Rolling mill

Details Rolling mill Rolling mill

2001-06-11

2003-01-28

Tolan, Ed (Department: 3725)

Metal deforming

By use of roller or roller-like tool-element

With carrier for roller-couple or tool-couple

C072S010600, C072S014500, C072S028200, C072S237000, C072S244000, C072S248000

Reexamination Certificate

active

06510721

ABSTRACT:

TECHNICAL FIELD
This invention relates to a rolling mill for rolling a strip material or a bar material, which passes through upper and lower work rolls, to a predetermined thickness. More particularly, the invention relates to a rolling mill preferred for use in hot rolling.
BACKGROUND ART
FIG. 15
schematically shows a conventional four high cross rolling mill, and
FIG. 16
schematically shows an essential part for illustrating a roll replacement operation in a cross rolling mill.
As shown in
FIG. 15
, upper and roller work roll chocks
002
and
003
as a pair are supported inside a housing
001
. Shaft portions of upper and lower work rolls
004
and
005
as a pair are rotatably supported by the upper and lower work roll chocks
002
and
003
, respectively, and the upper work roll
004
and the lower work roll
005
are opposed to each other. Upper and lower backup roll chocks
006
and
007
as a pair are supported above and below the upper and lower work roll chocks
002
and
003
. Shaft portions of upper and lower backup rolls
008
and
009
as a pair are rotatably supported by the upper and lower backup roll chocks
006
and
007
, respectively. The upper backup roll
008
and the upper work roll
004
are opposed to each other, while the lower backup roll
009
and the lower work roll
005
are opposed to each other. A screw down device
010
for imposing a rolling load on the upper work roll
004
via the upper backup roll chock
006
and the upper backup roll
008
is provided in an upper portion of the housing
001
.
Upper crossheads
011
and
012
for horizontally supporting the upper backup roll chock
006
and the upper work roll chock
002
are provided in the upper portion of the housing
001
and positioned on an entry side and a delivery side of the housing
001
. The upper crossheads
011
,
012
are horizontally movable by screw mechanisms
013
,
014
. Lower crossheads
015
and
016
for horizontally supporting the lower backup roll chock
007
and the lower work roll chock
003
are provided in a lower portion of the housing
001
and positioned on the entry side and the delivery side of the housing
001
. The lower crossheads
015
,
016
are horizontally movable by screw mechanisms
017
,
018
.
Thus, when rolling is performed, a strip S is fed from the entry side of the housing
001
, and passed between the upper work roll
004
and the lower work roll
005
given a predetermined load by the screw down device
010
, whereby the strip S is rolled. The rolled strip S is delivered from the delivery side and supplied to a subsequent step.
The screw mechanisms
013
,
014
,
017
,
018
are actuated before or during rolling, whereby the upper chocks
002
,
006
and the lower chocks
003
,
007
are moved in different directions via the crossheads
011
,
012
,
015
,
016
. As a result, the upper work roll
004
and the upper backup roll
008
, and the lower work roll
005
and the lower backup roll
009
are turned in opposite directions about a roll center so that their rotation axes may cross each other and the angle of their crossed axes may be set at a required angle. By so doing, the strip crown is controlled.
For roll replacement, moreover, the screw mechanisms
013
,
014
,
017
,
018
are actuated to separate the crossheads
011
,
012
,
015
,
016
from the chocks
002
,
003
,
006
,
007
and form gaps g between the roll chocks
002
,
003
,
006
,
007
and the crossheads
011
,
012
,
015
,
016
, as shown in FIG.
16
. Thus, the upper and lower work rolls
004
and
005
and the upper and lower backup rolls
008
and
009
can be withdrawn from a work side by a predetermined device without interference by the crossheads
011
,
012
,
015
,
016
, and can be replaced with new ones.
In all rolling mills including the foregoing four high cross rolling mill, hysteresis during vertical control of the work rolls
004
,
005
and backup rolls
008
,
009
in the housing
001
needs to be minimized in a rolling condition under a screw down force F to control the thickness of a rolled plate highly accurately. For this purpose, gaps G are formed between the work roll chocks
002
,
003
and backup roll chocks
006
,
007
and the crossheads
011
,
012
,
015
,
016
or housing
001
.
Thus, as shown in
FIG. 17
, even when deformation in an inward narrowing amount of &dgr; is caused to the housing
001
under the screw down load F during rolling, gaps of about 0.2 mm to 1.0 mm are present between the roll chocks
002
,
003
,
006
,
007
and the housing
001
or crossheads
011
,
012
,
015
,
016
, so that the horizontal dynamic stiffness of the rolling mill may be low. If rolling is performed with a high rolling force and a high percentage reduction in the thickness of the strip while the horizontal dynamic stiffness of the rolling mill is low, great vibrations probably attributed to, for example, friction between the strip S being rolled and the work rolls
004
,
005
(hereinafter referred to as mill vibrations) occur in the housing
001
or the work rolls
004
,
005
, thereby impeding high efficiency rolling.
As means of preventing vibrations in a rolling mill, Japanese Unexamined Patent Publication No. 1997-174122 discloses a rolling mill provided with a damper comprising a piston, a cylinder and an orifice between an upper work roll and a lower work roll. However, the vibration preventing device of the rolling mill disclosed in this publication is applied to cold rolling, and its application to hot rolling is difficult. That is, in cold rolling, a strip maintained in a room temperature condition is engaged at a low speed between upper and lower work rolls, and continuously rolled. In hot rolling, on the other hand, a strip heated in a high temperature state is engaged at a high speed between upper and roller work rolls, and rolled for each coil of a predetermined length. Thus, hot rolling causes a higher impact force at the time of engagement of the strip with the upper and lower work rolls, and faces impact more frequently, than cold rolling. Furthermore, hot rolling has a greater rolling amount of the strip (a higher rolling force on the strip) than cold rolling, so that the frictional force acting between the work roll and the strip is also higher. This is another factor which makes the impact force greater during engagement. As noted here, hot rolling generates a higher impact force during strip engagement than cold rolling. Hence, the aforementioned vibration preventing device of the rolling mill, which is applied to cold rolling, cannot fully prevent roll vibrations during rolling.
The present invention has been accomplished to solve these problems, and its object is to provide a rolling mill which eliminates gaps between roll chocks and a housing during rolling to increase horizontal dynamic stiffness, thereby suppressing mill vibrations and permitting high efficiency rolling.
DISCLOSURE OF THE INVENTION
A rolling mill of the present invention for attaining the above-mentioned object comprises a housing, upper and lower work roll chocks as a pair supported by the housing, upper and lower work rolls as a pair opposed to each other and having shafts rotatably supported by the upper and lower work roll chocks, screw down means provided in an upper portion of the housing and adapted to apply a predetermined pressure to the upper work roll, first upper and lower support means as a pair provided on one side in a transport direction of a strip material in the housing and adapted to support the upper and lower work roll chocks, and second upper and lower support means as a pair provided on the other side in the transport direction of the strip material in the housing and adapted to support the upper and lower work roll chocks, one of the first support means and the second support means is mechanical thrust means, while the other of the first support means and the second support means is hydraulic thrust means, and contraction portions are provided in hydraulic supply and discharge pipes of the hydraulic thrust means.
Thus, the f

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