{Specification}
{Title of Invention}
- 1 -
CONTROLLER AND CONTROL METHOD FOR HOT STRIP MILL
{Technical Field}
The present invention relates to a controller for a hot
strip mill that can reduce deviations in the mechanical
properties of rolled steel sheets and to a control method
for a hot strip mill.
{Background Art}
A hot strip mill stretches a steel slab heated to a
high temperature to reduce its original thickness to
several hundredths. The length of the steel slab is also
increased due to rolling. For example, a steel slab with a
thickness of 250 mm that has been heated to 1200°C at the
15 start of hot rolling is stretched to a thickness of 1.0 mm
at the completion of hot rolling.
The length of the steel slab, which is 1 m at the start
of rolling, is prolonged to 250 m at the completion of
rolling. It is an important issue in the control of a hot
20 strip mill to reduce deviations in the mechanical
properties of rolled material over their entire lengths.
To reduce deviations in the mechanical properties of
the rolled material, control on the basis of mechanical
property-prediction has been performed for the rolled
25 material. In this control on the basis of mechanical
- 2 -
property-prediction, planned process conditions are
calculated by using the chemical composition of the steel
slab to be rolled, the assured mechanical-property values
of the steel slab, and a mechanical-property prediction
5 model to set rolling process conditions, before rolling is
started.
Actual process conditions are obtained during rolling
to predict the mechanical properties anew from the
mechanical property model. If a predicted mechanical
10 property does not satisfy its corresponding assured
mechanical-property value, the rolling process conditions
are calculated again to make mill control settings again.
Japanese Patent No. 2509481 discloses an example of a
typical technology for control on the basis of the
15 mechanical property-prediction.
One issue in control on the basis of mechanical
property-prediction is precision of a mechanical-property
prediction model. If the precision of the mechanicalproperty
prediction model is inadequate, the mechanical
20 properties of the rolled material may not be assured.
Domestic Re-publication of PCT international
application WO 2006/040823 discloses a technology aimed at
having the mechanical properties of rolled material match
target values even if the precision of the mechanical-
25 property prediction model is inadequate.
- 3 -
With the technology disclosed in Domestic Republication
of PCT International Application WO 2006/040823,
mechanical-property sensors provided on a rolling line
measure the mechanical properties of the rolled material
5 under rolling and the rolling process conditions and
mechanical-property prediction model are corrected
according to measured values.
Assuming that the mechanical-property sensor is
preferably a non-contact, non-destructive sensor, detection
10 of the crystal grain size by a laser ultrasonic device is
disclosed. An electromagnetic ultrasonic device and a
magnetic flux detector are also described as other examples
of mechanical-property sensors.
An oxide film (scale), water, and a lubricant are
15 irregularly present on a steel slab that is undergoing hot
rolling. Water vapor is also generated around the steel
slab.
Therefore, mechanical-property values measured by the
above non-contact sensors include error. To reduce error in
20 measured mechanical-property values, a facility that keeps
the states above and around the steel slab constant is
necessary. Although the use of this type of facility is
possible, it is complicated and causes a problem in
practicality.
25 {Patent Literature 1}
- 4 -
Japanese Patent No. 2509481
{Patent Literature 2}
Domestic Re-publication of PCT International
Application WO 2006/040823
5 {Summary of Invention}
A problem with control on the basis of mechanical
property-prediction based on the technology disclosed in
Japanese Patent No. 2509481 lies in the precision of the
mechanical-property prediction model. If the precision of
10 the mechanical-property prediction model is inadequate, the
mechanical properties of rolled material may not be assured.
With the technology disclosed in Domestic Republication
of PCT International Application WO 2006/040823,
mechanical-property values measured by non-contact sensors
15 include error of measurement. To reduce this error of the
measured mechanical-property values, a facility that keeps
the state above and around the rolled material constant is
necessary. This type of facility is not only complicated
but also large, causing a problem in practicality.
20 An object of the present invention is to provide a
controller for a hot strip mill that can provide rolled
material having stable mechanical property without having
to add a complicated device even if the precision of the
mechanical-property prediction model is inadequate and to
25 provide a control method for a hot strip mill.
5
- 5 -
To solve the problems described above, a controller for
a hot strip mill of the present invention that includes a
finishing mill having rolling mills at a plurality of
stages, each of which rolls a material to be rolled, a runout
table to cool the rolled material rolled by the
finishing mill, and a coiler to coil the rolled material
cooled by the run-out table, the controller to control the
hot strip mill according to a rolling schedule, the
controller for a hot strip mill comprising: a deformation
10 resistance calculating unit to calculate a deformation
resistance of the material to have been rolled by at least
one rolling mill at a later stage of the rolling mills at
the plurality of stages; a cooling rate correcting unit to
calculate a correction value of a cooling rate at which the
15 run-out table cools the rolled material, according to the
deformation resistance calculated by the deformation
resistance calculating unit; and a cooling control unit to
control a cooling of the rolled material by the run-out
table by using the correction value of the cooling rate
20 calculated by the cooling rate correcting unit.
To solve the problems described above, a control method
for a hot strip mill of the present invention that rolls a
material to be rolled by using rolling mills at a plurality
of stages provided in a finishing mill, cools the rolled
25 material rolled by the finishing mill by using a run-out
- 6 -
table, and then coils the rolled material cooled by the
run-out table by using a coiler, according to a rolling
schedule, the control method for a hot strip mill
comprising the steps of: calculating a deformation
5 resistance of the material to have been rolled by at least
one rolling mill at a later stage of the rolling mills at
the plurality of stages; calculating a correction value of
a cooling rate at which the run-out table to cool the
rolled material according to the calculated deformation
10 resistance; and controlling the cooling rate of the rolled
material, which is performed by the run-out table, by using
the calculated correction value of the cooling rate.
The present invention can achieve a controller for a
hot strip mill that can provide rolled material having
15 stable mechanical properties without adding a complicated
device even if the precision of the mechanical-property
prediction model is inadequate and can also achieve a
control method for a hot strip mill.
20
25
{Brief Description of Drawings}
{Fig. 1} FIG. 1 is a schematic structural diagram
illustrating an example of a hot rolling process in a hot
strip mill to which a controller and a control method for a
hot strip mill according to the present invention are
applied.
{Fig. 2} FIG. 2 shows graphs that illustrate examples
- 7 -
of variations in rolling conditions in the example of a hot
rolling process in a hot strip mill shown in Fig. 1.
{Fig. 3} FIG. 3 shows histograms illustrating
deviations in the mechanical properties of steel sheets
5 manufactured under the rolling conditions indicated in FIG.
2.
{Fig. 4} FIG. 4 is a graph illustrating statistical
analysis results of deformation resistance of a rolled
material because of the variations in rolling conditions
10 shown in Fig. 2 at each rolling stage of the hot strip mill
shown in Fig. 1.
