U.S. patent application number 13/993101 was filed with the patent office on 2013-10-10 for rolling mill for producing steel for tubes and thin strip.
This patent application is currently assigned to SMS SIEMAG AKTIENGESELLSCHAFT. The applicant listed for this patent is Christoph Klein, Juergen Seidel. Invention is credited to Christoph Klein, Juergen Seidel.
Application Number | 20130263634 13/993101 |
Document ID | / |
Family ID | 45401054 |
Filed Date | 2013-10-10 |
United States Patent
Application |
20130263634 |
Kind Code |
A1 |
Seidel; Juergen ; et
al. |
October 10, 2013 |
ROLLING MILL FOR PRODUCING STEEL FOR TUBES AND THIN STRIP
Abstract
The invention relates to a rolling mill for producing metal
strips, preferably steel for tubes and/or thin strip, in which the
temperature control can be influenced between the finish stands Fi
and Fi+1 using a rapid heating device (induction heater),
characterized in that the distance between the stands Fi and Fi+1,
between which a rapid heating device is arranged, is 5 to 25 m, and
in addition to an induction heater, a roller flattening unit (for
example, roller leveler 14), and/or shears 8, and/or a driving
roller pair 12, and/or a descaling sprayer 15 are arranged as
additional units between the two stands. The roll stand Fi and/or
regions in front of the roll stand Fi further comprise actuators
for influencing the strip warping and/or strip ski-up/-down at the
strip head.
Inventors: |
Seidel; Juergen; (Kreuztal,
DE) ; Klein; Christoph; (Kreuztal-Eichen,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seidel; Juergen
Klein; Christoph |
Kreuztal
Kreuztal-Eichen |
|
DE
DE |
|
|
Assignee: |
SMS SIEMAG
AKTIENGESELLSCHAFT
Duesseldorf
DE
|
Family ID: |
45401054 |
Appl. No.: |
13/993101 |
Filed: |
December 14, 2011 |
PCT Filed: |
December 14, 2011 |
PCT NO: |
PCT/EP11/72815 |
371 Date: |
June 11, 2013 |
Current U.S.
Class: |
72/39 ; 72/201;
72/202 |
Current CPC
Class: |
B21B 45/06 20130101;
B21B 45/004 20130101; B21B 1/463 20130101; B21B 45/00 20130101;
B21B 45/04 20130101 |
Class at
Publication: |
72/39 ; 72/202;
72/201 |
International
Class: |
B21B 45/00 20060101
B21B045/00; B21B 45/06 20060101 B21B045/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 16, 2010 |
DE |
102010063279.1 |
Claims
1. Rolling mill for producing metal strips, preferably steel for
tubes and/or thin strip in which a rapid heating device (8) is
arranged between two, following one another, finishing stands (Fi,
Fi+1), characterized in that distance between the stands (Fi, Fi+1)
between which the rapid heating device (8) is arranged amounts to
5-25 m, and that in addition to the rapid heating device, at least
one further auxiliary unit, in particular a straightening unit,
preferably a roller straightening device (14) (62) is arranged.
2. Rolling mill according to claim 1, characterized in that the
rolling stand (Fi) which is arranged before the rapid heating
device (8), or/and regions before and after the rolling stand (1)
are equipped with actuators for influencing strip curvature and/or
strip-ski phenomenon on the strip head.
3. Rolling mill according to claim 1, characterized in that the
rolling stands (Fi, Fi+1) are finishing stands of preferably
compact continuous train.
4. Rolling mill according to claim 1, characterized in that it
advantageously forms a rolling mill of CPS-installation for
producing thin slabs with a thickness of .ltoreq.120 mm.
5. Rolling mill according to claim 1, characterized in that the
heating device, in particular, an induction heating device,
advantageously, with from 1 to 4 induction elements, is arranged
between the first and second stands (F1, F2) or/and between second
and third stands (F2, F3), or is insertable therebetween.
6. Rolling mill according to claim 1, characterized in that at
least one driving roller pair is arranged between the stand (Fi)
and the following stand (Fi+1) or is insertable therebetween.
