JPH01321011A - Method for heating hot sheet bar - Google Patents

Abstract

PURPOSE:To prevent generation of material defects in the rear end of a sheet bar by shifting a heater toward a side end in the width direction of the bar at the time of transferring the top end part in the length direction of the bar in the heating zone of the heater. CONSTITUTION:A pair of heaters 6, which are installed to face to each other in the width direction of a transferred hot sheet bar 3 and movable in the width direction of the bar 3, heat the bar 3 in a finish rolling mill 2 side. In that heating method, a pair of heaters 6 are installed at the central part in the width direction of the bar 3. When the top end in the length direction of the bar 3 is transferred in the eating zone of the heaters 6, the heaters 6 are shifted toward a side end in the width direction of the bar 3. As the result, abnormal growing of crystal grains in the length end part is prevented because the entire area in the length end part as well as edge parts of the hot bar 3 are heated. Therefore, a discarding area in the top part of the bar 3 is drastically reduced, so that the yield is improved.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a heating method for a hot sheet bar, and in particular to a heating method for heating a hot sheet bar by heating the widthwise end portions and longitudinal end portions of the hot sheet bar. ``Method for heating a sheet bar.''

[Conventional technology]

To explain the conventional method of rolling a hot sheet bar in copper strip rolling, generally speaking, in hot rolling, a heated slab with a thickness of 120 to 300 fins is rolled into a rough rolling mill with a thickness of 15 to 60 fins. Rolled into a sheet bar,
This is further rolled using a finishing mill until the desired product thickness is reached.

Here, as shown in FIG. 7, the hot sheet bar 3 rolled by the rough rolling mill 1 is transferred to the crosser 4 by the conveying table rollers 5, and the tip of the sheet bar is sheared. Next, the sheet bar 3 is transferred to a high-pressure injection type scaling device 11 having a nozzle 8 for removing surface scale, and then the sheet bar 3 is finish rolled by a finishing mill 2.

During the processing steps from rough rolling to finish rolling, part of the heat held by the hot sheet bar 3 is dissipated into the atmosphere. Since the amount of heat dissipated increases in proportion to the distance from the heat dissipation surface, there is a difference in the amount of heat dissipated into the atmosphere between the widthwise ends and the center of the hot sheet bar, and the temperature of the hot sheet bar increases. The side edges in the width direction are lower in temperature than the center portion in the width direction. For this reason, there was a problem in that material defects occurred at the side edges, and the quality of the finish-rolled product deteriorated.

Therefore, in order to solve this problem, as shown in FIG. 7, edge heaters 10 are installed to compensate for the temperature drop at both ends of the sheet bar 3, and the edge portions of the hot sheet bar are heated. It has been proposed to compensate for the temperature drop at the edge by increasing the temperature locally (e.g., "Tetsu to Hagane" No. 72).
(1986) No. 2, pp. 177-178).

In this edge heater, as shown in FIG. 7, a plurality of pairs of upper and lower induction heating coils IOA are installed at both edge portions of the hot sheet bar 3. Each pair of upper and lower induction heating coils IOA has a mechanism that follows the position corresponding to the edge portion of the hot sheet bar 3 even if the width of the hot sheet bar 3 changes.

In this way, in the above conventional example, edge heaters are used to prevent uneven temperature distribution in the width direction of the hot sheet bar 3 between the rough rolling mill 1 and the finishing mill 2. There is.

[Problem to be solved by the invention]

However, as a result of intensive study by the present inventors, heat dissipation from the seat bar occurs not only at the widthwise ends but also at the longitudinal ends (tip and rear ends) of the seat bar, and as a result, various problems arise. I found out what was happening.

That is, the first problem is that the material at the front and rear ends of the seat bar is defective. Finish rolling is normally performed to complete rolling at the Arz transformation point or higher. However, in the above-described conventional sheet bar rolling method, so-called grain gloss occurs in the localized temperature drop areas at the leading and trailing ends of the sheet bar, where abnormal growth of Ar = dotted crystal grains occurs. As a result, the workability of the product decreases, as well as the cold rollability, which is often performed in succession to hot rolling in recent years.

