Rolling method of wide flange beam in universal rolling mill

The method of rolling a wide flange beam results in an improved accuracy of the web thickness and the flange thickness in a universal rolling mill. Rolling a wide flange beam in a universal rolling mill having horizontal rolls and vertical rolls, switching over the positional control gain for each of drives for the horizontal rolls and drives for the vertical rolls by means of measured values of rolling load on the horizontal rolls and the vertical rolls during rolling, or filtering a control amount of the horizontal roll position calculated from a rolling load acting on the horizontal rolls and a control amount of the vertical roll position calculated from a rolling load acting on the vertical rolls to achieve different responses of horizontal roll rolling and vertical roll rolling, results in reducing mutual interference between horizontal roll rolling and vertical roll rolling caused through the rolling material.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method of rolling a wide flange beam by 
the use of a universal rolling mill comprising horizontal rolls and 
vertical rolls. More particularly, the present invention relates to a 
method of rolling, in a universal rolling mill, a wide flange beam 
excellent in accuracy of a web thickness and a flange thickness by causing 
a drive of the screw-down for the horizontal rolls and a drive of the 
screw-down for the vertical rolls to operate independently of each other 
by means of measured values of rolling load acting on the horizontal rolls 
and the vertical rolls during rolling, even with an unknown rigidity of 
the material to be rolled. 
2. Description of the Related Art 
There has conventionally been well known a technique of controlling the 
thickness of a flat sheet by causing a change in the rolling roll gap 
during rolling. As is described in the "Theory and Practices of Plate and 
Sheet Rolling" edited by the Iron and Steel Institute of Japan, p. 
229-231, a basic technique of measuring a rolling load with a load cell or 
the like, and causing a change in the roll gap in accordance with the 
following formula, thereby controlling the sheet thickness is known as the 
gauge meter AGC (Automatic Gauge Control): 
EQU .DELTA.S=-.alpha..DELTA.F/K.sub.m ( 1) 
where, .DELTA.S is an amount of change in the roll gap, .DELTA.F is a 
change in load from a lock-on load, K.sub.m is a mill rigidity, and 
.alpha. is a correction coefficient known as a tuning rate. 
Operation of the roll gap is performed by the use of an electrically driven 
screw-down motor or a hydraulic cylinder, and it is more often the common 
practice to use a hydraulic cylinder because of a better response and 
benefits in mechanical structure. 
By the use of the foregoing gauge meter AGC, a variation in flat sheet 
thickness .DELTA.h can be calculated by the following formula: 
##EQU1## 
Since the load .DELTA.F varies also with a variation in thickness, it can 
be expressed by the following formula: 
EQU .DELTA.F=Q.DELTA.h+.DELTA.F.sub.dis ( 3) 
where, Q is rigidity (plasticity constant) of the flat sheet, and 
.DELTA.F.sub.dis is a load disturbance caused by a variation in thickness 
on the entry side or a change in rolling temperature. From the foregoing 
formulae (2) and (3), the variation in flat sheet thickness .DELTA.h can 
be expressed eventually by the following formula: 
EQU .DELTA.h={(1-.alpha.)/(K.sub.m +(1-.alpha.)Q}.DELTA.F.sub.dis ( 4) 
where, it is known that the tuning rate .alpha., generally taking a value 
near 1, an error, if any, in flat sheet thickness .DELTA.h can be 
minimized even upon occurrence of a load disturbance .DELTA.F.sub.dis. 
While the formulae (1) to (4) have shown stationary properties of gauge 
meter AGC, a transient response depends upon dynamic properties of the 
drive. 
Now, the features of the gauge meter AGC will be briefly described below. 
As is described in the aforesaid reference, the gauge meter AGC has 
transient dynamic properties varying with rigidity (plasticity constant) 
of the material. However because the tuning rate generally takes a value 
near 1, the stationary properties do not depend upon rigidity Q or 
deformation property of the material, as shown in the formula (4). This 
control is achievable by only knowing the easily predictable mill rigidity 
K.sub.m even when rigidity Q of the material difficult to predict in 
general is unknown, as indicated by the formula (1). This is a feature of 
the gauge meter AGC. 
