JP2656428B2 - Control method of hot steel plate online cooling device - Google Patents

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 control method of an on-line hot steel sheet cooling apparatus for cooling a hot steel sheet being rolled by a hot rolling mill.

[0002]

2. Description of the Related Art With respect to the so-called controlled cooling of a hot steel sheet, in which the hot steel sheet is cooled after completion of hot rolling, the basic technology has been almost established, and many patents have already been filed. These known techniques relate to the control of a single cooling device as disclosed in, for example, Japanese Patent Application Laid-Open No. 60-87914, and also to a cooling method for achieving the original purpose by one cooling.

On the other hand, a cooling method to which the present invention is directed is an on-line cooling device set at a position adjacent to a hot rolling mill on an inlet side and / or an outlet side of a hot rolling mill in a hot steel sheet rolling line. Controlled cooling is achieved by cooling in all passes during a hot rolling mill or in a specified specific pass.
The purpose is to reduce the temperature waiting time of the rolling material, prevent the rolling structure from becoming coarse during air cooling immediately after rolling, or improve the structure in the thickness direction by rolling while maintaining a predetermined temperature pattern in the thickness direction. Since it is a cooling method and the number of required cooling times is plural, and 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.

Japanese Patent Application Laid-Open No. 55-106615 proposes a method for cooling a hot steel sheet during rolling in all passes of the hot steel sheet rolling. In this technology, cooling is applied to all passes during rolling, and furthermore, by delaying the start of cooling of a predetermined length at the front and tail ends of the hot steel plate, or by increasing or decreasing the amount of cooling water, the length direction of the hot steel plate is reduced. This is a cooling method for making the temperature distribution uniform.

[0005]

An on-line cooling device arranged at a position adjacent to a hot rolling mill in a hot rolling line, a hot steel sheet being rolled by a hot rolling mill, immediately after rolling in a plurality of rolling passes. Needless to say, in rolling and cooling in which cooling is performed, from the viewpoint of preventing a reduction in rolling efficiency, it is preferable to perform a rolling operation at the same rolling speed as a normal rolling pass without cooling even though it is a cooling application pass. No.

However, the rolling speed of a hot steel sheet is usually 2-6.
Considering that the cooling rate is about m / sec, for example, even if cooling is performed for 3 seconds, the cooling device length is required to be 6 to 18 m, and if a known cooling control method is used to uniformly cool the hot steel plate in the length direction, It is necessary to transport the hot steel sheet until the rolling tail end of the hot steel sheet passes through the outlet cooling device for each cooling application pass, and as the number of cooling application passes increases, the hot rolling mill In this case, it is not possible to prevent a long time in rolling that does not involve the rolling and a large decrease in rolling capacity.

[0007] In order to solve this problem, an on-line cooling apparatus capable of achieving uniform cooling in the length direction of the hot steel sheet by controlling the conveyance of the hot steel sheet in the same manner as in a normal rolling pass in which no cooling is applied to the cooling application path. Control development is required.

[0008]

SUMMARY OF THE INVENTION The present invention provides a rolling and cooling method for cooling a hot steel plate being rolled by a hot rolling mill in an on-line cooling device installed adjacent to a rolling mill exit side in a plurality of specific rolling passes. It is an object of the present invention to uniformly cool the longitudinal direction of the hot steel sheet by the same rolling / transport control (control of the transport distance from the rolling mill) as in the non-applicable rolling pass in the rolling pass to which cooling is applied. For this reason, in the present invention, similarly to the normal non-applied rolling pass, the cooling applied rolling pass starts the hot steel sheet stop control starting from the rolling mill feed-out signal, and performs a predetermined process from the rolling mill feed-out signal. After a lapse of time, of the plurality of cooling headers during the injection of the cooling medium in the online cooling device, the injection cutoff control of the cooling medium is started from the cooling header installed at the position farthest from the hot rolling mill, and a predetermined time. Order by interval So that they carry out cooling medium stop control of the cooling headers close to the rolling mill side. With this cooling control method, even though the hot steel plate is stopped in the online cooling device, the cooling plate is uniformly cooled in the longitudinal direction of the hot steel plate in the same manner as when the hot steel plate passes through the cooling device at a constant speed and breaks down. Can be achieved.

[0009]

In the hot rolling line shown in FIG.
The hot steel plate 2 being rolled in a specific rolling pass being rolled in a plurality of rolling passes for rolling up to the product thickness by an online cooling device 3 installed at a position adjacent to the exit side of the hot rolling mill 1 in a specific rolling pass. After cooling from the hot rolling mill, it is cooled at a predetermined cooling rate for a predetermined time.

