Steelmaking method and casting method

Abstract

The present invention provides a steelmaking method and a casting method that can efficiently produce high-grade steel and reduce carbon emissions. [Solution] The present invention includes the steps of preparing a first molten iron, preparing a first molten steel having an even lower carbon (C) content than the first molten iron, mixing the first molten iron and the first molten steel in a ratio ranging from 20.3:79.7 to 98.6:1.4, charging the second molten iron produced by the mixing into a refining vessel, and refining the second molten iron to produce a second molten steel, wherein the mixing process is carried out in stages over multiple stages, the mixed product produced in previous stages is used in subsequent stages, the first molten steel is mixed only in the first stage, and the first molten iron is mixed in all stages. The present invention is characterized by comprising the steps of: mixing the first molten iron and the first molten steel in a first ratio ranging from 20:80 to 80:20 to produce a mixed product; and mixing the first molten iron and the mixed product in a second ratio ranging from 7:93 to 93:7 to produce a second molten iron.

Description

Technical Field

[0001] The present invention relates to a steel manufacturing method and a casting method, and more particularly, to a steel manufacturing method and a casting method capable of efficiently manufacturing high-grade steel and reducing carbon generation.

Background Art

[0002] In order to address the crisis of climate change, efforts are being actively and vigorously made to develop carbon-neutral technologies that minimize carbon generation. For this reason, in the steel industry, research and development are being carried out on electric furnace technologies that can suppress carbon generation by using electricity to melt raw materials instead of blast furnaces that generate large amounts of carbon.

[0003] An electric furnace melts raw materials using the heat and arc generated at the electrode rod by supplying power to the electrode rod. However, since the molten steel produced in an electric furnace has a higher content of impurity elements compared to the hot metal produced in a blast furnace, there is a problem that it is difficult to produce high-grade steel materials such as outer panel materials for automobiles using the molten steel produced in an electric furnace.

[0004] The technology that is the background of the present invention is described in the following patent documents.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a steel manufacturing method and a casting method capable of efficiently manufacturing high-grade steel.

[0007] Furthermore, an object of the present invention is to provide a steelmaking method and a casting method that can reduce the generation of carbon. [Means for solving the problem]

[0008] The steelmaking method of the present invention is characterized by comprising the steps of: preparing a first molten iron; preparing a first molten steel having an even lower carbon (C) content than the first molten iron; mixing the first molten iron and the first molten steel in a ratio (%) in the range of 20.3:79.7 to 98.6:1.4; charging the second molten iron produced by the mixing into a refining vessel; and refining the second molten iron to produce a second molten steel.

[0009] The aforementioned mixing process may be carried out in stages over multiple stages, with the mixed product produced in a previous stage being used in subsequent stages, the first molten steel being mixed only in the first stage, and the first molten iron being mixed in all stages.

[0010] The aforementioned mixing process may include a process of mixing the first molten iron and the first molten steel in a first ratio ranging from 20:80 to 80:20 to produce a mixed product, and a process of mixing the first molten iron and the mixed product in a second ratio ranging from 7:93 to 93:7 to produce a second molten iron.

[0011] The steelmaking method of the present invention is characterized by comprising the steps of: preparing a first molten iron; preparing a first molten steel having an even lower carbon (C) content than the first molten iron; mixing the first molten iron and the first molten steel to produce a mixed product; mixing the first molten iron and the mixed product to produce a second molten iron; charging the second molten iron into a refining vessel; and refining the second molten iron to produce a second molten steel.

[0012] The first molten iron may include blast furnace molten iron produced in a blast furnace, and the first molten steel may include electric furnace molten steel produced in an electric furnace.

[0013] The process of preparing the first molten iron may include a process of producing the first molten iron in a blast furnace such that the carbon (C) content is 4.0 to 4.5% by weight.

[0014] During the production of the first molten iron, the temperature of the first molten iron may be adjusted to 1,350 to 1,500°C.

[0015] The process of preparing the first molten steel may include the process of producing the first molten steel in an electric furnace so that the carbon (C) content is 0.04 to 1.0% by weight and the oxygen (O) concentration is 5 to 400 ppm, and the process of adding a deoxidizing agent to the first molten steel to adjust the oxygen (O) concentration to 0 to 10 ppm.

[0016] During the production of the first molten steel, the temperature of the first molten steel may be adjusted to 1,580 to 1,700°C.

[0017] The process for producing the mixed molten metal may include the steps of: placing the first molten iron into a plurality of first transport containers having openings at the top that can be opened and closed; placing the first molten steel into a second transport container that is open at the top; arranging the second transport containers above a portion of the first transport containers; tilting the second transport containers to pour the first molten steel from the second transport containers into the portion of the first transport containers; and forming the mixed molten metal inside the portion of the first transport containers.

[0018] The process for producing the mixed molten metal may include the steps of: placing the first molten iron into a plurality of first transport containers having openings at the top that can be opened and closed; placing the first molten steel into a second transport container having a plurality of openings at the bottom that can be opened and closed; arranging the second transport containers above a portion of the first transport containers; opening the lower openings of the second transport containers and pouring the first molten steel from the second transport containers into the portion of the first transport containers; and forming the mixed molten metal inside the portion of the first transport containers.

[0019] In the process of manufacturing the molten metal mixture, the temperature of the molten metal mixture may be adjusted to 1,430 to 1,650 °C.

[0020] The process of manufacturing the second hot metal may include the process of providing a charging container with an open top, the process of arranging a first transport container containing the molten metal mixture among a plurality of first transport containers having an opening that can be opened and closed at the top above the charging container, the process of arranging a first transport container containing the first hot metal among a plurality of first transport containers above the charging container, the process of tilting the first transport container containing the first hot metal and the first transport container containing the molten metal mixture to pour the remaining molten metal mixture and the first hot metal into the charging container, and the process of forming the second hot metal inside the charging container.

[0021] The process of manufacturing the second hot metal may include the process of adjusting the carbon (C) content of the second hot metal to 2% by weight or more and less than 4% by weight, and the process of adjusting the temperature of the second hot metal to 1,350 to 1,500 °C.

[0022] The process of charging the second hot metal into the refining container may include the process of charging the second hot metal into the refining container so that the hot metal ratio (HMR) of the second hot metal is 35 to 100%.

[0023] The process of manufacturing the second molten steel may include the process of blowing bottom-blown gas into the refining container, and the process of adjusting the components of the second molten steel so that the nitrogen (N) content is in the range of 22 to 30 ppm, the copper (Cu) content is in the range of 0.02 to 0.04% by weight, and the nickel (Ni) content is in the range of 0.01 to 0.04% by weight.

[0024] The second molten steel may include Hyper NO steel, HNO steel, MNO steel, LNO steel, EDDQ steel, S-EDDQ steel, DQ steel, DDQ steel, API steel, AHSS steel, and ordinary steel.

[0025] When the reference emission amount of carbon dioxide is set to 1, the emission amount of carbon dioxide may be reduced to 0.25 in the process of preparing the first hot metal, the process of preparing the first molten steel, and the process of producing the second molten steel.