{Fig. 5} FIG. 5 shows scatter diagrams each of which
illustrates an example of a correlation between a
mechanical property and the deformation resistance of a
15 rolled material rolled by the rolling mill at the final
stage of a finishing mill of the hot strip mill shown in
Fig. 1.
{Fig. 6} FIG. 6 shows scatter diagrams each of which
illustrates an example of a correlation between a
20 mechanical property and the deformation resistance of a
rolled material rolled by a roughing mill and rolling mills
at early stages of the finishing mill of the hot strip mill
shown in Fig. 1.
{Fig. 7} FIG. 7 shows scatter diagrams each of which
25 illustrates an example of a correlation between the
- 8 -
combined deformation resistance of a rolled material at
finishing rolling and its mechanical property.
{Fig. 8} FIG. 8 shows graphs each of which compares
estimated values and actual values of a mechanical property
5 in finishing rolling, the estimated values being obtained
by using combined deformation resistance.
{Fig. 9} FIG. 9 is a control block diagram illustrating
the structure of a controller for a hot strip mill to which
the controller and control method for a hot strip mill
10 according to the first embodiment of the present invention
are applied.
{Fig. 10} FIG. 10 is a control block diagram
illustrating part of the structure of a controller for a
hot strip mill to which a controller and a control method
15 for a hot strip mill according to a second embodiment of
the present invention are applied.
{Detailed Description of the Embodiments}
A controller and a control method for a hot strip mill
that an embodiment of the present invention will be
20 described with reference to the drawings.
25
{Embodiment 1}
A controller and a control method for a hot strip mill
in a first embodiment will be described with reference to
FIG. 1, focusing on a hot rolling process.
FIG. 1 is a schematic diagram illustrating an example
- 9 -
of a hot rolling process in the controller and control
method for a hot strip mill in this embodiment.
In the hot rolling process, illustrated in FIG. 1, in
the hot strip mill, a material to be rolled like a slab is
5 heated in a heating furnace 100 so that the entire material
to be rolled is uniformly heated to, for example, 1200°C.
The thickness of the material to be rolled like a slab is,
for example, 200 mm.
A hot strip mill 1, which rolls the material to be
10 rolled like a slab that has been uniformly heated in the
heating furnace 100, has a plurality of devices, those
being from a scale breaker 101 at the upstream of the
process to a coiler 107 at the downstream.
The scale breaker 101 sprays water to the surface of
15 the slab to remove a scale formed on the surface of the
slab.
The material to be rolled like a slab which has been
uniformly heated in the heating furnace 100 passes through
the scale breaker 101, after which the slab passes through
20 a roughing mill 102 made up of rolling mills Rl and R2
provided at two stages, once or passes through it forward
and backward a plurality of times so that the slab is
rolled to a prescribed thickness according to a preset
rolling schedule.
25 Here, the rolling schedule is a set of settings of
- 10 -
rolling conditions for rolling mills disposed at stages;
the settings include a rolling reduction ratio and
temperature of the rolled material by rolling rolls in
these rolling mills and a desired-temperature history of
5 the rolled material cooled by a cooling device.
The slab rolled by the roughing mill 102 passes through
an intermediate cooling device 103 disposed downstream of
the roughing mill 102, during which the rolled slab is
cooled by the intermediate cooling device 103 to a
10 finishing rolling start temperature determined in the
rolling schedule.
After the slab has passed through the intermediate
cooling device 103, a scale formed on the surface of the
slab is removed by a scale breaker 104 disposed downstream
15 of the intermediate cooling device 103.
After the slab has passed through the scale breaker 104
and the scale on its surface has been removed, the slab
enters a finishing mill 105 disposed downstream of the
scale breaker 104; the finishing mill 105 includes rolling
20 mills at a plurality of stages (five mills F1 to F5 in this
embodiment) in a tandem form.
As described above, the finishing mill 105 includes
rolling mills at a plurality of consecutive stages (five
stages) in a tandem form. While passing through the rolling
25 mills at all stages of the finishing mill 105, the slab is
- 11 -
rolled in succession according to the rolling schedule and
is finished to a thin steel sheet with a thickness of, for
example, 2 mm.
The thin steel sheet rolled by the finishing mill 105
5 moves in a run-out table 106 disposed downstream of the
finishing mill 105 while being cooled at a prescribed
cooling rate, after which the thin steel sheet is coiled by
a coiler 107 disposed downstream of the run-out table 106.
Next, effects by variations in actual rolling
10 conditions in the hot strip mill 1 in this embodiment will
be described.
FIG. 2 shows graphs that illustrate examples of
variations in rolling conditions (temperature (°C) and
rolling reduction ratio) for the roughing mills R1 and R2
15 at two stages, which constitute the roughing mill 102, and
for the finishing mills F1 to F5 at five stages, which
constitute the finishing mill 105, the roughing mill 102
and finishing mill 105 being part of the hot strip mill 1.
The upper graph in FIG. 2 indicates variations in
20 temperature (°C) and the lower graph in FIG. 2 indicates
variations in the rolling reduction ratio.
To investigate effects by variations under these
rolling conditions, the temperature of the material to be
rolled was changed within a range of up to ±50°C with
25 respect to the temperature settings at the roughing mills
- 12 -
R1 and R2 and at the rolling mills F1 to F5. The rolling
reduction ratio was changed within a range of up to ±5%
with respect to the settings for the roughing mills R1 and
R2 and the rolling mills F1 to F5. After the rolled
5 material which has been finally rolled, its thickness is
maintained at a prescribed value, so the entire rolling
reduction ratio is constant over the rolling line.
FIG. 3 shows deviations in yield strength (MPa) and
tensile strength (MPa), which are mechanical properties of
10 a steel sheet manufactured by using the roughing mills R1
and R2, constituting the roughing mill 102, and the rolling
mills F1 to F5, constituting the finishing mill 105, the
roughing mill 102 and finishing mill 105 being part of the
hot strip mill 1, under the rolling conditions shown in FIG.
15 2. The upper graph in FIG. 3 indicates deviations in yield
strength (MPa), and the lower graph in FIG. 3 indicates
deviations in tensile strength (MPa) .
As shown in FIG. 3, when the rolling conditions were
changed, a deviation of up to 40 MPa was generated in yield
20 strength and a deviation of up to 20 MPa was generated in
tensile strength as variations in the actual rolling
conditions for the hot strip mill 1 in this embodiment.
Temperature, the rolling reduction ratio, deformation
resistance, and other data that can be obtained at each
25 stage of the hot strip mill 1 were statistically analyzed.
- 13 -
FIG. 2 shows analysis results of temperature and the
rolling reduction ratio, and FIG. 4 shows analysis results
of deformation resistance.
