JPH11320047A - Immersion nozzle for continuously casting steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the resistance to the sticking of Al2 O3 , the erosion resistance and the spalling resistance of a nozzle by constituting the whole nozzle or the whole part or a part of the inner hole part of the nozzle coming in contact with molten steel of a refractory containing the specific contents of spinel, periclase, graphite and inevitable impurities. SOLUTION: A spinel-periclase-graphite base refractory used to the whole body or a part of a nozzle is made to contain 50-95 wt.% spinel, 0-20 wt.% periclase, 5-30 wt.% graphite and <=3 wt.% inevitable impurities. In the case of using this refractory to the inner hole part of the nozzle, there is a method in which a raw material compound of the refractory constituting the inner hole part and a raw material compound of the refractory constituting the nozzle main body, are simultaneously press-formed into a prescribed nozzle shape or a method in which a compound kneading a refractory raw material for forming the refractory constituting the inner hole part is poured into the nozzle main body formed in advance and after forming, drying or burning is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an immersion nozzle for continuous casting of steel, and more particularly to an immersion nozzle for continuous casting of steel which suppresses blockage of the nozzle and has spalling resistance and erosion resistance. It is.

[0002]

In continuous casting of the Prior Art steel, conventionally, A1 ₂ O ₃ -SiO ₂ -C quality nozzles having excellent spalling resistance is most widely used. However, this material nozzle
When used in the casting of Al-killed steel, the problem of nozzle clogging due to deposition of A1 ₂ 0 ₃ inclusions in the molten steel occurs. On the other hand, when it is used for casting high oxygen content steel, high Mn content steel, stainless steel, or the like, there is a problem of nozzle erosion.

[0003] Clogging and melting of the nozzle not only causes a reduction in the service life of the refractory, but also hinders the steelmaking operation and adversely affects the quality of the steel material. Therefore, there is an urgent need to develop a nozzle for continuous casting of steel that has both blockage resistance and erosion resistance.

In such a situation, Japanese Patent Laid-Open Publication No.
No. 8 discloses that a) containing at least 90% by weight of A1 ₂ O ₃ and b) containing 9% of MgO.
A nozzle is disclosed in which one or more carbonless materials containing 90 wt% or more of ZrO ₂ and containing 90 wt% or more of ZrO ₂ are interpolated and used as a cylindrical sleeve.

[0005] Further, in order to reduce the clogging of the nozzle, the inner body of the immersion nozzle has a carbon or SiO ₂ content of less than 1% by weight, spinel of 1 to 40% by weight, and MgO of 0.5.
15 wt%, the remainder may be used refractory materials which are A1 ₂ O _3, it has been proposed in JP-A-5-237610.

[0006]

The main mechanism of clogging of the A1 ₂ O ₃ —SiO ₂ —C nozzle in the casting of Al-killed steel is considered as follows. First, in a refractory at a high temperature, a reaction of the formula (1) occurs between SiO ₂ and C used as a refractory raw material. And the generated SiO
(Gas, hereinafter referred to as “(g)”) and CO (g) diffuse to the interface between the nozzle and the molten steel, and Al in the molten steel and the formula (2)
The reaction of equation (3) is caused to generate a mesh-like A1 ₂ O ₃ layer on the operating surface of the nozzle. Since Organizationally very coarse mesh-like A1 ₂ O ₃ layer, A1 ₂ O ₃ inclusions in the molten steel-colliding thereon
It becomes easy to adhere. When the adhesion of A1 ₂ O ₃ inclusions progresses,
Blockage of the nozzle proceeds. SiO ₂ (s) + C (s) → SiO (g) + CO (g) (1) 3SiO (g) + 2 Al → A1 ₂ O ₃ (s) + 3 Si (2) 3 CO (g) + 2 Al → A1 ₂ O ₃ (s) + 3C (3) In the above formula, (s) represents a solid phase, (g) represents a gas phase, and Al , Si , and C represent Al , Si in a molten state in molten steel. And C respectively.

