U.S. patent application number 10/487436 was filed with the patent office on 2005-02-17 for device for processing a metal slab, plate or strip, and product produced using this device.
Invention is credited to Jacobs, Leonardus Joannes Mattheus, Van Der Winden, Menno Rutger.
Application Number | 20050034500 10/487436 |
Document ID | / |
Family ID | 19773913 |
Filed Date | 2005-02-17 |
United States Patent
Application |
20050034500 |
Kind Code |
A1 |
Van Der Winden, Menno Rutger ;
et al. |
February 17, 2005 |
Device for processing a metal slab, plate or strip, and product
produced using this device
Abstract
The invention relates to a device for processing a metal slab,
plate or strip, comprising a rolling mill stand with a roll nip
between two driveable rolls, the rolling mill stand being designed
to roll a metal slab, plate or strip between the rolls. According
to a first aspect of the invention, the device is provided with
feed means which are designed to guide the slab, plate or strip
between the rolls at an angle of between 5.degree. and 45.degree.
with respect to the perpendicular to the plane through the center
axes of the rolls. According to a second aspect of the invention,
the device is provided with one or more following rolling mill
stands with driveable rolls, and the rolling mill stand and one or
more following rolling mil stands are designed in such a manner
that, during use, their rolls have different peripheral velocities,
the difference in peripheral velocity amounting to at least 5% and
at most 100%.
Inventors: |
Van Der Winden, Menno Rutger;
(Br Leiden, NL) ; Jacobs, Leonardus Joannes Mattheus;
(Heemskerk, NL) |
Correspondence
Address: |
STEVENS DAVIS MILLER & MOSHER, LLP
1615 L STREET, NW
SUITE 850
WASHINGTON
DC
20036
US
|
Family ID: |
19773913 |
Appl. No.: |
10/487436 |
Filed: |
September 22, 2004 |
PCT Filed: |
August 16, 2002 |
PCT NO: |
PCT/NL02/00548 |
Current U.S.
Class: |
72/250 |
Current CPC
Class: |
C21D 7/00 20130101; B21B
2003/001 20130101; B21B 3/00 20130101; B21B 1/026 20130101; B21B
39/14 20130101; B21B 2275/05 20130101; B21B 1/22 20130101; B21B
39/04 20130101; B21B 3/02 20130101; C21D 8/0221 20130101; B21B
2267/065 20130101 |
Class at
Publication: |
072/250 |
International
Class: |
B21B 039/20 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 24, 2001 |
NL |
1018814 |
Claims
1. A device for processing a metal slab, plate or strip, comprising
a rolling mill stand with a roll nip between two driveable rolls,
the rolling mill stand being designed to roll a metal slab, plate
or strip between the rolls, wherein the device is provided with
feed means designed to guide the slab, plate or strip between the
rolls at an angle of between 5.degree. and 45.degree. with respect
to the perpendicular to the plane through the center axes of the
rolls.
2. The device as claimed in claim 1, wherein the feed means are
designed to guide the slab, plate or strip between the rolls at an
angle of between 10.degree. and 25.degree. with respect to the
perpendicular to the plane through the center axes of the
rolls.
3. The device as claimed in claim 1, wherein the feed means
comprise a feed surface or a roller table.
4. The device as claimed in claim 1, wherein the angle between the
feed means and the rolling mill stand is adjustable.
5. The device as claimed in claim 1, wherein the rolling mill stand
is designed in such a manner that, during use, the rolls have
different peripheral velocities, the difference in peripheral
velocity amounting to at least 5% and at most 100%.
6. The device as claimed in claim 5, wherein the rolls have a
different diameter and/or can be driven at different rotational
speeds.
7. The device as claimed in claim 1, wherein the device comprises
one or more following rolling mill stands with driveable rolls
which are positioned downstream of the rolling mill stand, as seen
in the rolling direction.
8. The device as claimed in claim 7, designed to feed the metal
slab, plate or strip, during use, at an angle of between 5.degree.
and 45.degree., to at least one of the one or more following
rolling mill stands.
