Note: Descriptions are shown in the official language in which they were submitted.
CA 02332953 2000-11-22
METHOD OF WINDING STRIPS
TECHNICAL FIELD
The present invention relates to a strip coiling method
in which a strip sent from a hot rolling mill is cut to a
predetermined length by a strip shear and the cut strip is
coiled by a mandrel of a coiler via coiling pinch rolls disposed
on the delivery side of a strip shear.
BACKGROUND ART
Figure 16 shows a general arrangement of a general
continuous hot rolling line. Conventionally, changeover of
coilers has been effected as described below when a strip cut
to a predetermined length by a strip shear is coiled by the
preceding material coiler and the following material coiler
alternately. As an, example, a case where coilers are changed
over from the preceding material coiler a to the following
material coiler b will be explained. A strip d sent from a
finishing mill c is cut to a predetermined length by a strip
shear a disposed on the downstream side of the finishing mill
c to divide the strip d into the preceding strip dl and the
following strip d2. Then, the preceding strip dl and the
following strip d2 are coiled by the preceding material coiler
a and the following material coiler b, respectively.
While the preceding strip dl is coiled by the preceding
material coiler a, a lower pinch roll g of a coiling pinch
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roll f disposed on the delivery side of the strip shear a is
moved to the upstream side. Thereby, the offset angle of the
coiling pinch roll f is changed to change the transfer direction
of the strip from the preceding material coiler a to the
following material coiler b. Immediately after the preceding
strip dl has gone through the coiling pinch roll f , the following
strip d2 is introduced to the following material coiler b to
coil the following strip dz by using the following material
coiler b. At this time, a triangular gate j prevents the
following strip d2 from going to the side of the preceding
material coiler a.
In recent years, as coiling equipment for continuous hot
rolling, a Carrousel reel type coiler has been used.
Figure 20 schematically shows an example of a continuous
hot rolling line in which a Carrousel reel type coiler is used.
The Carrousel reel type coiler has a first and second
mandrels 1 and.2. The first and second mandrels 1 and 2 are
revolvably disposed at an interval in the circumferential
direction on a revolution path 3 so that when one mandrel is
located at a coiling start position, the other mandrel is
located at a coiling finish position. For example, when the
first mandrel 1 is located at the coiling start position, the
preceding strip S1 sent from a finishing mill 4 is coiled by
a predetermined amount by the first mandrel 1, and then the
first mandrel 1 is revolved to the coiling finish position
while coiling the preceding strip S1. In this state, the tail
end of the preceding strip S1 is cut by a strip shear 5, and
the leading end of the following strip S2 is coiled by the
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second mandrel 2 located at the coiling start position. After
the coiling of the strip S1 is finished at the coiling finish
position, the coil of the coiled preceding strip S1 is delivered
from the mandrel 1, and the mandrel 1 waits until the leading
end of a strip following the following strip S2 is coiled around
the mandrel 1.
Above and below an upstream pass line P1 directed toward
the mandrel at the coiling start position (the first mandrel
1 in the figure), upstream sheet-running guides 6 to 13 for
guiding the leading end of the strip S toward the upstream
mandrel are disposed. Above and below a downstream pass line
P2 that branches off the upstream pass line P1 and is directed
toward the mandrel at the coiling finish pasition (the second
mandrel 2 in the f figure ) , downstream sheet-running guides 13
to 15 and a guide roller 20 for guiding the strip S coiled
by the mandrel at the coiling finish position are disposed.
The sheet-running guide 13 is disposed at a position where
the downstream pass line P2 branches off the upstream pass
line P1 so as to be used as both an upper guide for the upstream
pass line P1 and a lower guide for the downstream pass line
P2.
In Figure 20, reference numeral 16 denotes pinch rolls
disposed on the pass line P1 between the finishing mill 4 and
the strip shear 5, 17 denotes coiling pinch rolls disposed
on the pass line P1 on the delivery side of the strip shear
5, 18 denotes upstream wrapper rolls disposed movably so as
to come close to and go apart from the outer peripheral surface
of the mandrel at the coiling start position, and 19 denotes
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downstream wrapper rolls disposed movably so as to come close
to and go apart from the outer peripheral surface of the mandrel
at the coiling finish position. The upstream and downstream
wrapper rolls 18 and 19 and the upper guide 14 of the downstream
sheet-running guide is movable so as to be separated from the
revolution path 3 to allow the revolution of the first and
second mandrels 1 and 2 when the mandrels 1 and 2 revolves
on the revolution path 3.
In the conventional strip coiling method on the
above-described general hot rolling line, however, when the
strip is cut by the strip shear e, a tension given to the strip
by the finishing mill c and the preceding material coiler a
is released, so that the tail end of the preceding strip is
undesirably oversupplied on the delivery side of the coiling
pinch roll f as shown in Figure 17. In the worst case, there
arises a problem in that the tail end of the preceding strip
is caught by the triangular gate j, resulting in damage to
the sheet. Further, there arises a problem in that after the
tail end of the preceding strip S1 goes through the coiling
pinch roll f, the circumferential speed of the coiling pinch
roll f temporarily becomes lower than the transfer speed of
the following strip S2, so that the leading end of the following
strip S2 is oversupplied on the entrance side of the coiling
pinch roll f.
On the other hand, even in the conventional strip coiling
method on the hot rolling line on which the Carrousel reel
type coiler is provided, if the preceding strip S1 is cut by
the strip shear 5 while being coiled by the mandrel at the
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coiling f finish position ( the second mandrel 2 ) , a tension given
to the strip by the finishing mill 4 and the downstream mandrel
is released, so that the preceding strip S1 is undesirably
oversupplied on the delivery side of the coiling pinch rolls
17 disposed on the delivery side of the strip shear as shown
in Figure 21. In the worst case, there arises a problem in
that the preceding strip S1 is caught by the tip end of the
downstream sheet-running guide 13 located at a position where
the downstream pass line P2 branches off the upstream pass
line P1, resulting in damage to the sheet. Further, there
arises a problem in that after the tail end of the preceding
strip S1 goes through the coiling pinch rolls 17, the
circumferential speedof the coilingpinch rolls 17 temporarily
becomes lower than the transfer speed of the following strip
SZ, .so that the leading end of the following strip Sz is
oversupplied on the entrance side of the coiling pinch rolls
17.
The present invention has been achieved to solve the above
problems, and accordingly an object thereof is to provide a
strip coiling method in which after the tail end of a strip
coiled by a mandrel is cut by a strip shear, the strip can
be prevented from being oversupplied on the delivery side of
coiling pinch rolls disposed on the delivery side of the strip
shear, and the leading end of the following strip can be
prevented from being oversupplied on the entrance side of the
coiling pinch rolls.
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DISCLOSURE OF THE INVENTION
According to the present invention, there is provided
a strip coiling method in which a strip sent from a rolling
mill is cut to a predetermined length by a strip shear, and
a cut strip is coiled alternately by a mandrel of an
upstream coiler and a mandrel of a downstream coiler via
first coiling pinch rolls disposed on a delivery side of
said strip shear, characterized in that a relationship
between a target speed Vpl of second coiling pinch rolls
after a tail end of the strip coiled by a downstream
mandrel via second coiling pinch rolls disposed on an
entrance side of said downstream mandrel is cut by said
strip shear a target speed Vp2 of said first coiling pinch
rolls, a target sheet speed VS of a material following
immediately after a cutting operation, and a preset coiling
speed Vm of said downstream mandrel is set so that Vm > Vpl
> vp2 > Vs.
In the present invention, a force pulling the strip between
the strip shear and the coiling pinch rolls toward the
downstream side is applied to the strip having been cut, and
a force pulling the strip between the coiling pinch rolls and
the mandrel toward the downstream side is also applied to the
strip. Therefore, the preceding strip can be prevented from
being oversupplied on the delivery side of the coiling pinch
rolls. Moreover, since the circumferential speed of the
coiling pinch rolls is higher than the transfer speed of the
following material immediately after the cutting operation,
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the leading end of the following material can be prevented
from being oversupplied on the entrance side of the coiling
pinch rolls.
Preferably, in this case, the aforementioned mandrel
is a mandrel of a Carrousel reel type toiler, and the
relationship between a preset coiling speed Vm of the
mandrel after the tail end of the strip coiled by the
mandrel via the coiling pinch rolls, the target speed Vp of
the coiling pinch rolls at the time of the cutting
operation, and the sheet speed Vs of the following material
immediately after the cutting operation is set so that Vm >
Vp > Vs. Thereby, the preceding strip can be prevented from
being caught by the tip end of a sheet-running guide
located at a position where a pass line directed to the
mandrel at the coiling start position branches off a pass
line directed to the mandrel at the coiling finish
position.
