JPS59232250A - High purity ferroboron and its production - Google Patents

Abstract

PURPOSE:To form ferroboron having high purity by reducing a mixture composed of a boron source, iron source and reducing agent under specific conditions to produce low carbon ferroboron and remelting the ferroboron under specific conditions then cooling and holding the same. CONSTITUTION:A boron source such as boron oxide or the like, an iron source such as electrolytic iron or the like and a reducing agent such as charcoal are mixed and are charged into an electric furnace, by which the mixture is melted and reduced with <=0.5kW/cm<2> electrode power density and low darbon ferroboron contg. <=1.0% C and >=10% B is produced. The low carbon ferroboron is then thoroughly remelted in a temp. range of the m.p. +150-200 deg.C to remove Al then the molten ferroboron is cooled to the temp. just above the m.p. and is held at said temp. for a specified time to precipitate and separate C. The high purity ferroboron contg., by weight, >=10% B, <=0.5% C and <=0.05% Al and consisting of the balance Fe and inevitable impurities is thus obtd.

Description

[Detailed Description of the Invention] The present invention relates to high purity ferroboron and a method for producing the same.
1. Particularly relates to high purity ferroboron with a low content of C, Al, and a method for producing the same produced by an electric furnace method.

Conventionally, methods for producing ferroboron include the thermite method, in which boron compounds such as boronic oxide and halonic acid are reduced with aluminum powder, and the electric furnace method, in which boron compounds are reduced with a carbonaceous reducing agent in an electric furnace. However, the problem has been that the thermite method has low C but high Al, and the blast furnace method has relatively low Al but high C.

Table 1 shows the JIS standards for ferroboron, and Table 2 shows composition examples of products that are actually on the market.

Table 2 Ferroboron product composition examples (by weight) Boron significantly increases the hardenability of steel, improves high-temperature strength, and has high neutron absorption capacity.
It is mainly used to add boron to high-strength steel, heat-resistant alloy steel, etc., but in this case, the amount added is relatively small, so even if ferroboron has a lot of impurities as mentioned above, ferroboron may be used depending on the application. The reality is that they were able to somehow get by by using different types.

In recent years, amorphous alloys have attracted attention due to their various characteristic properties.9 In particular, FeBSi-based amorphous alloys are used as core materials for transformers because they have significantly lower iron loss than silicon steel sheets currently in use. , since it has the potential to become an energy-saving iron core material suitable for this era,
Research and development of industrial production methods for amorphous alloy thin sheets is being actively conducted.

Impurities in amorphous alloys, especially KAl, Ti,
P.

Even a small amount of S and the like significantly deteriorates the electromagnetic properties of the amorphous alloy, so it is necessary to keep the content extremely low. Furthermore, if the C content is high, there are major restrictions on other raw materials when producing an amorphous alloy, so it is desirable that the C content be as low as possible.

By the way, the ferroboron currently available on the market has a high content of these nine impurities as mentioned above, and therefore, such ferroboron cannot be used as a raw material for amorphous materials. Therefore, Fe −B − is used as a transformer core material.
It is no exaggeration to say that whether Si-based amorphous alloys can be used depends on whether highly purified and inexpensive ferroboron is available.

The purpose of the present invention is to:
The present invention provides a high purity ferroboron that can be suitably used as a raw material for amorphous alloys and other applications requiring high purity, and a method for producing the same.

This object of the present invention is achieved by the following two inventions.

The gist of the high purity ferroboron of the first invention is as follows.

That is, it is a high-purity ferroboron characterized by containing B: 10% or more, C: 0.5% or less, AA: 0.05% or less, and the remainder consisting of Fe and unavoidable impurities.

The gist of the second invention, which is a method for producing high-purity ferroboron, is as follows.

