KR900000783B1 - Materials for keeping warm the steel in the laddle - Google Patents

Abstract

Materials for keeping warm steel in ladle has advatages of preventing the absorption of alumina intermediate and reducing the heat radiation from the upper of the ladle steel that is refined in a converter, and comprises, in wt., 10-60% ash of coal briquettes, 10- 20% blast furnace sludge, 5-30% converter dust, 5-20% light and small dolomite white filter dust, 15-30% natural zeolite and 5-10% organic binder containing bentonite. The particle size of the bonded powder is 2-10 mm and the specific gravity is max. 0.7g/Cm2.

Description

Insulation material of ladle steel

1 is a bar graph showing the state of the thermal insulation layer 10 minutes after the input of the thermal insulation material in the induction melting stop bath.

2 is a graph showing the change in the thermal insulation temperature with the elapsed time in the thermal characteristic specifying device.

FIG. 3 is a bar graph showing the area ratio (cleanness) of inclusions in molten steel specimens after the insulation is added in Fe-Al-O system.

The present invention relates to a ladle lagging steel that can prevent the ladle molten steel temperature drop economically and efficiently after the converter outgoing, more specifically, using a steel binder and by-products of the commercial market, containing a plastic binder It relates to a heat insulating material for ladle steel bonded as bentonite.

In the steelmaking process, the molten steel received on the ladle after the converter has been subjected to secondary refining or cast continuously according to the product usage.

Molten steel temperature management after tapping since the secondary steel refining takes place for a long time, including gas bubbling, powder injection, degassing and RH bubbling, and injection. Has become the most fundamental factor for operational stability and quality improvement.

If the temperature of the ladle steel is severe and the converter tapping temperature is increased, the converter refractory life is greatly shortened and the loss of ferroalloy and deoxidizer at the time of tapping is increased, resulting in unstable operation, deterioration in quality, etc. This is a factor in the rise of manufacturing costs due to the increase in raw units.

For this reason, it is desirable to minimize the decrease in the molten steel temperature from the converter steel to the completion of injection.

Conventional ladle steel insulation is mainly based on the well-known supply alumina (Al ₂ O ₃ ), silica (SiO ₂ ), clay (clay) and natural bentonite and can only expect the thermal insulation effect depending on the composition, especially supply Since molten alumina is inexpensive and insulated, it contains more than 20% of most insulating materials, so that the floating capacity of the molten steel is separated and the absorption ability of the inclusions rising to the surface layer is lowered. many.

Non-metallic inclusions in molten steel are mostly composed of alumina (Al ₂ O ₃ ) composition produced by aluminum deoxidation, which contains 20% or more of alumina composition to the thermal insulation composition of the molten steel layer, and is incorporated into molten steel for oil transportation pipes. It will act as a major factor that adversely affects the quality of high-grade steel products such as shipbuilding and automotive.

In addition, because the inclusions in the molten steel promotes floating separation while the molten steel temperature is sufficiently maintained, the thermal insulation property as well as the thermal insulation composition of the ladle molten steel is also very important.

Recently, molten steel temperature management has become very important because the slag flowing into the upper surface of the ladle steel is mechanically blocked and the upper surface of the molten steel is almost exposed and the secondary refining is performed for manufacturing clean steel.

The inventors have observed that steel products, commercial by-products and domestic natural resources have been tested for different uses and disposed of at the time of disposal, and that they have good thermal insulation and beneficial effect on the quality of molten steel. With this in mind, the present invention has been proposed.

Accordingly, the present invention is effective in reducing the temperature drop of ladle steel after converter steel as well as granulating by combining granulated bentonite containing appropriate amount of steel mill and by-products in general and glass binders for domestic natural resources, as well as low alumina base metal inclusions. The purpose of the present invention is to provide a ladle insulation material which can improve the quality of molten steel by preventing the absorption ability and mixing in the molten steel.

EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention for achieving the said objective is demonstrated.

