JP3890023B2 - Induction heating device for hot rolling bar - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction heating apparatus for a hot rolling bar that is arranged in a hot rolling line and heats the entire width direction of the bar.
[0002]
[Prior art]
An induction heating device that heats the entire width direction of the bar after the rough rolling may be arranged between the rough rolling mill and the finish rolling mill of a hot rolling line such as steel.
[0003]
In a heating furnace for hot rolling, it is difficult to bake by changing the temperature of each adjacent slab intermittently, so that the temperature is changed by several tens of degrees Celsius in units of several slabs. Include. When one slab is charged into the heating furnace at a low temperature, if this slab is extracted from the heating furnace at a target temperature or higher and the furnace temperature is increased, the slab is charged around the low temperature charging material in the furnace. The resulting high temperature charge is burned wastefully above the target extraction temperature, causing heating furnace fuel loss. On the other hand, if an induction heating device that heats the entire width of the bar after rough rolling is arranged, even if a low-temperature material as described above is charged, the furnace temperature is extracted without changing the temperature, and after rough rolling, By performing induction heating over the entire length in the longitudinal direction of the bar, it is possible to ensure the target finish rolling temperature, and it is possible to reduce the heating furnace fuel loss.
[0004]
Further, when the slab is extracted from the heating furnace at a high temperature, a secondary scale is generated on the surface of the product and bites during rolling, which may impair the appearance of the final coil. In such a case, the bar surface is cooled during rough rolling to finish rolling in order to ensure the appearance of the surface. If induction heating is performed for the entire length in the longitudinal direction of the bar after rough rolling, power saving by reducing bar cooling power and reduction of productivity reduction loss by increasing the number of air cooling or rough rolling passes for bar cooling Can do.
[0005]
At the front and rear ends of the bar, the temperature of the bar is lowered, and this low temperature portion is cropped before finish rolling in order to prevent cracking of the low temperature portion during finish rolling. If an induction heating device that heats the entire width direction of the bar is arranged, the temperature can be increased by heating the low temperature portion, and the crop cutting margin at the front and rear end portions can be reduced to improve the rolling yield. Patent Document 1 discloses an invention in which a solenoid induction heating device that heats the entire width direction of a bar before and after a crop shear is installed between a rough rolling mill and a finish rolling mill. Since the front and rear ends of the bar are heated at the low temperature part when passing through the solenoid induction heating device, the defective shape part is removed without cutting to the low temperature part as in the prior art, resulting in a decrease in yield. It is said that
[0006]
It is known that the scale produced in steel with a high Si content is very difficult to peel off. In hot rolling of a Si-containing steel sheet, for example, as described in Patent Document 2, the slab heating temperature in hot rolling is set to a low temperature heating of 1170 ° C. or lower, and the shape to be easily formed is removed, and before finish rolling. A technique for performing descaling with high-pressure water is disclosed. Since the heating temperature is set to a low temperature of 1170 ° C. or lower, the steel sheet temperature before finish rolling is too low to make finish rolling difficult. For this reason, an induction heating device for a steel plate is installed between rough rolling and finish rolling, and the bar is heated before finish rolling to ensure an optimum temperature for finish rolling. As the induction heating device, a solenoid type induction heating device is used as described above. By using the solenoid type induction heating device, it is possible to heat the entire width of the steel plate.
[0007]
The induction heating device that is arranged in the hot rolling line and heats the entire width direction of the bar is naturally arranged at the heating position on the line when heating the bar, and the side of the rolling line is maintained when maintenance of the induction heating device is performed. Move to the standby position. Therefore, the induction heating device is arranged so as to traverse between the heating position and the standby position.
[0008]
[Patent Document 1]
JP-A-10-291016 [Patent Document 2]
Japanese Patent Laid-Open No. 2000-254724
[Problems to be solved by the invention]
Looking at the heating device for heating the bar 1 between the rough rolling mill 22 and the finish rolling mill 23 during hot rolling, a conventional solenoid induction heating as shown in FIG. 7 is used as a heating device for heating the entire width of the bar. A device 31 was used. There is also a transverse induction heating apparatus as a type of induction heating apparatus. The transverse induction heating apparatus has a pair of upper and lower inductors composed of an iron core and a coil, and the inductors are arranged to face the bar passing position in the vertical direction. Conventionally, the transverse induction heating apparatus has only been used as an edge heater for heating the width end portion of the bar.
