Method for manufacturing steel product

Abstract

According to the present disclosure, a method for manufacturing a steel product comprises the steps of: preparing a molten metal using an electric arc furnace; adjusting the composition of the molten metal; continuously casting the composition-adjusted molten metal to produce a slab; and rolling the slab to manufacture a steel product, wherein the step of preparing the molten metal using the electric arc furnace comprises the steps of: melting scrap fed into the furnace by energizing a plurality of electrodes; and reducing the amount of nitrogen incorporated into the molten metal by blowing a reducing or inert gas toward the scrap and / or the molten metal made from the scrap while energizing the plurality of electrodes.

Description

Steel product manufacturing method

[0001] The present disclosure relates to a method for manufacturing steel products through an electric furnace.

[0002] Recently, carbon-neutral technologies designed to minimize carbon dioxide emissions are being actively developed to address the climate change crisis. Accordingly, the steel industry is researching and developing hydrogen reduction steelmaking process technologies that use hydrogen instead of fossil fuels to produce direct reduced iron, which is then utilized to manufacture steel.

[0003] If hydrogen reduction steelmaking process technology is commercialized, it can replace not only blast furnace operations, which generate large amounts of carbon dioxide, but also converter operations by utilizing electric furnace operations.

[0004] An electric furnace is a facility that melts scrap by converting electrical energy into thermal energy; it supplies current to electrode rods to generate an arc between them and the raw materials, and uses the arc heat to melt raw materials such as scrap and ferroalloys to produce molten metal.

[0005] Although electric furnaces are environmentally friendly, the high energy of the arc causes N2 in the atmosphere to separate into N+N, and N is introduced into the molten metal by the airflow created with the arc, which increases the nitrogen content of the molten metal and may cause difficulties in manufacturing steel products such as electrical steel sheets.

[0006] Therefore, there is a need to develop a manufacturing method that can lower the nitrogen content during the production of molten metal in electric furnace operations.

[0007] One aspect of the present disclosure aims to provide a method for lowering the nitrogen content of molten metal produced in an electric furnace in the manufacture of steel products.

[0008] The technical problems to be solved in this document are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which this invention belongs from the description below.

[0009] According to an embodiment of the present disclosure, a method for manufacturing a steel product comprises the steps of: producing a molten metal using an arc furnace; controlling the composition of the molten metal; continuously casting the molten metal with controlled composition to produce a slab; and rolling the slab to produce a steel product. The step of producing a molten metal using an arc furnace comprises: a step of melting scrap metal charged into the furnace by passing current through a plurality of electrode rods; and a step of reducing the amount of nitrogen mixed into the molten metal by blowing a reducing or inert gas toward the scrap metal and / or the molten metal made from the scrap metal while passing current through the plurality of electrode rods.

[0010] In addition, the step of blowing a reducing or inert gas toward the molten metal made from the scrap metal includes a gas injection unit comprising a nozzle for injecting the reducing or inert gas and a gas pipe through which the reducing or inert gas flows, and the method of arranging the nozzle and the plurality of electrode rods such that the distance from the nozzle to the scrap metal is greater than the distance from any one of the plurality of electrode rods to the scrap metal.

[0011] The step of blowing a reducing or inert gas toward the molten metal produced from the above scrap metal includes a gas injection unit comprising a nozzle for injecting the reducing or inert gas and a gas pipe through which the reducing or inert gas flows, and the plurality of electrode rods and the nozzle include a method of penetrating into the arc furnace through a loop that opens and closes the upper part of the furnace body of the arc furnace.

[0012] The method includes a pipe that penetrates the loop through a pipe hole, a plurality of electrode rods that penetrate the loop through a plurality of electrode holes, and the pipe hole and the plurality of electrode holes being provided in the loop.

[0013] The method includes a distance from the rim forming the above-mentioned pipe hole to the rim forming one of the plurality of electrode holes that matches the distance to the rim forming one of the other electrode holes.

