JP2009102697A - Method for producing molten steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing molten steel by which in production of the molten steel using iron-scrap and blast furnace molten iron together, electric power consumption is reduced by efficiently melting the iron-scrap and at the same time, steel coming up to a high-class steel produced by a blast furnace-converter method can be produced by decreasing the concentration of impurities such as Cu mixed from the scraps as much as possible. <P>SOLUTION: The method for producing the molten steel is characterized in that the method is carried out using an arc-furnace provided with a melting chamber and a shaft type preheating chamber which is directly connected with the melting chamber and into which exhaust gas generated in the melting chamber is introduced, and that the blast furnace molten iron is directly charged into the melting chamber and also, while continuously or intermittently charging the iron-scrap into the preheating chamber so as to keep a state where the iron-scrap is present continuously in the preheating chamber and the melting chamber, the iron-scrap and the blast furnace molten iron in the melting chamber are heated with arc and the iron-scrap is melted to tap off the molten metal, then after mixing at least a part of the molten metal with the blast furnace molten iron thereby desulfurizing the molten metal, the molten metal is refined in a converter to obtain the molten steel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing molten steel using iron scrap and blast furnace hot metal as an iron source.

  In an arc furnace for steelmaking, an iron source such as iron scrap is heated and melted with arc heat, and then refined in the furnace to produce molten steel. However, since much electric power is consumed, the arc furnace melts during melting. Many methods have been proposed for preheating iron scrap using high-temperature exhaust gas generated from a room and melting the preheated iron scrap to reduce power consumption.

  A typical example of the invention previously proposed by the present inventors is an arc comprising a melting chamber and a shaft type preheating chamber directly connected to the melting chamber and into which exhaust gas generated in the melting chamber is introduced. Use a furnace to arc the iron scrap in the melting chamber while charging the steel scrap continuously or intermittently into the preheating chamber so that the iron scrap is continuously present in the preheating chamber and the melting chamber. When the iron scrap is melted by heating and melts at least one heat in the melting chamber, the iron scrap is discharged in a state where the iron scrap is continuously present in the preheating chamber and the melting chamber. This is a scrap melting method (see Patent Document 1).

  On the other hand, with the recent production of high-grade steel in an arc furnace, an operation in which hot metal is used as an iron source together with iron scrap to dilute impurities such as Cu, Sn, and Cr mixed from iron scrap is disclosed. Yes.

  For example, the present inventors are an operating method in an arc furnace including a melting chamber and a shaft-type preheating chamber that is directly connected to the melting chamber and into which exhaust gas generated in the melting chamber is introduced, While charging the blast furnace hot metal directly into the melting chamber and continuously charging iron scrap into the preheating chamber continuously or intermittently so that the iron scrap is continuously present in the preheating chamber and the melting chamber, When the iron scrap in the melting room and the blast furnace hot metal are heated with an arc to melt the iron scrap, the iron scrap is continuously present in the preheating chamber and the melting chamber when at least one heat of molten steel has accumulated in the melting chamber. An arc furnace operating method is proposed (see Patent Document 2).

Furthermore, the present inventors use the arcs described in Patent Documents 1 and 2 above as waste car press waste or waste home appliance waste obtained without performing shredder processing from a used automobile or used home appliance containing a large amount of Cu. It is melted in the same arc melting furnace as the furnace to produce hot metal. After a predetermined amount of hot metal is produced in the melting chamber, the hot water is poured out, and then mixed (diluted) with the blast furnace hot metal and then refined in the converter to obtain molten steel Has been proposed (see Patent Document 3).
JP-A-10-292990 JP 2000-17319 A JP 2002-173716 A

  By the technique described in Patent Document 2 above, the scrap is preheated and efficiently arc-melted, and at the same time, by mixing and using about 50% of blast furnace hot metal, the concentration of impurities such as Cu and Sn mixed from iron scrap can be reduced. Although it can be diluted, it is still far from the impurity concentration of steel produced by the blast furnace-converter method and cannot be applied to high-grade steel grades such as thin plates. For example, molten steel having a Cu concentration of about 0.2 mass% can be produced, but it is difficult to make it 0.05 mass% or less. This is because the Cu concentration in the blast furnace hot metal is about 0.01 to 0.02 mass%, but the Cu concentration in the scrap is about 0.4 mass%, the mixing ratio of scrap and hot metal is 1: 1, and the Cu concentration is It is because it becomes about 0.2 mass%.

