JP3793515B2 - Steel sheet hot rolling method and apparatus - Google Patents

Description

[0001]
BACKGROUND 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 making the temperature in the width direction of the rough bar on the entry side of the finish rolling mill have a predetermined temperature distribution. And the apparatus.
[0002]
[Prior art]
As shown in FIG. 1, hot rolling of a steel plate is performed by inserting a low-temperature slab 2 into a heating furnace 1, reheating it to a predetermined temperature, and then reheating the reheated slab 2 with a rough rolling mill 3. In order to recover the temperature drop at both edges of the coarse bar 4 in the width direction by using the crop shear 12, the edges of the coarse bar 4 are recovered by the edge heater 6. This is performed by heating the section and finishing and rolling it into a predetermined hot-rolled steel sheet with a continuous finish rolling mill 7 composed of a plurality of stands, then cooling with a cooling stand 8 on a run-out table and winding it with a coiler 9. Yes.
[0003]
In addition, when endless rolling is performed in which rough bars are joined to each other before finish rolling, as shown in FIG. 2, a low-temperature slab 2 is inserted into a heating furnace 1 to obtain a predetermined The slab 2 is reheated to a temperature, rolled to a predetermined thickness by a roughing mill 3 to form a rough bar 4, wound by a coil box 10, and the tip of the rough bar unwound from the coil box In order to recover the temperature drop at both edge portions in the width direction of the coarse bar 4 by cutting with the joining shear 11 and joining the trailing end of the preceding coarse bar and the leading end of the following coarse bar with the welding device 12. The two edge portions are heated and rolled into a predetermined hot-rolled steel plate by a continuous finish rolling mill 7 composed of a plurality of stands, cooled at a cooling stand 8 on a run-out table, and wound by a coiler 9. Has been done.
[0004]
In such a hot-rolling or endless rolling process of a hot-rolled steel sheet, since the low-temperature slab is reheated in a heating furnace, the occurrence of uneven heat is inevitable, and the rolled material has a plate thickness with respect to the plate width. Due to the small size, a temperature drop occurs at both edge portions of the coarse bar. These temperature drops do not have a predetermined temperature distribution in the width direction of the coarse bar (in this case, the temperature distribution is uniform), causing non-uniformity and causing non-uniform finishing temperatures.
[0005]
Therefore, if the temperature distribution in the width direction of the coarse bar becomes non-uniform, ear waves and medium elongation occur in the hot-rolled steel sheet during finish rolling, and the material properties such as the mechanical properties in the width direction of the hot-rolled steel sheet are non-uniform. The problem of becoming.
[0006]
In order to prevent such problems due to uneven 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 finish rolling mill, and rough rolling is performed by the rough rolling mill. It is known to heat the roughed bar. For example, between the rough rolling mill and the finish rolling mill, a solenoid type induction heating device for heating the rough bar across its entire width direction and an edge heater for heating both edge portions of the rough bar are provided, It has been proposed to heat a rough bar on the entry side of a finish rolling mill so as to have a uniform temperature in the width direction by a solenoid induction heating device and an edge heater (for example, Patent Document 1).
[0007]
The feature of the solenoid type induction heating device used here is that the coil is wound around the plate and a magnetic field is generated in parallel with the plate. The entire surface of the plate is heated centrally, and the temperature is averaged by heat transfer. Therefore, the temperature is increased by a uniform temperature over the entire width in a state where the temperature distribution in the plate width direction is substantially constant.
[0008]
That is, in the proposed technique, the entire width of the rough bar is uniformly heated in the width direction by a solenoid induction heating device in order to reduce the rolling load, and the width direction is uniform by heating both edge portions by an edge heater. It is intended to achieve a stable temperature distribution.
[0009]
However, as a result of studying the material properties in the width direction of the hot-rolled steel sheet, the present inventor has heated the edge portion of the coarse bar on the finishing rolling mill entrance side with an edge heater to increase the temperature distribution in the width direction. It has been found that there is a variation in the material properties in the width direction of the steel sheet obtained by finish rolling even when uniformized. That is, in the heating method in which the 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 material in the width direction of the hot rolled steel sheet is used. It was difficult to make the characteristics uniform. The cause was investigated through various experiments, 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, inevitably the temperature at the center of the slab thickness is low, and this temperature distribution is maintained even if the thickness is reduced by rolling. The cause is that the central portion is lower than the average temperature in the width direction and is higher toward the edge portion.
