Note: Descriptions are shown in the official language in which they were submitted.
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1 ~ACKGROUND OF THE INVENTION
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The present invention relates to a method for preventing
wandering of a strip in a hot rolling line and, more particularly,
to a method for correcting a hot rolled strip in which shape
defects of the hot rolled strip are corrected in the hot
rolling line and the wandering of the strip during the correction
is prevented.
Demands for increased flatness of hot rolled strip
have recently become more and more severe, and now, if sufficient
flatness is provided, hot rolled strips can be used in place of
more expensive cold rolled strips.
In the manufacture of steel strips by a continuous hot
rolling mill, the relatively large distance between the final
mill stand of the finishing mill and the coiler presents a
problem in that the strip bottom, having passed the final
finishing stand, becomes under zero tension and flutters. The
fluttering of the strip bo-ttom is a cause for such shape defects
as out of flatness, edge defect, and edge break and defective
appearance of the coil.
For this reason, hot rolled strips have been, after
rolling in the continuous hot rolling mill, temper-rolled and
simultaneously corrected in flatness. If the hot strip produced
by such mill had satisfactory flatness it would be possible to
eliminate the temper rolling step. Heretofore, however, it
has been necessary to conduct the temper rolling operation to
obtain the required flatness of the hot rolled strips.
As mentioned above, the insufficient flatness of the
hot rolled steel strips causes defective appearance of coil,
which presents noticeable problems in the succeeding production
steps such as, for example in the case of mother material for
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1 cold rolling, decrease in pickling efficiency resulting from
decrease in passability of plates in the pickling line and
wandering of the strip.
To overcome these problems, the inventors previously
presented a method in which a hot roller leveler is provided
between the final finishing mill and the coiler, so that the
flatness of the hot rolled steel strip is corrected by the roll
force of the hot roller leveler and the tension between the
finishing mill and the coiler (Japanese Patent Publication
No. 48182/78 which issued as Japanese Patent No. 968053).
It has been confirmed that such previous method
mentioned above sharply reduced the shape defects of strips such
as center buckles and edge waves. However, in the cases where
the thickness distribution of the strip in the widthwise
direction is not symmetrical, where the rolled shape is
extremely asymmetrical, where the temperature distribution of
the strip is asymmetrical (mainly due to unsatisfactory spray),
and where the parallelism among the units of the rolling line
is not complete tit is difficult to maintain complete parallelism
among the units throughout the long rolling line), the leveling
of the strip by the hot roller leve~er sometimes caused the
strip to wander sideways so violently that the strip edge hit
the support members tside guides etc.) to thereby cause edge
defects and, in the extreme case, make the coiling operation
impossible. ~ '
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to
prevent wandering of a strip under roller leveling in a hot
rolling line, thereby stabilizing the flatness correction of
the strip and improving the coil appearance of the strip.
1 In the method according to the present invention, in
order to achieve the above object, at least one hot roller
leveler comprising a plurality of leveler rolls is provided
between the finishing rolling mill and the coiler of the hot
rolling line to correct the flatness of the hot strip. The hot
roller leveler is constructed as follows:
a. At least one leveler roll is supported to be angularly
adjustable in a horizontal plane with respect to the
strip.
b. At least one leveler roll is supported to be angularly
adjustable in a vertical plane with respect to the strip.
c. At least one leveler roll is supported to be angularly
adjustable in a horizontal plane and in a vertical
plane, respectively, with respect to the strip.
d. At least one leveler roll is supported to be angularly
adjustable in a horizontal plane with respect to the
strip and at least one other leveler roll is supported
to be angularly adjustable in a vertical plane with
respect to the strip.
