Melting raw material preheating apparatus and preheating apparatus-fitted arc melting furnace

Abstract

To provide a melting raw material preheating apparatus and a preheating apparatus-fitted arc melting furnace, which can continue the operation of the arc melting furnace even if a trouble occurs in the melting raw material preheating apparatus.SOLUTION: A melting raw material preheating apparatus 3 preheats a melting raw material with an exhaust gas generated in an arc melting furnace 2 having a furnace cover opening / closing mechanism. The melting raw material preheating apparatus 3 comprises: a preheating apparatus body 46 which is movable to a distant position not overlapping with the upper part of the furnace body of the arc melting furnace 2; and an exhaust gas introduction duct 47 which introduces the exhaust gas into the preheating apparatus body 46. The preheating apparatus body 46 comprises: a raw material input port 56 for inputting a melting raw material; holding means 61 for holding the melting raw material; an exhaust gas introduction port 67 which is connected with the exhaust gas introduction duct 47; an exhaust gas exhaust port 68 for exhausting the exhaust gas used for preheating the melting raw material; a raw material exhaust port 58 which opens downwards in a bottom part of the preheating apparatus body 46; and a bottom part member 60 which is provided below the holding means 61 and opens / closes the raw material exhaust port 58.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a melting raw material preheating device that preheats melting raw materials such as metal scrap with exhaust gas from an arc melting furnace, and an arc melting furnace equipped with the preheating device.

Background Art

[0002] In an arc melting furnace, an arc is generated between an electrode inserted into the furnace body and a melting raw material such as metal scrap, and the melting raw material is melted by the arc heat. Since high-temperature exhaust gas is generated during melting from such an arc melting furnace, this high-temperature exhaust gas may be used to preheat the melting raw material to be melted next.

[0003] In an arc melting furnace equipped with a preheating device for use in preheating a melting raw material, for example, as shown in Patent Document 1 below, a cylindrical preheating device main body is provided on the furnace top of the arc melting furnace. The preheating device main body is configured to be movable by a carriage. When preheating the melting raw material, the preheating device main body is positioned near the furnace wall of the arc melting furnace, and when charging the preheated melting raw material into the furnace, the preheating device main body moves toward the center of the arc melting furnace. At this time, a furnace lid opening / closing mechanism is configured to be included on the preheating device side so that the preheating device main body and the furnace lid can move integrally.

[0004] However, in the arc melting furnace equipped with the preheating device configured in this way, when a failure occurs in a part on the preheating device side (for example, the carriage for movement), the arc melting furnace cannot lift and open / close the furnace lid alone, and there is a problem that the melting operation cannot be continued.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention is based on the above circumstances, and an object thereof is to provide a molten raw material preheating device and an arc melting furnace equipped with the preheating device that can continue the operation of the arc melting furnace even when a failure occurs in the device for preheating the molten raw material.

Means for Solving the Problems

[0007] Thus, the molten raw material preheating device according to the first aspect of the present invention is defined as follows. That is, A molten raw material preheating device that preheats the molten raw material with exhaust gas generated in an arc melting furnace having a furnace lid opening and closing mechanism, A preheating device main body that is movable to a position separated so as not to overlap the upper part of the furnace body of the arc melting furnace when viewed in elevation, An exhaust gas introduction duct that connects the arc melting furnace and the preheating device main body and introduces exhaust gas into the preheating device main body, Moving means for moving the preheating device main body forward and backward with respect to the arc melting furnace, Comprising The preheating device main body is A raw material inlet for charging the molten raw material, Holding means for holding the molten raw material, An exhaust gas inlet connected to the exhaust gas introduction duct, An exhaust gas outlet for discharging the exhaust gas used for preheating the molten raw material, A raw material outlet that opens downward at the bottom of the preheating device main body, A bottom member provided below the holding means for opening and closing the raw material outlet, Having

[0008] According to the molten raw material preheating device of the first aspect defined as above, the furnace lid opening and closing mechanism is provided on the arc melting furnace side. Even if the molten raw material preheating device fails, the furnace lid can be opened and closed by the furnace lid opening and closing mechanism provided on the arc melting furnace side, the function of charging the molten raw material into the furnace is maintained, and the melting operation in the arc melting furnace can be continued.

