JP2004058154A - Hot rolling method and apparatus for steel sheet - Google Patents

Abstract

A hot rolling method for manufacturing a hot-rolled steel sheet having no variation in material properties in the width direction by making the temperature distribution uniform over the entire width direction of the rough bar on the entrance side or the exit side of the finishing mill. And equipment.
In a hot rolling method for a steel sheet, a temperature increase amount is changed in a sheet width direction of a material to be rolled so that a temperature distribution in a width direction of a material to be rolled on an entrance side or an exit side of a finishing rolling machine is made uniform. The material to be rolled is heated, for example, at least the amount of temperature rise in the central portion in the sheet width direction of the material to be rolled is larger than the amount of temperature rise in the middle portion between the center portion and both edges in the sheet width direction. The heat of the steel sheet is characterized in that the material to be rolled is heated so that the amount of temperature rise at both edges in the width direction of the material to be rolled is larger than the amount of temperature rise in the middle portion in the width direction of the material. Rolling method.
[Selection diagram] None

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to hot rolling of a steel sheet, and in particular, a hot rolling method for producing a hot-rolled steel sheet with a high yield by controlling the temperature in the width direction of a coarse bar on the entrance side of a finishing rolling mill to have a predetermined temperature distribution. And an apparatus.
[0002]
[Prior art]
As shown in FIG. 1, hot rolling of a steel sheet is performed by charging a low-temperature slab 2 into a heating furnace 1 and reheating the slab 2 to a predetermined temperature. The coarse bar 4 is rolled into a coarse bar 4, and the leading and trailing ends of the coarse bar are cut using a crop shear 12. After the part is heated and finish-rolled to a predetermined hot-rolled steel sheet by a continuous finishing rolling mill 7 comprising a plurality of stands, it is cooled by a cooling stand 8 on a run-out table and wound up by a coiler 9. I have.
[0003]
Further, when endless rolling is performed in which rough bars are joined and finish rolling is performed before finish rolling, a low-temperature slab 2 is charged into a heating furnace 1 as shown in FIG. The slab 2 which has been reheated to the temperature and is reheated is rolled to a predetermined thickness by the rough rolling mill 3 to form the rough bar 4, which is wound up by the coil box 10 and the tip of the coarse bar unwound from the coil box is removed. It is cut by the joining shear 11, and the rear end of the preceding coarse bar and the front end of the following coarse bar are joined by the welding device 12, and the edge heater 6 is used to recover the temperature drop at both edges in the width direction of the coarse bar 4. After heating both edge portions with a continuous finishing mill 7 consisting of a plurality of stands and finish rolling to a predetermined hot-rolled steel sheet, the resultant is cooled in a cooling stand 8 on a run-out table and wound up by a coiler 9. Is being done.
[0004]
In the hot rolling or endless rolling process of such a hot-rolled steel sheet, since the low-temperature slab is reheated in a heating furnace, the occurrence of uneven heating is inevitable, and the thickness of the rolled material relative to the sheet width is inevitable. Due to the small size, a temperature drop occurs at both edges of the coarse bar. Such a temperature drop does not result in a predetermined temperature distribution (in this case, a uniform temperature distribution) in the width direction of the rough bar, resulting in non-uniformity, which causes a non-uniform finish temperature.
[0005]
Therefore, if the temperature distribution in the width direction of the rough bar becomes uneven, hot rolling and elongation occur in the hot-rolled steel sheet during finish rolling, and the material properties such as mechanical properties in the width direction of the hot-rolled steel sheet become uneven. And other problems arise.
[0006]
In order to prevent such a problem caused by non-uniform temperature distribution in the width direction of the rough bar, a heating device and an edge heater are provided between the rough rolling mill and the finishing rolling mill, and the rough rolling is performed by the rough rolling mill. It is known to heat a roughened bar. For example, between a rough rolling mill and a finishing rolling mill, a solenoid-type induction heating device for heating the rough bar over the entire width direction, and an edge heater for heating both edges of the rough bar are provided. It has been proposed to heat a rough bar on the entry side of a finishing mill to a uniform temperature in the width direction thereof by using a solenoid type induction heating device and an edge heater (for example, Patent Document 1).
[0007]
The characteristic of the solenoid type induction heating device used here is that it has a magnetic field characteristic that a coil is wound around the plate and a magnetic field is generated in parallel with the plate. Therefore, the temperature is increased over the entire width by a uniform temperature while the temperature distribution in the plate width direction is substantially constant.