Also, preferably, in a strip coiling method in which
a trip sent from a rolling mill is cut to a predetermined
length by a strip shear, and the cut strip is coiled
alternately by a mandrel of an upstream toiler and a
mandrel of a downstream toiler via first coiling pinch
rolls disposed on the delivery side of the strip shear, the
relationship between the target speed Vpl of the second
coiling pinch rolls after the tail end of the trip coiled
by a downstream mandrel via second coiling pinch rolls
disposed on the entrance side of the downstream mandrel is
cut by the strip shear, the target speed Vp2 of the (first
coiling pinch rolls, the target sheet speed Vs of the
following material immediately after the cutting operation,
and the preset coiling speed Vm of the downstream mandrel
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is set so that Vm > Vpl > Vp2 > Vs. Thereby,,damage to the
strip caused by the tail end of the preceding strip being
caught by a triangular gate can be prevented.
In this case, after the lower pinch roll of the first
coiling pinch rolls is offset and before the tail end of the
strip coiled by the downstream mandrel via the second pinch
rolls is cut, the strip is pressed by the upper pinch roll
of the first coiling pinch rolls in a state in which the speed
of the lower pinch roll is made lower than the target sheet
speed Vs of the following material until the actual torque
value of the lower pinch roll becomes the preset value, and
the pressing force at this time is made the preset pressing
force of the offset upper pinch roll applied to the strip,
by which the tail end of the strip coiled by the downstream
mandrel can be held properly by the f first coiling pinch rolls .
Also, preferably before the strip cut by the strip
shear is continuously coiled by the mandrel via the coiling
pinch rolls disposed on the delivery side of the strip
shear, the pressing force of the coiling pinch rolls is set
at a value not lower than a value P determined by P
2F(~u/~x) + 4(Mg/~x)((la/RL) + (lb/RU)}. Thereby, the
pressing force of the upper pinch roll can be set at the
optimum value. Therefore, the breakage of tail end of a
thin strip, improper introduction of a thick strip to the
toiler, or the like can be prevented.
In this case, after the pressing force is set, by
keeping a gap of the coiling pinch rolls for the time from
when the preceding strip comes off from the pinch rolls to
when the following strip is bitten by the pinch rolls, the
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defective biting of the following strip by the coiling
pinch rolls and other troubles can be prevented.
Further, preferably, before the strip coiling
operation performed by the mandrel is finished, the strip
coiling control carried out by the mandrel is changed over
from torque control to rotational speed control, and
thereafter a pressing roll is pressed on the strip to be
coiled into a coil shape to stop the rotation of the
mandrel. Thereby, the decrease in speed of coil caused by
the contact of the pressing roll can be prevented, so that
the occurrence of defective coiling such as loosened coil
outer and telescoping can be avoided, and the rotation of
coil can be stopped in a short time because the pressing
roll has a braking force when the rotation of coil is
stopped after the strip coiling operation is finished.
Further, preferably, before the strip coiling
operation performed by the mandrel is finished, the torque
control of strip is carried out by the mandrel to increase
the tension of strip, and thereafter the pressing roll is
pressed on the strip to be coiled into a coil shape to stop
the rotation of the mandrel. Thereby, the decrease in speed
of coil caused by the contact of the pressing roll can be
prevented, so that the occurrence of defective coiling such
as loosened coil outer and telescoping can be avoided, and
the rotation of coil can be stopped in a short time because
the pressing roll has a braking force when the rotation of
coil is stopped after the strip coiling operation is
finished.
Further, preferably, a deceleration-side torque limit
of a driving unit for the coiling pinch rolls is set so
that the circumferential speed of the coiling pinch rolls
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CA 02332953 2004-O1-15
is higher than the transfer speed of the following material
when the leading end of the following material is bitten by
the coiling pinch rolls disposed on the delivery side of
the strip shear after the strip is cut by the strip shear.
Thereby, even in the case of a strip having a great sheet
9a
thickness and high
CA 02332953 2000-11-22
bending rigidity, the following material can be prevented from
being oversupplied on the entrance side of the coiling pinch
rolls.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an explanatory view for illustrating a strip
coiling method in accordance with a first embodiment of the
present invention;
Figure 2 is an explanatory view for illustrating one
example of an operation pattern ( speed pattern ) of each part
at the time of cutting and coiling of a strip;
Figure 3 is an explanatory view for illustrating a state
of the preceding strip and the following strip in cutting and
after cutting of a strip;
Figure 4 is an explanatory view for illustrating a strip
coiling method in accordance with a second embodiment of the
present invention;
Figure 5 is a schematic perspective view of a driving
mechanism for coiling pinch rolls on the delivery side of a
strip shear, the view being used for illustrating a strip
coiling method in accordance with a third embodiment of the
present invention;
Figure 6 is a graph showing a time change of the rotational
speed and load torque of the coiling pinch roll on the delivery
side of the strip shear in the case where a torque limit on
a deceleration side is set;
Figure 7 is a graph showing a time change of the rotational
speed and load torque of the coiling pinch roll on the delivery
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side of the strip shear in a case where a torque limit on the
deceleration side is not set;
Figure 8 is a view for illustrating a fourth embodiment
of the present invention, showing a dynamic model of a coiling;
Figure 9 is a graph showing a measurement result of the
speed and torque of a mandrel at a stage at which coiling is
finished;
Figure 10 is a graph showing a measurement result of the
speed and torque of a mandrel at a stage at which coiling is
finished;
Figure 11 is a graph showing a relationship between the
pressing force and pressing amount on a strip caused by an
upper pinch roll of the coiling pinch rolls, the view being
used for illustrating a fifth embodiment of the present
invention;
Figure 12 is a time chart of the pressing force on a strip
caused by the upper pinch roll of the coiling pinch rolls and
a cylinder position reference;
Figure 13 is a time chart of the pressing force on a strip
caused by the upper pinch roll of the coiling pinch rolls and
a cylinder position reference;
Figure 14 is a side view of the coiling pinch rolls at
the time of offset;
Figure 15 is a side view showing a case where a strip
is pressed down by the upper pinch roll of the coiling pinch
rolls;
Figure 16 is a general schematic view of a general
continuous hot rolling line;
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Figure 17 is an explanatory view for illustrating
oversupply of the strip tail end at the delivery side of the
coiling pinch rolls;
Figure 18 is an explanatory view for illustrating a problem
arising when the pressing force on a strip caused by the upper
pinch roll of the coiling pinch rolls is weak;
Figure 19 is an explanatory view for illustrating
oversupply of the following strip leading end on the entrance
side of the coiling pinch rolls;
Figure 20 is a view schematically showing a Carrousel
reel type coiler; and
Figure 21 is an explanatory view for illustrating
oversupply of the strip tail end on the delivery side of the
coiling pinch rolls.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invent ion will now be described
with reference to the accompanying drawings.
First, a strip coiling method on a general hot rolling
line, which is a first embodiment of the present invention,
will be explained with reference to Figures 1 to 3.
Figure 1 schematically shows a portion of a continuous
hot rolling line on the downstream side of a strip shear. In
this embodiment, a case where a strip sent from a finishing
mill (not shown) is cut to a predetermined length by using
a strip shear 102, and the preceding strip S1 is coiled by
a mandrel 107 of a downstream coiler 104 via downstream coiling
pinch rolls (second coiling pinch rolls) 103, whereas the
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following strip S2 is coiled by a mandrel 107 of an upstream
coiler 101 via upstream coiling pinch rolls (first coiling
pinch rolls) 105 disposed on the delivery side of the strip
shear 102 is explained by way of example.
Both of the downstream coiler 104 and the upstream coiler
101 are provided with a torque detector 109 for detecting a
torque of a motor 108 for driving the mandrel 107, a torque
controller 110 for keeping the tension of a strip constant
by feedback controlling the motor 108 so that the detected
torque value obtained by the torque detector 109 coincides
with the target torque value, a pilot generator ( PLG ) 111 for
detecting the rotational state of the motor 108, and a speed
controller 112 for feedback controlling the motor 108 so that
the speed detection value obtained by the pilot generator 111
coincides with the target speed, as means for pulling the strip
coiled around the mandrel 107 with a predetermined coiling
tension.
Also, the downstream coiling pinch rolls 103 are provided
with a torque detector 114 for detecting a torque of a motor
113 for a lower pinch roll 103a, a pilot generator (PLG) 115
for detecting the rotational state of the motor 113, and a
speed controller 116 for feedback controlling the motor 113
so that the speed detection value obtained by the pilot
generator 115 coincides with the target speed VP1.
Further, the upstream coiling pinch rolls 105 are also
provided with a torque detector 118 for detecting a torque
of a motor 117 for a lower pinch roll 105x, a pilot generator
(PLG) 119 for detecting the rotational state of the motor 117,
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and a speed controller 120 for feedback controlling the motor
117 so that the speed detection value obtained by the pilot
generator 119 coincides with the target value VpZ. The lower
pinch roll 105a can be moved to the upstream side along a pass
line when the offset angle is changed to effect changeover
from the downstream coiler 104 to the upstream coiler 101,
and the upper pinch roll 105b can press a strip via a hydraulic
cylinder 121 to push down the strip. Also, the upper pinch
roll 105b is provided with a pressing force detector 122 for
detecting a pressing force applied to the upper pinch roll
105b.
The pressing force applied to the upper pinch roll 105b
via the hydraulic cylinder 121 is determined by feedback
controlling a servo valve 127 for switching oil supplied from
a hydraulic pump 126 to the hydraulic cylinder 121 by a pinch
roll pressing force controller 125 so that the detected
pressing force obtained by the pressing force detector 122
coincides with the preset pressing force set beforehand by
a compensation pressingforcesetter124. The pressing force
control for the pinch roll may be carried out by using air.
