JPH06106224A - Method for controlling on-line cooling device for hot steel sheet - Google Patents

Abstract

PURPOSE:To cool a hot steel sheet uniformly in the length direction in the same way that the hot steel sheet passes at a certain speed through an on-line cooling device by controlling infection and interruption of plural headers for cooling refrigerant after the hot steel sheet stops in the on-line cooling device. CONSTITUTION:In an application rolling pass for cooling the hot steel sheet 2 immediately after it is rolled by a hot mill 1, stop control of the hot steel sheet 2 is started from a mill fin flaw signal. After a specified time is counted from the same mill fin flaw signal, control of interruption of refrigerant in the upper and lower cooling headers 8 (i), 9 (i) mounted on the position farthest from the mill in the cooling headers of the rear on-line cooling device 3 wherein refrigerant arranged on the outlet side of the mill is being injected is started. The control of interruption is transferred to the cooling headers on the side near the mill in sequence at a specified interval. In this way, uniform cooling is accomplished in the longitudinal direction of the hot steel sheet and rolling capacity can be prevented from reducing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for controlling an on-line cooling device for hot-rolled steel sheets for cooling hot-rolled steel sheets during rolling by a hot rolling mill.

[0002]

2. Description of the Related Art A basic technique for cooling a hot steel sheet after completion of hot rolling, that is, a so-called controlled cooling of the hot steel sheet is almost established, and many patents have already been filed. These known techniques relate to control of a single cooling device as disclosed in, for example, Japanese Patent Laid-Open No. 60-87914, and to a cooling method that achieves the original purpose with a single cooling.

On the other hand, the cooling method targeted by the present invention is an online cooling device which is set at a position adjacent to the hot rolling mill on the inlet side and / or the outlet side of the hot rolling mill of the hot steel plate rolling line, It is possible to control the temperature by controlling all passes during rolling with a hot rolling mill or by cooling at specified specific passes.
The purpose was to shorten the temperature waiting time of rolling material, prevent the coarsening of the rolling structure during air cooling immediately after rolling, and improve the structure in the thickness direction by rolling with a prescribed temperature pattern in the thickness direction. It is a cooling method, the required number of times of cooling is multiple, and since it is cooling during rolling in the hot rolling mill, comprehensive control of the hot rolling mill and the online cooling device is essential, and the above-mentioned known technology is applied. Can not.

Incidentally, Japanese Patent Laid-Open No. 55-106615 proposes a method of cooling the hot steel sheet during rolling in all passes of hot steel sheet rolling. This technology applies cooling to all passes during rolling, and further delays the start of cooling of a predetermined length at the tip and tail of the hot steel plate, or increases or decreases the amount of cooling water to increase or decrease the length direction of the hot steel plate. This is a cooling method that makes the temperature distribution uniform.

[0005]

An on-line cooling device arranged adjacent to a hot rolling mill in a hot rolling line is used for immediately rolling a hot steel sheet being rolled by the hot rolling mill in a plurality of rolling passes. In the rolling and cooling to perform cooling, it is needless to say that it is preferable to perform the rolling operation at the same rolling speed as a normal rolling pass without cooling even though it is a cooling application pass, from the viewpoint of preventing reduction in rolling efficiency. Yes.

However, the rolling speed of hot-rolled steel sheet is usually 2 to 6
Considering that it is about m / sec, for example, even if it is cooled for 3 seconds, the cooling device length needs to be 6 to 18 m, and if it is intended to uniformly cool the hot steel sheet in the length direction by a known cooling control method. , It is necessary to convey the hot steel plate to the distance that the rolling tail end of the hot steel plate slips out of the exit side cooling device for each cooling application pass, and as the cooling application pass increases, the hot rolling mill increases the hot steel plate. It is not possible to prevent the wasteful time on rolling that does not bite into the rolling mill from becoming long and the rolling performance to drop significantly.

In order to solve this problem, an online cooling device capable of achieving uniform cooling in the lengthwise direction of the hot steel plate by transport control of the hot steel plate in the same manner as in the normal rolling pass in which the cooling application path does not apply cooling. Control development is needed.

