JP2805449B2 - Nozzle for continuous casting of molten steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting nozzle capable of effectively suppressing the narrowness of a nozzle through which molten steel passes in continuous casting of aluminum-killed steel or the like containing aluminum, and effectively suppressing clogging.

[0002]

2. Description of the Related Art A nozzle for continuous casting of molten steel is used for the following purposes.

[0003] In the continuous casting of molten steel, the continuous casting nozzle is used to prevent oxidation of the molten steel due to contact with air by injection of the molten steel between the tundish molds, to prevent the molten steel from being scattered, and to prevent non-metallic inclusions and molds. It is used for the purpose of rectification of pouring of molten metal to prevent surface floating substances from being caught in the slab.

Conventionally, the nozzle material for continuous casting of molten steel is mainly composed of graphite, alumina, silica, silicon carbide and the like, and recently zirconia is sometimes used as a constituent component. However, casting aluminum killed steel or the like has the following problems.

In aluminum-killed steel and the like, aluminum added as a deoxidizer reacts with oxygen present in molten steel to form α-killed steel.
Non-metallic inclusions such as alumina are formed. Therefore, when casting aluminum killed steel, etc., non-metallic inclusions such as α-alumina generated by oxidation of aluminum added as a deoxidizing agent adhere to the inner hole surface of the continuous casting nozzle, and are deposited and deposited. As a result, the inner hole is narrowed, and in the worst case, the inner hole is closed, which makes stable casting difficult. Alternatively, non-metallic inclusions such as α-alumina adhered and deposited in this manner are peeled off or fall off and are rolled up in the slab, resulting in deterioration of the quality of the slab.

In order to prevent the inner hole from being narrowed and clogged by the non-metallic inclusions such as α-alumina, the inner surface of the continuous casting nozzle for forming the inner hole is difficult to move toward the molten steel flowing through the inner hole. 2. Description of the Related Art A method of injecting an active gas to prevent non-metallic inclusions such as α-alumina present in molten steel from adhering and depositing on the inner surface of a continuous casting nozzle has been widely used.

[0007] However, the method of injecting the inert gas from the inner surface of the molten steel continuous casting nozzle forming the inner hole has the following problems.

That is, if the amount of the inert gas to be jetted is large, bubbles formed by the inert gas are caught in the slab, causing defects due to pinholes. Conversely, if the amount of the inert gas to be ejected is small, non-metallic inclusions such as α-alumina adhere to and accumulate on the inner surface of the continuous casting nozzle, and the inner hole becomes narrower and, in the worst case, clogs.

Further, it is structurally impossible to blow an inert gas uniformly from the inner surface of the continuous casting nozzle toward the molten steel flowing through the inner hole. The control of the inert gas to be ejected becomes unstable due to the deterioration of the structure and the structure of the material, and it becomes difficult to evenly eject the inert gas onto the inner surface of the continuous casting nozzle. As a result, α- Non-metallic inclusions such as alumina adhere to the inner surface of the continuous casting nozzle and accumulate to make the inner hole narrower and even clogged.

[0010]

In order to solve the above-mentioned problems without using a mechanical means such as injection of an inert gas, the following method has been proposed as a material measure for a nozzle for continuous casting of molten steel. Was used.

Japanese Patent Application Laid-Open No. 57-71860 discloses the following nozzle for continuous casting of molten steel containing graphite and calcia as main components. That is, it is a nozzle for continuous casting of molten steel formed of a refractory essentially consisting of:

10 to 50% by weight of graphite and 20 of calcia
Approximately 75% by weight and the remainder are formed of metal aluminum, silicon carbide or the like.

However, the above-mentioned nozzle for continuous casting of molten steel has the following problems. Calcia reacts quickly with non-metallic inclusions such as α-alumina to produce low melting point compounds.
As a result, there is an effect of preventing non-metallic inclusions such as α-alumina from adhering and depositing on the inner surface of the continuous casting nozzle inner hole. However, if calcia is present alone, it reacts violently with water or moisture in the air to form Ca (OH) ₂ even at room temperature, and collapses and powders. It cannot be used unless it is applied. Furthermore, since calcia has a large coefficient of thermal expansion, if it is heated so as to generate a non-uniform temperature distribution, a large thermal stress is generated inside the nozzle, so that the heat-resistant sprinkling property is greatly reduced.