[0010]
When the temperature drop part at the front and rear end of the bar is heated to reduce the crop cutting loss, the temperature drop at the rear end of the bar is larger as it approaches the leading edge or the rear end, and is steady at the leading edge or the rear end. A temperature drop of 200 ° C. or more may be observed compared to the site. When a conventional solenoid induction heating apparatus is used, if it is attempted to compensate for a temperature drop of 200 ° C. or more at the most advanced part or the rearmost part, a huge apparatus is required as the scale of the heating apparatus, resulting in a large capital investment. On the other hand, when a transverse induction heating device that heats the full width is used to heat the rear end of the bar tip, the induced current is concentrated on the most advanced part (or the last end) of the steel plate, resulting in the induced current. The amount of temperature rise at the leading edge (or the rearmost edge) of the rough bar greatly increases. For example, when a heating device having a heating capability of increasing the steady-state temperature by about 60 ° C. is used, the temperature increase amount at the most advanced portion (or the rearmost end portion) of the coarse bar can exceed 400 ° C. Thus, it has been found that by using the transverse induction heating apparatus, the crop loss cutting allowance can be reduced even when the temperature drop at the rear end of the coarse bar is large.
[0011]
For removal of scale generated in steel with high Si content, magnetic flux is generated in the steel plate because magnetic flux is generated in the rolling direction when heating is performed by a solenoid induction heating device that heats the full width of the bar before finish rolling. Eddy currents concentrate near the surface of the steel sheet, and the steel sheet surface is selectively heated. As a result, the temperature rise near the steel plate surface is about twice as high as the temperature rise at the center of the steel sheet, and the scale remains after exceeding the generation limit temperature of the secondary scale after scale removal. On the other hand, when heating is performed using a full-width heating transverse induction heating device to remove the scale of high-Si steel, magnetic flux is generated in the steel plate to penetrate the coarse bar in the plate thickness direction. The generated eddy current is in the rolling direction, and uniform heating is performed in the plate thickness direction. As a result, the temperature rise of the steel plate surface and the central portion is the same, and the temperature rise near the steel plate surface can be prevented from exceeding the generation limit temperature of the secondary scale, and the scale can be removed.
[0012]
In the solenoid type induction heating device 31, as shown in FIG. 7, the induction coil 32 is disposed so as to surround the bar 1 at the heating position. The transverse type induction heating apparatus 15 has a shape having a pair of upper and lower inductors as described above. However, since each inductor is a heavy object including an iron core, usually a rectangular frame as shown in FIG. 30 to fix the upper and lower inductors (3, 4). In the heating position 17, a square frame 30 is arranged so as to surround the bar 1.
[0013]
As described above, the induction heating device 2 is arranged so as to traverse between the heating position 17 on the rolling line and the standby position 18 beside the line. Therefore, in a situation where the bar 1 does not exist on the line, the induction heating device 2 can be moved from the heating position 17 to the standby position 18.
[0014]
During the hot rolling, if a trouble occurs such that the bar tip hits the finishing mill entrance guide, the bar stops before the finishing mill. At this time, the bar 1 is stopped immediately below the induction heating device 2. It is necessary to quickly remove the stopped bar 1. However, since the induction heating device 2 arranged so as to surround the stopped bar 1 interferes, it is not possible to secure a work space. Even if the induction heating device 2 is to be retracted to the standby position 18, in the case of the solenoid type induction heating device 31, the coil 32 surrounds the bar 1, and in the case of the transverse type induction heating device, a square-shaped frame. 30 surrounds the bar 1, and the induction heating device 2 cannot be moved to the standby position 18 when the bar 1 is stopped anyway. For this reason, the work space for removing the bar cannot be secured in the end, and the line down time becomes longer, resulting in a significant loss of productivity.
