JP2001113345A - Continuous casting method for steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuous casting method for casting a clean steel reducing refractory material components invaded into molten steel by restraining the erosion of an immersion nozzle portion in contact with the molten steel and the erosion of an immersion nozzle portion in contact with mold powder and/or slag, in the continuous casting of the steel. SOLUTION: At the portion of the immersion nozzle in contact with the molten steel, spinel quality and/or spinel.carbon quality are disposed, and at the portion thereof in contact with the mold powder and/or the slag, powder line material is disposed. At the other portion, the immersion nozzle disposed with this body material and mold powder having <3 wt.% fluorine content and 4-100,000 poises viscosity at 1,300 deg.C are used in combination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suppressing the erosion of a submerged nozzle in contact with molten steel and the submerged nozzle in contact with mold powder and / or slag in continuous casting of steel. Accordingly, the present invention relates to a continuous casting method for casting clean steel by reducing refractory raw material components entering molten steel.

[0002]

2. Description of the Related Art In continuous casting of steel, an alumina-graphite material containing and / or not containing fused silica is generally used as a main material, and a zirconia-graphite material and / or
Alternatively, an immersion nozzle using a zirconia-calcia-graphite material as a powder line material and a mold powder containing a fluorine component are used in combination. A technology combining the above immersion nozzle material and mold powder material (hereinafter referred to as "prior art 1")
In order to prevent inclusions caused by refractories and / or mold powder material from entering steel, the following technology is disclosed.

With respect to the immersion nozzle, the carbon pickup or mold powder is prevented from being entangled.
A technique in which an inert gas is blown into molten steel from an immersion nozzle to prevent the molten steel from coming into contact with the nozzle (JP-A-8-57613)
Japanese Patent Laid-Open Publication No. Sho 62-130754) is known.
(Hereinafter referred to as “prior art 2-1”). In addition, a refractory material composed of spinel or a refractory material composed of spinel and periclase is provided at a portion in contact with molten steel such as low carbon Al-killed steel, high oxygen steel, high Mn steel, stainless steel, and Ca-treated steel. An immersion nozzle (see Japanese Patent Application Laid-Open No. 10-305355), which has both erosion resistance and blockage resistance and suppresses inclusions due to refractories, is known (hereinafter referred to as "prior art 2-2").

On the other hand, mold powder is usually used as a flux for increasing fluidity and / or
"Raw materials containing fluorine components" such as fluorite, which can generate caspidyne (3CaO ・ 2SiO ₂・ CaF ₂ ) crystals, are generally used to control heat removal.
(Hereinafter referred to as “Prior Art 3”). However, the fluorine component
It promotes erosion of the immersion nozzle and indirectly makes it difficult to cast clean steel. Therefore, there is a need for a mold powder in which fluorine is absent or the fluorine component is reduced as much as possible.

[0005] Among them, the prior art relating to fluorine-free mold powder includes the following: a spray cooling water for cooling a slab, a secondary cooling water after cooling, and a machine cooling water having a neutral pH, a casting machine body and piping. Technology aimed at improving the durability of metal structures such as steel and concrete equipment (Japanese Patent Application Laid-Open No. 58-125349). ・ Similarly, spray cooling water for slab cooling, secondary cooling water after cooling, and machine cooling water Technology for maintaining the pH at neutral, preventing corrosion of the casting machine body and piping, and maintaining fluidity and slagging properties (JP-A-51-93728). Technology aimed at prevention (Japanese Patent Application Laid-Open No. 50-86423), Technology aimed at preventing environmental pollution, preventing corrosion of equipment surrounding the continuous casting machine, and preventing damage to the immersion nozzle (Japanese Patent Application Laid-Open No. 5-208250)・ Prevention of work environment deterioration due to silicon tetrafluoride reacted with silicate, secondary cooling Technology aimed at preventing pollution of rejected water (Japanese
No. 1-67227) (hereinafter referred to as “prior art 3-
1 ”).

The prior art relating to mold powder in which the fluorine component is reduced as much as possible includes the following: a technique for preventing damage to the immersion nozzle (Japanese Patent Laid-Open No. 5-269)
560), and a technology for preventing environmental pollution (Japanese Patent Laid-Open No. 51-132113) is known (hereinafter referred to as "prior art 3-2").

[0007]

By the way, in the case of casting using a conventional immersion nozzle (refer to the prior art 1), the inner tube and the powder line portion of the immersion nozzle are formed of molten steel, inclusions in the molten steel, mold powder. , Is eroded by slag. When the molten steel is melted in this way, the shape of the immersion nozzle changes, and the molten steel flow in the mold is disturbed, thereby causing a slab defect. In addition to the “change in the shape of the immersion nozzle”, the immersion nozzle material is further reacted with the molten element in the molten steel and / or the mold powder or slag to form low- or high-melting compounds. Changes the thermal conductivity. Due to this change in the thermal conductivity, the amount of heat removed from the molten steel through the immersion nozzle was not constant, so that the formation of a solidified shell was non-uniform, causing slab defects.

