JPH05254967A - Method for preventing deposition of al2o3 or the like on refractory - Google Patents

Abstract

PURPOSE:To prevent the deposition of Al2O3, etc., on a refractory and to effectively and stably obviate the clogging of a nozzle by coating the surface of a CaZrO3 refractory with an SiO2-base coating material and heat-treating the refractory with the temp. and time controlled. CONSTITUTION:A refractory (e.g. a submerged nozzle) contg. 50-80wt.% of the grain consisting of 5-35wt.% Ca0 and 95-65wt.% ZrO3, 10-30wt.% C and 5-25wt.% of a siliceous material is prepared. The refractory surface is coated with a coating material consisting of SiO2 or a coating material contg. >=1 kind among SiO2, Na2O, Al2O3, B2O3, ZrO2, K2O, Li2O, BaO, SrO, CaO, MgO, ZnO, CdO, PbO and Bi2O3. The refractory is then heat-treated at >=1200 deg.C for >=60min. Consequently, the CaZrO3 in the refractory reacts with the SiO2 in the coating material to form a low-m.p. material on the refractory surface, and the Al2O3 originated from molten steel is dissolved in the low-m.p. material and melted away.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a refractory used for, for example, a furnace for accommodating and treating molten steel, a ladle, a tundish, a vacuum degassing device, a molten steel distribution pipe such as a nozzle and a dip pipe, and an auxiliary facility such as a stopper. The present invention relates to a method for preventing adhesion of Al ₂ O _3, etc.

[0002]

2. Description of the Related Art In recent years, for example, in a continuous casting apparatus for steel, a refractory for continuous casting, especially a block of a dipping nozzle, has become a serious problem with the demand for strict steel quality and improved productivity. It is not uncommon for a large amount of Al ₂ O ₃ to adhere to the inner surface or the vicinity of the discharge port during use of an Al ₂ O ₃ -C quality immersion nozzle that has been widely used in the past and to be forced to stop casting. Many efforts have been made in the past to solve this problem. However, it cannot be said that the blockage phenomenon of the immersion nozzle has been solved.

To solve this problem, CaZr has recently been used.
A refractory material for an immersion nozzle containing O ₃ has been developed (Japanese Patent Application Laid-Open No. 57-71860) and has come into trial use. This CaZrO ₃ has the property of reacting with Al ₂ O ₃ to produce a low melting point substance, when using the refractory material immersion nozzle, Al ₂ CaZrO ₃ is produced in the molten steel O
_Since it reacts with ₃ to form a low-melting point substance, which easily melts, Al ₂ O ₃ does not adhere to or remains on the surface of the immersion nozzle, and nozzle clogging can be prevented.

[0004]

[Problems to be Solved by the Invention] However, CaZrO ₃
Even if using a nozzle containing, in some cases, the expected effect of preventing nozzle clogging may not be sufficiently expressed,
Stable expression of this nozzle blockage prevention effect,
It has become a major technical challenge for the use of nozzles containing CaZrO ₃ .

[0005]

According to the present invention, particles containing 5 to 35% by weight of CaO component and 65 to 95% by weight of ZrO ₂ component, 50 to 80% by weight, C 10 to 30% by weight and Si-based particles. SiO on the surface of the refractory containing 5-25% of material
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 or two or more layers of a coating material containing one or more components selected from O, ZnO, CdO, PbO, and Bi ₂ O ₃ are coated, and this is coated at 1200 ° C. or more for 60 minutes or more. A method for preventing adhesion of refractory materials such as Al ₂ O ₃ is characterized by heat treatment.

The present inventors analyzed a nozzle after use that contained CaZrO ₃ and showed a sufficient blocking preventing effect, and as a result, ZrO ₂ produced by decomposition of CaZrO _{3 on} the surface was produced.
And CaO supplied from this and Si originating from the antioxidant
O _2, Al ₂ O ₃ -C, further consisting of the molten steel caused by the Al ₂ O ₃
low melting point material aO--SiO ₂ system is detected. From this fact, in order to cause CaZrO ₃ to effectively act on Al ₂ O ₃ and prevent nozzle clogging, the nozzle and the antioxidant that covers the nozzle should be heat-treated before the start of use, and CaZrO ₃ should be prepared beforehand.
It has been found that it is effective to react with the component contained in the antioxidant to decompose it and generate a low melting point substance. The present invention has been made based on these findings.

