KR101382648B1 - Stopper refractory for continuous casting and manufacturing method thereof using the same - Google Patents

Abstract

The present invention relates to a method for producing a stopper refractory and a stopper for continuous casting, carbon (C): 10 to 20% by weight, zirconium diboride (ZrB ₂ ): 1 to 5% by weight, and the balance is composed of zirconia A rough stopper refractory material and a stopper manufacturing method using the same are provided.

Description

Stopper Refractory and Stopper Manufacturing Method for Continuous Casting {STOPPER REFRACTORY FOR CONTINUOUS CASTING AND MANUFACTURING METHOD THEREOF USING THE SAME}

The present invention relates to a continuous casting stopper refractories and stopper manufacturing method, more specifically, the main component is a zirconia and the continuous casting stopper refractory for the production and control thereof to improve the corrosion resistance to abrasion resistance and chemical erosion by adjusting the content of the additive component It is about a method.

In general, the tundish 10 used in the continuous casting device serves to discharge the molten steel 30 to the mold through the immersion nozzle 40 connected to the molten steel outlet formed on the bottom.

1 is a cross-sectional view showing a stopper 20 system according to the prior art, the molten steel 30 from the tundish 10 to the mold (not shown) is made through the immersion nozzle 40, the stopper 20 The amount of molten steel 30 introduced into the mold is adjusted as it moves up and down. At this time, the head portion 25 is formed at the end of the stopper 20.

The stopper 20 is a refractory for precisely controlling the flow rate of the molten steel 30, and the head portion 25 has high wear resistance by the molten steel 30 because the hot molten steel 30 flows at a high speed. In addition, in the case of high oxygen steels having high concentrations of Mn, Si, O, etc., the chemical damage is advanced by the reaction of Mn, Si, O, etc. with the refractory. Japanese Laid-Open Patent Publication No. 2004-17136 proposes a refractory plate for sliding nozzles with sufficient solvent resistance for special steels such as high-oxygen steel, and Japanese Laid-Open Patent No. 2002-047635 can be used for casting free cutting steel with high oxygen concentration. As a refractory having a solvent resistance, a magnesia refractories composed of magnesia and zirconium oxide have been proposed, and Japanese Patent No. 1996-06183 discloses an interface in contact with molten steel in order to prevent damage caused by carbon oxidation in refractory by oxygen in molten steel. The use of porous refractory has been suggested.

   In the case of the Japanese patents described above, the decarburized layer produced by oxidizing carbon in the refractory by excessive dissolved oxygen present in high oxygen steel was identified as a major shortening factor for wear damage caused by molten steel. An antioxidant for lowering the carbon content in the refractory or reducing the oxidation of carbon was blended.

However, under conditions of high oxygen content of several hundred ppm and high content of Mn, Si, etc. in high-oxygen steel, CO (g) is generated by reaction between molten steel and C in the refractory, or blown and refractory of Ar (g). As the interfacial temperature between the refractory and the molten steel is locally lowered due to heat transfer to the furnace, low melting point inclusions having a composition of MnO-FeO-SiO _2, etc., are precipitated in the vicinity of the interface.

In the case of the refractory having a low carbon content, when carbon in the refractory is lost by the reaction with molten steel, a large number of pores and oxide raw material particles remain at the interface with the molten steel. Therefore, the low melting point inclusions generated near the interface react with these oxide raw particles, causing a problem that the chemical erosion is significantly increased.

The present invention for solving the above problems is to provide a continuous casting stopper refractory and stopper manufacturing method that can be used for a long time in the continuous casting process of high oxygen steel.

In one or more embodiments of the present invention, a continuous casting stopper refractory material comprising carbon (C): 10 to 20 weight percent, zirconium diboride (ZrB ₂ ): 1 to 5 weight percent, and the balance consisting of zirconia may be provided. Can be.

In one or more embodiments of the present invention, the refractory may comprise up to 2 weight percent aluminum (Al), and a continuous casting stopper prepared by the composition may be provided.

In one or more embodiments of the invention, carbon (C): 10 to 20% by weight, zirconium diboride (ZrB ₂ ): 1 to 5% by weight, and the balance is formed by mixing a powder consisting of zirconia with a phenol resin Preparing a dragon clay; Manufacturing a molded body by injecting and pressing the clay into a mold; Drying the molded body to evaporate the solvent; Pyrolyzing the phenol resin; And heat treating the phenol resin pyrolyzed in a reducing atmosphere. A continuous casting stopper manufacturing method comprising a may be provided.

In one or more embodiments of the present invention, the pyrolysis is characterized in that it is made in the range of 800 ~ 1000 ℃, the reducing atmosphere is characterized in that made by coke powder.

