JPH0857611A - Nozzle for continuous casting - Google Patents

Abstract

PURPOSE: To stabilize a continuous casting operation for a long time and to improve and stabilize the quality of a cast slab by contriving the long service life and the stability of a long nozzle in the continuous casting of a metal, such as steel. CONSTITUTION: In the continuous casting of the metal, an oxidation resistant refractory layer 9 composed of Al2 O3 -SiO2 -MgO-Si-C containing a low melting glass component over the range of at least 5mm thickness, is integrally arranged on the outlet surface 2 of a non-immersion part in molten metal in non-contact with the molten metal during casting. By this constitution, the oxidizing deterioration of the outer surface part not immerced in the molten metal at the time of continuously casting the metal, is restrained and therefore, the extremely large effects on the profitability and reliability in the continuous casting operation, such as the safety and stability of casting, the stability of quality of the cast slab and the improvement of durability and the reduction in troubles of the nozzle itself, etc., can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous nozzle for casting metal such as steel. It is a long nozzle or a dipping nozzle used for pouring down molten metal between a ladle and a tundish and between a tundish and a mold. The present invention relates to suppression and reduction of oxidative deterioration due to contact between the surface of the nozzle for continuous casting and the atmosphere in the vicinity thereof during casting.

[0002]

2. Description of the Related Art Regarding the prior art, when performing continuous casting of steel, it prevents the molten steel that is attached to the molten steel discharge hole at the bottom of the ladle and poured down into the tundish from the ladle 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 the long nozzle is a factor that deteriorates or significantly destabilizes the quality of the slab due to the fact that the molten metal of steel comes into contact with the atmosphere and is oxidized as described above. To prevent oxidization of air, and to prevent turbulent flow of the molten metal that is poured down to rectify and suppress the inclusion of impurities such as slag and non-metallic inclusions near the tundish surface in the molten metal bath. It is possible to reduce the adverse effects on the quality of the cast slabs, etc., and to prevent the splash of molten metal to ensure the safety and stability of the continuous casting operation. As a general rule, the contact site with molten steel is Al ₂ O ₃ -C
A so-called slag line portion that comes into contact with the quality, tundish powder or slag is integrally used as a ZrO ₂ -C quality. The long nozzle 1 suppresses the progress of material deterioration due to air oxidation on the outer surface of the long nozzle during preheating in a temperature range of about 700 ° C. to 1200 ° C. before use and during casting in a higher temperature range. In order to vitrify by receiving the heat at the time of preheating or casting,
An anti-oxidant that acts to prevent contact between the outer surface and air is applied to the same surface. As an example of the material, SiO ₂ -A
The l ₂ O ₃ as a main aggregate, but those such as potassium silicate as a binder has been put into practical use, it is required that an extremely long time to enable the service of in long nozzle especially recently continuous casting Strong tendency, long nozzle 1 under these conditions
The metal case is attached and integrated through refractory mortar for the purpose of attaching and dropping molten steel droplets to the outer surface, fitting with the long nozzle support device in the upper neck part, and reinforcing the same part. 7 is a vitrified antioxidant coating partly due to the positional deviation on the surface of the long nozzle neck 8 at the lower end of the metal case 7 caused by repeated expansion and contraction with the rise and fall of high heat applied to the long nozzle 1 during casting. The material of the long nozzle 1 is directly exposed to the atmosphere from a damaged portion of the antioxidative coating to a local area or a wide area in proportion to the lapse of time, and the oxidation progresses. The outer surface of the long nozzle deteriorates due to oxidation, and if the degree of progress is strong, melting loss in the inner hole 5 due to molten steel and the generation of a hole penetrating due to convergence, so-called hole formation, or deterioration due to oxidation As a result, the strength of the long nozzle deteriorates and cracks occur due to external force such as impact when pouring, causing breakage and fracture, which is a factor that significantly shortens the life and reliability of the long nozzle. In the figure, 2 is the outer surface of the non-immersed part of the molten metal,
3 is an outer surface of the molten metal immersion part, 4 is a neck reinforcing hoop, and 6
Is the molten metal bath surface.

[0004]

In the above-mentioned long nozzle, the following problems have been revealed from the past, which has been an obstacle to the establishment of stable continuous casting.

Namely long long the oxidation prevention film on the outer surface under various conditions as against the use of the nozzle is broken, Al ₂ O as an oxidation phenomenon due to come into contact with the atmosphere _3- The carbon in the binder and the carbon (C) in the aggregate have been decarburized and disappeared, and due to the passage of time thereafter, not only the phenomenon of only the surface layer of the outer surface but also deeper toward the inner hole It will progress to.

In the above decarburized portion, 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 binder and the carbon of the aggregate. Depending on various conditions, unforgivable troubles such as punching, breakage, and cracking will be caused, which will have a serious adverse effect on the operation of continuous casting.

From the above, when a long nozzle is used for a long time in casting metal such as steel, oxidation of the material on the outer surface thereof does not easily occur, and stable continuous casting operation does not occur without strength deterioration. The development of a long nozzle that would make it possible was awaited.

[0008]

SUMMARY OF THE INVENTION From the background described above, the present invention aims to extend the life and stabilize a long nozzle in continuous casting of metal such as steel by solving these problems. It was made for the purpose of stabilizing the continuous casting operation for a long time and improving and stabilizing the quality of the slab.
The details will be described with reference to FIG. 2 by taking a long nozzle used for performing continuous casting of steel or the like as an example.