The analysis results of deformation resistance shown in
5 FIG. 4 indicate that the later the mill is positioned, the
larger deviations in deformation resistance are. The
deviations in deformation resistance in FIG. 4 show a
characteristic trend that is not shown in the deviations in
temperature and the rolling reduction ratio in FIG. 2.
10 Deformation resistance is average yield strength or
average yield stress generated when a material to be rolled
is plastically deformed by the rolling rolls of a rolling
mill. It is known that yield strength is determined by the
fine tissues of the material to be rolled (for example,
15 dislocation density, crystal grain size, the amount of
solid solution elements, the amount of deposition, and a
ratio between phase transformation tissues).
Accordingly, the fact that the later the rolling mill
is positioned, the larger deviations in deformation
20 resistance are, as shown in FIG. 4, indicates that as the
rolled material under rolling proceeds toward later stage
of the rolling mills at plurality of stages, which are
included in the hot strip mill 1, deviations in the fine
tissues of the rolled material become large.
25 Deviations in the rolling conditions for the roughing
- 14 -
mill R1 of the roughing mill 102 cause deviations in fine
tissues of the rolled material that has been rolled by the
roughing mill Rl and is to be rolled by the roughing mill
R2. Deviations in the rolling conditions for the roughing
5 mill R2 further increase deviations in fine tissues of the
rolled material. Thus, the later the rolling mill is
positioned, the larger deviations in deformation in fine
tissues of the rolled material are. When variations in the
rolling conditions are accumulated as deviations in fine
10 tissues of the rolled material, the accumulated variations
appear as variations in deformation resistance.
When deformation resistance is considered as the
mechanical properties of the rolled material, the above
correlation between deformation resistance and fine tissues
15 of the rolled material indicates the possibility that
deformation resistance may be used to control the
mechanical properties of the rolled material. To confirm
the possibility that deformation resistance may be used to
control the mechanical properties of the rolled material,
20 correlations between deformation resistance and the
mechanical properties of the rolled material were
investigated.
FIG. 5 shows scatter diagrams each of which illustrates
an example of a correlation between a mechanical property
25 and the deformation resistance of a rolled material rolled
- 15 -
by the rolling mill F5 at the final stage of the rolling
mills F1 to F5 constituting the finishing mill 105 in the
hot strip mill 1 in this embodiment.
As seen from the scatter diagrams in FIG. 5, there are
5 apparent correlations between the deformation resistance
(MPa) of the rolled material rolled by the rolling mill F5
at the final stage, which is indicated on the horizontal
axis, and yield strength (MPa) indicated on the vertical
axis and between the deformation resistance (MPa) and
10 tensile strength (MPa) indicated on the vertical axis.
The solid lines in the scatter diagrams in FIG. 5
indicate regression analysis results for the correlation
between deformation resistance and yield strength and the
correlation between deformation resistance and tensile
15 strength. The solid lines indicate that the latter the
rolling mill is positioned, the stronger the correlations
between the deformation resistance and yield strength of
the rolled material rolled by the rolling mill and between
its deformation resistance and tensile strength are.
20 The upper graph in FIG. 6 is a scatter diagram that
illustrates an example of a correlation between the
deformation resistance and the yield strength of a rolled
material rolled by the roughing mill R1 of the roughing
mill 102 in the hot strip mill 1 in this embodiment. The
25 graph in the middle of FIG. 6 is a scatter diagram that
- 16 -
illustrates an example of a correlation between the
deformation resistance and the yield strength of a rolled
material rolled by the rolling mill F1 of the finishing
mill 105. The lower graph in FIG. 6 is a scatter diagram
5 that illustrates an example of a correlation between the
deformation resistance and the yield strength of a rolled
material rolled by the rolling mill F3 of the finishing
mill 105.
The latter a rolling mill at the plurality of stages
10 constituting the hot strip mill 1 is positioned, the
stronger the correlations between the deformation
resistance and the yield strength of the rolled material
rolled by the rolling mill are. This is apparent from the
correlations, shown by the scatter diagrams in FIG. 5,
15 between the deformation resistance and yield strength of
the rolled material rolled by the rolling mill F5 and
between its deformation resistance and tensile strength and
from the correlations, shown by the scatter diagrams in FIG.
6, between the deformation resistances and the yield
20 strengths of the rolled materials rolled by rolling mills
of the hot strip mill 1.
It is also possible to more strengthen the correlation
between the mechanical properties and deformation
resistance of a rolled material rolled by the hot strip
25 mill 1 by using the deformation resistances of the rolled
- 17 -
material rolled by the rolling mills, at the plurality of
stages, constituting the hot strip mill 1 in combination in
rolling control for the hot strip mill 1. For example,
equation (1) below indicates the mechanical properties of a
5 rolled material as a function of combined deformation
resistance X, which is obtained by linearly combining
deformation resistances of the rolled material at all
stages of the finishing mill 105.
{Equation 1}
10 YSp =roQ ,
TSp = g(X)'
X= aF1XDRF1 + anxDRF2 +aFSxDRFS+ aF.-xDRF4 + · · · flFNXDRFN ,
SFI+an+aFa+aF.-+· ··aFN= 1
( 1)
In the equation (1) above, YSp indicates estimated yield
15 strength, TSp indicates estimated tensile strength, DRFn
indicates deformation resistance at rolling mill n of the
finishing mill 105, aFn indicates a ratio of contribution to
deformation resistance DRFn' in combined deformation
resistance X, at rolling mill n of the finishing mill 105,
20 and N is the number of rolling mills included in the
finishing mill 105.
FIG. 7 illustrates examples of rolling control for the
hot strip mill 1, in which the equation (1) is used, which
linearly combines the deformation resistances of a rolled
25 material obtained as a result of rolling by the rolling
- 18 -
mills F3 to F5 of the finishing mill 105 and represents the
linearly combined deformation resistances as a function of
combined deformation resistance X.
The upper graph in FIG. 7 is a scatter diagram that
5 illustrates a correlation between combined deformation
resistance X and the yield strength of a rolled material,
combined deformation resistance X being the average of the
deformation resistances of the rolled material obtained as
a result of rolling by the rolling mills F3 to F5 of the
10 finishing mill 105. The lower graph in FIG. 7 is a scatter
diagram that illustrates a correlation between combined
deformation resistance X and the tensile strength of the
rolled material.
In the scatter diagrams in FIG. 7, which represents
15 correlations, coefficients in equation (1) are: aFl = aF2
0; aF3 = aF4 = aFs = 1 I 3.
