Method of manufacturing steel

Abstract

A method for manufacturing steel according to one embodiment of the present invention comprises the steps of: preparing a first molten metal manufactured using a first raw material including iron ore and a second molten metal manufactured using a second raw material including iron scrap; mixing the first molten metal and the second molten metal to produce a third molten metal; adjusting the components of the third molten metal to produce a fourth molten metal; and manufacturing a product by processing the fourth molten metal.

Description

Technical Field

[0001] The present invention relates to a method of manufacturing steel. Background Art

[0002] Generally, there are two methods for making steel: the blast furnace-converter method and the electric arc furnace method.

[0003] The blast furnace-converter method includes the steps of charging iron ore and bituminous coal (eg, coke) into a blast furnace and melting them by hot air to produce molten iron, and charging the molten iron produced from the blast furnace into a converter to remove impurities such as carbon to produce molten steel.

[0004] The electric arc furnace method includes a process of melting iron scrap (STEEL SCRAP) in an electric arc furnace (ELECTRIC ARC FURNACE, EAF) to produce molten steel.

[0005] The molten steel produced by the above two methods is manufactured into semi-finished products through a continuous casting process, and the semi-finished products are manufactured into finished products through a subsequent rolling process.

[0006] On the other hand, recently, rapid climate change due to greenhouse gas emissions from various industrial fields has become an international issue.

[0007] Carbon dioxide is a representative greenhouse gas. The steel industry is known to be an industry with a high carbon dioxide emission ratio among many industries.

[0008] For example, the blast furnace-converter process uses carbon monoxide (CO) generated by burning coke (COKES) as a reducing agent, thereby emitting a large amount of carbon dioxide.

[0009] In this regard, currently, major steel companies are making many efforts and conducting research and development to reduce the amount of carbon dioxide emitted during the steelmaking process in accordance with international trends and regulations of various countries. Summary of the invention

[0010] Technical issues

[0011] In order to solve the above-mentioned problems, an object of the present invention is to provide a method for manufacturing steel that can reduce the amount of carbon dioxide emissions generated during the steelmaking process.

[0012] In particular, an object of the present invention is to provide a method for producing steel that can reduce carbon dioxide emissions using existing steelmaking facilities.

[0013] Problems of the present invention are not limited to the problems mentioned above, and those skilled in the art can clearly understand other problems not mentioned from the following description.

[0014] Technical Solution

[0015] A method for manufacturing steel according to an embodiment of the present invention includes: preparing a first molten metal manufactured using a first raw material including iron ore and a second molten metal manufactured using a second raw material including iron scrap; mixing the first molten metal and the second molten metal to manufacture a third molten metal; adjusting the composition of the third molten metal to manufacture a fourth molten metal; and manufacturing a product by processing the fourth molten metal.

[0016] The step of preparing the first molten metal may include: melting the first raw material in a blast furnace to produce the first molten metal; charging the first molten metal into a first transport vehicle; and moving the first transport vehicle.

[0017] The step of preparing the second molten metal may include the steps of melting the second raw material in an electric arc furnace (EAF) to produce the second molten metal; and selectively adding a carburizing agent according to whether the second molten metal has solidified.

[0018] Furthermore, the step of manufacturing the third molten metal includes: the step of charging the first molten metal into a mixing ladle which is open at the top and defines a space inside; and the step of charging the second molten metal into the mixing ladle.

[0019] According to an embodiment of the present invention, before the step of adding the carbonizing agent, the step of preparing the second molten metal may further include the step of filling the second molten metal into a first ladle having an open upper portion and defining a space therein.

[0020] According to an embodiment of the present invention, after the step of adding the carbonizing agent, the step of preparing the second molten metal may further include the step of filling the second molten metal into a first ladle having an open upper portion and defining a space therein.

[0021] According to one embodiment of the present invention, in the step of adding the carbonizer, when the temperature of the second molten metal at the measurement time point is defined as Ta, the solidification temperature of the second molten metal depending on the carbon content is defined as Tf, and the temperature change amount of the second molten metal during the cooling process from the measurement time point to the time point of mixing the first molten metal and the second molten metal is defined as △Tc, if Ta+△Tc≤Tf is satisfied, the carbonizer can be added to the second molten metal.

[0022] According to an embodiment of the present invention, in the step of adding the carbonizing agent, after the carbonizing agent is added, the solidification temperature of the second molten metal may be lower than Ta+ΔTc.

[0023] According to an embodiment of the present invention, the step of preparing the second molten metal may further include the step of adding a deoxidizer to the second molten metal.

[0024] According to an embodiment of the present invention, the third molten metal may include 15-50 weight percent of the second molten metal and the remainder of the first molten metal.

[0025] According to one embodiment of the present invention, the present invention includes: the steps of preparing a first molten metal containing carbon and a second molten metal containing a lower concentration of carbon than the first molten metal; the step of mixing the first molten metal and the second molten metal to produce a third molten metal; the step of adjusting the composition of the third molten metal to produce a fourth molten metal; and the step of manufacturing a product by processing the fourth molten metal.