7. Rolling mill according to claim 1, characterized in that a
device for correction or prevention of ski-phenomenon in the
intermediate strip is arranged between the stand (Fi) and the
following stand (Fi+1), preferably, before the heating device, or
is insertable therebetween.
8. Rolling mill according to claim 7, characterized in that the
device for correction or prevention of the ski-phenomenon is a
hold-down roller, a hold-down plate, a hold-down strut, a bending
and straightening machine, a strip held-straightening channel or a
strip head-pressing device.
9. Rolling mill according to claim 1, characterized in that at
least one rolling stand (Fi) has separate drives for the upper and
lower working rolls (Fia, Fib).
10. Rolling mill according to claim 1, characterized in that strip
cooling or strip heating means is located before a rolling stand
(Fi) with which temperature distribution over the slab or the strip
thickness is adjusted for influencing the ski-phenomenon and strip
curvature.
11. Rolling mill according to claim 1, characterized in that the
rolling stand (Fi) has, at a run-in side thereof, table
height-adjusting means with which the strip running position is
adjusted.
12. Rolling mill according to claim 1, characterized in that shears
are arranged between at least two rolling stands (Fi, Fi+1) or are
insertable therebetween.
13. Rolling mill according to claim 1, characterized in that a
descaling sprayer is arranged between at least two rolling stands
(Fi Fi+1) or is insertable therebetween.
14. Rolling mill according to claim 1, characterized in that a
distance between two, following one another stands (Fi, Fi+1) is
smaller than the intermediate strip length rolled between the
stands.
15. Rolling mill according to claim 1, characterized in that a heat
insulation hood is arranged between at least two rolling stands
(Fi, Fi+1), in particular, as a replacement for previously removed
units, or is insertable therebetween.
16. Rolling mill according to claim 1, characterized in that the
rolling mill is connected with a process model which controls and
regulates different measures and adjustments for influencing the
ski-phenomenon.
17. Rolling mill according to claim 1, characterized in that the
rapid heating device is formed compact and a power density, which
is inducted in the strip, amounts to at least 1,500 megawatt per
square meter, preferably, to about 4,000 megawatt (+/-18%) per
square meter.
Description
[0001] The invention relates to a rolling mill, in particular, a
CSP-installation for producing strips, in particular, steel for
tubes and/or thin strips, including a caster for producing thin
slabs and a rolling mill for rolling a thin slab to a strip or thin
strip.
[0002] Production of steel strips or steel plates by hot rolling is
adequately described in the state-of-the art. Corresponding
disclosures are found, e.g., in a paper of P. Uranga et al.,
"Improvement of Micro-structural Homogeneity in Thermo-mechanically
Processed Nb Steel by Thin Slab Casting," 43.sup.rd Mechanical
Working and Steel Processing Conference, Charlotte, ISS, Vol. 39,
pages 511-529; in a paper of Kinkenberg, et al., "Processing of
Niobium Microaloy API Grade Steel on a Thin Slab Plant", Material
Science Forum, Vols. 500-501, 2005, pages 253-260; and in a paper
of S. V. Subramanian, et al., "Process modeling of micro-alloyed
steel for near net shane casting" Proc. Of the Int. Conf. on
Thermomechanical Processing;" "Mechanics, Microstructure, ed. by E.
J. Palmiere et al., The University of Shefield, Shefield 2003,
pages 148-156.
[0003] CSP) (Compact Strip Production)--installations are casting
and rolling installations in which two separate working steps for
production of steel strip are closely connected with each other,
namely, the casting of liquid steel in thin slabs in the caster and
rolling of thin slabs in steel strip in the rolling installation.
With this, usually the rolling of the previously cast strand is
carried out directly with use of the casting heat or by adjusting
the desired rolling temperature using a compensation furnace or a
heating device between the caster and the rolling mill.
[0004] Conventional rolling mills of a thick slab installation have
at least one roughing stand or heavy-plate stand and a finishing
rolling train arranged after the roughing stand or heavy-plate
stand at a distance therefrom. While in the roughing stand or
heavy-plate stand, the thin slab is rolled, usually in a reversing
operation, to an intermediate strip with a predetermined thickness,
the rolling in the finishing rolling train takes place in tandem
operation, with the finishing rolling train being formed as a
continuous rolling train. While the distance between separate
stands of such finishing train is usually constant and usually
amounts to 5.5 m, the distance between the roughing stand or
heavy-plate stand and the first stand of the finishing train is
usually many times greater in order to insure the reversing
operation in the roughing stand or heavy plate stand. In this
connection, the distance between the roughing stand or heavy-plate
stand and the finishing train of about 50 m or more is no
rarity.
