U.S. patent application number 11/977999 was filed with the patent office on 2008-12-18 for high-strength and high-toughness aluminum alloy material for bumper beam and method for manufacturing the same.
This patent application is currently assigned to Hyundai Motor Company. Invention is credited to Yoo Dong Chung.
Application Number | 20080308196 11/977999 |
Document ID | / |
Family ID | 40131224 |
Filed Date | 2008-12-18 |
United States Patent
Application |
20080308196 |
Kind Code |
A1 |
Chung; Yoo Dong |
December 18, 2008 |
High-strength and high-toughness aluminum alloy material for bumper
beam and method for manufacturing the same
Abstract
The present invention discloses a high strength and high
toughness aluminum alloy for a bumper beam and a method for
manufacturing the same. The method includes: casting into a billet
an aluminum alloy which comprises aluminum as a principal element,
silicon (Si) of 0.1 wt. % or less, ferrum (Fe) of 0.2 wt. % or
less, copper of 0.45 wt. % to 0.60 wt. %, manganese (Mn) of 0.1 wt.
% to 0.20 wt. %, magnesium (Mg) of 1.3 wt. % to 1.5 wt. %, chromium
(Cr) of 0.1 wt. % or less, zinc of 4.5 wt. % to 5.1 wt. %, titanium
(Ti) of 0.04 wt. % or less, zirconium (Zr) of 0.08 wt. % to 0.12
wt. %, and inevitable impurities of 0.15 wt. % or less; extruding
the billet into a predetermined form to form an extrusion;
performing a solid-solutionization process to quench the extrusion;
subjecting the extrusion to an artificial age-hardening which is
performed at a temperature of about 120.degree. C. for 24 hours;
and subjecting the extrusion an over age-hardening which is
performed at a temperature of about 170.degree. C. to 185.degree.
C. for 1 hour to 3 hours.
Inventors: |
Chung; Yoo Dong;
(Gyeonggi-do, KR) |
Correspondence
Address: |
EDWARDS ANGELL PALMER & DODGE LLP
P.O. BOX 55874
BOSTON
MA
02205
US
|
Assignee: |
Hyundai Motor Company
Seoul
KR
|
Family ID: |
40131224 |
Appl. No.: |
11/977999 |
Filed: |
October 25, 2007 |
Current U.S.
Class: |
148/550 ;
420/532 |
Current CPC
Class: |
C22F 1/053 20130101;
C22C 21/10 20130101 |
Class at
Publication: |
148/550 ;
420/532 |
International
Class: |
C22F 1/053 20060101
C22F001/053; C22C 21/10 20060101 C22C021/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 2007 |
KR |
10-2007-0057548 |
Claims
1. An aluminum alloy material with high-strength and
high-toughness, comprising: aluminum as a principal element,
silicon (Si) of 0.1 wt. % or less, ferrum (Fe) of 0.2 wt. % or
less, copper of 0.45 wt. % to 0.60 wt. %, manganese (Mn) of 0.1 wt.
% to 0.20 wt. %, magnesium (Mg) of 1.3 wt. % to 1.5 wt. %, chromium
(Cr) of 0.1 wt. % or less, zinc of 4.5 wt. % to 5.1 wt. %, titanium
(Ti) of 0.04 wt. % or less, zirconium (Zr) of 0.08 wt. % to 0.12
wt. %, and inevitable impurities of 0.15 wt. % or less.
2. A method for manufacturing an aluminum alloy material for a
bumper beam, comprising: casting into a billet an aluminum alloy
which comprises aluminum as a principal element, silicon (Si) of
0.1 wt. % or less, ferrum (Fe) of 0.2 wt. % or less, copper of 0.45
wt. % to 0.60 wt. %, manganese (Mn) of 0.1 wt. % to 0.20 wt. %,
magnesium (Mg) of 1.3 wt. % to 1.5 wt. %, chromium (Cr) of 0.1 wt.