[0014] The method includes arranging the rim of the above-mentioned pipe hole to be surrounded by the plurality of electrode rods.

[0015] The above pipe holes are provided in the same number as the plurality of electrode holes, and one of the plurality of pipe holes is positioned adjacent to at least two of the plurality of electrode rods and positioned far from one or more other electrode rods.

[0016] The above nozzle forms a gas region at the bottom of the nozzle by blowing a reducing or inert gas toward the scrap metal and / or the molten metal, and the gas region includes a method of surrounding at least a portion of the outer surface of a plurality of electrode rods.

[0017] The above gas region includes a method of wrapping the ends of the plurality of electrode rods.

[0018] According to an embodiment of the present disclosure, an arc furnace comprises a loop including one or more piping holes and a plurality of electrode holes, one or more gas injection units including a nozzle penetrating the loop through the one or more piping holes, a plurality of electrode rods penetrating the loop through the plurality of electrode holes, and one or more controllers that supply a reducing gas or an inert gas into the arc furnace through the nozzle or conduct current to the plurality of electrode rods, and the controller controls the arc furnace to reduce the amount of nitrogen mixed into the molten metal by blowing a reducing gas or an inert gas toward the scrap metal and / or the molten metal made from the scrap metal while conducting current to the plurality of electrode rods.

[0019] According to an embodiment of the present disclosure, a reducing or inert gas is injected into the scrap metal or molten metal inside the electric furnace body to prevent the decomposition reaction of N2 in the atmosphere by the arc generated between the electrode rod and the scrap metal.

[0020] FIG. 1 is a flowchart schematically illustrating a method for manufacturing a steel product according to one embodiment of the present disclosure.

[0021] FIG. 2 is a schematic diagram illustrating an electrode furnace facility according to one embodiment of the present disclosure.

[0022] FIG. 3 is a schematic cross-sectional view of a part of an electric furnace according to one embodiment of the present disclosure.

[0023] FIG. 4 is a schematic diagram illustrating the arrangement of electrode rods and gas injection parts of an electric furnace according to one embodiment of the present disclosure.

[0024] FIG. 5 is a schematic diagram illustrating the arrangement of electrode rods and gas injection parts of an electric furnace according to another embodiment of the present disclosure.

[0025] The embodiments described in this specification are merely the most preferred embodiments of the present invention and do not represent all technical concepts of the present invention; therefore, it should be understood that various equivalents or modifications that can replace them at the time of filing this application are also included within the scope of the rights of the present invention.

[0026] Additionally, the same reference numerals or symbols presented in each drawing of the present disclosure represent parts or components that perform substantially the same function.

[0027] Furthermore, the terms used in this disclosure are for describing embodiments and are not intended to limit or restrict the disclosure. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this disclosure, terms such as “comprising” or “having” are intended to specify the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the disclosure, and do not preclude the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0028] Additionally, terms including ordinal numbers, such as “first,” “second,” etc., used in this disclosure may be used to describe various components, but said components are not limited by said terms, and said terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of this disclosure, the first component may be named the second component, and similarly, the second component may be named the first component. The term “and / or” includes a combination of a plurality of related described items or any of a plurality of related described items.

[0029] Furthermore, in this disclosure, the meaning of "identical" includes items that are similar in attributes or similar within a certain range. Additionally, "identical" means "substantially identical." The meaning of "substantially identical" should be understood as including within the scope of "identical" numerical values ​​that fall within the margin of error in manufacturing or differences that do not hold significance relative to a reference value.

[0030] In addition, terms such as "~part," "~unit," "~block," "~part," and "~module" may refer to a unit that processes at least one function or operation. For example, the above terms may refer to at least one piece of hardware such as an FPGA (field-programmable gate array) or ASIC (application specific integrated circuit), at least one piece of software stored in memory, or at least one process processed by a processor.

[0031] Singular expressions include plural expressions unless there is an obvious exception in the context.

[0032] Meanwhile, terms such as “front,” “rear,” “left,” and “right” used in the following description are defined based on the drawings, and the shape and position of each component are not limited by these terms.