[0005] Conventional rolling mills have, because of a usually
alignment arrangement of the thick slab--extraction roller table of
the slab furnace, the roughing stand or heavy plate stand, and the
finishing train, a large length, and require powerful stands, so
that investment costs are high. Energetically, conventional rolling
mills are inferior in comparison with CSP-installations. In
particular, during production of thin strips, the entry temperature
in the finishing train is very low, which makes rolling of thin
strips difficult. Also, the production of steel for tubes in a
conventional hot rolling mill, because of the necessary temperature
control, is very time-consuming and reduces the production of a
conventional rolling mill.
[0006] Accordingly, the object of the invention to provide a
rolling mill of the type described above in which the
above-described drawbacks can at least be reduced. Within the
meaning of the invention, the object of the invention is achieved
with a rolling mill having features of claim 1. Advantageous
embodiments of the invention are defined by dependent claims.
[0007] The rolling mill according to the present invention, in
particular, of a CSP-installation, advantageously consists of a
compact rolling mill for producing metal strips, especially steel
for tubes and/or thin strips, and in which the temperature between
two, following one another finishing stands Fi and Fi+1 can be
influenced by a rapid heating device, in particular, an induction
heating device. In addition to the rapid heating device,
advantageously a straightening unit, preferably, a roller
straightening device, and/or shears, or/and, optionally, a
descaling sprayer, or another strip cooling device can be arranged
between the stands Fi and Fi+1. All of the devices are so compactly
located that they fit in the spacing between the stands of 5-25 m.
Further, the stand Fi is equipped upstream of the rapid heating
device with actuators for influencing the strip warping and/or the
ski-phenomenon on the strip head.
[0008] Together with the straightening unit, advantageously, the
roller straightening device, and/or the shears and above-mentioned
actuators, a reliable passage in a limited space through the rapid
heating device, in particular, induction heating device, can be
insured with a minimal clearance in the thickness direction.
Dependent on the process, the rapid heating device, the shears,
and/or the descaling sprayer is (are) used or are displaced
sidewise, dependent on the to-be-rolled product, or there,
alternatively, a roller table, with or without heat insulation, or
a table can be arranged. Also for carrying out thin strip rolling,
shears can be provided between the stands, in order to take care of
as straight as possible heads and ends of the deformed strip.
[0009] As a result of additional devices between the stands, the
normal spacing between the stands, e.g., .gtoreq.5.5, is increased.
In order to eliminate a possible secondary scale formation,
advantageously, a single descaling sprayer is provided, which is
formed as a compact device and, advantageously, is arranged before
the stand Fi+1 behind the rapid heating device. For rolling of
strip, with high requirements to surface quality (e.g., for rolling
of thin strips), the descaling sprayer in front of the stand Fi+1
can be activated. During production of tubes, the descaling sprayer
can be optionally deactivated or removed from the rolling line.
[0010] In order to save space, optionally, a looper can be
dispensed with and, instead of it, means for regulating tension,
with or without a tension measuring roller, can be provided.
[0011] In comparison with conventional rolling mills with induction
heating between the roughing and finishing trains, the inventive
use of a rolling mill, preferably, a rolling mill of a
CSP-installation with corresponding additional units, noticeably
reduces the space occupied by the rolling mill. The use of
additional units, which are selectively inserted in the finishing
rolling mill, advantageously improves the rolling process as with
regard to carrying out the process so with regard to obtaining of a
corresponding structure. The additional units require, according to
the invention, little space and are arranged between two finishing
stands, the distance between which amounts to 5-25 m. On the other
hand, the space requirement between two stands with additional
units is much smaller than the length of the intermediate strip
which is rolled there.
[0012] Advantageously, a thin strip, which is cast by a caster of
CSP-installation, has a thickness, equal or less than 120 mm.