According to an embodiment of the present invention, by providing a continuous casting stopper refractory that can be used for a long time in the continuous casting process of high oxygen steel can contribute to improving the productivity of the continuous casting operation.

1 is a cross-sectional view of a stopper system according to the prior art.
2 is a cross-sectional photograph of a test piece of the reaction test of the refractory and inclusions according to an embodiment of the present invention.
3 is a cross-sectional photograph of a test piece of the reaction test of the refractory and inclusions according to the comparative example.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims. Like reference numerals refer to like elements throughout the specification.

In general, the stopper 20 used in the continuous casting process of high-oxygen steel having a high concentration of Mn, Si, O, etc., is damaged by the head 25 having a high flow rate of molten steel 30, which determines the service life. Damage of the stopper 20 due to high oxygen steel is mainly caused by carbon loss of refractory material by oxygen in the molten steel 30 and abrasion due to the flow of the molten steel 30. However, the oxygen concentration of the high oxygen steel increases to several hundred ppm, and MnO-FeO-SiO ₂ near the interface between the stopper 20 and the molten steel 30 under conditions containing Mn, Si, etc. added for various properties. Low melting point materials having a composition such as can be produced, and these can cause chemical damage of the refractory.

In the embodiment according to the present invention by inhibiting the reaction between the low melting point inclusions and the refractory of the MnO-FeO-SiO ₂ stopper refractory for continuous casting that can prevent chemical damage of the stopper 20 and the stopper 20 using the same Is provided.

The carbon present in the refractory of the stopper 20 reacts with locally attached MnO—FeO—SiO ₂ -based inclusions to reduce the Fe, Mn component and the like as shown in the following Reaction Formula (1). Therefore, the inclusions remaining after the reaction are changed to a composition having a high SiO ₂ content so that the chemical erosion of the refractory is relatively low.

(Mn, Fe, O) _inclusion + C _stopper- > CO (g) + (Mn) _melt + (Fe) _melt --------- (1)

In order to suppress chemical erosion as described above, the carbon content in the stopper refractory should be maintained at 10 to 20% by weight. If the carbon content is more than 20% by weight, wear due to the flow of molten steel 30 is increased, which is not preferable. In other words, carbon is weak in wear resistance. If the carbon content in the matrix exceeds 20% by weight, it can be easily worn even if the molten steel is not fast. If the carbon content is less than 10% by weight, the reduction to low melting point inclusions is reduced. Since the effect is small, the chemical erosion is increased, so the carbon content in the embodiment according to the present invention is limited to the above range.

In addition, in the embodiment according to the present invention, zirconium diboride (ZrB ₂ ) having a high hardness is added to reduce wear of the refractory due to the flow of molten steel 30. The zirconium diboride (ZrB ₂ ) decomposes under high oxygen partial pressure to form boron oxide (B ₂ O ₃ ), and the B ₂ O ₃ reacts with the refractory constituent raw material to promote low melting point. At this time, the reaction formula for the formation of boron oxide is as shown in the following formula (2).

ZrB ₂ + 5 / 2O _2- > B ₂ O ₃ + ZrO ₂ --------------- (2)

At this time, the zirconium diboride (ZrB ₂ ) is added 1 to 5% by weight, if the content is less than 1% by weight does not have a wear reduction effect, if more than 5% by weight of the oxidation produced under high oxygen partial pressure conditions Since boron (B ₂ O ₃ ) is active in the production of low melting point material is increased chemical damage, so the content of zirconium diboride in the embodiment according to the present invention is limited to the above range.

In addition, the stopper refractory of the embodiment according to the present invention may further include aluminum (Al), which is added to remove the oxygen present in the molten steel 30 during continuous casting of the steel to prevent oxidation of carbon (graphite). . In other words, the aluminum functions as a deoxidizer. In order to achieve the above object, in the embodiment according to the present invention, aluminum is added in an amount of 2% by weight or less. In this embodiment according to the present invention, so that the content of aluminum is limited to 2% by weight or less.

FIG. 2 is a cross-sectional photograph of a specimen subjected to a reaction test with inclusions having a composition of refractory (R) and MnO-FeO-SiO ₂ having a carbon content of 13 wt% according to the present invention, and FIG. 3 is a carbon content as a comparative example. This is a cross-sectional photograph of the specimens tested for reaction with inclusions having a composition of 4 wt% refractory (R) and MnO-FeO-SiO ₂ .

