U.S. patent application number 16/852619 was filed with the patent office on 2021-02-04 for unisource high-strength ultrasound-assisted method for casting large-specification 2xxx series aluminium alloy round ingot.
This patent application is currently assigned to Central South University. The applicant listed for this patent is Central South University. Invention is credited to Ripeng JIANG, Ruiqing LI, Xiaoqian LI, Zhilin LIU, Hao PENG, Lihua ZHANG, Xiaolin ZHAO.
Application Number | 20210032728 16/852619 |
Document ID | / |
Family ID | 1000004824980 |
Filed Date | 2021-02-04 |
United States Patent
Application |
20210032728 |
Kind Code |
A1 |
LI; Xiaoqian ; et
al. |
February 4, 2021 |
UNISOURCE HIGH-STRENGTH ULTRASOUND-ASSISTED METHOD FOR CASTING
LARGE-SPECIFICATION 2XXX SERIES ALUMINIUM ALLOY ROUND INGOT
Abstract
In the technical field of metal melting, a unisource
high-strength ultrasound-assisted method for casting
large-specification 2XXX series aluminum alloy round ingots applies
in an ingot guiding process, a unisource high-strength ultrasonic
vibration system to the center of a hot-top crystallizer,
ultrasound directly acts on the center position of a crystallizer,
and enough ultrasonic field energy is provided for a melt by
controlling the power of the ultrasonic vibration system, so that
an aluminum alloy solidification process is implemented under the
effect of ultrasound, homogenization of microstructures and
components of ingots is promoted, and the existing problems that
microstructures are thick and crystal phases are enriched due to
slow cooling of centers of large-specification round ingots are
effectively solved, meanwhile, the problems of great operation
difficulty and heavy workload during multisource ultrasonic
coupling are avoided.
Inventors: |
LI; Xiaoqian; (Changsha
(Hunan), CN) ; LI; Ruiqing; (Changsha (Hunan),
CN) ; JIANG; Ripeng; (Changsha (Hunan), CN) ;
ZHANG; Lihua; (Changsha (Hunan), CN) ; LIU;
Zhilin; (Changsha (Hunan), CN) ; PENG; Hao;
(Changsha (Hunan), CN) ; ZHAO; Xiaolin; (Changsha
(Hunan), CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Central South University |
Changsha (Hunan) |
|
CN |
|
|
Assignee: |
Central South University
Changsha (Hunan)
CN
|
Family ID: |
1000004824980 |
Appl. No.: |
16/852619 |
Filed: |
April 20, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22D 11/114 20130101;
C22C 21/12 20130101; C22C 1/026 20130101; B22D 7/005 20130101 |
International
Class: |
C22C 21/12 20060101
C22C021/12; C22C 1/02 20060101 C22C001/02; B22D 7/00 20060101
B22D007/00; B22D 11/114 20060101 B22D011/114 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 30, 2019 |
CN |
201910694820.8 |
Claims
1. A unisource high-strength ultrasound-assisted method for casting
large-specification 2XXX series aluminum alloy round ingots,
comprising the following steps: performing solidification and ingot
guiding by enabling melt of 2XXX series aluminum alloy to flow into
a hot-top crystallizer, after ingot guiding is started, applying a
set of ultrasonic vibration system to the center of a crystallizer
of the hot-top crystallizer, and when casting is about to end,
removing the ultrasonic vibration system, to obtain a
large-specification 2XXX series aluminum alloy round ingot; wherein
power of the ultrasonic vibration system being is 2.about.4 kw; and
wherein diameter of the large-specification 2XXX series aluminum
alloy round ingot is .gtoreq.500 mm.
2. The method according to claim 1, wherein the diameter of the
large-specification 2XXX series aluminum alloy round ingot is
500-1380 mm.
3. The method according to claim 1, wherein the ultrasonic
vibration system comprises an ultrasonic transducer, an amplitude
transformer and a radiation rod, length of the radiation rod being
490 mm.