[0008] To solve these problems, conventionally,
And tried to improve the mold powder, as described above, was used in combination "fluorine-based mineral is a Kasupidain _{(3CaO · 2SiO 2 · CaF 2} ) mold powder for the crystallized crystal" for controlling the heat removal amount (See Prior Art 3). However, the fluorine component in the mold powder, on the contrary, promotes the erosion of the powder line portion, and the sufficient effect has not yet been obtained. Further, in order to suppress the melting of the powder line portion, application of a mold powder having no fluorine component or a low fluorine component has been attempted (see the above-mentioned prior arts 3-1 and 3-2). ,
Conversely, heat extraction cannot be suppressed, and mold powder causes slab defects, and there is no complete solution at present.

Therefore, in the continuous casting of steel, various measures described above have been taken in order to cast clean steel, but these also exhibit a sufficient effect as described below. Absent.

In the above-mentioned prior art 2-1, "the technique of blowing an inert gas into the molten steel from the nozzle to prevent the molten steel from coming into contact with the nozzle", the blowing amount of the inert gas, the blowing angle, and the size of the bubble. It is necessary to control the accuracy and the like. If these are not controlled, the drift of the molten steel flow will occur on the contrary, and the molten steel flow collides with a part of the nozzle, resulting in local melting.

Also, due to the fluctuation of the molten metal level due to bubbling,
Mold powder and slag entrained in the molten steel filled in the mold are captured by the injected inert gas, but if the inert gas flow is not properly controlled, the nozzle may be severely melted. Is done. in this case,
Since the powder line and the mold powder do not always come into contact with each other, the normal nozzle material is melted. Furthermore, once the nozzle is melted down, the flow of the inert gas blown out of the nozzle becomes more and more deflected, which also promotes the nozzle damage. Then, the nozzle is melted and damaged, so that the steel is also contaminated.

In the above-mentioned prior art 2-2, the "immersion nozzle in which a refractory material composed of spinel or a refractory material composed of spinel and periclase is disposed in a portion which comes into contact with molten steel" is a commonly used alumina-graphite type. Meltability to molten steel is better than nozzles. Hereinafter, this point will be described in detail.

The present inventors have found that alumina-graphite materials commonly used as immersion nozzle materials generally undergo the following reactions with molten steel and are undesirable materials for clean steel casting. That is, since the carbon concentration in molten steel is extremely low, the graphite (C
(s): solid graphite) is rapidly dissolved in the molten steel by the reaction of formula (1), C (s) → C ...

Further, in the alumina (Al ₂ O ₃ ) in the alumina-graphite nozzle material, (FeO) is formed by the reaction of Fe (l) + O → (FeO) (2) And the dissolved elements in the molten steel penetrate as well. For example, if Mn is a dissolved element, (MnO) permeates alumina by the reaction of Mn + O → (MnO) (3). (Note that O 2 and Mn in the equations (2) and (3) indicate oxygen and manganese dissolved in the molten steel, and Fe (l) indicates the iron component in the molten steel.)

[0015] "Al formed by the infiltration of these substances
₂ O ₃ -FeO and “Al ₂ O ₃ -MnO” further react with the inclusions in molten steel, such as “FeO-MnO”, to form a liquid slag of “Al ₂ O ₃ -FeO-MnO” That is, the alumina is melted by the combination of the two factors.

Further, in order to increase the spalling resistance, it is customary to include fused silica in the alumina-graphite nozzle material.
Alternatively, it is further melted down, which is not desirable.

On the other hand, the permeation amount of (FeO), (MnO) and the like into the spinel is small, and the solid phase is maintained without forming a liquid phase even when inclusions such as FeO-MnO adhere. . That is, there is little erosion of the nozzle in which the spinel is distributed in the portion that comes into contact with the molten steel, and therefore, the molten steel contamination is reduced. As described above, for erosion of the immersion nozzle by molten steel,
The present inventors have clarified that spinel is a good material.

However, the erosion of the immersion nozzle by the powder slag is not improved by using the spinel material. This is due to the fluorine component in the powder slag. Therefore, it is conceivable to eliminate the fluorine component or use a mold powder having a low fluorine component (Japanese Patent Application Laid-Open Nos. 58-125349 and 58-125349 described in the prior arts 3-1 and 3-2). JP-A-51-93728, JP-A-50-86423,
JP-A-5-208250, JP-A-51-67227, JP-A-51-67227
5-269560, JP-A-51-132113).

However, since these mold powders do not contain a fluorine component or are low-fluorine component mold powders, their viscosity control and crystallization temperature control are poor, so that steel breakout, slab cracking, etc. At present, it has not been put into practical use because stable casting cannot be performed. That is, it is understood that it is difficult to obtain clean steel unless the erosion of the powder line material of the immersion nozzle is solved.

Therefore, an object of the present invention is to prevent the contamination of steel caused by refractories and to enable stable casting of steel having a high degree of cleanliness. That is, even if it comes into contact with molten steel and mold powder, it is almost melted. An object of the present invention is to provide a continuous casting method of steel capable of stably casting clean steel by using an immersion nozzle that does not have any problem.

