JPH06126397A - Nozzle for continuous casting - Google Patents

Abstract

PURPOSE:To improve the reliability of continuous casting by highly stabilizing the hermeticity and life of the nozzle for continuous casting, thereby stabilizing the operation of the continuous casting over a long period of time and improving and stabilizing the quality of a slab. CONSTITUTION:This nozzle for continuous casting of metal is constituted by disposing and integrating an oxidation resistant fire resisting material layer 5 consisting of Al2O3-SiO2-SiC-C contg. a low melting glass component over a 5 to 120mm range lower than the upper surface of a fitting surface 2 to a fire resisting member existing in the upper part where the nozzle does not come into contact with the molten metal during casting. As a result, the oxidation and the deterioration in the quality by contact of the fitting surface and the outside surface near this fitting surface with the atm. air at the time of the continuous casting including the time of preheating of the long nozzle are drastically and effectively suppressed, by which the long-time safety and stabilization of the continuous casting of the steel are assured, the grade of the quality of the slab is stabilized, the reliability of the continuous casting is enhanced and the cost is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long nozzle used for pouring down molten metal between a ladle and a tundish and between a tundish and a mold in continuous casting of metal such as steel. More specifically, the present invention relates to a nozzle for continuous casting such as a dipping nozzle, and more specifically, to suppress oxidative deterioration due to contact with a mating surface with a refractory member located in the upper part during preheating or during casting, and contact with the atmosphere in the vicinity thereof. It is about reduction.

[0002]

2. Description of the Related Art In the prior art, when performing continuous casting of steel, it is attached to the molten steel discharge hole at the bottom of the ladle to prevent the molten steel flowing down from the ladle into the tundish from contacting the atmosphere. It controls the oxidation of molten steel and prevents the splash of molten steel generated at that time, and also for the purpose of injecting molten steel from the ladle into the tundish while rectifying the molten steel flow and for the passage of molten steel downflow passages. A fire-resistant long nozzle (hereinafter referred to as a long nozzle) will be described below in detail with reference to FIG.

In continuous casting of steel, the function required of a long nozzle is air, which causes deterioration or marked instability of the quality of cast slabs as a result of the molten metal coming into contact with the atmosphere and oxidizing as described above. Prevents oxidization and prevents turbulent flow of the molten metal that is poured down to rectify and suppress the inclusion of impurities such as slag existing near the surface of the tundish and non-metallic inclusions in the molten metal bath. Therefore, it is possible to reduce the adverse effect on the quality of the slab and to prevent the splash of molten metal to ensure the safety and stability of the continuous casting operation. As the fitting surface 5, the fitting surface 5 with the refractory member located above is generally made of Al ₂ O ₃ —C. And this long nozzle 1 is about 70 before use.
In order to suppress the progress of material deterioration due to air oxidation of the outer surface of the long nozzle 1 at the time of preheating in the temperature range of 0 ° C to 1200 ° C, or in the case of casting in a higher temperature range, the above-mentioned preheating or casting At that time, it receives heat and vitrifies, and an antioxidant that acts to prevent contact between the outer surface and air is applied to the fitting surface 2 with the refractory member located above.

As an example of the material, a material in which SiO ₂ --Al ₂ O ₃ is the main aggregate and potassium silicate or the like is used as a binder has been put into practical use. There is a strong tendency to demand what is possible for an extremely long time, and under these conditions, the long nozzle 1 and the collector nozzle, which is a refractory member located at the upper part, depend on fitting during use. For the contact pressing action, physical action such as molten steel splash during casting, adhesion and drop of metal, and removal of foreign materials such as sealing material and adhered metal on the mating surface 5 performed every time the pot is replaced. The above-mentioned antioxidant coating applied to the same surface for maintenance by the operator of the above will be destroyed, and in proportion to the elapsed time thereafter, from the damaged portion of this antioxidant coating locally Gradually widespread Long nozzle material is exposed to the atmosphere directly Te and decarburization phenomenon slide into progress to advanced significant oxidation. Due to this oxidative decarburization, the fitting surface 2 with the refractory member located at the upper part of the long nozzle 1 is deteriorated in material quality, and as a result, it becomes a disadvantage that brings a disadvantage to continuous casting. That is, the deterioration of the fitting surface 2 causes the fitting portion to become rougher in the subsequent use of the long nozzle 1, and the airtightness is gradually deteriorated. Therefore, the reliability of the air sealing property originally required for the long nozzle 1 is improved. Property deteriorates and air is mixed into the steel to be cast, resulting in destabilization or deterioration of the quality of the slab, and the life of the long nozzle 1 itself is at a level where there is no problem at other parts. Since it deteriorates, it cannot be used anymore, and these are factors that impair the reliability and economy in the continuous casting operation.

