U.S. patent application number 13/127855 was filed with the patent office on 2012-02-02 for method for producing strips of metal, and production line for performing the method.
Invention is credited to Hellfried Eichholz, Rolf Franz, Markus Schaeperkoetter, Karl-Heinz Spitzer.
Application Number | 20120024434 13/127855 |
Document ID | / |
Family ID | 42242366 |
Filed Date | 2012-02-02 |
United States Patent
Application |
20120024434 |
Kind Code |
A1 |
Franz; Rolf ; et
al. |
February 2, 2012 |
METHOD FOR PRODUCING STRIPS OF METAL, AND PRODUCTION LINE FOR
PERFORMING THE METHOD
Abstract
The invention relates to a method of and a plant for making
hot-rolled strips of cast metal, wherein the cast strip is
subjected as a rough strip to at least a first step for
momogenizing the grain structure in a protective gas and the cast
strip is then subjected to at least a further heat-treatment step
before it is rolled to reduce its thickness. After the thickness
reduction the cast strip is subjected to a second step of
homogenization or recrystallization of its grain structure before
finally the strip is passed to a cutter and a finished rolled hot
piece is severed from the following strip.
Inventors: |
Franz; Rolf; (Kreuztal,
DE) ; Spitzer; Karl-Heinz; (Clausthal, DE) ;
Eichholz; Hellfried; (Ilsede, DE) ; Schaeperkoetter;
Markus; (Braunschweig, DE) |
Family ID: |
42242366 |
Appl. No.: |
13/127855 |
Filed: |
December 9, 2009 |
PCT Filed: |
December 9, 2009 |
PCT NO: |
PCT/EP09/08795 |
371 Date: |
October 14, 2011 |
Current U.S.
Class: |
148/602 ;
148/648; 148/653; 148/654; 164/262 |
Current CPC
Class: |
C21D 1/74 20130101; C21D
8/0263 20130101; B21B 1/26 20130101; C21D 8/0226 20130101; B21B
1/463 20130101 |
Class at
Publication: |
148/602 ;
148/648; 148/653; 148/654; 164/262 |
International
Class: |
C21D 8/02 20060101
C21D008/02; B22D 47/00 20060101 B22D047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 9, 2008 |
DE |
10 2008 061 206.5 |
Jul 8, 2009 |
DE |
10 2009 032 358.9 |
Claims
1. A method of making hot-rolled strips of cast steel, where a cast
steel strip is subjected as a rough strip to at least one
heat-treatment step and subsequently wound or stacked as a hot
strip, the method comprising the steps of sequentially: subjecting
the rough strip obtained from the casting step in a protective gas
atmosphere to an upstream step of homogenizing its structure by
maintaining a temperature at approximately 900 to 1000.degree. C.,
by reducing the temperature by approximately 200.degree. C., or by
increasing the temperature by approximately 250.degree. C.;
subjecting the homogenized rough strip to at least one additional
heat-treatment step by maintaining the temperature at 880 to
940.degree. C., by reducing the temperature by approximately
50.degree. C., or by increasing the temperature by approximately
50.degree. C.; subjecting the heat-treated rough strip to a
hot-rolling step having at least one pass, with the rough strip
undergoing a reduction in thickness of less than 49%; subjecting
the hot-rolled rough strip to a downstream homogenization step or
recrystallization of its structural composition, by maintaining the
temperature at approximately 700 to 900.degree. C., by reducing the
temperature by approximately 100.degree. C., or by increasing the
temperature by approximately 50.degree. C.; and passing the rough
strip through a cutter that is synchronized with the transport or
belt speed to cut the strip into pieces of rolled hot strip.
2. The method according to claim 1, wherein the casting step is
decoupled from the rolling step.
3. The method according to claim 1 wherein the transport speed of
the rough strip is influenced by a mass-flow controller.
