1. A coiling temperature controller having a knction of holding a strip temperature for a determinate time, by cooling a strip (15 1) rolled by a hot rolling mi11 (1 52) by a coiling cooling device (160) provided on a delivery side of the hot rolling mill, controlling an intermediate temperature when the strip passes through a predetermined intermediate position of the cooling deceive, to a predetermined target temperature, in addition to a coiling temperature before the strip is coiled by a down coiler (1 54), and setting a cooling condition in the vicinity of the intermediate position to air cooling, the coiling temperature controller comprising: a strip temperature prediction model (1 15) configured to acquire openinglclosing information of each of cooling headers (166) provided in the coiling cooling device, and predict the strip temperature by using the information; a target intermediate air cooling time table (1 13) configured to store a target value of air cooling time in the vicinity of the intermediate position in association with a steel grade, and a rolling condition of the strip; a water cooling prohibition header calculator (121) configured to perform calculation for selecting a cooling header that is prohibited from performing opening operation in the vicinity of the intermediate position, from rolling speed of the strip, and target intermediate air cooling time, for each part in a length direction of the strip, before cooling control; a water cooling prohibition flag table (124) configured to store information of the cooling header that is prohibited from performing the opening operation, in association with a strip part; a control reference calculator (122) for front side cooling configured to predict the intermediate temperature of the strip by using the strip temperature prediction model from information of opening/closing of cooling headers of a front side cooling device (1 63) provided between the hot rolling mill and the intermediate position, and calculate combination of opening and closing of the cooling headers of the front side cooling device for implementing a target intermediate temperature, by using a predicted result and information of the water cooling prohibition flag table; and a control reference calculator (123) for rear side cooling configured to predict the coiling temperature of the strip by using the strip temperature prediction model from information of opening/closing of cooling headers of a rear side cooling device (164) provided between the intermediate position and the down coiler, and calculate combination of opening and closing of the cooling headers of the rear side cooling device for implementing a target coiling temperature, by using a predicted result and the information of the water cooling prohibition flag table.

2. The coiling temperature controller according to claim 1, further comprising a speed pattern table (1 11) configured to store a speed pattern from discharge of the strip from the hot rolling mill to completion of coiling by the down coiler, wherein the water cooling prohibition header calculator is configured to: calculate passing speed when each part in the length direction of the strip passes through the intermediate position, by using information of the speed pattern table; calculate an air cooling distance necessary for securing the target intermediate air cooling time by multiplying the passing speed and the target intermediate air cooling time; and select the cooling header that is prohibited from performing opening operation, in association with the air cooling distance.

3. The coiling temperature controller according to claim 1, fbrther comprising: a mill delivery side thermometer for measuring a strip temperature on the delivery side of the hot rolling mill, an intermediate thermometer (1 71) for measuring a strip temperature at the intermediate position, and a coiling thermometer for measuring a strip temperature before the strip is coiled by the down coiler; a dynamic controller (1 702) for front side cooling configured to calculate a change amount of the number of opening cooling headers of a front side cooling controller to make an intermediate temperature coincide with a target temperature in accordance with a mill delivery side temperature and the intermediate temperature acquired from the strip during cooling control, and output the change amount; a dynamic controller (1703) for rear side cooling configured to calculate a change amount of the number of opening cooling headers of a rear side cooling controller to make a coiling temperature coincide with a target temperature in accordance with an intermediate temperature and the coiling temperature acquired from the strip during cooling control, and output the change amount; a water cooling prohibition header change unit (1705) configured to increase or decrease the cooling header that is prohibited from performing the opening operation; a rolling speed change unit (1706) configured to change the rolling speed of the strip; and an intermediate air cooling time calculator (1 704) configured to calculate actual intermediate air cooling time during cooling from the openinglclosing information of the cooling headers output from the dynamic controller for front side cooling, the opening/closing information of the cooling header output from the dynamic controller for rear side cooling, and strip speed, and activate either the water cooling prohibition header change unit or the rolling speed change unit, or both the water cooling prohibition header change unit and the rolling speed change unit when the actual intermediate air cooling time does not satisfy the target intermediate air cooling time.

4. The coiling temperature controller according to claim 3, wherein the intermediate air cooling time calculator (1704) is configured to activate the water cooling prohibition header change unit and then calculate actual intermediate air cooling time again when the calculated actual intermediate air cooling time does not satisfy the target intermediate air cooling time, and activate the rolling speed change unit when the actual intermediate air cooling time still does not satisfy the target intermediate air cooling time.

5. The coiling temperature controller according to claim 1, wherein a change amount of the number of opening cooling headers of a front side cooling controller is calculated to make an intermediate temperature coincide with a target temperature in accordance with a mill delivery side temperature and the intermediate temperature acquired from the strip during cooling control, a change amount of the number of opening cooling headers of a rear side cooling controller is calculated to make a coiling temperature coincide with a target temperature in accordance with an intermediate temperature and the coiling temperature acquired from the strip during cooling control, actual intermediate air cooling time during cooling is calculated from the openinglclosing information of the cooling headers and strip speed, selection of the cooling header that is prohibited from performing opening operation is changed such that the actual intermediate air cooling time satisfies the target intermediate air cooling time, and the actual intermediate air cooling time is then calculated again, when the calculated actual intermediate air cooling time does not satisfy the target intermediate air cooling time, and the strip speed is changed such that the actual intermediate air cooling time satisfies the target intermediate air cooling time, when the actual intermediate air cooling time still does not satisfy the target intermediate air cooling time.

6. A temperature control method comprising the steps of when a strip temperature is held for a deteminate time by cooling a strip (1 5 1) rolled by a hot rolling mill (152) by a coiling cooling device (160) provided on a delivery side of the hot rolling mill, controlling an intermediate temperature when the strip passes through a predetermined intermediate position of the cooling deceive, to a predetermined target temperature, in addition to a coiling temperature before the strip is coiled by a down coiler (1 54), and setting a cooling condition in the vicinity of the intermediate position to air cooling, selecting a cooling header (166) that is prohibited from performing opening operation in the vicinity of the intermediate position for each part in a length direction of the strip, from rolling speed of the strip, and a target value of air cooling time in the vicinity of the intermediate position, before cooling control; estimating the intermediate temperature of the strip from information of openinglclosing of cooling headers of a front side cooling device (163) provided between the hot rolling mill and the intermediate position, and calculating combination of opening and closing of the cooling headers of the front side cooling device for implementing a target intermediate temperature, by using a predicted result and information of the cooling header which is prohibited from performing opening operation; and estimating the coiling temperature of the strip from information of opening/closirig of cooling headers of a rear side cooling device (164) provided between the intermediate position and the down coiler, and calculating combination of opening and closing sf the cooling headers of the rear side cooling device for implementing a target coiling temperature, by using a predicted result and information of the cooling header which is prohibited from performing opening operation.

BACKGROUND OF THE INVENTION
(1) FIELD OF TJ3E INVENTION
The present invention relates to a coiling temperature controller of a hot rolling
line, and a control method thereof, and more particularly to a coiling temperature controller
5 suitable for the temperature control of DP (Dual Phase) steel or TRlP (Transformation Induced
Plasticity) steel, which requires making not only a coiling temperature but also an intermediate
temperature coincide with target temperatures, and hrther providing intermediate air cooling
time to hold a strip temperature at a temperature in the vicinity of the temperature for a
determinate time, and a control method thereof, thereby attaining the high quality of strip.
10
(2) DESCRIPTION OF THE RELATED ART
In strip cooling control for DP steel or TRIP steel, it is necessary to perform
control in consideration of not only a coiling temperature, but an intermediate temperature,
holding time at this temperature, cooling speed, and the like. Generally, holding time at the
15 intermediate temperature (hereinafter, referred to as intermediate air cooling time) affects a
volume fraction of ferrite, and therefore needs to be controlled in a certain range. When the
intermediate air cooling time is shorter or longer than this range, there is a problem that the
quality of the strip is deteriorated.