[0007] On the other hand, regarding the erosion mechanism of the A1 ₂ O ₃ -SiO ₂ -C nozzle in the casting of high oxygen content steel, high Mn content steel, stainless steel, etc., the following is clear from the study by the present inventors. Became. First, carbon in the refractory running surface is dissolved in the molten steel, i.e., C (s) → C ( 4) running surface is A1 ₂ O ₃ -SiO ₂ based oxides. After that, Mn, O, and Fe in the molten steel permeate the working surface in a state of MnO and FeO, that is, Mn + O → (MnO) (5) Fe (l) + O → (FeO) (6) In the above, (l) represents a liquid phase, and Mn represents Mn in a molten state in molten steel. Furthermore, MnO-FeO-based inclusions in the molten steel collide with and adhere to the working surface. MnO, which has been infiltrated with the two causes, FeO reacts with working surface in A1 ₂ O ₃ and SiO _2, and generates an _{A1 2 O 3 -SiO 2 -MnO-} FeO based liquid slag. When the slag is washed away in the flow of molten steel, refractory erosion occurs.

However, Japanese Patent Application Laid-Open No. 3-243258 or
The nozzle proposed in -237610 has the following problems. 1) Insertion or inner bore of nozzle in contact with molten steel
Since iO ₂ and graphite are hardly contained, when casting an Al-killed steel, the reaction of the formulas (1) to (3) is used to form a net-like A1 ₂ O
_It does not form _three layers and has some effect on suppressing nozzle blockage, but it is not so effective. It is usually porosity present in a few percent or more + in the refractory, the although the tissue is relatively dense than mesh A1 ₂ O ₃ layer, since too rough, in the molten steel on the working surface This is because it is unavoidable that A1 ₂ O ₃ inclusions are quickly attached. 2) On the other hand, if a dense material such as a ceramic having a porosity of several percent or less is used as the interpolating body or the inner body, the spalling resistance decreases, and the preheating or the in-use nozzle is cracked. There is fear. 3) When casting steel types such as high oxygen content steel, high Mn content steel and stainless steel, free A1 ₂ O in refractory
_In the presence of ₃ or ZrO ₂ , the refractory is eroded.

[0009] The present invention has been made in view of the above problems, and an object of the present invention is to provide a steel having both A1 ₂ O ₃ adhesion resistance, erosion resistance and spalling resistance. An object of the present invention is to provide an immersion nozzle for continuous casting.

[0010]

Means for Solving the Problems Accordingly, the present inventors have:
The present inventors have conducted research on various refractories and, in particular, have investigated and studied spinel-periclase-graphite-based refractories. As a result, they have found the following and completed the present invention.

That is, at a high temperature, the following reaction occurs between MgO or periclase in the spinel and graphite in the spinel-periclase-graphite refractory. MgO (s) + C (s) → Mg (g) + CO (g) (7) The generated Mg gas and CO gas diffuse to the interface between the refractory and the molten steel, where the refractory is generated by one of the following two reactions. A dense MgO layer is formed on the surface of the object. Reaction 1: Reaction between Mg gas and dissolved oxygen ( O 2 ) in molten steel, ie, Mg (g) + O → MgO (s) (8) Reaction 2: Reaction between Mg gas and CO gas, ie, Mg ( g) + CO (g) → MgO (s) + C (9) When this MgO layer is generated, when casting Al killed,
Due to the reactions as shown in the equations (1) to (3), a net-like A1 ₂ O ₃ layer is not generated on the operation side. Further, since the porosity of this MgO layer is close to zero and is very dense in terms of structure, the possibility that the A1 ₂ O ₃ inclusions in the molten steel impinge and adhere thereon is very small. That is, nozzle blockage due to the adhesion of A1 ₂ O ₃ inclusions is suppressed.

Further, this dense MgO layer suppresses erosion of the nozzle due to molten steel when casting steel types such as high oxygen content steel, high Mn content steel and stainless steel. The mechanism is considered as follows. 1) The reactivity between MgO and molten steel is low.
FeO hardly penetrates. 2) Since the solidus temperature of the MgO-spinel binary system is very high at 2000 ° C or higher, a liquid slag phase does not occur even if MnO and FeO penetrate and enter. 3) Since the MgO layer is dense, MnO-FeO-based inclusions in the molten steel cannot enter the inside of the nozzle.