% or less, zinc of 4.5 wt. % to 5.1 wt. %, titanium (Ti) of 0.04
wt. % or less, zirconium (Zr) of 0.08 wt. % to 0.12 wt. %, and
inevitable impurities of 0.15 wt. % or less; extruding the billet
into a predetermined form to form an extrusion; performing a
solid-solutionization process to quench the extrusion; subjecting
the extrusion to an artificial age-hardening which is performed at
a temperature of about 120.degree. C. for 24 hours; and subjecting
the extrusion an over age-hardening which is performed at a
temperature of about 170.degree. C. to 185.degree. C. for 1 hour to
3 hours.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119(a) on Korean Patent Application No. 10-2007-0057548 filed
on Jun. 13, 2007, the entire contents of which are incorporated
herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to a high strength and high
toughness aluminum alloy suitable for a bumper beam of a vehicle
and a method of manufacturing the same.
[0004] 2. Background Art
[0005] Researches on lightweight materials for reducing the weight
of a transportation machine such as a vehicle or an aircraft have
been undergone for years, and an aluminum alloy has been the most
popular material satisfying such a need.
[0006] Since an aluminum alloy has high strength and light weight,
it is extensively used as a material for a vehicle, an aircraft,
etc. or as a material for construction industry.
[0007] An aluminum alloy is currently being used in various
industrial fields, for example, as electrical and electronic parts
of telecommunication equipments, semiconductor devices and
computers, leisure supplies, and small-sized products such as
components of a vehicle.
[0008] An aluminum alloy is grouped into a casting aluminum alloy
and a wrought aluminum alloy. The wrought aluminum alloy is further
divided into: (i) a high-strength aluminum alloy such as a
duralumin based alloy, an Al--Cu--Mg based alloy, and an Al--Zn--Mg
based alloy; and (ii) a corrosion-resistant aluminum alloy such as
an Al--Mn based alloy and an Al--Mg--Si based alloy.
[0009] An aluminum alloy is identified by four digits which are
prescribed by Aluminum Association. 1000 to 8000 series are used,
in which 2000 and 7000 series denote a high-strength aluminum
alloy.
[0010] Recently, researches on the 7000 series alloy which has the
highest strength are actively being undergone. Since the 7000
series alloy is an Al--Zn--Mg based alloy containing MgZn2, its
age-hardening property is notable.
[0011] Representative 7000 series alloys are Al7003 and Al7021.
Such alloys are precipitation hardening alloys which can have a
high-strength property when heat treatment is additionally
performed after an extrusion process and are also heat-treatable
alloys which necessarily require heat treatment to cause the
strengthening effect by forming eduction through magnesium (Mg) and
zinc (Zn).
[0012] The heat treatment can be varied depending on the kind of
the aluminum alloy. T6 heat treatment is usually used for the 7000
series alloy. The T6 heat treatment is performed such that an alloy
is heated at a temperature of 400.degree. C. to 500.degree. C. to
be solid-solutionized and then rapidly cooled in water. The cooled
alloy is heated at a temperature of about 120.degree. C. for 24
hours to be artificially age-hardened.
[0013] Here, the age-hardening is a phenomenon that a metal
material gets hardened when it is disposed at a predetermined
temperature for a predetermined time. The age-hardening can be made
by naturally or artificially. That is, a metal material can be
hardened at a room temperature, or it can be hardened with heat
treatment.
[0014] One mechanism of the age hardening is a precipitation
phenomenon that a solid exists with another solid in different
phases.
[0015] The strength of the 7000 series aluminum alloy is increased
by increasing the contents of magnesium (Mg) and zinc (Zn) and
performing the artificial age-hardening so that MgZn2 can be
precipitated. In this instance, however, its resistance to
intergranular brittleness and intergranular stress corrosion gets
lowered.
[0016] In the 7000 series aluminum alloy, an atomic ratio of Zn/Mg
is about 2 to 2.5, and the zinc (Zn) content is set to 3 wt. % to
7.5 wt. % and the magnesium (Mg) content is set to a level that can
lead to quantitative reaction of MgZn2. It is why there is little
difference between magnesium (Mg) and zinc (Zn) in solid-solution
strengthening effect, and in an alloy that magnesium (Mg) is
excessively contained, Al3Mg2 which may be produced according to a
heat treatment condition is very harmful to stress corrosion.
[0017] As described, aluminum is being used in various alloy forms.