As a conventional method of implementing such control, for example, JP-A-
20 2006-5 15855 discloses a cooling facility that is capable of securing 5 seconds as intermediate air
cooling time between a first cooling stage and a second cooling stage. Additionally, JP-A-
2009-148809 discloses a method of independently presetting cooling references of headers of an
upstream bank and headers of a downstream bank with respect to an intermediate thermometer,
dynamically correcting the former by intermediate temperature FB, mill delivery side
26 temperature FF, and strip speed FF control in response to the result, so as to enhance
intermediate temperature control accuracy, and dynamically correcting the latter by coiling
temperature FB, intermediate temperature FF, strip speed FF control, so as to enhance coiling
temperature control accuracy. Furthermore, there is disclosed a method of calculating the
intermediate air cooling time by focusing the maximum speed of the strip, and reducing the
30 maximum speed of the strip when this value is not within a target range, to secure desired
intermediate air cooling time.
Both the above conventional technologies can perform control in consideration of
a cooling temperature pattern of the strip, or an intermediate temperature, but have the following
problems in view of accuracy improvement of temperature control, or intermediate air cooling
time observance. P-A-2006-5 15855 describes the providing of the facility that is capable of
5 securing 5 seconds as the intermediate air cooling time, but does not disclose a method of always
controlling the intermediate air cooling time that changes depending on strip speed, or a target
value of an intermediate temperature, in a determinate range. On the other hand, in JP-A-2009-
148809, the intermediate air cooling time is calculated in association with the maximum speed of
the strip, and therefore there is a problem that the intermediate air cooling time is longer than a
10 target range at the timing when the strip speed is lower than the maximum speed. Normally, the
strip is discharged from the mill at a low speed, thereafter accelerated to reach the maximum
speed, and thereafter decelerated toward rolling end, and a tail region thereof is discharged from
the mill at a low speed. Thus, while the effects of the strip speed on the intermediate air
cooling time are difl'erent depending on parts in a length direction of the strip, this point is not
15 considered in JP-A-2009-148809. Therefore, there is a problem that the intermediate air
cooling time is longer than the target range in a part where the strip speed is lower than the
maximum speed, and the quality of the strip is deteriorated.
SUMMARY OF THE INVENTION
20 Therefore, a problem to be solved by the present invention is to provide a coiling
temperature controller that is capable of controlling intermediate air cooling time in a target
range for each of parts in the length direction of a strip while implementing a target intermediate
temperature and a target coiling temperature, and a control method.
In order to solve the above problems, a coiling temperature controller according
25 to the present invention includes: a target intermediate air cooling time table configured to store
a target value of air cooling time in the vicinity of an intermediate position in association with a
steel grade and a rolling condition of a strip; a water cooling prohibition header calculator
configured to perform calculation for selecting a cooling header that is prohibited from
performing opening operation in the vicinity of the intermediate position, from rolling speed of
30 the strip and target intermediate air cooling time, for each of parts in a length direction of the
strip, before cooling control; a water cooling prohibition flag table configured to store
information of the cooling header that is prohibited from performing the opening operation, in
association with the strip part; a control reference calculator for front side cooling configured to
predict the intermediate temperature of the strip from information of opening/closing of each of
cooling headers of a front side cooling device provided between a hot rolling mill and the
intermediate position, and calculate combination of opening and closing of the cooling headers
of the front side cooling device for implementing a target intermediate temperature, by using a
predicted result and information of the water cooling prohibition flag table; and, a control
5 reference calculator for rear side cooling configured to predict the coiling temperature of the
strip from information of openinglclosing of each of cooling headers of a rear side cooling
device provided between the intermediate position and a down coiler, and calculate combination
of opening and closing of the cooling headers of the rear side cooling device for implementing a
target coiling temperature, by using a predicted result and the information of the water cooling
10 prohibition flag table.
The present invention is capable of implementing a target intermediate
temperature and a target coiling temperature, and further sontrolling intermediate air cooling
time in a target range for each of parts in a length direction of a strip.
Other object, features and advantages of the invention will become apparent from
15 the following description of the embodiment of the invention taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is an explanatory diagram showing a configuration of a control system
20 according to the present invention;
Fig. 2 is an explanatory diagram showing a configuration of a speed pattern table;
Fig. 3 is an explanatory diagram showing a configuration of a target temperature
table;
Fig. 4 is an explanatory diagram showing a configuration of a target intermediate
25 air cooling time table;
Fig. 5 is an example of assigning numbers to identify respective cooling headers;
Fig. 6 is an explanatory diagram showing a configuration of sn. cooling header
priority table;
Fig. 7 is an example of dividing a strip in a length direction, and assigning section
30 numbers;
Fig. 8 shows processes performed by water cooling prohibition header calculation
means;
Fig. 9 is an explanatory diagram showing a configuration of a water cooling
prohibition flag table;
- 4 -
Fig. 10 shows processes performed by control reference calculation means for
first half cooling, and control reference calculation means for second half cooling;
Fig. 11 shows prediction operation of a strip intermediate temperature using a
strip temperature prediction model;
6 Fig. 12 shows processes for determining whether each part of a strip is water
cooling or air cooling;
Fig. 13 shows prediction operation of a strip coiling temperature using the strip
temperature prediction model;
Fig. 14 shows a situation of control code transition of each section of the strip in
10 the course of calculation performed by the control reference calculation means for first half
cooling and the control reference calculation means for second half cooling;
Fig. 15 shows process performed by header pattern conversion means for first half
cooling;
Fig. 16 shows processes performed by header pattern conversion means for
15 second half cooling;
Fig. 17 is an explanatory diagram showing a configuration in which dynamic
control means is included; and
Fig. 18 shows processes performed by intermediate air cooling time calculation
means.
20
DESCRIPTION OF TIIE EMBODIMENTS
HereinaRer, preferred rnodes for carrying out the present invention are described
with reference to the drawings. Particularly, the description covers modes showing that in
coiling control of a strip after hot rolling, an intermediate temperature is held for a wide range of
25 parts in a length direction of a strip for target time even when the strip is classified in a special
steel grade requiring holding an intermediate temperature for a determinate time, and
consequently, the metallurgic quality of high class strips represented by DP steel or TRIP steel
requiring holding the intermediate temperature during cooling can be improved.
30 EMBODIR/IENT 1
Fig. 1 shows an embodiment according to the present invention. A coiling
temperature controller 100 receives various signals from an object 150 to be controlled, and
outputs a control signal to the object 150 to be controlled. Now, a configuration of the object
150 to be controlled is described. In this embodiment, the object 150 to be controlled is a
coiling cooling facility for hot rolling, and cools a strip 15 1 having a temperature of about 850°C
to about 900°C, which has been rolled with a mill 153 of a hot rolling mill 152, with a coiling
cooling device 160, and coils the strip 15 1 with a down coiler 154. The coiling cooling device
160 includes an upper cooling device 161 that water-cools the strip 15 1 from the upper side of
5 the strip 15 1, and a lower cooling device 162 that water-cools the strip 15 1 from the lower side
of the strip 15 1. A cooling header 166 includes a large number of nozzles mounted in the width
direction of the strip 15 1, and each cooling device includes a plurality of banlts 165 each having
a determinate number of cooling headers 166 combined in the length direction of the strip 15 1.
