Method for processing cold iron source, method for feeding 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] The present invention relates to a method for processing a cold iron source, a method for charging a cold iron source, and a method for producing molten steel. [Background technology]

[0002] For the purpose of recovering heat from the molten iron transport vessel and effectively utilizing the iron source, an operation has been widely performed in which a cold iron source such as iron scrap or ingot is placed in the molten iron transport vessel as an iron raw material before the molten iron tapped from a blast furnace is received in the molten iron transport vessel. In such an operation, the cold iron source is preheated by the heat of the refractory lining of the molten iron transport vessel and melted by the heat of the molten iron to be used as an iron raw material.

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

[0004] [Patent Document 1] JP 2007-169718 A [Patent Document 2] JP 2010-18867 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, looking ahead to future carbon neutral trends, new technologies will be required as the types of cold iron sources used for input will change. In the steelmaking process at steelworks, the aim is to increase the proportion of cold iron sources used in response to carbon neutrality. However, since the amount of cold iron sources generated within steelworks is limited, the proportion of light scrap (light scrap), which is one type of cold iron source purchased from outside the company, will increase. For this reason, the proportion of heavy scrap (heavy scrap) used within steelworks is expected to decrease relatively.

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

[0007] As mentioned above, in the current operation, heavy scrap with a large bulk density suitable for storage is used preferentially, but in the future, it will be necessary to increase the usage ratio of light scrap. However, in a molten iron transport vessel, where the upper limit of the amount of storage is determined by the stacking height, since light scrap has a smaller bulk density than heavy scrap, if the usage ratio of light scrap increases, the amount of storage will be significantly limited.

[0008] In addition, the method of Patent Document 2 moves the cold iron source charged to the end side of the furnace body, effectively utilizing the space in the furnace body to increase the amount of cold iron source that can be placed in. Therefore, if the proportion of lightweight scrap with a low bulk density used increases, the amount that can be placed is significantly limited.

[0009] Therefore, the present invention has been made in consideration of the above-mentioned problems, and has an object 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, which can increase the amount of cold iron source placed in a molten iron transport vessel when light scrap is used as at least a part of the cold iron source. [Means for solving the problem]

[0010] (1) According to one aspect of the present invention, there is provided a method for processing a cold iron source to be charged into a molten iron transport vessel before the molten iron is charged, the method comprising the steps of: 3 A method for processing a cold iron source is provided, which comprises pressing light scrap and forming a compression molded scrap. (2) In the method for processing cold iron sources according to (1) above, the bulk density of the light scrap is set to 1.5 t / m 3 The following applies. (3) In the method for processing cold iron sources according to the above (1) or (2), the bulk density of the compression-molded scrap is 2.5 t / m 3 That is all. (4) In the method for processing a cold iron source according to any one of the above (1) to (3), the shape of the compression-molded scrap is a rectangular parallelepiped with one side being 1.2 m or less. (5) In the method for processing a cold iron source according to any one of the above (1) to (4), a pressing pressure is set to 20 MPa or more when pressing the light scrap. (6) In the method for processing a cold iron source according to any one of the above (1) to (5), the light scrap contains zinc in an amount of 0.5 mass% or more. (7) In the method for processing a cold iron source according to any one of the above (1) to (6), the light scrap has a thickness of 10 mm or less. (8) According to one aspect of the present invention, there is provided a method for introducing a cold iron source, comprising introducing compression-molded scrap, which is the lightweight scrap processed by any one of the cold iron source processing methods (1) to (7), into a molten iron transport vessel before the molten iron is charged. (9) According to one aspect of the present invention, there is provided a method for producing molten steel, which uses the method for introducing a cold iron source as described in (8) above to introduce the compressed molded scrap into the molten iron transport vessel before the molten iron is charged, then the molten iron is charged into the molten iron transport vessel, the molten iron contained in the molten iron transport vessel is transported to a refining facility, and the molten iron is smelted in the refining facility to produce molten steel. Effect of the Invention

[0011] According to one aspect of the present invention, there are provided a method for processing a cold iron source, a method for introducing a cold iron source, and a method for producing molten steel, which can increase the amount of cold iron source placed in a molten iron transport vessel when light scrap is used as at least a part of the cold iron source. [Brief description of the drawings]

[0012] [Figure 1] FIG. 4 is an explanatory diagram showing a method of charging a cold iron source according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] In the following detailed description, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, identical or similar parts are given identical or similar symbols, and duplicated explanations are omitted. Each drawing is schematic and may differ from the actual one. In addition, 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 described below. The technical idea of ​​the present invention can be modified in various ways within the technical scope defined by the claims described in the claims.

[0014] <Method of adding cold iron source and method of manufacturing molten steel> A method for introducing a cold iron source and a method for producing molten steel according to an embodiment of the present invention will be described with reference to Fig. 1. In this embodiment, a molten iron transport vessel 1 is a torpedo, and compression-molded scrap 3 is used as the cold iron source. The compression-molded scrap 3 is obtained by compression-molding light scrap by a processing method described later.