[0026] The casting method of the present invention may include a process of preparing steel manufactured by the steelmaking method and a process of casting the prepared steel.

Advantages of the Invention

[0027] According to the present invention, by melting the first hot metal that generates a large amount of carbon during production compared to the first molten steel and the first molten steel having an even higher content of impurity elements compared to the first hot metal at a ratio (%) in the range of 20.3:79.7 to 98.6:1.4 to produce the second hot metal, and refining the second hot metal, high-quality second molten steel with the content of impurity elements and the content of carbon respectively controlled at desired levels can be produced in a sufficient amount. From this, when gradually reducing the production amount of the first hot metal and gradually increasing the production amount of the first molten steel to gradually achieve carbon neutrality, the production amount of high-grade steel with a low content of impurity elements, for example, extra-low carbon steel, can be effectively increased while significantly reducing the amount of carbon generated in the entire production process.

[0028] Also, according to the present invention, by melting the first hot metal and the first molten steel to produce a melted product, and then melting the first hot metal and the melted product to produce the second hot metal, the melting ratio of the first hot metal and the first molten steel can be finally adjusted to a desired ratio through an intermediate stage. Therefore, while melting a large amount of the first hot metal and a large amount of the first molten steel at an accurate melting ratio, homogenization of the second hot metal can be achieved. From this, the refining quality of the second molten steel can be improved. Therefore, the casting quality of the semi-finished product to be cast hereafter can be improved.

Brief Description of the Drawings

[0029] [Figure 1]This is a procedure diagram showing a steelmaking method according to the first embodiment of the present invention. [Figure 2] This is a step procedure diagram illustrating the overall process according to the first embodiment of the present invention. [Figure 3] This is a step procedure diagram illustrating in detail the molten metal mixing process according to the first embodiment of the present invention. [Figure 4] This is a procedure diagram showing a steelmaking method according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0030] The present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited in any way to the embodiments disclosed below and should be embodied in a variety of different forms. These embodiments are merely provided to complete the disclosure of the present invention and to fully inform those who are ordinary skill in the art of the scope of the invention. The drawings may be exaggerated in order to illustrate embodiments of the present invention, and in the drawings, the same reference numerals refer to the same components.

[0031] The present invention relates to a steelmaking method and a casting method. Hereinafter, embodiments of the present invention will be described in detail, using as an example the case in which the steelmaking method and casting method are applied to the production of high-grade steel, such as ultra-low carbon steel used in the casting of high-grade products such as automobile body panels in steelmaking operations, and to the casting of semi-finished products therefrom.

[0032] Needless to say, the steelmaking method of the present invention is applicable to various manufacturing processes for producing various molten materials. That is, the steelmaking method of the present invention is applicable to manufacturing processes for producing, for example, ordinary steel, alloy steel, etc. Similarly, the casting method of the present invention is applicable to various casting processes for casting various semi-finished products.

[0033] Figure 1 is a step diagram showing a steelmaking method according to the first embodiment of the present invention. Figure 2 is a step diagram illustrating the overall process according to the first embodiment of the present invention, and Figure 3 is a step diagram illustrating the molten metal mixing process according to the first embodiment of the present invention in detail.

[0034] As shown in Figures 1 to 3, the steelmaking method according to the first embodiment of the present invention includes the steps of: preparing a first molten iron (S110); preparing a first molten steel having an even lower carbon (C) content than the first molten iron (S120); mixing the first molten iron and the first molten steel in a ratio (%) in the range of 20.3:79.7 to 98.6:1.4 (S130); charging the second molten iron produced by the mixing into a refining vessel (S140); and refining the second molten iron to produce a second molten steel (S150).

[0035] The first molten iron may include blast furnace molten iron produced in a blast furnace. Furthermore, the first molten iron may have a high carbon (C) content of 4.0 to 4.5% by weight in its total weight. More specifically, the first molten iron may contain 4.0 to 4.5% by weight of carbon (C) in its entirety. In this case, the first molten iron may further contain silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), titanium (Ti), chromium (Cr), vanadium (V), nickel (Ni), copper (Cu), and nitrogen (N) in predetermined content ranges, with the remainder being iron (Fe).

[0036] As shown in Figures 1 and 2(a), blast furnace molten iron can be prepared in the process of preparing the first molten iron (S110). For this purpose, the process of preparing the first molten iron (S110) may include a process of producing a first molten iron in a blast furnace having a carbon (C) content of 4.0 to 4.5% by weight relative to the total weight. More specifically, the process of preparing the first molten iron (S110) may include a process of producing a first molten iron in a blast furnace containing 4.0 to 4.5% by weight of carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), titanium (Ti), chromium (Cr), vanadium (V), nickel (Ni), copper (Cu), and nitrogen (N) in predetermined content ranges, with iron (Fe) making up the remainder.

[0037] Here, if the carbon (C) content of the first molten iron deviates from the range of 4.0 to 4.5% by weight relative to the total weight of the first molten iron, there is a risk that the operational efficiency of the first molten iron production in the blast furnace will decrease, and it may become difficult to adjust the carbon (C) content of the second molten iron to the target content.

[0038] On the other hand, the process of preparing the first molten iron (S110) may include a process of providing the first molten iron produced in a blast furnace such that the carbon (C) content is 4.0 to 4.5% by weight relative to the total weight.

[0039] Furthermore, the process of preparing the first molten iron (S110) may include a process of adjusting the temperature of the first molten iron to 1,350-1,500°C. To this end, the blast furnace operating conditions, such as the amount of hot air and the amount of coke added, can be adjusted to produce the first molten iron at a temperature of 1,350-1,500°C in the blast furnace. Needless to say, various methods can be employed to adjust the temperature of the first molten iron to 1,350-1,500°C. On the other hand, if the temperature of the first molten iron is lower than 1,350°C, the temperature range of the second molten iron to be produced will be lower, which may necessitate a further heating process. Also, if the temperature of the first molten iron is higher than 1,500°C, there is a problem that the amount of carbon emitted from the blast furnace will increase.

[0040] The first molten steel may include electric furnace molten steel produced in an electric furnace. Furthermore, the first molten steel may have an even lower carbon (C) content than the first molten iron. That is, the first molten steel may have a low carbon (C) content of 0.04 to 1.0% by weight in its total weight. More specifically, the first molten steel may contain 0.04 to 1.0% by weight of carbon (C) in its entirety, and may further contain silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), titanium (Ti), chromium (Cr), vanadium (V), nickel (Ni), copper (Cu), and nitrogen (N), with iron (Fe) making up the remainder.

[0041] In the process of preparing a first molten steel having an even lower carbon (C) content than the first molten iron (S120), electric furnace molten steel can be prepared. For example, the process of preparing the first molten steel (S120) may include a process of producing the first molten steel in an electric furnace such that the carbon (C) content is 0.04 to 1.0% by weight and the oxygen (O) concentration is 5 to 400 ppm. More specifically, the process of preparing the first molten steel (S120) may include a process of producing a first molten steel in an electric furnace that contains 0.04 to 1.0% by weight of carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), titanium (Ti), chromium (Cr), vanadium (V), nickel (Ni), copper (Cu), nitrogen (N), with iron (Fe) making up the remainder, and with an oxygen (O) concentration of 5 to 400 ppm. At this time, the composition of the first molten steel produced in the electric furnace may be adjusted as described above by adjusting the type and amount of inputs such as directly reduced iron, scrap, and carburizing agents that are put into the electric furnace.