In this embodiment, a case where open or close is selected as an operation reference of each
10 cooling header 166 is described as an example. A mill delivery side thermometer 170 measures
the temperature of the strip 15 1 immediately after the strip 15 1 is rolled with the hot rolling mill
152, and an intermediate thermometer 17 1 provided near the central part of the coiling cooling
device 160 measures the temperature of the strip 15 1 during passing a thermometer installation
position, and a coiling thermometer 172 measures the temperature of the strip 15 1 immediately
15 before the strip 15 1 is coiled by the down coiler 154. In this embodiment, an object of coiling
temperature control is to make the temperatures of the strip 15 1 measured by the intermediate
thermometer 17 1 and the coiling thermometer 172 coincide with respective target temperatures,
and hold the intermediate temperature of the strip 15 1 near the intermediate thermometer 171 for
a determinate time. In this embodiment, a cooling device from the delivery side of the hot
20 rolling mill 152 to the intermediate thermometer 17 1, and a cooling device from the intermediate
thermometer 171 to the coiling thermometer 172 are hereinafter referred to as a first half cooling
device 163, and a second half cooling device 164, respectively, as shown in Fig. 1. In this
embodiment, the intermediate thermometer 17 1 is provided in the substantially middle of the
cooling device. However, it is technically possible to set such that the cooling distance of one
25 of the first half cooling device 163 and the second half cooling device 164 is long and the
coaling distance of the other is short.
Technically, an intermediate cooling device can be inserted between the first half
cooling device 163 and the second half cooling device 164. In this case, respective target
temperatures between the first half cooling device 163 and the intermediate cooling device, and
30 between the intermediate cooling device and the second half cooling device 164 are controlled.
Additionally, it is also technically possible to provide not only the single intermediate cooling
device, but also the two or more intermediate cooling devices.
In this case, for example, "front side" can be written in a generic concept in place
of the above wording "first half?', and "rear side" can be written in the generic concept in place of
- 6 -
the wording "second half '.
Target values of the coiling temperature and the intermediate temperature may be
constant in the length direction of the strip 15 1, or can be set to different values according to
respective parts. Incidentally, in order to enhance a coiling regulation property and a coiling
5 property of the strip 15 1 to the down coiler 154, the target temperatures of a top region and a tail
region of the strip 15 1 are often made higher than the target temperatures of a central part.
Now, a configuration of the coiling temperature controller 100 is shown.
Hereinafter, a set of openinglclosing patterns of the cooling headers 166 is referred to as a header
pattern. The coiling temperature controller 100 includes preset control means 110 for
10 calculating a control reference corresponding to the openinglclosing pattern of each cooling
header 166 before the strip 15 1 is cooled by the coiling cooling device 160, and header pattern
conversion means 130 for converting the control reference into the openinglclosing pattern of
each cooling header 166. In this embodiment, a case where the control reference is described
by a control code corresponding uniquely to the header pattern is described as an example, on the
15 model of the method disclosed in JP-A-2007-11802'7. However, as the descriptive method of
the header pattern, other representation method such as a bit pattern can be conceived.
The preset control means 11 0 includes a speed pattern table 11 1, a target
temperature table 112, a target intermediate air cooling time table 113, and a cooling header
priority table 114, and includes cooling reference calculation means 120 for acquiring
20 information (such as the steel grade of the strip 15 1, a target strip thickness, and a target strip
width) of a next cooled strip that is acquired from a host computer 50, and calculating a header
pattern for implementing desired cooling to the strip 15 1 by operation using a strip temperature
prediction model 115. Furthermore, the cooling reference calculation means 120 includes water
cooling prohibition header calculation means 121 for suppressing the opening operation of the
25 cooling header 166 near the intermediate thermometer 171 in order to secure intermediate water
cooling time, control reference calculation means 122 for first half cooling for calculating a
control reference for the first half cooling device 163, control reference calculation means 123
for second half cooling for calculating a control reference for the second half cooling device 164,
and water cooling prohibition flag table 124 for storing the information of the cooling header 166
30 whose opening operation is suppressed in each part of the strip 15 1, which is calculated by the
water cooling prohibition header calculation means 12 1.
The header pattern conversion means 130 includes header pattern conversion
means 13 1 for first half cooling for receiving the control reference from the control reference
calculation means 122 for first half cooling, and converting this into a header pattern for
controlling the first half cooling device 163, and header pattern conversion means 132 for second
half cooling for receiving the control reference from the control reference calculation means 123
for second half cooling, and converting this into a header pattern for controlling the second half
cooling device 164.
5 Fig. 2 shows a configuration of the speed pattern table 11 1. Fig. 2 shows an
example of a speed pattern in a case where the hot rolling mill 152 is a tandem mill. With
respect to the kind (steel grade), the strip thickness, and the strip width of the strip 15 1, speed
(initial speed) at the time of discharging the top region of the strip 15 1 from the mill 153,
acceleration (first acceleration) until the top region of the strip 15 1 is coiled by the down coiler
10 154 after the discharge, acceleration (second acceleration) until speed from the first acceleration
reaches maximum speed, the maximum speed, deceleration at the time of decelerating from the
maximum speed to final speed, and the final speed are accumulated for each classification of the
steel grade, the strip thickness, and the strip width. The cooling reference calculation means
120 identifies the steel grade, the strip thickness, and the strip width from the information on the
15 next cooled strip 15 1, which is received from the host computer 50, and extracts a corresponding
speed pattern from the speed pattern table 11 1. Herein, mpm (meter per minute) is rnlmin., and
denotes a distance at which the strip travels for a minute. For example, the table shows that a
speed pattern in which the initial speed is 390 mpm, the first acceleration is 2 mpds, the second
acceleration is 9 mpmls, the maximum speed is 550 mpm, the deceleration is 6 mpmls, and the
20 final speed is 550 rnpm is extracted, when the steel grade is DP1, the strip thickness is 3.0 to 4.0
mm, and the strip width is 1200 mm.
Fig. 3 shows a configuration of the target temperature table 112. The target
values of the intermediate temperature and the coiling temperature corresponding to the steel
grades are classified and stored. The cooling reference calculation means 120 determines the
25 steel grade of the relevant strip, extracts a corresponding target intermediate temperature and a
corresponding target coiling temperature from the target coiling temperature table 112, and
performs operation for calculating a cooling reference by using the extracted information. Fig.
3 shows that the strip should be cooled at a target intermediate temperature of 650°C and a target
coiling temperature of 200°C when the steel grade is DP1, for example.
30 Fig. 4 shows a configuration of the target intermediate air cooling time table 11 3.
Target intermediate air cooling time is classified and stored corresponding to the steel grade.
The cooling reference calculation means 120 determines the steel grade of the relevant strip,
extracts corresponding target intermediate air cooling time from the target intermediate air
cooling time table 113, and performs operation for water cooling prohibition header calculation
for suppressing opening operation by using strip speed extracted from the speed pattern table
11 1. Fig. 4 shows that the target intermediate air cooling time is 4.0 to 5.5 seconds when the
steel grade is DP1, for example.
Fig. 5 shows an example of assigning serial numbers for identifying the respective
5 cooling headers of the coiling cooling device 160. Fig. 5 shows an example of the first half
cooling device 163, in which the upper cooling device 16 1 and the lower cooling device 162
each have the fifty cooling headers 166. Numbers 1, 2, 3, ... are sequentially assigned from the
cooling header 166 near the mill 153. Although not shown in Fig. 5, numbers for identifying
the headers are similarly assigned to the headers of the second half cooling device 164. The
10 serial numbers are used for setup calculation described later, and assigned in association with the
degree of freedom for opening/closing. That is, in a case where opening/closing is possible for
each cooling header 166, the number is assigned to each cooling header 166, and Fig. 5 shows an
example of such a case. On the other hand, in a case where two cooling headers have a
common openinglclosing valve, and opening/closing is simultaneously perforrrled by the single
15 valve, a single number is assigned to the two cooling headers.
Fig. 6 shows a configuration of the cooling header priority table 114.
