KR101532672B1 - Refractory composition and slide gate plate for steel casting by using it - Google Patents

Abstract

The present invention relates to a refractory composition and a slide gate plate for a steel casting made therefrom, which comprises a main component including a plurality of components and constituting a basic composition, wherein the main component is CaO stabilized zirconia in an amount of not less than 75 wt% and not more than 90 wt% And carbon: 5 wt% or more to 15 wt% or less, and the carbon is composed of 4 wt% or more and 13 wt% or less of graphite impression and 1.0 wt% or more and 2.0 wt% or less of carbon black based on the total weight of the refractory composition, A refractory composition having increased corrosion resistance and resulfolability can be obtained by producing a slide gate plate for a steel casting having a refractory formed by firing, and is useful for casting special steel such as high-acid steel containing Nb, Mn and Cr It is possible to increase the resistance to chemical charring. Therefore, it is possible to save time and cost due to the maintenance of the slide gate plate refractory. In addition, productivity can be improved by suppressing the delay in casting operation due to unnecessary maintenance.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory composition and a slide gate plate for steel casting,

The present invention relates to a refractory composition and a slide gate plate for steel casting manufactured from the refractory composition. More particularly, the present invention relates to a refractory composition and a refractory composition capable of providing a high content of property during casting of a special steel such as Nb, Mn, The present invention relates to a slide gate plate for casting steel.

In a continuous casting process, molten steel is continuously injected into a mold having a predetermined shape, and the molten steel is continuously drawn into the lower side of the mold to form slabs, blooms, , Billet, and the like. At this time, the molten steel received in the ladle or molten steel introduced into the tundish is opened or blocked by the slide gate provided at the lower portion of the molten steel.

The slide gate includes a plurality of plates located under the ladle and / or the tundish, and the molten steel can be moved by the communication of the through holes formed in the plurality of plates. These slide gates are generally made of alumina (Al ₂ O ₃ ) -carbon (C) or spinel (MgAl ₂ O ₄ ) -carbon (C)

However, the slide gate is limited in its service life due to the loss of molten metal, oxidation and degradation by the molten steel and the nonmetal oxide, and nowadays. At this time, cracks are caused by heat shock at the initial stage of casting, deformation of the cassette, defective holding of surface pressure, support type and shape of the plate. In order to solve the above problems, it is required to reduce the coefficient of thermal expansion of the refractory material, to increase the thermal conductivity, to control the microstructure, to reinforce cassette management, and to improve the metal band fastening state of the plate.

At this time, in order to improve the wear resistance due to the molten steel or the non-metal oxide, it is possible to solve the problem by adding the carbon having high resistance to the wear of the molten steel and controlling the microstructure. However, Decarburize by oxidation during use of slide gate. Therefore, the tissue binding force due to these components is weakened, and accordingly, the pore phenomenon and the adhesion due to the non-metal oxide are easily performed, and a part of the refractory constituent part of the sliding plate is damaged.

Further, in the case of high-acid steel containing Mn, Cr and Nb, MnO and NbO react with the carbon and the oxide of the refractory material to form a low melting point material, thereby causing a problem of causing the melting loss.

Due to the rapid erosion of these alumina-carnitic or spinel-carbonaceous materials, the slide gate refractory is replaced several times after maintenance and the spent slide gate refractories are mostly buried in the landfill. Therefore, there is a problem in that environmental burden is incurred due to frequent maintenance and burial of waste refractory, and the cost to be consumed is increased.

KR 2002-0037015 A1 JP 1999-302073 A1

The present invention relates to a refractory composition composed of a zirconia-carbonaceous system capable of improving corrosion resistance and resistance to spalling during casting of special steel such as high-acid steel containing Nb, Mn and Cr, and a slide gate plate Lt; / RTI >

The present invention provides a refractory composition capable of improving the lifetime of a slide gate and reducing the number of maintenance operations, and a slide gate plate for a steel casting manufactured thereby.

