U.S. patent application number 16/067306 was filed with the patent office on 2019-01-10 for device and method for preparing large-sized high-quality aluminium alloy ingot.
This patent application is currently assigned to GENERAL RESEARCH INSTITUTE FOR NONFERROUS METALS. The applicant listed for this patent is GENERAL RESEARCH INSTITUTE FOR NONFERROUS METALS. Invention is credited to Yuelong BAI, Mingwei GAO, Jianchao LIU, Jun XU, Yujie YANG, Shaoming ZHANG, Zhifeng ZHANG.
Application Number | 20190009328 16/067306 |
Document ID | / |
Family ID | 59224516 |
Filed Date | 2019-01-10 |
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United States Patent
Application |
20190009328 |
Kind Code |
A1 |
ZHANG; Zhifeng ; et
al. |
January 10, 2019 |
DEVICE AND METHOD FOR PREPARING LARGE-SIZED HIGH-QUALITY ALUMINIUM
ALLOY INGOT
Abstract
Provided is a device for preparing a large-sized high-quality
aluminium alloy ingot, which is mainly composed of a uniform
cooler, a hot top, an oil-gas lubrication mold, an induction coil
and a dummy ingot, wherein the hot top is arranged above the
oil-gas lubrication mold, the induction coil is arranged outside
the oil-gas lubrication mold, the uniform cooler is arranged inside
the oil-gas lubrication mold, and the dummy ingot is arranged below
the oil-gas lubrication mold. Further provided is a method for
preparing a large-sized high-quality aluminium alloy ingot. The
device combines a partitioned gas supply mold with the uniform
cooler and an electromagnetic stirrer, and the effective coupling
of the three achieves forced and uniform solidification forming of
a melt under gas pressure contact conditions, such that a stable
and continuous gas film is formed between the melt and the mold.
The ingot has a smooth surface, and a fine and uniform internal
structure.
Inventors: |
ZHANG; Zhifeng; (Beijing,
CN) ; XU; Jun; (Beijing, CN) ; ZHANG;
Shaoming; (Beijing, CN) ; BAI; Yuelong;
(Beijing, CN) ; GAO; Mingwei; (Beijing, CN)
; LIU; Jianchao; (Beijing, CN) ; YANG; Yujie;
(Beijing, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL RESEARCH INSTITUTE FOR NONFERROUS METALS |
Beijing |
|
CN |
|
|
Assignee: |
GENERAL RESEARCH INSTITUTE FOR
NONFERROUS METALS
Beijing
CN
|
Family ID: |
59224516 |
Appl. No.: |
16/067306 |
Filed: |
June 15, 2016 |
PCT Filed: |
June 15, 2016 |
PCT NO: |
PCT/CN2016/085826 |
371 Date: |
June 29, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22D 11/07 20130101;
B22D 11/112 20130101; B22D 11/0401 20130101; B22D 11/049 20130101;
B22D 11/115 20130101; B22D 11/114 20130101 |
International
Class: |
B22D 11/07 20060101
B22D011/07; B22D 11/112 20060101 B22D011/112; B22D 11/115 20060101
B22D011/115 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 30, 2015 |
CN |
201511020092.0 |
Dec 30, 2015 |
CN |
201521131860.5 |
Claims
1. A device for preparing a large-sized high-quality aluminium
alloy ingot, comprising: a uniform cooler; a hot top; an oil-gas
lubrication mold; an induction coil; and a dummy ingot, wherein the
hot top is arranged above the oil-gas lubrication mold, the
induction coil is arranged outside the oil-gas lubrication mold,
the uniform cooler is arranged inside the oil-gas lubrication mold,
and the dummy ingot is arranged below the oil-gas lubrication
mold.
2. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 1, wherein the oil-gas lubrication
mold comprises a mold body and a graphite ring mounted above the
mold body, wherein the graphite ring is provided with a gas groove
and an oil groove on its outer wall, and wherein the oil groove is
separated from the gas groove, and is arranged on an upper portion
thereof.
3. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 2, wherein the gas groove is divided
into 3-20 sections for independent gas supply and control.
4. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 3, wherein each section of the gas
groove has a length of 100-500 mm.
5. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 2, wherein the graphite ring is made
of porous graphite.
6. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 2, wherein the mold body is provided
with upper and lower rows of water spraying holes, and wherein the
upper row of water spraying holes forms an angle of 15-30 degrees
with respect to a wall of the mold, and has a diameter of 1-5 mm;
while the lower row of water spraying holes forms an angle of 0-25
degrees with respect to the wall of the mold, and has a diameter of
2-8 mm.
7. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 6, wherein water volumes of the
upper and lower rows of water spraying holes are independently
controlled, and the diameter of the upper row of water spraying
holes is smaller than or equal to that of the lower row of water
spraying holes.
8. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 1, wherein a magnet yoke of the
induction coil is of a telescopic design, and is retractable in a
range of 0-100 mm, and wherein the induction coil generates an
electromagnetic field which is guided into a melt inside the mold
via the magnet yoke.
9. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 8, wherein the induction coil
generates a rotating electromagnetic field, a traveling wave
electromagnetic field or a compound electromagnetic field.
10. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 1, wherein an upper portion of the
uniform cooler is a heat insulation end, and a lower portion is a
cooling end, wherein the heat insulation end is provided with a
stirring blade.
11. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 10, wherein the heat insulation end
is of a cylindrical shape, and is made of high
temperature-resistant heat insulation ceramic material.
12. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 11, wherein the heat insulation end
has an outer diameter of 100-800 mm.
13. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 10, wherein the cooling end is made
of thermally conductive material.
14. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 13, wherein the cooling end is of a
spiral shape, and is made of graphite, copper, molybdenum, titanium
or composite materials thereof.
15. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 10, wherein the stirring blade is
made of high temperature-resistant material, and is arranged to be
0-8 in number.
16. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 15, wherein the stirring blade is
made of copper, molybdenum, titanium, ceramic or composite
materials thereof, and has a width of 10-100 mm and a thickness of
2-8 mm.
17. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 1, wherein the uniform cooler is one
or more in number, which is arranged to a height where the mold is
located, and has a rotational speed of 0-300 r/min.
18. The device for preparing a large-sized high-quality aluminium
alloy ingot according to claim 17, wherein a cooling medium
employed by the uniform cooler is air, nitrogen, water or oil, and
the flow of the cooling medium is 0-2000 L/min.
19. A method for preparing a large-sized high-quality aluminium
alloy ingot, the method comprising the steps of: pouring a melt
that has been refined and stabilized to be 80-100 degrees Celsius
higher than the liquidus temperature into a hot top during the
semi-continuous casting operation; introducing air and lubricating
oil into a gas groove and an oil groove arranged on an outer wall
of a graphite ring; controlling flows of upper and lower water
spraying holes; an alloy melt reaches an upper portion of a dummy
ingot through the hot top and a mold, and a liquid surface of the
melt is elevated; after the continuous casting operation is
initiated, the dummy ingot descends slowly, and increasing a flow
of cooling water slowly; and after the casting process is
stabilized, applying uniform cooling and electromagnetic applied to
obtain a large-sized high-quality aluminium alloy ingot in the
end.
20. The method for preparing a large-sized high-quality aluminium
alloy ingot according to claim 19, wherein the flow of air in the
gas groove is 500-5000 mL/min, while the oil groove supplies oil in
a pulsed manner, and has an oil supplying capacity of 60-100/s.
21. The method for preparing a large-sized high-quality aluminium
alloy ingot according to claim 19, wherein the flow of the upper
row of water spraying holes is 1-50 L/min, while that of the lower
row of water spraying holes is 20-100 L/min.
22. The method for preparing a large-sized high-quality aluminium
alloy ingot according to claim 19, wherein the speed of casting is
20-100 mm/min during the continuous casting operation.
23. The method for preparing a large-sized high-quality aluminium
alloy ingot according to claim 19, wherein the cooling intensity of
the uniform cooling is 500-5000 W/(m.sup.2k).
24. The method for preparing a large-sized high-quality aluminium
alloy ingot according to claim 19, wherein the shearing rate of the
electromagnetic stirring is 10-2000 s.sup.-1.
Description
TECHNICAL FIELD
[0001] The present invention belongs to the field of metal material
processing, and more particularly, to a device and method for
preparing a large-sized high-quality aluminium alloy ingot.
