JPH10306305A - Steelmaking method using two or more sets of converters - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steelmaking method which efficiently executes dephosphorizing refining and decarburizing refining in a converter and minimizes slag development. SOLUTION: This method uses two or more sets of converters provides the following processes. (a) Molten iron having <=0.3 wt.% Si content, is charged into one set of the converter, and the dephosphorizing refining is executed so that P content in the molten iron becomes P content (component standard value in the steel) needed for the crude steel or lower. (b) The dephosphorize- refined molten iron is charged into the other set of converter, and the decarburizing refining is executed without substantially charging slag-making material. (c) The decarburize-refined molten steel and only increased slag quantity during decarburizing refining are tapped or discharged from the other set of converter. In the case the Si content in the molten steel to be dephosphorize-refined exceeds 0.3 wt.%, the desiliconizing treatment is beforehand executed and the Si content is regulated to <=0.3 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for performing dephosphorization and refining of molten iron in a blast furnace in advance, and performing decarburization and refining of the dephosphorized and refined molten iron in a converter to produce steel from smooth and highly productive molten iron. About the method.

[0002]

2. Description of the Related Art In a conventional converter steelmaking method, dephosphorizing and decarburizing refining of molten iron in a blast furnace is performed in the same converter to perform a steelmaking operation. However, while the demands on the quality of steel materials have increased in recent years, with the expansion of continuous casting, and the spread of secondary refining of molten steel such as vacuum degassing and ladle refining, the tapping temperature in converters has increased, The dephosphorization capacity in the converter has been reduced. The reason for this is that the dephosphorization reaction proceeds disadvantageously as the temperature increases.

[0003] Therefore, a hot metal pretreatment method has been developed in which the hot metal charged into the converter is preliminarily treated, and in particular, the phosphorus (P) component is removed to some extent before the hot metal is charged into the converter. This method is, for example, a steelmaking method in which hot metal is dephosphorized and refined in a hot metal ladle or one converter, and the dephosphorized hot metal is transferred to another converter and decarburized and refined.

[0004] As such a technique, Japanese Patent Application Laid-Open No. 2-20071 is disclosed.
No. 5, Japanese Patent Publication No. 2-14404, Japanese Patent Publication No. 61-
There is a proposal in JP 23243 Gazette. In addition, the inventor of the present application has also remodeled a conventional steelmaking plant, provided working floor openings in the working floor in front of each of a plurality of converters, and received molten metal obtained by dephosphorizing hot metal in one converter. A refining method has been developed in which a hot pot is received, and the hot pot is transported to another converter through the opening of the work floor, charged into the converter, and decarburized and refined therein (Japanese Patent Laid-Open No. Hei 6 (1994)). -41624).

[0005]

In the above steelmaking method, the hot metal is dephosphorized and refined in one converter and the like, and the hot water is immediately discharged in another converter and the like within at least the dephosphorization and refining time. Decarburization and refining are necessary for smooth steelmaking operations.

FIG. 10 shows an outline of dephosphorization refining in a 340 ton converter before the present invention. The dephosphorization and refining of the hot metal is performed at a low temperature (1250-1400 ° C.), and the slag FeO (5-10
%), The slag is formed,
Immediately after tapping, the slag flows out of the furnace port or a large amount of slag flows into the hot pot, so that the sedation time as shown in the figure required about 4 minutes. Therefore, the dephosphorization refining time was, for example, about 36 minutes on average.

On the other hand, the decarburization refining time of this dephosphorized hot metal in another converter is 29 minutes on average due to various improvements, and is 27 minutes without slag coating. Therefore, the decarburization smelting furnace has at least 7 minutes, up to 9 minutes idle time,
Therefore, the steel making efficiency was reduced accordingly. Reducing the 7 minute play time results in about a 20% increase in production. In addition, during this idle time, the temperature inside the decarburization refining furnace was lowered, bricks were worn, etc., and the converter life was shortened.

