KR100328072B1 - Fabrication method of synthesized slag - Google Patents

Abstract

PURPOSE: A fabrication method of a synthesized slag which exhibits excellent efficiency in removal of non-metallic inclusions without dust scatter and decreased attack against ladle and furnace refractory bricks is provided. CONSTITUTION: The fabrication method of a synthesized slag includes the steps of blending 50 to 80 wt.% of limestone, 20 to 50 wt.% of waste alumina refractory material, 3 to 7 wt.% of waste magnesia refractory material and 3 wt.% or less of bentonite; and melting the mixture at higher than 1345°C for synthesis, followed by extraction and cooling.

Description

Synthetic Slag Manufacturing Method

The present invention relates to a method for producing a synthetic slag that can be used to adsorb and remove non-metallic inclusions contained in molten metal in a steelmaking process, and more particularly, corrosion resistance that can protect refractory erosion of furnaces or ladles during molten metal treatment. It relates to a method for producing synthetic slag.

Generally, synthetic slag is a material of melt-synthesized state mainly composed of CaO-Al ₂ O ₃ , unlike the composition of slag generated in the steelmaking process. This synthetic slag is not only applicable to raw materials for civil engineering and building materials, but also mainly used for flux used for adsorption removal of non-metallic inclusions. Especially, researches focused on positive use are being actively conducted. There are things like

a) Japanese Laid-Open Patent Publication No. 54-4218 discloses slag generated from blast furnace and Mg, CaC ₂ , Na ₂ CO ₃ , BaCO ₃ , CaCl ₂ , BaCl ₂ , NaAlF ₆ , Al, Ca-Si, Fe- A method of producing a synthetic slag is disclosed in which one or more of the groups consisting of Si are mixed and a shape is produced by using molasses in production;

b) Soviet patent publication SU439179 describes a method for producing synthetic slag used as a purification flux for structural steel and stainless steel, which is 20-40 wt% CaO and 18-32wt% Si ₂ O. And remainder CaF ₂ , which is used to improve the surface properties of the casting.

c) Japanese Laid-Open Patent Publication No. 52-99915 (New Nippon Steel Co., Ltd.) discloses a method for producing a synthetic slag used as a low-cost flux, which is limestone: 20-60% and CaO-SiO ₂ system. Alumina is added at a ratio of CaO / Al ₂ O ₃ = 1-3 for deoxidation in molten steel, and especially CaF ₂ is used at 20% or lower in order to lower the melting point of the flux. It is a method for producing synthetic slag in which the iron oxide content is added to 3% or less by adding a metal.

Synthetic slag prepared by the above-mentioned conventional method, in particular, the synthetic slag used as a plus contains CaO, CaF ₂ and SiO ₂ and the like, is hydrated with Ca (OH) ₂ by absorbing moisture in the air, and dehydrated and nonmetallic inclusions. At the time of adsorption, there is a problem in that a large amount of dust is generated by vaporizing due to high vapor pressure generation and being discharged out of the bath surface.

In order to solve the above problems, the present inventors have repeatedly conducted studies and experiments, and based on the results, the present invention is excellent in removing nonmetallic inclusions of molten iron and molten steel when using synthetic slag as a flux. The present invention provides a method for producing a corrosion resistant synthetic slag which has characteristics and is almost free from dust generation, which is suitable for preventing environmental pollution, and which can be manufactured at a low melting point and which can be protected from the erosion of roche or ladle. have.

1 is a graph showing the erosion depth of each composition by the rotary erosion test

Figure 2 is a graph showing the pour point temperature by the heating microscope of the synthetic slag with respect to the bentonite mixing ratio

In order to achieve the above object, the present invention is a method for producing a synthetic slag, limestone: 50-80% by weight and alumina waste refractory: 20-50% by weight of blended ingredients: 93-97% by weight and magnesia waste refractories : A method for producing synthetic slag, comprising mixing magnesia waste refractories in a blended material so as to be 3-7% by weight, followed by melt synthesis at a temperature of 1380 ° C. or higher, followed by extraction and cooling.

In addition, the present invention is to add the bentonite to the blended blended material so that the magnesia waste refractory material is mixed: 93% by weight or more and bentonite: 7% by weight or less by melting and synthesis at a temperature of 1345 ℃ or more, extraction, cooling It relates to a synthetic slag production method.

Hereinafter, the present invention will be described in detail.

The present invention is used to remove the oxygen component of the molten metal in the steelmaking process in the form of aluminum oxide in the molten steel, it can be used for adsorption and removal of not only alumina oxide but also other impurity oxides or non-metallic inclusions, The present invention relates to a method for producing erosion resistant synthetic slag having corrosion resistance.

The limestone may be any one of ordinary limestone (CaCO ₃ ), and a preferable limestone composition is shown in Table 1 below.