[0026] The step of preparing the first molten metal may include: charging the first molten metal into a first transport vehicle; and moving the first transport vehicle.

[0027] The step of preparing the second molten metal may include the step of selectively adding a carbonizing agent according to whether the second molten metal has solidified.

[0028] The step of manufacturing the third molten metal may include: the step of charging the first molten metal into a mixing ladle having an open upper portion and defining a space therein; and the step of charging the second molten metal into the mixing ladle.

[0029] According to an embodiment of the present invention, the carbon content of the first molten metal may be greater than 2 wt %, and the carbon content of the second molten metal may be less than 2 wt %.

[0030] According to an embodiment of the present invention, the first molten metal may be produced by melting raw materials including iron ore in a blast furnace, and the second molten metal may be produced by melting raw materials including iron scrap in an electric arc furnace (EAF).

[0031] According to an embodiment of the present invention, before the step of adding the carbonizing agent, the step of preparing the second molten metal may further include the step of filling the second molten metal into a first ladle having an open upper portion and defining a space therein.

[0032] According to an embodiment of the present invention, after the step of adding the carbonizing agent, the step of preparing the second molten metal may further include the step of filling the second molten metal into a first ladle having an open upper portion and defining a space therein.

[0033] According to an embodiment of the present invention, the step of preparing the second molten metal may further include the step of adding a deoxidizer to the second molten metal.

[0034] According to an embodiment of the present invention, the third molten metal may include 15-50 weight percent of the second molten metal and the balance of the first molten metal.

[0035] According to an embodiment of the present invention, the step of adding the carbonizing agent may be adjusted so that at the time of mixing the first molten metal and the second molten metal, the solidification temperature of the second molten metal is lower than the measured temperature of the second molten metal.

[0036] A method for manufacturing steel according to an embodiment of the present invention includes: a step of melting iron ore in a blast furnace to prepare a first molten metal; a step of melting iron scrap in an electric arc furnace to prepare a second molten metal; a step of adding a carburizing agent to the second molten metal; a step of mixing the first molten metal and the second molten metal to produce a third molten metal; a step of adjusting the composition of the third molten metal to produce a fourth molten metal; and a step of manufacturing a product by processing the fourth molten metal.

[0037] The step of preparing the first molten metal may include the steps of: charging the first molten metal into a first transport vehicle; and moving the first transport vehicle.

[0038] The step of manufacturing the third molten metal may include: the step of charging the first molten metal into a mixing ladle having an open upper portion and defining a space therein; and the step of charging the second molten metal into the mixing ladle.

[0039] Beneficial effects

[0040] In a method for manufacturing steel according to one embodiment of the present invention, the carbon dioxide emissions generated during the steelmaking process can be significantly reduced by mixing a second molten metal (i.e., molten steel) from an electric arc furnace whose carbon dioxide emissions are relatively less than that of a first molten metal (i.e., molten iron) produced in a blast furnace with the first molten metal to manufacture steel.

[0041] In the method for manufacturing steel according to an embodiment of the present invention, the second molten metal may be heated or a carbonizing agent may be added to prevent the second molten metal from solidifying before the first molten metal and the second molten metal are mixed.

[0042] In the method for manufacturing steel according to an embodiment of the present invention, a deoxidizer may be added to the second molten metal to prevent explosion or overflow that may occur when the first molten metal and the second molten metal are mixed. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 FIG. 1 is a flow chart showing a method for manufacturing steel according to an embodiment of the present invention.

[0044] Figure 2 To express Figure 1 Flow chart of the steps of preparing the first molten metal and the second molten metal and the step of mixing the first molten metal and the second molten metal shown in .

[0045] Figures 3 to 5 To express Figure 2 The steps of preparing the second molten metal are shown in the figures related to multiple embodiments.

[0046] Figure 6 to Figure 7 To express Figure 2 The steps of preparing the second molten metal are shown in the figures related to multiple embodiments.

[0047] Figures 8 to 10 To express Figure 1 0048] Figures related to various embodiments of the step of mixing the first molten metal and the second molten metal are shown in FIG. DETAILED DESCRIPTION

[0048] All terms (including technical terms and scientific terms) used in this specification have the same meanings as those commonly understood by ordinary technicians in the technical field to which the present invention belongs.

[0049] And, terms such as those defined in commonly used dictionaries should be interpreted as having meanings consistent with the meanings in the context of the relevant technology, unless interpreted as ideal or overly formal meanings, which are clearly defined herein.

[0050] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0051] Figure 1 FIG. 1 is a flow chart showing a method for manufacturing steel according to an embodiment of the present invention. Figure 2 To express Figure 1 Flowchart of the steps of preparing the first molten metal and the second molten metal and the step of mixing the first molten metal and the second molten metal shown in .

[0052] Reference Figure 1 The method for manufacturing steel according to an embodiment of the present invention refers to a process of manufacturing steel products by extracting iron from raw materials such as iron ore, iron scrap, etc.

