JP7060831B1 - Zirconia-Carbon Refractory Material, Immersion Nozzle, and Zirconia-Carbon Refractory Material Manufacturing Method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the corrosion resistance of a zirconia-carbon refractory material as compared with the prior art. A zirconia-carbon refractory material containing 70% by weight or more and 98% by weight or less of a zirconia raw material and 2% by weight or more and 30% by weight or less of a carbon raw material, wherein the zirconia raw material is a sieve having a nominal opening of 106 μm. The median diameter of the first part is 150 μm or more and 500 μm or less, and the median diameter of the second part is 1 μm or more and 30 μm or less, including the first part that cannot pass through the sieve and the second part that can pass through the sieve. The ratio W1 / W2 of the weight W1 of a part to the weight W2 of the second part is 2.0 or more and 6.0 or less. [Selection diagram] None

Description

The present invention relates to a zirconia-carbon refractory refractory material having high corrosion resistance, a dipping nozzle to which the refractory material is applied, and a method for manufacturing the refractory material.

In the continuous steel casting process, refractory materials with dipping nozzles are used to stably introduce molten steel from the tundish to the mold. The service life of the dip nozzle has a great influence on the productivity of continuous steel casting and the quality of steel slabs.

In order to prevent the molten steel from coming into contact with the atmosphere and oxidizing in the mold, a method of covering the molten steel surface during casting with a calcia-silica powder slag is widely used. The portion of the immersion nozzle (slag line) that comes into contact with the powder slag is eroded by both the molten steel and the molten slag, so that the melt damage is fast. Therefore, the corrosion resistance of the slag line can affect the service life of the entire nozzle.

As a material for the immersion nozzle, an alumina-carbon refractory is usually used for the nozzle body and the immersion part, but a zirconia-carbon refractory with relatively high corrosion resistance may be applied to the slag line. be. Carbon has a low coefficient of thermal expansion of its own and has a role of imparting sufficient spalling resistance to the nozzle.

Patent Document 1 (Japanese Unexamined Patent Publication No. 3-66462) describes carbon 7 to 25%, unstabilized zirconia 50 to 70%, stabilized zirconia 10 to 30%, silicon carbide 1 to 20%, and metallic silicon 1 to 5. %, Synthetic resin 6 to 20%, and unstabilized zirconia is 10 to 50% fine powder, of which 20 to 40% has a particle size of 44 μm or less and 5 to 25 has a particle size of 0.5 μm or less. % A zirconia-carbonaceous continuous casting immersion nozzle characterized by its use has been proposed.

Further, in Patent Document 2 (Japanese Unexamined Patent Publication No. 4-182049), at least the portion in contact with the molten slag contains 70 to 90% by weight of zirconia and 10 to 30% by weight of scaly graphite having a particle size of 500 μm or less. Zirconia particles are distributed so as to satisfy the following a and b.
a: The particle size distribution of the entire zirconia particles is composed of 30 to 65% by weight of particles having a particle size of more than 125 μm, 20 to 55% by weight of particles having a size of 125 to 45 μm, and 15 to 45% by weight of particles having a size of less than 45 μm.
b: With respect to the entire zirconia particles, between 45 to 355 μm of the standard sieve specified in JIS Z 8801, there are 355 to 250 μm, 250 to 180 μm, 180 to 125 μm, 125 to 90 μm, 90 to 63 μm between adjacent sieves. At least 3% by weight of zirconia particles are present in each of 63 to 45 μm.
Further, a dipping nozzle for continuous casting has been proposed, which is composed of a refractory material having a structure in which scaly graphite is present in 80% or more between adjacent zirconia particles exceeding 125 μm.

In Patent Document 3 (Japanese Unexamined Patent Publication No. 9-142927), it is a zirconia-carbon refractory using fused zirconia as a zirconia raw material, and among the crystal grains of the fused zirconia, particles having a size of 40 μm to 300 μm. A zirconia-carbon refractory is proposed in which 20% or more of the particles in the diameter range are healthy particles having no cracks and containing no low melt.

Further, in Patent Document 4 (Japanese Unexamined Patent Publication No. 11-302073), 70 to 95% by weight of a zirconia raw material and 5 to 30% by weight of graphite are used, and 70% or more of the zirconia grains having a particle size composition of 45 μm or less are used. A zirconia-graphitic refractory having excellent corrosion resistance and a nozzle for continuous casting using the zirconia-graphite refractory have been proposed.

