Note: Descriptions are shown in the official language in which they were submitted.
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[Document Name] Specification
[Title of the Invention] MAGNESIUM HOT ROLLING APPARATUS
[Technical Field]
[0001]
The present invention relates to a magnesium alloy hot rolling apparatus.
Priority is claimed on Japanese Patent Application No. 2007-269057, filed
October 16, 2007, the contents of which are incorporated herein by reference.
[Technical Background]
[0002]
To manufacture a magnesium alloy sheet, a round bar-shaped billet having, for
example, a diameter of approximately 300 to 400 mm and a length of
approximately 500
to 600 mm is molded by hot extrusion molding into a thick plate having a
thickness of,
for example, 10 mm or less. This thick plate is then cut to a predetermined
length (for
example, 3 m) so as to form a cut plate material, and this cut plate material
is then rolled
to a thickness of approximately 1 mm by rough rolling.
This magnesium alloy coil which has a thickness of approximately I mm is then
further rolled by finishing rolling so that a coil material having a thickness
of
approximately 0.2 to 0.5 mm or a coil having a thickness of 50 m or less (for
example,
30 to 40 m) is manufactured.
[0003]
Magnesium alloy not only requires a large amount of pressure if it is rolled
at
room temperature, but it also cracks easily. Accordingly, it is preferably
rolled using
hot rolling.
Conventional examples of apparatuses for the hot rolling of magnesium alloy
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are disclosed in FIG. I of patent document I and FIG. 1 of patent document 2.
The hot rolling apparatuses disclosed in these patent documents are provided
with a rolling mill which reciprocatingly rolls the magnesium alloy, and with
two heating
furnaces which are located on the upstream side and the downstream side of the
rolling
mill. The magnesium alloy is heated to a predetermined temperature by these
heating
furnaces and is rolled in the rolling mill.
[Patent document 1] Japanese Patent Publication No. 3521863
[Patent document 2] Japanese Patent Publication No. 3821074
[Disclosure of the Invention]
[Problems to be Solved by the Invention]
[0004]
However, in the hot rolling apparatuses disclosed in the aforementioned patent
documents 1 and 2, the winder portion at the distal end portion of the coil
and the
unprocessed portion at the rear end thereof are not able to be heated and
rolled with any
stability. Because of this, they cannot be used for finished product coils.
Furthermore,
they cause the yield to drop and have other drawbacks such as not allowing the
production volume to be increased.
[0005]
The present invention was conceived in view of the above described
circumstances and it is an object thereof to provide a magnesium alloy hot
rolling
apparatus which prevents any reduction in the quality of a product which is
due to
temperature variations during the hot rolling of a magnesium alloy, and which
makes it
possible to improve the yield and increase the production volume.
[Means for Solving the Problem]
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[0006]
In order to solve the above described problems, the following apparatuses are
employed in the present invention.
As a first aspects of the present invention, in a magnesium alloy hot rolling
apparatus in which winders that are able to apply heat to and then maintain
the
temperature of a magnesium alloy sheet while this sheet is in a coiled state
are installed
on both entry and exit sides of a rolling mill, and in which the magnesium
alloy sheet
undergoes a sequential thickness reduction via a plurality of reverse
rollings, the rolling
mill is provided with working rollers and back-up rollers whose surface
temperature can
be heated to a particular fixed temperature and then maintained at this
temperature.
[0007]
As a second aspects of the present invention, in the magnesium alloy hot
rolling
apparatus according to the above described first aspects of the present
invention, it is also
possible for the rolling mill to be a switchable stage rolling mill in which
it is possible for
small diameter working rollers which can be heated and then kept at a
particular
temperature to be installed.
[0008]
As a third aspects of the present invention, in the magnesium alloy hot
rolling
apparatus according to the above described first aspects of the present
invention, it is also
possible for a plurality of pairs of pinch rollers which incorporate vertical
rollers which
can be heated and then kept at a particular temperature to be placed between
the rolling
mill and each one of the pair winders so that stable transporting of the
magnesium alloy
coil is performed, and for tension adjustment apparatuses to be provided
between the
pinch rollers.
[Effects of the Invention]
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[0009]
According to the present invention, because working rollers and back-up
rollers
of a rolling mill enables to heat a magnesium alloy sheet and maintain the
temperature
thereof, it is possible to prevent any reduction in product quality which is
due to
temperature variations during the hot rolling of a magnesium alloy sheet.
Furthermore,
it is possible to improve the yield and increase the production capacity, and
to maintain a
superior quality in a sheet material or foil material.