The solid lines in FIG. 7 indicate regression analysis
results for the correlation between combined deformation
resistance X and yield strength and the correlation between
20 deformation resistance X and tensile strength as quadratic
functions f(X) =a + bX + cX2 and g(X) =a' + b'X + c'X2
•
FIG. 8 is graphs that compare actual values of yield
strength and tensile strength and their estimated values
obtained by quadratic functions f(X) and g(X), represented
25 by the solid lines in FIG. 7. The upper graph in FIG. 8
- 19 -
indicates estimated yield strength (MPa) and actual yield
strength (MPa) . The lower graph in FIG. 8 indicates
estimated tensile strength (MPa) and actual tensile
strength (MPa) .
5 If the estimated values and their corresponding actual
values completely match, data should be plotted on the
dashed lines in FIG. 8. Data points in FIG. 8 are
distributed only within a range of several MPa around the
dashed lines, indicating that the yield strength values
10 estimated by using the combined deformation resistance and
their corresponding actual values superiorly match and that
tensile strength values estimated by using the combined
deformation resistance and their corresponding actual
values superiorly match.
15 As described above, the deformation resistance after
rolling by the finishing rolling stages of the finishing
mill 105 in the hot strip mill 1 has a strong correlation
with the mechanical properties of the rolled material, so
the deformation resistance is used for mechanical-property
20 control for the rolled material under rolling.
In the controller and control method for the hot strip
mill 1 in this embodiment, to control the mechanical
properties, the rate at which the rolled material under
rolling was cooled in the run-out table 106 was feed-
25 forwarded.
- 20 -
In the cooling of a steel slab, it is known that the
higher the cooling rate is, the stronger the strength
becomes. Conventionally, to reduce deviations in the
mechanical properties of a steel slab, the run-out table
5 106 has been controlled so that its entrance temperature
and exit temperature are maintained at fixed values.
In the controller and control method for the hot strip
mill 1 in this embodiment, to reduce deviations, in the
mechanical properties of a rolled material under rolling,
10 which are caused by deviations in rolling conditions, the
cooling rate of the rolled material in the run-out table
106 is controlled by using measured values of the
deformation resistance of the rolled material rolled by the
rolling mills of the finishing mill 105 included in the hot
15 strip mill 1.
A problem with the use of deformation resistance in the
control of the mechanical properties of the rolled material
under rolling lies in the measurement of the deformation
resistance of the rolled material under rolling. It is
20 known that deformation resistance k is proportional to a
rolling load P, as indicated by equation (2) below.
{Equation 2}
P=QXkXLXb (2)
In the equation (2), Q is a roll force function
25 determined by geometrical conditions in rolling, L is a
- 21 -
projected roll contact length determined by the roll radius
of the rolling mill and the amount of rolling reduction,
and b is an average between the width of the rolled
material before being rolled and that after being rolled.
5 The projected roll contact length L is determined by using
equation (3) below.
{Equation 3}
( 3)
In the equation (3), R is the radius of the rolling
10 roll used in the rolling mill and ~h is the amount of
rolling reduction, which is defined as a difference between
the plate thickness of a roll entrance and the plate
thickness of a roll exit.
The roll force function Q can be calculated by, for
15 example, the Shida's equation, which is shown below as
equation (4).
{Equation 4}
Q=0.8+(0.45Ah/ h"' +0.04)( ~RI hu, -o.s) ( 4)
In the equation (4), hin is the plate thickness of the
20 roll entrance.
25
As is clear from the equation (3) and the equation (4),
the amount ~h of rolling reduction is necessary to
calculate the deformation resistance k from the rolling
load P.
The rolling load P can be measured by attaching load
- 22 -
cells to the rolling rolls of rolling mills. It is a
conventional practice to attach the load cells to the
rolling rolls of substantially all rolling mills to control
the plate thickness of the rolled material under rolling.
5 Accordingly, the rolling load P can be measured without
having to add any device.
As described above, there have been attempts to use the
rolling load P in the control of other than the plate
thickness. For example, Japanese Patent Laid-Open No. Hei
10 02(1990)-170924 and Japanese Patent Laid-Open No. 3979023
each disclose a technology by which the rolling load P of a
skin pass mill is used to control heat treatment
temperature at a pre-stage in skin pass rolling that is
carried out after heat treatment has been carried out at a
15 final stage in cold rolling.
20
Japanese Patent Laid-open No. 10-43808 and Japanese
Patent Laid-open No. 2006-55887 each disclose a technology
by which the rolling load P is used to control the
temperature of a rolled material under finishing rolling.
The amount ~h of rolling reduction, which is required
to obtain the deformation resistance k of the rolled
material rolled by the rolling mill from the rolling load P,
continues to change during rolling under automatic gage
control. Accordingly, it is difficult to use the
25 deformation resistance k of the rolling mill for control
- 23 -
purposes in hot rolling of a thin sheet.
If plate thickness meters are provided before and after
a pair of rolling rolls of the rolling mill, the amount dh
of rolling reduction can be measured. However, this is not
5 practical because the addition of the plate thickness
meters increases costs and the burden of maintenance.
Japanese Patent Laid-Open No. Sho 56(1981)-6716
discloses a technology by which the deformation resistance
of a rolled material rolled by the roughing mill at the
10 final stage of a roughing mill in hot strip rolling is used
to estimate the average temperature of the rolled material
and the temperature of the rolled material under rolling by
a finishing mill in hot strip rolling is controlled
according to the estimated average temperature. In roughing
15 rolling, however, automatic gage control may not be carried
out. The technology disclosed in Japanese Patent Laid-Open
No. Sho 56(1981)-6716 also does not consider changes in
projected roll-contact length under automatic gage control.
Japanese Patent Laid-Open No. Hei 04(1992)-327304
20 discloses a technology by which in hot rolling of thick
plates, the deformation resistance k of a rolled material
is used to control its mechanical properties. In hot
rolling of thick plates, however, a rolled material is
typically rolled by being moved forward and backward in one
25 rolling mill. Therefore, if plate thickness meters are
- 24 -
disposed before and after the rolling rolls of the rolling
mill, the amount ~h of rolling reduction can be easily
determined even during automatic gage control.
Next, the controller and control method for the hot
5 strip mill in the first embodiment in this application will
be described with reference to the control block diagram,
shown in FIG. 9, of the controller in the hot strip mill.
In the control block diagram, shown in FIG. 9, of the
controller in the hot strip mill in the first embodiment,
10 the controller 2, which is included in the hot strip mill 1
and controls it, includes a rolling schedule setting unit
20 that sets a rolling schedule, a rolling mill control
unit 201 that controls the hot strip mill 1 according to
the rolling schedule set by the rolling schedule setting
15 unit 20, an automatic gage control unit 202 that controls
the rolling reduction ratio of each of the rolling mills F1
to F5 constituting the finishing mill 105 in the hot strip
mill 1, a cooling control unit 215 that controls a cooling
rate at which the run-out table 106 in the hot strip mill 1
20 cools the rolled material, a deformation resistance
calculating unit 213 that calculates the deformation
resistance of the rolled material from the values of
rolling loads detected by load cells 211 attached to the
finishing mill 105, and a cooling rate correcting unit 214
25 that corrects the cooling rate controlled by the cooling
- 25 -
control unit 215 according to the deformation resistance
calculated by the deformation resistance calculating unit
213.