Next, a case where changeover from the downstream coiler
104 to the upstream coiler 101 is effected will be explained.
First, while the preceding strip S1 is coiled by the mandrel
107 of the downstream coiler 104, the lower pinch roll 105a
of the upstream coiling pinch rolls 105 is moved to the upstream
side along the pass line by a hydraulic cylinder (not shown) .
Thereby, the offset angle of the upstream coiling pinch rolls
105 is changed to change the transfer direction of a strip
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from the downstream coiler 104 to the upstream coiler 101 so
that immediately after the preceding strip S1 has gone through
the upstream coiling pinch rolls 105, the following strip SZ
can be introduced to the upstream coiler 101. In Figure 1,
reference numeral 128 denotes a triangular gate for preventing
the leading end of the following strip S2 from going to the
side of the downstream coiler 4.
When a strip is cut by the strip shear 102 in a state
in which the preceding strip S1 is coiled around the mandrel
107 of the downstream coiler 104, in the present invention,
when the cutting operation is performed, the coiling speed
Vm of the preceding strip S1 set by the speed controller 112
for the coiler 104 , the target speed Vp2 for the speed controller
120 on the side of the upstream coiling pinch rolls 105, the
target speed Vpl for the speed controller 116 on the side of
the downstream coiling pinch rolls 103, and the transfer speed
V9 of the following strip Sz immediately after the cutting
operation (=transfer speed of the strip just before the cutting
operation ) are set by a host computer ( not shown ) so that Vm
2 O J Vpl 7 Vp2 J Vg .
The following is the detailed description.
When the cutting operation of strip performed by the strip
shear 102 is finished in the state in which the preceding strip
S1 is coiled around the mandrel 107 of the downstream coiler
104, a cutting finish signal for telling that the cutting
operation has finished is sent from the strip shear 102 or
the host computer to the speed controller 112 for the downstream
coiler 104 , the speed controller 116 for the downstream coiling
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pinch rolls 103, and the speed controller 120 for the upstream
coiling pinch rolls 105.
If the cutting finish signal is sent at time to, the mandrel
107 of the downstream coiler 104 is changed over from tension
control by the torque controller 110 to speed control by the
speed controller 112 at timing of the time to . At the same
time, the speed controller 112 starts acceleration of coiling
speed of strip at the timing of the time to, and also, as indicated
by the curve I in Figure 2, speed control is started so that
the final speed Vm after the completion of acceleration with
the acceleration rate of x is expressed by the following
equation (1).
Vm = V9 x A ... (1)
where, Vg is the transfer speed of strip just before the cutting
operation, and A is a lead coefficient (a coefficient for
determining the final speed).
The state of the preceding strip S1 and the following
strip S2 at the time to is as shown in Figure 3(A).
During a delay time T1 from the time t0 of the acceleration
start to time tl, the speed of the downstream coiling pinch
rolls 103 is kept at the strip speed Vg just before the cutting
operation by the speed controller 116 for the downstream
coiling pinch rolls 103 . However, when the time tl is reached,
the speed controller 116 starts the increase in speed of the
downstream coiling pinch rolls 103, and also, as indicated
by the curve II in Figure 2 , speed control is started so that
the final speed Vpl after the completion of acceleration with
the acceleration rate of Y is expressed by the following
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equation (2). The time counting of the delay time T1 is
performed by a timer provided on the speed controller 116 or
the host computer.
Vpl = Vg x B . . . ( 2 )
where B is a lead coefficient, and the relationship between
the lead coefficients A and B is A > B.
Further, during a delay time T2 from the time to of the
acceleration start to time t2, the speed of the upstream coiling
pinch rolls 105 is kept at the strip speed Vs just before the
cutting operation by the speed controller 120 for the upstream
coiling pinch rolls I05 . However, when the time t2 is reached,
the speed controller 120 starts the increase in speed of the
upstream coiling pinch rolls 105, and also, as indicated by
the curve III in Figure 2, speed control is started so that
the final speed VPZ after the completion of acceleration with
the acceleration rate of Z is expressed by the following
equation (3). The time counting of the delay time T2 is
performed by a timer provided on the speed controller 120 or
the host computer ( not shown ) , and the relationship between
the delay times T1 and T2 is T1 < T2.
Vp2 = Vg x C . . . ( 3 )
where C is a lead coefficient, and the relationship between
the lead coefficients B and C is B > C.
Thereafter, time t3 is reached, as shown in Figure 3 ( B ) ,
the tail end of the preceding strip S1 and the leading end
of the following strip S2 are located between the upstream
coiling pinch rolls 105 and the strip shear 102, and the tail
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end of the preceding strip S1 is sufficiently separated from
the leading end of the following strip S2.
Further, as shown in Figure 2, time t4 is reached, the
coiling speed of the mandrel 107 of the downstream coiler 104
becomes the final speed Vm. When time is is reached, the speed
of the downstream coiling pinch rolls 103 becomes the final
speed Vpl. When time t6 is reached, the speed of the upstream
coiling pinch rolls 105 becomes the final speed VP2.
When time t, is reached, as shown in Figure 3(C), the
tail end of the preceding strip S1 is located between the
downstream pinch rolls 103 and the upstream coiling pinch rolls
105, and the leading end of the following strip S2 reaches
the upstream coiling pinch rolls 105.
Also, a speed ratio x of the final speed Vm to the final
speed Vpl and a speed ratio y of the final speed Vpl to the
final speed VP2 become as expressed by the following equations .
x = (A'Vm)/(B'Vpl) - A/B ... (5)
y = (B~Vpl)/(C~VPZ) - B/C ... (6)
Therefore, for example, assuming that the lead
coefficients A, B and C are A = 1.5, B = 1.1, and C = 1.05,
the speed ratios x and y are as follows.
Speed ratio x = (1.5/1.1) - 1.045 ... (7A)
Speed ratio y = (1.1/1.05) - 1.048 ... (7B)
The lead coefficients A, B and C are preferably higher
from the viewpoint of the coiling property of strip on the
downstream coiler 104. However, when the lead coefficients
are high, deceleration energy at the time of coiling is applied
to the strip, so that an excessive tension is produced on the
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strip after finish rolling, by which the width of strip
decreases, presenting a quality problem. Therefore, the lead
coefficients are determined empirically with an emphasis on
the coiling property according to the sheet thickness.
Further, it is preferable that for the speed ratio in
the acceleration process of the downstream coiler 104 and the
downstream coiling pinch ro11s103,the above-described speed
ratio x be ensured, and for the speed ratio in the acceleration
process of the downstream coiling pinch rolls 103 and the
upstream coiling pinch rolls 105, the above-described speed
ratio y be ensured.
To ensure the above-described speed ratio x for the speed
ratio in the acceleration process of the downstream coiler
104 and the downstream coiling pinch rolls 103, the following
equation holds by using Equation (5).
(Vs + X~T1)/Vg = A/B ... (8)
where X is the acceleration rate of the downstream coiler 104,
and T1 is the delay time shown in Figure 2.
By transforming Equation (8), the delay time T1 is
expressed by the following equation. The delay time T1 may
be set as given by the following equation.
T1 = (Ve/X)(A/B-1) ... (9)
Likewise, to ensure the above-described speed ratio y
for the speed ratio in the acceleration process of the
downstream coiling pinch rolls 103 and the upstream coiling
pinch rolls 105, the following equation holds.
T3 = (VS/Y)(B/C-1) ... (10)
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where Y is the acceleration rate of the coiling pinch
rolls 103, and T3 is time from the acceleration start of the
downstream coiling pinch rolls 103 to the acceleration start
of the upstream coiling pinch rolls 105 as shown in Figure
2. Therefore, the delay time T2 shown in Figure 2 may be set
so that T2 = (T1 + T3).
Further, it is necessary that the acceleration of the
downstream coiler 104, the downstream coiling pinch rolls 103,
and the upstream coiling pinch rolls 105 should be finished
before the leading end of the following strip S2 having been
cut reaches the upstream coiling pinch rolls 5 . Specif ically,
the relationship between the times tq, t5, t6 and t~ shown in
Figure 2 must meet the condition given by the following
equation.
t~>tq, t7>t5, t7>t6 . . . ( 11 )
Next, one example of the above condition will be explained
in detail.
For example, assuming that the distance between the
upstream coiling pinch rolls 105 and the strip shear 102 is
10 [m], and the speed Vg of strip just before the cutting
operation (= the transfer speed Vs of the following strip S2
immediately after the cutting operation) is 900 [mpm], the
time taken for the following strip SZ having been cut to reach
the upstream coiling pinch rolls 105 is 10 m/ ( 900 mpm/60 sec )
- 0.67 [sec].
Also, assuming that the lead coefficient A is 1.15, the
final speed Vm of the mandrel 107 of the downstream coiler
104 is Vm = 900 X 1 .15 = 1035 [mpm] . Also, since during 0. 67
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CA 02332953 2000-11-22
seconds, the speed increases from 900 [mpm] to 1035 [mpm],
the acceleration rate X becomes ( 1035-900 ) /0 . 67 = 201 [mpm/s ] .