[0009] In the present invention, the bottom member can be configured as a movable bed that can be raised and lowered and / or advanced and retracted with respect to the arc melting furnace (second aspect). In this way, the position of the bottom member with respect to the raw material discharge port of the preheating device main body can be changed as needed. For example, when the preheating device main body moves, by moving the bottom member following the preheating device main body, the falling scrap can be received by the bottom member, while the preheating scrap inside the preheating device main body can be charged into the furnace with the raw material discharge port in an open state at a predetermined position.

[0010] In the present invention, it is possible to provide means for scraping out the molten raw material received by the bottom member toward the inside of the furnace (third aspect).

[0011] In the present invention, the exhaust gas inlet can be provided below the holding means, and the exhaust gas outlet can be provided above the holding means (fourth aspect). In this way, since the exhaust gas introduced into the preheating device main body flows upward from below the holding means, when a plurality of stages of holding means are provided in the preheating device main body, the molten raw material (molten raw material scheduled to be discharged next) held by the lower holding means close to the raw material discharge port can be preheated more efficiently.

[0012] Further, in the present invention, a bypass duct can be further provided, one end of which is connected below the holding means of the preheating device main body, avoiding the preheating chamber in the preheating device main body where the molten raw material is stored, and guiding the exhaust gas introduced into the preheating device main body to the exhaust duct (fifth aspect). In this way, when the preheating of the molten raw material is not performed, the exhaust gas can be guided to the exhaust duct through a path that avoids the preheating chamber in the preheating device main body.

[0013] Further, in the present invention, either one of the end members of the furnace lid side duct and the end member of the preheating device side duct of the exhaust gas introduction duct, which are arranged opposite to each other, can be configured to be able to advance and retract with respect to the other (sixth aspect). By doing so, when the exhaust gas is circulated, the gap between the end members arranged opposite to each other can be reduced to suppress the suction of outside air. On the other hand, when the furnace body needs to be tilted, for example, when it is necessary to avoid interference during movement, the gap between the end members can be increased to make the space between the furnace lid side duct and the preheating device side duct in a separated state.

[0014] The arc melting furnace with a preheating device according to the seventh aspect of the present invention is defined as follows. That is An arc melting furnace with a preheating device, comprising an arc melting furnace having a furnace lid opening and closing mechanism and a melting raw material preheating device according to the first aspect, The arc melting furnace a rotating device that supports the furnace bottom of the furnace body and rotates the furnace body around the vertical axis; a pedestal that supports the piping and rotates together with the furnace body, The melting raw material preheating device is disposed above so as not to contact the furnace body and the pedestal. According to the arc melting furnace with a preheating device according to the seventh aspect defined as above, when the furnace body rotates by the rotating device and the pedestal rotates, interference with the melting raw material preheating device can be avoided.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0016] Next, the molten raw material preheating device of the present invention and the arc melting furnace with a preheating device will be described in detail with reference to the drawings. FIG. 1 is a diagram showing the schematic configuration of an arc melting furnace with a preheating device according to an embodiment of the present invention. The arc melting furnace 1 with a preheating device according to this embodiment includes an arc melting furnace 2 and a molten raw material preheating device 3. The arc melting furnace 2 includes a furnace body 7 for accommodating the molten raw material, a furnace lid 14 that can open and close the loading port 8 at the upper end of the furnace body 7, an electrode 17 that is inserted downward into the furnace body 7 through the furnace lid 14, and a rotating device 40. By applying a current such as three-phase alternating current to the electrode 17 to generate discharge, the molten raw material such as metal scrap loaded into the furnace body 7 is melted.

[0017] Each electrode 17 is arranged inside the furnace body 7 at equal intervals (120° intervals) around the central axis L of the furnace body 7 near the center of the furnace lid 14 that is substantially circular in plan view. Each electrode 17 is supported by a gripper 23 fixed to the tip of an electrode support arm 22 that extends in the horizontal direction. The electrode support arm 22 is fixedly connected to the upper end of an electrode support column 24 of a furnace lid and electrode lifting and swiveling device 21 provided on a platform 33. Each electrode 17 is configured such that its height can be adjusted by an electrode lifting mechanism incorporated in the furnace lid and electrode lifting and swiveling device 21.

[0018] The furnace lid 14 is suspended and supported by a furnace lid support arm 27 that extends horizontally from the upper end of a ram cylinder 26 of the furnace lid and electrode lifting and swiveling device 21. The furnace lid 14 can move up and down and swivel by a furnace lid opening and closing mechanism incorporated in the furnace lid and electrode lifting and swiveling device 21, and opens the loading port 8 of the furnace body 7 to enable the loading of the molten raw material into the furnace body 7.