[0010]
Therefore, the uniformity of the material characteristics in the plate width direction cannot be eliminated by the heating method using the edge heater.
[Patent Document 1]
Japanese Patent Laid-Open No. 9-314216
[Problems to be solved by the invention]
Therefore, the present invention changes the temperature increase amount in the plate width direction of the coarse bar (preferably increases the temperature increase amount in the central low temperature portion in the width direction), and in the width direction of the coarse bar on the entry side or the exit side of the finishing mill. It is an object of the present invention to provide a hot rolling method and apparatus for stably producing a hot-rolled steel sheet having a predetermined material characteristic in the width direction by using a predetermined temperature distribution.
[0012]
[Means for Solving the Problems]
In order to stably obtain a hot-rolled steel sheet having a predetermined material property in the width direction, the inventor needs to make the temperature in the width direction of the rough bar on the finishing rolling mill entrance side have a predetermined temperature distribution. For that purpose, a portion where the temperature drop is large in the plate width direction of the rough bar (preferably a low-temperature portion having a width of 1/2 of the center portion of the rough bar due to the low temperature of the center portion of the slab plate thickness during slab heating, and more preferably Found that the temperature in the width direction of the rough bar can be made to have a predetermined temperature distribution by heating the temperature of the two edges of the rough bar, which is generated at the time of rough rolling, from the plate width to 100 mm, and completed the present invention. .
[0013]
The gist of the present invention is as follows.
[0014]
(1) In the steel sheet hot rolling method, a plurality of transverse type induction heating devices are arranged at different positions along the rolling line so that the degree of overlap is different in the sheet width direction, and the finish rolling mill entry side or exit side The material to be rolled is heated by changing the temperature rise amount in the plate width direction of the plate width direction by the temperature rise control device so that the temperature in the width direction of the material to be rolled becomes a predetermined temperature distribution. Hot rolling method for steel sheet.
[0015]
(2) Heating is performed so that at least the temperature rise amount in the center portion of the material to be rolled is greater than the temperature rise amount in the middle portion between the center portion and both edges in the plate width direction. The method for hot rolling a steel sheet according to (1) above.
[0016]
(3) The above (1) or (1), wherein heating is performed so that a temperature increase amount at both edges in the sheet width direction of the material to be rolled is greater than a temperature increase amount in an intermediate portion in the width direction in the sheet width direction. 2) The hot rolling method of the steel plate as described.
[0017]
(4) The width direction temperature distribution of the material to be rolled on the entrance side of the transverse type induction heating device is grasped in advance, the maximum value of the width direction temperature is set as the reference temperature, and the temperature difference between each point in the width direction and the reference temperature is calculated. The above-mentioned (1) to (1), characterized in that, based on the temperature difference, a temperature increase amount at each point is determined so that the temperature in the width direction has a predetermined temperature distribution, and heating is performed according to the temperature increase amount. (3) The method for hot rolling a steel sheet according to any one of the above.
[0020]
(5) transverse type induction heating device, hot rolling of the steel sheet of the above (4), wherein the length of the core width in the width direction is different from at least two or more transverse type induction heating device Method.
[0021]
( 6 ) In a steel sheet hot rolling apparatus, a plurality of transformers that heat the material to be rolled at different positions in the sheet width direction along the rolling line by changing the temperature increase amount of the material to be rolled in the sheet width direction by the temperature increase amount control device. A steel plate characterized in that a berth-type induction heating device is disposed on a rough rolling mill entry side in a rolling line, between rough rolling mill rows, between a rough rolling mill and a finishing rolling mill, or between finishing rolling mill rows Hot rolling equipment.
[0022]
( 7 ) A plurality of transverses arranged such that at least the temperature rise in the center part in the sheet width direction of the material to be rolled is larger than the temperature rise in the middle part between the center part and both edges in the sheet width direction. The hot rolling apparatus for steel sheets according to ( 6 ) above, which is a die induction heating apparatus.