By performing the speed setting in this manner, because
the relationship of Vp2>Vs holds between the strip shear 102
and the coiling pinch rolls 105, a pulling force directed to
the downstream side is applied to the strip S1 having been
cut by the coiling pinch rolls 105. Also, because the
relationship Of Vpl>Vp2 holds between the coiling pinch rolls
105 and the coiling pinch rolls 103, a pulling force directed
to the downstream side is applied to the strip S1 by the coiling
pinch rolls 103. Further, because the relationship of Vm>Vpl
holds between the coiling pinch rolls 103 and the mandrel 107
of the downstream coiler 104, a pulling force directed to the
downstream side is applied to the strip S1 by the mandrel 107.
Therefore, the tail end of the preceding strip S1 is
prevented from being oversupplied on the delivery side of the
coiling pinch rolls 105, that is, between the coiler 104 and
the downstream coiling pinch rolls 103 and between the
downstream coiling pinch rolls 103 and the upstream coiling
pinch rolls 105. As a result, damage to the strip caused by
the tail end of the preceding strip S1 being caught by a
triangular gate 26 can be prevented. Further, because the
feed speed of the coiling pinch rolls 105 is set so as to be
higher than the transfer speed of the following strip SZ as
indicated by Vp2>Vg, the leading end of the following strip
S2 can be prevented from being oversupplied on the entrance
side of the coiling pinch rolls 105.
- 21 -
CA 02332953 2000-11-22
If the pressing force on the strip caused by the upper
pinch roll 105b is weak when the offset angle of the upstream
coiling pinch rolls 105 is changed, the tail end of the strip
coiled by the mandrel 107 of the downstream coiler 4 cannot
be held sufficiently by the upstream coiling pinch rolls 105,
so that the tail end of the strip is not pressed sufficiently
by the upstream coiling pinch rolls 105 and undesirably slips .
As a result, as shown in Figure 18, the tail end of the strip
is oversupplied between the downstream coiler I04 and the
upstream coiler 101. Therefore, in this embodiment, a
pressing force that can surely hold the strip by using the
upstream coiling pinch rolls 105 is set, by which before the
cutting operation is performed, the preceding strip S1 is surely
held by the upstream coiling pinch rolls 105.
The following is the detailed description.
In the case where the pressing force detector I22 for
the upstream .coiling pinch rolls 105 is provided on the side
of the upper pinch roll 105b as shown in Figure 1, when the
offset angle of the upstream coiling pinch rolls 105 is changed
in the state in which the preceding strip S1 is coiled around
the mandrel 107 of the downstream coiler 104, it is necessary
that the preceding strip S1 should be pressed down from the
pass line according to the offset amount of the lower pinch
roll 105a, and the strip S1 should be held between the upper
and lower pinch rolls 105b and 105a. In the example shown
in Figure 1, the upper pinch roll 105b of the upstream coiling
pinch rolls 105 presses the preceding strip S1 via the hydraulic
- 22 -
CA 02332953 2000-11-22
cylinder 121, and the pressing force at this time is set by
the compensation pressing force setter 124.
The compensation pressing force setter 124 sets a
compensation pressing forcefor surely holding the preceding
strip S1 between the upper pinch roll 105b and the lower pinch
roll 105a of the upstream coiling pinch rolls 105. After the
offset angle of the upstreamcoiling pinch rolls 105 is changed,
at proper timing during the time until the tail end of the
preceding strip S1 is cut by the strip shear 102, the speed
controller 120 is controlled so that the speed reference of
the lower pinch roll 105a is slightly lower than the sheet
speed VS of the preceding strip S1. In this state, the servo
valve 127 is feedback controlled via the pinch roll pressing
force controller 125 until the torque value T detected by the
torque detector 118 becomes the preset value To, and the strip
S1 is pressed continuously.
In the case where the speed reference of the lower pinch
roll 105a is made slightly lower than the sheet speed Vs of
the preceding strip S1, unless the preceding strip S1 is pressed
with a desirable pressing force, a load is scarcely applied
to the lower pinch roll 105a, so that the torque of the lower
pinch roll 105a does not increase. If the preceding strip
S1 is pressed with the desirable pressing force, the preceding
strip S1 slips with respect to the lower pinch roll 105a, so
that the load (torque) increases. By utilizing this, the
compensation pressing force ( in this case, the force that holds
the preceding strip S1 between the upper pinch roll 105b and
the lower pinch roll 105a) Ps (N) is estimated.
- 23 -
CA 02332953 2000-11-22
Taking the speed difference between the preceding strip
S1 and the lower pinch roll 105a as 0v (mpm) , the coefficient
of friction between the preceding strip S1 and the lower pinch
roll 105a, which changes according to the speed difference
Av, as ~,2 (w) , the actual torque of the lower pinch roll 105a
as T (N~m), and the radius of the lower pinch roll 105a as
r (m), the force Ps (N) for holding the preceding strip S1
between the upper pinch roll 105b and the lower pinch roll
105a is expressed as
Pg = T/[r~~u2(Ov)] ... (12)
Therefore, if the value of ~,z at the time of a predetermined
speed difference Ov is determined beforehand from Equation
(12), the compensation pressing force P$ can be determined
by measuring the actual torque T of the lower pinch roll.
In the pressing force setting method by using the
compensation pressing force setter 124, even if the strip is
cut by the strip shear 102, the compensation pressing force
Pgl that can hold the strip S1 between the upstream coiling
pinch rolls 105 to a degree such that the tail end of the
preceding strip S1 does not wrinkle is determined beforehand,
and when before the cutting operation is performed, the speed
of the lower pinch roll 105a is set so as to be lower than
the sheet speed V9 of the strip S1 by the predetermined speed
Ov, the torque value To of the lower pinch roll 105a at the
time when the compensation pressing force is PB1 is preset
in the compensation pressing force setter 124. Before the
cutting operation is performed, the compensation pressing
force setter 124 sends a signal to the speed controller 120
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CA 02332953 2000-11-22
so that the speed of the lower pinch roll 105a is lower than
the sheet speed Vs by Ov, and then sends a signal to the pinch
roll pressing force controller 125 so that the strip S1 is
pressed by the upper pinch roll 105b while measuring the actual
torque T of the lower pinch roll 105a by using the torque detector
118. The actual torque T is made a value not lower than T0.
Therefore, the strip S1 can be held surely between the upstream
coiling pinch rolls 105. In this state, the tail end of the
preceding strip S1 is cut by the strip shear 102.
When the compensation pressing force setter 124 is used
in this manner, since the pressing force is set considering
the actual force applied to the preceding strip S1, the
preceding strip S1 can be held surely between the upper pinch
roll 105b and the lower pinch roll 105a of the upstream coiling
pinch rolls 105 , whereby the occurrence of slip can be prevented .
As a result, the tail end of the preceding strip S1 can be
prevented satisfactorily from being oversupplied between the
downstream coiler 1 and the upstream coiler 6.
The control for ensuring the speed relationship of Vm
> VP1 > Vp2 > Vs by using the host computer and the pressing
of the preceding strip S1 by using the compensation pressing
force setter 24 are carried out until the tail end of the
preceding strip S1 is coiled around the mandrel 107 of the
downstream coiler 104.
Also, in this embodiment, the case where a strip is coiled
by the mandrel 107 of the downstream coiler 104 has been
described. However, the present invention can be applied to
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CA 02332953 2000-11-22
the case where a strip is coiled by the mandrel 107 of the
upstream coiler 101.
Next, a strip coiling method on a hot rolling line on
which a Carrousel reel type coiler is arranged, which is a
second embodiment of the present invention, will be described
with reference to Figure 4. Both of the Carrousel reel type
coiler and the continuous hot rolling line have the same basic
configuration as that of the conventional example (Figures
20 and 21 ) described before. Therefore, the same reference
numerals are applied to the same elements, and the duplicated
explanation is omitted.
Figure 4 schematically shows a portion of a continuous
hot rolling line on the downstream side of a strip shear. In
this embodiment, a case where a strip sent from a finishing
mill (not shown) is cut to a predetermined length by using
a strip shear 5, and the preceding strip S1 is coiled by a
mandrel at a coiling finish position (a second mandrel 2 in
the figure) via coiling pinch rolls 17 disposed on the delivery
side of the strip shear 5, whereas the following strip SZ is
coiled by a mandrel at a coiling start position ( a first mandrel
1 in the drawing) via coiling pinch rolls 17 is explained by
way of example.
The second mandrel 2 located at the co fling finish pos ition
is provided with a torque detector 34 for detecting a torque
of a motor 32 for driving the mandrel 2, a torque controller
36 for keeping the tension of a strip constant by feedback
controlling the motor 32 so that the detected torque value
obtained by the torque detector 34 coincides with the target
- 26 -
CA 02332953 2000-11-22
torque value, a pilot generator (PLG) 38 for detecting the
rotational state of the motor 32, and a speed controller 40
for feedback controlling the motor 32 so that the speed
detection value obtained by the pilot generator 38 coincides
with the target speed, as means for pulling a strip coiled
around the mandrel 2 with a predetermined coiling tension.
