KR100805730B1 - Method for using basic refractories for tundish coating materials to produce high quality steel - Google Patents

Abstract

Use of a basic coating composition for refractory materials in production of high-quality steel is provided to realize excellent workability on and removability from the interior materials for a tundish furnace, to collect and remove substance inserted in steel effectively, thereby improving the quality of molten steel. A basic coating composition for refractory materials in production of high-quality steel is used by: providing a composition by adding to a binder, cohesive agent, plasticizer and anti-spallation agent to 100 parts by weight of clinker obtained by kneading either or both of magnesia(MgO) and magnesite(MgCO6) with dolomite(MgCO6.CaCO6) and calcite(CaCO6) selected in such a manner that the molar ratio of magnesium oxide(MgO) to calcium oxide(CaO) is 9:1-1:9; coating the surface of an interior material for a tundish furnace with the composition; and heating the coated surface at 650-1000 deg.C for 1-2 hours for the use in casting.

Description

Method for using basic refractories for tundish coating materials to produce high quality steel}

The present invention relates to a method for using a basic coating material refractory composition for manufacturing clean steel, and more particularly, to cast molten steel having a high content of alumina, and to be applied on internal refractories for tundish furnace bodies to include steel inclusions. It relates to a method of using a basic coating material refractory composition for producing clean steel that can improve the collection and removal ability of the steel to improve the cleanliness of molten steel.

Magnesia-based coatings refractory composition is mainly used on the surface of the internal refractories for tundish furnace body used in the casting process to ensure the cleanliness of molten steel. However, this magnesia-based coating refractory composition has a low efficiency of separation and removal of alumina inclusions in molten steel, causing clogging of nozzles during continuous casting, which may cause obstacles during operation or inclusions in cast steel. There is a problem in that the quality is reduced by mixing.

One of the prior arts for solving this problem is disclosed in Japanese Laid-Open Patent Publication No. 61-132568. This method uses artificially treated limestone or mag-dolo clinker in addition to magnesia to provide the calcium oxide (CaO) component to the coating. This calcium oxide is the most effective component as a clean element for removing alumina. However, in such dry construction tundish coating material, the calcium oxide component is inevitably hydrated due to the reaction of "CaO + H ₂ O-> Ca (OH) ₂ ". In addition, since the refractory composition and water are mixed and used at the tip of the nozzle, there is a disadvantage in that the addition moisture is limited and expensive additives are used.

In addition, in order to prevent the occurrence of the hydration phenomenon of the refractory composition, the wet method of first mixing using alcohol instead of water has been limited in industrial applications due to the price.

In addition, considering that the tungsten hull lining material is generally a high siliceous refractory brick or an alumina-silica inflow material, the above-described conventional coating material has a reaction fusion between the tundish hull lining material and the coating material during casting, and after operation When dismantling the coating material, there is a problem that workability is greatly reduced.

The present invention has been proposed to solve this problem, and is not applicable to any of dry or wet construction methods because it does not involve a hydration reaction with water, as well as a turn consisting of a high siliceous refractory brick or an alumina-silica influent. It is an object of the present invention to provide a method of using a basic coating material refractory composition for preparing a clean steel having excellent dismantling ability of the coating material after use since there is little fusion reaction with the interior material for a dish furnace body.

Technical composition according to the present invention for achieving the above object is magnesium oxide (MgO) and calcium oxide (CaO) of magnesia (MgO), magnesite (MgCO ₃ ) so that the molar ratio of 9: 1 to 1: 9. Turns out the basic coating refractory composition for clean steel production by adding a binder, a flocculant, a plasticizer and an anti-thermal agent to 100 parts by weight of clinker composed by kneading dolomite (MgCO ₃ · CaCO ₃ ) and calcite (CaCO ₃ ) with one or both selected. The surface of the interior of the dish furnace body is coated and configured for use in casting operations after heating for 1 to 2 hours in the range of 650 to 1000 ° C.