The present invention provides a refractory composition and a slide gate plate for steel casting produced therefrom that can suppress or prevent the delay of continuous casting operation and increase the productivity and efficiency of the operation.

The refractory composition according to the embodiment of the present invention comprises a main component containing a plurality of components and constituting a basic composition, wherein the main component is CaO stabilized zirconia in an amount of 75 wt% or more to 90 wt% or less, carbon: 5 wt% or more to 15 wt % Of carbon black; and 1.0 wt% or more and 2.0 wt% or less of carbon black, based on the total weight of the refractory composition, of graphite: 4 wt% or more to 13 wt% or less.

The additive may further include at least one of an intensifier and an antioxidant.

The strength reinforcing agent and the antioxidant may include at least one of magnesium-aluminum powder and boron carbide.

The magnesium-aluminum powder may include not less than 4 wt% and not more than 8 wt% of the total weight of the refractory composition, and the boron carbide may include not less than 1 wt% and not more than 2 wt% of the total weight of the refractory composition.

The refractory composition may have a hot bending strength of 250 to 310 kg / cm 2 and an erosion depth of 0.1 mm or less.

The refractory composition may be used as a firing material for a slide gate plate of a continuous casting facility.

A slide gate plate for steel casting according to an embodiment of the present invention is a slide gate plate of a casting facility, which comprises a refractory formed by firing, the refractory being constituted by a zirconia-carbonaceous system and containing CaO stabilized zirconia: At least 15 wt% and not more than 90 wt% of carbon, and not less than 5 wt% and not more than 15 wt% of carbon, and the carbon is not less than 4 wt% and not more than 13 wt% To 2.0 wt% or less.

And may further comprise 4 to 8% by weight of magnesium-aluminum powder based on the total weight of the refractory.

And 1 to 2% by weight of boron carbide based on the total weight of the refractory.

The hot bending strength of the refractory may be 250 to 310 kg / cm 2, and the erosion depth may be 0.1 mm or less.

The steel may be a special steel containing high oxygen steel added with Nb, Mn and Cr.

According to the refractory composition of the present invention and the slide gate plate for steel casting manufactured by the method of the present invention, the main component of the refractory composition used in the slide gate plate included in the continuous casting facility is constituted of zirconia- And an antioxidant. Accordingly, it is possible to obtain a refractory composition having increased corrosion resistance and resulfolability, and can be used for casting special steel such as high-acid steel containing Nb, Mn and Cr to increase the resistance to chemical charcoal.

Therefore, the lifetime of the slide gate plate refractory can be prolonged to reduce the number of maintenance operations, and the time and cost required for maintenance can be reduced, and the delay in casting operation due to unnecessary maintenance can be suppressed, thereby improving the productivity of operation.

It is also possible to reduce the total amount of waste refractories generated when replacing the slide gate refractory, thereby reducing the environmental pollution that may occur due to landfill disposal, and reducing the cost of constructing new refractories.

1 is a view showing a nozzle unit provided in a general continuous casting facility and a continuous casting facility.
2 is a view showing a refractory composition according to an embodiment of the present invention.
FIG. 3 is a photograph showing the change of the slide gate plate manufactured by using the refractory composition according to the conventional and the present invention by the molten steel contact.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know. Wherein like reference numerals refer to like elements throughout.

Before describing the refractory composition according to the embodiment of the present invention, the continuous casting equipment will be briefly described, and the nozzle units 100 and 300 in which the refractory composition is used will be briefly described.

1 is a view showing nozzle units 100 and 300 provided in a general continuous casting facility and a continuous casting facility.

1, the continuous casting facility includes a ladle 10 for storing molten steel M transferred from a converter (not shown), a tundish 200 for supplying molten steel M from the ladle 10, A molten steel in the ladle 10 is supplied to the tundish 200 and a molten steel in the ladle 10 is supplied to the nozzle 400 for supplying the molten steel in the tundish 200 to the mold 400 100, 300).

