Manufacturing method of silicon alloys

Abstract

This invention provides a manufacturing method suitable for mass production that enables the production of silicon-based alloys with extremely low titanium concentrations without the need for high-grade raw materials. The raw materials, including a silicon source and a reducing agent, are heated and melted to produce a molten material, which is then subjected to additional refining. In the first stage of additional refining, a non-oxidizing gas containing nitrogen is blown into the molten material, and in the second stage of additional refining, an oxidizing gas containing oxygen is blown into the molten material.

Description

[Technical Field]

[0001] This invention relates to a method for producing silicon-based alloys with low levels of impurities. [Background technology]

[0002] Silicon alloys are alloys that contain silicon. Ferrosilicon, which contains silicon and iron, is a typical silicon alloy. Silicon alloys are mainly used as deoxidizing agents for steelmaking and as additives for adjusting the composition according to the type of steel. In particular, when silicon alloys are used to adjust the silicon concentration when melting steel slabs used in the manufacture of electrical steel sheets, a high concentration of impurity elements contained in the silicon alloy may lead to a deterioration of the properties of the electrical steel sheet product itself. For this reason, it is necessary to reduce the concentration of impurities contained in the silicon alloy.

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

[0004] Among the impurity elements that can be contained in silicon alloys, calcium and aluminum can be easily oxidized and removed as slag by blowing an oxidizing gas containing oxygen into the molten silicon alloy. 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 in an oxidizing gas. Given this technical background, one method for producing silicon alloys with low impurity concentrations is to use high-grade raw materials with extremely low levels of impurities.

[0005] Furthermore, as another means for producing silicon-based alloys with a low titanium concentration, 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 in a wet treatment to liberate and remove the titanium-containing phase. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 3-153839 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the use of high-purity, high-grade raw materials leads to increased manufacturing costs for silicon alloys. Furthermore, the wet process for producing ferrosilicon described in Patent Document 1 requires the crushing of ferrosilicon, making it unsuitable for mass production such as that required for steelmaking applications.

[0008] Therefore, in view of the above problems, the present invention aims to provide a manufacturing method suitable for mass production that can produce silicon-based alloys with extremely low titanium concentrations without using high-grade raw materials. [Means for solving the problem]

[0009] The inventors of the present invention, with the aim of reducing the concentration of titanium, in particular, among the impurities that may be contained in silicon alloys, diligently studied additional refining applied to the molten material in a method for producing silicon alloys in which raw materials containing a silicon source and a reducing agent are placed in an electric furnace and heated and melted to produce a molten material. As a result, they discovered that the concentration of titanium contained in the molten material can be reduced by applying additional refining by blowing in a non-oxidizing gas containing nitrogen before blowing in an oxidizing gas containing oxygen, and thus completed the present invention.

[0010] The gist configuration of the present invention is as follows. [1] A method for producing a silicon-based alloy, comprising heating and melting a raw material containing a silicon source and a reducing agent to form a melt, and subjecting the produced melt to additional refining, wherein in the first stage of the additional refining, a non-oxidizing gas containing nitrogen is blown into the melt, and then in the second stage of the additional refining, an oxidizing gas containing oxygen is blown into the melt.

[0011] [2] The raw material is charged into a first container, heated and melted to form the melt, the produced melt is transferred from the first container to a second container, and the additional refining is performed on the melt transferred to the second container. The method for producing a silicon-based alloy according to [1] above.

[0012] [3] The raw material is charged into a dual-purpose container, heated and melted to form the melt, and the additional refining is performed while the produced melt is held in the dual-purpose container. The method for producing a silicon-based alloy according to [1] above.

[0013] [4] In the first stage of the additional refining, the concentration of aluminum contained in the melt is 0.10% by mass or more. The method for producing a silicon-based alloy according to any one of [1] to [3] above.