[0005]

SUMMARY OF THE INVENTION In the above long nozzle for continuous casting of steel, the following problems have become apparent and have been an obstacle to establishing a stable continuous casting operation. It was

That is, when the long nozzle is used for a long time, as described above, the fitting surface 2 for connection with the refractory member such as the collector nozzle located above the fitting surface 2 and the vicinity thereof are preheated and As an oxidation phenomenon caused by the long nozzle 1 material itself coming into contact with the atmosphere when the above-mentioned antioxidant coating is destroyed under conditions such as various chemical and physical actions that are applied to the same part during use. Since the aggregate in the Al ₂ O ₃ -C material and the carbon (C) of the binder are decarburized and disappear, only the mating surface 2 and the surface layer portion in the vicinity thereof with the passage of time thereafter. Not only the phenomenon described above, but also progresses deeper toward the inside in the thickness direction.

In the above-mentioned oxidative decarburization part, the original strength of the material is largely reduced or completely lost due to the deterioration of the material mainly due to the disappearance of the carbon of the aggregate and the binder, and this part is lost during casting. Depending on various conditions, the fitting surface 2 may be roughened or chipped, resulting in an unacceptable defect that the fitting airtightness is impaired, resulting in a serious adverse effect on the continuous casting operation. Become.

From the above, when a long nozzle is used for a long time in continuous casting of a metal such as steel, oxidative decarburization of a material at a fitting surface 2 with a refractory member located above a collector nozzle or the like. There was a tendency to wait for the development of a long nozzle that is less likely to occur, prevents surface deterioration, prevents surface roughening, and enables stable continuous casting operations without impairing airtightness.

[0009]

SUMMARY OF THE INVENTION From the background described above, the present invention aims to solve the problems by improving the airtightness and long-term stability of the long nozzle in continuous casting of metal such as steel. This was achieved with the aim of improving the reliability of continuous casting by stabilizing the continuous casting operation for a long period of time and improving and stabilizing the quality of slabs. An example of a long nozzle used for this purpose will be described below with reference to the drawings.

In continuous casting of steel, when molten steel is poured down into a tundish from a ladle, this molten metal comes into contact with the atmosphere and undergoes air oxidation, which adversely affects the quality of the cast slab. A long nozzle used to stabilize the steel quality, to ensure safe operation, and to stabilize the quality of the molten metal by cutting off and hindering the splashing of the droplets generated when pouring the molten metal, and suppressing the generation of turbulent flow of the downflowing molten metal. During the preheating, casting and maintenance of the pot and during standby, and the atmosphere of the mating surface 2 for connection with the refractory member such as the collector nozzle or the upper nozzle located above it. With respect to the oxidative decarburization due to the contact of the above, by applying the material that is difficult to oxidize to the same portion, oxidative deterioration is prevented and its reliability is improved.

Long nozzles are generally Al ₂ O ₃ -C-S
An iO ₂ material system, an Al ₂ O ₃ -C system, or a material obtained by adding SiC to these is mainly used, and the surface of the fitting surface 2 made of such a material is SiO ₂ as described above.
-Al ₂ O ₃ is the main aggregate, and it is protected by an antioxidant coating that uses potassium silicate or the like as a binder, but since the coating thickness is as thin as 0.3 mm to 0.5 mm, When used over a period of time, the antioxidant coating is destroyed under the various conditions as described above, and the oxidative deterioration gradually progresses from that portion in direct proportion to the elapsed time thereafter. This phenomenon has a great adverse effect on the subsequent casting operation and the quality of the slab, as described above.

According to the present invention, the thickness of the long nozzle 1 is 5 mm below the top surface 3 including the fitting surface 2 and its vicinity for connecting with a refractory member such as a collector nozzle located above. To 120 millimeters, the oxidation resistant refractory material layer 5 is arranged and integrated, and the material composition is 40 to 75% by weight of A.
1 ₂ O ₃ and 1 to 30 weight percent of SiO ₂ , 1 to
An organic binder containing 20 weight percent SiC, 10 to 30 weight percent C, and 1 to 10 weight percent low melting glass component such as frit as an oxidation resistant material. After kneading and kneading and kneading the kneaded material, the kneaded material and the material kneaded material that forms the main body such as Al ₂ O ₃ -C are combined in the above-mentioned arrangement to fill the mold, and after pressure molding It is a long nozzle in a continuous casting nozzle obtained by firing in a reducing atmosphere.