[0019] The furnace lid 14 is provided with an opening 15 for discharging the high-temperature exhaust gas generated during melting upward. A waste gas introduction duct 47 that connects the arc melting furnace 2 and the preheating device main body 46 and introduces the exhaust gas into the preheating device main body 46 is connected to the opening 15.

[0020] The furnace body 7 includes a cylindrical side wall portion 9 and a furnace bottom portion 10, and is formed as a bottomed cylindrical container having an opening upward. At opposite positions of the side wall portion 9 of the furnace body 7, a tapping hole 11 for tapping molten steel and a slag tapping hole 12 for tapping molten slag are respectively provided (see FIG. 2).

[0021] The arc melting furnace 2 further includes a rotating device 40 for rotating the furnace body 7 and a tilting body 30 for tilting the furnace body 7. The tilting body 30 includes a pair of leg portions 31, 31, a tilting bed 32 for supporting the furnace body 7, and a platform 33. Engaging teeth 35a and 31a are respectively formed on the upper surface of the furnace base 35 that supports the tilting body 30 and the lower surface of the leg portion 31 in contact therewith. During tilting, the misalignment of the tilting body 30 with respect to the furnace base 35 is prevented by the engagement of these engaging teeth 35a and 31a.

[0022] One end side of a drive cylinder (not shown) is connected to this tilting body 30, and the furnace body 7 is configured to tilt together with the tilting body 30 by extending or shortening this drive cylinder. For example, by tilting the entire furnace body 7 so that the side of the tapping hole 11 faces downward, the molten metal (molten steel) of the melting raw material in the furnace body 7 is tapped from the tapping hole 11. Further, by tilting the entire furnace body 7 in the direction opposite to the above tapping (that is, so that the side of the slag tapping hole 12 faces downward), the slag generated during the melting operation can be discharged to the outside from the slag tapping hole 12.

[0023] The furnace body 7 of the arc melting furnace 2 is supported by the tilting bed 32 via a rotating device 40 that rotates the furnace body 7. Specifically, the rotating device 40 has a bearing member 42 fixed on the tilting bed 32 and a support frame 41 supported by the bearing member 42. The support frame 41 is an annular member with a gear body formed on its inner peripheral surface, and the furnace body 7 is fixed on its upper surface.

[0024] Inside the support frame 41, a gear body (not shown) is provided that meshes with the gear body on the inner peripheral surface and rotates the support frame 41 around the central axis L. When the gear body rotates, the furnace body 7 fixed on the support frame 41 via the insulating plate 43 rotates around the central axis L extending in the vertical direction. When the furnace body 7 rotates, the position of the electrode 17 does not change. Therefore, as the furnace body 7 rotates, the relative arrangement between the furnace body 7 and the electrode 17 changes. The specific configuration of the rotating device 40 for rotating the furnace body 7 is described in, for example, Japanese Patent Laid-Open No. 2016-95123.

[0025] In FIG. 1, reference numeral 37 denotes a pedestal that supports the pipes 38 and wiring 39 connected to the furnace body 7, and is provided on the platform 33. When the furnace body 7 is rotated by the rotating device 40, the pedestal 37 also pivots around the central axis L.

[0026] Next, the melting raw material preheating device 3 will be described. The melting raw material preheating device 3 preheats the metal scrap as the melting raw material with the high-temperature exhaust gas from the furnace body 7. The melting raw material preheating device 3 includes a rectangular tube-shaped preheating device main body 46 that constitutes the main body thereof, and an exhaust gas introduction duct 47 that connects the preheating device main body 46 and the arc melting furnace 2 and introduces the exhaust gas into the preheating device main body 46.

[0027] The exhaust gas introduction duct 47 is composed of a furnace lid side duct 49 with one end connected to the furnace lid 14 and a preheating device side duct 50 with one end connected to the preheating device main body 46. As shown in FIG. 2, the connection part between the furnace lid side duct 49 and the preheating device side duct 50 is composed of a flange-shaped end member 49a of the furnace lid side duct 49 and a flange-shaped end member 50a of the preheating device side duct 50 which are arranged opposite to each other.

