JP5321006B2 - Secondary refining equipment and method for molten steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow an immersion tube to be efficiently replaced in a secondary-refining facility by simplifying the secondary-refining facility. <P>SOLUTION: The secondary-refining facility 1 is provided with a turning table 10 rotatable in the horizontal direction. On the turning table 10, two sets of accommodation frames 21 capable of accommodating the immersion tubes 20 and two sets of ladles 22 for storing molten steel, are arranged in a form of the concentric circle of the turning table 10. Further, on the turning table 10, a frame elevating/lowering device 60 for elevating/lowering the accommodation frame 21 and a turning device for turning the immersion tube 20 accommodated in the accommodation frame 21, are arranged. In the lower part of the turning table 10, a ladle elevating/lowering device for elevating/lowering the ladle 22 at the treating position P1, is arranged. In the upper part of the turning table 10, a treatment device 90 for applying the secondary-refining to the molten steel while holding the immersion tube 20 at a prescribed height at the treating position P1, is arranged. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a secondary refining facility for dipping a dip tube in molten steel in a ladle and performing secondary refining of the molten steel inside the dip tube, and a secondary refining method using the secondary refining facility.

  In the steelmaking process of molten steel, secondary refining is performed to decarburize and degas the molten steel that has undergone primary refining in the converter. For this secondary refining, for example, a so-called CAS (Composition Adjustment by Sealed Argon bubbing) method is used in which a dip tube is immersed in molten steel in a ladle and the molten steel is subjected to secondary smelting inside the dip tube. Patent Document 1).

  During the secondary refining treatment, the refractory of the dip tube immersed in the molten steel is melted down, so that it is necessary to replace the dip tube periodically. The replacement of the dip tube after the secondary refining when the above-described CAS method is used is conventionally performed, for example, in the secondary refining equipment 200 shown in FIG. In the secondary refining equipment 200, first, the dip pipe 202 that has been subjected to secondary refining of the molten steel in the ladle 201 at the processing position Q1 is moved to the repair position Q2 by the processing carriage 203. Thereafter, the dip tube 202 is moved from the treatment cart 203 to the repair cart 204, and the repair cart 204 is moved to a predetermined position to repair the dip tube 202. At the same time, a new dip tube 202 is placed on the repair cart 204, the repair cart 204 is moved, and the new dip tube 202 is attached to the treatment cart 203. Thereafter, a new dip tube 202 is moved to the processing position Q1 by the processing carriage 203. In this way, in the secondary refining equipment 200, the dip tube 202 is replaced.

JP-A-61-143510

  However, when the dip tube 202 is replaced using the conventional secondary refining equipment 200, it takes time to move the processing carriage 203 between the processing position Q1 and the repair position Q2. Further, when the dip tube 202 is moved between the processing cart 203 and the repair cart 204 at the repair position Q2, it takes time to align the processing cart 203 and the repair cart 204. Therefore, it takes a lot of time to replace the dip tube 202.

  Thus, when it takes time to replace the dip tube 202, for example, when the processing amount (production amount) of molten steel is large, the ladle 201 is put on standby at the processing position Q1. As a result, the production amount of steel may decrease.

  Further, the conventional secondary refining equipment 200 requires a mechanism for moving the dip tube 202 between the treatment carriage 203 and the repair carriage 204 at the repair position Q2. Furthermore, a space for providing such a mechanism is required, and the area occupied by the secondary refining equipment 200 is large.

  This invention is made | formed in view of this point, and it aims at simplifying a secondary refining equipment and performing the replacement | exchange of the dip tube performed with the said secondary refining equipment efficiently.

  In order to achieve the above-mentioned object, the present invention is an equipment for immersing a dip tube in molten steel in a ladle and performing secondary refining of the molten steel inside the dip tube, and is a turntable that can rotate in a horizontal direction. On the turntable, a plurality of storage stands that can contain dip tubes and a ladle for storing molten steel are provided concentrically with the turntable, and further on the turntable, A platform elevating device for elevating and lowering the storage platform and a rotation device for rotating the dip tube accommodated in the storage platform are provided, and below the rotation platform, in a processing position for secondary refining of molten steel A ladle raising and lowering device for raising and lowering the ladle is provided, and a treatment device for secondary refining of molten steel is provided above the turntable by holding a dip tube at a predetermined height at the treatment position. It is characterized by having.

