JPH0577005A - Nozzle for continuous casting for steel making - Google Patents

Abstract

PURPOSE:To manufacture a nozzle for continuous casting, in which the sticking and the piling of non-metallic inclusions are not generated to the inner wall surface of the nozzle hole and the safe operation and the good quality are maintained and the manufacturing cost is not high even in the case the continuous operation is executed for a long time. CONSTITUTION:The refractory material incorporating three components of CaO, SiO2 and B2O3 as the essential components is composed of 5-50% refractory material incorporating 95-99% refractory material having (2:1) to (3:1) ratio of CaO:SiO2 and 1-5% B2O3, and >=95% of the total content of CaO, SiO2 and B2O3, and 10-35% carbon or graphite quality material and the balance the oxide refractory material and if necessary, carbide and/or nitride materials are added and constituted, and after kneading and forming by using organic binder, sintering is executed. This nozzle has the excellent heat resistance, slaking resistance and the stability of crystal and no transformation of the crystal form of 2CaO.SiO2, etc., even in the case of repeated heating and cooling and the sufficient characteristic as the refractory material and the functionality of very high reactivity, etc., on the contacting surface with the alumina.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long nozzle and a dipping nozzle used in a continuous casting method of steel from a ladle, a tundish and a tundish and a mold, and particularly, non-metallic inclusions are generated during casting. The present invention relates to a nozzle for continuous casting for steelmaking, which prevents the nozzle hole from being stuck or accumulated in the nozzle hole to make the nozzle hole thin or to be blocked.

[0002]

2. Description of the Related Art Generally, in the continuous casting method of steel, the molten metal is sequentially transferred from a ladle to a tundish and from the tundish to a mold for casting. During this period, the long nozzle and the dipping nozzle are used to cover and connect the molten metal to prevent oxidation. As the pouring time of these nozzles increased, non-metallic inclusions intervening in the molten metal gradually adhered to the inner surface of the hole, gradually advancing the deposition, narrowing the inside of the nozzle hole, and lowering the casting speed. Finally, normal casting cannot be performed and operation becomes impossible. In addition, even if the casting operation can be managed, a uniform flow rate can be maintained in dipping nozzles that have two or more discharge ports because the amount of non-metallic inclusions deposited and accumulated in each discharge hole is different. As a result, uneven flow occurs and the flow in the mold is disturbed, the solidification shell formed by the side walls in the mold lacks uniformity, and the non-metallic inclusions deposited and deposited are separated by the flow of molten metal and flow out. It becomes a serious problem because it is adversely affected by operations, quality and yield, such as sand scratches when it is caught in a billet.

[0003]

In order to solve these problems, at present, a hole is formed in the tip of the tundish stopper or the inner surface of the hole of the nozzle body, or a slit is formed inside the nozzle body, and it is not possible to connect through these portions. A structural improvement of measures such as blowing active gas and suppressing adhesion and deposition by the action effect of this gas, and also in terms of material, from conventional high alumina-graphite material to zirconia-graphite material or calcia-
Improvement measures such as arranging a material that can maintain high corrosion resistance and reduce adhesion such as partial use of zirconia material on the inner wall surface of the nozzle hole and make it a multi-layer type have been adopted, but still more The current situation is that it is insufficient and the current problems have not been resolved. By adopting this method, sometimes the bubbling phenomenon occurs in the mold due to the suction gas due to the good or bad operation, and the molten metal surface changes abnormally, causing problems in operation and quality, and for introducing gas. What you have to do,
Since the work for this introduction is required, the equipment cost, the labor cost, and the manufacturing cost such as the gas cost are increased, there is a strong demand for solving these problems.

[0004]

In view of the above-mentioned situation, the present invention is capable of safe operation and maintenance of quality without depositing and depositing non-metallic inclusions on the inner wall surface of the nozzle hole even when operating continuously for a long time. Since it is possible to make a nozzle for continuous casting that does not require high manufacturing cost, it has high reactivity with non-metallic inclusions.
The present invention product was completed by paying attention to the use of a material whose main reaction product is a low melting point product.

In the present invention, since the main component of the deposit is Al ₂ O ₃ (alumina), CaO ₃ , SiO ₂ , and B ₂ O ₃ materials having high reactivity with Al ₂ O ₃ (alumina) are used as the nozzle material. Is used as a part of.