Japanese Unexamined Patent Publication No. 3-66462 Japanese Unexamined Patent Publication No. 4-182049 Japanese Unexamined Patent Publication No. 9-142927 Japanese Unexamined Patent Publication No. 11-302073

However, the corrosion resistance of the zirconia-carbon refractory materials described in Patent Documents 1 to 4 is insufficient, and there is room for improvement.

Therefore, in order to further improve the productivity of continuous steel casting and the quality of steel slabs, it is required to improve the corrosion resistance of the zirconia-carbon refractory material as compared with the prior art.

The zirconia-carbon refractory material according to the present invention is a zirconia-carbon refractory material containing 70% by weight or more and 98% by weight or less of a zirconia raw material and 2% by weight or more and 30% by weight or less of a carbon raw material. The raw material includes a first portion that cannot pass through a sieve having a nominal opening of 106 μm specified in JIS Z 8801-1: 2019, and a second portion that can pass through the sieve, and the first portion, JIS Z 8801-1. The median diameter determined based on the integrated particle size distribution curve specified using the sieve defined in 2019 is 150 μm or more and 500 μm or less, and the median determined according to JIS Z 8825: 2013 of the second part. The diameter is 1 μm or more and 30 μm or less, and the ratio W1 / W2 of the weight W1 of the first portion to the weight W2 of the second portion is 2.0 or more and 6.0 or less.

Further, the immersion nozzle according to the present invention is characterized in that at least the slag line is made of the above-mentioned zirconia-carbon refractory material.

Further, the method for producing a zirconia-carbonaceous refractory material according to the present invention includes a mixing step of mixing 70% by weight or more and 98% by weight or less of the zirconia raw material and 2% by weight or more and 30% by weight or less of the carbon raw material. The zirconia raw material includes a first portion that cannot pass through a sieve having a nominal opening of 106 μm specified in JIS Z 8801-1: 2019 and a second portion that can pass through the sieve, and the first portion, JIS Z 8801-. The median diameter determined based on the integrated particle size distribution curve specified using the sieve defined in 1: 2019 is 150 μm or more and 500 μm or less, and is determined according to JIS Z 8825: 2013 of the second part. The median diameter is 1 μm or more and 30 μm or less, and the ratio W1 / W2 of the weight W1 of the first portion to the weight W2 of the second portion is 2.0 or more and 6.0 or less.

According to these configurations, the corrosion resistance of the zirconia-carbon refractory material can be improved as compared with the prior art. Further, by using a refractory material having improved corrosion resistance, the durability of the immersion nozzle can be improved.

Hereinafter, preferred embodiments of the present invention will be described. However, the scope of the present invention is not limited by the preferred embodiments described below.

The method for producing a zirconia-carbonaceous fireproof material according to the present invention is, as one embodiment, 2.0 times or more and 6.0 times or less the weight of the second portion and the second portion before the mixing step. It is preferable to include an adjusting step of mixing the first portion with the adjusted zirconia raw material to obtain the adjusted zirconia raw material, and it is preferable to use the adjusted zirconia raw material obtained in the adjusting step as the zirconia raw material in the mixing step.

According to this configuration, the weight ratio of the first portion to the second portion of the zirconia raw material can be arbitrarily adjusted, so that a refractory material having desired properties can be obtained.

The method for producing a zirconia-carbon refractory material according to the present invention is, as one embodiment, using a sieve having a nominal opening of 106 μm specified in JIS Z 8801-1: 2019 before the adjustment step to prepare a zirconia raw material. The first part and the second part separated in the separation step may be used as the first part and the second part in the adjustment step including the separation step for separating the first part and the second part. preferable.

According to this configuration, the zirconia raw material can be separated into the first part and the second part, and then the weight ratio between the first part and the second part can be adjusted. Regardless of the weight ratio, the weight ratio of the first part and the second part of the refractory material can be arbitrarily adjusted.

Further features and advantages of the invention will be further clarified by the following illustration of exemplary and non-limiting embodiments described with reference to the drawings.

It is sectional drawing of the immersion nozzle which concerns on embodiment. It is sectional drawing of the use state of the immersion nozzle which concerns on embodiment.

An embodiment of a zirconia-carbon refractory material, a dipping nozzle, and a method for manufacturing a zirconia-carbon refractory material according to the present invention will be described with reference to the drawings.