[0014] Due to the above-mentioned problems, it is difficult to actually use a continuous casting nozzle containing calcia alone.

JP-A-64-40154 discloses graphite-calcium zirconate. In this method, Al ₂ O _{3 as} an adhering substance reacts with CaO coming from calcium zirconate to change to a low-melting compound and to be lost. [CaO 23% (40 mol%)
~ 36% (55 mol%) containing calcium zirconate]
CaO · ZrO ₂ emits CaO decompose when in contact with alumina at molten steel temperatures but are based on (Kokoku see JP 59-19075) findings, the release rate is slow enough functionality by casting conditions It turns out that there are times when it does not.

Decomposition of CaO.ZrO ₂ releases it.
Silica (Si
O ₂ ) and magnesia (MgO) are effective,
This is disclosed in Japanese Patent Publication No. 14540/1991.

[0017] CaO, CaO-SiO ₂ having both properties as means and CaO component extender to facilitate movement aggregation into release-surface of CaO by the decomposition of ZrO ₂ (CaO40
-54%) is effective.
No. 9.

[0018] CaO-SiO ₂ having both properties as means and CaO component extender to facilitate movement aggregation into release-surface of CaO by decomposition of CaO-ZrO _2, 2CaO ·
It is effective to use a combination of SiO ₂ and 3CaO.SiO ₂ (total amount is 1 to 35% by weight).
And JP-A-4-73410.

In the case of Ca, ZrO ₂ and CaO,
_{O · SiO 2, 2CaO · SiO} 2, 3CaO · SiO 2 (1~
(35%), the operating surface structure after the reaction with Al ₂ O ₃ to produce a low melting point mineral becomes uneven, non-metallic inclusions accumulate and accumulate in the recesses, making it difficult to use for a long time. Become. Especially if there are many α-Al ₂ O ₃ in the steel α-Al ₂ O ₃
Rapidly accumulates and becomes difficult to use.

From the above, it is economical and relatively easy without using a mechanical method such as blowing out an inert gas. Although development of a casting nozzle is strongly desired, such a nozzle for continuous casting of molten steel has not yet been proposed.

[0021]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide an economical method without using a mechanical method such as jetting an inert gas. It is an object of the present invention to provide a nozzle for continuous casting of molten steel which does not cause a narrow inner hole for a long time and further does not cause blockage or structural deterioration.

The present invention consists of a refractory essentially consisting of:
Are arranged in one inner hole.

As a mineral composition, 40 to 65% by weight of calcium zirconate containing CaO.ZrO ₂ as a main component, graphite 1
0 to 35% by weight, calcium silicate mainly composed of CaO.SiO ₂ as mineral composition and 2Ca as mineral composition
A crystal-stabilized calcium silicate containing O.SiO ₂ and 3CaO.SiO ₂ as main components is used together, and the total is 1
-25% by weight, 5-25% by weight of pottery stone mainly composed of quartz and sericite as mineral species.

The nozzle for continuous casting of molten steel composed of the above-described refractory material suppresses calcia (CaO) as a component thereof from reacting violently with water or moisture in the air, and produces CaO.Si.
Calcium silicate mainly composed of O ₂ and 2CaO · S
Both of the crystal-stabilized calcium silicate containing SiO ₂ and 3CaO.SiO ₂ as a main component have no crystal transformation with respect to temperature change and thus do not have abnormal expansion and contraction. By reacting aluminum added as a deoxidizing agent on the inner hole surface with non-metallic inclusions such as α-alumina generated by reacting with oxygen present in the molten steel to form a low melting point compound, It is possible to prevent non-metallic inclusions such as α-alumina from adhering and further depositing on the inner surface of the molten continuous casting nozzle.