[0014] [5] When the concentration of titanium contained in the melt before starting the additional refining is [Ti]0 (% by mass), the mass of the melt to be subjected to the additional refining is M m (kg), 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 is (N2) (vol%), the relationship shown in Formula (1) holds. The method for producing a silicon-based alloy according to any one of [1] to [4] above. [Equation 1] Q g ≥ {7500·M m / ρ m / (N2)} × [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 material contains an iron source.

Advantages of the Invention

[0016] According to the present invention, it is possible to mass-produce a silicon-based alloy having an extremely low titanium concentration without using high-quality raw materials.

Embodiments for Carrying Out the Invention

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

[0018] <Heating and Melting of Raw Material> In the method for producing a silicon-based alloy according to the present invention, first, a melting reduction treatment is performed in which a raw material containing a silicon source and a reducing agent is heated and melted to generate a melt. The types of the silicon source and the reducing agent contained in the raw material are not particularly limited, and the types of the silicon source and the reducing agent corresponding to the component composition of the target silicon-based alloy may be appropriately selected. In the present invention, titanium contained in the melt can be removed by subjecting the generated melt to additional refining described below. Therefore, it is not necessary to use a high-quality silicon source having an extremely low titanium concentration, and the cost of the raw material can be reduced as compared with the prior art.

[0019] For example, silica can be used as a silicon source. For example, coke or charcoal can be used as a reducing agent. One type of raw material may be used for each of the silicon source and reducing agent, or two or more types of raw materials may be mixed and used. By heating and melting the raw materials containing silica and the reducing agent, the silica and the reducing agent react, reducing the silica and producing silicon.

[0020] The silicon alloy produced by the manufacturing method according to the present invention may be high-purity silicon or an alloy of silicon and iron, such as ferrosilicon. In the former case, the proportion of silicon contained in the silicon alloy may be 100% by mass. In the latter case, the raw materials include an iron source. Iron oxide can be used as the iron source, and typically iron ore can be used. The mass ratio of the iron source and silicon source contained in the raw materials when producing ferrosilicon can be appropriately adjusted according to the component composition of the ferrosilicon to be produced. The proportion of silicon contained in ferrosilicon is not particularly limited, but for example, it is preferably 10% by mass or more and 95% by mass or less. A more preferable proportion of silicon is 50% by mass or more and 80% by mass or less.

[0021] If the raw materials contain an iron source, the amount of reducing agent contained in the raw materials should be sufficient to reduce both the iron oxide and the silica. When raw materials containing iron oxide and a reducing agent are heated, the iron oxide is reduced to molten iron. The silicon produced by the reduction of the silica dissolves into the molten iron, forming a molten product of ferrosilicon.

[0022] <Phase 1 of Additional Refining> Next, the resulting molten material is subjected to additional refining. This additional refining is divided into a first and second phase. In the first phase of additional refining, a non-oxidizing gas containing nitrogen is blown into the molten material. By blowing a non-oxidizing gas containing nitrogen into the molten material, the reaction shown in chemical formula (1) below, namely the reaction in which titanium and nitrogen in the molten material combine to produce solid titanium nitride, can proceed. In the case of general steel materials with a low silicon concentration, the reaction of chemical formula (1) is unlikely to proceed, but in the case of silicon-based alloys with a high silicon concentration, the equilibrium solubility product of titanium and nitrogen concentrations decreases significantly, making it easier for titanium nitride to be produced from the molten material by the reaction of chemical formula (1). By separating and removing the titanium nitride produced in the molten material from the system by stirring, the concentration of titanium in the molten material can be reduced.

[0023] [C1] [Ti] + [N] → TiN(s) ···(1)

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

[0025] On the other hand, in additional refining, as mentioned above, it is effective to blow 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 research, it was found that when nitrogen gas and oxygen gas are blown into the molten material simultaneously, or when an oxidizing gas containing oxygen is blown in first, followed by the blowing in of a non-oxidizing gas containing nitrogen, the reaction of chemical formula (1) is inhibited, making it difficult to reduce the concentration of titanium contained in the molten material.

