U.S. patent application number 16/492031 was filed with the patent office on 2021-03-04 for grain refining with direct vibrational coupling.
This patent application is currently assigned to SOUTHWIRE COMPANY, LLC. The applicant listed for this patent is SOUTHWIRE COMPANY, LLC. Invention is credited to Kevin Scott GILL, Roland Earl GUFFEY, Venkata Kiran MANCHIRAJU, Michael POWELL, Victor Frederic RUNDQUIST.
Application Number | 20210060639 16/492031 |
Document ID | / |
Family ID | 1000005239807 |
Filed Date | 2021-03-04 |
View All Diagrams
United States Patent
Application |
20210060639 |
Kind Code |
A1 |
GILL; Kevin Scott ; et
al. |
March 4, 2021 |
GRAIN REFINING WITH DIRECT VIBRATIONAL COUPLING
Abstract
A molten metal conveyor having a receptor plate in contact with
molten metal during transport of the molten metal. The receptor
plate extends from an entrance where molten metal enters onto the
receptor plate to an exit where molten metal exits the receptor
plate. The molten metal conveyor has at least one vibrational
energy source which supplies vibrational energy directly to the
receptor plate in contact with molten metal. A corresponding method
for forming a metal product includes providing molten metal onto a
molten conveyor; cooling the molten metal by control of a cooling
medium flowing through a cooling passage in the or attached to the
conveyor; and coupling vibrational energy directly into a receptor
plate in contact with the molten metal on the conveyor.
Inventors: |
GILL; Kevin Scott;
(Carrollton, GA) ; POWELL; Michael; (Dallas,
GA) ; RUNDQUIST; Victor Frederic; (Carrollton,
GA) ; MANCHIRAJU; Venkata Kiran; (Villa Rica, GA)
; GUFFEY; Roland Earl; (Cloverport, KY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SOUTHWIRE COMPANY, LLC |
Carrollton |
GA |
US |
|
|
Assignee: |
SOUTHWIRE COMPANY, LLC
Carrollton
GA
|
Family ID: |
1000005239807 |
Appl. No.: |
16/492031 |
Filed: |
March 7, 2018 |
PCT Filed: |
March 7, 2018 |
PCT NO: |
PCT/US2018/021367 |
371 Date: |
September 6, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62468709 |
Mar 8, 2017 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22D 11/115 20130101;
B22D 11/003 20130101 |
International
Class: |
B22D 11/115 20060101
B22D011/115; B22D 11/00 20060101 B22D011/00 |
Claims
1. A molten metal conveyor comprising: a receptor plate in contact
with molten metal during transport of the molten metal; said
receptor plate extending from an entrance where molten metal enters
onto the receptor plate to an exit where molten metal exits the
receptor plate; and at least one vibrational energy source which
supplies vibrational energy directly to the receptor plate in
contact with molten metal.
2. The conveyor of claim 1, wherein said receptor plate comprises a
cooling channel for passage of a cooling medium.
3. The conveyor of claim 2, wherein said cooling medium comprises
at least one of water, gas, liquid metal, liquid nitrogen, and
engine oil.
4. The conveyor of claim 2, wherein said cooling channel is within
the receptor plate or said cooling channel comprises a conduit
attached to the receptor plate.
5. The conveyor of claim 1, further comprising a blower providing
gas flow to cool the receptor plate.
6. The conveyor of claim 1, further comprising an assembly which
mounts said receptor plate in relationship to a casting wheel of a
casting mill or to a tundish supplying molten metal to a mold.
7. The conveyor of claim 1, wherein at least one vibrational energy
source comprises at least one of an ultrasonic transducer, a
magnetostrictive transducer, and a mechanically driven vibrator
providing vibrational energy directly to the receptor plate in
contact with molten metal.
8. The conveyor of claim 1, wherein the vibration energy provided
to said receptor plate is in a range of frequencies up to 400
kHz.
9. (canceled)
10. The conveyor of claim 1, wherein the receptor plate comprises
at least one or more of niobium, a niobium alloy, titanium, a
titanium alloy, tantalum, a tantalum alloy, copper, a copper alloy,
rhenium, a rhenium alloy, steel, molybdenum, a molybdenum alloy,
stainless steel, a ceramic, a composite, or a metal.
11. (canceled)
12. (canceled)
13. The conveyor of claim 1, wherein the at least one vibrational
energy source comprises a plurality of transducers arranged in an
ordered pattern on the receptor plate.
14. The conveyor of claim 13, wherein the ordered pattern on the
receptor plate has a higher density of said transducers on one side
of the receptor plate.
15. (canceled)
16. (canceled)
17. The conveyor of claim 1, wherein the at least one vibrational
energy source comprises a piezoelectric transducer element attached
to the receptor plate.
18. The conveyor of claim 17, an ultrasonic booster coupled to the
piezoelectric transducer element attached to the receptor
plate.
19. The conveyor of claim 1, wherein the at least one vibrational
energy source comprises a magnetostrictive transducer element
attached to the receptor plate.
20. The conveyor of claim 1, further comprising an ultrasonic
degasser inserted in a molten metal flow channel.
21. The conveyor of claim 1, wherein the receptor plate has a
thickness of less than 10 cm.
22. The conveyor of claim 1, wherein the receptor plate has a
thickness between or between 0.5 cm and 5 cm or between 1 cm and 3
cm.
23. The conveyor of claim 1, wherein the receptor plate has a
thickness between 1.5 cm and 2 cm.
24. (canceled)
25. The conveyor of claim 1, wherein the receptor plate is disposed
above a casting wheel and provides the molten metal to a trough in
the casting wheel.
26. (canceled)
27. (canceled)
28. The conveyor of claim 1, wherein the receptor plate comprises a
lateral width between 2.5 cm and 300 cm.
29-44. (canceled)
45. A casting mill comprising: a casting mold configured to cool
molten metal, and the conveyor of claim 1.
46-50. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Ser. No. 62/468,709
(the entire contents of which are incorporated herein by
reference), filed Mar. 8, 2017, entitled Grain Refining with Direct
Vibrational Coupling.
[0002] This application is related to U.S. Ser. No. 62/372,592 (the
entire contents of which are incorporated herein by reference)
filed August 9, 2016, entitled ULTRASONIC GRAIN REFINING AND
DEGASSING PROCEDURES AND SYSTEMS FOR METAL CASTING. This
application is related to U.S. Ser. No. 62/295,333 (the entire
contents of which are incorporated herein by reference) filed Feb.
15, 2016, entitled ULTRASONIC GRAIN REFINING AND DEGASSING FOR
METAL CASTING. This application is related to U.S. Ser. No.
62/267,507 (the entire contents of which are incorporated herein by
reference) filed Dec. 15, 2015, entitled ULTRASONIC GRAIN REFINING
AND DEGASSING OF MOLTEN METAL. This application is related to U.S.
Ser. No. 62/113,882 (the entire contents of which are incorporated
herein by reference) filed Feb. 9, 2015, entitled ULTRASONIC GRAIN
REFINING. This application is related to U.S. Ser. No. 62/216,842
(the entire contents of which are incorporated herein by reference)
filed Sep. 10, 2015, entitled ULTRASONIC GRAIN REFINING ON A
CONTINUOUS CASTING BELT. This application is related to
PCT/2016/050978 (the entire contents of which are incorporated
herein by reference) filed Sep. 9, 2016, entitled ULTRASONIC GRAIN
REFINING AND DEGASSING PROCEDURES AND SYSTEMS FOR METAL CASTING.
This application is related to U.S. Ser. No. 15/337,645 (the entire
contents of which are incorporated herein by reference) filed Oct.
28, 2016, entitled ULTRASONIC GRAIN REFINING AND DEGASSING
PROCEDURES AND SYSTEMS FOR METAL CASTING.
[0003] This application is related to U.S. Ser. No. 62/460,287 (the
entire contents of which are incorporated herein by reference)
filed Feb. 17, 2017, entitled ULTRASONIC GRAIN
BACKGROUND
Field
[0004] The present invention is related to a method for producing
metal castings with controlled grain size, a system for producing
the metal castings, and products obtained by the metal
castings.
Description of the Related Art
[0005] Considerable effort has been expended in the metallurgical
field to develop techniques for casting molten metal into
continuous metal rod or cast products. Both batch casting and
continuous castings are well developed. There are a number of
advantages of continuous casting over batch castings although both
are prominently used in the industry.
[0006] In the continuous production of metal cast, molten metal
passes from a holding furnace into a series of launders and into
the mold of a casting wheel where it is cast into a metal bar. The
solidified metal bar is removed from the casting wheel and directed
into a rolling mill where it is rolled into continuous rod.
Depending upon the intended end use of the metal rod product and
alloy, the rod may be subjected to cooling during rolling or the
rod may be cooled or quenched immediately upon exiting from the
rolling mill to impart thereto the desired mechanical and physical
properties. Techniques such as those described in U.S. Pat. No.
3,395,560 to Cofer et al. (the entire contents of which are
incorporated herein by reference) have been used to
continuously-process a metal rod or bar product.
[0007] U.S. Pat. No. 3,938,991 to Sperry et al. (the entire
contents of which are incorporated herein by reference) shows that
there has been a long recognized problem with casting of "pure"
metal products. By "pure" metal castings, this term refers to a
metal or a metal alloy formed of the primary metallic elements
designed for a particular conductivity or tensile strength or
ductility without inclusion of separate impurities added for the
purpose of grain control.
[0008] Grain refining is a process by which the crystal size of the
newly formed phase is reduced by either chemical or
physical/mechanical means. Grain refiners are usually added into
molten metal to significantly reduce the grain size of the
solidified structure during the solidification process or the
liquid to solid phase transition process.
[0009] Indeed, a WIPO Patent Application WO/2003/033750 to Boily et
al. (the entire contents of which are incorporated herein by
reference) describes the specific use of "grain refiners." The '750
application describes in their background section that, in the
aluminum industry, different grain refiners are generally
incorporated in the aluminum to form a master alloy. A typical
master alloys for use in aluminum casting comprise from 1 to 10%
titanium and from 0.1 to 5% boron or carbon, the balance consisting
essentially of aluminum or magnesium, with particles of TiB.sub.2
or TiC being dispersed throughout the matrix of aluminum. According
to the '750 application, master alloys containing titanium and
boron can be produced by dissolving the required quantities of
titanium and boron in an aluminum melt. This is achieved by
reacting molten aluminum with KBF.sub.4 and K.sub.2TiF.sub.6 at
temperatures in excess of 800.degree. C. These complex halide salts
react quickly with molten aluminum and provide titanium and boron
to the melt.
[0010] The '750 application also describes that, as of 2002, this
technique was used to produce commercial master alloys by almost
all grain refiner manufacturing companies. Grain refiners
frequently referred to as nucleating agents are still used today.
For example, one commercial supplier of a TIBOR master alloy
describes that the close control of the cast structure is a major
requirement in the production of high quality aluminum alloy
products.
[0011] Prior to this invention, grain refiners were recognized as
the most effective way to provide a fine and uniform as-cast grain
structure. The following references (all the contents of which are
incorporated herein by reference) provide details of this
background work: [0012] Abramov, O. V., (1998), "High-Intensity
Ultrasonics," Gordon and Breach Science Publishers, Amsterdam, The
Netherlands, pp. 523-552. [0013] Alcoa, (2000), "New Process for
Grain Refinement of Aluminum," DOE Project Final Report, Contract
No. DE-FC07-98ID13665, Sep. 22, 2000. [0014] Cui, Y., Xu, C. L. and
Han, Q., (2007), "Microstructure Improvement in Weld Metal Using
Ultrasonic Vibrations, Advanced Engineering Materials," v. 9, No.
3, pp.161-163. [0015] Eskin, G. I., (1998), "Ultrasonic Treatment
of Light Alloy Melts," Gordon and Breach Science Publishers,
Amsterdam, The Netherlands. [0016] Eskin, G. I. (2002) "Effect of
Ultrasonic Cavitation Treatment of the Melt on the Microstructure
Evolution during Solidification of Aluminum Alloy Ingots,"
Zeitschrift Fur Metallkunde/Materials Research and Advanced
Techniques, v.93, n.6, June, 2002, pp. 502-507. [0017] Greer, A.
L., (2004), "Grain Refinement of Aluminum Alloys," in Chu, M. G.,
Granger, D. A., and Han, Q., (eds.), "Solidification of Aluminum
Alloys," Proceedings of a Symposium Sponsored by TMS (The Minerals,
Metals & Materials Society), TMS, Warrendale, Pa. 15086-7528,
pp. 131-145. [0018] Han, Q., (2007), The Use of Power Ultrasound
for Material Processing," Han, Q., Ludtka, G., and Zhai, Q., (eds),
(2007), "Materials Processing under the Influence of External
Fields," Proceedings of a Symposium Sponsored by TMS (The Minerals,
Metals & Materials Society), TMS, Warrendale, Pa. 15086-7528,
pp. 97-106. [0019] Jackson, K. A., Hunt, J. D., and Uhlmann, D. R.,
and Seward, T. P., (1966), "On Origin of Equiaxed Zone in
Castings," Trans. Metall. Soc. AIME, v. 236, pp.149-158. [0020]
Jian, X, Xu, H., Meek, T. T., and Han, Q., (2005), "Effect of Power
Ultrasound on Solidification of Aluminum A356 Alloy," Materials
Letters, v. 59, no. 2-3, pp. 190-193.
[0021] Keles, O. and Dundar, M, (2007). "Aluminum Foil: Its Typical
Quality Problems and Their Causes," Journal of Materials Processing
Technology, v. 186, pp.125-137. [0022] Liu, C., Pan, Y, and Aoyama,
S., (1998), Proceedings of the 5.sup.th International Conference on
Semi-Solid Processing of Alloys and Composites, Eds.: Bhasin, A. K,
Moore, J. J., Young, K. P., and Madison, S., Colorado School of
Mines, Golden, Colo., pp. 439-447. [0023] Megy, J., (1999), "Molten
Metal Treatment," U.S. Pat. No. 5,935,295, August, 1999 [0024]
Megy, J., Granger, D. A., Sigworth, G. K., and Durst, C. R.,
(2000), "Effectiveness of In-Situ Aluminum Grain Refining Process,"
Light Metals, pp. 1-6. [0025] Cui et al., "Microstructure
Improvement in Weld Metal Using Ultrasonic Vibrations," Advanced
Engineering Materials, 2007, vol. 9, no. 3, pp. 161-163.
[0026] Han et al., "Grain Refining of Pure Aluminum," Light Metals
2012, pp. 967-971.
[0027] Prior to this invention, U.S. Pat. Nos. 8,574,336 and
8,652,397 (the entire contents of each patent are incorporated
herein by reference) described methods for reducing the amount of a
dissolved gas (and/or various impurities) in a molten metal bath
(e.g., ultrasonic degassing) for example by introducing a purging
gas into the molten metal bath in close proximity to the ultrasonic
device. These patents will be referred to hereinafter as the '336
patent and the '397 patent.