That is, a boron source such as boronic oxide or halonic acid, an iron source such as electrolytic iron or silicon iron, and a reducing agent such as charcoal or low ash coal are mixed and charged into an electric furnace and melted. In the method for producing low-carbon ferroboron by reducing, the electrode power density in the smelting reduction is set to 0.5 KW/c++' as below: C:
1. C1 or less, B: A first step of producing low carbon ferroboron of 10% or more, and completely remelting the low carbon ferroboron obtained in the first step at a temperature range of +150 to 200 ° C. to just above the melting point. the second to cool and maintain at the temperature;
A method for producing high-purity ferroboron, comprising the steps of:

The C content of conventional electric furnace ferroboron currently available on the market is about 1 H at the lowest, and it is thought that it is impossible to stably produce something lower than this using the electric furnace method. However, while conducting experiments with various operating conditions of the electric furnace, the present inventors found that a very low C value could be obtained under certain conditions. As a result of investigating the cause, we found that the C content was related to the electrode current density of the electric furnace, so we investigated the relationship between the electrode power density and the C content in ferroboron using a 100 KVA Giro complete electric furnace. The results shown in Table 3 were obtained.

If the electrode power density changes, the temperature near the electrode changes, so we inferred that the above result was ultimately caused by a change in the temperature of the reaction sphere.Next, we investigated the solubility of C in ferroboron, and the results are shown in Table 4. I got the result.

The following facts became clear from the experimental results shown in Tables 3 and 4.

(a) If the electrode power density increases, the temperature force in the reaction sphere increases.

(b) As the temperature of the reaction zone increases, the solubility of C in the molten ferroboron increases.

According to the experimental results in Table 3, the electrode power density should be suppressed to 0.5) CW/rJ or less in order to constantly maintain the C content in the molten Schifferoboron at 1.0 cm or less. There was found. Therefore, the electrode power density during melting reduction in the first step in the present invention is set to 0.5KW/aA.
Limited to the following.

Next, the solubility of C in ferroboron has an inverse correlation with the content of B, and as the content of B becomes low, the solubility of C increases. In the present invention, the upper limit of the C content is 1.0% for the low carbon ferroboron in the first step.

The target is 0.5% after the re-dissolution in the second step. Therefore, in order to stably ensure C: 1.0% or less in the first step, the B content must be at least 10% or more, and if B is less than 10%, C: cannot guarantee a stable value of 1.0 or less.

In addition, if the C content of the ferroboron produced in the first step is high, the amount of slag produced in the second step will increase, resulting in B separated as carbide and ferroboron metal lost by being mixed into the slag layer. The amount increases, reducing the yield of B. Therefore, in the first step, it is necessary to reduce the C content as much as possible in order to improve the yield.

Therefore, in the present invention, the target components of the low carbon ferroboron produced in the first step are limited as follows.

B: 10 or more C: 1.0 or less Next, the purpose and effect of the second step of remelting in the present invention will be explained.

The purpose of the remelting step is to stably lower C and reduce Al. Al is mainly contained in the reducing agent, and its content is high, and it is not removed in the electric furnace of the first step, which is a reducing atmosphere, but the entire amount is transferred into the product, so it is important to carefully select the raw materials. However, it is impossible to reduce the amount to 0.2% or less. On the other hand, in the first step of smelting ferroboron in an electric furnace, the furnace conditions are unstable and it is difficult to maintain constant operating conditions. Therefore, the C content in ferroboron is also shown in Table 3. Since some degree of variation as described above is unavoidable, it is difficult to stably lower the C content only by smelting using an electric furnace in the first step.

For the above reasons, in the present invention, the low carbon ferroboron obtained in the first step is redissolved in the atmosphere. The melting furnace used for remelting is not particularly limited, but one in which the molten metal circulates and has many opportunities to come into contact with the atmosphere, such as a high-frequency electric furnace or a low-frequency electric furnace, is preferable.

The purpose of redissolving the low carbon ferroboron obtained in the first step in the atmosphere is to precipitate and separate impurities, especially Al and C. It is extremely heavy. First, the low carbon ferroboron obtained in the first step is charged into a high frequency electric furnace or the like and completely melted at a maximum temperature of 150 to 200° C. above the melting point of the alloy.