[0053] The method for manufacturing steel according to an embodiment of the present invention includes a step of preparing a first molten metal and a second molten metal ( S100 ), a step of mixing the first molten metal and the second molten metal ( S200 ), a step of adjusting a component of a third molten metal ( S300 ), and a step of manufacturing a product ( S400 ).

[0054] Reference Figure 2The step S100 of preparing the first molten metal and the second molten metal includes the step S110 of preparing the first molten metal and the step S120 of preparing the second molten metal.

[0055] Specifically, the step S110 of preparing the first molten metal may include the step S111 of manufacturing the first molten metal, the step S112 of charging the first molten metal, and the step S113 of moving the first molten metal.

[0056] For example, the first molten metal may be produced using a first raw material including iron ore.

[0057] Specifically, in step S111 of producing the first molten metal, iron ore and coke are charged into a blast furnace, and then hot air is injected into the blast furnace to reduce and melt the iron ore to produce the first molten metal.

[0058] That is, the first molten metal may be molten iron. The first molten metal may have a carbon content of 2 wt % or more based on the weight of the first molten metal.

[0059] However, the method for producing the first molten metal is not limited to the above. For example, hydrogen can be used as a reducing agent instead of coke, or the first raw material can be charged into the blast furnace in the form of reduced iron (eg, DRI, HBI, etc.).

[0060] In the step S112 of charging the first molten metal, the first molten metal produced in the blast furnace may be moved to a first transport vehicle, which may be a torpedo tank car (TLC).

[0061] However, the first transport vehicle is not limited thereto, and the first transport vehicle may be an open tank truck (OLC, OPEN LADLECAR).

[0062] In the step S113 of moving the first molten metal, the first transport vehicle charged with the first molten metal may be moved to the vicinity of a subsequent converter (CONVERTER) equipment.

[0063] The step S120 of preparing the second molten metal may include a step of manufacturing the second molten metal, a step of processing the second molten metal, and a step of moving the second molten metal.

[0064] In the step of processing the second molten metal, it may be determined whether the second molten metal has solidified, so that the temperature of the second molten metal is increased or a carbonizing agent is added.

[0065] Hereinafter, the step S120 of preparing the second molten metal will be described in more detail.

[0066] In this specification, Ta is defined as the temperature of the second molten metal at a measurement time point. The measurement time point refers to the time point at which the temperature of the second molten metal is first measured in order to determine whether the second molten metal has solidified.

[0067] Tf is defined as the solidification temperature of the second molten metal depending on the carbon content. For example, Tf satisfies the following formula 1.

[0068] [Formula 1: Tf = 1536.6 (°C) - {88X C wt%} (°C)]

[0069] ΔTc is defined as the temperature change of the second molten metal. Specifically, ΔTc refers to the temperature change of the second molten metal according to the time S required from the initial measurement time point to the time point when the first molten metal and the second molten metal are mixed. For example, ΔTc satisfies the following formula 2.

[0070] [Formula 2: △Tc=-1(℃ / min)XS(min)]

[0071] The unit of Ta, Tf and △Tc is °C. △Tc is a negative number.

[0072] Figures 3 to 7 To express Figure 2 The steps of preparing the second molten metal are shown in the figures related to multiple embodiments.

[0073] exist Figures 3 to 5 In the steps S120_A, S120_B, and S120_C of preparing the second molten metal shown in FIG. 1 , the second molten metal may be heated to prevent solidification of the second molten metal.

[0074] Reference Figure 3 The step S120_A of preparing the second molten metal includes the step S121_A of manufacturing the second molten metal, the step S122_A of charging the second molten metal, the step S123_A of confirming whether solidification has occurred, and the step S125_A of moving the second molten metal.

[0075] In the step S121_A of manufacturing the second molten metal, an electric arc furnace (EAF) may be used.

[0076] For example, the second raw material including ore based iron materials (OBM) based on iron ore and iron scrap may be melted in an electric arc furnace to produce molten iron.

[0077] Specifically, the second raw material may include hot briquetted iron (HBI) and iron scrap. For example, based on weight percentage, the second raw material may include 60% HBI and 40% iron scrap. However, this corresponds to an exemplary content ratio, and the present invention is not limited thereto.

[0078] In step S121_A, the second raw material may be put into the electric arc furnace. There may be excess molten metal inside the electric arc furnace. For example, the capacity of the excess molten metal may be about 60-70% of the capacity of the electric arc furnace. Moreover, the melting degree of the excess molten metal may be 70-80%.

[0079] In this embodiment, the excess molten metal in the electric arc furnace can be used to stably melt HBI, and the melting point of the excess molten metal can be adjusted to 70-80%, thereby preventing slag overflow during the HBI charging step.

[0080] When the remaining molten metal existing in the electric arc furnace is less than a preset amount, the remaining molten metal may be adjusted within a preset range by preferentially melting the iron scrap in the second raw material.

[0081] Furthermore, when the melting point of the remaining molten metal in the electric arc furnace is higher than a preset value, iron scrap may be added to the second raw material to adjust the melting point of the remaining molten metal to within a preset range.