[0042] Here, if the first molten steel contains less than 0.04% by weight of carbon (C) relative to its total weight, there is a risk that the operational efficiency will decrease when producing the first molten steel in an electric furnace. Furthermore, if the first molten steel contains more than 1.0% by weight of carbon (C) relative to its total weight, the amount of molten steel added to the second molten iron will increase in order to match the carbon content of the second molten iron, which leads to the problem of increasing the content of impurities originating from the first molten steel. On the other hand, the oxygen (O) concentration may be set to a value of 5 to 400 ppm depending on the carbon (C) content mentioned above when producing the first molten steel in an electric furnace.

[0043] Needless to say, the process of preparing the first molten steel (S120) may include a process of providing a first molten steel manufactured in an electric furnace, having a carbon (C) content of 0.04 to 1.0% by weight and an oxygen (O) concentration of 5 to 400 ppm relative to the total weight.

[0044] Furthermore, the process of preparing the first molten steel (S120) may include a process of adjusting the temperature of the first molten steel to 1,580-1,700°C. This process may be carried out while the first molten steel is being produced in the electric furnace. For example, while reducing iron, scrap, etc. are being directly melted in the electric furnace, the temperature of the first molten steel may be adjusted to 1,580-1,700°C by adjusting operating conditions such as the descent speed of the electrode rods and the amount of electricity supplied to the electrode rods. If the temperature of the first molten steel is lower than 1,580°C, the temperature range of the second molten iron produced from it will be lower, which may necessitate a further heating process. Also, if the temperature of the first molten iron is higher than 1,700°C, there is a problem that the consumption of electrode rods in the electric furnace will increase. On the other hand, various methods can be adopted for adjusting the temperature of the first molten steel to 1,580-1,700°C.

[0045] Furthermore, the process of preparing the first molten steel (S120) may include a step after the process of producing the first molten steel in an electric furnace, in which a deoxidizing agent is added to the first molten steel tapped from the electric furnace to adjust the oxygen (O) concentration to 0-10 ppm. In this case, the deoxidizing agent may include Al or Si-based deoxidizing agents. Here, the Al-based deoxidizing agent may contain an aluminum (Al) component, and the Si-based deoxidizing agent may contain a silicon (Si) component. Deoxidation of the first molten steel may be carried out, for example, in a ladle. Alternatively, the first molten steel may be stirred using an agitator such as an impeller or a bottom-blowing plug during deoxidation.

[0046] In the process of preparing the first molten steel (S120), by adjusting the oxygen (O) concentration of the first molten steel to 0-10 ppm, the boiling phenomenon associated with the oxidation reaction between oxygen (O) and carbon (C) in subsequent processes (for example, the process of mixing the molten steel) can be suppressed or prevented, thereby suppressing or preventing the mixed molten steel from overflowing due to the boiling phenomenon.

[0047] On the other hand, the order of the process of preparing the first molten iron (S110) and the process of preparing the first molten steel (S120) is not particularly limited. These processes may be carried out simultaneously or together, or they may be carried out sequentially according to a predetermined order.

[0048] Once the first molten iron and the first molten steel are prepared, a process (S130) is carried out in which the first molten iron and the first molten steel are mixed in a ratio (%) within the range of 20.3:79.7 to 98.6:1.4. In this process, the second molten iron can be produced. If the mixing ratio of the first molten iron and the first molten steel deviates from the aforementioned range, it may become difficult to reduce carbon emissions and difficult to secure a heat source for the converter.

[0049] The mixing process (S130) may be carried out in stages over multiple steps. Performing it in stages means that after the mixing in the previous step, the resulting mixture is used for the mixing in the next step. In other words, when the mixing process (S130) is carried out in stages over multiple steps, the mixture produced in the previous step can be used for the mixing in the next step. In this way, carrying out the mixing process (S130) in stages over multiple steps allows for more accurate adjustment of the mixing ratio compared to carrying out the mixing process (S130) in a single step, making it easier to adjust the composition and temperature of the second molten iron, and also allowing for more effective homogenization of the composition and temperature of the second molten iron.

[0050] On the other hand, when the mixing process (S130) is carried out in stages over multiple stages, the first molten steel can only be mixed in the first stage, while the first molten iron can be mixed in all stages. This method allows for a more precise matching of the mixing ratio between the first molten iron and the first molten steel. Below, the mixing process (S130) will be explained using the case where there are two stages as an example. However, the content explained below is applicable not only to the case where there are two stages, but also to other cases in a similar or similar manner.

[0051] As shown in Figures 2(a) and 2(b), the mixing process (S130) may include a primary mixing process and a secondary mixing process. Here, the primary mixing process may include a process of mixing the first molten iron and the first molten steel in a first ratio ranging from 20:80 to 80:20 to produce a mixed product. The secondary mixing process may include a process of mixing the first molten iron and the mixed product in a second ratio ranging from 7:93 to 93:7 to produce a second molten iron. Needless to say, the number of mixing processes can be varied, and therefore the mixing ratio in each process can also be varied.

[0052] The process of mixing the hot water according to the embodiment of the present invention (S130) will be described in more detail below, based on Figures 2(a) and 2(b), and Figures 3(a) to 3(f).

[0053] As explained above, the process of mixing the first molten iron and the first molten steel (S130) may include a process of mixing the first molten iron and the first molten steel in a first ratio of 20:80 to 80:20 to produce a mixed product, and a process of mixing the first molten iron and the mixed product in a second ratio of 7:93 to 93:7 to produce a second molten iron.

[0054] In this case, the process of manufacturing the molten metal may include the steps of: placing the first molten iron into a plurality of first transport containers having openings at the top that can be opened and closed; placing the first molten steel into a second transport container that is open at the top; arranging the second transport container above a portion of the plurality of first transport containers; pouring the first molten steel from the second transport container into a portion of the first transport containers; and forming the molten metal inside a portion of the first transport containers.

[0055] As shown in Figure 2(a), the first molten iron extracted from the blast furnace can be stored in multiple first transport containers. In this case, the first transport containers may have an opening at the top that can be opened and closed. For example, the first transport containers may be equipped with a molten iron mixing car (TLC, also called a torpedo car). Needless to say, there may be various types of first transport containers. On the other hand, some of the multiple first transport containers can be transported to a mixing area where primary mixing can be performed (Figure 3(d)), and the rest can be transported to a charging area where secondary mixing can be performed (Figure 3(f)). For example, there may be four first transport containers, of which two can be transported to the mixing area and the remaining two can be transported to the charging area. Needless to say, the number of first transport containers, the number of first transport containers transported to the mixing area, and the number of first transport containers transported to the loading area can be changed in various ways.