The second problem mentioned above is roll flaws. In a sheet bar made of a steel with high deformation resistance, when the above temperature drop occurs, the roll undergoes plastic deformation when the tip of the sheet bar is assembled into a finishing roll. For this reason, roll flaws may be transferred to the product surface, which may become surface defects and result in defective products. Therefore, it becomes necessary to suddenly replace the rolls, which lowers the operating rate.

In order to prevent the above-mentioned problem, it is necessary to cut off the longitudinal ends of the sheet bar, that is, the front and rear ends, but this poses a problem that the yield of the product decreases.

Therefore, in order to solve these problems, the present invention improves the yield by preventing material defects at the longitudinal ends of the sheet bar, and also improves the operating rate by preventing the occurrence of roll defects. The purpose of the present invention is to provide a method for heating a hot sheet bar.

[Means for Solving the Problems] In order to achieve the above object, the method for heating a hot sheet bar according to the present invention provides a method for heating a hot sheet bar according to the present invention. In the hot sheet bar heating method, the sheet bar is heated on the entry side of a finishing rolling machine by a heating device movable in the width direction, the pair of heating devices being disposed at the center of the sheet bar in the width direction,
When the longitudinal end of the sheet bar is conveyed to the heating region of the heating device, the heating device is moved toward the widthwise end of the sheet bar to heat the end, and then , the sheet bar is characterized in that the heating device arranged at the side end in the width direction heats the side end.

Furthermore, in the method for heating a hot sheet bar according to the present invention, after heating the side end portion of the sheet bar in the width direction, when the rear end portion in the longitudinal force direction of the sheet bar is conveyed to the heating region of the heating device. , the rear end portion is heated by moving the heating device toward the center portion in the width direction of the seat bar.

[Effect]

According to the method for heating a hot sheet bar according to claim (1), not only the edge portion but also the longitudinal tip portion of the sheet bar is heated over the entire region before finish rolling, and the temperature drop in this portion can be compensated for. Abnormal growth of crystal grains can be prevented, and as a result, material defects at the longitudinal ends of the sheet bar will not occur. Therefore, compared to conventional hot sheet bar rolling methods, it is possible to improve the yield while improving the workability and cold rollability of the product.

In addition, as a result of the temperature drop being prevented, the roll is not plastically deformed when the tip of the sheet bar made of a steel with high deformation resistance is bitten by the roll, so it is possible to prevent the occurrence of flaws in the roll.

Further, according to the method for heating a seat bar according to claim (2), since the rear end portion of the seat bar in the longitudinal direction is also heated over the entire region, it is possible to prevent material defects at this rear end portion.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 1st
The figure is a side view showing the configuration of an embodiment of an apparatus for carrying out the method of the present invention. In this embodiment, instead of the edge heater 10 shown in FIG.
An induction heating device 6 is provided for heating both. The induction heating device 6 is composed of a pair of upper and lower induction heating coils that are arranged opposite to each other with the seat bar 3 interposed therebetween. A total of two induction heating devices 6 are arranged on the upstream side and the downstream side of the Kuro 7 pusher (6
A, 6B). Further, as shown in the plan view of FIG. 2, two induction heating coils are provided in parallel in the width direction of the seat bar 3 (6A', 6B'). The output of these induction heating coils can be controlled separately, and the movement position of the seat bar 3 in the width direction can be adjusted.

The induction heating device used in this embodiment has a pair of upper and lower induction heating coils 30A, 30, as shown in the side view of FIG.
The upper induction heating coil 30A is fixed to the tip of the upper support arm 31A. Furthermore, a lower induction heating coil 30B is fixed to the tip of the lower support arm 31B. This pair of upper and lower support arms 31A, 31B are
It is swingably fixed to the left end of the support stand 38 of the trolley 32. An opening/closing hydraulic cylinder 35 is fixed to the right side of the upper support arm 31A, and an opening/closing hydraulic cylinder 36 is similarly fixed to the right end of the lower support arm 31B. 33 is a rail formed perpendicular to the rolling line, and 34 is a wheel for moving the cart 32 along the rail. In addition, 36 is a bearing stand of the conveyance roller 5.

Support arm 31A of the induction heating device shown in FIG.