The reactions of the formulas (7) to (9) are carried out
If an O layer is formed and the partial pressure of CO in the refractory increases, it will not proceed. At that time, the generated MgO layer has a thickness of only several
Because it is 0 μm, it does not adversely affect the spalling resistance of the nozzle.

Based on the above findings, the immersion nozzle for continuous casting of steel of the present invention has been completed. That is,
The immersion nozzle for continuous casting of steel according to the present invention is described as follows. In the immersion nozzle for continuous casting of steel, all or a part of the inner hole of the nozzle or the inner hole portion of the nozzle in contact with molten steel is spinel 5.
0 to 95% by weight, periclase 0 to 20% by weight, graphite 5 to 30
Weight of unavoidable impurities: 3% by weight or less Spinel-periclase-graphite type refractory nozzle for continuous casting of steel "(Claim 1) It is assumed that.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The immersion nozzle for continuous casting of steel according to the present invention is characterized in that at least a part of the inner hole of the nozzle in contact with molten steel has spinel.
50 to 95% by weight, periclase 0 to 20% by weight, graphite 5 to
It is characterized by being a spinel-periclase-graphite refractory with 30% by weight and unavoidable impurities of 3% by weight or less.

Here, if the graphite in the spinel-periclase-graphite refractory is 5% by weight or less, the spalling resistance of the nozzle is poor, and the nozzle may be cracked during preheating or use. Also, if the graphite is 30% by weight or more,
Even if an MgO layer is formed on the operating surface according to equations (7) to (9),
Poor bonding between the layer and the body makes it easier for the MgO layer to peel off from the body, and consequently does not have the required function.

On the other hand, if the periclase exceeds 20% by weight or the spinel exceeds 95% by weight, the spalling resistance of the nozzle similarly deteriorates. If the spinel content is less than 50% by weight, the ratio of periclase and graphite exceeds the required range, so that the formed MgO layer may be peeled off from the main body or the spalling resistance of the nozzle may be deteriorated.

Examples of the component of the spinel over peri clay Sioux used to refractory graphite A1 ₂ O _3, without the free A1 ₂ O ₃ containing materials, spinel (MgO · A1 ₂ O ₃₎ the use of raw material Is desirable. The use of free A1 ₂ O ₃ -containing raw material causes a spinel-forming reaction between A1 ₂ O ₃ and periclase inside the hot nozzle. Along with this reaction, the local part of the nozzle may expand or contract in some places, and the nozzle may be broken.

When a practical refractory raw material is used as the refractory raw material for the spinel-periclase-graphite refractory, unavoidable impurities may be present. Such inevitable impurities are preferably suppressed to 3% by weight or less. If it exceeds 3% by weight, (7) ~
A dense MgO layer cannot be formed by the reaction of the formula (9), and the nozzle is clogged or melted.

In the immersion nozzle for continuous casting of steel of the present invention, the above-mentioned spinel-periclase-graphite type refractory may be used for the entire nozzle, or if necessary, a local portion of the nozzle, for example, molten steel. May be used in the inner hole of the nozzle in contact with the nozzle. However, when the above-mentioned spinel-periclase-graphite refractory is used for at least a part of the portion around the discharge port of the inner hole, the other portion of the inner hole of the nozzle in contact with the molten steel is made of spinel. No refractory based on spinel or periclace.

In the production of the immersion nozzle for continuous casting of steel according to the present invention, the spinel-periclase-graphite-based refractory is used for the inner hole of the nozzle. A method in which the raw material composition of the periclase-graphite-based refractory and the raw material composition of the refractory constituting the nozzle body are simultaneously pressed and molded into a predetermined nozzle shape (simultaneous molding method). After casting or press-fitting a mixture obtained by kneading a mixture of refractory raw materials forming the spinel-periclase-graphite-based refractory constituting the inner hole portion of the nozzle body, drying and, in some cases, firing, Manufacturing method (interior method).