9. The device as claimed in claim 7, wherein at least one of the
one or more following rolling mill stands is designed in such a
manner that, during use, the rolls have different peripheral
velocities.
10. The device as claimed in claim 7, wherein at least one of the
one or more following rolling mill stands has a roll nip situated
outside the plane of symmetry of the roll nip of the rolling mill
stand.
11. The device as claimed in claim 7, wherein support rolls are
arranged upstream of the one or more following rolling mill stands,
as seen in the rolling direction, to support and/or guide the metal
slab, plate or strip.
12. The device as claimed in claim 1, provided on both sides with
feed means designed to pass the slab, plate or strip between the
rolls at an angle of between 5.degree. and 45.degree. with respect
to the perpendicular to the plane through the center axes of the
rolls, the angle between the feed means being adjustable between 0
and 45.degree. and the rolls being driveable in both directions of
rotation.
13. A device for processing a metal strip, comprising a rolling
mill stand with a roll nip between two driveable rolls, the rolling
mill stand being designed to roll the metal strip between the
rolls, wherein the device comprises one or more following rolling
mill stands with driveable rolls, and the rolling mill stand and
one or more following rolling mill stands are designed in such a
manner that, during use, their rolls have different peripheral
velocities, the difference in peripheral velocity amounting to at
least 5% and at most 100%.
14. The device as claimed in claim 13, wherein the difference in
peripheral velocity is at least 5% and at most 50%.
15. The device as claimed in claim 13, wherein the rolls of the
rolling mill stand and the following rolling mill stands have a
different diameter and/or are driveable at different rotational
speeds.
16. The device as claimed in claim 13, wherein at least one of the
one or more following rolling mill stands has a roll nip situated
outside the plane of symmetry of the roll nip of the rolling mill
stand.
17. The device as claimed in claim 13, wherein support rolls are
arranged upstream of the one or more following rolling mill stands,
as seen in the rolling direction, to support and/or guide the metal
strip.
18. The device as claimed in claim 13, wherein feed means are
arranged upstream of the rolling mill stand, as seen in the rolling
direction, and the feed means are designed to pass the strip
between the rolls at an angle of between 5.degree. and 45.degree.
with respect to the perpendicular to the plane through the center
axes of the rolls.
19. A metal slab, plate or strip produced using the device as
claimed in claim 1, the slab, strip or plate having a substantially
uniform shearing over its thickness.
20. A metal strip produced using the device as claimed in claim 13,
the strip having a substantially uniform shearing over its
thickness.
21. The metal slab, plate or strip as claimed in claim 19, wherein
the metal is aluminum or steel or stainless steel or copper or
magnesium or titanium or one of their alloys.
22. The device as claimed in claim 1, wherein the feed means are
designed to guide the slab, plate or strip between the rolls at an
angle of between 15.degree. and 25.degree. with respect to the
perpendicular to the plane through the center axes of the
rolls.
23. The device as claimed in claim 1, wherein the feed means are
designed to guide the slab, plate or strip between the rolls at an
angle of substantially 20.degree. with respect to the perpendicular
to the plane through the center axes of the rolls.
24. The device as claimed in claim 1, wherein the rolling mill
stand is designed in such a manner that, during use, the rolls have
different peripheral velocities, the difference in peripheral
velocity amounting to at least 5% and at most 50%.
25. The device as claimed in claim 1, wherein the rolling mill
stand is designed in such a manner that, during use, the rolls have
different peripheral velocities, the difference in peripheral
velocity amounting to at least 5% and at most 20%.
26. The device as claimed in claim 7, designed to feed the metal
slab, plate or strip, during use, to at least one of the one or
more following rolling mill stands, preferably at an angle of
between 10.degree. and 25.degree.
27. The device as claimed in claim 7, designed to feed the metal
slab, plate or strip, during use, to at least one of the one or
more following rolling mill stands, preferably at an angle of
between 15.degree. and 25.degree..