4. The method according to claim 3, wherein the depth of the
radiation rod of the ultrasonic vibration system immersing into the
melt is 15.about.480 mm.
5. The method according to claim 1, wherein frequency of the
ultrasonic vibration system is 15.about.30 khz.
6. The method according to claim 1, wherein an applying mode of the
ultrasonic vibration system is to vertically guide the radiation
rod into the melt from top to bottom.
7. The method according to claim 1, wherein before applying the
ultrasonic vibration system, also comprising: preheating the
radiation rod of the ultrasonic vibration system; wherein the
preheating temperature being is not lower than 350.degree. C.
Description
TECHNICAL FIELD
[0001] The present invention relates to the technical field of
metal smelting, and particularly relates to a unisource
high-strength ultrasound-assisted method for casting
large-specification 2XXX series aluminum alloy round ingots.
BACKGROUND
[0002] Aluminium alloy ring-shaped parts and cylindrical parts as
main load-carrying structural parts in aerospace structural parts
are complicated in stress state and high in comprehensive
performances and dimensional precision requirement, currently,
process schemes for preparing high-performance aluminium alloy
ring-shaped parts/cylindrical parts at home and abroad mainly adopt
integrated manufacturing, therefore, a preparation technology for
original high-quality ingots is of great importance, and
non-uniformity of microdefects or microstructures in original
blanks will be inherited to subsequently caused difference of
performances of ring-shaped parts/cylindrical parts. Especially, at
present, aerospace structural parts in China develop to be
large-scale, the required round ingot diameter is larger, while
along with increase of the diameter of aluminium alloy round
ingots, problems and conflicts in a casting process are more
prominent, for example, extremely non-uniform distribution of melt
temperature field and flow field caused by the problems of large
spatial scale effect, non-equilibrium solidification environment
and nonuniformity of blank component structures and forming
interfaces, finally causing extremely nonuniform distribution of
ingot microstructures and elements; especially, the core part of
the ingot is cooled slowly, easily forming thick solidified
microstructures and network-shaped AlCu eutectic phases, and easily
forming the defects of looseness, air holes and the like.
[0003] Targeted to the problems of great internal and external
temperature difference, serious composition segregation, thick and
nonuniform microstructures, and enrichment and segregation of
crystalline phases of the core parts of conventional
semi-continuous casting ingots, at present, aluminium alloy
production enterprises mainly apply a refiner to refine grain
microstructures, and optimize casting process parameters such as
casting temperature, casting rate and cooling water flow to weaken
segregation and refine microstructures; part of scientific research
institutions and colleges and universities adopt physical fields
such as electromagnetism to act on a solidification process to
regulate microstructure and composition uniformity.
[0004] However, along with increase of specifications and
dimensions of ingots, increase of use amount of the refiner will
cause substantial increase of cost, and in use, too little refiner
cannot reach an optimal refining requirement, while excessive
refiner will cause a phenomenon of "poisoning", that is, along with
increase of content of the refiner, after the refining capability
reaches a certain degree, increase of content cannot further
improve the refining capability, moreover, excessive refiner forms
segregation very easily, intensifying the nonuniformity degree of
ingot microstructures. While for an electromagnetic stirring
system, an electromagnetic device is mainly provided at the outer
periphery of a die to arouse macroscopic flow of a metal melt by
electromagnetic force, so as to promote the uniformity of a melt
temperature field; electromagnetic stirring systems of different
specifications need to be customized and mounted targeted to
different dies, resulting in enormous expense; moreover,
electromagnetic stirring process parameters adopted for ingots of
different specifications need to be debugged and optimized, and too
strong stirring capability may cause leakage of metal aluminium
liquid, causing safety accidents.
