U.S. patent application number 13/388410 was filed with the patent office on 2012-07-12 for apparatus for making thin hot strip.
This patent application is currently assigned to SMS Siemag Aktiengesellschaft. Invention is credited to Juergen Mueller, Markus Reifferscheid, Juergen Seidel, Ernst Windhaus.
Application Number | 20120175076 13/388410 |
Document ID | / |
Family ID | 43448280 |
Filed Date | 2012-07-12 |
United States Patent
Application |
20120175076 |
Kind Code |
A1 |
Seidel; Juergen ; et
al. |
July 12, 2012 |
APPARATUS FOR MAKING THIN HOT STRIP
Abstract
The invention relates to an apparatus for making a thin hot
strip (1) by roll casting in a continuous process, comprising a
casting machine (2) in which first a thin slab (3) is cast, at
least one rolling train (4, 5) downstream of the casting machine
(2) and in which the thin slab (3) is rolled using the primary heat
of the casting process, and a plurality of finish-rolling stands
(7) that, relative to a travel direction (F) of the strip (1), are
arranged in a downstream region (6) and that can roll the strip (1)
with work rolls (8) to a final thickness. To improve the
manufacture of a thin hot strip in the continuous process, the
invention provides that the work rolls (8) of the finish-rolling
stands (7) have a low-wear roll surface. Furthermore, the invention
relates to a method of making a thin hot strip (1) by roll casting
in a continuous process.
Inventors: |
Seidel; Juergen; (Kreuztal,
DE) ; Windhaus; Ernst; (Duisburg, DE) ;
Reifferscheid; Markus; (Korschenbroich, DE) ;
Mueller; Juergen; (Kaarst, DE) |
Assignee: |
SMS Siemag
Aktiengesellschaft
Dusseldorf
DE
|
Family ID: |
43448280 |
Appl. No.: |
13/388410 |
Filed: |
August 11, 2010 |
PCT Filed: |
August 11, 2010 |
PCT NO: |
PCT/EP10/04913 |
371 Date: |
March 30, 2012 |
Current U.S.
Class: |
164/424 |
Current CPC
Class: |
B21B 1/463 20130101;
B21B 2267/24 20130101; B21B 27/032 20130101 |
Class at
Publication: |
164/424 |
International
Class: |
B22D 11/12 20060101
B22D011/12 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 12, 2009 |
DE |
10 2009 037 278.4 |
Claims
1. An apparatus for making a thin hot strip by roll casting in a
continuous process, the apparatus comprising: a casting machine in
which a thin slab is cast, at least one rolling train downstream of
the casting machine and in which the thin slab is rolled using the
primary heat of the casting process, and a plurality of
finish-rolling stands that, relative to a travel direction of the
strip are in a downstream region and that can roll the strip with
work rolls to a final thickness, the work rolls of the
finish-rolling stands each having a low-wear outer surface formed
by a layer of powder metallurgical material or a metal-ceramic
composite material.
2-3. (canceled)
4. The apparatus according to claim 1, wherein the low-wear layer
of powder metallurgical material is produced by the HIP method.
5-6. (canceled)
7. The apparatus according to any one of the claims 1 to 6, wherein
all the work rolls of the rolling train have the low-wear roll
surface of low-wear powder metallurgical material or a
metal-ceramic composite material.
8-12. (canceled)
Description
[0001] The invention relates to an apparatus for making thin hot
strip by roll casting in a continuous process, comprising a casting
machine in which a thin slab is cast, at least one rolling train
downstream of the casting machine and in which the thin slab is
rolled using the primary heat of the casting process, and a
plurality of finish-rolling stands that, relative to a travel
direction of the strip, are in a downstream region and in which the
strip can be rolled with work rolls to a final thickness.
Furthermore, the invention relates to a method of producing a thin
hot strip by roll casting in a continuous process.
[0002] Plants of this type are known as thin slab/thin strip roll
casting plants under the name CSP plants. They allow an efficient
manufacture of hot strips if the rigid connection of is continuous
casting plant and rolling train and their temperature control is
managed by the overall system.
[0003] In EP 0 286 862 A1 and EP 0 771 596 B1, continuous rolling
with the casting heat is described. Here, the casting and the
rolling process directly follow one another. Cutting the continuous
strip is carried out with a shear right before the coiler.
[0004] Similar methods for making steel strips by combining the
casting and rolling plant are disclosed in EP 0 415 987 B2 and EP 0
889 762 B1.
[0005] An alternative technology is the rolling of individual slabs
or individual strips. For the discontinuous rolling of strips,
casting and rolling are decoupled. The casting speed is usually
very slow and the rolling speed takes place independently therefrom
at a high level in such a manner that the temperature for the final
shaping lies above the minimum temperature.
[0006] The manufacture of thin hot strip is of interest for many
applications. However, it is disadvantageous that during rolling
high work-roll wear occurs that makes it necessary to periodically
change work rolls primarily in the downstream rolling train stands,
viewed in the travel direction of the strip. Up to now, so-called
IC rolls are used at this location in most cases. These are rolls
made of a traditional roll material with a high carbide content and
interdendritic graphite. These rolls are characterized by uniform
wear and are operationally reliable. They are relative
insusceptible to thermal stress; in case of cracks, an orientation
with respect to the graphite takes place.