[0008]
In other words, in the above-mentioned proposed technology, the entire rough bar is uniformly heated in the width direction by a solenoid-type induction heating device in order to reduce the rolling load, and both edge portions are heated by an edge heater to make the width direction uniform. The purpose of this is to achieve a proper temperature distribution.
[0009]
However, as a result of the present inventor's research on the material properties of the hot-rolled steel sheet in the width direction, the rough bar on the entrance side of the finishing mill was heated by an edge heater with a large temperature drop by an edge heater to obtain a temperature distribution in the width direction. It has been found that even in the case of uniformity, there is variation in the width direction material properties of the steel sheet obtained by finish rolling. That is, in the heating method in which the entire rough bar is uniformly heated in the width direction between the rough rolling mill and the finish rolling mill, and both edge portions having a large temperature drop are heated by the edge heater, the width direction material of the hot-rolled steel sheet is heated. It was difficult to make the characteristics uniform. Various experiments were conducted to determine the cause, and it was found that there was a cause during slab heating in a heating furnace. That is, since the heating furnace heats the slab in a high-temperature atmosphere, the temperature at the center of the slab thickness is inevitably low, and this temperature distribution is maintained even when the thickness is reduced by rolling. The cause was that the temperature was lower at the center and higher toward the edge than the average temperature in the width direction.
[0010]
Therefore, the uniformization of the material properties in the width direction cannot be eliminated by the heating method using the edge heater.
[Patent Document 1]
JP-A-9-314216
[Problems to be solved by the invention]
Therefore, the present invention changes the amount of temperature rise in the width direction of the coarse bar (preferably, the amount of temperature rise in the central low-temperature portion in the width direction is large), and the width of the coarse bar in the width direction of the rough bar at the entrance or exit of the finishing mill. An object of the present invention is to provide a hot rolling method and apparatus for stably producing a hot rolled steel sheet having predetermined material properties in a width direction by setting a predetermined temperature distribution.
[0012]
[Means for Solving the Problems]
The present inventor, in order to stably obtain a hot-rolled steel sheet having predetermined material properties in the width direction, it is necessary to make the width direction temperature of the rough bar on the entrance side of the finishing rolling mill a predetermined temperature distribution, For that purpose, a portion where the temperature drop is large in the plate width direction of the coarse bar (preferably, a low-temperature portion having a half width of the central portion of the coarse bar due to a low temperature of the central portion of the slab thickness during slab heating, more preferably The present inventors have found that the temperature in the width direction of the coarse bar can be controlled to a predetermined temperature distribution by heating and raising the temperature of the coarse bar, which is the edge portion of the coarse bar, which is the both edge portions during the rolling, and reduce the temperature by 100 mm. .
[0013]
The gist of the present invention is as follows.
[0014]
(1) In the hot rolling method for a steel sheet, the amount of temperature rise is changed in the sheet width direction of the material to be rolled so that the temperature distribution in the width direction of the material to be rolled on the entrance side or the exit side of the finishing mill becomes a predetermined temperature distribution. A hot rolling method for a steel sheet, characterized by heating a material to be rolled.
[0015]
(2) The material to be rolled is heated so that the amount of temperature rise in the central portion in the sheet width direction is larger than the amount of temperature rise in the middle portion between the center portion and both edges in the sheet width direction. (1) The method for hot rolling a steel sheet according to the above (1).
[0016]
(3) The above (1) or (1) or (2), wherein the material to be rolled is heated so that the amount of temperature rise at both edges in the sheet width direction is larger than the amount of temperature rise in the middle portion in the width direction of the sheet. 2) The method for hot rolling a steel sheet according to the above.
[0017]
(4) The temperature distribution in the width direction of the material to be rolled on the inlet side of the heating device is grasped in advance, the maximum value of the temperature in the width direction is set as a reference temperature, and the temperature difference between the temperature at each point in the width direction and the reference temperature is calculated. The above-mentioned (1) to (3), wherein the amount of temperature rise at each point required so that the width-direction temperature distribution becomes a predetermined temperature distribution is determined based on the difference, and heating is performed according to the amount of temperature rise. The hot rolling method for a steel sheet according to any one of the above.