4. The method according to claim 1, further comprising the step,
before the hot rolling, of subjecting the rough strip to an
upstream heat-treatment step by maintaining the temperature at
approximately 880 to 940.degree. C., by reducing the temperature by
approximately 50.degree. C., or by increasing the temperature by
approximately 50.degree. C.
5. The method according to claim 1, further comprising the step,
after the hot rolling, of subjecting the rough strip to an upstream
heat-treatment step by maintaining the temperature at approximately
880 to 940.degree. C., by reducing the temperature by approximately
50.degree. C., or by increasing the temperature by approximately
50.degree. C.
6. The method according to claim 1, further comprising the step,
after the hot rolling, of subjecting the rough strip to an upstream
homogenization step for the recrystallization of the rough strip at
the edges, by maintaining the temperature at approximately 700 to
900.degree. C., by reducing the temperature by approximately
100.degree. C., or by increasing the temperature by approximately
50.degree. C.
7. The method according to claim 6, wherein the upstream
homogenization step, precedes passing the rough strip through the
cutter, the method further comprising the step after cutting of
winding or stacking the cut pieces of the rough strip as hot
strip.
8. A plant for carrying out the method of claim 1, the plant
comprising: at least one casting machine for producing a cast rough
strip of a predetermined thickness; at least one conveyor for
transporting the cast strip; at least one homogenization zone in
which the temperature is maintained, reduced, or increased in order
to to influence the structural composition of the cast rough strip;
at least one additional temperature zone in which the temperature
is maintained, reduced, or increased; at least one upstream roll
stand for partial deformation of the rough strip; at least one
cutter; at least one winding or stacker; an upstream homogenization
zone downstream of the casting machine and in which the temperature
is maintained, reduced, or increased; a temperature controller
downstream of the upstream homogenization zone for maintaining the
temperature, reducing the temperature, or increasing the
temperature; an upstream roll stand downstream of the temperature
controller reducing the rough strip in thickness of less than 49%
in at least one pass; a downstream homogenization zone downstream
of the roll stand in which the temperature is maintained, reduced,
or increased in order to obtain a recrystallization of the hot
strip at least at the edges; and a cutter downstream of the
downstream homogenization zone having a working speed synchronized
with the speed of the conveyor and with the rolled rough strip
being separated from the rough strip as a hot strip.
9. The plant according to claim 8, wherein the casting step is
decoupled from the rolling step.
10. The plant according to claim 8 further comprising: a mass-flow
controller comprised of a dancer roll or a looper downstream of the
upstream homogenization zone.
11. The plant according to claim 8, further comprising: a mass-flow
controller relative to the transport direction of the rough strip
between an upstream rough strip conveyor and a downstream rough
strip conveyor.
12. The plant according to claim 11, further comprising an upstream
temperature controller and a mass-flow controller downstream
relative to the transport direction of the belt of the upstream
homogenization zone, the mass-flow controller being provided
upstream of the downstream temperature controller.
13. The plant according to claim 12, further comprising: a conveyor
between the upstream temperature controller and the mass-flow
controller or between the mass-flow controller and the downstream
temperature controller.
14. The plant according to claim 8, further comprising: a coiler or
a stacker is provided downstream of the cutter.
Description
[0001] The invention relates to a method of continuous and
discontinuous production of hot-rolled strips made of cast metal,
in particular steel, having the features of the introductory clause
of claim 1.
[0002] The invention further relates to a plant for carrying out
the method according to the features of the introductory clause of
claim 9.
[0003] In a known method of horizontal strip casting, it is
possible for melts of different types of steel to be cast with less
than 20 mm strip thickness close to their final dimensions. Using
this method, lightweight steels in particular with a high content
of C, Mn, Al, and Si may be produced.
[0004] A production method of the production of hot-rolled thin
flat products is known from EP 1 047 510 [U.S. Pat. No. 6,527,882].
According to this method, steel melts are cast close to their final
dimensions in a range of 5 mm to 18 mm strip thickness and cooled
in a controlled manner and in a protective gas atmosphere before
reaching a single-stand roughing train.