In the cooling-applied rolling pass, when the cooling medium injection of a predetermined flow rate is started from the header selected by the cooling control device 7, the rolling mill control device 6 stops at the front side of the hot rolling mill 1. In order to roll and cool the hot steel sheet 2 that has been started, the conveyance of the hot steel sheet 2 is started.

The rolling control device 6 stops the hot steel plate 2 on the rear surface of the hot rolling mill 1 when the tail end portion of the hot steel plate 2 being rolled is bitten out of the hot rolling mill 1.

The cooling control device confirms the above-mentioned rolling mill biting, and starts cooling header cutoff control for uniform cooling in the longitudinal direction of the hot steel plate 2.

When predetermined cooling control to the tail end of the hot steel plate 2 is completed by the cooling control device 7 and setting of the hot rolling mill for the next pass rolling is completed, the rolling control device 6 Is started and rolling of the next rolling pass is performed.

In the case where the next rolling pass is a cooling application pass, the on-line cooling device 3 having the same structure as the above-described on-line cooling device 3 and installed in the direction opposite to the inlet / outlet side of the hot rolling mill 1 is used. Rolling and cooling are performed in the same manner as described 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 starting the transfer of the hot steel plate 2. There is.

[0015]

FIG. 1, FIG. 2 and FIG. 3 show an embodiment of the present invention.
This will be described with reference to FIG.

FIG. 1 shows the arrangement of the hot rolling mill 1 and the on-line cooling devices 3 and 3 'in the hot rolling line and the configuration of the control device. FIG. 2 shows the cooling header in the on-line cooling devices 3 and 3'. 8 (i), 9 (i), 8 '(i) and 9' (i) are shown in FIG. 3. FIG. 3 shows an on-line cooling device 3 (or 3) for making the length direction of the hot steel plate 2 uniform. ') Shows a time chart of cooling header cutoff control.

1 and 2, reference numeral 1 denotes a hot rolling mill installed on a hot rolling line, 2 denotes a hot steel plate, 4 denotes a conveying table, and the hot steel plate 2 is a hot rolling mill by a rolling control device 6. The sheet is conveyed in a forward direction or a reverse direction on a conveying table 4 which is controlled in synchronization with 1, and is rolled by a hot rolling mill 1 to a predetermined thickness.

Reference numerals 3 and 3 'denote on-line cooling devices installed at positions 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 sheet. An injection nozzle (not shown) is connected.

Reference numeral 5 denotes a higher-level computer that supervises the rolling control and the cooling control, and controls the rolling control device 6 and the cooling control device with respect to each control condition instruction value 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 the number of rolling passes, the set value of the rolling roll gap 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 sends the number of rolling passes to which cooling is applied, , And input conditions such as cooling conditions (number of headers used, cooling rate, etc.), and controls the online cooling device based on these conditions to cool the hot steel plate 2.

In the rolling pass of the hot steel sheet 2, the required cooling rate and cooling time of the cooling rolling pass are determined by the target steel type and size. For example, as in the case of a controlled rolling (hereinafter abbreviated as CR) material, CR rolling is started. In the 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 rolling passes for cooling are required.

On the other hand, in a steel type intended to improve the properties of the hot steel sheet 2 in the thickness direction by giving a specific temperature pattern in the thickness direction of the hot steel sheet 2 in a specific rolling pass, the number of cooling application passes is The rolling is limited to a specific thickness, and the number of rolling passes to which cooling is applied is small, but the cooling time per pass tends to be long.

The cooling speed and cooling time of the hot steel plate 2 in the cooling application path are controlled by controlling the cooling speed by the injection density of the cooling medium per unit area of the hot steel plate, and the cooling time by the length of the on-line cooling device and the passing speed. The control is performed by a combination. However, since these are known techniques, detailed description is omitted here.

Next, a control method of the hot rolling mill and the on-line cooling device of the present invention will be described with reference to FIG. 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 while being conveyed in the normal rotation direction of the hot rolling mill 1. Similarly, (i-
The 1) th pass and the (i + 1) th pass are non-cooling-applied passes, and these rolling passes are to be rolled while being conveyed in the reverse direction of the hot rolling mill 1.

During the rolling of the (i-1) th rolling pass where 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) built 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 stops the hot rolling mill 1 and the transport table 4. The control is started, and the hot steel plate 2 is stopped on 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 side of the hot rolling mill 1.
And 9 (i), and a cooling header opening / closing 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 at a predetermined flow rate is started from each of the cooling headers 8 (i) and 9 (i).