28. The device as claimed in claim 7, designed to feed the metal
slab, plate or strip, during use, at an angle of between 5.degree.
and 45.degree., to at least one of the one or more following
rolling mill stands, the angle being adjustable.
29. The device as claimed in claim 7, wherein at least one of the
one or more following rolling mill stands is designed in such a
manner that, during use, the rolls have different peripheral
velocities, the rolls having a different diameter
30. The device as claimed in claim 7, wherein at least one of the
one or more following rolling mill stands is designed in such a
manner that, during use, the rolls have different peripheral
velocities, the rolls being driveable at different rotational
speeds.
31. The device as claimed in claim 1, provided on both sides with
feed means designed to pass the slab, plate or strip between the
rolls at an angle of between 10.degree. and 25.degree. with respect
to the perpendicular to the plane through the center axes of the
rolls, the angle between the feed means being adjustable between 0
and 45.degree. and the rolls being driveable in both directions of
rotation.
32. The device as claimed in claim 13, wherein the difference in
peripheral velocity is at least at least 5% and at most 20%.
33. The device as claimed in claim 13, wherein feed means are
arranged upstream of the rolling mill stand, as seen in the rolling
direction, and the feed means are designed to pass the strip
between the rolls at an angle of between 10.degree. and 25.degree.
with respect to the perpendicular to the plane through the center
axes of the rolls.
34. The device as claimed in claim 13, wherein feed means are
arranged upstream of the rolling mill stand, as seen in the rolling
direction, and the feed means are designed to pass the strip
between the rolls at an angle of between 15.degree. and 25.degree.
with respect to the perpendicular to the plane through the center
axes of the rolls.
35. The device as claimed in claim 13, wherein feed means are
arranged upstream of the rolling mill stand, as seen in the rolling
direction, and the feed means are designed to pass the strip
between the rolls at an angle of between 5.degree. and 45.degree.
with respect to the perpendicular to the plane through the center
axes of the rolls, the feed means comprising a feed surface or a
roller table.
Description
[0001] The invention relates to a device for processing a metal
slab, plate or strip, comprising a rolling mill stand with a roll
nip between two driveable rolls, the rolling mill stand being
designed to roll a metal slab, plate or strip between the
rolls.
[0002] A device of this type is known and is in very widespread use
in the metal industry for reducing the thickness of a cast slab,
plate or strip and for improving the mechanical properties of a
slab, plate or strip. The rolling which is carried out using the
device takes place during the processing of thick slabs and plates,
usually at elevated temperature. During the rolling of thin plates
and strips, the plate or strip is not raised to an elevated
temperature prior to the rolling.
[0003] Working with the known device has the drawback that the
improvements to the mechanical properties are produced primarily in
the outermost layers of the rolled product and only to a lesser
extent or not at all in the interior of the product. This is true
in particular of thick slabs.
[0004] It is an object of the invention to provide a device for
processing a metal slab, plate or strip with which the mechanical
properties of the processed product can be improved.
[0005] It is another object of the invention to provide a device of
this type which allows mechanical properties of the interior of a
slab, plate or strip to be improved.
[0006] Yet another object of the invention is to provide a device
of this type which is able to improve the mechanical properties in
a simple way.
[0007] It is also an object of the invention to use the device
according to the invention to provide improved metal slabs, plates
and strips.
[0008] According to a first aspect of the invention, one or more of
these objects are achieved by a device for processing a metal slab,
plate or strip, comprising a rolling mill stand with a roll nip
between two driveable rolls, the rolling mill stand being designed
to roll a metal slab, plate or strip between the rolls, which
device is provided with feed means which are designed to guide the
slab, plate or strip between the rolls at an angle of between
5.degree. and 45.degree. with respect to the perpendicular to the
plane through the center axes of the rolls.
[0009] Surprisingly, it has been found that by feeding a metal
slab, plate or strip at an angle between the rolls of a rolling
mill stand, shearing occurs over the entire thickness of the slab,
plate or strip. This shearing is also more or less constant over
the entire thickness. Firstly, this allows grain refinement to
occur over the entire thickness. During standard rolling, shearing
and therefore grain refinement will only occur at the surfaces.