Thereby, there is provided a CSP-installation that alone, without
use of a reversing roughing stand, and with the use of a number of
finishing stands forming a rolling mill, is in a condition to
produce a desired production spectrum from a thick tube strip to a
thin strip.
[0013] As an example and a preferred embodiment, a method and the
production of a tube strip in a CSP-installation will be described.
The TM-method (thermomechanical method) in a CSP-installation
consists as a rule of a step of one or more deformations of an
austenitic initial structure in recrystallization temperature range
for producing a uniform, fine, recrystallized austenite structure,
and a following step of one or several deformations of the
recrystallized, austenitic structure for producing a
high-dislocation, extended in an area as much as possible,
non-recrystallized austenite structure (so-called pancake
structure). Thus, these steps can be called conditioning of the
austenite.
[0014] Finally, in a further step, cooling of austenitic structure
which has been produced in the first step, is carried out for
producing a fine-grain structure in the finished hot rolled strip
or hot rolled sheet with a phase conversion. The structure of the
finished hot rolled strip or hot rolled sheet consists of a
combination of ferrite, perlite, bainite, and martensite, wherein
the content of these four structure components can, respectively,
amounts to between 0% and 100%.
[0015] As a result of the above-described TM-method, it is also
possible to dispense with the above-mentioned step of deformation
in the non-recrystallized temperature range of the austenite. In
this case, the conditioning of the austenite takes place entirely
in the recrystallization temperature region of the austenite.
[0016] The difficulty with the mechanical hot rolling consists,
however, in that for producing the uniform, fine recrystallized
austenite grain in the recrystallization range, as large as
possible deformation should be undertaken. A fine recrystallised
structure is distinguished by the fact that not only the former,
non-uniform cast structure, but also individual coarse grains or
structure regions have to be completely transformed into a uniform,
fine recrystallised structure with small scatter around the mean
grain size. This condition frequently is not fulfilled or is
fulfilled incompletely and leads to an inadequately conditioned
austenite structure.
[0017] If a step of hot rolling in the non-crystallization
temperature range of the austenite follows the step of hot rolling
in the recrystallisation temperature range of the austenite, often
only little residual deformation for the succeeding actions in the
thermomechanical treatment remains when there is a large ratio of
the thickness of the finished hot strip or hot sheet and the
thickness of the slab or the intermediate strip. Even when
individual stands are taken out, this, on occasion, is not
sufficient to transform possibly still present residues of the cast
structure as well as individual coarse grains or structure regions
into a uniform flat pancake structure of non-recrystallised
austenite grains. An insufficiently conditioned austenite is also
present in this case.
[0018] Inadequately conditioned austenite has the disadvantageous
consequence in the finished hot strip or hot sheet consisting in
the presence of individual coarser grains outside the normal
distribution about the mean grain size and/or of structure regions
having a substructure characterized by small-angle grain
boundaries. However, structure regions of that kind lead to
deterioration in the mechanical properties of the strip or sheet,
particularly to a reduced toughness.
[0019] In correspondence with the description above of TM-method,
the deformation in the recrystallization range of the austenite is
of critical importance for the characteristics of the finished
steel strip or sheet. The degree of the deformation required in
first step of the thermomechanical treatment can, in fact, be
replaced in part by an elevated entry temperature. However, this
possibility is limited by the maximum furnace temperature as well
as by the cooling at the time of contact with the roll and by
thermal radiation between the stands when several stands
participate in this step.
[0020] Particularly advantageously is a CSP-installation in which a
heating device is arranged between two stands Fi and Fi+1 of the
rolling mill, in particular between a first stand F1 and the second
stand F2. If needed, the heating device can be removed from the
rolling mill and again inserted therein. A particularly
advantageous is an induction heating device, especially one with
one-four induction elements. Altogether, with such heating devices,
one strives for a construction as compact as possible with a high
power density. The power density lies, advantageously in a range
with at least 1500 mw per square meter, preferably, with about
4,000 mw per square meter, when measuring the power density that
has been just applied to the strip or induced therein. As an
inductor element, such constructional element is designated through
which power is applied to the strip. One or several induction
elements can provide induction heating.