[0082] In step S121_A, HBI may be added to the second raw material multiple times, thereby making it possible to melt HBI more stably.

[0083] The second molten metal may be produced by melting the second raw material in the electric arc furnace. That is, the second molten metal may be molten steel. The carbon content of the second molten metal may be 2 wt % or less based on the weight of the second molten metal.

[0084] However, the ore-based iron source included in the second raw material is not limited to HBI, and the ore-based iron source may be DRI or the like.

[0085] In the step S122_A of charging the second molten metal, the second molten metal melted in the electric arc furnace may be charged into the first ladle. The first ladle may be a container with an open top and a defined space inside. The inner space of the first ladle may be provided with a refractory layer.

[0086] In the step S123_A of confirming whether solidification has occurred, the temperature of the second molten metal is measured to determine whether the second molten metal has started to solidify before being mixed with the first molten metal.

[0087] The step S123_A of confirming whether solidification has occurred may be performed by a program of the control device.

[0088] In step S123_A, when Ta+Tc≤ΔTf is satisfied, solidification of the second molten metal may be started before mixing with the first molten metal.

[0089] In this case, step S124_A of heating the second molten metal is performed. Step S124_A may be performed by a ladle furnace (LF) refiner.

[0090] Specifically, in step S124_A, after the first ladle is moved to the LF refiner, the temperature of the second molten metal is raised to a temperature higher than Tf-ΔTc by arc heat of the LF refiner.

[0091] In other words, in step S124_A, the temperature of the second molten metal is increased so that the temperature of the second molten metal is higher than the solidification temperature of the second molten metal at the time point of mixing the first molten metal and the second molten metal.

[0092] In the step S125_A of moving the second molten metal, the first ladle containing the heated second molten metal is moved. For example, the first ladle may be moved to the vicinity of an electric arc furnace facility.

[0093] When Ta+ΔTc>Tf is satisfied, the second molten metal is determined not to solidify before being mixed with the first molten metal, and the step S125_A of moving the second molten metal may be performed without the step S124_A of heating the second molten metal.

[0094] According to an embodiment of the present invention, the step of preparing the second molten metal ( S120_A) may further include the step of adding a deoxidizer to the second molten metal.

[0095] The step of adding the deoxidizer may be performed simultaneously with the step S122_A of charging the second molten metal.

[0096] The deoxidizer can remove oxygen contained in the second molten metal. The deoxidizer can include an element highly reactive with oxygen. For example, the deoxidizer can be an alloy iron including at least one element of silicon, manganese, and aluminum.

[0097] The amount of the deoxidizer added can be determined according to the amount of oxygen in the second molten metal. For example, the amount of the deoxidizer added can be determined by the following formulas 4 to 6 according to the elements contained.

[0098] [Formula 4: Weight of oxygen contained in the second molten metal (kg) × {Al 2 O 3 The molecular weight of aluminum (54) / molecular weight of oxygen (48)]

[0099] [Formula 5: Weight of oxygen contained in the second molten metal (kg) × {SiO 2 Silicon molecular weight (28) / oxygen molecular weight (32)]

[0100] [Formula 6: Weight of oxygen contained in the second molten metal (kg) X {molecular weight of manganese in MnO (55) / molecular weight of oxygen (16)}]

[0101] For the sake of convenience, repeated descriptions of the same structures as those in the above-mentioned embodiment will be omitted in the following description.

[0102] Reference Figure 4 The step S120_B of preparing the second molten metal includes the step S121_B of manufacturing the second molten metal, the step S122_B of confirming whether solidification has occurred, the step S124_B of charging the second molten metal, and the step S125_B of moving the second molten metal.

[0103] In the step S121_B of manufacturing the second molten metal, an electric arc furnace may be used. For example, the second raw material including iron scrap may be melted in the electric arc furnace to manufacture the second molten metal.

[0104] However, the present invention is not limited to the above content. The second raw material may be iron ore or reduced iron (eg, DRI, HBI, etc.).

[0105] In the step of confirming whether solidification has occurred ( S122_B), it is confirmed whether the second molten metal has solidified before the first molten metal and the second molten metal are mixed.

[0106] In this embodiment, the step S122_B of confirming whether solidification has occurred may be performed in a state where the second molten metal exists in the electric arc furnace.

[0107] In step S122_B, when Ta+ΔTc≤Tf is satisfied, step S123_B of raising the temperature of the second molten metal is performed. Step S123_B may be performed by an electric arc furnace.

[0108] Specifically, in step S123_B, the temperature of the second molten metal is increased to a temperature higher than Tf-ΔTc by arc heat of the arc furnace.

[0109] That is, in step S123_B, the temperature of the second molten metal is increased so that the temperature of the second molten metal is higher than the solidification temperature of the second molten metal at the time of mixing the first molten metal and the second molten metal. However, the heating method of the electric arc furnace is not limited to the above.