[0023]
( 8 ) It is a plurality of transverse induction heating devices arranged 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 increase at the intermediate part in the width direction in the sheet width direction. The hot rolling apparatus for steel sheets according to ( 6 ) or ( 7 ) above, characterized in that
[0024]
( 9 ) In a steel sheet hot rolling apparatus, a plurality of transverse induction heating apparatuses that heat by changing the temperature rise in the sheet width direction of the material to be rolled, and an edge heater that heats both edge low temperature portions of the coarse bar The hot-rolling apparatus for steel sheets according to any one of ( 6 ) to ( 8 ) above, comprising:
[0025]
( 10 ) A plurality of transverse type induction heating devices that heat by changing the temperature increase amount in the sheet width direction of the material to be rolled in the width direction of the rough bar on the entry side of the finish rolling mill, and both in the width direction of the rough bar An edge heater that heats the edge low-temperature part and a temperature grasping device that grasps the widthwise temperature distribution of the coarse bar are arranged, and the maximum value in the widthwise direction grasped by the temperature grasping device is set as a reference temperature, and each point in the width direction A temperature difference between the reference temperature and a reference temperature, a device for determining a temperature increase amount at each point so that the temperature in the width direction has a predetermined temperature distribution based on the temperature difference, and the temperature increase amount And ( 6 ) to ( 9 ), comprising a plurality of transverse induction heating devices and a control device for operating the edge heater to uniformize the temperature distribution in the width direction of the coarse bars. The hot-rolling apparatus of the steel plate of any one of Claims 1.
[0028]
( 11 ) Among the above (6) to (10), the transverse induction heating device is at least two transverse induction heating devices having different lengths of the iron core width in the width direction . The hot-rolling apparatus of the steel plate of any one of Claims 1 .
[0029]
DETAILED DESCRIPTION OF THE INVENTION
It is known that when obtaining a hot-rolled steel sheet having a predetermined material property in the width direction, for example, a material variation in the width direction, it is necessary to make the temperature distribution in the width direction of the rough bar on the finishing mill entry side 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 edge portions of the rough bar generated during rough rolling by an edge heater.
[0030]
However, the hot-rolled steel sheet that is finish-rolled by heating both edge portions of the coarse bar with an edge heater has a variation in material properties in the width direction.
[0031]
Therefore, the present inventor conducted various experiments to find out the cause, and as a result, found out that there is a cause when heating the slab in the 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 has a high-temperature portion 14 around it, but includes a width direction including a ½ width. It is inevitable that the low temperature portion 13 is generated in the central portion. And when the surface temperature distribution of the slab on the roughing mill entry side is measured, the center part of the center line (CL) is low (1200 ° C.) with respect to the average temperature in the width direction as shown in FIG. It was high (1230 ° C).
[0033]
When a slab having such a temperature distribution is roughly rolled into a rough bar, as shown in FIG. 4 (a), both edge portions of the coarse bar 4 have a cooling capacity of 15, so the temperature distribution of the coarse bar is as shown in FIG. As shown in FIG. 4 (b), the temperature in the center portion of the center line ½ width of the center line is low (1033 ° C.) with respect to the width direction average temperature, and the intermediate portion between the center portion and the edge portion is high (1056 ° C.). ) And at least the width from both edges to the edge part of 100 mm (1002 ° C.), 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 finish rolling, and the central portion is 842 ° C. and the intermediate portion. 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 after heating in the heating furnace described above, the rough bar after rough rolling, and the steel sheet on the finish rolling side are shown in (a), (b) and (c) of FIG. Indicated. All had M-shaped width direction temperature distribution.
[0035]
In the conventional hot rolling method, the case where the edge part of a rough bar is heated with an edge heater will be described with reference to FIG.
[0036]
As shown in FIG. 6A, the surface temperature distribution in the slab width direction before rough rolling is 1200 ° C at the center of the center line (CL) and a high temperature distribution of 1230 ° C toward the edge. When both edge portions of the coarse bar are heated with an edge heater to compensate for the temperature drop at both edge portions of the coarsely rolled coarse bar, as shown in FIG. Is added, and the temperature of both edge portions is increased to 1056 ° C. However, the temperature of the central low temperature portion (1033 ° C.) does not increase, and the temperature distribution in the width direction is not uniformized. Conventionally, it was determined that the temperature distribution in the width direction of the coarse bar was made uniform.
