U.S. patent application number 11/504985 was filed with the patent office on 2008-02-21 for aluminum automotive heat shields.
This patent application is currently assigned to Commonwealth Industries, Inc.. Invention is credited to Zhong Li, Paul Platek.
Application Number | 20080041501 11/504985 |
Document ID | / |
Family ID | 39100247 |
Filed Date | 2008-02-21 |
United States Patent
Application |
20080041501 |
Kind Code |
A1 |
Platek; Paul ; et
al. |
February 21, 2008 |
Aluminum automotive heat shields
Abstract
Disclosed is a method for producing aluminum automotive heat
shields or panels such as from scrap derived molten aluminum alloy
using a continuous caster to cast the alloy into a slab. The method
comprises providing a molten aluminum alloy consisting essentially
of 0.1 to 0.7 wt. % Si, 0.2 to 0.9 wt. % Fe, 0.05 to 0.5 wt. % Cu,
0.05 to 1.3 wt. % Mn, 0.2 to 2.8 wt. % Mg, 0.3 wt. % max. Cr, 0.3
wt. % max. Zn, 0.2 wt. % max. Ti, the remainder aluminum,
incidental elements and impurities and providing a continuous
caster such as a belt caster, block caster or roll caster for
continuously casting the molten aluminum alloy. The molten aluminum
alloy is cast into a slab which is rolled into a sheet product and
then annealed. Thereafter, the sheet product is formed into the
automotive heat shield or panel with strength and formability as
required by the automotive industry.
Inventors: |
Platek; Paul; (Massillon,
OH) ; Li; Zhong; (Lexington, KY) |
Correspondence
Address: |
ANDREW ALEXANDER & ASSOCIATES
3124 KIPP AVENUE, P.O. BOX 2038
LOWER BURRELL
PA
15068
US
|
Assignee: |
Commonwealth Industries,
Inc.
|
Family ID: |
39100247 |
Appl. No.: |
11/504985 |
Filed: |
August 16, 2006 |
Current U.S.
Class: |
148/551 ;
420/534 |
Current CPC
Class: |
C22C 21/06 20130101;
C22F 1/047 20130101 |
Class at
Publication: |
148/551 ;
420/534 |
International
Class: |
C22F 1/04 20060101
C22F001/04 |
Claims
1. In the production of an aluminum automotive heat shields from a
molten: aluminum alloy using a continuous caster to cast the alloy
into a slab, the method comprising: (a) melting aluminum scrap to
provide a molten aluminum alloy consisting essentially of 0.1 to
0.7 wt. % Si, 0.2 to 0.9 wt. % Fe, 0.05 to 0.5 wt. % Cup 0.05 to
1.3 wt. % Mn, 0.2 to 2.8 wt. % Mg, 0.3 wt. % max. Cr, 0.3 wt. %
max. Zn, 0.2 wt. % max. Ti, the remainder aluminum, incidental
elements and impurities; (b) providing a continuous caster for
continuously casting said molten aluminum alloy; (c) casting said
molten aluminum alloy into a slab having a 0.2 to 2 inch thickness;
(d) rolling said slab into a sheet product; (e) annealing said
sheet product to an O-temper condition; and (f) forming said sheet
in said O-temper into said automotive heat shield.
2. In the production of the aluminum heat shield in accordance with
claim 1 wherein manganese is maintained in the range of 0.07 to 1.2
wt. %.
3. In the production of the aluminum heat shield in accordance with
claim 1 wherein magnesium is maintained in the range of 0.3 to 2.5
wt. %.
4. In the production of the aluminum heat shield in accordance with
claim 1 wherein iron is maintained in the range of 0.3 to 0.85 wt.
%.
5. In the production of the aluminum heat shield in accordance with
claim 1 wherein said continuous caster is a belt caster, a block
caster or a roll caster.
6. In the production of the aluminum heat shield or member in
accordance with claim 1 including annealing said sheet product in a
temperature range of 600.degree. to 1100.degree. F.
7. In the production of the aluminum heat shield in accordance with
claim 1 including annealing said sheet product in a temperature
range of 650.degree. to 950.degree. F.
8. In the production of the aluminum heat shield in accordance with
claim 7 including annealing for about 2 to 10 hours.
9. In the production of the aluminum heat shield in accordance with
claim 1 including continuously annealing said sheet product.
10. In the production of the aluminum heat shield in accordance
with claim 1 including hot rolling said slab to a hot rolled sheet
product.
11. In the production of the aluminum heat shield in accordance
with claim 1 including hot rolling said slab to a hot rolled sheet
product followed by cold rolling.
12. In the production of the aluminum heat shield in accordance
with claim 11 wherein said cold rolling provides a 20 to 90% gauge
reduction.
13. In the production of the aluminum heat shield in accordance
with claim 11 including annealing said cold rolled sheet
product.
14. In the production of the aluminum heat shield in accordance
with claim 13 wherein said cold rolled sheet product is annealed in
a temperature range of 600.degree. to 1000.degree. F.
15. In the production of the aluminum heat shield in accordance
with claim 1 wherein primary aluminum is added to bring said alloy
into said range.