Further, a side guide is provided on an entrance side,
or on an exit side, or on both sides of one or more hot roller
levelers constructed as described above, to prevent wandering
of the strip.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood from the
following description taken in connection with the accompanying
drawings in which:
Figs. 1 and 2 are illustrations of a finishing mill and
subsequent elements of a hot rolling line in which the method
according to the present invention is applied;
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1 Fig. 3 is a plan view of a leveler roll arranged to be
angularly adjustable in a horizontal plane with respect to the
strip;
Fig. 4 is a plan view of a leveler roll arranged to be
angularly adjustable in a vertical plane with respect to the
strip;
Pig. 5 is a side view taken from the line V-~ of Fig. 4;
Fig. 6 is a plan view of a leveler roll arranged
to be angularly adjustable in a horizontal plane and in a
vertical plane with respect to the strip;
Fig. 7 is a graph showing the wandering correcting
effect by the method according to the present invention;
Fig. 8 is a schematic side view of another embodiment
of the hot roller leveler used in the method according to the
present invention;
Fig. 9 is a graph similar to that of Fig. 7, showing
other wandering correcting effect;
Fig.10 is a plan view of a roller type side guide
adjustable in position, used in the method according to the
present invention;
Fig. 11 is a front view taken from the line XI-XI of
Fig. 10;
Fig. 12 is a plan view of a plate type side guide
adjustable in position, used in the method according to the
present invention;
Fig. 13 is a front view taken from the line XIII-XIII
of Fig. 12;
Figs. 14 to 16 are illustrations of examples of
arrangements in which a roller leveler is provided with one or
more side guides; and
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1 Figs. 17 to 19 are illustrations of examples of
arrangements in which a plurality of roller levelers are pro-
vided with one or more side guides.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference now to the drawings and more particularly
to Figs. 1 and 2 thereof, there are schematically illustrated
examples of a final mill stand and subsequent elements of a
hot rolling line. In the method according to the present
invention, as shown, one or more hot roller levelers 3 are
provided between a final mill stand 1 of a finishing mill and
a coiler 5 in the hot rolling line. A strip 6 having emerged
from the final stand 1 of the finishing mill passes a cooling
water spray zone 2, is leveled by the hot roller leveler 3,
passes through pinch rolls 4, and is coiled by the coiler 5.
In this hot rolling line, the hot roller leveler 3 is provided
in the neighborhood of the coiler 5 and preferably immediately
before the pinch rolls 4.
The hot roller leveler 3 comprising a plurality of
(three in the illustrated examples) leveler rolls 31 is pro-
vided in a single unit (Eig. 1) or in a plurality of units
(Fig. 2).
In the method according to the present invention, the
hot roller leveler 3 is constructed as follows:
a. At least one leveler roll 31 is supported to be angu-
larly adjustable in a horizontal plane with respect
to the strip 6 (Fig. 3).
b. At least one leveler roll 31 is supported to be
angularly adjustable in a vertical plane with respect
to the strip 6 (Eig. 4).
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t c. At least one leveler roll 31 is supported to be angularly
adjustable in a horizontal plane and in a vertical
plane, respectively, with respect to the strip 6 (Fig.6).
d. At least one leveler roll 31 is supported to be angularly
adjustable in a horizontal plane with respect to the
strip 6 and at least one other leveler roll 31 is
supported to be angularly adjustable in a vertical plane
with respect to the strip 6 ( Fig. 6).
Adjustment of the angle of the leveler roll 31 in the
horizontal plane is accomplished by, for example, the con-
struction shown in Fig. 3, in which one bearing 7a of the
leveler roll 31 is a pivot bearing and the other bearing 7b
thereof is so constructed as to be slidably movable in the
horizontal direction and is connected to a hydraulic cylinder
8 maintained horizontal.
The adjustment of the angle of the leveler roll 31 in
the vertical plane is accomplished by, for example, the
construction shown in Figs. 4 and 5, in which one bearing 7c
of the leveler roll 31 is so supported as to be pivotally movable
in a vertical plane and the other bearing 7d is connected to
a hydraulic cylinder 8 maintained vertical.