BACKGROUND OF THE INVENTION
[0002] As improved operational performances have been achieved for
large-sized whole-set equipment in the manufacturing industry, it
has become an inevitable trend that large-sized integrated
structures will be used more and more widely in such fields as
aerospace, rail transportation and shipbuilding. For example,
large-sized integrated aluminium materials and high-performance
thick plates are widely employed to develop large-sized transport
aircrafts, high-performance combat aircrafts and high-speed trains.
Moreover, as these materials are prepared by large-sized
high-quality aluminium alloy ingots, the preparation of the latter
is of great significance to improving the equipment capability of
the manufacturing industry.
[0003] The semi-continuous casting process is the primary method
for producing aluminium alloy ingots. However, common
semi-continuous casting techniques are subjected to certain
limitations, and therefore, during the preparation of large-sized
aluminium alloy ingots, they tend to be solidified from outside to
inside because of limited cooling manners. This will certainly lead
to a deep liquid cave for molten metal. Furthermore, as ingots are
large in dimensions, the uniformity of temperature fields would be
difficult to control during solidification, which, therefore, would
lead to a non-uniform solidified shell. In such cases, such issues
as wrinkles, segregation humps and even breakout would be prone to
occur at thinner areas of the solidified shell. In addition, as
ingots are large, and cooling effects are limited, the speed of
continuous casting would certainly be reduced. As such, the nuclei
formed in the melt would be few and non-uniform, and grains would
be unusually coarse. Therefore, large-sized aluminium alloy ingots
prepared by the traditional semi-continuous casting method are
featured by poor surface quality, coarse and non-uniform internal
structures, severe component segregation and low ingot yield, which
need to be subjected to surface or face milling prior to
deformation processing, thereby leading to high costs and serious
waste of materials.
[0004] To solve such problems, researchers have carried out a lot
of investigations, hoping to prepare non-segregated aluminium alloy
ingots featured by fine and uniform internal structures as well as
good surface quality.
[0005] Chinese Patent CN104550798A proposes an aluminium alloy
semi-continuous cast electromagnetic stirring device and method. In
this method, by combining direct current with permanent magnets,
the flow modes and flow intensities of different melts in the mold
region are designed according to sizes, shapes and material
components of aluminum ingots, and segregation behaviors of
alloying elements and growth patterns of dendrits are controlled to
realize structure homogenization and refinement. However, as this
invention employs a single cooling manner in which solidification
is achieved sequentially from outside to inside simply by means of
a mold, the problem of temperature non-uniformity that occurs
during solidification of the aluminium alloy melt still remains
unsolved. Particularly, for the preparation of large-sized ingots,
the stirring effects of the above-mentioned method on the melt are
limited. Consequently, temperature gradients are large within the
melt, and the liquid cave is very deep. In such cases, the speed of
casting is extremely slow, and thus, the improvement effects of
this method on the internal quality of ingots are limited.
[0006] With respect to improvements on the surface quality of
ingots, the gas film casting method, which is represented by the
Airslip technique from America and the AirsolVeil technique from
German, works as follows: a layer of gas film is formed between a
mold and an ingot's solidified shell so as to reduce the contact
pressure between the solidified shell and the inner wall of the
mold during solidification, thereby achieving solidification
forming of a melt under gas contact conditions. Based on this,
Chinese Patent CN100418667C makes improvements on the oil-gas
lubrication mold, and proposes a mold having integral design of
oil, air and water structure. In this patent, primary cooling is
omitted because of the heat insulation effects of the oil-gas film,
and secondary water cooling effects are enhanced through two rows
of water spraying holes, thereby improving the surface quality of
an ingot. However, the prior gas film casting method can hardly be
used to prepare a high-quality large-sized ingot. If the
large-sized ingot is cooled simply by the mold, the speed of
casting would be slow, and the initial solidified shell formed
after the melt is cooled in the mold would be very thin and
non-uniform. Moreover, as for the oil film casting technique, oil
gas can easily penetrate through the initial solidified shell, thus
leading to such problems as run-out and breakout. As such, the
production process is hard to control, and generally, the diameter
of the ingot can't exceed 300 mm (12 inches). Furthermore, the gas
film casting technique can't solve such problems as tiny and
uniform solidified structures as well as component segregation.
