JP2001214232A - Method for producing ferrochromium containing carbon of 9% or more - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily produce ferrochromium having a carbon content of 9% or more at a low cost. SOLUTION: A carbon source is fed into the molten metal of ferrochromium to control the content of carbon in the molten metal of ferrochromium to 9 wt.% or more. At this time, preferably, the molten metal of ferrochromium is produced by the remelting of undersize products produced in a crushing stage for a ferrochromium product, the molten metal of ferrochromium is heated to 1,680 deg.C or more, and the molten metal of ferrochromium is stored in a vessel lined by a carbonaseous refractory, and flux without substantially containing SiO2 is added to the inside of the vessel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a carbon material having a carbon content of 9 watts.
More specifically, a method for producing t% or more of ferrochrome is to supply a carbon source to a ferrochrome melt obtained by smelting a raw material such as chromium ore or a ferrochrome melt obtained by remelting high carbon ferrochrome. Carbon content of 9 wt%
The present invention relates to a method for producing ferrochrome.

[0002]

2. Description of the Related Art Conventionally, high carbon ferrochrome has been prepared by adding silica as a medium solvent to chromium ore (chromite containing impurities such as Al ₂ O ₃ and MgO) as a main raw material,
Further, coke is added as a reducing agent, and these raw materials are melt-reduced in a three-phase Elle-type electric furnace to produce. The chemical composition of the high carbon ferrochrome produced in this way is
As shown in JIS-G2303, chromium is 5
5 to 70 wt% (hereinafter referred to as “%”),
The chromium content is in the range of 9.0%, and the chemical composition of so-called charge chromium used worldwide is 50-55% chromium,
Carbon is less than 9%.

[0003] High carbon ferrochrome is used as an iron alloy in the steelmaking process when producing steel products such as stainless steel. However, if the carbon content in high carbon ferrochrome is directly added to the steel product, the carbon content of the steel product is reduced. Since the upper limit is exceeded, the carbon in the high carbon ferrochrome is usually removed from the molten steel after adding the high carbon ferrochrome to the molten steel. Therefore, in the steelmaking process, the lower the carbon content in high-carbon ferrochrome, the more advantageous it is. However, as described above, high-carbon ferrochrome is produced by reduction smelting under a carbon-saturated state in a three-phase Aerial electric furnace. Therefore, the carbon content inevitably becomes 8 to 9%. It is for this reason that the chemical composition of high carbon ferrochrome is defined as above.

Recently, it has been found that the use of high-carbon ferrochrome improves the magnetic properties of a weld in the welding of steel products. In this case, the higher the carbon content of the high-carbon ferrochrome, the higher the magnetic properties. In addition, the higher the carbon content, the better the pulverizability of the high-carbon ferrochrome and the superior the material for welding. Therefore, a high-carbon ferrochrome containing 9% or more, preferably 10% or more carbon is required. It became so.

As a method of increasing the carbon content to 9% or more in the smelting of high-carbon ferrochrome using a three-phase aeru-type electric furnace, a powdery chromium ore having no decarburizing ability is used.
%, And in order to lower the content of silicon, which reduces the solubility of carbon, there is a method of reducing the silicon content of ferrochromium by smelting under conditions where the reducing agent is slightly insufficient, and increasing the carbon content. .

However, according to the experience of the present inventors, even in this case, the silicon content is in the range of 0.2 to 1.0%, and the carbon content is at most about 9.0 to 9.5%. The content cannot be increased further. Also, during operation,
Because it is all fine ore, blowing up fine ore from inside the furnace,
Due to the lack of heat transfer due to the fine ore, the melting zone is reduced, etc., and the operation is extremely unstable and long-term operation is difficult.
In addition, since the reducing agent tends to be insufficient, the chromium yield is as low as about 85%, and there is a problem that the manufacturing cost is increased.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a low-cost and stable method for producing ferrochrome having a carbon content of 9% or more. It is to provide a manufacturing method.

[0008]

According to a first aspect of the present invention, there is provided a method for producing ferrochrome containing at least 9 wt% of carbon, wherein a carbon source is supplied into the molten ferrochrome so that the carbon content of the molten ferrochrome is at least 9 wt%. It is characterized by the following.

[0009] The method for producing ferrochrome containing 9 wt% or more of carbon according to the second invention is characterized in that in the first invention,
The above ferrochrome molten metal is obtained by re-dissolving a sieved product generated in a crushing step of a ferrochrome product.

