JP2954419B2 - Method for preventing adhesion of refractory to Al2O3 etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory used for a furnace for accommodating molten steel, a ladle, a tundish, a vacuum degassing apparatus, a nozzle, a flow pipe for molten steel such as a dipping pipe, a stopper, and other incidental equipment. And a method for preventing adhesion of Al ₂ O _{3 and the} like.

[0002]

2. Description of the Related Art In recent years, for example, in a continuous casting apparatus for steel, there has been a great problem of refractories for continuous casting, particularly clogging of immersion nozzles, in accordance with demands for stricter steel quality and improved productivity. A large amount of Al ₂ O ₃ adheres to the inner surface or the vicinity of the discharge port during use of the Al ₂ O ₃ —C-based immersion nozzle that has been widely used in the past, and it is not uncommon that casting is stopped. Many efforts have been made in the past to solve this problem. However, it is hard to say that the clogging phenomenon of the immersion nozzle has been solved.

In order to solve this problem, recently, CaZr
A refractory material for immersion nozzles containing O ₃ has been developed (Japanese Patent Application Laid-Open No. 57-71860) and has come to be used on a trial basis. This CaZrO ₃ has the property of reacting with Al ₂ O ₃ to generate a low-melting substance. When this refractory material is used for an immersion nozzle, CaZrO ₃ is converted to Al ₂ O generated in molten steel.
_Since it reacts with ₃ to generate a low-melting-point substance and is easily melted, Al ₂ O ₃ does not adhere to or remain on the surface of the immersion nozzle, and nozzle clogging can be prevented.

[0004]

However, CaZrO ₃
Even if a nozzle containing is used, in some cases, the expected effect of preventing nozzle blockage may not be sufficiently exhibited,
To stably develop this nozzle blocking prevention effect,
It has become a major technical challenge for using CaZrO ₃ -containing nozzles.

[0005]

Means for Solving the Problems The present invention includes a particle 50 to 80% by weight containing 65 to 95 wt% 5-35 wt% and ZrO ₂ component of CaO component, C10-30 wt% and Si system The surface of refractory containing 5 to 25% of material has SiO
₂ or SiO ₂ , Na ₂ O, Al ₂ O ₃ , B ₂ O ₃ , Zr
O ₂ , K ₂ O, Li ₂ O, BaO, SrO, CaO, Mg
One, two or more coating materials comprising one or more of O, ZnO, CdO, PbO and Bi ₂ O ₃ are coated, and the coating material is coated at 1200 ° C. or more for 60 minutes or more. This is a method for preventing refractories from adhering to Al ₂ O ₃ or the like, which is characterized by performing heat treatment.

The inventors of the present invention have analyzed a nozzle after use which contains CaZrO ₃ and has a sufficient effect of preventing clogging. As a result, the surface shows that ZrO ₂ formed by decomposition of CaZrO ₃
And CaO supplied from here and Si derived from antioxidant
Al ₂ O ₃ —C composed of O ₂ and Al ₂ O ₃ originating from molten steel
low melting point material aO--SiO ₂ system is detected. From this fact, in order to make CaZrO ₃ effectively work with Al ₂ O ₃ and prevent nozzle clogging, the nozzle and an antioxidant covering the nozzle are heat-treated before starting use, and the CaZrO _{3 is} preliminarily used.
It has been found that it is effective to react with the components contained in the antioxidant to decompose and generate a low melting point substance. The present invention has been made based on these findings.

[0007]

[Effect] For example, S is added to the surface of a nozzle containing CaZrO _3.
When a coating material containing iO ₂ as a main component is applied and heat treatment is performed at 1200 ° C. or more for 60 minutes or more, SiO ₂ in the coating material applied to the nozzle surface reacts with CaZrO ₃ in the nozzle material to form ZrO ₂ on the nozzle surface. low melting point material is produced in the CaO-SiO ₂ system and. When the nozzle is used (flows molten steel) in this state, the temperature of the molten steel in the vicinity of the molten steel contact surface of the nozzle is about 1550 ° C., and at this temperature, the CaO—
SiO ₂ based low-melting material becomes molten, this penetration is Al ₂ O ₃ of the molten steel origin, the melt is Al ₂ O ₃ -C
aO—SiO ₂ composition. The substance of this composition is CaO-
Since it has a lower melting point than the case of the SiO ₂ system and easily melts from the nozzle surface, it hardly adheres or remains on the nozzle surface, and as a result, nozzle clogging is prevented.

[0008] By the way, when the above-mentioned treatment is not performed as in the conventional case, CaZrO ₃ is produced at high temperature under the high temperature of S
It reacts directly with iO ₂ and Al ₂ O ₃ originating from molten steel. In this case, since the low-melting-point substance has not been generated in advance, the reaction hardly occurs, so that the low-melting-point substance is not smoothly generated. For this reason, Al ₂ O ₃ easily adheres, and the nozzle is easily blocked.