SUMMARY OF THE INVENTION
[0007] The prior gas film casting method can't be used to prepare
large-sized aluminium alloy ingots, as it has the disadvantage that
the ingots prepared thereby are featured by poor surface quality,
and coarse and non-uniform internal structures. In view of the
drawbacks of the prior semi-continuous casting method with respect
to the preparation of large-sized aluminium alloy ingots, the
present invention provides a new device and method for preparing a
large-sized high-quality aluminium alloy ingot. In this invention,
a melt is subjected to a combination of intra-mold intermediate
uniform cooling and extra-mold electromagnetic stirring during the
gas film casting operation. Therefore, when a large-sized
high-quality aluminium alloy ingot is prepared, the problems of
surface quality and internal quality that traditionally occur can
be solved simultaneously.
[0008] The main design idea of this invention is as follows: given
that the prior gas film casting method can hardly be used to
prepare large-sized (the diameter is greater than 300 mm) aluminium
alloy ingots, the mold in the present invention is designed to be
of a partitioned gas supply structure, which reduces the difference
in gas supply pressure on the graphite ring, and achieves stable
control of gas pressure, thereby ensuring that a stable and
continuous gas film can be formed between the melt and the mold.
Moreover, the alloy melt in the present invention is subjected to a
combination of intra-mold uniform cooling and extra-mold
electromagnetic stirring during the semi-continuous casting
operation, thereby increasing the cooling dimensions of the ingot
during solidification, strengthening the three-dimensional
convection of the melt during solidification, and improving the
uniformity of temperature and component fields for the bulky alloy
melt. Furthermore, in addition to ensuring the internal quality of
the ingot, the present invention is also intended to improve the
uniformity of initial solidification, increase the thickness of the
initially solidified shell, and prevent the initially solidified
shell and the oil-gas film from fracturing. Besides, it also aims
to reduce the contact pressure between the initially solidified
shell and the inner wall of the mold so as to achieve
solidification forming of a melt under gas pressure contact
conditions, thereby preparing a large-sized aluminium alloy ingot
with excellent surface quality and internal quality.
[0009] A new device for preparing a large-sized high-quality
aluminium alloy ingot is provided, which is mainly composed of a
uniform cooler, a hot top, an oil-gas lubrication mold, an
induction coil and a dummy ingot, wherein the hot top is arranged
above the oil-gas lubrication mold, the induction coil is arranged
outside the oil-gas lubrication mold, the uniform cooler is
arranged inside the oil-gas lubrication mold, and the dummy ingot
is arranged below the oil-gas lubrication mold.
[0010] The oil-gas lubrication mold comprises a mold body and a
graphite ring mounted above the mold body. The graphite ring is
provided with a gas groove and an oil groove on its outer wall,
wherein the gas groove is divided into 3-20 sections, and each
section of the gas groove has a length of 100-500 mm, and is
provided independently with an air intake passage for independent
gas supply and control; the oil groove is separated from the gas
groove, and is arranged on an upper portion thereof. The graphite
ring is prepared by porous graphite, and gas and lubricating oil
seep out of the mold through the graphite ring. The oil-gas
lubrication mold is designed to be of a partitioned gas supply
structure, which may reduce the difference between the gas amount
and gas pressure within the gas groove of a single gas supply
graphite ring, thereby achieving the object of stably controlling
gas pressure.
[0011] The oil-gas lubrication mold is provided with two rows of
water spraying holes. The mold body is provided with upper and
lower rows of water spraying holes, wherein the upper row of water
spraying holes forms an angle of 15-30 degrees with respect to a
wall of the mold, and has a diameter of 1-5 mm; while the lower row
of water spraying holes forms an angle of 0-25 degrees with respect
to the wall of the mold (this angle is greater than 0 degree, such
that cooling water can be ensured to be sprayed to an ingot without
being splashed back), and has a diameter of 2-8 mm. Water volumes
of the two rows of water spraying holes may be independently
controlled, and the diameter of the upper row of water spraying
holes needs to be smaller than or equal to that of the lower row of
water spraying holes.
[0012] The induction coil is arranged outside the mold. A magnet
yoke (iron core) is of a telescopic design, which is variable in
length, and retractable in a range of 0-100 mm. The electromagnetic
induction coil generates an electromagnetic field which is guided
into a melt inside the mold via the magnet yoke. The
electromagnetic coil may generate a rotating electromagnetic field,
a traveling wave electromagnetic field or a compound
electromagnetic field.