31B is an induction heating coil 3OA provided at the left end;
The length is sufficient to move 30B to the center of the seat bar 3. This induction heating device can be moved on the rails 33 at right angles toward the conveyance direction of the sheet bar 3 by rotating the wheels 32 by a drive device provided in the truck 32. That is, when moving the induction heating coils 30A and 30B to the widthwise center of the seat bar 3, by running the induction heating coils 30A and 30B on the rail 33 toward the seat bar, these induction heating coils are moved to the widthwise center of the seat bar. It is possible to move towards. Note that if the seat bar 3 is warped, the induction heating coil may be destroyed, so the opening/closing cylinders 35 and 36 are driven by the hydraulic circuit in the truck 32, and the support arms 31A and 31B are moved around the support shaft 39. It becomes possible to swing as the center.

Next, FIG. 4 shows a block diagram of the embodiment shown in FIG. 1 above. Note that the same parts as in FIG. 1 are given the same reference numerals, and the explanation thereof will be omitted. FIG. 4 is a side view of the rolling equipment, and its configuration will be explained first.

A high frequency power source 27 is connected to each of the induction heating coils 30A and 30B. Further, the drive device 22 is connected to the wheels 34. These drive device 22 and high frequency power source 27 are each connected to the controller 21.

On the upstream side of the induction heating coils 30A and 30B, a real metal detector (HMD) 25 for detecting passage of the tip of the seat bar 3 and a temperature sensor 26 for detecting the temperature of the seat bar are provided. The sensor 26 is connected to the controller 21 described above.

A measuring roll 23 equipped with a pulse generator that measures the amount of movement of the sheet bar 3 and generates pulses according to the amount of movement is connected to one of the transport rollers 5. A speed detector 24 for detecting the moving speed of the seat bar 3 is provided. These measuring rolls 23 and speed detector 24 are connected to the controller 21.

The controller 21 is configured by a microcomputer, for example, and has an interface (not shown).
The temperature value raised by the induction heating device 6 can be set by connecting a temperature setting circuit (not shown).

Next, the operation of the embodiment shown in FIG. 4 will be explained with reference to FIGS. 2 and 5. FIG. 2 is a plan view showing the moving state of the induction heating coil, and FIG. 5 is a graph showing the control state of the coil position, sheet bar conveyance speed, and coil output.

In FIG. 4, the seat bar 3 is conveyed toward the right in the drawing, and when the tip of the seat bar 3 reaches the HMD 25 (consisting of an infrared sensor), the HMD
25 is a theoretical value indicating that the tip of the seat bar 3 has arrived by detecting infrared rays from the seat bar 3.
1'' signal is output to the controller 21.

Next, the temperature sensor 26 starts temperature detection, detects the temperature at the tip of the seat bar 3, and outputs the detected signal to the controller 21. Note that as the temperature sensor, for example, an infrared thermometer can be used. controller 2
1, when the tip of the seat bar 3 is detected by a signal from the HMD 25, the induction heating coils 30A and 30B are separated so that the upper and lower pair of induction heating coils are not damaged due to warping of the tip of the hot seat bar 3. move it in the direction you want.

The controller 21 can detect the amount of movement of the sheet bar 3 based on the signal from the measuring roll 23. That is, the controller 21 can calculate the amount of movement of the sheet bar 3 by counting the number of pulses generated from the pulse generator of the measuring roll 23. Therefore, as shown in Figure 2, HM
By storing the distance from D25 to the induction heating coils 6A, 6A' in advance in the storage device of the controller 21, the time when the tip of the seat bar 3 reaches the induction heating coils 6A, 6A' is detected. be able to.

In FIG. 5, T1 corresponds to +11 in FIG. 2, and the sheet bar 3 is conveyed and the induction heating coils 6A, 6
This is the point in time when the heating region A' is reached.

At this time, the controller 2I controls the seat bar 3 (not shown).
A signal is output to the transport device to reduce its transport speed from just before T, time. Similarly, the controller 21 outputs a control signal to the high-frequency power source 27 to set the output of the induction heating coil to a high level.

