How to make steel

Abstract

A method for producing steel according to an embodiment of the present invention includes the steps of preparing a first molten metal prepared using a first raw material including iron ore and a second molten metal prepared using a second raw material including iron scrap, mixing the first molten metal with the second molten metal to prepare a third molten metal, adjusting the composition of the third molten metal to prepare a fourth molten metal, and processing the fourth molten metal to produce a product.

Description

[Technical Field]

[0001] The present application relates to a method for producing steel. [Background technology]

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

[0003] The blast furnace-converter process includes a process of producing molten iron by charging iron ore and bituminous coal (e.g., coke) into a blast furnace and melting them with hot air, and a process of producing molten steel by charging the molten iron tapped from the blast furnace into a converter and removing impurities such as carbon.

[0004] The electric arc furnace process includes a process of melting steel scrap in an electric arc furnace (EAF) to produce molten steel.

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

[0006] Meanwhile, rapid climate change caused by greenhouse gas emissions from various industrial sectors has recently become a hot topic internationally.

[0007] Carbon dioxide is a major greenhouse gas, and the steel industry is known to have one of the highest carbon dioxide emissions among various industrial sectors.

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

[0009] Therefore, major steel companies are currently making great efforts and conducting research and development to reduce the amount of carbon dioxide emitted from the steelmaking process in accordance with international trends and national regulations. Summary of the Invention [Problem to be solved by the invention]

[0010] In order to solve the above-mentioned problems, an object of the present invention is to provide a method for producing steel that can reduce the amount of carbon dioxide emitted from the steelmaking process.

[0011] In particular, an object of the present invention is to provide a method for producing steel that can utilize existing steelmaking facilities and reduce carbon dioxide emissions.

[0012] The objects of the present invention are not limited to those mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0013] A method for producing steel according to an embodiment of the present invention includes the steps of preparing a first molten metal prepared using a first raw material including iron ore and a second molten metal prepared using a second raw material including iron scrap, mixing the first molten metal with the second molten metal to prepare a third molten metal, adjusting the composition of the third molten metal to prepare a fourth molten metal, and processing the fourth molten metal to produce a product.

[0014] Here, the step of preparing the first molten metal includes the steps of melting the first raw material in a blast furnace to produce the first molten metal, receiving the first molten metal in a first transport vehicle, and moving the first transport vehicle.

[0015] The step of preparing the second molten metal includes the steps of melting the second raw material in an electric furnace (EAF) to prepare the second molten metal, and selectively adding a recarburizer depending on whether the second molten metal has solidified.

[0016] In addition, the step of producing the third molten metal includes the steps of receiving the first molten metal in a ladle having an open top and a defined space therein, and charging the second molten metal into the ladle.

[0017] According to an embodiment of the present invention, the step of preparing the second molten metal may further include the step of receiving the second molten metal in a first ladle having an open top and a defined space therein before the step of adding the recarburizer.

[0018] According to an embodiment of the present invention, the step of preparing the second molten metal may further include, after the step of adding the recarburizer, receiving the second molten metal in a first ladle having an open top and a defined space therein.

[0019] According to one embodiment of the present invention, the step of adding a recarburizer may include adding a recarburizer to the second molten metal if Ta+ΔTc≦Tf is satisfied, where Ta is the temperature of the second molten metal at the time of measurement, Tf is the solidification temperature of the second molten metal depending on the carbon content, and ΔTc is the temperature change caused by cooling the second molten metal from the time of measurement to the time of mixing the first molten metal and the second molten metal.

[0020] According to an embodiment of the present invention, in the adding of the recarburizer, a solidification temperature of the second molten metal after the addition of the recarburizer may be equal to or lower than Ta+ΔTc.

[0021] According to an embodiment of the present invention, the step of preparing the second molten metal may further include adding a deoxidizer to the second molten metal.

[0022] According to an embodiment of the present invention, the third molten metal may be 15 to 50 wt % of the second molten metal and the remainder may be the first molten metal.

[0023] According to one embodiment of the present invention, the method includes the steps of preparing a first molten metal containing carbon and a second molten metal containing a carbon concentration lower than that of the first molten metal, mixing the first molten metal with the second molten metal to prepare a third molten metal, adjusting the composition of the third molten metal to prepare a fourth molten metal, and processing the fourth molten metal to manufacture a product.

[0024] Here, the step of preparing the first molten metal includes the steps of receiving the first molten metal in a first transport vehicle and moving the first transport vehicle.

[0025] The step of preparing the second molten metal includes selectively adding a recarburizer depending on whether the second molten metal is solidified or not.