This continuous casting facility is a facility for continuous casting of molten steel. The molten steel M contained in the ladle 10 is supplied to the tundish 200 and then supplied to the molten steel M in the tundish 200 Separation of the inclusions is carried out. Thereafter, the molten steel M is injected into the mold 400 to cool the molten steel M to produce a cast steel having a predetermined shape.

The ladle 10 and the tundish 200 are manufactured in the shape of a hollow container capable of accommodating molten steel therein and the lower portion of the ladle 100 and the lower portion of the tundish 200 are provided with the ladle nozzle portion 100 And a tundish nozzle unit 300 are respectively provided to control the flow of the molten steel M from the ladle 10 and the tundish 200. [

The ladle nozzle unit 100 is connected to the lower part of the slide gates 150 and 350 and the slide gates 150 and 350 for blocking or opening the moving path of molten steel flowing into the tundish 200 from the ladle 10 And a shroud nozzle 170.

The tundish nozzle unit 300 is provided to cut off or open the moving path of the molten steel injected into the mold 400 from the tundish 200 and is provided with an upper nozzle A slide gate 350 disposed at the lower portion of the upper nozzle, and an immersion nozzle 370 disposed at the lower portion of the slide gate 350.

At this time, the slide gates 150 and 350, which are direct devices for controlling the flow of molten steel, open and close between the ladle 10 and the tundish 200 and / or between the tundish 200 and the mold 400 The ladle 10 and the tundish 200 and / or the tundish 200 and the mold 400 to control the communication between the ladle 10 and the tundish 200 and / The amount of molten steel injected into the mold 400 and the injection flow rate. The slide gates 150 and 350 are formed of upper plates 151 and 351, middle plates 153 and 353 and lower plates 155 and 355, and the plates 151, 351, 153, 353 and 155 The communication between the ladle 10 and the tundish 200 and / or the communication between the tundish 200 and the mold 400 by the communication of the through holes 151a, 351a, 153a, 353a, 155a, Can be controlled. That is, the slide gates 150 and 350 are formed by the sliding operation of the intermediate plates 153 and 353 between the upper plates 151 and 351 and the lower plates 155 and 355, The molten steel M can be injected into the tundish 200 or the mold 400 by communicating or shutting off the molten steel 155a or 355a.

Thus, the slide gates 150 and 350 can be made of a refractory material that can suppress damage due to high temperature, maintain sufficient strength, and withstand chemical effects and the like.

Accordingly, the refractory composition according to the embodiment of the present invention is used for manufacturing the slide gate plate of the nozzle part, and is constructed so as to improve the corrosion resistance and the anti-spalling property by the high-temperature molten steel.

Hereinafter, refractory compositions according to embodiments of the present invention will be described with reference to FIG.

2 is a view showing constituent components of a refractory composition according to an embodiment of the present invention.

The refractory composition according to the embodiment of the present invention is a refractory composition constituting a plate constituting a slide gate for controlling the flow of molten steel during continuous casting of special steel such as high-acid steel containing Nb, Mn and Cr Can be used. That is, the refractory composition is composed of a refractory component and includes a main component containing a plurality of components and constituting a basic composition. The main component is CaO stabilized zirconia in an amount of 75 wt% or more to 90 wt% or less, And not less than 5 wt% and not more than 15 wt%. At this time, the carbon may be composed of 4 wt% or more and 13 wt% or less of flaky graphite and 1 wt% or more and 2 wt% or less of carbon black based on the total weight of the refractory composition.

Here, the inclusion of the above-mentioned components includes elements constituting a constituent (main component, additive) for one constituent (refractory composition), and is used in the same meaning as that composed of a plurality of constituents contained in the refractory composition .

Typically, conventional alumina-carbonaceous and spinel-carbonaceous refractory compositions are characterized in that, in the case of a high-oxygen steel (especially Mn or Nb) -containing high oxygen steel containing Nb, Cr, Mn and Ca, To form a low-melting substance.