Further, the sheet bar 3 is conveyed, and at time T2 in FIG. 5, the induction heating coils 6A, 6A' are moved from the center in the width direction of the sheet bar to the edge portion. FIG. 2 (2) shows this state. Further, A in the graph of FIG. 5(1) indicates the positions of the induction heating coils 6A and 6A'. Fifth
In the figure, the conveyance speed of the sheet bar 3 is further reduced between T1 and T2, but this is because heating efficiency is improved by reducing the conveyance speed of the sheet bar 3.

The controller 21 calculates the difference between the temperature at the tip of the seat bar 3 measured by the temperature sensor 26 and the target temperature (preset in the controller with a setting device), and further calculates the difference so that this difference becomes zero. The conveyance speed of the sheet bar 3 can be controlled based on the thickness, material, etc. of the sheet bar.

Furthermore, when the sheet bar is conveyed, the induction heating coils 6A, 6A' move to the edge portion of the sheet bar at time T3 in FIG. At this time, as shown in the graph of FIG. 5(2), the coil conveyance speed is further reduced. In FIG. 2(3), the seat bar 3 enters the heating region of the downstream induction heating coils 6B, 6B'. This corresponds to time T3 in FIG.

As the sheet bar 3 is further conveyed, the coils 6B and 6B' are moved from the center toward the edges, as shown in FIG. 2(4).

Next, as shown in FIG. 2 (5), the coils 6B, 6B'
is moved to the edge portion (T4 in FIG. 5).

As shown in FIG. 2 (5), by moving the induction heating coil to the edge portion of the seat bar, in addition to heating the tip portion of the seat bar, heating of the edge portion of the seat bar is continued. At this time, as shown in the graph of FIG. 5(2), the coil conveyance speed becomes slightly high.

Next, after the sheet bar 3 is further conveyed, the sheet bar 3
Heating the rear end of the At this time, it is necessary to detect the rear end of the seat bar 3, but this is done by setting the length of the seat bar 3 in the controller 21 in advance and adjusting the amount of movement of the seat bar 3 using the measuring roll 23. Since it is constantly monitored, the rear end of the seat bar can be easily detected.

As shown in FIG. 2 (6), when the rear end of the seat bar 3 approaches the induction heating coils 6A, 6A', the coils 6A, 6A'
Move A' toward the center. This corresponds to time T3 in FIG. As shown in the graph of FIG. 5 (1), the coils 6A and 6A' move toward the center of the sheet bar, and at this time, as shown in the graph of FIG. 5 (2), the conveyance speed of the sheet bar increases. becomes smaller.

When the sheet bar is further conveyed, it reaches the state shown in (8) via FIG. 2 (7). In this state, the induction heating coil 6A
, 6A' move to the central position of the seat bar, and the moved area is heated by the movement of the induction heating coils 6A, 6A'.

The state in FIG. 2(8) corresponds to time T in FIG.

When the seat bar is further conveyed, the rear end of the seat bar enters the coils 6B and 6B' provided on the downstream side, and the coils 6B and 6
The coil B' moves toward the center. This corresponds to time T6 in FIG. As shown in FIG. 2 (9), as the sheet bar is further conveyed, the coils 6B, 6B' move toward the center, and finally, as shown in FIG. 2 (QO), the coils 6B, 6B' ′ also moves to the center. This point is T in Figure 5.

corresponds to After the induction heating coils 6B, 6B' move to the center of the seat bar, the coil output decreases from the H level to the L level at time T8, as shown in the graph of FIG. 5(3). Next, by repeating the operations (1) to 00) in FIG. 2, the continuously conveyed sheet bar can be heated.

In the above embodiment, one induction heating coil is provided on the upstream side and one downstream in the conveyance direction of the sheet bar 3, but more induction heating coils may be provided. Also,
- An induction heating coil may also be used. In this embodiment, since one coil is provided on each of the upstream and downstream sides, the area to be heated at the front end and rear end of the seat bar can be increased accordingly. Therefore, since the temperature drop in such a portion can be sufficiently compensated for, material defects in such a portion can be reliably prevented.

The induction heating coil generates an induced current in the seat bar 3 to heat the seat bar. The capacity of the induction heating coil can be made smaller as the expected amount of warpage (tolerance) of the tip of the seat bar 3 is smaller. It is necessary to use an induction heating coil. In addition, as in this embodiment, the sheet bar 3 is decelerated to heat the longitudinal end of the sheet bar, but when induction heating is performed without decelerating the conveying speed, induction heating of the corresponding capacity is required. equipment is required.