[Brief description of the drawings]
[0010]
[FIG. I] FIG 1 is a typical view showing the schematic structure of a hot
rolling
apparatus in an embodiment of the present invention.
[FIG 2] FIG 2 is a typical view showing the schematic structure of a
temperature maintaining and heating winder in the aforementioned embodiment.
[FIG. 3A] FIG 3A is a view showing an alteration of the setting of a rolling
mill
of the aforementioned embodiment.
[FIG 3B] FIG. 3B is a view showing an alteration of the setting of a rolling
mill
of the aforementioned embodiment.
[FIG 4A] FIG. 4A is a view showing an example of a different number of rolling
mill stages in the aforementioned embodiment.
[FIG. 4B] FIG. 4B is a view showing an example of a different number of
rolling
mill stages in the aforementioned embodiment.
[FIG 5] FIG. 5 is a view showing the schematic structure of a tension
adjustment
apparatus in the aforementioned embodiment.
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[Description of the Reference Numerals]
[0011]
100 ... Hot rolling apparatus (Magnesium alloy hot rolling apparatus)
1 ... First temperature maintaining and heating winder (winder)
5 2 ... Second temperature maintaining and heating winder (winder)
1 a, 2a ... Winder portions
1 b, 2b ... Heating and a temperature maintaining furnaces
3 ... Rolling mill (switchable stage rolling mill)
3a ... Working roller
3b ... Back-up roller
4 ... Pinch roller
5 ... Tension adjustment apparatus
S ... Magnesium alloy sheet
[Best Embodiments for Implementing the Invention]
[0012]
An embodiment of the present invention will now be described with reference
made to the drawings.
FIG. 1 is a front view showing the structure of a hot rolling apparatus 100 in
the
present embodiment.
As is shown in FIG 1, the hot rolling apparatus 100 (i.e., a magnesium alloy
hot
rolling apparatus) according to the present embodiment is provided with a
first
temperature maintaining and heating winder 1 (winder), a second temperature
maintaining and heating winder 2 (winder), a rolling mill 3, a plurality of
pairs of pinch
rollers 4, and a tension adjustment apparatus 5.
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[0013]
FIG 2 is a typical view showing the schematic structure of the first
temperature
maintaining and heating winder I and the second temperature maintaining and
heating
winder 2.
The two temperature maintaining and heating winders I and 2 are provided with
winder portions 1 a and 2a and with heating and a temperature maintaining
furnaces l b
and 2b.
The heating and a temperature maintaining furnaces lb and 2b have internal
heaters H.
[0014]
These temperature maintaining and heating winders 1 and 2 are installed on
both
the entry and exit sides of the rolling mill 3, and are able to heat up and
then maintain the
temperature of a magnesium alloy sheet while this sheet is in a coiled state.
They are
also able to freely wind on or unwind both end portions in a longitudinal
direction of a
magnesium alloy sheet S in a coil shape using the winder portions I a and 2a,
and to heat
the interiors of the heating and a temperature maintaining furnaces 1 b and 2b
to a
predetermined temperature (a first temperature) using the heaters H and then
maintain
this temperature. As a result, the magnesium alloy sheet S which has been
wound into a
coil shape (i.e., a magnesium alloy coil) is maintained at the predetermined
temperature.
The aforementioned (first temperature) is, for example, approximately 100 to
350 C, and from 200 to 250 C is preferable.
[0015]
The description will now return to FIG 1.
The rolling mill 3 (a rolling mill, a switchable stage rolling mill) has a
pair of
working rollers 3a that are placed between the aforementioned pair of
temperature
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maintaining and heating winders I and 2 in parallel with and facing each other
and that
are able to apply heat and maintain the temperature, a pair of back-up rollers
3b that are
provided in parallel with and facing the respective working rollers 3a and
that are able to
apply heat and maintain the temperature, a housing 3c which contains the two
pairs of
rollers 3a and 3b and supports them such that they are able to rotate freely,
and a drive
source (not shown) which drives the two pairs of rollers 3a and 3b to rotate.
[0016]
The working rollers 3a and the back-up rollers 3b are heating rollers which
can
be heated so that the surface temperature thereof is raised to a fixed
temperature and
maintain the temperature thereof (a second temperature), and, while feeding
the
magnesium alloy sheet S in one direction between the working rollers 3a, are
able to heat
the magnesium alloy sheet S so as to raise the temperature thereof and roll it
at the same
time. Thereby, the thickness of the magnesium alloy sheet S is reduced. The
working
rollers 3a and the back-up rollers 3b have a structure in which, for example,
a plurality of
rod-shaped cartridge heaters are embedded at predetermined intervals in the
axial
direction at positions which are a predetermined depth from the surface.