[0021]

Means for Solving the Problems In order to solve the above problems and achieve the object, the present inventors have made intensive studies,
"Along with supplying molten steel into the mold by the immersion nozzle,
In a method of continuous casting while supplying mold powder into the mold, spinel and / or spinel / carbon is disposed on a part or all of a portion of the immersion nozzle which comes into contact with molten steel, and the mold powder and / or An immersion nozzle in which the powder line material is placed in the area that comes into contact with the slag, and the body material is placed in other areas, and the fluorine content is less than 3 wt% and the viscosity at 1300 ° C is 4 poise to 100,000 poise. Continuous casting method of steel characterized by using in combination with mold powder "
(Claim 1) was invented.

Conventionally, a "fluorine component" has been inevitable in reducing the viscosity of the mold powder and controlling the heat removal. However, if a slag film having uniform properties and / or thickness is formed between the mold and the solidified shell, the fluorine component may be reduced. The inventors have found that there is no need to rely on components. In other words, to increase the viscosity of the mold powder, it can realize uniform slag film, Kasupidain (3CaO · 2SiO ₂ ·
It was found to be a substitute for the function (heat removal control) performed by CaF ₂ ). Moreover, the breaking strength at 1300 ° C is 3.7 g / c.
If m ² or more mold powder (claim 2), to generate a continuous slag film and found to be capable of continuous casting.

Further, regarding the immersion nozzle, the above-mentioned "spinel and / or spinel / carbon" includes "alumina, periclase, zirconia, calcia, titania, silicon carbide, silicon nitride, silicon nitride, boron nitride with respect to 100% by weight of spinel. , Aluminum nitride, boron carbide, zirconium boride, alone or in combination, from 0 to 50% by weight
It has been found that it is possible to use an immersion nozzle (claim 3). Further, as the “spinel carbon”, “carbon exceeds 0% by weight and 100% by weight of spinel
0% by weight or less "using an immersion nozzle (Claim 4).

The carbon that can be used here is selected from flaky graphite, flaky graphite, earthy graphite, coke, anthracite, quiche graphite, pitch, charcoal pyrolytic graphite, carbon black, and amorphous carbon resin binder carbon. It is carbon that combines one or two or more
(Claim 5).

As the powder line material, zirconia, magnesia, calcia, titania, alumina,
Spinel, carbon, silicon carbide, silicon nitride, boron nitride,
Examples thereof include aluminum nitride, boron carbide, and zirconium boride, which can be used alone or in combination (claim 6). Examples of the main body material include alumina, spinel, periclase, mullite, fused silica, carbon, zirconia, calcia, titania, silicon carbide, silicon nitride, boron nitride, aluminum nitride, boron carbide, and zirconium boride. One or more can be used (claim 7).

As the molten steel to be cast, aluminum killed steel,
All steel types such as silicon killed steel, high oxygen steel, stainless steel, steel for electrical steel sheets, calcium-treated steel, high manganese steel, free-cutting steel, boron steel, steel cord, case hardened steel, high titanium steel, etc. Item 8).

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the embodiment of the present invention will be described. As described above, the mold powder used in the present invention has a fluorine content of less than 3% by weight and 13% by weight.
It has a viscosity of 4 to 100,000 poise at 00C.
When the amount of fluorine in the mold powder is 3% by weight or more, the amount of erosion of the immersion nozzle, particularly the powder line portion, increases, and the molten steel is contaminated by the refractory raw material flowing out into the steel to obtain clean steel. Can not.

The viscosity of the mold powder (1300)
If the viscosity is less than 4 poise, non-uniform inflow of the mold powder occurs, crystals such as dicalcium silicate and tricalcium silicate develop in the molten mold powder, and the temperature fluctuation of the mold copper plate becomes large, resulting in poor heat removal. Not preferred for stability. On the other hand, when the viscosity is 10
If it exceeds 0000 poise, it is not preferable because melting is poor and slag bears are generated, and stable casting cannot be performed. In the present invention, the viscosity can be adjusted with, for example, Al ₂ O ₃ , CaO / SiO ₂ , and the viscosity can be adjusted to be high when Al ₂ O ₃ is large or CaO / SiO ₂ is low. .

Further, the mold powder used in the present invention is obtained by melting this mold powder and having a diameter of 7 m.
The maximum load when cutting a mold powder droplet when the platinum cylinder separates from the liquid surface when the platinum cylinder of m is pulled up at a constant speed is defined as "the breaking strength of the molten mold powder".
The breaking strength of the molten mold powder at 300 ° C. is 3.7.
g / cm ² or more is preferable. The breaking strength is 3.7 g / cm ²
If it is less than 10%, the liquid layer in the slag film is likely to break, which is not preferable.

