JP2022161032A - Castable refractory and molten steel ladle - Google Patents

Abstract

To provide a castable refractory that exhibits sufficient strength after curing, has high corrosion resistance against slag, is impervious to slag, and resists build deposition.SOLUTION: A castable refractory contains alumina, graphite, spinel, and strontium cement. The content of the graphite is 1-10 mass%, the content of the spinel is 18-37 mass%, the content of the strontium cement is 7-20 mass%, the content of magnesia is 8 mass% or less, and the content of alumina cement is 10 mass% or less.SELECTED DRAWING: None

Description

The present invention relates to castable refractories and ladle.

Alumina-magnesia castable refractories are commonly used as ladle linings.
A high-melting-point slag containing spinel (MgAl ₂ O ₄ ) as a main component, called a build, sometimes adheres to the inner surface (lining surface) of such a molten steel ladle (hereinafter, this is also referred to as “build-up”). .
In a ladle with build on the inside surface, the effective volume is reduced and the throughput per charge is reduced. Furthermore, there is a concern that the build will peel off together with the sound layer of the inner lining during the secondary refining, resulting in steel leakage troubles.

For example, Patent Document 1 discloses a technique for obtaining a "desired build-up prevention effect" by using "dolomite made of CaO (calcium oxide) and MgO (magnesium oxide)" for the lining of a molten steel ladle ( [0019]).

JP-A-2005-263516

As described above, builds may adhere to the hardened castable refractory.
Furthermore, it is preferable that the castable refractory should exhibit sufficient strength after curing, have excellent corrosion resistance to slag, and suppress slag penetration.

Therefore, the object of the present invention is to provide a castable refractory that exhibits sufficient strength after curing, has excellent corrosion resistance to slag, suppresses slag penetration, and suppresses build adhesion.

As a result of intensive studies, the inventors of the present invention have found that the above object can be achieved by adopting the following configuration, and completed the present invention.

That is, the present invention provides the following [1] to [6].
[1] Alumina, graphite, spinel, and strontium cement, the content of graphite is 1 to 10% by mass, the content of spinel is 18 to 37% by mass, A castable refractory having a strontium cement content of 7 to 20% by mass, a magnesia content of 8% by mass or less, and an alumina cement content of 10% by mass or less.
[2] The castable refractory according to [1] above, wherein the graphite includes flake graphite.
[3] The castable refractory according to [1] or [2] above, wherein the alumina contains calcined alumina, and the content of the calcined alumina is 1 to 18% by mass.
[4] The castable refractory according to [3] above, wherein the calcined alumina has a particle size of 20 μm or less.
[5] A molten steel ladle that is a container for holding molten steel, having, in order from the outside, a steel shell, a permanent lining, and a lining; A steel ladle using the hardened castable refractory described above.
[6] The molten steel ladle according to [5] above, wherein a part of the lining is a steel bath portion that contacts the molten steel.

According to the present invention, it is possible to provide a castable refractory that exhibits sufficient strength after curing, has excellent corrosion resistance to slag, suppresses slag penetration, and suppresses build adhesion.

It is a cross-sectional view showing a molten steel ladle. FIG. 3 is a cross-sectional view showing a state in which molten steel is subjected to continuous casting; 4 is a cross-sectional view showing an enlarged steel bath 5 containing artificial graphite 11. FIG. 4 is an enlarged cross-sectional view showing a steel bath portion 5 containing flake graphite 12. FIG.

[Molten steel pot]
First, based on FIGS. 1 and 2, while explaining the steel ladle, the build adhesion will also be explained.

FIG. 1 is a sectional view showing a molten steel ladle 1. FIG.
The molten steel ladle 1 is a container that holds molten steel 7 . The molten steel 7 is obtained, for example, by decarburizing molten iron in a converter (not shown). A slag 8 floats on the molten steel 7 .
A molten steel ladle 1 has, in order from the outside, a steel shell 2, a permanent lining 3 and an inner lining (bottom portion 4, steel bath portion 5 and slag line portion 6).
The lining is divided into a base portion 4 located at the bottom of the molten steel ladle 1, a steel bath portion 5 in contact with the molten steel 7, and a slag line portion 6 in contact with the slag 8.