[0033] Hereinafter, preferred embodiments according to the present disclosure will be described in detail with reference to the attached drawings.

[0034] FIG. 1 is a flowchart schematically illustrating a method for manufacturing a steel product according to one embodiment of the present disclosure, and FIG. 2 is a diagram schematically illustrating an electric furnace facility according to one embodiment of the present disclosure.

[0035] As shown in Fig. 1, in the process of manufacturing a steel product (P), scrap metal (scrap, F) is first prepared and fed into an electric furnace (100).

[0036] In an electric furnace (100), scrap metal (F) can be melted by arc heat and the molten metal (L) can be refined. (S100)

[0037] The molten metal (L) formed from the electric furnace (100) is moved by a ladle and its composition can be adjusted through a refining process (S110). In the refining process, some components are further removed to homogenize the composition and unnecessary impurities can be removed to manufacture a steel product (P).

[0038] The molten metal with controlled composition can be prepared to form a slab through a casting process. (S120) In the casting process, the molten metal with controlled composition can be continuously cast to produce a slab.

[0039] The slab can be rolled to be manufactured into a steel product (P). (S130) Additional processes, such as heating the slab to a temperature suitable for rolling, can be performed so that an efficient rolling process can proceed.

[0040] As shown in FIG. 2, the electric furnace (100) includes a furnace body (110) in the shape of a container with an open top that can accommodate a certain amount of raw material, and a roof (120) that covers the open top of the furnace body (110).

[0041] The electric furnace (100) is typically provided in the shape of a rod and includes an electrode rod (130) made of artificial graphite. By supplying current to the electrode rod (130), an arc is generated between the raw material and the electric furnace, and the raw material, such as scrap metal (F), is melted by the arc heat to produce a molten metal (L).

[0042] The electrode rod (130) can be inserted into the interior of the furnace body (110) through the electrode hole provided in the loop (120).

[0043] The electric furnace (100) may include a sensing unit for detecting the height of the electrode material filled in the furnace body (110). The electric furnace (100) may include a power supply unit connected to the electrode rod (130) so as to supply power to the electrode rod (130).

[0044] The electric furnace (100) may include a raw material supply unit configured to allow scrap metal (F) to be fed into the furnace body (110).

[0045] The furnace body (110) may have a cylindrical shape with an open top. For example, the furnace body (110) may have a cylindrical shape, in which case the furnace body (110) may have a cylindrical processing space. Alternatively, the furnace body (110) may have a roughly rectangular shape, in which case the furnace body (110) may have a rectangular internal space. In addition, the furnace body (110) may have various cylindrical shapes with an open top. The furnace body (110) may include an outer wall (110b) made of steel shell or metal and an inner wall (110b) constructed of refractory material on the inside of the outer wall.

[0046] The furnace body (110) may include a first discharge port (111) capable of discharging molten metal (L).

[0047] The furnace body (110) may include a second discharge port (112) capable of discharging slag (S) floating on the upper part of the molten metal (L).

[0048] Each of the first and second discharge ports (111, 112) may be provided on the side wall of the furnace body (110) or on the bottom of the furnace body (110). For example, as shown in FIG. 1, the first discharge port (111) may be provided on one side wall of the furnace body (110), and the second discharge port (112) may be provided on the other side wall of the furnace body (110). Of course, the first and second discharge ports (111, 112) are not limited to the locations described above and may be provided at various locations capable of discharging molten metal (L) and slag (S) to the outside.

[0049] A container (10, 20) capable of accommodating molten metal (L) and slag (S), respectively, may be placed on the outside of the furnace body (110).

[0050] A first container (10) may be placed below the first discharge port (111) on the outside of the furnace body (110), and a second container (20) may be placed below the second discharge port (112).

[0051] For example, the first container (10) in which the molten metal (L) discharged from the first outlet (111) is received can be a ladle.