[0026] The exact reason why it is difficult to reduce the titanium concentration in a molten material into which an oxidizing gas has been injected is unclear, but it is likely because the oxygen dissolved in the molten material hinders the progress of the reaction of chemical formula (1). Since oxygen is a surfactant, the oxygen dissolved in the molten material is adsorbed at the gas-liquid interface between the nitrogen gas bubbles injected and the molten material. This makes it difficult for nitrogen to dissolve in the molten material, thus hindering the progress of the reaction of chemical formula (1).

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

[0028] In the first stage of additional refining, the oxygen concentration in the molten material is preferably maintained at 0.01% by mass or less, and more preferably at 0.005% by mass or less. The lower the oxygen concentration in the molten material in the first stage of additional refining, the better; for example, it may be 0.000% by mass. The amount of oxygen dissolved in the molten material in the first stage of additional refining can be determined, for example, by taking a sample from the molten material before starting the additional refining or during the first stage of additional refining, taking care not to allow slag to mix in, and then performing a chemical analysis of the sample.

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

[0030] A silicon-based alloy in a molten state is obtained by heating and melting raw materials containing a silicon source and a reducing agent, and then subjecting the resulting molten material to additional refining in the first and second stages. A titanium concentration of 0.025% by mass or less in the obtained silicon-based alloy is preferable because it does not degrade the properties even when used in steel slabs for electrical steel sheets. A titanium concentration of 0.020% by mass or less is more preferable, and 0.015% by mass or less is even more preferable.

[0031] <Casting> In a preferred embodiment, a silicon alloy slab is produced by casting the molten material after further refining is complete. 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 placed in 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 in the second container is subjected to further refining. The first container can be any container that can heat and melt the raw materials. For example, an electric furnace, induction melting furnace, or 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 generated molten material is transferred from the first container to the second container. By transferring the molten material generated in the first container to the second container, the functions of each container can be separated, reducing equipment costs and increasing production efficiency. In addition, by transferring only the molten material from the first container to the second container, it is possible to prevent undissolved raw materials or slag generated by oxidation in the first container from mixing with the molten material in the second container.

[0034] The molten material transferred to the second container may be only a portion of the molten material produced in the first container. In this case, the entire molten material can be further refined by repeatedly performing additional refining on a portion of the molten material produced in the first container in the second container, or by simultaneously performing additional refining using multiple second containers. However, if the processing capacity of the second container is sufficiently high, the entire molten material produced in the first container may be transferred to the second container.

[0035] The second container can be any container that can separately blow non-oxidizing gas and oxidizing gas into the molten material. For example, a ladle capable of receiving the molten material transferred from the first container can be used as the second container. For blowing gas into the second container, for example, one or more porous plugs installed on the bottom of the container or one or more lances that can be immersed in the molten material inside the container can be used. Known valves or the like can be used to switch the gases blown into the molten material.

[0036] In another preferred embodiment, raw materials are placed in a multi-purpose container, heated and melted to produce a molten material, and the resulting molten material is held in the multi-purpose container while further refining is performed. The multi-purpose container can be any container that possesses the functions required for the first and second containers described above. That is, in this preferred embodiment, both the operation of heating and melting the raw materials and the operation of blowing non-oxidizing gas and oxidizing gas separately into the resulting molten material can be performed using a single multi-purpose container. When heating and melting raw materials and further refining the molten material are performed using a multi-purpose container, it is preferable to remove the slag produced by oxidation of the molten material once the heating and melting is complete.

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

[0038] From various studies, it was found that when a non-oxidizing gas containing nitrogen is blown in during the first stage of additional refining, if the aluminum concentration in the molten material is 0.10% by mass or higher, the titanium concentration reduction effect according to the present invention is not hindered. A higher aluminum concentration in the molten material is more preferable. A lower aluminum concentration in the molten material is preferable because the aluminum concentration can be reduced by blowing in an oxidizing gas without extending the special processing time. A lower aluminum concentration in the molten material is more preferable.