Particularly, in the 7000 series aluminum alloy, a high strength
property is achieved by adding magnesium (Mg) and zinc (Zn) as
principal elements and the other transition elements as secondary
elements. Such a high-strength aluminum alloy, instead of a heavy
steel material, is used to manufacture various parts which require
a high strength property.
[0018] A process for manufacturing a certain product by using the
7000 series aluminum alloy is as follows. An aluminum alloy in
which various transition elements are contained with a composition
ratio which satisfies a desired characteristic is cast into a
billet. The billet is extruded in a desired product form to form a
product extrusion. The product extrusion is then subject to the T6
heat treatment (i.e., solid solutionization) before hardened by the
artificial age-hardening, whereby a high-strength product is
manufactured.
[0019] However, the high-strength aluminum alloy material of 7000
series still has a problem in that while its elongation is high,
its toughness is so low as not to be sufficiently transformed by a
crash, which makes the alloy material not suitable for an aluminum
bumper beam of a vehicle.
SUMMARY OF THE INVENTION
[0020] The present invention has been made in an effort to solve
the aforementioned problems associated with prior arts.
[0021] The present invention provides a high-strength and
high-toughness aluminum alloy, which is Al--Zn--Mg based alloy,
comprising manganese (Mn), copper (Cu) and zirconium (Zr) as
additive elements. The composition ratio of the components is
adjusted in a predetermined range. In order to manufacture a
high-strength and high-toughness aluminum alloy material, the
aluminum alloy with a predetermined composition ratio is first cast
into a billet. The billet is extruded to mold an aluminum
extrusion. A solid solutionization process is performed to quench
the aluminum extrusion in order to completely solid-solutionize
alloy elements. The aluminum extrusion is then sequentially
subjected to an artificial age-hardening process which is performed
at a temperature of 120.degree. C. for 24 hours and an over
age-hardening process (i.e., T7 heat treatment) which is performed
at a temperature of about 170.degree. C. to 185.degree. C. for 1
hour to 3 hours. Therefore, a high-strength and high-toughness
aluminum alloy material is manufactured.
[0022] One aspect of the present invention provides a aluminum
alloy material with high-strength and high-toughness, comprising:
aluminum as a principal element, silicon (Si) of 0.1 wt. % or less,
ferrum (Fe) of 0.2 wt. % or less, copper of 0.45 wt. % to 0.60 wt.
%, manganese (Mn) of 0.1 wt. % to 0.20 wt. %, magnesium (Mg) of 1.3
wt. % to 1.5 wt. %, chromium (Cr) of 0.1 wt. % or less, zinc of 4.5
wt. % to 5.1 wt. %, titanium (Ti) of 0.04 wt. % or less, zirconium
(Zr) of 0.08 wt. % to 0.12 wt. %, and inevitable impurities of 0.15
wt. % or less.
[0023] Another aspect of the present invention provides a method
for manufacturing an aluminum alloy material for a bumper beam, the
method comprising: casting an aluminum alloy into a billet, the
aluminum alloy including aluminum as a principal element, silicon
(Si) of 0.1 wt. % or less, ferrum (Fe) of 0.2 wt. % or less, copper
of 0.45 wt. % to 0.60 wt. %, manganese (Mn) of 0.1 wt. % to 0.20
wt. %, magnesium (Mg) of 1.3 wt. % to 1.5 wt. %, chromium (Cr) of
0.1 wt. % or less, zinc of 4.5 wt. % to 5.1 wt. %, titanium (Ti) of
0.04 wt. % or less, zirconium (Zr) of 0.08 wt. % to 0.12 wt. %, and
inevitable impurities of 0.15 wt. % or less; extruding the billet
into a predetermined form to form an extrusion; performing a solid
solutionization process to quench the extrusion; subjecting the
extrusion to an artificial age-hardening which is performed at a
temperature of about 120.degree. C. for 24 hours; and subjecting
the extrusion an over age-hardening which is performed at a
temperature of about 170.degree. C. to 185.degree. C. for 1 hour to
3 hours.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The above and other features of the present invention will
be described in reference to certain exemplary embodiments thereof
with reference to the attached drawings in which:
[0025] FIG. 1 is a photograph illustrating a bumper beam made of a
high-strength and high-toughness aluminum alloy material according
to an exemplary embodiment, where the bumper beam is not destroyed
but transformed; and
[0026] FIG. 2 is a photograph illustrating a bumper beam
manufactured by a conventional aluminum alloy material, where the
bumper beam is destroyed.