Accordingly, an object of the present invention is to reduce the dephosphorization refining time, eliminate idle time in the decarburization refining furnace, ensure a smooth steelmaking operation, and improve the steelmaking efficiency. In the above dephosphorizing refining, the P content of the molten steel is refined to the P content of the crude steel component (a so-called standard value, usually 0.02 wt% or less), and in the decarburizing refining, substantially no dephosphorizing refining is performed. The aim is to improve efficiency.

Further, although the slag generated by the above steel making method has been reduced, it is desirable to further reduce it. Further, since the hot metal to be decarburized and refined has already been sufficiently dephosphorized and refined, there is no need for further dephosphorization. Therefore, in order to save expensive manganese alloys, manganese ore is charged as much as possible in decarburization refining and reduced to increase the Mn content of molten steel. At present, the reduction yield of Mn to molten steel is not sufficient.

[0010]

As a result of various studies on the above-mentioned problems, as a result of dephosphorizing and refining hot metal, the P content is reduced to the P content of a normal crude steel component (a so-called standard value, usually 0.0%).
(2 wt% or less), and found that the decarburization refining can be achieved by substantially performing only decarburization refining, and charging manganese ore as necessary, leading to the following invention.

A first invention is a steel making method using two or more converters, comprising the following steps. (A) In a converter, hot metal having a Si content of 0.3 wt% or less is charged, and the phosphorus (P) content of the hot metal is equal to or less than the P content (specified steel component value) required for crude steel. To dephosphorization,
(B) charging the dephosphorized and refined molten iron into another converter and performing decarburization and refining without substantially charging slag-making material; and (c) removing the decarburized and refined molten steel from the molten steel. Only the amount of slag increased during coal refining is discharged or discharged from the other converter as required.

In the above invention, in the dephosphorization refining, the P content of the hot metal is refined to the P content of the crude steel (specified component value of steel), so in the decarburization refining, calcined lime for refining P is refined. It is not necessary to insert a slag-making material, etc., so that the decarburization refining can be extremely simplified and the refining time can be shortened. Therefore, the steelmaking efficiency can be improved as a whole. The slag generated in the decarburization refining does not need to be discharged for each charge, but is discharged after a certain amount, that is, as required.

In a second aspect of the present invention, if the Si content of the hot metal to be subjected to the dephosphorization refining exceeds 0.3 wt%, a silicon removal treatment is performed in advance to reduce the Si content to 0.3 wt% or less. This is a steelmaking method using two or more converters. When the Si content of the hot metal for dephosphorizing and refining exceeds 0.3 wt%, a silicon removal treatment is performed in advance to reduce the Si content to 0.3 w%.
When the content is set to t% or less, the dephosphorization refining time can be shortened, and the P content of the hot metal can be easily refined to the P content of the crude steel (specified component value of the steel).

According to a third aspect of the present invention, the silicon removal treatment is performed in a blast furnace cast bed and / or in a hot metal ladle to reduce the Si content to 0.3 wt% or less. This is a steel making method using two or more converters. Since the silicon removal treatment in the blast furnace cast floor and the silicon removal treatment in the hot metal pot are conventionally performed and are relatively easy to carry out, when the Si content is 0.3 wt% or more, these methods are used. The methods can be applied alone or in duplicate.

According to a fourth aspect of the present invention, in the silicon removal treatment, the content of Si is reduced to 0.3 wt% or less in a converter for dephosphorization refining, the generated slag is discharged, and the dephosphorization refining is subsequently performed. This is a steelmaking method using two or more converters. By blowing oxygen gas in a converter (dephosphorization refining furnace) for performing dephosphorization refining, silicon removal can be performed in an extremely short time.