[0015] In this embodiment, first, the lifting magnet 2 is used to load the compression molded scrap 3 into the molten iron transport vessel 1 before the molten iron is charged (in one example of this embodiment, the vessel is empty) (loading process). The upper limit of the loading amount (loading amount) of the compression molded scrap 3 is set according to the bulk density, shape and pile height of the compression molded scrap 3, and is set to a pile height that does not cause problems such as splashing in the subsequent molten iron receiving process. After the placing process, the molten iron transport vessel 1 is transported to the blast furnace, and the molten iron tapped from the blast furnace is charged (receiving) into the molten iron transport vessel 1 (receiving process). After the receiving process, the compressed molded scrap 3 contained in the molten iron transport vessel 1 is melted by the received molten iron.

[0016] After the pig iron receiving process, the molten iron contained in the molten iron transport vessel 1 is transported to a refining facility, where the molten iron is refined to produce molten steel with the desired composition and temperature (refining process). In the refining process, for example, the molten iron may be transferred from the molten iron transport vessel 1 to another vessel such as a molten iron ladle, and then the refining process may be performed. Furthermore, a preliminary refining process may be performed while the molten iron is contained in the molten iron transport vessel 1. Furthermore, in the refining process, after desiliconization and dephosphorization are performed as necessary, a decarburization process (primary refining) is performed to produce molten steel with a low carbon concentration from the molten iron. Furthermore, secondary refining may be performed after the primary refining to adjust the composition and temperature of the molten steel.

[0017] In the refining process, the molten iron transport vessel 1 is transported to the refining equipment, and the molten iron contained therein is poured into another vessel such as a molten iron ladle, leaving the vessel empty. The processes from the placing process onwards are then carried out again, so that a series of processes from the placing process to the receiving process are repeated. When this series of processes is repeated, the molten iron transport vessel 1 is in a state heated by the molten iron contained therein, so that when the compressed molded scrap 3 is poured into the empty molten iron transport vessel 1, the compressed molded scrap 3 is heated by the heat of the molten iron transport vessel 1.

[0018] <Processing method of cold iron source> A method for processing the compression-molded scrap 3, which is the cold iron source input in the placing step, will be described. In the method for processing the cold iron source according to this embodiment, the compression-molded scrap 3 is produced using light scrap as a raw material. The raw material lightweight scrap has a bulk density of 2.0t / m 3 Less than 1.5t / m 3 The following is the iron scrap. The thickness of the lightweight scrap is preferably 10 mm or less. If the thickness of the lightweight scrap exceeds 10 mm, it may be difficult to form it by pressing with a press machine, which will be described later.

[0019] Furthermore, the light scrap preferably contains zinc at 0.5 mass% or more. Light scrap containing zinc at 0.5 mass% or more is, for example, galvanized scrap. Since such scrap containing zinc usually volatilizes, when it is used in equipment such as a converter-type refining equipment, attention must be paid to the adverse effect of the volatilized zinc on the dust collection equipment. However, in this embodiment, the compression-molded scrap 3 made from such light scrap is charged in the placing step, and the compression-molded scrap 3 is heated by the heat of the molten iron transport vessel 1 during the period up to the receiving step. Then, at least a part of the zinc contained in the compression-molten scrap 3 volatilizes during the period from the placing step to the receiving step, so that the impact of the zinc contained in the light scrap on the equipment can be reduced.

[0020] The compression-molded scrap 3 is molded by pressing the lightweight scrap with a press. The compression-molded scrap 3 has a bulk density of 2.5 t / m 3 The bulk density of the compression-molded scrap 3 is preferably 2.5 t / m or more. 3 By setting the bulk density of the compression-molded scrap 3 at 2.5 t / m or more, the shape after pressing can be maintained. 3 If the thickness is less than this, the compression molding scrap 3 may lose its shape when handled.

[0021] Moreover, the shape of the compression molded scrap 3 is preferably a rectangular parallelepiped with one side of 1.2 m or less, and more preferably a rectangular parallelepiped with one side of 0.7 m or less. If one side of the rectangular parallelepiped shape of the compression molded scrap 3 exceeds 1.2 m, the compression molded scrap 3 lifted by the lifting magnet 2 may collapse and fall under its own weight. For this reason, by making one side of the rectangular parallelepiped shape of the compression molded scrap 3 1.2 m or less, the compression molded scrap 3 can be easily handled by the lifting magnet 2. Furthermore, if one side of the rectangular parallelepiped shape of the compression molded scrap 3 exceeds 0.7 m, the input compression molded scrap 3 tends to pile up in the vertical direction, and the input amount may be reduced. For this reason, by making one side of the rectangular parallelepiped shape of the compression molded scrap 3 0.7 m or less, the compression molded scrap 3 input into the molten iron transport vessel 1 tends to roll after input, and the compression molded scrap 3 can be input into a wide range of the molten iron transport vessel 1. This allows the input amount of compression molding scrap 3 to be increased.