  On the other hand, it is possible to dilute the scrap by melting the scrap by the technique described in Patent Document 3, manufacturing the hot metal in an electric furnace, and mixing it with the blast furnace hot metal (for example, the blast furnace hot metal 4 relative to the electric furnace hot metal 1). If it mixes in the ratio, it will become 0.05 mass% Cu density | concentration). However, in order to produce a hot metal having a C concentration of about 4 mass%, a steel composition scrap having a carbon (C) concentration of 0.1 to 0.5 mass% is melted while adding a carbonaceous material such as coke in an electric furnace. The method in which the coke lump is put into the molten metal and carburized in the molten metal takes a very long time, and is impossible within the normal melting time (approximately 40 minutes to 1 hour) of the molten steel for one heat. In addition, there is a method in which fine coke powder having a particle size of 1 to 2 mm or less is blown into the molten metal for the purpose of speeding carburization, but this method has a problem that the coke powder does not stay in the molten metal and is scattered. It is. In addition, said "the amount of molten steel for 1 heat" is the amount of molten steel accommodated in one container of molten steel holding | maintenance conveyance containers, such as a ladle.

  The present invention has been made in view of such circumstances. The purpose of the present invention is to efficiently melt iron scrap and reduce the amount of power used when manufacturing molten steel using iron scrap and blast furnace hot metal in combination. It is an object of the present invention to provide a method for producing molten steel, which can reduce the concentration of impurities such as Cu mixed from scraps as much as possible and can produce steel comparable to high-grade steel produced by a blast furnace-converter method.

The features of the present invention for solving such problems are as follows.
According to a first aspect of the present invention, there is provided a molten steel manufacturing method using an arc furnace including a melting chamber and a shaft-type preheating chamber directly connected to the melting chamber and into which exhaust gas generated in the melting chamber is introduced. In addition to charging directly into the chamber, the iron in the melting chamber is charged while continuously or intermittently charging the iron scrap into the preheating chamber so that the iron scrap is continuously present in the preheating chamber and the melting chamber. Scrap and blast furnace hot metal are heated with an arc to melt iron scrap to discharge molten metal. Next, at least a portion of this molten metal is mixed with blast furnace hot metal and desulfurized, and then refined in a converter to produce molten steel. A method for producing molten steel, comprising: obtaining a molten steel.
The method for producing molten steel according to the second invention is characterized in that, in the first invention, oxygen is blown into the melting chamber.
The method for producing molten steel according to the third invention is characterized in that, in the second invention, carbonaceous material is blown into the melting chamber as an auxiliary heat source.
The method for producing molten steel according to the fourth invention is characterized in that, when carrying out the third invention, the carbon concentration of the molten metal discharged from the arc furnace is set to 2 mass% or more.

  In the above invention, it is preferable that the molten metal is discharged from the arc furnace in a state where iron scrap is continuously present in the preheating chamber and the melting chamber.

  In the present invention, the blast furnace hot metal is used by directly charging it into the melting chamber of the arc furnace. Therefore, the iron scrap is heated by the latent heat and sensible heat of the hot metal, and the iron scrap can be quickly melted with a small amount of power consumption. Also, since the blast furnace hot metal contains about 4 mass% of carbon, oxygen is blown into the melting chamber and the carbon in the hot metal is burned with oxygen, so that the combustion heat of carbon becomes a substitute for electric power energy and at the same time the generated high temperature Since the CO gas preheats the iron scrap in the shaft, the reduction of the power consumption and the speed of melting are further promoted. Further, the carbon material is blown into the melting chamber, and the carbon material is burned with oxygen, so that the carbon material exhibits the same effect as the carbon in the hot metal and contributes to the reduction of the electric power consumption. At the same time, the amount of C in the hot metal is prevented from decreasing. Further, when the molten metal discharged from the arc furnace is melted by introducing, for example, 50 mass% of blast furnace hot metal, it becomes approximately 0.2 mass% of Cu molten iron. 01 to 0.02 mass%) and a ratio of about 1: 4, a hot metal having a Cu concentration of 0.05 mass% or less can be obtained and can be applied to a steel type for a thin plate. In addition, since the desulfurization step is performed before refining in the converter, S mixed from the carbon material when the carbon material is blown in an auxiliary manner can be reduced.