The following can be exemplified as a nozzle base material for the present invention to exhibit its effects. That is, CaO
And 5 to 35 wt% and CaZrO ₃ containing ZrO ₂ 65 to 95 _{wt%, SiO 2, Al 2 O} 3, MgO, ZrO
_2, oxides _{etc., BN, SiC, B 4 C} , Si 3 N 4, Zr
A non-oxide such as B ₂ , TiC, TiN, AlN, or a metal such as Si, Ti, Mg, Ca, and a carbon material such as graphite;
And a base material obtained by kneading and molding with some additives such as a binder and then subjecting the mixture to a heat treatment as necessary.

On the other hand, examples of the coating material for coating the surface of the base material include those having the composition shown in Table 1, which are dipped in a brush, brush-coated, spray-coated, etc. to a thickness of 0.2 mm.
The surface is uniformly adhered with a thickness of the order. Examples of the heat treatment method include a method in which a nozzle coated with a coating agent is treated in a heat treatment furnace, and a method in which the coated nozzle is attached to a continuous casting facility and heated by a nozzle preheating device. The heat treatment temperature is required to be 1200 ° C. or higher in order to cause CaZrO ₃ and SiO ₂ to react, and the processing time is required to be 60 minutes or longer.

[0011]

[Table 1]

When the amount of the calcium zirconate clinker containing 5 to 35% by weight of the CaO component used in the present invention is set, if it is less than 50% by weight, the corrosion resistance is inferior, and more than 80% by weight. And inferior spall resistance. For this reason, the range of 50 to 80% by weight is desirable. If the CaO content of the calcium zirconate clinker is less than 5% by weight, the effect of preventing adhesion is not obtained, and if it exceeds 35% by weight, the content of ZrO ₂ is small and the corrosion resistance is poor. desirable.

Regarding the setting range of the compounding amount of the carbon material,
If it is less than 0% by weight, the effect on spall resistance is small, and
If the content exceeds 10% by weight, the corrosion resistance is reduced.

As the Si-based material, metal Si, SiC, S
iO ₂ , Si ₃ N ₄ , and ZrSiO ₄ are mentioned, which are added as a carbon material for preventing oxidation and as a sintering material for aggregate.
With respect to the setting range of the compounding amount, when the content is 5% by weight or less, the effect is small, and when the content is 25% by weight or more, on the contrary, the corrosion resistance is poor.

[0015]

EXAMPLE An immersion nozzle for continuous casting treated by the method according to the present invention was applied to a two-strand type continuous casting facility, and the effect was confirmed. Table 2 shows the materials of the nozzles used.

[0016]

[Table 2]

This is a nozzle containing CaZrO ₃ . This is shown in Table 1, namely, the lower layer of SiO ₂ and Si
It was covered with a coating material consisting of two upper layers mainly composed of O ₂ and containing Na ₂ O, Al ₂ O ₃ , B ₂ O ₃ and ZrO ₂ . This coating material has an antioxidant function and a low-melting-point substance generating function. Two nozzles thus obtained were prepared, mounted on both strands, and one strand side was heated to 800 ° C. with a preheating burner and held for 60 minutes. The two strands were heated to 1200 ° C. and held for 60 minutes, and then immediately subjected to continuous casting. The cast steel type was a low-carbon aluminum killed steel. As a result, on one strand side, the immersion nozzle closed during casting, and casting was abandoned.

On the other hand, no blockage occurred on the two strands treated by the method according to the invention. In the above, the present invention has been mainly described as being applied to a nozzle for continuous casting. However, the present invention exerts the same effect when applied to other nozzles, or refractories for other uses described above. Things.

[0019]

As described above, according to the present invention, CaZ
Al ₂ O for nozzles for continuous casting of, for example, steel containing rO ₃
Blockage due to ₃ or the like adhesion can be prevented very effectively and stably, and can greatly contribute to improvement in productivity of steel.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C04B 41/89 C04B 41/89 K (72) Inventor Daijiro Mizukoshi 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Kimitsu Inside the steelworks (72) Inventor Shigeaki Ogibayashi 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Kimitsu Works (58) Fields investigated (Int.Cl. ⁶ , DB name) C04B 41/87 B22D 11 / 10 310 B22D 11/10 330 B22D 41/54 C04B 41/89

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein the CaO component is 5 to 35% by weight and ZrO ₂
SiO ₂ component and particles 50 to 80% by weight containing 65 to 95 wt%, the surface of the refractory containing C10~30 wt% and Si-based material 5-25%, or SiO _2, Na
₂ O, Al ₂ O ₃ , B ₂ O ₃ , ZrO ₂ , K ₂ O, Li ₂ O, B
aO, SrO, CaO, MgO, ZnO, CdO, Pb
One or more layers of a coating material containing one or more components of O and Bi ₂ O ₃ are coated, and this is heat-treated at 1200 ° C. or more for 60 minutes or more. To prevent the adhesion of refractories such as Al ₂ O ₃ .