[0056] As shown in Figure 3(a), the first molten steel tapped from the electric furnace can be contained in a second transport container. In this case, the second transport container may have multiple openings at the bottom that can be opened and closed. Each of the multiple openings can be controlled to open or close by a sliding gate. The top of the second transport container can also be opened. For example, the second transport container may be equipped with a ladle. Needless to say, there can be various types of second transport containers. On the other hand, after containing the first molten steel, the second transport container can be transported to the mixing area. In this case, the second transport container can be transported to the mixing area using a tapping cart, crane, etc. (Figures 3(b) and 3(c)).

[0057] Subsequently, as shown in Figure 3(d), the second transport container (ladle) can be placed above the first transport container TLC. For example, the second transport container (ladle), which has been transported to the mixing area, can be placed on top of a platform installed in the mixing area, and the first transport container TLC can be driven under the platform and then stopped. Alternatively, the first molten iron and the first molten steel can be mixed by opening the opening at the bottom of the second transport container (ladle) and pouring the first molten steel from the second transport container (ladle) into the first transport container TLC. In addition, the first molten iron and the first molten steel can also be mixed by tilting the second transport container (ladle) and pouring the first molten steel from the second transport container (ladle) into the first transport container TLC.

[0058] Here, when mixing the first molten iron and the first molten steel, the first molten iron and the first molten steel may be divided into equal amounts within an error range and mixed in the same proportion within an error range. That is, the first molten iron to be mixed during the initial mixing can be divided into two first transport containers (TLCs) and stored in equal amounts within an error range. Furthermore, the two first transport containers (TLCs) can be sequentially inserted into the lower part of the mounting platform, and the opening and closing of the lower opening of the second transport container (ladle) can be controlled to divide and pour the first molten steel into each of the two first transport containers (TLCs) so that the same amount of first molten steel within an error range is poured from the second transport container (ladle) into each of the two first transport containers (TLCs). Similarly, in the tilting method, the tilting of the second transport container (ladle) can be controlled to pour the same amount of first molten steel within an error range into each of the first transport containers (TLCs). At this time, in each transport container TLC, the first molten iron and the first molten steel can be mixed in a first ratio ranging from 20:80 to 80:20.

[0059] Furthermore, a mixture of molten metal can be formed inside each of the multiple first transport containers TLC. That is, by using the kinetic energy of the first molten steel generated when the first molten steel is introduced, the first molten iron and the first molten steel can be mixed inside the first transport container TLC, thereby forming a mixture of molten metal inside the first transport container TLC.

[0060] On the other hand, during the process of manufacturing the mixed molten metal, the temperature of the mixed molten metal can be adjusted to 1,430 to 1,650°C. For example, by adjusting the transport time of each transport container and the rate at which the first molten steel is added, the range of temperature drop between the first molten iron and the first molten steel during mixing can be adjusted, thereby allowing the temperature of the mixed molten metal to be adjusted to 1,430 to 1,650°C.

[0061] On the other hand, in the process of manufacturing a molten metal, the molten metal can also be manufactured within a charging container by charging the first molten iron and the first molten steel into the charging container and mixing them.

[0062] Once the process of manufacturing the mixed molten metal is complete, a process of manufacturing a second molten iron may be carried out. The process of manufacturing a second molten iron may include the steps of providing a charging container with an open top, arranging a first transport container containing the mixed molten metal on top of a plurality of first transport containers having an opening at the top, arranging a first transport container containing the first molten iron on top of a plurality of first transport containers facing the first transport container containing the mixed molten metal on top of the charging container, tilting the first transport container containing the first molten iron and the first transport container containing the mixed molten metal to inject the mixed molten metal and the first molten iron into the charging container, and forming a second molten iron inside the charging container.

[0063] As shown in Figures 3(e) and 3(f), first, a charging container with an open top can be provided. In this case, the charging container can be placed in the charging area. The charging container may also be equipped with, for example, a charging ladle. Then, the first transport container (molten metal TLC) containing the mixed molten metal and the first transport container (molten iron TLC) containing the first molten iron can be transported above the charging container (charging ladle) and then placed facing each other. In this case, the charging container (charging ladle) may be positioned between these first transport containers. After this, the first transport container (molten metal TLC) containing the mixed molten metal and the first transport container (molten iron TLC) containing the first molten iron can be tilted toward the charging container (charging ladle) to pour the mixed molten metal and the first molten iron into the charging container (charging ladle). At this time, the first molten iron and the mixed material can be mixed in a second ratio in the range of 7:93 to 93:7.

[0064] Furthermore, a second molten iron can be formed inside multiple charging vessels (charging ladles). That is, by using the kinetic energy generated when the molten metal mixture and the first molten iron are added, the molten metal mixture and the first molten iron can be mixed inside the charging vessels (charging ladles), thereby forming a second molten iron inside the charging vessels (charging ladles).

[0065] On the other hand, in the process of producing the second molten iron, if the mixed molten metal has been produced in advance in a charging container, the first molten iron can be charged into the charging container containing the mixed molten metal, and the second molten iron can be produced within the said charging container.

[0066] On the other hand, in the process of producing the second molten iron, the carbon (C) content of the second molten iron can be adjusted to 2% by weight or more and less than 4% by weight, and the temperature of the second molten iron can be adjusted to 1,350 to 1,500°C. For example, by adjusting the amount of molten metal mixed with the first molten iron to satisfy the third ratio, the carbon (C) content of the second molten iron produced from the molten metal and the first molten iron can be adjusted to 2% by weight or more and less than 4% by weight. In addition, by adjusting the transport time of each transport container and the tilting speed of each transport container, the range of temperature drop of the molten metal and the first molten iron until they are mixed can be adjusted, and from this, the temperature of the second molten iron can be adjusted to 1,350 to 1,500°C.

[0067] In this case, if the carbon (C) content of the second molten iron is less than 2% by weight, it may become difficult to adjust the nitrogen (N) content of the second molten steel produced from it to 30 ppm or less. Furthermore, if the carbon (C) content of the second molten iron is 4% by weight or more, the amount of first molten iron mixed in increases, leading to a problem of increased carbon emissions. In addition, if the temperature of the second molten iron deviates from the temperature range of 1,350 to 1,500°C, it may become difficult to operate the converter normally.

[0068] As shown in Figures 1 and 2(b), once the process of manufacturing the second molten iron is complete, the process of charging the second molten iron into a refining vessel (S140) is carried out. At this time, the refining vessel may be equipped with a converter, for example. For example, once the manufacturing of the second molten iron is completed during charging, the charging vessel containing the second molten iron may be subjected to KR treatment and then transported to the converter side, raised above the converter, and then tilted to receive the second molten iron into the converter through the converter's opening. Alternatively, scrap may be charged into the converter. At this time, the second molten iron and scrap may be charged into the converter so that the hot metal ratio (HMR) of the second molten iron is between 35% and 100%. Here, the molten iron ratio refers to the ratio of the amount of molten iron charged into the converter to the total amount charged, which is the sum of the amount of molten iron charged into the converter and the amount of scrap charged into the converter.