[0013] The upper portion of the uniform cooler is a heat insulation
end, and the lower portion is a cooling end, wherein the heat
insulation end is provided with a stirring blade. During the
semi-continuous casting operation, the uniform cooler passes
through the hot top and stretches to a height where the mold is
located, and its bottom portion is flush with the mold. The uniform
cooler may be arranged to be one or more in number, and rotate at a
rotational speed of 0-300 r/min.
[0014] The heat insulation end is of a cylindrical shape, and has
an outer diameter of 100-800 mm. It is made of high
temperature-resistant heat insulation ceramic material, which has
heat insulation effects, thereby preventing the melt in the hot top
from being cooled; the cooling end is made of thermally conductive
material (e.g., graphite, copper, molybdenum, titanium and
composite materials thereof), and has cooling effects. The cooling
end of the uniform cooler is of a spiral shape, and thus, the
rotation of the uniform cooler will force a melt to flow downward.
The stirring blade is made of high temperature-resistant material
(e.g., copper, molybdenum, titanium, ceramic and composite
materials thereof), which is arranged to be 0-8 in number, and has
a width of 10-100 mm and a thickness of 2-8 mm. It rotates along
with the uniform cooler to force a melt to flow downward, such that
the melt is supplemented downward into the liquid cave in a
constant manner, thereby exhibiting dynamic and continuous uniform
cooling effects. A circulating cooling medium is introduced into
the uniform cooler, and reaches the cooling end through which it
exchanges heat with the melt; this cooling medium may be air,
nitrogen, water, oil and various other fluids, and has a flow of
0-2000 L/min.
[0015] Based on the above device, the present invention provides a
method for preparing a large-sized high-quality aluminium alloy
ingot. In the method, a melt that has been refined and stabilized
to be 80-100 degrees Celsius higher than the liquidus temperature
is poured into the hot top during the semi-continuous casting
operation; air and lubricating oil are introduced into the gas
groove and the oil groove arranged on the outer wall of the
graphite ring; flows of the upper and lower water spraying holes
are controlled; an alloy melt reaches the upper portion of the
dummy ingot through the hot top and the mold, and the liquid
surface of the melt is elevated to a desired height; after the
continuous casting operation is initiated, the dummy ingot descends
slowly, and the flow of cooling water is increased slowly; after
the casting process is stabilized, uniform cooling and
electromagnetic stirring are applied to obtain a large-sized
high-quality aluminium alloy ingot in the end.
[0016] During the semi-continuous casting operation, the flow of
air in the gas groove is 500-5000 mL/min, while the oil groove
supplies oil in a pulsed manner, and has an oil supplying capacity
of 60-100/s; the flow of the upper row of water spraying holes is
1-50 L/min, while that of the lower row of water spraying holes is
20-100 L/min; the speed of casting is 20-100 mm/min. The cooling
intensity of the uniform cooling is 500-5000 W/(m.sup.2k), and the
shearing rate of the electromagnetic stirring is 10-2000
s.sup.-1.
[0017] The innovation and technical progress of the present
invention are mainly manifested by the following aspects:
[0018] 1. During the semi-continuous casting operation of the
present invention, the design of a partitioned gas supply structure
for the oil-gas lubrication mold is artfully combined with the
application of intra-mold intermediate uniform cooling and
extra-mold electromagnetic stirring, and the intercoupling of the
cooling effects of the uniform cooler, the structure and rotational
speed of the stirring blade and the shearing strength of the
electromagnetic stirring may be controlled to achieve forced
uniform cooling and three-dimensional convection for the melt as a
whole. As such, the uniformity of temperature and component fields
is significantly improved while the cooling intensity is increased.
This not only fundamentally solves such problems as coarse and
non-uniform structures, macrosegregation and cracking present in
the large-sized aluminium alloy ingot prepared by the common
semi-continuous casting method, but also greatly improves the
uniformity of the initially solidified shell, and increases the
thickness thereof. As the contact pressure between the initially
solidified shell and the inner wall of the mold is effectively
reduced, solidification forming of a melt may be achieved under gas
pressure contact conditions, thus significantly improving the
surface quality of the ingot.