FIG. 2 is a cross-sectional view showing a state in which molten steel 7 is subjected to continuous casting.
In the molten steel ladle 1, secondary refining is performed to remove impurities from the molten steel 7 or add additive elements. Major secondary refining methods include RH (Ruhrstahl-Heraeus), LF (Ladle Furnace), VOD (Vacuum Oxygen Decarburization), and the like.
Molten steel 7 that has undergone secondary refining is drawn out from a hole provided in the bottom (including the bottom 4) of the molten steel ladle 1, passes through a tundish 10, and is subjected to continuous casting.

By the way, as shown in FIG. 2, as the molten steel 7 is drawn out, the slag 8 moves out of contact with the slag line portion 6 and gradually descends while contacting the steel bath portion 5 .
At this time, the refractory material in the slag line section 6 is difficult to wet with the slag 8 , but the refractory material in the steel bath section 5 is generally easy to wet with the slag 8 . Then, as the slag 8 descends, as shown in FIG. 2, the slag 8 may adhere to the surface of the steel bath portion 5 in order from above. That is, the build 9 may adhere to the inner surface of the molten steel ladle 1 (the surface of the steel bath portion 5 which is the lining).

The effective volume of the ladle 1 with the build 9 adhered is reduced compared to when the build 9 is not adhered. Therefore, the throughput of molten steel 7 per charge is reduced.
Furthermore, when the molten steel 7 is subjected to secondary refining or continuous casting, there is also a concern that the build 9 will peel off together with the healthy layer of the steel bath portion 5 .

However, by using the castable refractory of the present invention for the steel bath portion 5, adhesion of the build 9 can be suppressed.
Furthermore, the steel bath portion 5 using the castable refractory of the present invention exhibits sufficient strength, is excellent in corrosion resistance to the slag 8, and can also suppress the penetration of the slag 8.

[Castable refractories]
The castable refractory of the present invention contains alumina, graphite, spinel, and strontium cement, the graphite content is 1 to 10% by mass, and the spinel content is 18 to 37%. The strontium cement content is 7 to 20 mass%, the magnesia content is 8 mass% or less, and the alumina cement content is 10 mass% or less.

<Fire-resistant powder>
First, the refractory powder contained in the castable refractory of the present invention will be described.

"alumina"
The castable refractory of the present invention contains alumina as refractory powder.
Alumina is not particularly limited, and examples thereof include electrofused alumina, sintered alumina, and calcined alumina.
The content of alumina in the castable refractory of the present invention is appropriately adjusted depending on the content of other components.
The content of alumina in the castable refractory of the present invention is, for example, 40% by mass or more, preferably 44% by mass or more, and more preferably 48% by mass or more.
On the other hand, this content is, for example, 80% by mass or less, preferably 76% by mass or less, and more preferably 72% by mass or less.

(Electrically fused alumina and sintered alumina)
The castable refractory of the present invention preferably contains, as alumina, at least one selected from the group consisting of electrofused alumina and sintered alumina.
The content of at least one selected from the group consisting of electrofused alumina and sintered alumina in the castable refractory of the present invention is, for example, 31% by mass or more, preferably 35% by mass or more, and more preferably 39% by mass or more. preferable.
On the other hand, this content is, for example, 71% by mass or less, preferably 67% by mass or less, and more preferably 63% by mass or less.

(calcined alumina)
The castable refractory of the present invention can further contain calcined alumina as alumina.
The content of calcined alumina in the castable refractory of the present invention is, for example, 1% by mass or more, preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 6% by mass or more.
On the other hand, this content is, for example, 18% by mass or less, preferably 16% by mass or less, and more preferably 13% by mass or less.