[0026] The step of producing the third molten metal includes the steps of receiving the first molten metal in a ladle having an open top and a defined space therein, and charging the second molten metal into the ladle.

[0027] According to one embodiment of the present invention, the carbon content of the first molten metal may be 2 wt% or more, and the carbon content of the second molten metal may be 2 wt% or less.

[0028] According to one 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).

[0029] According to an embodiment of the present invention, the step of preparing the second molten metal may further include the step of receiving the second molten metal in a first ladle having an open top and a defined space therein before the step of adding the recarburizer.

[0030] According to an embodiment of the present invention, the step of preparing the second molten metal may further include, after the step of adding the recarburizer, receiving the second molten metal in a first ladle having an open top and a defined space therein.

[0031] According to an embodiment of the present invention, the step of preparing the second molten metal may further include adding a deoxidizer to the second molten metal.

[0032] According to an embodiment of the present invention, the third molten metal may be 15 to 50 wt % of the second molten metal and the remainder may be the first molten metal.

[0033] According to an embodiment of the present invention, the step of adding the recarburizer may be adjusted so that the solidification temperature of the second molten metal is lower than the measured temperature of the second molten metal at the time of mixing the first molten metal and the second molten metal.

[0034] A method for producing steel according to an embodiment of the present invention includes the steps of melting iron ore in a blast furnace to prepare a first molten metal, melting iron scrap in an electric furnace to prepare a second molten metal, adding a recarburizer to the second molten metal, mixing the first molten metal with the second molten metal to prepare a third molten metal, adjusting the composition of the third molten metal to prepare a fourth molten metal, and processing the fourth molten metal to produce a product.

[0035] The step of preparing the first molten metal includes the steps of receiving the first molten metal in a first transport vehicle and moving the first transport vehicle.

[0036] The step of producing the third molten metal includes the steps of receiving the first molten metal in a ladle having an open top and a defined space therein, and charging the second molten metal into the ladle. [Effects of the Invention]

[0037] A method for producing steel according to an embodiment of the present invention can significantly reduce carbon dioxide emissions generated during the steelmaking process by combining a second molten metal (i.e., molten steel) produced in an electric furnace, which emits relatively less carbon dioxide than a first molten metal (i.e., molten pig iron) produced in a blast furnace, with the first molten metal to produce steel.

[0038] In a method for producing steel according to an embodiment of the present invention, the problem of the second molten metal solidifying before the first and second molten metals are combined can be prevented by increasing the temperature of the second molten metal or adding a recarburizer.

[0039] In the method for manufacturing steel according to an embodiment of the present invention, a deoxidizer is added to the second molten metal, thereby preventing explosion or overflow that may occur when the first molten metal and the second molten metal are combined. [Brief explanation of the drawings]

[0040] [Figure 1] FIG. 1 is a flow chart illustrating a method of producing steel according to one embodiment of the present invention. [Figure 2] FIG. 2 is a flowchart showing the steps of preparing the first and second molten metals and mixing the first and second molten metals shown in FIG. [Figure 3] 3A to 3C are diagrams showing various embodiments of the step of preparing the second molten metal shown in FIG. [Figure 4] FIG. 4 shows various embodiments of the step of preparing the second molten metal shown in FIG. [Figure 5] 5A to 5C are diagrams showing various embodiments of the step of preparing the second molten metal shown in FIG. [Figure 6] 6A to 6C are diagrams showing various embodiments of the step of preparing the second molten metal shown in FIG. [Figure 7] FIG. 7 shows various embodiments of the step of preparing the second molten metal shown in FIG. [Figure 8] FIG. 8 shows various examples of the step of mixing the first and second molten metals shown in FIG. [Figure 9] FIG. 9 shows various examples of the step of mixing the first and second molten metals shown in FIG. [Figure 10] FIG. 10 shows various examples of the step of mixing the first and second molten metals shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0041] All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0042] Furthermore, terms such as those defined in commonly used dictionaries should be construed to have a meaning consistent with their meaning in the context of the relevant art, and are not to be construed in an idealized or overly formal sense unless expressly defined herein.

[0043] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0044] Fig. 1 is a flowchart showing a method for producing steel according to an embodiment of the present invention, and Fig. 2 is a flowchart showing the steps of preparing a first molten metal and a second molten metal and mixing the first molten metal and the second molten metal shown in Fig. 1.

[0045] Referring to FIG. 1, a method for producing steel according to an embodiment of the present invention refers to a process for extracting iron from raw materials such as iron ore, steel scrap, etc. to produce steel products.