  Although it seems possible to increase the proportion of the blast furnace hot metal charged in the arc furnace so that the Cu concentration of the molten metal discharged from the arc furnace is reduced from the beginning (for example, scrap 1 in the arc furnace). : Melting at the ratio of blast furnace hot metal 9), such an operation significantly reduces the scrap processing efficiency.

  Further, by maintaining the C concentration of the molten metal discharged from the arc furnace at 2 mass% or more, the problem of dust generation when mixed with the blast furnace molten iron is eliminated. When the C concentration is less than 2 mass% (for example, C concentration of 1.0 mass% or less), when mixed with blast furnace molten iron, C—O reaction occurs due to the reaction between C in the blast furnace molten iron and oxygen in the molten metal from the arc furnace. This will generate dust and cause environmental problems. Therefore, it is preferable that the C concentration of the molten metal discharged from the arc furnace is 2 mass% or more.

In order to set the C concentration of the molten metal discharged from the arc furnace to 2 mass% or more, the amount of the carbon material and oxygen blown into the arc furnace needs to be 1 kg or more of carbon material (as C content) with respect to 1 Nm ³ of oxygen. Thereby, even if oxygen is blown in, reduction of C in the blast furnace hot metal can be prevented, and when the scrap and the blast furnace hot metal are mixed at a ratio of 1: 1, C% of the molten metal finally obtained is about 2 mass% or more. be able to.

  In addition, "the molten steel for 1 heat" used by this invention is the amount of molten steel accommodated in one container of molten steel holding | maintenance conveyance containers, such as a ladle used for casting operations, such as continuous casting. The amount is determined from the lifting load of the crane of the building to be implemented. Moreover, the blast furnace hot metal used in the present invention refers to one manufactured in a blast furnace or a smelting reduction furnace.

  ADVANTAGE OF THE INVENTION According to this invention, when manufacturing molten steel using iron scrap and blast furnace hot metal together, iron scrap can be melt | dissolved efficiently and the amount of electric power used can be reduced, and the impurity concentration of molten steel can be lowered | hung.

  This makes it possible to produce steel that is equivalent to high-grade steel produced by blast furnace-converter using iron scrap.

  The present invention will be described with reference to the drawings. 1 and 2 show an embodiment of an arc furnace used for carrying out the present invention. 1 and 2 are schematic longitudinal sectional views of an arc furnace facility, FIG. 1 is a view showing a state in the middle of melting, and FIG. 2 is a view showing a state in which hot metal is charged into a melting chamber. FIG. 3 is an explanatory view of an embodiment of the present invention using the arc furnace shown in FIGS.

  1 and 2, an arc furnace 1 includes a melting chamber 2 and a preheating chamber 3, the inside of which is constructed of a refractory, and a shaft type is provided at the top of the melting chamber 2 having a furnace bottom electrode 6 at the bottom. The preheating chamber 3 and the water-cooled furnace wall 4 are disposed, and the upper opening of the furnace wall 4 not covered with the pre-heating chamber 3 is covered with a water-cooling furnace lid 5 that can be freely opened and closed. An upper electrode 7 made of graphite that can move up and down into the melting chamber 2 through the furnace lid 5 is provided, and the base of the DC arc furnace 1 is configured. The furnace bottom electrode 6 and the upper electrode 7 are connected to a DC power source (not shown), and an arc 19 is generated between the furnace bottom electrode 6 and the upper electrode 7.

  Above the preheating chamber 3, a bottom-opening type supply bucket 13 suspended from the traveling carriage 24 is provided, and an openable / closable supply port 20 provided at the upper portion of the preheating chamber 3 is provided from the supply bucket 13. Then, the iron scrap 15 is charged into the preheating chamber 3. The duct 21 provided at the upper end of the preheating chamber 3 is connected to a dust collector (not shown), and the high-temperature exhaust gas generated in the melting chamber 2 is sucked through the preheating chamber 3 and the duct 21 in this order, and the preheating chamber. The iron scrap 15 in 3 is preheated. Then, the preheated iron scrap 15 freely falls into the melting chamber 2 in accordance with the amount of the iron scrap 15 to be melted in the melting chamber 2 and is charged into the melting chamber 2.

