JPS6216265B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is an extremely low-silicon iron-manganese alloy and a method for refining the same, and its purpose is to stably and inexpensively provide an iron-manganese alloy with a Si content of 20 ppm or less. As is well known, iron-manganese alloys are widely used as deoxidizing and sulfurizing agents during steel smelting. In recent years, iron-manganese alloys have attracted attention as raw materials for manganese-based ferrites, but iron-manganese alloys contain a considerable amount of Si, and in order to use them as raw materials for manganese-based ferrites, it is necessary to remove Si in the composition.
Must be below 0.005%. An iron-manganese alloy is an alloy that is usually made by smelting iron ore and manganese ore in an electric furnace or blast furnace, and consists of 60 to 90% Mn, less than 8% C, and the remainder mainly Fe. ,FMnH,FMnM,
It refers to FMnL, and generally Si2.0%
Contains the following. In other words, iron-manganese alloys are manufactured by melting and reducing raw materials such as manganese ore, iron ore, reducing agents, and slag-forming agents in a blast furnace or electric furnace.
Inside the furnace, the molten metal layer produced by the reducing agent and the molten slag layer are in an equilibrium relationship, and the metal portion and the slag portion are separated and manufactured by tapping from the furnace at regular intervals. In the above, manganese [Mn] and silicon [Si] in the molten metal layer and silicic acid (SiO ₂ ) and manganese oxide (MnO) in the molten slag are in an equilibrium relationship in the furnace.
There is an equilibrium relationship between them as follows. [Si] + 2 (MnO) = (SiO ₂ ) + 2 [Mn] From the above formula, (MnO) is required in the slag in order to remove [Si] in the metal layer, and for that purpose, (MnO) in the slag is ) must be extremely high, which inevitably results in a decrease in Mn yield. Therefore, in current electric furnace operation,
The limit is 0.01% Si, and in order to obtain products with even lower Si content, it is necessary to use electrolytic manganese or distilled manganese, but these electrolytic manganese and distilled manganese have the disadvantage of being expensive. be. The applicant had previously proposed a method for refining iron-manganese alloys (see Japanese Patent Application No. 58-95323). This method involves adding an alkali metal salt or an oxide of iron or manganese to a molten iron-manganese alloy.
an oxidizing agent consisting of at least one species, and an oxide or halide of an alkali metal or alkaline earth metal;
This is a purification method in which Si, Al, etc. in an iron-manganese alloy are oxidized and removed by stirring and contacting a flux consisting of a flux consisting of at least one species. The above method is an effective method for removing Si in iron-manganese alloys.
However, this purification method requires a large amount of flux,
It is unfavorable from a thermoeconomic standpoint, is expensive, and moreover, it is difficult to stably obtain products with a Si content of 0.005% or less. As a result of intensive research to further improve the above-mentioned method, the present inventors have developed an iron-manganese alloy that can be reliably used as a raw material for ferrite with Si of 20 ppm or less by having the configuration described in the claims, and a method for producing the same. was able to be established. That is, the invention described in claim 1 (hereinafter referred to as the first invention) has Mn of 60 to 90%,
An ultra-low silicon iron-manganese alloy characterized by comprising 8% or less of C, 20ppm or less of Si, and the remainder mainly Fe, and the invention set forth in claim 2 (hereinafter referred to as the second invention), Mn60-90%, C8% or less, used as raw material for ferrite,
In producing ultra-low silicon iron-manganese alloys consisting of less than 20 ppm Si and the remainder mainly Fe, Mn 60 to 90
%, C8% or less, Si0.5~0.01% _SiO2 ≦5%, and CaO/
0.5 to 5% by weight of a flux consisting of SiO ₂ ≧5 is added, and oxygen gas is blown into the flux while stirring while maintaining the temperature of the molten metal at 1250 to 1700°C.
This is a method for producing an ultra-low silicon iron-manganese alloy that desiliconizes to less than 20 ppm Si. The present invention will be explained below based on the second invention. Iron-manganese alloy is used as a deoxidizing and desulfurizing agent for steel, and as is clear from the regulations of JISG2301, it is a high-carbon iron-manganese alloy (C7.5% or less), a medium-carbon iron-manganese alloy. (C2.0% or less) and low carbon iron-manganese alloy (C1.0% or less), and the Si content can be specified as 0.5 to 1.0% or less. The raw material in the second invention may be any of the above-mentioned high carbon iron-manganese alloy, medium carbon iron-manganese alloy, or low carbon iron-manganese alloy. In addition, the flux used in the present invention is
A CaO--CaF ₂ -based flux is desirable, but it is not necessarily limited to this, and if necessary, a CaO--CaCl ₂ -based flux or a single CaO flux may be used. In addition, the composition of the flux is SiO ₂ ≦5% or less,
In addition, the flux has a high basicity of CaO/SiO ₂ ≧5. The reason for setting SiO ₂ ≦5% and CaO/SiO ₂ ≧5 is that in order to transfer SiO ₂ in the iron-manganese alloy into the flux, it is necessary to reduce the SiO ₂ in the flux as much as possible. The guideline is to make the CaO/SiO ₂ larger than at least 3CaO−SiO ₂ and to make SiO ₂ larger than the 5
% or less. When oxygen gas is blown into the mixture of molten iron-manganese alloy and flux as described above, the concentration of the metal in the metal is
Si is immediately oxidized to become SiO ₂ , which is further transferred into the flux to achieve desiliconization.
Of course, manganese [Mn] in the metal is also oxidized by the blowing of oxygen gas as shown in the following formula. 2 [Mn] + O ₂ = 2MnO However, the MnO produced in the slag further reacts with silicon [Si] in the metal as shown in the following equation. 2MnO + [Si] = 2Mn + SiO ₂ m CaO + n SiO ₂ = m CaO・n SiO ₂ In other words, MnO reacts with [Si] in the metal, is reduced to Mn again, and migrates into the metal, so Mn
On the other hand, the loss of SiO 2 is relatively small, and SiO ₂ migrates into the flux, so it is possible to obtain a product with a stable [Si] content of 20 ppm or less in the metal. That is, in the present invention, since the flux added to the iron-manganese molten metal is highly basic, the activity of MnO is large, and MnO can efficiently react with [Si] in the metal, and moreover, it is possible to remove MnO, etc. from outside the system. Since there is no need to add any oxidizing agent, there is no fear of contamination by impurities, and therefore the processing cost is low. In addition, the oxygen gas jet not only has the function of directly oxidizing Si in the molten iron-manganese alloy, but also lowers the temperature in the reaction system to 1250 to 1700.
It is possible to maintain the temperature at 0.degree. C. and to improve the stirring contact between the molten metal and the flux. Therefore, in carrying out the present invention, it is desirable to use a ladle equipped with a lance for bottom blowing. That is, in order to make sufficient contact between the molten iron-manganese alloy and the flux, oxygen gas, Ar gas, or both gases are blown from a lance at the bottom of the ladle and mixed with stirring, or oxygen gas is injected from the top of the ladle. Oxidize Si in the iron-manganese alloy by blowing or using both together, and oxidize at the same time.
SiO ₂ can be transferred into the flux and desiliconized in a short time. Furthermore, addition of flux and oxygen gas blowing may be carried out once, but may be carried out two or more times in consideration of the amount of molten iron-manganese alloy, the capacity of the ladle, etc. The drawing shows an example of the Si content in the iron-manganese molten metal in the treatment of the second invention. At (point B on the horizontal axis), it is observed that the Si content in the iron-manganese alloy decreases all at once to 10 to 20 ppm. In addition, in this experimental example, after the second desiliconization treatment (point C on the horizontal axis),
There is no substantial change from the initial desiliconization treatment, and in this case, the Si content can be reduced to 20 ppm or less with one desiliconization treatment. As described above, the present invention can provide an ultra-low silicon iron-manganese alloy with a Si content of 20 ppm or less, which has been difficult to achieve in the past, and in producing the ultra-low silicon iron-manganese alloy, SiO ₂ ≦5%
Moreover, by adding a flux of CaO/SiO ₂ ≧5 and blowing oxygen gas into the flux, it is possible to reliably produce an ultra-low silicon iron-manganese alloy. Example: A ladle with a lance for blowing bottom-blown gas,
A molten manganese alloy was taken, flux was added thereto, and oxygen gas and Ar gas were blown from a bottom-blowing lance to remove silicon. Table 1 shows the type and amount of flux used, the amount of gas used, and the results in this case.

