WO2003045608A1

WO2003045608A1 - Method for continuous casting of steel

Info

Publication number: WO2003045608A1
Application number: PCT/JP2001/010444
Authority: WO
Inventors: Osamu Nomura; Akihiro Morita; Shigeki Uchida; Tomoaki Omoto; Wei Lin
Original assignee: Shinagawa Refractories Co., Ltd.
Priority date: 2001-11-29
Filing date: 2001-11-29
Publication date: 2003-06-05
Also published as: CA2454946A1; AU2002222564A1; KR20040079407A; EP1449603A1; TW590823B; US20040159419A1; CN1589187A; JP2001353561A

Abstract

A method for continuous casting of steel, characterized in that use is made of a combination of a mold powder having a fluorine content of less than 3 wt % and exhibiting a viscosity at 1300 °C of 4 to 10,000 poise and an immersion nozzle comprising a refractory material containing alumina as a primary component (specifically, an alumina refractory and/or alumina-carbon refractory). The method allows the stable production of a clean cast steel product with little melting loss and with no deposit of alumina, also in the case when an immersion nozzle comprising a refractory material containing alumina as a primary component is used.

Description

Description Continuous production of steel <Technical field>

The present invention relates to a method for continuously producing steel, and particularly to a method for continuously producing steel, in which a refractory material containing a specific mold powder and alumina as main materials (specifically, an alumina-based refractory and / or an alumina-based refractory material). The present invention relates to a method for continuously producing steel, which is used in combination with an immersion nozzle composed of (carbon-based refractory). Background technology>

In continuous steelmaking, generally, alumina / graphite-based material containing and / or not containing fused silica is used as the main body material, and zirconia · graphite-based material and / or zirconia · force Lucia · graphite-based material is powdered. An immersion nozzle as a line material and a mold powder containing a fluorine component are used in combination.

The technology combining the above immersion nozzle material and mold powder material

1 "), the following technology is disclosed to prevent inclusions due to refractories and Z or mold powder material from entering steel.

For the immersion nozzle, a technique was used to prevent the contact between the molten steel and the nozzle by blowing an inert gas into the molten steel from the immersion nozzle to prevent the coil pickup or mold powder from being wrapped around. — See Japanese Patent Application Laid-Open No. 77613 and Japanese Patent Application Laid-Open No. Sho 62-130754 (hereinafter referred to as “prior art 2-1”).

In addition, low-carbon A1 killed steel, high-oxygen steel, high-Mn steel, stainless steel, Ca-treated steel, and other parts that come into contact with molten steel are made of a refractory material made of spinel, or a refractory material made of spinel and polyclase. There is known an immersion nozzle (see Japanese Patent Application Laid-Open No. H10-305355) in which an immersion nozzle is provided, which has both erosion resistance and blocking resistance and suppresses inclusions caused by refractories. "Prior art 2-2"). On the other hand, the mold powder, usually as a fluxing agent to increase the fluidity, and / or, as it is possible to heat extraction control, Kasupidai emissions _{_{(3CaO · 2Si0 2 · CaF 2}} ) can be generated crystals "Raw materials containing a fluorine component" such as natural fluorite are generally used (hereinafter referred to as "prior art 3").

However, the fluorine component promotes the erosion of the immersion nozzle and indirectly makes the production of clean steel difficult. Therefore, it is necessary to use a mold pad which is free of fluorine or has a reduced fluorine component.

Among these technologies, the conventional technologies for fluorine-free mold powder include: (1) spray cooling water for one-side cooling, secondary cooling water after cooling, and machine cooling water at neutral pH; Technology aimed at improving the durability of metal structures and concrete equipment (JP-A-58-125349);

• Similarly, スプレー Maintain the neutral pH of spray cooling water for piece cooling, secondary cooling water after cooling, and machine cooling water, and 腐食 Prevent corrosion of the machine body and piping, maintain fluidity and slagging properties. Technology for the purpose of (JP-A-51-93772),

• Technology aimed at preventing the generation of fluorine that is harmful to humans and animals (Japanese Patent Laid-Open No. 50-86432)

• Technology aimed at preventing environmental pollution, preventing corrosion of peripheral equipment of the serial machine, and preventing damage to the immersion nozzle (Japanese Patent Publication No. 5-2080250).

• Technology aimed at preventing the deterioration of the working environment due to silicon tetrafluoride reacted with silicate and the contamination of secondary cooling water (Japanese Patent Laid-Open No. 51-672227).