  ADVANTAGE OF THE INVENTION According to this invention, the dip tube hold | maintained at the processing apparatus can be immersed in the molten steel in a ladle in a process position, and the secondary refining of molten steel can be performed inside the said dip tube. In addition, when replacing the dip tube that has been repaired after the completion of the secondary refining, the dip tube to be replaced was accommodated in one of the plurality of storage stands at the processing position. Then, rotate the turntable to stop the other receiving stand at the processing position, raise the other receiving stand by the stand lifting device, and hold the new dip tube accommodated in the other receiving stand by the processing device. can do. That is, the dip tube can be replaced at the processing position. Accordingly, it is not necessary to replace the dip tube at a repair position different from the processing position as in the prior art described above. In addition, when replacing the dip tube, it is not necessary to align both the treatment cart and the repair cart as in the prior art described above, and it is easy to align the dip tube with respect to the treatment device simply by rotating the turntable. Can be done. Therefore, according to the present invention, the dip tube can be exchanged efficiently in a short time. Furthermore, it is not necessary to provide a mechanism for moving the dip tube between the treatment carriage and the repair carriage at the repair position as in the prior art described above, and the area occupied by the secondary refining equipment can be reduced.

  A plurality of ladles may be provided on the turntable.

  An exchanging device for exchanging the dip tube or the ladle of the storage frame at a position different from the processing position may be provided above the turntable.

  Another aspect of the present invention is a method for secondary refining of molten steel using the secondary refining equipment, wherein after a new dip tube is accommodated in the plurality of accommodating racks, the turntable is rotated. The one storage frame is stopped at the processing position, the one storage frame is raised to a predetermined height by the frame lifting device, and a new dip tube is stored in the one storage frame by the processing device. A dip tube holding step for holding the ladle, and then rotating the turntable to stop the ladle at the processing position, raising the ladle by the ladle lifting device, and holding the ladle by the processing device. The dip tube is immersed in the molten steel in the ladle, and a secondary refining of the molten steel is performed inside the dip tube, and when replacing the dip tube, the turntable is rotated. Stop the one storage platform at the processing position. The one storage platform is raised by the platform lifting device, and the dip tube held by the processing device is stored in the one storage platform, and then the one storage platform is placed on the turntable by the platform lifting device. The other storage platform is stopped at the processing position by rotating the turntable, the other storage platform is raised to a predetermined height by the platform lifting device, and the other It is characterized by holding a new dip tube accommodated in the accommodation stand.

  According to the present invention, the area occupied by the secondary refining equipment can be reduced to simplify the secondary refining equipment, and the dip tube can be replaced efficiently in a short time.

  Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 is a plan view showing an outline of the configuration of the secondary refining equipment 1 according to the present embodiment. In addition, in FIG. 1, the processing position P1 is a position which performs the secondary refining of molten steel, and the repair position P2 is a position which replaces the dip tube or ladle of the storage frame. The processing position P1 and the repair position P2 are set to face each other.

  The secondary refining equipment 1 has a turntable 10 as a turntable that can rotate in a horizontal direction around a central axis C. The turntable 10 is supported by the base 11 as shown in FIG. The rotation of the turntable 10 is driven by a motor, and the power is transmitted to the swivel bearing 13 via the speed reducer 12, whereby the turntable 10 is rotated. In the turntable 10, a through hole 14 that penetrates in the thickness direction of the turntable 10 is formed at a place where a ladle 22 described later is placed.

  On the turntable 10, as shown in FIG. 1, the accommodation stand 21 which can accommodate the dip tube 20, and the ladle 22 which stores molten steel are mounted. A plurality of, for example, two storage racks 21 and ladles 22 are provided, and the two storage racks 21 and ladles 22 are provided concentrically with the turntable 10. Two accommodation stands 21 are provided adjacent to each other. Further, the two ladles 22 are provided at a position rotated about 90 degrees along the circumferential direction of the turntable 10 from the storage platform 21, and the respective ladles 22 are placed facing each other. In addition, the number of the accommodation stand 21 and the ladle 22 is not limited to the said embodiment, Two or more units | sets may be sufficient.

  As shown in FIG. 3, the dip tube 20 has a substantially cylindrical main body 30. The main body 30 is hollow and has an open bottom surface. A shaft portion 31 is provided on the upper portion of the main body portion 30. A flange 32 is provided at the upper end of the shaft portion 31. Further, for example, four deposit seats 33 are provided on the outer surface of the shaft portion 31.