DETAILED DESCRIPTION
[0027] Reference will now be made in detail to the embodiments of
the present invention, examples of which are illustrated in the
accompanying drawings, wherein like reference numerals refer to the
like elements throughout. The embodiments are described below in
order to explain the present invention by referring to the
figures.
[0028] As well known, in the 7000 series aluminum alloy, an Al7021
alloy includes manganese (Mn) 0.1 wt. % or less, magnesium (Mg) of
1.2 wt % to 1.8 wt. % and zinc (Zn) of 5 wt. % to 6 wt. %. As
Aluminum Association reported, it has the tensile strength of about
420 MPa and elongation of about 13%.
[0029] Therefore, even though the Al7021-T6 alloy has the high
tensile strength, it may be easily destroyed due to low elongation
and a low impact value, so that it is not suitable for a vehicle
bumper beam.
[0030] An aluminum alloy for a bumper beam according to a preferred
embodiment of the present invention has high toughness and high
impact resistance unlike the conventional 7000 series aluminum
alloy, e.g., Al7021. To this end, the contents of manganese (Mn),
copper (Cu), zinc (Zn), and magnesium (Mg) are adjusted so as to
increase toughness, leading to have impact resistance. As shown in
Table 1, the aluminum alloy according to a preferred embodiment of
the present invention contains aluminum as a principal element, and
silicon (Si) of 0.1 wt. % or less, ferrum (Fe) of 0.2 wt. % or
less, copper of 0.45 wt. % to 0.60 wt. %, manganese (Mn) of 0.1 wt.
% to 0.20 wt. %, magnesium (Mg) of 1.3 wt. % to 1.5 wt. %, chromium
(Cr) of 0.1 wt. % or less, zinc of 4.5 wt. % to 5.1 wt. %, titanium
(Ti) of 0.04 wt. % or less, zirconium (Zr) of 0.08 wt. % to 0.12
wt. %, and inevitable impurities of 0.15 wt. % or less.
TABLE-US-00001 TABLE 1 Composition Ratio (weight %) Si Fe Cu Mn Mg
Cr Zn Ti Zr 0.11 0.21 0.45~0.6 0.1~0.2 1.3~1.5 0.11 4.5~5.1 0.041
0.08~0.12
[0031] The reason why the aluminum alloy according to a preferred
embodiment of the present invention has the above composition ratio
is described below in detail.
(1) Manganese (Mn): 0.1 wt. % to 0.20 wt. %
[0032] Manganese (Mn) is added to increase elongation when an
aluminum alloy is cast into a billet. A transition element Mn
materializes particles within an alloy to affect an elongation
improvement, but when its ratio is increased, processibility is
lowered, so that a mold or a processing machine gets worn and torn.
For these reasons, the manganese (Mn) content is restricted to a
range that elongation is increased but processibility is not
affected, i.e., 0.1 wt. % to 0.20 wt. %.
(2) Magnesium (Mg): 1.3 wt. % to 1.5 wt. %
[0033] Magnesium (Mg) is added to increase the alloy strength. If
magnesium (Mg) is excessively added, a process hardening phenomenon
of an alloy gets hastened, so that processibility is lowered, and
extrusion may be impossible according to the size and shape of a
product. In order to prevent this, the magnesium (Mg) content is
restricted to 1.3 wt. % to 1.5 wt. %.
(3) Zinc (Zn): 4.5 wt. % to 5.1 wt. %
[0034] Zinc is also added to increase the alloy strength. It is
preferable to add zinc at maximum in order to maximize the alloy
strength, but if its content is equal to or more than 6 wt. %, a
crack occurs during processing. Such a crack occurs because zinc
(Zn) is combined with magnesium (Mg) to form MgZn2, but remaining
zinc (Zn) which is not combined with magnesium (Mg) exists in the
alloy as an impurity. For these reasons, the zinc (Zn) content is
restricted to 4.5 wt. % to 5.1 wt. %.