The first mandrel 1 located at the coiling start position
is also provided with a torque detector 33 for detecting a
torque of a motor 31 for driving the mandrel 1, a torque
controller 35 for keeping the tension of the strip constant
by feedback controlling the motor 31 so that the detected torque
value obtained by the torque detector 33 coincides with the
target torque value, a pilot generator (PLG) 37 for detecting
the rotational state of the motor 31, and a speed controller
39 for feedback controlling the motor 31 so that the speed
detection value obtained by the pilot generator 37 coincides
with the target speed, as means for pulling a strip coiled
around the mandrel 1 with a predetermined coiling tension.
Further, the coiling pinch rolls 17 have a pilot generator
(PLG) 42 for detecting the rotational state of a motor 41 for
a lower pinch roll 17a, and a speed controller 43 for feedback
controlling the motor 41 so that the speed detection value
obtained by the pilot generator 42 coincides with the target
speed Vp. An upper pinch roll 17b of the coiling pinch rolls
17 is capable of pressing a strip via a hydraulic cylinder
44 for pressing the strip toward the lower pinch roll 17a.
Next, a case where changeover is effected from the mandrel
at the coiling finish position (the second mandrel 2 in the
- 27 -
CA 02332953 2000-11-22
figure) to the mandrel at the coiling start position (the first
mandrel 1 in the figure) will be explained. First, the upper
pinch roll 17b of the coiling pinch rolls 17 is pushed down
by the hydraulic cylinder 44 so that the preceding strip S1
is held between the upper pinch roll 17b and the lower pinch
roll 17a while the strip S1 is coiled by the second mandrel
2. In this state, the tail end of the strip S1 is cut by the
strip shear 5. In this embodiment, the relationship between
'the coiling speed Vm of the preceding strip S1 set by the speed
controller 40 for the mandrel 2 after the cutting operation,
the target speed Vp for the speed controller 43 for the coiling
pinch rolls 17 at the time of the cutting operation, and the
sheet speed Vg of the preceding strip S1 just before the cutting
operation is set by a host computer (not shown) so that vm
> Vp > Vg .
By performing the speed setting in this manner, because
the relationship of Vp > Vs holds between the strip shear 5
and the coiling pinch rolls 17, a pulling force directed to
the downstream side is applied to the strip S1 having been
cut by the coiling pinch rolls 17. Also, because the
relationship of Vm > Vp holds between the coiling pinch rolls
17 and the mandrel 2 , a pulling force directed to the downstream
side is applied by the mandrel 2.
Therefore, the preceding strip S1 can be prevented from
oversupplied on the delivery side of the coiling pinch rolls
17. As a result, damage to a sheet caused by the preceding
strip S1 being caught by the tip end of a downstream sheet
guide 13 lying at a position where a downstream pass line P2
- 28 -
CA 02332953 2000-11-22
branches off an upstream pass line P1. Further, because the
speeds are set so that the relationship of VP > VS holds, that
is, the feed speed Vp of the coiling pinch rolls 17 is higher
than the transfer speed V$ of the following strip S2, the leading
end of the following strip S2 can be prevented from being
oversupplied at the entrance side of the coiling pinch roll
17. For the sheet speed Vs, an actual value can be determined
from the target speed of the mandrel 2 just before the cutting
operation or the roll rotational speed of the finishing mill.
The speeds Vm and Vp may be set so as to meet the above condition
based on the actual value of the sheet speed Vs.
Before the cutting operation is performed, a tension can
be given to the strip S1 by the f finishing mill and the mandrel
2, and the coiling control executed by the mandrel 2 before
that is preferably carried out by controlling the coiling
torque.
Specifically, the motor 32 is feedback controlled so that
the detected torque value of the motor 3 2 obtained by the torque
detector 34 coincides with the target torque value in order
to keep the tension of the strip S1 constant. Then, the tail
end of the strip S1 is cut by the strip shear 5, and after
a while, the speed of the mandrel 2 is decreased and the rotation
thereof is stopped while the strip S1 coiled into a coil shape
is pressed by wrapper rolls 19. After the rotation of the
mandrel 2 is stopped, the coil of the strip S1 is removed from
the mandrel 2.
Also, after the strip S1 is cut by the strip shear 5,
a tension cannot be given to the strip S1 between the finishing
- 29 -
CA 02332953 2000-11-22
mill and the mandrel 2 . Therefore, after the cutting operation,
the coiling control executed by the mandrel 2 is changed over
from torque control to speed control. Thereby, before the
cutting is performed, a tension can be applied to the strip
S1 by the torque control to coil the strip S1 tightly, and
after the cutting is performed, the coiling speed of the strip
S1 can be set so that Vm > Vp > Vg as described above.
The coiling control of the mandrel 2 may be changed over
from torque control to speed control in advance before the
preceding strip sl is cut by the strip shear 5.
Next, a strip coiling method in accordance with a third
embodiment of the present invention will be described with
reference to Figures 5 to 7. Although this embodiment can
be applied to the above-described f first and second embodiments,
a case where it is applied to the first embodiment will be
described by way of example. In this embodiment, therefore,
the same reference numerals are applied to the same elements
in Figure 1, and the duplicated explanation of the first
embodiment is omitted.
Before a strip is cut, the coiling pinch rolls 105 on
the delivery side of the strip shear rotate at the same speed
as the target sheet speed Vg (m/s) of the strip. When the
strip is cut by the shear strip 102, the target sheet speed
Vp2 (m/s) of the coiling pinch rolls 105 is set at a value
higher than the target sheet speed Vs of the strip, and the
preset coiling speed Vm (m/s) of the preceding strip S1 is
set at a value higher than the target sheet speed VP2 of the
coiling pinch rolls 105. Therefore, the rotational speed of
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CA 02332953 2000-11-22
the coiling pinch rolls 105 increases after the strip is cut.
The sheet speed of the preceding strip S1 tends to increase
to the preset coiling speed Vm. Since the coiling pinch rolls
105 press the preceding strip S1, the rotational speed of the
coiling pinch rolls 105 sometimes increases to a value close
to the preset coiling speed Vm along with the increase in the
sheet speed of the preceding strip S1.
At this time, the target sheet speed Vp2 of the coiling
pinch rolls 105 is set at the preset coiling speed Vm, that
is, a value lower than the sheet speed of the preceding strip
S1 having been cut, so that the motor 117 (a driving unit)
for the lower pinch roll 105a of the coiling pinch rolls 105
produces a torque such that the speed of the coiling pinch
rolls 105 is decreased. Therefore, after the cutting
operation, the load torque of the motor 117 changes from the
direction of forward rotation to the direction of reverse
rotation. After the tail end of the preceding strip S1 has
gone through the coiling pinch rolls 105, the speed of the
coiling pinch rolls 105 decreases . In the case where the strip
has a great sheet thickness and high bending rigidity, however,
a force for pressing the preceding strip S1 caused by the coiling
pinch rolls 105 is large, so that the torque on the deceleration
side of the motor 117 when the preceding strip S1 passes between
the coiling pinch rolls 105 becomes high. Therefore, when
the speed of the coiling pinch rolls 105 decreases after the
tail end of the preceding strip S1 has passed between the coiling
pinch rolls 105, in spite of the speed setting of Vpz > Vs,
as shown in Figure 7, the rotational speed of the coiling pinch
- 31 -
CA 02332953 2000-11-22
rolls 105 momentarily takes a value lower than the target sheet
speed of strip (the speed of the following strip), and
thereafter the rotational speed stabilizes into the preset
sheet speed vp2.
The time from when the tail end of the preceding strip
S1 has gone through the coiling pinch rolls 105 to when the
leading end of the following strip S2 is bitten by the coiling
pinch rolls 105 is as short as about 0.3 second. Therefore,
if the leading end of the following strip SZ is bitten by the
coiling pinch rolls 105 when the rotational speed of the coiling
pinch rolls 105 is lower than the sheet speed Vs of the following
strip S2 as described above, the strip feed speed of the coiling
pinch rolls 105 becomes lower than the sheet speed of the
following strip S2, so that, as shown in Figure 19, the leading
end or the following strip SZ is oversupplied on the entrance
side of the coiling pinch rolls 5.
In this embodiment, therefore, a deceleration-side
torque limit Tmax (N~m) is set on the motor 117, which is the
driving unit for the coiling pinch rolls 105, by which the
motor 117 is controlled by the speed controller 120 so that
the load torque of the motor 117 does not exceed the
deceleration-side torque limit TmBX~
The value of the torque limit TmaX such that when the leading
end of the following strip S2 is bitten by the coiling pinch
rolls 105, the rotational speed of the coiling pinch rolls
105 is not lower than the sheet speed vs of the following strip
SZ as shown in Figure 6 can be determined beforehand as described
below.
- 32 -
CA 02332953 2000-11-22
The value of the torque limit TmaX to be set on the motor
117 for driving the lower pinch roll 105a will be explained
with reference to Figure 5 taking a case where the lower pinch
roll 105a of the coiling pinch rolls 105 is driven as an example.