[0018]
(5) The hot rolling method for a steel sheet according to any one of (1) to (4), wherein at least two or more heating devices are arranged along the rolling line.
[0019]
(6) The heating apparatus according to any one of (1) to (5), wherein the heating apparatus is a transverse induction heating apparatus capable of heating the material to be rolled by changing the amount of temperature rise in the sheet width direction. The hot rolling method for a steel sheet according to any one of the preceding claims.
[0020]
(7) The hot-rolling of a steel sheet according to (6), wherein the transverse induction heating device is at least two or more transverse induction heating devices having different iron core widths in the width direction. Method.
[0021]
(8) In the hot rolling apparatus for a steel sheet, a heating apparatus for heating the material to be rolled by changing the temperature increase in the width direction of the material to be rolled is provided on the rough rolling mill entrance side in the rolling line, between the rough rolling mill rows, and rough rolling. A hot-rolling apparatus for a steel sheet, wherein the hot-rolling apparatus is disposed between a rolling mill and a finishing mill or between rows of finishing mills.
[0022]
(9) A heating device in which the amount of temperature rise at least in the central portion in the sheet width direction of the material to be rolled is larger than the amount of temperature rise in the intermediate portion between the center portion and both edges in the sheet width direction. (8) The hot-rolling apparatus for a steel sheet according to the above (8).
[0023]
(10) The heating device according to the above (8), wherein the heating device is such that the amount of temperature rise at both edges in the sheet width direction of the material to be rolled is larger than the amount of temperature rise at the middle portion in the width direction of the sheet width direction. Or the hot-rolling apparatus of the steel plate of (9).
[0024]
(11) A hot-rolling apparatus for a steel sheet, which includes a heating device for heating the material to be rolled by changing a temperature rising amount in a sheet width direction, and an edge heater for heating both edge low-temperature portions of the rough bar. The hot-rolling apparatus for a steel sheet according to any one of the above (8) to (10), characterized in that:
[0025]
(12) On the entry side of the finishing mill, a heating device for heating by changing the temperature rise amount in the width direction of the material to be rolled in the width direction of the rough bar and heating both edge low-temperature portions in the width direction of the rough bar. An edge heater and a temperature grasping device that grasps the temperature distribution in the width direction of the coarse bar are arranged, and the maximum value of the temperature in the width direction grasped by the temperature grasping device is used as a reference temperature, and the temperature of each point in the width direction, the reference temperature, and the like. And a device for determining the amount of temperature rise at each point required so that the temperature in the width direction has a predetermined temperature distribution based on the temperature difference, a heating device and an edge heater based on the amount of temperature rise A hot-rolling of the steel sheet according to any one of the above (8) to (11), further comprising: apparatus.
[0026]
(13) The hot-rolling apparatus for a steel sheet according to any one of (8) to (12), wherein at least two or more heating apparatuses are arranged along the rolling line.
[0027]
(14) The heating device according to any one of (8) to (13), wherein the heating device is a transverse induction heating device capable of heating the material to be rolled by changing the amount of temperature rise in the sheet width direction. The hot-rolling apparatus for a steel sheet according to any one of the above.
[0028]
(15) The hot-rolling of a steel sheet according to (14), wherein the transverse induction heating device is at least two or more transverse induction heating devices having different core widths in the width direction. apparatus.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
It is known that in order to obtain a predetermined material property in the width direction, for example, to obtain a hot-rolled steel sheet having no variation in the material in the width direction, it is necessary to make the temperature distribution in the width direction of the coarse bar on the entrance side of the finishing mill uniform. ing. Conventionally, it has been considered that the temperature distribution in the width direction of the rough bar becomes uniform by raising the temperature drop at both edges of the rough bar caused by the rough rolling by the edge heater.
[0030]
However, the hot-rolled steel sheet which has been subjected to finish rolling by heating both edges of the rough bar by an edge heater has variations in material properties in the width direction.
[0031]
The inventor of the present invention has conducted various experiments to determine the cause, and as a result, has found out that the cause is present during slab heating in a heating furnace.
[0032]
That is, since the heating furnace heats the slab in a high-temperature atmosphere, as shown in FIG. 3A, the heated slab 2 becomes a high-temperature portion 14 around the slab 2, but in a width direction including a half width. It is inevitable that a low-temperature portion 13 is generated at the center. Then, when the surface temperature distribution of the slab on the rough rolling mill entry side was measured, as shown in FIG. 3 (b), the center of the center line (CL) was lower than the average temperature in the width direction (1200 ° C.), (1230 ° C.).