[0005] Moreover, an ultrasound-assisted casting technology also
starts to be applied to production of large-specification aluminium
alloy ingots, while higher ultrasonic energy is generally needed
for solidification of large-dimension ingots, therefore, combined
action of multiple groups of ultrasound is needed, application of
multiple ultrasonic vibration sources needs to be optimized and
controlled in a targeted mode, a process for intercoordination and
matching optimization between parameters of different frequencies,
powers, phase differences and ultrasonic distances and positions is
complicated, and workload is heavier.
SUMMARY
[0006] The present invention is directed to provide a unisource
high-strength ultrasound-assisted method for casting
large-specification 2XXX series aluminum alloy round ingots, the
method provided by the present invention being convenient in
operation, saved in cost and high in production efficiency by
processing a melt at the center position of a crystallizer by
adopting an ultrasonic vibration source.
[0007] In order to achieve the foregoing purpose of the present
invention, the present invention provides the following technical
scheme:
[0008] A unisource high-strength ultrasound-assisted method for
casting large-specification 2XXX series aluminum alloy round
ingots, including the following steps:
[0009] performing solidification and ingot guiding by enabling melt
of 2XXX series aluminium alloy to flow into a hot-top crystallizer,
after ingot guiding is started, applying a set of ultrasonic
vibration system to the center of a crystallizer of the hot-top
crystallizer, and when casting is about to end, removing the
ultrasonic vibration system, to obtain a large-specification 2XXX
series aluminum alloy round ingot;
[0010] power of the ultrasonic vibration system being 2.about.4 kw;
and diameter of the large-specification 2XXX series aluminum alloy
round ingot being .gtoreq.500 mm
[0011] Optimally, the diameter of the large-specification 2XXX
series aluminum alloy round ingot is 500-1380 mm
[0012] Optimally, the ultrasonic vibration system includes an
ultrasonic transducer, an amplitude transformer and a radiation
rod, length of the radiation rod being 490 mm
[0013] Optimally, the depth of the radiation rod of the ultrasonic
vibration system immersing into the melt is 15.about.480 mm
[0014] Optimally, frequency of the ultrasonic vibration system is
15.about.30 khz.
[0015] Optimally, an applying mode of the ultrasonic vibration
system is to vertically guide the radiation rod into the melt from
top to bottom.
[0016] Optimally, before applying the ultrasonic vibration system,
the method also includes: preheating the radiation rod of the
ultrasonic vibration system; the preheating temperature being not
lower than 350.degree. C.
[0017] The present invention provides a unisource high-strength
ultrasound-assisted method for casting large-specification 2XXX
series aluminum alloy round ingots, according to the present
invention, in an ingot guiding process, a unisource high-strength
ultrasonic vibration system is applied to the center of a hot-top
crystallizer, ultrasound directly acts on the center position of a
crystallizer, and enough ultrasonic field energy is provided for a
melt by controlling the power of the ultrasonic vibration system,
so that an aluminium alloy solidification process is implemented
under the effect of ultrasound, homogenization of microstructures
and components of ingots is promoted, and the existing problems
that microstructures are thick and crystal phases are enriched due
to slow cooling of centers of large-specification round ingots are
effectively solved, meanwhile, the problems of great operation
difficulty and heavy workload during multisource ultrasonic
coupling are avoided; according to the present invention, the
quantity of adopted ultrasonic sources is few, operation is
convenient, cost is saved, and production efficiency can be
effectively improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a schematic diagram of a unisource high-strength
ultrasound-assisted device for casting large-specification 2XXX
series aluminum alloy round ingots, wherein 1--smelting furnace,
2--diversion trench, 3--aluminium melt, 4--hot-top heat
preservation cap, 5--crystallizer, 6--cooling water, 7-ultrasonic
vibration system, 8-aluminium ingot, 9-ingot guiding plate;
[0019] FIG. 2 is a casting site map after applying ultrasound in
embodiment 1;
[0020] FIG. 3 is low-power detection results of a common ingot and
an ultrasonic ingot in embodiment 1;
[0021] FIG. 4 is a low-power microstructure diagram of radial
directions of the common ingot and the ultrasonic ingot in
embodiment 1 from the core part to the side part;
[0022] FIG. 5 is radial Cu content distribution of the common ingot
and the ultrasonic ingot in embodiment 1; and
[0023] FIG. 6 is a crystal phase comparison diagram of the common
ingot and the ultrasonic ingot in embodiment 1 in different
positions.