SUMMARY
[0028] In one embodiment of the present invention, there is
provided a molten metal conveyor having a receptor plate in contact
with molten metal during transport of the molten metal. The
receptor plate extends from an entrance where molten metal enters
onto the receptor plate to an exit where molten metal exits the
receptor plate. The molten metal conveyor has at least one
vibrational energy source which supplies vibrational energy
directly to the receptor plate in contact with molten metal.
[0029] In one embodiment of the present invention, there is
provided a method for forming a metal product that includes
providing molten metal onto a molten conveyor; cooling the molten
metal by control of a cooling medium flowing through a cooling
passage in the or attached to the conveyor; and coupling
vibrational energy directly into a receptor plate in contact with
the molten metal on the conveyor.
[0030] It is to be understood that both the foregoing general
description of the invention and the following detailed description
are exemplary, but are not restrictive of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] A more complete appreciation of the invention and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings, wherein:
[0032] FIG. 1 is a schematic of a continuous casting mill according
to one embodiment of the invention;
[0033] FIG. 2 is a schematic of a molten metal conveyor having
multiple magnetostrictive transducers attached along a longitudinal
length of a vibratory plate;
[0034] FIG. 3 is a schematic of a molten metal conveyor having a
piezoelectric ultrasonic transducer attached to a vibratory plate
54;
[0035] FIG. 4 is a schematic of multiple transducers attached in a
two dimensional array to a bottom of vibratory plate;
[0036] FIG. 5 is a schematic of multiple transducers attached to a
bottom of vibratory plate with a higher density at the end of the
vibratory plate dispensing the molten metal;
[0037] FIG. 6A is a side view of metal conveyor showing interior
channels for the cooling medium to flow therein;
[0038] FIG. 6B is a view of a metal conveyor/ pouring device
according to the invention;
[0039] FIG. 7 is a schematic of a casting wheel configuration
according to one embodiment of the invention utilizing a molten
metal processing device in the casting wheel;
[0040] FIG. 8 is a schematic of a casting wheel configuration
according to one embodiment of the invention showing a vibrational
probe device coupled directly to the molten metal cast in the
casting wheel;
[0041] FIG. 9 is a schematic of a stationary mold utilizing the
vibrational energy sources of the invention;
[0042] FIG. 10A is a cross sectional schematic of selected
components of a vertical casting mill;
[0043] FIG. 10B is a cross sectional schematic of other components
of a vertical casting mill;
[0044] FIG. 10C is a cross sectional schematic of other components
of a vertical casting mill;
[0045] FIG. 10D is a cross sectional schematic of other components
of a vertical casting mill;
[0046] FIG. 11 is a schematic of an embodiment of the invention
utilizing both ultrasonic degassing and ultrasonic grain
refinement;
[0047] FIG. 12 is a schematic of an illustrative computer system
for the controls and controllers depicted herein;
[0048] FIG. 13 is a flow chart depicting a method according to one
embodiment of the invention;
[0049] FIG. 14 is an ACSR wire process flow diagram;
[0050] FIG. 15 is an ACSS wire process flow diagram; and
[0051] FIG. 16 is an aluminum strip process flow diagram;
DETAILED DESCRIPTION
[0052] Grain refining of metals and alloys is important for many
reasons, including maximizing ingot casting rate, improving
resistance to hot tearing, minimizing elemental segregation,
enhancing mechanical properties, particularly ductility, improving
the finishing characteristics of wrought products and increasing
the mold filling characteristics, and decreasing the porosity of
foundry alloys. Usually grain refining is one of the first
processing steps for the production of metal and alloy products,
especially aluminum alloys and magnesium alloys, which are two of
the lightweight materials used increasingly in the aerospace,
defense, automotive, construction, and packaging industry. Grain
refining is also an important processing step for making metals and
alloys castable by eliminating columnar grains and forming equiaxed
grains.
[0053] Grain refining is a solidification processing step by which
the crystal size of the solid phases is reduced by either chemical,
physical, or mechanical means in order to make alloys castable and
to reduce defect formation. Currently, aluminum production is grain
refined using TIBOR, resulting in the formation of an equiaxed
grain structure in the solidified aluminum. Prior to this
invention, use of impurities or chemical "grain refiners" was the
only way to address the long recognized problem in the metal
casting industry of columnar grain formation in metal castings.
Additionally, prior to this invention, a combination of 1)
ultrasonic degassing to remove impurities from the molten metal
(prior to casting) along and 2) the above-noted ultrasonic grain
refining (i.e., at least one vibrational energy source) had not
been undertaken.
[0054] However, there are large costs associated with using TIBOR
and mechanical restraints due to the input of those inoculants into
the melt. Some of the restraints include ductility, machinability,
and electrical conductivity.
[0055] Despite the cost, approximately 68% of the aluminum produced
in the United States is first cast into ingot prior to further
processing into sheets, plates, extrusions, or foil. The direct
chill (DC) semi-continuous casting process and continuous casting
(CC) process has been the mainstay of the aluminum industry due
largely to its robust nature and relative simplicity. One issue
with the DC and CC processes is the hot tearing formation or
cracking formation during ingot solidification. Basically, almost
all ingots would be cracked (or not castable) without using grain
refining.
[0056] Still, the production rates of these modern processes are
limited by the conditions to avoid cracking foiniation. Grain
refining is an effective way to reduce the hot tearing tendency of
an alloy, and thus to increase the production rates. As a result, a
significant amount of effort has been concentrated on the
development of powerful grain refiners that can produce grain sizes
as small as possible. Superplasticity can be achieved if the grain
size can be reduced to the sub- micron level, which permits alloys
not only to be cast at much faster rates but also rolled/extruded
at lower temperatures at much faster rates than ingots are
processed today, leading to significant cost savings and energy
savings.
[0057] At present, nearly all aluminum cast in the world either
from primary (approximately 20 billion kg) or secondary and
internal scrap (25 billion kg) is grain refined with heterogeneous
nuclei of insoluble TiB.sub.2 nuclei approximately a few microns in
diameter, which nucleate a fine grain structure in aluminum. One
issue related to the use of chemical grain refiners is the limited
grain refining capability. Indeed, the use of chemical grain
refiners causes a limited decrease in aluminum grain size, from a
columnar structure with linear grain dimensions of something over
2,500 .mu.m, to equiaxed grains of less than 200 .mu.m. Equiaxed
grains of 100 .mu.m in aluminum alloys appear to be the limit that
can be obtained using the chemical grain refiners commercially
available.
[0058] The productivity can be significantly increased if the grain
size can be further reduced. Grain size in the sub-micron level
leads to superplasticity that makes forming of aluminum alloys much
easier at room temperatures.
[0059] Another issue related to the use of chemical grain refiners
is the defect formation associated with the use of grain refiners.
Although considered in the prior art to be necessary for grain
refining, the insoluble, foreign particles are otherwise
undesirable in aluminum, particularly in the form of particle
agglomerates ("clusters"). The current grain refiners, which are
present in the form of compounds in aluminum base master alloys,
are produced by a complicated string of mining, beneficiation, and
manufacturing processes. The master alloys used now frequently
contain potassium aluminum fluoride (KAIF) salt and aluminum oxide
impurities (dross) which arise from the conventional manufacturing
process of aluminum grain refiners. These give rise to local
defects in aluminum (e.g. "leakers" in beverage cans and "pin
holes" in thin foil), machine tool abrasion, and surface finish
problems in aluminum. Data from one of the aluminum cable companies
indicate that 25% of the production defects is due to TiB.sub.2
particle agglomerates, and another 25% of defects is due to dross
that is entrapped into aluminum during the casting process.
TiB.sub.2 particle agglomerates often break the wires during
extrusion, especially when the diameter of the wires is smaller
than 8 mm.
[0060] Another issue related to the use of chemical grain refiners
is the cost of the grain refiners. This is extremely true for the
production of magnesium ingots using Zr grain refiners. Grain
refining using Zr grain refiners costs about an extra $1 per
kilogram of Mg casting produced. Grain refiners for aluminum alloys
cost around $1.50 per kilogram.
[0061] Another issue related to the use of chemical grain refiners
is the reduced electrical conductivity. The use of chemical grain
refiners introduces in excess amount of Ti in aluminum, causes a
substantial decrease in electrical conductivity of pure aluminum
for cable applications. In order to maintain certain conductivity,
companies have to pay extra money to use purer aluminum for making
cables and wires.
[0062] A number of other grain refining methods, in addition to the
chemical methods, have been explored in the past century. These
methods include using physical fields, such as magnetic and
electro-magnetic fields, and using mechanical vibrations.
High-intensity, low-amplitude ultrasonic vibration is one of the
physical/mechanical mechanisms that has been demonstrated for grain
refining of metals and alloys without using foreign particles.
However, experimental results, such as from Cui et al, 2007 noted
above, were obtained in small ingots up to a few pounds of metal
subjected to a short period of time of ultrasonic vibration. Little
effort has been carried out on grain refining of CC or DC casting
ingots/billets using high-intensity ultrasonic vibrations.
[0063] As used herein, embodiments of the present invention will be
described using terminologies commonly employed by those skilled in
the art to present their work. These terms are to be accorded the
common meaning as understood by those of the ordinary skill in the
arts of materials science, metallurgy, metal casting, and metal
processing. Some terms taking a more specialized meaning are
described in the embodiments below. Nevertheless, the term
"configured to" is understood herein to depict appropriate
structures (illustrated herein or known or implicit from the art)
permitting an object thereof to perform the function which follows
the "configured to" term. The term "coupled to" means that one
object coupled to a second object has the necessary structures to
support the first object in a position relative to the second
object (for example, abutting, attached, displaced a predetermined
distance from, adjacent, contiguous, joined together, detachable
from one another, dismountable from each other, fixed together, in
sliding contact, in rolling contact) with or without direct
attachment of the first and second objects together.
[0064] U.S. Pat. No. 4,066,475 to Chia et al. (the entire contents
of which are incorporated herein by reference) describes a
continuous casting process. In general, FIG. 1 depicts continuous
casting system having a casting mill 2 having a delivery device 10
(such as tundish) which provides molten metal to a pouring spout 11
which directs the molten metal to a peripheral groove contained on
a rotary mold ring 13. An endless flexible metal band 14 encircles
both a portion of the mold ring 13 as well as a portion of a set of
band-positioning rollers 15 such that a continuous casting mold is
defined by the groove in the mold ring 13 and the overlying metal
band 14. A cooling system is provided for cooling the apparatus and
effecting controlled solidification of the molten metal during its
transport on the rotary mold ring 13. The cooling system includes a
plurality of side headers 17, 18, and 19 disposed on the side of
the mold ring 13 and inner and outer band headers 20 and 21,
respectively, disposed on the inner and outer sides of the metal
band 14 at a location where it encircles the mold ring. A conduit
network 24 having suitable valving is connected to supply and
exhaust coolant to the various headers so as to control the cooling
of the apparatus and the rate of solidification of the molten
metal.
[0065] By such a construction, molten metal is fed from the pouring
spout 11 into the casting mold and is solidified and partially
cooled during its transport by circulation of coolant through the
cooling system. A solid cast bar 25 is withdrawn from the casting
wheel and fed to a conveyor 27 which conveys the cast bar to a
rolling mill 28. It should be noted that the cast bar 25 has only
been cooled an amount sufficient to solidify the bar, and the bar
remains at an elevated temperature to allow an immediate rolling
operation to be performed thereon. The rolling mill 28 can include
a tandem array of rolling stands which successively roll the bar
into a continuous length of wire rod 30 which has a substantially
uniform, circular cross-section.
[0066] FIG. 1 shows controller 500 which controls the various parts
of the continuous casting system shown therein, as discussed in
more detail below. Controller 500 may include one or more
processors with programmed instructions (i.e., algorithms) to
control the operation of the continuously casting system and the
components thereof.
[0067] U.S. Pat. No. 9,481,031 to Han et al. (the entire contents
of which are incorporated herein by reference) describes a molten
metal processing device including a molten metal containment
structure for reception and transport of molten metal along a
longitudinal length thereof. The device further included a cooling
unit for the containment structure including a cooling channel for
passage of a liquid medium therein, and an ultrasonic probe
disposed in relation to the cooling channel such that ultrasonic
waves are coupled through the liquid medium in the cooling channel
and through the molten metal containment structure into the molten
metal.
[0068] As described in the '031 patent, an ultrasonic wave probe
provided ultrasonic vibrations (UV) through the liquid medium and
through a bottom plate of a molten metal containment structure into
which liquid metal was supplied. In the '031 patent, the ultrasonic
wave probe was shown inserted into the liquid medium passage. As
described in the '031 patent, a relatively small amount of
undercooling (e.g., less than 10.degree. C.) at the bottom of the
channel results in a layer of small nuclei of purer aluminum being
formed. The ultrasonic vibrations from the bottom of the channel
creates pure aluminum nuclei which then are used as nucleating
agents during solidification resulting in a uniform grain
structure. As described in the '031 patent, the ultrasonic
vibrations from the bottom of the channel disperse these nuclei and
breaks up dendrites that forms in the undercooled layer. These
aluminum nuclei and fragments of dendrites are then used to form
equiaxed grains in the mold during solidification resulting in a
uniform grain structure.
[0069] In one embodiment of the present invention, ultrasonic grain
refining involves application of ultrasonic energy (and/or other
vibrational energy) for the refinement of the grain size. While the
invention is not bound to any particular theory, one theory is that
the injection of vibrational energy (e.g., ultrasonic power) into a
molten or solidifying alloy can give rise to nonlinear effects such
as cavitation, acoustic streaming, and radiation pressure. These
nonlinear effects can be used to nucleate new grains, and break up
dendrites during solidification process of an alloy.
[0070] Under this theory, the grain refining process can be divided
into two stages: 1) nucleation and 2) growth of the newly formed
solid from the liquid. Spherical nuclei are formed during the
nucleation stage. These nuclei develop into dendrites during the
growth stage. Unidirectional growth of dendrites leads to the
formation of columnar grains potentially causing hot
tearing/cracking and non-uniform distribution of the secondary
phases. This in turn can lead to poor castability. On the other
hand, uniform growth of dendrites in all directions (such as
possible with the present invention) leads to the formation of
equiaxed grains. Castings/ingots containing small and equiaxed
grains have excellent formability.
[0071] Under this theory, when the temperature in an alloy is below
the liquidus temperature; nucleation may occur when the size of the
solid embryos is larger than a critical size given in the following
equation:
r * = 2 .sigma. sl .DELTA. G V ##EQU00001##
where r* is the critical size, .sigma..sub.sl is the interfacial
energy associated with the solid-liquid interface, and
.DELTA.G.sub.V, is the Gibbs free energy associated with the
transformation of a unit volume of liquid into solid..
[0072] Under this theory, the Gibbs free energy, .DELTA.G,
decreases with increasing size of the solid embryos when their
sizes are larger than r*, indicating the growth of the solid embryo
is thermodynamically favorable. Under such conditions, the solid
embryos become stable nuclei. However, homogeneous nucleation of
solid phase having size greater than r* occurs only under extreme
conditions that require large undercooling in the melt.