In the long nozzle 1 according to the present invention, the fitting surface 2 and its vicinity are protected by the oxidation resistant refractory material layer 5, so that even if exposed to the atmosphere, the fitting surface 2 and its vicinity are not oxidized and deteriorated. Greatly suppressed. Further, if the surface coating of the above-mentioned conventionally used antioxidant is applied together with the application of this oxidation resistant material to the same portion, the effect can be further enhanced, and an advantageous result can be obtained. .

The long nozzle of the present invention is constructed as described above, and oxidation during the continuous casting including the preheating in the conventional long nozzle is caused by the contact between the fitting surface and the outer surface in the vicinity thereof with the atmosphere. Greatly and effectively suppresses the deterioration of the material, ensures the safety and stability of continuous casting of steel for a long time, realizes high quality stabilization of the slab quality, enhances the reliability of continuous casting, and reduces the cost. It brings useful effects such as tightening if possible.

Here, the fitting surface 2 for connecting with a refractory member such as a collector nozzle located above the long nozzle 1 and Al containing a low melting glass component arranged in the vicinity of the fitting surface 2.
The thickness of the oxidation-resistant refractory material layer 5 made of ₂ O ₃ -C-SiO ₂ -SiC is set in the range of 5 mm to 120 mm because when the thickness is 5 mm or less, the oxidation resistance effect time is short and it can withstand long-term use. Because I can't do it again, 12
If it is 0 mm or more, it will reach below the inner hole 4 of the long nozzle. Since this oxidation resistant material is inferior in molten steel erosion resistance compared to the main body material, it must be limited to the range where molten steel does not contact. It is due to.

[0016]

The example of the long nozzle of the present invention is configured as described above, and suppresses oxidative deterioration of the fitting surface and its vicinity during long-time use between the ladle and the tundish in continuous casting of steel. , Safe and stable casting, preventing oxidation of steel and mixing of non-metallic inclusions, stabilizing quality, improving yield and extending long nozzle life, resulting in economically very useful effect As a result, the reliability of continuous casting was improved.

[0017]

As an example of the long nozzle of the present invention, this was mounted in a continuous casting of steel between a ladle having a capacity of 150 tons and a tundish, and continuous casting of ordinary steel was attempted. The following results were obtained. It was

With a total of 271 charges, the number of tests was 20 and the casting of molten steel of 150 tons was performed once.
The average service life was 13.6 charges / piece. The average service life of the conventional long nozzle in the same casting machine is 11.6 charges / piece, and the long nozzle of the present invention is 16.8.
It became the improvement effect of the service life percentage.

The airtightness as an effect on the slab quality was verified by the result of the 10th charge, and the N2 concentration was 67.6.
% Improvement was confirmed. (

[Table 1] reference)

[0020]

[Table 1]

(*) Note 1) The table compares the air-sealing properties of the conventional product and the product of the present invention by expressing the N2 concentration incorporated in the steel in the unit of PPm. 2) The measuring method was to measure the molten steel sampled from the ladle and the tundish by the thermal conductivity method. 3) shows the N ₂ concentration in the tundish molten steel mean value of the measured value at 10 charge casting of values obtained by subtracting the N ₂ concentration in ladle molten steel. 4) The service life of the long nozzle was an average value of 20 n, which resulted in a 2.0 charge improvement over the conventional product.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a conventional long nozzle.

FIG. 2 is a vertical sectional view of a long nozzle of the present invention.

[Explanation of symbols]

 1 Long nozzle 2 Fitting surface 3 Top surface 4 Inner hole 5 Oxidation resistant fireproof material layer

Claims (1)

[Claims] In continuous casting of metal, a low-melting glass component is spread over a range of 5 mm to 120 mm below the upper surface of a fitting surface of a refractory member located at an upper portion that does not come into contact with molten metal during casting. Including Al ₂ O ₃ —SiO ₂
A nozzle for continuous casting, characterized in that an oxidation resistant refractory material layer made of SiC-C is arranged and integrated.