[0005] The blank hot strip is cooled, heated, or its temperature is
maintained in a controlled fashion in a unit provided downstream of
the roughing train, and the edges of the hot strip are
reheated.
[0006] The single-stand roughing train is followed by a multistand
finishing train, a run-out roller table having a device for cooling
the hot strip, and coilers upstream and downstream for winding the
hot strip.
[0007] The rolling temperature upstream of the multistand finishing
train may be controlledly set by the device for cooling, heating,
or maintaining the temperature of the hot strip, in the austenite
or ferrite range or in the transition range from austenite to
ferrite.
[0008] In addition, WO 2006/066551 [US 20100059196] discloses a
method of the production of hot strips of lightweight steel that
has particularly good cold deep drawability and has Fe, Mn, Si, and
Al as its primary elements. The rough strip produced by casting
upstream passes through a device for homogenization in a protective
gas with optional maintenance of the temperature, cooling, or
heating. The rough strip is subsequently subjected to a hot-rolling
step having at least one pass with a total degree of deformation of
at least 50%. After the last pass, the hot strip is cooled and
wound up. The hot-rolling step occurs inline or decoupled depending
on the ratio of casting speed to rolling speed.
[0009] The homogenization zone is intended to equalize the
temperature over the surface of the hot strip and reduce tension
within the hot strip independently of whether the temperature level
is maintained, increased, or decreased.
[0010] The question of whether the rolling step should occur inline
or decoupled from the casting step essentially becomes a function
of the different speeds in the casting and rolling step, with the
recrystallization behavior of the workpiece having significance as
well.
[0011] In the casting step, a direct connection exists between the
material in the liquid phase in the pouring region of the melt and
the later process steps of the hardened workpiece via the cast
strip.
[0012] The cast strip is guided to further processing along a
transport path. The subsequent method steps may be: straightening,
rolling, cutting, and winding (reeling, coiling). These and other
components of a casting system may lead to fluctuations in the
tension and mass flow in the cast strip. If these disruptions
continue in the direction of the liquid steel, casting disruptions
may occur as well as negative influences on the cast strip such as,
for example, fluctuations in thickness, overflows, edge
constrictions, and tears in the strip or the flow.
[0013] The object of the invention is to refine a method of the
production of hot strips by a strip caster and a strip caster
having a coiler or stacker in such a way that the method steps is
following the casting step do not have any negative influence on
the quality and material properties of the cast strip being
produced and that the cast strip, after the casting step, may be
separated into pieces of predetermined size that can be transported
and/or stored such as, for example, stacked sheets or coils.
[0014] This object is attained according to the invention by the
features of the independent claims 1 and 8.
[0015] Thus, according to the characterizing features of claim 1,
the rough strip produced by strip casting passes through a
homogenization zone in a protective gas atmosphere in order to
homogenize its structural composition in conjunction with
maintaining the temperature of the rough strip, reducing the
temperature, or increasing the temperature [, driver, looper,
driver error]. Then the rough strip passes through a temperature
controller in order to maintain the temperature of the rough strip,
reduce the temperature, or increase the temperature of the rough
strip. Thereafter, the rough strip is subjected to a reduction in
thickness of less than 49% in a hot-rolling step having at least
one pass. Finally, the rough strip passes through a downstream
homogenization zone before it is separated as a hot strip from the
following rough strip.
[0016] In the upstream homogenization zone, an inert-gas
argon/CO.sub.2-nitrogen mixture is used. In the upstream
homogenization zone, the temperature is maintained in the region of
900 to 1000.degree. C., reduced by 200.degree. C., and increased by
250.degree. C.
[0017] In order for the workpiece to be able to be bent into a
coil, it must have a suitable structural composition that allows
deformation under tensile and compressive stress.
[0018] These structural properties may be attained by the one or
more rolling steps with one pass up to a degree of deformation of
49%.