[0073] Under this theory, the nuclei formed during solidification
can grow into solid grains known as dendrites. The dendrites can
also be broken into multiple small fragments by application of the
vibrational energy. The dendritic fragments thus formed can grow
into new grains and result in the formation of small grains; thus
creating an equiaxed grain structure.
[0074] In other words, ultrasonic vibrations transmitted into the
undercooled liquid metal create nucleation sites in the metals or
metallic alloys to refine the grain size. The nucleation sites can
be generated via the vibrational energy acting as described above
to break up the dendrites creating in the molten metal numerous
nuclei which are not dependent on foreign impurities.
[0075] Here, in one embodiment of the invention, an ultrasonic
device is not configured to have ultrasonic waves exclusively
coupled through a liquid medium in a cooling channel and then
through a bottom plate of a molten metal containment structure into
the molten metal. Instead, in this embodiment, ultrasonic waves are
directly coupled to a plate or receptor in contact with molten
metal.
[0076] One or more magnetostrictive ultrasonic devices may be
attached directly to the plate or receptor in contact with molten
metal during transport of the molten metal. The receptor plate may
extend longitudinally from an entrance where molten metal enters
onto the receptor plate to an exit where molten metal exits the
receptor plate. Indeed, FIG. 2 depicts a molten metal conveyor 50
(sidewalls not shown) having multiple magnetostrictive transducers
52 attached and evenly spaced apart along a longitudinal length of
vibratory (ultrasonic) plate 54. The transducers 52 need not be
evenly spaced. Furthermore, the transducers can be spaced with a
lateral separation in a direction of the width of the plate 54.
FIG. 2 depicts the surface of the molten metal 53 above plate 54.
The molten metal traveling above plate 54 can be confined in a flow
channel of any shape including rectangular, square, or round.
[0077] In one embodiment of the invention, the thickness of the
molten metal traveling above plate 54 is less than 10 centimeters
thick in one embodiment. In this embodiment, the thickness of the
molten metal can be less than 1 centimeter. Alternatively, the
thickness of the molten metal can be less than a half of a
centimeter.
[0078] Accordingly, the receptor plate 54 can have a lateral width
equal to or less than a longitudinal length, or the lateral width
can be equal to or less than a half of the longitudinal length; or
the lateral width can be equal to or less than a third of the
longitudinal length. For example, the receptor plate 54 can have a
lateral width between 2.5 cm and 300 cm. The length of the receptor
plate 54 can be between 2.5 cm to 300 cm. Moreover, the receptor
plate 54 can have a lateral width which tapers down in width toward
the exit. The dimensions of the receptor plate 54 in one embodiment
can vary up to (but not limited to) 220 cm wide and 70 cm long,
although other dimensions can be used. The dimensions may be
inversed with 220 cm being a length and 70 cm being a width.
[0079] Further, the receptor plate 54 can be disposed across a wide
range of angular disposition from a near horizontal orientation
(within 20 angular degrees) to a near vertical orientation (within
20 angular degrees), with gravity forcing the molten metal to the
exit. More specifically, the receptor plate 54 can be disposed
within 10 angular degrees (or 5 angular degrees) from a horizontal
orientation with gravity forcing the molten metal to the exit.
Alternatively, the receptor plate 54 can be disposed within 10
angular degrees (or 5 angular degrees) from a vertical orientation
with gravity forcing the molten metal to the exit. The surface of
the plate on which the molten metal is conveyed (or flows) can be
smooth, polished, rough, raised, indented, and/or textured.
Alternatively, the receptor plate 54 can be disposed at any angular
position from horizontal (or near horizontal) to vertical (or near
vertical). This wide angular range permits molten metal to be
conveyed along the receptor plate 54 whether the vibratory plate is
applied in a level pour system or a down spout scenario into a
casting mold.
[0080] In one embodiment of the invention, there is included a
controller (e.g., controller 500) controlling at least one of a
pour rate of the molten metal onto the receptor plate and/or a
cooling rate of the molten metal on the receptor plate. The
controller is preferably programmed to adjust the pour rate such
that a height of the molten metal above the receptor plate is
between 1.25 cm and 10 cm, or between 2.5 cm and 5 cm, or between 3
cm and 4 cm. By having a sheet-like flow of molten metal along the
receptor plate 54, the nuclei induced and released from the
receptor plate 54 can be uniformly dispersed into the volume of the
molten metal instantaneously on the receptor plate 54. If the
surface area of the receptor plate is considered as the area
available for the generation of the nuclei, then having a
sheet-like form of molten metal will also serve to cool the molten
metal more thoroughly throughout the volume of the metal
instantaneously on the receptor plate 54. Without achieving this
cooling throughout, nuclei released could be re-melted into molten
metal and loss as from the total count of nuclei flowing into the
mold or casting wheel. Accordingly, by having controller 500
control the height of the molten metal on the receptor plate 54,
there is a synergetic effect when using the sheet-like molten metal
in that there are both more nuclei per unit volume generated and
less nuclei loss due to re-melting.
[0081] Components of the molten metal conveyor 50 can be made from
a metal such as titanium, stainless steel alloys, low carbon steels
or H13 steel, other high-temperature materials, a ceramic, a
composite, or a polymer. Components of the molten metal conveyor 50
can also be made from one or more of niobium, a niobium alloy,
titanium, a titanium alloy, tantalum, a tantalum alloy, copper, a
copper alloy, rhenium, a rhenium alloy, steel, molybdenum, a
molybdenum alloy, stainless steel, and a ceramic. The ceramic can
be a silicon nitride ceramic, such as for example a silica alumina
nitride or SIALON.
[0082] While not shown in FIG. 2, the magnetostrictive transducers
52 have an internal coil wrapped around a stack of magnetic layers.
The coil provides a high frequency current producing a high
frequency magnetic field which induces extraction and compression
of the stack, and thereby impresses vibrations on plate 52.
[0083] Magnetostrictive transducers are typically composed of a
large number of material plates that will expand and contract once
an electromagnetic field is applied. More specifically,
magnetostrictive transducers suitable for the present invention can
include in one embodiment a large number of nickel (or other
magnetostrictive material) plates or laminations arranged in
parallel with one edge of each laminate attached to the bottom of a
process container or other surface to be vibrated. A coil of wire
is placed around the magnetostrictive material to provide the
magnetic field. For example, when a flow of electrical current is
supplied through the coil of wire, a magnetic field is created.
This magnetic field causes the magnetostrictive material to
contract or elongate, thereby introducing a sound wave into a fluid
in contact with the expanding and contracting magnetostrictive
material. Typical ultrasonic frequencies from magnetostrictive
transducers suitable for the invention range from 20 to 200 kHz.
Higher or lower frequencies can be used depending on the natural
frequency of the magnetostrictive element.
[0084] For magnetostrictive transducers, nickel is one of the most
commonly used materials. When a voltage is applied to the
transducer, the nickel material expands and contracts at ultrasonic
frequencies. In one embodiment of the invention, the nickel plates
are directly silver brazed to a stainless steel plate. With
reference to FIG. 2, the stainless steel plate of the
magnetostrictive transducer is the surface that is vibrating at
ultrasonic frequencies and (as shown in FIG. 2 is attached to
vibratory (ultrasonic) plate 54.
[0085] U.S. Pat. No. 7,462,960 (the entire contents of which are
incorporated herein by reference) describes an ultrasonic
transducer driver having a giant magnetostrictive element.
Accordingly, in one embodiment of the invention, the
magnetostrictive element can be made from rare-earth-alloy-based
materials such as Terfenol-D and its composites which have an
unusually large magnetostrictive effect as compared with early
transition metals, such as iron (Fe), cobalt (Co) and nickel (Ni).
Alternatively, the magnetostrictive element in one embodiment of
the invention can be made from iron (Fe), cobalt (Co) and nickel
(Ni).
[0086] Alternatively, the magnetostrictive element in one
embodiment of the invention can be made from one or more of the
following alloys iron and terbium; iron and praseodymium; iron,
terbium and praseodymium; iron and dysprosium; iron, terbium and
dysprosium; iron, praseodymium and dysprodium; iron, terbium,
praseodymium and dysprosium; iron, and erbium; iron and samarium;
iron, erbium and samarium; iron, samarium and dysprosium; iron and
holmium; iron, samarium and holmium; or mixture thereof.
[0087] U.S. Pat. No. 4,158,368 (the entire contents of which are
incorporated herein by reference) describes a magnetostrictive
transducer. As described therein and suitable for the present
invention, the magnetostrictive transducer can include a plunger of
a material exhibiting negative magnetostriction disposed within a
housing. U.S. Pat. No. 5,588,466 (the entire contents of which are
incorporated herein by reference) describes a magnetostrictive
transducer. As described therein and suitable for the present
invention, a magnetostrictive layer is applied to a flexible
element, for example, a flexible beam. The flexible element is
deflected by an external magnetic field. As described in the '466
patent and suitable for the present invention, a thin
magnetostrictive layer can be used for the magnetostrictive element
which consists of Tb(1-x) Dy(x) Fe.sub.2. U.S. Pat. No. 4,599,591
(the entire contents of which are incorporated herein by reference)
describes a magnetostrictive transducer. As described therein and
suitable for the present invention, the magnetostrictive transducer
can utilize a magnetostrictive material and a plurality of windings
connected to multiple current sources having a phase relationship
so as to establish a rotating magnetic induction vector within the
magnetostrictive material. U.S. Pat. No. 4,986808 (the entire
contents of which are incorporated herein by reference) describes a
magnetostrictive transducer. As described therein and suitable for
the present invention, the magnetostrictive transducer can include
a plurality of elongated strips of magnetostrictive material, each
strip having a proximal end, a distal end and a substantially
V-shaped cross section with each arm of the V is formed by a
longitudinal length of the strip and each strip being attached to
an adjacent strip at both the proximal end and the distal end to
form and integral substantially rigid column having a central axis
with fins extending radially relative to this axis.
[0088] U.S. Pat. No. 6,150,753 (the entire contents of which are
incorporated herein by reference) describes ultrasonic transducer
assembly, having a cobalt-base alloy housing with at least one
planar wall section, and at least one ultrasonic transducer mounted
to the planar wall section, the ultrasonic transducer operatively
arranged to impart an ultrasonic vibrating force to the planar wall
section of the housing. Both the background material and
descriptions in the '753 patent, describing ways to mount
ultrasonic transducers to stainless steel plates, can be used in
the present invention to form mechanically stable coupling between
transducers 52/56 and vibratory (ultrasonic) plate 54. For example,
the ULTIMET.RTM. brand alloy, available from Haynes International,
Inc. of Kokomo, Ind. ULTIMET.RTM. is a cobalt-chromium alloy
suitable for the present invention. This alloy has a nominal
chemical composition (weight percent) as follows: cobalt (54%),
chromium (26%), nickel (9%), molybdenum (5%), tungsten (2%), and
iron (3%). This alloy also contains trace amounts (less than 1%
weight percent) of manganese, silicon, nitrogen and carbon.
[0089] U.S. Pat. No. 5,247,954 (the entire contents of which are
incorporated herein by reference) describes a method of bonding of
the piezoelectric ceramic transducers which does not exceed
250.degree. C. This method can be used in the present invention to
form mechanically stable coupling between transducers 52/56 and
vibratory (ultrasonic) plate 54. For example, a low temperature
brazing alloy is used to bond between a silvered piezoelectric
ceramic transducers and a pre-metalized surface of plate 54. This
solder can be a pre-formed 96.5% tin, 3.5% silver, and melts at
about 221.degree. C. Such a solder would stick to silver and
silver/tungsten surfaces which had been fired onto surface of plate
54 prior to application of the low temperature solder. The
attachment of the piezoelectric ceramic transducers to plate 54
would then take place in a furnace operating at 230.degree. C.
[0090] In one embodiment of the invention, one or more
piezoelectric ultrasonic devices are attached directly to the plate
or receptor in contact with molten metal. FIG. 3 depicts a molten
metal conveyor 50 (sidewalls not shown) having in this depiction
one piezoelectric ultrasonic transducer 56 attached to the
vibratory (ultrasonic) plate 54. In this embodiment, it is
preferable (but not necessary) to use booster 58 to increase the
ultrasonic power delivered to the plate.
[0091] In one aspect of the invention, piezoelectric transducers
supplying the vibrational energy can be formed of a ceramic
material that is sandwiched between electrodes which provide
attachment points for electrical contact. Once a voltage is applied
to the ceramic through the electrodes, the ceramic expands and
contracts at ultrasonic frequencies. In one embodiment of the
invention, piezoelectric transducer serving as vibrational energy
source 40 is attached to a booster, which transfers the vibration
to the probe. U.S. Pat. No. 9,061,928 (the entire contents of which
are incorporated herein by reference) describes an ultrasonic
transducer assembly including an ultrasonic transducer, an
ultrasonic booster, an ultrasonic probe, and a booster cooling
unit. The ultrasonic booster in the '928 patent is connected to the
ultrasonic transducer to amplify acoustic energy generated by the
ultrasonic transducer and transfer the amplified acoustic energy to
the ultrasonic probe. The booster configuration of the '928 patent
can be useful here in the present invention to provide energy to
the ultrasonic probes directly or indirectly in contact with the
liquid cooling medium discussed above. Indeed, in one embodiment of
the invention, an ultrasonic booster is used in the realm of
ultrasonics to amplify or intensify the vibrational energy created
by a piezoelectric transducer. The booster does not increase or
decrease the frequency of the vibrations, it increases the
amplitude of the vibration. (When a booster is installed backwards,
it can also compress the vibrational energy.) In one embodiment of
the invention, a booster connects between the piezoelectric
transducer and the probe. In the case of using a booster for
ultrasonic grain refining, below are an exemplary number of method
steps illustrating the use of a booster with a piezoelectric
vibrational energy source:
[0092] 1) An electrical current is supplied to the piezoelectric
transducer. The ceramic pieces within the transducer expand and
contract once the electrical current is applied, this converts the
electrical energy to mechanical energy.
[0093] 2) Those vibrations in one embodiment are then transferred
to a booster, which amplifies or intensifies this mechanical
vibration.
[0094] 3) The amplified or intensified vibrations from the booster
in one embodiment are then propagated to the probe. The probe is
then vibrating at the ultrasonic frequencies, thus creating
cavitations.
[0095] 4) The cavitations from the vibrating probe impact the
casting band, which in one embodiment is in contact with the molten
metal.
[0096] 5) The cavitations in one embodiment break up the dendrites
and create an equiaxed grain structure.
[0097] In the embodiment of FIG. 3, while not shown, there may be
more than one ultrasonic transducer 56 with such transducers
attached and evenly spaced apart along a longitudinal length of
vibratory (ultrasonic) plate 54. As above, transducers 56 need not
be evenly spaced. Furthermore, the transducers 56 can be spaced
with a lateral separation in a direction of the width of the plate
54.
[0098] FIG. 4 is depiction of multiple transducers 52/56 attached
in a two dimensional array to the bottom of vibratory plate 54. The
attachment pattern need not be a regular grid pattern (as shown).