The grain size of the calcined alumina is preferably 20 μm or less.
The "particle size" means the particle size at 90% of the integrated value in the particle size distribution determined by the laser diffraction/scattering method according to JIS R 1629 (1997) (the same shall apply hereinafter).

"graphite"
The castable refractory of the present invention contains graphite as refractory powder.
Graphite does not get wet easily with molten slag and is superior in oxidation resistance to pitch and carbon black. Therefore, the castable refractory of the present invention can suppress build adhesion after curing.
From the viewpoint of obtaining such effects, the content of graphite in the castable refractory of the present invention is 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more.

On the other hand, if the castable refractory contains too much graphite, the C concentration in the molten steel increases, and the decarburization blowing time increases.
Therefore, the content of graphite in the castable refractory of the present invention is 10% by mass or less, preferably 8% by mass or less, and more preferably 5% by mass or less.

Graphite includes, for example, artificial graphite and natural graphite.
Specific examples of natural graphite include flake graphite, flake graphite, earthy graphite, and the like.
Among these, scale-like graphite or scale-like graphite is preferable to artificial graphite for the reasons explained below.

FIG. 3 is an enlarged sectional view showing the steel bath 5 containing the artificial graphite 11. As shown in FIG. FIG. 4 is an enlarged cross-sectional view showing the steel bath 5 containing flake graphite 12. As shown in FIG.
As shown in FIG. 4, the graphite flakes 12 are arranged so that their longitudinal direction is horizontal during construction. Therefore, the area A ₂ (see FIG. 4) where the flake graphite 12 contacts the molten steel 7 is smaller than the area A ₁ (see FIG. 3) where the artificial graphite 11 contacts the molten steel 7 . Therefore, flake graphite 12 is less likely to dissolve in molten steel 7 than artificial graphite 11 .
Slag 8 (not shown in FIGS. 3 and 4) is less likely to permeate steel bath portion 5 where graphite remains, and adhesion of build 9 (not shown in FIGS. 3 and 4) is further suppressed. be. Such an effect is more obtained when flake graphite 12 that is difficult to dissolve in molten steel 7 is used.

《Spinel》
Alumina and magnesia react, for example, at a temperature of 1300° C. or higher to produce spinel (Al ₂ O ₃ +MgO→MgAl ₂ O ₄ ).
The generated spinel dissolves with γ-Al ₂ O ₃ and generates lattice defect spinel in the presence of CO gas. Lattice-defective spinel has a lower MgO concentration than theoretical spinel (MgAl ₂ O ₄ ), and is therefore inferior to theoretical spinel in corrosion resistance to molten slag.

Therefore, the castable refractory of the present invention contains spinel (for example, electrofused spinel, sintered spinel, etc.) as the MgO component instead of magnesia (or instead of part of magnesia) from the beginning. In this case, lattice defect spinels are less likely to be generated. Therefore, the castable refractory of the present invention has excellent corrosion resistance to slag after hardening.

Consider, for example, a castable refractory containing an MgO component of 7% by weight.
Alumina - 22% by mass of spinel - 5% by mass of graphite castable refractory, as compared with a castable refractory of alumina - 7% by mass of magnesia - 5% by mass of graphite, the amount of melt loss is 1/1.5 to 1/5 can be reduced to

The castable refractories of the present invention contain spinels corresponding to a MgO content of 5-10% by weight.

Specifically, the spinel content in the castable refractory of the present invention is 18% by mass or more, preferably 23% by mass or more, more preferably 28% by mass or more, more preferably 28% by mass or more, for the reason that it has excellent corrosion resistance to slag. More than % by mass is more preferable.

