Method for processing a cold iron source, method for introducing a cold iron source, and method for producing molten steel

Abstract

To provide a method for processing a cold iron source, a method for feeding a cold iron source, and a method for producing molten steel, which can increase a placed amount of the cold iron source in a case where lightweight scrap is used as at least a part of the cold iron source placed in a hot metal transfer vessel.SOLUTION: Provided is a processing method for a cold iron source to be fed into a hot metal transfer vessel 1 before the hot metal is charged. A lightweight scrap having a bulk density of 2.0 t / m3 or less is pressed, and compression molded scrap 3 is formed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a method for processing a cold iron source, a method for introducing a cold iron source, and a method for producing molten steel. [Background technology]

[0002] For the purpose of recovering the heat contained in the molten iron transport container and effectively utilizing the iron source, it has been widely practiced to pre-fill the molten iron transport container with cold iron sources such as iron scrap and ingots as raw materials before receiving the molten iron tapped from the blast furnace. In such operations, the cold iron sources are preheated by the heat contained in the refractory lining of the molten iron transport container and melted by the heat of the molten iron to be used as raw materials for iron.

[0003] For example, Patent Document 1 discloses a method for installing cold iron sources, in order to reduce the impact on the refractory lining, that cold iron sources with a thickness of 5 mm or less and a length of 500 mm or less are used until the stacking height of the cold iron sources reaches 200 mm. Furthermore, Patent Document 2 discloses a method for maximizing the amount of scrap iron that can be placed in a torpedo, which is a molten iron transport container with a small opening, by moving the introduced scrap iron within the furnace body. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2007-169718 [Patent Document 2] Japanese Patent Publication No. 2010-18867 [Overview of the project] [Problems that the invention aims to solve]

[0005] Incidentally, looking ahead to future trends in carbon neutrality, the types of cold iron sources used for production will change, requiring new technologies. In the steelmaking process at steel mills, there is a goal to increase the proportion of cold iron sources used as a measure to achieve carbon neutrality. However, since there is a limit to the cold iron sources generated within steel mills, the proportion of lightweight scrap, one of the cold iron sources purchased from outside, will increase. As a result, the proportion of heavy scrap used within steel mills is expected to decrease relatively.

[0006] In the method described in Patent Document 1, lightweight scrap is used as cushioning material in the lower stacking height, but heavy scrap is used entirely in the remaining higher stacking height. In the method described in Patent Document 1, the upper limit of the amount of cold iron source to be placed in the molten iron transport container is determined by the stacking height, so heavy scrap with high bulk density is used preferentially. If the amount of cold iron source placed exceeds the upper limit, the cold iron source will be piled up to near the mouth of the molten iron transport container, and when the molten iron is received in the blast furnace after placement, the tapping flow will hit the cold iron source, causing problems such as splashing.

[0007] As mentioned above, in current operations, heavy scrap with a high bulk density suitable for storage is used preferentially, but it will be necessary to increase the proportion of light scrap used in the future. However, in molten iron transport containers, where the maximum storage capacity is determined by the stacking height, the bulk density of light scrap is lower than that of heavy scrap, so increasing the proportion of light scrap used will severely limit the storage capacity.

[0008] Furthermore, the method described in Patent Document 2 involves moving the introduced cold iron source towards the end of the furnace body, thereby effectively utilizing the space within the furnace body and increasing the amount of cold iron source that can be placed inside. As a result, if the proportion of lightweight scrap with a low bulk density used increases, the amount that can be placed inside becomes severely limited.

[0009] Therefore, the present invention has been made in view of the above-mentioned problems, and aims to provide a method for processing a cold iron source, a method for introducing a cold iron source, and a method for producing molten steel that can increase the amount of cold iron source placed in a molten iron transport container when lightweight scrap is used as at least a part of the cold iron source placed in the container. [Means for solving the problem]