The lower pinch roll 105a is driven by the motor I17 via
gears 221 and 222 . Figure 5 shows a state in which the preceding
strip S1 is pressed by the pinch rolls 105. In this state,
the sheet speed Vg of the preceding strip S1 is higher than
the preset sheet speed VP2 of the lower pinch roll 105a, so
that the lower pinch roll 105a is subjected to a force of F
(N) from the preceding strip S1, and the motor 117 produces
a torque TM (N~m) against this force.
Taking a force which the lower pinch roll 105a is subjected
to from the preceding strip S1 at time t as F ( t ) ( N) , a torque
which the motor 117 produces against this force as TM ( t ) ( N ~ m ) ,
a moment of inertia between the lower pinch roll 105a and the
gear 221 as J2 ( N ~ m2 ) , a moment of inertia between the motor
117 and the gear 222 as Jl (N ~m2 ) , an angular velocity of the
lower pinch roll 105a just before the tail end of the preceding
strip S1 goes through the coiling pinch rolls 105 as u~z ( rad/sec ) ,
an angular velocity of the motor 117 as wl ( rad/sec ) , a torque
produced on the gear 222 as T(t) (N~m), the speed reducing
ratio of the gear 221 to the gear 222 as i, and the roll diameter
of the lower pinch roll 105a as D (m) , a dynamic equation of
Equation ( 13 ) holds . The sign of TM is such that the torque
on the forward rotation side (acceleration side) is +, and
the torque on the reverse rotation side (deceleration side)
is -.
- 33 -
CA 02332953 2000-11-22
1 D dw2
i '~t~ - F~t~ 2 = JZ dt . . . ( 13 )
Also, a dynamic equation of Equation ( 14 ) holds between
the motor 117 and the gear 222.
dcol
TM~t~ - T~~~ = J ~ dt . . . ( 14 )
Eliminating T(t) from Equations (13) and (14), the
following equation (15) holds.
T~,~~~ -i~F~t~ ~ _ (JI +Jz ~d2)d il . . . 15
( )
Integration of Equation (15) yields the following
Equation (16).
~1 ~~~t~ - i ~ F~t~ ~ D l dt = (J1 + J2 . i2 ~'~ dwl . . . ( 16 )
2
where wtl and wt2 are the angular velocities of the lower pinch
roll 105a at times tl and t2, respectively. In Equation ( 16 ) ,
for the time from when the tail end of the preceding strip
S1 has gone through the coiling pinch rolls 105 to when the
leading end of the following strip S2 is bitten by the coiling
pinch rolls 105, F(t) is equal to zero.
Here, a speed change amount ~w (rad/sec) of the lower
pinch roll 105a for the time from when the tail end of the
preceding strip S1 has gone through the coiling pinch rolls
105 (t = 0) to when the leading end of the following strip
S2 is bitten by the coiling pinch rolls 105 (t = t2 (sec))
is calculated. The minus sign of ~w means deceleration, and
the plus sign thereof means acceleration.
- 34 -
CA 02332953 2000-11-22
Thereupon, Equation ( 16 ) is expressed by the following
equation (16A).
2
~TM~t~dt = (J1 + J~ ' iz )~" dwl . . . ( 16A )
a
The value TM~t~ changes from TmaX to the plus side when
the preceding strip S1 goes through the coiling pinch rolls
105 . To evaluate the change amount 0w in a severer ( larger )
direction, it is simply assumed that TM~t~ = Tmax~ by which the
following equation (17) holds.
z
~'~aX ' dt = (J1 + Jz ' i2 y' dcul . . . ( 17 )
By reducing Equation ( 17 ) , the change amount Ow of the
lower pinch roll time t2 after the tail end of the preceding
strip S1 goes through the pinch rolls is expressed by the
following equation (18).
Ocu = ~"°" ' t2 . . . ( 18 )
J1 + Jz ' iz
If the transfer speed VS of the leading end of the following
strip S2 satisfies the following equation ( 19 ) , oversupplying
of the leading end of the following strip SZ on the entrance
side of the lower pinch roll 105a does not occur.
V$ s (cuo + ~cu) D . . . ( 19 )
Since cuo is not lower than a preset angular velocity cup2
of the lower pinch roll 105a, there is no problem even when
an approximation of wo ~ c~,2 is given. Therefore, Tmax for
preventing the occurrence of oversupplying of the leading end
of the following strip S2 on the entrance side of the coiling
- 35 -
CA 02332953 2000-11-22
pinch rolls 105 has only to satisfy the relationship of the
following equation (20-4) from Equations (18) and (19).
VB s (wo + ~cu) D - cupz + ~°°" ~ tz x D . . . ( 20-I )
2 J1 + Jz ~ 1z 2
V x 2 ~"a,~ ' t ( 2 0-2 )
S D - wP2 5 J1 + Jz ~212 . . .
(J1 + J2 ~ i2 ) 2Va - ~pz 5 ~X . . . ( 20-3 )
t2
~J + J ~ i2 ) (V - cu ~ D / 2)
1 z a Pz s T~x ". (20-4)
Dtz
From Equation ( 20-4 ) , Vg - c~2 ~ D/2 = Vs - VP2, which means
VP2 > Vg. Therefore, it is found from Equation (20-4) that
TmaX takes a value not lower than a minus value. That is to
say, the deceleration-side torque limit is calculated.
The transfer speed Vs of the leading end of the following
strip S2, the moment of inertia Jl between the motor 117 and
the gear 222, the moment of inertia J2 between the lower pinch
roll 105a and the gear 221, the diameter D of the lower pinch
roll 105a, the speed reducing ratio i, and the preset angular
velocity cupz of the lower pinch roll 105a have been found in
advance. Also, the time t2 from when the tail end of the
preceding strip S1 goes through the coiling pinch rolls 105
to when the leading end of the following strip S2 is bitten
- 36 -
CA 02332953 2000-11-22
by the coiling pinch rolls 105 has been found in advance from
the relationship between the transfer speed Vg of the following
strip SZ and the coiling speed Vm of the preceding strip S1.
Therefore, the value of TmaX that satisfies Equation (20-4)
has only to be set in advance.
If the deceleration-side torque limit TmaX is set on the
motor 117 for driving the coiling pinch rolls 105 beforehand
in this manner, while the coiling pinch rolls 105 presses the
preceding strip S1 after the strip is cut, the load torque
on the deceleration side of the motor 117 created based on
a speed difference between the target coiling speed Vm of the
preceding strip S1 (the preset coiling speed of the downstream
coiler 104 ) and the target sheet speed VP2 of the coiling pinch
rolls 105 does not become excessive. Even immediately after
the tail end of the preceding strip S1 goes through the coiling
pinch rolls 105, the rotational speed of the coiling pinch
rolls 105 does not become lower than the sheet speed Vg of
the following strip S2.
Next, a strip coiling method in accordance with a fourth
embodiment of the present invention will be described with
reference to Figures 8 to 10.
In coiling a strip in continuous hot rolling, stable sheet
transfer and coiling are performed by giving a tension to the
strip between the finishing mill and the mandrel. As means
for giving the tension, the tension reference given to the
strip when the strip is coiled, that is, the tension reference
preset properly so as to correspond to the coiling temperature
condition in coiling, the steel type of strip to be coiled,
- 37 -
CA 02332953 2000-11-22
or the like is generally given in advance, and tension control
is carried out in coiling by producing a rotational torque
on the mandrel in coiling, which torque is such that a tension
having a value equal to the tension reference can be given
to the strip.
In continuous hot rolling, a strip sent from the finishing
mill is coiled by a plurality of mandrels alternately after
being cut. Therefore, the time from coiling finish to coiling
start of next strip per one mandrel is short, so that a coil
(strip) having been coiled must be removed in the shortest
possible time, and preparation for next coiling must be
completed in a short time. For this purpose, it is necessary
to stop the rotation of mandrel in a short time after the
completion of coiling. However, since the wrapper roll
(pressing roll ) is brought into contact with the strip surface
coiled in a coil shape before the completion of coiling, the
wrapper roll produces a torque such as to hinder the rotation
of mandrel during coiling operation, so that the speed of the
mandrel itself is undesirably decreased. As a result, a
looseness of strip occurs between the wrapper roll and the
pinch roll, so that a phenomenon of oversupplying of strip
takes place.
To simulate this phenomenon by a general hot rolling
coiling model, the coil is assumed to be a rigid body of rotation,
by which a model shown in Figure 8 can be thought.
Specifically, taking the inside diameter of coil as a
(m) , the outside diameter thereof as b (m) , the tension acting
on the strip as T (KN), the torque occurring on the mandrel
- 38 -
CA 02332953 2000-11-22
as T~ (KN~m), the inertia force of coil as I~, and the angular
velocity thereof as w (rad/s), an equation derived by the
dynamics of motion of the coil is expressed as
I~(dw/dt) - TMD(a/2)-T(b/2)-4F ... (21)
where F is the tension produced by one wrapper roll . A coiler
in a general hot rolling shop is provided with four wrapper
rolls.