[Chemical Formula 1]

(2)

The low melting point compound thus formed is weak against thermal shock and causes a phenomenon in which a surface is slowly peeled off due to a load applied to a surface crack or an inclusion, that is, structural spalling. In order to reinforce this disadvantage, in the present invention, an Al ₂ O ₃ component in which a SiO ₂ component, which is easily reacted with Mn, is discharged as much as possible and a low-melting product is formed by reaction between MnO and an Nb oxide A refractory composition capable of improving the corrosion resistance and the anti-scrubbing property, and a slide gate plate for steel casting manufactured thereby.

Each component contained in the refractory composition according to the embodiment of the present invention is shown in Table 1 below.

division ingredient weight%
chief ingredient Zirconia CaO stabilized zirconia 75 to 90 Carbon Impression graphite 5 to 15 4 to 13 Carbon black 1-2 additive
Strengthening agents and antioxidants Mg-Al powder 4 to 8 Boron carbide 1-2

The main component contains a plurality of components of the refractory composition and forms the basic composition, and the main component may include zirconia and carbon. That is, the main component is a component constituting at least 80% by weight based on 100% by weight of the refractory composition.

[Zirconia]: 75 to 90 wt%

Zirconia (zirconium oxide) is a refractory material for increasing corrosion resistance, and generally has a high melting point (2677 ° C) and low thermal conductivity, and is used as a heat-resistant material. At this time, zirconia can use partially stabilized zirconia (PSZ). That is, any one of CaO-stabilized zirconia and MgO-stabilized zirconia containing 3% by weight of CaO may be used. More preferably, CaO partially stabilized fused zirconia having a stable cubic structure at a high temperature can be used. Such stabilized zirconia stabilizes the cubic shaping mold, which is a high temperature phase, to room temperature by employing CaO, MgO and Y ₂ O ₃ , and can increase heat resistance and chemical stability. Therefore, it can be used for refractory and heat-resistant parts.

The content of CaO stabilized zirconia in the refractory composition may be 75 wt% or more and 90 wt% or less. The higher the content of CaO stabilized zirconia in the composition range of the refractory composition is, the more the content of the CaO stabilized zirconia increases to increase the content of the molten steel. However, if the content exceeds 90 wt%, the thermal shock resistance may be deteriorated. If the content of CaO stabilized zirconia is less than 75 wt%, the corrosion resistance may be deteriorated. Therefore, CaO stabilized zirconia may be included in the above range.

[Carbon]: 5 to 15 wt%

The carbon is used for improving the resistance to infiltration (resistance to permeation) of molten steel and reducing the thermal shock damage of the refractory constituting the plate, and the content of the refractory composition may be 5 wt% or more and 15 wt% or less. At this time, carbon may be composed of flaky graphite for increasing the thermal shock resistance of the zirconia-carbonaceous refractory and carbon black for strength reinforcement.

The impression graphite is intended to suppress penetration of molten steel to improve the anti-scrubbing property, and may be constituted by 4 wt% or more and 13 wt% or less with respect to the total weight of the refractory composition. If the content of graphite is less than 4 wt%, oxidation resistance and damage caused by molten steel increase. If the graphite content exceeds 13 wt%, the effect of increasing strength is insufficient, thereby increasing wear and damage caused by molten steel.

Carbon black is intended to increase the strength of the refractory composition, and is easily incorporated into a three-dimensional carbon matrix formed by carbonization of an organic binder for firing refractories, so that formation of a three-dimensional carbon matrix can be further promoted have. Thus, it is advantageous in terms of low expansion, low carbonization, high strength and high humanization. At this time, if the content of carbon black is less than 1 wt%, the strength reinforcing effect is insufficient. If the content is more than 2 wt%, the modulus of elasticity is increased and the thermal shock resistance may be reduced.

Therefore, by using graphite and carbon black in the above-mentioned amounts, that is, by combining graphite with carbon black in an appropriate amount and using them as a carbonaceous material, the effects of oxidation resistance and damage inhibition obtained by using graphite impression are obtained By using carbon black, it is possible to obtain low expansion, low carbonization, high strength, and high toughening.