[Composition of refractory material]
The zirconia-carbon refractory material (hereinafter, may be simply referred to as “fireproof material”) according to the present embodiment is 70% by weight or more and 98% by weight or less of the zirconia raw material and 2% by weight or more and 30% by weight or less of the carbon raw material. And, including.

When the refractory material contains 70% by weight or more of the zirconia raw material, a refractory material having good corrosion resistance can be obtained. Further, since the refractory material contains 98% by weight or less of the zirconia raw material, 2% by weight or more of the carbon raw material or the like can be used, and the refractory material can be imparted with advantageous properties such as spalling resistance. The refractory material preferably contains 75% by weight or more of the zirconia raw material. Further, the refractory material preferably contains 95% by weight or less of the zirconia raw material.

When the refractory material contains 2% by weight or more of the carbon raw material, a refractory material having good spalling resistance can be obtained. Further, when the refractory material contains 30% by weight or less of the carbon raw material, 70% by weight or more of the zirconia raw material can be used, and a refractory material having good corrosion resistance can be obtained. The refractory material preferably contains 5% by weight or more of the carbon raw material. Further, the refractory material preferably contains 25% by weight or less of the carbon raw material.

The carbon raw material may include one or more known carbon raw materials such as various graphites, carbon blacks, pitches, and resin charcoals. When a plurality of types of carbon raw materials are used, the total weight of the plurality of types of carbon raw materials is 2% by weight or more and 30% by weight or less of the refractory material. The purity of the carbon raw material is preferably 95% by weight or more, more preferably 97% by weight or more.

The refractory material may contain other components of the zirconia raw material and the carbon raw material as additives. Examples of such additives include elemental substances such as zirconium, aluminum, silicon, magnesium, chromium, titanium, and boron, alloys, oxides, carbides, borides, and nitrides. When the refractory material contains one or more of the substances exemplified above as additives, the oxidation resistance and strength of the refractory material can be improved. When the refractory material contains an additive, the total content of the additive is preferably 8% by weight or less, and more preferably 5% by weight or less. When the total content of the additives is within the above range, a refractory material having corrosion resistance equivalent to that in the case where no additive is not contained and having improved oxidation resistance and strength can be obtained.

(Composition of zirconia raw materials)
The zirconia raw material contained in the refractory material according to the present embodiment preferably contains 90% by weight or more of the zirconia component. When the zirconia raw material contains 90% by weight or more of the zirconia component, the corrosion resistance of the refractory material tends to be good. The content of the zirconia component in the zirconia raw material is more preferably 92% by weight or more.

As a residue other than the zirconia component in the zirconia raw material, a zirconia stabilizer, an unavoidable impurity, and the like may be contained. As the zirconia stabilizer, one or more kinds of substances known as zirconia stabilizers (for example, calcia, magnesia, yttrium, etc.) may be used. Inevitable impurities may include silica, alumina, iron oxide and the like.

The zirconia raw material includes a first portion that cannot pass through a sieve having a nominal opening of 106 μm and a second portion that can pass through the sieve as defined in JIS Z 8801-1: 2019. That is, the first portion is a particle having a large particle size in the zirconia raw material, and the second part is a particle having a small particle size in the zirconia raw material.

The median diameter of the first part is 150 μm or more and 500 μm or less. When the median diameter of the first portion is 150 μm or more, the porosity of the obtained refractory material becomes an appropriate level, and the strength of the refractory material tends to be good. Further, when the median diameter of the first portion is 500 μm or less, the size of the pores in the obtained refractory material becomes an appropriate level, and the wear resistance of the refractory material to molten steel and molten slag flow tends to be good. The median diameter of the first portion is preferably 200 μm or more. The median diameter of the first portion is preferably 450 μm or less.

When determining the median diameter of the first part, first, a sample whose median diameter is to be determined is classified using a plurality of sieves. Next, the weight of each classified category is measured, and a weight-based integrated particle size distribution curve is created. Finally, the particle diameter at which the integrated weight is 50% in the integrated particle size distribution curve is determined as the median diameter. The plurality of sieves used here are all sieves having various nominal openings specified in JIS Z 8801-1: 2019, for example, the nominal openings are 106 μm, 125 μm, 180 μm, 250 μm, respectively. Those of 355 μm, 500 μm, 710 μm, and the like can be used.