According to a fifth aspect of the present invention, in the converter for performing the decarburization refining, manganese ore is further charged, and the manganese (Mn) content of the molten steel at the end point is maximized to satisfy the Mn standard value required for the crude steel. A steelmaking method using two or more converters, characterized in that the Mn content is increased within the upper limit.
When manganese ore is further charged in the converter for decarburization refining, manganese ore is reduced by the carbon (C) of hot metal, so that the Mn content is increased within the upper limit of the Mn standard value required for crude steel. Can save expensive manganese alloys. Further, in the present invention, the slag remaining in the furnace is not diluted with the MnO concentration because the slag-making material is not substantially charged in the decarburization refining. Therefore, the Mn content of the charged manganese ore is efficiently reduced to molten steel, and the manganese yield is dramatically improved.

According to a sixth aspect of the present invention, when the manganese ore is charged, silica (SiO ₂ ) contained in the manganese ore is charged.
To a predetermined basicity (CaO wt% / SiO ₂ wt
%, Hereinafter abbreviated as CaO / SiO ₂ ).
A steelmaking method using two or more converters, wherein a slag-making material containing aO is charged. Manganese ore is, for example, 1
It contains 0 wt% or less of silica (SiO ₂ ), and in some cases, lowers the basicity of slag (CaO / SiO ₂ ). Prevents body wear and double phosphorus.

According to a seventh aspect of the present invention, in the converter for performing the decarburization refining, two or more converters are characterized in that a slag solidifying agent is charged before charging the dephosphorized and refined hot metal. This is the steelmaking method used. In a converter for decarburization refining, if a slag solidifying agent is charged prior to charging of hot metal, safe refining can be performed without bumping even if dephosphorized refining hot metal is charged.

An eighth invention is a steelmaking method using two or more converters, wherein the slag solidifying agent is lightly fired dolomite and / or green dolomite. Lightly burned dolomite and / or raw dolomite dissolves easily in slag,
The gO concentration can be increased to protect the furnace body brick and prolong the life of the furnace body.

A ninth invention is a steelmaking method using two or more converters, wherein the entire amount of scrap is charged before charging the hot metal into the converter for performing the dephosphorization refining. . If the entire amount of the scrap is charged before charging the hot metal into the converter for performing the dephosphorization refining, the scrap is easily melted, and there is an effect of increasing the production of the dephosphorized refining hot metal.

According to a tenth aspect of the present invention, there is provided a steelmaking method using two or more converters, wherein a part or all of the scrap is magnetically separated from slag produced by dephosphorization refining and / or decarburization refining. Is the way. Part or all of the scrap is magnetically separated from the slag generated by the dephosphorization refining and / or decarburization refining, so that slag generation is smooth even at a low hot metal temperature, and the P content at the end point is stable. And then lower.

An eleventh invention is a steelmaking method using two or more converters, wherein the decarburization refining is performed within the dephosphorization refining time. By performing the decarburization refining within the dephosphorization refining time, the dephosphorization refining hot metal can perform the decarburization refining without waiting time, and the steelmaking efficiency can be improved.

A twelfth invention is characterized in that the one and / or the other converters are any of a top-blowing converter, a bottom-blowing converter and a top-bottom-blowing converter. This is a steelmaking method using The above-mentioned dephosphorization refining and decarburization refining can be carried out in any of a top-blowing converter, a bottom-blowing converter, and a top-bottom-blowing converter.

According to a thirteenth invention, a steel making method using two or more converters is characterized in that at least 80% or more of the steel making method according to any one of the above 1 to 12 is carried out in a series of converter operations. It is. When charging in the steelmaking method according to any of the first to twelfth aspects is performed in a series of converter operations, for example, at least 80% or more in one day operation, the MnO concentration in the slag gradually increases, and the manganese content increases. This has the effect of increasing the yield. The other charges are charges for performing ordinary refining, that is, dephosphorizing refining and decarburizing refining in the same converter.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The outline of dephosphorization refining in a converter for hot metal is, as is well known, after charging hot metal, blowing oxygen from a lance, charging a predetermined amount of calcined lime, etc. Si
This is a step of generating slag mainly containing O ₂ , FeO and the like, and removing phosphorus from the hot metal. When the dephosphorization and refining of the hot metal is completed, the furnace is dropped and the hot water is supplied to the ladle through the tap hole.