16. In a method for the production of an aluminum automotive heat
shield from molten aluminum alloy using a continuous caster to cast
the alloy into a slab, the method comprising: (a) melting aluminum
scrap to provide a molten aluminum alloy consisting essentially of
0.1 to 0.7 wt. % Si, 0.2 to 0.9 wt. % Fe, 0.05 to 0.5 wt. % Cu,
0.05 to 1.3 wt. % Mn, 0.2 to 2.8 wt. % Mg, 0.3 wt. % max. Cr, 0.3
wt. % max. Zn, 0.2 wt. % max. Ti, the remainder aluminum,
incidental elements and impurities; (b) providing a continuous
caster for continuously casting said molten aluminum alloy; (c)
casting said molten aluminum alloy into a slab having a thickness
in the range of 0.2 inch to 2 inches; (d) hot rolling said slab
into a hot rolled sheet product, said hot rolling starting in a
temperature range of 700.degree. to 1100.degree. F. and ending in a
temperature of 400.degree. to 825.degree. F.; (e) annealing said
hot rolled sheet product to an O-temper condition, said hot rolled
sheet product in said condition having a tensile strength in the
range of 12 to 35 ksi, a yield strength in the range of 5 to 20
ksi, and an elongation greater than 15%; and (f) forming said sheet
product in said O-temper condition into said heat shield.
17. The method in accordance with claim 16 wherein magnesium is
maintained in the range of 0.3 to 2.5 wt. %.
18. The method in accordance with claim 16 wherein iron is
maintained in the range of 0.3 to 0.85 wt. %.
19. The method in accordance with claim 16 including annealing said
hot rolled sheet in a temperature range of 600.degree. to
1100.degree. F.
20. The method in accordance with claim 16 including annealing said
hot rolled sheet in a temperature range of 700.degree. to
950.degree. F.
21. The method in accordance with claim 19 including annealing for
about 2 to 10 hours.
22. The method in accordance with claim 16 including continuously
annealing said sheet product.
23. A method for producing an aluminum automotive heat shield from
molten aluminum alloy using a continuous caster to cast the alloy
into a slab, the method comprising: (a) melting aluminum scrap to
provide a molten aluminum alloy consisting essentially of 0.1 to
0.7 wt. % Si, 0.2 to 0.9 wt. % Fe, 0.05 to 0.5 wt. % Cu, 0.05 to
1.3 wt. % Mn, 0.2 to 2.8 wt. % Mg, 0.3 wt. % max. Cr, 0.3 wt. %
max. Zn, 0.2 wt. % max. Ti, the remainder aluminum, incidental
elements and impurities; (b) providing a continuous caster for
continuously casting said molten aluminum alloy; (c) casting said
molten aluminum alloy into a slab using said caster, the slab
having a thickness in the range of 0.2 to 2 inches thick; (d) hot
rolling said slab into a hot rolled sheet product; (e) cold rolling
said hot rolled sheet product to a thickness in the range of 0.01
inch to 0.1 inch to provide a cold rolled sheet product; (f)
annealing said cold rolled sheet product to provide an annealed
sheet product, said annealed sheet product having a tensile
strength in the range of 12 to 35 ksi, a yield strength in the
range of 5 to 20 ksi and an elongation greater than 15%; and (g)
forming said annealed sheet product into said automotive heat
shield.
24. The method in accordance with claim 23 including annealing said
cold rolled product to an O-temper.
25. The method in accordance with claim 23 including annealing in a
temperature range of 600.degree. to 1000.degree. F.
26. The method in accordance with claim 23 including annealing for
about 2 to 10 hours.
27. The method in accordance with claim 23 including continuously
annealing said sheet product.
28. The method in accordance with claim 23 wherein said cold
rolling provides a 20 to 90% gauge reduction.
29. A method for producing aluminum automotive heat shield from
molten aluminum alloy using a continuous caster to cast the alloy
into a slab, the method comprising: (a) providing a molten aluminum
alloy consisting essentially of 0.1 to 0.7 wt. % Si, 0.2 to 0.9 wt.
% Fe, 0.05 to 0.5 wt. % Cu, 0.05 to 1.3 wt. % Mn, 0.2 to 2.8 wt. %
Mg, 0.3 wt. % max. Cr, 0.3 wt. % max. Zn, 0.2 wt. % max. Ti, the
remainder aluminum, incidental elements and impurities; (b)
providing a continuous caster for continuously casting said molten
aluminum alloy; (c) casting said molten aluminum alloy into a slab
having a thickness in the range of 0.2 to 2 inches; (d) hot rolling
said slab into a hot rolled sheet product, said hot rolling
starting in a temperature range of 700.degree. F. to 1100.degree.
F. and ending in a temperature range of 400.degree. to 825.degree.
F.; (e) annealing said hot rolled sheet product to provide an
annealed sheet product; (f) cold rolling said annealed sheet
product to a thickness in the range of 0.01 inch to 0.1 inch to
provide a cold rolled sheet product; (g) annealing said cold rolled
sheet product to provide a sheet product having a tensile strength
in the range of 12 to 35 ksi, a yield strength in the range of 5 to
20 ksi and an elongation of greater than 15%; and (h) forming said
annealed sheet product into said automotive heat shield.
30. The method in accordance with claim 29 including batch
annealing said hot rolled sheet product.
31. The method in accordance with claim 29 including continuous
annealing said hot rolled sheet product.
32. The method in accordance with claim 29 including annealing said
hot rolled sheet product in a temperature range of 650.degree. to
1000.degree. F.
33. The method in accordance with claim 29 including annealing in a
temperature range of 650.degree. to 950.degree. F.
