KR19990051489A - Synthetic Slag Manufacturing Method - Google Patents

Abstract

The present invention relates to a method for producing synthetic slag, the object of which is that when using the synthetic slag as a flux, it has excellent characteristics to remove the non-metallic inclusions of molten iron and molten steel, and also there is little dust generation suitable for preventing environmental pollution In particular, the present invention provides a method for producing an erosion resistant synthetic slag that can be manufactured at a low melting point and can be protected from erosion of a furnace or ladle.

In order to achieve the above object, the present invention provides a method for producing a synthetic slag, 3-7 weight of magnesia waste refractories with respect to the blended material blended with limestone: 50-80% by weight, alumina waste content: 20-50% by weight. The present invention relates to a method for producing a synthetic slag characterized in that the mixture is melted at a temperature of 1380 ° C. or more, followed by extraction and cooling, and the present invention further provides bentonite to a blended material in which the magnesia waste refractories are mixed. The present invention relates to a method for producing a synthetic slag, which is added at 7 wt% or less, melt-synthesized at a temperature of 1345 占 폚 or higher, and then extracted and cooled.

Description

Synthetic Slag Manufacturing Method

The present invention relates to a method for producing a synthetic slag that can be used for the adsorption removal of non-metallic inclusions contained in the molten metal in the steelmaking process, and more specifically, to prevent erosion of the refractory of the furnace or ladle during molten metal treatment. It relates to a method for producing erosive 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) According to Japanese Patent Application Laid-Open No. 54-4218, 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 -Synthetic slag manufacturing method for producing a shape by using molasses at the time of mixing one or more of the group consisting of Si.

b) Soviet patent publication SU439179 discloses a method for preparing 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 a remainder CaF ₂ , a method for producing a synthetic slag, which is particularly used for improving the surface properties of a casting;

d) Japanese Laid-Open Patent Publication No. 52-99915 proposed by New Nippon Steel suggests a synthetic slag that is used as a low-cost flux, which is composed of limestone: 20-60% and CaO-SiO ₂ system. Alumina is added in the ratio of CaO / Al ₂ O ₃ = 1-3 for deoxidation in molten steel.In particular, CaF ₂ is used in 20% or less in order to lower the melting point of the flux. Synthetic slag production method to add iron oxide content 3% or less.

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 of manufacturing a corrosion resistant synthetic slag that has characteristics and is almost free from dust generation, which is suitable for preventing environmental pollution, and that can be manufactured at a low melting point and that 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 provides a method for producing a synthetic slag, 3-7 weight of magnesia waste refractories with respect to the blended material blended with limestone: 50-80% by weight, alumina waste content: 20-50% by weight. It relates to a method of producing synthetic slag, characterized in that the mixture by mixing the melt at a temperature of 1380 ℃ or more, followed by extraction and cooling,

In addition, the present invention relates to a method for producing synthetic slag which is added to the blended raw material of magnesia waste refractory to 7% by weight or less of bentonite, melt-synthesized at a temperature of 1345 ℃ or more and then extracted and cooled.

Hereinafter, the present invention will be described in detail.

The present invention is used to remove the oxygen component of molten metal in the steelmaking process in the form of aluminum oxide in the molten steel, it can be used to adsorb and remove 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 of limestone (CaCO ₃ ), and the preferred limestone composition is shown in Table 1 below.

Ingredient CaO MgO SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ Thermal loss (1100 ℃) Limestone (% by weight) 48.5-55.6 0.1-3.5 1.5-4.8 0.2-2.1 0.1-2.5 37.5-43.8

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.