[0015]
The present invention provides an induction heating apparatus that can secure a work space for removing bars by moving and retracting the induction heating apparatus 2 to a standby position 18 when the bar 1 stops just below the induction heating apparatus 2. This is the first purpose.
[0016]
A table roller 13 is arranged between the rough rolling mill and the finishing mill, and the bar 1 moves on the table roller. When the induction heating device is disposed on the rolling line, the induction heating device is disposed between the table roller. Since the induction heating device arranged so as to be laterally movable between the heating position and the standby position requires a required space below the bar passing position, it may be necessary to increase the height of the table roller. In the transverse induction heating apparatus, when the lifting / lowering device 11 for lifting the lower inductor 4 is provided, the required space below the bar passing position is further increased, and the height of the table roller 13 is further increased.
[0017]
When the height of the table roller 13 increases, the rigidity of the table roller decreases. When the tip of the bar moving on the table roller collides with the table roller, the fixed part of the table roller base is cracked, resulting in equipment failure. If the adjacent table rollers are connected by a structural member, it is possible to increase the overall rigidity. However, since such a structural member 14 hinders the lateral movement of the induction heating device 2, as shown in FIG. In addition, the structural member cannot be disposed between the installation position of the induction heating device 2, that is, between the table roller 13b and the table roller 13c. In particular, when a plurality of induction heating devices 2 are arranged in a line in the line direction as shown in FIG. 8B, table rollers (FIG. 8) arranged between the plurality of induction heating devices (2a, 2b). In the case of (b), no structural member can be arranged at 13c).
[0018]
A second object of the present invention is to provide an induction heating apparatus that can sufficiently ensure the rigidity of table rollers before and after the induction heating apparatus.
[0019]
[Means for Solving the Problems]
That is, the gist of the present invention is as follows.
(1) An induction heating device 2 that is arranged in a hot rolling line and heats the entire width direction of the bar 1, and the induction heating device 2 includes inductors (3, 4) composed of an iron core 5 and a coil 6. The inductors are arranged vertically opposite to the passing position of the bar 1, and the upper inductor 3 is held by a gantry 8 that can move along the rails 9. An induction heating apparatus for a hot rolling bar, wherein both the lower inductor 4 can traverse between a heating position 17 on the rolling line and a standby position 18 beside the line.
(2) The hot rolling bar induction heating device according to (1) above, wherein the upper inductor 3 and the lower inductor 4 are connected on the standby position 18 side.
(3) A table roller 13 on which the bar 1 travels is disposed before and after the induction heating device 2, and the table rollers 13 before and after the induction heating device 2 are connected to each other by a structural member 14 at least on one side in the width direction. The induction heating apparatus for a hot-rolled bar according to the above (1) or (2), wherein
(4) One or both of the upper inductor 3 and the lower inductor 4 are disposed so as to be movable up and down by a lifting device 11. The induction heating device for a hot rolling bar as described in (3) above,
(5) The induction heating device for a hot rolling bar according to (3) or (4) above, wherein the induction heating device 2 is arranged in a plurality in a line in the line direction.
(6) The hot rolling bar induction heating device according to any one of (3) to (5) above, wherein the table roller 13 and the structural member 14 are electrically insulated.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
As described above, a solenoid induction heating device 31 as shown in FIG. 7 is conventionally used as a heating device that heats the entire width of the bar 1 between the roughing mill 22 and the finishing mill 23 during hot rolling. It was. If the transverse induction heating device 15 is used as a full-bar width heating device, the edge portion of the bar 1 to be heated may be overheated, or the inductor shape is complicated and a large current cannot flow. This is because there is a problem that it is difficult to make a capacity device. As for the heating efficiency, when compared with a bar with a normal thickness of 30 to 50 mm, the transverse method is 65%, while the solenoid method is 75%, which is higher. The amount of capital investment is also less for the solenoid system with a simple structure. For the reasons described above, the transverse system has difficulty in adopting as an apparatus for heating the entire width of the bar. In the solenoid induction heating device 31, as shown in FIG. 7, the coil 32 is arranged so as to go around the bar 1, and the iron core 33 is arranged on the upper surface and the lower surface of the bar 1.