(4) Copper (Cu): 0.45 wt. % to 0.60 wt. %
[0035] Copper (Cu) is added to increase an extrusion pressure. It
does not show good stress corrosion cracking property, but a bumper
beam is used in the circumstances that are not greatly affected by
corrosion. In the present invention, it is important to achieve
high elongation and high toughness, and copper (Cu) of 0.45 wt. %
to 0.6 wt. % is added.
(5) Zirconium (Zr): 0.08 wt. % to 0.12 wt. %
[0036] Zirconium (Zr) is added as an aluminum alloy material
according to the present invention. In order to achieve a fine
structure and high toughness, zirconium (Zr) of 0.08 wt. % to 0.12
wt. % is added.
[0037] A method for manufacturing the aluminum alloy material
according to an exemplary embodiment of the present invention is
described below in detail.
[0038] The aluminum alloy having the above described composition
ratio is first cast into a billet by a typical casting method. The
billet is extruded in a desired form to mold an aluminum extrusion.
The aluminum extrusion is then subjected to a heat treatment
process.
[0039] The heat treatment method according to the exemplary
embodiment of the present invention is performed such that alloy
elements are quenched by performing a solid solutionization process
in order to completely solid-solutionize alloy elements, is
subjected to an artificial age-hardening which is performed at a
temperature of about 120.degree. C. for 24 hours, and is
additionally subjected to an averaging (i.e., T7 heat treatment) or
over age-hardening which is performed at a temperature of about
170.degree. C. to 185.degree. C. for 1 hours to 3 hours.
[0040] An experimental example according to the exemplary
embodiment of the present invention is described below in
comparison with a comparison example. A spirit and scope of the
present invention is not limited to the experimental example
described below.
EXPERIMENTAL EXAMPLE ("EE") AND COMPARISON EXAMPLE ("CE")
[0041] Bumper beams of the experimental and comparison examples are
manufactured such that aluminum alloys having the below composition
ratios of Table 2 are cast into billets by a typical casting
method, the billets are extruded to form a bumper beam extrusion.
The bumper beam extrusions are then subjected to the T6 heat
treatment and then subjected to an over age-hardening which is
performed at a temperature of 180.degree. C. for one hour. Here,
Comparison Example represents the Al7021 alloy.
TABLE-US-00002 TABLE 2 Composition Ratio (weight %) Si Fe Cu Mn Mg
Cr Zn Ti Zr EE 0.046 0.078 0.664 0.147 1.356 0.001 4.89 0.034 0.115
CE 0.081 0.132 0.113 0.095 1.250 0.098 5.75 0.024
[0042] Tensile strength, yield strength, elongation, impact energy
of the bumper beams manufactured according to the experimental and
comparison examples are measured, and the measurement result is
shown in Table 3.
TABLE-US-00003 TABLE 3 Tensile Strength Yield Strength Impact
Energy (MPa) (MPa) Elongation (%) (Kgm/cm.sup.2) EE 404.4 371.2
15.6 8.4 CE 401.2 374.2 16.0 2.0
[0043] As can be seen in Table 3, the aluminum alloy bumper beam
manufactured by additionally performing the overaging heat
treatment process according to the present invention have four
times improved impact energy (toughness) in comparison with the
conventional aluminum alloy bumper beam even though strength and
elongation are similar.
[0044] As described above, the high-strength and high-toughness
aluminum alloy according to preferred embodiments of the present
invention has manganese (Mn), copper (Cu) and zirconium (Zr) as
principal elements, but unlike the 7000 series aluminum alloy,
e.g., Al7021, the contents of manganese (Mn), copper (Cu), zinc
(Zn), and magnesium (Mg) are adjusted to increase toughness and
have high impact resistance. The aluminum alloy with such a
composition is cast into a billet, the billet is quenched through
the solid solutionization process and is extruded into a bumper
beam extrusion, and the bumper beam extrusion is sequentially
subjected to the artificial age-hardening and over age-hardening,
thereby providing the high-strength and high-toughness bumper
beam.
[0045] Although the present invention has been described with
reference to certain exemplary embodiments thereof, it will be
understood by those skilled in the art that a variety of
modifications and variations may be made to the present invention
without departing from the spirit or scope of the present invention
defined in the appended claims, and their equivalents.
* * * * *