The adjustment of the angle of the leveler roll 31 in
the horizontal plane and in the vertical plane, respectively,
is accomplished by, for example, the construction shown in
Fig. 6, in which the bearings 7a and 7b shown in Fig. 3 are
combined with the bearings 7c and 7d shown in Fig. 4 respectively.
The construction shown in Fig. 1, in which one unit of
the roller leveler 3 comprising the three leveler rolls 31 is
provided between the finishing mill 1 and the coiler 5, will
now be described in detail for the purpose of confirming the
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1 effects of each of the rolls. From an idealistic view-point,
however, use of a hot roller leveler having more rolls preferable
since the greater the number of the rolls is, the higher are the
effects obtained thereby in flatness correction and descaling
of the strip. The roller leveler may be of a four-high type
having back-up rolls for supporting deflection of the work rolls
or may be of a two-high type having only the work rolls.
In the hot roller leveler 3 shown in Fig. 1, the
wandering of the strip 6 traveling on the line can be corrected
by adjusting the angle of the leveler roll 31 positioned on
the upper side of the strip in combination with one or two of
the two leveler rolls 31, 31 positioned on the under side of
the strip.
Fig. 7 shows the results of tests on the relation
between an angle of inclination e in a horizontal plane of the
leveler roll 31 and an amount of wandering ~x of the strip 6.
In Fig. 7, the horizontal axis denotes the angle of inclination
e of the roll and the vertical axis denotes the amount of
wandering per unit time Ax/~t.
The strip used in this test was a common hot-rolled
steel strip of thickness of 1.6 - 3.2 mm and width of 900 -
1300 mm. In Fig. 7, ~ indicates the case in which only the
leveler roll 31 positioned at the left on the under side of the
strip 6 was adjusted in angle, B indicates the case in which
only the leveler roll 31 positioned on the upper side of the
strip 6 was adjusted in angle, and C denotes the case in which
all the three leveler rolls 31, 31, 31 were adjusted in angle.
Fig. 7 shows that in any of the cases, the greater
the angle of inclination e of the roll is, the greater the
amount of wandering Ax of the strip 6 and that when the angle
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1 of inclination e of the roll varies in the reverse direction,
the amount of wandering ox of the strip also varies in the reverse
direction. Fig. 7 shows further ~hat the effect by adjustment
of the angle of the leveler roll is greater in the intermediate
roll than in the roll on the entrance or exit side and that
the greatest effect is achieved by adjusting the angles of all
the rolls.
Accordingly, in the method according to the present
invention, the wandering of the strip can be cancelled and pre-
vented by adjusting the angle of at least one of the three
leveler rolls 31 with the strip 6 in the horizontal plane.
Fig. 9 shows the results,of tests on the relation between
the angle of inclination e of the roll and the amount of wandering
~x of the strip 6 in the hot roller leveler having five leveler
rolls 31 as shown in Fig. 8. In Fig. 9, the vertical and the
horizontal axes denote the same items as in Fig. 7. In Fig. 9,
D denotes the case in which one leveler roll 31 positioned at
the left on the under side of the strip 6 is inclined in the
vertical plane, E denotes the case in which one leveler roll 31
positioned at the left on the upper side of the strip 6 is
inclined in the vertical plane, F denotes the case in which both
said leveler rolls 31, 31 are inclined simultaneously in the
vertical plane, and G denotes the case in which one leveler roll
31 positioned at the left on the upper side of the strip 6 is
inclined in the vertical plane and one leveler roll 31 positioned
at the right on the under side of the strip 6 is simùltaneously
inclined in the horizontal plane.
The strip used in this test was a common hot-rolled
steel strip of thickness of 1.2 - 3~2 mm and width of 900 -
1300 mm.