  The accommodation stand 21 is supported by the support stand 40. The storage frame 21 has an upper frame 41 and a lower frame 42. The upper frame 41 is configured by assembling a plurality of frames on a plate 41a. Among the plurality of frames, the upper frame 41 b is engaged with the deposit seat 33 of the dip tube 20 so that the dip tube 20 is accommodated in the upper frame 41. The lower gantry 42 is composed of a frame provided between the upper gantry 41 and the support base 40. Between the plate 41a of the upper frame 41 and the lower frame 42, for example, a bearing 43 is provided so that the upper frame 41 can be rotated independently of the lower frame 42 by a rotation device 50 described later.

  A rotation device 50 that rotates the upper frame 41 is provided inside the lower frame 42. That is, the rotating device 50 can rotate the dip tube 20 accommodated in the upper frame 41. The rotation device 50 has a motor 51. A reduction gear 52 is connected to the motor 51. On the speed reducer 52, a rotating portion 54 that comes into contact with the plate 41 a of the upper frame 41 is provided via a shaft 53. The shaft 53 is supported by a support portion 55 fixed to the support base 40.

  The accommodation platform 21 is provided with a platform lifting device 60 that raises and lowers the accommodation platform 21. The gantry lifting device 60 is provided on the turntable 10 as shown in FIGS. 3 and 4. The gantry lifting device 60 includes the above-described support base 40 and a lift frame 61 fixed to the support base 40. The elevating frame 61 is composed of two vertical frames 61a extending in the vertical direction and a horizontal frame 61b provided between the two vertical frames 61a and extending in the horizontal direction.

  A main frame 62 is provided outside the two vertical frames 61a along the vertical frame 61a. The main frame 62 extends from the turntable 10 in the vertical direction.

  Between the two vertical frames 61 a, two cylinders 63 that raise and lower the support base 40 and the lifting frame 61 are provided. For example, a hydraulic cylinder is used as the cylinder 63. The tip 63a of the cylinder 63 is fixed to a shaft 64 provided in the horizontal direction between the two vertical frames 61a.

  A sprocket 65 is provided on the shaft 64 between the vertical frame 61a and the tip end portion 63a. The sprocket 65 is provided with a chain 66, and the sprocket 65 functions as a moving pulley. Accordingly, the moving distance between the support base 40 and the lifting frame 61 is twice the operating distance of the cylinder 63. One end of the chain 66 is connected to a first chain storage portion 67 provided on the support base 40. On the other hand, the other end of the chain 66 is connected to a second chain storage portion 68 provided in the vertical frame 61a.

  A first guide roller 69 is provided on the lower surface of the support base 40. The first guide roller 69 guides the lifting and lowering of the support base 40 and the lifting frame 61 on the main frame 62. The main frame 62 is provided with a second guide roller 70. The second guide roller 70 guides the lifting and lowering of the support base 40 and the lifting frame 61 on the vertical frame 61a. The main frame 62 and the vertical frame 61a are formed in a rail shape so that the first guide roller 69 and the second guide roller 70 can guide the lifting and lowering of the support base 40 and the lifting frame 61. Further, another guide roll (not shown) may be further provided between the main frame 62 and the vertical frame 61a.

  When the accommodation platform 21 is moved up and down using the platform lifting device 60 as described above, by operating the cylinder 63, the chain 66 is moved up and down with the support platform 40 via the shaft 64 and the sprocket 65 as shown in FIG. The frame 61 is moved up and down. Thereby, the accommodation stand 21 supported by the support base 40 moves up and down.

  Below the turntable 10, as shown in FIG. 2, a ladle lifting device 80 that lifts and lowers the ladle 22 at the processing position P <b> 1 is provided. The ladle raising / lowering device 80 is a position facing the ladle 22 at the processing position P1, and is disposed in the concave portion 81 on the floor surface on which the base 11 is provided. The ladle elevating device 80 includes an elevating unit 82 that elevates and lowers by, for example, a hydraulic cylinder (not shown). The elevating part 82 is formed in a size that can penetrate the through hole 14 of the turntable 10. And the raising / lowering part 82 which passed the through-hole 14 contact | abuts to the lower surface of the ladle 22, and the said ladle 22 can be raised / lowered.