Before the rolling of the rolled material starts, the
5 rolling schedule setting unit 20 determines a rolling
schedule, which includes the rolling reduction ratios and
temperatures of the rolled material under rolling at the
roughing mills R1 and R2 of the roughing mill 102 and the
rolling mills F1 to F5 of the finishing mill 105, the
10 roughing mill 102 and finishing mill 105 being part of the
hot strip mill 1, and also includes a desired-temperature
history for the intermediate cooling device 103. The
rolling schedule setting unit 20 then outputs the
determined rolling schedule to the rolling mill control
15 unit 201.
Here, the temperature history denotes temperature T (t),
which changes with time, at a single point or a plurality
of points set at, for example, the head, center, and tail
in the rolling direction) on the rolled material. These
20 temperature history setting points are set on the rolled
material in its rolling direction at fixed intervals, for
example, 5-m intervals.
The rolling mill control unit 201 sets the temperature
history setting points of the rolled material to be rolled
25 by the roughing mills R1 and R2 of the roughing mill 102
- 26 -
and the rolling mills F1 to F5 of the finishing mill 105,
the roughing mill 102 and finishing mill 105 being part of
the hot strip mill 1, on the rolled material in its rolling
direction at fixed intervals, for example, 5-m intervals,
5 according to the rolling schedule determined by and
received from the rolling schedule setting unit 20.
The load cell 211 is attached to each of rolling roll
in the rolling mills F1 to F5 constituting the finishing
mill 105 in the hot strip mill 1. Rolling load values
10 detected by each load cell 211 are input to the automatic
gage control unit 202.
The automatic gage control unit 202 determines amounts
by which the upper and lower positions of the rolling rolls
in each of the rolling mills F1 to F5 of the finishing mill
15 105 are corrected, according to the rolling load values
detected by the relevant load cell 211. The automatic gage
control unit 202 then outputs the determined amounts to a
driver that drives the rolling rolls of the rolling mills
F1 to F5 of the finishing mill 105. This driver, which
20 drives the rolling rolls, is not essential in this
application, so the driver is not shown in FIG. 9.
The rolling load values detected by the load cell 211
attached to the rolling mill at the final stage of the
finishing mill 105 (rolling mill F5, for example) are also
25 input to the deformation resistance calculating unit 213.
- 27 -
Furthermore, plate thickness meters 212 are attached to
the entrance and exit of the rolling mill F5 at the final
stage of the finishing mill 105. Plate thickness values
detected by the plate thickness meters 212 attached to the
5 entrance and exit of the rolling mill F5 at the final stage
are input to the deformation resistance calculating unit
213.
The deformation resistance calculating unit 213 has
calculators that calculate the equation (1), the equation
10 (2), the equation (3), and the equation (4) described above.
The rolling loads of the rolling mill, which are detected
by the load cells 211, and the plate thickness values
detected by the plate thickness meters 212 at the entrance
and exit of the rolling mill F5 at the final stage of the
15 finishing mill 105 are input to the calculators included in
the deformation resistance calculating unit 213 so that the
deformation resistance at the rolling mill F5 at the final
stage of the finishing mill 105 is obtained at each of the
temperature history setting points described above.
20 The detected rolling load values and plate thickness
values are input at intervals shorter than intervals at
which the deformation resistance is output. Accordingly, if
data processing is performed on a plurality of rolling load
values and a plurality of plate thickness values before the
25 deformation resistance is obtained, the precision of
- 28 -
calculated deformation resistance values can be improved.
Known digital filter processing is preferable because
it is one of the simplest data processing methods. However,
an analog integration circuit, for example, may be used.
5 Alternatively, the deformation resistance may be calculated
each time the rolling load and plate thickness are input
and data processing may be performed on a plurality of
deformation resistance values, after which a single
deformation resistance value for the temperature history
10 setting points on the rolled material may be output.
Deformation resistance kn, which has been calculated by
the deformation resistance calculating unit 213 and
corresponds to temperature history setting point n on the
rolled material, is input to the cooling rate correcting
15 unit 214.
A calculator that calculates the equation (5) below is
provided in the cooling rate correcting unit 214. The
calculator is used to calculate a cooling rate correction
value ~Crn, which is applied to temperature history setting
20 point n, from the deformation resistance kn according to the
equation (5).
{Equation 5}
(5)
25
- 29 -
In the equation (5), g is a control gain, Sis a
representative value of a mechanical property, which is,
for example, yield strength or tensile strength, and ksET is
the deformation resistance, of the rolled material, that
5 has been predicted from rolling schedule settings made by
the rolling schedule setting unit 20. To predict this
deformation resistance ksET' a mechanical-property
prediction model may be used.
A mechanical-property prediction model for predicting
10 the deformation resistance ksET of a rolled material from
rolling schedule settings is disclosed in, for example, J.
Yanagimoto et al., Transactions of the ASME, Vol. 120, pp.
316-322 (1998).
To predict deformation resistance ksET' a database
15 including previous records may be used. Alternatively,
deformation resistance ksET may be predicted by using a
combination of a database including previous records and a
mechanical-property prediction model.
In addition, ~S/~Cr, which is the denominator on the
20 right side of the equation (5), and ~S/~k, which is the
numerator on the right side of the equation (5), may be
similarly determined by using a database including previous
records or a combination of a database including previous
records and a mechanical-property prediction model.
25 The cooling rate correcting unit 214 calculates the
- 30 -
cooling rate correction value ~Crn, which is applied to
temperature history setting point n, and outputs the
calculated value to the cooling control unit 215.
The cooling control unit 215 adds the cooling rate
5 correction value ~Crn calculated by the cooling rate
correcting unit 214 to a cooling rate value Crn, which is
applied to temperature history setting point n, the cooling
rate value Crn being set according to the rolling schedule
set by the rolling schedule setting unit 20. The cooling
10 control unit 215 then controls a plurality of cooling
nozzles 216 provided in the run-out table 106 according to
the value obtained by the addition.
The plurality of cooling nozzles 216 are disposed in
the run-out table 106 in its rolling direction. The cooling
15 control unit 215 controls the opening of each of the
cooling nozzles 216 to control the cooling rate and
temperature histories of the rolled material under rolling.
One or a plurality of run-out table thermometers 217
are provided in the run-out table 106. The run-out table
20 thermometer 217 measures the temperature of the rolled
material under rolling and outputs the measured temperature
to the cooling control unit 215.
A driver is disposed in the run-out table thermometer
217; it controls a position of the run-out table
25 thermometer 217 so that it is located at an optimized
- 31 -
position.