[0008]

SUMMARY OF THE INVENTION The present invention is a rolling and cooling system in which a hot-rolled steel sheet being rolled by a hot rolling mill is cooled by an on-line cooling device installed adjacent to the rolling mill outlet side in a plurality of specific rolling passes. In the above, in the cooling applied rolling pass, the problem is to uniformly cool the hot steel plate in the length direction by the same rolling / conveyance control (conveyance distance control from the rolling mill) as in the non-applied rolling pass. Therefore, in the present invention, the cooling-applied rolling pass, as well as the normal non-applied rolling pass, starts the stop control of the hot-rolled steel sheet starting from the biting signal of the rolling mill, and the predetermined from the rolling-bite signal of the rolling mill. After a lapse of time, of the plurality of cooling headers during the injection of the cooling medium in the online cooling device, the cooling medium injection cutoff control is started from the cooling header installed at the position farthest from the hot rolling mill, and the predetermined cooling header is started. Order by interval So that they carry out cooling medium stop control of the cooling headers close to the rolling mill side. By this cooling control method, even if the hot steel plate is stopped in the online cooling device, it is cooled uniformly in the lengthwise direction of the hot steel plate as if it passed through the cooling device at a constant speed and slipped through. Can be achieved.

[0009]

In the hot rolling line shown in FIG. 1, the hot rolling mill 1
The hot-rolled steel sheet 2 being rolled by means of the online cooling device 3 installed at the adjacent position on the outlet side of the hot rolling mill 1 in a specific rolling pass being rolled by a plurality of rolling passes for rolling to the product sheet thickness. Immediately after being bitten out from the hot rolling mill, it is cooled at a predetermined cooling rate for a predetermined time.

In the cooling application rolling pass, when the injection of the cooling medium at a predetermined flow rate is started from the header selected by the cooling control device 7, the rolling mill control device 6 stops on the front side of the hot rolling mill 1. In order to roll and cool the hot steel plate 2 being rolled, the transport of the hot steel plate 2 is started.

The rolling control device 6 stops the hot steel sheet 2 on the rear surface of the hot rolling mill 1 when the tail end of the hot steel sheet 2 being rolled bites from the hot rolling mill 1.

The cooling control device confirms the above-mentioned rolling out of the rolling mill and starts the cooling header shutoff control for uniform cooling of the hot steel plate 2 in the length direction.

When the cooling control device 7 completes the predetermined cooling control up to the tail end of the hot steel plate 2 and the setting of the hot rolling mill for the next pass rolling is completed, the rolling control device 6 causes the hot steel plate 2 to finish. And the next rolling pass is rolled.

When the next rolling pass is a cooling application pass, the online cooling device 3 having the same structure as the above-mentioned online cooling device 3 is installed in the opposite direction to the inlet / outlet side of the hot rolling mill 1. 'The rolling and cooling are performed in the same manner as above, but it is necessary to confirm that a predetermined flow rate of the cooling medium is flowing from the selected cooling header of the online cooling device 3'before the transfer of the hot steel plate 2 is started. There is.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to.

FIG. 1 shows the equipment layout relationship between the hot rolling mill 1 of the hot rolling line and the online cooling devices 3 and 3 ', and the configuration of the control device, and FIG. 2 is a cooling header in the online cooling devices 3 and 3'. 8 (i), 9 (i), 8 '(i), 9' (i) is shown in FIG. 3, and FIG. 3 shows an online cooling device 3 (or 3) for making the length direction of the hot steel plate 2 uniform. The time chart of the cooling header cutoff control of ') is shown.

In FIGS. 1 and 2, 1 is a hot rolling mill installed in a hot rolling line, 2 is a hot steel plate, 4 is a conveying table, and the hot steel plate 2 is a hot rolling mill by a rolling control device 6. 1 is conveyed in the forward rotation direction or the reverse rotation direction on the conveyance table 4 which is synchronously controlled with 1, and is rolled by the hot rolling mill 1 to a predetermined plate thickness.

Reference numerals 3 and 3 ′ are online cooling devices installed on the front side and the rear side of the hot rolling mill 1 adjacent to the hot rolling mill 1. Cooling headers 8 (i) and 9 (i), or 8 '(i) and 9' (i), and each cooling header has a plurality of cooling media in a direction orthogonal to the traveling direction of the hot steel plate. An injection nozzle (not shown) is connected.

Reference numeral 5 is a high-level computer which controls the rolling control and the cooling control. The rolling control device 6 and the cooling control device 5 respond to the respective control condition instruction values input in advance to the rolling control device 6 and the cooling control device 7. The control conditions necessary for the control of No. 7 are calculated.

The rolling control device 6 receives from the host computer 5 the number of rolling passes, the rolling roll gap set value for each rolling pass,
Upon receiving input conditions such as a rolling speed, the hot rolling mill 1 and the transport table 4 are controlled based on these conditions, and the hot steel plate 2 is rolled.

The cooling control device 7 receives the number of cooling-applied rolling passes from the host computer 5, the pass number. , And cooling conditions (number of headers used, cooling rate, etc.) are input, the online cooling device is controlled based on these conditions, and the hot steel plate 2 is cooled.