  As shown in FIG. 1, a processing device 90 that performs secondary refining of molten steel by holding the dip tube 20 at a predetermined height at the processing position P <b> 1 is provided on the side of the turntable 10. In the processing apparatus 90, secondary refining of molten steel is performed by the CAS method, and an oxygen lance (not shown) and an exhaust pipe (not shown) are connected to the dip tube 20 for secondary refining. In the processing apparatus 90, as a type for holding the dip tube 20, a moving type using a carriage (not shown) that carries the dip tube 20 and moves, or a fixing method for fixing the dip tube 20 as shown in FIG. 6. There is. For example, in the fixing method, as shown in FIG. 6, a holding arm 91 that holds the dip tube 20 and a support column 92 that supports the holding arm 91 and extends vertically from the floor surface are provided. The holding arm 91 extends to above the dip tube 20 arranged at the processing position P1. For example, a circular through hole 93 is formed in the holding arm 91. The dip tube 20 can be inserted through the through-hole 93 and held by the holding portion 94 provided on the upper surface of the support arm 91.

  As shown in FIG. 7, the holding portion 94 has a pair of arc-shaped holding portions 95 and 95. The clamping unit 95 is provided with an arm 96 that moves the clamping unit 95 in the horizontal direction around the fulcrum F. The horizontal movement of the arm 96 is performed by opening and closing a motor cylinder 97 provided on the arm 96. The sandwiching portion 95 sandwiches the dip tube 20 and the flange 32 of the dip tube 20 is locked to the sandwiching portion 95 so that the dip tube 20 can be held. Further, the holding part 95 is opened and closed in the horizontal direction with respect to the dip tube 20 so that the dip tube 20 can be held and released.

  When performing secondary refining of molten steel using the above processing apparatus 90, the ladle 22 is raised by the ladle lifting device 80 while the dip tube 20 is held by the processing apparatus 90, as shown in FIG. The lower part of the dip tube 20 is immersed in the molten steel in the ladle 22. Thereafter, an oxygen lance or exhaust pipe is connected to the dip tube 20, oxygen gas or oxidizing gas is blown into the dip tube 20, vacuum evacuation is performed in the dip tube 20, and the molten steel in the ladle 22 is discharged. Secondary refining is performed.

  As shown in FIG. 1, a crane 100 is provided on the side of the turntable 10 as an exchange device for exchanging the dip tube 20 or ladle 22 that needs to be repaired at the repair position P2. The crane 100 can access up to above the dip tube 20 or the ladle 22 disposed at the repair position P2. Further, the crane 100 can move up and down while holding the dip tube 20 or the ladle 22.

  The secondary refining equipment 1 according to the present embodiment is configured as described above. Next, a method for performing secondary refining of the molten steel in the ladle 22 and replacing the dip tube 20 using the secondary refining equipment 1 will be described. In the description of the present embodiment, of the two storage racks 21, one storage rack is the first storage rack 21A, and the other storage rack is the second storage rack 21B. In the dip tube 20, a new dip tube before the secondary refining is a new dip tube 20A, and a dip tube that needs repair after the secondary refining is an old dip tube 20B.

  First, as shown in FIG. 9, the new dip tube 20 </ b> A is accommodated in the first accommodation platform 21 </ b> A and the second accommodation platform 21 </ b> B using the crane 100 at the repair position P <b> 2. At this time, two ladles 22 are placed on the turntable 10. Thereafter, the turntable 10 is rotated to stop the first storage platform 21A at the processing position P1. And the 1st accommodation stand 21A is raised to predetermined height by the stand raising / lowering device 60. During this ascent, the new dip tube 20A accommodated in the first accommodation platform 21A is rotated by the rotation device 50 to a predetermined position, that is, a position appropriately held by the processing device 90. Then, as shown in FIG. 10, the new dip tube 20 </ b> A in the first storage frame 21 </ b> A is held by the processing device 90. Thereafter, the empty first storage frame 21 </ b> A is lowered onto the turntable 10 by the frame lifting device 60.

  When the empty first storage platform 21A is placed on the turntable 10, the turntable 10 is rotated to stop the ladle 22 at the processing position P1, as shown in FIG. And the ladle 22 is raised with the ladle raising / lowering apparatus 80, and the lower part of the new dip tube 20A hold | maintained by the processing apparatus 90 is immersed in the molten steel in the ladle 22. FIG. Thereafter, an oxygen lance or an exhaust pipe is connected to the new dip tube 20A, oxygen gas or oxidizing gas is blown into the new dip tube 20A, and evacuation or the like in the new dip tube 20A is performed. Secondary refining of molten steel is performed.

