in the case of reducing firing, there is a risk of reducing zirconia, and therefore, oxidizing firing is preferable.

Further, this material is usually made of pitch,
It is also possible to impregnate a tar, a resin, etc. to impart surface stability by densifying the sliding surface.

The zirconia-based sliding nozzle plate has a high bulk specific gravity due to its raw material characteristics. Therefore, if the entire sliding nozzle plate is made of zirconia, the weight of the plate increases, and in actual operation, the workability of setting the plate in the cassette of the sliding nozzle device or removing it for replacement is deteriorated. Therefore, as a large ladle plate, insert a zirconia ring only in the part that directly contacts the molten steel, and use the base material of the conventional alumina carbon material for the other parts. You can

[0024]

[Function] Zirconia does not form a substance having a melting point lower than the temperature of molten steel even when it reacts with CaO, and therefore is not damaged by the Ca component in Ca-treated steel and CaO in slag. The same can be said for magnesia, but magnesia has a high coefficient of thermal expansion, and thus greatly impairs spalling resistance, which is one of the required characteristics of the sliding nozzle plate. On the other hand, zirconia has a relatively low coefficient of thermal expansion. Furthermore, there are various degrees of stabilization, each having different thermal expansion characteristics. Therefore, spalling resistance can be imparted by reducing the thermal expansion of a brick made of a zirconia raw material alone. Furthermore, the spalling resistance can be improved by combining zirconia raw materials having different degrees of stabilization. Even if the degree of stabilization is different, since it is basically a zirconia raw material, it is possible to maintain high corrosion resistance.

As zirconia, monoclinic zirconia and cubic zirconia are known as stable phases. Monoclinic zirconia has a small coefficient of thermal expansion, and when it is used as a main raw material, the sliding nozzle plate has very excellent spalling resistance.

However, the monoclinic zirconia transforms into a tetragonal crystal upon heating and returns to the monoclinic crystal upon cooling. Due to the contraction and expansion at that time, the sliding nozzle plate is deformed and cracked during firing. On the other hand, the refractory made of cubic zirconia does not expand or contract due to heating / cooling, but has a relatively high coefficient of thermal expansion as compared with monoclinic zirconia, and is inferior in spalling resistance as a sliding nozzle plate. Therefore, the zirconia sliding nozzle plate needs to contain both monoclinic zirconia and cubic zirconia as mineral phases.

Partially stabilized zirconia having a degree of stabilization of less than 50% or unstabilized zirconia has a larger shrinkage during the phase transition of zirconia as compared with partially stabilized zirconia having a degree of stabilization of 50% or more or stabilized zirconia. . By utilizing this property, the thermal expansion coefficient of the plate material can be lowered and the spalling resistance can be imparted. When used in combination with a zirconia raw material having a degree of stabilization of 50% or more, fine voids are generated at the boundaries of the zirconia raw materials having different degrees of stabilization due to the difference in thermal expansion characteristics due to the thermal effect during use. These voids can absorb the thermal stress generated during use, and can further reduce the progress of cracks caused by thermal spalling.

[0028]

EXAMPLE A zirconia-based plate material of the present invention was applied to an insert ring 4 provided on each nozzle hole 3 surface of an upper plate 1 and a lower plate 2 of a sliding nozzle formed of alumina carbon material shown in FIG. .

Examples 1 to 3 are for showing the coexistence effect of monoclinic zirconia and cubic zirconia, and Examples 4 and 5 show the application effect of zirconia raw materials having different degrees of stabilization.

Example 1 A refractory raw material consisting of 100% by weight of 80% -stabilized zirconia and phenol resin as a binder were externally applied to the refractory raw material 2
The compound added by weight% was kneaded, molded into an SN plate insertion ring shape by friction, baked at 1700 ° C., and then pitch impregnated.

Example 2 A refractory raw material composed of 100% by weight of 50% stabilized zirconia and phenol resin as a binder were externally applied to the refractory raw material 2
The compound added by weight% was kneaded, molded into an SN plate insertion ring shape by friction, baked at 1700 ° C., and then pitch impregnated.

Example 3 A refractory raw material consisting of 100% by weight of 30% stabilized zirconia and a phenol resin as a binder were externally applied to the refractory raw material 2
The compound added by weight% was kneaded, molded into an SN plate insertion ring shape by friction, baked at 1700 ° C., and then pitch impregnated.