Secondly, the shearing closes up pores in the metal which are
usually formed during the casting of aluminum, for example.
Therefore, using the device according to the invention closes up
pores over the entire thickness of the material. Both effects are
important mainly for relatively thick material. The shearing also
causes the eutectic particles which may be present in the material
to be broken up, which results in an improved toughness. The feed
means which are added to the device in accordance with the
invention therefore results, in a simple manner, in an improvement
to the material which it produces. Feeding a slab, plate or strip
in at an angle also leads to the rolls having an improved grip on
the front of the material which is introduced, with the result that
the reduction in thickness of the material does not have to be as
great as in standard rolling, in which the material is introduced
between the rolls at an angle of 0.degree.. The feeding in at an
angle also prevents or reduces the "refusal" of a slab, when the
rolling mill stand does not take hold of the slab on account of the
reduction being too high.
[0010] In addition to rolling a slab, plate or strip made from a
single metal or a single metal alloy, the device according to the
invention can also be used to roll a slab, strip or plate
comprising two or more layers of metal, in which case the metal
layers may consist of the same metal alloy, of different metal
alloys or of different metals or metal alloys.
[0011] The feed means are preferably designed to introduce the
slab, plate or strip between the rolls at an angle of between
10.degree. and 25.degree. with respect to the perpendicular to the
plane through the center axes of the rolls, more preferably at an
angle of between 15.degree. and 25.degree., and even more
preferably at an angle of substantially 20.degree.. In the case of
feeding at between 10.degree. and 25.degree. and preferably between
15.degree. and 25.degree., the shearing is relatively great while
the angle is not so great as to impede feed to the roll nip. In
many cases, it has been found that the feeding can be carried out
optimally at an angle of substantially 20.degree..
[0012] According to an advantageous embodiment of the device, the
feed means comprise a feed surface or a roller table. This easily
allows the material to be fed at an angle between the rolls. Other
designs of the feed means are also possible.
[0013] The angle between the feed means and the rolling mill stand
is preferably adjustable. This allows the angle to be adapted to
the thickness of the slab, plate or strip as desired, for example
if the thickness of the material means that a specific introduction
angle is desirable. Then, if desired the further rolling using the
device can be continued at a different angle.
[0014] To increase the degree of shearing, the rolling mill stand
is preferably designed in such a manner that, during use, the rolls
have different peripheral velocities, the difference in peripheral
velocity amounting to at least 5% and at most 100%, and preferably
at least 5% and at most 50%, more preferably at least 5% and at
most 20%. The difference in peripheral velocity is partly
determined by the thickness of the material; in addition, the
shearing increases as the difference in peripheral velocity between
the rolls becomes greater. Greater shearing is advantageous since
it leads to greater grain refinement and improved closing up of the
pores. On the other hand, if there is a high difference in
velocity, there is a high risk of slipping between the rolls and
the material, which would result in irregular shearing.
[0015] According to an advantageous embodiment, the rolls have a
different diameter and/or can be driven at different rotational
speeds. This makes it possible to obtain the difference in
peripheral velocity.
[0016] The device is preferably provided with one or more following
rolling mill stands with driveable rolls which are positioned
downstream of the rolling mill stand, as seen in the rolling
direction. This allows a slab, plate or strip to be subjected to a
rolling operation two or more times without interruption, so that a
desired result can be achieved more quickly using this device.
Obviously, it is also possible for the material to be passed
through the same device twice, but this takes more time,
particularly when strip material is being rolled.
[0017] According to an advantageous embodiment, the device is
designed, during use, to feed the metal slab, plate or strip to at
least one of the one or more following rolling mill stands at an
angle of between 5.degree. and 45.degree., preferably at an angle
of between 10.degree. and 25.degree. and more preferably between
15.degree. and 25.degree., the angle preferably being adjustable.
As a result, at these rolling mill stands the material is passed
between the rolls at an angle, and therefore is subjected to
shearing over the entire thickness at these rolling mill stands.