[0019] 2. The oil-gas lubrication purifier for large-sized
aluminium alloy is designed to be of a partitioned gas supply
structure, which may reduce the difference between the gas amount
and gas pressure within the gas groove of a single gas supply
graphite ring, thereby stably controlling the gas pressure; oil is
supplied in a pulsed manner, such that a stable and continuous gas
film can be formed between the melt and the mold so as to reach the
effect of stable lubrication; this manner solves the technical
problem that the gas film casting method can't be used to prepare
the large-sized aluminium alloy ingot (whose diameter is greater
than 300 mm), and the prepared ingot is smooth in surface.
[0020] 3. The large-sized ingot prepared by the present invention
is featured by fine grains, uniform components and smooth surface.
The speed of casting is rapid, which significantly reduces the
costs resulted from subsequent homogenization and processing
operations, thereby improving the production efficiency and the
pass percent. The whole set of method is simple and feasible, and
has good implementation effects, which may be utilized to achieve
industrial production.
[0021] In the present invention, the partitioned gas supply mold is
artfully combined with the uniform cooler and the electromagnetic
stirrer, wherein the design of the partitioned gas supply mold can
achieve stable control of gas pressure, the uniform cooler
increases the cooling dimensions of the ingot during
solidification, and the electromagnetic stirrer strengthens the
three-dimensional convection of the melt during solidification. As
such, the uniformity of temperature and component fields of the
bulky alloy melt is improved. The effective coupling of the three
units can achieve forced and uniform solidification forming of a
melt under gas pressure contact conditions, such that a stable and
continuous gas film can be formed between the melt and the mold.
The prepared ingot has not only a smooth surface, but also a fine
and uniform internal structure. The large-sized high-quality
aluminium alloy ingot prepared by the present invention is featured
by a high production efficiency, and can readily be combined with
large-scale industrial production. Therefore, the device and method
of the present invention have a broad industrial application
prospect in such manufacturing fields as aerospace, rail
transportation and ships.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a schematic diagram illustrating the structure of
a device of the present invention for preparing a high-quality
large-sized aluminium alloy ingot.
[0023] FIG. 2 is a schematic diagram illustrating the partitioning
of a graphite ring.
[0024] FIG. 3 is an enlarged diagram illustrating a partial area E
of a mold of FIG. 1.
[0025] FIG. 4 is a schematic diagram illustrating a uniform
cooler.
[0026] FIGS. 5a and 5b are pictures illustrating the surface
appearances of 7075 aluminium alloy ingots (.PHI.=582 mm) prepared
respectively by the common semi-continuous casting method and the
present invention.
[0027] FIGS. 6a and 6b illustrate the microstructures of 7075
aluminium alloy ingots (.PHI.=582 mm) prepared respectively by the
common semi-continuous casting method and the present
invention.
[0028] Main reference numerals are illustrated as follows:
TABLE-US-00001 1 - uniform cooler; 2 - hot top; 3 - melt; 4 -
oil-gas lubrication mold; 5 - magnet yoke; 6 - coil; 7 - graphite
ring; 8 - water spraying holes; 9 - ingot; 10 - dummy ingot; 11 -
oil groove; 12 - gas groove; 13 - upper row of water spraying 14 -
lower row of water spraying holes; holes; 15 - heat insulation end;
16 - stirring blade; 17 - cooling end.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The present invention may be implemented based on the
following embodiments, but not limited thereto. These embodiments
are merely for the purpose of illustrating the implementation
process of the present invention, and not intended to limit the
scope of the present invention in any way. In the following
embodiments, various processes and methods that have not been
described in detail are conventional methods known in the art.
[0030] As shown in FIG. 1, the device of the present invention
comprises a uniform cooler 1, a hot top 2, a melt 3, an oil-gas
lubrication mold 4, a magnet yoke 5, a coil 6, a graphite ring 7,
water spraying holes 8, an ingot 9, a dummy ingot 10, etc. The hot
top 2 is arranged above the oil-gas lubrication mold 4, the coil 6
and the magnet yoke 5 are arranged outside the oil-gas lubrication
mold 4, the uniform cooler 1 is arranged inside the oil-gas
lubrication mold 4, and the dummy ingot 10 is arranged below the
oil-gas lubrication mold 4.