The median diameter of the second portion is 1 μm or more and 30 μm or less. When the median diameter of the second portion is 1 μm or more, the porosity of the obtained refractory material becomes an appropriate level, and the melting damage of the refractory material can be suppressed. Further, when the median diameter of the second portion is 30 μm or less, the size of the pores in the obtained refractory material becomes an appropriate level, and the melting damage of the refractory material can be suppressed. The median diameter of the second portion is preferably 5 μm or more. The median diameter of the second portion is preferably 25 μm or less.

The median diameter of the second part is determined according to JIS Z 8825: 2013.

The ratio W1 / W2 of the weight W1 of the first portion to the weight W2 of the second portion is 2.0 or more and 6.0 or less. When the ratio W1 / W2 is 2.0 or more, the porosity of the obtained refractory material becomes an appropriate level, and the corrosion resistance of the refractory material tends to be good. Further, when the ratio W1 / W2 is 6.0 or less, the size of the pores in the obtained refractory material becomes an appropriate level, and the wear resistance of the refractory material to molten steel and molten slag flow tends to be good. Moreover, the corrosion resistance tends to be good. The ratio W1 / W2 is preferably 2.5 or more. Further, the ratio W1 / W2 is preferably 5.0 or less.

[Structure of immersion nozzle]
Next, an embodiment of the immersion nozzle according to the present invention will be described. The immersion nozzle 1 according to the present embodiment is provided on the substantially cylindrical main body portion 2, the discharge port 3 opening on the side surface of the main body portion 2 on the tip 21 side, and the base end 22 side of the main body portion 2. It has a connection portion 4 (FIG. 1). Both parts are made of refractory material.

The immersion nozzle 1 is used in a state where the connection portion 4 is connected to an upstream process device (not shown) such as a tundish and the discharge port 3 is immersed in the molten steel M in the mold (not shown). (Fig. 2). The molten steel M flows into the mold from the upstream process via the immersion nozzle.

The main body 2 has a slag line 23 near the center in the longitudinal direction (FIGS. 1 and 2). The slag line 23 is a portion arranged near the liquid surface of the molten steel M in the state of use of the immersion nozzle 1, and is a portion that frequently comes into contact with the slag S. The slag line 23 is made of the zirconia-carbon refractory material according to the above embodiment.

The portion of the main body 2 other than the slag line 23 may be made of the zirconia-carbon refractory material according to the above embodiment, or may be made of another refractory material. The other refractory material may be a material known as a refractory material used for the immersion nozzle, and for example, alumina containing 45% by weight or more and 65% by weight or less of the alumina raw material and 10% by weight or more and 35% by weight or less of the carbon raw material. -Can be a carbon refractory material. The balance of the refractory material may contain, for example, silica. When the refractory material contains silica, its content can be 30% by weight or less of the refractory material.

As in the above description of the zirconia raw material, the alumina raw material may contain components other than the alumina component. For the definition of carbon raw material, refer to the above explanation.

When different refractory materials are used for the slag line 23 and other portions, the width and position of the portion made of the zirconia-carbonaceous refractory material according to the above embodiment (that is, the slag line 23) is the width of the slag S. And the position does not have to be exactly the same, and the width and position of the slag line 23 may be determined in consideration of the width and position of the average slag S in the process in which the immersion nozzle 1 is used. From the viewpoint of more preferably preventing damage to the immersion nozzle 1 due to contact with the slag S, the slag line 23 has a width and position including the average width and position of the slag S in the process in which the immersion nozzle 1 is used. It is preferable to be provided. In this case, the width of the slag line 23 is wider than the average width of the slag S in the process.

[Manufacturing method of immersion nozzle (refractory material)]
Finally, an embodiment of the method for manufacturing a dipping nozzle according to the present invention will be described. Here, the immersion nozzle is also an example of the refractory material according to the present embodiment. The method for manufacturing a dipping nozzle according to the present embodiment includes (1) a separation step, (2) an adjustment step, (3) a mixing step, and (4) a molding step.

(1) Separation step The separation step is a step of separating the first part and the second part of the zirconia raw material. The zirconia raw material as a starting material is sieved using a sieve having a nominal opening of 106 μm specified in JIS Z 8801-1: 2019, and the zirconia raw material remaining on the sieve is obtained as the first part, and the zirconia raw material that has passed through the sieve is obtained. As the second part. As the zirconia raw material that has not been classified as the starting material, a commercially available product can be used.