On the other hand, a castable refractory with too much spinel is prone to deeper slag penetration after contact with molten steel after hardening. In this case, when spalling occurs, the peel thickness tends to increase.
Therefore, from the viewpoint of suppressing slag penetration, the content of spinel in the castable refractory of the present invention is 37% by mass or less, preferably 32% by mass or less, more preferably 27% by mass or less, and 22% by mass. More preferred are:

《Magnesia》
As described above, the castable refractories of the present invention contain spinel instead of all or part of magnesia.
Specifically, the content of magnesia (for example, sintered magnesia) in the castable refractory of the present invention is 8% by mass or less, preferably 5% by mass or less, and 1% by mass for the reason that it has excellent corrosion resistance to slag. % or less, more preferably 0.5 mass % or less, particularly preferably 0.1 mass % or less, and most preferably 0 mass %.

《Other refractory powders》
The castable refractory of the present invention may contain other refractory powders in addition to the alumina, graphite and spinel mentioned above.
Other refractory powders include, for example, metal powders such as Si, Al, and Al—Si alloys; siliceous raw materials such as silica fume; silica/alumina raw materials such as clay; carbides such as SiC and B ₄ C; etc.

However, the content of other refractory powder in the castable refractory of the present invention is, for example, 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less, and 0.5% by mass or less. is more preferred.
Specifically, for example, the content of the metal powder is preferably 5% by mass or less, more preferably 3% by mass or less. The content of the siliceous raw material, the silica/alumina raw material, and the carbide is preferably 1% by mass or less, more preferably 0.5% by mass or less.

<Binder>
Next, the binder contained in the castable refractory of the present invention will be explained.

《Strontium cement》
The castable refractory of the present invention contains strontium cement as a binder instead of part or all of alumina cement for the following reasons.

CaO in the alumina cement reacts with, for example, calcined alumina of 20 μm or less at a high temperature of 1400° C. or higher to form plate crystals of CaAl ₁₂ O ₁₉ (CaAl ₄ O ₇ +4 Al ₂ O ₃ →CaAl ₁₂ O ₁₉ ), causing a volume expansion. This tends to occur when the amount of calcined alumina is large (for example, 5% by mass or more).
Generally, at high temperatures of 1400° C. or higher, Al ₂ O ₃ , MgO, CaO, SiO ₂ and the like react to form low-temperature melts, which causes sintering shrinkage. Therefore, volumetric expansion is not a big problem.
However, when the castable refractory contains graphite, the graphite suppresses sintering, resulting in increased volume expansion and cracking in the hardened castable refractory.
Therefore, strontium cement is used as a binder in place of part or all of the alumina cement. This can suppress the occurrence of cracks due to volume expansion.

As strontium cement, for example, commercial products containing SrAl ₂ O ₄ and Al ₂ O ₃ can be used.

From the viewpoint of exhibiting sufficient strength after curing, the content of strontium cement in the castable refractory of the present invention is 7% by mass or more, preferably 9% by mass or more, and more preferably 11% by mass or more.
On the other hand, the content of strontium cement in the castable refractory of the present invention is 20% by mass or less, preferably 14% by mass or less, more preferably 11% by mass or less, for the reason that the corrosion resistance to slag is excellent after curing. preferable.

《Alumina cement》
For the reasons mentioned above, the content of alumina cement is small in the castable refractory of the present invention.
Specifically, the content of alumina cement in the castable refractory of the present invention is 10% by mass or less, preferably 4% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less. , 0.1% by weight or less is particularly preferred, and 0% by weight is most preferred.

<Dispersant>
A dispersant may be added to the castable refractory of the present invention.
Examples of the dispersant include polycarboxylic acid, polyacrylic acid, polyether-based dispersant, naphthalenesulfonic acid, and the like, and these may be used alone or in combination of two or more.
The amount of polycarboxylic acid to be added is preferably 0.75 to 2.50 parts by mass, more preferably 0.95 to 2.30 parts by mass, per 100 parts by mass of the castable refractory of the present invention.
The amount of polyacrylic acid, polyether-based dispersant and naphthalenesulfonic acid added is preferably 0.05 to 0.15 parts by mass, respectively, with respect to 100 parts by mass of the castable refractory of the present invention. 0.07 to 0.12 parts by mass is more preferred.