In addition to the main components shown in Table 1, at least one of the strength reinforcing agent and the antioxidant may be added as an additive in order to prevent oxidation of the refractory composition and to increase the strength. That is, the additive may increase the strength and inhibit and prevent oxidation of the carbon of the refractory composition in order to suppress the occurrence of problems due to oxidation during use of the refractory material. Accordingly, the additive may include at least one of the following metal powders, Mg-Al powder and boron carbide.

[Additive, metal powder]: 4 to 8 wt%

The metal powder includes Al powder and Mg-Al powder. For the steel casting such as high-acid steel containing Nb, Mn and Cr, Mg-Al powder can be used have. That is, when Al powder is used, Al may react with molten steel to form Al ₄ O ₃ and then transition to Al ₂ O ₃ , which may cause deterioration in corrosion resistance. Therefore, when Mg powder is used, It is preferable to reduce the total amount of Al contained. The Mg-Al powder may include not less than 4 wt% and not more than 8 wt% of the total weight of the refractory composition. If the content of the Mg-Al powder is less than 4 wt%, the strength reinforcement and the prevention of oxidation are insufficient. If the content of Mg-Al powder is more than 8 wt%, the elastic modulus may increase and the thermal shock resistance may be deteriorated. Therefore, the content of the Mg-Al powder may be included in the above range.

[Additive, boron carbide]: 1 to 2 wt%

Boron carbide (B4C) is generally made by heating a compound of boron and carbon at 2800 ° C, has a high hardness, a low coefficient of thermal expansion, and is chemically stable. Boron carbide is contained in the refractory composition to inhibit or prevent oxidation of refractory by molten steel. The boron carbide may include 1 wt% or more to 2 wt% or less based on the total weight of the refractory composition. If the content of boron carbide is less than 1 wt%, the effect of preventing the oxidation of carbon is insufficient. If the content of boron carbide is more than 2 wt%, a low melting point material may be generated due to reaction with molten steel. Therefore, the content of boron carbide in the above range may be included.

An organic binder is added to the refractory composition comprising the above components and kneaded. As the organic binder to be added at the time of kneading, pitch, tar, silicone resin, furan resin and phenol resin may be used, and those showing residual carbon by heat treatment may be used. Any one of them or a mixture of any of them may be used. In order to increase the bond formation of carbon, it is possible to use an organic binder having a high proportion of residual carbon as much as possible.

As described above, the kneaded product obtained by adding the organic binder to the refractory composition can be produced as a refractory plate through calcining at a low temperature (1000 DEG C or less) or calcining in an oxidizing or reducing atmosphere at a high temperature (1400 DEG C or more) have.

Hereinafter, experimental results for confirming whether a refractory composition according to an embodiment of the present invention is compatible with a slide gate plate during continuous casting of a high-temperature process environment and a high oxygen-containing steel will be described in detail with reference to Examples and Comparative Examples.

A refractory composition as shown in Table 2 below is prepared. Thereafter, 5.0% of phenol resin as the total weight of each refractory composition was added and kneaded, and a plate-like specimen of 25x25x125mm size was produced through firing and rolling.

In general, when the refractory composition is applied to a plate of a slide gate, important properties for evaluating the characteristics of the refractory composition include brittleness and thermal shock resistance which can be evaluated with respect to abrasion resistance and erosion resistance that can withstand high temperature molten steel and special steel having high oxygen content , Erosion resistance and oxidation resistance. The hot bending strength, thermal shock resistance and erosion / oxidation depth of the refractory were tested using the prepared specimens.

Here, the hot bending strength was measured using the specimen, and the hot bending strength was measured at a temperature of 1400 ° C. using the three point bending strength test method.

Further, a thermal shock resistance test was conducted. Thermal shock resistance indicates resistance to thermal shock. The resistance to thermal shock is maintained at 1400 ° C in an electric furnace. The specimen is held in an electric furnace for 30 minutes, then cooled to room temperature and cooled. And the number of points at which the

In order to confirm the degree of corrosion resistance of the refractory composition, the erosion test and the penetration test were carried out. In the erosion test, the refractory specimen is placed in a plate form in the crucible of the electric furnace, and Nb-Mn-Fe type high oxygen molten steel is introduced. After reacting at 1580 ° C for 3 hours, high oxygen molten steel was discharged, and the center of the eroded specimen was cut to measure the eroded length.