[0037]
When the rough bar heated at both edges by finishing with an edge heater is finish-rolled, the temperature distribution in the width direction of the rough bar is maintained even if the plate thickness is reduced. As shown in FIG.6 (c), the center part was low temperature (842 degreeC) rather than the width direction average temperature.
[0038]
An example in which a solenoid type induction heating device is used as a coarse bar heating device to heat the coarse bar in the entire width direction will be described with reference to FIG.
[0039]
The temperature distribution in the width direction of the slab is shown in FIG. As shown in FIG. 7B, the temperature distribution in the width direction of the rough bar obtained by roughly rolling the slab of this temperature distribution is 1033 ° C. at the central low temperature portion, 1056 ° C. at the maximum intermediate temperature, and 1002 ° C. at the edge portion. Met. When this rough bar is uniformly heated in the width direction by a solenoid induction heating device, the overall temperature rises by the amount of temperature increase indicated by the oblique lines, with the central portion at 1046 ° C., the middle portion at 1069 ° C., and the edge portion at 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 whose width direction is uniformly heated by a solenoid type induction heating device is rolled by a finishing mill, a hot rolled steel sheet having an M-shaped width direction temperature distribution is obtained as shown in FIG. can get.
[0040]
As described above, the present inventor, when performing hot rolling using a slab heated in a heating furnace, heats both edge portions of the coarse bar with an edge heater during the rolling as in the past, or a solenoid. In the method of heating by heating the rough bar in the width direction almost uniformly in the mold induction heating device, contrary to the conventional way of thinking, the temperature distribution in the width direction of the steel sheet on the finishing mill entry side is not necessarily uniform, As a result, a new finding has been obtained that the material properties in the width direction of the hot-rolled steel sheet vary.
[0041]
And, due to the two factors of heating the slab by the heating furnace and allowing the edge portion to cool at the time of rolling, the temperature distribution in the width direction of the rough bar is not uniform, the variation in the material properties in the width direction of the steel plate I found out that it is the cause of.
[0042]
Therefore, in the present invention, in order to uniformize the temperature distribution in the width direction of the rough bar on the entry side or the exit side of the finishing mill, the temperature increase amount is changed in the sheet width direction to equalize the temperature distribution in the width direction of the rough bar. I decided to let them. At this time, preferably, the temperature rise amount in the central low temperature portion including the half width of the coarse bar is at least an intermediate portion between the central portion and both edges in the plate width direction (1/4 width and 3 / 4 portion), and more preferably, the low-temperature portion of both edge portions in the plate width direction (at least from both ends of the width to the center side of the 100 mm plate) is more than the plate width intermediate portion. The temperature was increased by an edge heater so as to increase, 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 the material to be rolled such as a rough bar is a position of a ½ width lower than the maximum temperature of the temperature distribution in the width direction as described above. It means the area | region of the board width center part containing. Further, the plate width “intermediate portion” means a region including the maximum temperature portion of the temperature distribution in the width direction except the “center portion” in the width direction and including the positions of the 1/4 width and the 3/4 width as described above. To do.
[0043]
As the heating device, a gas heating device can be used as long as the temperature increase distribution in the width direction is a heating device whose central portion has a particularly large temperature increase amount and decreases toward the end portion, and is concentrated in the width direction central portion. 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 apparatus is inexpensive in equipment cost, but scale is likely to be generated on the surface of the coarse bar. In addition, when a spark is generated between the coarse bar and the electrode in the energization heating device, the coarse bar may be wrinkled. Unlike the solenoid type induction heating device, the transverse type induction device has the characteristic that the specific part in the width direction of the coarse bar can be heated uniformly according to the iron core width. If a plurality of narrow transverse induction heating devices are arranged along the rolling line and two or more transverse induction heating devices having a width narrower than the coarse bar width are used in combination, the desired width can be obtained. The direction specific part 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 at the upper and lower positions of a steel plate 21. This is because it is easy, does not cause wrinkles on the surface of the rough bar, and the surface is not overheated due to its characteristics, so there is no restriction on the arrangement relationship with other equipment such as a rolling mill and deske. .
[0044]
Hereinafter, the present invention will be described with reference to the drawings.
[0045]
In the hot rolling apparatus shown in FIG. 1, as schematically shown in FIG. 9 (a) between the rough rolling mill and the finish rolling mill, there is an overlapping degree in the sheet width direction at different positions along the rolling line. A transverse rolling induction heating device and an edge heater arranged differently were provided to form a hot rolling device.