FIG. 10 shows the outline of the conventional hot metal dephosphorization refining. Following scrap loading, for example, 340 ton of hot metal
After charging, calcined lime (6 ton / ch) as a slag-making material,
Oxygen blowing is carried out for about 13 minutes while charging fluorite (0.6 ton / ch), raw dolomite and the like depending on circumstances.

Thereafter, rinsing is performed for about 3 minutes to separate the hot metal and the slag. After that, the conventional method waits about 4 minutes to calm down the slag forming, and then discharges the hot water. As shown in the figure, the dephosphorization refining time is about 36 minutes. On the other hand, the time for decarburizing and refining this dephosphorizing refining was about 29 minutes, and the converter for decarburizing and refining (hereinafter referred to as a decarburizing converter) had a non-operating time of about 7 minutes.

FIG. 1 shows the outline of the dephosphorization refining in the 340-ton converter according to the present invention, FIG. 2 shows the relationship between the Si content and the dephosphorization refining time, and FIG. 3 shows the distribution of the refining time. As shown in FIG. 2, in the conventional example, the S
Although the i content was about 0.3 to 0.5 wt%, the present invention desirably uses hot metal of 0.3 wt% or less, so that the dephosphorization refining time is 32.2 minutes or less, and about 10% The productivity can be improved.

In the recent blast furnace operation, there is no problem in the above operation because the Si content of the hot metal is 0.3 wt% or less. However, in unsteady operation (such as after blast furnace shut down), Si
However, in such a case, silicon removal is performed in advance using a hot metal pot or the like to prevent the dephosphorization refining time from being prolonged.

In the present invention, since the hot metal containing 0.3% by weight or less of Si is used, the amount of slag is, as shown in FIG.
0 to 50 kg / ton) (20 to 30 kg / ton)
ton, refer to FIG. 6). Since slag forming during refining is small, no sedation time (4 minutes in the prior art) is required, and as shown in FIG.
It could be reduced to 2.2 minutes, approaching the decarburization refining time.

In addition, in the dephosphorizing refining of the present invention, P is usually required for crude steel (specified value), even though the dephosphorizing refining is carried out with a substantially same basicity and a smaller amount of slag. It is refined to 0.02 wt% or less (see FIG. 6).
Therefore, P need not be refined in the decarburization refining.
It is estimated that smooth slag generation was performed because the amount of slag was small.

In the dephosphorization refining of the present invention, in order to ensure sufficient dephosphorization refining and shortening of the refining time,
The basicity of the slag is set to about 1.5 to 5. If necessary, reduce coke by 0.5t to suppress slag forming.
Charge about on / ch. In order to promote dephosphorization refining, the concentration of FeO in the slag is increased. For this purpose, iron ore or mill scale is charged in the middle stage of blowing (see FIG. 1).

Next, FIG. 4 shows the situation of the decarburization refining. Since the purpose of this refining is mainly for decarburization refining, the amount of oxygen to be blown is increased. Since the P content of the hot metal is already below the standard value (0.02 wt%), slag-making materials such as calcined lime, which are conventionally used in large quantities, are generally charged except for the first charge in a series of blowing. do not do. Therefore, the amount of slag generated in the furnace is 10 to 30 kg / ton as shown in FIG.
n and small. In addition, the amount of slag to be discharged after tapping, as a rule, remains in the furnace, which is greatly reduced as compared with the conventional method (see FIG. 6).

In the decarburization refining of the present invention, manganese ore is charged as much as possible. The Mn content of the blast furnace hot metal is usually 0.2 to 0.3 wt%, and the Mn content of the dephosphorized and refined hot metal is usually 0.15 to 0.25 wt%.
The same is true for decarburization refining. On the other hand, M
The n content (standard value) depends on the type of steel, but is, for example, 0.40 to 0.60 wt% for low carbon steel and 1.0 to 1.2 wt% for high manganese steel, for example. Therefore, usually at the time of tapping, an expensive manganese alloy is added to the standard value.