[0021]
The present invention has been able to achieve the object of the present invention by adopting the transverse induction heating device 15 having such a difficulty as a heating device for induction heating the entire width direction of the bar 1.
[0022]
The transverse induction heating device 15 has a pair of inductors composed of the iron core 5 and the coil 6, and the upper and lower inductors are arranged vertically opposite to the passing position of the bar 1. Conventionally, as shown in FIG. 6, the upper and lower inductors (3, 4) are fixed using a square frame 30.
[0023]
In the present invention, as shown in FIG. 1, the upper inductor 3 is held by a gantry 8 that can move along the rail 9. The rail 9 is disposed above the induction heating device 2 and at a height that does not interfere with various operations on the line, and the gantry 8 moves along the rail 9 so that the gantry 8 is perpendicular to the bar traveling direction. Move horizontally. The upper inductor 3 held by the gantry 8 moves laterally with the movement of the gantry 8 and can move between the heating position 17 and the standby position 18 of the induction heating device.
[0024]
The lower inductor 4 is also arranged so as to be movable between the heating position of the induction heating device and the standby position. Normally, the movement is performed by a carriage 7 disposed below the lower inductor 4.
[0025]
Thus, both the upper inductor 3 and the lower inductor 4 can traverse between the heating position 17 on the rolling line and the standby position 18 beside the line. Further, since there is no square-shaped frame 30 as in the prior art, even if the bar 1 is stopped on the rolling line, the upper and lower inductors are moved from the heating position 17 to the standby position 18 without being affected by the bar 1. Can be rampant. Similarly, even if the table rollers 13 before and after the induction heating apparatus are connected by the structural member 14 as shown in FIG. 2, the upper and lower inductors can freely traverse between the heating position 17 and the standby position 18. it can.
[0026]
The lateral movement device 10 for traversing the upper inductor 3 and the lower inductor 4 may be provided separately for each inductor. In the example shown in FIG. 1B, the upper inductor 3 is driven by a lateral movement device 10 b disposed on the gantry 8, and the lower inductor 4 is driven by a lateral movement device 10 a connected to the carriage 7. Alternatively, as shown in FIG. 1A, it is preferable to connect the upper and lower inductors and move them in conjunction with each other because the upper and lower inductors can be traversed by a single lateral movement device 10. When connecting the upper and lower inductors, it is necessary that the upper inductor and the lower inductor are connected on the standby position side. When the bar is stopped on the rolling line, or when the front and rear table rollers are connected by structural members, the connection part interferes with the connection at the anti-standby position side. This is because the heating device cannot be traversed.
[0027]
Since the induction heating device of the present invention has the above-described structure, as shown in FIG. 2 without impairing the function of traversing the induction heating device 2 between the heating position 17 and the standby position 18. The table rollers 13 before and after the induction heating device can be connected by the structural member 14 at least on one side in the width direction. As a result, even if the height of the table roller 13 is increased by installing the induction heating device, the rigidity of the table roller can be increased by connecting with the structural member 14, and the bar moving on the table roller Even if the tip collides with the table roller, there is no equipment failure that causes the fixed part of the table roller base to crack.
[0028]
When the transverse induction heating device 15 has the lifting device 11 for lifting the lower inductor 4 as shown in FIG. 1, the required space below the bar passing position is further increased, and the height of the table roller 13 is increased. Is even higher. Since the rigidity of the table roller 13 can be increased by connecting with the structural member 14 as in the present invention, even when the lifting device 11 for lifting and lowering the lower inductor is provided, a sufficiently rigid table roller and can do.
[0029]
When only one set of the induction heating device 2 is arranged in the hot rolling line, the table rollers (13b, 13c) before and after the induction heating device are structured with the adjacent table rollers on the side where the induction heating device 2 is not arranged. It has been possible to connect with the member 14 conventionally (FIG. 8A). On the other hand, when a plurality of induction heating devices are arranged in a line in the line direction, conventionally, the structural roller 14 is completely disposed on the table roller 13b disposed between the plurality of induction heating devices (2a, 2b). It was not possible to arrange (FIG. 8B). In the present invention, even when a plurality of induction heating devices are arranged in a row, the structural member can be connected between all the adjacent table rollers, so that the improvement effect by applying the present invention is particularly great.