  An oxygen blowing lance 8 and a carbonaceous material blowing lance 9 that pass through the furnace lid 5 and can move up and down in the melting chamber 2 are provided, and oxygen is blown into the melting chamber 2 from the oxygen blowing lance 8, and the carbonaceous material. From the blowing lance 9, carbon materials such as coke, char, coal, charcoal, and graphite are blown into the melting chamber 2 using air, nitrogen, or the like as a carrier gas. Also, on the opposite side of the melting chamber 2 from the part where the preheating chamber 3 is installed, there is a steel outlet 11 in which the outlet side is pressed against the furnace bottom by a door 22 and filled with packed sand or mud agent. The side wall is provided with an outlet 12 that is pressed on the outlet side by a door 23 and filled with stuffed sand or mud agent. A burner 10 is attached to the furnace cover 5 at a position corresponding to the upper part of the steel outlet 11. The burner 10 burns fossil fuels such as heavy oil, kerosene, pulverized coal, propane gas, and natural gas in the melting chamber 2 by air or oxygen or oxygen-enriched air. The burner 10 can be attached as needed.

  A crane (not shown) is installed above the melting chamber 2, and the upper electrode 7, the oxygen blowing lance 8, the carbonaceous material blowing lance 9, and the furnace lid 5 from which the burner 10 has been removed in advance are opened, The molten iron 16 is charged into the melting chamber 2 from the supply ladle 14a conveyed by the crane.

  In operation in the DC arc furnace 1, first, iron scrap 15 is charged into the preheating chamber 3 from the supply bucket 13. The iron scrap 15 charged into the preheating chamber 3 is also charged into the melting chamber 2 and eventually fills the preheating chamber 3. Next, as shown in FIG. 2, the supply ladle 14 a that opens the furnace lid 5 and accommodates the blast furnace molten iron 16 is conveyed directly above the melting chamber 2 by a crane, and is supplied from the supply ladle 14 a to the melting chamber 2. The hot metal 16 is charged into After the completion of charging, the furnace lid 5 is closed and the upper electrode 7 is lowered into the melting chamber 2. Further, flux such as quicklime and fluorite is charged into the melting chamber 2 from a supply port (not shown) provided in the furnace wall 4. In order to uniformly charge the iron scrap 15 into the melting chamber 2, the iron scrap 15 can be charged into the melting chamber 2 on the side opposite to the preheating chamber 3 with the furnace lid 5 opened.

  Next, while feeding a direct current between the furnace bottom electrode 6 and the upper electrode 7, the upper electrode 7 is moved up and down, or between the blast furnace hot metal 16 and the upper electrode 7, or the charged iron scrap 15 and the upper electrode. 7 is generated, and the iron scrap 15 is melted by arc heat. At the same time, the flux is melted to produce molten slag 18. The molten slag 18 keeps the generated molten metal 17 warm. If the amount of the molten slag 18 is too large, it can be discharged from the spout 12 during operation.

  When the oxygen blowing lance 8 and the carbonaceous material blowing lance 9 can be inserted into the melting chamber 2 after energization, the oxygen and carbonaceous material are supplied from the oxygen blowing lance 8 and the carbonaceous material blowing lance 9 as shown in FIG. Is preferably blown into the molten iron 16 or molten slag 18 in the melting chamber 2.

The carbon in the hot metal 16 reacts with oxygen to be decarburized, and the reaction product CO gas forms the molten slag 18 and the arc 19 is wrapped in the molten slag 18, so that the heat receiving efficiency of the arc 19 is increased. Further, the high-temperature CO gas generated in large quantities and the CO ₂ gas generated by combustion of this CO gas efficiently preheats the iron scrap 15 in the preheating chamber 3. Oxygen blowing amount per tonne 15 Nm ³ of the molten metal 17 to be retained in the melting chamber 2 between the dissolution start to tapping (hereinafter referred to as "Nm ³ / t".) Is preferably not less than.

  The carbonaceous material blown into the melting chamber 2 and dissolved in the molten metal 17 or suspended in the molten slag 18 reacts with oxygen to generate combustion heat and acts as an auxiliary heat source to reduce the amount of power used. At the same time, as with the carbon originally present in the hot metal 16, the heat deposition efficiency of the arc 19 is increased and the preheating efficiency of the iron scrap 15 is improved. The amount of carbon material blown is determined according to the amount of oxygen blown. That is, it is preferable to blow in a carbon material in which the carbon amount of the carbon material to be blown is equal to or more than the chemical equivalent of the blown oxygen. If the amount of carbon material to be blown is small and the amount of blown oxygen is small, for example, when the ratio of the blast furnace hot metal and scrap is 1: 1, the final C concentration of the molten metal 17 becomes 2 mass% or less, which is not preferable.