[0021] At the end of the installation, the rolling mill, preferably
a continuous rolling mill is used within which the above-described,
in the example, deformation steps are used at high temperature and,
if needed, with a support of a heating device between the finishing
stands and, at an optional cooling of rolls at lower temperatures.
Here, no roughing stand or heavy-plate stand, which is conventional
for thick slab installations, is used.
[0022] Advantageously, the deformation steps are joined together,
which means that all of the involved stands are simultaneously
operated in accordance with entry of thin slabs or intermediate
strips. On this occasion, the rolling stands operate in tandem, so
that operationally, the thin slab or the intermediate strip
simultaneously passes through common rolling stands. Separate
stands can be displaced and, thus, would not take part in the
deformation operation.
[0023] In a continuous operation, a method can be used in which the
cast strand need not be cut in slabs, but rather is continuously,
preferably, through a tunnel furnace, is fed to a hot rolling mill,
is rolled in a hot rolled strip, is separated before a reel, and is
wound in a coil. This process prevents accumulation of scrap as no
head or foot ends of a strip are produced. In addition, even
thinner strips with advantageously a thickness less than 1 mm can
be produced because the danger of a rise (hills) during entry of a
thinner strip in the last stand of the hot rolling mill at the
start is reduced. During continuous rolling, the feeding speed of
the first active stand is reduced to the casting speed which can
lead to increased temperature losses before and/or during the hot
rolling process. However, for rolling, high rolling temperatures
and, thus, heating of the strip is necessary to avoid rolling
temperatures in the ferrite phase and/or the two-phase area
austenite plus ferrite.
[0024] One of such method and appropriate apparatuses permit in
principle the production of different steels with a reduced
austenite phase area, e.g., with silicon content of more than 1%.
For this, for rolling, higher rolling temperatures are necessary to
reliably avoid rolling temperatures in the ferrite phase and/or the
intermediate phase austenite plus ferrite. Such steel goods can be
produced, without further addition, on the inventive
CSP-installation.
[0025] During the production of strips or thin strips, as discussed
above, advantageously an induction heating is provided between the
front stands or at least in the region between the front stands.
Advantageously, the induction heating is provided between the first
and second or/and the second and third stands of the finishing
mill.
[0026] The induction heating, however, is characterized by a
comparatively small penetration in the thickness direction and is a
sensible component. During rolling in a finishing mill, in
particular in the first stand, often, so-called skis, or other such
strip cambers, or unflatness are present on the head, which
endanger passage of tube strips or thin strips through the
induction heating means or other units (shears, descaling sprayer)
between two finishing stands. Besides, the above-mentioned ski-up
or ski-down phenomenon makes the insertion of the pre-rolled
intermediate strip in a following stand very difficult. In an
unfavorable case, the intermediate strip can damage the units
between the two finishing stands.
[0027] The reduction or elimination of skis can, e.g., be carried
out with hold-down rollers or bending and straightening devices.
However, it is most advantageous when in the inventive
installation, the pre-rolled intermediate strip heads are cut off
by a suitable cutting device. Optionally, with such a cutting
device, both the head and the end of a pre-rolled intermediate
strip can be cut off when thin finished strips are produced in a
batch operation.
[0028] In a further advantageous embodiment of the inventive
installation, dependent on the rolled strip material, descaling
means can be arranged downstream, in the rolling direction, of the
heating means for heating the intermediate strip, if necessary,
after the strip passes through the heating device and the
downstream located drive roller pair and before the intermediate
strip enters in one or several finishing rolling stands. Thereby,
it is insured that an almost impurities-free thin strip or a tube
strip can be finish-rolled, without the scale damaging the surface
of the strip or thin strip.
[0029] In order to insure a reliable passage of the intermediate
strip through the devices between two finishing stands, there is
provided, according to the invention, a number of possible control
elements which can be used separately or in any arbitrary
combination.
[0030] The rolling stand itself can have a twin drive and different
speed settings on the upper and lower rolls dependent, e.g., on an
entry thickness, thickness reduction, material or the temperature,
and different diameters of the upper and lower working rolls.
