JP2008045149A - Method for producing flux for steelmaking - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing flux for steelmaking with which the flux for steelmaking excellent in solubility and presevability can be obtained in reduced using amount of CaF<SB>2</SB>or without using CaF<SB>2</SB>. <P>SOLUTION: This method for producing flux for steelmaking includes; a first process for mixture-treating a plurality of raw material compositions; a second process for heating and melting the mixture obtained in the first process; and a third process for making glassy-state of the obtained solid flux for steelmaking by rapidly cooling the heated and melted mixture by crushing them with water. In this way, since the produced flux for steelmaking becomes an amorphous solid improved in the glassy degree, this flux is easily melted and the removing efficiency of inclusion becomes high and the loss of molten metal temperature can be reduced and it is hardly made into the powder, and the preservability is improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a method for producing a flux for steelmaking, and more specifically, to a method for producing a flux for steelmaking in which the vitrification degree is improved by quenching a molten raw material mixture by water granulation.

With the advancement of quality requirements for steel materials, the need for high-purity steel is increasing, and reduction of impurities such as oxygen, phosphorus, sulfur, and hydrogen in steel material production is required. Since it is inefficient to perform such high purification only by converter refining, it is practical to share some refining processes such as desulfurization with hot metal pretreatment before and after converter refining and secondary steel refining. It is now widely used.

For steelmaking, a general term for inclusion removal agents such as desulfurization agents and slagging agents, which are added to remove inclusions such as phosphorus and sulfur, degassing, and promote slag production in the refining process of molten steel This is called flux.
For example, CaO is conventionally used as a desulfurization agent and a dephosphorization agent in refining molten steel. Moreover, in the molten steel secondary refining process, CaO, Na ₂ CO ₃ , CaC ₂ , Mg, calcium aluminate (12CaO · 7Al ₂ O ₃ ) and the like are used as desulfurizing agents.

CaO having a desulfurizing effect and a dephosphorizing effect is excellent in economic efficiency and is most commonly used as a steelmaking flux, but has a high melting point (2572 ° C.) and low desulfurization and dephosphorization efficiency. Therefore, when CaO is used alone as a flux for steel making, it causes a loss of molten metal temperature and an increase in the amount of desulfurization soot due to an increase in the amount used, resulting in problems such as an increase in desulfurization treatment cost and a decrease in workability. Invite. Therefore, about 40% by weight of CaF ₂ (fluorite: melting point 935 ° C.) with respect to CaO is added as a melting material.
In addition to CaO, a desulfurization agent for calcium aluminate (12CaO · 7Al ₂ O ₃ ) having an advantage that it has a low melting point (1360 ° C.) and has a sulfide absorption ability and can suppress a resulfurization reaction. (See, for example, Patent Document 1).

JP-A-8-325628

However, since conventionally used steelmaking fluxes are crystalline, their melting points are generally high, and there is a problem in terms of workability such as long time for melting. Furthermore, since the flux for crystalline steelmaking has a large heat of melting, there is also a problem that it causes a loss of molten metal temperature.
As described above, the addition of CaF ₂ as a flux for improving the solubility has been conventionally performed, but in recent years, fluorine emission regulations for the environment have been implemented, and desulfurized soot containing fluoride ions. Therefore, it is desired to reduce the amount of CaF ₂ used or not to use CaF ₂ from the viewpoint of environmental conservation.
In addition, conventional steelmaking fluxes that are crystalline or sintered have high hygroscopicity, and if stored for a long period of time, they react with moisture in the air and break down into powder, which also has a problem in terms of storage stability. .

The present invention has been made in view of such circumstances, to reduce the amount of CaF _2, or without the use of CaF _2, steelmaking flux which can provide excellent steelmaking flux solubility and preservability It aims at providing the manufacturing method of.

The method for producing a flux for steelmaking according to the present invention in accordance with the object includes a first step of mixing a plurality of raw material compositions, a second step of heating and melting the mixture obtained in the first step, and the heating. A third step of quenching the molten mixture by water granulation and vitrifying the resulting solid steelmaking flux.

The method of manufacturing a steel flux according to the present invention, the raw material composition and CaO source of 30 to 60 mol%, may be _Al 2 _{O 3} source of 40 to 70 mol%.

In the method of steelmaking flux according to the present invention, the raw material composition and 30 to 70 mole% of the CaO source, and _Al 2 _{O 3} source 15 to 35 mol%, 15 to 35 mol% of CaF ₂ The raw material composition is preferably 40 mol% of a CaO source, 30 mol% of an Al ₂ O ₃ source, and 30 mol% of a CaF ₂ source.

