U.S. patent application number 12/602277 was filed with the patent office on 2010-07-15 for method for hot rolling and for heat treatment of a steel strip.
Invention is credited to Joachim Ohlert, Ingo Schuster, Juergen Seidel, Peter Sudau.
Application Number | 20100175452 12/602277 |
Document ID | / |
Family ID | 40030935 |
Filed Date | 2010-07-15 |
United States Patent
Application |
20100175452 |
Kind Code |
A1 |
Ohlert; Joachim ; et
al. |
July 15, 2010 |
METHOD FOR HOT ROLLING AND FOR HEAT TREATMENT OF A STEEL STRIP
Abstract
The invention relates to a process for hot rolling and for heat
treatment of a strip (1) of steel. To make it possible to produce
high-strength and very high-strength strips having satisfactory
toughnesses more economically in a continuous production plant, the
process provides the steps: a) heating of the slab to be rolled; b)
rolling of the slab to the desired strip thickness; c) cooling of
the strip (1), with the strip (1) having a temperature above
ambient temperature (T.sub.0) after cooling; d) rolling up of the
strip (1) to produce a coil (2); e) rolling off of the strip (1)
from the coil (2); f) heating of the strip (1); g) cooling of the
strip (1) and h) transport of the strip (1) to a further
destination, with the strip (1) having a temperature above ambient
temperature (T.sub.0) before heating as per step T).
Inventors: |
Ohlert; Joachim; (Koeln,
DE) ; Schuster; Ingo; (Willich, DE) ; Sudau;
Peter; (Hilchenbach, DE) ; Seidel; Juergen;
(Kreuztal, DE) |
Correspondence
Address: |
KF ROSS PC
5683 RIVERDALE AVENUE, SUITE 203 BOX 900
BRONX
NY
10471-0900
US
|
Family ID: |
40030935 |
Appl. No.: |
12/602277 |
Filed: |
June 4, 2008 |
PCT Filed: |
June 4, 2008 |
PCT NO: |
PCT/EP08/04435 |
371 Date: |
March 19, 2010 |
Current U.S.
Class: |
72/200 |
Current CPC
Class: |
C21D 8/0463 20130101;
C21D 8/0426 20130101; B21B 1/26 20130101; C21D 8/0252 20130101;
C21D 9/48 20130101; C21D 8/0226 20130101; C21D 8/0263 20130101;
C21D 9/46 20130101; C21D 8/0452 20130101 |
Class at
Publication: |
72/200 |
International
Class: |
B21B 1/00 20060101
B21B001/00; C21D 8/02 20060101 C21D008/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 22, 2007 |
DE |
10 2007 029 280.7 |
Feb 20, 2008 |
DE |
10 2008 010 062.5 |
Claims
1. A method for hot rolling and for heat treatment of a strip of
steel, the method comprising the steps of: a) heating the slab to
be rolled; b) rolling the slab to the desired strip thickness; c)
cooling the strip, wherein after cooling the strip has a
temperature above the ambient temperature; d) coiling the strip
into a coil; e) uncoiling the strip from the coil; f) heating the
strip; g) cooling the strip and h) removing the strip, wherein
before the heating according to step f), the strip has a
temperature above the ambient temperature and wherein when carrying
out step d), the coil is located at a coiling station and that when
carrying out step e), it is located at an uncoiling station
spatially remote from the coiling station, wherein the coil is
transported from the coiling station to the uncoiling station
between steps d) and e) in a thermally insulated manner.
2. (canceled)
3. The method according to claim 1 wherein step e) directly follows
step d).
4. The method according to claim 1 wherein during cooling or after
cooling according to step c) and/or according to step g), the strip
is subjected to a straightening process.
5. The method according to claim 1 wherein between the uncoiling
according to step e) and the heating according to step f), the
strip is subjected to a straightening process.
6. The method according to claim 1 wherein between the heating
according to step f) and the removal according to step h), the
strip is subjected to a straightening process.
7. The method according to claim 4 wherein the straightening
process is effected by deflecting the strip around base,
deflecting, driving or other rollers.
8. The method according to claim 5 wherein the straightening
process is carried out by means of a skin-pass frame.