(2) Adjustment step The adjustment step is a step of obtaining an adjusted zirconia raw material in which the ratio W1 / W2 of the weight W1 of the first portion and the weight W2 of the second portion is adjusted to 2.0 or more and 6.0 or less. More specifically, the first portion and the second portion obtained in the separation step are weighed respectively, and the weight W1 of the weighed first portion is 2.0 times or more 6 times the weight W2 of the weighed second portion. After making the ratio 0 times or less, mix the two. The method of mixing the first part and the second part is not particularly limited as long as the two types of powder can be uniformly mixed, and for example, both are put into a mixer to drive the stirring blade of the mixer. An example is a method of mixing and mixing.

(3) Mixing Step The mixing step is a step of mixing 70% by weight or more and 98% by weight or less of the zirconia raw material and 2% by weight or more and 30% by weight or less of the carbon raw material. Here, the adjusted zirconia obtained in the adjusting step is used as the zirconia raw material. The method of mixing the zirconia raw material and the carbon raw material is not particularly limited as long as the two types of powder can be uniformly mixed, and for example, both are put into a mixer and the stirring blade of the mixer is driven. An example is a mixing method. When producing a refractory material containing an additive, the zirconia raw material, the carbon raw material, and the additive are mixed in this step. In addition, the binder used in the next molding step is also mixed.

(4) Molding Step The molding step is a step of molding the mixture obtained in the mixing step to obtain a refractory material having a desired shape. Known methods can be applied as methods for obtaining refractory materials in the molding process, which may typically include procedures such as weighing, kneading, molding, drying, baking, and processing of the mixture. The method generally includes a preforming step (weighing, kneading, molding, drying) in which the mixture is placed in a mold to form a desired shape (immersion nozzle in this embodiment) and a firing step in which the preformed mixture is fired. (Baking, processing) and may be included.

As the binder used in the preforming step, a known binder can be used. Examples of such binders include organic binders such as phenolic resins, furan resins, pitches, and tars, and inorganic binders such as phosphates and silicates.

Further, as a molding method used when forming the shape of the immersion nozzle in the preforming step, for example, a molding method such as cold hydrostatic isotropic pressure pressing (CIP molding) can be used.

When the composition of the refractory material to be used is changed depending on the part of the immersion nozzle as described above, a different mixture (premixed with zirconia raw material or the like) is used for each part.

The firing conditions in the firing step are not particularly limited. For example, the firing atmosphere is not particularly limited, and can be appropriately selected from an atmospheric atmosphere, a reducing atmosphere, an inert atmosphere, and the like. Further, the firing temperature is not particularly limited, and may be, for example, 700 ° C. or higher and 1200 ° C. or lower.

(Other manufacturing methods)
In the above, as an embodiment of the method for manufacturing a dipping nozzle according to the present invention, a method including (1) separation step, (2) adjustment step, (3) mixing step, and (4) molding step has been described as an example. .. However, the combination of configurations included in the method for manufacturing a dipping nozzle according to the present invention is not limited to the above combination. For example, if a zirconia raw material having a median diameter of 150 μm or more and 500 μm or less and a zirconia raw material having a median diameter of 1 μm or more and 30 μm or less can be procured by a method such as purchase, the adjustment step and the mixing step are performed without performing the separation step. Can be carried out. If the zirconia raw material having a weight ratio W1 / W2 of 2.0 or more and 6.0 or less between the first part and the second part can be procured by a method such as purchase, the mixing step is performed without performing the separation step and the adjustment step. Can be carried out.

In the above, the method of manufacturing the immersion nozzle has been described as an example, but when the refractory material according to the present embodiment is used for a member other than the immersion nozzle, pre-molding corresponding to the shape of the member is performed in the molding process. Just do it.

[Other embodiments]
It should be understood that with respect to other configurations, the embodiments disclosed herein are exemplary in all respects and the scope of the invention is not limited thereto. Those skilled in the art will be able to easily understand that modifications can be made as appropriate without departing from the spirit of the present invention. Therefore, another embodiment modified without departing from the spirit of the present invention is naturally included in the scope of the present invention.

Hereinafter, the present invention will be further described with reference to examples. However, the following examples do not limit the present invention.

[Test 1] Corrosion resistance evaluation According to the following procedure, samples of each example of Examples and Comparative Examples were prepared and their corrosion resistance was evaluated.