[0007]

[Function] For example, S is formed on the nozzle surface 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 and ZrO _{2 is} applied to the nozzle surface. And a CaO—SiO ₂ -based low melting point substance is generated. When the nozzle is used (the molten steel is circulated) in this state, the temperature of the molten steel in the vicinity of the molten steel contact surface 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
the aO-SiO ₂ composition. The substance of this composition is CaO-
Since it has a lower melting point than that of the SiO ₂ type and easily melts from the nozzle surface, it rarely adheres to and remains on the nozzle surface, and as a result, clogging of the nozzle is prevented.

By the way, if the above treatment is not carried out as in the conventional case, CaZrO ₃ is S derived from an antioxidant at high temperature.
It will directly react with iO ₂ and Al ₂ O ₃ derived from molten steel. In this case, since the low-melting point substance has not been generated in advance, the reaction is unlikely to occur, so that the low-melting point substance is not smoothly generated. For this reason, Al ₂ O ₃ is likely to adhere, and the nozzle is likely to be clogged.

The following can be exemplified as the nozzle base material for the effect of the present invention. 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 such as BN, SiC, B ₄ C, Si ₃ N ₄ , Zr
Non-oxides such as B ₂ , TiC, TiN and AlN, or metals such as Si, Ti, Mg and Ca, and carbon materials such as graphite,
And a base material obtained by kneading and molding with a slight amount of an additive such as a binder and then heat-treating as necessary.

On the other hand, as a coating material for coating the surface of the base material, the one having the composition shown in Table 1 can be exemplified, and the coating material is dipped, brushed, sprayed, etc.
The surface is attached uniformly with a certain thickness. 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, or a heat treatment method in which the coated nozzle is mounted in a continuous casting facility and heated by a nozzle preheating device. The heat treatment temperature needs to be 1200 ° C. or higher in order to react CaZrO ₃ and SiO ₂ , and the treatment time needs to be 60 minutes or longer.

[0011]

[Table 1]

Regarding the set range of the amount of calcium zirconate clinker containing CaO component used in the present invention in an amount of 5 to 35% by weight, if the amount is less than 50% by weight, the corrosion resistance will be poor, and it will exceed 80% by weight. And, the result is inferior spall resistance. Therefore, the range of 50 to 80% by weight is desirable. Regarding the CaO content of the calcium zirconate-based clinker, if it is less than 5% by weight, there is no effect in preventing adhesion, and if it exceeds 35% by weight, the ZrO ₂ content is small and the corrosion resistance is poor. desirable.

Regarding the setting range of the blending amount of the carbonaceous material, 1
If it is less than 0% by weight, the effect on spall resistance is small and
If it exceeds 10% by weight, the corrosion resistance decreases, so that the range of 10 to 30% by weight is desirable.

Metals such as Si, SiC, and S are used as the Si-based material.
Examples include iO ₂ , Si ₃ N ₄ and ZrSiO _{4, which} are added as an antioxidant for carbon materials and as a sintering material for aggregates.
Regarding the setting range of the blending amount, if the amount is 5% by weight or less, the effect is small, and if it is 25% by weight or more, the corrosion resistance is deteriorated.

[0015]

EXAMPLE The immersion nozzle for continuous casting treated by the method according to the present invention was applied to a two-strand type continuous casting facility to confirm the effect. Table 2 shows the nozzle materials used.

[0016]

[Table 2]

A nozzle containing CaZrO ₃ . This has the composition shown in Table 1, that is, the lower layer of SiO ₂ and Si.
It was coated with a coating material consisting of two layers of an upper layer containing O ₂ as a main component 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 2 strand side was heated to 1200 ° C., held for 60 minutes, and then immediately subjected to continuous casting. The casting grade was low carbon aluminized steel. As a result, the dipping nozzle was clogged during casting on the 1st strand side, and casting was abandoned.

On the other hand, no clogging occurred on the side of the two strands treated by the method of the present invention. In addition, although the present invention has been mainly described above applied to the nozzle for continuous casting, the present invention has the same effect even when applied to other nozzles or refractories for other applications described above. It is a thing.

[0019]

As described above, according to the present invention, CaZ
Al ₂ O containing nozzles for continuous casting of eg steel containing rO ₃
It is possible to very effectively and stably prevent the blockage due to the adhesion of ₃ etc., which can greatly contribute to the improvement of the productivity of steel.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Daijiro Mizukoshi 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Co., Ltd. Kimitsu Steel Co., Ltd. Stock Company Kimitsu Works

Claims (1)

[Claims] 1. A CaO component of 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 two or more components of O and Bi ₂ O ₃ mixed together are coated to form one layer or two or more layers, which are heat-treated at 1200 ° C. or more for 60 minutes or more. Method for preventing adhesion of Al ₂ O ₃ etc. to refractories.