By this high-temperature remelting, Al contained in the impurities is oxidized and becomes AIt 20 a, which floats and separates. The reason why the maximum temperature for remelting was limited to melting point +150 to 200°C is as follows. That is, the higher the temperature, the more effective it is for the purpose of removing Ad, but at the same time B, the main component, is also oxidized and the yield is reduced.

Therefore, Ad is removed by oxidation, but the temperature range where the yield of B does not decrease much is melting point +150 to 200B: 10 to 1
In the case of less than 6 Cal diron, the temperature range is 1550 to 1750°C.

Although Al among impurities is removed by the above-mentioned high-temperature remelting, C is not removed. Therefore, in the present invention, the molten metal completely remelted at the maximum temperature in the above 2 is held in the cooling port at that temperature for a certain period of time until it reaches just above the melting point of the alloy. The holding temperature just above the melting point is preferably melting point +30 to 50°C, and the above B: 10 to 16
Chi, C: 135 for low carbon ferroboron of 1 chi or less
A temperature range of 0 to 1600<0>C is preferred and a holding time of about 5 minutes may be used. The purpose of cooling to just above the melting point after remelting at this maximum temperature is to precipitate and separate the contained C.

In the low carbon ferroboron produced in the first step, C exists in the form of free carbon or B+Si carbide, but as the molten metal temperature decreases, the solubility of this C decreases and the C is precipitated and separated. The holding time is set to provide a time margin of η necessary for the precipitation separation of C, and the precipitation separation is almost completed in a holding time of about 5 minutes, and the C content becomes 0.5% or less. The high-purity ferroboron from which the impurities Ad and C have been separated and removed by remelting in this manner is cast into a mold to become a finished product.

The high purity ferroboron thus obtained had the following composition and contained extremely few impurities. That is, B: 10 or more, C: 0.5 or less, Al: 0.05 or less, and the remainder consists of Fe and unavoidable impurities.

Examples of the first step and second step of the present invention will be described below.

Example 1 Boron oxide 10.2#, electrolytic iron 10.8#, charcoal 4.0
kg 1 coke 0.8# and coal 0.6# were mixed in advance in a ratio of 100 KVA single-phase single-phase giro set electric furnace, and operation was performed by changing the electrode power density. Obtained the results in the table.

As is clear from Table 5, even if KB is 10% or more during the production of low carbon ferroboron in the first step, if the average power density exceeds 0.5 KW/-, the C content of one blowing product becomes high. It is difficult to maintain an Al content of 1.0% or less, and the Al content is also high.

Example 2 Hydrolic acid 10.2 slag, silicon iron scrap 10.77+? , charcoal 4
．． To 0? , coal i, oh, and coke 0.8 kg were mixed in advance and charged into a 100 KVA single-phase Giro electric furnace and operated at an average electrode power density of 0.5 KW/-. As a result, the following results were obtained. It was possible to obtain a low carbon ferroboron having an excellent composition.

B: 15-16 C: 0.3-0.7 Al: 0.02-0.19 Example 3 6 with different C and Al contents obtained in the primary step of Examples 1 and 2 20 types of low carbon ferroporon test materials each
A secondary process remelting test was conducted in a 30Aiil high-frequency electric furnace, and the relationship between the removal rate of C and Al and the yield of B was compared. The redissolution comparative test was carried out in the following manner. That is, after each low-carbon ferroboron sample material was charged into the furnace and energized until it was completely melted, the temperature was raised until the molten metal temperature was 1700.
The temperature was maintained at ~175°C for 5 minutes, then the temperature was lowered to 1600°C, and the temperature was maintained at 1550-1600°C for 5 minutes, after which it was cast into a mold and left to cool to obtain high purity ferroboron.

Changes in C and Al contents before and after redissolution and the yield of B are shown in Table 6.

As is clear from Table 6, as for the C content, the higher the amount of C in the low-carbon ferroboron in the primary step, the better the removal rate. % or more, the yield of B tends to worsen as C before redissolution increases.