[0028] Here, the end member 50a of the preheating device side duct 50 is externally fitted so as to be slidable in the axial direction of the duct main body 50b. A cylinder rod 52 that extends or contracts with respect to a cylinder tube 51 attached to the duct main body 50b is attached to the end member 50a. By advancing and retreating the end member 50a with respect to the opposing end member 49a, the gap δ between these end members can be adjusted. When preheating the metal scrap in the preheating device main body 46, the end member 50a is advanced to be in a state close to the opposing end member 49a. On the other hand, when tilting the furnace body 7 or the like, when it is necessary to avoid interference between the furnace lid side duct 49 and the preheating device side duct 50 due to movement, the end member 50a can be retracted (increasing the gap δ) to make a clearance state with the opposing end member 49a. Note that the configuration of the connection part between the furnace lid side duct 49 and the preheating device side duct 50 is not limited to this. As long as either one of the end members 49a and 50a can advance and retreat with respect to the other, it can be appropriately changed as necessary. For example, it is also possible to attach the cylinder tube 51 for advancing and retreating the end member 50a to the frame body 74 or the carriage 76.

[0029] Next, the preheating device main body 46 that constitutes the main body of the molten raw material preheating device 3 is composed of a square tube-shaped member with a heat-resistant structure. For example, as the heat-resistant structure, there are heat-resistant steel, a water-cooled tube (water-cooled panel) structure, etc., and a heat insulating material (refractory) is attached to the inner surface or the outer surface as necessary. The preheating device main body 46 is supported by a frame body 74 in which columns and crossbeams are connected. As shown in FIG. 3, this frame body 74 is erected on a carriage 76 provided with wheels 75 that roll on rails 55 laid on a foundation beam 54. A pair of rails 55, 55 are arranged in parallel and linearly with the arc melting furnace 2 interposed therebetween, as shown in FIG. 2. The preheating device main body 46 supported by the frame body 74 can approach and separate from the arc melting furnace 2 along the rails 55 by moving the wheels 75 of the carriage 76 by a drive mechanism (not shown). In this example, as shown in FIG. 1, the preheating device main body 46 preheats the melting raw material at a position that does not overlap with the upper part of the furnace body of the arc melting furnace 2 in a front elevation view. When loading the preheated melting raw material into the furnace, the preheating device main body 46 moves closer to the center (left side in the figure) of the arc melting furnace 2. Also, during maintenance, the preheating device main body 46 can be moved to a position further away from the arc melting furnace 2 than the preheating position (a position on the right side in the figure compared to the preheating position).

[0030] FIG. 3 is a longitudinal sectional view in a direction orthogonal to the moving direction of the preheating device main body 46 in FIG. 1. In the figure, 56 is a raw material inlet at the upper end of the preheating device main body 46, which is opened and closed by a pair of cover plates 57, 57 that are driven to open and close left and right by a drive mechanism (not shown). 58 is a raw material discharge port that opens downward at the bottom of the preheating device main body 46, and 60 is a bottom member that opens and closes the raw material discharge port 58. The upper surface 60a of the bottom member 60 constitutes the bottom surface of the preheating device main body 46.

[0031] The bottom member 60 is configured as a movable bed that can be lifted and lowered and can move forward and backward with respect to the arc melting furnace 2, as shown in FIG. 4. In the figure, 77 is a fixed bed provided below the preheating device main body 46, and its upper surface 77a is a horizontal flat surface. At the position of the fixed bed 77 facing the raw material discharge port 58 of the preheating device main body 46, as shown in FIG. 4(A), a cylinder device 78 is embedded upward, and a cylinder rod 79 that extends or contracts with respect to the cylinder part of the cylinder device 78 abuts against the lower surface of the bottom member 60 to lift and lower the bottom member 60. Further, a cylinder device 80 is mounted horizontally on the upper surface 77a of the fixed bed 77. The cylinder rod 81 of the cylinder device 80 extends or contracts substantially parallel to the moving direction of the preheating device main body 46 with respect to the cylinder portion of the cylinder device 80, and its tip is connected to a holding frame 82 that holds the bottom member 60 on the upper surface 77a of the fixed bed 77. The bottom member 60 is configured to be moved in the approaching and separating directions with respect to the arc melting furnace 2 via the holding frame 82. Note that the configuration for moving the bottom member 60 is not limited to the example of FIG. 4 and can be appropriately changed as needed. For example, a mechanism for holding and lifting the bottom member 60 can be provided, and a cart-like structure that can move forward and backward on a guide rail installed on the fixed bed 77 by power from a motor or the like can be adopted.