[0052] Scrap metal (F) may include direct reduced iron (DRI). Scrap metal (F) is not limited to direct reduced iron and may include scrap with a higher iron (Fe) content compared to the direct reduced iron.

[0053] The electrode rod (130) is partially inserted and positioned in the processing space of the furnace body (110) to generate heat. The electrode rod (130) receives power to generate heat and serves to supply heat to the scrap metal (F) loaded into the furnace body (110). Here, power may refer to voltage or current, and the heat generated from the electrode rod (130) may be resistance heat or arc heat. The resistance heat or arc heat generated from the electrode part (200) melts or dissolves the scrap metal (F), thereby producing molten metal (L), such as molten iron.

[0054] The electrode rod (130) may be provided with a plurality of electrode rods spaced apart from each other.

[0055] For example, the electrode rod (130) may include three electrode rods (130a, 130b, 130c). The three electrode rods (130a, 130b, 130c) may be arranged in a triangular shape to surround the center (122) of the loop (120). (See FIG. 4)

[0056] The length (d2) of the distance (DL2) between each electrode rod (130a, 130b, 130c) may be the same for each. Each electrode rod (130a, 130b, 130c) may be arranged with a length (d1) of the same spacing distance (DL1) from the center (131) of each electrode rod (130a, 130b, 130c). (See FIG. 4) However, not limited thereto, the electrode rod (130) may include six electrode rods arranged in a row.

[0057] Three electrode rods (130a, 130b, 130c) can be arranged to penetrate vertically through a loop (120) covering a furnace body (110) having a roughly cylindrical shape.

[0058] The loop (120) may include an electrode hole (123) through which an electrode rod (130) passes. The electrode hole (123) may be provided in a number corresponding to a plurality of electrode rods (130a, 130b, 130c). For example, the electrode hole (123) of an electric furnace (100) including three electrode rods (130a, 130b, 130c) may be provided in three.

[0059] Three electrode rods (130a, 130b, 130c) may be provided to penetrate the electrode hole (123) corresponding to each electrode rod (130a, 130b, 130c) in the vertical direction.

[0060] The end (132) of each electrode rod (130a, 130b, 130c) can be arranged to be placed inside the furnace body (110) through the electrode hole (123).

[0061] The end (132) of the electrode rod (130) can be defined as a part of the electrode rod (130) extending from the bottom of the electrode rod (130) upward in the vertical direction. The end (132) may include the bottom of the electrode rod (130), and the area or height of the end (132) is not limited to numerical values.

[0062] The electric furnace (100) may include a lifting section capable of moving a plurality of electrode rods (130) in an up-and-down direction.

[0063] The lifting unit may be configured to move a plurality of electrode rods in the up-and-down direction as a whole. The lifting unit may also be configured to move each electrode rod in the up-and-down direction.

[0064] The lifting unit can adjust the distance between the bottom of the electrode rod (130) and the scrap metal (F) or slag (S) inside the furnace body (110). When the electrode rod (130) is immersed in the slag (S) generated during the melting of the scrap metal (F) by the lifting unit, resistance heat can be generated by the slag (S), and when the electrode rod (130) is separated from the scrap metal (F) or slag (S) by the lifting unit, arc heat can be generated between the electrode rod (130) and the raw material (M) or slag (S).

[0065] The lifting section may be configured to lower the electrode rod (130) so that the electrode rod (130) and the raw material maintain a constant distance during the operation of the electric furnace (100), thereby preventing the gap between the electrode rod (130) and the raw material (F) from widening as the scrap metal (F) melts. This is because the electrode rod (130) and the raw material inside the furnace body (110) must be maintained at a constant distance from each other so that an arc can be generated to melt the raw material.

[0066] When the operation of melting scrap metal (F) by arc heat is carried out, as the arc is generated, the N2 in the atmosphere remaining between the electrode rod (130) and the scrap metal (F) is separated into N+N due to the high energy, and N (nitrogen) may be generated in the atmosphere.

[0067] N generated by the arc heat can be introduced into the molten metal (L) by the airflow created along with the arc.