DESCRIPTION OF THE EMBODIMENTS
[0024] The present invention provides a unisource high-strength
ultrasound-assisted method for casting large-specification 2XXX
series aluminum alloy round ingots, including the following
steps:
[0025] performing solidification and ingot guiding by enabling melt
of 2XXX series aluminium alloy to flow into a hot-top crystallizer,
after ingot guiding is started, applying a set of ultrasonic
vibration system to the center of a crystallizer of the hot-top
crystallizer, and performing ingot guiding under the action of the
ultrasonic vibration system, and when casting is about to end,
removing the ultrasonic vibration system, to obtain a
large-specification 2XXX series aluminum alloy round ingot.
[0026] According to the present invention, the diameter of the
large-specification 2XXX series aluminum alloy round ingot is
.gtoreq.500 mm, optimally, 500.about.1380 mm, more optimally,
600.about.1250 mm.
[0027] According to the present invention, there is no special
requirement for a preparation method of the melt of the 2XXX series
aluminum alloy, just a method familiar to a person skilled in the
art may be adopted. In specific embodiments of the present
invention, a preparation process of the melt of the 2XXX series
aluminum alloy optimally includes dispensing, smelting, component
adjustment and purification treatment.
[0028] According to the present invention, the dispensing may be
performed just according to a basic principle in a nominal
component specification scope of alloy designation, and alloy raw
materials used in dispensing include pure aluminium,
aluminium-copper intermediate alloy and intermediate alloy of other
elements, specific variety being selected according to components
of a target alloy ingot.
[0029] According to the present invention, in the smelting process,
optimally, firstly, feeding a pure aluminium ingot into a furnace,
rising furnace temperature to 750.degree. C. and preserving heat
until the aluminium ingot is completely smelted, and then gradually
adding other metals in batches, and slagging off and stirring after
all the metals are smelted.
[0030] According to the present invention, the component adjustment
specifically includes: sampling to-be-tested components after all
alloy raw materials are smelted, and supplementing material or
diluting according to a component test result, so as to ensure that
melt component content meets the design requirement, and standing
for a period of time after component adjustment is completed and
then discharging out of the furnace.
[0031] According to the present invention, the purification
treatment optimally includes online degassing and impurity removal,
specifically, an online degassing and filtering device is provided
in a diversion trench between the smelting furnace and the
crystallizer. According to the present invention, a rotating nozzle
inert gas flotation method (called as an SNIF melt purifying method
for short) is optimally adopted for the degassing, specifically,
argon is introduced into a rotating nozzle in a degassing box which
can be heated for heat preservation to be sprayed into an aluminium
melt, and by virtue of the high speed rotation of the nozzle, argon
is dispersed to be tiny bubbles, to stir the melt to intensify mass
and heat transfer, so as to play the roles of degassing and
deslagging in a floating-up process. According to the present
invention, a foamed ceramic filter box is optimally adopted for
filtering to remove impurities, a spongy ceramic filter in the
filter box is mainly made from materials such as aluminium oxide
and chromium oxide, and a foamed ceramic filtering and purification
principle belongs to a deep filtering mechanism, is large in
filtering capability, and is applicable to filtering and
purification in continuous casting and roll-casting production; in
specific embodiments of the present invention, optimally, a refiner
is applied to a diversion trench, so as to further purify a melt,
and refine grains; according to the present invention, there is no
special requirement for the variety of the refiner, just a refiner
familiar to a person skilled in the art may be used.