The amount of such limestone is preferably 50-80% by weight in the proportion of CaO-Al ₂ O ₃ based on the alumina waste refractories. Since the amount of CaO increases, the melt synthesis becomes difficult, and even if the alumina waste refractories exceed 50 wt%, the amount of Al ₂ O ₃ increases, resulting in a high melting point composition, making the melt synthesis difficult. In addition, the particle size of the limestone is preferably not more than 35 mesh (0.5mm) is usually 80% or more because the fuel consumption is different due to the difference in the time taken to melt depending on the mixing state at the time of mixing to be.

The alumina waste refractories may be used a conventional one, the typical chemical components are shown in Table 2 below.

The amount of the alumina waste refractories is preferably 20-50%. The reason for this is that when the amount of the alumina waste refractories is less than 20%, the high melting point CaO component is increased, making it difficult to melt the synthetic slag, 50%. This is because the Al ₂ O ₃ content is increased when the melt synthesis is moved to a high melting point is difficult to melt. In addition, it is preferable to maintain the particle size of the alumina waste refractories to be 90% or more because the difference in melting time occurs depending on the mixing state during mixing.

In the present invention, the magnesia waste refractory material is added to the blended raw material blended to have the composition as described above so that the content of magnesia waste refractory material in the blended raw material is 3-7% by weight, mixed, and then directly added to the melting furnace at a temperature of 1380 ° C. or higher. After assembling through the granulation process, and dried and put into the melting furnace, the powder or granulation raw material is dissolved in the melting furnace, thereby completely synthesizing the melt, and this state is a melt-synthesized flux. The molten synthetic flux is a synthetic slag is prepared by extraction and cooling in a conventional manner in the molten state.

At this time, the preferable composition of the magnesia waste refractories is shown in Table 3 below.

The main component of the synthetic slag prepared as described above may be represented by xCaO.yAl ₂ O ₃ , and if the compounding condition of the present invention is satisfied, the chemical composition is maintained by maintaining an appropriate R (x / y) value, which is a molar ratio of CaO and Al ₂ O ₃ . It has low distribution and variation, is synthesized uniformly, and contains MgO component of magnesia waste refractories, and shows the erosion resistance effect to protect the furnace or ladle refractories from erosion when used for adsorption of nonmetallic inclusions of molten metal.

Conventionally, since limestone or alumina is used to prepare the flux for removing inclusions, each melting temperature is very high, so that the melted mixture can be melted at a high temperature of about 1500 ° C. However, in the present invention, limestone and alumina waste refractories are used. The low melting point components in the sludge and the activity of the used waste refractories are high, so the reaction is excellent. Thus, the synthetic slag melt-synthesized at the melting temperature of 1380 ° C., which is lower than the conventional melting point, can be produced. It is very desirable for the characteristics that can greatly reduce the amount of heat required and environmentally friendly recycling of waste refractories.

In addition, in the present invention, bentonite is added to the magnesia waste refractories-containing blended material having the above composition so that the content of bentonite in the blended material is 7% or less in order to achieve lower melting point.

That is, when bentonite is added and blended so that the bentonite content of the blended material is 7% by weight or less, melt synthesis is possible at about 1345 ° C lower than 1380 ° C. However, when the content of bentonite is 7% or more, the content of impurities increases, which is not preferable because it affects the erosion of refractory materials and the removal ability of non-metallic inclusions when using synthetic slag. Preferably, the bentonite is a powder having 80% or more of 200 mesh (0.074mm) or less. This is because it is more effective in increasing the viscosity of bentonite blended raw material, and it is possible to maintain the strength and the action of reducing dust during assembly. In addition, the preferred composition of the bentonite is shown in Table 4 below.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

This example was carried out to determine the blended weight percentage of limestone and alumina waste refractories. It was blended so as to have a weight of 200 g in the ratio as shown in Table 5 and melted for 2 hours at a melting temperature of 1380 ℃ to extract the synthetic slag in the molten synthetic state and then cooled. For the cooled synthetic slag specimens, the absorbance was measured according to KSL1001 (absorption test of ceramic ceramic tiles), and the results are shown in Table 5 below.

As shown in Table 5, in the case of Comparative Examples (1) and (2) outside the mixing conditions according to the present invention, the absorption rate shows 3.5% and 5.8%, and the absorption rate is considerably high. Shows. This can be seen as a condition that only a slight sintering occurs and the normal melt synthesis is not achieved, in the case of Inventive Example (1-5) that satisfies the compounding conditions of the present invention indicates that the water absorption is 1% or less.

It was confirmed that the melt-synthesized state was melted sufficiently even by the naked eye. In other words, if the absorption rate is high, the state of melt synthesis is poor. In the case of Comparative Example (1-2), a higher temperature condition is required for complete melting, but the melting temperature increases rapidly in the state diagram of CaO-Al ₂ O ₃ . When melting, it is necessary to maintain a high temperature state is difficult to use.

On the contrary, in the case of Inventive Example (1-5), it means that the molten state is complete at a temperature of 1380 ° C. and that the composition is well synthesized, and that a homogeneous molten synthetic slag can be produced. Since it can be synthesized at a low temperature, it indicates that the heat can be greatly reduced. Considering only the pure relationship between CaO and Al ₂ O ₃ , in the CaO-Al ₂ O ₃ state diagram, the melting temperature of Comparative Example (1,2) is 1500 ℃ or higher, so that high temperature energy is required and the melting time is excessive. Component deviations and inhomogeneities of the material are exhibited.