Finally, evaluation (○ / X) showed fit / nonconformity. The evaluation contents of each of the examples and the comparative examples will be described in detail below.

division Example Comparative Example One 2 One 2 3 4 5 of mine
anger
article
castle
water
(medium
Amount
%) CaO stabilized zirconia 75 90 - - 91 74 75 Alumina - - 88 - - - 15 magnesia - - - 90 - - - Impression graphite 13 4 3 5 4 16 4 Carbon black 2 One 3 - - - One Al Powder - - 5 5 4 - - Mg-Al powder 8 4 - - - 9 5 Boron carbide 2 One One - One One 0 Organic binders (phenolic resin) +5 +5 +5 +5 +5 +5 +5 Hot bending strength
(Kg / cm2) 1400 ° C × 3 hr 310 250 280 220 110 120 250 Thermal shock resistance
(number) Initial crack initiation 6 5 3 2 3 3 3 Erosion depth (mm) 0.1 0.41 2.5 0.1 2 2 2 Oxidation depth (mm) 0 0 2.5 3 1.5 0 0 Evaluation (○ / X) ○ ○ X X X X X

Here, Examples 1 and 2 of Table 2 are made up of materials constituting the refractory composition proposed by the present invention. That is, it is composed of a main component composed of CaO stabilized zirconia and impression graphite carbon black constituting carbon, and an additive composed of Mg-Al powder and boron carbide contained in the main component. On the other hand, Comparative Examples 1 to 5 are examples of the refractory composition which does not use the main component of the refractory composition proposed in the present invention, or which is out of the content range of the main component. That is, in Comparative Example 1, alumina (Al ₂ O ₃ ) was used instead of CaO-stabilized zirconia, and in Comparative Example 2, magnesia (MgO) was used in place of CaO-stabilized zirconia. In Comparative Example 3 and Comparative Example 4, the content of the main component was outside the range suggested by the present invention. In Comparative Example 5, alumina was further used in addition to the main component of the present invention.

[Example 1]

Example 1 consisted of the contents of the refractory composition within the ranges given in Table 2. That is, the main constituents and additives constituting the present invention are included in the present invention, and include% by weight within the content range of the main component and the additive shown in Table 1. It was confirmed that the specimens including these contents had a thermal bending strength of 310 kg / cm 2, a time point of the first thermal shock at which cracks occurred, a erosion depth of 0.1 mm and an oxidation depth of 0 mm. In addition, a suitable evaluation can be obtained with a slide gate plate for casting special steel such as high-acid steel containing Nb, Mn and Cr. This can be explained in detail with reference to FIG. 3 (c).

Referring to FIG. 3 (c), the erosion test result of the specimen prepared as in Example 1 is shown. At this time, the specimen of Example 1 made of the refractory composition of the embodiment of the present invention was oxidized by oxidation of the elements contained in the molten steel constituting the high-acid steel containing Nb, Mn and Cr in the vicinity of the reaction surface in contact with molten steel It can be confirmed that the damaged part does not occur, and it can be confirmed that the specimen shows the entire refractory sound layer.

[Example 2]

In Example 2, as in Example 1, the main constituents and the constituents constituting the additive are included in the weight percentages within the content ranges shown in Table 1. At this time, it can be confirmed that the specimen produced according to the composition of Example 2 had a hot bending strength of 250 kg / cm 2, a time point of the number of thermal shocks at which cracks occurred at the beginning, 5, an erosion depth of 0.1 mm and an oxidation depth of 0 mm . In addition, a suitable evaluation can be obtained with a slide gate plate for casting a special steel. On the other hand, in Example 2, the content of carbon and Mg-Al powder was relatively low compared to Example 1, and the low bending strength was low in Example 1 and the number of times of heat shock was shortened.