9. The method according to claim 1 wherein the strip is subjected
to a straightening process during the heating according to step
f).
10. The method according to claim 1 wherein the cooling of the
strip according to step c) comprises a laminar cooling and
intensive cooling.
11. The method according to claim 1 wherein the cooling of the
strip according to step g) comprises a laminar cooling.
12. The method according to claim 1 wherein the cooling of the
strip according to step c) and/or according to step g) takes place
in zones over the width of the strip.
13. The method according to claim 1 wherein the cooling of the
strip according to step g) comprises air cooling.
14. The method according to claim 1 wherein the cooling of the
strip according to step g) is carried out by means of a
high-pressure bar so that cleaning and/or descaling of the strip
takes place at the same time.
15. The method according to claim 1 wherein the heating of the
strip according to step f) comprises inductive heating.
16. The method according to claim 15 wherein the inductive heating
of the strip takes place in an inert gas atmosphere.
17. The method according to claim 1 wherein the heating of the
strip according to step f) is effected by direct flame impingement
of the strip.
18. The method according to claim 17 wherein the direct flame
impingement of the strip is effected by a gas jet comprising at
least 75% oxygen in which a gaseous or liquid fuel is mixed.
19. The method according to claim 18 wherein the direct flame
impingement is effected by a gas jet comprising pure oxygen.
20. The method according to claim 1 wherein the removal of the
strip according to step h) comprises coiling the strip.
21. The method according to claim 1 wherein the removal of the
strip according to step h) comprises pushing off plate-like cut
portions of the strip.
22. The method according to claim 1 wherein before the cooling
according to step c) the strip has a temperature of at least
750.degree. C.
23. The method according to claim 1 wherein after the cooling
according to step c) and before coiling according to step d), the
strip has a temperature of at least 25.degree. C. and at most
400.degree. C., preferably between 100.degree. C. and 300.degree.
C.
24. The method according to claim 1 wherein after the heating
according to step f), the strip has a temperature of at least
400.degree. C., preferably between 400.degree. C. and 700.degree.
C.
25. The method according to claim 1 wherein the heating of the
strip according to step f) is effected so that the strip has
different temperatures over its width.
26. The method according to claim 1 wherein after the cooling
according to step g) and before removal according to step h), the
strip has a temperature of at most 200.degree. C., preferably
between 25.degree. C. and 200.degree. C.
27. The method according to claim 1 wherein the steps e) to g) are
carried out in reversing mode for which a coiling station located
after the cooling according to step g) is used.
28. The method according to claim 1 wherein the flatness of the
strip and/or the temperature of the strip is measured at least at
two locations in the strip treatment installation for monitoring
the quality of the strip.
29. The method according to claim 1 wherein the running speed of
the strip through the strip treatment installation, the in
particular zone-related strip heating, the adjustment of the
straightening rolls and/or the in particular zone-related cooling
are controlled or regulated by a process model.
30. The method according to claim 1 wherein during passage through
the strip treatment installation, the strip is held under a defined
strip tension at least in sections by means of drivers.
31. (canceled)
32. The method according to claim 1 wherein a strip tension is
built up by means of drivers before and after the cooling of the
strip.
33. The method according to claim 1 wherein a strip is guided
transversely to its longitudinal axis by means of a lateral
guidance.
34. The method according to claim 33 wherein the lateral guidance
takes place in the area of the cooling of the strip.
35. The method according to claim 34 wherein the lateral guidance
takes place in the area of the laminar cooling of the strip.
36. The method according to claim 32 wherein lateral guidance of
the strip takes place before the driver and opens after passing the
strip head and closes at the strip end.
37. The method according to claim 1 wherein a measurement of the
strip temperature is made by means of a low-temperature radiation
pyrometer.
38. The method according to claim 1 wherein a measurement of the
strip temperature is made before, inside and/or after the cooling
and/or heating devices.
Description
[0001] The invention relates to a method for hot rolling and for
heat treatment of a strip of steel.