The mold powder used in the present invention is
Strand cement, wollastonite, synthetic calcium silicate
Material such as aluminum, perlite, fly ash, etc.
SiO_TwoRaw materials, carbonates, glass powder, frit powder, etc.
Na_TwoO, K_TwoO, Li_TwoO raw material, magnesium carbonate,
MgO raw materials such as seawater MgO powder and dolomite powder, borax,
B of colemanite, glass powder, frit powder, etc._TwoO_Threeoriginal
Coal, such as coal, coke powder, scale graphite, and carbon black
It can be made from raw materials. However, NaF, CaF _TwoWhat
Contains no fluoride. Specifically, the base material
The above SiO_Two, Na_TwoO, K_TwoO, Li_TwoO, MgO, B_Two
O_ThreeAnd carbonaceous raw materials as appropriate, and
Al_TwoO_Three, CaO / SiO_TwoAdjust the viscosity with
It can be manufactured by adjusting.

For example, the chemical composition is SiO ₂ : 25
70 wt%, CaO: 10 to 50 wt%, Na ₂ O,
One or more selected from the group consisting of Li ₂ O and K ₂ O: 3 to 20 wt%, MgO: 20 wt% or less, the fluorine component as inevitable impurities: 3 wt% or less, carbon: 0 0.5 to 8% by weight and CaO
It is obtained by mixing each of the above-mentioned raw materials adjusted so that the weight ratio of / SiO ₂ is in the range of 0.2 to 1.5, and then uniformly mixing with a mixer. Also liquid (e.g. water)
And, if necessary, an organic binder or an inorganic binder. Extrusion granulation, stirring granulation, tumbling granulation, fluid granulation,
It can be granulated by a method such as spray granulation and used in the form of granules.

Next, an embodiment of an immersion nozzle used in combination with the above-mentioned mold powder will be described. In the present invention, a portion of the immersion nozzle which comes into contact with molten steel is: , Zirconia, calcia, titania, silicon carbide, silicon nitride, boron nitride, aluminum nitride, boron carbide, zirconium boride alone or in combination of 0 to 50% by weight
And / or 100% by weight of spinel, and more than 0% by weight and less than 40% by weight of spinel / carbon are distributed to various molten steels. On the other hand, an immersion nozzle having high corrosion resistance can be provided.

Here, for 100% by weight of spinel,
Alumina, periclase, zirconia, calcia, titania, silicon carbide, silicon nitride, boron nitride, aluminum nitride, boron carbide, and zirconium boride are preferably used alone or in combination in a proportion of 50% by weight or less, more preferably spinel. With respect to 100% by weight, their proportion is 2
0% or less, which is more effective. Their proportion is 50
If the amount is more than 10% by weight, the effect of the refractory material is more limited than the effect of the spinel, and it becomes impossible to provide a highly corrosion-resistant immersion nozzle.

As described above, at the site that comes into contact with molten steel,
Amount of alumina, periclase, zirconia, calcia, titania, silicon carbide, silicon nitride, boron nitride, aluminum nitride, boron carbide, zirconium boride, alone or in combination, of 50% by weight or less with respect to 100% by weight of spinel. In addition to distributing the spinel material, it is possible to distribute the spinel material / carbon of more than 0% by weight and 40% by weight or less with respect to 100% by weight of the spinel material in combination with or alone. it can.

As shown in the above formula (1), carbon is
There is concern about molten steel contamination due to rapid melting in molten steel,
Not desirable. However, the present inventors have found that a more desirable effect is exhibited by using carbon in combination with spinel.

That is, by arranging the “spinel carbon material” at the portion that comes into contact with the molten steel, the carbon layer near the working surface extremely in contact with the molten steel in the early stage of casting is certainly quickly dissolved in the molten steel. However, it was found that a dense layer of spinel was rapidly formed at the mark where the carbon layer disappeared, and no further dissolution of carbon proceeded. Further, it was found that the amount of dissolved carbon in the early stage of casting was 0.05 ppm or less, which was much lower than the carbon concentration in the ultra-low carbon steel, and was not at the level of molten steel contamination.

Therefore, the carbon content is less than a certain amount.
(40% by weight or less) of the spinel carbon material was found to have high erosion resistance to molten steel. Further, since carbon can be used, the coefficient of thermal expansion of the material can be reduced, and the spalling resistance can be increased as compared with the case where spinel is used alone. That is, it was found that a more preferable embodiment of the present invention is a material which increases spalling resistance and reduces erosion as much as possible, and disposing the material at a portion which comes into contact with molten steel.

Here, as the carbon, flaky graphite, flaky graphite, earthy graphite, coke, anthracite, quiche graphite, pitch, charcoal pyrolytic graphite, carbon black, and amorphous carbon resin binder carbon can be used. .

The carbon content of the spinel carbon is preferably 40% by weight or less, more preferably 10% by weight.
% By weight or more and 30% by weight or less. When the amount of carbon exceeds 40% by weight, the amount of dissolved carbon near the working surface increases, and a large amount of pores are generated on the working surface after dissolving the carbon. Subsequently, the dense layer of spinel forms these pores. It becomes difficult to cover. As a result, the dissolution of carbon behind the working surface progresses, and the microstructure cannot be physically maintained by spinel alone, which leads to erosion and contamination of steel, which is not preferable.