Of the rolling passes of the hot steel sheet 2, the required cooling rate and cooling time of the cooling-applied rolling pass are determined by the target steel type and size. For example, CR rolling start like a controlled rolling (hereinafter abbreviated as CR) material. In cooling for the purpose of shortening the air cooling time to the temperature, the cooling time per pass is short, but a considerably large number of cooling-applied rolling passes are required.

On the other hand, in a steel type for which a specific temperature pattern is applied in the plate thickness direction of the hot steel plate 2 in a specific rolling pass to improve the properties of the hot steel plate 2 in the plate thickness direction, the number of cooling application passes is Limited to rolling with a specific strip thickness, the number of cooling-applied rolling passes is small, but the cooling time per pass tends to be long.

The cooling rate and the cooling time of the hot steel plate 2 in the cooling application pass are controlled by the cooling medium injection density per unit area of the hot steel plate and the cooling time by the on-line cooling device captain and the strip running speed. Although they are controlled by a combination, since these are known techniques, detailed description will be omitted here.

Next, with reference to FIG. 3, a method for controlling the hot rolling mill and the online cooling device of the present invention will be described. For convenience of explanation, it is assumed that the cooling-applied rolling pass is the (i) th rolling pass, and this rolling pass is rolled and cooled during conveyance in the forward direction of the hot rolling mill 1. Similarly, (i-
It is assumed that the 1) th pass and the (i + 1) th pass are cooling non-application passes, and these rolling passes are rolled in the reverse direction of the hot rolling mill 1 during conveyance.

During rolling of the (i-1) th rolling pass to which cooling is not applied, the rolling mill biting signal A of the hot steel plate 2 (usually a signal of a load cell (not shown) incorporated in the hot rolling mill) Is turned off, the rolling control device 6 changes the transport control signal B of the hot rolling mill 1 and the transport table 4 from reverse transport to stop, and the hot rolling mill 1 and the transport table 4 are stopped. The control is started and the hot steel plate 2 is stopped at the front side of the hot rolling mill 1.

Similarly, the cooling control device 7 includes a plurality of cooling headers 8 (i) used for cooling among the cooling headers of the online cooling device 3 installed on the rear surface side of the hot rolling mill 1.
And 9 (i) and cooling header open / close signal C for injecting a cooling medium from each selected cooling header.
(I) is changed from closed to open, and the injection control of the cooling medium of a predetermined flow rate is started from each cooling header 8 (i) and 9 (i).

The upper and lower pairs of cooling headers 8 (i) and 9 (i) are installed at the same distance from the hot rolling mill 2.
The opening and closing control of the cooling header opening and closing signals are the same for both upper and lower sides. For convenience of explanation, the number of cooling headers selected is 7, and the cooling header closest to the hot rolling mill 1 is No. 1. 1, the farthest cooling header is N
o. 7

While the (i-1) th rolling pass is completed and the hot steel sheet 2 is stopped in front of the hot rolling mill 1, the rolling control device 6 and the cooling control device 7 perform the next cooling application rolling. When the setting of the hot rolling mill 1 and the online cooling device 3 of the (i) th rolling pass, which is the pass, is completed, the rolling control device 6 changes the conveyance control signal B from stop to normal rotation conveyance, and the hot rolling mill 2 Also, the transport table 4 is started in the forward direction, and the hot steel plate 2
The rolling and cooling of the (i) -th rolling pass of are started.

When the (i) th pass of the hot steel plate 2 is started and the leading end of the hot steel plate 2 is bit into the hot rolling mill 1, the rolling mill biting signal A is turned on and each of the hot steel plates 2 is turned on. The part is cooled by the online cooling device 2 immediately after rolling by the hot rolling mill 1.

When the hot rolling mill 1 bites out the tail end portion of the hot steel plate 2 and the hot rolling mill biting signal A is turned off, the rolling control device 6 changes the feeding control signal B from the forward feeding to the stop. After changing, the stop control of the hot rolling mill 1 and the transport table 4 is started, and the hot steel plate 2 is stopped at the rear surface side of the hot rolling mill 1.

Similarly, the cooling control device 7 starts from the rolling mill biting signal A OFF and starts a plurality of cooling headers 8 (1 to 1) of the online cooling device 3 installed on the rear surface side of the hot rolling mill 1. 7) and 9 (1 to 7), the injection cutoff control of the cooling medium is started.

Cooling headers 8 (1-7) and 9 (1-
In the injection cutoff control of 7), the injection of the cooling medium is started from the cooling headers 8 (7) and 9 (7) which are arranged at the position farthest from the hot rolling mill 1 during the injection of the cooling medium. Then, the injection cutoff is sequentially transferred to the cooling header close to the hot rolling mill 1, and the upper and lower cooling headers cut off the injection at the same timing.