That is, at least in the inner wall of the nozzle hole, at least the discharge hole portion is made of a CaO--SiO ₂ --B ₂ O ₃ -based material having a CaO: SiO ₂ content of 2: 1 to 3: 1 in a molar ratio of B ₂ O 1 to ₃
5% to 50% of a refractory material, which is composed of 5% and has a total content of CaO, SiO ₂ and B ₂ O ₃ of 95% or more, is used as a graphite material to form non-metallic inclusions. The inventors have found a nozzle material effective for reacting with Al ₂ O ₃ (alumina), which is the main component of the product, to flow out as a low-melting material, and to prevent the adhesion and deposition on the inner wall of the nozzle hole. (Reason for limitation) CaO ・ SiO ₂・ B ₂ O ₃ based materials are 2CaO, SiO ₂
The reason why 3CaO and SiO ₂ are used. When it is 2CaO · SiO ₂ or less, fire resistance is lost and corrosion resistance becomes a problem. When it is 3CaO · SiO ₂ or more, free CaOa is contained, which causes a big problem in that a hydration reaction occurs during storage during production. To get out.
Further, the content of boric acid (B ₂ O ₃ ) is set to 1 to 5% because B ₂
The purpose of containing O ₃ is that CaO / SiO ₂ based material is a heating / cooling process, and 2CaO / SiO ₂ which is the main component at 725 ° C. is easily transformed from β type to γ type with a volume increase of about 12%. This is contained in order to suppress this transition phenomenon in which a pulverization phenomenon occurs and disintegrates, and within 1%, the effect is small and unstable. If it is 5% or more, there is a problem that heat resistance is impaired. Regarding the amount of CaO / SiO ₂ / B ₂ O ₃ based material added (5% to 50%) If the amount is less than 5%, the reaction amount is small and the reaction does not improve the deposition phenomenon. This is because when b is 50% or more, the corrosion resistance is low and the durability is low. Device and graphite material 10% -35% The purpose of device and graphite material is (a) corrosion resistance,
(B) To improve heat resistant spalling. a When it is 10% or less, the corrosion resistance and the heat-resistant spalling resistance are obtained. If b is 35% or more, the strength of the nozzle itself becomes low. This is because, if it deviates from this range, the required characteristics for use cannot be sufficiently satisfied. In addition to these raw materials, it is also effective to add a carbide or nitride material in order to prevent oxidation of the carbon material by sintering.

[0007]

In the raw materials used in the EXAMPLE, CaO · SiO ₂ ·
Table 1 shows raw materials for producing B ₂ O ₃ based materials and CaO—ZrO ₂ based materials, and Table 2 shows the mixing ratio of the raw materials. Table 3 shows the chemical composition values of the raw materials used in the examples. Among the raw materials shown in Table 3, CaO-SiO ₂ · B ₂ O ₃ based materials and CaO ·
For the production of ZrO ₂ -based materials, the raw materials shown in Table 1
Grind to a particle size of 4μ or less, mix with the mixing ratio shown in Table 2, add non-hydrogen resin in a wet pan, knead, granulate to a size of 6 mm × 6 mm × 8 mm with a briquette machine, then dry, This is melted using an electric furnace, the furnace is tilted and transferred to a ladle, and cooled to prepare the test material for use.

[0008]

INDUSTRIAL APPLICABILITY Refractory materials within the scope of the present invention are shown in Example 2
As shown in (1), CaO, SiO ₂ , and B ₂ O ₃ having high reactivity with alumina, which is the main component of the non-metallic inclusions in the molten steel, are constituted as essential components. Moreover, CaO and SiO ₂
And the molar ratio is 2: 1 to 3: 1 and B ₂ O _{3 is} 1% to 5%.
It is also excellent in heat resistance, digestion resistance and crystal form stability due to the limitation to 2 even after repeated heating and cooling.
CaO, SiO ₂ etc. also have no crystal form transition and r2CaO,
As a refractory material, it has sufficient characteristics such as the fact that no heterogeneous crystal such as SiO ₂ is formed, and it has functionality such as very high reactivity at the contact surface with alumina. In addition, since it is manufactured by cooling after being electrically melted, it is possible to obtain a homogeneous material and has high crystallinity, and the stability of the material is also high, and the quality and stability of the refractory material are stable. It is possible to obtain a high-quality material.