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1 Fig. 9 shows that in any of the cases, the greater the
angle of inclination e of the roll is, the greater becomes the
amount of wandering ~x of the strip and that when the angle of
inclination e of the roll varies in the reverse direction, the
amount of wandering Qx of the strip also varies in the reverse
direction. Fig. 9 shows further that the effect by adjustment
of the angle of the leveler roll is greater in the intermediate
roll than in the roll on the entrance or exit side and that the
effect is enhanced by combining the adjustment of the angle of
inclination of the roll in the vertical plane with the adjustment
of the angle of inclination of the roll in the horizontal plane.
One reason for combining the adjustment of the angle
of inclination of the roll in the vertical plane with that in
the horizontal plane is that when the roll to be adjusted in
the vertical plane is inclined at a large angle in the vertical
plane the intermesh of the leveler roll varies from one edge
of the strip to the other, and if the angle of inclination of
the roll in the vertical plane is made large when the amount of
wandering of the strip is large the shape of the strip at one
2~ edge will be changed into, for example, an edge wave to cause
shape defects. For this reason, the angle of inclination of
the roll in the vertical plane is preferably made small and
the adjustment thereof is preferably combined with the adjustment
of the angle of inclination of the roll in the horizontal
plane.
Practically, it is simplest and most effective to
incline the entire leveler unit in the horizontal and/or the
vertical planes.
In the method according to the present invention
3~ descxibed hereinabove, by adjusting the angle of inclination of
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1 the leveler roll so as to cancel the wandering of the steel
strip during hot rolling thereof, it is made possible to move
the strip centrally of the line to thereby prevent the edges of
the strip from abutting against the guides which would cause
edge defects and to thereby enable the strip to be leveled
stabl~.
~ hile the foregoing description is made with reference
to the example in which the hydraulic cylinder 8 is used as the
means for inclining the leveler rolls 31, it will be obvious to
those skilled in the art that the hydraulic cylinder ~ may ~e
replaced b~v any other suitable inclining means such, for example,
as a rack and pinion mechanism and a link and lever mechanism.
For safer and securer prevention of wandering of the
steel strip, it is preferable to use a position-adjustable
roller type side guide 9 as shown in Figs. lO and 11 or a
position-adjustable plate type side guide 10 as shown ir. Figs. 12
and 13.
In the construction including only one unit of the
hot roller leveler 3, the side guide 9 or 10 is provided either
on the entrance side of the leveler 3 ~Fig. 14) or on the exit
side thereof (Fig. 15) or on each of the entrance and exit sl;des
thereof (Fig. 16).
In the construction including a plurality of the roller
levelers 3, the side guide 9 or 10 is provided only on the
entrance or o~ the exit side of each leveler or on each of said
sides thereof as necessary. Alternatively, the side guide 9
or 10 may be effectively provided in the manner as shown in
any of Figs. 17 to 19.
In the method according to the present invention, as
described hereinabove~ severe wandering of the steel strip is
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1 forcibly restrained by adjusting the angle of inclination of
the leveler roll 3.l and shifting the strip quickly to the central
zone of the line while holding the edges of the strip 6 with the
side guide 9 or 10. Accordingly, it is made.possible to render
stable leveling of the hot rolled steel strip and to sharply
increase the grade of the strip flatness in the hot rolling
line.
By increasing the intermesh of the leveler rolls and
effectively utilizing the leveler as back tension means for
coiling after the coil end passes through the final mill stand,
it is made possible to obtain effects such as prevention of
edge break and other edge defects resulted from a zero tension
state afier the passing of the coil end through the final mill
stand and as grade up of the coiling form.
The leveling operation according to the present
invention can be easily automated by providing a sensor of the
amount of wandering of the strip and connecting the output of
the sensor to the means for adjust.ing the angle of the leveler
roll.
Further, the method according to the present invention
provides additional advantages such as increase in descaling
effect leading to increase in efficiency of the pickling line
because the scale on the surface of the hot rolled strip is
easily cracked by repeated bending under tension width
leveler rolls.
While there has been described and illustrated a present
preferred method of practicing the invention, it is to be dis-
tinctly understood that the invention is not limited thereto
but may be otherwise variously practiced within the scope of
the following claims.
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