[0032] According to the present invention, there is no special
requirement for specific operation parameters of the degassing and
filtering, just needing to operate according to a method familiar
to a person skilled in the art.
[0033] Moreover, in a smelting process, smelting time and chemical
components should be strictly controlled, and on the premise of
ensuring that the alloy is completely smelted, shortening labor
hour and reducing burning loss as far as possible.
[0034] A melt of the 2XXX series aluminum alloy flows into a
hot-top crystallizer to be be subject to solidification and ingot
guiding, after ingot guiding is started, a set of ultrasonic
vibration system is applied to the center of a crystallizer of the
hot-top crystallizer, and when casting is about to end, the
ultrasonic vibration system is removed, to obtain a
large-specification 2XXX series aluminum alloy round ingot.
According to the present invention, there is no special requirement
for the structure of the hot-top crystallizer, just a hot-top
crystallizer familiar to a person skilled in the art may be used.
According to the present invention, the hot-top crystallizer
includes a hot-top heat preservation cap, a crystallizer, an ingot
guiding plate and a cooling water system (a structure being as
shown in FIG. 1); after being smelted in a smelting furnace, a melt
enters the hot-top crystallizer from a diversion trench, is
primarily cooled by the cooling water system firstly to be
solidified to be a shell in the hot-top crystallizer, and then
along with the downward traction of the ingot guiding device, the
solidified shell moves downwards and is cooled for a second time
directly by cooling water to be further solidified, so as to form
an ingot. According to the present invention, after ingot guiding
is started, an ultrasonic vibration system is applied, and an
applying mode is optimally to vertically guide a radiation rod into
a melt from top to bottom, ensuring that the liquid level of the
melt in the crystallizer is steady when the radiation rod is
immersed into the melt; according to the present invention,
optimally, after ingot guiding is started, an ultrasonic vibration
system is applied when the length of the ingot is 200 mm
[0035] According to the present invention, the ultrasonic vibration
system is composed of an ultrasonic transducer, an amplitude
transformer and a radiation rod, wherein the transducer is
connected with an ultrasonic power source to generate ultrasonic
vibration, an amplitude transformer magnifies amplitude, while the
radiation rod directly contacts with an acting object to emit
ultrasonic wave; length of the radiation rod being optimally 490
mm. According to the present invention, the depth of the radiation
rod of the ultrasonic vibration system immersing into the melt is
15.about.480 mm, optimally, 50.about.450 mm, further optimally,
100.about.400 mm, frequency of the ultrasonic vibration system is
optimally 10.about.30 khz, more optimally, 18.about.28 kHz, further
optimally, 19.about.21 kHz, and power is optimally 2.about.4 kw,
more optimally, 2.5.about.3.5 kw. According to the present
invention, the frequency and power of the ultrasonic vibration
system are controlled within the foregoing scope, so as to provide
enough ultrasonic field energy, and promote homogenization of the
microstructure and components of the ingot.
[0036] Before ultrasonic vibration is applied, according to the
present invention, optimally, the radiation rod of the ultrasonic
vibration system is preheated; the preheating temperature is
optimally not lower than 350.degree. C., more optimally, is
400.about.450.degree. C.; before preheating, the present invention
also optimally includes: cleaning the surface of the radiation rod,
and there is no special requirement for the surface cleaning, just
needing to thoroughly clean impurities on the surface of the
radiation rod; after preheating, the present invention also
optimally includes: performing no-load debugging on the ultrasonic
vibration system, and by no-load debugging, the present invention
ensures that the amplitude output of the end face of the radiation
rod of the ultrasonic vibration system is .gtoreq.15
micrometers.
[0037] In the whole process of processing an aluminium alloy melt
by ultrasonic vibration, stability of ultrasonic parameters is
ensured by automatic tracking and adjusting functions of an
ultrasonic power system, and the ultrasonic vibration system should
not be disturbed in an operating process, so as to avoid
disturbance of ultrasonic parameters and fluctuation of aluminium
liquid.