[0068] Accordingly, the N content of the molten metal (L) increases, and due to the high N concentration, difficulties may arise in producing steel products (P), such as automotive steel sheets or electrical steel sheets, which require low nitrogen, when steel products (P) are manufactured through subsequent processes.

[0069] To prevent this, an electric furnace (100) according to one embodiment of the present invention may include a gas injection unit (140) that injects an inert gas or a reducing gas (hereinafter, gas (G)) in the direction of scrap metal (F) and / or molten metal (L) to prevent N from entering the molten metal (L) when an arc occurs.

[0070] The following describes the gas injection unit (140) in detail.

[0071] FIG. 3 is a schematic diagram illustrating a cross-section of a part of an electric furnace according to one embodiment of the present disclosure, and FIG. 4 is a schematic diagram illustrating the arrangement of an electrode rod and a gas injection part of an electric furnace according to one embodiment of the present disclosure.

[0072] As illustrated in FIG. 3, as the gas injection unit (140) injects gas (G), a gas layer (Z) is formed between the end (132) of the electrode rod (130) and the scrap metal (F) and / or molten metal (L), and when an arc is generated by the gas layer (Z), it is possible to prevent the N2 in the atmosphere between the end (132) of the electrode rod (130) and the scrap metal (F) and / or molten metal (L) from reacting to separate into nitrogen.

[0073] That is, a gas injection unit (140) is provided to inject gas (G) toward scrap metal (F) and / or molten metal (L) so that a gas layer (Z) is formed on top of the scrap metal (F) and / or molten metal (L), and the gas layer (Z) can prevent nitrogen from forming on top of the scrap metal (F) and / or molten metal (L) and thereby limit the inflow of nitrogen into the molten metal (L).

[0074] The gas layer (Z) is a region where gas (G) remains in the atmosphere and can also be named a gas region (Z). Depending on the type of gas (G), it can also be named an inert region or a reducing region.

[0075] The gas injection unit (140) may include a gas pipe (141) through which gas (G) flows and a nozzle (142) through which gas is injected.

[0076] The nozzle (142) may be positioned toward the scrap metal (F) and / or molten metal (L) so that the gas (G) is sprayed toward the scrap metal (F) and / or molten metal (L).

[0077] Gas (G) sprayed toward the scrap metal (F) and / or molten metal (L) may fall by gravity and form a layer on the scrap metal (F) and / or molten metal (L).

[0078] The gas (G) injected through the nozzle (142) can be arranged to be injected toward at least a portion of the ends (132a, 132b, 132c) of each of the three electrode rods (130a, 130b, 130c).

[0079] The nozzle (142) sprays gas (G) downward, and the sprayed gas (G) may be arranged to collide with at least a portion of the ends (132a, 132b, 132c) of each of the three electrode rods (130a, 130b, 130c) as it flows downward.

[0080] The injected gas (G) forms a gas layer (Z), and the gas layer (Z) can be formed to surround at least a portion of each end (132a, 132b, 132c) of the three electrode rods (130a, 130b, 130c).

[0081] The gas layer (Z) may be formed to extend from the scrap metal (F) and / or molten metal (L) to an area that encloses at least a portion of each end (132a, 132b, 132c) of the three electrode rods (130a, 130b, 130c). This is to form the gas layer (Z) in an area where N2 is likely to decompose into nitrogen.

[0082] The distance from the nozzle (142) to the scrap metal (F) can be arranged to be longer than the distance from any one of the ends (132a, 132b, 132c) of the three electrode rods (130a, 130b, 130c) to the scrap metal (F).

[0083] The height of the point where gas (G) is sprayed from the nozzle (142) can be arranged to be higher than the height of each end (132a, 132b, 132c) of the three electrode rods (130a, 130b, 130c).

[0084] This is so that the gas (G) sprayed from the nozzle (142) reaches at least a portion of the ends (132a, 132b, 132c) of each of the three electrode rods (130a, 130b, 130c) during the flow.