The method for producing ferrochrome containing 9 wt% or more of carbon according to the third invention is characterized in that, in the first invention or the second invention, the molten ferrochrome is heated to a temperature of 1680 ° C. or more. Things.

According to a fourth aspect of the present invention, there is provided the method for producing ferrochrome containing 9 wt% or more of carbon according to any one of the first to third aspects, wherein the molten ferrochrome is lined with a carbonaceous refractory. And a flux substantially free of SiO ₂ is added to the container.

According to the present invention, a molten ferrochrome such as a general high-carbon ferrochrome obtained by smelting chromium ore,
Alternatively, even in the case of a molten metal having a low carbon content such as a ferrochrome molten metal obtained by re-dissolving a sieved product generated in a crushing step of a high carbon ferrochrome product or the like, a carbon source is supplied and carburized. In addition, ferrochrome having a carbon content of 9% or more can be stably manufactured at low cost.

[0013] The sieved product (also referred to as an undersize product) generated in the crushing step of a ferrochrome product is usually re-dissolved in the ferrochrome smelting process to produce a product. It is preferable to redissolve the sieved product to obtain a ferrochrome melt used in the present invention. This is because the sieved product inherently requires a re-dissolution treatment, and by using the ferrochrome melt used in the present invention, the amount of re-dissolution as a sieved product is reduced, and the re-dissolution cost is reduced, contributing to a reduction in manufacturing cost. Because. Also, since the carbon solubility of the ferrochrome melt increases in proportion to the temperature, the temperature of the melt is increased to 1680 ° C. in order to increase the carbon solubility.
It is preferable to make the above.

It is preferable to use a container lined with a carbonaceous refractory as a container for holding the ferrochrome molten metal, since it is less damaged by the molten metal even at a high temperature range of 1600 ° C. or higher and can be used stably. .

The lower the silicon content in the ferrochrome melt, the greater the carbon solubility of the ferrochrome melt and the easier the carbonization. If slag containing SiO ₂ onto the molten metal melt surface is present, SiO ₂ in the slag is reduced by carbon in the molten metal increases the silicon content in the molten metal, carburization becomes difficult. In order to prevent this, it is preferable to use a flux that does not substantially contain SiO ₂ . Even if chromium ore is added, SiO ₂ brought from chromium ore is diluted by the added flux, and S
The reduction reaction of iO ₂ is suppressed. Here, substantially SiO
_The meaning of not containing ₂ means that it may be contained as a small amount of impurities.

[0016]

Embodiments of the present invention will be described below. A solid ferrochrome such as high-carbon ferrochrome, medium-carbon ferrochrome, or low-carbon ferrochrome is charged and heated and melted in a refining furnace having a heating means such as an Elu-type electric furnace, a direct-current electric furnace, or an induction melting furnace. Generate molten metal. As described above, it is preferable to use a sieved product of ferrochrome as the dissolving raw material. Further, among the sieved products, it is particularly preferable to use a sieved product of high carbon ferrochrome. By using a high-carbon ferrochrome sieved product, it is possible to achieve a desired carbon content of 9% or more with a smaller carburization amount than that of a medium-carbon or low-carbon ferrochrome sieved product.

On the other hand, when using a general molten metal such as high carbon ferrochrome obtained by smelting chromium ore in a smelting furnace such as a three-phase electric furnace, a ladle is held from the smelting furnace. Even if the molten metal is once received in a container and then supplied to a refining furnace having a heating means such as an aerial electric furnace, a direct current electric furnace or an induction melting furnace, or a ladle refining furnace. It is also possible to use a refining furnace having a means for heating the molten metal in the ladle and process the molten metal in a holding container. The atmosphere during the treatment may be any of an air atmosphere, an inert gas atmosphere, or a pressurized or reduced pressure atmosphere.

At this time, the container for carburizing the molten metal includes a magnesia-based refractory lining, a magnesia-chromium-based refractory lining, a magnesia-dolomite-based refractory lining, an alumina-based refractory lining, and a carbonaceous-based refractory lining. Containers such as refractory lining can be used,
As described above, it is preferable to use a container lined with a carbonaceous refractory. Here, the carbonaceous refractory is a general term for commonly used refractories containing carbon as a main component, such as graphite bricks and carbon stamps.