【table】

[Table] As is clear from Table 1, in the method of the present invention, Si in the product is 20 ppm or less, whereas as shown in Comparative Example 1, even if CaO/SiO ₂ ≧5, SiO in the flux is ₂ If ≧5%, it is not possible to reduce the Si content in the product to 20ppm or less. In addition, as shown in Comparative Example 2, CaO/SiO ₂ ≦5
Therefore, if SiO ₂ ≧5%, Si cannot be reduced to 50 ppm or less.

[Brief explanation of the drawing]

The drawing is a graph showing an example of the behavior of the Si content in the raw material and the iron-manganese alloy after desiliconization treatment.

Claims (1)

[Claims] 1. Mn60-90%, C8 used as raw material for ferrite
% or less, Si20ppm or less, and the remainder mainly consists of Fe. 2 Mn60-90%, C8 used as raw material for ferrite
% or less, Si20ppm or less, and the remainder mainly consists of Fe.
For a molten iron-manganese alloy consisting of Mn 60-90%, C 8% or less, Si 0.5-0.01%, and the remainder mainly Fe, a flux consisting of SiO ₂ ≦5% and CaO/SiO ₂ ≧5 is added from 0.5 to 0.5%. An ultra-low silicon iron-manganese alloy characterized by adding 5% by weight of silicon, blowing oxygen gas into the alloy, stirring it, and maintaining the temperature of the molten metal at 1250 to 1700°C to desiliconize the Si to 20 ppm or less. Purification method.