[Hardened body]
First, water is added to the castable refractory of the present invention, and the mixture is kneaded using a mixer or the like to form a kneaded clay. In other words, you get kneaded clay.
The water to be added is not particularly limited, and for example, industrial water, tap water and the like are used.
The amount of water to be added is preferably 3 to 10 parts by mass, more preferably 4 to 7 parts by mass, per 100 parts by mass of the castable refractory of the present invention.
First, only the castable refractory material of the present invention may be dry-kneaded, and then water-kneaded while adding water or after adding water.
The dry kneading time and the water kneading time are appropriately set according to the amount of castable refractory to be kneaded, the type of mixer to be used, and the like.

The kneaded soil obtained by kneading is poured into a predetermined mold or pot. When pouring into a molten steel ladle, a mold called a core is put in and vibration is applied as appropriate. It can also be applied to spray materials.
After that, the kneaded soil is cured and hardened, and then the formwork is removed. The curing time can be appropriately determined according to the composition of the kneaded soil. It may then be dried. The drying temperature and drying time can be adjusted as appropriate.
Thus, a hardened castable refractory is obtained. By using such a hardened body as the steel bath of the steel ladle (see FIGS. 1 and 2), adhesion of the build to the steel bath can be suppressed.

EXAMPLES The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the following examples.

<Preparation of castable refractories>
The components (refractory powder and binder) shown in Table 1 below are mixed in the amounts shown in Table 1 below (unit: parts by mass) in a total amount of 2.5 kg, put into a universal mixer, and stirred for 1 minute. , to obtain a castable refractory.
Water and polycarboxylic acid were added to the resulting castable refractory in the amounts shown in Table 1 below, and the mixture was stirred for 3 minutes to obtain a kneaded clay.

The details of the components shown in Table 1 below are as follows.
・Electro-fused alumina (5-1 mm): electro-fused alumina with a particle size of 1 to 5 mm ・Electro-fused alumina (1-0 mm): electro-fused alumina with a particle size of 1 mm or less ・calcined alumina: calcined alumina with a particle size of 20 μm or less・Flake graphite: Flake graphite with a particle size of 0.18 to 1 mm ・Artificial graphite: Artificial graphite with a particle size of 0.106 to 0.5 mm ("G30" manufactured by Chuetsu Graphite Co., Ltd.)
・ Spinel: Electrofused spinel with a particle size of 1 mm or less ・ Magnesia: Sintered magnesia with a particle size of 1 mm or less ・ Silica fume: “971u” manufactured by Elchem Co., Ltd.
・ Strontium cement: “A09N” manufactured by Denka
・Alumina cement: “Hi” manufactured by Denka

<evaluation>
Using the obtained castable refractory (kneaded clay), the following evaluations were performed. The results are shown in Table 1 below.

《Bending strength》
The kneaded clay was poured into a mold of 40×40×160 mm and vibrated for 30 seconds using a table-like vibrator. After one day had passed, the frame was removed and dried at 110° C. for 24 hours to obtain a test piece as a cured product.
Using the obtained test piece, a bending test was performed according to JIS R 2553:2005 to obtain bending strength (unit: MPa). It can be evaluated that the larger this value is, the more sufficient the strength is.

《Linear change rate and apparent porosity》
A cured test piece was obtained in the same manner as described above.
The obtained test piece was heat-treated. Specifically, the obtained test pieces (excluding the test piece of Comparative Example 1) were placed in a silicon carbide container together with coke breeze, covered, and subjected to reduction firing at 1400° C. for 3 hours. The test piece of Comparative Example 1 was heated at 1400° C. for 3 hours in the atmosphere without being placed in a silicon carbide container.
A linear change rate (unit: %) was determined according to JIS R 2554:2005 using the heat-treated test piece.
Furthermore, the apparent porosity (unit: %) was determined according to JIS R 2205-1992 using the heat-treated test piece.