In the above embodiment, when the tip of the seat bar 3 enters the induction heating coil, heating is performed by increasing the gap between the induction heating coils 30A and 30B, but after the tip passes through, By narrowing this gap, it is possible to heat the edge portion, thereby significantly improving heating efficiency.

A pinch roller can be provided upstream of the induction heating coil shown in FIG. 1 to correct the warpage of the tip of the sheet bar 3. By correcting the warpage and flattening the tip of the sheet bar 3 by the pinch roller, the gap between the upper induction heating coil and the lower induction heating coil in the induction heating device 6 and the sheet bar 3 passing through can be set small. can. Therefore, the capacity of these heating coils can be significantly reduced to reduce equipment costs.

Further, there is no need to make the heating coil a movable type that moves vertically toward the seat bar 3.

Next, specific examples will be described. FIG. 6 is a graph showing the amount of temperature drop at the longitudinal end of a sheet bar at 1050° C. that has been rough rolled in a hot rough rolling mill. The graphs in Figures 6(A) and (C) show the amount of temperature drop at the tip of the seat bar, and the graphs in Figure 6(B)
and (D) is a graph showing the amount of temperature drop at the rear end of the seat bar. Furthermore, FIGS. 6(A) and (B)
The graph in (C) and (D) is for the case where only the edge portion of the sheet bar is heated, and the graphs (C) and (D) are for heating both the edge portion and the front and rear ends of the sheet bar based on the apparatus shown in the above example. This is a graph of the case. In addition, the 6th
In the figure, FET indicates the finish rolling machine entrance temperature, and FD
T indicates the finish rolling mill outlet temperature.

The sheet bar thickness used in this example was 35 mm,
The thickness of the product finished rolled by the finish rolling mill is 2 mm.

Normally, when the temperature drop at the longitudinal end of the sheet bar exceeds 30° C., material defects due to grain gloss usually occur in that portion. Therefore, as shown in FIG. 6(A), a region of poor material quality at the tip of the sea I bar occurs to a length of nearly 5 m. Further, as shown in FIG. 6(B), the material defective portion at the rear end of the seat bar extends to 2 m. On the other hand, when the temperature is increased by 40°C at the tip of the sheet bar as shown in FIG. 6(C), the number of defective materials decreases to within 2 m from the tip. Further, as shown in FIG. 6(D), the defective material portion at the rear end of the seat bar is reduced to within a range of 1 m. Therefore, by increasing the temperature of the longitudinal end of the sheet bar by 40°C,
For general low carbon materials at 0m, the conventional example in which the longitudinal ends of the sheet bar are not heated was to cut off 5m at the leading end and 2m at the rear end, but as in the present invention, the front and rear ends of the sheet bar are heated. By doing so, the amount of cutting off at the leading end is reduced to 2 m, and the amount of cutting off at the rear end is reduced to 1 m. As a result, per 1000m of seat bar, the amount of cutoff at the tip is reduced by 3m and the amount of cutoff at the rear end is reduced by 1m, so the small stop improvement is improved by 0.4%.
improvement, leading to significant cost reductions. That is, 3
A hot strip mill that produces about 1,000,000 tons/day will save about 150,000 tons/year of crude steel, resulting in a significant cost reduction.

Furthermore, even when a sheet bar made of a steel with high deformation resistance and whose tip end was heated to 40'C as described above was bitten by a finishing roll 100 times, no flaws were generated in the roll. On the other hand, when a sheet bar made of a steel with high deformation resistance was bitten into a finishing roll 20 times based on a conventional example in which the leading and trailing ends were not heated, it was confirmed that flaws occurred in the roll. .

As can be seen from this specific example, the heating area at the longitudinal end of the sheet bar is approximately 200 m at the tip.
It can be seen that it is sufficient to heat a width of a little more than m, and a width of a little more than about 100 mm at the rear end. However, this does not preclude heating a wider area.

As explained above, according to the present embodiment, material defects at the longitudinal end portions of the sheet bar are prevented, and as a result, the end stops can be prevented from occurring as described above, and the rolls can be prevented from being scratched.