[0033]
When a slab having such a temperature distribution is roughly rolled into a coarse bar, as shown in FIG. 4 (a), since both edges of the coarse bar 4 have a large cooling temperature 15, the temperature distribution of the coarse bar is as shown in FIG. As shown in FIG. 4 (b), the temperature at the center of half the width of the center line is lower (1033 ° C.) and the middle between the center and the edge is higher (1056 ° C.) than the average temperature in the width direction. ), And the temperature became lower (1002 ° C.) at least toward the edge portion from both edges to 100 mm, and the temperature distribution was M-shaped. When the rough bar having such a temperature distribution is finish-rolled, as shown in FIG. 4 (c), the M-shaped temperature distribution is maintained even when the plate thickness is reduced by the finish rolling, and the central part is 842 ° C., and the middle part is 842 ° C. Had the highest temperature (865 ° C.) and the edge portion was 800 ° C.
[0034]
The respective temperature distributions in the width direction of the slab heated by the heating furnace described above, the rough bar after the rough rolling, and the steel sheet on the finish rolling exit side are shown in (a), (b), and (c) of FIG. Indicated. Each of them had an M-shaped temperature distribution in the width direction.
[0035]
The case where the edge portion of the rough bar is heated by the edge heater in the conventional hot rolling method will be described with reference to FIG.
[0036]
As shown in FIG. 6A, the surface temperature distribution in the slab width direction before the rough rolling is such that the temperature at the center of the center line (CL) is 1200 ° C. and the temperature at the center of the center line is 1230 ° C. When both edges of the coarse bar are heated by an edge heater to compensate for a temperature drop at both edges of the coarsely-rolled coarse bar, as shown in FIG. Is added, and the temperature of both edges rises to 1056 ° C. However, the temperature (1033 ° C.) in the central low-temperature portion does not rise, and the temperature distribution in the width direction is not made uniform. In this state, it has been conventionally determined that the temperature distribution in the width direction of the coarse bar has been made uniform.
[0037]
When the rough bar whose both edges are heated by the edge heater is finish-rolled, the temperature distribution in the width direction of the rough bar is maintained even when the thickness becomes thin, and the temperature distribution in the width direction of the hot-rolled steel sheet on the exit side of the finishing mill is maintained. As shown in FIG. 6C, the central portion was lower (842 ° C.) than the average temperature in the width direction.
[0038]
Further, an example of a case where a coarse bar is heated in the entire width direction by using a solenoid-type induction heating device as a heating device for the coarse bar will be described with reference to FIG.
[0039]
FIG. 7A shows the temperature distribution in the width direction of the slab. As shown in FIG. 7 (b), the temperature distribution in the width direction of the rough bar obtained by roughly rolling the slab having this temperature distribution is 1033 ° C. in the central low temperature part, 1056 ° C. in the middle part, and 1002 ° C. in the edge part. Met. When this coarse bar is uniformly heated in the width direction by a solenoid-type induction heating device, the entire temperature rises by an amount indicated by oblique lines, and the central portion is 1046 ° C, the middle portion is 1069 ° C, and the edge portion is 1015 ° C. Become. However, also in this case, the temperature distribution in the width direction is an M-shaped temperature distribution. Therefore, when a rough bar heated uniformly in the entire width direction by a solenoid type induction heating device is rolled by a finishing mill, as shown in FIG. 7 (c), a hot rolled steel sheet having an M-shaped temperature distribution in the width direction is obtained. can get.
[0040]
As described above, the present inventor has proposed a method of heating both edges of a rough bar with an edge heater in the middle of rolling as in the related art when hot rolling is performed using a slab heated in a heating furnace, or a solenoid. In the method of heating the rough bar in the width direction with the die induction heating device, the temperature distribution in the width direction of the steel sheet on the entrance side of the finishing mill is not necessarily uniform, contrary to the conventional idea. As a result, a new finding was obtained that the widthwise material properties of the hot-rolled steel sheet vary.
[0041]
The unevenness of the temperature distribution in the width direction of the rough bar due to the heating of the slab by the heating furnace and the cooling of the edge portion at the time of rolling is not uniform. Was found to be the cause.