In addition, the mixing ratio of the binder is binder 2 to 100 parts by weight of clinker composed of kneading dolomite (MgCO ₃ · CaCO ₃ ) and calcite (CaCO ₃ ) with one or both selected from magnesia (MgO), magnesite (MgCO ₃ ) It is preferred to add 4 parts by weight, 0.5 to 2 parts by weight of flocculant, 3 to 5 parts by weight of plasticizer and 0.1 to 0.5 parts by weight of anti-thermal agent.

In addition, it is preferable to use one of silicic acid or soda phosphate as a binder, slaked lime or magnesium sulfate as a flocculant, clay or silica flower as a plasticizer, and organic fibers or equity as an anti-thermal agent.

delete

Hereinafter, the technical configuration of the present invention will be described in detail through specific examples.

The most characteristic constitution of the present invention is magnesium oxide (MgO) and calcium oxide (CaO) Magnesia (MgO), magnesite (MgCO ₃ ), dolomite (MgCO ₃ CaCO ₃ ) so that the molar ratio of 9: 1 to 1: 9 ) And calcite (CaCO ₃ ) to form a clinker (clinker).

The magnesite, dolomite, calcite is produced by the pyrolysis reaction upon heating to produce the magnesium oxide and calcium oxide required in the present invention and can be easily purchased on the market, it was selected as a raw material for making a basic coating material refractory composition in the present invention. In the present invention, since an important clean element is generated in the process of heating the coating material to a high temperature, a hydration problem as in the prior art does not occur.

The magnesia (magnesia) as MgO provides the magnesium oxide which is the main element of the basic coating material refractory composition according to the present invention as it is.

The magnesite (magnesite) is a mineral belonging to the trigonal system and is also called crypt. Its main component is MgCO ₃ , its hardness is 3.5 ~ 4.5, its specific gravity is 3 ~ 3.1, colorless, grey, white, yellow, red. It is translucent and is used as a raw material of refractory materials and magnesium. The purity of magnesia is not particularly limited, but considering the sinterability and dismantling properties of the coating material, it is preferable that the remaining components except magnesium carbonate (MgCO ₃ ) are less than 5 wt%.

The dolomite is a trigonal mineral, also known as dolomite and high limestone. The main component is MgCO ₃ · CaCO ₃ , the hardness is 3.5 ~ 4, specific gravity is 2.8 ~ 2.9, white, gray or pink, yellow, brown, green. Since it is formed by dolomite of calcite, it has properties similar to calcite described later.

The calcite is a mineral belonging to a hexagonal system, and is a kind of anhydrous carbonate mineral, showing the most various forms of minerals. The main component is CaCO ₃ , the hardness is 3, specific gravity is 2.6 ~ 2.8, colorless, white, gray, green, red, yellow and the like. The purity of the calcite is not particularly limited, but considering the sinterability and dismantling properties of the coating material, it is preferable that the remaining components except CaCO ₃ are less than 5% by weight.

There is no particular limitation as to the clinker particle size of the basic coating material refractory composition for manufacturing clean steel according to the present invention, but the magnesia, magnesite, dolomite, and calcite have a particle size of 1 to 2 mm at 20% by weight and 80% by weight at 1 mm or less for sinterability. It is desirable to have a configuration.

Of the minerals constituting the clinker of the basic coating material refractory composition for manufacturing clean steel, except for magnesia, the following pyrolysis reaction occurs to provide the magnesium oxide (MgO) and calcium oxide (CaO) required to form the present invention. do.

Magnesite: MgCO _3- > MgO + CO ₂ (about 700 ^o C)

Dolomite: MgCO ₃ ^. CaCO _3- > MgO (about 800 ^o C) + CaO (about 950 ^o C) + 2CO ₂

Calcite: CaCO _3- > CaO + CO ₂ (about 900 ^o C)

On the other hand, the clinker of the basic coating material refractory composition for manufacturing clean steel of the present invention is preferably mixed so that the magnesium oxide (MgO) and calcium oxide (CaO) in the molar ratio of 9: 1 to 1: 9.