The present invention, in weight percent, briquette material: 10-60%, blast furnace sludge: 5-20%, total dust: 5-30%, light small dolomite back filter dust: 5-20% domestic Calcined benzoite containing 15-30% of phase natural zeolite and organic binder: 5-10%, and has a apparent specific gravity of less than 0.7g / cm3 and a particle size of 2-10mm after lamination. It is about insulation.

The reason for the numerical limitation will be described below.

Briquettes contain silica and a little alumina, calcium oxide (CaO), potassium oxide (K ₂ O), and unburned carbon (carbon) .The main components of silica are general insulating materials. In addition, unburned carbon is reburned in contact with hot molten steel after the molten steel is injected into the upper surface of the molten steel. However, the briquette alone does not significantly improve the level of the conventional ladle insulation, and in particular, it is difficult to bind into granules, and thus, components having insulation and bonding strength should be added in an appropriate composition.

The briquette material is preferably added at 10-60% by weight (hereinafter referred to as%), because the thermal insulation power is lowered at 10% or less, and slag formation and bonding force are reduced at 60% or more.

The blast furnace sludge and the electric furnace dust are composed of carbon (carbon), ferrous iron (FeO) and iron dioxide (Fe ₂ O ₃ ) as main components, and these particles are very fine and have a high specific surface area, and thus high temperature reaction is extremely active and powdery bonding strength is achieved. As a component having excellent properties, it is preferable to add 5-20% in the case of blast furnace sludge and 5-30% in the case of total dust, because the initial endotherm due to the lack of combustion reaction when both components are 5% or less. This increases and the heat retention after combustion is lowered, and if the blast furnace sludge is 20% or more, and in the case of total furnace dust 30% or more, the combustion reaction is sufficient, but since the refractory composition tends to be slag, the heat retention is low.

The addition of an oxidizing agent of sodium nitrate (NaNO ₃ ) and calcium nitrate (K ₂ NO ₃ ) to the blast furnace sludge and the whole furnace dust can promote an intense combustion reaction in a faster time, but the sludge or dust of the present invention is moisture (H ₂ O) Even when the mass is less than 10%, an intense combustion reaction occurs when the temperature reaches 1000 ° C., so that the addition of these oxidation promoters is not necessary at all.

In addition, expanded pearl rock, acid-treated graphite, etc., widely used as an expanding agent, are very expensive, but the natural zeolite of the present invention is abundant resources in Korea, and only a process of treating the natural state with powder requires stable supply and extremely low price. Inexpensive but more than twice the volume expansion near 1400 ℃ below the molten steel temperature.

This is because the volume expansion of natural zeolite is stable at room temperature, but the lattice structure changes around 1400 ℃, accompanied by the volume expansion of the lattice, and the volume expansion temperature is around 1400 ℃ which is much lower than 1600-1700 ℃, the ladle steel temperature of steelmaking process. Therefore, it can be seen that the volume expansion of the natural zeolite is promoted extremely actively.

In addition, natural zeolite not only expands in volume but also has silica as its main component, which not only enhances thermal insulation sustainability after combustion of the thermal insulation material, but also fundamentally prevents reincorporation or removal of alumina inclusions in molten steel. to be.

However, when 15% or less is added, the thermal insulation is less expandable, and since it is slag at 30% or more, the preferred amount of natural zeolite added to the thermal insulation of the present invention is 15-30%.

In addition, since the light dolomite bag filter dust is mostly dolomite and contains a considerable amount of calcium oxide (CaO), it provides excellent insulation as a refractory composition after combustion of the heat insulating material as well as desulfurization and dephosphorization reaction at the molten steel interface contact portion. And effectively absorbs non-metallic inclusions such as alumina, which are separated and floated in molten steel, to be accommodated in the thermal insulation layer, thereby providing a dual effect to greatly improve the cleanliness of molten steel. Is limited for the same reasons as in the case of the blast furnace sludge and the former furnace dust.

In addition, the calcined vantonite is used as a binder in the powder form and is a strength settlement that greatly improves the disadvantages of known clay and bentonite.

Generally known clay nabentonite is mainly used in the molding of the molding sand of the same component, and as a binder of the heat insulating material composition is weak in its function, it is used by mixing a tar system with clay or bentonite.