[0002] The hardening and subsequent tempering of steel components
is common practice. This has the result that a desired combination
of strength and toughness of the material can be specifically
adjusted. This technology is also used in principle in the
production of high-strength steel sheet in sheet plants. It is
described in EP 1 764 423 [US 2008/0283158]. In this case, after
heating the slab and rolling down to the final thickness on the
heavy plate stand in a plurality of reversing passes, the sheet is
cooled to room temperature at high speed, for example, i.e. the
hardening process is carried out. This is followed by the tempering
process, i.e. re-heating of the strip to, for example, 600.degree.
C. followed by renewed cooling. Thus, sheet having different
properties can be produced flexibly in small batch sizes in a sheet
stand.
[0003] As in the sheet production sector, the demand for types of
steel having very high strength is also increasing continuously in
strip production, i.e. the demand for so-called high-strength and
ultrahigh strength steels. These materials are used, inter alia, in
motor vehicles, cranes, containers and in pipes.
[0004] It is thus the object of the present invention to provide a
method whereby high-strength and ultrahigh-strength strip having
sufficient toughness can be produced more economically in a strip
plant. In particular, it should advantageously be possible to
produce QT steels by this method.
[0005] The solution of this object by the invention is
characterized in that the method comprises the steps:
[0006] a) heating the slab to be rolled;
[0007] b) rolling the slab to the desired strip thickness;
[0008] c) cooling the strip, wherein after cooling the strip has a
temperature above the ambient temperature;
[0009] d) coiling the strip into a coil;
[0010] e) uncoiling the strip from the coil;
[0011] f) heating the strip;
[0012] g) cooling the strip and
[0013] h) removing the strip,
[0014] wherein before heating according to step f), the strip has a
temperature above the ambient temperature.
[0015] In a preferred embodiment of the invention, when carrying
out step d) the coil is located at a coiling station wherein, when
carrying out step e) the coil is preferably located at an uncoiling
station spatially remote from the coiling station and wherein the
coil is transported from the coiling station to the uncoiling
station between steps d) and e) in a thermally insulated manner,
possibly via a heat-insulating coil store.
[0016] Step e) can directly follow step d).
[0017] During cooling or after cooling according to step c) and/or
according to step g), the strip can be subjected to a straightening
process. It can also be subjected to a straightening process
between the uncoiling according to step e) and the heating
according to step f). It can also be subjected to a straightening
process between the heating according to step f) and the removal
according to step h). Said straightening process can be effected by
deflecting the strip around base, deflecting, driving or other
rollers.
[0018] The straightening process is usually carried out by means of
a roller straightening machine or screwed-down strip deflecting
rollers or, according to a special embodiment of the invention, on
a so-called skin-pass frame.
[0019] The strip can also be subjected to a straightening process
during the heating according to above step f).
[0020] The cooling of the strip according to step c) can comprise a
laminar cooling and downstream intensive cooling. The cooling of
the strip according to step g) can also comprise a laminar cooling
or alternatively or additively air cooling.
[0021] At least parts of the cooling device can be configured as
zone cooling which acts in zones over the width of the strip.
[0022] The cooling of the strip can also be carried out by means of
a high-pressure bar so that cleaning and/or descaling of the strip
is possible at the same time.
[0023] The heating of the strip according to step f) can comprise
inductive heating. Alternatively, direct flame impingement of the
strip can be effected. In the latter case, it is preferably
provided that the direct flame impingement of the strip is effected
by a gas jet comprising at least 75% oxygen, preferably comprising
almost pure oxygen, in which a gaseous or liquid fuel is mixed.
[0024] A further development provides that the inductive heating of
the strip takes place in inert gas (protective gas).
[0025] The removal of the strip according to step h) can comprise
coiling the strip. The removal of the strip according to step h)
according to claim 1 can also comprise pushing off plate-like cut
portions of the strip.
[0026] Before the cooling according to step c) the strip preferably
has a temperature of at least 750.degree. C.
[0027] After the cooling according to step c) and before coiling
according to step d), the strip preferably has a temperature of at
least 25.degree. C. and at most 400.degree. C., preferably between
100.degree. C. and 300.degree. C.
[0028] A further development furthermore provides that after the
heating according to step f), the strip preferably has a
temperature of at least 400.degree. C., preferably between
400.degree. C. and 700.degree. C. Meanwhile, after the cooling
according to step g) and before the removal according to step h),
the strip can preferably have a temperature of at most 200.degree.