For example, the attachment pattern could be irregularly spaced.
Alternatively, the attachment pattern could be with a higher
density transducers 52/56 at the end of the vibratory plate 54
receiving the molten metal or at a higher density at the end of the
dispensing the molten metal. FIG. 5 is depiction of multiple
transducers 52/56 attached in to the bottom of vibratory plate 54
with a higher density at the end of the dispensing the molten
metal. FIG. 5 also shows that the transducers can be placed in a
diagonal configuration along the length of the receptor plate. In
one embodiment of the invention, the vibrational energy is imparted
with mechanically driven vibrators. The mechanically driven
vibrators would take the place of any one or all of the transducers
52/56 noted above.
[0099] Mechanical vibrators useful for the invention can operate
from 8,000 to 15,000 vibrations per minute, although higher and
lower frequencies can be used. In one embodiment of the invention,
the vibrational mechanism is configured to vibrate between 565 and
5,000 vibrations per second. In one embodiment of the invention,
the vibrational mechanism is configured to vibrate at even lower
frequencies down to a fraction of a vibration every second up to
the 565 vibrations per second. Ranges of mechanically driven
vibrations suitable for the invention include e.g., 6,000 to 9,000
vibrations per minute, 8,000 to 10,000 vibrations per minute,
10,000 to 12,000 vibrations per minute, 12,000 to 15,000 vibrations
per minute, and 15,000 to 25,000 vibrations per minute. Ranges of
mechanically driven vibrations suitable for the invention from the
literature reports include for example of ranges from 133 to 250
Hz, 200 Hz to 283 Hz (12,000 to 17,000 vibrations per minute), and
4 to 250 Hz. Furthermore, a wide variety of mechanically driven
oscillations can be impressed in the casting wheel 30 or the
housing 44 by a simple hammer or plunger device driven periodically
to strike the casting wheel 30 or the housing 44. In general, the
mechanical vibrations can range up to 10 kHz. Accordingly, ranges
suitable for the mechanical vibrations used in the invention
include: 0 to 10 KHz, 10 Hz to 4000 Hz, 20 Hz to 2000 Hz, 40 Hz to
1000 Hz, 100 Hz to 500 Hz, and intermediate and combined ranges
thereof, including a preferred range of 565 to 5,000 Hz.
[0100] Regardless of the type of transducer used, the transducers
are placed in mechanical and acoustic contact with plate 54. Silver
brazing (or another type of high temperature alloy) could be used
to join the transducer housing or the booster housing to plate 54.
A cooling medium (compressed air, water, ionic fluids etc.) can
flow through interior channels of plate 54. FIG. 6A is a side view
of metal conveyor 50 showing interior channels 60 for the cooling
medium to flow disposed in a thickness of the plate 54 and disposed
below sidewalls 62. The cooling medium is used to reduce the
temperature of the metal flowing across the plate. While there may
be some coupling of the vibrational energy through the cooling
medium, the majority of the vibrational energy is directly coupled
from the transducer through a metal section of plate 54 into the
molten aluminum.
[0101] In one embodiment of the invention, a cooling medium
(compressed air, water, ionic fluids etc.) can flow across the
bottom side of the plate 54. The cooling medium is used to reduce
the temperature of the metal flowing across the plate. This cooling
method is external from the plate and is not disposed in (or
confined within) the thickness of the plate 54. Here, in one
example, a forced air vortex system blows a gas across the bottom
side of plate 54.
[0102] The thickness of the vibratory plate 54 can vary between 5
cm and 0.5 cm. The thickness of the vibratory plate 54 can also
vary between 3 cm and 1 cm. The thickness of the vibratory plate 54
can also vary between 2 cm and 1.5 cm. The thickness of the
vibratory plate 54 is not necessarily uniform along its length or
width. The vibratory plate 54 can have thinner sections which may
act more as a diaphragm and amplify the vibrations. For thin
vibratory plates, cooling may be provided by the attachment of
cooling tubes to plate 54 and/or sidewalls 62. While depicted here
with transducers mounted to the bottom of plate 54, the transducers
could also or alternatively be placed on side wall 62.
[0103] In one embodiment of the invention, the vibratory plate 54
can be the bottom of a pouring device, such as the bottom of
pouring spout 11 shown in FIG. 1. Alternatively, the molten metal
conveyor 50 can accept molten metal from pouring spout 11 and then
deliver molten metal into a casting wheel. FIG. 6B is a view of a
metal conveyor/ pouring device 55 according to the invention. In
the device 55 shown in FIG. 6B, there is a pouring device (e.g.,
pouring spout 11 shown in FIG. 1 or tundish 245 in FIG. 10) is
configured and positioned to deliver molten metal onto the molten
metal conveyor 50 discussed above. The molten metal is conveyed
along the molten metal conveyor 50 (for example by gravity) where
it is subject to cooling and the vibrational energy noted above.
The molten metal exiting the molten metal conveyor 50 contains
nuclei numerous nuclei which are not dependent on foreign
impurities.
[0104] While water is a convenient cooling medium, other coolants
can be used. In one embodiment of the invention, the cooling medium
is a super chilled liquid (e.g., liquids at or below 0.degree. C.
to -196.degree. C. liquid, that is a liquid between the
temperatures of ice and liquid nitrogen). In one embodiment of the
invention, a super chilled liquid such as liquid nitrogen is
coupled with an ultrasonic or other vibrational energy source. The
net effect is an increase in the solidification rates allowing
faster processing. In one embodiment of the invention, the cooling
medium exiting the probe(s) will not only create cavitations but
will also atomize and super cool the molten metal. In a preferred
embodiment, this results in an increase in the heat transfer in the
zone of the casting wheel.
[0105] In one embodiment of the invention, as shown in FIG. 7,
casting mill 2 includes a casting wheel 30a having a containment
structure 32 (e.g., a trough or channel in the casting wheel 30) in
which molten metal is poured (e.g., cast). FIG. 7 shows an
embodiment where a molten metal processing device 34 is optionally
included. Molten metal processing device 34 is described in the
above-noted U.S. Ser. No. 15/337,645 (the entire contents of which
are incorporated herein by reference). A band 36 (e.g., a steel
flexible metal band) confines the molten metal to the containment
structure 32 (i.e., the channel). Rollers 38 allow the molten metal
processing device 34 to remain in a stationary position on the
rotating casting wheel as the molten metal solidifies in the
channel of the casting wheel and is conveyed away from the molten
metal processing device 34.
[0106] In brief, molten metal processing device 34 includes an
assembly 42 mounted on the casting wheel 30. The assembly 42
includes at least one vibrational energy source (e.g., vibrator
40), a housing 44 (i.e., a support device) holding the vibrational
energy source 42. The assembly 42 includes at least one cooling
channel 46 for transport of a cooling medium therethrough. The
flexible band 36 is sealed to the housing 44 by a seal 44a attached
to the underside of the housing, thereby permitting the cooling
medium from the cooling channel to flow along a side of the
flexible band opposite the molten metal in the channel of the
casting wheel.
[0107] The casting band (i.e., a receptor of vibrational energy)
can be made of at least one or more of chrome, niobium, a niobium
alloy, titanium, a titanium alloy, tantalum, a tantalum alloy,
copper, a copper alloy, nickel, a nickel alloy, rhenium, a rhenium
alloy, steel, molybdenum, a molybdenum alloy, aluminum, an aluminum
alloy, stainless steel, a ceramic, a composite, or a metal or
alloys and combinations of the above.
[0108] A width of the casting band can range between 25 mm to 400
mm. In another embodiment of the invention, a width of the casting
band ranges between 50 mm to 200 mm. In another embodiment of the
invention, a width of the casting band ranges between 75 mm to 100
mm.
[0109] A thickness of the casting band can range between 0.5 mm to
10 mm. In another embodiment of the invention, a thickness of the
casting band ranges between 1 mm to 5 mm. In another embodiment of
the invention, a thickness of the casting band ranges between 2 mm
to 3 mm.
[0110] As molten metal passes under the metal band 36 under
vibrator 40, when the optional molten metal processing device 34 is
utilized, vibrational energy is additionally supplied to the molten
metal as the metal begins to cool and solidify. In one embodiment
of the invention, the vibrational energy is imparted with
ultrasonic transducers generated for example by piezoelectric
devices ultrasonic transducer. In one embodiment of the invention,
the vibrational energy is imparted with ultrasonic transducers
generated for example by a magnetostrictive transducer. In one
embodiment of the invention, the vibrational energy is imparted
with mechanically driven vibrators (to be discussed later). The
vibrational energy in one embodiment permits the formation of
multiple small seeds, thereby producing a fine grain metal product.
These sources of vibrational energy are the same type of sources as
described above in reference to FIGS. 2-5.
[0111] In one aspect, the channel of the casting wheel 30 can be a
refractory metal or other high temperature material such as copper,
irons and steels, niobium, niobium and molybdenum, tantalum,
tungsten, and rhenium, and alloys thereof including one or more
elements such as silicon, oxygen, or nitrogen which can extend the
melting points of these materials.
[0112] In one embodiment of the invention, the source of ultrasonic
vibrations for vibrational energy (to plate 54 or for use in the
molten metal processing device 34) provides a power of 1.5 kW at an
acoustic frequency of 20 kHz. This invention is not restricted to
those powers and frequencies. Rather, a broad range of powers and
ultrasonic frequencies can be used although the following ranges
are of interest. [0113] Power: In general, powers between 50 and
5000 W for each sonotrode, depending on the dimensions of the
sonotrode or probe. These powers are typically applied to the
sonotrode to ensure that the power density at the end of the
sonotrode is higher than 100 W/cm.sup.2, which may be considered
the threshold for causing cavitation in molten metals depending on
the cooling rate of the molten metal, the molten metal type, and
other factors. The powers at this area can range from 50 to 5000 W,
100 to 3000 W, 500 to 2000 W, 1000 to 1500 W or any intermediate or
overlapping range. Higher powers for larger probe/sonotrode and
lower powers for smaller probe are possible. In various embodiments
of the invention, the applied vibrational energy power density can
range from 10 W/cm.sup.2 to 500 W/cm.sup.2, or 20 W/cm.sup.2 to 400
W/cm.sup.2, or 30 W/cm.sup.2 to 300 W/cm.sup.2, or 50 W/cm.sup.2 to
200 W/cm.sup.2, or 70 W/cm.sup.2 to 150 W/cm.sup.2, or any
intermediate or overlapping ranges thereof. [0114] Frequency: In
general, 5 to 400 kHz (or any intermediate range) may be used.
Alternatively, 10 and 30 kHz (or any intermediate range) may be
used. Alternatively, 15 and 25 kHz (or any intermediate range) may
be used. The frequency applied can range from 5 to 400 KHz, 10 to
30 kHz, 15 to 25 kHz, 10 to 200 KHz, or 50 to 100 kHz or any
intermediate or overlapping ranges thereof.
[0115] While described above with respect to ultrasonic and
mechanically driven embodiments (applicable to plate 54 or for use
in the molten metal processing device 34), the invention is not so
limited to one or the other of these ranges, but can be used for a
broad spectrum of vibrational energy up to 400 KHz including single
frequency and multiple frequency sources. Additionally, a
combination of sources (ultrasonic and mechanically driven sources,
or different ultrasonic sources, or different mechanically driven
sources or acoustic energy sources to be described below) can be
used.
[0116] Aspects of the Invention
[0117] In one aspect of the invention, the vibrational energy (from
low frequency mechanically-driven vibrators in the 8,000 to 15,000
vibrations per minute range or up to 10 KHz and/or ultrasonic
frequencies in the range of 5 to 400 kHz) can be applied to the
molten metal conveyor 50 or molten metal processing device 34 or
both. In one aspect of the invention, the vibrational energy can be
applied at multiple distinct frequencies. In one aspect of the
invention, the vibrational energy can be applied to a variety of
metal alloys including, but not limited to those metals and alloys
listed below: Aluminum, Copper, Gold, Iron, Nickel, Platinum,
Silver, Zinc, Magnesium, Titanium, Niobium, Tungsten, Manganese,
Iron, and alloys and combinations thereof; metals alloys including-
Brass (Copper/Zinc), Bronze (Copper/Tin), Steel (iron/Carbon),
Chromalloy (chromium), Stainless Steel (steel/Chromium), Tool Steel
(Carbon/Tungsten/Manganese, Titanium (Iron/aluminum) and
standardized grades of Aluminum alloys including--1100, 1350, 2024,
2224, 5052, 5154, 5356. 5183, 6101, 6201, 6061, 6053, 7050, 7075,
8XXX series; copper alloys including, bronze (noted above) and
copper alloyed with a combination of Zinc, Tin, Aluminum, Silicon,
Nickel, Silver; Magnesium alloyed with- Aluminum, Zinc, Manganese,
Silicon, Copper, Nickel, Zirconium, Beryllium, Calcium, Cerium,
Neodymium, Strontium, Tin, Yttrium, rare earths; Iron and Iron
alloyed with Chromium, Carbon, Silicon Chromium, Nickel, Potassium,
Plutonium, Zinc, Zirconium, Titanium, Lead, Magnesium, Tin,
Scandium; and other alloys and combinations thereof.
[0118] In one aspect of the invention, the vibrational energy (from
low frequency mechanically-driven vibrators in the 8,000 to 15,000
vibrations per minute range or up to 10 KHz and/or ultrasonic
frequencies in the range of 5 to 400 kHz) is coupled through plate
54 or band 36 or both into the solidifying metal respectively in
molten metal conveyor 50 or under molten metal processing device
34. In one aspect of the invention, the vibrational energy is
mechanically coupled between 565 and 5,000 Hz. In one aspect of the
invention, the vibrational energy is mechanically driven at even
lower frequencies down to a fraction of a vibration every second up
to the 565 vibrations per second. In one aspect of the invention,
the vibrational energy is ultrasonically driven at frequencies from
the 5 kHz range to 400 kHz.
[0119] In one aspect, the cooling medium can be a liquid medium
such as water. In one aspect, the cooling medium can be a gaseous
medium such as one of compressed air or nitrogen. As noted above, a
forced air vortex system can be used to supply a gas for cooling
plate 54. In one aspect, the cooling medium can be a phase change
material. It is preferred that the cooling medium be provided at a
sufficient rate to undercool the metal adjacent the band 36 (less
than 5 to 10.degree. C. above the liquidus temperature of the alloy
or even lower than the liquidus temperature).
[0120] In one aspect of the invention, equiaxed grains within the
cast product are obtained without the necessity of adding impurity
particles, such as titanium boride, into the metal or metallic
alloy to increase the number of grains and improve uniform
heterogeneous solidification. Instead of using the nucleating
agents, in one aspect of the invention, vibrational energy can be
used to create nucleating sites.