[0110] In step S122_B, when Ta+ΔTc>Tf is satisfied, step S123_B of raising the temperature of the second molten metal may be omitted.

[0111] After step S122_B (or step S123_B), step S124_B of charging the second molten metal and step S125_B of moving the second molten metal may be performed.

[0112] According to this embodiment, the step of preparing the second molten metal ( S120_B) may further include the step of adding a deoxidizer to the second molten metal. The type and amount of the deoxidizer may be the same as those in the above embodiment ( S120_A).

[0113] Reference Figure 5 The step S120_C of preparing the second molten metal includes the step S121_C of manufacturing the second molten metal, the step S122_C of charging the second molten metal, the step S123_C of confirming whether solidification has occurred, and the step S125_C of moving the second molten metal.

[0114] In the step S121_C of manufacturing the second molten metal, an electric arc furnace may be used. For example, the second raw material including iron scrap may be melted in an electric arc furnace to manufacture the second molten metal. That is, the second molten metal may be molten steel. Based on the weight of the second molten metal, the carbon content of the second molten metal may be less than 2wt%.

[0115] In the step of charging the second molten metal S122_C, the second molten metal melted in the electric arc furnace may be charged into the first ladle.

[0116] In the step of confirming whether solidification has occurred ( S123_C ), it may be confirmed whether the second molten metal has solidified before the first molten metal and the second molten metal are mixed. The step S123_C may be performed in a state where the second molten metal is charged into the first ladle.

[0117] For example, in step S123_C, when Ta+ΔTc≤Tf is satisfied, step S124_C of raising the temperature of the second molten metal is performed. Step S124_C may be performed by an electric arc furnace.

[0118] Specifically, step S124_C may include the steps of moving the first ladle filled with the second molten metal to the arc furnace, charging the second molten metal into the arc furnace, heating the second molten metal, and recharging the heated second molten metal into the first ladle.

[0119] In the step of raising the temperature of the second molten metal, the temperature of the second molten metal is raised to a temperature higher than Tf-ΔTc by using an electric arc furnace. For example, the electric arc furnace can raise the temperature of the second molten metal by using arc heat.

[0120] That is, step S124_C raises the temperature of the second molten metal so that the temperature of the second molten metal is higher than the solidification temperature of the second molten metal at the time of mixing the first molten metal and the second molten metal. However, the heating method of the electric arc furnace is not limited to the above content.

[0121] When Ta+ΔTc>Tf is satisfied, step S124_C can be omitted.

[0122] After step S123_C (or step S124_C), step S125_C of moving the second molten metal may be performed.

[0123] According to this embodiment, the step of preparing the second molten metal ( S120_C) may further include the step of adding a deoxidizer to the second molten metal. The type and amount of the deoxidizer may be the same as those in the above embodiment ( S120_A).

[0124] exist Figure 6 to Figure 7 In the steps S120_D and S120_E of preparing the second molten metal shown in FIG. 1 , a carbonizing agent may be added to the second molten metal in order to prevent the second molten metal from solidifying.

[0125] Reference Figure 6 The step S120_D of preparing the second molten metal includes the step S121_D of manufacturing the second molten metal, the step S122_D of confirming whether solidification has occurred, the step S124_D of charging the second molten metal, and the step S125_D of moving the second molten metal.

[0126] In the step S121_D of manufacturing the second molten metal, an arc furnace may be used. For example, the second raw material including iron scrap may be melted in the arc furnace to manufacture the second molten metal. That is, the second molten metal may be molten steel. Based on the weight of the second molten metal, the carbon content of the second molten metal may be less than 2wt%.

[0127] In the step S122_D of confirming whether solidification has occurred, the temperature of the second molten metal is measured to determine whether the second molten metal has begun to solidify before being mixed with the first molten metal.

[0128] When Ta+ΔTc≤Tf is satisfied, solidification of the second molten metal may start before mixing with the first molten metal.

[0129] In this case, step 123_D of adding a carburizing agent to the second molten metal is performed. Step 123_D adjusts the solidification temperature of the second molten metal after the carburizing agent is added to be lower than Ta+ΔTc.

[0130] That is, in step S123_D, the solidification temperature of the second molten metal is adjusted to be lower than the temperature of the second molten metal immediately before being mixed with the first molten metal.

[0131] After step S122_D (or step S123_D), step S124_D of charging the second molten metal into the first ladle and step S125_D of moving the second molten metal may be performed.

[0132] According to this embodiment, the step of preparing the second molten metal ( S120_D) may further include the step of adding a deoxidizer to the second molten metal. The type and amount of the deoxidizer may be the same as those in the above embodiment ( S120_A).

[0133] Reference Figure 7 The step S120_E of preparing the second molten metal includes the step S121_E of manufacturing the second molten metal, the step S122_E of charging the second molten metal, the step S123_E of confirming whether solidification has occurred, and the step S125_E of moving the second molten metal.