[0046] A method for manufacturing steel according to an embodiment of the present invention includes a step S100 of preparing a first molten metal and a second molten metal, a step S200 of mixing the first molten metal and the second molten metal, a step S300 of adjusting the composition of the third molten metal, and a step S400 of manufacturing a product.

[0047] Referring to FIG. 2, the step S100 of preparing the first and second molten metals includes a step S110 of preparing the first molten metal and a step S120 of preparing the second molten metal.

[0048] Specifically, the step S110 of preparing the first molten metal may include a step S111 of producing the first molten metal, a step S112 of receiving the first molten metal, and a step S113 of transferring the first molten metal.

[0049] For example, the first molten metal may be produced using a first raw material that includes iron ore.

[0050] Specifically, in step S111 of producing the first molten metal, iron ore and cokes are charged into a blast furnace, and then hot air is injected into the blast furnace to reduce and melt the iron ore, thereby producing the first molten metal.

[0051] That is, the first molten metal may be molten pig iron. The carbon content of the first molten metal may be 2 wt % or more based on the weight of the first molten metal.

[0052] However, the method for producing the first molten metal is not limited to the above-described method. For example, it is also possible to use hydrogen gas as a reducing agent instead of coke, or to charge the first raw material into the blast furnace in the form of reduced iron (e.g., DRI, HBI, etc.).

[0053] In the step of receiving the first molten metal (S112), the first molten metal produced in the blast furnace may be transferred to a first transport vehicle. The first transport vehicle may be a TLC (TORPEDO LADLE CAR).

[0054] However, the first transport vehicle is not limited to this, and the first transport vehicle may be an OLC (Open Ladder Car).

[0055] In step S113 of transferring the first molten metal, the first transport vehicle receiving the first molten metal may be moved to the vicinity of the following converter facility.

[0056] The step S120 of preparing the second molten metal may include the steps of producing the second molten metal, treating the second molten metal, and transferring the second molten metal.

[0057] In the step of treating the second molten metal, whether or not the second molten metal has solidified can be determined, and the temperature of the second molten metal can be increased or a recarburizer can be added.

[0058] Hereinafter, the step S120 of preparing the second molten metal will be described in more detail.

[0059] In this specification, Ta is defined as the temperature of the second molten metal at the time of measurement, where the time of measurement refers to the time when the temperature of the second molten metal is first measured to determine whether the second molten metal has solidified.

[0060] 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:

[0061] [Formula 1: Tf=1536.6(℃)-{88 XC wt%}(℃)]

[0062] ΔTc is defined as the amount of temperature change of the second molten metal. Specifically, ΔTc means the amount of temperature change of the second molten metal due to the time (S) required from the time of initial measurement to the time when the first molten metal and the second molten metal are combined. For example, ΔTc satisfies the following formula 2.

[0063] [Formula 2: △Tc=-1(℃ / min)XS(min)]

[0064] The units of Ta, Tf and ΔTc are °C. ΔTc is a negative number.

[0065] 3 to 7 are diagrams showing various embodiments of the step of preparing the second molten metal shown in FIG.

[0066] Steps S120_A and S120_B of preparing the second molten metal shown in FIGS. 3 to 5; S At 120_C, the second melt can be heated to prevent it from solidifying.

[0067] Referring to FIG. 3, step S120_A of preparing the second molten metal includes step S121_A of producing the second molten metal, step S122_A of receiving the second molten metal, step S123_A of checking whether the second molten metal has solidified, and step S125_A of transferring the second molten metal.

[0068] In step S121_A of producing the second molten metal, an electric arc furnace (EAF) can be used.

[0069] For example, iron ore-based ore-derived iron sources (OBM's) and a secondary feedstock including iron scrap can be melted in an electric furnace to produce molten iron.

[0070] Specifically, the second raw material may include hot briquetted iron (HBI) and scrap iron. For example, the second raw material may include 60% HBI and 40% scrap iron by weight. However, this is an exemplary content ratio and the present invention is not limited thereto.

[0071] In step S121_A, the second raw material may be charged into the electric furnace. Residual molten metal may be present inside the electric furnace. For example, the volume of the residual molten metal may be about 60 to 70% of the capacity of the electric furnace. The solubility of the residual molten metal may be 70 to 80%.

[0072] In this embodiment, HBI can be stably melted using the remaining molten metal in the electric furnace. In addition, the solubility of the remaining molten metal is adjusted to 70-80%, which prevents the overflow of slag during the HBI charging step.

[0073] If the amount of residual molten metal present inside the electric furnace is less than a preset amount, the amount of residual molten metal can be adjusted to within a preset range by preferentially melting the iron scrap from the second raw material.