  And the above-mentioned secondary refining of the molten steel is repeated a predetermined number of times using one dip tube 20. The predetermined number of times is the number of times that the refractory of one dip tube 20 is melted and the dip tube 20 needs to be repaired. When such secondary refining is sequentially performed on each ladle 22, the turntable 10 is rotated to stop the ladle 22 before the secondary refining of molten steel is performed at the processing position P1. The ladle 22 for which the next refining has been completed is stopped at the repair position P2. Then, the ladle 22 is replaced by the crane 100 at the repair position P2 while the secondary refining of the molten steel is performed at the processing position P1.

  Thereafter, the turntable 10 is rotated to stop the empty first accommodation platform 21A at the processing position P1. And the empty 1st accommodation stand 21A is raised with the stand raising / lowering device 60, and as shown in FIG. 12, the old dip tube 20B hold | maintained by the processing apparatus 90 is accommodated in the said empty 1st accommodation stand 21A. . Thereafter, the first accommodation platform 21 </ b> A is lowered onto the turntable 10 by the platform lifting device 60.

  Thereafter, the turntable 10 is rotated to stop the second storage platform 21B at the processing position P1. And the 2nd accommodation stand 21B is raised to predetermined height with the stand raising / lowering apparatus 60. FIG. During the ascent, the new dip tube 20A accommodated in the second accommodation platform 21B is rotated to a predetermined position by the rotation device 50. And as shown in FIG. 13, the new dip tube 20A in the 2nd accommodation stand 21B is hold | maintained by the processing apparatus 90. As shown in FIG. After that, the empty second storage platform 21 </ b> B is lowered onto the turntable 10 by the platform lifting device 60. In this manner, the dip tube 20 is exchanged at the processing position P1.

  Thereafter, the turntable 10 is rotated to stop the first accommodation platform 21A at the repair position P2. And in the repair position P2, as shown in FIG. 14, the old dip tube 20B in the 1st accommodation stand 21A is replaced | exchanged for the new dip tube 20A by the crane 100. As shown in FIG. The replaced old dip tube 20B is moved to a predetermined position, and a refractory or the like is repaired by a repair device (not shown).

  According to the above embodiment, the dip tube 20 held in the processing apparatus 90 is immersed in the molten steel in the ladle 22 at the processing position P1, and secondary smelting of the molten steel is performed inside the dip tube 20. Can do. In addition, the dip tube 20 can be replaced at the processing position P1. Thus, in one processing position P1, the secondary refining of molten steel and the exchange of the dip tube 20 can be performed together. In addition, it is possible to easily align the dip tube 20 with respect to the processing device 90 only by rotating the turntable 10. Therefore, according to the present embodiment, the dip tube 20 can be exchanged efficiently in a short time. In particular, since the processing apparatus 90 using the CAS method can perform secondary refining of molten steel simply by holding the dip tube 20 with the holding portion 94, if the secondary smelting equipment 1 of the present embodiment is used, the dip tube is used. Exchange of 20 can be performed efficiently.

  In addition, since the secondary refining of the molten steel and the replacement of the dip tube 20 can be performed at one processing position P1, the area occupied by the secondary refining equipment 1 can be reduced.

  In addition, since the ladle 22 is provided on the turntable, the secondary refining is completed at the repair position P2 while the secondary refining of the molten steel in the ladle 22 is performed at the processing position P1. The ladle 22 can be replaced. Therefore, a series of secondary refining of molten steel can be performed in a shorter time.

  In the above embodiment, the holding arm 91 of the processing apparatus 90 is supported by the support pillar 92, but may be supported by a processing carriage (not shown) that can travel above the processing position P1. Good.

  The present invention is useful for secondary refining of molten steel and replacement of the dip tube in a secondary smelting facility in which the dip tube is immersed in the molten steel in the ladle and the secondary refining of the molten steel is performed inside the dip tube. It is.