《Erosion Index and Slag Penetration Thickness》
The kneaded clay was poured into a mold of a trapezoidal column of 53/78×35×160 mm and vibrated for 30 seconds using a table-like vibrator. After one day had passed, the frame was removed and dried at 110° C. for 24 hours to obtain a test piece as a cured product.

The following tests were performed using the dried test pieces.
Specifically, eight test pieces were used as one set, and alumina mortar was used to bond them in an octagonal shape to form an enclosure, which was installed inside a high-frequency induction furnace.
6.8 kg of electrolytic iron was placed in an enclosure made of a test piece, and the temperature was raised to 1650° C. while flowing nitrogen. After that, a mixed reagent of 4.4 g of ferric oxide, 18.4 g of silicon dioxide, 49.2 g of aluminum oxide, 113.8 g of calcium oxide and 14.2 g of magnesium oxide was added. It was held for 3 hours while replacing the reagent every hour. After that, the steel was tapped.
The dimensional change before and after the test was measured for the most eroded portion of each test piece, and normalized as an index (corrosion index) with Comparative Example 1 being 100. It can be evaluated that the smaller the erosion index, the better the corrosion resistance.

Further, Ca surface analysis was performed using a fluorescent X-ray device on the portion of each test piece where erosion was small, and the slag permeation thickness (unit: mm) was obtained. It can be evaluated that the smaller this value is, the more the slag penetration can be suppressed.

《Build Thickness》
The kneaded clay was poured into a mold of φ30×160 mm and vibrated for 30 seconds using a table-like vibrator. After one day had passed, the frame was removed and dried at 110° C. for 24 hours to obtain a test piece as a cured product.
The obtained test piece was heat-treated. Specifically, the obtained test pieces (excluding the test piece of Comparative Example 1) were placed in a silicon carbide container together with coke breeze, covered, and subjected to reduction firing at 1400° C. for 3 hours. The test piece of Comparative Example 1 was heated at 1400° C. for 3 hours in the atmosphere without being placed in a silicon carbide container.

Using the heat-treated test pieces (including the test piece of Comparative Example 1), the following tests were performed.
Specifically, first, 36 g of ferric oxide, 36 g of silicon dioxide, 352.8 g of aluminum oxide, 162.8 g of calcium carbonate, and 34.8 g of magnesium oxide were placed in a magnesia crucible, and an electric furnace in which nitrogen was flowed. Inside, the temperature was raised to 1650° C. and melted to obtain molten slag.
A test piece was immersed in the molten slag, held for 1 hour, and then pulled out. After allowing the pulled test piece to cool to room temperature, it was cut in half lengthwise to determine the build thickness (unit: mm) at the portion where the slag (build) adhered the most. It can be evaluated that the smaller this value is, the more the build adhesion can be suppressed.

<Summary of evaluation results>
As shown in Table 1 above, Comparative Example 1, which did not contain graphite, had a large value of build thickness and was insufficient in suppressing build adhesion.
Comparative Example 2 containing graphite and containing a large amount of magnesia (not containing spinel) had a large erosion index and insufficient corrosion resistance.
In Comparative Example 3 containing a large amount of alumina cement (no strontium cement), the test piece expanded and cracked after heating at 1400°C.
Comparative Example 4, which contained a small amount of strontium cement, had a small bending strength value and insufficient strength.
Comparative Example 5, in which the spinel content was low, had a large erosion index and insufficient corrosion resistance.
Comparative Example 6, in which the spinel content was high, had a large value of slag penetration thickness, and the suppression of slag penetration was insufficient.

In Comparative Example 7, which contained a large amount of strontium cement, the test piece expanded and cracked after heating at 1400°C.
Part of the magnesia was replaced with spinel, but Comparative Example 8, in which the amount of replacement was small (the content of magnesia was high), had a large erosion index and insufficient corrosion resistance.