34. The method in accordance with claim 29 wherein said cold
rolling provides a 25 to 80% gauge reduction.
35. The method in accordance with claim 29 wherein said annealing
cold rolled sheet provides a 25 to 80% gauge reduction.
36. The method in accordance with claim 29 wherein manganese is
maintained in the range of 0.07 to 1.2 wt. %.
37. The method in accordance with claim 29 wherein magnesium is
maintained in the range of 0.3 to 2.5 wt. %.
38. The method in accordance with claim 29 wherein iron is
maintained in the range of 0.3 to 0.85 wt. %.
39. The method in accordance with claim 29 wherein said cold rolled
sheet product has a thickness in the range of 0.01 inch to 0.1
inch.
40. In an automobile, an aluminum heat shield comprised of an alloy
containing 0.1 to 0.7 wt. % Si, 0.2 to 0.9 wt. % Fe, 0.05 to 0.5
wt. % Cu, 0.05 to 1.3 wt. % Mn, 0.2 to 2.8 wt. % Mg, 0.3 wt. % max.
Cr, 0.3 wt. % max. Zn, 0.2 wt. % max. Ti, the remainder aluminum,
incidental elements and impurities, the alloy being derived from
aluminum scrap.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to aluminum alloy vehicular heat
shields or panels made from scrap aluminum and more particularly,
it relates to a method of melting scrap aluminum and casting it
into sheet having good forming characteristics and to forming the
sheet into vehicular heat shields or panels.
[0002] In many instances, continuous casting of molten aluminum
into slab utilizing twin belt, twin roll or block casters is
favored over DC casting because continuous casting can result in
substantial energy savings and total conversion cost savings
compared to the DC cast method. In the continuous casting process,
molten metal is continuously introduced to an advancing mold and a
slab is produced which may be continuously formed into a sheet
product which is collected or wound into a coil. However, the
continuous casting is not without problems. For example, it has
been discovered that the alloy composition and the processing steps
must be carefully controlled in order to have the formability level
to avoid cracking during forming and yet have the requisite
strength properties in the final product. That is, the alloy
derived from scrap and the processing thereof must be carefully
controlled to provide sheet having the formability suited to the
fabricating steps necessary to form the final product or part. If
the alloy and processing steps are not controlled, then in the
forming steps, fracture can occur and the formed parts have to be
scrapped. Thus, there is a great need for selection of an aluminum
alloy, continuous casting thereof, and thermal mechanical
processing methods which provide a sheet product having forming
characteristics and strength properties which permit forming
operations such as bending, stamping, deep drawing, stretching or
crimping during production of vehicular heat shields or panels
while avoiding problems of fracturing or cracking, for example.
[0003] With respect to the use of aluminum scrap, U.S. Pat. Nos.
4,260,419, 4,235,646 and 4,269,632 disclose that consumer scrap is
recycled into aluminum sheet and aluminum beverage containers.
Aluminum scrap is melted in a heated furnace to form a melt
composition. The melt is adjusted to form the present composition,
consisting essentially of silicon, 0.1-1.0%; iron 0.1-0.9%;
manganese 0.4-1.0%; magnesium 1.3-2.5%; copper 0.05-0.4%; and
titanium, 0-0.2%, the balance being essentially aluminum. Aluminum
scrap comprising consumer scrap, plant scrap, and can making scrap
is heated to form the melt composition, which requires a minimum
amount of adjustment to arrive at the present alloy composition.
The composition is suitable for fabrication into sheet having
strength and formability properties making it suitable for
container manufacture.
[0004] U.S. Pat. No. 6,355,090 discloses a method of producing an
aluminum alloy for automotive parts, comprising adding a scrap of
an aluminum wrought alloy or a pure aluminum ingot to an aluminum
alloy casting scrap, melting the mixture to dilute impurities, and
if necessary, adjusting elements of the resultant. According to the
above method, aluminum alloy casting scraps, which contain large
amounts of impurities and have been difficult to recycle into other
articles until now, can be converted to an aluminum alloy material
that is applicable as a wrought material usable as a higher-grade
material.
[0005] U.S. Patent Publication 2004/0213695 discloses recycle
friendly aluminum alloys which are variants of AA 3000 and AA 5000
series alloys containing higher than usual amounts of silicon and
iron. The alloys contain in percentages by weight, more than
0.6-2.0% silicon, 0.9-2.4% iron, wherein the ratio of the amount of
iron to the amount of silicon is in the range of 1.2-1.8:1. Other
components of the alloys may include 0-0.4% copper, 0-1.5%
manganese, 0-5.0% magnesium, 0-0.5% zinc, 0-3.5% chromium, 0-0.1%
titanium and the balance aluminum and incidental impurities.
[0006] U.S. Pat. No. 4,411,707 discloses an aluminum container
scrap alloy is processed by a modified chill roll cast process into
a highly formable sheet material suitable for use as a container
end stock, by employing at least a 60% cold reduction followed by
an anneal for about two hours at a temperature of from about
825.degree. F. to about 900.degree. F., followed by cold reduction
to final gauge.
[0007] U.S. Pat. No. 4,840,852 discloses Aluminum alloy products
particularly for automotive applications, e.g., panel members, may
be produced from a body of aluminum base alloy consisting
essentially of, by weight, 0.5 to 0.85% Si, 0.25 to 0.55% Mg, 0.05
to 0.4% Fe, 0.75 to 1.1% Cu, the balance essentially aluminum and
incidental elements and impurities. The alloy body may be
homogenized at a temperature in the range of 900.degree. to
1100.degree. F. and thereafter worked into a wrought product such
as sheet which may be continuously solution heat treated and
quenched and aged to a T4 condition prior to forming into vehicular
panel members, for example.