As described above, in Examples 1 and 2 produced according to the embodiment of the present invention, SiO ₂ and Al ₂ O ₃ in the refractory composition can be discharged as much as possible, and the casting of the high-acid steel and the special steel to which Nb, Mn, It is confirmed that the refractory composition has excellent properties (erosion resistance, invasiveness and thermal shock resistance) by suppressing or preventing the formation of a low melting point material produced by the reaction with cast steel.

[Comparative Example 1 and Comparative Example 2]

In Comparative Example 1, as shown in Table 2, alumina was used as a main component of the refractory composition of the present invention in place of CaO stabilized zirconia. At this time, it can be confirmed that the specimen produced according to the composition of Comparative Example 1 exhibited a hot bending strength of 280 kg / cm 2, a time point of the number of thermal shocks at which cracks occurred at the beginning, 3, an erosion depth of 2.5 mm and an oxidation depth of 2.5 mm . That is, it can be seen that the corrosion resistance is lowered by increasing the content of alumina in the refractory composition. That is, in Comparative Example 1, for a special steel such as high-acid steel containing Nb, Mn and Cr as a conventional alumina-cementum refractory composition, molten steel reacts with Al ₂ O ₃ to decrease corrosion resistance, An inadequate evaluation can be obtained for the plate of the sliding gate. This can be explained in detail with reference to FIG. 3 (a). That is, as shown in FIG. 3 (a), it can be seen that the specimen manufactured in Comparative Example 1 was eroded due to oxidation damage at a predetermined depth from the reaction surface in contact with molten steel.

In Comparative Example 2, as shown in Table 2, magnesia was used as a main component of the refractory composition of the present invention in place of CaO-stabilized zirconia. At this time, it can be confirmed that the specimen produced according to the composition of Comparative Example 2 had a bending strength of 220 kg / cm 2, a time point of the number of thermal shocks at which cracks occurred at first, 2, an erosion depth of 0.1 mm and an oxidation depth of 3 mm . That is, in Comparative Example 2, for a special steel such as high-acid steel containing Nb, Mn, and Cr with a conventional spinel-carbon based refractory composition, molten steel reacts with MgO to lower thermal shock resistance, It is possible to obtain an inadequate evaluation of the slide gate plate for a special steel casting. This can be described in detail with reference to FIG. 3 (b). That is, as shown in FIG. 3A, the specimen manufactured in Comparative Example 2 reacts with oxygen in the molten steel from the reaction surface in contact with the molten steel to form the MgO layer in the molten steel contact portion. In this way, it can be seen that the oxidation depth of the spinel-carbonaceous refractory is increased by the transformation of the refractory structure due to the reaction of Mg. At this time, in the spinel-carbonaceous refractory photograph, the region indicated by the oxidized damage region is a region due to the phenomenon of the structure being broken due to the reaction of Mg, unlike Comparative Example 1. [

[Comparative Example 3 and Comparative Example 4]

In Comparative Example 3 and Comparative Example 4, the content of CaO stabilized zirconia was outside the content range of CaO stabilized zirconia proposed in the present invention and contained the content of carbon within the content range, but only impression graphite was used as a kaolin, The composition was constructed.

That is, in Comparative Example 3, the content of CaO-stabilized zirconia exceeds the range of the content of the proposal, and an excessive amount of the CaO-stabilized zirconia is contained, which may deteriorate the thermal shock resistance. Further, in Comparative Example 4, the content of CaO-stabilized zirconia is contained so as to be less than the content of the proposed content, so that corrosion resistance and wear resistance may be deteriorated. Here, the specimen produced according to the composition of Comparative Example 3 had a hot bending strength of 110 kg / cm 2, a time point of the number of thermal shocks at which cracks were initially generated at 3, an erosion depth of 2 mm and an oxidation depth of 1.5 mm, The specimens produced by this method showed that the hot bending strength was 120 kg / ㎠, the number of heat shocks at the time of initial cracking was 3, the erosion depth was 2 mm and the oxidation depth was 0 mm.