Table 4 shows the results of the substitution test of the high-alumina-graphite material for the immersion nozzle material with the fused alumina, using the C material in the above trial materials, and Table 5 shows the material in which 25% of the C material was added. The test results for the addition amount of the graphite material are shown below. Further, Table 6 shows the comparison of the component value differences between the CaO—SiO ₂ —B ₂ O ₃ materials and the comparison test results with the conventional material comparative material. still,
This test material was manufactured by mixing the materials based on the compounding ratios shown in Tables 4, 5 and 6, heating the materials to 30 ° C and kneading, leaving them in the room, cooling them, and then hog them into a rubber press. Then, it is pressure-molded at a pressure of 1000 kg / cm ² , filled in a coke breeze in a sheath at a maximum temperature of 1350 ° C. in a tunnel kiln, baked, and then machined to produce an immersion nozzle having a predetermined shape. The erosion test and the adhesion test are performed by cutting out a 40 × 40 × 250 sample from the produced immersion nozzle material, immersing it in the molten metal of the high frequency induction furnace while rotating it 12 times / minute, and holding it for 120 minutes. .. In the erosion test, 3% Al was added to the molten metal (steel) and the molten metal temperature was 1580 ° C ± 10.
The conditions were controlled to. Table 7 shows the results of a practical test using an actual machine. The stable C used in the present invention is shown in the results of these series of basic tests and practical tests in an actual machine.
adhesion of non-metallic inclusions by aO-SiO ₂ -B ₂ O ₃ refractory material is also very small good. In particular, as shown in the results of practical tests using an actual machine, as a result of using the comparative product of Table 6 as a conventional product and Table 6 of the present invention as immersion nozzles of the same tundish respectively, as a result, the amount of deposits of the conventional product on the surface was There is unevenness, the product of the present invention is very small with respect to 12 to 20 mm, that is, 1 to 3 mm and 1.5 to 3.5 mm, respectively, and the surface is smooth, and the non-metallic inclusions adhering to the product do not flow out. There is no drift due to deposition, and a great improvement effect can be obtained in terms of work quality, steel quality, yield, etc. In Table 2, the (hydration resistance) electric melt was crushed and adjusted to 3 to 2 mm to prepare a sample. This sample is put in water, and after boiling time, it is dried for 10 hours in a constant temperature bath at about 105 ° C. a. Weight increase (digestion amount) b. Pulverization rate (amount (2% or less by weight) that became 2 mm or less) (Heat resistance) Shows a state after cooling in a holding furnace for 3 hours at a predetermined temperature. A. No change B. The softened state is shown. C. Semi-molten state D. A state in which the sample is melted and dipped in a siki stand. The sample is cut out from the melt to a size of 30 × 30 × 30. (Functional test) The molten material is crushed to 3 to 1 mm 45%,
1% to 0.1 mm (15%) and 0.1% (40% or less), 5% resin was added and kneaded, pressure-molded at a pressure of 1000 kg / cm ² , and then baked at 1550 ° C. to obtain a sample. Sample size 50 x 50 x 20 and 2 pieces of alumina 44mm underneath
It shows the state after being coated on the surface of the plate and held at 1550.degree. A. No change B. 1/3 change C.I. 2/3 change is shown. D. Table 7 shows the results of a comparative test using an actual machine that almost reacts. Conditions of use 1. Steel grade, low carbon aluminum killed steel 2. Size of slag 220 x 1150 to 1500 Material used 6 Table 6 Comparative example Table 6 Invention product

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

[Table 7]

Claims (1)

[Claims] In a refractory material containing three components of CaO, SiO ₂ , and B ₂ O ₃ as essential components, the refractory material having a CaO: SiO ₂ ratio of 2: 1 to 3: 1 is 95% to 99%, and B ₂ O _{3 is} 1% to 5%. %,
CaO, SiO _2, B ₂ total amount of O ₃ is up 10% to 35% and the balance of the refractory material of 5% to 50% carbon and or graphitic material containing 95% or more oxide refractory materials ,
A continuous casting nozzle for steel making, which comprises kneading and forming a material containing a carbide or nitride material, if necessary, using an organic binder, and then firing.