(Hereinafter referred to as “prior art 3-1”).

Further, as the prior art relating to the mold powder in which the fluorine component has been reduced as much as possible, a technique for preventing damage to the immersion nozzle (Japanese Patent Application Laid-Open No. Hei 5-269650); Technology (Japanese Unexamined Patent Publication No.

(Hereinafter referred to as "prior art 3-2"). By the way, in the case of the construction using the conventional immersion nozzle (see the above-mentioned conventional technology 1), the inner pipe and the powder line of the immersion nozzle are not immersed in molten steel, inclusions in molten steel, mold powder. First, it is eroded by slag. When melted in this way, the shape of the immersion nozzle changes, and the molten steel flow in the mold is disturbed, causing a piece defect.

In addition to this "change in shape of the immersion nozzle", the immersion nozzle material reacts with the molten elements in the molten steel and / or the mold powder and slag to form low- and high-melting compounds that are formed during production. The thermal conductivity of the immersion nozzle changes. Due to this change in thermal conductivity, the amount of heat extracted from the molten steel through the immersion nozzle was not constant, and as a result, the formation of a solidified shell was not uniform, which caused fragment defects.

To solve these problems, conventionally, attempts Miteori improved by mold powder, as described above, a "fluorine-based mineral to control the heat removal amount Kasupidain _{_{(3CaO · 2Si0 2 · CaF 2}} ) crystals (See above-mentioned prior art 3). However, the fluorine component in the mold powder, on the contrary, promotes erosion of the powder line part, and at present it is not possible to obtain a sufficient effect.

There have also been attempts to apply mold powders that have no fluorine component or low fluorine component in order to suppress erosion of the powder line part (see the above-mentioned conventional technologies 3-1, 3-2). ), Conversely, heat removal could not be suppressed, and mold powder caused chip defects, and there was no complete solution. Therefore, in the continuous production of steel, various measures described above have been taken in order to produce clean steel, but these also do not exert a sufficient effect as described below. .

According to the above-mentioned prior art 2-1 “Technology in which inert gas is blown into molten steel from a nozzle to prevent the molten steel from contacting with the nozzle”, the amount of inert gas blown, the blow angle, the size of bubbles, etc. Needs to be controlled with high accuracy. If these are not controlled, the drift of the molten steel flow will instead occur, causing the molten steel flow to impinge on a part of the nozzle, causing local erosion and alumina adhesion.

In addition, mold powder and slag entrained in the molten steel filling the mold due to fluctuations in the molten metal level due to publishing are captured by the injected inert gas. However, if the inert gas flow is not properly controlled, the nozzle will be severely eroded. In this case, since the powder line and the mold powder do not necessarily come into contact with each other, the normal nozzle material portion including the nozzle discharge hole portion and the inner tube portion is eroded.

In addition, once the nozzle is eroded, the flow of inert gas blown out of the nozzle becomes more and more deflected, further contributing to erosion and / or alumina deposition of the nozzle. Then, the nozzle is melted and the steel is contaminated.

The conventional technology 2-2 "Immersion nozzle in which a refractory material made of spinel or a refractory material made of spinel and vericlase is disposed in a portion that comes into contact with molten steel" is a commonly used alumina-graphite nozzle. Thus, the erosion resistance to molten steel is better. Hereinafter, this point will be described in detail.

The present inventors have clarified that an alumina-graphite material generally used as an immersion nozzle material generally causes the following reaction with molten steel, and is an undesirable material for producing clean steel. That is, since the carbon concentration in molten steel is extremely low, the graphite (C (s): solid graphite) in the alumina-graphite nozzle material is

C (s) → C (1)

By the reaction of, it is rapidly dissolved in molten steel.

Further, in the alumina of the alumina-graphite nozzle material (A1 ₂ 0 _3),

F e (l) + 0 → (F e 0) Equation (2)

(F e O) penetrates by the reaction, and the dissolved element in the molten steel also penetrates similarly. For example, if M n is a dissolved element,

M n + O → (M n O) Equation (3)

(MnO) permeates alumina. (Note that 0 and Mn in equations (2) and (3) indicate oxygen and manganese dissolved in the molten steel, and Fe (l) indicates the iron component in the molten steel. )

Produced by penetration of these substances _{_{"Al 2 0 3 -FeO""}} Al 2 0 3 -MnO" is still more inclusions in the molten steel "" react with _{such, "FeO-MnO Al 2 0} 3 -FeO-MnO "liquid Generate lag. That is, the alumina is melted down by the combination of the two factors.