[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 can 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 in the molten material before the start of additional refining is [Ti]0 (mass%), and the total mass of the molten material subjected to additional refining is M m (kg), density of the molten material is ρ m (kg / m 3 ), Q is the flow rate of the non-oxidizing gas injected into the molten material during the first phase of additional refining. g (Nm 3When the concentration of nitrogen in the non-oxidizing gas is (N2)(vol%), the relationship shown in equation (1) holds true.

[0041] [Math 2] Q g ≥ {7500·M m / ρ m / (N2)} × [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 equation (1), a sufficient amount of nitrogen is supplied to the molten material to compensate for the nitrogen consumed by the formation of titanium nitride, and the reaction of chemical equation (1) is not hindered. This makes it possible to stably produce silicon-based alloys with a low titanium concentration.

[0043] <Flow rate of oxidizing gas> In a preferred embodiment, the oxygen gas equivalent flow rate in the oxidizing gas injected per kg of molten material during the second stage of additional refining is 0.2 × 10⁻⁶ -4 Nm 3 / min or more, 3.0 x 10 -4 Nm 3 It is less than / min. The oxygen equivalent flow rate in the oxidizing gas blown in per 1 kg of molten material is 0.2 × 10⁻⁶. -4 Nm 3 If the flow rate is 3.0 × 10⁻¹ / min or higher, calcium and aluminum that may be present in the molten silicon alloy can be oxidized and removed as slag. -4 Nm 3 If the value is below / min, excessive consumption of oxidizing gas will not occur.

[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 if the flow rate of the non-oxidizing gas satisfies formula (1), it is preferable that it be 10 minutes or more from the viewpoint of allowing the reaction of chemical formula (1) to proceed sufficiently. It is more preferable that the time for injecting the non-oxidizing gas be 20 minutes or more. Furthermore, it is preferable that the time for injecting the non-oxidizing gas be 40 minutes or less in order to avoid excessive consumption 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 it is preferable to be 20 minutes or more from the viewpoint of sufficiently oxidizing and removing calcium and aluminum. It is more preferable to blow the oxidizing gas for 30 minutes or more. It is preferable to blow the oxidizing gas for 60 minutes or less from the viewpoint of not consuming an excessive amount of oxidizing gas. [Examples]

[0046] <Example 1> A predetermined amount of raw materials, including iron ore, silica, and coke, were placed in an electric furnace and heated to melt them, reducing the iron ore and silica to produce approximately 5 tons of molten ferrosilicon. Next, the entirety of the produced molten ferrosilicon was poured into a ladle. The mass of the molten material in the ladle at this time was M. m The amounts were as 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 additional refining was 75% by mass of silicon and the titanium concentration [Ti]0 as shown in Table 1. Of the composition of the resulting molten material, the remainder, excluding silicon and titanium, was mostly iron, with other impurity elements including calcium and aluminum.

[0047] Next, using a porous plug installed at the bottom of the ladle, the first phase of additional refining gas was blown into the molten material to perform additional refining. The gas blowing time for the first phase of additional refining was between 5 and 21 minutes. The gas composition, nitrogen concentration (N2) in the gas, and gas flow rate Q used in the first phase of additional refining were as follows: gTable 1 shows the values ​​of the right-hand side of equation (1) calculated based on these values. The density ρ of the molten ferrosilicon in equation (1) m The value is 3153 kg / m 3 That's what I decided.

[0048] Next, after the first phase of additional refining was completed, a sample was taken again from the ladle and chemically analyzed for the concentration of aluminum in the molten material. The obtained aluminum concentrations are shown in Table 1. Since the aluminum concentrations shown in Table 1 are analytical values ​​of samples taken after the completion of the first phase of additional refining, it can be inferred that the aluminum concentration in the molten material during the first phase of additional refining was consistently maintained at or above the concentrations shown in Table 1.