C., preferably between 25.degree. C. and 200.degree. C.
[0029] The heating of the strip can take place at different
intensity over the strip width.
[0030] Finally, it can be provided that the steps e) to g) are
carried out in reversing mode for which a coiling station located
after the cooling according to step g) is used.
[0031] It can furthermore be provided that the flatness of the
strip and/or the temperature of the strip (the latter preferably by
means of a temperature scanner) is measured at least at two
locations in the strip treatment installation for monitoring the
quality of the strip.
[0032] The running speed of the strip through the strip treatment
installation, the, in particular, zone-related strip heating, the
adjustment of the straightening rolls and/or the in particular
zone-related cooling can be controlled or regulated by a process
model.
[0033] During passage through the strip treatment installation, the
strip can be held under a defined strip tension at least in
sections by means of drivers. This applies particularly in the area
of the intensive cooling section.
[0034] In order to ensure that the strip runs centrally in the
driver, in the roller straightening unit or in the intensive
cooling section, a strip lateral guide is preferably located in
front thereof.
[0035] An alternative embodiment of the method for hot rolling and
for heat treatment of a strip of steel comprises the steps:
[0036] a) heating the slab to be rolled;
[0037] b) rolling the slab to the desired strip thickness;
[0038] c) cooling the strip, wherein after cooling the strip has a
temperature above the ambient temperature;
[0039] d) coiling the strip on a first coiler;
[0040] e) reversing the strip between the first coiler and a second
coiler wherein the strip is subject to heating between the
coilers,
[0041] wherein before the heating according to step e), the strip
has a temperature above the ambient temperature.
[0042] This method can also be combined with the aforesaid
embodiments.
[0043] In the case of materials for which no tempering is required,
i.e. for which the strength and toughness properties already meet
the requirements after step d), process steps a) to d) can be used
by themselves alone.
[0044] The following further developments have proved
successful:
[0045] A strip tension can be built up by means of drivers before
and after the cooling of the strip.
[0046] The strip can be guided transversely to its longitudinal
axis by means of a lateral guidance. The lateral guidance can
preferably take place in the area of the cooling of the strip, in
particular in the area of the laminar cooling of the strip.
[0047] The lateral guidance of the strip can furthermore take place
before the driver and can open after passing the strip head and
close again at the strip end for the purpose of guidance.
[0048] Measurement of the strip temperature can be made by means of
a low-temperature radiation pyrometer. The measurement of the strip
temperature can preferably be made before, inside and/or after the
cooling and/or heating devices.
[0049] The production spectrum of a hot wide strip mill differs
appreciably from that of a heavy plate mill. A plurality of
high-strength and ultrahigh strength types of steel newly developed
over the last few decades now exist, whose properties can be
adjusted by specific rolling and/or cooling strategies. A suitable
method for this is quenching of the strip at a high cooling rate
after rolling, followed by re-heating to temperatures above the
phase-transformation temperature.
[0050] The classical QT steels (Q: quenched; T: tempered) which can
be produced in this way are already produced on heavy plate stands.
However, they can be produced substantially more economically in
hot wide strip mills.
[0051] Moreover, thinner, ultrahigh-strength strips having lower
temperature and thickness tolerance as well as strip flatness can
be produced more reliably on hot strip mills. It is therefore
appropriate and advantageous to shift parts of production from
heavy plate stands to strip mills.
[0052] In addition, there are many new types of steel which cannot
be produced on heavy plate stands. The method presented here is
particularly suitable for the group of multi-phase steels. By means
of a significantly enlarged spectrum of temperature-time profiles
and in particular, by means of the possibility of is interrupting
the cooling and temporarily increasing the temperature again, it is
possible to produce structures having almost any combinations of
phase constituents which cannot be envisaged at the present time.
In addition, it is possible to make precipitation processes take
place and thus specifically introduce second phases which are a
characteristic of modern types of steels.
[0053] In addition, properties required for the higher alloy
contents in conventional production can be adjusted by the method
presented.
