Method for producing silicon-based alloy

Abstract

Provided is a production method which is suitable for mass production and by which a silicon-based alloy having an extremely low concentration of titanium can be produced without using high-quality raw materials. Raw materials including a silicon source and a reducing material are heated and melted to produce a melt, and the produced melt is subjected to additional refining. A non-oxidizing gas containing nitrogen is blown into the melt in a first stage of the additional refining, and an oxidizing gas containing oxygen is blown into the melt in a second stage of the additional refining.

Description

Method for producing silicon-based alloys

[0001] The present invention relates to a method for producing a silicon-based alloy with few impurities.

[0002] Silicon-based alloys are alloys containing silicon. Ferrosilicon, which contains silicon and iron, is a typical silicon-based alloy. Silicon-based alloys are mainly used as deoxidizers for steelmaking and as additives for adjusting the composition according to each steel grade. In particular, when silicon-based alloys are used to adjust the silicon concentration when melting steel slabs used in the production of electrical steel sheets, a high concentration of impurity elements contained in the silicon alloy may lead to deterioration of the characteristics of the electrical steel sheet product itself. For this reason, it is necessary to reduce the concentration of impurities contained in silicon alloys.

[0003] Generally, silicon-based alloys are produced by charging iron ore as an iron source, silica stone as a silicon source, and coke, charcoal, or the like as a reducing agent into an electric furnace, and alloying iron and silicon while melting and reducing the iron ore and silica stone. The purity of the resulting silicon-based alloy depends on the concentration of impurities contained in these raw materials.

[0004] Among the impurity elements that may be contained in silicon-based alloys, calcium and aluminum can be easily oxidized by blowing an oxidizing gas containing oxygen into a molten silicon-based alloy and removed as slag. On the other hand, titanium, for example, is thermodynamically less susceptible to oxidation than calcium and aluminum, making it difficult to completely remove by blowing an oxidizing gas. Given this technological background, one method for producing silicon-based alloys with low impurity concentrations is to use high-quality raw materials with extremely low impurity concentrations.

[0005] As another method for producing a silicon-based alloy having a low concentration of titanium, for example, Patent Document 1 describes a method in which calcium-containing ferrosilicon is crushed and the crushed ferrosilicon is immersed in an aqueous solution containing ferric chloride to liberate and remove the titanium-containing phase by a wet treatment.

[0006] Japanese Patent Application Publication No. 3-153839

[0007] However, the use of high-purity, high-grade raw materials increases the production cost of silicon-based alloys. Furthermore, the production of ferrosilicon by the wet processing described in Patent Document 1 requires crushing of the ferrosilicon, making it unsuitable for mass production such as for steelmaking.

[0008] In view of the above problems, the present invention aims to provide a manufacturing method suitable for mass production that can produce a silicon-based alloy with an extremely low titanium concentration without using high-quality raw materials.

[0009] The present inventors have conducted extensive research into a method for producing silicon-based alloys in which raw materials containing a silicon source and a reducing agent are charged into an electric furnace and heated and melted to produce a molten material, with the aim of reducing the concentration of impurities that may be contained in the silicon-based alloy, particularly titanium. As a result, they have found that the concentration of titanium contained in the molten material can be reduced by performing additional refining in which a non-oxidizing gas containing nitrogen is blown into the molten material before blowing in an oxidizing gas containing oxygen, thereby completing the present invention.

[0010] The gist of the present invention is as follows: [1] A method for producing a silicon-based alloy, which comprises heating and melting raw materials containing a silicon source and a reducing agent to produce a molten material, and subjecting the produced molten material to additional refining, characterized in that a non-oxidizing gas containing nitrogen is blown into the molten material in a first period of the additional refining, and then an oxidizing gas containing oxygen is blown into the molten material in a second period of the additional refining.

[0011] [2] The method for producing a silicon-based alloy according to the above [1], comprising the steps of: charging the raw materials into a first container, heating and melting them to produce the molten material; transferring the produced molten material from the first container to a second container; and subjecting the molten material transferred to the second container to the additional refining.

[0012] [3] The method for producing a silicon-based alloy according to the above [1], wherein the raw materials are charged into a multi-purpose container, heated and melted to produce the molten material, and the produced molten material is subjected to the additional refining while being held in the multi-purpose container.

[0013] [4] A method for producing a silicon-based alloy according to any one of [1] to [3] above, wherein the concentration of aluminum contained in the molten material is 0.10 mass% or more in the first period of the additional refining.

