KR100380755B1 - Refractory with high quality - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to carbon-containing zirconia-based refractory materials used in refractory nozzles for immersion nozzles in the steelmaking field, and an object thereof is to provide carbon-containing zirconia-based refractory materials having excellent corrosion resistance.

In order to achieve the above object, the present invention, in the ZrO ₂ -C-based refractory composition containing 70-80% by weight of zirconia, the zirconia is ultrafine unstabilized (pure) zirconia: 4-8% by weight and the remaining stabilizer The gist of the carbon-containing zirconia-based refractory composition excellent in corrosion resistance which consists of partial-stabilized electrolytic zirconia using CaO is made into the summary.

Description

Refractory with high quality carbon-containing zirconia-based fireproof composition

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to carbon-containing zirconia refractories used in refractory nozzles for immersion nozzles in steelmaking, and more particularly, to carbon-containing zirconia refractories with excellent corrosion resistance.

In general, the refractory material of steel casting immersion nozzles requires heat spalling, wear resistance, and high corrosion resistance compared to other refractory materials. The mold powder line part which is in contact with the slag is different in the refractory material of the inner diameter part and the outer diameter part when playing, the inner diameter part uses alumina-carbon material, and the outer diameter part contacting the slag requires higher corrosion resistance to the slag. For this reason zirconia-carbon refractory is used.

Therefore, it is common to use zirconia having excellent corrosion resistance among inorganic oxides as the refractory raw material for the outer diameter of the immersion nozzle mold powder line part.

Inorganic oxides such as zirconia are physically and chemically stable, but the wettability of slag is easy, and there is a drawback of spalling due to thermal expansion at high temperatures. Although it has its drawbacks, impression graphite, which has excellent wettability against slag, high thermal conductivity and low thermal expansion, is used together with inorganic oxides.

Normally, ZrO ₂ -C type refractory material used in the outer diameter part of the immersion nozzle mold powder line is a stabilizer having a stable cubic structure even at high temperature by adding CaO. Partially stabilized pre-fused zirconia (CaE structure or stabilization rate: 75- 80%), and the refractory composition is composed of 70-80% by weight of partially stabilized electrolytic zirconia using CaO as a stabilizer, 15-20% by weight of graphite graphite, 1-2% by weight of antioxidant, and a binder.

However, partially stabilized electrolytic zirconia using CaO as a stabilizer tends to destabilize the stable cubic structure at high temperature into a monoclinic structure that is unstable at high temperature due to slag, and thus acts as a major factor in reducing corrosion resistance of the immersion nozzle.

Therefore, in order to improve corrosion resistance, the main method is to suppress destabilization of partially stabilized electrolytic zirconia using CaO as a stabilizer. Such a method uses zirconia, which rarely destabilizes, uses other materials of high corrosion resistance, or coats a surface, but has limitations in application due to high cost and low productivity. In another method, the densification of the tissues to suppress the infiltration of slag to improve the corrosion resistance, but due to the limitation of the densification of the tissues, the degree of corrosion resistance is less than expected.

The present invention has been devised to further improve the corrosion resistance of the zirconia carbonaceous refractory, to stabilize the fully stabilized fused zirconia powder using Y ₂ O ₃ as a stabilizer less destabilizing or tissue densification and suppress the reaction with slag It is an object of the present invention to provide a zirconia carbonaceous refractory material that can ensure high corrosion resistance by mixing ultra-fine powder unstable (pure) zirconia powder.

1 is a process chart of manufacturing high-purity cubic zirconia single crystal by the skull method;

2 is an exemplary view showing an erosion test apparatus using an induction melting furnace;

3 is a cross-sectional view taken along line A-A and line B-B of FIG. 2.

* Description of the symbols for the main parts of the drawings *

One… Refractory specimen 2. Crucible

3... Slag 4... ship chartering

10... Induction melting furnace

The present invention for achieving the above object is ZrO ₂ -C-based refractory composition containing 70-80% by weight of zirconia, the zirconia is fully stabilized pre-melting zirconia using Y ₂ O ₃ as a stabilizer: 5-50% by weight and The remaining stabilizer consists of partially stabilized electrolytic zirconia using CaO.

In addition, in a ZrO ₂ -C-based refractory composition containing 70-80% by weight of zirconia, the zirconia is an ultrafine unstabilized (pure) zirconia: 4-8% by weight and partially stabilized pre-fused zirconia using CaO as the remaining stabilizer. It is composed.

In addition, in a ZrO ₂ -C type refractory composition containing 70-80% by weight of zirconia, the zirconia is fully stabilized pre-fused zirconia using Y ₂ O ₃ as a stabilizer: 5-50% by weight, ultrafine unstable (pure) Zirconia Powder: Consists of 4-8% by weight and partially stabilized electrolytic zirconia using CaO as the remaining stabilizer.