Then, a carbon source is supplied to the molten metal and carbonized. As a carbon source to be used, carbonaceous materials such as coke, char, coal, charcoal, and graphite, carbon in a lining of a carbonaceous refractory, carbon in a graphite electrode, and the like can be used. It is preferable to use a carbon material such as coke. As a method of adding the carbon material, a method in which the material is laid beforehand on the hearth of a refining furnace, a method in which the material is added to a sifted product as a melting raw material, and a method in which the material is blown into the molten metal through a lance immersed in the molten metal are used. There is a method of addition, a method of adding it by placing it on the surface of the molten metal, etc., but from the viewpoint of protection of the furnace body lining, improvement of carburizing efficiency, etc., part is spread on the hearth and the remainder is blown in or added. It is preferable to mix and add it to a vulgar product. When forming slag on the surface of molten metal,
Since the contact between the carbonaceous material and the molten metal is impaired, it is not preferable to add it on the surface of the molten metal. As described above, it is preferable to raise the temperature of the molten metal to 1680 ° C. or higher at least after the addition of the carbonaceous material.

Before and after the addition of the carbonaceous material, the molten metal is prevented from being oxidized and
Forming molten slag on the surface of molten metal for heat retention
Is preferred. The slag composition is in a molten state at about 1600 ° C.
Any composition may be used as long as the composition is
Slag is formed from the viewpoint of improving carburizing efficiency
The flux to be added is substantially SiO 2 _Two 
It is preferable to use a flux containing no. this
Fluxes that satisfy the conditions include quicklime and dolomite.
G, magnesia clinker, alumina powder, and smelting
Use of slag and refractory brick debris generated in the process
it can. In the experience of the present inventors, about 30% of CaO
About 40% MgO and about 30% Al_Two O_Three And from
When the flux is used, the desiliconization reaction of the molten metal and
The desulfurization reaction is accelerated, and stable
We have confirmed that it is possible to make charcoal.

Prior to the addition of the flux, chromium ore may be added to adjust the chromium content of the molten metal. Since chromium ore is melted and reduced by carbon, the chromium content in the molten metal can be increased. Further, since a part of the chromium ore is reduced by silicon in the molten metal, there is also an effect of reducing silicon in the ferrochrome molten metal.

After raising the temperature of the molten metal to a predetermined temperature, a sample for analysis is taken from the molten metal as required, and it is confirmed that the carbon content of the molten metal is 9% or more, preferably 10% or more. After the carburizing process, the molten metal is cast by a cast iron machine or the like.

By carburizing the molten ferrochrome in this manner, it is possible to stably produce ferrochrome containing 9% or more of carbon at low cost. In the present invention, the chromium content of ferrochrome containing 9 wt% or more of carbon is intended to be in the range of 50 to 70%, and therefore, metal chromium, iron, or the like can be added for component adjustment.

[0024]

EXAMPLES Example 1 Using a 500 kVA aerial type electric furnace lined with magnesia refractory, the sieved product generated in the crushing process of high carbon ferrochrome products was dissolved, and coke was used as a carburizing agent. Example 1 will be described. The high-carbon ferrochrome sieve has a chromium content of 6
7.0%, silicon content 0.8%, carbon content 8.4
%, 250 kg of this was used per heat. 5k
g of coke was spread on an electric furnace hearth, and the remaining 5 kg was melted through an immersion lance and then added to the molten metal by blowing. or,
Slag (CaO: 36%, SiO ₂ : 37%, Mg generated during smelting of low carbon ferrochrome as flux)
O: 13%, Al ₂ O ₃ : 11%) was added as a flux in an amount of about 30 kg per heat.

After dissolving the sieved product, the temperature of the molten metal is adjusted to 17
The temperature was raised to four levels (test numbers 1 to 4) in the range of 00 to 1790 ° C. When the temperature reached that temperature, an analytical sample was taken from the molten metal, poured out into a ladle, and then cast with a cast iron machine. In Test No. 4, an analysis sample was collected from the molten metal during heating of the molten metal to investigate the relationship between the molten metal temperature and the carbon content. Table 1 shows the melt temperature in each test and the chemical composition of the obtained ferrochrome. Table 2 shows the results of an examination of the relationship between the melt temperature and the carbon content in Test No. 4.