As shown in FIG. 3, when the carbon content of the stopper refractory is low, the reaction layer A ′ with the inclusions is thickly formed, and large and small bubbles P are formed, and the reaction between the refractory and the inclusions is performed. Whereas metal droplet (M ') is formed on the reaction layer, the refractory (R) of the embodiment according to the present invention is a metal droplet (metal droplet) generated as the inclusions are reduced, as shown in FIG. (M) is present at the interface, and the reaction layer (A) is hardly confirmed.

The stopper composition in the embodiment according to the present invention is suitable for a zirconia raw material having a relatively higher melting point of the reactants than alumina, spinel, and magnesia, which are highly reactive with SiO ₂ and the like, considering the reaction between the remaining inclusions and the refractory component.

Hereinafter, embodiments of the present invention will be described in more detail.

First, zirconia, carbon (phosphorite graphite), and zirconium diboride (ZrB ₂ ) powder having a purity of 99% that was phase stabilized with CaO was mixed with a phenol resin as a binder to prepare a molding clay. Zirconia raw materials were used having a size of 1mm or less, and phenol resin was used CERABOND CB-8060 of Gangnam Hwaseong Fort. The molded clay was embedded in a mold and uniaxially pressurized to form a molded body. The prepared molded product was put in an oven at 200 ° C. and dried for 12 hours to evaporate the solvent. Since the phenol resin is pyrolyzed at 500 to 600 ° C., the phenol resin is maintained at 800 to 1000 ° C. for 3 hours. After that, the test specimen was prepared by incorporating the specimen into a coke powder and heat-treating it in a reducing atmosphere.

Wear characteristics of the prepared specimens were evaluated by a shot blast method. At this time, the blast (Blast) powder using SiC having an average particle diameter of 2mm, the injection pressure was carried out at 4bar, room temperature. After spraying for 1 minute, the amount of wear was measured.

The reaction test with the MnO-FeO-SiO ₂ -based inclusions used a rotary erosion tester. After the test specimen was processed, it was constructed inside the erosion tester.

Thereafter, a reagent having a composition of MnO: 60%, SiO ₂ : 25%, FeO: 10%, MnS: 5% similar to the low melting point inclusion composition present in the high oxygen steel was prepared by mixing. After the prepared powder was added to the erosion machine maintained at 1500 ° C. and maintained for 30 minutes, the process of excluding the residue was repeated five times. The residue is a mixed powder melt present inside the reaction, and the reason for repeating the exclusion process is to introduce a new flux because the components of the flux may be changed and may not be eroded properly. To do this. After cooling the erosion machine, the constructed specimens were dismantled and cut along the centerline of the specimen to measure the eroded thickness.

Table 1 summarizes the specimen manufacturing conditions and test results. In the comparative example, the amount of wear and chemical erosion were large, but in the case of the example, it was found that the wear resistance and the corrosion resistance to chemical erosion were excellent. In particular, in the case of Comparative Example 2 it can be seen that the content of carbon (graphite) is 30% by weight, the wear amount and erosion thickness is very large. In addition, as in Comparative Example 3, the content of carbon is the same as in the embodiment of the present invention, but it can be confirmed that the amount of wear is very large by not adding zirconium diboride.

Specimen preparation conditions and test results Raw material compounding ratio Specimen Characteristic Carbon content (%) ZrB ₂ content (%) % Wear Erosion Thickness (mm) Comparative Example One 5 2 21 7.5 2 30 2 65 8.9 3 15 0 52 4.3 4 15 10 10 12.8 Example 5 15 2 22 3.8 6 15 3 20 4.1

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (7)

Carbon (C): greater than 10 to 20 weight percent, zirconium diboride (ZrB ₂ ): 1 to 5 weight percent, and the remainder is a continuous casting stopper refractory consisting of zirconia. The method of claim 1,
And the refractory includes not more than 2 weight percent (not including 0 weight percent) of aluminum (Al). Carbon (C): more than 10 to 20 weight percent, zirconium diboride (ZrB ₂ ): 1 to 5 weight percent, and the balance by mixing a powder composed of zirconia with a phenol resin to prepare a molding clay;
Manufacturing a molded body by injecting and pressing the clay into a mold;
Drying the molded body to evaporate the solvent;
Pyrolyzing the phenol resin; And
Heat-treating the phenol resin pyrolyzed in a reducing atmosphere;
Continuous casting stopper manufacturing method comprising a. The method of claim 3,
The pyrolysis is a continuous casting stopper manufacturing method, characterized in that made in the range of 800 ~ 1000 ℃. The method of claim 3,
The reducing atmosphere is a continuous casting stopper manufacturing method characterized in that made of coke powder. The method of claim 3,
The powder is,
A method for producing a continuous casting stopper, comprising aluminum (Al) of 2 weight percent or less (not including 0 weight percent). A continuous casting stopper produced by the composition of claim 1.

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