The principle, action and effect of the material are that the use of a high CaO-containing material and the use of pottery stone having a low melting point are used together. This smoothes the nozzle inner surface,
It has been found that non-metallic inclusions are liable to adhere, and that the irregularities are reduced. Further reacted with α-Al ₂ O ₃ adhered by crystallization of calcium silicate mainly comprising CaO · SiO ₂ and 2CaO · SiO ₂ and 3CaO · SiO _{2 α-A}
It can reduce the melting point of l ₂ O ₃ .

The CaO component reacts with Al ₂ O ₃ to produce CaO.A
l ₂ O ₃ , 3CaO.Al ₂ O ₃ , and finally 12CaO.7
Since it becomes a low-melting substance having a melting point lower than the melting temperature such as Al ₂ O ₃ and is lost, it is effective in preventing clogging without deposition.

More specifically, the mineral composition is CaO
・ Calcium zirconate containing ZrO ₂ as a main component is C
aO is contained in a range of up to less than 36% by weight,
It was melted and adjusted at the above high temperature. This has the same thermal expansion characteristics as stabilized zirconia, and since calcia does not exist alone, calcia does not react violently with water or moisture in the air, thereby preventing deterioration of the structure of the nozzle.

The above-mentioned calcium zirconate in the range of 40 to 89% by weight is composed of calcium silicate containing CaO.SiO ₂ as a main component and 2CaO.SiO ₂ and 3CaO.
When coexisting with a crystal-stabilized calcium silicate containing SiO ₂ as a main component, calcia (CaO) dissolved in calcium zirconate easily moves to the surface of calcium zirconate particles. CaO SiO ₂ CaO.SiO ₂ 48.3% 51.7% 2CaO.SiO ₂ 65.1% 34.9% 3CaO.SiO ₂ 73.7% 26.3%

That is, calcia (CaO) for reacting with α-Al ₂ O ₃ , which is the main component of the nonmetallic inclusions adhering to the inner pore surface, moves and aggregates on the surface of the calcium zirconate particles, and calcia at the grain boundaries (CaO) concentration is increased. Further, by using each of the calcium silicates together, a catalytic function of accelerating the reaction with the silica (CaO) in the calcium silicate is exhibited.

Calcium silicate containing CaO.SiO ₂ as a main component does not cause a hydration reaction if the molar ratio of CaO to SiO ₂ is 1: 1. No crystal transformation occurs due to the rise. Also, 2CaO.SiO ₂ and 3CaO.Si
The crystal-stabilized calcium silicate containing O ₂ as a main component has a molar ratio of CaO to SiO ₂ of 2-3: 1 and is synthesized together with B ₂ O ₃ having a function of a crystal stabilizer of 1 to 5% by weight. Also, no hydration reaction occurs, and no crystal transformation to the γ phase occurs due to a rise in temperature, so that the structure of the nozzle does not deteriorate.

The calcium silicate containing CaO · SiO ₂ as a main component is preferably 40 to 54% by weight of CaO.
Crystal-stabilized calcium silicate mainly composed of CaO.SiO ₂ and 3CaO.SiO ₂ is 62 to 73% by weight of CaO.
Is preferable.

Furthermore, as a result of various investigations as a means for smoothing the surface properties of the working surface, it was found that as an additive having both functions of decomposing and releasing CaO and ZrO ₂ , and moving and aggregating to the particle surface, pottery stone and fine powder were used. The addition proved to be effective.

As a mineral seed, the porcelain stone mainly composed of quartz and sericite is preferably 5 to 25% by weight, and in order to have a surface smoothness, it is desirable that the melting point is 1300 to 1500 ° C.

From the above, the disadvantages of calcia are overcome and the reaction between calcia and α-alumina is continued for a long time to produce a low melting point compound, and thus to the surface of the inner hole of non-metallic inclusions such as α-alumina. It is an object of the present invention to provide a nozzle for continuous casting of molten steel capable of effectively suppressing adhesion of molten steel for a long time.