[0007] However, overall, the wear on these rolls is relatively
high. This involves limited rolling times.
[0008] Also, generally known are work rolls in rolling stands that
have a special low-wear roll surface that is in particular formed
by a layer of low-wear material. Such rolls are known as HSS rolls
or semi-HSS roll or as PM rolls.
[0009] The designation HSS stands for high-speed steel and for a
material that has a relatively low carbide content. After casting,
a reaustenitization with a subsequent hardening and annealing takes
place.
[0010] PM rolls are rolls that are manufactured according to the
HIP method (hot isostatic pressing). Here, powdered shell material
is compressed under high pressure. With the HIP method, a roll core
is conventionally pre-fabricated (spheroidal cast iron or forged).
Then, the HSS shell material is bonded with the core. For this
purpose, the core as well as the powdered shell material is heated
in special HIP plants under a very high gas pressure acting
all-around and high temperature (approx. 1100.degree. C.) above its
yield point and made denser at the same time.
[0011] However, up to now, such rolls are not used for finish
rolling but only in the upstream end of a rolling stand line. The
reason for this is that these rolls are very sensitive, i.e. in
case of excessively rolled strip ends or due to other defects,
surface cracks or thermal cracks and thus an early failure of the
roll can occur that makes the use of them in a finish-rolling stand
basically inefficient or even impossible.
[0012] Thus, the object of the invention is to develop an apparatus
and a method of the manufacture of a thin hot strip of the
above-mentioned type in such a manner that an increased
productivity and higher efficiency can be achieved.
[0013] With respect to the apparatus design, this object is solved
according to the invention in that the work rolls of the finishing
roll stands have a low-wear roll surface. This is in particular
achieved in that the roll surface is formed by a layer of low-wear
material.
[0014] The low-wear layer can consist in a manner known per se of a
powder metal material. In this case, the low-wear layer is
preferably produced by the so-called HIP method (hot isostatic
pressing method).
[0015] The low-wear layer can also consist of a metal-ceramic
composite material (so-called "cermet").
[0016] According to the invention, the work rolls are designed as
HSS rolls or semi-HSS rolls (high-speed steel rolls).
[0017] Advantageously, all the work rolls of the rolling train have
low-wear roll surfaces.
[0018] The method of making a thin hot strip by roll casting in a
continuous process is characterized in that as work rolls of the
finish-rolling stands, work rolls with a low-wear roll surface are
used, in particular work rolls with a layer of low-wear
material.
[0019] To ensure a safe rolling process and a high service life of
the rolls at least in the area of the finish-rolling stands, the
roll gap between the work rolls is opened prior to entry of the
strip and, after entry of the strip, the roll gap is adjusted to
the target value. The roll gap is preferably set to a value at
which rolling without damage is possible at a thickness that can be
rolled in a save manner.
[0020] Accordingly, at least in the area of the finish-rolling
stands, prior to exiting of the strip, the roll gap is set from the
target value to a higher value.
[0021] Advantageously, the strip is rolled in the finish-rolling
stands to a final strip thickness between 0.5 mm and 1.5 mm.
[0022] The basic idea of the invention is focused on the previously
unknown and unusual fact that for finish rolling a thin hot strip
by roll casting in a continuous process, low-wear work rolls are
used that are previously known as such, that, however, could not be
used due the high roll load during finish rolling.
[0023] This is supported or made possible by the described
process-related measures that ensure that also during finish
rolling, an excessive loading of the work rolls does not take
place.
[0024] With the continuous rolling provided according to the
invention, rolling failures can be avoided so that the use of work
rolls with low-wear roll surface is possible also in the finish
rolling area. Here, rolling without threading in and threading out
takes place over a rather long period (several hours) at the
rolling train. At the beginning or the end, the mentioned special
measures, such as opening the stands for the safe rolling of
greater final thickness, can be taken to keep the work roll load in
the finish-rolling stand low. The manufacture losses are relatively
small here because the lost lengths are minor compared to the total
length of continuously rolled strips.
[0025] Under the conditions of the continuous rolling while using
low-wear work rolls (in particular HSS rolls, PM rolls), the
efficient manufacture of thin strips is particularly advantageous.
Less roll changes and thus fewer interruptions during casting take
place. Therefore, rolling programs or casting sequences can be
extended while achieving better strip shapes because now the work
roll wear is lower also in the downstream stands.
[0026] The productivity of the overall system can be increased by
extending the rolling programs or casting sequences.
[0027] Embodiments of the invention are illustrated in the drawing.
Therein:
[0028] FIG. 1 shows schematically a roll casting plant according to
a first embodiment of the invention with roughing train and
finishing train; and
[0029] FIG. 2 shows a casting plant in an embodiment according to
the invention with a compact rolling train as an alternative to
FIG. 1.