Hereinafter, the present invention will be described in detail.

As mentioned above, ZrO ₂ -C refractory composition is composed of 70-80% by weight of partially stabilized electrolytic zirconia, 15-20% by weight graphite, 1-2% by weight antioxidant. At this time, zirconia can withstand high temperatures and have high corrosion resistance to slag, the amount of which is 70-80% by weight. The reason is that if the content of the molten zirconia exceeds 80% by weight, the spalling resistance is lowered.

The present invention is thus to suppress the de-stabilization of the partially stabilized zirconia with CaO ZrO ₂ -C jeonyung based main ingredient in stabilization of the refractory composition consisting of zero-1) with a Y ₂ O ₃ stabilized to zero completely stabilized zirconia containing jeonyung Or 2) ultrafine unstable (pure) zirconia, or together with the powder of 1) 2).

First, 1) fully stabilized premelt zirconia using Y ₂ O ₃ as a stabilizer contained in a zirconia carbonaceous refractory composition is less destabilized than partially stabilized premelt zirconia using CaO as a stabilizer, thereby improving the corrosion resistance of the refractory composition. At this time, what is important is its content.

According to the present invention, a fully stabilized electrolytic zirconia using zirconia containing 70-80% by weight of a ZrO ₂ -C-based refractory composition as Y ₂ O ₃ as a stabilizer: 5-50% by weight and partially stabilized electrolytic zirconia using CaO as the remaining stabilizer It is necessary to do The reason for this is that when the total stabilized electrolytic zirconia containing Y ₂ O ₃ as a stabilizer is contained in less than 5% by weight, there is no improvement in corrosion resistance. When it exceeds 50% by weight, the corrosion resistance is improved, but since the raw material is expensive, the use of a large amount is restricted.

Then, the fully stabilized jeonyung zirconia with Y ₂ O ₃ as a stabilizer to be applied to the present invention is also possible to use a powder obtained by crushing by-products generated in the high purity cubic zirconia single-crystal manufacturing process using a Y ₂ O ₃ wherein the stabilizer Fully stabilized molten zirconia refers to a cubic structure of Y ₂ O ₃ as a stabilizer or to 100% of a molten zirconia with a stabilization rate, and to partially stabilized molten zirconia using CaO as a stabilizer. It means an electrically melted zirconia with a rate greater than 0% and less than 100%, and the ultrafine unstabilized zirconia refers to ultrafine, unstabilized pure zirconia.

For reference, a manufacturing process of high-purity cubic zirconia single crystal zirconia will be described with reference to FIG. 1. In order to manufacture high-purity cubic zirconia single crystals of high melting point (2500-2600 ℃), a scull method that can obtain a high temperature by induction heating method is generally used, and unstabilized zirconia in an inducible cold crucible When the raw material 22 in which 10 mol% of the unstabilized zirconia powder is mixed with the powder and the stabilizer (Y ₂ O ₃ ) is filled with metal zirconium (Zr) 21 as shown in FIG. The metal is first induction melted. Unstabilized zirconia powder and stabilizer powder around the molten zirconium 23 are melted by molten zirconium as shown in Fig. 1 (b).

However, since the cooling vessel 31 is a coolant flows at a high pressure, the temperature around the cooling vessel is considerably lower than the inside of the vessel, and the zirconia powder around and on the cooling vessel 31 is sintered without melting, and the high purity cubic single crystal is the temperature of the melt. It is obtained by gradually lowering the seed crystals 25 formed at the bottom of the sintered body 24 as shown in Fig. 1 (C).

In the process, as shown in (d) of FIG. 1 (d), other crystals are generated on top of the high-purity cubic single crystal, which is a low-oxygen cubic single crystal 26 or a low-melting impurity containing a very small amount in the initial unstable zirconia powder. It is a low-purity cubic single crystal 26 that moves to the top in the process and is employed in a cubic single crystal. The single crystal 26 is not a product because of poor quality, remelting and high purity. If such remelting is more than three times, it cannot be used as a regeneration material to obtain a high-purity cubic single crystal and is treated as a by-product.

In FIG. 1, reference numeral 30 denotes an induction heating coil.

The by-product is a stabilized zirconia crystal containing a large amount of high-priced Y ₂ O ₃ can not be used as a high-purity cubic single crystal manufacturing raw material, but is a raw material that can be used as a refractory raw material. If the powder is pulverized by the by-product obtained as described above can be applied to the present invention, more preferably the particle size of the powder is 0.5mm or less.