[0134] In the step S121_E of manufacturing the second molten metal, an electric arc furnace may be used. For example, the second raw material including iron scrap may be melted in the electric arc furnace to manufacture the second molten metal. That is, the second molten metal may be molten steel. Based on the weight of the second molten metal, the carbon content of the second molten metal may be less than 2wt%.

[0135] In the step of charging the second molten metal S122_E, the second molten metal produced in the electric arc furnace may be charged into the first ladle.

[0136] In the step S123_E of confirming whether solidification has occurred, the temperature of the second molten metal charged into the first ladle is measured to determine whether the second molten metal has started to solidify before being mixed with the first molten metal.

[0137] When Ta+ΔTc≤Tf is satisfied, solidification of the second molten metal may start before mixing with the first molten metal.

[0138] In this case, step 124_E of adding a carburizing agent to the second molten metal is performed. Step 123_D of adjusting the solidification temperature of the second molten metal after the carburizing agent is added to be lower than Ta+ΔTc.

[0139] That is, in step S124_E, the solidification temperature of the second molten metal is adjusted to be lower than the temperature of the second molten metal immediately before being mixed with the first molten metal.

[0140] After step S123_E (or step S124_E), step S125_E of moving the second molten metal may be performed.

[0141] According to this embodiment, the step of preparing the second molten metal ( S120_E) may further include the step of adding a deoxidizer to the second molten metal. The type and amount of the deoxidizer may be the same as those in the above embodiment ( S120_A).

[0142] Figures 8 to 10 To express Figure 1 0048] Figures related to various embodiments of the step of mixing the first molten metal and the second molten metal are shown in FIG.

[0143] Reference Figure 8 , the step S200_A of mixing the first molten metal and the second molten metal includes the step S210_A of charging the first molten metal into the second ladle and the step S220_A of mixing the second molten metal into the second ladle.

[0144] In step S210_A, the second molten metal charged into the first conveying vehicle is charged into the second ladle. The second ladle may be a container with an open top and a defined space inside. The second ladle may have an inner space larger than the first ladle.

[0145] In step 220_A, the second molten metal charged into the first ladle may be mixed into the second ladle. In this embodiment, the second ladle may be a mixing ladle in which the first molten metal and the second molten metal are mixed.

[0146] Thus, in step S200_A, the third molten metal may be produced by mixing the first molten metal and the second molten metal.

[0147] The third molten metal may include 15-50 wt % of the second molten metal and the balance of the first molten metal based on the weight of the third molten metal.

[0148] When the ratio of the second molten metal is less than 15 wt %, the effect of reducing carbon dioxide may be imperfect due to the high content of molten iron.

[0149] On the contrary, when the ratio of the second molten metal is greater than 50 wt %, the subsequent converter operation may not be smoothly performed due to the shortage of molten iron, which is the main heat source during the converter operation.

[0150] For the sake of convenience, repeated descriptions of the same structures as those in the above-mentioned embodiment will be omitted in the following description.

[0151] Reference Fig. 9 The step S200_B of mixing the first molten metal and the second molten metal includes the step S210_B of charging the first molten metal into the second ladle, the step S220_B of charging the second molten metal into the storage furnace, and the step S230_B of mixing the second molten metal into the second ladle.

[0152] In step S210_B, the second molten metal charged into the first transfer vehicle is charged into the second ladle.

[0153] In step 220_B, the second molten metal charged into the first ladle may be charged into the storage furnace. The storage furnace may have an inner space larger than that of the first ladle. Step S220_B may be performed separately from step S210_B.

[0154] In step S230_B, at least a portion of the second molten metal charged into the storage furnace may be mixed into the second ladle. Thus, in step S200_B, a third molten metal may be produced by mixing the first molten metal and the second molten metal.

[0155] The third molten metal may include 15-50 wt % of the second molten metal and the balance of the first molten metal based on the weight of the third molten metal.

[0156] Reference Fig.10 , the step S200_C of mixing the first molten metal and the second molten metal includes a step S210_C of charging the second molten metal into the first conveying vehicle and a step S220_C of charging the third molten metal into the second ladle.

[0157] In step S210_C, the second molten metal charged into the first ladle is charged into the first transport vehicle, thereby, in the first transport vehicle, the first molten metal and the second molten metal can be mixed to produce a third molten metal.

[0158] That is, different from the above-mentioned embodiments S200_A and 200_B, in this embodiment, the first transport vehicle plays the role of a mixing ladle.

[0159] The third molten metal may include 15-50 wt % of the second molten metal and the balance of the first molten metal based on the weight of the third molten metal.

[0160] In step 220_C, the third molten metal charged into the first transfer vehicle may be charged into the second ladle.

[0161] Re-reference Figure 1 In the step S300 of adjusting the composition of the third molten metal, impurities (eg, silicon, phosphorus, sulfur) in the third molten metal charged into the second ladle may be removed to reduce the carbon content to produce a fourth molten metal.

[0162] To this end, in step S300 , the third molten metal may be subjected to a pretreatment process, a converter process, and a LF process.

[0163] However, the present invention is not limited to the above contents, and a vacuum degassing process, a BAP process, etc. may be performed.