[0085] In addition, when the gas layer (Z) is formed, the gas layer (Z) is formed up to an area that covers at least a portion of each end (132a, 132b, 132c) of the three electrode rods (130a, 130b, 130c).

[0086] The gas injection unit (140) and the electrode rod (130) can be arranged to penetrate the loop (120).

[0087] The gas injection unit (140) and the electrode rod (130) can be arranged so that the nozzle (142) and the end (132) of the electrode rod (130) are positioned inside the furnace body (110) by penetrating the upper surface (121) of the loop (120).

[0088] The loop (120) may include an electrode hole (123) through which an electrode rod (130) passes and a pipe hole (124) through which a gas pipe (141) of a gas injection unit (140) passes.

[0089] The electric furnace (100) may include an electrode rod sleeve (133) that is positioned on the upper surface (121) of the loop (120) and is provided to cover an electrode hole (123) through which an electrode rod (130) passes on the upper surface (121) of the loop (120).

[0090] The electrode rod sleeve (133) includes a hollow corresponding to the electrode hole (123), and the inner surface forming the hollow may be arranged to face the outer surface of the electrode rod (130).

[0091] The electrode rod sleeve (133) may be provided to cover at least a portion of the outer surface of the electrode rod (130) located above the electrode hole (123) in the electrode rod (130).

[0092] The electrode rod sleeve (133) can be made of a material that is fire-resistant to temperatures of approximately 1500 degrees or higher.

[0093] The electrode rod sleeve (133) can be positioned on the upper side of the loop (120) such that the center of the hollow and the center of the electrode hole (123) are positioned at a location that corresponds approximately in the vertical direction.

[0094] The electrode rod sleeves (133) may be provided in a number corresponding to the number of electrode rods (130). An electric furnace (100) according to an embodiment of the present invention may include three electrode rod sleeves (133) corresponding to three electrode rods (130a, 130b, 130c).

[0095] The electric furnace (100) may include a pipe sleeve (144) that is positioned on the upper surface (121) of the roof (120) and is provided to cover a pipe hole (124) through which a gas injection unit (140) passes on the upper surface (121) of the roof (120).

[0096] The pipe sleeve (144) includes a hollow corresponding to the pipe hole (124), and the inner surface forming the hollow may be arranged to face the outer surface of the gas pipe (141).

[0097] A pipe sleeve (144) may be provided to cover at least a portion of the outer surface of the gas pipe (141) located above the pipe hole (124) in the gas pipe (141).

[0098] The pipe sleeve (144) can be made of a material that is fire-resistant to temperatures of approximately 1500 degrees or higher.

[0099] The pipe sleeve (144) can be positioned on the upper side of the loop (120) such that the center of the hollow and the center of the pipe hole (124) are positioned at a location that corresponds approximately in the vertical direction.

[0100] As shown in FIG. 4, the length (d2) of the distance (DL2) between the center (143) of the gas injection unit (140) and the center (131) of each of the three electrode rods (130a, 130b, 130c) can be formed equally.

[0101] The center (143) of the gas injection unit (140) can be arranged to be positioned at a location corresponding to the center (122) of the loop (120).

[0102] The distance between the center of the pipe hole (124) and the center of the three electrode holes (123) can be formed equally.

[0103] The distance between the rim forming the pipe hole (124) and each rim forming the three electrode holes (123) can be formed equally.

[0104] The rim forming the piping hole (124) can be arranged to be surrounded by three electrode rods (130a, 130b, 130c).

[0105] The distance between the center of the pipe sleeve (144) and the center of the three electrode rod sleeves (133) can be formed equally.

[0106] Three electrode rods (130a, 130b, 130c) can be arranged in a triangular shape to surround the center (122) of the loop (120).

[0107] The gas injection unit (140) can be placed on an internal space (I) surrounded by three electrode rods (130a, 130b, 130c).

[0108] The gas injection unit (140) can be placed in a triangular internal space (I) formed by three electrode rods (130a, 130b, 130c).