The difficulty in predicting a material rigidity is caused by plastic 
deformation of the material. Because plastic deformation largely depends 
upon material quality and temperature, it is difficult to predict this 
phenomenon. Since a mill complies with elastic deformation, on the other 
hand, prediction of deformation thereof is easy. 
The foregoing gauge meter AGC is widely applied to flat rolling mills. 
Because of the difficulty in mechanical structure, however, there are 
available only a few cases of application of the gauge meter AGC to a 
universal rolling mill for rolling a wide flange beam having a web portion 
12 and flange portions 14 as shown in FIG. 6. However, in accordance with 
the same technique as that of a flat rolling mill, it suffices to conduct 
rolling as follows: 
EQU .DELTA.S.sub.h =-.alpha..DELTA.F.sub.w /K.sub.mh ( 5) 
EQU .DELTA.S.sub.v =-.alpha..DELTA.F.sub.f /K.sub.mv ( 6) 
where, h is a horizontal roll, v is a vertical roll, .DELTA.F.sub.w is a 
rolling load of the web portion 12 and .DELTA.F.sub.f is a rolling load of 
the flange portion 14. 
It is estimated, as in the case of flat rolling, that this control permits 
reduction of errors in web and flange thickness. 
As described above, application of the gauge meter AGC to a universal 
rolling mill can easily be conceived. An important difference from flat 
rolling is however that the web portion 12 and the flange portions 14 in a 
wide flange beam 10 are connected, and rolling of the web portion 12 and 
the flange portions 14 mutually exerts an effect. For example, when the 
vertical roll gap is tightened to reduce the thickness of the flange 
portions 14, the load acting on the horizontal rolls is known to be 
reduced. Therefore, independent application of the gauge meter AGC to 
vertical roll rolling and horizontal roll rolling as described above would 
result in a serious mutual influence of the web portion and the flange 
portions, hence causing interference between the vertical rolls and the 
horizontal rolls and leading to undesirable vibration. 
FIG. 5 illustrates a structure of a universal rolling mill 20 in a case 
where roll screw-down is performed by means of a hydraulic cylinder. In 
FIG. 5, horizontal rolls 22 reduce from above and below the web portion 12 
of a wide flange beam, and vertical rolls 24 reduce from right and left 
the flange portions 14 of the side flange beam. 
The horizontal rolls 22 are provided, for example, with hydraulic cylinders 
26 and 28 for the upper horizontal roll for screwing down at right and 
left ends of the upper horizontal roll shaft, and hydraulic cylinders 30 
and 32 for the lower horizontal roll are provided for a similar purpose 
for the lower horizontal roll 22. The vertical rolls 24 are similarly 
provided, for example, with hydraulic cylinders 34 and 36 for the left 
vertical roll for screwing down the left vertical roll from front and back 
thereof, and hydraulic cylinders 38 and 40 for the right vertical roll for 
screwing down similarly the right vertical roll from front and back 
thereof. These hydraulic cylinders are arranged above and below, and at 
right and left because the entire universal mill must form a 
point-symmetry for rolling a wide flange beam. 
In order to apply the gauge meter AGC, it is necessary to measure the load 
during rolling. A load cell is provided for each drive for this purpose. 
More specifically, as shown in FIG. 5, the right and left hydraulic 
cylinders 26 and 28 for the upper horizontal roll are provided with load 
cells 42 and 44 for the upper horizontal roll, respectively, and the right 
and left hydraulic cylinders 30 and 32 for the lower horizontal roll are 
provided with load cells 46 and 48 for the lower horizontal roll, 
respectively. The front and rear hydraulic cylinders 34 and 36 for the 
left vertical roll are provided with load cells 50 and 52 for the left 
vertical roll, respectively, and the front and rear hydraulic cylinders 38 
and 40 for the right vertical roll are provided with load cells 54 and 56 
for the right vertical roll, respectively. 