Ingredient Al ₂ O ₃ MgO SiO ₂ CaO Fe ₂ O ₃ Alumina Waste Refractories (wt%) 94.5-98.6 0.1-1.5 0.8-3.3 0.1-3.5 0.2-2.1

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, after mixing 3-7% by weight of magnesia waste refractories to the blended raw materials formulated to have the composition as described above, the mixture is put into a direct melting furnace at a temperature of 1380 ℃ or more and assembled through an assembly process, and then dried to a melting furnace. In the melting furnace, the powder or granulated raw material is dissolved in the melting furnace, whereby complete synthesis is achieved. This state is 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.

ingredient MgO Al ₂ O ₃ SiO ₂ CaO Fe ₂ O ₃ K ₂ O + Na ₂ O Magnesia Waste Refractories (% by weight) 94.0-98.8 0.5-2.3 1.1-4.6 0.3-3.7 0.5-2.8 ≤0.2

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, in order to achieve lower melting point, bentonite is added to 7% or less of magnesia waste refractory-containing blended material having the above composition.

In other words, when the bentonite is added in an amount of 7% or less with respect to the weight of the blending material, the compound may be melted at about 1360 ° C. rather than 1380 ° C. However, when the bentonite is added in an amount of 7% or more, the content of impurities increases, which is not preferable because it affects the erosion of the refractory and the removal ability of the nonmetallic inclusions when using the 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.

ingredient CaO Al ₂ O ₃ SiO ₂ MgO Fe ₂ O ₃ K ₂ O + Na ₂ O Bentonite (% by weight) 1.21-2.96 11.9-17.2 67.1-71.2 0.65-2.18 0.9-2.4 5.62-12.4

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.

Comparative Example 1 Inventive Example 1 Inventive Example 2 Inventive Example 3 Inventive Example 4 Inventive Example 5 Comparative Example 2 Limestone (% by weight) 42.5 50 57.5 65 72.5 80 87.5 Alumina Waste Refractories (wt%) 57.5 50 42.5 35 27.5 20 12.5 Water absorption% 3.5 0.5 0.2 0.1 0.1 0.6 5.8

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, high temperature must be maintained, which makes it difficult to utilize.

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

In this embodiment, 1%, 3%, 5%, 7%, and 9% of magnesia waste refractories are mixed with the compounding condition of the invention example (2) in Example 1, and the corrosion resistant synthetic slag is prepared in the composition shown in Table 6 below. We tried to derive the manufacturing conditions.

Comparative Example 3 Inventive Example 6 Inventive Example 7 Inventive Example 8 Comparative Example 4 Limestone 56.9 55.8 54.6 53.5 52.3 Alumina Waste Refractories 42.1 41.2 40.4 39.5 38.7 Magnesia Waste Refractories One 3 5 7 9

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 it is preferable to use 3-7% by weight when using magnesia waste refractories in the production of synthetic slag.

Example 3

In this example, bentonite was added by adding 1%, 3%, 5%, and 7% to the compounding material of the erosion resistant synthetic slag of Inventive Example (6), and the compounding conditions are shown in Table 7 below.

Inventive Example 6 Inventive Example 9 Inventive Example 10 Inventive Example 11 Inventive Example 12 Limestone 54.6 54.05 52.96 51.87 50.58 Alumina Refractories 40.4 40.0 39.19 38.38 35.57 Magnesia Waste Refractories 5 4.95 4.85 4.75 4.65 Bentonite 0 One 3 5 7

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 FIG. 2, it can be seen that the addition of bentonite below 7% results in a lower pour point temperature compared to Example 6, which is a case in which no bentonite is 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).

Also, at 7% or more of bentonite, the pour point temperature is very low, but this is not preferable because it damages the refractories of the ladle or furnace, and the melting point is much lowered in the results of the present example, which may damage the refractory. 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%, 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, 3-7% by weight of magnesia waste refractories is mixed with a blended material of limestone: 50-80% by weight and alumina waste refractories: 20-50% by weight, followed by melt synthesis at a temperature of 1380 ° C or higher, followed by extraction and cooling. Method for producing synthetic slag In the method for producing a synthetic slag, 3-7% by weight of magnesia waste refractories are mixed with a blended material of limestone: 50-80% by weight and alumina waste refractories: 20-50% by weight, and bentonite 7 is mixed with the magnesia waste refractory. Method for producing synthetic slag, characterized in that the addition by weight or less, melt-synthesizing at a temperature of 1345 ℃ or more, extraction and cooling