[0008] U.S. Pat. No. 5,582,660 discloses a process for fabricating
an aluminum alloy rolled sheet particularly suitable for use for an
automotive body, the process comprising: (a) providing a body of an
alloy comprising about 0.8 to about 1.3 wt. % silicon, about 0.2 to
about 0.6 wt. % magnesium, about 0.5 to about 1.8 wt. % copper,
about 0.01 to about 0.1 wt. % manganese, about 0.01 to about 0.2
wt. % iron, the balance being substantially aluminum and incidental
elements and impurities: (b) working the body to produce a sheet;
(c) solution heat treating the sheet; and (d) rapidly quenching the
sheet. In a preferred embodiment, the solution heat treat is
performed at a temperature greater than 840.degree. F. and the
sheet is rapidly quenched. The resulting sheet has an improved
combination of excellent formability and good strength.
[0009] U.S. Pat. No. 5,641,417 discloses tailored aluminum blanks,
such as structural automotive components, formed by gas tungsten
arc welding a plurality of aluminum or aluminum-alloy sections.
Preferably, a backup plate having a shallow longitudinal groove or
a plurality of longitudinal grooves and a beveled electrode are
employed. A preferred embodiment comprises the use of a multi-torch
assembly for initial cleaning and subsequent smoothing of the
resulting weld.
[0010] U.S. Pat. No. 6,086,690 discloses a process of producing an
aluminum alloy sheet article of high yield strength and ductility
suitable, in particular, for use in manufacturing automotive
panels. The process comprises casting a non heat-treatable aluminum
alloy to form a cast slab, and subjecting said cast slab to a
series of rolling steps to produce a sheet article of final gauge,
preferably followed by annealing to cause recrystallization. The
rolling steps involve hot and warm rolling the slab to form an
intermediate sheet article of intermediate gauge, cooling the
intermediate sheet article, and then warm and cold rolling the
cooled intermediate sheet to final gauge at a temperature in the
range of ambient temperature to 340.degree. C. to form said sheet
article. The series of rolling steps is carried out continuously
without intermediate coiling or full annealing of the intermediate
sheet article. The invention also relates to the alloy sheet
article produced by the process.
[0011] U.S. Pat. No. 6,193,818 discloses a process for forming an
aluminum alloy strip, including the steps of a) obtaining an
aluminum alloy consisting essentially of, by weight, 0.5 to 13% Si,
0 to 2% Mg, 0 to 2% Cu, 0 to 1% Mn, 0 to 2% Fe, other elements less
than 0.5% each and less than 2% total, and remainder Al; and b)
continuously casting the aluminum alloy between twin cooled rolls
having a force applied thereto, to obtain a cast strip of thickness
between 1.5 and 5 mm, and optionally cold rolling the cast strip.
The force applied to the rolls is maintained below an amount
represented by a straight line between a point A and a point B on a
graph of specific applied force (y-axis) vs. cast width (x-axis),
where point A is (1.5 mm, 750 tons/meter at cast width) and point B
is (5 mm, 500 tons/meter of cast width).
[0012] U.S. Pat. No. 6,207,299 discloses a coating layer for sheet
metal that is comprised of an aluminum-silicon alloy having low
emissivity. The coated sheet metal may be used as heat shield
material, particularly for heat sources having temperatures greater
than 500.degree. C., which sources may be, e.g., the hotter parts
of the conduits of automotive exhaust systems. The sheet metal may
be sheet steel coated on at least one of its principal surfaces
with a layer of a coating comprised of an alloy of silicon in the
amount of 7-11 wt. % and aluminum in the amount of 87-93 wt. %. The
coated surface of the sheet has a monochromatic emissivity less
than 0.15 for all wavelengths in the range of 1.5-15 microns.
[0013] U.S. Pat. No. 6,267,922 discloses an aluminum alloy
containing the following elements in the stated amounts:
0.6.ltoreq.Mg.ltoreq.0.9; 0.25.ltoreq.Si.ltoreq.0.6;
0.25.ltoreq.Cu.ltoreq.0.9; Fe.ltoreq.0.4; Mn.ltoreq.0.4; the total
of the amounts of Cu, Si and Mg being, in atomic weight percent,
more than 1.2% and less than 1.8%. These alloys may be subjected to
homogenization at about 470 to 560.degree. C. for more than four
hours, hot rolling at a temperature in the range of 400 to
580.degree. C., cold rolling, solutionizing at a temperature in the
range of 470 to 580.degree. C., and natural aging at ambient
temperature. The alloys may then be used as structural components
for all aluminum vehicles and may be recycled with other aluminum
alloys used in such vehicles.
[0014] U.S. Pat. No. 6,280,543 discloses an invention directed to a
continuous casting of flat rolled sheets selected from automotive
sheet, can body sheet, and endstock which exhibits properties
comparable to the same products made from World Class Ingot. A
preferable embodiment for the continuous caster is a vertical
continuous caster.
[0015] U.S. Pat. No. 5,993,573 discloses a process for continuously
casting aluminum alloys and improved aluminum alloy compositions.