In the case of alumina waste refractories in the production of the synthetic slag of the present invention, the case of 50% or more corresponds to Comparative Example (1), and less than 20% corresponds to Comparative Example (2). It is preferable that the formulation of municipal alumina waste refractories is 20-50% by weight. In addition, limestone accounts for 50-80% by weight.

Example 2

As shown in Table 6, the magnesia waste refractories in the blending material of Inventive Example (2) in Example 1 is 1%, 3%, 5%, 7%, 9 Blended to make a blended raw material.

The mixture of the content ratios as shown in Table 6 is maintained for 2 hours at the melting temperature of 1380 ℃, extracted by cooling the synthetic slag in the molten state, after preparing the synthetic slag and erosion resistance of the furnace or ladle for molten metal treatment In order to test, the erosion resistance was tested by rotating the synthetic slag in the molten state and measuring the erosion depth of the refractory. Magnesia refractory material was used for the inner wall material of the melt rotational erosion tester used in this example and a thickness of 50 mm was used. LPG was used as the heat source of the burner for melting, and the temperature was tested for 6 hours at 20 RPM at 1600 ° C. The inner wall of the rotary erosion tester was lifted and the eroded inner wall thickness was measured. The results are shown in FIG. 1. .

As shown in FIG. 1, the comparative example (3) has an erosion depth of 15 mm and shows an erosion rate of 30%. Inventive Example (6-8) shows that the erosion rate was kept below 10%. In Comparative Example (4), the amount of magnesia waste refractories in the amount of Inventive Example (8) may be sufficient, and it may be regarded as an upper limit of utilization of magnesia waste refractories having no effect.

Therefore, it can be seen from the results of this example that when using magnesia waste refractories in the production of synthetic slag, the content of magnesia waste refractories in the final blended material is preferably 3-7% by weight.

Example 3

As shown in Table 7 below, bentonite was added to the blending material of the erosion resistant synthetic slag of Inventive Example 6 so that the bentonite content of the blending material was 1%, 3%, 5%, and 7% to prepare the blending material. It was.

Melting temperature of the sample having a mixing ratio as shown in Table 7 was measured by measuring the pour point temperature of the sample through a heating microscope to measure the melt synthesis temperature and the results are shown in FIG.

As shown in Figure 2, it can be seen that when the bentonite is added to 7% or less in the blended raw material, the pour point temperature is lower than in Example (6), which is not added.

As shown in Example 9-9 of the present invention, the temperature of the pour point is lowered on the heating microscope, thereby lowering the actual melting temperature. Therefore, in the present invention, the pour point temperature in Inventive Example (12) is 1345 ° C, and the pour point temperature is formed at a temperature drop of 28 ° C as compared to Inventive Example (6).

In addition, when the content of bentonite in the blended material is 7% or more, the pour point temperature becomes very low, but this is not preferable because it damages the refractories of the ladle or the furnace body. There is this. However, by increasing the concentration of MgO component in the synthetic slag of the present invention, the damage to the wall of the furnace or ladle is related to the concentration gradient, it can be seen that the erosion resistant synthetic slag of the present invention is relatively stable.

Therefore, according to the results of the present embodiment, when the molten synthetic slag is manufactured by mixing bentonite within 7% in the blended raw material, the molten synthetic slag can be sufficiently produced at the pour point temperature of 1345 ° C or higher.

As described above, the present invention mixes magnesia waste refractories and bentonite with limestone and alumina waste refractories to produce a corrosion resistant synthetic slag for removing non-metallic inclusions at a low melting point, so that the melt is melted at a lower temperature than before. It can be said to have important meanings in terms of environment-friendly recycling, and it can be used for the removal and removal of non-metallic inclusions in the steelmaking process, contributing to the development of the steel industry, and reducing the generation of dust in environmental pollution problems to maintain a pleasant environment. have.

Claims (2)

In the method for producing a synthetic slag, Magnesia waste refractories were mixed with the blended raw materials such that limestone: 50-80 wt% and alumina waste refractories: 20-50 wt%, 93-97 wt%, and magnesia waste refractories: 3-7 wt%. Next, after the melt synthesis at a temperature of 1380 ℃ or more, the synthetic slag manufacturing method characterized in that the extracted synthetic slag in the melt synthesized state and then cooled In the method for producing a synthetic slag, Magnesia waste refractories were mixed with the blended raw materials such that limestone: 50-80 wt% and alumina waste refractories: 20-50 wt%, 93-97 wt%, and magnesia waste refractories: 3-7 wt%. Next, bentonite was added to the blended blended material such that the magnesia waste refractory material was mixed: 93 wt% or more and bentonite: 7 wt% or less, melt-synthesized at a temperature of 1345 ° C. or higher, and then synthesized in a melt-synthesized state. Synthetic slag manufacturing method characterized in that the slag is extracted and then cooled

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