Hereinafter, a case where the first half cooling device 163, and the second half cooling device
164 each includes the ten banks 165, and each bank includes the cooling headers 166 with five
degrees of freedom is described as an example. The first half cooling device 163, and the
20 second half cooling device 164 each have fifty degrees of freedom for openinglclosing, and the
assigned numbers of each cooling device are 1 to 50. The cooling header priority table 114
includes a priority table 601 for first half cooling headers and a priority table 602 for second half
cooling headers, and the cooling headers 166 assigned with numbers 1 to 50 are assigned with
the priorities of numbers 1 to 50 in the order of opening. As the priority, the order of the
25 cooling headers 166 which are preferentially opened is stored with respect to the steel grade, the
strip thickness, and the cooling header section (upper cooling headers or lower cooling headers).
For example, it is found from the priority table 601 for first half cooling headers that when the
steel grade is DP1, and the strip thickness is 8.0 to 10.0 mm, the priority of the cooling header
166 assigned with number 50 is the highest among each of the upper cooling headers and the
30 lower cooling headers. This shows that the cooling header 166 assigned with number 50 is
opened with the highest priority. Hereinafter, the higher priorities are assigned to the cooling
headers in the order of closeness to the intermediate thermometer 171, and the lower priorities
such as 50, 49, 48, ... are assigned to the cooling headers 166 in the order of closeness to the mill.
In this case, the cooling headers 166 are continuously opened, and cooling speed may be
excessive depending on the strip thickness or the strip speed of the strip 15 1. In Fig. 6, an
example of a strip thickness of 2.0 to 4.0 mm shows the assignment of priorities in a case of
suppressing cooling speed, and the priorities are not consecutive between adjacent headers. In
this case, the consecutive cooling headers 166 are the combination of opening and closing, and
5 cooling speed is suppressed. Also in the priority table 602 for second half cooling headers, the
priorities are assigned in a similar manner. For example, when the steel grade is DPl, and the
strip thickness is 4.0 to 6.0 mm, the cooling headers 166 assigned with numbers 1, 2, 3,4 and 5
in each of the upper and lower cooling headers are assigned with the priorities of 1, 3, 5, 7 and 9.
Various factors other than cooling speed affects the assignment of the priorities to
10 the cooling headers 166. Various priorities are often assigned to the cooling headers 166 by
reason of implementation of cooling curve which aims at brther processing on the strip 15 1, the
securing of the openinglclosing room of the cooling headers during cooling, or the like. In
either case, it is possible to handle by changing the table contents in Fig. 6. In this
embodiment, classification items are set to the steel grade, the strip thickness, and the upper or
15 lower cooling headers 166. However, the strip width, or the like may be added. Additionally,
although the upper headers and the lower headers are assigned with the same priorities in this
embodiment, but can be assigned with different priorities.
In this embodiment, the reference of openinglclosing to each cooling header 166
is independently given to each part in the length direction of the strip 15 1. Fig. 7 shows an
20 example of dividing the strip in the length direction, and defining sections. The strip 15 1 is
divided from the top region to the tail region into sections 701, and section numbers 1 to n are
assigned to the sections 70 1. In operation prior to cooling, a reference related to a water
cooling prohibition (opening prohibition) header, and a reference related to the opening/closing
of the cooling header 166 are calculated are calculated for each section 701 by the following
25 method.
Fig. 8 shows processes performed by the water cooling prohibition header
calculation means 121. The water cooling prohibition header calculation means 121 calculates
a distance necessary for satisfying target intermediate air cooling time in the vicinity of the
intermediate thermometer 171 for each section of the strip 15 1, and assigns water cooling
30 prohibition flags to the cooling headers 166 in this range, thereby allowing opening prohibition
during cooling. In S8-1, target intermediate air cooling time in a classification under which the
next cooled strip 15 1 falls is acquired from the target intermediate air cooling time table 113, and
a speed pattern in the relevant classification is hrther acquired from the speed pattern table 11 1.
In S8-2, a necessary air cooling distance is calculated for each of the sections 701 in the length
direction of the strip 15 1. The necessary air cooling distance is calculated in the following
processes. First, from the speed pattern, a speed V at which the section 701 passes the
intermediate thermometer 171 is obtained. The speed V can be calculated by a predetermined
algebraic calculation at the timing of each of before acceleration, during first acceleration, during
5 second acceleration, during traveling at maximum speed, during deceleration, and aRer
completion of deceleration of the strip 15 1. For example, when the timing is during the first
acceleration, the speed V is expressed by the following [EXPRESSION 11:
[EmRESSION 11
10 where L1 denotes a distance between the inill 153 and the intermediate
thermometer 17 1, and vl denotes initial speed, and Accl denotes first acceleration.
Herein, section number i during first acceleration when the strip 15 1 passes the
intermediate thermometer 171 is given by the [EXPWSSION 21:
[EXIPRESSION 21
15 0 5 i < Lz/s
where i denotes section number, L:! denotes a distance between the intermediate
thermometer 171 and the down coiler 154, s denotes a section length in the length direction of
the strip 15 1.
With such algebraic calculation, the speed of the section 701 corresponding to
20 each of during second acceleration, during traveling at maximum speed, during deceleration,
during completion of deceleration when the strip 15 1 passes the intermediate thermometer 17 1
can be calculated. Then, in S8-3, an air cooling range (distance between air cooling start and
air cooling end, in the vicinity of the intermediate thermometer 171) is calculated. When the
speed is denoted by V, and the target air cooling time is denoted by T, a distance Lair necessary
25 for securing air cooling is given by the following [EXPRESSION 31:
[EXPRESSION 31
Lair = V x T
As a matter of course, from [EXPBESSION 31, the higher the strip speed V is, or
the longer the target intermediate air cooling time is, the longer the necessary distance Lair is.
30 From the target intermediate air cooling time table 11 3 of the strip 15 1, the target intermediate
air cooling time is given by a range, and therefore, in this case, a median in the target
intermediate air cooling time range may simply be set to the target intermediate air cooling time
T in [EXPIQESSION 31. In order to secure the distance Lair, (Lai~-12i)s calculated as an air
cooling range from the intermediate thermometer 171 on each of the mill side and the down
coiler side of the intermediate thermometer 17 1. In this embodiment, the air cooling range is
equally divided into the upstream and the downstream of the intermediate thermometer 17 1.
However, when equal dividing is not proper by the arrangement of the intermediate thermometer
5 17 1, the upstream and the downstream may be divided according to a proper ratio in order to
secure the distance Lair and the air cooling range may be obtained. In S8-4, the cooling
headers 166 corresponding to the air cooling range are obtained, and the water cooling
prohibition flags are assigned. The mounting position of each cooling header 166 is fixed, and
therefore the cooling header 166 corresponding to the air cooling range can be identified from
10 distance information from the intermediate thermometer 171. In S8-5, it is confirmed whether
or not the processes are terminated for all sections. When the processes are not terminated, the
processes of S8-2 to S8-4 are repeated. When the processes are terminated, the information on
the water cooling prohibition flag of each section 701 is output to the water cooling prohibition
flag table 124 in S8-6.
15 Fig. 9 shows a configuration of the water cooling prohibition Rag table 124. The
water cooling prohibition flag table 124 includes a water cooling prohibition flag table 901 for a
first half cooling device, in which water cooling prohibition information on the cooling headers
of the first half cooling device 163 is accumulated, and a water cooling prohibition flag table 902
for a second half cooling device, in which water cooling prohibition information on the cooling
20 headers of the second half cooling device 164 is accumulated, and each of the cooling headers
assigned with numbers 1 to 50 is assigned with a flag of 0 or 1 for each section number.