For the purpose of improving the spalling resistance and the oxidation resistance, SiC can be added.

[0036]

[Action] The content of zirconia clinker composed mainly of CaO · ZrO ₂ as mineral composition is desirably 40 to 65 wt%. If the content is less than 40% by weight, the calcia content required to react with α-alumina, which is the main component of the nonmetallic inclusions, is poor or the corrosion resistance to molten steel is poor, and the nozzle bore as shown in FIG. In the case of disposing it on the surface layer, there is a possibility that the part disappears in a short time, and a sufficient effect cannot be expected.

If it exceeds 65% by weight, the coefficient of thermal expansion increases, and the spalling resistance deteriorates. The graphite content is 1
The content is preferably 0 to 35% by weight. In consideration of thermal conductivity and oxidation resistance, it is desirable to use natural graphite. If the graphite content is less than 10% by weight, the heat-resistant spalling property is inferior, while if it exceeds 35% by weight, the corrosion resistance decreases.

The CaO content in calcium silicate whose main component is CaO.SiO ₂ is at most 54.
If the content is more than 10% by weight, the mineral composition becomes unstable, and the hydration reaction of calcia (CaO) is likely to occur, which may cause structural deterioration. Further, CaO content in the crystal stabilized calcium silicate as a main component 2CaO · SiO ₂ and 3CaO · SiO ₂ as the mineral composition 62-73 wt%, SiO ₂ content of 26 to 34 wt%, and stable crystalline The content of B ₂ O ₃ as an agent is in the range of 1 to 5% by weight, and the total of the three is preferably 95% by weight or more. Otherwise, the crystal transformation to the γ phase is likely to occur, In addition, the hydration reaction of calcia (CaO) is likely to occur, which may cause tissue deterioration.

The above two calcium silicates are used in combination, and the total content thereof is desirably 1 to 25% by weight.

The content of both calcium silicates is 1
If the amount is less than 25% by weight, the effect of moving and agglomerating calcia (CaO) in the calcium zirconate to the particle surface cannot be obtained. If the amount exceeds 25% by weight, the refractory structure is easily deteriorated and the corrosion resistance is reduced. At the same time, the heat spalling property is greatly reduced.

Mineral Ceramics mainly composed of quartz and sericite have an average particle size of 44 μm or less and a content of 5 % by weight.
If the amount is less than 25%, the effect of moving and aggregating calcia from the pottery stone to the particle surface cannot be obtained. Further, even when the melting point of the pottery stone is 1300 ° C. or lower, a similar state may occur. Next, the nozzle for continuous casting of molten steel of the present invention will be described with reference to the drawings.

FIG. 1 is an example of a schematic vertical cross section showing an embodiment of a molten steel continuous casting nozzle as an immersion nozzle of the present invention. The nozzle 3 for continuous casting of molten steel of the embodiment is used as an immersion nozzle disposed between a tundish and a mold. As shown in FIG. 1, in a continuous casting nozzle 3 for molten steel as an immersion nozzle having an inner hole 1 along the axis thereof through which molten steel flows, the nozzle 3 for the continuous casting of molten steel forming the inner hole 1. The part 2 is formed of a refractory having the above-mentioned chemical composition. According to the nozzle 3 for continuous casting of molten steel as the immersion nozzle of the embodiment, the nozzle 3 for continuous casting of molten steel forming the inner hole 1
Adhesion and deposition of non-metallic inclusions such as α-alumina existing in the molten steel in the portion 2 of the molten steel are suppressed for a long time.

[0043]

Next, the effects of the present invention will be described with reference to examples.