Comparative Example 1 For comparison, 100% by weight of 100% stabilized zirconia
2% by weight of phenol resin as a binder was added to the refractory raw material consisting of kneaded, and the mixture was molded into an SN plate insertion ring shape by friction.
After firing at 00 ° C., pitch impregnation treatment was performed.

Comparative Example 2 Similarly, a refractory raw material consisting of 100% by weight of unstable zirconia was kneaded with a mixture of phenol resin as a binder and 2% by weight of external resin, and kneaded by SN.
It was molded into a plate insertion ring shape and fired at 1700 ° C. This product had remarkable cracks and deformation after firing, and could not be used as an insertion ring for a sliding nozzle plate.

In Table 1, Examples 1, 2, 3 and Comparative Examples 1, 2 are shown.
The blending ratio and characteristics of the insertion ring 4 of the sliding nozzle plate are shown. In Examples 1 and 2, there was almost no deformation after firing, and in Example 3, the deformation after firing was slight.
It was possible to use it as a sliding nozzle plate insertion ring by processing. The insertion ring of the sliding nozzle plate of Comparative Example 1 had no deformation after firing, but it was confirmed by a table test that it had poor spalling resistance.

[0036]

[Table 1] Among the examples of the present invention, the insertion ring of Example 1 was replaced with Al ₂
The SN plate obtained by inserting it into the O ₃ -C system SN plate base material was used in an actual furnace as a sliding nozzle plate of a 250-ton ladle for Ca treatment of steel. As a result, in the conventional Al ₂ O ₃ -C-based material, the molten steel flow rate could not be controlled due to melting loss during use of the first charge, whereas when the product of the present invention was used, the molten steel flow rate could be controlled. Even after the charge was used, the hot water did not stop and could be reused.

Example 4 A mixture of 90% by weight of stabilized zirconia and 10% by weight of unstabilized zirconia coarse particles, to which 2% by weight of phenol resin was added as a binder by external coating, was kneaded. It was molded into a tundish SN plate shape, baked at 1600 ° C., and then impregnated with pitch.

Example 5 A mixture of a refractory raw material comprising 85% by weight of stabilized zirconia and 15% by weight of unstabilized zirconia fine powder and 2% by weight of phenol resin as a binder by external coating was kneaded and mixed by friction. After molding into a dish SN plate shape and firing at 1600 ° C., pitch impregnation treatment was performed.

Table 2 shows the blending ratio and characteristics of Examples 4 and 5. In Examples 4 and 5, since stabilized zirconia was used as the main raw material, there was no cracking or deformation during firing even when manufactured as a tundish SN plate integral body larger than the insertion ring shape. Furthermore, it was found that the unstable zirconia had a spalling resistance comparable to that of Example 1 due to the effect.

[0040]

[Table 2] Of the materials of the present invention, the material of Example 5 was used in an actual furnace as a 60 t tundish SN plate of a steel mill where Ca treatment of steel is being carried out. As a result, in the conventional alumina carbonaceous SN plate, a molten pool failure occurred even after one charge was used, whereas the material of the present invention has a slight melting loss and can be used in a maximum of 5 continuous castings. Met.

[0041]

INDUSTRIAL APPLICABILITY According to the present invention, spalling resistance is imparted by coexistence of monoclinic zirconia and cubic zirconia raw materials, and a highly erodible steel represented by Ca alloy treated steel is cast. It dramatically improves the durability of the sliding nozzle plate used for the above.

[Brief description of drawings]

FIG. 1 shows an example of a sliding nozzle plate to which the present invention is applied.

[Explanation of symbols]

 1 Upper plate 2 Lower plate 3 Nozzle hole 4 Insert ring

Claims (2)

[Claims] 1. A main mineral phase is composed of monoclinic zirconia and cubic zirconia and contains 90% of ZrO ₂ as a chemical component.
Zirconia sliding nozzle plate containing more than wt%. 2. A main mineral phase is composed of monoclinic zirconia and cubic zirconia and contains 90% of ZrO ₂ as a chemical component.
Zirconia sliding nozzle plate containing more than 50% by weight, partially stabilized zirconia containing less than 50% by weight of cubic zirconia as zirconia or 3 to 40% by weight of unstable zirconia, and partially stable containing more than 50% by weight of cubic zirconia. A zirconia-based sliding nozzle plate prepared by blending a blend of 60 to 97% by weight of stabilized zirconia or stabilized zirconia.