In the present invention, zirconia, magnesia, calcia, titania,
Alumina, spinel, carbon, silicon carbide, silicon nitride,
Boron nitride, aluminum nitride, boron carbide, and zirconium boride can be used alone or in combination. Conventionally, a zirconia-carbon material has been mainly used as a material having high erosion resistance to mold powder containing a fluorine component. Therefore, a high-priced material was to be applied.However, according to the present invention, a mold powder containing almost no fluorine component can be used, and a material arbitrarily selected from the above materials can be used. Can be used arbitrarily.

In the present invention, alumina, spinel, periclase, mullite, fused silica, and the like, which do not come into contact with molten steel or mold powder, are used.
Carbon, zirconia, calcia, titania, silicon carbide, silicon nitride, boron nitride, aluminum nitride, boron carbide, and zirconium boride can be used alone or in combination.

The integrated composite immersion nozzle provided with the above-mentioned "material in contact with molten steel (spinel and / or spinel / carbon)", "powder line material" and "body material" is as follows. Can be made.
That is, any of an integral molding method, a cast molding method, a castable molding method, a sleeve insertion method, a thermal spraying method, a coating method, and the like may be used.

The "integral molding method" means that after preparing the kneaded material for each of the materials to be provided, they are loaded into the composite nozzle forming mold in order so as to have a predetermined arrangement. A method of producing a molded body by a conventional uniaxial press molding and / or CIP molding, or a temporary molding by a uniaxial press molding and / or a CIP molding using only the main body material or a combination of the main body material and the powder line material. Then, after the molten material in contact with the molten steel is loaded on the inner surface side of the main body material, and in some cases, the powder line material is loaded on the powder line position on the outer side of the main body material, uniaxial press forming and / or C
This is a method of performing main molding of IP molding to produce a molded body. (Incidentally, the boundary between the materials may have a blurred structure in which both are mixed.)

The "casting method" means that a material for a body material in a powdery state is poured into a mold, dewatered and deframed, and then the molten steel contact material and powder line material in a powdery state are removed from the body material. This is a method in which a molded product is obtained by pouring between the inside and outside and the mold, dewatering and then removing the frame. In addition, the molding order of the main body material and the other materials may be reversed, or both may enter the boundary portion between the molten steel contact portion and the main body material and / or the boundary portion between the powder line material and the main body material. You may make it the mixed blur structure. Further, various casting methods such as pressure casting, centrifugal casting, and electrophoretic casting can be used.

The "castable molding method" is the same as a method for producing a normal amorphous material. That is, the castable material for the main body material is poured into the nozzle mold frame, cured and then removed. Thereafter, the castable material for the molten steel contact portion and the powder line material are poured between the main body material and the formwork, and then removed after curing. This is a method of obtaining a molded body by framing. In addition, the molding order of the above three materials may be reversed, or each of the boundary portions may have a blurred structure in which both are mixed. Furthermore, vibration may be applied at the time of castable pouring.

The "sleeve insertion method" means that the respective materials are separately molded by integral molding, cast molding, castable molding or the like, and the sleeve-shaped molten steel contact portion material and powder line material are loaded into the main body material. Is the way. On the boundary surface between the molten steel contact portion material and the main body material, a mortar capable of joining them, a clay made of both materials, and the like are provided. In addition, in order to form a blurred structure in which both boundaries intersect, it is preferable to form irregularities on the respective contact surfaces in advance.

The "spraying method" is a method in which a molten steel contact portion material and / or powder line material in a plasma state is sprayed onto a body material previously obtained as a molded body to obtain a composite nozzle. is there.

The "coating method" means that a solution having a viscosity adjusted by mixing and adding a hardener and a molten steel contact portion material or a hardener and a powder line material is used for a body material previously obtained as a molded body. This is a method obtained by applying to each predetermined arrangement position. The application can be performed a plurality of times.

Further, the above-mentioned methods can be combined to produce the above-mentioned integrated composite immersion nozzle. For example,
When combining the "integral molding method" and the "castable molding method", first, the body material and the powder line material are uniaxially press-molded and / or C
In the IP molding, a method in which a castable material for a molten steel contact portion is poured between an integrally molded product and a mold, cured, and then demolded to obtain a molded product can be adopted.

The molded article obtained by each of the above means is then subjected to a drying step and a baking step according to a conventional method to obtain a product, ie, the integrated immersion nozzle. The term “integrally combined” refers to a state in which three types of materials, that is, a molten steel contact portion material, a powder line material, and a main body material are physically and / or chemically joined.

In the continuous casting method of steel according to the present invention in which the immersion nozzle obtained as described above and the above-mentioned mold powder are combined, the invention relates to an aluminum-killed steel, a silicon-killed steel, a high oxygen steel, a stainless steel, a steel for electrical steel sheets. It can be applied to all types of steel, such as calcium-treated steel, high-manganese steel, free-cutting steel, boron steel, steel cord, case hardened steel, and high titanium steel.

[0052]

EXAMPLES Next, examples and comparative examples will be described, and the “continuous casting method of steel” combining an immersion nozzle provided with the material specified in the present invention and a mold powder also specified in the present invention will be described. Although specifically described, the present invention
It is not limited by the following examples.