[0054] Advantages of the separate arrangement of the rolling and
cooling process on the one hand and the tempering process on the
other hand are the flexibility of the method (no mixed rolling is
necessary), the flexible adjustment of the temperature time profile
of the strip and that one's own coils or coils from other
installations can be processed. Coils or plates can also be cut
depending on the intended use of the strip or the coilability. The
plates are preferably cut at higher temperature, i.e. at the
tempering temperature.
[0055] Advantages of the coupled arrangement of the rolling and
cooling process and the tempering process are the particularly
large energy saving and in the case of coils which are difficult to
coil and bind, the use of a special coiler with direct transfer to
avoid the so-called watch-spring problem. Furthermore, rapid
further processing or delivery of the strip in the case of direct
further processing is achieved. Finally, mention should be made of
the greater possibility for influencing the microstructure of the
strip in the arrangements mentioned.
[0056] Exemplary embodiment of the invention are shown in the
drawings. In the figures:
[0057] FIG. 1 shows schematically a hot strip mill for producing a
steel strip according to a first embodiment of the invention,
[0058] FIG. 2 shows an alternative embodiment of the hot strip mill
to FIG. 1,
[0059] FIG. 3 shows an exemplary temperature profile of the strip
over the conveying direction of the hot strip mill,
[0060] FIG. 4 shows the fundamental structure of a straightening
machine with integrated intensive cooling as a section from the hot
strip mill according to FIG. 1 or 2,
[0061] FIG. 5 shows the fundamental structure of a straightening
machine with integrated heating as a section from the hot strip
mill according to FIG. 1 or 2,
[0062] FIG. 6 shows schematically a hot strip mill with an
alternative embodiment of a first process step.
[0063] FIG. 1 shows a hot strip mill in which a strip 1 is
initially processed in a first process stage (given by I) and then
in a second process stage (given by II).
[0064] In the first process stage, i.e. in a rolling and cooling
process, a slab is first rolled in a multi-stand rolling mill. Of
the rolling mill, only the last three finishing stands 7 are shown
in which the strip 6 having an intermediate thickness has been
rolled. The temperature distribution in the strip or the flatness
can then be measured. The strip 1 then passes in the conveying
direction F into a strip cooling system 8 which is divided here
into an intensive laminar cooling system 9 with so-called edge
masking and a laminar strip cooling system 10. The conveying speed
is, for example, 6 m/s. The cooled strip 1 then enters into an
intensive cooling system 11 in which, according to a preferred
embodiment of the invention, a straightening machine and driver are
integrated (details in FIG. 4). Drivers can be provided before and
after the intensive cooling system 11.
[0065] The intensive cooling system 11 can be followed by another
measurement of the temperature distribution and the flatness of the
strip. A low-temperature radiation pyrometer is preferably used at
these low temperatures. A temperature measurement is also feasible
inside the intensive cooling system between two squeeze or driver
rolls for the purpose of temperature-coolant regulation.
[0066] The strip 1 is then coiled in a coiling station 3 by a
coiler 12 or 13.
[0067] The coil 2 then enters the second process stage, i.e. the
tempering process.
[0068] Here the coil 2 is initially uncoiled in an uncoiling
station 4 and then fed to a straightening machine 14 (this can be
located before and/or after the following furnace). After a
temperature equalization has taken place over the length and width
of the strip in a zone 15, the strip 1 enters into a furnace 16. It
is possible and advantageous to integrate a straightening machine
in the furnace 16 similarly to the cooling (details in FIG. 5).
Here the strip 1 can be heated in continuous or in reversing mode.
An oxyfuel furnace or an induction furnace are preferably used, the
heating time being between 10 and 600 seconds.
[0069] This is followed by trimming shears 17 or shears 18. The
strip 1 then enters into a laminar strip cooling system or
alternatively into an air cooling system 19. This can be followed
by a straightening machine 20. A plate pushing unit 21 or a coiler
22 in a coiling station 5 are then furthermore indicated in FIG.
1.
[0070] A skin-pass stand can also be arranged here instead of a
straightening machine 14 or 20.
[0071] Coils from other hot strip mills can also be introduced
instead of the uncoiling station 4.
