KR100830829B1 - A composite of tundish coating material for high oxygen steel - Google Patents

Abstract

A tundish coating composition for the preparation of high oxygen molten steel is provided to permit various construction method for coating, to reduce raw material cost and to reduce the specific gravity of the coating by employing a composition comprising natural calcite and aluminum nitrate. A tundish coating composition for the preparation of high oxygen molten steel comprises binder, coagulant, plasticizer and spalling resistant agent for 100% by weight of clinker consisting of calcite and aluminum in the molar rate of 9:1-6:4. The clinker has 20% by weight of 1-2mm particle and 80% by weight of at most 1mm particle. The other ingredient in the calcite except CaCO3 is in the amount of at most 10% by weight for sintering and demounting of the coating. The aluminum nitrate has unreacted metal aluminum in the amount of less than 1% by weight for stalling resistance at pre-heating after construction. The coating is constructed in a dry method which is carried out while mixing fire-resistant composition and water at the edge of nozzle or in a wetting method which is carried out after mixing fire-resistant composition and water sufficiently in a kneader.

Description

A composite of tundish coating material for high oxygen steel}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a basic coating composition for the manufacture of high oxygen molten steel, which is applied and applied on a built-in refractory for tundish furnace used in casting molten steel. The present invention relates to a tungsten gotting material composition for producing high-oxygen molten steel, which is capable of improving inclusion and removal of inclusions and improving cleanliness of molten steel.

In general, magnesia-based coating materials are mainly used on the surface of tundish-embedded refractories used in the casting process to ensure the cleanliness of molten steel, but continuous casting due to insufficient efficiency of floating separation and removal of alumina inclusions in molten steel. Nozzle clogging occurs during the operation, which causes problems during operation, or is mixed with inclusions in the cast, thereby degrading cast quality.

In order to solve this problem, a large amount of calcium (Ca) is added during secondary refining or casting operations, or artificially treated limestone or mag-dolo clinker other than magnesia introduced in Japanese Patent Application Laid-Open No. 61-132568 can be used. There is a way to use the CaO component in the coating material. However, in such dry construction tundish coating material, it is impossible to use the mixture first with water due to the inevitable hydration of CaO component by the reaction of "CaO + H ₂ O → Ca (OH) ₂ ". Since the refractory composition and water are mixed and used, not only the addition moisture is limited, but also expensive additives are used.

In addition, in order to prevent the occurrence of hydration of the refractory composition, the wet method of first mixing using alcohol instead of water has shown a limitation in industrial application due to a price problem. In general, considering the fact that the tundish lining material is a high siliceous refractory brick or an alumina-silica inflow material, in the coating material of the cited invention, a reaction fusion occurs between the tundish inner material and the coating material during casting, and thus the coating material is prepared after the operation. When dismantling, there is a disadvantage in that the disassembly is poor.

Accordingly, the present invention is to improve the conventional problems as described above, the object is to provide a composition capable of producing a tundish coating material for producing high oxygen molten steel excellent in cleanliness of molten steel, excellent in workability and dismantling of the coating material To provide.

In order to achieve the above object, the present invention, to the 100% by weight of the clinker configured to have a ratio of calcite and aluminum nitride in a molar ratio of 9: 1 to 6: 4, an additive consisting of a conventional binder, flocculant, plasticizer and anti-thermal agent Characterized in that made.

On the other hand, the technical means according to the present invention is characterized in that the clinker has a granularity of 20% by weight, 1% or less, 80% by weight of 1mm or less.

Referring to the function and operation of the present invention, as described above.

The chemical composition of the calcite according to the present invention is not particularly limited, but in order to secure the sinterability and dismantling property of the coating material, the sum of the remaining components except CaCO ₃ is preferably 10% by weight or less. In addition, the manufacturing method and chemical composition of aluminum nitride, which is an artificial raw material, are not particularly limited. However, when metal aluminum is used as a starting material, unreacted metal aluminum is 1% by weight or less for preheating after construction. desirable.

Although the particle size of the clinker is not particularly limited as a constitution of the tundish coating material manufacturing method for producing high oxygen molten steel according to the present invention, granules having 1 to 2 mm of 20 wt% and 1 mm or less of 80 wt% are preferable.

There is no particular limitation on the type and content of the binder, flocculant, plasticizer and anti-expansion agent used in the tundish coating material composition for producing high oxygen molten steel according to the present invention, and a conventional one may be used. That is, conventional additives such as a binder of silicic acid and soda phosphate, a coagulant of slaked lime and magnesium sulfate, a plasticizer of clay and silica flower, a stake, an organic fiber, and a metal anti-heating agent may be used.

The construction method of the coating material using the tundish coating material composition for producing high-oxygen molten steel according to the present invention is not particularly limited, and "a dry method in which the refractory composition is mixed with water at the nozzle end" and "the refractory composition and water kneader" It is possible to use any of the "wet method, which is sufficiently mixed in the first and then constructed".

Hereinafter, look at in detail.

The calcite used in the present invention causes the following pyrolysis upon heating.

CaCO ₃ → CaO + CO ₂ (about 900 ℃)

After coating the coating material on the surface of the tundish interior material by applying the tundish coating composition for producing high oxygen molten steel according to the present invention, when heating before casting should be sufficiently maintained in the range of about 800 ℃ to 1000 ℃, at least CO ₂ It must be maintained for at least 1 hour to facilitate generation and discharge.