[0010] (1) According to one aspect of the present invention, a method for processing a cold iron source to be introduced into a molten iron transport container before molten iron is charged, wherein the bulk density is 2.0 t / m³ 3 A method for processing cold iron sources is provided, which involves pressing the following lightweight scrap to form compression-molded scrap. (2) In the processing method for the cold iron source described in (1) above, the bulk density of the lightweight scrap is 1.5 t / m³ 3 The following applies: (3) In the processing method for the cold iron source described in (1) or (2) above, the bulk density of the compressed molded scrap is 2.5 t / m³ 3 That concludes this section. (4) In any one of the cold iron source processing methods described in (1) to (3) above, the shape of the compression-molded scrap is a rectangular parallelepiped with sides of 1.2 m or less. (5) In any of the cold iron source processing methods described in (1) to (4) above, the pressing pressure is set to 20 MPa or higher when pressing the lightweight scrap. (6) In any one of the cold iron source processing methods described in (1) to (5) above, the lightweight scrap contains 0.5 mass% or more of zinc. (7) In any one of the cold iron source processing methods described in (1) to (6) above, the lightweight scrap has a thickness of 10 mm or less. (8) According to one aspect of the present invention, a method for introducing a cold iron source is provided, which involves introducing the lightweight scrap, which is compression-molded scrap processed by any one of the cold iron source processing methods (1) to (7) above, into a molten iron transport container before the molten iron is charged into it. According to one aspect of the present invention, using the method for charging the chill iron source described in (8) above, after charging the compression-molded scrap into the molten iron transfer container before the molten iron is charged, the molten iron is charged into the molten iron transfer container, the molten iron contained in the molten iron transfer container is transferred to a refining facility, and the molten iron is subjected to steelmaking treatment in the refining facility to produce molten steel, a method for producing molten steel is provided.

Effects of the Invention

[0011] According to one aspect of the present invention, when using lightweight scrap as at least a part of the chill iron source placed in the molten iron transfer container, a method for processing the chill iron source, a method for charging the chill iron source, and a method for producing molten steel are provided, in which the amount of placement can be increased.

Brief Description of the Drawings

[0012] [Figure 1] It is an explanatory diagram showing a method for charging a chill iron source according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0013] In the following detailed description, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals, and redundant descriptions are omitted. Each drawing is schematic and may include cases where it is different from the actual one. Further, the embodiments shown below are examples of devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention does not specify the materials, structures, arrangements, etc. of the components as the following. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

[0014] <Method for Charging Chill Iron Source and Method for Producing Molten Steel> Referring to FIG. 1, a method for charging a cold iron source and a method for manufacturing molten steel according to an embodiment of the present invention will be described. In this embodiment, the hot metal transfer container 1 is top-sealed, and the compression-molded scrap 3 is used as the cold iron source. The compression-molded scrap 3 is obtained by compression-molding lightweight scrap by a processing method described later.

[0015] In this embodiment, first, using the lifting magnet 2, the compression-molded scrap 3 is charged into the hot metal transfer container 1 in a state before hot metal is charged (in an example of this embodiment, a state where the inside is empty) (charging step). The upper limit of the charging amount (placement amount) of the compression-molded scrap 3 is set according to the bulk density, shape, and stacking height of the compression-molded scrap 3, and is set to a stacking height that does not cause troubles such as splashing in the subsequent hot metal receiving step. After the charging step, the hot metal transfer container 1 is transported to the blast furnace, and the hot metal discharged from the blast furnace is charged (received) into the hot metal transfer container 1 (hot metal receiving step). Incidentally, after the hot metal receiving step, the compression-molded scrap 3 accommodated in the hot metal transfer container 1 is melted by the received hot metal.

[0016] After the hot metal receiving step, the hot metal accommodated in the hot metal transfer container 1 is transported to the refining equipment, and the hot metal is smelted in this refining equipment to produce molten steel having the target components and temperature (refining step). In the refining step, for example, the refining treatment may be performed after the hot metal is transferred from the hot metal transfer container 1 to another container such as a hot metal ladle. Also, a preliminary refining treatment may be performed while the hot metal is accommodated in the hot metal transfer container 1. Further, in the refining step, after performing desiliconization treatment, dephosphorization treatment, etc. as necessary, decarburization treatment (primary refining) is performed to produce molten steel having a low carbon concentration from the hot metal. Further, after the primary refining, secondary refining for adjusting the components and temperature of the molten steel may be performed.

[0017] In the refining process, the molten iron transport container 1 is transported to the refining equipment, after which the molten iron to be contained is transferred to another container such as a molten iron ladle, leaving the container empty. Then, the processing from the receiving process onward is repeated, so the series of processes from the receiving process to the receiving process is repeated. When this series of processes is repeated, the molten iron transport container 1 becomes heated by the molten iron it contained, so when compressed molded scrap 3 is put into the empty molten iron transport container 1, the compressed molded scrap 3 is heated by the heat of the molten iron transport container 1.

