KR20020037015A - Refractory with high quality - Google Patents

Abstract

PURPOSE: A zirconia-carbon(ZrO2-C) refractory used for immersion nozzle in steel-making fields is provided, which has much improved abrasion resistance by adding ultrafine unstabilized zirconia and Y2O3-stabilized zirconia to conventional ZrO2-C refractory using CaO-partially stabilized zirconia. CONSTITUTION: The ZrO2-C refractory composition comprises 70-80wt.% of CaO partially stabilized zirconia, 15-20wt.% of crystalline and 1-2wt.% of anti-oxidant, where CaO partially stabilized zirconia consists of 5-50wt.% of Y2O3-stabilized zirconia and the remains of CaO-partially stabilized zirconia, 4-8wt.% ultrafine unstabilized zirconia less than 5micrometer in size and the remains of CaO partially stabilized zirconia, and 5-50wt.% of Y2O3-stabilized zirconia, 4-8wt.% ultrafine unstabilized zirconia, and the remains of CaO-partially stabilized zirconia.

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 is made of alumina-carbon material, and the outer diameter part which is in contact with the slag has high corrosion resistance to the slag. Zirconia-carbon refractory is used because it is required.

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.

Usually, ZrO ₂ -C type refractory material used in the outer diameter of the immersion nozzle mold powder line part contains CaO partial stabilized electrolytic zirconia (cubic crystal structure or stabilization rate: 75-80%) which has stable cubic crystal structure even at high temperature. The refractory composition consists of 70-80% by weight of CaO partially stabilized zirconia, 15-20% by weight of graphite, and 1-2% by weight of antioxidant.

However, CaO partial stabilization pre-fused zirconia tends to destabilize the stable cubic structure at high temperature into unstable monoclinic structure due to the slag component, which acts as a major factor in reducing the corrosion resistance of the immersion nozzle.

Therefore, in order to improve corrosion resistance, it is a main method to suppress destabilization of CaO partial stabilization electrolytic zirconia. 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 is devised to further improve the corrosion resistance of the zirconia carbonaceous refractory, Y ₂ O ₃ fully stabilized electrolytic zirconia powder or less fine destabilization that inhibits the reaction with the slag and slag less destabilization It is an object to provide a zirconia carbonaceous refractory material that can be mixed with zirconia powder to ensure high content.

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 a ZrO ₂ -C-based refractory composition containing 70-80% by weight of zirconia, the zirconia is Y ₂ O ₃ fully stabilized electrolytic zirconia: 5-50% by weight and the remaining CaO partial stabilization It is composed of electrolytic zirconia.

Further, in a ZrO ₂ -C type fire resistant composition containing 70-80% by weight of zirconia, the zirconia is composed of ultra fine unstable zirconia: 4-8% by weight and the remaining CaO partially stabilized zirconia.

In addition, in the ZrO ₂ -C type refractory composition containing 70-80% by weight of zirconia, the zirconia is Y ₂ O ₃ fully stabilized electrolytic zirconia: 5-50% by weight, ultra-fine powder unstable zirconia powder: 4-8% % And the remaining CaO partial stabilization electrolytic zirconia.

Hereinafter, the present invention will be described in detail.

As mentioned above, the ZrO ₂ -C-based refractory composition consists of 70-80% by weight of CaO partially stabilized zirconia, 15-20% by weight graphite, and 1-2% by weight of 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 to contain 1) Y ₂ O ₃ fully stabilized pre-fused zirconia, or 2) ultra-fine powder in order to suppress destabilization of CaO partial stabilization electrolytic zirconia, the main raw material of the ZrO ₂ -C-based refractory composition It contains a clarified zirconia, or together with the powder of 1) 2), it is characterized by.

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

According to the present invention, it is necessary to make zirconia containing 70-80% by weight of the ZrO ₂ -C-based refractory composition into Y ₂ O ₃ fully stabilized electrolytic zirconia: 5-50% by weight and the remaining CaO partially stabilized electrolytic zirconia. The reason is that if Y ₂ O ₃ fully stabilized electrolytic zirconia is contained in less than 5% by weight, there is no improvement in corrosion resistance. If 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.

In addition, Y ₂ O ₃ fully stabilized electrolytic zirconia applied to the present invention may use a powder obtained by pulverizing by-products generated during the production of high-purity cubic zirconia single crystals.

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 strengthening 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 ultra-fine unstable zirconia increases the densification of the refractory and the viscosity of the slag penetrated into the tissue, thereby inhibiting the destabilization of the CaO partial stabilization electrolytic zirconia by the slag This is improved.

The amount of ultrafine unstabilized zirconia contained in accordance with the present invention is 70-80% by weight of zirconia contained in a ZrO ₂ -C-based refractory composition ultrafine unstable zirconia: 4-8% by weight and the remaining CaO partially stabilized fused zirconia It is to be. 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 zirconia powder at this time.