FIG. 7 illustrates a common control configuration of the gauge meter AGC 
based on hydraulic cylinder screw-down popularly applied in flat plate, 
cold or hot rolling. In FIG. 7, 60 is a load cell, showing a load F 
provided as an output. The portion enclosed by dotted lines represents a 
controller or arithmetic unit 68. The portion within the dotted lines 
shows a computing logic in the arithmetic unit. The arrows represent the 
flow of signals, and the symbol on the arrow, the value of signal. The 
symbol +/- on or to the left of the arrow means addition/subtraction of 
the value of signal. The squares within the dotted lines means that an 
input signal from the left is multiplied by a parameter shown by a signal 
in the square and a resultant signal is issued as an output. A servo valve 
62 is adjusted by means of a final output signal from the arithmetic unit 
68 to move a cylinder 64 through a hydraulic piping 66. A cylinder 
positional signal S.sub.FBK is fed back to the arithmetic unit 68. Among 
the signals within the dotted lines, .DELTA.F represents a deviation from 
the lock-on load F.sub.o, K.sub.m is a mill constant, .alpha. is a tuning 
rate, .DELTA.S is an AGC control amount, S.sub.o is a (hydraulic) cylinder 
positioning value before biting, S.sub.FBK is a measured value of cylinder 
position, and G is a cylinder position control gain. The positioning time 
must be adjusted so that the cylinder positioning time before biting does 
not become excessively longer, since the positioning time depends upon 
this control gain G. The control gain G is therefore usually adjusted so 
as to ensure execution of cylinder position setting at the highest 
possible speed, while observing a response of the hydraulic cylinder 64 
and the like. 
FIG. 8 illustrates a case of independent application of the flat rolling 
gauge meter AGC shown in FIG. 7 to horizontal rolling and vertical rolling 
on a universal mill 20. The upper portion relative to a one-point chain 
line corresponds to horizontal rolling, and the lower portion, to vertical 
rolling. In this thickness controller, the gauge meter AGC apparatus 70 
based on screw-down by the hydraulic cylinder of the horizontal roll and 
the gauge meter AGC apparatus 72 based on screw-down by the hydraulic 
cylinder of the vertical roll are independent of each other. In FIG. 8, 
F.sub.h is a load acting on the horizontal roll 22, .DELTA.F.sub.h is a 
deviation from the horizontal roll lock-on load F.sub.h0, K.sub.hm is a 
mill constant in the vertical direction of the universal mill 20, .alpha. 
is a tuning rate, .DELTA.S.sub.h is a horizontal roll AGC control amount, 
S.sub.h0 is a set value of the horizontal roll cylinder position before 
biting, and G.sub.hi (i=1 to 4) is a positional control gain for each 
cylinder. Similarly, variables such as F.sub.v, .DELTA.F.sub.v, F.sub.v0, 
.DELTA.S.sub.v and G.sub.vi (i=1 to 4) are defined also for the vertical 
roll 24. K.sub.vm is a mill constant in the transverse direction of the 
universal mill 20. Usually, the cylinder positional control gains G.sub.hi 
and G.sub.vi must be adjusted so as to ensure rapid positional setting 
before biting. 
FIG. 9 illustrates the result of control in a case of application of the 
controller shown in FIG. 8. As is clear from FIG. 9, as a result of mutual 
influence of the web and the flanges of a wide flange beam occurring 
during rolling, a behavior suggesting vibration appears immediately upon 
start of control, resulting in a large thickness deviation. 
To solve this problem, there is proposed a method of eliminating 
interference taking account of the mutual influence when controlling the 
flange portions and the web portion, as described in the "Non-Interference 
Thickness Control of Large-Scale Rolling Mill, Iron and Steel-Making 
Research, No. 317 (1985), p. 48-58" and Japanese Examined Patent 
Publication No. 63-66608. More specifically, by the use of a linearized 
rolling load model describing the mutual influence of the web portion and 
the flange portions during rolling, the proposed method comprises the 
steps of operating drives so as to prevent mutual interference, thereby 
eliminating the interference phenomenon. 