The upper and lower pairs of cooling headers 8 (i) and 9 (i) installed at the same distance from the hot rolling mill 2
Opening / closing control is performed at the same timing, and the cooling header opening / closing signal is shared between upper and lower sides. For convenience of explanation, the number of cooling headers selected is seven, and the cooling header closest to the hot rolling mill 1 is no. 1. The farthest cooling header is N
o. 7 is assumed.

When the (i-1) th rolling pass is completed and the hot steel plate 2 is stopped at the front of the hot rolling mill 1, the rolling control device 6 and the cooling control device 7 perform the next cooling applied 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 transport control signal B from stop to forward transport, and the hot rolling mill 2 And the transfer table 4 is started in the normal rotation direction,
(I) Rolling and cooling of the (i) th rolling pass are started.

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

When the hot rolling mill 1 starts biting the tail end of the hot steel plate 2 and the hot rolling mill biting signal A is turned off, the rolling control device 6 changes the transport control signal B from normal transport to stop. Then, the stop control of the hot rolling mill 1 and the transfer table 4 is started, and the hot steel plate 2 is stopped on the rear side of the hot rolling mill 1.

Similarly, the cooling control device 7 starts the plurality of cooling headers 8 (1 to 1) of the on-line cooling device 3 installed on the rear side of the hot rolling mill 1 starting from the above-mentioned rolling mill biting signal A off. 7) and 9 (1 to 7) start the injection cutoff control of the cooling medium.

The cooling headers 8 (1 to 7) and 9 (1 to
In the injection cutoff control of 7), the injection of the cooling medium is started from the cooling headers 8 (7) and 9 (7) arranged at the position farthest from the hot rolling mill 1 while the cooling medium is being injected. Then, the injection cutoff is sequentially shifted 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.

First, the opening / closing signal C7 of the cooling headers 8 (7) and 9 (7) for starting to shut off the cooling medium is obtained from the following equation (1) from the rolling mill biting signal A off of the hot steel plate 2. After T (7) seconds obtained in the above, the state is changed from the open state 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 (m) from the hot rolling mill to the first cooling header N: Number of cooling headers during injection of cooling medium (seven) Lp: distance between cooling headers (m) V: feeding speed of hot steel sheet immediately before starting conveyance stop control (m / sec) Next cooling header 8 The cooling header opening / closing signal C6 of (6) and 9 (6) is obtained from T (7) obtained by the above equation (1).
Change from open to closed after Lp / V (sec).

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

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

T (i) = T (i−1) + Lp / V (2) Note that the control timings of the expressions (1) and (2) start the conveyance stop control of the hot steel plate 2. The speed change from the start to the stop is ignored, and strictly speaking, the passing speed V in the above formula needs to be corrected with the passing speed change amount from the start control to the stop of the stop control of the hot steel plate. The time that occurs is short,
The effect is small even if the speed change is ignored, and there is no problem in practical use.

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

After confirming that the opening / closing signal C1 of the cooling headers 8 (1) and 9 (1) to be shut off finally changes from open to closed, and that the cooling medium shutoff control is completed, the transport control signal B is reversed from the stop. And the reverse transport control of the hot rolling mill 2 and the transport table 4 is started, and the (i + 1) -th rolling of the hot steel plate 2 is executed.

The cooling header 8 by the cooling controller 7 starting from the above-described rolling biting signal A off of the hot steel plate 2
In (i) and 9 (i), the injection interception control of the cooling medium is used to determine the inter-pass time T (0) of the (i) -th rolling pass to which cooling is applied, in which the hot steel plate 2 is not bitten by the hot rolling mill 1. It can be minimized (the inter-pass time of the rolling pass to which cooling is applied is reduced to about the same time as the inter-pass time of the rolling pass to which cooling is not applied), and the hot steel plate 2 can achieve uniform cooling in the longitudinal direction from the front end to the tail end.

In the above embodiment, the control method of the on-line cooling device for minimizing the inter-pass time T (0) of the cooling application rolling pass and uniformly cooling the hot steel plate 2 from the front end to the tail end is described. As described above, the leading end and the tail end of the hot steel sheet 2 are more easily supercooled than the center part, and in order to make the temperature distribution uniform, the leading end and the tail end of the hot steel sheet are less cooled than the center part. It is common to prevent supercooling.

An embodiment in which the control method of the on-line cooling device 3 of the present invention is applied to moderate cooling of the front end portion and the tail end portion in order to equalize the temperature in the longitudinal direction of the hot steel plate 2 will be described below. explain.