In the case of simultaneous molding, a raw material composition of a refractory constituting the nozzle body such as A1 ₂ O ₃ —SiO ₂ —C obtained by kneading a phenol resin or a polysaccharide as a vinegar and an inner hole portion. The refractory raw material composition of the present invention can be manufactured by filling a predetermined position in a mold, molding by CIP or the like, drying, and then forming an unfired product or firing. In addition,
The refractory constituting the nozzle body and the refractory of the present invention constituting the inner hole are preferably kneaded with the same kind of binder.

In the case of the interior method, a kneaded raw material mixture is poured into a nozzle body prepared in advance by a conventional method using a binder similar to the body or a binder such as silicate or phosphate, or is subjected to press molding. After that, it can be dried and, if necessary, fired to produce. However, in a method of inserting and loading an interior part separately formed by pressure molding, pouring or press-fitting into a nozzle body previously prepared by a conventional method, the nozzle body is adapted to the refractory constituting the nozzle body (adhesion stability). ) Is not preferred. In particular, since the refractory constituting the inner hole portion of the present invention is composed of the spinel-periclase-graphite-based refractory, the main body has an A1 ₂ O ₃ -C or A1 ₂ O ₃ -SiO ₂ -C refractory. The above-mentioned simultaneous molding method or interior method is preferable in order to increase the expandability and maintain the adhesiveness stably when heated to a high temperature during use.

Similarly, the refractory constituting the inner hole portion and the refractory of the main body are more familiar when kneaded with the same kind of binder as described above, and the adhesiveness can be stabilized. As for the particle size of the starting material composition for forming the refractory material of the present invention, the particle size ratio of 1 mm or less and 0.5 mm or less is preferably 60% by weight or more. Otherwise, the particle size of the raw material is too large, and the refractory structure may be embrittled during use or the particles may fall off. In particular, when performing simultaneous molding, the moldability is often poor and a satisfactory molded body cannot be obtained.

[0025] ZrO ₂
A refractory having a conventional composition such as a -C refractory can be disposed. The refractory material constituting the nozzle body, can be used conventionally used in which A1 ₂ O ₃ -SiO ₂ -C refractories materials appropriately. A1 ₂ O ₃ —SiO ₂ —C refractory material having a conventional composition can be used. For example, A1 ₂ O
₃ 30 to 90 wt%, SiO ₂ 0 to 35 wt%, it is possible to use those having a composition of C 1O～35 wt%. Also, ZrO ₂
For C-based refractories, when CaO-stabilized ZrO ₂ is used, for example, ZrO ₂ 66 to 88% by weight, CaO 2 to 4% by weight and
Those having a composition of C1O to 30% by weight can be used. As a material for ZrO ₂ , CaO-stabilized ZrO ₂ is generally widely used. In addition, MgO-stabilized ZrO ₂ and Y ₂ O ₃
Stabilized ZrO ₂ , badderite or the like can be used.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and the "items specifying the present invention".
Can be appropriately changed and modified within the range described above.

(First Embodiment) FIG. 1 is a view showing a first embodiment of a nozzle according to the present invention (distribution pattern 1). Periclase-graphite refractory (50-95% by weight spinel,
Periclase 0-20% by weight, graphite 5-30% by weight, unavoidable impurities 3% by weight or less).

(Second Embodiment) FIG. 2 is a view showing a second embodiment of the nozzle according to the present invention (distribution pattern 2). Reference numeral 21 denotes the spinel-periclase-graphite system. The inner hole part made of a refractory is shown. 22 is Al ₂ O ₃ -S
Shows the nozzle body composed of iO ₂ -C refractory, 23 is
It shows a powder line portion composed of a ZrO ₂ -C refractory.

(Third Embodiment) FIG. 3 is a view showing a nozzle according to a third embodiment of the present invention (distribution pattern 3). Reference numeral 31 denotes the spinel-periclase-graphite system. 2 shows a portion around a discharge port in an inner hole portion made of a refractory. 32 shows the nozzle body consists of Al ₂ O ₃ -SiO ₂ -C refractory material, 33 shows a powder line portion constituted by the ZrO ₂ -C refractory material.