(Preparation of sample)
The contents of the zirconia raw material and the carbon raw material, the media of the first part and the second part are carried out by the same procedure as the separation step, the adjustment step, and the mixing step described in the section of "Manufacturing method of immersion nozzle (refractory material)" above. A mixture was obtained in which the diameter and the weight ratio W1 / W2 of the first portion and the second portion were variously adjusted. The mixture was preformed into blocks by a known method and then calcined at 1000 ° C. in a reducing oxidation atmosphere. A part of the block after firing was cut out with a diamond cutter, and the surface was polished to obtain a test piece having a size of 20 mm × 20 mm × 200 mm.

(Erosion test)
In a high frequency electric furnace, 20 kg of steel was melted and the molten steel was kept at 1560 ° C. Subsequently, the test piece was immersed in molten steel, and powder slag was further added to the molten steel surface. Then, the test piece was rotated at a rotation speed of 50 rpm. After 2 hours, the test piece was pulled up from the molten steel and cooled by allowing to cool. After the temperature of the test piece was lowered to room temperature, the melt loss thickness of the test piece was measured at the portion in contact with the powder slag.

(Test results)
(1) Differences due to the difference in the median diameter of the first portion In Examples 1 to 5 and Comparative Examples 1 to 3, the difference in corrosion resistance due to the difference in the median diameter of the first portion was evaluated. In addition, in common in Examples 1 to 5 and Comparative Examples 1 to 3, the zirconia raw material is 88% by weight, the carbon raw material is 12% by weight, the median diameter of the second part is 15 μm, and the ratio W1 / W2 is 3. It was set to 5.5.

As shown in Table 1, when the median diameter of the first portion is 150 to 500 μm (Examples 1 to 5), the melt damage is compared with the case where the median diameter deviates from the above range (Comparative Examples 1 to 3). The thickness was small.

Table 1: Differences due to median diameter in the first part

(2) Differences in the second portion depending on the median diameter In Examples 6 to 10 and Comparative Examples 4 and 5, the difference in corrosion resistance due to the difference in the median diameter of the second portion was evaluated. In addition, in common in Examples 6 to 10 and Comparative Examples 4 and 5, the zirconia raw material was 90% by weight, the carbon raw material was 9% by weight, the additive was 1% by weight, and the median diameter of the first portion was 300 μm. , The ratio W1 / W2 was set to 3.5. Here, in each of the examples, zirconium borohydride was used as an additive.

As shown in Table 2, when the median diameter of the second portion is 1 to 30 μm (Examples 6 to 10), compared with the case where the median diameter deviates from the above range (Comparative Examples 4 and 5), the solution is dissolved. The loss thickness was small.

Table 2: Differences due to the median diameter of the second part

(3) Differences due to the ratio W1 / W2 In Examples 11 to 15 and Comparative Examples 6 and 7, the difference in corrosion resistance due to the difference in the ratio W1 / W2 was evaluated. In addition, in common with Examples 11 to 15 and Comparative Examples 6 and 7, the zirconia raw material was 86% by weight, the carbon raw material was 12% by weight, the additive was 2% by weight, and the median diameter of the first portion was 280 μm. , The median diameter of the second part was set to 10 μm. Here, in each of the examples, a mixture of boron carbide and metallic silicon (weight ratio 1: 1) was used as an additive.

As shown in Table 3, when the ratio W1 / W2 is 2.0 to 6.0 (Examples 11 to 15) and when the ratio W1 / W2 deviates from the above range (Comparative Examples 6 and 7). In comparison, the erosion thickness was small.

Table 3: Differences due to ratios W1 / W2

(4) Differences due to the content of each raw material In Examples 16 to 20 and Comparative Examples 8 and 9, the difference in corrosion resistance due to the difference in the contents of the zirconia raw material and the carbon raw material was evaluated. In addition, in common with Examples 16 to 20 and Comparative Examples 8 and 9, the additive was 5% by weight, the median diameter of the first portion was 420 μm, the median diameter of the second portion was 16 μm, and the ratio W1 / W2 was set. It was set to 4.2. Here, in each of the examples, a mixture of zirconium borohydride, boron carbide, and titanium carbide (weight ratio 1: 1: 3) was used as an additive.

As shown in Table 4, when the zirconia raw material is 70 to 93% by weight and the carbon raw material is 2 to 25% by weight (Examples 16 to 20), the content of the zirconia raw material deviates from the above range. The erosion thickness was smaller than when (Comparative Example 8) and when the content of the carbon raw material deviated from the above range (Comparative Examples 8 and 9). In Comparative Example 9, when the test piece was pulled up from the molten steel after immersion, it was found that the test piece was cracked, so that the melt loss thickness could not be measured.