[0121] During operation, molten metal at a temperature
substantially higher than the liquidus temperature of the alloy
flows by gravity from molten metal conveyor 50 into the channel of
casting wheel 30 and optionally passes under the molten metal
processing device 34 where it is exposed to vibrational energy
(i.e.. ultrasonic or mechanically-driven vibrations). The
temperature of the molten metal flowing into the channel of the
casting depends on the type of alloy chosen, the rate of pour, and
the size of the casting wheel channel, among others. For aluminum
alloys, the casting temperature can range from 1220 F to 1350 F,
with preferred ranges in between such as for example, 1220 to 1300
F, 1220 to 1280 F, 1220 to 1270 F, 1220 to 1340 F, 1240 to 1320 F,
1250 to 1300 F, 1260 to 1310 F, 1270 to 1320 F, 1320 to 1330 F,
with overlapping and intermediate ranges and variances of +/-10
degrees F. also suitable. The channel of casting wheel 30 is cooled
to ensure that the molten metal in the channel is close to the
sub-liquidus temperature (e.g., less than 5 to 10.degree. C. above
the liquidus temperature of the alloy or even lower than the
liquidus temperature, although the pouring temperature can be much
higher than 10.degree. C.). During operation, the atmosphere about
the molten metal may be controlled by way of a shroud (not shown)
which is filled or purged for example with an inert gas such as Ar,
He, or nitrogen. The molten metal on the casting wheel 30 is
typically in a state of thermal arrest in which the molten metal is
converting from a liquid to a solid.
[0122] As a result of the undercooling close to the sub-liquidus
temperature, solidification rates are not slow enough to allow
equilibrium through the solidus-liquidus interface, which in turn
results in variations in the compositions across the cast bar. The
non-uniformity of chemical composition results in segregation. In
addition, the amount of segregation is directly related to the
diffusion coefficients of the various elements in the molten metal
as well as the heat transfer rates. Another type of segregation is
the place where constituents with the lower melting points will
freeze first.
[0123] In the ultrasonic or mechanically-driven vibration
embodiments of the invention, the vibrational energy agitates the
molten metal as it cools, regardless of the molten metal being in
molten metal conveyor 50 or under molten metal processing device
34. In this embodiment, the vibrational energy is imparted with an
energy which agitates and effectively stirs the molten metal. In
one embodiment of the invention, the mechanically-driven
vibrational energy serves to continuously stir the molten metal as
it cools. In various casting alloy processes, it is desirable to
have high concentrations of silicon into an aluminum alloy.
However, at higher silicon concentrations, silicon precipitates can
form. By "remixing" these precipitates back into the molten state,
elemental silicon may go at least partially back into solution.
Alternatively, even if the precipitates remain, the mixing will not
result in the silicon precipitates being segregated, thereby
causing more abrasive wear on the downstream metal die and
rollers.
[0124] In various metal alloy systems, the same kind of effect
occurs where one component of the alloy (typically the higher
melting point component) precipitates in a pure form in effect
"contaminating" the alloy with particles of the pure component. In
general, when casting an alloy, segregation occurs, whereby the
concentration of solute is not constant throughout the casting.
This can be caused by a variety of processes. Microsegregation,
which occurs over distances comparable to the size of the dendrite
arm spacing, is believed to be a result of the first solid formed
being of a lower concentration than the final equilibrium
concentration, resulting in partitioning of the excess solute into
the liquid, so that solid formed later has a higher concentration.
Macrosegregation occurs over similar distances to the size of the
casting. This can be caused by a number of complex processes
involving shrinkage effects as the casting solidifies, and a
variation in the density of the liquid as solute is partitioned. It
is desirable to prevent segregation during casting, to give a solid
billet that has uniform properties throughout.
[0125] Accordingly, some alloys which would benefit from the
vibrational energy treatment of the invention include those alloys
noted above.
[0126] FIG. 8 is a schematic of a casting wheel configuration
according to one embodiment of the invention specifically with a
vibrational probe device 86 having a probe (not shown) inserted
directly to the molten metal cast in a casting wheel 80. Molten
metal can be supplied to the casting wheel 80 by the molten metal
conveyor 50 (described above). The probe of the vibrational probe
device 86 would be of a construction similar to that known in the
art for ultrasonic degassing. FIG. 8 depicts a roller 82 pressing
band 88 onto a rim of the casting wheel 80. The vibrational probe
device 86 couples vibrational energy (ultrasonic or mechanically
driven energy) directly or indirectly into molten metal cast into a
channel (not shown) of the casting wheel 80. As the casting wheel
80 rotates counterclockwise, the molten metal transits under roller
82 and comes in contact with optional molten metal cooling device
84.
[0127] In this embodiment, vibrational energy can be coupled into
the molten metal in casting wheel 80 while it is being cooled
through an air or gas. In another embodiment, acoustic oscillators
(e.g., audio amplifiers) can be used to generate and transmit
acoustic waves into the molten metal. In this embodiment, the
ultrasonic or mechanically-driven vibrators discussed above would
be replaced with or supplemented by the acoustic oscillators. Audio
amplifiers suitable for the invention would provide acoustic
oscillations from 1 to 20,000 Hz. Acoustic oscillations higher or
lower than this range can be used. For example, acoustic
oscillations from 0.5 to 20 Hz; 10 to 500 Hz, 200 to 2,000 Hz,
1,000 to 5,000 Hz, 2,000 to 10,000 Hz, 5,000 to 14,000 Hz, and
10,000 to 16,000 Hz, 14,000 to 20,000 Hz, and 18,000 to 25,000 Hz
can be used. Electroacoustic transducers can be used to generate
and transmit the acoustic energy.
[0128] In one embodiment of the invention, the acoustic energy can
be coupled through a gaseous medium directly into the molten metal
where the acoustic energy vibrates the molten metal. In one
embodiment of the invention, the acoustic energy can be coupled
through a gaseous medium indirectly into the molten metal where the
acoustic energy vibrates the band 36 or other support structure
containing the molten metal, which in turn vibrates the molten
metal.
[0129] The present invention also has utility in stationary molds
and in vertical casting mills.
[0130] For stationary mills, the molten metal would be poured into
a stationary cast 62 such as the one shown in FIG. 9, which itself
has a molten metal processing device 34 (shown schematically). In
one embodiment, the molten metal processing device 34 would be
replaced or supplemented with the molten metal conveyor 50. In this
way, vibrational energy (from low frequency mechanically-driven
vibrators operating up to 10 KHz and/or ultrasonic frequencies in
the range of 5 to 400 kHz) can induce nucleation at points in the
stationary cast where the molten metal is beginning to cool from
the molten state and enter the solid state (i.e., the thermal
arrest state).
[0131] FIGS. 10A-10D depict selected components of a vertical
casting mill. More details of these components and other aspects of
a vertical casting mill are found in U.S. Pat. No. 3,520,352 (the
entire contents of which are incorporated herein by reference). As
shown in FIGS. 10A-10D, the vertical casting mill includes a molten
metal casting cavity 213, which is generally square in the
embodiment illustrated, but which may be round, elliptical,
polygonal or any other suitable shape, and which is bounded by
vertical, mutually intersecting first wall portions 215, and second
or corner wall portions, 217, situated in the top portion of the
mold. A fluid retentive envelope 219 surrounds the walls 215 and
corner members 217 of the casting cavity in spaced apart relation
thereto. Envelope 219 is adapted to receive a cooling fluid, such
as water, via an inlet conduit 221, and to discharge the cooling
fluid via an outlet conduit 223.
[0132] While the first wall portions 215 are preferably made of a
highly thermal conductive material such as copper, the second or
corner wall portions 217 are constructed of lesser thermally
conductive material, such as, for example, a ceramic material. As
shown in FIGS. 10A-10D, the corner wall portions 217 have a
generally L-shaped or angular cross section, and the vertical edges
of each corner slope downwardly and convergently toward each other.
Thus, the corner member 217 terminates at some convenient level in
the mold above the discharge end of the mold which is between the
transverse sections.
[0133] In operation, molten metal flows from a tundish 245 into a
casting mold that reciprocates vertically and a cast strand of
metal is continuously withdrawn from the mold. The molten metal is
first chilled in the mold upon contacting the cooler mold walls in
what may be considered as a first cooling zone. The tundish 245
could include as part of its configuration the molten conveyor 50
or the molten conveyor 50 could be disposed between tundish 245 and
molten metal casting cavity 213. Heat is rapidly removed from the
molten metal in this zone, and a skin of material is believed to
form completely around a central pool of molten metal.
[0134] In one embodiment of the invention, the vibrational energy
sources of the molten conveyor 50 generate nuclei in the molten
metal before the metal flows into the stationary mold. In one
embodiment of the invention, the above-described ultrasonic grain
refining is combined with above-noted ultrasonic degassing to
remove impurities from the molten bath before the metal is
cast.
[0135] FIG. 11 is a schematic depicting an embodiment of the
invention utilizing both ultrasonic degassing and ultrasonic grain
refinement. As shown therein, a furnace is a source of molten
metal. The molten metal is transported in a launder from the
furnace. In one embodiment of the invention, an ultrasonic degasser
is disposed in the path of launder prior to the molten metal being
provided into a casting machine (e.g., casting wheel) containing an
ultrasonic grain refiner (not shown). In one embodiment of the
invention, the ultrasonic degasser is disposed in the molten metal
conveyor 50 prior to the molten metal being provided into a casting
machine (e.g., poured onto a casting wheel).
[0136] While not limited to the following specific ultrasonic
degassers, the '336 patent describes degassers which are suitable
for different embodiments of the present invention. One suitable
degasser would be an ultrasonic device having an ultrasonic
transducer; an elongated probe comprising a first end and a second
end, the first end attached to the ultrasonic transducer and the
second end comprising a tip; and a purging gas delivery system,
wherein the purging gas delivery system may comprise a purging gas
inlet and a purging gas outlet. In some embodiments, the purging
gas outlet may be within about 10 cm (or 5 cm, or 1 cm) of the tip
of the elongated probe, while in other embodiments, the purging gas
outlet may be at the tip of the elongated probe. In addition, the
ultrasonic device may comprise multiple probe assemblies and/or
multiple probes per ultrasonic transducer.
[0137] While not limited to the following specific ultrasonic
degassers, the '397 patent describes degassers which are also
suitable for different embodiments of the present invention. One
suitable degasser would be an ultrasonic device having an
ultrasonic transducer; a probe attached to the ultrasonic
transducer, the probe comprising a tip; and a gas delivery system,
the gas delivery system comprising a gas inlet, a gas flow path
through the probe, and a gas outlet at the tip of the probe. In an
embodiment, the probe may be an elongated probe comprising a first
end and a second end, the first end attached to the ultrasonic
transducer and the second end comprising a tip. Moreover, the probe
may comprise stainless steel, titanium, niobium, a ceramic, and the
like, or a combination of any of these materials. In another
embodiment, the ultrasonic probe may be a unitary SIALON probe with
the integrated gas delivery system therethrough. In yet another
embodiment, the ultrasonic device may comprise multiple probe
assemblies and/or multiple probes per ultrasonic transducer.
[0138] In one embodiment of the invention, ultrasonic
degasification using for example the ultrasonic probes discussed
above complements ultrasonic grain refinement. In various examples
of ultrasonic degasification, a purging gas is added to the molten
metal e.g., by way of the probes discussed above at a rate in a
range from about 1 to about 50 L/min. By a disclosure that the flow
rate is in a range from about 1 to about 50 L/min, the flow rate
may be about 1, about 2, about 3, about 4, about 5, about 6, about
7, about 8, about 9, about 10, about 11, about 12, about 13, about
14, about 15, about 16, about 17, about 18, about 19, about 20,
about 21, about 22, about 23, about 24, about 25, about 26, about
27, about 28, about 29, about 30, about 31, about 32, about 33,
about 34, about 35, about 36, about 37, about 38, about 39, about
40, about 41, about 42, about 43, about 44, about 45, about 46,
about 47, about 48, about 49, or about 50 L/min. Additionally, the
flow rate may be within any range from about 1 to about 50 L/min
(for example, the rate is in a range from about 2 to about 20
L/min), and this also includes any combination of ranges between
about 1 and about 50 L/min. Intermediate ranges are possible.
Likewise, all other ranges disclosed herein should be interpreted
in a similar manner.
[0139] Embodiments of the present invention related to ultrasonic
degasification and ultrasonic grain refinement may provide systems,
methods, and/or devices for the ultrasonic degassing of molten
metals included but not limited to, aluminum, copper, steel, zinc,
magnesium, and the like, or combinations of these and other metals
(e.g., alloys). The processing or casting of articles from a molten
metal may require a bath containing the molten metal, and this bath
of the molten metal may be maintained at elevated temperatures. For
instance, molten copper may be maintained at temperatures of around
1100.degree. C., while molten aluminum may be maintained at
temperatures of around 750.degree. C.
[0140] As used herein, the terms "bath," "molten metal bath," and
the like are meant to encompass any container that might contain a
molten metal, inclusive of vessel, crucible, trough, launder,
furnace, ladle, and so forth. The bath and molten metal bath terms
are used to encompass batch, continuous, semi-continuous, etc.,
operations and, for instance, where the molten metal is generally
static (e.g., often associated with a crucible) and where the
molten metal is generally in motion (e.g., often associated with a
launder).
[0141] Many instruments or devices may be used to monitor, to test,
or to modify the conditions of the molten metal in the bath, as
well as for the final production or casting of the desired metal
article. There is a need for these instruments or devices to better
withstand the elevated temperatures encountered in molten metal
baths, beneficially having a longer lifetime and limited to no
reactivity with the molten metal, whether the metal is (or the
metal comprises) aluminum, or copper, or steel, or zinc, or
magnesium, and so forth.
[0142] Furthermore, molten metals may have one or more gasses
dissolved in them, and these gasses may negatively impact the final
production and casting of the desired metal article, and/or the
resulting physical properties of the metal article itself. For
instance, the gas dissolved in the molten metal may comprise
hydrogen, oxygen, nitrogen, sulfur dioxide, and the like, or
combinations thereof. In some circumstances, it may be advantageous
to remove the gas, or to reduce the amount of the gas in the molten
metal. As an example, dissolved hydrogen may be detrimental in the
casting of aluminum (or copper, or other metal or alloy) and,
therefore, the properties of finished articles produced from
aluminum (or copper, or other metal or alloy) may be improved by
reducing the amount of entrained hydrogen in the molten bath of
aluminum (or copper, or other metal or alloy). Dissolved hydrogen
over 0.2 ppm, over 0.3 ppm, or over 0.5 ppm, on a mass basis, may
have detrimental effects on the casting rates and the quality of
resulting aluminum (or copper, or other metal or alloy) rods and
other articles. Hydrogen may enter the molten aluminum (or copper,
or other metal or alloy) bath by its presence in the atmosphere
above the bath containing the molten aluminum (or copper, or other
metal or alloy), or it may be present in aluminum (or copper, or
other metal or alloy) feedstock starting material used in the
molten aluminum (or copper, or other metal or alloy) bath.