[0019] This deformation step triggers a recrystallization of the
workpiece. In the subsequent downstream homogenization zone, the
thus treated hot strip undergoes recrystallization at least at its
edges while the temperature of the hot strip is maintained, if the
temperature is reduced, or if the temperature is increased.
[0020] In the downstream homogenization zone downstream of the
upstream roll stand, the workpiece is able to recrystallize and is
therefore able to withstand tensile and compressive stress. This
method of recrystallization is particularly suitable for
lightweight steels that, among other things, may have a very wide
solidification range, i.e. a larger or smaller "temperature window"
from the beginning of the hardening of the melt to complete curing
and have zero solidity and ductility temperatures that depend on
the "window."
[0021] After the rough strip has passed through the downstream
homogenization zone, the hot strip is guided to a cutter with a
working speed synchronized to the roller or transport belt speed,
subdivided into pieces of rough strip of predetermined length, and
wound into a coil in a winding system.
[0022] However, the hot strip may also be cut directly after
leaving the downstream homogenization zone, the pieces of hot strip
of a particular length then being conveyed to a stacking system by
suitable conveyors and stacked there as plates.
[0023] In the embodiment of the method according to the invention,
the casting step is decoupled from the rolling step.
[0024] This has advantage that, on the one hand, the casting speed
may be selected as a function of the progression of the
solidification step and, on the other hand, the hot-rolling step is
able to occur at a defined hot-strip temperature until a
predetermined degree of deformation is attained.
[0025] In another embodiment of the method according to the
invention, after the upstream homogenization of the structural
composition, the transport speed of the rough strip is varied by a
mass-flow controller. This prevents disruptions from the following
process steps within the production method from negatively
influencing the casting step and the cast strip and prevents
overflows, edge constrictions, and tears in the strip or the
flow.
[0026] According to the features of claim 9, the plant for carrying
out the method according to the invention comprises a casting
machine known per se and downstream of which an upstream
homogenization zone is provided in a protective-gas atmosphere for
influencing the structural composition of the cast rough strip and
where the temperature of the rough strip is maintained, reduced, or
increased.
[0027] An upstream temperature controller for maintaining,
reducing, or increasing the temperature of the rough strip is
provided downstream of the upstream homogenization zone.
[0028] Relative to the transport direction of the rough strip, a
downstream temperature controller is provided downstream of the
upstream temperature controller, with a mass-flow controller
integrated between an upstream and a downstream rough strip
conveyor; in the downstream temperature controller, the cast strip
is brought to a suitable rolling temperature, by maintaining,
reducing, or increasing the temperature of the cast strip.
[0029] An upstream roll stand is provided downstream of the
downstream temperature controller to subject the rough strip to a
reduction in thickness of less than 49% at the appropriate
temperature in at least one pass. In a downstream homogenization
zone provided downstream of the upstream roll stand, the rough
strip, now hot, is recrystallized at a temperature of 700 to
900.degree. C., particularly at the edges of the hot strip, such
that the workpiece is able to absorb tensile and compressive forces
as well as plastic deformations that occur during winding or
stacking without damage to the structural composition.
[0030] Finally, downstream of the downstream homogenization zone is
a cutter operated at a working speed that is synchronized with the
transport speed of the hot-strip conveyor. In the cutter, the
hot-rolled hot strip continually approaching the device is wound
after being cutting and is stacked as plates.
[0031] In an additional embodiment of the plant according to the
invention, a mass-flow controller is provided downstream of the
upstream temperature controller and is embodied as a dancer roll or
a looper. The mass-flow controller, viewed in the transport
direction of the strip, is integrated between an upstream rough
strip conveyor and a downstream rough strip conveyor.
[0032] Moreover, in the invention, upstream of the roll stand is a
downstream temperature controller in which the rough strip is
brought to a suitable rolling temperature so that the rough strip
may be subjected to a hot-rolling step having at least one pass,
and the rough strip, as a hot strip, then has a degree of
deformation less than 49%.
[0033] Finally, according to the invention a coiler or stacker in
which the hot strip is wound into a coil or deposited as individual
plates is provided downstream of the cutter.