[0074] In addition, if the solubility of the residual molten metal present inside the electric furnace is higher than a preset value, iron scrap from the second raw material can be added to adjust the solubility of the residual molten metal to within a preset range.

[0075] In step S121_A, the HBI of the second raw material may be added multiple times, thereby allowing the HBI to be dissolved more stably.

[0076] The second molten metal may be produced by melting the second raw material in the electric 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.

[0077] However, the ore-derived iron source contained in the second raw material is not limited to HBI, and the ore-derived iron source may be DRI or the like.

[0078] In step S122_A of receiving the second molten metal, the second molten metal melted in the electric furnace may be received in the first ladle. The first ladle may be a container having an open top and a defined internal space. A refractory layer may be disposed in the internal space of the first ladle.

[0079] In the step S123_A of checking whether solidification has occurred, the temperature of the second molten metal is measured to determine whether solidification of the second molten metal begins before the second molten metal is combined with the first molten metal.

[0080] The step S123_A of checking whether or not coagulation has occurred can be performed by a program that controls the equipment.

[0081] In step S123_A, if Ta+Tc≦ΔTf is satisfied, solidification of the second molten metal can begin before it is combined with the first molten metal.

[0082] In this case, Step S124_A of increasing the temperature of the second molten metal is performed. Step S124_A can be performed by an LF (LADLE FURNACE) refining machine.

[0083] Specifically, in step S124_A, the first ladle is moved to the LF refiner, and then the temperature of the second molten metal is increased to a temperature higher than Tf-ΔTc by using arc heat of the LF refiner.

[0084] 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 when the first molten metal and the second molten metal are mixed is higher than the solidification temperature of the second molten metal.

[0085] In 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 the converter equipment.

[0086] If Ta+ΔTc>Tf is satisfied, it is determined that the second molten metal will not solidify before being combined with the first molten metal, and step S125_A of transferring the second molten metal may be performed without going through step S124_A of raising the temperature of the second molten metal.

[0087] According to an embodiment of the present invention, the step S120_A of preparing the second molten metal may further include the step of adding a deoxidizer to the second molten metal.

[0088] The step of adding the deoxidizer may be performed simultaneously with the step S122_A of receiving the second molten metal.

[0089] The deoxidizer can remove oxygen contained in the second molten metal. The deoxidizer can include an element that is highly reactive with oxygen. For example, the deoxidizer can be an ferroalloy containing at least one element selected from the group consisting of silicon, manganese, and aluminum.

[0090] The amount of deoxidizer to be added can be determined depending on the amount of oxygen in the second molten metal. For example, the amount of deoxidizer to be added can be determined by the following formulas 4 to 6 depending on the contained elements.

[0091] [Equation 4: Weight of oxygen contained in the second molten metal (kg) x {molecular weight of aluminum in Al2O3 (54) / molecular weight of oxygen (48)}]

[0092] [Equation 5: Weight of oxygen contained in the second molten metal (kg) x {molar mass of silicon in SiO2 (28) / molecular mass of oxygen (32)}]

[0093] [Equation 6: Weight of oxygen contained in the third molten metal (kg) x {molecular weight of manganese in MnO (55) / molecular weight of oxygen (16)}]

[0094] In the following, an embodiment different from the above-described embodiment will be described. For convenience of explanation, the following description will omit redundant description of the same configuration as the above-described embodiment.

[0095] Referring to FIG. 4, step S120_B of preparing the second molten metal includes step S121_B of producing the second molten metal, step S122_B of checking whether the second molten metal has solidified, step S124_B of receiving the second molten metal, and step S125_B of transferring the second molten metal.

[0096] In step S121_B of producing the second molten metal, an electric furnace may be used, for example, by melting the second raw material including iron scrap in the electric furnace to produce the second molten metal.

[0097] However, the present invention is not limited to the above content. The second raw material may be iron ore or reduced iron (for example, DRI, HBI, etc.).

[0098] In the step S122_B of checking whether solidification has occurred, it is checked whether the second molten metal is solidified before the first molten metal and the second molten metal are combined.

[0099] In this embodiment, step S122_B of checking whether solidification has occurred may be performed while the second molten metal is present in the electric furnace.

[0100] If Ta+ΔTc≦Tf is satisfied in step S122_B, step S123_B of increasing the temperature of the second molten metal is performed. Step S123_B may be performed using an electric furnace.

[0101] Specifically, in step S123_B, the temperature of the second molten metal is increased to a temperature higher than Tf-ΔTc by using the arc heat of the electric furnace.