  Further, as the iron scrap 15 in the melting chamber 2 is melted, the iron scrap 15 in the preheating chamber 3 falls free in the melting chamber 2 in accordance with the amount melted in the melting chamber 2 and decreases. In order to compensate for the decrease, iron scrap 15 is charged into the preheating chamber 3 from the supply bucket 13. The charging of the iron scrap 15 into the preheating chamber 3 is performed continuously or intermittently so that the iron scrap 15 is continuously present in the preheating chamber 3 and the melting chamber 2. At that time, it is preferable that the amount of the iron scrap 15 continuously present in the preheating chamber 3 and the melting chamber 2 is 50 mass% or more of the iron scrap 15 of a single hot water discharge amount.

  In this way, the iron scrap 15 and the molten iron 16 are heated to melt the iron scrap 15, and the molten metal 17 is stored in the melting chamber 2, and the carbon concentration of the molten metal 17 is measured. The carbon concentration of the molten metal 17 is adjusted to 2% or more by adjusting the carbon material blowing amount. Next, the melting chamber 2 is tilted by a tilting device (not shown), and the molten metal 17 is discharged from the hot water outlet 11 to the molten metal holding conveyance container 30 (FIG. 3). In this case, since the iron scrap 15 is buried and coexists in the molten metal 17, the molten metal temperature is about 1400 ° C., and a high degree of molten metal superheat cannot be obtained. Therefore, it is preferable to heat the molten metal 17 with the burner 10 at the time of hot water discharge in order to prevent troubles associated with a decrease in the molten metal temperature such as blockage of the hot water outlet 11.

  After the hot water, as shown in FIG. 3, in the pan 31 containing the blast furnace molten iron, the molten metal from the arc furnace is mixed with the blast furnace molten iron so as to be about 1: 4 (arc furnace molten metal 1: blast furnace molten iron 4). After the desulfurization step of desulfurizing the molten metal in the pan 31, the decarburization process is performed in the converter 32 to obtain molten steel.

  On the other hand, the arc furnace 1 discharges the molten metal 17 and discharges the molten slag 18. Then, the melting chamber 2 is returned to the horizontal position by a tilting device, and stuffed sand or mud material is placed in the outlet 11 and the outlet 12. Then, the blast furnace hot metal 16 is charged again into the melting chamber 2 and the operation is continued. The next heating (heat) can start melting with the preheated iron scrap 15.

  In this way, by heating and melting the iron scrap 15 and the blast furnace hot metal 16, the iron scrap 15 is heated by the latent heat and sensible heat of the hot metal 16, and melted in the first heat of operation. The iron scrap 15 is not preheated, but all the iron scrap 15 melted by the subsequent heat is preheated and can be operated with extremely high preheating efficiency, thereby improving productivity and reducing power consumption. It becomes possible. Moreover, since the molten metal after the discharge from the arc furnace is further mixed with the blast furnace hot metal, even if the Cu concentration in the scrap is high, it is also used for producing high-grade steel having a Cu concentration of 0.05 mass% or less due to the dilution effect of the blast furnace hot metal. be able to. At this time, by maintaining the C concentration of the molten metal discharged from the arc furnace at 2 mass% or more, the problem of dust generation when mixing the molten metal discharged from the arc furnace and the blast furnace molten iron can be avoided.

  In the above description, the blast furnace hot metal 16 is charged into the melting chamber 2 before the start of melting. However, the charging time of the blast furnace hot metal 16 into the melting chamber 2 is not limited to the above, and it is in the middle of melting. May be. Further, the method for charging the molten iron 16 is not limited to the above, and a rod that penetrates the furnace wall 4 may be provided and charged from the rod. If it is charged with firewood, it is not necessary to open and close the furnace lid 5, and further improvement in productivity and reduction in power consumption are achieved. In the above description, the case where the arc furnace 1 is a direct current type has been described. However, the present invention can be applied without any problem even when an alternating current type arc furnace is used.