The opening / closing signal C7 of the cooling headers 8 (7) and 9 (7) which first starts the cutoff of the cooling medium is expressed by the following formula (1) from the turning off of the rolling mill biting signal A of the hot steel plate 2. After T (7) seconds obtained in step S1, the open state is changed to the closed state, and the injection cutoff control of the cooling medium is executed.

T (7) = (L1 + (N−1) × Lp) / V (1) where L1: distance from hot rolling mill to first cooling header (m) N: Number of cooling headers during injection of cooling medium (7) Lp: Distance between cooling headers (m) V: Passing speed of hot steel sheet immediately before starting transport stop control (m / sec) Next cooling header 8 The cooling header open / close signal C6 of (6) and 9 (6) is calculated from T (7) obtained by the above equation (1),
Change from open to closed after Lp / V (seconds).

Similarly, the cooling header open / close signals C5, C4, C3, C2, and C1 are sequentially changed at the time intervals T (i) from open to closed, and the cooling medium cutoff control of each cooling header is executed.

Cooling headers 8 (6) / 9 (6) through 8
In order to perform the cooling medium injection cutoff control of (1) / 9 (1), a general formula showing a time interval for changing the cooling header open / close signals C6 to C1 from open to closed is shown as the formula (2). .

T (i) = T (i−1) + Lp / V (2) It should be noted that the control timings of the equations (1) and (2) are such that the transport stop control of the hot steel plate 2 is started. The speed change from the start to the stop is neglected. Strictly speaking, the strip running speed V in the above equation needs to be corrected by the strip running speed change amount from the start control to the stop of the hot steel plate. The time it occurs is short,
Even if the speed change is ignored, the effect is small and there is no practical problem.

When the rolling mill biting signal A of the (i) th rolling pass is turned off, the rolling control device 6 prepares for the next (i + 1) th rolling pass such as the reduction setting of the hot rolling mill 1. To start.

Finally, it is confirmed that the opening / closing signal C1 of the cooling headers 8 (1) and 9 (1) to be shut off is changed from open to closed, and the cooling medium shutoff control is completed. Then, the reverse rotation conveyance control of the hot rolling mill 2 and the conveyance table 4 is started, and the (i + 1) th rolling of the hot steel sheet 2 is executed.

The cooling header 8 by the cooling control device 7 is started from the rolling bite signal A off of the hot steel plate 2 as described above.
In the injection cutoff control of the cooling medium of (i) and 9 (i), the interpass time T (0) in which the hot steel plate 2 is not engaged with the hot rolling mill 1 in the (i) th rolling pass to be cooled is set. The time can be minimized (the time between passes of the cooling-applied rolling pass can be shortened to the same degree as the time between passes of the cooling-unapplied rolling pass), and the hot-rolled steel plate 2 can achieve uniform cooling in the length direction from the tip to the tail end.

In the above embodiment, the control method of the on-line cooling device which minimizes the inter-pass time T (0) of the cooling-applied rolling pass and uniformly cools the hot steel plate 2 from the front end to the rear end thereof is described. As described above, the leading end and the tail end of the hot steel plate 2 are more easily overcooled than the central part, and the leading end and the tail end of the hot steel plate are cooled more than the central part in order to make the temperature distribution uniform. It is common to prevent overcooling.

An embodiment in which the control method of the on-line cooling device 3 of the present invention is applied to alleviate the cooling of the tip end and the tail end in order to make the temperature of the hot steel plate 2 uniform in the lengthwise direction will be described below. explain.

The tip of the hot steel plate 2 is for cooling during continuous threading, and a method of preventing supercooling of the tip of the steel sheet during continuous threading is described in JP-A-62-158518, for example, starting cooling header injection and There are known techniques such as tracking control of end timing, and these techniques can be applied.

However, the above-mentioned known technique is premised on a cooling method in which the hot steel plate passes through the inside of the cooling device at a constant speed, and the cooling control method of the present invention uses the cooling device at the tip of the hot steel plate at a constant speed. Although it passes through, the tail end does not pass through the cooling device, and therefore the above-mentioned known technique cannot be applied to uniformize the temperature of the tail end of the hot steel plate 2.

Rolling control device 6 in the cooling application rolling pass
The rolling control of the hot steel sheet 2 (control of the hot rolling mill 1 and the carrying table 4) is the same as that in the above-described embodiment.