[0049] Next, the second phase of additional refining gas was injected into the molten material, and the additional refining process was continued. The gas injection time for the second phase of additional refining was between 23 and 50 minutes. Table 1 shows the gas composition, oxygen concentration in the gas, and gas flow rate used during the second phase of additional refining. After the second phase of additional refining was completed, samples were taken from the ladle three times and chemically analyzed. Table 1 shows the titanium concentration in the molten material after additional refining. As shown in Table 1, in Comparative Examples 1 to 4, the same gas composition was injected into the molten material during both the first and second phases of additional refining.

[0050] [Table 1]

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

[0052] On the other hand, in Comparative Examples 1 to 8, the ferrosilicon did not satisfy the conditions for the silicon alloy manufacturing method according to the present invention because the gas blown into the molten material in the first stage of additional refining was not an oxidizing gas. As a result, 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 and ferrosilicon with a low titanium concentration.

[0053] <Example 2> The silica was reduced using the same method as in Example 1, except that the raw materials did not contain iron ore, and approximately 5 tons of molten silicon were produced. Next, all of the produced molten silicon was poured into a ladle. The mass of the molten silicon in the ladle at this time was M. m The amounts were as 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 additional refining was 99% silicon by mass and titanium [Ti]0 in the amounts shown in Table 2. Of the composition of the generated molten material, the remainder, excluding silicon and titanium, consisted of impurity elements such as 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 for the first phase of additional refining was 5 minutes or more and 16 minutes or less. The gas injection time for the second phase of additional refining was 28 minutes or more and 50 minutes or less. The gas composition, nitrogen concentration (N2) in the gas, and gas flow rate Q for the first phase of additional refining were as follows: g Based on these values, the value of the right-hand side of equation (1), the concentration of aluminum in the molten material, the gas composition, oxygen concentration in the gas, and gas flow rate during the second stage of additional refining, and the concentration of titanium in the molten material after additional refining are shown in Table 2. The density of the silicon molten material in equation (1) is ρ. m The value is 2500 kg / m 3 In comparative examples 9 to 12, the same gas composition was injected into the molten material during the first and second stages of additional refining.

[0055] [Table 2]

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

[0057] On the other hand, in Comparative Examples 9 to 13, the silicon samples did not satisfy the conditions for the silicon alloy manufacturing method according to the present invention because the gas blown into the molten material in the first stage of additional refining was not a non-oxidizing gas. As a result, 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 and silicon with a low titanium concentration.

Claims

1. A molten material is produced by heating and melting raw materials containing a silicon source and a reducing agent. A method for producing a silicon-based alloy, comprising further refining the molten material produced, In the first stage of the additional refining, after blowing a non-oxidizing gas containing nitrogen into the molten material, A method for producing a silicon alloy, characterized in that an oxidizing gas containing oxygen is blown into the molten material during the second stage of the additional refining process.

2. The raw materials are placed in the first container and heated to melt them, thereby producing the molten material. The generated molten material is transferred from the first container to the second container. A method for producing a silicon-based alloy according to claim 1, wherein the molten material transferred to the second container is subjected to the additional refining.

3. The aforementioned raw materials are placed in a multi-purpose container and heated to melt them, thereby producing the molten material. A method for producing a silicon-based alloy according to claim 1, wherein the generated molten material is held in the multi-purpose container while the additional refining is performed.

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

5. The concentration of titanium in the molten material before the start of the additional refining is [Ti] ０ (Mass %), the mass of the molten material subjected to the additional refining is M ｍ (kg), the density of the molten material is ρ ｍ (kg / m ３ ), the flow rate of the non-oxidizing gas blown into the molten material is Q ｇ (Nm ３ ( / min), the concentration of nitrogen in the non-oxidizing gas is (N ２ A method for producing a silicon-based alloy according to any one of claims 1 to 3, wherein the relationship shown in formula (1) holds when the ratio is (vol%). [Mathematics 1] Q ｇ ≧ {7500・M ｍ / ρ ｍ / (N) ２ )} × [Tig ０ １．５ ・・・(1)

6. A method for producing a silicon-based alloy according to any one of claims 1 to 3, wherein the raw materials include an iron source.

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