[0018] <Processing method for cold iron sources> The processing method for the compressed molded scrap 3, which is a cold iron source introduced in the loading process, will be described. In the processing method for the cold iron source according to this embodiment, the compressed molded scrap 3 is produced using lightweight scrap as a raw material. The lightweight scrap used as raw material has a bulk density of 2.0 t / m³. 3 The following is preferably 1.5 t / m 3 The following are examples of iron scrap. Furthermore, lightweight scrap is preferably 10 mm or less in thickness. If the lightweight scrap is thicker than 10 mm, it may be difficult to shape it using the press machine described later.

[0019] Furthermore, lightweight scrap preferably contains 0.5 mass% or more of zinc. Examples of lightweight scrap containing 0.5 mass% or more of zinc include galvanized scrap. When using such zinc-containing scrap in equipment such as converter-type refining facilities, care must be taken to avoid adverse effects of volatile zinc on dust collection equipment, as zinc usually volatilizes. However, in this embodiment, by introducing compression-molded scrap 3 made from such lightweight scrap as raw material in the loading process, the compression-molded scrap 3 is heated by the heat of the molten iron transport container 1 before reaching the iron receiving process. Then, at least a portion of the zinc contained in the compression-molded scrap 3 volatilizes between the loading process and the iron receiving process, thus reducing the impact of zinc contained in the lightweight scrap on the equipment.

[0020] Compression-formed scrap 3 is formed by pressing lightweight scrap in a press machine. Compression-formed scrap 3 has a bulk density of 2.5 t / m³. 3 Preferably, the bulk density of the compression-molded scrap 3 is 2.5 t / m³. 3 By doing so, the shape after pressing can be maintained. On the other hand, the bulk density of the compression-molded scrap 3 is 2.5 t / m³. 3 If the value is less than this, the compressed molded scrap 3 may lose its shape when handled.

[0021] Furthermore, the shape of the compression-molded scrap 3 is preferably a rectangular parallelepiped with sides of 1.2m or less, and more preferably a rectangular parallelepiped with sides of 0.7m or less. If the rectangular parallelepiped shape of the compression-molded scrap 3 has sides exceeding 1.2m, the compression-molded scrap 3 lifted by the lifting magnet 2 may collapse under its own weight and fall. Therefore, by making the sides of the rectangular parallelepiped shape of the compression-molded scrap 3 1.2m or less, handling of the compression-molded scrap 3 with the lifting magnet 2 becomes easier. Moreover, if the rectangular parallelepiped shape of the compression-molded scrap 3 has sides exceeding 0.7m, the compressed-molded scrap 3 that is put in tends to pile up vertically, which may reduce the amount that can be put in. Therefore, by making the sides of the rectangular parallelepiped shape of the compression-molded scrap 3 0.7m or less, the compression-molded scrap 3 put into the molten iron transport container 1 tends to roll around after being put in, and the compression-molded scrap 3 can be put into a wide area inside the molten iron transport container 1. This allows for a greater increase in the amount of compression-molded scrap 3 that can be added.

[0022] Furthermore, it is preferable that the rectangular parallelepiped shape of the compression-molded scrap 3 has a side length of 0.2m or more. If the side length of the rectangular parallelepiped shape of the compression-molded scrap 3 is less than 0.2m, the loading time by the lifting magnet 2 will be extended. Since the number that can be transported at once by the lifting magnet 2 is limited, if the compression-molded scrap 3 is small, a large amount of loading time will be required. For this reason, by making the side length of the rectangular parallelepiped shape of the compression-molded scrap 3 0.2m or more, it is possible to prevent an extension of the loading time by the lifting magnet 2. Furthermore, the pressing pressure when pressing the lightweight scrap is preferably 20 MPa or more. By pressing with such a pressing pressure, it is possible to suppress the deformation of the compression-molded scrap 3 after being charged.

[0023] In this embodiment, the bulk density is 2.0 t / m 3 Preferably, it is 1.5 t / m or less 3 The compression-molded scrap formed by pressing the following lightweight scrap, which preferably has a bulk density of 1.5 t / m or less, is used as a chill source in the placement process. As a result, when using lightweight scrap as the chill source used in the placement process, the amount of placement can be increased. By setting the bulk density of the lightweight scrap to 1.5 t / m or less, it is possible to utilize the lightweight scrap that is generated in large quantities. 3 By doing so, it is possible to utilize the lightweight scrap that is generated in large quantities.