[0014] [5] The concentration of titanium contained in the molten material before the start of the additional refining is [Ti] ０ (mass%), the mass of the molten material to be subjected to the additional refining is M ｍ (kg), and the density of the melt is ρ ｍ (kg / m ３ ), the flow rate of the non-oxidizing gas blown into the melt is Q ｇ (Nm ３ / min), and the concentration of nitrogen in the non-oxidizing gas (N ２ ) (vol %), the relationship shown in mathematical formula (1) holds. [Mathematical formula 1] Q ｇ ≧ {7500・M ｍ / ρ ｍ / (N ２ ) × [Ti] ０ １．５ ...(1)

[0015] [6] The method for producing a silicon-based alloy according to any one of [1] to [5] above, wherein the raw materials include an iron source.

[0016] According to the present invention, it is possible to mass-produce silicon-based alloys with extremely low titanium concentrations without using high-quality raw materials.

[0017] In one embodiment, the present invention relates to a method for producing a silicon-based alloy, which comprises heating and melting raw materials containing a silicon source and a reducing agent to produce a molten material, and then subjecting the molten material to additional refining, characterized in that a non-oxidizing gas containing nitrogen is blown into the molten material in a first period of the additional refining, and then an oxidizing gas containing oxygen is blown into the molten material in a second period of the additional refining.

[0018] <Heat-melting of raw materials> In the method for producing a silicon-based alloy according to the present invention, first, a melt-reduction process is performed in which raw materials containing a silicon source and a reducing agent are heated and melted to produce a molten material. The types of silicon source and reducing agent contained in the raw materials are not particularly limited, and the types of silicon source and reducing agent may be appropriately selected depending on the component composition of the target silicon-based alloy. In the present invention, titanium contained in the molten material can be removed by subjecting the produced molten material to additional refining, as described below. This eliminates the need to use a high-quality silicon source with an extremely low titanium concentration, thereby reducing the cost of raw materials compared to conventional techniques.

[0019] As the silicon source, for example, silica stone can be used. As the reducing agent, for example, coke or charcoal can be used. For the silicon source and the reducing agent, one type of raw material may be used for each, or two or more types of raw materials may be mixed and used. By heating and melting raw materials containing silica stone and a reducing agent, the silica stone and the reducing agent react with each other, and the silica stone is reduced to produce silicon.

[0020] The silicon-based alloy produced by the production method according to the present invention may be high-purity silicon, or may be an alloy of silicon and iron such as ferrosilicon. In the former case, the silicon content of the silicon-based alloy may be 100% by mass. In the latter case, the raw material contains an iron source. Iron oxide, typically iron ore, may be used as the iron source. When producing ferrosilicon, the mass ratio of the iron source and the silicon source contained in the raw materials can be appropriately adjusted depending on the component composition of the ferrosilicon to be produced. The silicon content of the ferrosilicon is not particularly limited, but is preferably 10% by mass or more and 95% by mass or less. A more preferred silicon content is 50% by mass or more and 80% by mass or less.

[0021] When the raw materials contain an iron source, the amount of reducing agent contained in the raw materials may be an amount necessary to reduce both the iron oxide and the silica. When the raw materials containing the iron oxide and the reducing agent are heated, the iron oxide is reduced to produce molten iron. The silicon produced by the reduction of the silica dissolves in the molten iron, producing a molten material made of ferrosilicon.

[0022] <First Phase of Additional Refining> Next, the resulting molten material is subjected to additional refining. Additional refining is divided into a first phase and a subsequent second phase. In the first phase of additional refining, a non-oxidizing gas containing nitrogen is blown into the molten material. Blowing a non-oxidizing gas containing nitrogen into the molten material can promote the reaction shown in chemical formula (1) below, i.e., the reaction in which titanium and nitrogen in the molten material combine to form solid titanium nitride. When the silicon concentration is low, as in general steel, the reaction of chemical formula (1) does not proceed easily. However, in the case of silicon-based alloys with a high silicon concentration, the equilibrium solubility product of the titanium and nitrogen concentrations is significantly reduced, making it easier for titanium nitride to be formed from the molten material through the reaction of chemical formula (1). The titanium concentration in the molten material can be reduced by separating and removing the titanium nitride formed in the molten material from the system by stirring.

[0023] [Chemical formula 1] [Ti] + [N] → TiN(s) ... (1)

[0024] The nitrogen-containing non-oxidizing gas used in the first stage of additional refining may be nitrogen gas alone or a mixture of nitrogen gas and an inert gas, such as argon.