Furthermore, a finishing later-stage thermometer 218 is
provided ahead of the run-out table 106 and a coiling
early-stage thermometer 219 is provided behind the run-out
5 table 106. The temperatures measured by the finishing
later-stage thermometer 218 and coiling early-stage
thermometer 219 are output to the cooling control unit 215.
The cooling control unit 215 performs feedback control
on the amount of cooling water supplied from the cooling
10 nozzles 216 disposed in the run-out table 106 according to
the temperatures measured by the run-out table thermometer
217, finishing later-stage thermometer 218, and coiling
early-stage thermometer 219 so that the cooling rate of the
rolled material under rolling becomes the sum of the
15 cooling rate Crn and the cooling rate correction value ~Crn.
To correct the cooling rate of the rolled material, a
rolled material conveyer 220 disposed in the run-out table
106 may be controlled to change a speed at which the rolled
material is conveyed, besides controlling the amount of
20 cooling water supplied from the cooling nozzles 216
disposed in the run-out table 106.
For example, to increase the cooling rate of the rolled
material at temperature history setting point n, it
suffices to control the rolled material conveyer 220 so
25 that the conveying speed of the rolled material is lowered
- 32 -
when the temperature history setting point of the rolled
material passes under a cooling nozzle 216 that supplies a
less amount of cooling water.
This method, in which the cooling rate of the rolled
5 material is controlled by having the rolled material
conveyer 220 control the conveying speed of the rolled
material, depends on the setting of the amount of cooling
water supplied from the cooling nozzles 216. Therefore, the
method is preferably used by also setting the amount of
10 cooling water supplied from the cooling nozzles 216 to
improve the capability to correct the cooling rate of the
rolled material.
A mechanical-property inspecting device 221 that
inspects the mechanical properties of the rolled material
15 may be provided between the run-out table 106 and the
coiler 107.
Examples of mechanical-property inspecting devices 221
include known ultrasonic grain size measuring devices,
electromagnetic ultrasonic devices, magnetic flux detectors,
20 and indentors. The mechanical-property inspecting device
221 inspects the mechanical properties of the rolled
material at each temperature history setting point and
outputs inspection results to the cooling rate correcting
unit 214.
25 In addition to the calculator that calculates the
- 33 -
equation (5), the cooling rate correcting unit 214 includes
a calculator that calculates the equation (8) indicated
later. The calculator can use the mechanical-property
inspection results of the rolled material, which are given
5 by the mechanical-property inspecting device 221, to
correct and update data on ~S/~Cr and ~S/~k, which are
respectively the denominator and numerator on the right
side of the equation (5), enabling deviations in the
mechanical properties of the rolled material to be reduced.
10 After having been cooled by the run-out table 106, the
rolled material has been cooled to about 600°C. Accordingly,
the mechanical-property inspecting device 221 disposed
behind the run-out table 106 is advantageous in terms of
heat resistance when compared with a case in which the
15 mechanical-property inspecting device 221 is disposed ahead
of the run-out table 106.
The mechanical-property inspecting device 221 can be
disposed closer to the rolled material by an according
amount. This is also advantageous in terms of precision in
20 mechanical property measurement. Furthermore, the thickness
of the rolled material has been thinned to several
millimeters. This is also advantageous in terms of
precision in measurement in the thickness direction of the
rolled material.
25 Since the mechanical-property inspecting device 221
- 34 -
described above is disposed ahead of the coiler 107, the
mechanical properties of the rolled material can be easily
inspected by the mechanical-property inspecting device 221
at each of the temperature history setting points set over
5 the entire length of the rolled material.
The above-described controller of the hot strip mill in
the first embodiment in this application precisely
calculates the deformation resistance of the rolled
material rolled by the rolling mill F5 at the final stage
10 of the finishing mill 105 and controls the openings of the
cooling nozzles 216 in the run-out table 106 in a feed
forward manner by using the calculated deformation
resistance, as described above. Therefore, even if the
precision of the mechanical-property prediction model is
15 not so adequate, rolled materials with stable mechanical
properties can be provided without having to add a
complicated device.
In this embodiment, therefore, even if the precision of
the mechanical-property prediction model is not so adequate,
20 a controller and a control method for a hot strip mill that
can provide rolled materials with stable mechanical
properties without having to add a complicated device can
be achieved.
{Embodiment 2}
25 Next, a controller and a control method for a hot strip
- 35 -
mill in a second embodiment will be described with
reference to FIG. 10.
The basic structures of the controller and control
method for a hot strip mill in the second embodiment shown
5 in FIG. 10 are the same as the basic structures of the
controller and control method for a hot strip mill in the
first embodiment shown in FIG. 9, so descriptions common to
the first embodiment and the second embodiment will be
omitted, and only structures different from the first
10 embodiment will be described.
With the controller and control method for a hot strip
mill in this embodiment, the correlations, indicated by the
equation (1), between the combined deformation resistance X
and the mechanical properties are used, the combined
15 deformation resistance X being a combination of deformation
resistances of a rolled material by rolling mills at a
plurality of stages of a finishing mill.
To calculate the deformation resistance of a rolled
material rolled by the rolling mills at the plurality of
20 stages of the finishing mill 105, the amount 8h of rolling
reduction by the rolling mill at each stage needs to be
obtained. However, it is not preferable to attach the plate
thickness meter 212 between the rolling mills at each two
stages because costs and the burden of maintenance increase.
25 With the controller and control method for a hot strip
- 36 -
mill in this embodiment, therefore, data obtained from the
automatic gage control unit 202 is used to calculate the
amount ~h of rolling reduction by the rolling mill at each
stage and the deformation resistance k of the rolled
5 material without adding the plate thickness meters 212
among the rolling mills at the plurality of stages of the
finishing mill 105.
Specifically, it is assumed that when a rolled material
to be rolled is not present, a gap between the upper
10 rolling roll and the lower rolling roll of rolling mill n
of the finishing mill 105 is Hn. When a rolled material to
be rolled enters the gap between the upper rolling roll and
the lower rolling roll so that the rolled material is
rolled, the gap Hn changes to a gap Hn', which is larger
15 than Hn, due to the reaction force of the rolled material.
Since the deformation of the rolling rolls is elastic
deformation, a proportional relationship indicated by the
equation (6) below holds between a rolling load Pn and the
gap Hn', which is formed between the upper rolling roll and
20 the lower rolling roll.
{Equation 6}
Pn.=Kn (Hn'-Hn) (6)
In the equation (6), the proportional coefficient Kn
indicates the rigidity of a roll, which is analytically or
25 experimentally identified for each rolling roll.
- 37 -
In hot rolling, a material to be rolled is assumed to
undergo complete plastic deformation by rolling mills, so
the plate thickness hn of the rolled material at the exit of
the rolling rolls of rolling mill n matches Hn'.