The result of this is that the material undergoes considerable
shearing in one pass through the device. The same benefits apply as
for the rolling mill stand to which the material is fed first.
[0018] It is preferably also true of the following rolling mill
stands that at least one of the one or more following rolling mill
stands is designed in such a manner that, during use, the rolls
have a different peripheral velocity, in which case the rolls
preferably have a different diameter and/or can be driven at
different rotational speeds. By also providing the rolls of the
following rolling mill stands with a different peripheral velocity,
the shearing which is imparted to the material as it passes through
the device is increased further. The same statements apply here as
those made in connection with the difference in velocity between
the rolls of the first rolling mill stand through which the
material is passed.
[0019] According to a preferred embodiment, at least one of the one
or more following rolling mill stands has a roll nip which is
situated outside the plane of symmetry of the roll nip of the
rolling mill stand. As a result, it is easy for the material to be
passed at an angle to said following rolling mill stand.
[0020] It is preferable for support rolls to be arranged upstream
of the one or more following rolling mill stands, as seen in the
direction of rolling, in order to support and/or guide the metal
slab, plate or strip. These support rolls can feed the material to
the following rolling mill stands, for example, at the desired
angle.
[0021] According to a preferred embodiment of a device without
following rolling mill stands, the device is provided on both sides
with feed means which are designed to pass the slab, plate or strip
between the rolls at an angle of between 5.degree. and 45.degree.
with respect to the perpendicular to the plane through the center
axes of the rolls, preferably at an angle of between 10.degree. and
25.degree., the angle between the feed means being adjustable
between 0 and 45.degree. and it being possible for the rolls to be
driven in both directions of rotation. With the aid of this device,
it is possible for material to be passed back and forth through the
device, and each time the material can be supplied at an angle of
between 5 and 45.degree. and preferably between 10.degree. and
25.degree. and can be guided out of the device at an angle of
0.degree..
[0022] According to a second aspect of the invention, one or more
of the abovementioned objects is achieved by a device for
processing a metal strip, comprising a rolling mill stand with a
roll nip between two driveable rolls, the rolling mill stand being
designed to roll the metal strip between the rolls, which device is
provided with one or more following rolling mill stands with
driveable rolls, and in that the rolling mill stand and one or more
following rolling mill stands are designed in such a manner that,
during use, their rolls have different peripheral velocities, the
difference in peripheral velocity amounting to at least 5% and at
most 100%.
[0023] In this device, therefore, the material is passed through
two or more rolling mill stands, the rolls of each rolling mill
stand in each case having a different peripheral velocity from one
another. As a result, the material is passed without interruption
through two or more rolling mill stands which each apply shearing
to the material across the entire thickness of the material.
Therefore, using this device leads to considerable shearing of the
material, with the associated advantages as described above.
[0024] This device according to the second aspect of the invention
can also be used, in addition to the rolling of a slab, plate or
strip consisting of a single metal or a single metal alloy, to roll
a slab, strip or plate comprising two or more layers of metal, in
which case the layers of metal may consist of the same metal alloy,
of different metal alloys or of different metals or metal
alloys.
[0025] In this device, the difference in peripheral velocity is
preferably at least 5% and at most 50%, and preferably at least 5%
and at most 20%, for the same reasons as those explained above.
[0026] In this case too, it is preferable for the rolls of the
rolling mill stand and the following rolling mill stands to have
different diameters and/or to be driveable at different rotational
speeds, as explained in connection with the first aspect of the
invention.
[0027] According to an advantageous embodiment, in this case too,
at least one of the one or more following rolling mill stands has a
roll nip which is situated outside the plane of symmetry of the
roll nip of the rolling mill stand, for similar reasons to those
given in connection with the device according to the first aspect
of the invention.
[0028] Also, in this case it is preferable for support rolls to be
arranged upstream of the one or more following rolling mill stands,
as seen in the direction of rolling, in order to support and/or
guide the metal strip. This is for the same reasons as those which
have been explained above.