Here, the structure of the immersion nozzle used in the following Examples and Comparative Examples will be described with reference to FIGS. FIG. 1 is a diagram illustrating an example of a immersion nozzle structure having a discharge port, and FIG. 2 is a diagram illustrating another example of a immersion nozzle structure having a discharge port. FIG. 3 is a view showing an example of a straight type immersion nozzle having no discharge port.

The immersion nozzle shown in FIG. 1 is a type of immersion nozzle having a discharge port portion. In FIG. 1, reference numeral 1 denotes an inner tube portion of the immersion nozzle which comes into contact with molten steel, and 2 denotes a immersion nozzle which also comes into contact with molten steel. The discharge port portion of the immersion nozzle, 3 is a powder line portion that contacts the mold powder and / or slag, and 4 is
This is the main body of the immersion nozzle. This immersion nozzle is, as shown in FIG. 1, a discharge port 2a of the immersion nozzle which comes into contact with molten steel.
Is an immersion nozzle having a structure in which the main body 4 and the discharge port 2 are integrally integrated.

The immersion nozzle shown in FIG. 2 is a type of immersion nozzle having a discharge port like the immersion nozzle shown in FIG. However, it is not the one having an integrated structure as shown in FIG. 1 (see “part 2a” in FIG. 1), and as shown in FIG. 2, the part of the discharge port 2b of the immersion nozzle that comes into contact with the molten steel is This is an immersion nozzle having a structure having a discharge port 2 made of the same material. The reference numerals 1 to 4 in FIG. 2 are the same as above, 1 is an inner tube portion, 2 is a discharge port portion, 3 is a powder line portion, and 4 is a main body portion.

The immersion nozzle shown in FIG.
Is a straight type immersion nozzle having no discharge port. In FIG. 3, reference numeral 5 denotes a nozzle tip portion that comes into contact with molten steel, and other symbols are the same as those described above, where 1 is an inner tube portion, 3 is a powder line portion,
Is a main body.

Table 1 shows the chemical compositions (sample numbers 1 to 34) of the mold powders used in the following examples (comparative examples).
Table 2 shows the chemical composition (sample numbers 35 to 48) of the mold powder used in the comparative example.
In addition, the “fluorine component”, “viscosity (at
1300 ° C.), “break strength (at 1300 ° C.)” are shown in Tables 1 to 3. Further, in order to clarify the mold powder used in the examples and comparative examples, the numbers of the examples and comparative examples were Table 1
To Table 3 below. In addition, the sample number 1 of Table 1-Table 3
The mold powders of 8, 17 to 26, 35 to 37 and 40 to 44 are "powder products" obtained by mixing with a mixer so as to have a predetermined chemical composition ratio. For the mold powders of Sample Nos. 9 to 16, 27 to 34, 38 to 38 and 45 to 48 other than those described above, after mixing the raw material powder, a solution consisting of 90% by weight of water and 10% by weight of sodium silicate was added to the powder. ３０30% by weight to prepare a slurry, spray-granulate the slurry, and dried to obtain “granules”
And is finally prepared to have a predetermined chemical composition.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3]

(Examples 1 to 70, Comparative Examples 1 to 28) Examples 1 to 70 are shown in Tables 4 to 14,
Tables 15 to 22 show Comparative Examples 1 to 28.
(Note that, for Tables 4 to 22, unless otherwise specified,
These tables are collectively abbreviated as “table”. The following Examples 1 to 70 and Comparative Examples 1 and 2
In each of Examples 8, the molten steel ("steel type" in the table) was supplied into the mold by a nozzle, and continuous casting was performed while supplying mold powder into the mold. In addition, the structure of the nozzle used in each example is shown by the drawing number in the table. In addition, the mold powder used in each example was composed of those having the chemical compositions of the sample numbers 1 to 48 in Tables 1 to 3, the sample numbers were shown in the table, and the mold powder used was “ Fluorine component "" viscosity (a
t 1300 ° C.) ”and“ break strength (at 1300 ° C.) ”only.

Further, “%” of the material of each nozzle portion in the table
Means "% by weight". In addition, “MgO ・ Al
“ ₂ O ₃ ” stands for “spinel” and “MgO” stands for “pericles”
Means Further, “ZrO ₂ ” can be converted to normal “CaO, MgO,
Y ₂ O ₃ stabilized zirconia ”was used.

"Stable casting" and "Nozzle erosion amount" in each example
(Erosion loss of the inner tube, the inside of the discharge port, and the powder line) "Steel cleanliness" and "Steel defect rate" were evaluated as follows, and the evaluation results are shown in Tables 4 to 22.