The process includes the steps of (a) heating the cast strip
before, during or after hot rolling to a temperature in excess of
the output temperature of the cast strip from the chill blocks and
(b) stabilization or back annealing in an induction heater of cold
rolled strip produced from the cast strip.
[0016] U.S. Pat. No. 5,514,228 discloses a method for manufacturing
aluminum sheet stock which includes hot rolling an aluminum alloy
sheet stock, annealing and solution heat treating it without
substantial intermediate cooling and rapid quenching.
[0017] U.S. Pat. No. 5,833,775 discloses an aluminum alloy sheet
and a method for producing an aluminum alloy sheet. The aluminum
alloy sheet is useful for forming into drawn and ironed container
bodies. The sheet preferably has an after-bake yield strength of at
least about 37 ksi and an elongation of at least about 2 percent.
Preferably the sheet also has earing of less than about 2
percent.
[0018] The continuous casting of molten aluminum and rolling slab
produced therefrom into a sheet product is disclosed in various
patents. For example, U.S. Pat. No. 5,976,279 discloses a process
for continuously casting aluminum alloys and improved aluminum
alloy compositions. The process includes the steps of continuously
annealing the cold rolled strip in an intermediate anneal using an
induction heater and/or continuously annealing the hot rolled strip
in an induction heater. The alloy composition has mechanical
properties that can be varied selectively by varying the time and
temperature of a stabilizing anneal.
[0019] U.S. Pat. No. 6,264,765 discloses a method and apparatus for
casting, hot rolling and annealing non-heat treatment aluminum
alloys. The method and apparatus comprises continuous casting, hot
rolling and in-line inductively heating the aluminum sheet to
obtain the mechanical properties within the specification tolerance
of the hot rolled product.
[0020] U.S. Pat. No. 5,985,058 discloses a process for continuously
casting aluminum alloys and improved aluminum alloy compositions.
The process includes the step of heating the cast strip before,
during or after hot rolling to a temperature in excess of the
output temperature of the cast strip from the chill blocks. The
alloy composition has a relatively low magnesium content yet
possesses superior strength properties.
[0021] In spite of these disclosures, there is a great need for
selection of aluminum alloy derived from aluminum scrap and method
for-producing vehicular heat shield parts or members utilizing a
continuous caster, optimized thermal mechanical processing, to
provide good strength and levels of formability which permit ease
of forming into intricate parts without cracking.
[0022] The term "formability" when used herein is used to describe
the ease with which a sheet of metal can be shaped through plastic
deformation. Formability of a metal can be evaluated by measuring
strength, ductility, and the amount of deformation to cause
failure.
[0023] The term "aluminum" when used herein is meant to include
aluminum and its alloys.
[0024] The term "automotive" or "automobile" as used herein is
meant to include automobile and other vehicles and other transport
parts or members having similar construction. The term "heat
shield" as used herein is meant a shield made from aluminum and
used to deflect heat on an automobile or other vehicle.
SUMMARY OF THE INVENTION
[0025] It is an object of the invention to provide an improved, low
cost process utilizing aluminum scrap including continuous casting
and rolling to continuously produce aluminum sheet product having
consistent levels of formability.
[0026] It is another object of the invention to provide a process
including continuously casting a slab from a melt derived from
aluminum scrap and rolling the slab into a sheet product suitable
for use in producing vehicular parts such as heat shields.
[0027] It is still another object of the invention to provide a
process employing continuous casting of molten aluminum derived
from aluminum scrap into slab and rolling the slab into sheet
product for meeting the forming requirements, such as bending,
stamping, stretching or deep drawing of heat shields.
[0028] And yet it is another object of the invention to provide an
improved process for producing aluminum sheet product employing a
continuous caster to produce slab, continuously rolling the slab to
produce a sheet product and annealing the sheet product for forming
into vehicular heat shields or panels.
[0029] It is yet another object of the invention to provide a
process for producing vehicular formed exhaust heat shields, which
includes melting aluminum scrap to form an alloy, continuously
casting the aluminum alloy into a slab, rolling the slab to a sheet
product and annealing the sheet product to provide good levels of
formability, and thereafter forming the sheet product into a
panel.
[0030] And yet it is another object of the invention to provide a
process for casting an aluminum scrap derived molten alloy
preferably comprising 0.1 to 0.7 wt. % Si, 0.2 to 0.9 wt. % Fe,
0.05 to 0.5 wt. % Cu, 0.05 to 1.3, wt. % Mn, 0.2 to 2.8, wt. % Mg,
0.3 wt. % max. Cr, 0.3 wt. % max. Zn, 0.2 wt. % max. Ti, the
remainder aluminum, incidental elements and impurities, casting the
alloy into a slab which is hot rolled and annealed to provide a
sheet product suitable for forming into a heat shield suitable for
an automobile such as an exhaust or engine heat shield.
[0031] In accordance with these objects, there is provided a
process for producing aluminum vehicular heat shields or members
from molten aluminum alloy made from aluminum scrap, the process
using a continuous caster, e.g., a belt caster, to cast the alloy
into a slab. The method comprises providing a molten aluminum alloy
consisting essentially of 0.1 to 0.7 wt. % Si, 0.2 to 0.9 wt. % Fe,
0.05 to 0.5 wt. % Cu, 0.05, preferably 0.3, to 1.3 wt. % Mn, 0.2,
preferably 0.3, to 2.5 or 2.8 wt. % Mg, 0.3 wt. % max. Cr, 0.3 wt.