5 Accordingly, the plate thickness hn at the exit of the
rolling rolls of rolling mill n can be calculated from the
rolling load Pn, roll gap Hn in the absence of a rolled
material, and the proportional coefficient Kn of the rolling
rolls, according to the equation (6). The calculation
10 result can be used to obtain the amount ~h of rolling
15
20
reduction by each rolling mill of the finishing mill 105,
which includes N mills, as indicated by the equation (7)
below.
{Equation 7}
~h1 = Ht+Pxi.Kt- ho
~112= H2+PJ&- (H1+PJiKJ
.MlN= HN+PNIKN- (HIH+PN·IIKN·V
{0127}
( 7)
When there is no rolled material between the upper
rolling roll and the lower rolling roll at each rolling
mill of the finishing mill 105, roll gaps H1 to HN and
rigidity coefficients K1 to KN of the rolling rolls are
25 constants that are analytically or experimentally
- 38 -
predetermined as described above.
Therefore, by attaching the rolling loads P1 to PN
measured by load cells 211 to the rolling mills at all
stages of the finishing mill 105 are assigned to the
5 equation (7), it is possible to obtain the amounts ~h2 to
~hN of rolling reduction by rolling mills at all stages
excluding the first stage, that is, the second mill to mill
N of the finishing mill 105, without having to attach the
plate thickness meter 212 between each rolling mills.
10 A calculator that calculates the equation (6) and a
calculator that calculates the equation (7) are provided in
each deformation resistance calculator 231 included in a
combined deformation resistance calculating unit 230.
By assigning the amounts ~h 2 to ~hN of rolling reduction,
15 calculated by the calculators provided in the deformation
resistance calculator 231 according to the equation (7),
and the rolling loads P2 to PN measured by the load cells
211 to the calculators that are provided in a combined
deformation resistance calculator 233 in the combined
20 deformation resistance calculating unit 230 and calculate
the equations (2) to (4), it is possible for the combined
deformation resistance calculator 233 to calculate the
deformation resistances k2 to kN of the rolled material
rolled by rolling mills at all stages excluding the first
25 stage, that is, the second mill to mill N of the finishing
- 39 -
mill 105.
Then, the deformation resistances k2 to kN, calculated
by the combined deformation resistance calculator 233, of
the rolled material rolled by rolling mills at all stages
5 excluding the first stage, that is, the second mill to mill
N of the finishing mill 105, are applied to calculators,
provided in the combined deformation resistance calculator
233, that calculate the equation (1) to obtain the
deformation resistance X with the weight aF1 of the
10 deformation resistance at the first stage being set to 0.
With the controller and control method for a hot strip
mill, shown in FIG. 10, the load cell 211 is provided for a
rolling roll of each of the rolling mills F1 to F5 of the
finishing mill 105. The rolling loads P1 to PN of the
15 rolling mills F1 to F5, measured by the load cells 211
provided for the rolling rolls of these rolling mills, are
input to the automatic gage control unit 202 and combined
deformation resistance calculating unit 230.
The combined deformation resistance calculating unit
20 230 has one or a plurality of deformation resistance
calculators 231, which concurrently operate in parallel and
also has the same number of delay circuits 232 as the
number one less than the number of rolling mills
constituting the finishing mill 105.
25 Typically, the number of deformation resistance
- 40 -
calculators 231, each of which has a calculator that
calculates the equation (6) and another calculator that
calculates the equation (7), matches the number of rolling
mills included in the finishing mill 105. Depending on the
5 performance of a processor included in the deformation
resistance calculator 231, the number of deformation
resistance calculators 231 may be one less than the number
of rolling mills included in the finishing mill 105. In the
descriptions below, an example of a typical structure
10 having the same number of deformation resistance
calculators 231 as the number of roll pairs will be taken.
With the finishing mill 105, shown in FIG. 10, which
includes the rolling mills F1 to F5, a first deformation
resistance calculator 231 receives rolling load P1 , which is
15 applied by the rolling mill F1 and measured by the relevant
load cell 211, through the relevant delay circuit 232 and
also directly receives the rolling load P2, which is applied
by the rolling mill F2, without involving the relevant
delay circuit 232, after which the first deformation
20 resistance calculator 231 calculates the amount ~h 2 of
rolling reduction by using the calculator that is provided
in the first deformation resistance calculator 231 and
calculates the equation (7). Then the first deformation
resistance calculator 231 assigns the calculated amount ~h2
25 of rolling reduction and the measured rolling load P2 to the
- 41 -
calculators that are provided in the combined deformation
resistance calculator 233 and calculate the equation (2) to
the equation (4) to calculate the deformation resistance k2
of the rolled material for all temperature history settings
5 set on the rolled material.
The delay time in the delay circuit 232 is set so that
it is substantially equal to a time taken by the rolled
material under rolling to move from the rolling rolls of
the rolling mill Fl to the rolling rolls of the rolling
10 mill F2. The rolling load is input at intervals shorter
than intervals at which the deformation resistance is
output. Accordingly, if data processing is performed on a
plurality of rolling loads and plate thicknesses before
these deformation resistance values are obtained, the
15 precision of the deformation resistance values can be
improved.
Known digital filter processing is preferable because
it is one of the simplest data processing methods. However,
an analog integration circuit, for example, may be used.
20 Alternatively, the deformation resistance of the rolled
material may be calculated each time the rolling load is
input and data processing may be performed on a plurality
of deformation resistance values, after which a single
deformation resistance value for the temperature history
25 setting points may be output. Second to fourth deformation
5
- 42 -
resistance calculators also calculate, from inputs supplied
from the rolling loads P2 to PN, the deformation resistances
k3 to kN of the rolled material at temperature history
setting points.
The deformation resistances k1 to kN calculated by the
deformation resistance calculators 231 are input to the
combined deformation resistance calculator 233. The
combined deformation resistance calculator 233 uses the
calculator that calculates the equation (1) to calculate
10 the combined deformation resistance X at each temperature
history setting point on the rolled material from the
deformation resistances k2 to kN calculated by the
deformation resistance calculator 231. In this calculation,
the weight aF1 is assumed to be 0 and the weights an to aFs
15 are all assumed to be, for example, one-fourth.
Other various methods of setting the weights aF2 to aFs
can be considered besides this example. For example, the
weights aF2 to aFs may be proportional to the standard
deviations of the rolling loads P2 to PN. Combined
20 deformation resistance Xm calculated for each temperature
history setting point is output from the combined
deformation resistance calculator 233 to the cooling rate
correcting unit 214.