In addition, to increase spalling resistance, it is common practice to include fused silica in the alumina / graphite nozzle material. , Not desirable.

On the other hand, the permeation amount of (FeO) and (MnO) into the spinel is small, and the solid phase is maintained without generating a liquid phase even if inclusions such as FeO-MnO adhere. That is, there is little erosion of the nozzle in which the spinel is distributed at the part in contact with the molten steel, and therefore, the molten steel contamination is reduced.

However, arranging dissimilar materials in the part in contact with the molten steel, the main body and the powder line, leads to increased manufacturing costs. In addition, erosion of the immersion nozzle by powder slag is not improved by using a spinel material. This is due to the fluorine component in the powder slag.

Therefore, it is conceivable to eliminate the fluorine component or to use a low-fluorine component mold powder (Japanese Patent Publication No. 58-125349 disclosed in the above-mentioned prior art 3-1 and 3-2). JP-A-51-93728, JP-A-50-86423, JP-A-5-208250, JP-A-51-67227, JP-A-5-269560, JP-A-51-132113 See).

However, because these mold powders do not contain a fluorine component, or because they are low-fluorine component mold powders, viscosity control and crystallization temperature control are poor, and breakout of steel and cracking of steel frequently occur. At present, however, it has not been stable and has not been put to practical use.

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. In view of the above-mentioned problems of the prior art, the inventors of the present invention have stated that “specific mold powder (fluorine amount is less than 3% by weight and viscosity at 130 ° C. is not less than 4% by The following mold powder) ", and" The above specific mold powder, Specific immersion nozzle (Spinel and Z or spinel carbon are placed on part or all of the part of the immersion nozzle that comes into contact with molten steel, and powder line material is placed on the part that comes into contact with mold powder and z or slag. And a submerged nozzle in which the main body material is disposed at other locations) and a method for continuously producing steel ”(see JP-A-2001-113345).

As a result of further research after the above-mentioned developed invention, the present inventors have found that, by using the specific mold powder, surprisingly, it is not necessary to combine the specific immersion nozzle with the powder. Even when using an immersion nozzle composed of a refractory material mainly composed of alumina, including one line section, it is possible to produce clean steel with almost no erosion and no adherence of alumina. The inventors have found that the present invention can be performed and completed the present invention.

Therefore, an object of the present invention is to prevent contamination of steel due to refractories, to enable stable production of highly clean steel, and to use the same “alumina” as a main material from the viewpoint of manufacturing an immersion nozzle. Therefore, it is an object of the present invention to provide a method for continuously producing steel, which has an operational effect that can be produced extremely easily. Invention disclosure>

In order to solve the above problems and achieve the object, the inventors of the present invention have made intensive studies and, based on the above findings, have stated, "The molten steel is supplied into the mold by the immersion nozzle, and the mold powder is contained in the mold. In the method of continuous production while supplying the powder, the amount of fluorine is less than 3% by weight and 130.000. A continuous steel making method characterized by using a combination of an immersion nozzle made of a refractory material as a main material. " In the past, the "fluorine component" was inevitable for reducing the viscosity of the mold powder and controlling the heat removal. However, if a slag film with uniform properties and / or thickness is formed between the mold and the solidified shell, the fluorine component will be eliminated. The present inventors have found that there is no need to rely on the information. In other words, to increase the viscosity of the mold powder, it can realize uniform slag film, Kasupidain function _{_{(3CaO '2Si0 2' CaF 2}} ) play (unplug Heat control).

In addition, it was found that a continuous slag film could be produced and a continuous production was possible if the breaking strength at 130 ° C. was 3.7 g / cm ² or more. . The chemical composition of the mold powder used in the present _{_{invention, A 1 2 0 3: 5~2}} 5 _{wt%, S i 0 2: 2} 5~7 0 wt%, C a O: 1 0~5 0 wt %, Mg 0: 20% by weight or less, F: 0 to 2% by weight (inevitable impurities) are preferable.