In the method for producing a flux for steelmaking according to the present invention, the mixture of the heated and melted raw material composition is quenched by water granulation, so that crystallization is suppressed, and the resulting steelmaking flux is amorphous with improved vitrification. Become a solid. Such an amorphous steelmaking flux dissolves in a shorter time than a crystalline steelmaking flux having the same composition, and the heat of dissolution becomes smaller and the hatchability is improved. For this reason, the steelmaking flux provided by the present invention is easy to melt, so that the inclusion removal efficiency is high and the molten metal temperature loss can be reduced, so it was used as a degassing agent for ladle without a heat source. In particular, it has a remarkable effect.
Further, since the unit of use can be reduced, the amount of slag generated can be reduced, and the processing cost can be reduced.
Furthermore, by improving the degree of vitrification, it reacts with moisture in the air and becomes difficult to be pulverized, so the steelmaking flux provided by the present invention is compared with a crystalline steelmaking flux having the same composition. Improves storage stability.

The method of manufacturing a steel flux according to the present invention, as a raw material composition, and CaO source of 30 to 60 mol%, in the case of using the 40 to 70 mole% _Al 2 _{O 3} source and does not contain CaF ₂ The slag produced as a result of using the steelmaking flux to remove inclusions such as desulfurization of molten steel does not contain fluorine. For this reason, slag can be used for roadbed materials and the like that are particularly strict with respect to the fluorine content, so that it is possible to reduce the cost required for processing the slag and reduce waste.

The method of manufacturing a steel flux according to the present invention, as a raw material composition, and CaO source of 30 to 70 mol%, and 15 to 35 mole% _Al 2 _{O 3} source, and CaF ₂ source 15 to 35 mol% In addition to lowering the melting temperature by improving the vitrification degree of the steelmaking flux, the melting temperature can be further lowered by the addition of CaF ₂ , so that workability is improved.
In particular, as the raw material composition, and 40 mole% of the CaO source, and _Al 2 _{O 3} source 30 mol%, in the case of using a CaF ₂ source 30 mol%, the removal of the quick inclusions for easily melted It is possible to operate, and it is possible to obtain a steelmaking flux with a small molten metal temperature loss by adding a smaller amount of CaF ₂ than before.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
The steelmaking flux produced by the method for producing a steelmaking flux according to the first embodiment of the present invention includes, for example, inclusions such as desulfurization treatment of molten steel composed of molten steel for ordinary steel, molten steel for stainless steel, and the like. The composition is adjusted to a composition that can be used at the temperature at the time of removal (for example, about 1550 to 1650 ° C.), and the mixture of a plurality of raw material compositions that has been heated and melted is rapidly cooled by granulation to suppress crystallization. The glass is melted at a temperature lower than the quality, and the molten metal temperature loss is reduced.
In addition, the particle size of this steelmaking flux (for example, desulfurizing agent) is about 3 to 25 mm when added to an RH degassing tank or ladle. When used for a tundish (input stirring method) of continuous casting to 1 mm or less, the thickness is adjusted to about 1 to 3 mm according to the use conditions.

The method for producing a flux for steelmaking according to the first embodiment of the present invention is for producing a flux for steelmaking used for desulfurization of molten steel in converter refining or secondary refining of molten steel. and CaO source of 30 to 60 mol% being a second step of heating and melting a first step of mixing processes and _Al 2 _{O 3} source of 40 to 70 mol%, the mixture obtained in the first step And a third step of quenching the mixture heated and melted in the second step by water granulation.

Here, if CaO is less than 30 mol%, the inclusion removal performance of the obtained steelmaking flux is remarkably lowered. On the other hand, when CaO exceeds 60 mol%, the obtained steelmaking flux is not easily softened or melted in the molten steel, so that it is impossible to achieve high inclusion removal efficiency quickly.
Further, the Al ₂ O ₃ is less than 40 mol%, steelmaking flux obtained easily softened in molten steel, or no longer to melt, it is impossible to realize a fast and high inclusions removal efficiency. On the other hand, Al ₂ when O ₃ is more than 70 mol%, the resulting amount of CaO contained in the steel-making flux decreases inclusions removal performance is remarkably lowered.

Each process of the manufacturing method of the flux for steel manufacture which concerns on the 1st Embodiment of this invention is demonstrated. First, a CaO source and an Al ₂ O ₃ source are blended in the above-described proportions.
The raw material used here is, for example, quick lime, limestone, dolomite, etc. as the CaO source, and bauxite, shale shale, alumina, etc., as the Al ₂ O ₃ source. At the time of blending, the above-mentioned CaO source and Al ₂ O ₃ source are respectively converted into CaO and Al ₂ O ₃ for blending. As CaO source and _Al 2 _{O 3} source, can of course be used the CaO and _Al 2 _{O 3} is a reagent, respectively.