[0143] Attempts to reduce the amounts of dissolved gasses in molten
metal baths have not been completely successful. Often, these
processes in the past involved additional and expensive equipment,
as well as potentially hazardous materials. For instance, a process
used in the metal casting industry to reduce the dissolved gas
content of a molten metal may consist of rotors made of a material
such as graphite, and these rotors may be placed within the molten
metal bath. Chlorine gas additionally may be added to the molten
metal bath at positions adjacent to the rotors within the molten
metal bath. While chlorine gas addition may be successful in
reducing, for example, the amount of dissolved hydrogen in a molten
metal bath in some situations, this conventional process has
noticeable drawbacks, not the least of which are cost, complexity,
and the use of potentially hazardous and potentially
environmentally harmful chlorine gas.
[0144] Additionally, molten metals may have impurities present in
them, and these impurities may negatively impact the final
production and casting of the desired metal article, and/or the
resulting physical properties of the metal article itself. For
instance, the impurity in the molten metal may comprise an alkali
metal or other metal that is neither required nor desired to be
present in the molten metal. Small percentages of certain metals
are present in various metal alloys, and such metals would not be
considered to be impurities. As non-limiting examples, impurities
may comprise lithium, sodium, potassium, lead, and the like, or
combinations thereof. Various impurities may enter a molten metal
bath (aluminum, copper, or other metal or alloy) by their presence
in the incoming metal feedstock starting material used in the
molten metal bath.
[0145] Embodiments of this invention related to ultrasonic
degasification and ultrasonic grain refinement may provide methods
for reducing an amount of a dissolved gas in a molten metal bath
or, in alternative language, methods for degassing molten metals.
One such method may include operating an ultrasonic device in the
molten metal bath, and introducing a purging gas into the molten
metal bath in close proximity to the ultrasonic device. The
dissolved gas may be or may comprise oxygen, hydrogen, sulfur
dioxide, and the like, or combinations thereof. For example, the
dissolved gas may be or may comprise hydrogen. The molten metal
bath may comprise aluminum, copper, zinc, steel, magnesium, and the
like, or mixtures and/or combinations thereof (e.g., including
various alloys of aluminum, copper, zinc, steel, magnesium, etc.).
In some embodiments related to ultrasonic degasification and
ultrasonic grain refinement, the molten metal bath may comprise
aluminum, while in other embodiments, the molten metal bath may
comprise copper. Accordingly, the molten metal in the bath may be
aluminum or, alternatively, the molten metal may be copper.
[0146] Moreover, embodiments of this invention may provide methods
for reducing an amount of an impurity present in a molten metal
bath or, in alternative language, methods for removing impurities.
One such method related to ultrasonic degasification and ultrasonic
grain refinement may comprise operating an ultrasonic device in the
molten metal bath, and introducing a purging gas into the molten
metal bath in close proximity to the ultrasonic device. The
impurity may be or may comprise lithium, sodium, potassium, lead,
and the like, or combinations thereof For example, the impurity may
be or may comprise lithium or, alternatively, sodium. The molten
metal bath may comprise aluminum, copper, zinc, steel, magnesium,
and the like, or mixtures and/or combinations thereof (e.g.,
including various alloys of aluminum, copper, zinc, steel,
magnesium, etc.). In some embodiments, the molten metal bath may
comprise aluminum, while in other embodiments, the molten metal
bath may comprise copper. Accordingly, the molten metal in the bath
may be aluminum or, alternatively, the molten metal may be
copper.
[0147] The purging gas related to ultrasonic degasification and
ultrasonic grain refinement employed in the methods of degassing
and/or methods of removing impurities disclosed herein may comprise
one or more of nitrogen, helium, neon, argon, krypton, and/or
xenon, but is not limited thereto. It is contemplated that any
suitable gas may be used as a purging gas, provided that the gas
does not appreciably react with, or dissolve in, the specific
metal(s) in the molten metal bath. Additionally, mixtures or
combinations of gases may be employed. According to some
embodiments disclosed herein, the purging gas may be or may
comprise an inert gas; alternatively, the purging gas may be or may
comprise a noble gas; alternatively, the purging gas may be or may
comprise helium, neon, argon, or combinations thereof;
alternatively, the purging gas may be or may comprise helium;
alternatively, the purging gas may be or may comprise neon; or
alternatively, the purging gas may be or may comprise argon.
Additionally, in some embodiments, the conventional degassing
technique can be used in conjunction with ultrasonic degassing
processes disclosed herein. Accordingly, the purging gas may
further comprise chlorine gas in some embodiments, such as the use
of chlorine gas as the purging gas alone or in combination with at
least one of nitrogen, helium, neon, argon, krypton, and/or
xenon.
[0148] However, in other embodiments of this invention, methods
related to ultrasonic degasification and ultrasonic grain
refinement for degassing or for reducing an amount of a dissolved
gas in a molten metal bath may be conducted in the substantial
absence of chlorine gas, or with no chlorine gas present. As used
herein, a substantial absence means that no more than 5% chlorine
gas by weight may be used, based on the amount of purging gas used.
In some embodiments, the methods disclosed herein may comprise
introducing a purging gas, and this purging gas may be selected
from the group consisting of nitrogen, helium, neon, argon,
krypton, xenon, and combinations thereof.
[0149] The amount of the purging gas introduced into the bath of
molten metal may vary depending on a number of factors. Often, the
amount of the purging gas related to ultrasonic degasification and
ultrasonic grain refinement introduced in a method of degassing
molten metals (and/or in a method of removing impurities from
molten metals) in accordance with embodiments of this invention may
fall within a range from about 0.1 to about 150 standard liters/min
(L/min). In some embodiments, the amount of the purging gas
introduced may be in a range from about 0.5 to about 100 L/min,
from about 1 to about 100 L/min, from about 1 to about 50 L/min,
from about 1 to about 35 L/min, from about 1 to about 25 L/min,
from about 1 to about 10 L/min, from about 1.5 to about 20 L/min,
from about 2 to about 15 L/min, or from about 2 to about 10 L/min.
These volumetric flow rates are in standard liters per minute,
i.e., at a standard temperature (21.1.degree. C.) and pressure (101
kPa).
[0150] In continuous or semi-continuous molten metal operations,
the amount of the purging gas introduced into the bath of molten
metal may vary based on the molten metal output or production rate.
Accordingly, the amount of the purging gas introduced in a method
of degassing molten metals (and/or in a method of removing
impurities from molten metals) in accordance with such embodiments
related to ultrasonic degasification and ultrasonic grain
refinement may fall within a range from about 10 to about 500 mL/hr
of purging gas per kg/hr of molten metal (mL purging gas/kg molten
metal). In some embodiments, the ratio of the volumetric flow rate
of the purging gas to the output rate of the molten metal may be in
a range from about 10 to about 400 mL/kg; alternatively, from about
15 to about 300 mL/kg; alternatively, from about 20 to about 250
mL/kg; alternatively, from about 30 to about 200 mL/kg;
alternatively, from about 40 to about 150 mL/kg; or alternatively,
from about 50 to about 125 mL/kg. As above, the volumetric flow
rate of the purging gas is at a standard temperature (21.1.degree.
C.) and pressure (101 kPa).
[0151] Methods for degassing molten metals consistent with
embodiments of this invention and related to ultrasonic
degasification and ultrasonic grain refinement may be effective in
removing greater than about 10 weight percent of the dissolved gas
present in the molten metal bath, i.e., the amount of dissolved gas
in the molten metal bath may be reduced by greater than about 10
weight percent from the amount of dissolved gas present before the
degassing process was employed. In some embodiments, the amount of
dissolved gas present may be reduced by greater than about 15
weight percent, greater than about 20 weight percent, greater than
about 25 weight percent, greater than about 35 weight percent,
greater than about 50 weight percent, greater than about 75 weight
percent, or greater than about 80 weight percent, from the amount
of dissolved gas present before the degassing method was employed.
For instance, if the dissolved gas is hydrogen, levels of hydrogen
in a molten bath containing aluminum or copper greater than about
0.3 ppm or 0.4 ppm or 0.5 ppm (on a mass basis) may be detrimental
and, often, the hydrogen content in the molten metal may be about
0.4 ppm, about 0.5 ppm, about 0.6 ppm, about 0.7 ppm, about 0.8
ppm, about 0.9 ppm, about 1 ppm, about 1.5 ppm, about 2 ppm, or
greater than 2 ppm. It is contemplated that employing the methods
disclosed in embodiments of this invention may reduce the amount of
the dissolved gas in the molten metal bath to less than about 0.4
ppm; alternatively, to less than about 0.3 ppm; alternatively, to
less than about 0.2 ppm; alternatively, to within a range from
about 0.1 to about 0.4 ppm; alternatively, to within a range from
about 0.1 to about 0.3 ppm;
[0152] or alternatively, to within a range from about 0.2 to about
0.3 ppm. In these and other embodiments, the dissolved gas may be
or may comprise hydrogen, and the molten metal bath may be or may
comprise aluminum and/or copper.
[0153] Embodiments of this invention related to ultrasonic
degasification and ultrasonic grain refinement and directed to
methods of degassing (e.g., reducing the amount of a dissolved gas
in bath comprising a molten metal) or to methods of removing
impurities may comprise operating an ultrasonic device in the
molten metal bath. The ultrasonic device may comprise an ultrasonic
transducer and an elongated probe, and the probe may comprise a
first end and a second end. The first end may be attached to the
ultrasonic transducer and the second end may comprise a tip, and
the tip of the elongated probe may comprise niobium. Specifics on
illustrative and non-limiting examples of ultrasonic devices that
may be employed in the processes and methods disclosed herein are
described below.
[0154] As it pertains to an ultrasonic degassing process or to a
process for removing impurities, the purging gas may be introduced
into the molten metal bath, for instance, at a location near the
ultrasonic device. In one embodiment, the purging gas may be
introduced into the molten metal bath at a location near the tip of
the ultrasonic device. In one embodiment, the purging gas may be
introduced into the molten metal bath within about 1 meter of the
tip of the ultrasonic device, such as, for example, within about
100 cm, within about 50 cm, within about 40 cm, within about 30 cm,
within about 25 cm, or within about 20 cm, of the tip of the
ultrasonic device. In some embodiments, the purging gas may be
introduced into the molten metal bath within about 15 cm of the tip
of the ultrasonic device; alternatively, within about 10 cm;
alternatively, within about 8 cm; alternatively, within about 5 cm;
alternatively, within about 3 cm; alternatively, within about 2 cm;
or alternatively, within about 1 cm. In a particular embodiment,
the purging gas may be introduced into the molten metal bath
adjacent to or through the tip of the ultrasonic device.
[0155] While not intending to be bound by this theory, the use of
an ultrasonic device and the incorporation of a purging gas in
close proximity, results in a reduction in the amount of a
dissolved gas in a bath containing molten metal. The ultrasonic
energy produced by the ultrasonic device may create cavitation
bubbles in the melt, into which the dissolved gas may diffuse.
However, in the absence of the purging gas, many of the cavitation
bubbles may collapse prior to reaching the surface of the bath of
molten metal. The purging gas may lessen the amount of cavitation
bubbles that collapse before reaching the surface, and/or may
increase the size of the bubbles containing the dissolved gas,
and/or may increase the number of bubbles in the molten metal bath,
and/or may increase the rate of transport of bubbles containing
dissolved gas to the surface of the molten metal bath. The
ultrasonic device may create cavitation bubbles within close
proximity to the tip of the ultrasonic device. For instance, for an
ultrasonic device having a tip with a diameter of about 2 to 5 cm,
the cavitation bubbles may be within about 15 cm, about 10 cm,
about 5 cm, about 2 cm, or about 1 cm of the tip of the ultrasonic
device before collapsing. If the purging gas is added at a distance
that is too far from the tip of the ultrasonic device, the purging
gas may not be able to diffuse into the cavitation bubbles. Hence,
in embodiments related to ultrasonic degasification and ultrasonic
grain refinement, the purging gas is introduced into the molten
metal bath within about 25 cm or about 20 cm of the tip of the
ultrasonic device, and more beneficially, within about 15 cm,
within about 10 cm, within about 5 cm, within about 2 cm, or within
about 1 cm, of the tip of the ultrasonic device.
[0156] Ultrasonic devices in accordance with embodiments of this
invention may be in contact with molten metals such as aluminum or
copper, for example, as disclosed in U.S. Patent Publication No.
2009/0224443, which is incorporated herein by reference in its
entirety. In an ultrasonic device for reducing dissolved gas
content (e.g., hydrogen) in a molten metal, niobium or an alloy
thereof may be used as a protective barrier for the device when it
is exposed to the molten metal, or as a component of the device
with direct exposure to the molten metal.
[0157] Embodiments of the present invention related to ultrasonic
degasification and ultrasonic grain refinement may provide systems
and methods for increasing the life of components directly in
contact with molten metals. For example, embodiments of the
invention may use niobium to reduce degradation of materials in
contact with molten metals, resulting in significant quality
improvements in end products. In other words, embodiments of the
invention may increase the life of or preserve materials or
components in contact with molten metals by using niobium as a
protective barrier. Niobium may have properties, for example its
high melting point, that may help provide the aforementioned
embodiments of the invention. In addition, niobium also may form a
protective oxide barrier when exposed to temperatures of about
200.degree. C. and above.
[0158] Moreover, embodiments of the invention related to ultrasonic
degasification and ultrasonic grain refinement may provide systems
and methods for increasing the life of components directly in
contact or interfacing with molten metals. Because niobium has low
reactivity with certain molten metals, using niobium may prevent a
substrate material from degrading. Consequently, embodiments of the
invention related to ultrasonic degasification and ultrasonic grain
refinement may use niobium to reduce degradation of substrate
materials resulting in significant quality improvements in end
products. Accordingly, niobium in association with molten metals
may combine niobium's high melting point and its low reactivity
with molten metals, such as aluminum and/or copper.
[0159] In some embodiments, niobium or an alloy thereof may be used
in an ultrasonic device comprising an ultrasonic transducer and an
elongated probe. The elongated probe may comprise a first end and a
second end, wherein the first end may be attached to the ultrasonic
transducer and the second end may comprise a tip. In accordance
with this embodiment, the tip of the elongated probe may comprise
niobium (e.g., niobium or an alloy thereof). The ultrasonic device
may be used in an ultrasonic degassing process, as discussed above.
The ultrasonic transducer may generate ultrasonic waves, and the
probe attached to the transducer may transmit the ultrasonic waves
into a bath comprising a molten metal, such as aluminum, copper,
zinc, steel, magnesium, and the like, or mixtures and/or
combinations thereof (e.g., including various alloys of aluminum,
copper, zinc, steel, magnesium, etc.).
[0160] In various embodiments of the invention, a combination of
ultrasonic degassing and ultrasonic grain refinement is used. The
use of the combination of ultrasonic degassing and ultrasonic grain
refinement provides advantages both separately and in combination,
as described below. While not limited to the following discussion,
the following discussion provides an understanding of the unique
effects accompanying a combination of the ultrasonic degassing and
ultrasonic grain refinement, leading to improvement(s) in the
overall quality of a cast product which would not be expected when
either was used alone. These effects have been realized and by the
inventors in their development of this combined ultrasonic
processing.