[0042]
Therefore, in the present invention, in order to equalize the temperature distribution in the width direction of the coarse bar on the entrance side or the exit side of the finishing mill, the amount of temperature rise is changed in the sheet width direction to equalize the temperature distribution in the width direction of the coarse bar. I decided to let it. At this time, preferably, the amount of temperature rise in the center low-temperature portion of the plate width including the half width of the coarse bar is at least an intermediate portion between the center portion and both edges in the plate width direction (と width and 3/3 width). (Including the four widths) so as to be greater than the amount of temperature rise, and more preferably, the low-temperature portions of both edge portions (at least from both ends of the width to the center of the plate 100 mm) in the plate width direction are more than the middle portion of the plate width. The temperature was raised so as to increase by the edge heater, and the temperature distribution in the width direction of the coarse bar was made uniform. In the present invention, the “central part” or “central low-temperature part” in the width direction of a material to be rolled such as a rough bar refers to a position at a half width lower than the highest temperature in the width-direction temperature distribution as described above. Includes the area at the center of the plate width. In addition, the plate width “intermediate portion” means a region including the highest temperature portion of the temperature distribution in the width direction, excluding the “center portion” in the width direction as described above, and including the positions of the １ ／ width and the ／ width. I do.
[0043]
As the heating device, any heating device can be used as long as the temperature rise distribution in the width direction is particularly large in the central portion and the amount of temperature rise is large toward the end, and a gas heating device concentrated in the central portion in the width direction. Alternatively, an energizing device capable of energizing and heating only the central portion can be used, but the most preferable heating is heating by a transverse induction heating device. That is, the gas heating device is inexpensive, but scale tends to occur on the surface of the rough bar. Further, in the electric heating device, if a spark is generated between the rough bar and the electrode, the rough bar may be flawed. Unlike the solenoid type induction heating device, the transverse type induction device has a characteristic that the specific portion in the width direction of the coarse bar can be uniformly heated according to the iron core width, so the width is larger than the coarse bar width. By arranging a plurality of narrow transverse induction heating devices along the rolling line and using two or more transverse induction heating devices in combination with two or more iron cores narrower than the coarse bar width, the desired width can be obtained. The direction specific portion can be heated. In addition, as shown in FIG. 8, the transverse induction heating device 20 is configured by winding a coil 19 around an iron core 18 and can be used by being disposed above and below a steel plate 21 for handling. Because it is easy, and does not cause scratches on the surface of the rough bar, and does not overheat the surface due to its characteristics, there is no restriction on the arrangement relationship with other equipment such as rolling mills, desks and the like. .
[0044]
Hereinafter, the present invention will be described with reference to the drawings.
[0045]
In the hot rolling apparatus shown in FIG. 1, an induction heating apparatus and an edge heater are disposed between a rough rolling mill and a finishing rolling mill, as schematically shown in FIG. And
[0046]
The width of the iron core is narrower than the width of the coarse bar, and the width of the core is three. A delivery width direction thermometer 26 is provided. The rough bar 4 rolled by the rough rolling mill is conveyed in the direction of the arrow by a table roll. The width-direction temperature distribution of the coarse bar 4 is measured by the entrance-side width-direction thermometer 22, and the amount of temperature rise of the coarse bar by heating each of the transverse induction heating devices 23, 24, 25 is increased based on the width-direction temperature distribution. Determined by the temperature control device. The coarse bar is heated in the vicinity of its central low-temperature portion by the transverse induction heating device 23, and then heated by the transverse induction heating device 24 in the middle portion including the central portion and in the vicinity of 1/4 width. The heating device 25 heats the middle part including the central part and around the 3/4 width. Then, both edge low-temperature portions (at least from the end in the plate width direction to the center side of the plate 100 mm) of the coarse bar are heated by the edge heater 6 (so as to be larger than the temperature increase in the middle portion in the plate width direction). You. These heating and heating amounts are controlled by a heating amount control device. The temperature distribution in the width direction of the coarse bar after heating is measured by the outlet side width direction thermometer 26. If the temperature distribution in the width direction measured by the exit side width direction thermometer is not uniform, the measured data is fed back to the transverse induction heating device 23 and the temperature rise amount control device of the edge heater 6 for control. The output of the heating amount of each heating device is changed and controlled by the device, and the temperature distribution in the width direction of the coarse bar is made uniform. In order to make the temperature distribution in the width direction uniform, it is most preferable to make the temperature deviation of the temperature distribution in the width direction 0 ° C. In the present invention, the temperature deviation of the temperature distribution in the width direction is 10 ° C. or less, preferably 5 ° C. or less. Is acceptable.