[0025] On the other hand, in additional refining, as described above, it is effective to inject an oxidizing gas containing oxygen into the molten material to oxidize the calcium and aluminum impurities contained in the molten material and remove them as slag. However, according to the inventor's investigations, it was found that if nitrogen gas and oxygen gas are injected into the molten material simultaneously, or if an oxidizing gas containing oxygen is injected first and then a non-oxidizing gas containing nitrogen is injected, the reaction of chemical formula (1) is inhibited, making it difficult to reduce the concentration of titanium in the molten material.

[0026] Although it is not clear why it is difficult to reduce the titanium concentration in a melt into which an oxidizing gas has been blown, it is thought that this is probably because oxygen dissolved in the melt hinders the progress of the reaction represented by chemical formula (1). Because oxygen is a surface active element, oxygen dissolved in the melt is adsorbed at the gas-liquid interface between the bubbles of nitrogen gas blown in and the melt. This makes it difficult for nitrogen to dissolve in the melt, which is thought to hinder the progress of the reaction represented by chemical formula (1).

[0027] Therefore, in the present invention, a nitrogen-containing non-oxidizing gas is blown into the molten material in the first period of additional refining, and then an oxygen-containing oxidizing gas is blown into the molten material in the second period of additional refining. The nitrogen-containing non-oxidizing gas used in the first period of additional refining does not contain oxygen. This allows the reaction of chemical formula (1) to proceed in the first period of additional refining, and the titanium concentration in the molten material can be efficiently reduced.

[0028] In the first phase of additional refining, the concentration of oxygen contained in the molten material is preferably maintained at 0.01% by mass or less, and more preferably maintained at 0.005% by mass or less. The lower the concentration of oxygen contained in the molten material in the first phase of additional refining, the more preferable it is, and it may be, for example, 0.000% by mass. The amount of oxygen dissolved in the molten material in the first phase of additional refining can be determined, for example, by taking a sample from the molten material before the start of additional refining or during the first phase of additional refining, taking care not to mix in slag, and then chemically analyzing the sample.

[0029] <Second Stage of Additional Refining> In the second stage of additional refining, an oxidizing gas containing oxygen is blown into the molten material. As described above, by blowing an oxidizing gas into the molten material, calcium and aluminum, which are impurity elements that may be contained in the silicon-based alloy, are oxidized and can be removed as slag. The oxidizing gas containing oxygen used in the second stage of additional refining may be oxygen gas alone, or a mixed gas of oxygen gas and nitrogen gas, or air.

[0030] A molten silicon-based alloy is obtained by heating and melting raw materials containing a silicon source and a reducing agent, and then subjecting the resulting molten material to first and second additional refining stages. The titanium concentration in the resulting silicon-based alloy is preferably 0.025% by mass or less, since this prevents deterioration of the properties even when used in steel slabs for electrical steel sheets. The titanium concentration in the silicon-based alloy is more preferably 0.020% by mass or less, and even more preferably 0.015% by mass or less.

[0031] <Casting> In a preferred embodiment, a slab of a silicon-based alloy is produced by casting the molten material after the additional refining is completed. The casting method is not particularly limited, and can be carried out, for example, by solidifying the molten material in a mold.

[0032] <Container> In a preferred embodiment, raw materials are charged into a first container, heated and melted to produce a molten material, the molten material is transferred from the first container to a second container, and the molten material transferred to the second container is subjected to additional refining. The first container may be any container that can heat and melt the raw materials. For example, an electric furnace, an induction melting furnace, or a plasma arc melting furnace is preferred as the first container in the present invention because it can efficiently heat and melt the raw materials by supplying external energy as a heat source.

[0033] Next, the resulting molten material is transferred from the first container to the second container. By transferring the molten material from the first container to the second container, the functions of each container can be separated, reducing equipment costs and increasing production efficiency. Furthermore, by transferring only the molten material from the first container to the second container, it is possible to prevent the remaining raw materials in the first container and slag produced by oxidation from being mixed into the molten material in the second container.

[0034] The molten material transferred to the second vessel may be a portion of the molten material produced in the first vessel. In this case, a portion of the molten material produced in the first vessel may be subjected to additional refinement repeatedly in the second vessel, or a plurality of second vessels may be used to simultaneously perform additional refinement, thereby subjecting all of the molten material to additional refinement. However, if the processing capacity of the second vessel is sufficiently high, all of the molten material produced in the first vessel may be transferred to the second vessel.