[0164] In the step S400 of manufacturing the product, the fourth molten metal may be used to manufacture a semi-finished product, and the semi-finished product may be used to manufacture a finished product.

[0165] Specifically, in step S400, the fourth molten metal may be manufactured into a semi-finished product through a continuous casting process. For example, the semi-finished product may be a slab or a billet. However, it is not limited thereto, and the semi-finished product may also be a billet.

[0166] Then, the semi-finished product can be manufactured into a finished product through a rolling process. The rolling process can be a hot rolling process or a cold rolling process. The finished product can be a steel plate or a wire.

[0167] In a method for manufacturing steel according to one embodiment of the present invention, the carbon dioxide emissions generated during the steelmaking process can be significantly reduced by mixing a second molten metal (i.e., molten steel) from an electric arc furnace whose carbon dioxide emissions are relatively less than that of a first molten metal (i.e., molten iron) produced in a blast furnace with the first molten metal to manufacture steel.

[0168] The method for manufacturing steel according to an embodiment of the present invention can prevent the problem that the second molten metal solidifies before the first molten metal and the second molten metal are mixed by raising the temperature of the second molten metal or adding a carburizing agent.

[0169] According to the method for manufacturing steel of an embodiment of the present invention, a deoxidizer may be added to the second molten metal to prevent explosion or even overflow that may occur when the first molten metal and the second molten metal are mixed.

[0170] As described above, while observing the preferred embodiments according to the present invention, it is obvious to those skilled in the art that the present invention can be embodied in different specific forms other than the embodiments described above without departing from the spirit or scope thereof.

[0171] For example, in the embodiments of the present invention, it is described that the second molten metal is heated or a carburizer is added to prevent the second molten metal produced in the electric arc furnace from solidifying, but conversely, the first molten metal can also be heated or a carburizer can be added to prevent the first molten metal produced in the blast furnace from solidifying.

[0172] Furthermore, in the above-described embodiment of the present invention, the first molten metal is described as molten iron produced in a blast furnace, but the first molten metal may be produced using an electric arc furnace.

[0173] That is, the above-described embodiments should be regarded as illustrative rather than restrictive, and thus the present invention is not limited to the description but may be modified within the scope of the appended claims and the equivalents thereof.

Claims

1. A method for manufacturing steel, the method comprising: The step of preparing a first molten metal produced using a first raw material including iron ore and a second molten metal produced using a second raw material including iron scrap; a step of mixing the first molten metal and the second molten metal to produce a third molten metal; a step of adjusting the composition of the third molten metal to produce a fourth molten metal; and The step of manufacturing a product by processing the fourth molten metal.

2. The method for manufacturing steel according to claim 1, wherein the step of preparing the second molten metal comprises: The step of melting the second raw material in an electric arc furnace to produce a second molten metal; The step of charging the second molten metal into a first ladle having an open top and defining a space therein; a step of confirming whether the second molten metal has solidified; as well as the step of moving the first ladle, and In the step of confirming whether the second molten metal has solidified, When the temperature of the second molten metal at the measurement time point is defined as Ta, The solidification temperature of the second molten metal depending on the carbon content is defined as Tf, When the temperature change amount of the second molten metal during cooling from the measurement time point to the time point when the first molten metal and the second molten metal are mixed is defined as ΔTc, If Ta+ΔTc≤Tf is satisfied, the temperature of the second molten metal is raised to Tf-ΔTc or higher by the LF refiner.

3. The method for manufacturing steel according to claim 1, wherein the step of preparing the second molten metal comprises: The step of melting the second raw material in an electric arc furnace to produce a second molten metal; a step of confirming whether the second molten metal has solidified; The step of charging the second molten metal into a first ladle which is open at the top and defines a space therein; as well as the step of moving the first ladle, In the step of confirming whether the second molten metal has solidified, When the temperature of the second molten metal at the measurement time point is defined as Ta, The solidification temperature of the second molten metal depending on the carbon content is defined as Tf, When the temperature change amount of the second molten metal during cooling from the measurement time point to the time point when the first molten metal and the second molten metal are mixed is defined as ΔTc, If Ta+ΔTc≤Tf is satisfied, the temperature of the second molten metal is additionally raised in the electric arc furnace to a temperature equal to or higher than Tf-ΔTc.

4. The method for manufacturing steel according to claim 1, wherein the step of preparing the second molten metal comprises: The step of melting the second raw material in an electric arc furnace to produce a second molten metal; a step of adding a deoxidizer to the second molten metal; The step of charging the second molten metal into a first ladle having an open top and defining a space therein; a step of confirming whether the second molten metal has solidified; as well as the step of moving the first ladle, In the step of confirming whether the second molten metal has solidified, When the temperature of the second molten metal at the measurement time point is defined as Ta, The solidification temperature of the second molten metal depending on the carbon content is defined as Tf, When the temperature change amount of the second molten metal during cooling from the measurement time point to the time point when the first molten metal and the second molten metal are mixed is defined as ΔTc, If Ta+ΔTc≤Tf is satisfied, the temperature of the second molten metal is raised to be equal to or higher than Tf-ΔTc.