Further, the immersion nozzle used in combination with the mold powder is an immersion nozzle composed of a refractory material mainly composed of alumina, specifically, an alumina-based refractory and / or an alumina-carbon type. Made of refractory. Further, the refractory material "silica (Si0 _2), silicon carbide (SiC), boron carbide (B ₄ C), silicon nitride (Si ₃ N _4), nitride § Ruminiumu (A1N), zirconium boride (ZrB ₂₎ , boride magnesium (Mg ₃ B _2), sulfuric acid di Rukoniumu (ZrS0 _4), silicon (Si), containing one or more selected from aluminum (A1) "can be used immersion nozzle I found something. Aluminum 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, All steel types such as titanium steel.

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

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

Reference numerals in the figure, 1 denotes the inner pipe of the immersion nozzle that comes into contact with the molten steel, 2 denotes the discharge port of the immersion nozzle that comes into contact with the molten steel, 3 denotes the line of the immersion nozzle that comes into contact with the mold powder, Is the main part of the immersion nozzle, 5 is the straight type immersion nozzle This is the tip of the nozzle that comes into contact with molten steel.

Hereinafter, an embodiment of the present invention will be described. As described above, the mold padder used in the present invention has a fluorine content of less than 3% by weight and a viscosity at 1300 ° C. of 4 to 100,000 boise. .

If the amount of fluorine in the mold powder is 3% by weight or more, the amount of erosion of the immersion nozzle, especially in the powder line, increases, and the refractory material that has flowed into the steel contaminates the molten steel to obtain clean steel. Can not.

In addition, if the viscosity of the mold powder (viscosity at 1300 ° C) is less than 4 voids, uneven flow of the mold powder will occur, and in the molten mold powder, such as dicalcium silicate and tricalcium silicate, etc. Undesirably, crystals develop and the temperature fluctuation of the molded copper plate increases, resulting in unstable heat removal. On the other hand, if the above viscosity is 10

If it exceeds 0000 vois, it is not preferable because melting becomes poor and slag bears are formed, and stable production cannot be performed.

In the present invention, the viscosity, for example, _{_{A 1 2 0 3, CaO /}} S i0 can adjust ₂ or the like, in the case when A 1 ₂ 0 ₃ is large and C a 0 / S i 0 ₂ is low The viscosity can be adjusted higher.

Further, the mold powder used in the present invention melts the mold powder, and cuts the mold powder droplets when the platinum cylinder having a diameter of 7 mm is pulled up at a constant speed in the platinum powder when it separates from the liquid surface. When the maximum load at time is defined as "the breaking strength of the molten mold powder", the breaking strength of the molten mold powder at 1300 ° C is preferably 3.7 g / cm ² or more. If the breaking strength is less than 3.7 g / cm ² , the liquid layer in the slag film tends to break, which is not preferable. The mold powder used in the present invention is composed of base materials such as portland cement, wollastonite, and synthetic calcium silicate, and S powders such as perlite and fly ash.

10 ₂ Raw materials, carbonates, glass powder, frit powders, etc. Na ₂₀ , K ₂₀ , Li ₂₀ raw materials, Magnesium carbonate salts, seawater MgO powder, MgO raw materials such Doromai preparative flour, borax, co Remanai doo, glass powder, B ₂ 0 ₃ material such as frit powder, co one box powder, scaly graphite, carbonaceous materials such as carbon black From. However, NaF, fluoride, such as CaF ₂ does not contain.

Specifically, by adding the above base material _{_{S i 0 2, Na 2 0}} , K 2 0, Li 2 0, MgO, respective materials of the B ₂ 0 ₃ and carbonaceous appropriate, and, as described above can be prepared by adjusting the viscosity, etc. _{_{a 1 2 0 3, C aO}} / S i0 2. For example, as a chemical composition, A 1 ₂ 0 _3: 5~25 wt%, S i 0 _2: 25~70 wt%, C aO: 10~ 50 _{wt%, Na 2 0, L i} 2 0 and K ₂ 0 comprising one or more compounds selected from the group: 3 to 20 wt%, MgO: 20 wt% or less, the fluorine component as inevitable impurities: 3 wt% or less, carbon: 0.5 to 8 wt consists%, and, CaO / 3:. 10 0. ₂ weight ratio 2 to 1 after mixing the adjusted respective raw materials of the above to be within a range of 5, to uniformly mixed in a mixer Is obtained.

In addition, a liquid (eg, water) and an organic binder or an inorganic binder are added as required, and the mixture is granulated by a method such as extrusion granulation, stirring granulation, tumbling granulation, fluidized granulation, or spray granulation. However, granules can also be used. Next, an embodiment relating to a material of an immersion nozzle used in combination with the mold powder will be described.