[0044]

EXAMPLES Formulations 1 to 5 (hereinafter referred to as "samples of the present invention") having a chemical composition within the scope of the present invention shown in Table 1 and formulations 6 to 6 having a chemical composition outside the scope of the present invention. 10 (hereinafter referred to as “comparative sample”), a powder and solution of phenolic resin in the range of 5 to 10% by weight were added, and the mixture was kneaded and kneaded. 30 mm x 30 mm for testing the amount of nonmetallic inclusions and corrosion resistance to solution
A molded body having a size of × 230 mm and a molded body having a diameter of 100 mm, an inner diameter of 60 mm and a length of 250 mm for testing spalling resistance were formed, and each of the obtained molded bodies was subjected to a temperature of 1000 ° C. to 1200 ° C. The refractories 1 to 10 were prepared by reducing and firing at a temperature within the range described above.

[0045]

Table 1 shows the physical property values (porosity and bulk specific gravity) of each of the above-mentioned samples 1 to 5 of the present invention and comparative samples 6 to 10.

Next, the outer diameter 100 mm and the inner diameter 60
Inventive Samples 1 to 5 and Comparative Samples 6 to 10 each having dimensions of mm and 250 mm in length were heated in an electric furnace at a temperature of 1500 ° C. for 30 minutes and quenched with water to investigate spalling resistance. . Table 1 shows the results.

Next, the aforementioned 30 mm × 30 mm × 23
Samples 1 to 5 of the present invention having dimensions of 0 mm and Comparative Samples 6 to 10 were immersed in molten steel at a temperature of 1550 ° C. for 180 minutes containing aluminum in the range of 0.3 to 0.05% by weight respectively. Melting rate (%) and α
-The adhesion amount of nonmetallic inclusions such as alumina was investigated. Table 1 shows the results.

As is clear from Table 1, the sample of the present invention is excellent in spalling resistance and does not adhere non-metallic inclusions such as α-alumina despite the low erosion rate.
Therefore, the inner hole of the nozzle for continuous casting of molten steel can be made narrower, and the clogging can be effectively suppressed.

On the other hand, in Comparative Sample 6, the spalling resistance was remarkably poor due to the large content of the zirconia clinker, and non-alumina such as α-alumina was not generated due to the absence of calcium silicate. It is clear that the amount of metal inclusions is large.

In Comparative Sample 7, the corrosion resistance to molten steel was remarkably poor due to the large content of calcium silicate, and in Comparative Sample 8, the graphite content was large. Sample 7 for comparison
It is clear that the corrosion resistance to molten steel is remarkably inferior as in the above.

Therefore, according to the nozzle for continuous casting of molten steel of the present invention, the structure of the refractory is not deteriorated, the inner hole is narrowed by non-metallic inclusions such as α-alumina, and the clogging is stably suppressed for a long time. can do.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view in a case where a composition material of the present invention is provided on a surface layer of an inner hole in contact with molten steel.

FIG. 2 is a longitudinal sectional view in a case where the composition material of the present invention is provided in a surface layer portion of an inner hole and a lower portion (a molten steel immersion portion) of a molten steel continuous casting nozzle.

[Explanation of symbols]

 1 inner hole 2 part 3 nozzle for continuous casting of molten steel

Claims (2)

(57) [Claims] 1. A least calcium bore surface portion in contact with molten steel is composed mainly of CaO-ZrO ₂ as mineral composition, Jirukoneito 40-65 wt%, graphite 10 to 35
% By weight , a calcium silicate mainly composed of CaO.SiO ₂ as a mineral composition, and 2CaO.multidot.
Crystal depreciation mainly composed of SiO ₂ and 3CaO · SiO ₂
A combination of a constant reduction of calcium silicates, if the combination both
The total content is 1 to 25% by weight, the mineral type is 5 to 25% by weight of pottery stone mainly composed of quartz and sericite, and an organic binder is added, kneaded, molded and fired in a non-oxidizing atmosphere. A nozzle for continuous casting of molten steel, characterized in that: 2. The crystal-stabilized calcium silicate comprises C
aO62~73 wt%, SiO ₂ 26 to 34 wt%, with stabilizer B ₂ O ₃ 1 to 5 wt% of the range the composition, the three parties of the total 95% by weight or more, quartz as mineral species, sericite 2. The nozzle for continuous casting of molten steel according to claim 1, wherein the particle size of the pottery stone as a main component is 44 μm or less.