[0069] In the process of charging the second molten iron into the refining vessel (S140), the charging order of the second molten iron and the scrap can be changed in various ways. For example, the scrap may be charged first, followed by the second molten iron. Alternatively, the scrap may be charged first, followed by the second molten iron. Furthermore, the second molten iron and the scrap may be charged together. On the other hand, if the molten iron ratio of the second molten iron is to be 100%, only the second molten iron may be charged into the converter. In the process of charging the second molten iron into the refining vessel (S140), by charging the second molten iron so that the molten iron ratio is 55-100%, the second molten steel produced can be used as a high-grade steel, such as Hyper NO steel, HNO steel, MNO steel, LNO steel, EDDQ steel, S-EDDQ steel, DQ steel, DDQ steel, API steel, and AHSS steel, as described later.

[0070] On the other hand, before charging the second molten iron into the refining vessel, the second molten iron may be pre-treated using a KR (Kanvara reactor) (mechanically agitated desulfurization equipment) as needed, to adjust, for example, reduce, the components of silicon (Si), sulfur (S), and phosphorus (P) in the second molten iron.

[0071] Next, the process of producing the second molten steel (S150) is carried out. That is, a lance may be inserted into the furnace opening of the converter and placed at the top of the converter, and then oxygen (O) may be supplied into the lance. As a result, oxygen (O) can be blown from the lance into the second molten iron inside the converter, and refining, for example, oxygen blowing, can be carried out. As a result, the second molten iron can be produced as the second molten steel. At this time, a bottom-blowing nozzle may be used to blow bottom-blowing gas, for example argon gas, into the converter to stir the second molten iron, or the composition of the second molten steel may be adjusted. At this time, ferrosilicon (Fe-Si), for example, may be added to the converter as a heat booster.

[0072] Furthermore, in the process of producing the second molten steel (S150), the composition of the second molten steel may be adjusted so that the nitrogen (N) content is in the range of 22 to 30 ppm, the copper (Cu) content is in the range of 0.02 to 0.04% by weight, and the nickel (Ni) content is in the range of 0.01 to 0.04% by weight.

[0073] In accordance with the second process for producing molten steel (S150), one of the following types of steel can be produced: Hyper NO steel (Hyper grade Non-grain Oriented electrical steel), HNO steel (High grade Non-grain Oriented electrical steel), MNO steel (Middle grade Non-grain Oriented electrical steel), LNO steel (Low grade Non-grain Oriented electrical steel), EDDQ (Extra Deep Drawing Quality) steel, S-EDDQ (Super Extra Deep Drawing Quality) steel, DQ (Drawing Quality) steel, DDQ (Deep Drawing Quality) steel, API (American Petroleum Institute) steel, AHSS steel (Advanced High Strength steel), and ordinary steel. That is, the second molten steel produced according to the first embodiment of the present invention may include Hyper NO steel, HNO steel, MNO steel, LNO steel, EDDQ steel, S-EDDQ steel, DQ steel, DDQ steel, API steel, AHSS steel, and ordinary steel. Among these, Hyper NO steel, HNO steel, MNO steel, and LNO steel may be steels for electrical steel sheets. EDDQ steel and S-EDDQ steel may be steels for automobile exterior panels. Furthermore, DQ steel and DDQ steel may be steels for automobile interior panels. On the other hand, since the content of each component of the aforementioned steel types is known, a detailed explanation of these steel types will be omitted here.

[0074] On the other hand, in the process of producing the second molten steel (S150), an additional heat source may be added to the converter. In this case, the heat source may include Si-containing ferrous alloys and carbon. The heat source can be introduced into the converter before or during the blowing of the second molten iron.

[0075] Furthermore, once the production of the second batch of molten steel is complete, the second batch can be tapped from the converter. At this time, sampling of the second batch of molten steel may be performed before and after tapping, and the temperature of the second batch of molten steel may be measured. Alternatively, the tapped second batch of molten steel may be transported to the next process. In this case, the next process may include a casting process.

[0076] On the other hand, in the first embodiment of the present invention, by producing a mixed product using the first molten steel, the carbon dioxide emissions in the process of preparing the first molten iron, the process of preparing the first molten steel, and the process of producing the second molten steel can be reduced to a level lower than the baseline emissions.

[0077] More specifically, with a baseline emission level of 1, carbon dioxide emissions can be reduced to 0.25 in the processes of preparing the first molten iron, preparing the first molten steel, and manufacturing the second molten steel. In other words, carbon dioxide emissions can be reduced to 25% of the baseline emission level. Here, the baseline emission level may refer to the carbon dioxide emissions in the processes of preparing the first molten iron and manufacturing the second molten steel when the process of preparing the first molten steel is omitted and the first molten iron is charged into the converter instead of the second molten iron for refining. In this case, for example, the baseline emission level may be 1.90 to 1.95 ton CO2 / ton of carbon dioxide (CO2) in terms of carbon source units.

[0078] Furthermore, the resulting reduction in carbon dioxide emissions may be, for example, 0.5 to 1.90 ton CO2 / ton of carbon dioxide (CO2) per carbon source unit. In this case, the higher the proportion of the first molten steel used in the mixing process, that is, the greater the amount of the first molten steel produced, and the lower the amount of the first molten iron produced, the greater the reduction in carbon dioxide emissions in the processes of producing the first molten iron, the first molten steel, and the second molten steel.

[0079] In other words, through the process described above, in the first embodiment of the present invention, 0.5 to 1.90 tons of carbon dioxide (CO2) per carbon source can be emitted from the process of preparing the first molten iron (S110) to the process of producing the second molten steel (S150). That is, 0.5 to 1.90 tons of carbon dioxide (CO2) can be emitted until 1 ton of the second molten steel is produced. More preferably, 0.86 to 1.50 tons of carbon dioxide (CO2) per carbon source can be emitted. That is, preferably, 0.86 to 1.50 tons of carbon dioxide (CO2) can be emitted until 1 ton of the second molten steel is produced.

[0080] As described above, in the first embodiment of the present invention, a first molten iron and a first molten steel are mixed in a ratio (%) in the range of 20.3:79.7 to 98.6:1.4, the second molten iron produced by the mixing is charged into a refining vessel, and the second molten iron is refined to produce a second molten steel. This makes it possible to reduce the content of impurities caused by the first molten steel to a target level, and to produce a sufficient amount of high-quality second molten steel in which the content of important components such as carbon, copper, and nickel is controlled to desired levels, while reducing carbon emissions and achieving carbon neutrality.

[0081] The steelmaking method according to the first embodiment of the present invention will be described below with more specific examples.