[0038] According to the present invention, there is no special
requirement for the casting temperature, casting speed, spraying
water pressure and cooling water flow of a melt in the
crystallizer, just needing to set according to specific
conditions.
[0039] When casting is about to end, according to the present
invention, an ultrasonic vibration system in the hot-top
crystallizer is removed, and in specific embodiments of the present
invention, specific removal time of the ultrasonic vibration system
can be determined according to the specification of the ingot and
remaining height of the melt in the crystallizer, just needing to
ensure that ingot is smoothly ended and formed. When the ultrasonic
vibration system is removed, optimally, turning off the ultrasonic
power source firstly, then slowly lifting up the ultrasonic
vibration system by using a lifting table, and moving to a safety
zone, keeping steady in a moving process, so as to avoid
fluctuation of the aluminium liquid and rolling-in of an oxidation
film; a removed ultrasonic vibration system should be further
ventilated to cool and the surface of the radiation rod is
thoroughly cleaned.
[0040] According to the present invention, a unisource ultrasonic
vibration system is applied to the center of a hot-top
crystallizer, and effects such as cavitation, acoustic streaming
and stirring caused by ultrasonic vibration act on the interior of
an aluminium melt, so as to accelerate heat transfer and convection
of the melt, promote uniformity of solidification temperature field
and flow field, and finally achieve the purpose of controlling the
microstructure and components of the ingot to be uniform.
[0041] According to the present invention, the action of ultrasound
in a crystallizer can be divided into two parts according to acting
positions, which are respectively actions on a liquid metal zone
and a solid-liquid mixed zone in a smelting pool. In the liquid
metal zone, a cavitation effect generated by ultrasonic vibration
firstly has effects of digassing and impurity removal. There are
usually many microcosmic insoluble solid heterogeneous particles
(such as oxide, carbide, nitride and the like) in a metal melt, in
actual production, crystal nucleus are preferably formed by
attaching to the surfaces of the heterogeneous particles, however,
in general conditions, because the surfaces of the heterogeneous
particles have some surface defects such as narrow cracks, grooves,
bosses and fissures, most heterogeneous particles are in an inert
state and fail to become effective heterogeneous nucleus to
participate in nucleus forming. However, under the cavitation
effect of high-strength ultrasound, impact pressure caused by
cavitation bubble collapse impacts the surfaces of particles
constantly, to play a role of cleaning the surfaces of the
heterogeneous particles; cavitation bubbles are accompanies with a
series of two-order phenomena in an oscillating process, for
example, enabling liquid itself to generate ring current, causing
vibrating bubbles to have very high velocity gradient and viscous
stress, and prompting damage and falling-off of dirt on the surface
of a cleaned member; meanwhile, high-speed microjet generated by
ultrasonic cavitation can remove or weaken a dirt bed on the
boundary of a solid surface to go deep into holes, groove, slits
and micropores in the surfaces of particles, so as to improve the
wettability of the heterogeneous particles; moreover, ultrasonic
vibration also can arouse severe vibration of the heterogeneous
particles in metal liquid, so as to improve the wettability of the
heterogeneous particles in the liquid metal. In a word, applying of
an ultrasonic field has a severe activation effect for these
heterogeneous particles, and can transform the heterogeneous
particles into effective crystal nucleus to participate in a
solidification and nucleus forming process. Moreover, the acoustic
streaming effect of ultrasound can drive disturbance of a smelting
pool flow field, so as to promote uniform distribution of a
temperature field on one hand, and uniformly disperse activated
heterogeneous particles to different positions on the other hand,
and thus promoting uniformity of a temperature field, a flow field
and solidified microstructures in a smelting pool.