It is the top view which showed the outline | summary of the structure of the secondary refining equipment concerning this Embodiment. It is the longitudinal cross-sectional view which showed the outline of the structure of the secondary refining equipment of the turntable vicinity. It is the side view which showed the outline of the structure of a storage frame, a frame raising / lowering apparatus, and a rotation apparatus. It is the side view which showed the outline of the structure of the gantry raising / lowering apparatus. It is explanatory drawing which showed a mode that the accommodation stand rose. It is the side view which showed the outline of the structure of a processing apparatus. It is the top view which showed the outline of the structure on the holding | maintenance arm of a processing apparatus. It is explanatory drawing which showed a mode that the secondary refining of molten steel is performed with a processing apparatus. It is explanatory drawing which shows a mode that the new dip tube was accommodated in two accommodation stand in a repair position. It is explanatory drawing which shows a mode that the processing apparatus hold | maintained the new dip tube of the 1st accommodation stand in the process position. It is explanatory drawing which shows a mode that the ladle was arrange | positioned in the processing position. It is explanatory drawing which shows a mode that the old dip tube was accommodated in the 1st accommodation stand in the process position. It is explanatory drawing which shows a mode that the processing apparatus was made to hold | maintain the new dip tube of a 2nd accommodation stand in a processing position. It is explanatory drawing which shows a mode that the dip tube of the 1st accommodation stand was replaced | exchanged in the repair position. It is the top view which showed the outline | summary of the structure of the conventional secondary refining equipment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Secondary refining equipment 10 Turntable 11 Base 12 Reduction gear 13 Slewing bearing 14 Through-hole 20 Immersion pipe 20A New immersion pipe 20B Old immersion pipe 21 Accommodation stand 21A First accommodation stand 21B Second accommodation stand 22 Ladle 30 Main body 31 Shaft portion 32 Flange 33 Deposit seat 40 Support base 41 Upper base 41a Plate 41b Upper frame 42 Lower base 43 Bearing 50 Rotating device 51 Motor 52 Decelerator 53 Shaft 54 Rotating portion 55 Support portion 60 Base lifting device 61 Lifting frame 61a Vertical Frame 61b Horizontal frame 62 Main frame 63 Cylinder 63a Tip 64 Shaft 65 Sprocket 66 Chain 67 First chain storage 68 Second chain storage 69 First guide roller 70 Second guide roller 80 Ladle lifting device 8 DESCRIPTION OF SYMBOLS 1 Concave part 82 Elevating part 90 Processing apparatus 91 Holding arm 92 Support pillar 93 Through-hole 94 Holding part 95 Clamping part 96 Arm 97 Motor cylinder 100 Crane C Center axis F Support point P1 Processing position P2 Repair position

Claims (4)

A dip tube is immersed in the molten steel in the ladle, and the equipment performs secondary refining of the molten steel inside the dip tube,
It has a turntable that can rotate horizontally,
On the turntable, a plurality of storage stands that can contain dip tubes and ladles for storing molten steel are provided concentrically on the turntable,
Furthermore, on the turntable, a stand lifting device for raising and lowering the accommodation stand and a turning device for turning a dip tube accommodated in the accommodation stand are provided,
Below the turntable is provided with a ladle lifting device that raises and lowers the ladle at a processing position for secondary refining of molten steel,
A secondary refining equipment for molten steel, characterized in that a processing device for secondary refining of molten steel is provided above the turntable by holding a dip tube at a predetermined height at the processing position. . The secondary refining equipment for molten steel according to claim 1, wherein a plurality of ladles are provided on the turntable. 3. The molten steel according to claim 1, wherein an exchange device is provided above the turntable to replace the dip tube or the ladle of the storage frame at a position different from the processing position. Secondary refining equipment. A method for performing secondary refining of molten steel using the secondary refining equipment according to claim 1,
After the new dip tube is accommodated in the plurality of accommodating platforms, the rotating platform is rotated to stop the one accommodating platform at the processing position, and the one lifting platform is brought to a predetermined height by the platform lifting device. A dip tube holding step of raising and holding a new dip tube housed in the one housing frame by the processing device;
Thereafter, the rotating table is rotated to stop the ladle at the processing position, the ladle is raised by the ladle lifting device, and the dip tube held by the processing device is placed inside the ladle. A treatment step of immersing in molten steel and performing secondary refining of the molten steel inside the dip tube,
When exchanging the dip tube, the rotating table is rotated to stop the one receiving frame at the processing position, and the one receiving frame is raised by the frame lifting device, and the one receiving frame is After accommodating the dip tube held by the processing device, the one lifting platform is lowered onto the turntable by the stand lifting device, and the turntable is rotated to move the other holding stand to the processing position. The other storage platform is raised to a predetermined height by the platform lifting device, and a new dip tube accommodated in the other storage platform is held by the processing device. Secondary refining method.

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