% max. Zn, 0.2 wt. % max. Ti, the remainder aluminum, incidental
elements and impurities and providing a continuous caster such as a
belt caster for continuously casting the molten aluminum alloy.
Thereafter, the sheet product is formed into heat shields such as
automotive exhaust shields to direct heat away from automotive
body.
[0032] Alternatively, the hot rolled sheet may be cold rolled after
hot rolling, and then annealed prior to the forming steps. In yet
another embodiment, the hot rolled sheet may be annealed or even
homogenized and then cold rolled to a cold rolled sheet product.
The cold rolled product can be annealed to provide a product suited
to the various forming steps.
[0033] These and other objects will become apparent from a reading
of the specification and claims appended hereto.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a schematic of a continuous caster, hot rolling
mill and rolls of sheet material.
[0035] FIG. 2 is a flow chart showing steps in the invention.
[0036] FIG. 3 is a schematic showing typical heat shields as used
on an automobile.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0037] The automotive heat shields of the invention are comprised
of an aluminum base alloy derived from aluminum scrap, the alloy
containing controlled amounts of magnesium, iron, silicon and
manganese for the required strength and formability in the sheet
product produced by the casting and thermomechanical process. The
total amounts of the alloying elements are required to be
controlled to meet the strength requirement without causing casting
difficulty in the process. Further, the amount of alloying elements
also is required to be controlled to meet the formability
requirements, especially the amount of iron, manganese and
silicon.
[0038] Accordingly, the aluminum base alloy consists essentially of
0.1 to 0.7 wt. % Si, 0.2 to 0.9 wt. % Fe, 0.05 to 0.5 wt. % Cu,
0.05 to 1.3, wt. % Mn, 0.2 to 2.8, wt. % Mg, 0.3 wt. % max. Cr, 0.3
wt. % max. Zn, 0.2 wt. % max. Ti, the remainder aluminum,
incidental elements and impurities. Preferably, magnesium is
maintained in the range of 0.3 to 2.5 wt. % and manganese is
preferably maintained in the range of 0.07 to 0.8 or 1.2 wt. %.
Further, preferably iron is maintained in the range of 0.25 or 0.3
to 0.85 wt. %, typically 0.3 to 0.8 wt. % and silicon is maintained
in the range of 0.15 to 0.65 wt. %. Impurities are preferably
limited to not more than 0.05 wt. % each and the combination of
impurities should not be greater than 0.15 wt. % total.
[0039] Thus, it will be understood that to use an alloy of the
above composition derived from aluminum scrap in the process of the
invention to form automotive heat shields having the requisite
properties requires careful control of the elements in the alloy
and the casting thereof to avoid forming intermetallic particle
structures adverse to the forming operation. That is, it will be
appreciated that in the present process, there is great difficulty
in balancing all the constituents in the alloy for strength and
procedural steps necessary to forming a sheet product having
desirable properties for forming into the final product while
avoiding undesirable properties which leads to fracture or
cracking, for example, during the forming process.
[0040] Not only is it important to have alloying elements and
impurities in the controlled amounts as herein described, but the
slab produced by continuous casting, the sheet formed from the slab
and automotive heat shields fabricated from the sheet must be
prepared in accordance with specific method steps in order to
produce sheet and automotive heat shields therefrom having the
desirable characteristics.
[0041] Thus, referring now to FIG. 1, there is shown a schematic
illustration of a belt caster and rolling mill 2 for producing
sheet suitable for forming into automotive heat shields in
accordance with the invention.
[0042] In FIG. 1, molten aluminum 10 obtained from aluminum scrap
is provided in a furnace or reservoir 12. The aluminum scrap can be
almost all types of non-heat treatable and 6xxx series heat
treatable aluminum scrap such as aluminum building and construction
materials, used beverage containers, food containers, truck trailer
siding, and auto parts, for example. Molten aluminum from reservoir
12 is typically passed through a filter and degasser (not shown)
and is then directed along line 14 to a tundish 16 from where it is
metered through a nozzle 18 into an advancing mold created by
revolving belts 20 and 22 and side dam blocks (not shown). Belts 20
and 22 are turned by means of rolls 24. Molten metal, e.g., molten
aluminum, is solidified to form a continuous slab 15 between belts
20 and 22 which are chilled using coolant spray 26. The belt caster
is described in U.S. Pat. Nos. 3,864,973; 3,921,697; 4,648,438;
4,940,076 and 4,972,900, incorporated herein by reference as if
specifically set forth. Improved nozzles for a belt caster are set
forth in U.S. Pat. No. 5,452,827, incorporated herein by
reference.
[0043] From FIG. 2, it will be seen that molten aluminum 10 is
derived from aluminum scrap. Minor adjustments may be made to the
alloy composition by adding prime aluminum when necessary. However,
it is desired to use very small amounts of prime aluminum to favor
economics of the process. Further, preferably, the aluminum scrap
is comprised of non-heat treatable and heat treatable aluminum
alloys such as, for example, Aluminum Association (AA) alloys 1050,
1100, 3003, 3004, 3105, 5052, 5754, 5182, 6061 and 6111, whose
compositions are included herein as if specifically set forth. By
"scrap derived" as used herein is meant that most of the alloy used
in the process comes from scrap, and primary aluminum is only used
when it necessary to adjust the alloy within the composition ranges
provided herein. FIG. 2 is a flow chart showing manufacturing steps
of the invention.