Aluminum nitride according to the tundish coating material composition for producing high oxygen molten steel according to the present invention

2AlN + 3 [O] in steel → Al ₂ O ₃ + 2 [N] in steel

It is used to enhance the binding force of the tundish coating material by using the reaction with the CaO component generated after calcite heating from the Al ₂ O ₃ component produced by the reaction of.

Since aluminum nitride used in the present invention uses dissolved oxygen in molten steel when producing alumina, it does not generate a large amount of low melting point calciium aluminate (nAl ₂ O ₃ · mCaO) as compared to using alumina clinker from the beginning as a starting material. It does not have the advantage that the contents of the tundish coating material is improved.

In the tundish coating composition for producing high oxygen molten steel according to the present invention, the ratio of calcite and aluminum nitride should be 9: 1 to 6: 4 in molar ratio.

When the ratio of calcite and aluminum nitride is greater than 9: 1, the CaO is excessive in the tungsten coating material composition for producing high oxygen molten steel, resulting in a reaction with internal refractories for tundish,

_{nAl 2 O 3 in refractories + mCaO} in coating materials → nAl 2 O 3 · mCaO

Reaction and

_{xSiO 2 in refractories + yCaO in coating} materials → xSiO 2 · yCaO

By the reaction of calcidium aluminate (nAl ₂ O ₃ · mCaO) and calium silicate (xSiO ₂ · yCaO) to produce a coating material and tundish interior material is reacted-fusion and decomposability after use is reduced.

On the other hand, the ratio of calcite and aluminum nitride is in the tundish coating material composition for producing high oxygen molten steel when the molar ratio is 6: 4 or less

_{nAl 2 O 3 in steel + mCaO} in coating materials → nAl 2 O 3 · mCaO

Due to the reaction, the CaO component to generate low melting point calcium aluminate (nAl ₂ O ₃ · mCaO) is insufficient, and the efficiency of trapping and separation of the alumina component in the molten steel is lowered, thereby degrading the cleanliness of the molten steel. Also,

2Al + 3 [O] in steel → Al ₂ O ₃ + 2 [N] in steel

It is not preferable because a large amount of nitrogen pick-up from AlN to steel used to enhance the binding force of the tundish coating material from the Al ₂ O ₃ component produced by the reaction of.

Examples are provided to help understand the present invention. However, the following examples are intended to better understand the content of the present invention, the present invention is not limited by the examples.

EXAMPLE

To 100% by weight of clinker composed of calcite and aluminum nitride shown in Table 1 in a molar ratio of 9: 1 to 6: 4, sodium phosphate as a binder, magnesium sulfate as a coagulant, clay as a plasticizer, and a stake as an antithermal agent, respectively. Kneading was carried out by extrapolation in the range of 3% by weight, 1% by weight, 4% by weight and 0.2% by weight or less. Then, dry or wet construction was sprayed on a 60-ton capacity tundish so as to have a thickness of 20 mm on the surface of the alumina-silica inlet.

In case of dry construction, water was extrapolated 10% by weight to 100% by weight of the mixture of the refractory composition at the tip of the nozzle, and in the case of wet construction, water by extrapolation was added by 100% by weight of the mixture of the refractory composition. After kneading, it was constructed.

After the coating material was cured at room temperature, heated and preheated (1100 ° C.), low carbon steel was cast in four castings to obtain Examples 1 to 4.

In addition, the basic coating material refractory composition was prepared in a range outside the range of the examples of the basic coating material refractory composition for manufacturing clean steel according to the present invention, to obtain Comparative Examples 1 and 2.

TABLE 1

Example Comparative example One 2 3 4 One 2 Calcite: Aluminum Nitride (Molar Ratio) 9: 1 6: 4 8: 2 7: 3 10: 1 5: 5 Construction method deflation Wet Wet deflation deflation Wet Steel cleanliness ^{1 )} Good Good Good Good Bad Good Reaction after coating-welding none none none none none Occur Constructability Good Good Good Good Good Good

1) Judging from the amount of alumina contained in the tundish slag after casting (good if the increase of alumina content in the slag before casting is more than 30% by weight, and bad if less than 10% by weight).

As shown in Table 1, Examples 1 to 4 according to the present invention was able to obtain the desired effect of the present invention, Comparative Examples 1 to 2 outside the scope of the present invention to secure the cleanliness of the steel or , Dissolution property was lowered due to the reaction-fusion with the tundish-embedded refractory.

As described above, according to the present invention, since it does not involve a hydration reaction by reaction with water, it is not only applicable to both dry and wet construction methods, but also a tundish interior material composed of a high siliceous refractory brick or an alumina-silica influent. There is almost no reaction fusion with and has the advantage of excellent dismantling of the coating material after use.

In addition, since it uses a natural calcite raw material, it is inexpensive and easy to use industrially, and there is an advantage that low specific gravity of the coating material is possible by CO ₂ generated by the fireproof composition during preheating.

While the invention has been shown and described with respect to particular embodiments, it will be appreciated that the invention can be varied and modified without departing from the spirit or scope of the invention as set forth in the claims below. It will be appreciated that those skilled in the art can easily know.

Claims (3)

100% by weight of clinker formed by mixing calcite and aluminum nitride, by adding an additive composed of conventional binders, flocculants, plasticizers and anti-thermal agents, The clinker is a tungsten coating material composition for producing high oxygen molten steel, characterized in that the mixing ratio of the calcite and the aluminum nitride is 9: 1 to 6: 4 in molar ratio. delete The method of claim 1, The clinker is 1 ~ 2mm 20 wt%, 1mm or less tungsten coating material composition for producing high oxygen molten steel, characterized in that it has a granularity of 80% by weight.