In such a method of control for eliminating interference between the 
horizontal rolls and the vertical rolls by means of a rolling load model, 
it is necessary to provide a model strictly describing the rolling 
phenomenon, and the following problems have been posed. 
(1) In the wide flange beam rolling presenting a three-dimensional 
deformation property, it is very difficult to prepare a model strictly 
describing the rolling phenomenon because of the difficulty in applying 
the well-known rolling theory. 
(2) In general, a plastic deformation phenomenon is a non-linear model, and 
it is difficult to completely eliminate interference because of this 
non-linearity. 
(3) A driving equipment generally exhibits a high-order response, and it is 
difficult to ensure elimination of interference with the high-order 
response also in view. 
Even with an unknown rigidity of the material difficult to predict in 
general, a feature of the flat rolling gauge meter AGC is to permit 
achievement thereof by knowing only the mill rigidity. However, simple 
application of the flat rolling gauge meter AGC to a universal mill causes 
the problem as described above. 
SUMMARY OF THE INVENTION 
The present invention has therefore an object to permit achievement of 
control of the web thickness and the flange thickness even with an unknown 
rigidity of the material also in a universal mill as in the flat rolling 
gauge meter AGC. 
The present invention provides a rolling method of a wide flange beam on a 
universal rolling mill, when rolling a wide flange beam by the use of a 
universal mill comprising horizontal rolls and vertical rolls, comprising 
the step of independently operating drives of the screw-down for the 
horizontal rolls and drives of the screw-down for the vertical rolls by 
means of measured values of rolling load acting on the horizontal rolls 
and the vertical rolls during rolling, thereby controlling the web 
thickness and the flange thickness of the wide flange beam. 
Other features and advantages of the present invention will be apparent 
from the following detailed description including variations thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As a result of extensive tests and studies, the present inventors found a 
method of rolling a wide flange beam excellent in accuracy of the web 
thickness and the flange thickness. 
When introducing the conventional flat rolling gauge meter AGC into a 
universal mill, mutual interface occurs in the horizontal roll rolling and 
the vertical roll rolling because the plurality of drives have responses 
of substantially the same order and mutually exert influence to 
substantially the same extent. An adverse effect caused by the mutual 
influence can be alleviated by excluding this condition. The present 
invention was developed on the basis of such findings. The invention 
provides a method of rolling for controlling the web thickness and the 
flange thickness of a wide flange beam by independently operating drives 
of the screw-down for horizontal rolls and drives of the screw-down for 
vertical rolls by means of measured values of rolling load acting on the 
horizontal rolls and the vertical rolls during rolling. 
Now, embodiments of the invention will be described in detail below with 
reference to the drawings. 
FIG. 1 is a block diagram illustrating an operation within controller 68 of 
a first embodiment of the invention. This covers a case where, taking 
account of a positional control gain, the method of the invention is 
independently applied for horizontal rolling and vertical rolling in the 
thickness control method of flat rolling. The upper portion relative to 
the one-point chain line corresponds to horizontal rolling, and the lower 
portion, to vertical rolling. 
In FIG. 1, C.sub.h and C.sub.v represent coefficients for multiplication of 
horizontal or vertical roll positional control gains G.sub.hi and 
G.sub.vi, which are not changed, i.e., C.sub.h =C.sub.v =1.0, when the 
method of the invention is not applied. When applying the method of the 
invention, these gains are multiplied by prescribed values C.sub.h0 and 
C.sub.v0, respectively. This change in gains permits change in response of 
the horizontal roll drive of the screw-down and the vertical roll drive of 
the screw-down. By appropriately changing the response, it is possible to 
minimize interference between the horizontal roll rolling and the vertical 
roll rolling caused by mutual influence between the web and the flanges. 
FIG. 3 illustrates the result of control in a use of the controller of the 
first embodiment shown in FIG. 1 under the same rolling conditions as in 
FIG. 9. Switching of gains comprised, as a result of examination of 
various rolling conditions, changing to C.sub.h0 =0.8 for the horizontal 
rolls, and to C.sub.v0 =1.0 for the vertical rolls, when executing the 
invention provides a reduction in vibration. Other appropriate values may 
also be used. As is clear from the comparison of FIGS. 3 and 9, the 
vibrational behavior caused by the interference between horizontal roll 
rolling and vertical roll rolling is reduced, thus permitting confirmation 
of a remarkable effect. 