In the present invention, there is no need to perform dephosphorization refining in decarburization refining. Therefore, in the present invention, manganese ore (for example, Mn about 50 wt%, Fe about 10 wt% or less, SiO 2
₂ about 10 wt% or less). When manganese ore is added during refining, it is efficiently reduced, and the Mn content of the molten steel can be increased to the maximum and the upper limit of the Mn content of the crude steel, thereby enabling more economical steelmaking operations.

However, since manganese ore contains SiO ₂ , the manganese ore is dissolved, and a slag forming material containing CaO is charged so as to have a basicity (1.5 to 5). The manganese ore is charged as much as possible to minimize the addition of expensive manganese ferroalloys. As for the Mn content of the manganese ore, the MnO concentration of the slag is maintained high before the blowing, and the manganese ore is less diluted by the slag-making material, so that the reduction yield of manganese to molten steel is high.

Further, what is characteristic of the decarburization refining of the present invention is that a slag solidifying agent is charged before charging the dephosphorized and refined hot metal. In this case, when the dephosphorized hot metal is charged, it has an effect of suppressing the bumping phenomenon of the hot metal, and secures safe operation. Examples of the slag solidifying agent include brick waste, calcined lime, lightly burned dolomite, raw dolomite, and the like. Of the slag solidifying agents, lightly burned dolomite and raw dolomite are desirable from the viewpoint of solubility, economy, and prolonging the life of the furnace.

Addition of lightly-burned dolomite and / or raw dolomite before charging the dephosphorized hot metal into the decarburizing refining furnace has the effect of sufficiently dissolving the slag in the decarburizing refining and increasing the MgO concentration. Since such slag itself contains MgO up to the solubility limit, the slag has an effect of suppressing wear of the furnace body brick made of magnesium (MgO) brick and extending the life of the furnace body.

Further, after the molten steel is discharged, the furnace body is tilted so that the slag remaining in the furnace adheres to the bricks in the furnace, so-called slag coating is performed. This slag coating greatly contributes to prolonging the life of the furnace, and the life of the furnace is about the same as that of the dephosphorizing smelting furnace. Accordingly, not only the time cycle of the dephosphorization refining time and the decarburization refining time become the same, but also the furnace life of both furnaces becomes almost the same, and a smooth and consistent steelmaking operation becomes possible.

In the present invention, slag discharged from the decarburization smelting furnace by the above slag coating is up to about 10
kg / ton, if it is small, it will not be discharged at all. As already mentioned, the amount of slag generated by dephosphorization refining is also 40 kg /
ton or less, some of which can be recycled,
The amount of slag discharged to the outside per ton of crude steel is about 40k
g / ton or less.

In the present invention, since the dephosphorizing refining time can be shortened as compared with the conventional method, it is possible to temporally charge the entire amount of scrap prior to charging the hot metal into the converter for performing the dephosphorizing refining. . In addition, dephosphorization refining is performed at low temperature (1300 to 1300).
1400 ° C.), but since the amount of carbon in the hot metal is high, the scrap is easily melted, so that the scrap can be charged. The amount of scrap charged is within about 10 wt% of the amount of hot metal from the viewpoint of heat balance. The charging of scrap has the effect of increasing the production of dephosphorized hot metal.

In addition, a part or all of the scrap is
It can be used as magnetic separation of slag generated in dephosphorization refining and decarburization refining. The magnetic separation waste is a portion (about 50 wt%) containing a large amount of granular iron and the like obtained by separating slag generated in dephosphorization refining and decarburization refining by a magnetic separator. Since the magnetic waste contains about 50 wt% of the dissolved slag, the slag generation is smooth even when the hot metal temperature is low, and the P content at the end point is more stable and can be further reduced.