If the molar ratio of magnesium oxide and calcium oxide is greater than 9: 1, the low melting point is caused by the reaction of "nAl ₂ O ₃ (molten steel) + mCaO (coating material)-> nAl ₂ O ₃ · mCaO" in the basic coating material refractory composition for manufacturing clean steel. Because of the formation of calcium aluminate (nAl ₂ O ₃ · mCaO), the lack of CaO component, the efficiency of trapping and separation of the alumina component in the molten steel is reduced and the cleanliness of the molten steel is reduced.

When the molar ratio of magnesium oxide and calcium oxide is greater than 1: 9, CaO is excessive in the basic coating material refractory composition for manufacturing clean steel, and the reaction with the internal component refractory material for tundish, that is, nAl ₂ O ₃ (refractory material) + mCaO (coating material)- > nAl ₂ O ₃ Calcium aluminate (nAl ₂ O ₃₎ by chemical reactions such as "mCaO" or by chemical reactions such as "xSiO ₂ (refractory) + yCaO (coating material)-> xSiO ₂ · yCaO" MCaO) and calcisium silicate (xSiO ₂ yCaO) are produced, and the coating material and the tundish lining material refractory are fused to decompose after use.

In addition, the present invention is 100 parts by weight of clinker composed of magnesia, magnesite, dolomite and calcite such that magnesium oxide (MgO) and calcium oxide (CaO) is in a molar ratio of 9: 1 to 1: 9, binder, flocculant, plasticizer and It comprises a heat inhibitor.

Furthermore, the binder, flocculant, plasticizer and anti-explosion agent 2 to 4 parts by weight of the clinker consisting of magnesia, magnesite, dolomite and calcite constituting the basic coating material refractory composition for manufacturing clean steel according to the present invention 2 to 4 parts by weight of the binder, 0.5 to flocculant It is preferred to include 2 parts by weight, 3 to 5 parts by weight of a plasticizer and 0.1 to 0.5 parts by weight of the heat inhibitor. This is to determine the content ratio that can optimize the function of each additive within the range that does not reduce the sinterability and release of the clinker according to the present invention through a number of experiments.

On the other hand, the type of the binder, flocculant, plasticizer and anti-explosion inhibitor is not particularly limited and may be a conventional one. Silicate or sodium phosphate as a binder, lime and magnesium sulfate as a flocculant, clay and silica flowers as a plasticizer, and equity, organic fibers, or metals are widely used as anti-thermal agents.

In the present invention, a method of using the basic coating material refractory composition for manufacturing clean steel is not particularly limited, and the "dry method in which the refractory composition and water are mixed at the tip of the nozzle is constructed" and "the refractory composition and water are sufficiently mixed first in a kneader. Any of the "wet method after construction" can be used.

However, after the basic coating material fireproof composition for manufacturing clean steel of the present invention is coated on the surface of the tundish interior material by a dry or wet method, it is preferable to sufficiently heat it for 1 to 2 hours in the range of 650 to 1000 ^o C. This facilitates the generation and discharge of carbon dioxide (CO ₂ ) in the coating material refractory composition before actual operation to prevent the coating agent from falling off due to the rapid generation of carbon dioxide during actual casting.

If the preheating temperature is lower than 650 ° C., the generation of carbon dioxide does not occur sufficiently, and even if it exceeds 1000 ° C., the amount of carbon dioxide is saturated and there is no economy. In addition, when the preheating time is less than 1 hour, the generated carbon dioxide is not sufficiently discharged, and after 2 hours, the generated carbon dioxide is almost completely discharged and thus it is not economical.

Hereinafter, a preferred embodiment of the present invention will be described in detail.