In the present invention, a material constituting the immersion nozzle is a refractory material mainly composed of alumina, and a preferred embodiment is an alumina-based refractory and / or an alumina-carbon refractory.

Moreover, the alumina-based refractories, alumina - carbon-based refractories, silica (Si0 _2), carbonization silicon (SiC), boron carbide (B ₄ C), silicon nitride (Si ₃ N _4), aluminum nitride (A1N ), zirconium boride (ZrB _2), magnesium boride (Mg ₃ B _2), it can also be used those containing one or more selected from zirconium sulfate (ZrS0 _4), thus A wide range of materials can be used.

In another preferred embodiment, silicon (Si), aluminum (A1) Contains one or more. By blending such a metal, the metal reacts with the refractory material and / or the components in the air, particularly in the powder line portion of the immersion nozzle, at a high temperature during use to generate a metal reactant. This metal reactant strengthens the powder line and contributes to improved durability. Further, if the powder line portion contains carbon, the metal also functions as an antioxidant for carbon. Thus, an excellent immersion nozzle can be provided by blending the above metal. The content of silicon (Si) and aluminum (A1) is preferably 0.1 to 15% by weight, and more preferably 1 to 8% by weight. If the content is less than 0.1% by weight, the above-mentioned effect of the metal cannot be obtained. If the content exceeds 15% by weight, a large amount of metal reactant is generated, so that the refractory structure due to the volume increase is produced. This leads to the destruction of steel and loss of the effect of the refractory material of the main aggregate, which is not preferable. In the present invention, the same material can be used for the powder line portion and the main body portion of the immersion nozzle. The reason for this is that the specific mold powder of the present invention (mold powder having a fluorine content of less than 3% by weight and a viscosity at 1300 ° C. of 4 to 1000 vise) is used. is there.

Hitherto, as a material having high erosion resistance to a fluorine component-containing mold powder, a zirconium / iron / carbon material has been mainly used. This material is more expensive than ordinary refractory materials, and even with this material, the powder line has a large amount of erosion, which may be a factor in determining the life of the immersion nozzle.

However, according to the present invention, by using a high-viscosity mold powder containing little or no fluorine component, almost no or no erosion due to the fluorine component is eliminated. The material does not need to be used for the powder line part, and the above-mentioned material (a fire-resistant material mainly composed of alumina) can be arbitrarily used for the powder line part. As a result, the same material as the main body part is used. Now you can do it. <Example>

Next, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Here, the structure of an immersion nozzle that can be used in the following examples and comparative examples will be described with reference to FIGS. 1 to 3. FIG. 1 is a diagram showing an example of an immersion nozzle structure having a discharge port, and FIG. 2 is a diagram showing 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 that has a discharge port. In Fig. 1, 1 is the inner tube of the immersion nozzle that comes into contact with molten steel, and 2 is the immersion nozzle that also contacts the molten steel. The discharge port portion 3 is a powder line portion that comes into contact with the mold powder and / or slag, and the reference numeral 4 is a main portion of the immersion nozzle.

As shown in Fig. 1, this immersion nozzle is a immersion nozzle having a structure in which the discharge port 2a of the immersion nozzle that comes into contact with the molten steel has the body 4 and the discharge port 2 integrated integrally.

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 does not have an integrated structure as shown in Fig. 1 (see "Part 2a" in Fig. 1), and as shown in Fig. 2, the discharge port 2b of the immersion nozzle that comes into contact with molten steel. This is an immersion nozzle having a structure in which the portion of the nozzle is formed as a discharge port 2 made of the same material. 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.

Unlike the immersion nozzles shown in FIGS. 1 and 2, the immersion nozzle shown in FIG. 3 is a straight type immersion nozzle having no discharge port. Reference numeral 5 in FIG. 3 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, and 4 is a main body portion. Table 1 shows the chemical composition of the mold powder (sample numbers 1 to 7) used in the following examples, and Table 2 shows the chemical composition of the mold powder for comparison (sample numbers 8 to 21). Shown in Tables 1 and 2 also show the “fluorine component”, “viscosity (at 1300 ° C), and“ breaking strength (at 1300 ° C) ”of each mold powder.