[0035] The second vessel may be any vessel capable of individually injecting a non-oxidizing gas and an oxidizing gas into the molten material. For example, a ladle capable of receiving the molten material transferred from the first vessel may be used as the second vessel. For example, one or more porous plugs installed on the bottom of the vessel or one or more lances immersed in the molten material in the vessel may be used to inject the gas into the second vessel. A known valve or the like may be used to switch the gas injected into the molten material.

[0036] In another preferred embodiment, raw materials are charged into a dual-purpose vessel, heated and melted to produce a molten material, and the resulting molten material is subjected to additional refining while being held in the dual-purpose vessel. The dual-purpose vessel may be any vessel that combines the functions required for the first and second vessels described above. That is, in this preferred embodiment, both the operations of heating and melting the raw materials and separately blowing a non-oxidizing gas and an oxidizing gas into the resulting molten material can be performed using a single dual-purpose vessel. When the dual-purpose vessel is used to heat and melt the raw materials and to perform additional refining of the molten material, it is preferable to remove slag generated by oxidation of the molten material after the heating and melting are completed.

[0037] <Aluminum Concentration> In a preferred embodiment, the aluminum concentration in the molten material is 0.10% by mass or more during the first stage of additional refining. It is preferable that the aluminum concentration in the molten material is always maintained at 0.10% by mass or more during the first stage of additional refining. Because additional refining is usually performed in an air atmosphere, contact of the molten material with the air promotes oxidation of calcium and aluminum. When the aluminum concentration in the molten material, which has a deoxidizing effect, falls below a certain level, oxygen dissolved in the molten material is adsorbed at the gas-liquid interface between nitrogen gas bubbles and the molten material, thereby hindering the progress of the reaction of chemical formula (1) as described above.

[0038] Through various studies, it was found that the effect of reducing the titanium concentration according to the present invention is not hindered when injecting a nitrogen-containing non-oxidizing gas into the molten metal in the first stage of additional refining as long as the aluminum concentration in the molten metal is 0.10 mass% or more. It is more preferable that the aluminum concentration in the molten metal is 0.20 mass% or more. It is preferable that the aluminum concentration in the molten metal is 1.5 mass% or less, since this allows the aluminum concentration to be reduced by injecting an oxidizing gas without extending the special treatment time. It is more preferable that the aluminum concentration in the molten metal is 1.0 mass% or less.

[0039] If the aluminum concentration in the molten material is expected to fall below 0.10 mass% during the first stage of additional refining, an aluminum-containing alloy may be added to the molten material before or during the first stage of additional refining to increase the aluminum concentration.

[0040] <Flow Rate of Non-Oxidizing Gas> In a preferred embodiment, the concentration of titanium contained in the molten material before the start of additional refining is [Ti] ０ (mass%), the total mass of the molten material to be subjected to additional refining is M ｍ (kg), and the density of the melt is ρ ｍ (kg / m ３ ), the flow rate of the non-oxidizing gas injected into the smelt in the first stage of additional refining is Q ｇ (Nm ３ / min), and the concentration of nitrogen in the non-oxidizing gas (N２ ) (vol %), the relationship shown in formula (1) holds.

[0041] [Equation 2] Q ｇ ≧ {7500・M ｍ / ρ ｍ / (N ２ ) × [Ti] ０ １．５ ...(1)

[0042] In the first stage of additional refining, if the flow rate of the non-oxidizing gas satisfies the relationship shown in formula (1), a sufficient amount of nitrogen is supplied to the molten material to compensate for the nitrogen consumed in the formation of titanium nitride, and the progress of the reaction shown in formula (1) is not impeded. This allows for the stable production of silicon-based alloys with low titanium concentrations.

[0043] <Flow Rate of Oxidizing Gas> In a preferred embodiment, the flow rate of oxygen gas in the oxidizing gas injected per kg of molten material in the second stage of additional refining is 0.2 × 10 －４ Nm ３ / min or more, 3.0 x 10 －４ Nm ３ / min or less. The oxygen gas equivalent flow rate in the oxidizing gas blown per kg of melt is 0.2 × 10 －４ Nm ３ / min or more, calcium and aluminum that may be contained in the silicon-based alloy melt are oxidized and can be removed as slag. －４ Nm ３ / min or less, the oxidizing gas is not consumed excessively.