In the present invention, since the decarburization refining can be performed within the dephosphorization refining time, the dephosphorization refining hot metal can be decarburized and refined without waiting time, and the steelmaking efficiency can be improved. . The converter in the present invention may be any of a top-blown oxygen converter, a bottom-blown oxygen converter, and a top-blown oxygen converter.

Further, the manganese reduction yield is improved by repeating the above-described steel making method a number of times in a series of operations, for example, one day operation. This will be described below. In the operation of the present invention, the Mn content of the manganese ore is determined by the T.M. Since Fe is low and the MnO concentration of the slag is maintained high before blowing, much of the manganese ore charged is reduced.

The reduction yield of the manganese ore is greatly increased depending on the above-mentioned embodiments of the present invention, for example, a charge in which substantially no slag-making material is charged, or a ratio of a charge in which manganese ore is charged in a series of operations. Change. This will be described with reference to FIG. FIG. 7 shows that assuming that the total number of charges per day (usually about 40 charges) is 100%, increasing the ratio of the number of charges for practicing the present invention within one day improves the manganese yield. Here, for example, a ratio of 50% means that if the charge is 40 charges per day, 20 charges are the charges of the present invention.

The 40 charges may be performed in any manner. For example, an operation in which five charges using manganese ore are successively performed, and then five charges are performed in a normal converter operation (a refining operation in which dephosphorization refining and decarburization refining are performed in the same converter, that is, a charge in which manganese ore is not charged). Is repeated four times a day.

The manganese yield on the vertical axis in FIG.
It means the ratio (%) of the amount of manganese in the tapped steel to the total amount of manganese charged in the converter (the amount of manganese in the slag and the amount of manganese in the manganese ore). From FIG. 7, it is desirable that the manganese yield is about 60 to 80% when the charge for charging the manganese ore is 80% or more.

[0048]

EXAMPLES In order to confirm the effects of the present invention, low carbon steel (C:
Medium carbon steel (C: 0.1-0.2w)
t%) and a high carbon steel (C: more than 0.2 wt%) were each manufactured in 50 charges, and the change of the component composition in the manufacturing process is shown in FIGS. 8 and 9. Hot metal Si content is 0.3wt%
By using the following hot metal, the P content of the crude steel is refined to 0.02 wt% or less. Further, the Mn content of the crude steel could be increased in accordance with the charged amount of manganese ore. Other refining data are as shown in FIGS.

[0049]

According to the present invention, the Si content is 0.3%.
By dephosphorizing and refining hot metal of less than wt% and decarburizing and refining this hot metal, the dephosphorizing refining, which was longer than the conventional decarburizing refining time, can be shortened and approaching the decarburizing refining time including the slag coating time. Can be. Therefore, the so-called steel making time can be reduced by about 20% as a whole.

Further, in the present invention, the hot metal is refined in a converter to reduce the phosphorus (P) content of the hot metal to a P content (specified component value of steel) required for the crude steel, and is subjected to dephosphorization refining. Hot metal is charged into a converter, and decarburization refining is performed without substantially charging slag-making material. Therefore, in a converter for decarburization refining, manganese ore is charged, and the Mn content can be increased within the upper limit of the Mn standard value required for crude steel, and a very economical steelmaking method can be realized. . In addition, this steelmaking method can minimize the amount of slag generated, and thus has the effect of saving resources. Therefore, the industrial effects of the present invention are remarkable.

[Brief description of the drawings]

FIG. 1 is a view showing a dephosphorization refining step in the present invention.

FIG. 2 is a diagram showing a decarburization refining step in the present invention.

FIG. 3 is a diagram showing the relationship between the amount of Si in hot metal and the dephosphorization refining time.

FIG. 4 is a diagram showing a dephosphorization refining time of hot metal in the present invention.

FIG. 5 is a diagram showing a dephosphorization refining time and a decarburization refining time of hot metal in the present invention.