(Fourth Embodiment) FIG. 4 is a view (distribution pattern 4) showing a fourth embodiment of the nozzle of the present invention, wherein reference numeral 41 denotes the spinel-periclase-graphite system. 2 shows an inner hole made of a refractory. 42 is Al ₂ O ₃
Shows the nozzle body constructed in -SiO ₂ -C refractory material, 43
Indicates a powder line portion composed of a ZrO ₂ -C refractory.

In order to further clarify the present invention,
The distribution pattern for comparison is shown below. Figures 5 and 6
Is a view showing distribution patterns 5 and 6 different from distribution patterns 1 to 4 in the first to fourth embodiments of the nozzle of the present invention, wherein 52 and 62 are Al ₂ O ₃ —SiO ₂ -Nozzle body composed of a -C refractory, and 53 and 63 are ZrO2-C
It shows a powder line portion made of a refractory material. Reference numeral 61 denotes an inner hole made of a high-purity alumina refractory.

[0032]

Next, examples of the present invention will be described together with comparative examples.
The invention will be specifically described. [Examples 1 to 5] FIG.
The ones shown were used. The powder line section 23 is made of ZrO_Two−
C-based refractories (80% by weight of CaO stabilized ZrO, 20% by weight of graphite)
The nozzle body 22 is composed of a common A1_TwoO_Three−SiO_Two−C system resistant
Fire (SiO_Two 25% by weight, C 28% by weight, The rest is A1_TwoO_Three)so
Configured. The above-mentioned spinel
A periclase-graphite system was used. Table 1 shows the raw material composition.
Show. The thickness of the refractory of the inner hole 21 is 8 mm.
You.

[0033]

[Table 1]

[Comparative Example 1] The material distribution pattern of the nozzle shown in FIG. 5 was used. Powder line section 53
Is a ZrO ₂ -C refractory (CaO stabilized ZrO 80% by weight, graphite 20
% By weight), and the nozzle body 52 is made of a common A1 ₂ O ₃ -S
It was composed of an iO ₂ -C refractory (SiO ₂ 25% by weight, C 28% by weight, the rest being A1 ₂ O ₃ ).

Comparative Example 2 A nozzle material distribution pattern
Then, the one shown in FIG. 6 was used. Powder line section 63
Is ZrO_Two-C refractory (80% by weight of CaO stabilized ZrO, graphite
 20% by weight), and the nozzle main body 62 is a common A1_TwoO_Three
−SiO_Two-C refractory (SiO_Two 25% by weight, C 28% by weight, remaining
Riha A1_TwoO_Three). High as refractory for inner hole 61
Purity A1_TwoO_Three(Thickness: 8 mm) was used.

In order to evaluate the effect of the nozzle of the present invention, an actual machine test was performed. [Test 1] This test is a low-carbon Al-killed steel [Composition (% by weight) is C: 0.08, Si: 0.03, Mn: 0.2, P: 0.01,
S: 0.01, Al: 0.05, O: 0.003] is a test when casting. The casting temperature was 1580 ° C. and the casting time was 250 minutes. Result of the test, whereas the thickness respective working surface of the nozzle of Comparative Example 1 and Comparative Example 2 is 12 mm, there is A1 ₂ O ₃ deposition layer of 15 mm, the nozzle of Examples 1 to 5 are all
A1 ₂ O ₃ deposition layer is only 2-4 mm, it was observed significant A1 ₂ O ₃ deposition reducing effect. In addition, there was no cracking or falling off of the nozzle, and the operation was safe. However, when the nozzle of Comparative Example 2 was used, one of the four nozzles broke during use.

[Test 2] In this test, a high oxygen content steel [composition (% by weight) is C: 0.003, Si: 0.002, Mn: 0.
3, P: 0.01, S: 0.01, Al: 0.001 ppm, O: 0.06]. The casting temperature was 1560 ° C. and the casting time was 230 minutes. As a result of the test, the maximum damage thickness of the inner pipe was determined by the nozzles of Comparative Examples 1 and 2 respectively.
In contrast to 8 mm and 11 mm, the nozzles of Examples 1 to 5 were only 1 to 3 mm, and the nozzle erosion was remarkably small. Also in this case, the nozzle could be safely operated without any cracking or falling off of the nozzle.