The host computer 5 determines a control required range (steel plate length Lb at the tail end of the hot steel plate) of the hot steel plate 2 from the dimensions and cooling conditions in the rolling pass of the hot steel plate 2, and inputs it to the cooling control device 7 in advance. .

The rolling control device 6 calculates an expected distance Ls from when the hot steel plate 2 bites the hot rolling mill 1 to when it stops, and inputs it to the cooling control device 7. However, if the variation in the expected stop distance Ls is small, it may be practically measured in advance and treated as a fixed value.

The cooling control device 7 uses (L1 + Ls +) by using the input values Lb and Ls and the distance L1 to the cooling header installed at the position closest to the rolling mill.
Lb) is calculated and the cooling headers 8 (n) and 9 (n) closest to (L1 + Ls + Lb) are determined.

Then, as in the above-described embodiment, the hot rolling mill 1 out of the cooling headers 8 (i) and 9 (i) during the injection of the cooling medium.
Cooling header 8 (7), which is installed farthest from
From 9 (7), the cooling medium being jetted is supplied with a predetermined time interval T
(7) and T (i) are sequentially shut off.

The injection cutoff control timing is 8 (n), 9
Upon reaching (n), cooling headers 8 (n), 9
(N) Cooling header 8 installed on the rolling mill side
The injection of (i) and 9 (i) is controlled to be shut off all at once.

According to this cooling control method, the tail end portion Lb of the hot steel sheet is less cooled than the central portion, and cooling with a uniform temperature distribution in the length direction can be achieved.

[0053]

INDUSTRIAL APPLICABILITY The present invention uses an online cooling device installed at a position adjacent to a hot rolling mill in a hot rolling line to cool immediately after rolling only to a specific designated rolling pass during rolling. In the applied online cooling method, after the hot steel plate has stopped in the online cooling device, injection blocking control of multiple cooling medium injection cooling headers is performed, and the hot steel plate slips through the online cooling device at a constant speed. Similar to the above, uniform cooling can be achieved in the length direction of the hot steel sheet.
By implementing this on-line cooling control method, it is possible to perform the rolling control in the cooling-applied rolling pass in the same manner as in the normal cooling-unapplied pass, and it is possible to prevent the reduction of the rolling capacity.

[Brief description of drawings]

FIG. 1 is a block diagram showing an arrangement of online cooling devices installed at positions on the front and rear surfaces of a hot rolling mill adjacent to a rolling mill of a hot rolling line to which the present invention is applied, and a configuration of control equipment of each equipment. Is.

FIG. 2 is a front view showing a cooling header arrangement in an online cooling device and a positional relationship with a hot rolling mill.

FIG. 3 is a time chart showing the transfer timing of hot steel plates and the control timing of each cooling header. 1: Hot rolling mill 2: Hot rolled steel plate 3: Rear surface online cooling device 3 ': Front surface online cooling device 5: Host computer 6: Rolling control device 7: Cooling control device 8: Upper cooling header 9: Lower cooling header

Claims (3)

[Claims] 1. A plurality of hot rolling mills installed on a hot rolling mill line are provided at a position adjacent to the hot rolling mills on the front side and / or the rear side of the hot rolling mill, above and below the hot rolling plate passing position, and in a traveling direction. Using an online cooling device in which a cooling header for cooling medium injection is arranged, the hot steel sheet being rolled by the hot rolling mill is cooled immediately after rolling in a plurality of designated rolling passes. In the rolling pass to which the cooling is applied, the stop control of the hot steel plate is started by using the rolling mill biting signal of the hot steel sheet as a starting point, and after counting a predetermined time from the same rolling mill biting signal as the starting point. Among the cooling headers on the outlet side of the rolling mill and injecting the cooling medium, the cooling medium of the cooling header arranged at the farthest position from the rolling mill is started to be cut off and the rolling is sequentially performed at predetermined time intervals. To the cooling side near the machine A method for controlling a hot steel plate online cooling device, characterized in that the shutoff control of the cooling medium is transferred to the lidder. 2. The cooling medium injection cutoff control is started from the cooling header farthest from the rolling mill among the cooling headers which are injecting the cooling medium disposed on the delivery side of the rolling mill, and rolling is sequentially performed at predetermined time intervals. The hot-rolled steel sheet online according to claim 1, wherein the cooling medium of the cooling header closer to the rolling mill is shut off from a predetermined cooling header at the same time when the cooling medium shutoff control is performed to the cooling header closer to the rolling mill. Cooling device control method. 3. The cooling medium cutoff completion signal of the cooling header subjected to cutoff control at the end is used as one of the starting points of the hot steel plate conveyance start control for rolling the next rolling pass of the hot steel plate. The method for controlling the hot steel plate online cooling device according to claim 2.