[0161] In ultrasonic degassing, chlorine chemicals (utilized when
ultrasonic degassing is not used) are eliminated from the metal
casting process. When chlorine as a chemical is present in a molten
metal bath, it can react and form strong chemical bonds with other
foreign elements in the bath such as alkalis which might be
present. When the alkalis are present, stable salts are formed in
the molten metal bath, which could lead to inclusions in the cast
metal product which deteriorates its electrical conductivity and
mechanical properties. Without ultrasonic grain refinement,
chemical grain refiners such as titanium boride are used, but these
materials typically contain alkalis.
[0162] Accordingly, with ultrasonic degassing eliminating chlorine
as a process element and with ultrasonic grain refinement
eliminating grain refiners (a source of alkalis), the likelihood of
stable salt formation and the resultant inclusion formation in the
cast metal product is reduced substantially. Moreover, the
elimination of these foreign elements as impurities improves the
electrical conductivity of the cast metal product. Accordingly, in
one embodiment of the invention, the combination of ultrasonic
degassing and ultrasonic grain refinement means that the resultant
cast product has superior mechanical and electrical conductivity
properties, as two of the major sources of impurities are
eliminated without substituting one foreign impurity for
another.
[0163] Another advantage provided by the combination of ultrasonic
degassing and ultrasonic grain refinement relates to the fact that
both the ultrasonic degassing and ultrasonic grain refinement
effectively "stir" the molten bath, homogenizing the molten
material. When an alloy of the metal is being melted and then
cooled to solidification, intermediate phases of the alloys can
exist because of respective differences in the melting points of
different alloy proportions. In one embodiment of the invention,
both the ultrasonic degassing and ultrasonic grain refinement stir
and mix the intermediate phases back into the molten phase.
[0164] All of these advantages permit one to obtain a product which
is small-grained, having fewer impurities, fewer inclusions, better
electrical conductivity, better ductility and higher tensile
strength than would be expected when either ultrasonic degassing or
ultrasonic grain refinement was used, or when either or both were
replaced with conventional chlorine processing or chemical grain
refiners were used.
[0165] Metal Products
[0166] In one aspect of the present invention, products including a
cast metallic composition can be formed in a channel of a casting
wheel or in the casting structures discussed above without the
necessity of grain refiners and still having sub-millimeter grain
sizes. Accordingly, the cast metallic compositions can be made with
less than 5% of the compositions including the grain refiners and
still obtain sub-millimeter grain sizes. The cast metallic
compositions can be made with less than 2% of the compositions
including the grain refiners and still obtain sub-millimeter grain
sizes. The cast metallic compositions can be made with less than 1%
of the compositions including the grain refiners and still obtain
sub-millimeter grain sizes. In a preferred composition, the grain
refiners are less than 0.5% or less than 0.2% or less than 0.1%.
The cast metallic compositions can be made with the compositions
including no grain refiners and still obtain sub-millimeter grain
sizes.
[0167] The cast metallic compositions can have a variety of
sub-millimeter grain sizes depending on a number of factors
including the constituents of the "pure" or alloyed metal, the pour
rates, the pour temperatures, the rate of cooling. The list of
grain sizes available to the present invention includes the
following. For aluminum and aluminum alloys, grain sizes range from
200 to 900 micron, or 300 to 800 micron, or 400 to 700 micron, or
500 to 600 micron. For copper and copper alloys, grain sizes range
from 200 to 900 micron, or 300 to 800 micron, or 400 to 700 micron,
or 500 to 600 micron. For gold, silver, or tin or alloys thereof,
grain sizes range from 200 to 900 micron, or 300 to 800 micron, or
400 to 700 micron, or 500 to 600 micron. For magnesium or magnesium
alloys, grain sizes range from 200 to 900 micron, or 300 to 800
micron, or 400 to 700 micron, or 500 to 600 micron. While given in
ranges, the invention is capable of intermediate values as well. In
one aspect of the present invention, small concentrations (less
than 5%) of the grain refiners may be added to further reduce the
grain size to values between 100 and 500 micron. The cast metallic
compositions can include aluminum, copper, magnesium, zinc, lead,
gold, silver, tin, bronze, brass, and alloys thereof.
[0168] The cast metallic compositions can be drawn or otherwise
formed into bar stock, rod, stock, sheet stock, wires, billets, and
pellets.
[0169] Computerized Control
[0170] The controller 500 in FIG. 1 (for example) can be
implemented by way of the computer system 1201 shown in FIG. 12.
The computer system 1201 may be used as the controller 500 to
control the casting systems noted above or any other casting system
or apparatus employing the ultrasonic treatment of the present
invention. While depicted singularly in FIG. 1 as one controller,
controller 500 may include discrete and separate processors in
communication with each other and/or dedicated to a specific
control function.
[0171] In particular, the controller 500 can be programmed
specifically with control algorithms carrying out the functions
depicted by the flowchart in FIG. 13.
[0172] FIG. 13 depicts a flowchart whose elements can be programmed
or stored in a computer readable medium or in one of the data
storage devices discussed below. The flowchart of FIG. 13 depicts a
method of the present invention for inducing nucleation sites in a
metal product. At step element 1802, the programmed element would
direct the operation of pouring molten metal, into a molten metal
conveyor. At step element 1804, the programmed element would direct
the operation of cooling the molten metal for example by control of
the flow or passage of a liquid medium through a cooling channel in
or attached to the conveyor. At step element 1806, the programmed
element would direct the operation of coupling vibrational energy
directly into a receptor plate in contact with the molten metal on
the conveyor. In this element, the vibrational energy would have a
frequency and power which induces nucleation sites in the molten
metal, as discussed above. At step 1804, cooling of the molten
metal could occur by control of a cooling medium flowing by the
receptor plate as for example by control of vortex cooling blowing
across the receptor plate.
[0173] Elements such as the molten metal temperature, pouring rate,
cooling flow through the cooling channel passages, and mold
cooling, and elements related to the control and draw of the cast
product through the mill, including control of the power and
frequency of the vibrational energy sources (for example the
vibrational energy sources of molten metal conveyor 50), would be
programmed with standard software languages (discussed below) to
produce special purpose processors containing instructions to apply
the method of the present invention for inducing nucleation sites
in a metal product.
[0174] More specifically, computer system 1201 shown in FIG. 12
includes a bus 1202 or other communication mechanism for
communicating information, and a processor 1203 coupled with the
bus 1202 for processing the information. The computer system 1201
also includes a main memory 1204, such as a random access memory
(RAM) or other dynamic storage device (e.g., dynamic RAM (DRAM),
static RAM (SRAM), and synchronous DRAM (SDRAM)), coupled to the
bus 1202 for storing information and instructions to be executed by
processor 1203. In addition, the main memory 1204 may be used for
storing temporary variables or other intermediate information
during the execution of instructions by the processor 1203. The
computer system 1201 further includes a read only memory (ROM) 1205
or other static storage device (e.g., programmable read only memory
(PROM), erasable PROM (EPROM), and electrically erasable PROM
(EEPROM)) coupled to the bus 1202 for storing static information
and instructions for the processor 1203.
[0175] The computer system 1201 also includes a disk controller
1206 coupled to the bus 1202 to control one or more storage devices
for storing information and instructions, such as a magnetic hard
disk 1207, and a removable media drive 1208 (e.g., floppy disk
drive, read-only compact disc drive, read/write compact disc drive,
compact disc jukebox, tape drive, and removable magneto-optical
drive). The storage devices may be added to the computer system
1201 using an appropriate device interface (e.g., small computer
system interface (SCSI), integrated device electronics (IDE),
enhanced-IDE (E-IDE), direct memory access (DMA), or
ultra-DMA).
[0176] The computer system 1201 may also include special purpose
logic devices (e.g., application specific integrated circuits
(ASICs)) or configurable logic devices (e.g., simple programmable
logic devices (SPLDs), complex programmable logic devices (CPLDs),
and field programmable gate arrays (FPGAs)).
[0177] The computer system 1201 may also include a display
controller 1209 coupled to the bus 1202 to control a display, such
as a cathode ray tube (CRT) or liquid crystal display (LCD), for
displaying information to a computer user. The computer system
includes input devices, such as a keyboard and a pointing device,
for interacting with a computer user (e.g. a user interfacing with
controller 500) and providing information to the processor
1203.
[0178] The computer system 1201 performs a portion or all of the
processing steps of the invention (such as for example those
described in relation to providing vibrational energy to a liquid
metal in a state of thermal arrest) in response to the processor
1203 executing one or more sequences of one or more instructions
contained in a memory, such as the main memory 1204. Such
instructions may be read into the main memory 1204 from another
computer readable medium, such as a hard disk 1207 or a removable
media drive 1208. One or more processors in a multi-processing
arrangement may also be employed to execute the sequences of
instructions contained in main memory 1204. In alternative
embodiments, hard-wired circuitry may be used in place of or in
combination with software instructions. Thus, embodiments are not
limited to any specific combination of hardware circuitry and
software.
[0179] The computer system 1201 includes at least one computer
readable medium or memory for holding instructions programmed
according to the teachings of the invention and for containing data
structures, tables, records, or other data described herein.
Examples of computer readable media are compact discs, hard disks,
floppy disks, tape, magneto-optical disks, PROMs (EPROM, EEPROM,
flash EPROM), DRAM, SRAM, SDRAM, or any other magnetic medium,
compact discs (e.g., CD-ROM), or any other optical medium, or other
physical medium, a carrier wave (described below), or any other
medium from which a computer can read.
[0180] Stored on any one or on a combination of computer readable
media, the invention includes software for controlling the computer
system 1201, for driving a device or devices for implementing the
invention, and for enabling the computer system 1201 to interact
with a human user. Such software may include, but is not limited
to, device drivers, operating systems, development tools, and
applications software. Such computer readable media further
includes the computer program product of the invention for
performing all or a portion (if processing is distributed) of the
processing performed in implementing the invention.
[0181] The computer code devices of the invention may be any
interpretable or executable code mechanism, including but not
limited to scripts, interpretable programs, dynamic link libraries
(DLLs), Java classes, and complete executable programs. Moreover,
parts of the processing of the invention may be distributed for
better performance, reliability, and/or cost.
[0182] The term "computer readable medium" as used herein refers to
any medium that participates in providing instructions to the
processor 1203 for execution. A computer readable medium may take
many forms, including but not limited to, non-volatile media,
volatile media, and transmission media. Non-volatile media
includes, for example, optical, magnetic disks, and magneto-optical
disks, such as the hard disk 1207 or the removable media drive
1208. Volatile media includes dynamic memory, such as the main
memory 1204. Transmission media includes coaxial cables, copper
wire and fiber optics, including the wires that make up the bus
1202. Transmission media may also take the form of acoustic or
light waves, such as those generated during radio wave and infrared
data communications.
[0183] The computer system 1201 can also include a communication
interface 1213 coupled to the bus 1202. The communication interface
1213 provides a two-way data communication coupling to a network
link 1214 that is connected to, for example, a local area network
(LAN) 1215, or to another communications network 1216 such as the
Internet. For example, the communication interface 1213 may be a
network interface card to attach to any packet switched LAN. As
another example, the communication interface 1213 may be an
asymmetrical digital subscriber line (ADSL) card, an integrated
services digital network (ISDN) card or a modem to provide a data
communication connection to a corresponding type of communications
line. Wireless links may also be implemented. In any such
implementation, the communication interface 1213 sends and receives
electrical, electromagnetic or optical signals that carry digital
data streams representing various types of information.
[0184] The network link 1214 typically provides data communication
through one or more networks to other data devices. For example,
the network link 1214 may provide a connection to another computer
through a local network 1215 (e.g., a LAN) or through equipment
operated by a service provider, which provides communication
services through a communications network 1216. In one embodiment,
this capability permits the invention to have multiple of the above
described controllers 500 networked together for purposes such as
factory wide automation or quality control. The local network 1215
and the communications network 1216 use, for example, electrical,
electromagnetic, or optical signals that carry digital data
streams, and the associated physical layer (e.g., CAT 5 cable,
coaxial cable, optical fiber, etc). The signals through the various
networks and the signals on the network link 1214 and through the
communication interface 1213, which carry the digital data to and
from the computer system 1201 may be implemented in baseband
signals, or carrier wave based signals. The baseband signals convey
the digital data as unmodulated electrical pulses that are
descriptive of a stream of digital data bits, where the term "bits"
is to be construed broadly to mean symbol, where each symbol
conveys at least one or more information bits. The digital data may
also be used to modulate a carrier wave, such as with amplitude,
phase and/or frequency shift keyed signals that are propagated over
a conductive media, or transmitted as electromagnetic waves through
a propagation medium. Thus, the digital data may be sent as
unmodulated baseband data through a "wired" communication channel
and/or sent within a predetermined frequency band, different than
baseband, by modulating a carrier wave. The computer system 1201
can transmit and receive data, including program code, through the
network(s) 1215 and 1216, the network link 1214, and the
communication interface 1213. Moreover, the network link 1214 may
provide a connection through a LAN 1215 to a mobile device 1217
such as a personal digital assistant (PDA) laptop computer, or
cellular telephone.
[0185] More specifically, in one embodiment of the invention, a
continuous casting and rolling system (CCRS) is provided which can
produce pure electrical conductor grade aluminum rod and alloy
conductor grade aluminum rod coils directly from molten metal on a
continuous basis. The CCRS can use one or more of the computer
systems 1201 (described above) to implement control, monitoring,
and data storage.
[0186] In one embodiment of the invention, to promote yield of a
high quality aluminum rod, an advanced computer monitoring and data
acquisition (SCADA) system monitors and/or controls the rolling
mill (i.e., the CCRS). Additional variables and parameters of this
system can be displayed, charted, stored and analyzed for quality
control.
[0187] In one embodiment of the invention, one or more of the
following post production testing processes are captured in the
data acquisition system.
[0188] Eddy current flaw detectors can be used in line to
continuously monitor the surface quality of the aluminum rod.
Inclusions, if located near the surface of the rod, can be detected
since the matrix inclusion acts as a discontinuous defect. During
the casting and rolling of aluminum rod, defects in the finished
product can come from anywhere in the process. Incorrect melt
chemistry and/or excessive hydrogen in the metal can cause flaws
during the rolling process. The eddy current system is a
non-destructive test, and the control system for the CCRS can alert
the operator(s) to any one of the defects described above. The eddy
current system can detect surface defects, and classify the defects
as small, medium or large. The eddy current results can be recorded
in the SCADA system and tracked to the lot of aluminum (or other
metal being processed) and when it was produced.
[0189] Once the rod is coiled at the end of the process the bulk
mechanical and electrical properties of cast aluminum can be
measured and recorded in the SCADA system. Product quality tests
include: tensile, elongation, and conductivity. The tensile
strength is a measure of the strength of the materials and is the
maximum force the material can withstand under tension before
breaking. The elongation values are a measure of the ductility of
the material. Conductivity measurements are generally reported as a
percentage of the "international annealed copper standard" (IACS).
These product quality metrics can be recorded in the SCADA system
and tracked to the lot of aluminum and when it was produced.
[0190] In addition to eddy current data, surface analysis can be
carried out using twist tests. The cast aluminum rod is subjected
to a controlled torsion test. Defects associated with improper
solidification, inclusions and longitudinal defects created during
the rolling process are magnified and revealed on the twisted rod.