An embodiment of the present invention using the DC arc furnace shown in FIG. 1 will be described below. In the arc furnace, the melting chamber has a furnace diameter of 7.2 m, a height of 4 m, the preheating chamber has a width of 3 m, a length of 5 m, a height of 7 m, and a furnace capacity of 180 tons. First, about 70 tons of normal-temperature iron scrap is charged into the preheating chamber, and then about 70 tons of hot metal (carbon concentration: 4.5 mass%) and 30 tons of normal-temperature iron scrap are charged into the melting chamber. Then, using a graphite upper electrode having a diameter of 30 inches, melting was started with a maximum power supply capacity of 750 V and 130 KA. Immediately after energization, quick lime and fluorite were added, and oxygen was blown into the melting chamber at 1800 Nm ³ / hr from an oxygen blowing lance and coke at 36 kg / min from a charcoal blowing lance. Quicklime and fluorite were heated to form molten slag, and by blowing oxygen and coke, the molten slag formed and the tip of the upper electrode was buried in the molten slag. The voltage at this time was set to 550V. For scrap melting, the oxygen blowing rate was 15 Nm ³ / t, the coke blowing rate was 18 kg / t, and the power consumption was 130 kWh / t.

  Then, when the iron scrap in the preheating chamber descends as it melts, the iron scrap is charged into the preheating chamber with the supply bucket, and continues to melt while maintaining the iron scrap height in the preheating chamber at a constant height, and When 140 tons or more of molten metal was generated in the melting chamber, 140 tons of molten metal was discharged into a ladle. The molten metal was heated with a heavy oil burner when the hot water was discharged. The carbon concentration of the molten metal at the time of tapping was 2.3 mass%, and the molten metal temperature was 1420 ° C. The Cu concentration was 0.18 mass%. After pouring, 70 tons of blast furnace hot metal was charged again into the melting chamber, and then oxygen and coke blowing was resumed. When the amount of molten metal reached 140 tons or more, 140 tons of hot water was repeatedly discharged.

  On the other hand, about 70 tons of half of the molten metal (carbon concentration is 2.3 mass%, Cu concentration is 0.18 mass%) is mixed with 230 tons of blast furnace hot metal and desulfurized to a total of 300 tons. After decarburizing and raising the temperature to 1620 ° C., the molten steel was removed and cast by a continuous casting machine. The steel at this time had a Cu concentration of 0.5 mass%. About 70 tons of the other half of the molten metal discharged from the arc furnace to the ladle was similarly processed and cast.

It is one Embodiment of the arc furnace used for implementation of this invention, and is a longitudinal cross-sectional schematic diagram of an arc furnace equipment. It is one Embodiment of the arc furnace used for implementation of this invention, and is a longitudinal cross-sectional schematic diagram of an arc furnace equipment. Explanatory drawing of one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Arc furnace 2 Melting chamber 3 Preheating chamber 4 Furnace wall 5 Furnace lid 6 Furnace bottom electrode 7 Upper electrode 8 Oxygen blowing lance 9 Carbon material blowing lance 10 Burner 11 Steel outlet 12 Steel outlet 13 Supply bucket 14a, b Supply Ladle 15 Iron scrap 16 Hot metal 17 Molten metal 18 Molten slag 19 Arc 20 Supply port 21 Duct 22 Door 23 Door 24 Traveling carriage 30 Molten metal holding and conveying container 31 Pot 32 Converter

Claims (4)

  Using an arc furnace equipped with a melting chamber and a shaft type preheating chamber that is directly connected to the melting chamber and into which exhaust gas generated in the melting chamber is introduced, the blast furnace hot metal is directly charged into the melting chamber, Heat the iron scrap and blast furnace hot metal in the melting chamber with an arc while continuously or intermittently charging the steel scrap into the preheating chamber so that the preheating chamber and the melting chamber are continuously present. A method for producing molten steel, comprising melting iron scrap and discharging molten metal, then mixing and desulfurizing at least part of the molten metal with blast furnace hot metal, and then refining in a converter to obtain molten steel.   The method for producing molten steel according to claim 1, wherein oxygen is blown into the melting chamber.   The method for producing molten steel according to claim 2, wherein carbonaceous material is blown into the melting chamber as an auxiliary heat source.   The method for producing molten steel according to claim 3, wherein the carbon concentration of the molten metal discharged from the arc furnace is 2 mass% or more.

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