[0031] For influencing the temperature distribution of the rolled
product in thickness direction, the adjustment of slab and strip
cooling before the rolling stand Fi can be carried out so that as
symmetrical as possible temperature profile over the thickness of
the rolled stock is provided, or by a well-aimed temperature
trimming, the ski-phenomenon is influenced. Alternatively, to this
end, trimming of the slab temperatures on upper and lower sides is
possible in front of a stand with a heating device.
[0032] There is further provided for table height adjustment before
the finishing sand Fi so that a predetermined slab entry position
into the roll gap (e.g., the rolling stock middle=rolling gap
middle) is reliably established.
[0033] The occurrence of a non-linear strip run (ski, amber,
curvature) can be particularly easily prevented by using a
straightening unit. This device for correction or prevention of
skis or strip camber in form of a straightening unit can be, in
addition to a roller straightening machine, also a hold-down
roller, a hold-down plate, a hold-down strut, a bending and
straightening machine, a strip head-straightening channel, a strip
head pressing device.
[0034] As it has already been discussed above, a ski can be cut off
the rolling stock with shears.
[0035] Finally, occurrence of unevenness in the intermediate strip,
in particular before the entry into the heating device can be
detected advantageously with suitable surface distance sensors.
Suitable sensors such as mechanical, optical, or the like are known
to one of ordinary skill in the art. Based on the alarm signal,
control means which is connected with the sensors, can initiate
appropriate measures for eliminating or reducing the detected
non-linear strip run, or turn the intermediate strip or slab
back.
[0036] Not only the heating device can protect the above-described
devices from damage by strip curvatures, but also the damage, in
particular produced by induction heating as a result of cooling
water remaining on the strip or thin strip, can be minimized by
using suitable blowers advantageously located between the rolling
stands of the inventive finishing rolling mill or inserted
therebetween.
[0037] The above-mentioned auxiliary units and measures for
ski-elimination can be used preferably in a CSP-finishing mill for
different application. However, they can also be inserted between
the finishing stands of a conventional rolling mill.
[0038] Induction heating and auxiliary units can be fixedly
arranged or displaced in and out from the rolling line. As a
substitute for the movable units, a heat insulation hood is
provided.
[0039] The invention will now be explained in detail below with
reference to the drawings which show several embodiments of the
inventive CSP-installation. The drawings show:
[0040] FIG. 1 a first embodiment of the invention in which
induction heating means and a driving roller pair are arranged
between two stands of a schematically shown strip hot rolling
mill;
[0041] FIG. 2 a second embodiment of the invention with a device
for correction/prevention of a ski-phenomenon on the intermediate
strip head which is arranged upstream of the heating device in a
strip rolling direction;
[0042] FIG. 3 a third embodiment of the inventive hot rolling mill
in which a heating device is arranged between a device for
correction/prevention of a ski-phenomenon on the intermediate strip
head and a descaling sprayer, with all three being located between
two rolling stands of a hot rolling mill;
[0043] FIG. 4 a fourth embodiment of an inventive hot rolling mill
with arranged one after another, in the rolling direction shears,
rapid heating means, driving rollers, and descaler; and
[0044] FIG. 5 a fifth embodiment of an inventive hot rolling
mill.
[0045] FIG. 1 shows a portion of a hot rolling mill 2 according to
the first embodiment in which a metal strip 1 runs through a first
rolling stand designated as Fi and a second rolling stand
designated as Fi+1. The distance between the stands Fi and Fi+1
amounts to from 5 m to 25 m. After exiting the finishing stand Fi,
the strip 1 runs directly in induction heating means 8 and,
finally, into the driving roller pair 12. This driving roller pair
12 can provide a strip tension (even before the strip head reaches
the following stand) of the strip 1 and, the water which remains on
the strip 1, can be easily squeezed. A minimal tension control can
be carried out between the stands Fi and Fi+1. The driving roller
pair 12 helps to precisely adjust the set speed in the stand Fi+1.
Alternatively, a tension measuring roller or a looper (not shown)
can be arranged between the stands in order to insure the mass flow
rate. Finally, downstream of the rolling stand Fi+1 in the rolling
direction, there is provided a cooling section 11 for cooling the
strip 1, which was heated in the heating device 8 to a temperature
above the recristallization temperature, to a temperature lying in
a non-recristallization region. Both devices 8 and 12 can change
their places. Also, arrangement of the driving roller pair 12
before or behind the heating device 8 can be contemplated.