In the above-described equation ( 21 ) , at a stage before
the wrapper roll comes into contact with the strip, the third
term in the right-hand s fide is zero . In a case where the mandrel
carries out tension control steadily, the occurring torque
on the mandrel is controlled so that the f first term and the
second term are balanced, and therefore the left-hand side
of the equation becomes zero.
In a non-steady state at the moment when the wrapper roll
comes into contact with the strip, the left-hand side of the
equation becomes minus, so that a negative angular velocity
occurs . That is, the speed of the mandrel decreases . In this
case, the tension given to the strip decreases, and the strip
loosens between the wrapper roll and the pinch roll. This
looseness causes defective coiling such as loosened coil outer
coiling and telescoping.
In this embodiment, therefore, stable coiling of strip
in continuous hot rolling is achieved. Although this
embodiment can be applied to the above-described first and
second embodiments, ~ a case where it is applied to the second
embodiment is described by way of example. In this embodiment,
therefore, the same reference numerals are applied to the same
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elements in Figure 4, and the duplicated explanation of the
second embodiment is omitted.
In this embodiment, for example, when a strip is cut by
the strip shear 5, the rotation control of the motor 32 for
the mandrel 2 lying at the coiling finish position is changed
over from the torque control having been carried out to the
rotational speed control. Specifically, the changeover to
the rotational speed control may be effected at timing when
the strip shear 5 is operated. Alternatively, since if the
strip is cut by the shear 5 in a state in which the torque
control of the mandrel 2 is carried out, the tension having
been given to the strip is released, and therefore the
rotational speed of the mandrel increases, an upper limit value
of the rotational speed may be set in advance so that when
the actual rotationalspeed reachesthe aforementioned value,
the changeover to the speed control is effected automatically.
The wrapper rolls 19 are arranged at equal intervals along
the outer periphery of the coil . They are provided retractably
with respect to the mandrel 2 via a hydraulic pump and a hydraulic
cylinder provided with a servo valve (both not shown), and
is capable of being rotated by a driving power source (not
shown ) . In this embodiment, after the mandrel 2 is changed
over to the rotational speed control at the time when the cutting
operation is performed, the wrapper rolls 19 are brought into
contact with the outer peripheral surface of coil to brake
the coil. The wrapper rolls 19 also function as a guide when
the coiling operation of strip is started by the mandrel 2.
Also, the relative position of the wrapper coil 19 with respect
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to the coil may be detected by using a position detector (not
shown) to increase the accuracy of contact with the coil.
Next, in a case where the torque control of the mandrel
2 of the coiler is continued until the completion of coiling
of strip as before and in a case where the torque control of
the mandrel 2 is switched to the rotational speed control along
with the cutting of strip just before the completion of coiling,
actual changes of the rotational speed (sheet speed: mpm) and
torque of the mandrel 2 were measured.
The measurement results are shown in Figures 9 and 10.
Figure 9 shows the case where the torque control was continued,
and Figure 10 shows the case where the torque control was
switched to the rotational speed control. Specifically, in
Figure 9, a decrease in rotational speed of mandrel when the
wrapper rolls 19 come into contact with the coil is shown
definitely. However, when the control is changed over to the
speed control at the time of strip cutting as shown in Figure
10, it is found that the decrease in rotational speed of mandrel
is less, and the coil is not loosened.
Here, it is preferable that the rotational speed of the
mandrel 2 be higher than the transfer speed of the preceding
strip S1. The reason for this is that when the mandrel 2 is
switched from the torque control to the rotational speed
control, by setting the target of the speed control value so
as to be somewhat higher the actual speed at that time, the
mandrel 2 can surely pull the strip.
Also, by setting the time when the wrapper rolls 19 begin
to come into contact with the coil between the time when the
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strip is cut and the time when the strip goes through the coiling
pinch rolls 17, the wrapper rolls 19 can be brought into contact
with the coil while the mandrel 2 is subjected to speed control,
and also the wrapper rolls 19 can quickly start an operation
for braking the rotation of the coil.
The following is a description of another mode.
As described above, before the strip is cut by the strip
shear 5, the mandrel 2 is subjected to torque control so that
the strip coiled around the mandrel 2 is pulled with a
predetermined coiling tension, by which coiling is performed.
Thereafter, the strip is cut by the strip shear 5 . Here, after
the cutting operation, the torque control of the mandrel 2
is continued. After the strip is cut, the coiling operation
is continued in a state in which a tension is given to the
strip by the pinch rolls 17 and the mandrel 2.
Next, when the wrapper rolls 19 are brought into contact
with the coil, if the mandrel 2 performs the coiling operation
with a torque such that the same tension as before is given
to the strip, at the moment when the wrapper rolls 19 are brought
into contact with the coil, the rotational speed of the mandrel
2 decreases, and therefore the tension decreases, resulting
in the occurrence of looseness of coiling. Therefore, when
the wrapper rolls 19 are brought into contact with the outer
peripheral surface of coil, the preset value of the tension
is changed to a value higher than the previous preset value.
In the above-described equation (21), the strip tension is
decreased by 4F by bringing four wrapper rolls 19 into contact
with the outer peripheral surface of coil, so that the preset
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value of the tension has only to be made higher by a value
not lower than 4F when the wrapper rolls 19 are brought into
contact with the coil.
Next, a strip coiling method in accordance with a fifth
embodiment of the present invention will be described with
reference to Figures 11 to 15. Although this embodiment can
be applied to the above-described first and second embodiments ,
a case where this embodiment is applied in place of pressing
force setting by using the compensation pressing force setter
124 in the first embodiment is described by way of example.
In this embodiment, therefore, the same reference numerals
are applied to the same elements in Figure 1, and the duplicated
explanation of the first embodiment is omitted.
If the pressing force applied to the strip by the upper
pinch roll 105b is improper when the of f set angle of the upstream
coiling pinch rolls 105 is changed, for a thin strip, the tail
end of the preceding strip S1 coiled by the downstream coiler
104 cannot be held sufficiently between the upstream coiling
pinch rolls 105. Therefore, the tail end of the preceding
strip S1 comes off from the upstream coiling pinch rolls 105
and is oversupplied, and hits the triangular gate 128, so that
breakage of tail end may occur. For a thick strip, in some
cases, the following strip Sz cannot be introduced to the
upstream coiler 101 correctly.
Also, in the case where a strip having relatively long
time from when the preceding strip S1 goes through the coiling
pinch rolls 105 after the cutting operation to when the
following strip Sz is bitten by the coiling pinch rolls 105,
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CA 02332953 2000-11-22
if the pressing force of the coiling pinch rolls 105 is being
controlled, the pressing load is made zero by the sheet
coming-off of the preceding strip S1. Therefore, a gap of
the coiling pinch rolls 105 operates in the closing direction,
so that there is a danger of occurring defective biting of
the following strip Sz.
In this embodiment, therefore, in order to prevent
breakage of the tail end of strip and to make the bending
direction of the following strip optimum, a proper pressing
force on the delivery side of the strip shear is set. Also,
in this embodiment, the leading end of the following strip
is prevented from being improperly bitten by the coiling pinch
rolls.
The following will be a detailed description.
Figure 14 shows a state in which the lower pinch roll
105a is retracted to the upstream side by an offset amount
of OL with respect to the upper pinch roll _ 105b. Figure 15
shows a state in which after the lower pinch roll 105a is offset,
the upper pinch roll 105b is pressed down with a pressing force
P.
A product P ~ ~x of the pressing force P of the pinch rolls
105 times a vertical displacement ~x of the pinch roll 105
caused by the pressing force P means work done by the pressing
force P .
If a pressing force applied by the upper pinch roll 105b
when the upper pinch roll 105b is located at position x is
taken as P ( x ) , the work done when the upper pinch roll 105b
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is pressed down from a position of x = 0 to a position of x
- ~x is expressed by the following equation (22).
~P(x) ~ dx . . . ( 22 )
On the other hand, if the upper pinch roll 105b presses
down the strip by Ox, the strip is displaced in the direction
in which the tension is given as shown in Figure 15. If the
displacement at this time is taken as 0u, the work necessary
to displace the strip by Du against the tension F is F~Du.
Also, in order to press down the strip to the state shown
in Figure 15 by the upper pinch roll 105b, bending deformation
is applied to the strip along the outer peripheral surface
of the lower pinch roll 105a on the entrance side of the pinch
rolls 105, and re-bending deformation along the lower pinch
roll 105a by the bending deformation and re-bending deformation
along the outer peripheral surface of the upper pinch roll
105b by the bending deformation are applied on the delivery
side of the pinch rolls 105.
The bending work done when a bend of a bending length
1 is created with a radius of curvature R by a bending moment
MH produced on the strip is expressed as MH ~ ( 1/R) . Taking the
radiuses of the lower pinch roll 105a and the upper pinch roll
105b as Rz and RU, respectively, and the length along the roll
of a portion of the lower pinch roll 105a around which the
strip is bent and the length along the roll of a portion of
the upper pinch roll 105b around which the strip is bent as
18 and lb respectively, the work for effecting bending
deformation of the strip along the outer peripheral surface
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of the lower pinch roll 105a is expressed as MH ~ ( 1a/Rz ) , and
the re-bending deformation along the lower pinch roll 105a
by the bending deformation on the delivery side of the pinch
rolls 105, the bending deformation of strip along the outer
peripheral surface of the upper pinch roll 105b, and the work
for effecting the re-bending deformation along the outer
peripheral surface of the upper pinch roll 105b by the bending
deformation are expressed as MH ~ ( 1a/RL ) , MH ~ ( lb/RU ) , and
MB ~ ( lb/RU ) , respectively .