According to the present invention, in continuous casting of steel, when the molten steel is poured down from a ladle into the tundish, the molten metal of the steel comes into contact with the atmosphere and undergoes air oxidation, which adversely affects the quality of the slab. It is used for stabilizing the steel quality and safe and stable operation of the steel by interrupting the contact with the atmosphere, hindering the splashing of the droplets at the time of melt pouring, and suppressing the generation of turbulent flow of the flowing molten metal. While the long nozzle is being cast, oxidation due to contact with the atmosphere on the outer surface that does not come into contact with the molten metal is prevented by the application of a material that is difficult to oxidize to the same part, and its reliability is improved. It is a waste.

Long nozzles are generally Al ₂ O ₃ --C--S
The iO ₂ material system, the Al ₂ O ₃ -C system, or a material obtained by adding SiC to these is mainly used, and on the outer surface of the non-immersed part that does not come into contact with the molten metal of such a material, As described above, even if the surface is protected by the antioxidant film, the film thickness is 0.3 mm to 0.
Since the thickness is as thin as 53 mm, the antioxidant coating is destroyed under various conditions as described above when used for a long time, and the oxidation gradually progresses from that portion in direct proportion to the elapsed time thereafter. The progress of this oxidation causes various troubles and has a bad influence on the subsequent casting operation and the quality of the cast piece.

According to the present invention, the outer surface 2 of the non-immersed metal in the long nozzle 1 has a thickness of at least 5 from the outer surface.
In the range of millimeters, the oxidation resistant refractory material layer 9 is a multi-layered structure including two or more layers and is integrally formed by arranging it as an inclined material layer with the main body member material, and the material composition is 25 to 90. Wt% Al ₂ O ₃ and 1-30 wt% SiO ₂
And 5 to 25% by weight of MgO, 1 to 15% by weight of Si, 1 to 30% by weight of C, and 0.2 to 10% by weight of a low melting glass component such as a frit, and an oxidation resistant material. The aggregate was mixed, an organic binder was added, and the mixture was kneaded, and the kneaded clay having the adjusted grain size was put into the mold so as to be arranged with the body member kneaded clay such as Ai ₂ O ₃ -C. The long nozzle refractory member of the present invention is obtained by filling, press-molding, and then firing.

The outer surface of this long nozzle is protected by the above-mentioned oxidation resistant material, the oxidation of the body material portion is eliminated even when exposed to the atmosphere, and the oxidation resistant protective layer itself is oxidized as compared with the conventional one. The progress is greatly suppressed, and the thermal shock resistance is greatly improved and stabilized by arranging the graded material layer between the main body material and this oxidation resistance. It is advantageous to apply a surface coating of an antioxidant that has been conventionally applied along with the application of the material to the same part because the effect can be further enhanced.

The long nozzle of the present invention is constructed as described above, and it is possible to effectively effectively oxidize and deteriorate the material due to contact with the atmosphere on the outer surface which does not come into contact with molten steel during continuous casting in the conventional long nozzle. Useful effects such as suppression, safety and stabilization of continuous casting of steel for a long time, high level stabilization of slab quality to improve reliability of continuous casting, and cost reduction Will bring about.

Here, Al ₂ O ₃ − containing a low-melting glass component is arranged on the outer surface of the non-immersed portion of the long nozzle in the molten steel bath.
The thickness of the oxidation-resistant refractory material layer 9 made of SiO ₂ -MgO-Si-C is set to be at least 5 mm from the outer surface because when the thickness is 5 mm or less, the inclined material layers are arranged in two or more layers. Because it is physically impossible.

[0015]

The example of the long nozzle of the present invention is configured as described above, and suppresses the oxidative deterioration of the outer surface of the long nozzle 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 to stabilize quality, improve the yield, and improve the durability of long nozzles, and bring extremely useful effects economically As a result, the reliability of continuous casting was improved.

[0016]

As an example of the long nozzle of the present invention, this was set in a 150-ton ladle by continuous casting of steel and an attempt was made to cast ordinary steel. The following results were obtained.

Number of tests: 18 Ladles once: 150 tons of molten steel is cast as one charge.
The average service life was 15.4 charges / piece. In addition, the average service life of the conventional long nozzle in the same casting machine was 11.6 charges / piece, which was a service life improving effect of 33.1%.

Next, there was no trouble with the long nozzle during casting, and stable results were obtained against the conventional 1.2% trouble rate. It can be inferred from this result as well, but also for stabilizing the quality of steel. It can be said to be effective.

As described above, the continuous casting nozzle of the present invention is
By controlling the oxidative deterioration of the outer surface that is not immersed in the molten metal during continuous casting of metal, casting safety and stability, stabilization of the quality of the slab, improvement of the durability of the nozzle itself and reduction of troubles, etc. The continuous casting operation has an extremely large effect on economy and reliability.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a conventional long nozzle.

FIG. 2 is an explanatory diagram of a long nozzle of the present invention.

[Explanation of symbols]

 1 Long nozzle 2 External surface of non-immersed metal melt 3 External surface of metal melt immersion part 4 Neck reinforcement hoop 5 Inner hole 6 Metal melt bath surface 7 Metal case 8 Neck 9 Oxidation resistant fire resistant material layer Same graded material layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C04B 41/89 K

Claims (1)

[Claims] In continuous casting of metal, an Al ₂ O ₃ -containing low-melting glass component is formed over a range of at least 5 mm in thickness from the outer surface of the non-immersed portion of the metal that does not come into contact with the molten metal during casting.
An oxidation resistant refractory material layer made of SiO ₂ -MgO-Si-C, which is a multi-layer structure including two or more layers and is formed integrally with the main body member material by arranging it as a graded material layer. Casting nozzle.