5. The method for manufacturing steel according to claim 1, wherein the step of preparing the first molten metal comprises: The step of melting the first raw material in a blast furnace to produce a first molten metal; The step of charging the first molten metal into a first transport vehicle; as well as the step of moving the first transport vehicle, The step of preparing the second molten metal comprises: The step of melting the second raw material in an electric arc furnace (EAF) to produce a second molten metal; as well as a step of selectively adding a carbonizing agent according to whether the second molten metal has solidified, The step of producing the third molten metal includes the step of charging the second molten metal into the first transport vehicle.

6. The method for manufacturing steel according to claim 1, wherein the step of preparing the second molten metal includes the step of selectively adding a carburizing agent according to whether the second molten metal has solidified. The step of producing the third molten metal includes the step of charging the second molten metal charged into the storage furnace into a mixing ladle already charged with the first molten metal.

7. The method for manufacturing steel according to claim 1, wherein the step of preparing the first molten metal comprises: The step of melting the first raw material in a blast furnace to produce a first molten metal; The step of charging the first molten metal into a first transport vehicle; as well as the step of moving the first transport vehicle, The step of preparing the second molten metal comprises: a step of melting the second raw material in an electric arc furnace (EAF) to produce a second molten metal; and a step of selectively adding a carbonizing agent according to whether the second molten metal has solidified, The step of producing the third molten metal comprises: The step of filling the first molten metal into a mixing ladle which is open at the top and defines a space inside; and The step of charging the second molten metal into the mixing ladle.

8. A method for manufacturing steel, the method comprising: The step of preparing a first molten metal containing carbon and a second molten metal containing a lower concentration of carbon than the first molten metal; a step of mixing the first molten metal and the second molten metal to produce a third molten metal; a step of adjusting the composition of the third molten metal to produce a fourth molten metal; and The step of manufacturing a product by processing the fourth molten metal.

9. The method for manufacturing steel according to claim 8, wherein the step of preparing the second molten metal comprises: The step of charging the second molten metal into a first ladle having an open top and defining a space therein; The step of increasing the temperature of the second molten metal charged into the first ladle by means of an LF refiner; as well as the step of moving the first ladle, In the step of increasing the temperature, the temperature of the second molten metal is adjusted so that the temperature of the second molten metal is higher than the solidification temperature of the second molten metal at the time of mixing the first molten metal and the second molten metal.

10. The method for manufacturing steel according to claim 8, wherein the step of preparing the second molten metal comprises: The step of further increasing the temperature of the second molten metal in an electric arc furnace; The step of charging the second molten metal into a first ladle having an open top and defining a space therein; as well as the step of moving the first ladle, In the additional temperature raising step, the temperature of the second molten metal is adjusted so that the measured temperature of the second molten metal is higher than the solidification temperature of the second molten metal at the time of mixing the first molten metal and the second molten metal.

11. The method for manufacturing steel according to claim 8, wherein the step of preparing the second molten metal comprises: a step of adding a deoxidizer to the second molten metal; The step of charging the second molten metal into a first ladle having an open top and defining a space therein; a step of increasing the temperature of the second molten metal filled into the first ladle; as well as the step of moving the first ladle, In the step of raising the temperature, the temperature of the second molten metal is adjusted so that the measured temperature of the second molten metal is higher than the solidification temperature of the second molten metal at the time of mixing the first molten metal and the second molten metal.

12. The method for manufacturing steel according to claim 8, wherein the step of preparing the first molten metal comprises: The step of charging the first molten metal into a first transport vehicle; as well as the step of moving the first transport vehicle, The step of preparing the second molten metal includes the step of selectively adding a carbonizing agent according to whether the second molten metal has solidified. The step of producing the third molten metal includes the step of charging the second molten metal into the first transport vehicle.

13. The method for manufacturing steel according to claim 8, wherein the step of preparing the second molten metal includes the step of selectively adding a carburizing agent according to whether the second molten metal has solidified. The step of producing the third molten metal includes the step of charging the second molten metal charged into the storage furnace into a mixing ladle already charged with the first molten metal.

14. The method for manufacturing steel according to claim 8, wherein the step of preparing the first molten metal comprises: The step of charging the first molten metal into a first transport vehicle; as well as the step of moving the first transport vehicle, The step of preparing the second molten metal includes the step of selectively adding a carbonizing agent according to whether the second molten metal has solidified. The step of producing the third molten metal comprises: The step of filling the first molten metal into a mixing ladle which is open at the top and defines a space inside; as well as The step of charging the second molten metal into the mixing ladle.

15. The method for manufacturing steel according to claim 8, wherein the carbon content of the first molten metal is 2 wt% or more, The carbon content of the second molten metal is less than 2 wt %.

16. The method for manufacturing steel according to claim 8, wherein the third molten metal includes 15-50 weight percent of the second molten metal and the balance of the first molten metal.

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