[0032] The bottom member 60 configured as a movable bed closes the raw material discharge port 58 of the preheating device main body 46 when preheating the metal scrap in the preheating device main body 46, suppresses the leakage of the exhaust gas introduced into the preheating device main body 46, and receives the metal scrap (falling scrap S1) that has fallen from the preheating chamber 65. When the preheating device main body 46 moves toward the arc melting furnace 2, it follows and receives the falling scrap S1 during the movement. Further, when the preheating device main body 46 moves toward the center of the furnace body of the arc melting furnace 2, the raw material discharge port 58 of the preheating device main body 46 is opened at a predetermined position to enable the discharge of the preheated scrap into the furnace.

[0033] In the present embodiment, as shown in FIG. 1, a scraper 59 is attached to the edge of the raw material discharge port 58 of the preheating device main body 46, specifically, to the rear edge (the right side in the figure) when moving toward the arc melting furnace 2, in a downward extending manner. This is to scrape the falling scrap S1 on the upper surface 60a of the bottom member 60 into the furnace during the process of the preheating device main body 46 moving to the center of the furnace body of the arc melting furnace 2 (see FIG. 7).

[0034] Reference numeral 61 is a holding means for holding the metal scrap S which is a melting raw material, and is provided in two stages in the preheating apparatus main body 46. As shown in Fig. 3, the holding means 61 mainly comprises a pair of swingable forks 64, 64 which are formed by arranging a large number of heat-resistant steel fingers 63 in parallel at small intervals in a direction perpendicular to the paper surface on a horizontally extending rotating shaft 62 disposed along the side walls of the opposed preheating apparatus main body 46. In this fork 64, the fingers 63 can be swung together with the rotating shaft 62 by a drive mechanism portion (not shown). According to the holding means 61, as shown by the solid line in Fig. 3, the metal scrap S is held in a state where the fingers 63 are substantially horizontal. Then, as shown by the two-dot chain line in the figure, if the fingers 63 are tilted downward, a scrap dropping port is formed between the tips of the opposed fingers 63. In this example, by installing the upper and lower two-stage holding means 61, two preheating chambers 65 (upper preheating chamber 65a and lower preheating chamber 65b) are formed in the preheating apparatus main body 46.

[0035] As shown in Fig. 1, an exhaust gas inlet 67 which is connected to the preheating apparatus side duct 50 in the exhaust gas introduction duct 47 is provided on the side wall below the lower preheating chamber 65b of the preheating apparatus main body 46, and an exhaust gas outlet 68 which is connected to the exhaust duct 70 is provided on the side wall above the upper preheating chamber 65a of the preheating apparatus main body 46 as shown in Fig. 3. The high-temperature exhaust gas introduced into the preheating apparatus main body 46 through the exhaust gas inlet 67 flows upward in the preheating apparatus main body 46, heats the metal scrap stored in the preheating chambers 65a, 65b, and then is discharged to the exhaust duct 70. The other end of this exhaust duct 70 is connected to the intake port of a blower for blowing to a dust collecting apparatus (not shown).

[0036] Also, a second exhaust gas outlet 72 is provided in the side wall below the lower preheating chamber 65b of the preheating device main body 46. One end of a bypass duct 71 is connected to this second exhaust gas outlet 72. The other end of the bypass duct 71 is connected to an exhaust duct 70, and the bypass duct 71 forms a bypass flow path that guides exhaust gas to the exhaust duct 70 while avoiding the preheating chambers 65a and 65b in the preheating device main body 46. Near the second exhaust gas outlet 72 of the bypass duct 71 and near the exhaust gas outlet 68 of the exhaust duct 70, dampers 71a and 70a are respectively provided as switching means that are operated when switching the flow path of the exhaust gas. Note that as the switching means here, it is also possible to use a partition valve instead of a damper.

[0037] In the middle of the exhaust duct 70, as shown in FIG. 3, a connection part composed of end members 70b and 70c arranged opposite to each other is provided. Here, the end member 70c on the downstream side in the exhaust gas flow direction is configured to be able to move forward and backward with respect to the opposing end member 70b, similar to the case of the exhaust gas introduction duct 47. When preheating the metal scrap in the preheating device main body 46, the end member 70c is advanced to be in a state close to the opposing end member 70b. On the other hand, when moving the preheating device main body 46, the end member 70c is retracted (increasing the gap between the end members) to make a cut-off state with the opposing end member 70b.