[0044] <Gas Injection Time> The time for injecting the non-oxidizing gas into the molten material, i.e., the time for the first stage of additional refining, is not particularly limited, but when the flow rate of the non-oxidizing gas satisfies formula (1), it is preferable that the time be 10 minutes or more from the viewpoint of sufficiently progressing the reaction of chemical formula (1). The time for injecting the non-oxidizing gas is more preferably 20 minutes or more. Furthermore, it is preferable that the time for injecting the non-oxidizing gas be 40 minutes or less from the viewpoint of not consuming excessive amounts of the non-oxidizing gas.

[0045] The time for blowing the oxidizing gas into the molten material, i.e., the time for the second stage of additional refining, is not particularly limited, but is preferably 20 minutes or more from the viewpoint of sufficiently oxidizing and removing calcium and aluminum. The time for blowing the oxidizing gas is more preferably 30 minutes or more. The time for blowing the oxidizing gas is preferably 60 minutes or less from the viewpoint of not consuming excessive oxidizing gas.

[0046] Example 1 A predetermined amount of raw materials including iron ore, silica stone, and coke was charged into an electric furnace, and the raw materials were heated and melted to reduce the iron ore and silica stone, thereby producing approximately 5 tons of molten ferrosilicon. Next, the entire molten ferrosilicon produced was poured into a ladle. The mass M of the molten material in the ladle at this time was ｍ The amounts are shown in Table 1. Next, a sample was taken from the ladle and chemically analyzed. According to the chemical analysis, the composition of the molten material before the start of the additional refining was 75 mass% silicon, 10 mass% titanium [Ti] ０ The amounts are shown in Table 1. The remainder of the composition of the resulting melt, excluding silicon and titanium, was mostly iron, and impurity elements such as calcium and aluminum were also contained.

[0047] Next, a porous plug was installed at the bottom of the ladle to inject gas into the molten metal in the first stage of additional refining. The gas injection time in the first stage of additional refining was 5 minutes or more and 21 minutes or less. The components of the gas used in the first stage of additional refining, the concentration of nitrogen in the gas (N ２ ), gas flow rate Q ｇ The values ​​of the right side of the formula (1) calculated based on these values ​​are shown in Table 1. The density ρ of the molten ferrosilicon in the formula (1) ｍ The value is 3153 kg / m ３ It was decided.

[0048] Next, after the first phase of additional refining was completed, a sample was again taken from the ladle and chemically analyzed for the aluminum concentration contained in the molten material. The obtained aluminum concentrations are shown in Table 1. The aluminum concentrations shown in Table 1 are analytical values ​​of samples taken after the first phase of additional refining was completed, so it is presumed that the aluminum contained in the molten material during the first phase of additional refining was always maintained at a concentration equal to or higher than the concentration shown in Table 1.

[0049] Next, gas for the second stage of additional refining was injected into the molten material to continue the additional refining. The gas injection time for the second stage of additional refining was 23 minutes or more and 50 minutes or less. The gas components used, the oxygen concentration in the gas, and the gas flow rate during the second stage of additional refining are shown in Table 1. Next, after the second stage of additional refining was completed, samples were taken from the ladle three times and chemically analyzed. The titanium concentration in the molten material after the additional refining is shown in Table 1. As shown in Table 1, in Comparative Examples 1 to 4, gases with the same components were injected into the molten material during the first and second stages of additional refining.

[0050]

[0051] According to Table 1, in the ferrosilicon of Examples 1 to 15, in which a non-oxidizing gas containing nitrogen was injected in the first period of additional refining and then an oxidizing gas containing oxygen was injected in the second period of additional refining, the titanium concentration after the additional refining was lower than that before the start of additional refining. In these Examples, the titanium concentration after the additional refining was 0.024 mass% or less. In the ferrosilicon of Examples 6 to 15, in which the aluminum concentration in the molten material in the first period of additional refining was 0.10 mass% or more, the titanium concentration after the additional refining was 0.018 mass% or less, which was even better. In addition, in the ferrosilicon of Examples 11 to 15, in which the flow rate of the non-oxidizing gas in the first period of additional refining satisfied formula (1), the titanium concentration after the additional refining was 0.012 mass% or less, which was even better.

[0052] On the other hand, in the ferrosilicon of Comparative Examples 1 to 8, which did not satisfy the conditions of the method for producing a silicon-based alloy according to the present invention because the gas blown into the molten material in the first period of additional refining was not a non-oxidizing gas, there was no change in the titanium concentration in the molten material before and after additional refining, and it was not possible to obtain a molten material or ferrosilicon with a low titanium concentration.