[0042] In a solid-liquid mixed zone (that is, a solidification
front zone), when the ultrasonic depth is constantly increased to
directly act an ultrasonic cavitation effect to a solidification
front, microjet and high-frequency vibration generated by
ultrasonic cavitation may play the roles of impacting and vibrating
for primary dendritic crystals and secondary dendritic crystals,
possibly causing falling-off of the secondary dendritic crystals
from the neck, and the falling-off free dendritic crystals are more
liable to be uniformly distributed in a smelting pool along with
the stirring action of ultrasonic acoustic streaming, so as to
increase nucleus forming nucleus, and refine a solidified
microstructure. Meanwhile, when ultrasonic vibration acts on a
solid-liquid coexisting zone as a vibration energy, it may also
arouse co-frequency resonance so as to cause a lot of primary
crystals growing to a same dimension to generate common vibration,
inhibit further growth of the crystals, promote uniformity of
crystal microstructure, and finally play the roles of refining
grains, reducing content of alloying elements of microstructures of
the core part and inhibiting enrichment of thick crystal
phases.
[0043] According to the present invention, a unisource
high-strength ultrasonic system is applied to the center of a
crystallizer, which uses few ultrasonic sources, is convenient to
operate and saves cost, and can effectively solve the problem of
great difficulty in operation control of the prior art and increase
the production efficiency on the basis of ensuring ingot
quality.
[0044] The following describes the scheme provided by the present
invention in details with reference to embodiments, however, these
cannot be understood as limitation to the protection scope of the
present invention.
Embodiment 1
[0045] Ultrasonic semi-continuous casting of .PHI.1100 mm 2219
aluminium alloy with length of 3000 mm
[0046] 1. A Casting Process
[0047] 1) Debugging and Preparation Before Casting
[0048] Detecting 20-ton casting equipment, ensuring that
.quadrature. in the part of a smelting furnace, a heating device,
an electromagnetic stirring device and a furnace dumping power
device operate normally; .quadrature. in a diversion trench and an
online degassing and impurity removal part, checking whether a
deslagging and heating device works normally, whether a rotating
nozzle is normal and available, whether a filter plate is abraded
seriously, and whether a refiner wire feeder works normally, and
ensuring that the diversion trench is thoroughly cleaned, without
aluminium residue and the like; .quadrature. in the part of a
crystallizer: checking whether a hot-top cap and a graphite
crystallizer are seriously abraded and need to be changed, and
whether an ingot guiding device works normally, and ensuring that
an oil-gas lubrication system and a cooling water system work
normally.
[0049] 2) Alloy Matching and Smelting
[0050] Strictly controlling smelting time and chemical components
in a smelting process, and on the premise of ensuring that alloy is
completely smelted, shortening labor hour and reducing burning loss
as far as possible. Specific operations are: firstly feeding a pure
aluminium ingot into a furnace, starting heating equipment to rise
furnace temperature to 750.degree. C. and preserving heat for a
period of time to ensure that the aluminium ingot is completely
smelted, then gradually adding other metals in batches, and after
the metals are completely smelted, sampling to-be-tested components
by electromagnetic and manpower stirring in match with slagging-off
and stirring, then selecting to supplement material or dilute
according to component test results, standing for 10 min after
refining is completed, and then discharging out of a furnace, the
scope of ally components being as shown in table 1.
TABLE-US-00001 TABLE 1 Aluminium alloy element matching table (mass
fraction, %) Alloy elements Si Fe Cu Mn Mg Zn Ti V Zr Al
Specialized <0.2 <0.3 5.8~6.8 0.2~0.4 <0.02 <0.1
0.02~0.1 0.05~0.15 0.1~0.25 Balance scope (%) a 0.006 0.03 5.96
0.38 0.002 0.005 0.059 0.07 0.11 Balance
[0051] 3) Online Degassing and Impurity Removal of Aluminium
Liquid
[0052] Providing an online degassing and filtering device in a
diversion trench between the smelting furnace and the crystallizer.
An inert gas flotation method (called as SNIF melt purifying method
for short) with a rotating nozzle is adopted for degassing. A
foamed ceramic filtering method is adopted for filtering for
deslagging.