Therefore, the sum of work necessary for the bending and
re-bending deformation effected on the entrance and delivery
sides of the pinch rolls 105 is 2MH~ ( 1$/RL ) + ( lb/RU ) } .
A value obtained by deducting the work for displacing
the strip by Du in the direction of the tension F from the
work necessary for moving the upper pinch roll 105b from the
position of x = 0 to the position of x = 4x is balanced with
the work necessary for effecting the bending and re-bending
deformation of the strip, so that the following equation ( 23 )
holds.
~P(x) ~ dx - F ~ 0u=2MH{(le/Rz)+(lb/RU)} ... (23)
Here, MH can be expressed by the following equation ( 24 ) .
MH = (1/6)aB~tz~w ... (24)
where aH is the yield stress of strip, t is the thickness of
strip, and w is the width of strip.
The inventors have verified that if the upper pinch roll
105b is pressed down further from the state in which the upper
pinch roll 105b begins to come into contact with the strip,
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CA 02332953 2000-11-22
the load necessary for pressing down the upper pinch roll 105b
increases linearly as the upper pinch roll 105b is pressed
down during the time when the strip is deformed elastically.
Figure 11 shows the relationship between the pressing force
of the upper pinch roll and the displacement in the downward
direction of the upper pinch roll. For this relationship,
the inclination is determined according to the size of pinch
roll, the material and size of strip, or the like. Therefore,
if P ( x ) is assumed to be a linear function such that P ( 0 ) _
OandP(~x)=Po,P(x) is expressedasP(x)=Po~x/~x. Therefore,
Equation (23) is expressed by the following equation (25),
and the following equation ( 26 ) holds from Equations ( 25 ) and
(24).
~ ~PaWx-FWu=2MB~(1a/RL)+(lb/RU)} ... (25)
Po-- -F~ 2~u + 4 la + lb , 1 ,~H.t2~w ... (26)
Ox 0x RL RU 6
where
Po: pressing force of pinch roll
F: tension of strip
0u: displacement of strip caused by the tension F
Ox: vertical displacement of pinch roll caused by the pressing
force P
MH: bending moment created on strip = (1/6) aB~tz~w
aH: yield stress of strip
t: thickness of strip
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CA 02332953 2000-11-22
w: width of strip
1a: length along the roll of a portion of lower pinch roll
around which the strip is coiled
Rz: radius of pinch roll
lb: length along the roll of a portion of upper pinch roll
around which the strip is coiled
RU: radius of upper pinch roll
The displacement Ox and 0u can be calculated geometrically .
The yield stress QH of the strip is a value determined according
to material, and the thickness t and the width w of the strip
is determined according to the treated material. Therefore,
if the tension F of the strip is determined from the rotational
speed of the coiler and the rotational speed of the pinch rolls,
the optimum pressing force P can be calculated. In this
embodiment, the pressing force of the coiling pinch roll is
set at a value not lower than Po determined by the
above-described equation (26).
Figures 12 and 13 are charts showing the actual pressing
force and the cylinder position reference for pressing down
the pinch roll. Figure 12 shows a case where the pressing
force setting in this embodiment is not performed, and Figure
13 shows this embodiment. The pressing force suddenly
decreases to a no-load condition when the preceding strip comes
off from the pinch rolls . If the pressing force decreases,
as shown in Figure 12, the cylinder position reference acts
in the direction such that the pressing force is kept to operate
the pinch roll in the pressing direction. Therefore, there
is the possibility of occurring defective biting of the
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CA 02332953 2000-11-22
following strip. Even if defective biting does not occur,
when the following strip is bitten by the pinch rolls, the
pressing force increases suddenly and then is restored to the
preset value, and the cylinder position reference changes
rapidly so that the pinch rolls are operated in the opening
direction, so that overaction causes hunting.
Contrarily, in Figure 13, the servo valve is locked so
that the cap of pinch roll is kept constant until the preceding
strip comes off from the pinch rolls and the following strip
is bitten by the pinch rolls after the pressing force is set,
by which the cylinder position is held, so that the cylinder
position reference is kept constant. Therefore, there is no
possibility of occurring defective biting of the following
strip.
INDUSTRIAL APPLICABILITY
As is apparent from the above description, according to
the present invention, an effect can be achieved that the
preceding strip can be prevented from being oversupplied on
the delivery side of the coiling pinch rolls, and also the
leading end of the following material can be prevented from
being oversupplied on the entrance side of the coiling pinch
rolls.
Also, in the case where the present invention is applied
to a hot rolling line provided with a Carrousel reel type coiler,
the relationship between the preset coiling speed Vm of the
mandrel after the tail end of the strip coiled by the mandrel
via the coiling pinch rolls, the target speed Vp of the coiling
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CA 02332953 2000-11-22
pinch rolls at the time of the cutting operation, and the sheet
speed Vs of the following material immediately after the cutting
operation is set so that Vm > Vp > Vg. Thereby, an effect can
be achieved that the preceding strip can be prevented from
being caught by the tip end of the sheet-running guide located
at a position where the pass line directed to the mandrel at
the coiling start position branches off the pass line directed
to the mandrel at the coiling finish position.
Further, in the casewhere the present invention is applied
to a general hot rolling line, the relationship between the
target speed VP1 of the second coiling pinch rolls when the
tail end of the strip coiled by the downstream mandrel via
the second coiling pinch rolls disposed on the entrance side
of the downstream mandrel is cut, the target speed Vp2 of the
first coiling pinch rolls disposed on the delivery side of
the strip shear, the target sheet speed Vg of the following
material immediately after the cutting operation, and the
preset coiling speed Vm of the downstream mandrel is set so
that Vm > Vpl > Vp2 > V9. Thereby, an effect can be achieved
that damage to the strip caused by the tail end of the preceding
strip being caught by the triangular gate can be prevented.
In this case, after the lower pinch roll of the first
coiling pinch rolls is offset and before the tail end of the
strip coiled by the downstream mandrel via the second pinch
rolls is cut, the strip is pressed by the upper pinch roll
of the first coiling pinch rolls in the state in which the
speed of the lower pinch roll is made lower than the target
sheet speed Vg of the following material until the actual torque
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value of the lower pinch roll becomes the preset value, and
the pressing force at this time is made the preset pressing
force of the offset upper pinch roll applied to the strip,
by which the tail end of the strip coiled by the downstream
mandrel can be held properly by the first coiling pinch rolls.
Therefore, an effect can be achieved that the slip of the strip
tail end with respect to the upstream coiling pinch rolls can
surely be eliminated.
Also, before the strip cut by the strip shear is
continuously coiled by the mandrel via the coiling pinch rolls
disposed on the delivery side of the strip shear, the pressing
force of the coiling pinch rolls is set at a value not lower
than a value P determined by P = F ( Du /fix ) + 2 ( M$/Ox ) ( ( la /r )
+ (lb/R)~. Thereby, the pressing force of the upper pinch
roll can be set at the optimum value. Therefore, an effect
can be achieved that the breakage of tail end of a thin strip,
improper introduction of a thick strip to the coiler, and other
troubles can be prevented.
In this case, after the pressing force is set, by keeping
the gap of the coiling pinch rolls for the time from when the
preceding strip comes off from the pinch rolls to when the
following strip is bitten by the pinch rolls, an effect can
be achieved that the defective biting of the following strip
by the coiling pinch rolls and other troubles can be prevented.
Further, before the strip coiling operation performed
by the mandrel is finished, the strip coiling control carried
out by the mandrel is changed over from torque control to
rotational speed control, and thereafter the pressing roll
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is pressed on the strip to be coiled into a coil shape to stop
the rotation of the mandrel. Alternatively, before thestrip
coiling operation performed by the mandrel is finished, the
torque control of strip is carried out by the mandrel to increase
the tension of strip, and thereafter the pressing roll is
pressed on the strip to be coiled into a coil shape to stop
the rotation of the mandrel . Thereby, effects can be achieved
that the decrease in speed of coil caused by the contact of
the pressing roll can be prevented, the occurrence of defective
coiling such as loosened coil outer and telescoping can be
avoided, and the rotation of coil can be stopped in a short
time because the pressing roll has a braking force when the
rotation of coil is stopped after the strip coiling operation
is finished.
Further, the deceleration-side torque limit of the
driving unit for the coiling pinch rolls is set so that the
circumferential speed of the coiling pinch rolls is higher
than the transfer speed of the following material when the
leading end of the following material is bitten by the coiling
pinch rolls disposed on the delivery side of the strip shear
after the strip is cut by the strip shear. Thereby, an effect
can be achieved that even in the case of a strip having a great
sheet thickness and high bending rigidity, the following
material can be prevented from being oversupplied on the
entrance side of the coiling pinch rolls.
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