[0046]
In a transverse-type induction heating device 23, 24, 25 core width is narrower three than crude bar width along the rolling line different positions, arranged to overlap degree in the plate width direction are different, of the iron core width the inlet side widthwise thermometer 22 of three to the entry side of the transverse-type induction heating device 23, 24, 25 as a temperature determination apparatus in the width direction, are set up egress widthwise thermometer 26 on the outlet side. The coarse bar 4 rolled by the coarse rolling mill is conveyed in the direction of the arrow by a table roll. The inlet side width direction thermometer 22 measures the width direction temperature distribution of the coarse bar 4, and based on the width direction temperature distribution, increases the amount of temperature rise of the coarse bar due to the heating of each transverse induction heating device 23, 24, 25. Determined by temperature control device. The coarse bar is heated in the vicinity of the central low-temperature portion by the transverse induction heating device 23, and then the intermediate portion including the central portion including the central portion is heated by the transverse induction heating device 24, and further the transverse induction. The heating unit 25 heats the intermediate part including the central part and in the vicinity of 3/4 width. The low temperature portions of both edges of the coarse bar (at least from the end in the plate width direction to the center of the 100 mm plate) are heated by the edge heater 6 (so as to be larger than the temperature increase in the intermediate portion in the plate width direction). The These heating temperature elevation amounts are controlled by a temperature elevation amount control device. The temperature distribution in the width direction of the coarse bar after heating is measured by the exit-side width direction thermometer 26. If the temperature distribution in the width direction measured by the outlet width direction thermometer is not uniform, the measurement data is fed back to the transverse type induction heating device 23 and the temperature rise control device for the edge heater 6 for control. By changing the output of the temperature rise amount of each heating device by the device, the temperature distribution in the width direction of the coarse bar is made uniform. In order to make the width direction temperature distribution uniform, it is most preferable to set the temperature deviation of the width direction temperature distribution to 0 ° C. In the present invention, the temperature deviation of the width direction temperature distribution is 10 ° C. or less, preferably 5 ° C. or less. Is acceptable.
[0047]
Here, the plurality of induction heating devices do not necessarily have the same iron core width, and 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 24 and 25 have an iron core width that is twice the iron core width and the induction heating device. Two units 23 may be arranged.
[0048]
The plurality of transverse induction heating devices and edge heaters are not necessarily limited to the arrangement order as shown in FIGS. 9A and 9B, but are preferably 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, but the furnace temperature in the heating furnace, the slab temperature on the outlet side of the heating furnace, etc. Width direction on the entrance side of the transverse induction heating device by numerical calculation based on the actual measured temperature of and the rough bar transport conditions (rough rolling conditions, transport 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, a width direction thermometer can be provided on the exit side of the finish rolling mill to grasp the width direction temperature distribution on the entrance side of the transverse induction heating apparatus.
[0050]
An example of the temperature rise characteristic of the transverse induction heating apparatus will be described with reference to FIG.
[0051]
FIGS. 10A to 10C show the temperature rise distribution of the coarse bar 4 due to heating when three heating devices 23, 24, and 25 having the same iron core width are used. FIG. 10 shows an example in which the temperature of the coarse bar is uniformly increased up to 40 ° C. corresponding to each iron core width of the heating device. Note that the temperature rise gradually decreases outside the width of the iron core.
[0052]
In the temperature rise distribution that can be raised by the three transverse type induction heating devices, since the three temperature rise amounts are combined, as shown in FIG. 10 (d), each of the heating devices 23, 24, and 25 is heated. 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 rough bar having an M-shaped temperature distribution with a central maximum low-temperature portion of 1060 ° C. and an intermediate maximum temperature of 1100 ° C. is the total heating amount shown in FIG. 10 (e) of three transverse induction heating devices. By (40 ° C.), the central portion in the width direction can be uniformized to a temperature distribution of 1100 ° C. Further, since both edge portions are heated by the edge heater, the temperature is raised 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 uniformized to 5 ° C. or less. The deviation of the material characteristics (for example, strength TS) obtained by this can also be suppressed to 5% or less.