Note that the mold powders of Sample Nos. 1 to 7, 8 to 10 and 13 to 17 in Tables 1 and 2 were obtained by mixing powders having a predetermined chemical composition ratio using a mixer. Goods ". For the mold powders of sample numbers 11, 12 and 18 to 21 other than the above, after mixing the raw material powder, a solution consisting of 90% by weight of water and 10% by weight of sodium silicate was mixed with 20 to 30% by weight. It is a "granule" obtained by adding the slurry to produce a slurry, spray-granulating the slurry, and drying the slurry, which is finally prepared to have a predetermined chemical composition.

0

Table 1 Chemical composition of mold powder used in Examples

O

d

Sample number 1 2 3 4 5 6 7

O C

Mo SiO _z 36 39 50 49 48 31 31

I of _{_{Al 2 0 3 7 21 10 10}} 18 7 7 Le Science CaO 36 35 20 19 16 43 43 de sets MgO 4 1 10 10 8 6 8 Pas forming _{_{Na 2 0 + Li 2 0 +}} K 2 0 5 2 6 8 6 8 6 ゥ MnO + BaO + SrO + B ₂ 0 ₃ 8 0 1 1 1 0 0 Data I fm F 1 0 0 0 0 2 2

% Total carbon 3 2 3 3 3 3 3

CaO / SiO _z (weight ratio) 1.00 0.90 0.33 1.40 1.40

'Fluorine component (% by weight) 100 0 0 0 2 2

-Viscosity (at1300 ° C) (Boys) 30 20 40 50 100 5 5

-Breaking strength (at 1300 ° C) (g / cm ^Z ) 5 8 10 3.7 5 6 5

Table 2 (Part 1) Chemical composition of comparative mold powder

Table 2 (Part 2) of the comparative mold powder having the chemical composition Sample No. 15 16 17 18 19 20 21 Mo _{Si0 2 30 30 29 27 26 25} 22

Al ₂ 0 ₃ 10 7 5 9 8 7 4 Iodine Al CaO 34 36 38 40 42 42 38 D group MgO 6 8 3 5 5 0 8 Na ₂ 0 + Li ₂ 0 + K ₂ 0 8 6 10 3 2 5 6 Ϊ Ϊ Tongue MnO + BaO + SrO + B ₂ 0 ₃ 0 0 0 0 0 0 0

I amount F 9 10 11 13 15 18 19

% Total carbon 3 3 4 3 2 3 3

CaO Si0 ₂ (weight ratio) 1.12 1.20 1.30 1.50 1.60 1.65 1.70

'Fluorine component (% by weight) 9 10 11 13 15 18 19

-Viscosity (at1300 ° C) (Boys) 1.8 1.3 1.0 0.9 0.8 0.3 0.2

-Breaking strength (at ¹ 300 ° C) (g / cm ² ) 2.7 2.4 2.8 1.3 1.5 0.7 0.5 (Examples 1 to 17, Comparative Examples 1 to 6)

Examples 1 to 17 are shown in Tables 3 and 4, and Comparative Examples 1 to 6 are shown in Table 5.

In each of the following Examples 1 to 17 and Comparative Examples 1 to 6, molten steel (“steel type” in the table) was supplied into a mold by a nozzle, and The continuous production was performed while supplying mold powder to the plant. The structure of the nozzle used in each example is indicated 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 Sample Nos. 1 to 21 in Tables 1 and 2 above. The sample numbers are shown in the table, and the mold powder used was used. Only the "fluorine component", "viscosity (at 1300 ° C)" and "breaking strength (at 1300 ° C)" of "No. of materials for each nozzle site" in the table indicate "% by weight". In each example, “stable structure”, “nozzle erosion amount or alumina adhesion amount (each erosion amount of inner tube, discharge port inside, powder line)”, “steel cleanliness” and “steel defect rate” are as follows. Table 3 to Table 5 show the evaluation results.

• Evaluation of stable structure

"Stable structure" indicates whether a stable structure is possible or not. During the fabrication, a BO prediction warning [A system that predicts the occurrence of B.O. (break fault) by continuous measurement of the mold surface temperature. No evaluation method when using a stem]

The case where no [accidental breakage of the immersion nozzle during fabrication due to erosion of the powder line and / or the molten steel contact area] did not occur was judged as "OK", and the others were judged as "No".