[0044] Another casting apparatus that may be used in the present
invention is a block caster wherein the blocks are connected to
function as belts and is included herein as a belt caster. As
described with respect to belt caster 3, a tundish and nozzle are
provided to transfer molten metal to the blocks of the block caster
wherein solidification occurs to provide a solidified slab 15 and
the blocks are chilled to aid in solidification of the molten
metal.
[0045] Yet another apparatus that may be utilized to cast a
continuous strip or slab 15 is a roll caster which includes two
rolls which rotate to provide the continuously advancing mold. As
in the belt caster, a tundish and nozzle are used to transfer
molten aluminum to the mold defined by the two rolls. Again, the
rolls are normally chilled to aid in solidification of the molten
metal into a strip or slab. The different casters are described in
U.S. Pat. No. 5,452,827. By the use of the term "continuous caster"
is meant to include all these casters.
[0046] Molten aluminum alloy of the invention is introduced to the
caster in a temperature range of about 1230.degree. to 1350.degree.
F., typically 1250.degree. to 1300.degree. F., and exits the caster
at a temperature in the range of 750.degree. to 1150.degree. F.,
typically 860.degree. to 1050.degree. F. In addition, typically the
continuous slab exiting the continuous caster has a thickness in
the range of 0.2 to 2 inches, for example, 0.25 to 1 inch. A
typical slab thickness for the belt caster is about 0.5 to 1 inch.
Belt casting speed can range from 10 to 40 ft/min, depending on the
thickness of the slab. It is important to adhere to these casting
conditions in order to achieve the volume and quality required for
the end product. Thus, the present invention provides continuous
cast slab for forming into sheet material with high cost savings
and yet retains the desirable properties such as formability.
[0047] After exiting the caster, the slab 15 is directed to rolling
mill 30 where it is rolled to form a rolled strip or flat product
34 using preferably a hot mill. Hot mill 30 is comprised of one or
more pairs of oppositely opposed rolls 32 which reduces the
thickness of the slab a controlled amount as it passes between each
stand of rolls. Three sets of hot mill stands or rolls are
illustrated in FIG. 1. For example, slab 15 having a thickness of
about 0.2 to 1 inch would be reduced to a sheet product having a
thickness of about 0.01 to 0.1 inch. Typically, for automotive heat
shields the sheet product would have a thickness in the range of
0.015 to 0.04 or 0.08 inch, for example, depending on the
application. The temperature of the slab entering hot mill 30 would
typically be in the range of about 700.degree. to 1050.degree. F.,
if no heat is added. Typically, temperature of sheet product
exiting mill 30 would be in the range of 350.degree. to 700.degree.
F. In another aspect of the invention, the slab from caster 3 may
be heated prior to hot rolling (not shown in FIG. 1) to a
temperature of 800.degree. to 1100.degree. F. to increase the
rolling temperature prior to hot rolling. Thus, slab entering the
hot mill can have temperatures of about 700.degree. to 1100.degree.
F.
[0048] Hot mill 30 can reduce the thickness of the slab about 60 to
98% of its original thickness, with a typical reduction being 75 to
95%. Depending on the end use of the sheet product, heat may be
applied to the strip or slab between hot stands in addition to or
instead of heating prior to the hot mill.
[0049] The temperature of the aluminum alloy sheet exiting the hot
mill can be in the range of about 350.degree. to 825.degree. F.,
depending on whether there was heat input before or during hot
rolling.
[0050] After hot rolling, hot rolled strip 34 can have a
deformation texture and deformed grain structure. The hot rolled
strip can have a partially or fully recrystallized grain structure
with an optimum texture depending on previous heat input and
rolling reduction. If the structure remains deformed and a
recrystallized grain structure is necessary for the end product,
then annealing of the hot rolled strip 34 can be applied to promote
recrystallization of the deformed structures. For example, it is
important for automotive application using the aluminum alloy of
the invention to have a fine, fully recrystallized grain structure
with random texture for the purpose of forming automotive heat
shields in accordance with the invention. Thus, in the present
invention, it is preferred that the hot rolled sheet be fully
annealed to O-temper in annealer 40. If the hot rolled strip is
already recrystallized with an optimum texture, then annealing is
not required. Hot rolled sheet in the fully annealed condition can
have a tensile strength in the range of 12 to 35 ksi, a yield
strength in the range of 5 to 20 ksi and an elongation greater than
15%.
[0051] Referring to FIG. 1, it will be seen in the embodiment
illustrated that the hot rolled sheet product is directed to a
continuous annealer 40, using a heater such as an infrared,
solenoidal or transverse flux induction heater. While any
continuous heater may be used, an induction heater is preferred.
Continuous anneal may also be required if cold rolling (not shown
in FIG. 1) of the hot rolled strip is necessary. Thus, the hot or
cold rolled strip may be continuously annealed in annealer 40 in a
temperature range of 600.degree. to 1100.degree. F. in time periods
from 0.3 to 60 seconds in order to effect fully recrystallized
sheet having fine grains and highly desired formability properties.
However, care is required that the sheet product is not over
annealed to the point where secondary recrystallization occurs.
Secondary recrystallization is the growth of fine grains into
undesirable coarse grains which are detrimental to formability.