[0072] In contrast, a direct connection of the two process stages I
and II can be seen in FIG. 2 (the installation is not shown fully
fitted). The last stands of a hot wide strip mill (finishing mill
7), the strip cooling system 8, and the coilers 12 and 13 of the
first process stages are shown similarly here. The last coiler 23
is provided for winding the higher-strength strips. In this case,
this can advantageously comprise a special coiler for simple
winding of the high-strength steels. In this case, the coiler 23 is
a so-called transfer coiler. The coil does not need to be bound
there. Pivotable pinch rolls hold the strip under tension during
turning into the unwinding position. The winding is therefore
directly followed by further processing in the tempering line
(second process stage). The further transport takes place similarly
to the solution according to FIG. 1.
[0073] Particular advantages here are the energy saving for strips
of higher winding temperature and the rapid further transport of
the coils from the first to the second process stage. It is thus
provided that the strip 1 already has a temperature above the
ambient temperature To before the heating in the furnace 16.
[0074] In addition, for special strip it is also possible to
provide reversing of the strip between the two coilers 23 and 22 in
to be able to carry desired temperature profiles or treatments of
the strip.
[0075] Preferably in the case of shorter strip and/or sufficiently
dimensioned component spacings, direct further transport of the
strip 1 from the first process stage to the second process stage is
provided without intermediate coiling of the strip 1 and/or
subsequent reversing from coiler 22 to coiler 23. In this case,
therefore the coiler 23 is not used but after the strip end runs
out from the roll mill the tempering process is carried out
directly at low or initially high and then lower speed.
[0076] Alternatively, this operating mode is applied to strip
independently of the thickness and the speed. Then the coiler 23 is
initially not used and the furnace is also not operating. The strip
is wound on coiler 22. The tempering process is then carried out
reversingly between coiler 22 and 23.
[0077] A preferred temperature profile for the strip 1 along the
strip mill is shown in FIG. 3 in correspondence with FIG. 2. The
cooling at the end of the line is preferably water or air
cooling.
[0078] However, cooling can also be effected by means of a
high-pressure beam. Cleaning or descaling of the strip surface is
thereby carried out at the same time.
[0079] The production quantity of the rolling plant is usually
higher than in the tempering process since the rolling speed of the
strip is greater than the tempering speed. A so-called mixing
rolling operation is therefore possible to optimally utilize the
rolling mill. This means that a number of strips is wound on
coilers 12 and 13 whilst the further processing of the
higher-strength strip takes place in the tempering line.
[0080] The production of the strip is therefore divided according
to the invention substantially into two process stages which will
be specified subsequently as an example with further optional
steps.
[0081] First Process Stage: [0082] Heating of slabs (thick or thin
slabs) and subsequent rolling in a multi-stand hot wide strip mill;
[0083] Intensive cooling of the strip on the delivery roller table;
[0084] Passing through a straightening machine; [0085] Winding the
strip into a coil.
[0086] In order to improve the flatness of the high-strength strip,
strip edge heating before a conventional finishing train, edge
masking in the first cooling section units and a straightening
machine are advantageous.
[0087] At higher winding temperatures, fast coil transport to the
subsequent second process stage is advantageous to save heating
energy during tempering. The coil can then be transported under a
heat insulating hood to reduce the temperature loss and ensure more
uniform material properties.
[0088] Second Process Stage: [0089] Unwinding the coil, [0090]
Optionally straightening the strip in a straightening machine if
lack of flatness is present; [0091] Optionally equalizing the strip
temperature by zonal cooling or heating before the actual tempering
treatment for making the strip temperature uniform over the strip
length and width; [0092] Tempering the strip, i.e. continuous
re-heating by means of induction heating or energetically
advantageously in a gas-heated continuous furnace (e.g. oxyfuel
furnace using so-called DFI method); [0093] Trimming the strip;
[0094] Subsequent cooling of the strip; [0095] Renewed
straightening of the strip; [0096] Renewed winding of the strip
into a coil.
[0097] Alternatively, the strips can be cut into plates before the
furnace, after the furnace and/or directly before the plate pushing
unit. The cutting of plates is particularly advantageous in the
case of strip which is difficult to wind. Cutting at the tempering
temperature is advantageous since the strip has a lower strength
there.