[0102] That is, in step S123_B, the temperature of the second molten metal is increased so that the temperature of the second molten metal at the time of mixing the first molten metal and the second molten metal becomes higher than the solidification temperature of the second molten metal. However, the heating method of the electric furnace is not limited to the above-mentioned method.

[0103] If Ta+ΔTc>Tf is satisfied in step S122_B, step S123_B of increasing the temperature of the second molten metal can be omitted.

[0104] After step S122_B (or step S123_B), the second molten metal is received. S 124_B and step S125_B of moving the second molten metal may be performed.

[0105] According to this embodiment, the step S120_B of preparing the second molten metal 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-described embodiment S120_A.

[0106] Referring to FIG. 5, step S120_C of preparing the second molten metal includes step S121_C of producing the second molten metal, step S122_C of receiving the second molten metal, step S123_C of checking whether the second molten metal has solidified, and step S125_C of transferring the second molten metal.

[0107] In step S121_C of producing the second molten metal, an electric furnace may be used. For example, the second raw material including iron scrap may be melted in the electric furnace to produce the second molten metal. 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.

[0108] In Step S122_C of receiving the second molten metal, the second molten metal melted in the electric furnace can be received in the first ladle.

[0109] In the step S123_C of checking whether solidification has occurred, it can be checked whether the second molten metal has solidified before the first molten metal and the second molten metal are mixed. The step S123_C can be performed in a state where the second molten metal is received in the first ladle.

[0110] For example, if Ta+ΔTc≦Tf is satisfied in step S123_C, step S124_C of increasing the temperature of the second molten metal is performed. Step S124_C may be performed using an electric furnace.

[0111] Specifically, step S124_C may include the steps of moving the first ladle receiving the second molten metal to an electric furnace, charging the second molten metal into the electric furnace, heating the second molten metal, and re-receiving the heated second molten metal into the first ladle.

[0112] In the step of increasing the temperature of the second molten metal, the temperature of the second molten metal is increased to a temperature higher than Tf-ΔTc using an electric furnace. For example, the electric furnace may increase the temperature of the second molten metal using arc heat.

[0113] That is, in step S124_C, the temperature of the second molten metal is increased so that the temperature of the second molten metal at the time of mixing the first molten metal and the second molten metal becomes higher than the solidification temperature of the second molten metal. However, the heating method of the electric furnace is not limited to the above-mentioned method.

[0114] If Ta+ΔTc>Tf is satisfied, step S124_C can be omitted.

[0115] After step S123_C (or step S124_C), step S125_C of transferring the second molten metal may be performed.

[0116] According to this embodiment, the step S120_C of preparing the second molten metal 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-described embodiment S120_A.

[0117] In the steps S120_D and S120_E of preparing the second molten metal shown in FIGS. 6 and 7, a carburizing agent may be added to the second molten metal to prevent solidification of the second molten metal.

[0118] Referring to FIG. 6, step S120_D of preparing the second molten metal includes step S121_D of producing the second molten metal, step S122_D of checking whether the second molten metal has solidified, step S124_D of receiving the second molten metal, and step S125_D of transferring the second molten metal.

[0119] In step S121_D of producing the second molten metal, an electric furnace may be used. For example, the second raw material including iron scrap may be melted in the electric furnace to produce the second molten metal. 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.

[0120] In the step S122_D of checking whether solidification has occurred, the temperature of the second molten metal is measured to determine whether solidification of the second molten metal begins before the second molten metal is combined with the first molten metal.

[0121] If Ta + ΔTc ≦ Tf is satisfied, solidification of the second molten metal can begin before it is combined with the first molten metal.

[0122] In this case, the second molten metal is added with a recarburizer. S 123_D is performed. S 123_D adjusts the solidification temperature of the second molten metal after adding the carburizer so that it is lower than Ta + △Tc.

[0123] 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 it is combined with the first molten metal.

[0124] After step S122_D (or step S123_D), the second molten metal is received in the first ladle. S 124_D and step S125_D of transferring the second molten metal may be performed.

[0125] According to this embodiment, the step of preparing the second molten metal (S120_D) may further include adding a deoxidizer to the second molten metal. The type and amount of the deoxidizer may be the same as those in the above-described embodiment (S120_A).

[0126] Referring to FIG. 7, step S120_E of preparing the second molten metal includes step S121_E of producing the second molten metal, step S122_E of receiving the second molten metal, step S123_E of checking whether the second molten metal has solidified, and step S125_E of transferring the second molten metal.