The aforementioned (second temperature) is, for example, approximately 150
to 350 C or less.
[0017]
As a result of this, the rolling mill 3 stably reduces the thickness of the
magnesium alloy sheet S so as to cause it to become elongated.
Moreover, the rolling mill 3 performs reciprocating rolling by reversing the
feed
direction of the magnesium alloy sheet S at a predetermined timing. By doing
this, the
rolling mill 3 causes the magnesium alloy sheet S to become elongated by
reducing the
thickness thereof from, for example, a thickness of approximately I nun to a
thickness of
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approximately 0.2 to 0.5 mm or to 50 pm or less (for example, to 30 to 40 m).
[0018]
Here, the rolling mill 3 of the present embodiment is a switchable stage
rolling
mill in which it is also possible for small diameter working rollers to be
installed. FIG.
3A shows a rolling mill 3 which has been set as a four-stage structure (i.e.,
the structure
shown in FIG 1), while FIG. 3B shows a rolling mill 3 which has been set as a
ten-stage
structure. This type of rolling mill 3 is normally set as the four-stage
structure shown in
FIG 3A, however, for a thin material, for example, for a 50 m foil material,
as is shown
in FIG. 3B, the rolling mill 3 can be altered to a ten-stage structure which
has a pair of
small-diameter working rollers 3d and two vertically aligned pairs of
horizontal support
rollers 3e provided on an intermediate path thereof.
[0019]
FIG. 4 shows another structural example of this type of rolling mill 3. FIG.
4A
shows a rolling mill 31 having a six-stage structure, while FIG 4B shows a
rolling mill
32 having a ten-stage structure.
The rolling mill 31 has a pair of working rollers 3a and two pairs of back-up
rollers 3b, while the rolling mill 32 has a pair of working rollers 3a and
four pairs of
back-up rollers 3b.
Here, of the four pairs of back-up rollers 3b of the rolling mill 32, the two
pairs
on the inner side (i.e., the ones in contact with the working rollers 3a) are
known as
intermediate rollers.
[0020]
The description will now return to FIG. 1.
Similar to the above described working rollers 3a and back-up rollers 3b, the
pinch rollers 4 have a plurality of rod-shaped cartridge heaters embedded at
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predetermined intervals in the axial direction at positions which are a
predetermined
depth from the surface. These pinch rollers 4 are heating rollers whose
surface
temperature is raised to a suitable temperature and the temperature is
maintained (for
example, from 150 C to 350 C), and provide auxiliary transporting for the
magnesium
alloy sheet S which is traveling left or right in conjunction with the
reciprocating rolling
of the rolling mill 3. A plurality of sets of these pinch rollers 4 are
provided
respectively between the rolling mill 3 and the first temperature maintaining
and heating
winder 1, and between the rolling mill 3 and the second temperature
maintaining and
heating winder 2.
By adjusting the transporting speed, the pinch rollers 4 can be made to impart
suitable tensile force to the magnesium alloy sheet S which is being rolled by
the rolling
mill 3.
[0021]
The tension adjustment apparatuses 5 are sandwiched between two adjacent
pairs of pinch rollers 4 and, as is shown in FIG. 5, are each provided with
two fixed
rollers 5a and one dancer roller Sb. The magnesium alloy sheet S is entrained
such that
the dancer roller 5b is suspended between the two fixed rollers 5a by the
magnesium
alloy sheet S, and the tension thereof is controlled by the vertical movement
of the dancer
roller Sb such that measurement values of a separately installed tension meter
(not
shown) stay constant.
[0022]
In this type of structure, a hot rolling apparatus 100 performs finishing
rolling on
the magnesium alloy sheet S. Hereinafter, the operation of the hot rolling
apparatus 100
will be described.
[0023]
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The magnesium alloy sheet S is rolled by the rolling mill 3 while being
transported in one direction by being unwound from the _first temperature
maintaining
and heating winder 1 and wound onto the second temperature maintaining and
heating
winder 2, or by being unwound from the second temperature maintaining and
heating
5 winder I and wound onto the first temperature maintaining and heating winder
2.
The temperature of the magnesium alloy sheet S drops somewhat between the
first temperature maintaining and heating winder I and the second temperature
maintaining and heating winder 2. However, because the working rollers 3a, the
back-up rollers 3b and the pinch rollers 4 are heating rollers, there is
little temperature
10 drop or temperature variation in the material caused by the material
contacting these
rollers.