Bentonite mixed with a tar-based has a disadvantage of generating a significant odor when using a heat insulating material, powder due to lack of bonding force.

The calcined bentonite has a very good bonding strength by adding an appropriate amount of organic binder having excellent coking force in the process of calcining and producing natural bentonite, less than 5% of the cohesion is weak in the presence of a powder form and slag at 10% or more Since it promotes and lowers heat retention, the addition amount is preferably 5-10%.

The apparent specific gravity of the thermal insulation material of the present invention is preferably 0.7g / cm 3 or less to minimize the endothermic amount immediately after the thermal insulation material is added, and the bonding particle size of the thermal insulation material is 2-10mm to give an adequate space ratio and specific surface area to favor combustion reaction and heat retention. It is preferable to set it as the size of.

The reason why the cleanliness of the steel is improved when the thermal insulator of the present invention configured as described above is improved, firstly, the content of alumina is small in terms of the thermal insulation composition, and calcium oxide (CaO), dolomite (MgO), silica sand (SiO ₂ ) and trace amounts of alkali Metals readily absorb and accept alumina inclusions, which are deoxidation products, and secondly, there are few alumina inclusions re-incorporated into the molten steel from the thermal insulation layer. Because.

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

Dissolve at 1650 ℃ in 50Kg high frequency induction furnace to make a stop bath, and inject melting 500g of thermal insulation material having the component ratio of Table 1 into the cross section of 314cm2 crucible and observe the state of thermal insulation layer after 10 minutes. 1 is shown.

In addition, it is shown in FIG.

In addition, after dissolving electrolytic iron in a 50Kg induction furnace, a certain amount of Al was added to form a deoxidation product, and 500 g of a heat insulating material having a composition ratio shown in Table 1 was added thereto, and after 10 minutes, each molten steel sample was collected to obtain a surface analysis method (Image Analyzer Luzes). -500) to examine the inclusion area ratio to determine the cleanliness, and the result is shown schematically in FIG.

TABLE 1

As shown in FIG. 1, the insulation layer is divided into a molten slag layer and an unmelted powder layer, and the inventive material AD has a thicker powder layer than the comparative material. As shown, the inventive material AD is superior to the heating portion upper layer temperature, that is, the thermal insulation than the conventional example without the input of the comparative material and the thermal insulation material, the thermal insulation layer of the inventive material AD has a very small slag layer as well as natural Zeolite volume expansion, light dolomite bag filter dust, and appropriate amount of calcined bentonite make thermal insulation refractory to increase heat release resistance. On the other hand, in the case of the comparative material, except for supplying alumina, carbon, clay, and bentonite are mostly, so that slagization of the thermal insulation material is promoted, which is disadvantageous in thermal insulation.

As shown in FIG. 3, when the present invention AD is added, the inclusion area ratio is almost 0.01% or less, whereas when the comparative material is added, the inclusion area ratio is 0.023%. It can be seen that the case is much better than that of the comparative material.

As described above, the present invention can improve the added value by recycling the dust and sludges disposed of in the steel industry by providing an improved thermal insulation material, and can contribute to ladle temperature management and quality stability by reinforcing the thermal insulation function of the ladle thermal insulation material significantly In addition, it is possible to greatly contribute to the production of clean steel by minimizing the re-incorporation of the alumina-based inclusions from the slag layer to promote the separation and floating of the non-metallic inclusions in the molten steel with sufficient temperature.

Claims (1)

Insulation material of ladle steel to reduce the heat release of the upper surface of ladle steel after converting steel in the steelmaking process with little alumina inclusions in the steel, briquette material: 10-60%, blast furnace sludge: 10-20%, Total Roast Dust: 5-30%, Light Dolomite Bag Filter Dust: 5-20%, Natural Zeolite: 15-30% and Calcined Bentonite Containing Organic Binder: 5-10%. A ladle lagging steel, characterized in that -10 mm and an apparent specific gravity is 0.7 g / cm 3 or less.

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