[0054]
In addition, it is preferable that the iron core width | variety of the narrowest transverse type | formula induction heating apparatus used by this invention shall be in the range of 400-700 mm. This is because a typical minimum sheet width of a hot-rolled steel sheet is 550 to 800 mm, so that a transverse heating apparatus having a width of 100 to 150 mm narrower than this is required to suppress the edge heating and perform the center heating. Because it becomes.
[0055]
Also, more than in the case of obtaining a hot rolled steel sheet without variations in the material in the plate width direction has been described an example of a uniform width direction temperature distribution of the coarse bars of the finishing mill entry side, reversed sheet width direction Needless to say, in order to obtain steel plates having different material properties, heating can be performed in the plate width direction so as to give a temperature deviation in the plate width direction in accordance with the respective material properties.
[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 formed into a rough bar having a thickness of 30 mm by a rough rolling machine. Next, the coarse bar is heated so that the temperature rise in the central portion is the largest as compared with the three transverse induction heating devices that are narrower than the coarse bar shown in FIG. 9B, and the edge portion is concentrated by the edge heater. Heating was performed. Subsequently, the finished rolling mill was finished and rolled 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 in order to secure the finishing delivery target temperature of 860 ° C., the finishing entry temperature needs to be 1100 ° C.
[0058]
The temperature distribution of the finishing entry side temperature changes due to the temperature decrease due to the temperature distribution in the width direction and the thermal rundown in the coil longitudinal direction. This is compensated by three heating devices and an edge heater.
[0059]
The steel plate has a temperature distribution before heating by the entrance side width direction thermometer of 1080 ° C. at the center, 1100 ° C. at the highest point of the middle portion, and 1040 ° C. at the coldest point of the edge portion. Heat up to a maximum of 20 ° C in 1/2 part of the central part with three transverse induction heating devices, and lower the temperature rise in the central part between the central part and the edge part than in 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 of the temperature distribution in the width direction before rolling was made uniform up to 3 ° C., and as a result, a steel plate with less material (strength) variation 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 finish rolling can be made uniform, and the hot rolling without variation in material properties such as the mechanical properties in the width direction by finish rolling. The remarkable effect that a steel plate can be obtained arises. Further, according to the hot rolling apparatus of the present invention, the central low temperature portion of the rough bar before finish rolling can be selectively heated and heated, so that the temperature distribution in the width direction 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 apparatus.
FIGS. 3A and 3B are diagrams for explaining temperature distribution in the width direction of a slab reheated in a heating furnace. FIG. 3A shows a low temperature part at the center of the slab thickness, and FIG. 3B shows a low temperature at the center part in the width direction of the slab. It is a figure which shows that there exists a part.
4A and 4B are diagrams showing the temperature distribution in the width direction of a steel sheet after rough rolling and finish rolling, in which FIG. 4A is a rough bar, FIG. 4B is the temperature distribution in the width direction after rough rolling, and FIG. It is a figure which shows the width direction temperature distribution.
5A is a graph showing temperature distributions in the width direction of a slab, FIG. 5B is a rough bar, and FIG. 5C is a steel sheet after finish rolling.
6A and 6B are diagrams showing a temperature distribution in the width direction when both edge portions of a rough bar are heated by an edge heater and hot rolled, wherein 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.
FIGS. 7A and 7B are diagrams showing a temperature distribution in the width direction when a rough bar is heated and hot-rolled by a solenoid type induction heating device, where FIG. 7A is a slab, FIG. 7B is a rough bar heated by an edge heater, and FIG. (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 apparatus.