[0098] In the case of thicker strip and/or high-strength steels
which can no longer be cut, a flame cutting machine, a laser
cutting machine or a thermal cutting machine can be provided for
cutting.
[0099] The said oxyfuel furnace in which the so-called DFI oxyfuel
method (direct flame impingement) is carried out for tempering
comprises a special furnace in which (almost) pure oxygen instead
of air and gaseous or liquid fuel are mixed and the resulting flame
is directed directly onto the strip. This not only optimizes the
combustion process but also reduces the nitrogen oxide emissions.
The scale properties are also favorable or the scale growth is very
small (operated with air undershooting). The high flow rate of the
gases even has a cleaning effect on the strip surface. This type of
heating is particularly advantageous with regard to strip surface
quality. High heat densities with as good efficiency as in
inductive heating can be achieved with this method.
[0100] Instead of a successively arranged cooling section and
inline straightening machine in the first or second process stage,
the straightening machine and the strip cooling can also be
accommodated combined in one unit. The straightening rollers are
then at the same time used as water squeeze rollers and thus ensure
a cooling effect which is as uniform as possible over the width of
the strip since any strip transverse curvature and lack of flatness
is eliminated directly it forms. The straightening rollers are
adjusted individually depending on the strip temperature and the
material quality with the assistance of a straightening machine
model so that overstretching of the strip surface is avoided.
Drivers before and after the cooling section unit ensure strip
tension for as long as possible even when the stand or the coiler
tension is not built up. Part of the strip cooling can be carried
is out in the form of strip zone cooling in order to be able to
actively influence the temperature distribution. The
cooling-straightening unit is indicated in FIGS. 1 and 2. Details
on this are deduced from FIG. 4. Possible arbitrary combinations
for straightening, cooling and squeezing can be seen in this
figure. For the secure threading-in process of the strip head
particularly in the case of thinner strip, the
cooling-straightening unit is executed as raisable and pivotable as
indicated in FIG. 4 (see double arrow). The straightening rolls are
individually adjustable.
[0101] A temperature scanner for the strip can be provided before
and/or after the joint arrangement of straightening machine and
cooling which can be seen in FIG. 4. A strip head form detector
(for detecting a ski or waves) can be positioned in front of the
installation shown.
[0102] Drivers 24, a pure cooler unit 25, straightening rolls 26
and combined squeeze rolls/drivers 27 can be identified in detail
in FIG. 4. Furthermore, nozzles of intensive cooling system can be
seen.
[0103] In this case, an alternating arrangement of cooling,
straightening and drive roller units is possible. The amount of
straightening is adjusted individually depending on the material of
the strip and the temperature. The straightening-cooling unit is
raisable and pivotable.
[0104] As can be seen in FIG. 5, the straightening and heating
process 14, 16 of the second process stage can also be combined
with the installation shown. Similarly, the amount of straightening
can be adapted to the present strip temperature and the strip
material. In this case, the skin effect (higher surface
temperature) of the induction heating (or a direct flame
impingement in the DFI oxyfuel method) has a positive effect. At
the same time, the straightening rolls hold the strip in position
and avoid lack of flatness so that (inductive) heating which is as
efficient as possible is possible in the long fillet portion of the
strip. Drivers 29 before and after the heating-straightening unit
hold the strip under tensile stress 30. For secure threading in of
the strip head, the induction coils 32 as well as the straightening
and transfer rollers 31 are designed as vertically adjustable.
[0105] The use of the cooling-straightening unit (FIG. 4) or the
heating-straightening unit (FIG. 5) is not restricted to a strip
installation but can also be provided in a heavy plate
installation.
[0106] A temperature scanner for the strip can be provided before
and/or after the joint arrangement of straightening machine and
heating which can be seen in FIG. 5.
[0107] In order to be able to influence the temperature
distribution over the strip width in the second process stage
during the inductive heating, transverse field inductors are used,
inter alia, which can be displaced transversely to the strip
running direction or conveying direction F. By this means, if
necessary, the strip edges for example can be heated more strongly
or heated less intensively.