Table 4: Differences due to the content of each raw material

[Test 2] Evaluation of actual immersion nozzle The immersion nozzle whose slag line portion is made of the refractory material of Example 3 according to the procedure described in the section of "Manufacturing method of immersion nozzle (refractory material)" above (hereinafter, "implementation"). An example nozzle ”) and a dipping nozzle whose slag line portion is made of the refractory material of Comparative Example 3 (hereinafter referred to as“ Comparative Example Nozzle ”) were prepared. In both the example nozzle and the comparative example nozzle, an alumina-carbon refractory material containing 68% by weight of an alumina raw material, 15% by weight of silica, and 27% by weight of a carbon raw material was used for a portion other than the slag line. In addition, the dimensions of the example nozzle and the comparative example nozzle were the same. That is, only the refractory material of the slag line differs between the example nozzle and the comparative example nozzle.

Each immersion nozzle was used for actual continuous steel casting, and the length of continuous usable time was measured. The type of cast steel and the type of powder slag used were the same for the example nozzle and the comparative example nozzle.

The Example nozzle and the Comparative Example nozzle used for 3 hours were cut, and the melt loss thickness of the slag line of the nozzle was measured. The erosion thickness of the example nozzle was one-third of the erosion thickness of the comparative example nozzle. From this result, it was found that the refractory material of Example 3 exhibits higher corrosion resistance than the refractory material of Comparative Example 3 even in an environment of actual continuous steel casting.

The present invention can be used, for example, as a zirconia-carbon refractory material, a dipping nozzle, and a method for producing the zirconia-carbon refractory material used for continuous steel casting.

1: Immersion nozzle 2: Main body 21: Tip of main body 22: Base end of main body 23: Slag line 3: Discharge port 4: Connection part M: Molten steel S: Slag

Claims (5)

Zirconia raw material 70% by weight or more and 98% by weight or less,
A zirconia-carbon refractory material containing 2% by weight or more and 30% by weight or less of a carbon raw material.
The zirconia raw material includes a first portion that cannot pass through a sieve having a nominal opening of 106 μm specified in JIS Z 8801-1: 2019, and a second portion that can pass through the sieve.
The median diameter determined based on the integrated particle size distribution curve specified by the sieve specified in JIS Z 8801-1: 2019 in the first part is 150 μm or more and 500 μm or less.
The median diameter of the second part determined according to JIS Z 8825: 2013 is 1 μm or more and 30 μm or less.
A zirconia-carbon refractory material having a ratio W1 / W2 of the weight W1 of the first portion to the weight W2 of the second portion of 2.0 or more and 6.0 or less. A dipping nozzle whose slag line is at least the zirconia-carbon refractory material according to claim 1. A mixing step of mixing 70% by weight or more and 98% by weight or less of the zirconia raw material and 2% by weight or more and 30% by weight or less of the carbon raw material is included.
The zirconia raw material includes a first portion that cannot pass through a sieve having a nominal opening of 106 μm specified in JIS Z 8801-1: 2019, and a second portion that can pass through the sieve.
The median diameter determined based on the integrated particle size distribution curve specified by the sieve specified in JIS Z 8801-1: 2019 in the first part is 150 μm or more and 500 μm or less.
The median diameter of the second part determined according to JIS Z 8825: 2013 is 1 μm or more and 30 μm or less.
A method for producing a zirconia-carbon refractory material, wherein the ratio W1 / W2 of the weight W1 of the first portion to the weight W2 of the second portion is 2.0 or more and 6.0 or less. Prior to the mixing step, an adjusting step of mixing the second portion and the first portion of 2.0 times or more and 6.0 times or less the weight of the second portion to obtain an adjusted zirconia raw material is included.
The method for producing a zirconia-carbon refractory material according to claim 3, wherein the adjusted zirconia raw material obtained in the adjusting step is used as the zirconia raw material in the mixing step. Prior to the adjustment step, a separation step of separating the first portion and the second portion of the zirconia raw material by using a sieve having a nominal opening of 106 μm specified in JIS Z 8801-1: 2019 is included.
The method for producing a zirconia-carbon refractory material according to claim 4, wherein the first portion and the second portion separated in the separation step are used as the first portion and the second portion in the adjustment step.

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