[0127] In step S121_E of producing the second molten metal, an electric furnace may be used. For example, the second raw material including iron scrap may be melted in the electric furnace to produce the second molten metal. 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.

[0128] In Step S122_E of receiving the second molten metal, the second molten metal produced in the electric furnace can be received in the first ladle.

[0129] In the step S123_E of checking whether solidification has occurred, the temperature of the second molten metal received in the first ladle is measured to determine whether solidification of the second molten metal begins before it is combined with the first molten metal.

[0130] If Ta + ΔTc ≦ Tf is satisfied, solidification of the second molten metal can begin before it is combined with the first molten metal.

[0131] In this case, adding a recarburizer to the second molten metal S Step 124_E is performed. S124_E The solidification temperature of the second molten metal after adding the recarburizer is adjusted to be lower than Ta + △Tc.

[0132] 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 it is combined with the first molten metal.

[0133] After step S123_E (or step S124_E), step S125_E of transferring the second molten metal may be performed.

[0134] 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-described embodiment (S120_A).

[0135] 8 to 10 are diagrams showing various embodiments of the step of mixing the first molten metal and the second molten metal shown in FIG.

[0136] Referring to FIG. 8, step S200_A of mixing the first molten metal and the second molten metal includes step S210_A of receiving the first molten metal into the second ladle and step S220_A of mixing the second molten metal into the second ladle.

[0137] In step S210_A, the second molten metal received by the first transport vehicle is received in a second ladle. The second ladle may be a container with an open top and a defined internal space. The second ladle may have an internal space larger than that of the first ladle.

[0138] step S In 220_A, the second molten metal received in the first ladle can be mixed with the second ladle. In this embodiment, the second ladle may be a mixing ladle for mixing the first molten metal and the second molten metal.

[0139] Thereby, in step S220_A, a third molten metal may be produced by mixing the first molten metal and the second molten metal.

[0140] The third melt may contain 15 to 50 wt % of the second melt, based on the weight of the third melt, and the remainder being the first melt.

[0141] If the proportion of the second molten metal is less than 15 wt%, the carbon dioxide reduction effect may be insufficient due to the high content of molten pig iron.

[0142] On the other hand, if the second molten metal exceeds 50 wt%, there may be a shortage of molten iron, which is the main heat source during electric furnace operation, and the subsequent electric furnace operation may not be carried out smoothly.

[0143] In the following, an embodiment different from the above-described embodiment will be described. For convenience of explanation, the following description will omit redundant explanations of the same configurations as the above-described embodiment.

[0144] Referring to FIG. 9, the step S200_B of mixing the first molten metal and the second molten metal includes the step S210_B of receiving the first molten metal into a second ladle, and the step S210_B of receiving the second molten metal into a storage furnace. SThe method includes step S230_B of combining the first molten metal and the second molten metal in a second ladle.

[0145] In step S210_B, the second molten metal received in the first transport vehicle is poured into a second ladle.

[0146] step S In step S220_B, the second molten metal received in the first ladle may be received in a storage furnace. The storage furnace may have an internal space larger than that of the first ladle. Step S220_B may be performed separately from step S210_B.

[0147] In step S230_B, at least a portion of the second molten metal received in the storage furnace may be mixed with the second ladle, thereby producing a third molten metal in step S200_B by mixing the first molten metal and the second molten metal.

[0148] The third molten metal may contain 15 to 50 wt % of the second molten metal based on the weight of the third molten metal, with the remainder being the first molten metal.

[0149] Referring to FIG. 10, the step S200_C of mixing the first molten metal and the second molten metal includes a step S210_C of receiving the second molten metal into a first transport vehicle and a step S220_C of receiving the third molten metal into a second ladle.

[0150] In step S210_C, the second molten metal received in the first ladle is transferred to the first transport vehicle, whereby the first molten metal and the second molten metal are mixed in the first transport vehicle to produce a third molten metal.

[0151] That is, the above-mentioned embodiment S200_A, S Unlike 200_B, in this embodiment, the first transport vehicle serves as a mixing ladle.

[0152] The third molten metal may contain 15 to 50 wt % of the second molten metal based on the weight of the third molten metal, with the remainder being the first molten metal.

[0153] step SAt 220_C, the third molten metal can be received in the second ladle within the first transport vehicle.

[0154] Referring again to FIG. 1, in step S300 of adjusting the composition of the third molten metal, impurities (e.g., silicon, phosphorus, sulfur) in the third molten metal received in the second ladle can be removed to reduce the carbon content, thereby producing a fourth molten metal.