The cooling rate correcting unit 214 in this embodiment
25 functions in the same way as the cooling rate correcting
- 43 -
unit 214 in the first embodiment, except that the combined
deformation resistance X is used instead of the deformation
resistance k. Specifically, the calculator that is provided
in the cooling rate correcting unit 214 and calculates the
5 equation (8) below, calculates a correction value for the
cooling rate from the combined deformation resistance Xm for
a temperature history setting point m on the rolled
material. The cooling of the rolled material by the run-out
table 106 is controlled according to the calculated value.
10 {Equation 8}
11Cr, = e !J.S I M (X .. .,. -X,) ( 8)
!J.S I l:lCr ""'
In the equation (8) calculated by the calculator
15 provided in the cooling rate correcting unit 214, e is a
control gain and S is a typical mechanical-property value
(yield strength or tensile strength, for example) . XsET,
which is predicted from the rolling schedule settings, is a
combination of the deformation resistances of the rolled
20 material rolled by the rolling mills at all stages of the
finishing mill 105; the deformation resistances are
calculated by the calculators, provided in the combined
deformation resistance calculator 233, that calculate the
equation (1). To predict XsET' a mechanical-property
25 prediction model may be used.
- 44 -
A mechanical-property prediction model, which predicts
the deformation resistance of a rolled material rolled by
the rolling mill at each stage of the finishing mill 105
from rolling schedule settings, is disclosed in, for
5 example, J. Yanagimoto et al., Transactions of the ASME,
Vol. 120, pp. 316-322 (1998).
To predict XsETr a database including previous records
may be used. Alternatively, XsET may be predicted by using a
combination of a database including previous records and a
10 mechanical-property prediction model.
In addition, ~S/~X and ~S/~Cr may be similarly
determined by using a database including previous records
or a combination of a database including previous records
and a mechanical-property prediction model.
15 With the controller and control method for a hot strip
mill in the second embodiment of this application, the
deformation resistance of the rolled material rolled by
each rolling mill of the finishing mill 105 and the
combined deformation resistance, which is a combination of
20 the deformation resistances at all rolling mills of the
finishing mill 105, are precisely calculated as described
above. The openings of the cooling nozzles 216 in the runout
table 106 are controlled in a forward feed manner by
using the calculated combined deformation resistance.
25 Accordingly, even if the precision of the mechanical-
45 -
property prediction model is not so adequate, stable
mechanical properties can be assured without having to add
a complicated device.
With the controller and a control method for a hot
5 strip mill in the second embodiment of this application,
control of a hot strip mill can be improved.
10
The second embodiment of this application does not
require the plate thickness meters that have been needed in
the first embodiment.
In the second embodiment, therefore, even if the
precision of the mechanical-property prediction model is
not so adequate, a controller and a control method for a
hot strip mill that can provide rolled materials with
stable mechanical properties without having to add a
15 complicated device can be achieved.
The present invention can be applied to a controller
and a control method for a hot strip mill.

{Claims}
{Claim 1}
A controller for a hot strip mill that includes a
finishing mill having rolling mills at a plurality of
5 stages, each of which rolls a material to be rolled, a runout
table to cool the rolled material rolled by the
finishing mill, and a coiler to coil the rolled material
cooled by the run-out table, the controller to control the
hot strip mill according to a rolling schedule, the
10 controller for a hot strip mill comprising:
a deformation resistance calculating unit to calculate
a deformation resistance of the material to have been
rolled by at least one rolling mill at a later stage of the
rolling mills at the plurality of stages;
15 a cooling rate correcting unit to calculate a
correction value of a cooling rate at which the run-out
table cools the rolled material, according to the
deformation resistance calculated by the deformation
resistance calculating unit; and
20 a cooling control unit to control a cooling of the
rolled material by the run-out table by using the
correction value of the cooling rate calculated by the
cooling rate correcting unit.
{Claim 2}
25 The controller for a hot strip mill according to claim
- 47 -
1, wherein:
a pair of plate thickness meters to measure a thickness
of the rolled material is attached to an entrance and an
exit at a final stage of a finishing mill; and
5 the deformation resistance calculating unit calculates
the deformation resistance of the rolled material according
to thickness values of the rolled material measured by the
plate thickness meter.
{Claim 3}
10 The controller for a hot strip mill according to claim
1, wherein:
a load cell is attached to a roll of each of the
rolling mills at the plurality of stages of the finishing
mill to measure a rolling load; and
15 the deformation resistance calculating unit calculates
the deformation resistance of the rolled material according
to at least one rolling load value measured by the load
cell.
{Claim 4}
20 The controller for a hot strip mill according to claim
2 or 3, wherein the cooling control unit controls an amount
of cooling water supplied from cooling nozzles provided in
the run-out table.
{Claim 5}
25 The controller for a hot strip mill according to claim
- 48 -
2 or 3, wherein the cooling control unit controls a
conveying speed at which the rolled material is conveyed by
a conveying unit in the run-out table.
{Claim 6}
5 The controller for a hot strip mill according to claim
2 or 3, wherein:
a mechanical-property inspecting device to inspect a
mechanical property of the rolled material is provided
between the run-out table and the coiler; and
10 a mechanical property inspection value of the rolled
material inspected by the mechanical-property inspecting
device is input to the cooling rate correcting unit so that
the cooling rate at which the run-out table cools the
rolled material is controlled.
15 {Claim 7}
A control method for a hot strip mill that rolls a
material to be rolled by using rolling mills at a plurality
of stages provided in a finishing mill, cools the rolled
material rolled by the finishing mill by using a run-out
20 table, and then coils the rolled material cooled by the
run-out table by using a coiler, according to a rolling
schedule, the control method for a hot strip mill
comprising the steps of:
calculating a deformation resistance of the material to
25 have been rolled by at least one rolling mill at a later
- 49 -
stage of the rolling mills at the plurality of stages;
calculating a correction value of a cooling rate at
which the run-out table to cool the rolled material
according to the calculated deformation resistance; and
5 controlling the cooling rate of the rolled material,
which is performed by the run-out table, by using the
calculated correction value of the cooling rate.
{Claim 8}
The control method for a hot strip mill according to
10 claim 7, wherein the controlling of the cooling of the
rolled material by the run-out table is performed to
control an amount of cooling water supplied from cooling
nozzles provided in the run-out table.
{Claim 9}
15 The control method for a hot strip mill according to
claim 8, wherein the controlling of the cooling of the
rolled material by the run-out table is achieved to control
a conveying speed of the rolled material by the run-out
table.
20 the controlling of the cooling of the rolled material
is performed to control a conveying speed of the run-out
table to convey the rolled material.
{Claim 10}
The control method for a hot strip mill according to
25 claim 7, wherein a mechanical property of the rolled
- 50 -
material is inspected between the run-out table and the
coiler to obtain a mechanical-property inspection result of
the rolled material, and
the correction value of the cooling rate is corrected
5 by using the mechanical-property inspection result of the
rolled material for control purposes.