Herein, 0 denotes the cooling header 166 which is allowable for water cooling, and 1 denotes the
cooling header 166 which is prohibited from water cooling. In Fig. 9, for example, in section
number 1 in the water cooling prohibition flag table 901 for a first half cooling device, cooling
25 headers 166 assigned with numbers 44 to 50 are prohibited from water cooling (prohibited from
performing opening operation). That is, the seven headers close to the intermediate
thermometer 17 1 are prohibited from water cooling. In section number 5 1, at least cooling
headers 166 assigned with numbers 42 to 50 are prohibited from water cooling. This
corresponds to the fact that the speed at the time of passing the intermediate thermometer 171 is
30 faster than the speed of section number 1 which is the top region of the strip. Similarly, in the
water cooling prohibition flag table 902 for a second half cooling device, cooling headers 166
assigned with numbers 1 to 7 are prohibited from water cooling (prohibited from performing
opening operation) in section number 1. That is, seven cooling headers 166 close to the
intermediate thermometer 17 1 are prohibited from water cooling. In section number 5 1, at least
cooling headers 166 assigned with numbers 1 to 9 are prohibited from water cooling. In section
number 5 1, a larger number of cooling headers 166 are prohibited from water cooling, compared
to the top region of the strip.
In this embodiment, the header pattern of each section 701 is expressed by a
5 corresponding control code. The control codes are values corresponding to the priorities of the
cooling headers to be opened. For example, when the control code is 10, it is shown that
cooling headers 166 whose priorities are 1 to 10 are opened, cooling headers 166 whose
priorities are 11 or more is closed. Fig. 10 shows algorithms performed by the control reference
calculation means 122 for first half cooling and the control reference calculation means 123 for
10 second half cooling. The algorithms performed by the both means are the same. However, in
a case of the control reference calculation means 122 for first half cooling, a target temperature
and a predicted temperature are an intermediate temperature, and in a case of the control
reference calculation means 123 for second half cooling, a target temperature and a predicted
temperature are a coiling temperature. A first acceleration start position, a second acceleration
15 start position, a steady speed start position, a deceleration start position for shifting from the
steady speed to the final speed, which are calculated as the length of the strip 15 1 discharged
from the mill 153, are calculated on the basis of the values in a classification corresponding to
the next cooled strip 15 1, which is acquired from the speed pattern table 1 1 1 in S 10- 1. Then,
the speed pattern from the discharging start of the strip 15 1 at the mill 153 to the coiling
20 completion at the down coiler 154 is calculated. The first acceleration start position SLls, the
second acceleration start position SL2a, the steady speed start position SLcs, the deceleration
start position SLds, and the deceleration completion position SLde can be calculated by the
following [EXPRESSION 41 to [EXPRESSION 81, respectively.
[EXPRESSION 41
2 5 SLls = Lsc
where Lsc is a constant.
[EXPRESSION 51
SL2s = Lmd
where Emd denotes a distance between the mill 157 and the down coiler 154.
30 [EXPRESSION 61
(vla12 = Lmd x 2 x Accl + Vmax x Vmax
SLcs = f Lmd + (Vmax - Vla)/Acc2 x (Vmax + Vla)/2)
where Vla denotes first acceleration end speed, Accl denotes first acceleration,
Acc2 denotes second acceleration, and Vmax denotes maximum speed.
[ErnRESSION 71
SLds = (Striplen - (Vmax - Vf)/Dcc x (Vmax + Vf)/2 - dccmargin}
where Striplen denotes a strip length, Vf denotes final speed, Dcc denotes
deceleration, and dccmargin denotes a margin as to how long ago the deceleration is completed
5 from the tailing-off of the strip 15 1 from the mill 157.
[EXPmSSION 81
SLde = (Striplen - dccmargin}
In accordance with the calculated speed pattern, in S 10-2 and the subsequent
steps, a header pattern that implements the target temperature is calculated with operation using
10 the strip temperature prediction model 11 5. In this embodiment, an example is shown where
sections into which the strip is divided in the length direction are defined, and the header pattern
is calculated for each section in accordance with linear inverse interpolation.
In S 10-3, two control codes tiL and nH, between which a control code of a
solution is present, are defined for each section of the strip I 5 1. Herein, a solution is present
15 between hll open and hll closing of the cooling header, and therefore nL = 0, and nH = nmax
are uniformly set. Since nmax denotes the number of the cooling headers 166, in this
embodiment, nmax is 50 in each case of the first half cooling device 163 and the second half
cooling device 164. Herein, the number of cooling headers that are opened simply increases
with increase in the number of control codes, and therefore in a case of nl < n2, target
20 temperatures Tcl and Tc2 corresponding to these header patterns satisfy Tcl > Tc2. In SlO-3,
an average of control codes nL and nH is set to no. Then, in SlO-4, an intermediate or coiling
temperature TcO of each section corresponding to the control code no is predicted with operation
using the strip temperature prediction model 115. In S10-5, a sign of a predicted temperature
TcO with respect to a target temperature Ttarget is determined for each section. In a case of TcO
25 > Ttarget, a solution is present between the control codes no and fl, and therefore the control
code no is newly set as nL. On the contrary, in a case of Tc0 < Ttarget, a solution is present
between the control codes no and nL, and therefore the control code no is newly set as nH. In
S 10-6, a termination condition of the algorithm is determined. When the termination condition
is not satisfied, the processes in S 10-3 to S10-5 are repeatedly performed. The termination of
30 the algorithm may simply be determined provided that any of the following conditions is
established:
e the processes in S 10-3 to S 10-5 have been repeated a determinate number of
times or more;
e a deviation between the predicted temperature TcO and the target temperature
Ttarget is a determinate value or less; and
the control code no coincides with either the control code nHL or nL.
As a method of assigning a control code, unlike this embodiment, a control code in a state where
all cooling headers are closed is set as 50, and a control code in a state where all cooling headers
5 are opened is set as 0, so that assignment can be performed corresponding to these.
Fig. I 1 shows detailed processes of temperature prediction operation
corresponding to S 10-4 of Fig. 10, in a case of the control reference calculation means 122 for
first half cooling. As a temperature prediction operation method, an example of dividing the
strip I5 1 in the length direction, and performing diRerence calculation of the cooling behavior of
10 the strip 15 1 until the tail region of the strip passes the intermediate thermometer 171 from the
discharging start at the mill 153 at a determinate time interval A is shown. In S 11- 1, calculation
time is updated, and a strip speed Vt at the relevant time is Eurther calculated from the speed
pattern generated in S10-1 of Fig. 10. In S11-2, a discharge length Ln at the mill 153 at the
current time is calculated by using the calculated strip speed. The discharge length Ln is a
15 length of the strip discharged from the mill after rolling, and can be calculated by the following
expression, where Ln-1 denotes a discharge length at previous calculation time:
[EXPRESSION 91
Ln = Ln- 1 + AaVt
where A denotes a calculation cycle of strip temperature prediction calculation,
20 and Vt denotes discharge speed of the strip 15 1 from the mill 153.
In Sll-3, the completion of the operation is determined. When the mill discharge length Ln
becomes larger than a value obtained by adding a distance between the mill 153 and the
intermediate thermometer 17 1 to an entire length of the strip 15 1, all the intermediate
temperature prediction calculation corresponding to a single strip is terminated, and therefore the
25 operation is completed. In a case where the operation is not completed, the temperature
tracking of the strip is performed in S 11-4. That is, it is found, from the relation between Ln
and Ln-1, how long the strip travels after the time is elapsed by A with respect to a position of
the strip at previous time, and therefore a process of moving a temperature distribution of the
strip by a corresponding distance is performed. Tn Sl l-5, a mill delivery side temperature is set
30 to the strip 15 1 discharged from the mill during A. In S 11-6, it is determined, from the
information? on opening/closing of the headers which are present above and below each part of
the strip 15 1 at the relevant time, whether each part is water cooling or air cooling.
Fig. 12 shows processes of determining water cooling/air cooling of the strip part
corresponding to S 11-6. In S 12-1, a control code of the relevant part of the strip is extracted.
In S 12-2, the header numbers of the upper and lower cooling headers in the relevant part of the
strip are identified, and the priorities of the relevant headers are further extracted fiom the
cooling header priority table 114. In S12-3, the water cooling prohibition flag table 124 is
searched, and water cooling prohibition flags corresponding to the relevant section and the
5 relevant cooling headers are acquired. When the water cooling prohibition header is 1, the
relevant cooling headers are set to be closed, and the relevant part is set to air cooling in S12-4.