[Test 3] In this test, a high Mn-containing steel [composition (% by weight) was C: 0.04, Si: 0.02, Mn: 1.5, P:
0.01, S: 0.01, O: 0.01]. As a result of the test, the maximum damage thickness of the inner tube after casting at 1560 ° C. for 210 minutes was 10 mm and 13 mm for the nozzles of Comparative Examples 1 and 2, respectively, whereas the nozzles of Examples 1 to 5 were Each was only 1 to 4 mm, and the erosion of the nozzle was much reduced. In addition, there was no cracking or falling off of the nozzle.

[Test 4] This test was conducted on stainless steel [Composition (% by weight): C: 0.05, Si: 0.5, Mn: 1.0, P:
0.04, S: 0.02, Ni: 8.0, Cr: 18.0, O: 0.005]. Test result, 1550 ℃ 26
The maximum damage thickness of the inner tube after casting for 0 minutes is 8 mm and 9 mm for the nozzles of Comparative Examples 1 and 2, respectively, while the nozzles of Examples 1 to 5 are only 0.5 to 9 mm. It was 2 mm, which greatly reduced nozzle erosion. In addition, there was no cracking or falling off of the nozzle.

[Test 5] This test was performed on Ca-treated steel [Composition (% by weight) was C: 0.05, Si: 0.3, Mn: 0.8, P: 0.0]
1, S: 0.01, Al: 0.02, Ca: 0.003, O: 0.002]. Tested at 1580 ° C
The maximum damage thickness of the inner tube after casting for 200 minutes is Comparative Example 1.
The nozzles of Examples 1 to 5 were only 2 mm, whereas the nozzles of Comparative Example 2 were 8 mm and 10 mm, respectively, and the erosion loss of the immersion nozzle was significantly reduced. In addition, there was no cracking or falling off of the nozzle.

[0041]

As described above in detail, in the immersion nozzle for continuous casting of steel of the present invention, at least a part of the inner hole of the nozzle in contact with the molten steel has 50% to 95% by weight of spinel and 0% to 20% by weight of periclase. , Graphite 5-30% by weight, unavoidable impurities
By using a refractory of spinel-periclase-graphite system of 3% by weight or less, when used for casting Al-killed steel, nozzle clogging due to adhesion of A1 ₂ O _{3 in} steel is significantly suppressed, and When used for casting oxygen-containing steel, high Mn-containing steel, stainless steel and Ca-treated steel, the nozzle erosion was significantly reduced. In addition, there was no risk of the nozzle breaking, and safe operation was possible. That is, the immersion nozzle for continuous casting of steel of the present invention has an excellent effect of having both A1 ₂ O ₃ adhesion resistance, erosion resistance and spalling resistance.

[Brief description of the drawings]

FIG. 1 is a view showing a first embodiment of a nozzle of the present invention.

FIG. 2 is a view showing a second embodiment of the nozzle of the present invention.

FIG. 3 is a view showing a third embodiment of the nozzle of the present invention.

FIG. 4 is a view showing a fourth embodiment of the nozzle of the present invention.

FIG. 5 is a diagram showing a material distribution pattern of a conventional nozzle (Comparative Example 1).

FIG. 6 is a diagram illustrating a material distribution pattern of a conventional nozzle (Comparative Example 2).

[Explanation of symbols]

12 Nozzle body (spinel-periclase-graphite-based refractory) 21, 41 Inner hole (spinel-periclase-graphite-based refractory) 31 Area around discharge port of inner hole (spinel-periclase-graphite) Refractory) 61 Inner hole (high-purity alumina) 22, 32, 42, 52, 62 Nozzle body (Al ₂ O ₃ —Si
O ₂ -C refractories 23, 33, 43, 53, 63 Powder line (Zr
O ₂ -C refractory)

Claims (1)

[Claims] 1. A submerged nozzle for continuous casting of steel, wherein the entire nozzle or the whole or a part of the inner hole of the nozzle in contact with molten steel has a spinel content of 50 to 95% by weight, periclase.
0-20% by weight, graphite 5-30% by weight, unavoidable impurities 3
An immersion nozzle for continuous casting of steel, which is a spinel-periclase-graphite-based refractory of up to% by weight.