[0046] FIG. 2 shows a further embodiment of the hot rolling mill 2
according to the invention in which again the finishing stand Fi
and the finishing stand Fi+1 are shown. Again, a heating device 8
for a rapid heating of the metal strip 1 by induction heating is
arranged between the rolling stands Fi and Fi+1.
[0047] In the rolling direction W, a device 14 for
correction/prevention of a ski-phenomenon on the intermediate strip
that have left the finishing stand Fi, is arranged between the
finishing sand Fi and the heating device 8. Such a device 14 for
correction/prevention a ski-up or -down can, e.g., be formed as a
bending and straightening driver or as a hold-down roller. Such
device 14 should correct a phenomenon of, e.g., elevated strip head
after exiting a rolling stand (a so-called ski-up), i.e., to
eliminate or to reduce it to an acceptable achievable minimum.
First of all, this serves to prevent downtime resulting from
imprecise or non-entry of the intermediate strip head in a
following unit, e.g., the rapid heating device 8, other units
(shears, descaling sprayer/or each further stand Fi+1). In order to
prevent the ski-phenomenon, the hot rolling mill according to the
invention has a least one rolling stand, preferably, the first
rolling stand Fi, with separated and not connected with each other
drives for the upper working roll Fia and the lower working roll
Fib. Thereby, with a suitable control of the drives, the ski-up or
also ski-down-phenomenon is reduced to a minimum value already
during rolling.
[0048] FIG. 3 shows a third embodiment of the inventive hot rolling
mill 2 in which between the first shown rolling stand Fi and the
second shown rolling stand Fi+1, a rapid heating device 8 follows
the device 14 for correction of the ski-phenomenon on the
intermediate strip head. Between the rapid heating device 8 and the
rolling stand Fi+1, a descaling sprayer 15 is arranged with which
the scale that sticks to the surface of the strip 1, can again be
reliably removed. Optionally, this embodiment of the invention can
have a driving roller pair (not shown) and/or a cooling section
(not shown).
[0049] FIG. 4 shows a fourth embodiment of the inventive hot
rolling mill 2 in which between the first shown rolling stand Fi
and the second shown rolling stand Fi+1, there are arranged, in the
rolling direction W of the strip 1, shears 13, rapid heating device
8, driving roller pair 12, and descaling sprayer 15. While the
rapid heating device 8, the driving roller pair 12, and the
descaling sprayer 15 function in the same way as in the embodiments
according to FIGS. 2-4, the shears 13 serves primarily for cutting
off the strip head and, if necessary, the strip end on which rolled
tongues or bends (so-called ski) can be formed. Thus, the shears 13
replaces, on one hand, devices shown in previous embodiments (not
shown here) for correction/prevention of a ski-phenomenon and, in
addition, the shears 13 advantageously support a further rolling
process by cutting off the tongues which can adversely influence
the running of the strip 1 and the working rolls of the following
stands.
[0050] In FIG. 5, a fifth embodiment of the inventive hot rolling
mill 2 is shown in which there are arranged, in the rolling
direction of the strip 1, finishing stand Fi, device 14 for
correction/prevention of a ski-up, shears 13, and rapid heating
device 8. After exiting the rapid heating device 8, the metal strip
1 enters a driving roller pair 12 which squeeze the residual water
that remained on the metal strip 1. After leaving the driving
roller pair 12, the metal strip 1 enters the descaling sprayer 15
in which the residual scale that has formed on the surface of the
strip 1, is reliably removed before entry of the strip 1 in the
finishing stand Fi+1. Finally, dependent on application, the strip
1 that have been heated in the rapid heating device 8, can be
cooled again in the cooling section 11 and be rolled to a finished
strip thickness.
[0051] The rapid heating device 8 and the shears 13 can be
arranged, viewing in the strip running direction, alternatively or
in reverse.
[0052] In case the distance between the stands should be further
reduced, the rapid heating device 8 and the descaling sprayer 15
can be located, viewing in the strip running direction, at the same
location and, alternatively, be displaced sidewise in the rolling
line so that either the descaling sprayer 15 or the rapid heating
device 8 is used.
* * * * *