[0038] Next, the operation during the melting operation in the arc melting furnace 1 with a preheating device will be described. First, the electrode 17 is pulled up from the furnace lid 14 and retracted laterally. After lifting the furnace lid 14 upward, it is then swiveled laterally to open the charging port 8 of the furnace body 7 (see FIG. 5). Then, the metal scrap (unpreheated metal scrap) is charged into the furnace by the scrap bucket 85 suspended by the crane wire and moved onto the arc melting furnace 2.

[0039] Next, as shown in Fig. 6, the furnace lid 14 is returned to its original position on the arc melting furnace 2, and the electrode 17 is inserted into the furnace. On the other hand, in the preheating device main body 46, the metal scrap is charged from the raw material charging port 56 by the scrap bucket 85 suspended by the crane wire and moved onto the preheating device main body 46, and the metal scrap S is stored in each preheating chamber 65a, 65b. When charging the metal scrap from the raw material charging port 56, it is connected only to the bypass duct 71 (open the damper 71a shown in Fig. 3 and close the damper 70a). Thereby, it is possible to suppress the fine metal scrap from being sucked into the exhaust duct 70. Note that the scrap bucket for charging the metal scrap into the arc melting furnace 2 and the scrap bucket for charging the metal scrap into the preheating device main body 46 can be different scrap buckets.

[0040] Then, the electrode 17 is energized to heat and melt the metal scrap in the furnace. The exhaust gas generated at this time rises in the furnace and is introduced into the preheating device main body 46 through the opening 15 of the furnace lid 14 and the exhaust gas introduction duct 47 as shown by the arrow in Fig. 6. The exhaust gas passes through the gap of the finger 63 of the holding means 61 provided in the lower stage to heat the metal scrap S in the lower preheating chamber 65b, and then passes through the gap of the finger 63 of the holding means 61 provided in the upper stage to heat the metal scrap S in the upper preheating chamber 65a. Then, the exhaust gas after heating the metal scrap S is discharged through the exhaust duct 70 (see Fig. 3).

[0041] Then, after the bulk of the undissolved metal raw material in the furnace is reduced by the melting of the metal scrap initially charged into the furnace, the metal scrap preheated in the preheating device main body 46 is additionally charged (recharged). Specifically, as shown in Fig. 7(A), on the arc melting furnace 2 side, the electrode 17 is pulled up from the furnace lid 14 and retracted laterally, and after the furnace lid 14 is lifted upward, it is swung laterally to open the charging port 8 of the furnace body 7. Regarding the preheating device main body 46 side, after lowering the bottom member 60 that had closed the raw material discharge port 58, the preheating device main body 46 and the bottom member 60 are moved toward the furnace body side in a synchronized state.

[0042] Then, as shown in FIG. 7(B), when the tip of the bottom member 60 reaches a predetermined position beyond the edge of the loading port 8 of the furnace body 7 and the movement of the bottom member 60 is stopped, and the preheating device main body 46 is continuously moved toward the center of the furnace body, the dropped scrap S1 received on the upper surface 60a of the bottom member 60 is scraped into the furnace by the scraper 59.

[0043] Thereafter, the preheating device main body 46 stops when it reaches the center of the furnace body 7. At this time, the raw material discharge port 58 of the preheating device main body 46 is in an open state. Here, (as shown by the two-dot chain line in FIG. 3), when the fingers 63 constituting the lower holding means 61 open, the preheated metal scrap S is charged (recharged) into the furnace.

[0044] After the recharging, the furnace lid 14 is returned to its original position above the arc melting furnace 2, the electrode 17 is inserted into the furnace, and the heating and melting are restarted. When melting the metal scrap, three hot spots (positions close to the electrode) and cold spots (positions far from the electrode) are generated at three locations in the circumferential direction of the furnace body 7, and the metal scrap is melted unevenly. Therefore, in this example, the furnace body 7 is rotated around the vertical axis L (see FIG. 1) with the furnace lid 14 separated upward to exchange the positions of the hot spots and the cold spots. By doing so, the uniformity of the melting of the metal scrap can be enhanced.

[0045] After passing through the melting period in which the metal scrap charged into the furnace body 7 is melted to produce molten steel, and the heating period in which the generated molten steel is heated and its components are adjusted, the furnace body 7 is tilted to tap the molten steel. When the tapping is completed, the tilting is returned to the original position and a series of operations ends.