Comparative Example 9, which contained a small amount of graphite (artificial graphite), had a large value of build thickness and insufficient suppression of build adhesion.
Comparative Example 10, in which the content of graphite (flaky graphite) was small, had a large value of build thickness, and the suppression of build adhesion was insufficient.

In contrast, invention examples 1 to 22 had a corrosion index of 110 or less, which is acceptable for practical use, and exhibited sufficient corrosion resistance.
Inventive Examples 1 to 22 had smaller build thickness values than Comparative Example 1, and build adhesion was sufficiently suppressed.
Inventive Examples 1 to 22 had a bending strength value greater than that of Comparative Example 4, indicating sufficient strength.
In invention examples 1 to 22, the value of the slag permeation thickness was smaller than that of comparative example 7, and slag permeation was sufficiently suppressed.

Among Invention Examples 1 to 22, when comparing Invention Example 5 and Invention Example 14, which differ only in the type of graphite, Invention Example 5 using flake graphite is better than Invention Example 14 using artificial graphite. The value of slag penetration thickness was small, and the value of build thickness was also small.

Comparing Invention Examples 5, 12 and 13 among Invention Examples 1 to 22, the corrosion index decreased as the spinel content increased. On the other hand, as this content decreased, the value of slag penetration depth decreased.

Comparing Invention Examples 4, 5 and 6 among Invention Examples 1 to 22, the flexural strength increased as the strontium cement content increased. On the other hand, as this content decreased, the erosion index decreased.

<Additional test>
Next, using 12.5 tons of the castable refractory material of Invention Example 5, the steel bath section 5 of the steel ladle 1 described with reference to FIGS. 1 and 2 was produced. At this time, after the frame was removed, water glass was applied to the surface of the steel bath portion 5 in contact with the molten steel 7 using a brush in order to prevent oxidation due to preheating. After the second charge, when the water glass was melted, the adhesion state of Build 9 was observed.
For comparison, 13.5 tons of the castable refractory of Comparative Example 1 was used to prepare the steel bath 5 of another molten steel ladle 1 .
A magnesia-carbon brick was used for the slag line portion 6 of both steel ladle 1 .
In these ladle 1, molten steel 7 containing a large amount of Al to which build 9 tends to adhere was subjected to secondary refining and then subjected to continuous casting. After that, the inside of the molten steel ladle 1 was visually observed.
As a result, a large amount of build 9 adhered to the surface of the steel bath portion 5 using the castable refractory of Comparative Example 1. On the other hand, on the surface of the steel bath portion 5 using the castable refractory of Invention Example 5, build 9 adhered less.

1: Molten steel pot 2: Iron skin 3: Permanent tension 4: Bottom part 5: Steel bath part 6: Slag line part 7: Molten steel 8: Slag 9: Build 10: Tundish 11: Artificial graphite 12: Flake graphite

Claims (6)

alumina;
graphite;
Spinel and
containing strontium cement and
The graphite content is 1 to 10% by mass,
The spinel content is 18 to 37% by mass,
The content of the strontium cement is 7 to 20% by mass,
The content of magnesia is 8% by mass or less,
A castable refractory having an alumina cement content of 10% by mass or less. 2. The castable refractory of claim 1, wherein the graphite comprises flake graphite. The alumina contains calcined alumina,
The castable refractory according to claim 1 or 2, wherein the calcined alumina content is 1 to 18% by mass. 4. The castable refractory according to claim 3, wherein the calcined alumina has a particle size of 20 [mu]m or less. A molten steel ladle that is a container for holding molten steel,
From the outside, it has a steel skin, permanent lining and lining,
A steel ladle using the hardened castable refractory according to claim 1 or 2 as part of the lining. 6. The molten steel ladle of claim 5, wherein a portion of said lining is a steel bath portion that contacts said molten steel.

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