[0029] It is preferable for feed means to be arranged upstream of
the rolling mill stand, as seen in the direction of rolling, these
feed means being designed to guide the strip between the rolls at
an angle of between 5.degree. and 45.degree. with respect to the
perpendicular to the plane through the center axes of the rolls,
preferably at an angle of between 10.degree. and 25.degree. and
more preferably between 15.degree. and 25.degree., the feed means
preferably comprising a feed surface or a roller table. This
measure enables the rolls to gain a good grip on the material which
is to be introduced.
[0030] The invention also relates to a slab, plate or strip
produced using the above devices, the slab, plate or strip having a
substantially uniform shearing over its thickness.
[0031] The metal is preferably aluminum or steel or stainless steel
or copper or magnesium or titanium or one of their alloys. These
are metals which are in industrial use, and it is desirable for
them to have good mechanical properties.
[0032] The invention will be explained below on the basis of an
exemplary embodiment and with reference to the appended drawing, in
which:
[0033] FIG. 1 shows a highly diagrammatic illustration of an
exemplary embodiment of a device according to the invention.
[0034] The FIGURE shows an embodiment of the device 1 with a first
rolling mill stand 11 and two following rolling mill stands 12, 13,
diagrammatically indicated by a rectangle. Each rolling mill stand
has respective rolls 11a,b, 12a,b and 13a,b. Upstream of the first
rolling mill stand 11 there is a feed surface 10 over which a slab
of metal 2, for example of aluminum, can be supplied. The means for
supplying the slab 2 and the means for driving the rolling mill
stands are not shown; means of this type are known to the person
skilled in this field.
[0035] In this exemplary embodiment, the rolling mill stands are
arranged in such a manner that rolling mill stand 11 and 13 have a
common plane of symmetry P which runs through the center of their
respective roll nips. The plane Q through the center axes of the
rolls 11a, 11b of the rolling mill stand 11 is perpendicular
thereto, as is the plane T through the center axes of the rolls
13a, 13b of the rolling mill stand 13.
[0036] The rolling mill stand 12 has a plane S passing through the
center axes of its rolls 12a, 12b, which is likewise perpendicular
to the plane P. The plane of symmetry R through the center of the
roll nip of the rolling mill stand 12, however, is offset upward
with respect to the plane P. As a result, the slab 2 is passed at
an angle to rolling mill stand 12 and then at an angle to rolling
mill stand 13.
[0037] The feed surface 10 is at an angle .alpha. with respect to
the plane P, .alpha. usually being approximately 20.degree.. The
angle .alpha. is adjustable and can be matched to the type and
thickness of the material.
[0038] Support and guide rolls 15a,b 16a,b, 17a,b and 18a,b are
arranged between the rolling mill stands 11, 12 and 13 in order to
guide the slab 2 to the rolling mill stands 12 and 13 after it has
been rolled in rolling mill stand 11 and to support it over this
path.
[0039] The rolls 11a and 11b have different diameters, so that,
given an identical angular velocity, they have different peripheral
velocities. The rolls 12a, 12b also have different diameters, but
in this case the difference in size is reversed. This arrangement
means that the shearing in the slab 2 as it passes through the
rolling mill stands 11, 12 will have an inverted profile. The
material which is displaced during passage through rolling mill
stand 11 is, as it were, displaced back during passage through
rolling mill stand 12.
[0040] In this exemplary embodiment, the rolling mill stand 13 has
rolls 13a, 13b with an identical diameter. This stand rolls the
slab 2 in the customary way, but it is also possible for the rolls
13a, 13b to be provided with a different rotational speed and
therefore a different peripheral velocity. If the latter situation
applies, the rolling mill stand 13 will also contribute to the
shearing in the slab 2.
[0041] It will be clear that the device according to the invention
can be used to roll slabs, plates and strips of different types of
metal, such as steel, aluminum, stainless steel, copper, magnesium
or titanium, and it is also possible to roll two or more slabs of
metal resting on top of one another. The slabs may consist of
different metals or different alloys from one another. If
necessary, adjustments which lie within the scope of the person
skilled in the art may be made to the device.