[0030]
In the space between the upper and lower inductors of the transverse induction heating device 15, an induced current having an axis in the direction perpendicular to the bar 1 is induced. When there is a bar in this space, an induced current 28 flows inside the bar 1 as shown in FIG. 5, and the bar 1 is heated. On the other hand, if a current path centered in a direction perpendicular to the bar is formed in a member with a part other than the bar or a part including the bar, an induced current is also induced in the current path. Become.
[0031]
In the present invention, when the table rollers arranged before and after the induction heating device are connected by the structural member 14, when the bar enters the table roller, the bar 1-table roller 13-structural member 14-table roller 13 -Conduction between the bars 1 becomes a closed loop, and a current path is formed. This current path is a path through which an induced current can flow. When an induced current flows through this current path, a spark is generated between the bar and the table roller, which is not preferable.
[0032]
In the present invention, by electrically insulating the table roller 13 and the structural member 14, the formation of the closed loop as described above can be prevented, and the generation of the induced current and the accompanying spark can be prevented. It becomes possible to do.
[0033]
As a specific insulating means, an electrical insulating layer is provided between the table roller 13 and the structural member 14. As an insulating material for insulation, an epoxy resin having a volume resistance of 10 ¹³ Ω · cm or more in class and a heat resistance of 180 ° C. or more is desirable. When fastening the sandwiched insulating material, it is desirable to use a washer and a member in which the bolt hole is insulated with ceramic coating or the like.
[0034]
As shown in FIG. 4, the transverse induction heating apparatus 2 for induction heating the entire width direction of the bar used in the present invention has two vertical portions 26 and one horizontal portion 27 as iron cores (5a, 5b). The U-shaped iron core (5a, 5b) is formed so that the two vertical portions 26 face the surface of the bar 1 and the width of the iron core covers the entire width of the bar 1. Is preferably arranged so as to face the upper surface side and the lower surface side of the bar 1, and the coil 6 is disposed so as to surround each vertical portion (26a, 26b). A magnetic field is generated by the coil 6 surrounding the vertical portion 26, and the magnetic field is formed in two U-shaped iron cores facing each other to become a loop magnetic field. Since the end surfaces of the vertical portions 26 of the respective iron cores face each other, a magnetic field is generated between both end surfaces, and the bar 1 is disposed between the both end surfaces, so that a magnetic field is formed perpendicular to the bar surface. Since the width of the iron core has a width that covers the entire width of the bar 1, a magnetic field perpendicular to the bar 1 is formed over the entire width of the bar 1. By passing an alternating current through the coil 6 surrounding the iron core, the magnetic field penetrating the bar 1 also becomes an alternating magnetic field, and an eddy current is formed as an induced current in the bar.
[0035]
Regarding the relationship between the width of the bar 1 to be heated and the width W of the iron core 5, the width of the bar is preferably wider than the iron core width W. The transverse type induction heating device 15 may overheat the edge portion (width direction end portion) of the bar 1 to be heated, but by generating the eddy current at the edge portion by making the iron core width W narrower than the bar width. This is because the overheating of the edge portion can be suppressed. This makes it possible to heat the entire width of the bar uniformly.
[0036]
The heating / heating capacity of the bar varies depending on the interval between the iron cores arranged facing the upper surface side and the lower surface side of the bar. The narrower the distance between the iron cores, the greater the amount of temperature rise of the bar due to heating. Therefore, the interval between the iron cores is normally set as narrow as possible. However, the tip of the bar may have a warped shape, and if the interval between the iron cores of the induction heating device 2 is narrow, the tip of the bar having the warp cannot enter the gap between the iron cores. Overhang may occur. In the present invention, by providing an elevating device 11 that raises and lowers the upper and lower inductors, the interval between the iron cores is enlarged when the bar tip enters the induction heating device 2, and the interval between the iron cores is reduced after entering the tip. Therefore, a countermeasure for increasing the heating temperature raising capability is performed.