Evaluation of stable casting “Stable casting” indicates whether stable casting is possible or not, and a BO prediction alarm during casting [BO (breakout) is generated by continuous measurement of mold surface temperature. Of the immersion nozzle during the casting due to melting of the powder line and / or the molten steel contact area. When there was no, "OK" was given, and the other cases were "NO". Evaluation of nozzle erosion amount “Nozzle erosion amount [mm / (steel ton)]” is shown by nozzle erosion dimension per ton of casting amount. The greater the amount of nozzle erosion, the shorter the nozzle life, and the more impurities are eroded into the steel, thus contaminating the steel. -Evaluation of steel cleanliness "Steel cleanliness" was evaluated based on the degree of sliver flaws. The index “100” indicates the case where there is no sliver flaw, and the index “0” indicates the case where the steel does not become a product due to the sliver flaw. -Evaluation of steel defect rate "Steel defect rate" was evaluated by surface cracking. The case where the surface crack was negligible was marked with “○”, the case where the steel did not turn into a product due to the surface crack was marked with “×”, and the case where the steel surface was processed into a product was marked with “△”.

[0065]

[Table 4]

[0066]

[Table 5]

[0067]

[Table 6]

[0068]

[Table 7]

[0069]

[Table 8]

[0070]

[Table 9]

[0071]

[Table 10]

[0072]

[Table 11]

[0073]

[Table 12]

[0074]

[Table 13]

[0075]

[Table 14]

[0076]

[Table 15]

[0077]

[Table 16]

[0078]

[Table 17]

[0079]

[Table 18]

[0080]

[Table 19]

[0081]

[Table 20]

[0082]

[Table 21]

[0083]

[Table 22]

As is apparent from Tables 4 to 14, Example 1 in which the immersion nozzle provided with the material specified in the present invention and the mold powder also specified in the present invention were combined.
-In Example 70, "Evaluation of stable casting" is all "OK"
Thus, it was found that stable casting was possible. In addition, the evaluation result of the “nozzle erosion amount” shows that “0 mm / (steel ton)” was obtained for both the inner pipe and the inner part of the discharge port, and “0.05 mm / (steel ton) or less” for the powder line. Thus, the amount of nozzle erosion was extremely small, and the improvement of the nozzle life was recognized.

Further, the index based on the “steel cleanliness evaluation” is as follows:
All were "80 or more", and it was found that no sliver damage was observed. In addition, from the “Steel defect rate evaluation result”, although “△” was evaluated in some of the examples, there was no case in which the steel did not become a product due to surface cracking. And the surface cracks of the steel were negligible.

Further, Examples 1 to 7 shown in Tables 4 to 14 were used.
From 0, by combining the immersion nozzle provided with the material specified in the present invention and the mold powder also specified in the present invention, high oxygen steel, high manganese steel, free-cutting steel, stainless steel, high titanium steel, It has been confirmed that it can be effectively applied to all types of steel for electrical steel sheets, steel cord, case hardened steel, aluminum killed steel, silicon killed steel, calcium treated steel, and boron steel.

On the other hand, in Comparative Examples 1 to 14 using the immersion nozzle not distributing the material specified in the present invention and not using the mold powder specified in the present invention,
As is clear from Tables 16 and 18, the “stable casting evaluation results” were both “No” and stable casting was impossible. In addition, the evaluation result of the “nozzle erosion amount” shows that “0.4 mm / (steel ton) or more” for both the inner tube and the inner part of the discharge port, and “0.20 mm / (steel ton)” for the powder line.
As described above, the nozzle erosion amount was extremely large.
0 or less ", and the" results of steel defect rate evaluation "were all" x ", and were not products due to surface cracks.

On the other hand, in the comparative examples 15 to 21 in which the immersion nozzle provided with the material specified in the present invention was used but the mold powder specified in the present invention was not used, as apparent from Table 20, " The "stable casting evaluation results" were all "no", and stable casting was impossible. Also,
In the evaluation result of “Nozzle erosion amount”, the inner pipe part and the inner part of the discharge port were both “0.0mm / (steel ton)”, and although no erosion was observed in this part, the powder line part did not. It was “0.31 mm / (steel ton) or more”, and the amount of erosion at this site was extremely large. Further, the index according to the “steel cleanliness evaluation” is “70 or less”, sliver flaws are recognized, and the “steel defect rate evaluation results” are all “Δ”, indicating that the steel surface having a surface crack Could be a product by processing.

Further, in the comparative examples 22 to 28 in which the mold powder specified in the present invention was used but the immersion nozzle not provided with the material specified in the present invention was used, as is clear from Table 22, " The "stable casting evaluation results" were all "no", and stable casting was impossible. Also,
According to the evaluation result of “nozzle erosion amount”, both the inner pipe portion and the inner portion of the discharge port are “0.05 mm / (steel ton) or more”, and the erosion loss of this portion is extremely large. 0.01 to 0.05 mm / (steel ton) ". Further, the index according to “Evaluation of steel cleanliness” is “60 or less”, sliver flaws are recognized, and “Steel defect rate evaluation results” are all “Δ”, indicating that the steel surface having surface cracks Could be a product by processing.

When the evaluation results of Comparative Examples 1 to 28 and the evaluation results of Examples 1 to 70 of the present invention are compared with each other, it is found that the immersion nozzle provided with the material specified in the present invention is similar to the immersion nozzle specified in the present invention. It has been found that, for the first time, stable casting becomes possible by combining with the mold powder, and that the nozzle life is improved since the nozzle is hardly melted. In addition, sliver scars are hardly observed,
Moreover, it was found that the surface cracks of the steel were negligible.