Here, the reason why the oxidation depth value of Comparative Example 4 is relatively low as compared with Comparative Example 3 can be obtained by reducing the amount of Al contained in the refractory composition by using Mg-Al powder as an additive.

[Comparative Example 5]

Comparative Example 5 provides a refractory composition containing CaO stabilized zirconia and carbon, which are the main constituents of the refractory composition of the present invention, but additionally alumina (Al ₂ O ₃ ) added. Thus, it can be seen that the refractory fabricated according to the present invention is not suitable for the slide gate plate for special steel casting because the corrosion resistance is reduced by the reaction of the elements in the molten steel with alumina.

As described above, Examples 1 and 2 satisfying the proposed constituent components and the proposed content range of the present invention are suitable to be used as a refractory composition for a special steel such as high-acid steel containing Nb, Mn and Cr, Or a refractory composition containing Al ₂ O ₃ and MgAl ₂ O ₄ which forms a low melting point material by reaction with an oxide in a high oxygen steel containing Nb, Mn and Cr, is characterized in that at least one of the characteristics of refractories shown in Table 2 It can be understood that it is not suitable as a slide gate plate for casting special steels such as high-acid steel containing Nb, Mn and Cr because of low characteristics in Examples 1 and 2.

Although the present invention has been described with reference to the accompanying drawings and the preferred embodiments described above, the present invention is not limited thereto but is limited by the following claims. Accordingly, those skilled in the art will appreciate that various modifications and changes may be made thereto without departing from the spirit of the following claims.

M: molten steel 10: ladle
200: tundish 100, 300: nozzle part
150, 350: slide gate 151, 351: upper plate
151a, 351a: upper through-holes 153, 353: intermediate plate
153a, 353a: intermediate passage 155, 355: lower plate
155a, 355a: lower through hole 170: shroud nozzle
370: immersion nozzle 400: mold

Claims (11)

1. A refractory composition for use as a sintering material for a slide gate plate in a continuous casting facility of a special steel containing high-acid steel containing Nb, Mn and Cr,
And further comprising at least one of an intensifier and an antioxidant as main components and additives which comprise a plurality of components and constitute a basic composition,
Wherein the main component is CaO stabilized zirconia in an amount of 75 wt% or more and 90 wt% or less, carbon: 5 wt% or more and 15 wt% or less,
The carbon is composed of 4 wt% to 13 wt% of impression graphite and 1.0 wt% to 2.0 wt% of carbon black based on the total weight of the refractory composition,
Wherein the strength reinforcing agent comprises 4 wt% or more to 8 wt% or less of magnesium-aluminum powder based on the total weight of the refractory composition. delete The method according to claim 1,
Wherein the strength reinforcing agent and the antioxidant comprise boron carbide. The method of claim 3,
Wherein the boron carbide includes 1 wt% or more to 2 wt% or less based on the total weight of the refractory composition. The method of claim 1, 3, or 4,
Wherein the refractory composition has a hot bending strength of 250 to 310 kg / cm 2 and an erosion depth of 0.1 mm or less. delete A sliding gate plate for casting equipment for casting special steel containing high-acid steel containing Nb, Mn and Cr,
And a refractory molded by firing,
The refractory is composed of a zirconia-carbonaceous material and contains CaO stabilized zirconia in an amount of 75 wt% or more to 90 wt% or less, carbon 5 wt% or more to 15 wt%, and magnesium-aluminum powder 4 wt% or more to 8 wt% ,
Wherein the carbon is composed of 4 wt% or more and 13 wt% or less of graphite, and 1.0 wt% or more and 2.0 wt% or less of carbon black, based on the total weight of the refractory. delete The method of claim 7,
Further comprising 1 to 2% by weight of boron carbide based on the total weight of the refractory. The method according to claim 7 or 9,
Wherein the refractory has a hot bending strength of 250 to 310 kg / cm 2 and an erosion depth of 0.1 mm or less. delete

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