[0047]
Here, the plurality of induction heating devices do not necessarily have to have the same iron core width, and they may be appropriately changed according to the temperature distribution in the plate width direction. For example, as shown in FIG. 9 (b), instead of the induction heating devices 24 and 25 of FIG. 9 (a), the induction heating devices 27 and 27 each having a core width twice as large as the induction heating devices 24 and 25. 23 units may be arranged.
[0048]
It is not necessary to limit the arrangement order of the plurality of transverse induction heating devices and the edge heaters as shown in FIGS. 9A and 9B, but it is preferable that they are close to each other in consideration of the overall temperature controllability. .
[0049]
As a temperature grasping device, it is preferable to install a width-direction thermometer in the vicinity of the transverse induction heating device as described above in terms of accuracy, but the temperature inside the heating furnace, the temperature of the slab on the exit side of the heating furnace, etc. The width direction on the entrance side of the transverse induction heating device is calculated by numerical calculation based on the measured temperature of the bar and the rough bar transfer conditions (rough rolling conditions, transfer speed, time from the heating furnace to the induction heating device, etc.) to the vicinity of the induction heating device. A device for grasping the temperature distribution may be provided. Alternatively, it is also possible to provide a width direction thermometer on the exit side of the finish rolling mill to grasp the temperature distribution in the width direction on the entrance side of the transverse induction heating device.
[0050]
An example of the temperature rise characteristics of the transverse induction heating device will be described with reference to FIG.
[0051]
FIGS. 10A to 10C show the temperature rise distribution of the rough bar 4 by heating when three heating devices 23, 24, and 25 having the same iron core width are used. FIG. 10 shows an example of a case where the temperature of the coarse bar is uniformly increased up to 40 ° C. corresponding to the width of each iron core of the heating device. The temperature rise gradually decreases outside the core width.
[0052]
The temperature distribution that can be raised by the three transverse induction heating devices is the sum of the three temperature rise amounts, and as shown in FIG. 10 (d), the heating devices 23, 24, and 25 respectively increase the temperature. The temperature rise amounts of 28, 29, and 30 are overlapped to form a gentle mountain-shaped temperature rise distribution in which the temperature rise amount is changed in the width direction.
[0053]
Therefore, for example, a coarse bar having an M-shaped temperature distribution in which the central maximum low temperature portion is 1060 ° C. and the intermediate maximum temperature is 1100 ° C. is a total temperature increase amount of three transverse induction heating devices shown in FIG. (40 ° C.) makes it possible to uniform the temperature distribution at the center in the width direction to 1100 ° C. In addition, since both edge portions are heated by the edge heater, the temperature is increased by the temperature increase amount 16 of the edge heater. As a result, the temperature deviation in the width direction of the coarse bar is uniformed to 5 ° C. or less. The deviation of the obtained material properties (for example, strength TS) can be suppressed to 5% or less.
[0054]
The iron core width of the narrowest transverse induction heating device used in the present invention is preferably in the range of 400 to 700 mm. Because the typical minimum width of the hot-rolled steel sheet is 550 to 800 mm, in order to suppress the edge heating and perform the central heating, a transverse heating device having a width 100 to 150 mm narrower than this is required. Because it becomes.
[0055]
In the above, when obtaining a hot-rolled steel sheet having no variation in the material in the width direction in the width direction, an example in which the temperature distribution in the width direction of the rough bar on the finishing rolling mill entry side is made uniform has been described. Needless to say, in order to obtain a steel sheet having different material properties in different directions, it is possible to achieve heating by applying a temperature deviation in the sheet width direction according to each material property in the sheet width direction.
[0056]
【Example】
A slab having a thickness of 250 mm and a width of 1250 mm heated to 1200 ° C. in a heating furnace was converted into a coarse bar having a thickness of 30 mm by a rough rolling mill. Next, the coarse bar is heated by three transverse induction heating devices having a width smaller than that of the coarse bar shown in FIG. 9B so that the amount of temperature rise in the central portion becomes the largest, and the edge portion is concentrated by the edge heater. Heating was performed. Then, the product was subjected to finish rolling on a finish rolling mill to produce a hot-rolled steel sheet having a thickness of 2 mm and a width of 1250 mm.