The leading end of the hot steel plate 2 is used for cooling during continuous passing. The method for preventing supercooling of the leading end of the continuous passing steel plate is described in, for example, Japanese Patent Application Laid-Open No. 62-158518. There are known techniques such as end timing tracking control, and these techniques are applicable.

However, the above-mentioned known technology is based on the premise that a cooling method is used when a hot steel sheet passes through a cooling device at a constant speed, and the cooling control method of the present invention uses the cooling device at a constant speed at the tip of the hot steel plate. However, since the tail end does not pass through the cooling device, the above-mentioned known technique cannot be applied to uniform the temperature of the tail end of the hot steel plate 2.

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

The host computer 5 obtains the required control range (the steel plate length Lb at the tail end of the hot steel plate) from the supercooling prevention from the dimensions and the cooling conditions of the hot steel plate 2 in this rolling pass, 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 starts to bite the hot rolling mill 1 until it stops, and inputs it to the cooling control device 7. However, if the expected stop distance Ls has a small variation, it may be measured in advance and treated as a fixed value, which is practically acceptable.

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

Next, in the same manner as in the above-described embodiment, the hot rolling mill 1 of the cooling headers 8 (i) and 9 (i) during the injection of the cooling medium.
Cooling header 8 (7) installed farthest from
From 9 (7), the cooling medium being injected is discharged at a predetermined time interval T
(7) and shut off sequentially at T (i).

When the injection cutoff control timing is 8 (n), 9
When reaching (n), the cooling headers 8 (n), 9
(N) Cooling header 8 installed on the rolling mill side
(I) Injection control of 9 (i) is simultaneously controlled.

By this cooling control method, the cooling of the tail end portion Lb of the hot steel sheet is moderated from that of the central portion, and cooling with a uniform temperature distribution in the length direction can be achieved.

[0053]

According to the present invention, cooling immediately after rolling is performed only in a specific designated rolling pass during rolling using an on-line cooling device installed adjacent to a hot rolling mill in a hot rolling line. In the applied online cooling method, when the hot steel sheet stops inside the online cooling device, then performs the injection cutoff control of the cooling header for cooling medium injection, and the hot steel plate falls through the inside of the online cooling device at a constant speed. As in the above, uniform cooling in the length direction of the hot steel sheet can be achieved.
The realization of this online cooling control method enables the same rolling control as the normal cooling non-application pass in the cooling application rolling pass, thereby preventing a reduction in rolling capacity.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an arrangement of online cooling devices installed at positions adjacent to a rolling mill on the front and rear surfaces of a hot rolling mill in a hot rolling line to which the present invention is applied, and a configuration of control equipment of each equipment. It 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 control timing of the transfer of the hot steel sheet and the control timing of each cooling header. 1: Hot rolling mill 2: Hot 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)

(57) [Claims] 1. A plurality of hot rolling mills installed in a hot steel sheet rolling line, a plurality of hot rolling mills being positioned adjacent to the front and / or rear hot rolling mills in the vertical and advancing directions of the hot steel sheet passing position. Using an online cooling device in which a cooling header for cooling medium injection is arranged, a hot steel plate being rolled by a hot rolling mill, in a cooling control for performing cooling immediately after rolling a plurality of designated rolling passes, immediately after rolling In the rolling pass to which the cooling is applied, the stop control of the hot steel sheet is started with the rolling mill biting signal of the hot steel sheet as a starting point, and after counting a predetermined time with the same rolling mill biting signal as the starting point, Of the cooling headers that are arranged on the rolling mill exit side and are injecting the cooling medium, the injection cutoff control of the cooling medium of the cooling header arranged farthest from the rolling mill is started, 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, wherein the control of shutting off a cooling medium is transferred to a heat sink. 2. A cooling medium injection cutoff control is started from a cooling header farthest from a rolling mill among cooling headers injecting a cooling medium arranged on a rolling mill outlet side, and rolling is sequentially performed at predetermined time intervals. 2. The hot steel sheet online according to claim 1, wherein, when shifting to the cooling medium shutoff control to the cooling header closer to the mill, the cooling medium of the cooling header closer to the rolling mill is simultaneously shut off from a predetermined cooling header. Cooling device control method. 3. The method according to claim 1, wherein the cooling medium cutoff completion signal of the cooling header finally controlled to be cut off is one of the starting points of the hot steel sheet transfer start control for rolling the next rolling pass of the hot steel sheet. The control method of the hot steel plate online cooling device according to claim 2.