[0030] In FIG. 1, an apparatus for making a thin hot strip 1 is
illustrated. Manufacture of the strip is carried out by roll
casting in a continuous process. For this purpose, a
continuous-casting machine 2 is provided in which first a thin slab
3 is cast. A downstream rolling train 4, 5 is provided, relative to
a travel direction F of the slab or the strip. In the rolling train
4, 5, the thin slab 3 is gradually rolled to form the finished
strip while using the primary heat of the casting process. To this
end, a roughing train 4 and a finishing train 5 are provided. The
finishing train 5 has a plurality of finish-rolling stands 7 that,
relative to the travel direction F, are in a downstream region 6 of
the rolling train 4, 5. The strip 1 is rolled here to a final
thickness lying preferably between 0.5 mm and 1.5 mm. The rolling
of the strip in the finish-rolling stands 7 is carried out with
work rolls 8 supported by backing rolls.
[0031] Here it is essential that the work rolls 8 of the
finish-rolling stands 7 have a low-wear roll surface. In
particular, the roll surface is formed by a layer of low-wear
material.
[0032] Rolls of this type--as explained above--are known as such in
the prior art. However, up to now, they were never used for finish
rolling a strip 1.
[0033] With respect to the rolls used with wear resistant surface,
reference is made to the article of M. Andersson et al
"Introduction of enhanced indefinite chill and high-speed steel
rolls in European hot strip mills" in "Ironmaking and Steelmaking",
2004, Vol. 31, No. 5, page 383 ff, and to EP 1 365 869 B1 (in
particular paragraph [0014]).
[0034] The HIP method is illustrated in more detail in the article
of Ch. Willems et al "PM-HIP-Losungen fur Werkzeuge and Formen" in
"Stahl", 1998, issue 6, page 38 to 40.
[0035] Metal-ceramic composites, also called cermets, are used as
wear-resistant materials in a variety of components due to the
combination of high hardness and fracture toughness that is used
also in the present case.
[0036] Preferably, the low-wear work rolls can be used in all
stands of the hot strip train, thus, also in the roughing train 4
(the latter measure is already known as such in the prior art).
[0037] Here, the process flow is such that excessively rolled strip
ends or general failures and thus damage to the work rolls can be
avoided by the following measures:
[0038] Threading in with an open roll gap or threading in the strip
head can take place at product dimensions that can be generated
safely (thicker finished strip). Only after threading in the strip
into the finishing stand, is the thickness of the roll gap set to a
target thickness that is critical to generate, preferably to a
value below 1.5 mm.
[0039] Furthermore, continuous rolling for a plurality of coils is
provided for the long filet part of the strip.
[0040] Also, threading out the strip can take place again with a
greater final thickness or open roll gap.
[0041] The apparatus shown in FIG. 2 differs from the one according
to FIG. 1 substantially only in that here a compact rolling train 4
is provided. However, viewed in the travel direction F, it also has
a downstream part 6 in which work rolls 8 with low-wear roll
surface are provided. In this plant, a continuous rolling process
or, alternatively, a batch mode can be carried out.
[0042] In the figures, various mechanisms that are known per se,
are illustrated that, however, are not a priority for the
invention.
[0043] However, in particular to be referenced is an induction
furnace 9 and a holding furnace 10 that are operated in a is
conventional manner. Furthermore, a cooler 11 is to be mentioned
downstream of which a coiler 12 for winding up the finished strip
to form coils 13 is provided.
[0044] As already mentioned above, the work rolls 8 used in the
finish-rolling stands 7 are known as such under the designations
HSS rolls, semi-HSS rolls, PM-HIP rolls, or cermet rolls. Other
shell materials that are wear resistant are also possible; however,
they are usually sensitive.
[0045] The length of the rolling program is usually determined by
the depth or shape of wear of the work rolls or--associated
therewith--by the desired strip shape. Particularly disturbing is a
strong strip edge-drop or beads caused for example by high edge
wear.
[0046] Furthermore, also the roll surface quality as well as the
strip surface quality influences significantly the length of the
rolling program. Not only considerable roughness but also marks on
the roll surface caused for example by excessively rolled strip
ends are relevant here.
[0047] Specifically in case of thin strips, high wear occurs.
Particularly apparent is the wear effect when rolling a width. In
conventional hot strip trains, the danger of excessive strip end
rolling or other rolling defects is high.
[0048] Thus, this technology, namely the thin-strip rolling in a
continuous thin-slab plant using low-wear work rolls (also in the
last stand) is particularly suitable. Continuous rolling technology
prevents rolling defects, and the low-wear rolls improve the
quality of the product and allow for an extension of the rolling
program length.
[0049] The combination of direct charging (casting with subsequent
rolling at minimal energy supply) and the extension of the casting
sequences make the described technology particularly efficient.
REFERENCE NUMBER LIST
[0050] 1 Hot strip (strip) [0051] 2 Casting machine
[0052] 3 Thin slab [0053] 4 Rolling train [0054] 5 Rolling train
[0055] 6 Downstream region [0056] 7 Finish-rolling stand [0057] 8
Work roll [0058] 9 Induction furnace [0059] 10 Holding furnace
[0060] 11 Cooler [0061] 12 Coiler [0062] 13 Coil [0063] F Travel
direction
* * * * *