[0109] The purpose is to efficiently inject gas (G) into the area adjacent to each end (132a, 132b, 132c) of the three electrode rods (130a, 130b, 130c) using a single gas injection unit (140).

[0110] The length (d1) of the distance (DL1) between each electrode rod (130a, 130b, 130c) can be provided equally.

[0111] The purpose is to inject approximately equal amounts of gas (G) into the areas adjacent to each end (132a, 132b, 132c) of the three electrode rods (130a, 130b, 130c) using a single gas injection unit (140).

[0112] In this way, a low-nitrogen steel product (P) can be manufactured by generating a low-nitrogen molten metal (L) in an electric furnace process (S100) through a gas injection unit (140).

[0113] Hereinafter, a gas injection unit (140) according to another embodiment of the present invention will be described. Other configurations besides the plurality of gas injection units (140a, 140b, 140c) described below are identical to the electric furnace (100) according to the above embodiment, so redundant descriptions are omitted.

[0114] FIG. 5 is a schematic diagram illustrating the arrangement of electrode rods and gas injection parts of an electric furnace according to another embodiment of the present disclosure.

[0115] The gas injection unit (140) may include a plurality of gas injection units (140a, 140b, 140c).

[0116] Multiple gas injection units (140a, 140b, 140c) may be provided in a number corresponding to the multiple electrode rods (130).

[0117] According to one embodiment of the present invention, the electrode rod (130) is provided with three electrode rods (130a, 130b, 130c), and the plurality of gas injection units (140a, 140b, 140c) can be provided with three gas injection units (140a, 140b, 140c).

[0118] Each of the three gas injection units (140a, 140b, 140c) can be placed between the three electrode rods (130a, 130b, 130c).

[0119] Three electrode rods (130a, 130b, 130c) are arranged in a triangular shape around the center (122) of the loop (120), and three gas injection units (140a, 140b, 140c) can each be arranged on the sides of the triangular shape formed by the arrangement of the three electrode rods (130a, 130b, 130c).

[0120] Accordingly, any one of the plurality of gas injection units (140a, 140b, 140c) may be positioned adjacent to at least two electrode rods and far from another electrode rod.

[0121] For example, the first gas injection unit (140a) may be positioned adjacent to the first electrode rod (130a) and the second electrode rod (130b), but may be positioned farther from the third electrode rod (130c) than from the first electrode rod (130a) and the second electrode rod (130b). In this case, the first gas injection unit (140a) may be positioned at the center of the first electrode rod (130a) and the second electrode rod (130b), so that the distance from the first gas injection unit (140a) to each of the first electrode rod (130a) and the second electrode rod (130b) is equal.

[0122] When three electrode rods (130a, 130b, 130c) are named as the first electrode rod (130a), the second electrode rod (130b), and the third electrode rod (130c), the gas injection unit positioned between the first electrode rod (130a) and the second electrode rod (130b) may be named the first gas injection unit (140a), the gas injection unit positioned between the second electrode rod (130b) and the third electrode rod (130c) may be named the second gas injection unit (140b), and the gas injection unit positioned between the first gas injection unit (140a) and the third electrode rod (130c) may be named the third gas injection unit (140c).

[0123] Gas (G) is injected from a plurality of gas injection units (140a, 140b, 140c), and as gas (G) is injected independently at each location of the plurality of gas injection units (140a, 140b, 140c), the gas distribution in the gas layer (Z) can be provided more uniformly.

[0124] The length (d4) of the distance (DL4) between the center (122) of the loop (120) and the center (143) of each of the three gas injection units (140a, 140b, 140c) can be formed equally.

[0125] Three gas injection units (140a, 140b, 140c) can be arranged in a triangular shape to surround the center (122) of the loop (120).

[0126] Three gas injection units (140a, 140b, 140c) can each be arranged to be surrounded by three electrode rods (130a, 130b, 130c).

[0127] Each gas injection unit (140a, 140b, 140c) is designed to efficiently inject gas (G) into the area adjacent to each end (132a, 132b, 132c) of the three electrode rods (130a, 130b, 130c).