[0046] The above described an example of charging using the preheated scrap in the preheating device main body 46. However, if the molten raw material preheating device 3 malfunctions and cannot move from the preheating position, etc., as shown in FIG. 5, normal metal scrap that has not been preheated can be charged into the furnace as the charging molten raw material by the scrap bucket 85, and the melting operation can be continued. In the case where preheating cannot be performed due to a malfunction of the molten raw material preheating device 3, the dampers 70a, 71a (see FIG. 3) for switching the exhaust gas flow path disposed in the duct can be operated to switch the exhaust gas flow path to a bypass path that does not pass through the preheating chambers 65a, 65b.

[0047] According to the molten raw material preheating device 3 of the present embodiment configured as described above, the furnace lid opening and closing mechanism is provided on the arc melting furnace 2 side. Even if the molten raw material preheating device 3 malfunctions, the furnace lid 14 can be opened and closed by the furnace lid opening and closing mechanism provided on the arc melting furnace 2 side, the function of charging metal scrap into the furnace is maintained, and the melting operation in the arc melting furnace 2 can be continued.

[0048] Further, in the molten raw material preheating device 3 of the present embodiment, the bottom member 60 is configured as a movable bed that can move up and down and can move forward and backward with respect to the arc melting furnace 2. When the preheating device main body 46 moves, by moving the bottom member 60 following the preheating device main body 46, the dropped scrap S1 can be received by the bottom member 60, while the preheated scrap in the preheating device main body 46 can be charged into the furnace with the raw material discharge port 58 in an open state at a predetermined position.

[0049] Further, in the molten raw material preheating device 3 of the present embodiment, the metal scrap (dropped scrap S1) received by the bottom member 60 can be scraped out toward the furnace by the scraper 59 attached to the edge of the raw material discharge port 58.

[0050] Also, in the melting raw material preheating device 3 of the present embodiment, the exhaust gas inlet 67 of the preheating device main body 46 is provided below the holding means 61, and the exhaust gas outlet 68 is provided above the holding means 61. Since the exhaust gas introduced into the preheating device main body 46 flows upward from below the holding means 61, when a plurality of stages of holding means 61 are provided in the preheating device main body 46, the metal scrap held by the lower holding means 61 close to the raw material discharge port 58 (the metal scrap scheduled to be discharged next) can be preheated more efficiently.

[0051] Also, in the melting raw material preheating device 3 of the present embodiment, one end is connected below the holding means 61 of the preheating device main body 46, avoiding the preheating chambers 65a and 65b in the preheating device main body 46 where metal scrap is stored, and a bypass duct 71 for guiding the exhaust gas introduced into the preheating device main body 46 to the exhaust duct 70 is further provided. When the preheating of the metal scrap is not performed, the exhaust gas can be guided to the exhaust duct 70 through a path that avoids the preheating chambers 65a and 65b in the preheating device main body 46. Also, when loading metal scrap from the raw material inlet 56, by connecting only to the bypass duct 71 (opening the damper 71a shown in FIG. 3 and closing the damper 70a), it is possible to suppress the suction of fine metal scrap into the exhaust duct 70.

[0052] Also, in the melting raw material preheating device 3 of the present embodiment, the end member 50a of the preheating device side duct 50 of the exhaust gas introduction duct 47 is configured to be able to move forward and backward with respect to the end member 49a of the opposing furnace lid side duct 49. Therefore, when flowing the exhaust gas, the gap δ between the opposing end members can be reduced to suppress the suction of outside air. On the other hand, when it is necessary to avoid interference during movement, such as when tilting the furnace body 7, the gap δ between the end members can be increased to make the space between the furnace lid side duct 49 and the preheating device side duct 50 in a separated state.

[0053] In the arc melting furnace 1 with a preheating device according to this embodiment, when the furnace body 7 of the arc melting furnace 2 rotates, the melting raw material preheating device 3 is arranged at a position away from the furnace body 7 and above the gantry 37 as shown in FIG. 1. Therefore, when the furnace body 7 rotates by the rotating device 40 and the gantry 37 pivots, interference with the melting raw material preheating device 3 can be avoided.