Furthermore, although no particular tendency was observed regarding the A7 content, it was found that all showed excellent removal rates of 75 inches or more. As described above, if the C content in the low carbon ferroboron in the first step exceeds 1.0, the yield of B decreases, so in the present invention, the target C content in the low carbon ferroboron in the first step is Considering the yield of B, c': 1. Q% or less,
B: 109!1 or more. 1. Therefore, it has been found that a yield of B of 95 yen or more can be secured under these limiting conditions.

Example 4 Using the same raw materials and equipment as in Examples 1 and 2, reduce and dissolve -C with V/cn key to electrode power density U 0.4 to 0.51 B: 10 to 11 C: 0,3 ~0.8 Section A1: 0.07~0. A low carbon ferroboron of 5 cm was obtained.

Each test material was remelted in the same 3 kg high frequency electric furnace as in Example 3 at a temperature of 1550 to 1600°C with a melting point of +15°C to 200°C to precipitate and separate Al, then the molten metal temperature was lowered to 1400°C, and the melt temperature was lowered to 1350°C. The mixture was maintained at a temperature of 1400° C. for 5 minutes to precipitate and separate C, and then cast into a mold. In this way, a final product of excellent high purity ferroboron having the following composition and low C and Al contents could be obtained.

B: 10-11 coefficient C: 0.2-0.4 coefficient 1': 0.01-0.03% As is clear from the above examples, the present invention provides a boron source,
In a method for producing low-carbon ferroboron in which a low-carbon iron source and a reducing agent such as charcoal are mixed and charged and melted and reduced in an electric furnace, the electrode power density is first adjusted to 0.5 KW/cn'' or less to lower the temperature of the reaction zone. By keeping C relatively low
A method was adopted in which a primary low carbon ferroboron having a content of B: 1.0% or less and B: 10% or more was produced, and then this single blown product was redissolved in the atmosphere.

Therefore, when remelting, first the melting point of the alloy is +150~
A method was adopted in which C was precipitated and separated by raising the temperature to a maximum temperature of 200°C to completely melt one blowing product and removing Al, then cooling to a temperature just above the melting point and holding at that temperature for about 5 minutes. Therefore, we were able to achieve the following effects.

(b) C in one blowing product is 30 to 70 by remelting treatment.
%, AIK was able to be separated by precipitation with a removal rate of 80 cm or more.

(b) Within the limited range of the present invention, an excellent yield of 95% or more of B could be achieved in the redissolution step.

(/→ With the present invention, B: 10% or more, C2, 0.5 or less i: o, 05 or less, high purity 1 with extremely low impurities that have not been seen in the conventional market.
! (Feropolone can be obtained at low cost.Ii'e-B
-It has become possible to fully meet the demand for Si-based amorphous alloys, etc.

Agent: Patent Attorney Takeo Nakaji

Claims (3)

[Claims] (1) A high-purity ferroboron characterized by containing B: 10% or more, C: 0.5% or less, A4: 0.05% or less, with the remainder consisting of Fe and inevitable impurities. (2) Boron sources such as boron oxide and halonic acid, iron sources such as electrolytic iron and silicon iron, and reducing agents such as charcoal and low ash coal are mixed and charged into an electric furnace and melted. In the method for producing low carbon ferroboron by reducing, the electrode power density in the melting reduction is 0.5/- or less, C: l, Q% or less, B: 10
% or more of low carbon ferroboron, and the low carbon ferroboron obtained in the first step is heated to a melting point of +150
A method for producing high-purity ferroboron, comprising a second step of completely remelting in a temperature range of ~200°C, cooling to just above the melting point, and maintaining at that temperature. (3) In the case of B:IO to 16, the remelting in the second step is performed at a maximum temperature of 1550 to 1750°C, a holding temperature of 1350 to 1600°C, and a holding time of about 5 minutes, as set forth in claim 2. A method for producing high-purity ferroboron.