[0031] The oil-gas lubrication mold 4 comprises a mold body and a
graphite ring 7 mounted above the mold body. The graphite ring 7 is
provided with a gas groove 12 and an oil groove 11 on its outer
wall, wherein the gas groove 12 is of a sectional design. As shown
in FIG. 2, the gas groove 12 is divided into 3-20 sections, and
each section of the gas groove 12 has a length of 100-500 mm, and
is provided independently with an air intake passage for
independent gas supply and control; the oil groove 11 is separated
from the gas groove 12, and is arranged on an upper portion
thereof. The graphite ring 7 is prepared by porous graphite, and
gas and lubricating oil seep out of the mold through the graphite
ring 7.
[0032] The oil-gas lubrication mold 4 is provided with two rows of
water spraying holes, as shown in FIG. 3; water volumes of the two
rows of water spraying holes are independently controlled; the
upper row of water spraying holes 13 forms an angle of 15-30
degrees with respect to an inner wall of the oil-gas lubrication
mold 4, and has a diameter of 1-5 mm; while the lower row of water
spraying holes 14 forms an angle of 0-25 degrees (greater than 0
degree) with respect to a wall of the oil-gas lubrication mold 4,
and has a diameter of 2-8 mm; the diameter of the upper row of
water spraying holes needs to be smaller than or equal to that of
the lower row of water spraying holes.
[0033] The magnet yoke 5 is of a telescopic design. The magnet yoke
5 is variable in length, and is retractable in a range of 0-100 mm.
The electromagnetic induction coil 6 generates an electromagnetic
field which is guided into a melt inside the mold via the magnet
yoke 5. The electromagnetic coil 6 may generate a rotating
electromagnetic field, a traveling wave electromagnetic field or a
compound electromagnetic field.
[0034] During the semi-continuous casting operation, the uniform
cooler 1 passes through the hot top 2 and stretches to a height
where the oil-gas lubrication mold 4 is located. The uniform cooler
1 may be arranged to be one or more in number, and rotate at a
rotational speed of 0-300 r/min. As shown in FIG. 4, the uniform
cooler 1 is composed of an upper heat insulation end 15 and a lower
cooling end 17, and the heat insulation end 15 is provided with a
stirring blade 16; the upper heat insulation end 15 is of a
cylindrical shape, which has an outer diameter of 100-800 mm, and
is made of high temperature-resistant heat insulation material; the
cooling end 17 is made of thermally conductive material, such as
graphite, copper, molybdenum, titanium and composite materials
thereof; the cooling end 17 of the uniform cooler 1 is of a spiral
shape, and thus, the rotation of the uniform cooler 1 will force a
melt to flow downward; the stirring blade is arranged to be 0-8 in
number, and has a blade width of 10-100 mm and a thickness of 2-8
mm; the stirring blade 16 is made of high temperature-resistant
material, such as copper, molybdenum, titanium, ceramic and
composite materials thereof, and rotates along with the uniform
cooler 1; during operation, it will drive the melt to converge
towards the cooling end 17 of the uniform cooler 1; a circulating
cooling medium is introduced into the uniform cooler 1, and reaches
the cooling end 17 through which it exchanges heat with the melt,
wherein the cooling medium may be air, nitrogen, water, oil and
various other fluids, and has a flow of 0-2000 L/min. To achieve
the continuous and dynamic uniform supercooling of a melt, the melt
is made to pass through the bottom portion of the uniform cooler
for cooling, and then continues to flow downward into the mushy
zone of a liquid cave, thereby achieving the continuous and dynamic
uniform cooling of the melt as well as forced feeding, and
preparing a large-sized fine-grained homogeneous ingot.
[0035] The application method is as follows: during the
semi-continuous casting operation, the overall device is preheated
to 80-200 degrees Celsius, and a melt that has been refined and
stabilized to be 80-100 degrees Celsius higher than the liquidus
temperature is poured into this device. During the continuous
casting operation: air and lubricating oil are introduced into the
gas groove 12 and the oil groove 11 arranged on the outer wall of
the graphite ring 7, wherein the flow of air is 500-5000 mL/min,
while oil is supplied in a pulsed manner, with the oil supplying
capacity being 60-100/s; the electromagnetic coil 6 is initiated,
and the current is 10-200 A; the flow of the upper row of water
spraying holes 13 is controlled to be 1-50 L/min, while that of the
lower row of water spraying holes 14 is controlled to be 20-100
L/min; the speed of casting is 20-100 mm/min.