[0024]
When the unwinding of the magnesium alloy sheet S from the first temperature
maintaining and heating winder I (or the second temperature maintaining and
heating
winder 2) has finished, the hot rolling apparatus 100 reverses the rolling
direction. The
hot rolling apparatus 100 repeats this process so that the magnesium alloy
sheet S is
rolled reciprocatingly, and the thickness of the magnesium alloy sheet S is
sequentially
reduced. As a result, a sheet material having a thickness of approximately 0.2
to 0.5
mm, or a foil material having a thickness of 50 pm or less (for example, 30 to
40 m) is
manufactured.
Here, specific examples of pass schedules of finishing rolling performed by
this
hot rolling apparatus 100 are shown below in Table 1.
[0025]
[Table 1]
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Pass Entry side Reduction Rolling Working roller Rolling Rolling
No. thickness amount temperature diameter(mm) speed load
(mm) (mm) ( C) (m/sec) (ton)
1 1.00 0.30 200 165 30 60
2 0.70 0.21 200 165 30 58
3 0.49 0.15 200 165 30 55
4 0.34 0.10 200 165 30 52
0.24 0.07 200 165 30 50
6 0.17 0.05 150 60 30 30
7 0.12 0.04 150 60 30 29
8 0.08 0.02 150 60 30 28
9 0.06 0.02 150 60 30 27
Final thickness 0.04 mm
[0026]
In the above pass schedule, the magnesium alloy sheet S is a coil material
having a material quality of AZ3IB, a thickness of 1.00 mm, and a width of 300
mm.
5 The rolling mill 3 has four stages. The diameter of each roller of the
working roller
pairs 3a is 165 rmn, and the barrel length thereof is 500 mm, while the
diameter of each of
the back-up rollers 3b is 300 mm, and the diameter of each of the pinch
rollers 4 is 150
mm.
Moreover, in the above described example, the temperature which the interiors
of the two temperature maintaining and heating winders 1 and 2 are heated to
and held at
is 250 C, while the working rollers 3a, the back-up rollers 3b, and the pinch
rollers 4 are
heating rollers having internal heaters and the surface temperature of these
is set to 200
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C.
The rolling speed was set to a fixed speed of 30 ml minute, and nine passes
(i.e.,
four and a half reciprocations) of reciprocating rolling were performed
resulting in a foil
material having a final thickness of 0.04 mm being obtained. Moreover, on the
sixth
pass, the rolling mill was switched to a ten-stage small-diameter mill (i.e.,
to working
rollers having a diameter of 4) 60 mm), and this was subsequently used until
the final pass
(i.e., the ninth pass).
[0027]
The magnesium alloy sheet S is soft during the rolling process due to the high
temperature, and there is a possibility that pitting will remain if high
pressure is also
applied to areas other than those areas where the rolling mill 3 is used.
However, in the
hot rolling apparatus 100 of the present invention, because the magnesium
alloy sheet S
is nipped in a plurality of locations by a plurality of groups of pinch
rollers 4, the force
with which each pinch roller 4 nips the magnesium alloy sheet S is small as a
result of
being dispersed, and there is no concern that pitting from the pinch rollers 4
will remain.
[0028]
Moreover, in this hot rolling apparatus 100, the tension of the magnesium
alloy
sheet S is kept constant from one pinch roller 4 to the next pinch roller 4 by
the tension
adjustment apparatus 5. As a result, any twisting or wrinkling of the
magnesium alloy
sheet S is prevented, and stable rolling is guaranteed.
[0029]
According to this type of hot rolling apparatus 100, because a magnesium alloy
sheet S is rolled while substantially the entire length thereof is heated and
held at a
predetermined temperature, it is possible to suppress any drop in the
temperature of the
magnesium alloy sheet S, and it is possible to prevent any deterioration in
the quality of a
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product which is caused by temperature variations during the hot rolling.
Accordingly,
it is possible to improve the yield and increase the production volume, and it
is also
possible to maintain a superior finished product, namely, a superior quality
in the sheet
material or foil material.
[0030]
Note that in the present embodiment four-stage, six-stage, and ten-stage
rolling
mills are illustrated, however, the present embodiment is not limited to this.
[Industrial applicability]
[0031]
Because the magnesium alloy hot rolling apparatus of the present invention is
constructed such that working rollers and back-up rollers of the rolling mill
are able to
apply heat to a magnesium alloy sheet and to hold the temperature thereof, it
is possible
to prevent any deterioration in the quality of a product which is caused by
temperature
variations during the hot rolling of the magnesium alloy sheet. Furthermore,
it is
possible to improve the yield and increase productivity, and it is also
possible to maintain
a superior quality in the sheet material or foil material.