[0082] First, the first molten iron is prepared. That is, the first molten iron is manufactured in a blast furnace. In this case, the first molten iron may contain, by total weight, more than 0 and 4.5% by weight or less of carbon (C), more than 0 and 0.5% by weight or less of silicon (Si), more than 0 and 0.3% by weight or less of manganese (Mn), more than 0 and 0.12% by weight or less of phosphorus (P), more than 0 and 0.015% by weight or less of sulfur (S), more than 0 and 0.06% by weight or less of titanium (Ti), more than 0 and 0.01% by weight or less of chromium (Cr), more than 0 and 0.01% by weight or less of vanadium (V), more than 0 and 0.015% by weight or less of nickel (Ni), more than 0 and 0.01% by weight or less of copper (Cu), more than 0 and 0.001% by weight or less of nitrogen (N), and the remainder may consist of iron (Fe). Furthermore, the temperature of the first molten iron can be adjusted within the range of 1,350 to 1,500°C. The values ​​presented herein are for illustrative purposes only and are not intended to limit the present invention.

[0083] Furthermore, a first batch of molten steel is prepared. That is, the first batch of molten steel is manufactured in an electric furnace. In this case, the first molten steel may contain, by total weight, more than 0 and 0.15% by weight or less of carbon (C), more than 0 and 0.04% by weight or less of silicon (Si), more than 0 and 0.045% by weight or less of manganese (Mn), more than 0 and 0.009% by weight or less of phosphorus (P), more than 0 and 0.023% by weight or less of sulfur (S), more than 0 and 0.001% by weight or less of titanium (Ti), more than 0 and 0.001% by weight or less of chromium (Cr), more than 0 and 0.043% by weight or less of vanadium (V), more than 0 and 0.039% by weight or less of nickel (Ni), more than 0 and 0.071% by weight or less of copper (Cu), and more than 0 and 0.004% by weight or less of nitrogen (N), with the remainder being iron (Fe). Furthermore, the oxygen (O) concentration of the first molten steel can be adjusted to 5-400 ppm. Also, the nitrogen (N) concentration of the first molten steel can be adjusted to 0.002-0.006% by weight. Furthermore, the temperature of the first molten steel can be adjusted to 1,580-1,700°C. In addition to these, after the production of the first molten steel, it can be tapped from the electric furnace, and a deoxidizing agent can be added to the tapped first molten steel to adjust the oxygen (O) concentration to 0-10 ppm. At this time, as with the production of the first molten iron, the values ​​presented for the first molten steel are for illustrative purposes only and are not intended to limit the present invention.

[0084] Once the first molten iron and the first molten steel are prepared, the first molten iron and the first molten steel are combined. For this purpose, a predetermined amount of the first molten iron is placed in a mixing cart, and a predetermined amount of the first molten steel is received in a ladle. The mixing cart containing the first molten iron and the ladle containing the first molten steel are then transported to the mixing area. At this time, the temperature drop range of the first molten iron may be greater than 0°C and 76°C or less. The temperature drop range of the first molten steel may be between 140°C and 170°C.

[0085] The primary mixing process is carried out in the mixing area. At this time, the first molten steel can be mixed with the first molten iron in the mixing truck by tilting the ladle or opening the opening at the bottom of the ladle and letting the first molten steel fall from the ladle into the mixing truck. Thus, the mixed product is manufactured in the mixing truck. At this time, the first molten iron and the first molten steel can be mixed in a first ratio in the range of 20:80 to 80:20. For example, the mixed product can be manufactured by mixing 200 tons of the first molten iron with 80 tons of the first molten steel, and the mixed product can be manufactured by mixing 80 tons of the first molten iron with 200 tons of the first molten steel. Furthermore, the mixed product can be manufactured by mixing 134 tons of the first molten iron with 146 tons of the first molten steel. Needless to say, a mixed product can be produced by mixing 100 tons of first molten iron with 40 tons of first molten steel, and a mixed product can be produced by mixing 40 tons of first molten iron with 100 tons of first molten steel. Furthermore, a mixed product can be produced by mixing 67 tons of first molten iron with 73 tons of first molten steel. Here, the mixed product can be produced in multiple machines, for example, two molten iron mixing machines, and the amount of mixed product produced in each machine may be the same within a margin of error.

[0086] At this time, two molten metal carts containing the mixed molten metal are moved to the loading area. Here, the temperature drop range of the mixed molten metal may be in the range of 45 to 73°C. At the same time, two molten metal carts containing the first molten iron are set up and moved to the loading area. At this time, the temperature drop range of the first molten iron may be greater than 0°C and 76°C or less. Through this process, a total of four molten metal carts are positioned in the loading area.

[0087] Then, a secondary mixing process is performed during charging. At this time, the secondary mixing process can be performed so that the first molten iron and the mixed material are mixed in a second ratio in the range of 7:93 to 93:7. To this end, the mixing cart containing the first molten iron and the mixing cart containing the mixed material are placed facing each other, and the charging ladle is positioned between them. At this time, each mixing cart is tilted to pour the first molten iron and the mixed material into the charging ladle, and the second molten iron is produced in the charging ladle. After the secondary mixing process is completed, the ladle containing the second molten iron is transported to the converter side. At this time, the temperature drop range of the second molten iron may be in the range of 71 to 85°C or lower.

[0088] At this time, by performing the primary and secondary mixing as described above, the second molten iron to be produced will ultimately be made by mixing the first molten iron and the first molten steel in a ratio (%) within the range of 20.3:79.7 to 98.6:1.4.

[0089] When the second molten iron reaches the location where the converter is installed, the second molten iron is poured into the converter. Scrap can also be added to the converter according to the molten iron ratio. At the time the second molten iron is poured into the converter, the second molten iron, by total weight, contains: carbon (C) at 1.9% or more and 4.5% or less; silicon (Si) at 0% or more and 0.252% or less; manganese (Mn) at 0% or more and 0.173% or less; phosphorus (P) at 0% or more and 0.065% or less; sulfur (S) at 0% or more and 0.019% or less; and titanium (Ti) at 0% or less. It may contain more than 0 and 0.031% by weight or less of chromium (Cr), more than 0 and 0.027% by weight or less of vanadium (V), more than 0 and 0.008% by weight or less of nickel (Ni), more than 0 and 0.025% by weight or less of copper (Cu), more than 0 and 0.036% by weight or less of nitrogen (N) in amounts of 0.002% to 0.01% by weight, with the remainder being iron (Fe). Needless to say, the values ​​presented for the second molten iron are for the purpose of explaining the first embodiment and are not intended to limit the present invention.

[0090] Then, the second molten iron is refined in a converter to produce a second molten steel. In this case, as a comparative example, under different conditions from the experimental example below, for example, with a molten iron ratio of 47.9%, the second molten steel was put into the converter together with scrap, and a heat source was added to perform refining. The second molten steel produced from this process can be used as, for example, MNO steel, LNO steel, DQ steel, DDQ steel, API steel, AHSS steel, and ordinary steel, but it does not meet the requirements for Hyper NO steel, HNO steel, EDDQ steel, and S-EDDQ steel. This is thought to be because, during charging into the converter, the molten iron ratio decreased compared to the experimental example below, leading to an increase in the amount of scrap added. As a result, the second molten steel produced from the second molten iron was adjusted to deviate from the range of 22-30 ppm for nitrogen (N), 0.02-0.04 wt% for copper (Cu), and 0.01-0.04 wt% for nickel (Ni).