[0053] Example 2 Silica rock was reduced in the same manner as in Example 1, except that iron ore was not included in the raw materials, to produce approximately 5 tons of molten silicon. Next, the entire molten silicon produced was tapped into a ladle. The mass M of the molten silicon in the ladle at this time was ｍ The amounts are shown in Table 2. Next, a sample was taken from the ladle and chemically analyzed. According to the chemical analysis, the composition of the molten material before the start of the additional refining was 99 mass% silicon, 10 mass% titanium [Ti] ０ The amounts are shown in Table 2. The remainder of the component composition of the resulting melt, excluding silicon and titanium, was impurity elements including calcium and aluminum.

[0054] Next, the molten material was subjected to additional refining in the same manner as in Example 1. The gas injection time in the first stage of additional refining was 5 minutes or more and 16 minutes or less. The gas injection time in the second stage of additional refining was 28 minutes or more and 50 minutes or less. The components of the gas used in the first stage of additional refining, the concentration of nitrogen in the gas (N ２ ), gas flow rate Q ｇ The value of the right side of the formula (1) calculated based on these values, the concentration of aluminum contained in the melt, the components of the gas used in the second stage of the additional refining, the concentration of oxygen in the gas, and the flow rate of the gas, as well as the concentration of titanium contained in the melt after the additional refining are shown in Table 2. ｍ The value is 2500 kg / m ３ In Comparative Examples 9 to 12, gases having the same composition were injected into the molten material in the first and second stages of additional refining.

[0055]

[0056] According to Table 2, in the silicon of Examples 16 to 24, in which a non-oxidizing gas containing nitrogen was injected in the first period of additional refining and then an oxidizing gas containing oxygen was injected in the second period of additional refining, the titanium concentration after additional refining was lower than that before the start of additional refining. In these examples, the titanium concentration after additional refining was 0.018 mass% or less. In the silicon of Examples 19 to 24, in which the aluminum concentration in the molten material in the first period of additional refining was 0.10 mass% or more, the titanium concentration after additional refining was 0.014 mass% or less, which was even better. In addition, in the silicon of Examples 22 to 24, in which the flow rate of the non-oxidizing gas in the first period of additional refining satisfied Equation (1), the titanium concentration after additional refining was 0.009 mass% or less, which was even better.

[0057] On the other hand, in the silicon of Comparative Examples 9 to 13, which did not satisfy the conditions of the method for producing a silicon-based alloy according to the present invention because the gas blown into the molten material in the first period of additional refining was not a non-oxidizing gas, there was no change in the titanium concentration in the molten material before and after additional refining, and it was not possible to obtain a molten material or silicon with a low titanium concentration.

Claims

1. A method for producing a silicon-based alloy, comprising heating and melting raw materials containing a silicon source and a reducing agent to produce a molten material, and then subjecting the molten material to additional refining, wherein a non-oxidizing gas containing nitrogen is blown into the molten material in a first period of the additional refining, and then an oxidizing gas containing oxygen is blown into the molten material in a second period of the additional refining.

2. The method for producing a silicon-based alloy according to claim 1, comprising the steps of: charging the raw materials into a first vessel, heating and melting them to produce the molten material; transferring the produced molten material from the first vessel to a second vessel; and subjecting the molten material transferred to the second vessel to the additional refining.

3. The method for producing a silicon-based alloy according to claim 1, wherein the raw materials are charged into a multi-purpose vessel, heated and melted to produce the molten material, and the molten material is retained in the multi-purpose vessel while undergoing the additional refining.

4. A method for producing a silicon-based alloy according to any one of claims 1 to 3, wherein the aluminum concentration in the molten material during the first stage of the additional refining is 0.10 mass % or more.

5. The concentration of titanium contained in the molten material before the start of the additional refining is [Ti] ０ (mass%), the mass of the molten material to be subjected to the additional refining is M ｍ (kg), and the density of the melt is ρ ｍ (kg / m ３ ), the flow rate of the non-oxidizing gas blown into the melt is Q ｇ (Nm ３ / min), and the concentration of nitrogen in the non-oxidizing gas (N ２ 5. The method for producing a silicon-based alloy according to claim 1, wherein the relationship shown in mathematical formula (1) holds when Q is set to 0.01 (vol%). [Mathematical formula 1] Q ｇ ≧ {7500・M ｍ / ρ ｍ / (N ２ ) × [Ti] ０ １．５ ...(1) 6. The method for producing a silicon-based alloy according to any one of claims 1 to 5, wherein the raw materials include an iron source.

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