Generally, these defects manifest in the form of a seam that is
parallel to the rolling the direction. A series of parallel lines
after the rod is twisted clockwise and counterclockwise indicates
that the sample is homogeneous, while non-homogeneities in the
casting process will result in fluctuating lines. The results of
the twist tests can be recorded in the SCADA system and tracked to
the lot of aluminum and when it was produced.
[0191] Sample and Product Preparation
[0192] The samples and products can be made with the CCR system
noted above utilizing the enhanced vibrational energy coupling
and/or enhanced cooling techniques detailed above. The casting and
rolling process starts as a continuous stream of molten aluminum
from a system of melting and holding furnaces, delivered through a
refractory lined launder system to either an in-line chemical grain
refining system or the ultrasonic grain refinement system discussed
above. Additionally, the CCR system can include the ultrasonic
degassing system discussed above which uses ultrasonic acoustic
waves and a purge gas in order to remove dissolved hydrogen or
other gases from the molten aluminum. From the degasser, the metal
would flow to a molten metal filter with porous ceramic elements
which further reduce inclusions in the molten metal. The launder
system would then transport the molten aluminum to the tundish.
From the tundish, the molten aluminum would be poured into a mold
formed by the peripheral groove of a copper casting ring and a
steel band, as discussed above. Molten aluminum would be cooled to
a solid cast bar by water distributed through spray nozzles from
multi-zone water manifolds with magnetic flow meters for critical
zones. The continuous aluminum cast bar exits the casting ring onto
a bar extraction conveyor to a rolling mill.
[0193] The rolling mill can include individually driven rolling
stands that reduce the diameter of the bar. The rod would be sent
to a drawing mill where the rods would be drawn to predetermined
diameters, and then coiled. Once the rod was coiled at the end of
the process the bulk mechanical and electrical properties of cast
aluminum would be measured. The quality tests include: tensile,
elongation, and conductivity. The Tensile strength is a measure of
the strength of the materials and is the maximum force the material
can withstand under tension before breaking. The elongation values
are a measure of the ductility of the material. Conductivity
measurements are generally reported as a percentage of the
"international annealed copper standard" (IACS).)
[0194] 1) The Tensile strength is a measure of the strength of the
materials and is the maximum force the material can withstand under
tension before breaking. The tensile and elongation measurements
were carried out on the same sample. A 10'' gage length sample was
selected for tensile and elongation measurements. The rod sample
was inserted into the tensile machine. The grips were placed at
10'' gauge marks. Tensile Strength=Breaking Force (pounds)/Cross
sectional area (.pi.r.sup.2) where r(inches) is the radius of the
rod.
[0195] 2) % Elongation=((L.sub.1=L.sub.2)/L.sub.1).times.100.
L.sub.1 is the initial gage length of the material and L.sub.2 is
the final length that is obtained by placing the two broken samples
from the tension test together and measuring the failure that
occurs. Generally, the more ductile the material the more neck down
will be observed in the sample in tension.
[0196] 3) Conductivity: Conductivity measurements are generally
reported as a percentage of the "international annealed copper
standard" (IACS). Conductivity measurements are carried out using
Kelvin Bridge and details are provided in ASTM B193-02. IACS is a
unit of electrical conductivity for metals and alloys relative to a
standard annealed copper conductor; an IACS value of 100% refers to
a conductivity of 5.80.times.107 siemens per meter (58.0 MS/m) at
20.degree. C.
[0197] The continuous rod process as described above could be used
to produce not only electrical grade aluminum conductors, but also
can be used for mechanical aluminum alloys utilizing the ultrasonic
grain refining and ultrasonic degassing. For testing and quality
control, the ultrasonic grain refining process, cast bar samples
would be collected and etched.
[0198] FIG. 14 is an ACSR wire process flow diagram. It shows the
conversion of pure molten aluminum into aluminum wire that will be
used in ACSR wire. The first step in the conversion process is to
convert the molten aluminum into aluminum rod. In the next step the
rod is drawn through several dies and depending on the end diameter
this may be accomplished through one or multiple draws. Once the
rod is drawn to final diameters the wire is spooled onto reels of
weights ranging between 200 and 500 lbs. These individual reels
would be stranded around a steel stranded cable into ACSR cables
that contains several individual aluminum strands. The number of
strands and the diameter of each strand will depend on for example
on customer requirements.
[0199] FIG. 15 is an ACSS wire process flow diagram. It shows the
conversion of pure molten aluminum into aluminum wire that will be
used in ACSS wire. The first step in the conversion process is to
process the molten aluminum into aluminum rod. In the next step,
the rod is drawn through several dies and depending on the end
diameter this may be accomplished through one or multiple draws.
Once the rod is drawn to final diameters the wire is spooled onto
reels of weights ranging between 200 and 500 lbs. These individual
reels would be stranded around a steel stranded cable into ACSS
cables that contains several individual aluminum strands. The
number of strands and the diameter of each strand will depend on
the customer requirements. One difference between the ACSR and ACSS
cable is that, once the aluminum is stranded around the steel
cable, the whole cable is heat treated in furnaces to bring the
aluminum to a dead soft condition. It is important to note that in
ACSR the strength of the cable is derived from the combination of
the strengths due to the aluminum and steel cable while in the ACSS
cable most of the strength comes from the steel inside the ACSS
cable.
[0200] FIG. 16 is an aluminum strip process flow diagram, where the
strip is finally processed into metal clad cable. It shows that the
first step is to convert the molten aluminum into aluminum rod.
Following this the rod is rolled through several rolling dies to
convert it into strip, generally of about 0.375'' in width and
about 0.015 to 0.018'' thickness. The rolled strip is processed
into donut shaped pads that weigh approximately 600 lbs. It is
important to note that other widths and thicknesses can also be
produced using the rolling process, but the 0.375'' width and 0.015
to 0.018'' thickness are the most common. These pads are then heat
treated in furnaces to bring the pads to an intermediate anneal
condition. In this condition, the aluminum is neither fully hard
nor in a dead soft condition. The strip would then be used as a
protective jacket assembled as an armor of interlocking metal tape
(strip) that encloses one or more insulated circuit conductors.
[0201] The ultrasonic grain refined materials of this invention
utilizing the direct vibrational energy coupling described above
can be fabricated into the above-noted wire and cable products,
using the processes described above.
[0202] Generalized Statements of the Invention
[0203] The following statements of the invention provide one or
more characterizations of the present invention and do not limit
the scope of the present invention.
[0204] Statement 1. A molten metal conveying device (i.e., a
conveyor), comprising: a receptor plate in contact with molten
metal, at least one vibrational energy source which supplies (e.g.,
which has a configuration which supplies) vibrational energy (e.g.,
ultrasonic, mechanically-driven, and/or acoustic energy) directly
to the receptor plate in contact with molten metal, optionally
while the molten metal is cooled. The receptor plate extends from
an entrance where molten metal enters onto the receptor plate to an
exit where molten metal exits the receptor plate.
[0205] Statement 2. The device of statement 1, wherein the receptor
plate has at least one channel for passage of cooling medium.
Statement 3. The conveyor of statement 2, wherein said cooling
medium comprises at least one of water, gas, liquid metal, liquid
nitrogen, and engine oil. Statement 4. The conveyor of statement 2,
wherein said cooling channel is within the receptor plate or said
cooling channel comprises a conduit attached to the receptor plate.
Statement 5. The conveyor of statement 1, further comprising a
blower providing gas flow to cool the receptor plate.
[0206] Statement 6. The conveyor of statement 1, further comprising
an assembly which mounts said receptor plate in relationship to a
casting wheel of a casting mill or to a tundish supplying molten
metal to a mold.
[0207] Statement 7. The conveyor of statement 1, wherein at least
one vibrational energy source comprises at least one of an
ultrasonic transducer, a magnetostrictive transducer, and a
mechanically driven vibrator providing vibrational energy directly
to the receptor plate in contact with molten metal. Statement 8.
The conveyor of statement 1, wherein the vibration energy provided
to said receptor plate is in a range of frequencies up to 400
kHz.
[0208] Statement 9. The conveyor of statement 1, wherein the
receptor plate has at least one of a smooth finish, a polished
finish, a rough finish, a raised finish, a textured finish, and an
indented finish. Statement 10. The conveyor of statement 1, wherein
the receptor plate comprises at least one or more of niobium, a
niobium alloy, titanium, a titanium alloy, tantalum, a tantalum
alloy, copper, a copper alloy, rhenium, a rhenium alloy, steel,
molybdenum, a molybdenum alloy, stainless steel, a ceramic, a
composite, or a metal. Statement 11. The conveyor of statement 10,
wherein the ceramic comprises a silicon nitride ceramic. Statement
12. The conveyor of statement 11, wherein the silicon nitride
ceramic comprises a silica alumina nitride.
[0209] Statement 13. The conveyor of statement 1, wherein the at
least one vibrational energy source comprises a plurality of
transducers arranged in an ordered pattern on the receptor plate.
Statement 14. The conveyor of statement 13, wherein the ordered
pattern on the receptor plate has a higher density of said
transducers on one side of the receptor plate. Statement 15. The
conveyor of statement 14, wherein the higher density of said
transducers on one side of the receptor plate is on a molten metal
exit side. Statement 16. The conveyor of statement 14, wherein the
higher density of said transducers on one side of the receptor
plate is on a molten metal entrance side.
[0210] Statement 17. The conveyor of statement 1, wherein the at
least one vibrational energy source comprises a piezoelectric
transducer element attached to the receptor plate. Statement 18.
The conveyor of statement 17, an ultrasonic booster coupled to the
piezoelectric transducer element attached to the receptor plate.
Statement 19. The conveyor of statement 1, wherein the at least one
vibrational energy source comprises a magnetostrictive transducer
element attached to the receptor plate. Statement 20. The conveyor
of statement 1, further comprising an ultrasonic degasser inserted
in a molten metal flow channel.
[0211] Statement 21. The conveyor of statement 1, wherein the
receptor plate has a thickness of less than 10 cm. Statement 22.
The conveyor of statement 1, wherein the receptor plate has a
thickness between 0.5 cm and 5 cm, or between 1 cm and 3 cm.
Statement 23. The conveyor of statement 1, wherein the receptor
plate has a thickness between 1.5 cm and 2 cm. Statement 24. The
conveyor of statement 1, wherein the receptor plate has different
thicknesses in different sections.
[0212] Statement 25. The conveyor of statement 1, wherein the
receptor plate is disposed above a casting wheel and provides the
molten metal to a trough in the casting wheel. Statement 26. The
conveyor of statement 1, wherein the receptor plate is attached to
a vertical mold and provides the molten metal to an interior of the
vertical mold.
[0213] Statement 27. The conveyor of statement 1, wherein the
receptor plate comprises a lateral width equal to or less than a
longitudinal length, or the lateral width equal to or less than a
half of the longitudinal length; or the lateral width equal to or
less than a third of the longitudinal length. Statement 28. The
conveyor of statement 1, wherein the receptor plate comprises a
lateral width between 2.5 cm and 300 cm. Statement 29. The conveyor
of statement 1, wherein the receptor plate comprises a lateral
width which tapers down in width toward the exit.
[0214] Statement 30. The conveyor of statement 1, wherein the
receptor plate is disposed in a near horizontal orientation with
gravity forcing the molten metal to the exit. Statement 31. The
conveyor of statement 1, wherein the receptor plate is disposed
within or equal to 45 angular degrees from a horizontal orientation
with gravity forcing the molten metal to the exit. Statement 32.
The conveyor of statement 1, wherein the receptor plate is disposed
within or equal to 45 angular degrees from a vertical
orientation.
[0215] Statement 33. The conveyor of statement 1, further
comprising a controller controlling at least one of a pour rate of
the molten metal onto the receptor plate and a cooling rate of the
molten metal on the receptor plate. Statement 34. The conveyor of
statement 33, wherein the controller is programmed to adjust the
pour rate such that a height of the molten metal above the receptor
plate is between 1.25 cm and 10 cm.
[0216] Statement 35. A method for forming a metal product,
comprising: providing molten metal onto a molten conveyor which
transports the molten metal along a receptor plate of the conveyor
in contact with the molten metal; cooling the molten metal by
control of a cooling medium flowing by the receptor plate or
through a cooling passage in or attached to the receptor plate; and
coupling vibrational energy directly into the receptor plate.
[0217] Statement 36. The method of statement 35, wherein coupling
energy comprises supplying said energy from at least one of an
ultrasonic transducer or a magnetostrictive transducer or a
mechanically-driven vibrator to said probe. Statement 37. The
method of statement 36, wherein supplying said energy comprises
providing the energy in a range of frequencies from 5 and 400 kHz.
Statement 38. The method of statement 35, wherein cooling comprises
cooling the molten metal by application of at least one of water,
gas, liquid metal, liquid nitrogen, and engine oil as a coolant of
the receptor plate.
[0218] Statement 39. The method of statement 35, wherein providing
molten metal comprises pouring the molten metal from a pouring
device of a casting wheel onto the receptor plate. Statement 40.
The method of statement 39, further comprising pouring the molten
metal from the receptor plate into a trough of the casting wheel.
Statement 41. The method of statement 35, wherein providing molten
metal comprises pouring the molten metal from a tundish of a
vertical mold onto the receptor plate. Statement 42. The method of
statement 41, further comprising pouring the molten metal from the
receptor plate into the vertical mold. Statement 43. The method of
statement 35, further comprising pouring the molten metal from the
receptor plate into a continuous casting mold. Statement 44. The
method of statement 35, further comprising pouring the molten metal
from the receptor plate into a horizontal or vertical casting
mold.
[0219] Statement 45. A casting mill comprising: a casting mold
configured to cool molten metal, and the conveyor of any one of
statement s 1-34. Statement 46. The mill of statement 45, wherein
the mold comprises a continuous casting mold. Statement 47. The
mill of statement 45, wherein the mold comprises a horizontal or
vertical casting mold.
[0220] Statement 48. A system for forming a metal product,
comprising: means for providing molten metal onto a molten
conveyor; means for controlling a cooling medium flowing through a
cooling passage in or attached to a receptor plate of the conveyor
in contact with the molten metal; means for coupling vibrational
energy directly into the receptor plate; and a controller including
data inputs and control outputs, and programmed with control
algorithms which permit operation of any one of the step elements
recited in statements 35-44.
[0221] Statement 49. A system for forming a metal product,
comprising: the conveyor of any one of the statements 1-34; and a
controller including data inputs and control outputs, and
programmed with control algorithms which permit operation of any
one of the step elements recited in statements 35-44.
[0222] Statement 50. A system for forming a metal product,
comprising: a pouring device for pouring molten metal; a casting
wheel for forming a continuous casting of the metal product; and an
assembly coupling the conveyor of any one of the statements 1-34 to
the casting wheel; and a controller including data inputs and
control outputs, and programmed with control algorithms which
permit operation of any one of the step elements recited in
statements 35-44.
[0223] Numerous modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
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