The materials of the immersion nozzles shown in FIGS. 1 to 3, the mold powders shown in Tables 1 and 2 and the nozzles shown in Tables 4 to 13 used in Examples 1 to 70 are as follows.
It is an example shown as an example of the present invention, and the present invention is not limited to these contents, and various combinations can be used within the scope of matters specifying the invention of claims 1 to 8.

[0092]

As described in detail above, the present invention provides a continuous casting method using a combination of an immersion nozzle capable of suppressing erosion caused by molten steel and a mold powder substantially free of a highly erodible fluorine component. As a result, impurities due to refractory raw materials do not enter molten steel, so that ultra-clean steel can be obtained, and slab defects due to refractories are drastically reduced, thereby improving slab yield. , A remarkable effect occurs.

Further, the immersion nozzle used in the present invention has high performance and low cost due to the improvement of the nozzle life and the reduction in thickness and weight because there is almost no erosion. Combined with specified mold powder, aluminum killed steel, silicon killed steel, high oxygen steel, stainless steel, steel for electrical steel sheet, calcium treated steel, high manganese steel, free cutting steel, boron steel, steel cord, case hardened steel It can be applied to all types of steel such as high titanium steel, and has an extremely high industrial value.

[Brief description of the drawings]

FIG. 1 is a view showing an example of a immersion nozzle structure of a type having a discharge port used in Examples (including Comparative Examples) of the present invention.

FIG. 2 is a view showing another example of a immersion nozzle structure having a discharge port used in Examples (including Comparative Examples) of the present invention.

FIG. 3 is a diagram showing an example of a straight type immersion nozzle having no discharge port used in Examples (including Comparative Examples) of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Internal pipe part of immersion nozzle which contacts molten steel 2 Discharge nozzle part of immersion nozzle which contacts molten steel 3 Powder line part of immersion nozzle which contacts mold powder 4 Body part of immersion nozzle 5 Contact with molten steel of straight type immersion nozzle Nozzle tip

Continued on the front page (72) Inventor Shigeki Uchida 2-2-1 Otemachi, Chiyoda-ku, Tokyo Shinagawa White Brick Co., Ltd. (72) Tomoaki Omoto 2-2-1 Otemachi, Chiyoda-ku, Tokyo Shinagawa Shira Brick Co., Ltd. (72) Inventor Hayashi ▲ Way ▼ 2-2-1 Otemachi, Chiyoda-ku, Tokyo Shinagawa Shiro Brick Co., Ltd. F term (reference) 4E004 FB00 JA00 NC01 4E014 DA01

Claims (8)

[Claims] 1. A method for feeding molten steel into a mold by an immersion nozzle and continuously casting while supplying mold powder into the mold, wherein a part or all of a portion of the immersion nozzle that comes into contact with the molten steel is spinel-type. And / or a spinner material / carbon, a powder line material at a portion which comes into contact with the mold powder and / or slag, and a body material at the other portion, and a fluorine amount of 3 Less than 4% by weight and less than 4 poise
A continuous casting method for steel, comprising using a combination of a mold powder having a size of 00 poise or less. 2. The continuous casting method according to claim 1, wherein the mold powder has a breaking strength at 1300 ° C. of 3.7 g / cm ² or more. 3. The spinel substance and / or the spinel substance of the spinel substance / carbon, based on 100% by weight of spinel, alumina, periclase, zirconia, calcia, titania, silicon carbide, silicon nitride, boron nitride, aluminum nitride, The continuous casting method for steel according to claim 1, characterized in that boron carbide or zirconium boride is spinel-based, alone or in combination, in a proportion of 0 to 50% by weight. 4. The spinel carbon contains more than 0% by weight of carbon with respect to 100% by weight of spinel.
The method for continuous casting of steel according to claim 1, wherein the content is 0% by weight or less. 5. The carbon of the spinel carbon is carbon of scaly graphite, flaky graphite, earthy graphite, coke, anthracite, quiche graphite, pitch, charcoal pyrolytic graphite, carbon black and amorphous carbon resin binder carbon. The method for continuously casting steel according to claim 1 or 4, wherein the method comprises at least one kind. 6. The powder line material may be zirconia, magnesia, calcia, titania, alumina, spinel, carbon, silicon carbide, silicon nitride, boron nitride, aluminum nitride, boron carbide, zirconium boride alone or in combination. The method for continuously casting steel according to claim 1, wherein the steel is used. 7. The body material may be alumina, spinel, periclase, mullite, fused silica, carbon,
2. The continuous casting method according to claim 1, wherein zirconia, calcia, titania, silicon carbide, silicon nitride, boron nitride, aluminum nitride, boron carbide, and zirconium boride are used alone or in combination. 8. The molten steel may be aluminum-killed steel, silicon-killed steel, high-oxygen steel, stainless steel, steel for electrical steel sheets, calcium-treated steel, high-manganese steel, free-cutting steel, boron steel, steel cord, case hardened steel or The method for continuously casting steel according to claim 1, wherein high titanium steel is used.