As described above, when Y ₂ O ₃ fully stabilized electrolytic zirconia or ultrafine unstabilized zirconia powder is contained together with CaO partially stabilized electrolytic zirconia, the corrosion resistance is improved, but when the two powders are included together, the corrosion resistance is further improved.

At this time, the content ratio is 5-50% by weight of zirconia Y ₂ O ₃ fully stabilized zirconia containing 70-80% by weight of ZrO ₂ -C-based refractory composition, ultrafine unstabilized zirconia: 4-8% by weight and What is necessary is just to carry out the remaining CaO partial stabilization electrolytic zirconia.

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

Y ₂ O ₃ fully stabilized electrolytic zirconia powder (0.5mm-) 5-50% by weight, and cubic crystal structure (stabilization rate), which is a pulverized by-product generated in the manufacturing process of high purity cubic crystal Y ₂ O ₃ zirconia as shown in Table 1 below. 75-80% CaO partially stabilized electrolytic zirconia powder (0.5mm-) 23-80% by weight, ultrafine unstabilized zirconia powder (5μm-) 3-12% by weight, and purity 95% Kneaded by adding 11% by weight of peroleazine as a binder to the raw material mixture consisting of 18% by weight and 1% by weight of the metal antioxidant, and kneaded to 1mm- and dried for 30 minutes at 90 ℃ in a dryer and cold Molded by the pressure-pressure method (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 Figures 2 and 3, the method is installed in the crucible () with induction melting in the form of a hexagonal plate Then, slag (C / S = 1.3) (3) and iron (4) in Table 1 below were added and melted, reacted at 1580 ° C. for 3 hours, and then slag and molten steel were discharged, and the eroded specimen (1 The center of the cut) was cut to measure the length of erosion. 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 irrespective of the amount used when Y ₂ O ₃ fully stabilized electrolytic zirconia was used. In addition, the corrosion resistance was also improved regardless of the amount of Y ₂ O ₃ fully stabilized electrolytic zirconia, was the best when the amount used is 15% by weight.

In addition, the invention example (7-11) has improved physical properties and corrosion resistance than the conventional fine powder unstabilized zirconia powder, and the invention example (9) was the best, but corrosion resistance than the invention example (1-6) Fell.

Thus, whereas Comparative Example 1 has the corrosion resistance fell than the case of using Y ₂ O ₃ or zirconia fully stabilized jeonyung second differential sorry purifying 4-8 wt.% Zirconia powder.

In Comparative Example (2-3), when the amount of CaO partially stabilized electrolytic zirconia was increased, the penetration of slag increased, and the destabilization of CaO partially stabilized electrolytic zirconia was promoted, resulting in poor corrosion resistance. Although suppressed, the increase in the amount of graphite increases, the amount of oxidation of the graphite is increased, the densification of the tissue is lowered, thereby resulting in the release of the CaO partially stabilized electrolytic zirconia aggregate, thereby further reducing corrosion resistance.

In Comparative Example (4-6), when the ultrafine unstabilized zirconia powder was used in an amount of 3% by weight or less and 10% by weight or more, the physical properties were increased, but it was hot rather than contributing to slag penetration inhibition and tissue densification. Corrosion resistance fell because the amount of unstabilized zirconia with poor properties increased.

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 Y ₂ O ₃ fully stabilized pre-fused zirconia and ultra-fine unstable zirconia powder are mixed, and the physical properties are similar, regardless of the amount used, Y ₂ O ₃ Corrosion resistance was improved when fully stabilized fused zirconia or ultrafine unstable zirconia powder was used alone.

At this time, the corrosion resistance is different depending on the amount of Y ₂ O ₃ fully stabilized electrolytic zirconia or ultrafine unstabilized zirconia powder, but the ultrafine unstabilized zirconia powder inhibits the reaction between slag and zirconia aggregate, thereby improving the corrosion resistance. In particular, the Y ₂ O ₃ fully stabilized electrolytic zirconia and ultrafine unstabilized zirconia powder showed the best corrosion resistance in the case of 20% and 6% by weight of the invention example (15), respectively.

On the contrary, in Comparative Example (7-9), when the amount of Y ₂ O ₃ fully stabilized fused zirconia and ultrafine unsaturated paper was low, the mixed effect did not appear. When the amount of ultrafine unsaturated zirconia powder increased, The corrosion resistance was lowered because the amount of unstabilized zirconia was lower than that of Y ₂ O ₃ fully stabilized zirconia, rather than the contribution of slag penetration and reaction inhibition by densification of tissue.

As described above, according to the present invention, compared to the conventional zirconia carbonaceous refractory composition using only CaO partially stabilized fused zirconia, by inhibiting destabilization of CaO partially stabilized fused zirconia, excellent physical properties and corrosion resistance, and also by-products to be disposed of By using it as a raw material, it 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 composed of ultrafine unstabilized zirconia: 4-8% by weight and the remaining CaO partially stabilized fused zirconia. The fireproof composition according to claim 1, wherein the ultrafine unstable zirconia is a powder having a particle size of 5 μm or less.