[0052] Instead of continuous annealing, the hot rolled sheet may be
batch annealed. That is, hot rolled sheet 42 is wound into coils 48
or 49. These coils are then placed in a furnace and soaked in a
temperature range of 600.degree. to 1000.degree. F. for 2 to 10
hours to provide the rolled sheet in a fully annealed or 0-temper
condition. If the slab has been hot rolled to a gauge suitable for
forming, then no further thermal mechanical processing is necessary
and the sheet is in condition for the forming steps. If the slab
has been hot rolled to an intermediate gauge, then after annealing,
the annealed material is subjected to cold rolling followed by
further annealing to provide sheet in the O-temper for forming
operations.
[0053] After hot rolling, the hot rolled sheet or flat product may
be allowed to cool prior to other operations. For example, after
hot rolling, with or without annealing and cooling, the resulting
strip 42 may be cold rolled (not shown in FIG. 1) to a sheet
product having a final gauge. The cold rolling may be performed by
passing strip 42 through several pairs or stands comprising a cold
mill to provide the cold rolling required to produce the final
gauge. Cold rolling can reduce the thickness of strip 42 by 20% to
80% or 90%. Final gauge can range from 0.01 to 0.04 or even 0.1
inch, typically 0.015 to 0.08 inch, for automotive heat shield
applications. It will be appreciated that the cold rolling, which
is rolling at lower than 350.degree. F., can be performed in a cold
rolling line separate from the subject continuous casting and
rolling line.
[0054] After cold rolling to final gauge, the sheet product is
subject to further anneal to ensure the required crystallographic
texture and grain structure necessary for forming into the final
automotive product.
[0055] After hot rolling or annealing sheet 42 may be subject to a
continuous rapid quenching such as cold water quench 50 prior to
further operations. Quench 50, if used and shown after anneal, can
be located at different locations in the process.
[0056] Referring to FIG. 2, it will be seen that in an alternate
process annealed hot rolled sheet may subject to cold rolling
followed by further annealing prior to forming. In a further
embodiment or alternate process, after hot rolling, the sheet may
be directly cold rolled followed by annealing of the cold rolled
sheet prior to being formed into heat shields or members. The cold
rolled and annealed sheet, along the rolling direction, can have a
tensile strength in the range of 12 to 35 ksi, a yield strength in
the range of 5 to 20 ksi and an elongation greater than 15%.
Further, the finish gage coils may go through one or a combination
of steps before the forming process, such as tension leveling,
slitting, surface pretreatment, lubrication or cut-to-length.
[0057] All ranges provided herein are meant to include all the
numbers within the range as if specifically set forth, e.g., 1 to 5
would include 1.1, 1.2, 1.3, etc., or e.g., 2, 3, 4.
[0058] FIG. 3 is a schematic of an automobile illustrating examples
of typical uses of heat shields on automobiles. The automobile is
shown in outline form. For example, in FIG. 3, there is shown a
heat shield 52 which is often used to shield plug wires and water
hoses from exhaust heat emanating from exhaust pipe 54 of engine
56. Directing heat away from these components greatly extends their
useful life.
[0059] Another shield that is sometimes employed is located on the
firewall and is identified by the reference number 58. This is
useful in directing heat from engine 56 away from the inside of the
automobile.
[0060] And yet another use is shield 60 which is used to direct
heat from catalytic converter 62 downwards and away from the
automobile body. This use or shield is particularly important
because the catalytic converter can become very hot as it burns
pollutants in the exhaust stream.
[0061] Next in the exhaust system there is shown heat shield 64
which is used to direct downwardly the exhaust heat emanating from
pipe 66. Also, exhaust muffler 68 is provided with a shield 70 to
direct heat away from the automobile bottom and gas tank. Thus,
this shield is important from a safety standpoint.
[0062] The following example is further illustrative of the
invention.
EXAMPLE
[0063] Aluminum scrap was melted to provide an aluminum base alloy
containing 0.23 wt. % Si, 0.54 wt. % Fe, 0.16 wt. % Cu, 1.0 wt. %
of Mn, 0.91 wt. % Mg, 0.03 wt. % Cr, 0.05 wt. % Zn, 0.013 wt. % Ti,
and incidental elements and impurities. The melt was fed to a twin
belt caster at a temperature of 1280.degree. F. and solidified to
produce a 0.875 inch thick slab existing the caster at a
temperature of 1020.degree. F. The slab was directly fed into a
three stand hot rolling mills and rolled to a gauge of 0.90 inch.
The temperature of introducing the slab to the hot rolling mill was
at about 950.degree. F. and the temperature of exiting the mill was
at about 475.degree. F. The hot rolled sheet was wound into a coil.
The coil was cold rolled to a final gauge of 0.035 inch and
annealed in an anneal furnace at 850.degree. F. for four hours. The
annealed coil was tension leveled and slit into the required width.
The material had properties in the rolling direction before forming
into automotive heat shields of: ultimate tensile strength of 28.7
ksi, yield strength of 13.2 ksi, elongation of 16.3%. The material
was formed into heat shields. Thus, the scrap based alloy can be
cast in a twin belt caster, rolled into a sheet product, stamped or
shaped into an automotive heat shields with sufficient strength and
formability.
[0064] It will be seen that the continuous caster can be used to
produce a slab which can be thermomechanically treated to form a
sheet product having the properties for forming into vehicular
parts or heat shields.
[0065] Having described the presently preferred embodiments, it is
to be understood that the invention may be otherwise embodied
within the scope of the appended claims.
* * * * *