[0026]

[Table 1]

[0027]

[Table 2]

As shown in Table 1, it was found that ferrochrome containing 9% or more of carbon can be stably produced by carburizing a high-carbon ferrochrome melt. or,
As shown in Table 2, there is a correlation between the temperature of the molten metal and the carbon content. As the temperature of the molten metal increases, the solubility of carbon increases.
It was found that if the temperature of the molten metal was increased to 80 ° C. or more, the carbon content became 9.5% or more. In addition, damage to the lining of the magnesia refractory was observed, which is considered to be due to the reduction reaction of magnesia with carbon.

Example 2 Lined with carbonaceous refractory
Using a 500 kVA aerial electric furnace
Dissolve the sieved product generated in the crushing process of the yellow chrome product,
Example 2 using coke as a carburizing agent will be described. High
The sieved product of carbon ferrochrome has a chromium content of 67.0.
%, Silicon content 0.8%, carbon content 8.4%,
This was used in an amount of 250 kg per heat. 5kg
Spread on the hearth of the electric furnace, and mix the remaining 5 kg with the sieved product.
Were added together. The test was performed 7 times in total, and test numbers 5 to 8
Then, when smelting low carbon ferrochrome as flux
Slag (CaO-SiO)_Two -MgO-Al_Two 
O_Three ) And in Test Nos. 9 to 11, SiO _Two 
CaO—MgO—Al substantially free of_Two O_Three System
Lux was used. Further, in tests 5 to 8, the flux
Basicity ([CaO + MgO] / SiO_Two Investigate the impact of
In Test Nos. 5 and 6, the basicity was set to 1.5
In Test Nos. 7 and 8, low-carbon ferrochrome slag was magnetized.
Shea was added to adjust the basicity to 3.3. These flags
Approximately 30 kg was added per heat.

After dissolving the sieved product, the molten metal is heated to a temperature in the range of 1730 to 1800 ° C., and when the temperature reaches the temperature, an analytical sample is collected from the molten metal and discharged into a ladle, and then cast. Cast in a pig machine. Table 3 shows the melt temperature, the flux, and the chemical composition of the obtained ferrochrome in each test.

[0031]

[Table 3]

As shown in Table 3, in all tests, carbon was 9
% Of ferrochrome could be produced.
Further, in the case of the present embodiment lined with a carbonaceous refractory, in the flux used in Test Nos. 5 to 8, SiO ₂ in the flux is reduced by carbon, and the amount of silicon increases to suppress the amount of increase in carbon. Was done. Even in Test Nos. 7 and 8 in which the basicity was increased, reduction of SiO ₂ occurred with an increase in the temperature of the molten metal. On the other hand, in Test Nos. 9 to 11 using a flux substantially not containing SiO ₂ , a desiliconization reaction of the molten metal by the flux occurred, and the silicon content was reduced. Accordingly, the carbon content rose to a value exceeding 10%.
In Test Nos. 9 to 11, 0.3% was used at the stage of the sieved product.
It was confirmed that the contained aluminum was reduced to about 0.03%. No damage was found on the lining of the carbonaceous refractory.

[0033]

According to the present invention, a chromium ore obtained by remelting a molten ferrochrome such as a high-carbon ferrochrome obtained by smelting or a sifted product generated in a crushing step of a ferrochrome product. Even in the case of a molten metal having a low carbon content such as a molten ferrochrome, a carbon source can be supplied to the molten metal and carburized to produce ferrochrome having a carbon content of 9% or more at low cost and stably. .

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Shibuya 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Inventor Chifumi Matsumura 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. F-term (reference) 4K001 AA08 BA24 CA01

Claims (4)

[Claims] 1. A method for producing ferrochrome containing 9% by weight or more of carbon, wherein a carbon source is supplied into the molten ferrochrome to make the carbon content of the molten ferrochrome 9% by weight or more. 2. The method for producing ferrochrome containing 9 wt% or more of carbon according to claim 1, wherein the molten ferrochrome is obtained by re-dissolving a sieved product generated in a crushing step of a ferrochrome product. 3. The method for producing ferrochrome containing 9% by weight or more of carbon according to claim 1 or 2, wherein the molten ferrochrome is heated to a temperature of 1680 ° C. or more. 4. The ferrochrome molten metal is contained in a container lined with a carbonaceous refractory, and a flux substantially free of SiO ₂ is added to the container. The method for producing ferrochrome containing 9 wt% or more of carbon according to any one of claims 1 to 3.