[0053] 4) Ultrasonic Casting
[0054] Performing ultrasonic processing on the rear half section of
an ingot in a semi-continuous casting process, and finally
comparing microstructures of two segments of the ingot, specific
steps of ultrasound-assisted casting experiment are as follows:
[0055] Preheating a diversion trench, the inner wall of a
crystallizer and an ultrasonic radiation rod. Opening a furnace
mouth after temperature is steady and tilting the smelting furnace
for pouring, opening cooling water of the crystallizer, starting an
ingot guiding device after aluminium liquid flows into the
crystallizer for a certain height, meanwhile, opening secondary
cooling water to spray the system, at the moment, an ingot guiding
plate moves downwards to pull down the ingot, starting
semi-continuous casting, and when the length of the ingot is 1500
mm, vertically applying a set of ultrasonic vibration system from a
position above the center of the crystallizer and vibrating,
wherein the depth of the ultrasonic radiation rod immersing into
the aluminium liquid is about 200 mm, frequency is 30 khz, and
power is 4 kw, and when casting is about to end, removing the
ultrasonic vibration system, to obtain an aluminium alloy ingot,
wherein the upper half section (0.about.1500 mm) of the obtained
ingot is common ingot, and the lower half section (1500.about.3000
mm) is ultrasonic ingot.
[0056] A schematic diagram of a device used in the present
embodiment is as shown in FIG. 1, the right of FIG. 1 is a
schematic diagram of an applying position of the ultrasonic
vibration system in the crystallizer, and r represents the radius
of the crystallizer; a casting site after being applied with
ultrasound is as shown in FIG. 2.
[0057] 2. Microstructure Analysis
[0058] FIG. 3 is low-power detection results of common ingot and
ultrasonic ingot, it is known from FIG. 3 that the grain size of
the ultrasonic ingot is reduced, microstructures become tiny and
are uniformly distributed, and the center of the ingot is about in
level 2.5; while the center of the common ingot is in level 4. A
further enlarged drawing is as shown in FIG. 4, in FIG. 4, (a) is a
low-power microstructure diagram of the common ingot from the core
part to the side part, (b) is a low-power microstructure diagram of
the ultrasonic ingot from the core part to the side part; and it is
obviously known from FIG. 4 that the microstructure of the core
part of the common ingot is thick.
[0059] FIG. 5 is radial Cu content distribution of the common ingot
and the ultrasonic ingot, wherein (a) is common ingot, (b) is
ultrasonic ingot; it is known from the result that the ultrasonic
ingot is uniformly distributed, and it is known by computation that
the maximum radial segregation rate of Cu element of the common
ingot is 7%, and that of the ultrasonic ingot is 5%, indicating
that the ultrasonic ingot is smaller in deviation, and uniform in
components.
[0060] FIG. 6 is a crystal phase comparison diagram of the common
ingot and the ultrasonic ingot, wherein R represents the radius of
an aluminium alloy round ingot, and it is known from FIG. 6 that
the crystal phase microstructures of the ultrasonic ingot are tiny
and uniform; while the intra-crystal crystal phases of the common
ingot are thick and are distributed in a network form.
[0061] It is known from the foregoing embodiment that according to
the present invention, a unisource high-strength ultrasonic
vibration system is applied to the center of the hot-top
crystallizer, so as to promote the homogenization of the
microstructures and components of ingots and grain refining, to
obtain high-quality aluminium alloy ingots; moreover, according to
to the present invention, few ultrasonic sources are adopted,
operation is convenient, and cost is saved, the problem of great
difficulty in operation control in multisource ultrasonic coupling
can be effectively solved, and production efficiency is
increased.
[0062] The foregoing descriptions are merely preferred
implementation modes of the present invention, it should be noted
that a person of ordinary skill in the art may make some
improvements and modifications without departing from the principle
of the present disclosure, and these all should be deemed as
falling within the protection scope of the present invention.
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