[0022] Furthermore, it is preferable that the rectangular parallelepiped shape of the compression molding scrap 3 has one side of 0.2 m or more. If one side of the rectangular parallelepiped shape of the compression molding scrap 3 is less than 0.2 m, the time required for the lifting magnet 2 to feed the scrap 3 is extended. Since the number of scraps that the lifting magnet 2 can carry at one time is limited, if the compression molding scrap 3 is small, a long time is required for the scrap to be fed. For this reason, by making one side of the rectangular parallelepiped shape of the compression molding scrap 3 0.2 m or more, the extension of the time required for the lifting magnet 2 to feed the scrap 3 can be prevented. 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 prevent the compression-molded scrap 3 from losing its shape after being charged.

[0023] In this embodiment, the bulk density is 2.0 t / m 3 Less than 1.5t / m 3 The following lightweight scrap is pressed to produce compressed scrap, which is used as the cold iron source in the placing step. This allows the amount of lightweight scrap to be increased when it is used as the cold iron source in the placing step. Note that the bulk density of the lightweight scrap is 1.5 t / m 3 By doing the following, it is possible to utilize light-weight scrap, which is generated in large quantities.

[0024] <Modification> Although the present invention has been described above with reference to specific embodiments, it is not intended that the invention be limited by these descriptions. By referring to the description of the present invention, other embodiments of the present invention including various modifications in addition to the disclosed embodiments will be apparent to those skilled in the art. Therefore, it should be understood that the embodiments of the invention described in the claims also include embodiments including these modifications described herein, either alone or in combination. For example, in the above embodiment, only the compressed molded scrap 3 is charged as the cold iron source in the placing step, but the present invention is not limited to this example. For example, in addition to the compressed molded scrap 3, other iron sources such as heavy scrap, light scrap, reduced iron, etc. may be further charged as the cold iron source in the placing step.

[0025] In the above embodiment, the shape of the compression molded scrap 3 is a rectangular parallelepiped, but the present invention is not limited to this example. The shape of the compression molded scrap 3 may be other shapes, such as a spherical shape or a cylindrical shape. By making the shape of the compression molded scrap 3 a rectangular parallelepiped, press molding becomes easier. Furthermore, in the above embodiment, the molten iron transport vessel 1 is a torpedo, but the present invention is not limited to this example. The molten iron transport vessel 1 may be a vessel of another shape, such as a ladle.

[0026] Furthermore, in the above embodiment, the compression molded scrap 3 is charged using the lifting magnet 2 in the placing step, but the present invention is not limited to this example. The method of charging the compression molded scrap 3 in the placing step may be any method capable of charging the compression molded scrap 3 into the molten iron transport vessel 1, and may be, for example, another method using a bucket or the like. EXAMPLES

[0027] Next, an example carried out by the present inventor will be described. In the example, the cold iron source was charged into a torpedo, which is a molten iron transport vessel 1, using the cold iron source charging method according to the above embodiment, and the amount of the cold iron source placed was investigated. 3 The following lightweight scrap was pressed to produce compression-molded scrap 3. The compression-molded scrap 3 had a bulk density of 2.5 t / m 3 The shape is a rectangular parallelepiped with each side measuring between 0.2m and 1.2m. In addition, as a conventional method, the amount of cold iron source placed in the molten iron transport vessel 1 was also investigated. In the example and comparative example, the cold iron source was placed in the vessel until the piled-up height of the cold iron source reached a predetermined height.

[0028] As a result of the verification, the amount of light scrap placed in the comparative example was 7 tons per torpedo, whereas the amount of compression molded scrap placed in the example was 15 tons per torpedo. Therefore, it was confirmed that the cold iron source processing method and the cold iron source charging method according to the above embodiment can increase the amount of light scrap placed in the molten iron transport vessel 1 when light scrap is used as at least a part of the cold iron source. [Explanation of symbols]

[0029] 1 Molten iron transport vessel 2 Lifting Magnets 3. Compression molding scrap

Claims

1. A method for processing cold iron sources to be charged into a molten iron transport vessel before the molten iron is charged, comprising the steps of: ３ A method for processing cold iron sources, comprising pressing the following lightweight scraps to produce compression-molded scraps:

2. The bulk density of the lightweight scrap is 1.5 t / m ３ 2. The method for processing a cold iron source according to claim 1, wherein:

3. The bulk density of the compression molding scrap is 2.5 t / m ３ The method for processing a cold iron source according to claim 1.

4. 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 one side being 1.2 m or less.

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

6. The method for processing a cold iron source according to claim 1 , wherein the light scrap contains zinc in an amount of 0.5 mass% or more.

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

8. A method for charging a cold iron source, comprising charging the compression-molded scrap formed by the method for processing a cold iron source according to any one of claims 1 to 7 into a molten iron transport vessel before the molten iron is charged.

9. A method for producing molten steel, comprising: using the method for introducing a cold iron source as defined in claim 8 to introduce the compression molded scrap into the molten iron transport vessel before the molten iron is charged; then, charging the molten iron into the molten iron transport vessel; transporting the molten iron contained in the molten iron transport vessel to a refining facility; and smelting the molten iron in the refining facility to produce molten steel.

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