Next, 2) ZrO ₂ -C-based refractory composition contains ultrafine unstable (pure) zirconia, which increases the densification of the refractory and the viscosity of the slag penetrated into the tissue, thereby partially stabilizing pre-fused zirconia using CaO as a stabilizer. Corrosion resistance is improved by suppressing destabilization of.

The amount of ultrafine unstabilized (pure) zirconia contained according to the present invention is 70-80% by weight of zirconia contained in the ZrO ₂ -C type refractory composition, and ultrafine unstabilized (pure) zirconia: 4-8% by weight The remaining stabilizer is partially stabilized electrolytic zirconia using CaO. This is because there is no addition effect at less than 4% by weight, and if it exceeds 8% by weight, the corrosion resistance is lower.

It is more preferable to use 5 micrometers or less of the ultrafine unstabilized (pure) zirconia powder at this time.

As described above, when fully stabilized pre-fused zirconia or ultrafine unstabilized (pure) zirconia powder using Y ₂ O ₃ as a stabilizer is added together with partially stabilized pre-fused zirconia using CaO as a stabilizer, the corrosion resistance is improved. If it contains, corrosion resistance will further improve.

At this time, the content ratio is 5-50% by weight of fully stabilized fused zirconia using Y ₂ O ₃ as a stabilizer of zirconia contained in the ZrO ₂ -C type refractory composition as a stabilizer, ultrafine unstable (pure) zirconia It is good to make partial stabilization electrolytic zirconia using 4-8 weight% and CaO as a remainder stabilizer.

In the ZrO ₂ -C refractory composition constituted according to the present invention, as in the conventional refractory composition, 15-20% by weight of impression graphite, which serves to suppress slag penetration and improve spalling resistance, and prevent oxidation of the impression graphite. 1-2 weight percent metal antioxidant and a binder.

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

As shown in Table 1, 5-50% by weight of fully stabilized electrolytic zirconia powder (0.5mm-) and cubic structure using Y ₂ O ₃ as a stabilizer for grinding by-products generated during the manufacturing of high-purity cubic Y ₂ O ₃ zirconia. Partially stabilized fused zirconia powder (0.5mm-) 23-80% by weight, and ultrafine unstabilized (pure) zirconia powder (5μm-) 3-12% by weight And 11% by weight of perolesin as a binder was kneaded to a raw material mixture consisting of 10-18% by weight of impression graphite having a purity of 95% and 1% by weight of a metal antioxidant. After drying for 30 minutes at 90 ℃ in a dryer was molded by cold isotropic pressing (CIP) and calcined in a reducing atmosphere at a temperature of 900-1000 ℃.

ingredient weight(%) ZrO ₂ Y ₂ O ₃ CaO SiO ₂ Al ₂ O ₃ TiO ₂ Fe ₂ O ₃ HfO ₂ content 80.5-81.8 16.6-17.1 0.02 0.05 0.05 0.02 0.02 1.0

Thus, the corrosion resistance of the fired molding was measured, and the results are shown in Tables 2 and 3.

Here, the corrosion resistance was evaluated for the corrosion resistance of the specimen using a commonly used high frequency induction melting furnace, as shown in Figs. 2 and 3, the method in the crucible (2) by induction melting in the hexagonal plate shape After installation, the slag (C / S = 1.3) (3) and the iron piece (4) shown in Table 1 below were added and melted, reacted at 1580 ° C. for 3 hours, and the slag and molten steel were discharged, and the eroded specimen ( The center of 1) was cut and the length of erosion was measured. In addition, the porosity, bending strength, and compressive strength of other physical properties were measured in accordance with the method for measuring the properties of the standard refractory material.

As shown in Table 2, Inventive Example (1-6) improved physical properties regardless of the amount used when fully stabilized electrolytic zirconia using Y ₂ O ₃ as a stabilizer. In addition, the corrosion resistance was also improved regardless of the amount of fully stabilized electrolytic zirconia using Y ₂ O ₃ as a stabilizer, the best when the amount is 15% by weight.

In addition, the invention example (7-11) improved the physical properties and corrosion resistance than the conventional finely stabilized (pure) zirconia powder regardless of the amount of use, and the invention example (9) was the best, but the invention example (1-6) Corrosion resistance fell.

Thus, whereas Comparative Example 1 has the corrosion resistance fell than the case of using a fully stabilized with Y ₂ O ₃ as a stabilizer of zirconia jeonyung or second differential sorry purification (pure) 4-8% by weight of zirconia powder.