FIG. 6 is a diagram showing changes in the composition of hot metal and molten steel in the present invention.

FIG. 7 is a diagram showing the relationship between the implementation ratio of the present invention and the manganese yield in a series of operations.

FIG. 8 is a diagram showing changes in the component compositions of hot metal and slag in dephosphorization refining when various carbon steels are manufactured according to the present invention.

FIG. 9 is a diagram showing changes in the component compositions of molten steel and slag in decarburization refining when various carbon steels are manufactured according to the present invention.

FIG. 10 is a diagram showing a process of dephosphorization refining before the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Kodaira 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Inside Nihon Kokan Co., Ltd. (72) Inventor Ichiro Kikuchi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan (72) Inventor Manabu Arai, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Nihon Kokan Co., Ltd. (72) Hideei Tanaka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Co., Ltd. (72) Inventor Kazutoshi Kawashima 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Shigeru Inoue 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Stock In company

Claims (13)

[Claims] 1. A steel making method using two or more converters, comprising the following steps: (A) A converter is charged with hot metal having a silicon (hereinafter referred to as Si) content of 0.3 wt% or less, and the phosphorus (hereinafter referred to as P) content of the hot metal is required for crude steel. Dephosphorizing and refining to a P content (specified component value of steel) or less, (b) charging the dephosphorized and refined hot metal into another converter, and decarburizing without substantially charging slag-making material Refining is performed. (C) Only the molten steel subjected to the decarburization and refining and the slag amount increased during the decarburization and refining are discharged or discharged from the other converter as necessary. 2. When the Si content of the hot metal to be subjected to the dephosphorization refining exceeds 0.3 wt%, a silicon removal treatment is performed in advance,
The steel making method using two or more converters according to claim 1, wherein the Si content is 0.3 wt% or less. 3. The silicon removal treatment is performed in a blast furnace cast floor and / or in a hot metal ladle.
The steel making method using two or more converters according to claim 2, wherein the Si content is set to 0.3 wt% or less. 4. The desiliconization treatment is characterized by refining the Si content to 0.3 wt% or less in a converter for dephosphorization refining, discharging generated slag, and subsequently performing dephosphorization refining. A steelmaking method using two or more converters according to claim 2. 5. The converter for performing the decarburization refining further comprises charging manganese ore to maximize the manganese (hereinafter referred to as Mn) content of molten steel at the end point, to the Mn standard value required for crude steel. The steelmaking method using two or more converters according to any one of claims 1 to 4, wherein the Mn content is increased within an upper limit. 6. A method for charging the manganese ore, wherein the manganese ore further contains CaO so that silica (SiO ₂ ) contained in the manganese ore has a predetermined basicity (CaO wt% / SiO ₂ wt%). The steelmaking method using two or more converters according to claim 5, wherein a slag material is charged. 7. The converter for performing decarburization refining, wherein a slag solidifying agent is charged prior to charging of the dephosphorized and refined hot metal. Steelmaking method using two or more converters. 8. The steel making method using two or more converters according to claim 1, wherein the slag solidifying agent is light-burned dolomite and / or green dolomite. 9. The two or more converters according to claim 1, wherein the entire amount of scrap is charged into the converter for performing the dephosphorization refining before charging the hot metal. Steelmaking method using 10. The two or more converters according to claim 9, wherein part or all of the scrap is magnetically separated from slag produced by dephosphorization refining and / or decarburization refining. Steelmaking method. 11. The steelmaking method using two or more converters according to claim 1, wherein the decarburization refining is performed within the dephosphorization refining time. 12. The converter according to claim 1, wherein the one and / or the other converters are any of a top-blowing converter, a bottom-blowing converter and a top-bottom-blowing converter. A steelmaking method using two or more converters as described. 13. The method according to claim 1, wherein the steelmaking process is carried out in a series of converter operations at least 80 times.
%, Wherein two or more converters are used.