[0108] Equalization of the strip temperature over the length and
the width of the strip by specific cooling (zone cooling) or
heating at warm or cold strip sections can optionally take place
before heating the strip to the tempering temperature. This should
be provided in particular when coils not completely cooled to
ambient temperature are to be handled. By this means the passage of
the coil through the coil store can be shortened. A coil tracking
system (model) as well as the measured temperature distributions
during unwinding of the coil are used for optimum control of the
heating or cooling systems.
[0109] Welded-to-order, high wear-resistant roller materials are
used for the straightening rolls in order to ensure a long life and
good strip quality.
[0110] Temperature scanners and flatness meters within the line
indirectly monitor the quality of the strip and serve as a signal
for adjusting and regulating members such as, for example, for the
throughput speed, the heating power, the adjustment of the
straightening rolls and the cooling which are controlled by a
process model.
[0111] FIG. 6 shows the first process stage in a somewhat modified
embodiment. By analogy with FIG. 1, FIG. 6 shows the rear part of
the finishing train 7, laminar strip cooling units 9, 10 as well as
an intensive cooling system 11 and the coiling stations 3. In this
embodiment the intensive cooling system 11 and a strip
straightening unit 36.1, 36.2 are located at various positions.
Drivers 34 and 35 are located before and after the intensive
cooling system 11. A strip tension can hereby be maintained within
the intensive cooling system 11 for almost the entire strip length
without the strip being clamped in the stand or coiler system.
Thus, any strip waves which may occur are pulled out and a cooling
effect which is as uniform as possible is achieved.
[0112] In order to ensure that the strip runs centrally in the
drivers 34, 35 and/or in the intensive cooling system 11, a strip
lateral guide 33.1 is particularly advantageously located in front
thereof. After the strip head has passed the driver 33.1 and the
intensive cooling system 11, the lateral guide 33.1 is opened again
so that the water flow in the laminar strip cooling system 10 is
not hindered. The guide 33.2 then takes over the guiding task for
the remainder of the strip. Similarly for the strip end the guide
33.1 is briefly adjusted again after the end has left the finishing
train to counteract any straying of the strip end. In order to
minimize the cooling section length, the lateral guide 33.1 is
therefore preferably located inside the strip cooling unit 10.
[0113] The straightening rolls 36.1, 36.2 before the respective
coiling stations 3 are dipped into the strip plane after building
up the strip tension and provide a strip straightening effect by
looping around the base, deflecting or drive rollers. A similar
operating mode is practiced when deflecting rollers 26 (see FIG. 4)
are located inside the intensive cooling section 11.
REFERENCE LIST
[0114] 1 Strip (after the finishing train with final thickness)
[0115] 2 Coil [0116] 3 Coiling station [0117] 4 Uncoiling station
[0118] 5 Coiling station [0119] 6 Strip (inside the finishing train
with intermediate thickness) [0120] 7 Finishing train [0121] 8
Strip cooling [0122] 9 Intensive laminar strip cooling [0123] 10
Laminar strip cooling [0124] 11 Intensive cooling [0125] 12 Coiler
[0126] 13 Coiler [0127] 14 Straightening machine [0128] 15 Zone
[0129] 16 Furnace [0130] 17 Trimming shears [0131] 18 Shears [0132]
19 Air cooling or laminar strip cooling [0133] 20 Straightening
machine [0134] 21 Plate pushing unit [0135] 22 Coiler [0136] 23
Coiler [0137] 24 Driver [0138] 25 Pure cooling unit [0139] 26
Straightening roll [0140] 27 Squeeze roll/driver [0141] 28 Nozzles
of intensive cooling system [0142] 29 Driver [0143] 30 Tensile
stress [0144] 31 Transfer roller [0145] 32 Induction coil [0146]
33.1 Lateral guide before the first driver/before the intensive
cooling [0147] 33.2 Lateral guide before the coiler driver [0148]
34 Driver before the intensive cooling [0149] 35 Driver after the
intensive cooling [0150] 36.1 Straightening roll before the first
winding station 36.2 Straightening roll before the second winding
station [0151] I. First process stage [0152] II. Second process
stage [0153] F Conveying direction [0154] To Ambient
temperature
* * * * *