FIG. 9 is a diagram showing an example in which a transverse induction heating device is arranged. (A) Example where three transverse induction heating devices with the same core width are arranged (b) Example where two transverse induction heating devices with different iron core widths are arranged [Fig. 10] Iron core width is equivalent It is a figure for demonstrating the width direction temperature distribution at the time of heating up with three transverse type | mold induction heating apparatuses of a width | variety.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Slab 3 Coarse rolling mill 4 Coarse bar 5 Crop shear 6 Edge heater 7 Continuous finish rolling mill 8 Cooling stand 9 Coiler 10 Coil box 11 Joining shear 12 Welding device 13 Low temperature part 14 High temperature part 15 Cooling large 16 Edge heater Temperature rise by 17 Heat rise by solenoid type induction heating device 18 Iron core 19 Coil 20 Transverse type induction heating device 21 Steel plate 22 Thermometer (incoming side)
23-25, 27 Transverse type induction heating device 26 Thermometer (outside)
28 Temperature rise 29 of the heating device 23 Temperature rise 30 of the heating device 24 Temperature rise of the heating device 25

Claims (11)

In the hot rolling method for steel sheets, a plurality of transverse induction heating devices are arranged at different positions along the rolling line so as to have different degrees of overlap in the width direction of the steel sheet, so that the coating material on the entrance or exit side of the finish rolling mill is arranged. The heat of the steel sheet is characterized in that the material to be rolled is heated by changing the temperature rising amount in the sheet width direction of the material to be rolled by the temperature rising amount control device so that the temperature in the width direction of the rolled material has a predetermined temperature distribution. Hot rolling method.   Heating is performed such that at least the temperature rise in the central part in the sheet width direction of the material to be rolled is greater than the temperature rise in the middle part between the center part and both edges in the sheet width direction. Item 2. A method for hot rolling a steel sheet according to Item 1.   3. The steel sheet according to claim 1, wherein heating is performed so that a temperature increase amount at both edges in the sheet width direction of the material to be rolled is greater than a temperature increase amount at an intermediate portion in the width direction in the sheet width direction. Hot rolling method. Preliminarily grasp the width direction temperature distribution of the material to be rolled on the entrance side of the transverse type induction heating device, use the maximum value of the width direction temperature as the reference temperature, determine the temperature difference between the temperature at each point in the width direction and the reference temperature, The temperature increase amount at each point required so that the temperature in the width direction has a predetermined temperature distribution is determined based on the temperature difference, and heating is performed according to the temperature increase amount. A method for hot rolling a steel sheet according to claim 1. 5. The steel sheet hot rolling method according to claim 4 , wherein the transverse induction heating apparatus is at least two transverse induction heating apparatuses having different lengths of the iron core width in the width direction. In steel sheet hot rolling equipment, multiple transverse inductions that heat the material to be rolled at different positions in the sheet width direction along the rolling line by changing the temperature rise amount of the material to be rolled in the sheet width direction by the temperature rise control device Hot rolling of a steel sheet, characterized in that the heating device is disposed on the roughing mill entry side in the rolling line, between the roughing mill rows, between the roughing mill and the finishing rolling mill, or between the finishing rolling mill rows apparatus. A plurality of transverse inductions arranged so that at least the temperature rise in the center of the material to be rolled is greater than the temperature rise in the middle between the center and both edges in the plate width direction The hot-rolling apparatus for steel sheets according to claim 6 , wherein the apparatus is a heating apparatus . It is a plurality of transverse type induction heating devices arranged so 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 increase at the intermediate part in the width direction of the sheet width direction. The hot-rolling apparatus for steel sheets according to claim 6 or 7 . In a steel sheet hot rolling apparatus, a plurality of transverse type induction heating apparatuses that heat by changing the temperature increase amount in the sheet width direction of the material to be rolled, and an edge heater that heats both edge low-temperature parts of the coarse bar The hot-rolling apparatus for steel sheets according to any one of claims 6 to 8 , wherein A plurality of transverse type induction heating devices for heating by changing the heating amount in the sheet width direction of the material to be rolled in the width direction of the rough bar on the entry side of the finish rolling mill, and the low-temperature parts on both edges in the width direction of the rough bar An edge heater for heating the temperature and a temperature grasping device for grasping the temperature distribution in the width direction of the coarse bar are arranged, the maximum value of the width direction temperature grasped by the temperature grasping device is set as a reference temperature, and the temperature at each point in the width direction determine the temperature difference between the reference temperature, widthwise temperature based on the temperature difference and the device for determining the Atsushi Nobori amount of each point needed to have a predetermined temperature distribution, multiple based on該昇temperature amount 10. The apparatus according to claim 6 , further comprising: a transverse type induction heating device and a control device that operates the edge heater to uniformize the temperature distribution in the width direction of the rough bar. Steel sheet hot rolling equipment. 11. The transverse induction heating apparatus according to claim 6, wherein the transverse induction heating apparatus is at least two or more transverse induction heating apparatuses having different lengths of the iron core width in the width direction. Steel sheet hot rolling equipment.

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