[0057]
The finishing rolling speed at this time is 1000 mpm, and the finishing incoming side temperature needs to be 1100 ° C. in order to secure the finishing outgoing target temperature of 860 ° C.
[0058]
The temperature distribution of the finishing-side temperature changes due to the temperature distribution in the width direction and the temperature drop due to the thermal rundown in the longitudinal direction of the coil. This is compensated for by three heating devices and an edge heater.
[0059]
The steel sheet has a temperature distribution of 1080 ° C. at the center, 1,100 ° C. at the highest point in the middle part, and 1,040 ° C. at the coldest point at the edge before heating by the entry-side width direction thermometer. A maximum of 20 ° C is heated in a half of the central part by a total of three transverse induction heating devices, and the temperature in the central part between the central part and the edge part is smaller than that of the central part. The deviation is eliminated, and the edge portion is intensively heated by 60 ° C. by the edge heater. As a result, the deviation in the temperature distribution in the width direction before rolling was made uniform up to 3 ° C., and as a result, a steel sheet having less variation in the material (strength) in the width direction and the longitudinal direction was obtained.
[0060]
【The invention's effect】
According to the hot rolling method of the present invention, the temperature distribution in the width direction of the rough bar before the finish rolling can be made uniform, and the finish rolling does not cause variations in the material properties such as mechanical properties in the width direction. The remarkable effect that a steel plate can be obtained arises. Further, according to the hot rolling apparatus of the present invention, since the central low-temperature portion of the rough bar before the finish rolling can be selectively heated and heated, the widthwise temperature distribution can be made uniform. Produces an effect.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a conventional continuous hot rolling apparatus.
FIG. 2 is a diagram showing an outline of a conventional endless rolling device.
3A and 3B are diagrams for explaining a temperature distribution in a width direction of a slab reheated by a heating furnace, wherein FIG. 3A shows that a low-temperature portion is present at a center portion of a slab thickness, and FIG. It is a figure showing that there is a part.
4A and 4B are diagrams showing the temperature distribution in the width direction of the steel sheet after the rough rolling and the finish rolling, in which (a) is a coarse bar, (b) is a temperature distribution in the width direction after the rough rolling, and (c) is a temperature distribution after the finish rolling. It is a figure which shows the temperature distribution in the width direction.
5A is a diagram showing a slab, FIG. 5B is a diagram showing a coarse bar, and FIG. 5C is a diagram showing a temperature distribution in the width direction of a steel sheet after finish rolling.
FIGS. 6A and 6B are diagrams showing a temperature distribution in a width direction when hot rolling is performed by heating both edge portions of a rough bar by an edge heater, where FIG. 6A is a slab, FIG. 6B is a rough bar heated by an edge heater, And (c) is a figure which shows each width direction temperature distribution about the steel plate after finish rolling.
FIG. 7 is a view showing a temperature distribution in a width direction when a rough bar is heated by a solenoid type induction heating device and hot-rolled, (a) is a slab, (b) is a rough bar heated by an edge heater, and (C) is a figure which shows each width direction temperature distribution about the steel plate after finish rolling.
FIG. 8 is a diagram for explaining a transverse induction heating device.