[0034] Additional features and advantages of the invention may be
found in the following description and in the illustrated
embodiment shown in the drawing, in which:
[0035] FIG. 1 is a schematic view of the plant for carrying out the
method according to the invention for strip casting close to the
final dimensions, having a winder and/or stacker.
[0036] The single FIG. 1 is schematic view of a plant according to
the invention for carrying out the method according to the
invention. The plant has a casting machine 1 in the form of a
horizontal strip caster for carrying out the casting method or
casting step and having a conveyor in the form of an endless
conveyor belt 2 and two deflection rollers 3, 3'. The casting
machine 1 is moreover provided with a side wall 4 that prevents the
poured melt 5 from flowing down to the right and left sides of the
conveyor 2. The melt 5 is fed to the casting machine 1 from a ladle
6 and flows through an outlet opening 7 ing the base of the ladle 6
into a feed tank 8. This feed tank 8 is formed as an overflow
tank.
[0037] Devices for intensive cooling of the bottom of the support
reach of the conveyor 2 and the complete housing surrounding the
casting machine 1 and containing the corresponding protective gas
atmosphere are not shown in greater detail.
[0038] After the melt 5 has been poured onto the moving conveyor 2,
intensive cooling results in solidification and the formation of a
cast or rough strip 9 that is completely solidified to a large
extent by the time it reaches the downstream end of the conveyor
2.
[0039] In order to equalize temperature and reduce tension, a
homogenizing zone 10 follows the casting machine 1. The
homogenizing zone is formed by a heat-insulated enclosure 11 and a
roller conveyor. This upstream homogenizing zone may be used to
maintain the temperature of the cast rough strip 9, further cool
it, or, alternately, to heat it somewhat. In particular, provision
is made in this upstream homogenization zone 10 for the cast or
rough strip 9 to be subjected to an upstream step for homogenizing
its structure, by maintaining a temperature at approximately 900 to
1000.degree. C., by reducing the temperature by approximately
200.degree. C., or, alternately, by increasing the temperature by
approximately 250.degree. C., in a protective gas atmosphere
composed of an inert-gas mixture of argon-CO.sub.2-nitrogen.
[0040] Subsequently, the cast rough strip 9 passes through an
upstream temperature controller 12 and is then conducted to a
downstream temperature controller 15 by an upstream rough-strip
conveyor 14 and a downstream rough-strip conveyor 14' by a
mass-flow controller 13 provided between the upstream rough strip
conveyor 14 and the downstream rough strip conveyor 14' and
comprised of a dancer roll or a looper. In this downstream
temperature controller 15, the cast rough strip 9 is brought to the
rolling temperature before it is then subjected to a hot-rolling
step in a following upstream roll stand 16, with at least one pass
being conducted until the cast rough strip 9 has a degree of
deformation of less than 49% of the total deformation. In this
upstream temperature controller 15, the cast rough strip 9 is
maintained at a temperature of approximately 880 to 940.degree. C.,
its temperature is reduced by approximately 50.degree. C., or,
alternately, its temperature is increased by approximately
50.degree. C. After passing through the upstream roll stand 16, the
cast rough strip 9 is subsequently conveyed to a downstream
homogenization zone 17 in which the cast rough strip 9 is subjected
to a downstream homogenization step, in particular for
recrystallization of the structural composition. This occurs in
that the temperature of the cast rough strip 9 in the downstream
homogenization zone 17 is maintained at a temperature of
approximately 700 to 900.degree. C., its temperature is reduced by
approximately 100.degree. C., or its temperature is increased by
approximately 50.degree. C. Downstream of the downstream
homogenization zone 17, the cast rough strip 9 then passes through
a subdividing unit 18 in the form of a cutter that is synchronized
with the transport or belt speed, and is then conveyed as pieces of
fully rolled hot strip that have been separated from the cast rough
strip 9 to a coiler 19 or a stacker 20.
* * * * *