In Comparative Example (2-3), when the amount of partially stabilized electrolytic zirconia using CaO as a stabilizer was increased, the penetration of slag increased, and the destabilization of partially stabilized electrolytic zirconia using CaO as a stabilizer was promoted, resulting in poor corrosion resistance. In case of decrease of, the penetration of slag was suppressed, but as the amount of graphite increased, the oxidation amount of graphite increased, the density of tissue decreased. As a result, the destabilization of partially stabilized electrolytic zirconia aggregates using CaO as a stabilizer was promoted, which led to more corrosion resistance. Degraded.

In Comparative Example (4-6), ultrafine unstable (pure) zirconia powder was used in an amount of 3% by weight or less and 10% by weight or more. Corrosion resistance was deteriorated because the amount of unstable (pure) zirconia, which is less hot, was increased rather than densifying.

division Foot honor Comparative Example 12 13 14 15 16 17 7 8 9 Compounding wt% CaO Partial Stabilization Electrolytic Zirconia 0.5 ~ 0.075mm 35 35 32 30 20 10 35 32 10 0.075 ~ mm 29 24 20 17 7 5 28 20 - Y ₂ O ₃ Fully stabilized fusion zirconia 0.5 ~ 0.075mm 5 5 8 10 20 30 5 8 30 0.075 ~ mm - 5 7 10 20 20 - 7 20 Ultrafine unstable zirconia (5㎛) 4 4 5 6 6 8 5 10 13 Impression graphite (95%) 15 15 15 15 15 15 15 15 15 Metal antioxidants One One One One One One One One One Phenolic Resin 11 11 11 11 11 11 11 11 11 Properties Volume specific gravity (g / cm 3) 3.49 3.49 3.49 3.48 3.47 3.47 3.49 3.48 3.47 Porosity (%) 16.6 16.4 16.3 16.6 16.8 16.9 16.6 16.7 17.1 Room temperature bending strength (kg / ㎠) 82 89 91 87 84 81 83 85 79 Room temperature compressive strength (kg / ㎠) 281 289 295 287 282 282 279 280 268 Characteristics of use corrosion Erosion Length (mm) 4.5 4.4 4.2 3.9 4.3 4.6 4.7 4.9 5.81 Erosion Index 73.8 72.1 68.9 63.9 70.5 75.4 77.1 80.3 95.3

As shown in Table 3, Inventive Example (12-17) is a case where a mixture of fully stabilized fused zirconia and ultrafine unstabilized (pure) zirconia powder using Y ₂ O ₃ as a stabilizer is used, regardless of the amount of use. This was similar, and the corrosion resistance was improved than when fully stabilized fused zirconia or ultrafine unstabilized (pure) zirconia powder using Y ₂ O ₃ alone was used.

At this time, the corrosion resistance is different depending on the amount of fully stabilized fused zirconia or ultrafine unstable (pure) zirconia powder using Y ₂ O ₃ as a stabilizer, but the ultrafine unstabilized (pure) zirconia powder and slag and zirconia aggregate By suppressing the reaction, corrosion resistance was improved. In particular, 20 wt% and 6 wt% of Inventive Example (15) of the fully stabilized pre-melted zirconia and ultrafine unstabilized (pure) zirconia powder using Y ₂ O ₃ showed the best corrosion resistance.

On the other hand, Comparative Example (7-9) is a case where the amount of fully stabilized electrolytic zirconia and ultrafine unsaturated (pure) zirconia using Y ₂ O ₃ as a stabilizer is small, and no mixed effect was observed. When the amount of purified (pure) zirconia powder was increased, the hot properties were higher than the stabilized zirconia with Y ₂ O ₃ as a stabilizer, rather than the contribution of slag penetration and reaction suppression due to tissue densification. This was degraded.

As described above, according to the present invention, it is excellent in physical properties and corrosion resistance by suppressing the destabilization of the partially stabilized pre-fused zirconia using CaO as a stabilizer, compared to the conventional zirconia carbonaceous refractory composition using only partially stabilized pre-fused zirconia using CaO as a stabilizer. In addition, by using the by-product to be disposed of as raw materials can be manufactured at a low price. Furthermore, the fire resistant composition of the present invention has a useful effect that can be applied to the refractory to the outer diameter portion of the immersion nozzle for playing.

Claims (2)

In the ZrO ₂ -C type refractory composition containing 70-80% by weight of zirconia, The zirconia is ultrafine unstable (pure) zirconia: 4-8% by weight and partially stabilized electrolytic zirconia using CaO as the remaining stabilizer, carbon-containing zirconia-resistant refractory composition excellent in corrosion resistance. The zirconia-containing carbon-containing zirconia refractory composition of claim 1, wherein the ultrafine unstable (pure) zirconia is a powder having a particle size of 5 μm or less.