When the water cooling prohibition flag is not 1, the largelsmall relation of the priorities of the
cooling headers 166 acquired from the cooling header priority table 114 in S12-5 and a control
code of a section that includes the relevant part is compared. When the control code is equal to
10 or larger than the priorities, the headers are set to be opened and the relevant part is set to water
cooling in S 12-6. When the control code is smaller than the priorities of the relevant cooling
headers 166, the header is set to be closed, and the relevant part is set to air cooling in S 12-4.
In a case where the part is water cooling, a heat transfer coefficient is calculated
in accordance with, for example, [EXPRESSION 101 in Sll-7 of Fig. 11.
15 [EXPRESSION 101
hw = 9.72" ~o~*Q"."f ~(2*.5 - 1.15 *log~w)*~/(pl+p~))0~G46- /T(w~)s ~
where o denotes water quantity density, Tw denotes a water temperature, D
denotes a nozzle diameter, pl denotes a nozzle pitch in a line direction, pc denotes a nozzle pitch
in a direction orthogonal to a line, and Tsu denotes a surface temperature of the strip 15 1.
20 [EXPRESSION 101 is a heat transfer coefficient in a case of so-called laminar cooling. In
addition to this, various methods such as spray cooling are known as water cooling method, and
several calculation formulas of a heat transfer coefficient are known. Even when cooling
methods are the same, expressions are sometimes different by reflecting the latest experimental
knowledge and the like. On the other hand, in a case where the part is air cooling, a heat
25 transfer coeEcient is calculated in accordance with, for example, [EXPRESSION 111.
[EXPRESSION 1 11
hr = o-Ef[ (273 + ~su)/100-) ~((2 73 + ~a)/100)~]/(-~ Tsau)
where cs denotes the Stefan-Boltzmann constant (= 4.88), c denotes emissivity, Ta
denotes an air temperature PC), and Tsu denotes a surface temperature of the strip 15 1.
30 Heat transfer coefficient expressions represented by [EXPWSSION 101 and [EXPmSSION 111
are calculated in accordance with cooling states of the front and back of the strip 15 1, and heat
transfer amounts on each of the strip surfaces are quantified. In S 11-9, the temperature of each
part of the strip 15 I is calculated by adding and subtracting the transfer of the heat quantity
during A on the basis of a temperature before the lapse of A, so that a temperature distribution of
the strip between the mill 153 and the intermediate thermometer 171 is calculated. As a result,
a strip temperature at a mounting position of the intermediate thermometer 171 is obtained, and a
strip temperature at upstream with respect to the mounting position of the intermediate
thermometer 171 is used for the next or subsequent calculation. In a case where heat transfer in
5 a thickness direction of the strip 15 1 is ignored, a strip temperature for each part in the length
direction of the strip 15 1 can be calculated by [EXPRESSION 121.
[EXPRESSION 1 21
Tn = Tn-1 - (ht i-hb )*A/(p*C*B)
where Tn denotes a current strip temperature, Tn- 1 denotes a strip temperature
10 before A, ht denotes a heat transfer coeEicient of the strip front surface, hb denotes a heat
transfer coefficient of the strip back surface, p denotes density of the strip, C denotes specific
heat of the strip, and B denotes a thickness of the strip.
In a case where heat transfer in the thickness direction of the strip 15 1 need to be
considered, calculation can be attained by solving a well-known heat equation. The heat
15 equation is expressed by [EXPRESSION 131, and a method of dividing the strip 15 1 in the
thickness direction and calculating a difference with a computer are published in various
documents.
[EXPRESSION 131
aT/& = { h/(p*c) 1 (#T/&~)
20 where h denotes heat conductivity, and T denotes a material temperature.
Then, until necessary calculation from the mill 153 to the intermediate thermometer 171 in the
length direction of the strip in the line is completed in S 11- 10, the processes in S11-6 to S11-9
are repeated. Additionally, the processes in S 11 -1 to S 11-10 are repeated until the termination
of the operation is determined in S 11-3.
25 Fig. 13 shows detailed processes of temperature prediction operation
corresponding to S 10-4 of Fig. 10, in a case of the control reference calculation means 123 for
second half cooling. Although the entire processes are mostly similar to those of Fig. 11, an
object to be calculated is a strip located from the intermediate thermometer 171 to the down
coiler 154. Therefore, a part passing the intermediate thermometer 171 of the strip is identified
30 in S 13-5, and a target intermediate temperature is set to the part. In S13-6 to S 13-9, strip
temperatures from the mounting position of the intermediate thermometer 171 to the down coiler
154 are calculated. That is, the temperatures of the strip 15 1 from the intermediate
thermometer 171 to the down coiler 154 are calculated in S 13-9. Additionally, the calculation
completion of the strip that is present between the intermediate thermometer 17 1 and the down
coiler 154 at the relevant time is determined in S 13 - 10.
Fig. 14 shows an example of the change of the control codes by optimization of
Fig. 10. In the first process, the process is performed with respect to the same initial values (nL
= 0, nN[ = nmax, nmax is the number of headers, and therefore is 50 in this embodiment) for each
5 part, and therefore the control codes in all sections 701 of the strip 15 1 are updated to 25, as
shown in the first process of Fig. 14. In the second process, updated control codes are different
depending on the temperature prediction results of the respective parts of the strip 15 1 for control
code 25 that are larger or smaller than Ttarget. Fig. 14 shows an example in which parts close
to the top region and the rear region of the strip 15 1 having low strip speed are updated to such a
10 control code that the header is closed, and the central part of the strip 15 1 having high strip speed
is updated to such a control code that the header is opened. Specifically, as shown in the
second process of Fig. 14, the top region and the rear region are updated to 12 which is an
average of the control codes, as a result of the updating to nI, = 0, and nF-I = 25 in the first
process of S10-5. On the other hand, the central part is updated to 37 which is an average of
15 the control codes, as a result of the updating to nL = 25, and nH = 50 in the first process of $10-
5. Thus, the processes in S10-3 to 10-6 of Fig. 10 are repeated for each of the control reference
calculation means 122 for first half cooling and the control reference calculation means 123 for
second half cooling, so that the control codes are sequentially updated.
Fig. 15 shows an algorithm performed by the header pattern conversion means
20 13 1 for first half cooling. In S 15-1, a distance Lh from the top region of the strip 15 1 that
passes directly under the cooling headers is calculated. In S1S-2, it is determined whether or
not the distance Lh is smaller than 0. In a case where the distance Lh is smaller, the strip 15 1
has not reached the relevant cooling headers, and therefore the process jumps to S15-5. In a
case where the distance Lh is larger, the strip 15 1 has reached the relevant cooling headers, and
25 therefore a control code for first half cooling corresponding to the distance Lh is extracted in
S 15-3. That is, the distance Lh and the strip part of Fig. 7 are collated, and a control code for
first half cooling of a part corresponding to the distance Lh is extracted. In S15-4, it is possible
to determine, from the control code for first half cooling of the relevant part, a priority such that
cooling headers with up to the priority are to be opened. Therefore, by using this information
30 and the information stored in the cooling header priority table 114, the openinglclosing of the
relevant cooling headers are determined. In S 15-5, it is determined whether operation is
terminated for all the cooling headers. In a case where the operation is not terminated, the
processes in S 15- 1 to S 15-4 are repeated until the operation is terminated.