[0054] Although the embodiments of the present invention have been described in detail above, this is merely an example, and the present invention can be configured in various modified forms without departing from its gist. (1) For example, in the above embodiment, two preheating chambers are provided in the preheating device main body. However, the number of preheating chambers provided in the preheating device main body can also be one or three or more. (2) Also, in the above embodiment, an example is given in which a melting raw material preheating device is combined with an arc melting furnace equipped with a rotating device. However, the melting raw material preheating device of the present invention can also be combined with an arc melting furnace not equipped with a rotating device. (3) Also, in the above embodiment, an example is given in which a bypass duct 71 connecting the second exhaust gas discharge port 72 provided on the side wall of the preheating device main body 46 and the exhaust duct 70 is provided. However, in some cases, it is also possible to provide a bypass duct so as to directly connect the upstream exhaust gas introduction duct 47 and the downstream exhaust duct 70 so that exhaust gas does not enter the preheating device main body 46.

[0055] (4) Also, in the above embodiment, an example is given in which a pair of cover plates 57, 57 that are opened and closed by driving left and right are provided at the raw material inlet 56. However, for example, as shown in the example of FIG. 8, it is also possible to change the pair of cover plates 57, 57 to a single cover 57B. At that time, it is also possible to configure the exhaust gas discharge port 68 to be provided on the single cover 57B.

[0056] (5) Also, as the scraping means for the falling scrap, a configuration different from the scraper in the above embodiment can be used, for example, a pusher device having a stroke capable of pushing the falling scrap into the furnace. (6) Also, in the above-described embodiment, non-preheated metal scrap was first charged into the furnace. However, when performing a series of melting operations (raw material charging ~ melting ~ tapping) continuously, it is possible to first charge preheated metal scrap into the furnace.

Explanation of Signs

[0057] 1 Arc melting furnace with preheating device 2 Arc melting furnace 3 Melting raw material preheating device 7 Furnace body 10 Furnace bottom 21 Furnace lid · Electrode lifting and swiveling device (furnace lid opening and closing mechanism) 37 Stand 40 Rotating device 46 Preheating device main body 47 Exhaust gas introduction duct 49 Furnace lid side duct 49a End member 50 Preheating device side duct 50a End member 56 Raw material inlet 58 Raw material outlet 59 Scraper (scraping means) 60 Bottom member 61 Holding means 65 Preheating chamber 67 Exhaust gas inlet 68 Exhaust gas outlet 70 Exhaust duct 71 Bypass duct 76 Cart (moving means) S Metal scrap (melting raw material)

Claims

1. A melting raw material preheating device that preheats a melting raw material with exhaust gas generated in an arc melting furnace having a furnace lid opening and closing mechanism, A preheating device main body that is movable to a position separated so as not to overlap the upper part of the furnace body of the arc melting furnace when viewed in elevation, An exhaust gas introduction duct that connects the arc melting furnace and the preheating device main body and introduces exhaust gas into the preheating device main body, Moving means for moving the preheating device main body forward and backward with respect to the arc melting furnace, Comprising, The preheating device main body, A raw material inlet for charging the melting raw material, Holding means for holding the melting raw material, An exhaust gas inlet connected to the exhaust gas introduction duct, An exhaust gas outlet for discharging the exhaust gas used for preheating the melting raw material, A raw material outlet that opens downward at the bottom of the preheating device main body, A bottom member provided below the holding means for opening and closing the raw material outlet, A melting raw material preheating device having.

2. The melting raw material preheating device according to claim 1, wherein the bottom member is constituted by a movable bed that can be raised and lowered and / or moved forward and backward with respect to the arc melting furnace.

3. The melting raw material preheating device according to claim 1, further comprising means for scraping out the melting raw material received by the bottom member toward the furnace.

4. The melting raw material preheating device according to claim 1, wherein the exhaust gas inlet is provided below the holding means, and the exhaust gas outlet is provided above the holding means.

5. One end is connected below the holding means of the preheating device main body, avoiding the preheating chamber in the preheating device main body where the melting raw material is stored, and a bypass duct for guiding the exhaust gas introduced into the preheating device main body to an exhaust duct is further provided. The melting raw material preheating device according to claim 4.

6. The melting raw material preheating device according to claim 1, wherein one of the end members of the furnace lid side duct and the end member of the preheating device side duct, which are arranged opposite to each other, of the exhaust gas introduction duct is configured to be movable forward and backward with respect to the other.

7. An arc melting furnace with a preheating device configured to include an arc melting furnace having a furnace lid opening and closing mechanism and the melting raw material preheating device according to claim 1, The arc melting furnace, A rotating device that supports the furnace bottom of the furnace body and rotates the furnace body around the vertical axis, A gantry that supports a pipe and rotates together with the furnace body. The melting raw material preheating device is an arc melting furnace with a preheating device, which is arranged upward so as not to contact the furnace body and the gantry.

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