FIG. 9 is a diagram showing an example in which a transverse induction heating device is arranged. (A) Example in which three transverse induction heating devices having the same core width are arranged. (B) Example in which two transverse induction heating devices having different core widths are arranged. It is a figure for explaining width direction temperature distribution at the time of raising temperature by three transverse induction heating devices of width.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Slab 3 Rough rolling mill 4 Rough bar 5 Crop shear 6 Edge heater 7 Continuous finishing rolling mill 8 Cooling stand 9 Coiler 10 Coil box 11 Joining shear 12 Welding equipment 13 Low temperature part 14 High temperature part 15 Cooling large 16 Edge heater Temperature rise by heating 17 Temperature rise by solenoid type induction heating device 18 Iron core 19 Coil 20 Transverse type induction heating device 21 Steel plate 22 Thermometer (entrance side)
23-25, 27 Transverse induction heating device 26 Thermometer (outside)
28 heating amount of heating device 23 29 heating amount of heating device 24 heating amount of heating device 25

Claims (15)

In the hot rolling method for a steel sheet, the amount of temperature increase in the width direction of the material to be rolled is changed so that the temperature in the width direction of the material to be rolled on the entrance or exit side of the finishing rolling mill has a predetermined temperature distribution. A hot rolling method for a steel sheet, comprising heating a material. Heating is performed so that at least a temperature rise amount in a central portion of the material to be rolled in the sheet width direction is larger than a temperature increase amount in an intermediate portion between the center portion and both edges in the sheet width direction. Item 4. The method for hot rolling a steel sheet according to Item 1. The steel sheet according to claim 1 or 2, wherein the material to be rolled is heated such that the amount of temperature rise at both edge portions in the sheet width direction is larger than the amount of temperature rise at an intermediate portion in the width direction in the sheet width direction. Hot rolling method. The temperature distribution in the width direction of the material to be rolled on the inlet side of the heating device is grasped in advance, the maximum value of the temperature in the width direction is set as the reference temperature, the temperature difference between the temperature at each point in the width direction and the reference temperature is obtained, and the The method according to any one of claims 1 to 3, wherein a heating amount at each point required so that the width direction temperature has a predetermined temperature distribution is determined, and heating is performed according to the heating amount. A method for hot rolling a steel sheet as described in the above. The hot rolling method for a steel sheet according to any one of claims 1 to 4, wherein at least two or more heating devices are arranged along the rolling line. The heating device is a transverse induction heating device capable of heating the material to be rolled by changing the amount of temperature rise in the width direction of the material to be rolled, the heating device being a transverse induction heating device. Hot rolling method of steel sheet. The hot rolling method for a steel sheet according to claim 6, wherein the transverse induction heating device is at least two or more transverse induction heating devices having different core widths in the width direction. In a hot rolling device for steel sheets, a heating device that changes the temperature in the width direction of the material to be rolled and heats the material by changing the amount of heating is provided on the rough rolling mill entrance side in the rolling line, between the rough rolling mill rows, and the rough rolling mill. A hot-rolling apparatus for a steel sheet, wherein the hot-rolling apparatus is arranged between rolling mills or between finishing rolling mill rows. The heating device is such that at least the temperature rise amount in the central portion in the sheet width direction of the material to be rolled is larger than the temperature rise amount in the middle portion between the center portion and both edges in the sheet width direction. The hot-rolling apparatus for a steel sheet according to claim 8. The heating device according to claim 8 or 9, wherein the heating device is such that the amount of temperature rise at both edge portions in the sheet width direction of the material to be rolled is larger than the amount of temperature rise at the middle portion in the width direction in the sheet width direction. Hot rolling equipment for steel sheet. In a hot rolling device for a steel sheet, a heating device that heats the material to be rolled by changing a heating amount in a sheet width direction, and an edge heater that heats both edge low-temperature portions of the coarse bar are provided. The hot-rolling apparatus for a steel sheet according to any one of claims 8 to 10. On the entry side of the finish rolling mill, a heating device that heats by changing the amount of temperature rise in the sheet width direction of the material to be rolled in the width direction of the rough bar, and an edge heater that heats both edge low-temperature portions in the width direction of the rough bar. A temperature grasping device for grasping the temperature distribution in the width direction of the coarse bar is disposed, and the maximum value of the temperature in the width direction grasped by the temperature grasping device is used as a reference temperature, and the temperature difference between the temperature at each point in the width direction and the reference temperature. And a device that determines the amount of temperature rise at each point required so that the widthwise temperature has a predetermined temperature distribution based on the temperature difference, and operates a heating device and an edge heater based on the amount of temperature rise. The hot-rolling apparatus for a steel sheet according to any one of claims 8 to 11, further comprising: a control device configured to uniformize a temperature distribution in a width direction of the coarse bar. The hot rolling apparatus for a steel sheet according to any one of claims 8 to 12, wherein at least two or more heating apparatuses are arranged along the rolling line. The heating device is a transverse induction heating device capable of heating the material to be rolled by changing the amount of temperature rise in the sheet width direction, wherein the heating device is a transverse induction heating device. A hot-rolling apparatus for a steel sheet as described above. The hot-rolling apparatus for a steel sheet according to claim 14, wherein the transverse induction heating apparatus is at least two or more transverse induction heating apparatuses having different core widths in the width direction.

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