In this first embodiment, the value of control gain was switched over by 
changing the value of the multiplying coefficient C.sub.h or C.sub.v of 
the horizontal roll or vertical roll positional control gain. The method 
of switching over the control gain is not however limited to this, but the 
value of control gain G.sub.hi or G.sub.vi may directly be changed. 
In general, a larger positional control gain results in a more rapid 
response of the drives, and a smaller gain leads to a slower response 
thereof. By the utilization of this feature, in the first embodiment, the 
influence of interference is alleviated and the interference caused by the 
mutual interference between the web portion and the flange portions is 
minimized by achieving responses of the drives of the screw-down for the 
horizontal rolls and the drives of the screw-down for the vertical rolls, 
of which one is more rapid, and the other is slower. 
Now, the control mechanism of a second embodiment of the invention will be 
described below with reference to FIG. 2. 
FIG. 2 is a block diagram illustrating the controller of the second 
embodiment of the invention. The second embodiment covers a case where, 
taking account of filtering of the positional control amount, the 
invention is directly applied for horizontal rolling and vertical rolling 
in the flat rolling thickness control method. The upper portion relative 
to the one-point chain line corresponds to horizontal rolling, and the 
lower portion, to vertical rolling. 
In FIG. 2, T.sub.h and T.sub.v represent time constants of (primary) 
filtering imparted to the horizontal rolls or vertical roll positional 
control amount. The filtering 1/(1+T.sub.h .multidot.S) and 1/(1+T.sub.v 
.multidot.S) represents a first order transfer function. By means of these 
time constants T.sub.h and T.sub.v, it is possible to change responses of 
the horizontal roll positional control and the vertical roll positional 
control. By appropriately changing responses, interference between 
horizontal roll rolling and vertical roll rolling caused by the mutual 
influence between the web and the flanges can be minimized. 
FIG. 4 illustrates the result of control in a use of the controller of the 
second embodiment shown in FIG. 2 under the same rolling conditions as in 
FIG. 9. In the controller of the second embodiment, T.sub.h =100 msec and 
T.sub.v =0 (no filtering) were adopted as filtering time constants from 
various rolling conditions. These values were determined by 
experimentation but other values may be used as well. As is evident from 
the comparison of FIGS. 4 and 9, vibrational behavior caused by the 
interference between horizontal roll rolling and vertical roll rolling, 
thus permitting confirmation of a remarkable effect. 
In the second embodiment, the interference caused by the mutual influence 
of the web portion and the flange portions is minimized by alleviating the 
effect of interference by adopting responses of the horizontal roll 
positional control and the vertical roll positional control, of which one 
is more rapid and the other is slower. 
In wide flange beam rolling, the flange thickness is in many cases required 
to have a higher accuracy than the web thickness. In this case, it 
suffices to use a more rapid response of vertical roll positional control, 
and a slightly slower response of horizontal roll positional control. 
While, in this second embodiment, .DELTA.S.sub.h and .DELTA.S.sub.v are 
filtered, the step is not limited to this, but any manner may be applied 
so far as it permits a change in control response. 
Further, in the foregoing embodiments, roll screw-down has been 
accomplished by the use of hydraulic cylinders. The manner of screw-down 
is not limited to this, but it is needless to mention that the invention 
is similarly applicable even in roll screw-down by the use of an 
electrically driven motor as a drive. 
ADVANTAGES 
According to the invention, it is possible to accomplish thickness control, 
even with an unknown rigidity of the material, as in the flat rolling 
gauge meter AGC, in a universal rolling mill, by reducing interference 
caused by a mutual influence between the web portion and the flange 
portions. This technique permits manufacture of a wide flange beam 
excellent in the accuracy of the web thickness and the flange thickness.