[0037]
A plurality of transverse type induction heating devices can be arranged in series to form a set of full width induction heating devices as a whole. Each induction heating device has a medium capacity, and the necessary capacity can be ensured as a whole. Conventionally, there has been a problem that it is difficult to produce a large-capacity induction heating device, but this problem can be solved by arranging a plurality of medium-capacity heating devices. In hot rolling, there are many types of bars ranging from wide to narrow. Set the core width of each induction heating device arranged in series as the optimum core width for narrow bars, and when performing hot rolling of wide bars, separate induction heating devices in different directions in the bar width direction It is also possible to heat the entire width of the bar by shifting to.
[0038]
The transmission frequency of the transverse induction heating device is preferably about 100 to 500 Hz. In the solenoid type induction heating apparatus, a frequency of about 1500 Hz was used. However, in order to increase the heat penetration depth and to prevent a failure due to local heat generation of the self-constituting member, Thus, it is preferable to be about 100 to 500 Hz.
[0039]
【The invention's effect】
In an induction heating apparatus for a hot rolling bar that is arranged in a hot rolling line and heats the entire width direction of the bar, the present invention employs a transverse type induction heating apparatus, and the upper inductor is movable on a rail. When the bar is stopped immediately below the induction heating device, the induction heating device can be moved to and retracted to the standby position to secure a work space for removing the bar.
[0040]
In the present invention, by adopting the above configuration, the table rollers before and after the induction heating device are connected to each other by a structural member at least on one side in the width direction, and the rigidity of the table roller can be sufficiently secured.
[Brief description of the drawings]
FIG. 1 is a front view showing an induction heating device of the present invention.
FIG. 2 is a perspective view showing the vicinity of the induction heating apparatus of the present invention.
FIG. 3 is a plan view showing a hot rolling line in which the induction heating apparatus of the present invention is installed.
FIG. 4 is a perspective view showing a transverse induction heating apparatus of the present invention.
FIG. 5 is a perspective view showing an induction current generated in a bar by a transverse induction heating device.
FIG. 6 is a front view showing a conventional induction heating device.
FIG. 7 is a perspective view showing a solenoid type induction heating device.
FIG. 8 is a perspective view showing the vicinity of a conventional induction heating device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bar 2 Induction heating apparatus 3 Upper inductor 4 Lower inductor 5 Iron core 6 Coil 7 Carriage 8 Mount 9 Rail 10 Lateral movement apparatus 11 Lifting apparatus 12 Wheel 13 Table roller 14 Structural member 15 Transverse type induction heating apparatus 17 Heating position 18 Standby position 21 Bar traveling direction 22 Rough rolling mill 23 Finishing rolling mill 24 Heating furnace 25 Winding machine 26 Vertical section 27 Horizontal section 28 Inductive current 30 Frame 31 Solenoid induction heating apparatus 32 Coil 33 Iron core

Claims (6)

An induction heating device that is arranged in a hot rolling line and heats the entire width direction of the bar, the induction heating device having an inductor composed of an iron core and a coil, and the inductor is vertically arranged with respect to the passing position of the bar The upper inductor is held by a pedestal that can move along the rails. An induction heating device for a hot rolling bar, characterized in that it can traverse between the two. The induction heating apparatus for a hot-rolled bar according to claim 1, wherein the upper inductor and the lower inductor are connected on the standby position side. A table roller on which a bar travels is disposed before and after the induction heating device, and the table rollers before and after the induction heating device are connected to each other by a structural member at least on one side in the width direction. 3. An induction heating apparatus for a hot rolling bar according to 1 or 2. The induction heating device for a hot-rolled bar according to claim 3, wherein one or both of the upper inductor and the lower inductor are arranged to be moved up and down by a lifting device. The induction heating apparatus for a hot rolling bar according to claim 3 or 4, wherein the induction heating apparatus is arranged in a row in a line direction and is arranged in a plurality. The induction heating device for a hot rolling bar according to any one of claims 3 to 5, wherein the table roller and the structural member are electrically insulated.

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