• Evaluation of nozzle erosion volume

"Nozzle erosion amount [mm / (steel ton)]" is shown as nozzle erosion size per ton of forged volume. The greater the amount of nozzle erosion, the shorter the life of the nozzle, and the more impurities that are eroded into the steel, thus contaminating the steel.

• Alumina adhesion amount

Indicates the amount of alumina adhered when aluminum killed steel was produced. Alumina adheres to the inner tube of the nozzle and / or the inside of the discharge port. Stable structure becomes impossible. In some cases, molten steel stops flowing through the nozzle, and 铸 the production stops. Therefore, it can be said that the nozzle is so good that no alumina adheres.

• Evaluation of steel cleaning degree

"Steel cleanliness" was evaluated based on the degree of sliver scratch. 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 slipper flaw.

• Evaluation of steel defect rate

"Steel defect rate" was evaluated by surface cracking. "〇" indicates that the surface cracking was negligible, "χ" indicates that the steel did not turn into a product due to surface cracking, and "△" indicates that the steel surface could be processed into a product.

Table 3 (Part 1) Examples 1 to 5

Example

1 ■ oo Λ ■ + Ό Nozzle part material S (Fig. 1) (Fig. 2) (Fig. 1) (Fig. 2) (Fig. 1) Inner pipe part Al ₂ 0 ₃ 80 70 90 60 65

C 20 30 10 30 30

Si0 ₂ 0 0 0 10 5 Additive type

Amount of added calories

No

Discharge port Al ₂ 0 ₃ 80 70 90 60 65 size C 20 30 10 30 30

Si 0 ₂ 0 0 0 10 5

Additive amount

Powder Al ₂ 0 ₃ 80 70 90 60 65 Line section C 20 30 10 30 30 and SiO _z 0 0 0 10 5 Main body Additive type

Additive amount

Sample No. [5] [1] [7] [4] [1] MOPA

Fluorine component (wt%) 0 1 2 0 1

¹ヮ

Ruda

Viscosity (at1300 ° C) (Boys) 100 30 5 50 30 r 1

Breaking strength (at 1300 ° C) (g / cm ² ) 5.0 5.0 5.0 3.7 5.0 Aluminum Aluminum Aluminum Aluminum Aluminum Aluminum

Killed Killed Killed Killed Killed Stable structure Available Available Available Available Available Available Nozzle erosion amount Inner tube 0 0 0 0 0 Evaluation or inside discharge outlet 0 0 0 0 0 valent Alumina adhered powder line 0 0 0 0 0 Steel cleanliness 100 100 100 100 100 Steel defect rate 〇〇〇〇 o

Table 5 Comparative Example "! ~ 6

Comparative example

I n

Ό Ό

Nozzle part Material structure (Fig. 1) (Fig. 2) (Fig. 2) (Fig. 2) (Fig. 2) (Fig. 1) Inner pipe Al ₂ 0 ₃ 100 100 100 70 80 80 100

C 30 20

Si0 ₂

Additive type

Additive amount

No

Discharge port Al ₂ 0 ₃ 100 70 90 70 80 100 Size C 30 10 30 20

SiO _z

種類 Additive type ― ― ― ― ― ― Amount of additive

Powder Al ₂ 0 ₃ 100 70 90 60 70 50 Line section C 30 10 20 20 20 and Si0 ₂ ― ― ― 10 Main body Additive type ZrU ₂ Zr (J2 additive amount 20 30 Sample No. [8] [10] [12 ] [20] [13] [11] Mono <<

1 _rt Fluorine component (% by weight) 5 8 12 18 8 10 1

Ruda

1 Viscosity (at 1300 ° C) (Voize) 2 1.5 1.2 0.3 2.0 0.5 U 1

Breaking strength (at 1300 ° C) (g / cm ² ) 3.5 3.2 2.5 0.7 3.0 1.0 Electromagnetic Ca treated steel ^ Aluminum stainless steel 间 Steel grade

Steel plate Steel code Killless steel Raw steel Stable structure No No No No No No.Nozzle erosion amount Inner tube 0.02 0.03 0.04 0.01 0.05 0.02 Evaluation or inside discharge port 0.07 0.05 0.08 0.04 0.09 0.03 value 0.60 0.40 Steel cleanliness 30 40 30 50 20 40 Steel defect rate XXXXXX As is clear from Tables 3 to 5, by using the mold powder specified in the present invention, the inner pipe, the discharge port, the powder line, and the main body are all made of an alumina-carbon refractory nozzle. (Examples 1 to 11), or using an immersion nozzle made of an alumina-based refractory (Example 12), that is, using a refractory of the same quality, The evaluations were all "OK", indicating that a stable structure was possible. Further, as can be seen from Examples 1 to 17, it was also found that a stable structure could be similarly obtained by using the same material for both the powder line portion and the main body portion.