[0036] An alloy melt reaches the upper portion of the dummy ingot
10 through the hot top 2 and the mold 4, and the liquid surface of
the melt is elevated to a desired height; after the continuous
casting operation is initiated, the dummy ingot 10 descends slowly,
and the flow of cooling water is increased slowly; after the
casting process is stabilized, uniform cooling and electromagnetic
stirring are applied until the casting process is completed,
wherein the cooling intensity of the uniform cooling is 500-5000
W/(m.sup.2k), and the shearing rate of the electromagnetic stirring
is 10-2000 s.sup.-1.
[0037] The 7075 aluminium alloy rounded ingot (.PHI.=582 mm)
prepared by the present invention is required to have a smooth
surface, and a fine and uniform internal structure. The specific
implementation is as follows:
[0038] The structural schematic diagram of the device is as shown
in FIG. 1. The oil-gas lubrication mold 4 employs a partitioned gas
supply system, and the graphite ring 7 is provided externally with
a gas groove 12 and an oil groove 11, wherein the gas groove 12 is
divided into 4 sections, and each section of the gas groove 12 has
a length of 456 mm, and is provided independently with an air
intake passage for independent gas supply and control; the oil
groove 11 is separated from the gas groove 12, and is arranged on
an upper portion thereof, and the graphite ring 7 is prepared by
porous graphite. The upper row of water spraying holes 13 forms an
angle of 25 degrees with respect to a wall of the mold, and has a
diameter of 2 mm; while the lower row of water spraying holes 14
forms an angle of 10 degrees with respect to the wall of the mold,
and has a diameter of 5 mm. Water volumes of the two rows of water
spraying holes may be independently controlled.
[0039] The uniform cooler 1 is arranged on a casting platform, and
has a diameter of 300 mm. The cooler, the hot top and the mold are
concentric, and the bottom end of the uniform cooler 1 is flush
with that of the mold. The heat insulation end 15 of the uniform
cooler 1 is made of high temperature-resistant heat insulation
ceramic material, and has a diameter of 300 mm and a thickness of
10 mm; the lower cooling end 17 has a diameter of 350 mm, and is
made of graphite; the blade is 3 in number, and has a width of 50
mm. The uniform cooler 1 has a rotational speed of 60 r/min.
[0040] The electromagnetic coil is arranged on the periphery of the
oil-gas lubrication mold 4, which may generate a rotating
electromagnetic field that applies shearing to an alloy melt, and
the magnet yoke has a length of 50 mm.
[0041] During the semi-continuous casting operation, a melt that
has been refined and stabilized to be 100 degrees Celsius higher
than the liquidus temperature is poured into the hot top. Air and
lubricating oil are introduced into the gas groove 12 and the oil
groove 11 arranged on the outer wall of the graphite ring 7,
wherein the flow of air is 1430 mL/min, while oil is supplied in a
pulsed manner, with the oil supplying capacity being 80/s; the flow
of the upper row of water spraying holes 13 is controlled to be 20
L/min, while that of the lower row of water spraying holes 14 is
controlled to be 30 L/min; the speed of casting is 65 mm/min. The
alloy melt reaches the mold through the hot top 2, and the liquid
surface of the melt is elevated to a desired height; after the
continuous casting operation is initiated, the dummy ingot 10
descends slowly, and the flow of cooling water is increased slowly;
after the casting process is stabilized, uniform cooling and
electromagnetic stirring are applied until the casting process is
completed, wherein the cooling intensity of the uniform cooling is
1210 W/(m.sup.2k), and the shearing rate of the electromagnetic
stirring is 110 s.sup.-1.
[0042] Through comparison of surface quality and internal
structures between the 7075 aluminium alloy rounded ingot
(.PHI.=582 mm) prepared by the common semi-continuous casting
method and that prepared by the present invention, it is found that
the ingot prepared by the common semi-continuous casting method is
featured by poor surface quality and course internal structures, as
shown in FIGS. 5a and 6a; however, the ingot prepared by the
present invention has a smooth surface, a fine and uniform internal
structure, and an average grain size of 154 .mu.m, as shown in
FIGS. 5b and 6b.
* * * * *