These raw material compositions are mixed so as to be as uniform as possible, and then charged into a melting furnace. As the melting furnace, any of a flat furnace, a vertical furnace, an electric furnace, etc. can be used, but in order to avoid contamination of impurities such as P and S from the furnace material, the furnace lining material is preferably composed of carbon. An electric furnace is preferred. A mixture melted in an arc electric furnace, which is an example of an electric furnace, that is, a melted material is aged for a certain time (for example, 5 to 20 minutes) and then rapidly cooled by water granulation.

Rapid cooling by water granulation is performed by putting the dissolved material directly into a water tank. The melt directly in contact with the cooling water in the water tank is rapidly cooled to become a glassy solid having a flaky or sandy appearance. Since the solid produced by cooling is solidified before crystallization proceeds, most of the solid is amorphous, and the crystallized portion is also refined as a result of preventing crystal growth. Yes. Therefore, the obtained steelmaking flux is softened or melted at a lower temperature than the crystalline flux having the same composition, and the heat energy consumed at that time is less than that of the crystalline flux.

The obtained steelmaking flux contains moisture, and there is a risk of causing a steam explosion if it is put into a converter or the like as it is. Therefore, drying is performed to remove moisture. Drying can be performed by any known means such as a dryer.

The method for producing a flux for steelmaking according to the second embodiment of the present invention is for producing a flux for steelmaking used for desulfurization of molten steel in converter refining or secondary refining of molten steel. and 30 to 70 mole% of the CaO source is a composition, and 15 to 35 mole% _Al 2 _{O 3} source, a first step of mixing processes and CaF ₂ source 15 to 35 mol%, in the first step It has the 2nd process of heat-melting the obtained mixture, and the 3rd process of rapidly cooling the mixture heat-melted at the 2nd process by granulation.

Here, if CaO is less than 30 mol%, the desulfurization performance of the obtained flux for molten steel will fall remarkably. On the other hand, when CaO exceeds 70 mol%, the obtained flux for molten steel is not easily softened or melted in the molten steel, so that it is impossible to achieve high inclusion removal efficiency quickly.
If Al ₂ O ₃ is less than 15 mol%, the resulting steelmaking flux will not be easily softened or melted in the molten steel, and it will not be possible to achieve high inclusion removal efficiency quickly. On the other hand, Al ₂ when O ₃ is more than 35 mol%, the resulting amount of CaO contained in the steel-making flux decreases inclusions removal performance is remarkably lowered.
On the other hand, if the CaF ₂ content is less than 15 mol%, the resulting steelmaking flux is not easily softened or melted in the molten steel, so that it is impossible to achieve a high and high inclusion removal efficiency. On the other hand, when the CaF ₂ exceeds 35 mol%, which can cause a problem in use of the roadbed of slag such as to produce a result of the removal processing of inclusions.

About each process of the manufacturing method of the flux for steel manufacture which concerns on the 2nd Embodiment of this invention, since the manufacturing method which concerns on the said 1st Embodiment is the same except the raw material composition to be used, it is here. Only the raw material composition to be used will be described.
First, a CaO source, an Al ₂ O ₃ source, and a CaF ₂ source are blended in the ratios described above. The raw material used here is, for example, limestone, limestone, dolomite, etc., as a CaO source, for example, Al ₂ O ₃ source, for example, bauxite, clay soil shale, alumina, etc., and a CaF ₂ source, for example, fluorite. During compounding is performed CaO source described above, _Al 2 _{O 3} source, and the CaF ₂ source, a formulation in terms of CaO and _Al 2 _O 3, CaF _2, respectively. Of course, as a CaO source, an Al ₂ O ₃ source, and a CaF ₂ source, the reagents CaO, Al ₂ O ₃ , and CaF ₂ can be used, respectively.

Next, examples carried out for confirming the effects of the present invention will be described. Here, FIG. 1 is a graph showing the relationship between the scattering angle (2θ) obtained by X-ray diffraction measurement of the steelmaking flux in Example 1 and the X-ray diffraction intensity, and FIG. It is a graph which shows the relationship between the scattering angle (2 (theta)) obtained by X-ray-diffraction measurement, and X-ray-diffraction intensity.
FIG. 3 shows the relationship between the scattering angle (2θ) and the X-ray diffraction intensity obtained from the X-ray diffraction measurement of CaO used as the raw material composition for the steelmaking flux in Examples 1 and 2 of the present invention. FIG. 4 is a graph showing the scattering angle (2θ) and X-rays obtained from X-ray diffraction measurement of Al ₂ O ₃ used as a raw material composition for a steelmaking flux in Examples 1 and 2 of the present invention. It is a graph which shows the relationship of diffraction intensity, respectively.
The X-ray diffraction measurement was performed using a Rigaku RINT2000 type automatic X-ray diffractometer (vertical goniometer) at an acceleration voltage of 40 kV and an acceleration current of 200 mA.