Further, in this embodiment, the heating device is installed before the crop shear, but the heating device is not limited to this, and it can also be installed after the crop shear.

Furthermore, the number of induction heating devices installed is not limited to that of this embodiment, and more than one heating device can be installed.

Further, in this embodiment, the arrival of the tip of the seat bar is detected by an infrared sensor, but the present invention is not limited to this, and other optical sensors can also be used.

Further, in this embodiment, the rear end of the seat bar is detected based on a distance tracking method using a microcomputer, but the passage of the rear end of the seat bar can be detected using another optical sensor.

Furthermore, in this example, both the leading and trailing ends of the sheet bar are heated, but from the standpoint of preventing roll scratches and improving walking to some extent, only the leading end of the sheet bar is heated. However, it is also possible not to heat the rear end.

Furthermore, although induction heating has been described in this embodiment, the present invention is not limited to this, and the same objective can be achieved using other heating means.

Further, in this embodiment, the output of the induction heating coil is adjusted to two levels, H level and L level, but based on the difference between the target temperature at which the seat bar is to be heated and the actual temperature,
This can also be controlled in stages.

〔Effect of the invention〕

As explained above, according to the method for heating a hot sheet bar according to claim (1), not only the edge portion of the hot sheet bar but also the entire longitudinal tip portion is heated, so that the longitudinal end portion As a result of preventing abnormal growth of crystal grains in
The occurrence of material defects in such portions can be avoided. Therefore, the area where the front and rear ends of the seat bar are cut off is significantly reduced, and as a result, the walking distance is improved. In addition, sheet bars made of steel with high deformation resistance can prevent the occurrence of roll flaws, making it possible to avoid sudden roll replacements.
Operation rate improves.

Furthermore, according to the method for heating a hot seat bar according to claim (2), since the entire rear end portion in the longitudinal direction of the seat bar is also heated, it is possible to avoid the occurrence of material defects in such a portion. Minute stride will further improve.

[Brief explanation of the drawing]

FIG. 1 is a side view showing the configuration of an embodiment of an apparatus for carrying out the method of heating a hot sheet bar according to the present invention, and FIG.
The figure is a plan view showing the moving state of the induction heating coil, FIG. 3 is a side view showing the configuration of the induction heating device, and FIG.
Figure 5 is a graph showing the control status of the induction heating coil position, sheet bar conveyance speed, and coil output; Figure 6 is a graph showing the sheet bar conversion length or product conversion length and temperature drop amount. The graph shown in Figure 7 shows the relationship between
FIG. 2 is a side view showing the configuration of a conventional hot sheet bar rolling apparatus. In the figure, 1 is a hot rough rolling mill, 2 is a finishing mill, 3 is a sheet bar, 5 is a conveyance roller, 6 is an induction heating device, 6A, 6B
, 6A', 6B', 30A, 30B are induction heating coils,
10 is an edge heater, 21 is a controller, 22 is a coil drive device, 23 is a measuring roll, 24 is a speed detector, 25 is a hot metal detector, 26 is a temperature sensor, and 27 is a high frequency power source. Patent applicant: Kawasaki Steel Corporation Representative Patent attorney: Tetsuya Mori

Claims (2)

[Claims] (1) Hot rolling in which the sheet bar is heated on the entry side of the finishing rolling machine by a pair of heating devices that are disposed opposite to each other in the width direction of the hot sheet bar being conveyed and are movable in the width direction of the sheet bar. In the heating method for a sheet bar, the pair of heating devices are arranged at the widthwise central portion of the sheet bar, and when the longitudinal end of the sheet bar is conveyed to the heating region of the heating device, the heating device is heated. By moving the sheet bar toward a side end in the width direction, the tip thereof is heated, and then, the heating device disposed at the side end in the width direction of the sheet bar heats the side end. A method for heating a hot sheet bar, characterized by: (2) After heating the widthwise side end portions of the sheet bar, when the longitudinal rear end portion of the sheet bar is conveyed to the heating area of the heating device, the heating device is placed at the widthwise center of the sheet bar. 2. The method of heating a hot sheet bar according to claim 1, wherein the rear end portion is heated by moving the sheet bar toward the rear end portion.