[0091] Furthermore, as an experimental example, a second molten steel was produced by changing the molten iron ratio, charging temperature, and heat source of the second molten iron according to the conditions shown in Table 1 below, and the second molten steel was produced according to each case. Examples of the types of steel that can be used with the second molten steel produced are also listed in Table 1 below.

[0092] [Table 1]

[0093] The experimental example shown in Table 1 corresponds to the first embodiment of the present invention. Referring to this, the molten iron ratios were set to 56.1% and 56.4%, respectively, and the temperature was set to 1,350-1,500°C. The second molten steel was then fed into the converter along with scrap, and the temperature of the heat source was set to 1,458°C for refining. The second molten steel produced from this can be used in various applications as Hyper NO steel, HNO steel, MNO steel, LNO steel, EDDQ steel, S-EDDQ steel, DQ steel, DDQ steel, API steel, AHSS steel, and ordinary steel. This is thought to be because the second molten steel produced from the second molten iron had its nitrogen (N) content adjusted to the range of 22-30 ppm, its copper (Cu) content to the range of 0.02-0.04 wt%, and its nickel (Ni) content to the range of 0.01-0.04 wt%. From this, it can be seen that high-grade steel can be produced when the steelmaking process according to the first embodiment is carried out.

[0094] Thus, according to the first embodiment of the present invention, a first molten iron is prepared, a first molten steel having an even lower carbon (C) content than the first molten iron is prepared, and the first molten iron and the first molten steel are mixed in a first ratio in the range of 160:80 to 220:20 to produce a second molten iron. Furthermore, by refining the second molten iron to produce a second molten steel, the nitrogen (N) content of the second molten steel can be adjusted to a range usable for high-grade steel, while reducing the amount of first molten iron used, thereby reducing the total amount of carbon generated in the entire process.

[0095] As described above, the first embodiment of the present invention has been explained, but the present invention can be configured in a wide variety of ways, including the second to fourth embodiments described below.

[0096] Figure 4 is a procedure diagram showing a steelmaking method according to a second embodiment of the present invention.

[0097] In the first embodiment of the present invention described above, the second molten iron is produced by mixing the first molten iron and the first molten steel in a first ratio. However, the present invention is not limited thereto, and in the second embodiment of the present invention described below, the first molten iron and the first molten steel may be mixed to produce a mixed product, and the second molten iron may be produced by mixing the first molten iron and the mixed product. In this case, the mixing ratios can be changed in various ways.

[0098] The steelmaking method according to the second embodiment of the present invention will be described below with reference to Figure 4. In this description, the second embodiment will be explained in detail, with an emphasis on features that distinguish it from the first embodiment of the present invention described above, and any content that overlaps with the description of the first embodiment of the present invention described above will be omitted or briefly explained.

[0099] As shown in Figure 4, the steelmaking method according to the second embodiment of the present invention includes the steps of: preparing a first molten iron (S210); preparing a first molten steel having an even lower carbon (C) content than the first molten iron (S220); mixing the first molten iron and the first molten steel to produce a mixed product (S230); mixing the first molten iron and the mixed product to produce a second molten iron (S240); charging the second molten iron into a refining vessel (S250); and refining the second molten iron to produce a second molten steel (S260).

[0100] At this time, the process of preparing the first molten iron (S210), the process of preparing the first molten steel having an even lower carbon (C) content than the first molten iron (S220), the process of charging the second molten iron into the refining vessel (S250), and the process of refining the second molten iron to produce the second molten steel (S260) can be the same or similar in configuration and method as the process of preparing the first molten iron (S110), the process of preparing the first molten steel having an even lower carbon (C) content than the first molten iron (S120), the process of charging the second molten iron produced by mixing into the refining vessel (S140), and the process of refining the second molten iron to produce the second molten steel (S150) in the first embodiment of the present invention described above, so an explanation of these will be omitted.

[0101] In the process of mixing the first molten iron and the first molten steel to produce a mixed product (S230), the first molten iron can be contained in multiple first transport containers, the first molten steel in a second transport container, and the second transport container can be placed above a portion of the multiple first transport containers. The first molten steel can then be poured from the second transport container into a portion of the first transport containers, and the mixed product can be formed inside the portion of the first transport containers.

[0102] At this time, while the first molten steel is being poured in, the weight of the second transport container can be measured using a weight measuring device, such as a load cell. The control unit receives the weight from the load cell and can determine the amount of the first molten steel to be discharged. Based on the determined discharge amount, the control unit can control the operation of the tilter that tilts the second transport container to adjust its tilt angle. For example, the operation of the tilter can be controlled so that the tilt angle of the second transport container decreases as the discharge amount approaches a standard discharge amount. This allows for precise control of the amount of the first molten steel being poured in. Similarly, the control unit can control the operation of the slide gate that opens and closes the opening at the bottom of the second transport container to adjust the opening of the slide gate according to the amount of the first molten steel being discharged.

[0103] In the process of producing a second molten iron by mixing the first molten iron with a mixed material (S240), a charging container is provided, and of the multiple first transport containers, the first transport container containing the mixed material is placed above the charging container, and of the multiple first transport containers, the first transport container containing the first molten iron is placed above the charging container, and the first transport container containing the first molten iron and the first transport container containing the mixed material are tilted to inject the mixed material and the first molten iron into the charging container, thereby forming the second molten iron inside the charging container. At this time, the first molten iron and the mixed material may be mixed in a predetermined ratio. Alternatively, the mixing ratio of the first molten iron and the mixed material when producing the second molten iron may be determined according to the mixing ratio of the first molten iron and the first molten steel when producing the mixed material. In other words, the final mixing ratio of the first molten iron and the first molten steel for producing the second molten iron may be set as a predetermined ratio, and the mixing ratio of the first molten iron and the first molten steel at the time of producing the mixed product may be obtained from the process of mixing the first molten iron and the first molten steel to produce the mixed product (S230). For this reason, the mixing ratio of the first molten iron and the first molten steel at the time of producing the mixed product is determined according to the mixing ratio of the first molten iron and the first molten steel at the time of producing the mixed product, so that the final mixing ratio reaches the predetermined ratio. On the other hand, the configurations of the steelmaking methods of the first and second embodiments of the present invention described above can be changed by combining them with each other.

[0104] On the other hand, according to a third embodiment of the present invention, in the process of producing a molten metal by primary molten metal mixing and the process of producing a second molten iron by secondary molten metal mixing, the molten metal mixing can be carried out in a refining vessel, for example, a converter. That is, the first molten iron and the first molten steel can be charged into a converter and mixed together to produce a molten metal, and the first molten iron can be charged into the converter from which the molten metal mixing has been produced to produce the second molten iron. As a result, intermediate processes such as transportation are omitted until the materials are charged into the converter, and a drop in temperature can be suppressed or prevented. From this temperature perspective, the amount of power required for heating can be reduced by lowering the tapping temperature from the electric furnace.