Fig. 16 shows an algorithm performed by the header pattern conversion means
- 18-
132 for second half cooling. In S 16-1, a distance Lh from the top region of the strip 15 1 that
passes directly under the cooling headers is calculated. In S16-2, it is determined whether or
not the distance Lh is smaller than 0. In a case where the distance Lh is smaller, the strip 15 1
has not reached the relevant cooling headers, and therefore the process jumps to S 16-5. In a
5 case where the distance Lh is larger, the strip 15 1 has reached the relevant cooling headers, and
therefore a control code for second half cooling corresponding to the distance Lh is extracted in
S 16-3. That is, the distance Lh and the strip part of Fig. 15 are collated, and a control code for
second half cooling of a part corresponding to the distance Lh is extracted. In S 16-4, it is
possible to determine, from the control code for second half cooling of the relevant part, a
10 priority such that cooling headers with up to the priority are to be opened. Therefore, by using
this information and the information stored in the cooling header priority table 114, the
openinglclosing of the relevant cooling headers can be determined. In S 16-5, it is determined
whether operation is terminated for all the cooling headers. In a case where the operation is not
terminated, the processes in S 16- 1 to S 16-4 are repeated until the operation is terminated.
16 In this embodiment, the number of the cooling headers in each of the first half
cooling device 163 and the second half cooling device 164 is 50. However, the values of the
first half cooling device 163 and the second half cooling device 164 are sometimes different
according to a facility, and various values are employed as the number of the cooling headers.
Thus, in the coiling cooling steps in hot rolling, in a case where in addition to the
20 coiling temperature of the strip, the intermediate temperature is controlled to coincide with a
target, the header pattern reference for properly suppressing the opening operation of the headers
according to the strip speed is previously calculated for each part in the length direction of the
strip with the calculation prior to cooling, thereby enabling cooling satisfying the target
intermediate air cooling time. Additionally, when the intermediate air cooling time is
25 calculated during cooling, and this deviates from a target range, the opening/closing pattern and
the strip speed of a cooling header is changed such that the intermediate air cooling time is
within the target range, so that the stable intermediate air cooling time can be obtained for each
part in the length direction of the strip. At this time, the openinglclosing patterns of the cooling
headers are operated first. When the intermediate air cooling time is still not within the target
30 range, the strip speed is changed, so that the intermediate air cooling time can be controlled in a
state where an effect on the strip temperature is minimized.
Consequently, it is possible to improve quality in a strip of a special cooling
condition such as DP steel and TRIP steel.
- 19 -
EM1430DIMENT 2
A second embodiment of the present invention is shown. While the invention of
Embodiment 1 is a method of calculating the cooling reference of the strip 15 1 in accordance
with the result of preset operation prior to cooling, in this embodiment, a cooling status of a strip
5 15 1 is monitored during cooling, and a cooling reference is corrected as needed, thereby
maintaining stable cooling performance in the length direction of the strip 15 1. Dynamic
control means 1701 that is newly included in this embodiment has a hnction of acquiring
measured temperatures of a mill delivery side thermometer 170, an intermediate thermometer
17 1 and a coiling thermometer 172, and speed of the strip 15 1 in real time, and changing a
10 control reference, when the strip 15 1 is cooled by a coiling cooling device 160, and includes
dynamic control means 1702 for first half cooling for controlling the openinglclosing of cooling
headers 166 of a first half cooling device 163 to make an intermediate temperature at a position
of the intermediate thermometer 171 coincide with a target temperature, and dynamic control
means 1703 for second half cooling for controlling the openinglclosing of cooling headers 166 of
15 a second half cooling device 164 to make a coiling temperature at a position of the coiling
thermometer 172 coincide with a target temperature. Furthermore, the dynamic control means
1701 includes intermediate air cooling time calculation means 1704 for calculating intermediate
air cooling time from the speed of the strip 15 1 and the information on the opening/closing of the
cooling headers 166 of the first half cooling device 163 and the second half cooling device 164,
20 and activating either water cooling prohibition header change means 1705 or rolling speed
change means 1706, or both the water cooling prohibition header change means 1705 and the
rolling speed change means 1706 when the target intermediate air cooling time is not satisfied,
and the water cooling prohibition header change means 1705 for performing a process of
decreasing the number of water cooling prohibition headers when the intermediate air cooling
25 time is longer than the target, and a process of increasing the number of water cooling
prohibition headers when the intermediate air cooling time is shorter than the target, and the
rolling speed change means 1706 for perEorming a process of increasing the rolling speed when
the intermediate air cooling time is longer than the target, and a process of decreasing the rolling
speed when the intermediate air cooling time is shorter than the target.
30 Fig. 18 shows processes performed by the intermediate air cooling time
calculation means 1704. In S18-1, the intermediate air cooling time is calculated from an actual
value Va of the strip speed acquired from an object 150 to be controlled, and the information on
the openinglclosing of the cooling headers of the first half cooling device 163 and the second
half cooling device 164. Specifically, an air cooling range in the vicinity of the intermediate
thermometer 171 is obtained from the information on the openinglclosing of the cooling headers
of the first half cooling device 163 and the second half cooling device 164, and an intermediate
air cooling time Tm is given from the length Lm of the air cooling range in the vicinity of the
intermediate thermometer 17 1 and Va by the following [EXPRESSION 141:
5 [EXPIU3SSION 141
Tm = LmIVa
In S 18-2, it is determined whether or not the intermediate air cooling time Tm
satisfies target intermediate air cooling time of the relevant classification extracted from a target
intermediate air cooling time table 11 3. When the intermediate air cooling time Tm satisfies,
1.0 the process is terminated. When the intermediate air cooling time Tm does not satisfy, the
water cooling prohibition header change means 1705 is activated in ,518-3. When the
intermediate air cooling time is longer than the target, the water cooling prohibition header
change means 1705 cancels the water cooling prohibition headers in distant order from the
intermediate thermometer 17 1, and performs a process of decreasing the number of the water
15 cooling prohibition headers. As a result, the air cooling range becomes short, and air cooling
time can be shortened. On the other hand, when the intermediate air cooling time is shorter
than the target, the water cooling prohibition header change means 1705 performs a process of
increasing the number of the water cooling prohibition headers in close order from the
intermediate thermometer 17 1. As a result, the air cooling range becomes long, and air cooling
20 time can be lengthened. In S 18-4, it is determined whether or not the dissatisfaction of the
target intermediate air cooling time is eliminated as a result of change in the number of the water
cooling prohibition headers. The increaseldecrease of the number of the water cooling
prohibition headers is limited by temperature control or the physical restriction of the number of
the cooling headers, and therefore desired target intermediate air cooling time is not always
25 obtained by the operation of the number of the cooling headers. In a case where the
dissatisfaction of the target intermediate air cooling time is solved, the process is terminated. In
a case where the dissatisfaction of the target intermediate air cooling time is not solved, the
rolling speed change means 1706 is activated in S 18-3. When the intermediate air cooling time
is longer than the target, the rolling speed change means 1706 performs a process of decreasing
30 the intermediate air cooling time by increasing the rolling speed. When the intermediate air
cooling time is shorter than the target, the rolling speed change means 1706 performs a process
of increasing the intermediate air cooling time by decreasing the rolling speed. A value AV of
changed strip speed is given by, for example, [EmRESSIQN 141.
[EXPRES §ION 141
- 21 -
AV = GI x ATn
where ATn denotes a deviation between the target intermediate air cooling time
and actual air cooling time, and G1 denotes gain.
The target intermediate air cooling time may simply be defined by a median in the range of the
5 target intermediate air cooling time of the relevant classification, which is extracted from the
target intermediate air cooling time table 1 13.
In this embodiment, there has been shown an example where, when the target
intermediate air cooling time is not satisfied, the water cooling prohibition headers first changed.
In this case, the strip speed is kept constant, and therefore an eRect on the strip temperature can
10 be minimized, and only holding time can be controlled. On the other hand, when the
dissatisfaction is not solved by the change of the water cooling prohibition headers, the strip
speed is changed. However, when the strip speed is increased, a mill delivery side temperature,
an intermediate temperature, and a coiling temperature are increased. When the strip speed is
reduced, the mill delivery side temperature, the intermediate temperature, and the coiling
15 temperature are reduced. In a case where the strip speed is changed, the holding time can be
controlled, but it is necessary to pay attention to the change of a strip temperature.