(Example 1)
CaO was used as a CaO source, and Al ₂ O ₃ was used as an Al ₂ O ₃ source. These were blended at a molar ratio of 12: 7, mixed uniformly, and heated and dissolved in an arc furnace. The obtained dissolved substance was put into a water granulating tank and subjected to water granulation. The glassy solid obtained by water granulation was recovered and dried with a dryer.
The result of the X-ray diffraction measurement performed on the steelmaking flux thus obtained is shown in FIG. As apparent from the comparison with FIGS. 3 and 4, X-ray diffraction peaks derived from CaO, Al ₂ O ₃ and crystalline 12CaO.7Al ₂ O ₃ in the raw material composition were hardly observed, and the 2θ value was observed. However, a broad diffraction gland with a low intensity was observed around 25 to 35 degrees. This result shows that the vitrification degree of the obtained flux for steel making is very high.

(Example 2)
The CaO as CaO source, _Al a 2 _{O 3} source as _Al 2 _{O 3,} a CaF ₂ respectively used as CaF ₂ source, were uniformly mixed raw material composition containing a molar ratio 40:30:30, It was heated and melted in an arc furnace. The obtained dissolved substance was put into a water granulating tank and subjected to water granulation. The glassy solid obtained by water granulation was recovered and dried with a dryer.
FIG. 2 shows the results of X-ray diffraction measurement performed on the steelmaking flux thus obtained. As is clear from comparison with FIG. 3 and FIG. 4, diffraction peaks derived from CaO, Al ₂ O ₃ , CaF ₂ , and calcium fluoroaluminate in the raw material composition were observed, but all had low strength. . This result shows that most of the obtained flux for steelmaking is glassy although some crystal components are present.

The present invention is not limited to the above-described embodiment, and can be changed without changing the gist of the present invention. For example, a part or all of the above-described embodiment and modification examples are combined. The present invention also includes a case where the method for producing a flux for steel making according to the present invention is configured.
For example, in the above embodiment, the raw material composition is mixed without being pulverized, but the raw material composition may be mixed after being pulverized, or the raw material composition is first mixed so as to be substantially uniform. And may be crushed.
Further, in the above-described embodiment, the pulverized product is directly crushed by putting it into the water tank. However, the pulverized product may be sprayed with pressure water.

It is a graph which shows the relationship between the scattering angle (2 (theta)) obtained from the X-ray-diffraction measurement of the flux for steel manufacture in Example 1 of this invention, and X-ray diffraction intensity. It is a graph which shows the relationship between a scattering angle (2 (theta)) and X-ray diffraction intensity obtained from the X-ray-diffraction measurement of the flux for steel manufacture in Example 2 of this invention. It is a graph which shows the relationship between a scattering angle (2 (theta)) and X-ray diffraction intensity obtained from the X-ray-diffraction measurement of CaO used as the raw material of the steelmaking flux in Example 1 and 2 of this invention. In Examples 1 and 2 of the present invention obtained by the X-ray diffraction measurement of Al ₂ O ₃ used as a steelmaking flux material is a graph scattering angle and (2 [Theta]) shows the relationship between the X-ray diffraction intensity.

Claims (4)

A first step of mixing a plurality of raw material compositions;
A second step of heating and melting the mixture obtained in the first step;
And a third step of vitrifying the obtained solid steelmaking flux by quenching the heated and melted mixture by water granulation, and a method for producing a steelmaking flux. The method of manufacturing a steel flux according to claim 1, wherein the raw material composition and CaO source of 30 to 60 mol%, of the steelmaking flux which is a _Al 2 _{O 3} source of 40 to 70 mol% Production method. 2. The method for producing a flux for steelmaking according to claim 1, wherein the raw material composition comprises 30 to 70 mol% of a CaO source, 15 to 35 mol% of an Al ₂ O ₃ source, and 15 to 35 mol% of a CaF ₂ source. A method for producing a flux for steel making, wherein: The method of manufacturing a steel flux according to claim 3, the CaO source of the raw material composition 40 mol%, and _Al 2 _{O 3} source 30 mol%, and characterized in that the CaF ₂ source 30 mol% A method for manufacturing a flux for steelmaking.

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