[0024] <Modification> Although the present invention has been described above by referring to specific embodiments, it is not intended to limit the invention by these descriptions. By referring to the description of the present invention, those skilled in the art will also understand other embodiments of the present invention including various modifications together with the disclosed embodiments. Therefore, it should be understood that the embodiments of the invention described in the claims also cover embodiments including these modifications described herein alone or in combination. For example, in the above embodiment, only the compression-molded scrap 3 is charged as the chill source in the placement process, but the present invention is not limited to such an example. For example, in the placement process, in addition to the compression-molded scrap 3, other iron sources such as heavy scrap, lightweight scrap, and reduced iron may be further charged as the chill source.

[0025] Also, in the above embodiment, the shape of the compression-molded scrap 3 is a rectangular parallelepiped, but the present invention is not limited to such an example. The shape of the compression-molded scrap 3 may be other shapes such as spherical or cylindrical. By setting the shape of the compression-molded scrap 3 to a rectangular parallelepiped, press molding becomes easy. Furthermore, although the molten iron transport container 1 is a torpedo in the above embodiment, the present invention is not limited to this example. The molten iron transport container 1 may be a container of other shapes, such as a pan-shaped container.

[0026] Furthermore, although the above embodiment describes the loading of the compressed molded scrap 3 using a lifting magnet 2 during the loading process, the present invention is not limited to this example. The method for loading the compressed molded scrap 3 during the loading process can be any method that allows the compressed molded scrap 3 to be loaded into the molten iron transport container 1, and may include other methods such as using a bucket. [Examples]

[0027] Next, an example of an invention carried out by the inventors will be described. In the example, the cold iron source was introduced into a torpedo, which is a molten iron transport container 1, using the cold iron source introduction method according to the above embodiment, and the amount of cold iron source introduced was investigated. In the example, the thickness was 10 mm or less and the bulk density was 1.5 t / m 3 Compression-molded scrap 3 was formed by pressing the following lightweight scrap. Compression-molded scrap 3 has a bulk density of 2.5 t / m³. 3 The above describes a rectangular prism shape with sides between 0.2m and 1.2m. Furthermore, the amount of material to be placed in the molten iron transport container 1 was also investigated using a conventional method in which lightweight scrap that has not been press-formed was used as a cold iron source. In both the example and the comparative example, the cold iron source was added until the stacked height of the cold iron source reached a predetermined height.

[0028] Verification revealed that in the comparative example, the amount of lightweight scrap stored per torpedo was 7 tons, while in the embodiment, the amount of compression-molded scrap stored per torpedo was 15 tons. Therefore, it was confirmed that, according to the cold iron source processing method and input method of the above embodiment, the amount of storage can be increased when lightweight scrap is used as at least a portion of the cold iron source stored in the molten iron transport container 1. [Explanation of Symbols]

[0029] 1. Molten iron transport container 2 Lifting Magnets 3 Compression-molded scrap

Claims

1. A method for processing a cold iron source that is introduced into a molten iron transport container before molten iron is charged, wherein the bulk density is 2.0 t / m³. ３ The following lightweight scraps are pressed and compressed to form the scraps: The bulk density of the aforementioned lightweight scrap is set to 1.5 t / m³ or less. A method for processing a cold iron source, wherein the bulk density of the compression-molded scrap is 2.5 t / m³ or more.

2. The method for processing a cold iron source according to claim 1, wherein the shape of the compression-molded scrap is a rectangular parallelepiped with sides of 1.2 m or less.

3. The method for processing a cold iron source according to claim 1, wherein the pressing pressure is 20 MPa or more when pressing the lightweight scrap.

4. The method for processing a cold iron source according to claim 1, wherein the lightweight scrap contains 0.5 mass% or more of zinc.

5. The method for processing a cold iron source according to claim 1, wherein the lightweight scrap has a thickness of 10 mm or less.

6. A method for introducing a cold iron source, comprising introducing the compression-molded scrap, formed by the cold iron source processing method described in any one of claims 1 to 5, into a molten iron transport container before the molten iron is charged into it.

7. A method for producing molten steel, comprising: using the method for introducing a cold iron source according to claim 6, introducing the compression-molten scrap into the molten iron transport container before the molten iron is charged into it; charging the molten iron into the molten iron transport container; transporting the molten iron contained in the molten iron transport container to a refining facility; and producing molten steel by smelting the molten iron in the refining facility.

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