As shown in Table 1, in 100 parts by weight of magnesia, magnesite, dolomite and calcite in a molar ratio of 9: 1 to 1: 9, sodium phosphate as a binder, magnesium sulfate as a coagulant, clay as a plasticizer, and clay as heat inhibitor The shares were added and kneaded in the range of 3 parts by weight, 1 part by weight, 4 parts by weight and 0.2 parts by weight, respectively, to prepare a basic coating material refractory composition clinker for producing clean steel. The clinker was sprayed dry or wet on a 60 tonne capacity tundish to be 20 mm thick on the surface of the alumina-silica inlet. In the case of dry construction, 10 parts by weight of water was added to 100 parts by weight of the kneaded material of the refractory composition clinker at the tip of the nozzle. In the case of wet construction, 20 parts by weight of water was added to 100 parts by weight of the kneaded material of the refractory composition clinker. After construction. After the coating material was cured at room temperature and heated and preheated (1100 ^° C.), low-carbon steels were continuously cast 4 times to obtain Examples 1 to 4.

Also, Comparative Examples 1 and 2 were obtained by preparing a basic coating material fire resistant composition in a range outside the range of the examples of the basic coating material fire resistant composition for producing clean steel of the present invention.

Table 1

Example Comparative example One 2 3 4 One 2 MgO: CaO (molar ratio) 9: 1 1: 9 8: 2 2: 8 11: 1 1: 11 Construction method deflation Wet Wet deflation deflation Wet River cleanliness Good Good Good Good Bad Good Reaction Fusion Welding after Use none none none none none Occur Constructability Good Good Good Good Good Good

As shown in Table 1, Examples 1 to 4 according to the present invention was determined to be excellent in terms of cleanliness, reaction fusion, and workability of the steel. The cleanliness of the steel is judged to be good if the increase in the amount of alumina contained in the tundish slag before and after the casting is 30% by weight or more, and poor when it is 10% by weight or less. On the contrary, in Comparative Examples 1 and 2, the cleanliness of steel was weakly secured or fused with refractories for tundish interior, thereby degrading disassembly.

According to the method of using the basic coating material refractory composition for manufacturing clean steel according to the present invention configured as described above, the clean separation of alumina inclusions in molten steel with high efficiency can be produced by calcium oxide. In addition, instead of using artificially treated limestone or mag-dololo clinker as a source of calcium oxide, natural calcite or dolomite raw materials are used, so it is inexpensive and easy to use industrially, and is produced as a fireproof composition during preheating. There is also an effect that the specific gravity of the coating material can be reduced by carbon dioxide.

Claims (4)

Magnesium oxide (MgO) and calcium oxide (CaO) are selected from one or both of magnesia (MgO), magnesite (MgCO ₃ ) and dolomite (MgCO ₃ CaCO ₃ ) and the molar ratio of 9: 1 to 1: 9. Basic coating material refractory composition for clean steel manufacturing by adding a binder, a flocculant, a plasticizer and an anti-heating agent to 100 parts by weight of clinker formed by kneading calcite (CaCO ₃ ), and coating the surface of the interior material for tundish furnace body, 650 ~ 1000 ℃ range Method of using a basic coating fireproof composition for producing clean steel, characterized in that used for casting after heating for 1 to 2 hours. According to claim 1, Magnesia (MgO), Magnesite (MgCO ₃ ) selected from one or both of the dolomite (MgCO ₃ · CaCO ₃ ) and calcite (CaCO ₃ ) consisting of 100 parts by weight of clinker kneader binder 2 to 4 parts by weight, 0.5 to 2 parts by weight of flocculant, 3 to 5 parts by weight of plasticizer and 0.1 to 0.5 parts by weight of anti-thermal agent is used. The method according to claim 1 or 2, characterized in that one of silicic acid or soda phosphate as a binder, slaked lime or magnesium sulfate as a flocculant, clay or silica flower as a plasticizer, and organic fiber or equity as an anti-thermal agent is used. Method of using a basic coating material refractory composition for manufacturing clean steel. delete