[0155] To this end, in step S300, the third molten metal may undergo a hot metal pretreatment process, a converter process, and an LF process.

[0156] However, the present invention is not limited to the above, and a vacuum degassing process, a BAP process, etc. may be additionally performed.

[0157] In step S400 of manufacturing a product, a semi-finished product can be made from the fourth molten metal, and a finished product can be made from the semi-finished product.

[0158] Specifically, in step S400, the fourth molten metal may be formed into a semi-finished product by a continuous casting process. For example, the semi-finished product may be a slab or a billet. However, the semi-finished product is not limited thereto, and may be a bloom.

[0159] The semi-finished product can then be rolled into a finished product, which can be a hot rolling process or a cold rolling process. The finished product can be a steel sheet or a wire rod.

[0160] A method for producing steel according to an embodiment of the present invention can significantly reduce carbon dioxide emissions generated during the steelmaking process by combining a second molten metal (i.e., molten steel) produced in an electric furnace, which emits relatively less carbon dioxide than a first molten metal (i.e., molten pig iron) produced in a blast furnace, with the first molten metal to produce steel.

[0161] In a method for producing steel according to an embodiment of the present invention, the problem of the second molten metal solidifying before the first and second molten metals are combined can be prevented by increasing the temperature of the second molten metal or adding a recarburizer.

[0162] In the method for manufacturing steel according to an embodiment of the present invention, a deoxidizer is added to the second molten metal to prevent an explosion or overflow that may occur when the first molten metal and the second molten metal are combined.

[0163] While the preferred embodiments of the present invention have been described above, it will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or scope of the present invention.

[0164] For example, in the above-described embodiment of the present invention, the second molten metal produced in the electric furnace is heated or a recarburizer is added to prevent the second molten metal from solidifying. However, conversely, the first molten metal produced in the blast furnace can be heated or a recarburizer can be added to prevent the first molten metal from solidifying.

[0165] Furthermore, in the above-described embodiment of the present invention, the first molten metal is described as molten pig iron produced in a blast furnace, but the first molten metal can also be produced using an electric furnace.

[0166] That is, the above-described embodiments should be considered as illustrative rather than restrictive, and the present invention is not limited by the above description, but may be modified within the scope of the appended claims and their equivalents.

Claims

1. 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; mixing the first molten metal with the second molten metal to prepare a third molten metal; adjusting the composition of the third molten metal to produce a fourth molten metal; and a method of producing steel comprising the step of processing the fourth molten metal to produce a product.

2. The step of preparing the second molten metal includes: melting the second raw material in an electric furnace to prepare a second molten metal; receiving the second molten metal into a first ladle having an open top and a space defined therein; determining whether the second molten metal has solidified; and moving the first ladle; Including, The step of checking whether the second molten metal has solidified includes: The temperature of the second molten metal at the time of measurement is defined as Ta, The solidification temperature of the second molten metal depending on the carbon content is defined as Tf, When the amount of temperature change of the second molten metal that occurs from the time of measurement to the time of mixing the first molten metal and the second molten metal is defined as ΔTc, 2. The method for producing steel according to claim 1, wherein when Ta + ΔTc≦Tf is satisfied, the temperature of the second molten metal is increased to Tf−ΔTc or higher through an LF refining machine.

3. The step of preparing the second molten metal includes: melting the second raw material in an electric furnace to prepare a second molten metal; checking whether the second molten metal has solidified; receiving the second molten metal in a first ladle having an open top and a space defined therein; and moving the first ladle; Including, The step of checking whether the second molten metal has solidified includes: The temperature of the second molten metal at the time of measurement is defined as Ta; The solidification temperature of the second molten metal depending on the carbon content is defined as Tf; When the amount of temperature change of the second molten metal that occurs from the time of measurement to the time of mixing the first molten metal and the second molten metal is defined as ΔTc, 2. The method for producing steel according to claim 1, wherein when Ta+ΔTc≦Tf is satisfied, the temperature of the second molten metal is further increased to Tf−ΔTc or higher in an electric furnace.

4. The step of preparing the second molten metal includes: melting the second raw material in an electric furnace to prepare a second molten metal; adding a deoxidizer to the second molten metal; receiving the second molten metal into a first ladle having an open top and a space defined therein; determining whether the second molten metal has solidified; and moving the first ladle; Including, The step of checking whether the second molten metal has solidified includes: The temperature of the second molten metal at the time of measurement is defined as Ta; The solidification temperature of the second molten metal depending on the carbon content is defined as Tf; When the amount of temperature change of the second molten metal that occurs from the time of measurement to the time of mixing the first molten metal and the second molten metal is defined as ΔTc, 2. The method for producing steel according to claim 1, wherein when Ta+ΔTc≦Tf is satisfied, the temperature of the second molten metal is increased to Tf−ΔTc or higher.