Further, "nozzle erosion amount or alumina adhesion" is all "0", "steel purity" is "100", and "steel defect rate" is all "〇". The surface cracks of the steel were negligible.

On the other hand, in Comparative Examples 1 to 6 in which the mold powder specified in the present invention was not used, as is clear from Table 5, “stable structure” was “No”, and Construction was impossible. In addition, "nozzle erosion amount", "steel cleanliness" and "steel defect rate" were also inferior. Further, even if the material of the inner tube member is the same as that of the embodiment, it is inferior. This is because a flow in a direction opposite to the flow direction of the molten steel is simultaneously generated during the production. As a result, the powder comes into contact with the inner pipe part due to the backflow, causing erosion and the like, resulting in inferior results as shown in Table 5. Comparing the evaluation results of Comparative Examples 1 to 6 with the evaluation results of Examples 1 to 17 of the present invention, the use of the mold powder specified in the present invention enables a stable structure for the first time. Also, it was found that the nozzle life was improved because the nozzle was extremely low in erosion. Furthermore, it was found that almost no slipper flaws were observed, and that the surface cracks of the steel were negligible.

The immersion nozzles of FIGS. 1 and 2 used in Examples 1 to 17 (the immersion nozzles of FIG. 3 can be used naturally) and the mold powder shown in Table 1 of the present invention This is an example shown as an example, and the present invention is not limited to these contents, and various combinations can be used within the scope of matters specifying the invention. <Industrial applicability>

As described in detail above, the present invention relates to a continuous steel pipe using a combination of a mold powder in which a fluorine component having high erosion properties is substantially absent and a dipping nozzle composed of a refractory material mainly composed of alumina. It is characterized by a fabrication method.

This prevents impurities due to the refractory raw material from entering the molten steel, and suppresses the adhesion of alumina in the nozzle, thereby enabling a stable structure and obtaining ultra-clean steel. In addition, remarkable effects such as remarkable improvement in refractory-related defects due to drastic reduction of refractory defects.

In addition, the immersion nozzle used in the present invention has almost no erosion, so that the nozzle life can be improved, and high performance and low cost can be achieved by thinning and weight reduction. Combined with the specified mold powder, 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 It can be applied to all types of steel, such as high titanium steel, and has an extremely high industrial value.

Furthermore, from the viewpoint of the production of the immersion nozzle, since the same “refractory material mainly composed of alumina” is used, there is an advantage that it can be manufactured extremely easily.

Claims

The scope of the claims

1. In a method of supplying molten steel into a mold by an immersion nozzle and continuously molding while supplying mold powder into the mold,

It is characterized by using a combination of a mold powder with a fluorine content of less than 3% by weight and a viscosity at 1300 ° C of 4 to 100,000 boil and an immersion nozzle composed of a refractory material mainly composed of alumina. Continuous steel making method.

2. The method for continuously producing steel 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 mold powder, chemical composition, A 1 ₂ 0 _3: 5~25 wt%, S i 0 _2: 25~70 wt%, C aO-: 10 to 50 wt%, MgO: 20 wt% or less, 3. The method for continuously producing steel according to claim 1 or 2, wherein F is in the range of 0 to 2% by weight (inevitable impurities).

4. The method for continuously producing steel according to claim 1, wherein the refractory material mainly composed of alumina is composed of an alumina-based refractory and / or an alumina-carbon-based refractory.

5. The alumina-based refractory and / or alumina - carbon-based refractory, shea silica (Si0 _2), silicon carbide (SiC), boron carbide (B ₄ C), silicon nitride (Si ₃ N _4), aluminum nitride two © beam (A1N), zirconium boride (ZrB _2), boride magnesium (Mg ₃ B _2), sulfuric acid zirconyl two © beam (ZrS0 _4), silicon (Si), 1 kind selected from aluminum (A1) 5. The method for continuously producing steel according to claim 4, wherein the steel comprises two or more types.

6. 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 6. The method for continuously producing steel according to claim 1, wherein steel, steel cord, case hardened steel, or high titanium steel is used.