[0042] The device which has been described above and is illustrated
in FIG. 1 results in a slab, plate or strip being guided through
and rolled by the device in the form of a coil. It will be clear
that rolling mill stands may also be arranged in other ways with
respect to one another, that it is possible to use more or fewer
rolling mill stands and that the device can also be used only with
rolling mill stand 11. The rolls may also optionally have different
diameters and/or be driven at different angular velocities. The
supporting and/or guiding of the slab, plate or strip can also be
carried out using other means.
[0043] It is also possible for the feed surface 10 to be replaced
by other feed means, such as a roller table, or a single feed roll
for strip material, which feed roll has to be arranged in such a
manner that the strip material is passed into the roll nip of the
rolling mill stand 11 at the angle .alpha..
[0044] Another embodiment of the device according to the invention
(not shown) is that in which the feed surface 10 is omitted and in
which there are at least two rolling mill stands, for example
rolling mill stand 11 and rolling mill stand 12, the rolls of these
rolling mill stands having different peripheral velocities and the
difference in peripheral velocity amounting to at least 5% and most
100%. The arrangement and further design of the rolling mill stands
may be identical to that shown in FIG. 1 and can be altered in a
similar way.
[0045] The invention will be explained with reference to an
exemplary embodiment.
[0046] Experiments were carried out using slabs of aluminum AA7050
with a thickness of 32.5 mm. These slabs were rolled once in a
rolling device with two rolls, of which the top roll had a diameter
of 165 mm and the bottom roll had a diameter of 135 mm. After
rolling, the slabs had a thickness of 30.5 mm.
[0047] The slabs were introduced at different angles varying
between 5.degree. and 45.degree.. The temperature of the slabs when
they were introduced into the rolling device was approximately
450.degree. C. The two rolls were driven at a speed of 5
revolutions per minute.
[0048] After rolling, the slabs had a certain curvature, which was
highly dependent on the angle of introduction. The straightness of
the slab after rolling can to a large extent be determined by the
angle of introduction, in which context the optimum angle of
introduction will be dependent on the degree of reduction in the
size of the slab, the type of material and alloy, and the
temperature. For the slabs of aluminum which have been rolled in
the experiment described above, an optimum angle of introduction is
approximately 20.degree..
[0049] A shear angle of 20.degree. was measured in the slabs of
aluminum which were rolled in accordance with the experiment
described above. Using this measurement and the reduction in the
size of the slab, it is possible to calculate an equivalent strain
in accordance with the following formula: 1 eq = 2 3 ( xx 2 + yy 2
) .
[0050] This formula is used to make it possible to present the
strain in one dimension and is known from the book "Fundamentals of
metal forming" by R. H. Wagoner and J. L. Chenot, John Wiley &
Sons, 1997.
[0051] Therefore, in the slabs which have been rolled in accordance
with the experiment, the equivalent strain is 2 eq = 2 3 ( ( ln (
32.5 30.5 ) ) 2 + ( 1 2 ( tan 20 .degree. ) ) 2 ) 0.25 .
[0052] In the case of rolling with an ordinary roll, shearing does
not take place across the thickness of the plate and the equivalent
strain is therefore only 3 eq = 2 3 ln ( 32.5 30.5 ) 2 0.07
[0053] (working on the basis of a uniform strain over the entire
thickness of the plate).
[0054] Therefore, the rolling using the method according to the
invention results in an equivalent strain which is three to four
times higher than with conventional rolling without any difference
in peripheral velocity. A high equivalent strain means less
porosity in the slab, greater recrystalization and therefore
greater grain refinement, and more extensive breaking up of the
second-phase particles (constituent particles) in the slab. These
effects are generally known to the person skilled in this field of
engineering if the equivalent strain increases. Therefore, the
rolling according to the invention means that the resulting
properties of the material are greatly improved as a result of the
use of the method according to the invention.
* * * * *