5. The step of preparing the first molten metal includes: melting the first raw material in a blast furnace to produce a first molten metal; receiving the first molten metal into a first transport vehicle; and moving the first transport vehicle; The step of preparing the second molten metal includes: Melting the second raw material in an electric furnace (EAF) to produce a second molten metal; and selectively adding a recarburizer depending on whether the second molten metal is solidified or not; The step of preparing the third molten metal comprises: The method of claim 1 including the step of charging said second molten metal into said first transport vehicle.

6. The step of preparing the second molten metal includes: selectively adding a recarburizer depending on whether the second molten metal is solidified or not; The step of preparing the third molten metal comprises:

2. The method for producing steel according to claim 1, further comprising the step of charging the second molten metal received in a storage furnace into a ladle containing the first molten metal.

7. The step of preparing the first molten metal includes: melting the first raw material in a blast furnace to produce a first molten metal; receiving the first molten metal into a first transport vehicle; and moving the first transport vehicle; The step of preparing the second molten metal includes: Melting the second raw material in an electric furnace (EAF) to produce a second molten metal; and selectively adding a recarburizer depending on whether the second molten metal is solidified or not; The step of preparing the third molten metal comprises: pouring the first molten metal into a ladle having an open top and a defined space therein; and 2. The method of claim 1, including the step of charging the second molten metal into the ladle.

8. preparing a first molten metal containing carbon and a second molten metal containing a lower concentration of carbon than the first molten metal; mixing the first molten metal with the second molten metal to prepare a third molten metal; adjusting the composition of the third molten metal to produce a fourth molten metal; and processing the fourth molten metal to produce a product.

9. The step of preparing the second molten metal includes: receiving the second molten metal into a first ladle having an open top and a space defined therein; raising the temperature of the second molten metal received in the first ladle through an LF refining machine; and moving the first ladle; 9. The method for producing steel according to claim 8, wherein the step of increasing the temperature comprises adjusting the temperature of the second molten metal so that the temperature of the second molten metal at the time of mixing the first molten metal and the second molten metal is higher than a solidification temperature of the second molten metal.

10. The step of preparing the second molten metal includes: further heating the second molten metal in an electric furnace; receiving the second molten metal in a first ladle having an open top and a space defined therein; and moving the first ladle; 9. The method for producing steel according to claim 8, wherein the additional heating step comprises adjusting the temperature of the second molten metal so that a measured temperature of the second molten metal at the time of mixing the first molten metal and the second molten metal is higher than a solidification temperature of the second molten metal.

11. The step of preparing the second molten metal includes: adding a deoxidizer to the second molten metal; receiving the second molten metal into a first ladle having an open top and a space defined therein; raising the temperature of the second molten metal received in the first ladle; and moving the first ladle; 9. The method for producing steel according to claim 8, wherein the step of increasing the temperature comprises adjusting the temperature of the second molten metal so that a measured temperature of the second molten metal at the time of mixing the first molten metal and the second molten metal is higher than a solidification temperature of the second molten metal.

12. The step of preparing the first molten metal includes: receiving the first molten metal into a first transport vehicle; and moving the first transport vehicle; The step of preparing the second molten metal includes: selectively adding a recarburizer depending on whether the second molten metal is solidified or not; The step of preparing the third molten metal comprises: The method of claim 8 including the step of charging said second molten metal into said first transport vehicle.

13. The step of preparing the second molten metal includes: selectively adding a recarburizer depending on whether the second molten metal is solidified or not; The step of preparing the third molten metal comprises:

9. The method for producing steel according to claim 8, further comprising the step of charging the second molten metal received in a storage furnace into the ladle containing the first molten metal.

14. The step of preparing the first molten metal includes: receiving the first molten metal into a first transport vehicle; and moving the first transport vehicle; The step of preparing the second molten metal includes: selectively adding a recarburizer depending on whether the second molten metal is solidified or not; The step of preparing the third molten metal comprises: pouring the first molten metal into a ladle having an open top and a defined space therein; and 9. The method of claim 8, including the step of charging the second molten metal into the ladle.

15. The carbon content of the first molten metal is 2 wt % or more, 9. The method of claim 8, wherein the carbon content of the second melt is less than or equal to 2 wt. %.

16. 9. The method of claim 8, wherein the third melt is 15-50 wt. % of the second melt and the remainder is the first melt.

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