As the sequence of control performed when the target intermediate air cooling
time is not satisfied, it is also considered that the strip speed is first changed, and then, the water
cooling prohibition headers are changed. Additionally, the degrees of the dissatisfaction of the
20 target intermediate air cooling time may be suitably proportionally divided, and the definition of
the water cooling prohibition header and the strip speed may be simultaneously changed.
The present invention is widely applicable to cooling control for high class strips
requiring controlling an intermediate temperature, and holding air cooling at a temperature in the
vicinity of the temperature for a determinate time, in cooling control of hot rolling line.
25 It should be further understood by those skilled in the art that although the
foregoing description has been made on embodiments of the invention, the invention is not
limited thereto and various changes and modifications may be made without departing from the
spirit of the invention and the scope of the appended claims.
- 22 -
CLAIMS :
1. A coiling temperature controller having a knction of holding a strip temperature
for a determinate time, by cooling a strip (15 1) rolled by a hot rolling mi11 (1 52) by a coiling
cooling device (160) provided on a delivery side of the hot rolling mill, controlling an
intermediate temperature when the strip passes through a predetermined intermediate position of
the cooling deceive, to a predetermined target temperature, in addition to a coiling temperature
before the strip is coiled by a down coiler (1 54), and setting a cooling condition in the vicinity of
the intermediate position to air cooling, the coiling temperature controller comprising:
a strip temperature prediction model (1 15) configured to acquire openinglclosing
information of each of cooling headers (166) provided in the coiling cooling device, and predict
the strip temperature by using the information;
a target intermediate air cooling time table (1 13) configured to store a target value
of air cooling time in the vicinity of the intermediate position in association with a steel grade,
and a rolling condition of the strip;
a water cooling prohibition header calculator (121) configured to perform
calculation for selecting a cooling header that is prohibited from performing opening operation in
the vicinity of the intermediate position, from rolling speed of the strip, and target intermediate
air cooling time, for each part in a length direction of the strip, before cooling control;
a water cooling prohibition flag table (124) configured to store information of the
cooling header that is prohibited from performing the opening operation, in association with a
strip part;
a control reference calculator (122) for front side cooling configured to predict the
intermediate temperature of the strip by using the strip temperature prediction model from
information of opening/closing of cooling headers of a front side cooling device (1 63) provided
between the hot rolling mill and the intermediate position, and calculate combination of opening
and closing of the cooling headers of the front side cooling device for implementing a target
intermediate temperature, by using a predicted result and information of the water cooling
prohibition flag table; and
a control reference calculator (123) for rear side cooling configured to predict the
coiling temperature of the strip by using the strip temperature prediction model from information
of opening/closing of cooling headers of a rear side cooling device (164) provided between the
intermediate position and the down coiler, and calculate combination of opening and closing of
the cooling headers of the rear side cooling device for implementing a target coiling temperature,
by using a predicted result and the information of the water cooling prohibition flag table.
2. The coiling temperature controller according to claim 1, further comprising
a speed pattern table (1 11) configured to store a speed pattern from discharge of
the strip from the hot rolling mill to completion of coiling by the down coiler, wherein
the water cooling prohibition header calculator is configured to:
calculate passing speed when each part in the length direction of the strip passes
through the intermediate position, by using information of the speed pattern table;
calculate an air cooling distance necessary for securing the target intermediate air
cooling time by multiplying the passing speed and the target intermediate air cooling time; and
select the cooling header that is prohibited from performing opening operation, in
association with the air cooling distance.
3. The coiling temperature controller according to claim 1, fbrther comprising:
a mill delivery side thermometer for measuring a strip temperature on the delivery
side of the hot rolling mill, an intermediate thermometer (1 71) for measuring a strip temperature
at the intermediate position, and a coiling thermometer for measuring a strip temperature before
the strip is coiled by the down coiler;
a dynamic controller (1 702) for front side cooling configured to calculate a
change amount of the number of opening cooling headers of a front side cooling controller to
make an intermediate temperature coincide with a target temperature in accordance with a mill
delivery side temperature and the intermediate temperature acquired from the strip during
cooling control, and output the change amount;
a dynamic controller (1703) for rear side cooling configured to calculate a change
amount of the number of opening cooling headers of a rear side cooling controller to make a
coiling temperature coincide with a target temperature in accordance with an intermediate
temperature and the coiling temperature acquired from the strip during cooling control, and
output the change amount;
a water cooling prohibition header change unit (1705) configured to increase or
decrease the cooling header that is prohibited from performing the opening operation;
a rolling speed change unit (1706) configured to change the rolling speed of the
strip; and
an intermediate air cooling time calculator (1 704) configured to calculate actual
intermediate air cooling time during cooling from the openinglclosing information of the cooling
headers output from the dynamic controller for front side cooling, the opening/closing
information of the cooling header output from the dynamic controller for rear side cooling, and
strip speed, and activate either the water cooling prohibition header change unit or the rolling
speed change unit, or both the water cooling prohibition header change unit and the rolling speed
change unit when the actual intermediate air cooling time does not satisfy the target intermediate
air cooling time.
4. The coiling temperature controller according to claim 3, wherein
the intermediate air cooling time calculator (1704) is configured to activate the
water cooling prohibition header change unit and then calculate actual intermediate air cooling
time again when the calculated actual intermediate air cooling time does not satisfy the target
intermediate air cooling time, and activate the rolling speed change unit when the actual
intermediate air cooling time still does not satisfy the target intermediate air cooling time.
5. The coiling temperature controller according to claim 1, wherein
a change amount of the number of opening cooling headers of a front side cooling
controller is calculated to make an intermediate temperature coincide with a target temperature in
accordance with a mill delivery side temperature and the intermediate temperature acquired from
the strip during cooling control,
a change amount of the number of opening cooling headers of a rear side cooling
controller is calculated to make a coiling temperature coincide with a target temperature in
accordance with an intermediate temperature and the coiling temperature acquired from the strip
during cooling control,
actual intermediate air cooling time during cooling is calculated from the
openinglclosing information of the cooling headers and strip speed,
selection of the cooling header that is prohibited from performing opening
operation is changed such that the actual intermediate air cooling time satisfies the target
intermediate air cooling time, and the actual intermediate air cooling time is then calculated
again, when the calculated actual intermediate air cooling time does not satisfy the target
intermediate air cooling time, and
the strip speed is changed such that the actual intermediate air cooling time
satisfies the target intermediate air cooling time, when the actual intermediate air cooling time
still does not satisfy the target intermediate air cooling time.
6. A temperature control method comprising the steps of
when a strip temperature is held for a deteminate time by cooling a strip (1 5 1)
rolled by a hot rolling mill (152) by a coiling cooling device (160) provided on a delivery side of
the hot rolling mill, controlling an intermediate temperature when the strip passes through a
predetermined intermediate position of the cooling deceive, to a predetermined target
temperature, in addition to a coiling temperature before the strip is coiled by a down coiler (1 54),
and setting a cooling condition in the vicinity of the intermediate position to air cooling,
selecting a cooling header (166) that is prohibited from performing opening
operation in the vicinity of the intermediate position for each part in a length direction of the
strip, from rolling speed of the strip, and a target value of air cooling time in the vicinity of the
intermediate position, before cooling control;
estimating the intermediate temperature of the strip from information of
openinglclosing of cooling headers of a front side cooling device (163) provided between the hot
rolling mill and the intermediate position, and calculating combination of opening and closing of
the cooling headers of the front side cooling device for implementing a target intermediate
temperature, by using a predicted result and information of the cooling header which is
prohibited from performing opening operation; and
estimating the coiling temperature of the strip from information of
opening/closirig of cooling headers of a rear side cooling device (164) provided between the
intermediate position and the down coiler, and calculating combination of opening and closing sf
the cooling headers of the rear side cooling device for implementing a target coiling temperature,
by using a predicted result and information of the cooling header which is prohibited from
performing opening operation.