[0105] The following describes a casting method according to a fourth embodiment of the present invention. The casting method according to the fourth embodiment of the present invention may include a process of preparing steel manufactured by the steelmaking methods according to the first to third embodiments of the present invention described above, and a process of casting the prepared steel.

[0106] First, steel produced by the steelmaking method according to the first to third embodiments described above is prepared. For example, according to the steelmaking method according to the first to third embodiments, the steel produced in the converter is tapped from the converter into a ladle. At this time, the ladle is transported to a casting facility, where the steel is cast to produce semi-finished products. At this time, the semi-finished products may be various, such as slabs, thin slabs, coils, billets, and blooms. The configuration and method of the casting equipment for casting these may also vary.

[0107] The embodiments of the present invention described above are for illustrative purposes only and not for limiting purposes. It should be noted that the configurations and methods disclosed in the embodiments of the present invention can be combined and intersected to form various shapes, and these modified embodiments can also be considered to fall within the scope of the present invention. That is, the present invention can be embodied in various different shapes within the scope of the claims and equivalent technical ideas, and practitioners in the art to which the present invention pertains should understand that various embodiments are possible within the scope of the technical ideas of the present invention.

Claims

1. The process of preparing the first molten iron, A process for preparing a first molten steel having an even lower carbon (C) content than the first molten iron, The process of mixing the first molten iron and the first molten steel in a ratio (%) within the range of 20.3:79.7 to 98.6:1.4, The process of charging the second molten iron produced by the aforementioned mixing of molten metals into a refining vessel, The process of refining the second molten iron to produce a second molten steel, A steelmaking method characterized by including the following:

2. The aforementioned mixing process is carried out in stages over multiple stages, and the mixed product produced in a previous stage is used in the next stage of mixing. The first molten steel is mixed only on the first batch. The steelmaking method according to claim 1, characterized in that the first molten iron is mixed in every batch.

3. The aforementioned process of combining the hot water is, A process of mixing the first molten iron and the first molten steel in a first ratio in the range of 20:80 to 80:20 to produce a mixed product, A process for producing a second molten iron by mixing the first molten iron and the mixed material in a second ratio in the range of 7:93 to 93:7, The steelmaking method according to claim 1, characterized by including the following:

4. The process of preparing the first molten iron, A process for preparing a first molten steel having an even lower carbon (C) content than the first molten iron, A process of mixing the first molten iron and the first molten steel to produce a mixed product, A process of producing a second molten iron by combining the first molten iron and the mixed molten metal, The process of charging the second molten iron into the refining vessel, The process of refining the second molten iron to produce a second molten steel, A steelmaking method characterized by including the following:

5. The first molten iron includes blast furnace molten iron produced in a blast furnace. The steelmaking method according to any one of claims 1 to 4, characterized in that the first molten steel includes electric furnace molten steel produced in an electric furnace.

6. The process of preparing the first molten iron is as follows: The steelmaking method according to claim 5, characterized by including a step of producing the first molten iron in a blast furnace such that the carbon (C) content is 4.0 to 4.5% by weight.

7. The steelmaking method according to claim 6, characterized in that the temperature of the first molten iron is adjusted to 1,350 to 1,500°C while the first molten iron is being manufactured.

8. The process of preparing the first molten steel is as follows: A process for producing the first molten steel in an electric furnace such that the carbon (C) content is 0.04 to 1.0% by weight and the oxygen (O) concentration is 5 to 400 ppm, The process involves adding a deoxidizing agent to the first molten steel to adjust the oxygen (O) concentration to 0-10 ppm, The steelmaking method according to claim 5, characterized by including the following:

9. The steelmaking method according to claim 8, characterized in that the temperature of the first molten steel is adjusted to 1,580 to 1,700°C while the first molten steel is being produced.

10. The process for producing the aforementioned mixed molten metal is as follows: A process of placing the first molten iron into a plurality of first transport containers having openings at the top that can be opened and closed, The process of placing the first molten steel into a second transport container with an open top, The process of placing the second transport container on top of a portion of the first transport containers, A process of tilting the second transport container and pouring the first molten steel from the second transport container into a portion of the first transport containers, The process of forming the molten metal inside a portion of the first transport containers, The steelmaking method according to claim 3 or 4, characterized by including the following:

11. The process for producing the aforementioned mixed molten metal is as follows: A process of placing the first molten iron into a plurality of first transport containers having openings at the top that can be opened and closed, A process of placing the first molten steel into a second transport container having multiple openings at the bottom that can be opened and closed, The process of placing the second transport container on top of a portion of the first transport containers, The process of opening the lower opening of the second transport container and pouring the first molten steel from the second transport container into a portion of the first transport containers, The process of forming the molten metal inside a portion of the first transport containers, The steelmaking method according to claim 3 or 4, characterized by including the following:

12. The steelmaking method according to claim 3 or 4, characterized in that, in the process of manufacturing the molten metal, the temperature of the molten metal is adjusted to 1,430 to 1,650°C.

13. The process for producing the second molten iron is as follows: The process of providing a charging container with an open top, A process of arranging, among a plurality of first transport containers having an opening at the top that can be opened and closed, the first transport container containing the mixed molten material above the charging container, A process of positioning, among a plurality of first transport containers, the first transport container containing the first molten iron above the charging container, The process of tilting the first transport container containing the first molten iron and the first transport container containing the mixed molten metal to pour the mixed molten metal and the remainder of the first molten iron into the charging container, The process of forming the second molten iron inside the charging container, The steelmaking method according to claim 3 or 4, characterized by including the following:

14. The process for producing the second molten iron is as follows: A process for adjusting the carbon (C) content of the second molten iron to 2% by weight or more and less than 4% by weight, The process of adjusting the temperature of the second molten iron to 1,350 to 1,500°C, The steelmaking method according to claim 3 or 4, characterized by including the following:

15. The process of charging the second molten iron into the refining vessel is as follows: The steelmaking method according to claim 5, characterized in that it includes a step of charging the second molten iron into the refining vessel such that the hot metal ratio (HMR) of the second molten iron is 35 to 100%.

16. The process for producing the second molten steel is as follows: The process of blowing bottom-blowing gas into the refining vessel, A process of adjusting the composition of the second molten steel so that the nitrogen (N) content is in the range of 22 to 30 ppm, the copper (Cu) content is in the range of 0.02 to 0.04% by weight, and the nickel (Ni) content is in the range of 0.01 to 0.04% by weight, The steelmaking method according to claim 15, characterized by including the following:

17. The steelmaking method according to claim 15, characterized in that the second molten steel includes Hyper NO steel, HNO steel, MNO steel, LNO steel, EDDQ steel, S-EDDQ steel, DQ steel, DDQ steel, API steel, AHSS steel, and ordinary steel.

18. The steelmaking method according to claim 5, characterized in that, with a baseline emission of carbon dioxide of 1, the emission of carbon dioxide is reduced to 0.25 in the process of preparing the first molten iron, the process of preparing the first molten steel, and the process of manufacturing the second molten steel.

19. A process for preparing steel produced by the steelmaking method described in any one of claims 1 to 4, The process of casting the prepared steel, A casting method characterized by including the following:

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