[0128] The length (d3) of the distance (DL3) between the three gas injection units (140a, 140b, 140c) can be provided equally.

[0129] The purpose is for the three gas injection units (140a, 140b, 140c) to inject approximately equal amounts of gas (G) into the areas adjacent to each end (132a, 132b, 132c) of the three electrode rods (130a, 130b, 130c).

[0130] Although the technical concept of the present invention has been explained above through specific embodiments, the scope of the present invention is not limited to these embodiments. Various embodiments that can be modified or varied by those skilled in the art within the scope that does not deviate from the gist of the technical concept of the present invention as specified in the claims shall also be considered to fall within the scope of the present invention.

Claims

1. A method for manufacturing a steel product, wherein the method comprises the steps of: preparing a molten metal using an arc electric furnace; controlling the composition of the molten metal; continuously casting the molten metal with controlled composition to produce a slab; and rolling the slab to produce a steel product. The step of preparing the molten metal using the above-mentioned arc furnace is, A step of melting scrap metal loaded inside the furnace by energizing a plurality of electrode rods; and A method comprising the step of reducing the amount of nitrogen mixed into the molten metal by blowing a reducing or inert gas toward the scrap metal and / or the molten metal made from the scrap metal while energizing the plurality of electrode rods.

2. In Paragraph 1, The step of blowing a reducing or inert gas toward the molten metal made from the scrap metal comprises a gas injection unit including a nozzle for injecting the reducing or inert gas and a gas pipe through which the reducing or inert gas flows. A method in which the nozzle and the plurality of electrode rods are arranged such that the distance from the nozzle to the scrap metal is greater than the distance from any one of the plurality of electrode rods to the scrap metal.

3. In Paragraph 1, The step of blowing a reducing or inert gas toward the molten metal made from the scrap metal comprises a gas injection unit including a nozzle for injecting the reducing or inert gas and a gas pipe through which the reducing or inert gas flows. A method in which the plurality of electrode rods and the nozzle penetrate into the interior of the arc furnace through a loop that opens and closes the upper part of the electric furnace body.

4. In Paragraph 3, The above pipe penetrates the loop through the pipe hole, and The above plurality of electrode rods penetrate the loop through the plurality of electrode holes, and A method in which the above piping hole and the above plurality of electrode holes are provided in the loop.

5. In Paragraph 4, A method in which the distance from the rim forming the pipe hole to the rim forming any one of the plurality of electrode holes matches the distance to the rim forming any one of the other electrode holes.

6. In Paragraph 4, A method in which the rim of the above-mentioned pipe hole is arranged to be surrounded by the above-mentioned plurality of electrode rods.

7. In Paragraph 4, The above piping holes are provided in the same number as the above plurality of electrode holes, and A method in which one of the plurality of piping holes is positioned adjacent to at least two of the plurality of electrode rods and positioned far from one or more other electrode rods.

8. In Paragraph 1, The nozzle forms a gas region at the bottom of the nozzle by blowing a reducing or inert gas toward the scrap metal and / or the molten metal, and A method in which the above gas region surrounds at least a portion of the outer surface of the plurality of electrode rods.

9. In Paragraph 8, The above gas region surrounds the ends of the plurality of electrode rods, a method.

10. As an arc electric furnace, The above arc furnace is a loop including one or more piping holes and a plurality of electrode holes; One or more gas injection units including one or more nozzles penetrating the loop through one or more pipe holes; A plurality of electrode rods penetrating the loop through the plurality of electrode holes; and It includes one or more controllers that supply a reducing gas or an inert gas into the arc furnace through one or more nozzles or energize the plurality of electrode rods. The above one or more controllers are, An arc furnace that controls the arc furnace to reduce the amount of nitrogen mixed into the molten metal by blowing a reducing or inert gas toward the scrap metal and / or the molten metal made from the scrap metal while energizing the plurality of electrode rods.

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