Note: Descriptions are shown in the official language in which they were submitted.
CA 02628229 2008-05-01
DESCRIPTION
6000-SERIES ALUMINIUM EXTRUDED MATERIAL SUPERIOR IN
PAINT-BAKING HARDENABILITY AND
METHOD FOR MANUFACTURING THE SAME
Technical Field
The present invention relates to a 6000-series aluminium (Al-Mg-Si
alloy) extruded material superior in paint-baking hardenability, which can be
improved in terms of yield strength when subjected to a thermal history
corresponding to paint baking as well as when subjected to thermal refining.
The present invention can be applied to members subjected to a thermal history
corresponding to paint baking, such as structural members of vehicles (e.g.,
automobiles), including frame structural members such as a side sill, a side
member, a cross member, and a door frame.
Background Art
In recent years, aluminium alloys used for structural members of
automobiles and the like have been gaining attention from the viewpoint of
global environmental protection. However, prices per unit weight of
aluminium are more expensive than those of steel. With the use of aluminium,
component costs tend to become expensive while weight reduction can be
achieved. Thus, when aluminium alloys are applied to structural members of
automobiles and the like, it is necessary to reduce the price of aluminium
extruded material to be used.
Structural members of automobiles and the like can be manufactured by
the following manufacturing steps of: extrusion molding ---> stretch
straightening
--> cutting (aluminium extrusion step); secondary processing involving bending
(depending on types of structural members of automobiles and the like); and
1
CA 02628229 2008-05-01
thermal refining -> painting -+ paint baking. During such steps of
manufacturing structural members of automobiles and the like, an aluminium
extruded material is subjected to two thermal histories corresponding to
thermal
refining and paint baking. In addition, when an aluminium extruded material in
the state after secondary processing is treated by thermal refining, the load
efficiency deteriorates, resulting in expensive product prices. Thus, it is
preferable to abolish thermal refining (if possible) or thermal refining upon
secondary processing so as to use the step of increasing the yield strength of
an
aluminium extruded material with the use of a thermal history corresponding to
paint baking.
In addition, it is preferable that structural members of automobiles and
the like have yield strengths at low levels upon secondary processing and the
yield strengths of such structural members be secured to such an extent that
the
members are applicable when used as frame structural members such as a side
sill, a side member, a cross member, and a door frame.
Further, when a 6000-series aluminium alloy, which is an Al-Mg-Si
alloy, contains MgZSi and excessive Mg (or excessive Si) in total amounts of
not
less than 0.6 wt % in stoichiometric composition, so-called "negative effects"
arise. In such case, the yield strength of such alloy after natural aging
increases compared with such strength immediately after extrusion, while the
yield strength after aging treatment decreases compared with cases in which
such alloy is not allowed to stand at room temperature. Preferably, the
aluminium extruded profile having paint-baking hardenability does not
experience yield strength increase even when allowed to stand at room
temperature and efficiently exhibits performance after being subjected to a
thermal history corresponding to paint baking.
For the application of aluminium alloy plates, various methods have
been suggested for the purposes of improving paint-baking hardenability with
the use of a thermal history corresponding paint baking. Examples of such
2
CA 02628229 2008-05-01
methods that have been disclosed include a method wherein the alloy content is
adjusted and Be or B is added (JP Patent Publication (Kokai) No. 6-2063 A
(1994)) and a method wherein the cooling rate after solution treatment is
controlled (JP Patent Publication (Kokai) No. 9-176806 A (1997)).
Further, for the application of an aluminium extruded profile, JP Patent
Publication (Kokai) No. 2004-204321 A discloses a method wherein working
strain is introduced by stretch straightening, secondary processing, or the
like
following extrusion such that aging is accelerated.
Furthermore, JP Patent Publication (Kokai) No. 2002-235158 A
discloses a method for producing an aluminum alloy extruded profile that is
superior in bending workability and has paint-baking hardenability: wherein an
aluminum alloy ingot containing Mg (0.3% to 1.3% by mass), Si (0.2% to 1.2%
by mass), and Sn (0.01% to 0.3% by mass) with the balance comprising Al with
inevitable impurities is preheated at 400 to 550 C and subjected to hot
extrusion
molding, followed by cooling to 50 C or less at a cooling rate of 50 C/min or
more; and wherein the alloy is subjected to stabilizing treatment in the
temperature range of 50 to 140 C within 24 hours (hereafter abbreviated as
"hr") after the extrusion molding in a manner such that the alloy is retained
for
0.5 to 50 hr while having a yield strength of 120 N/mm2 or less
Disclosure of the Invention
When an aluminium extruded profile having paint-baking hardenability
is applied to structural members of automobiles and the like, it is preferable
that
such aluminium extruded profile have a yield strength of 180 MP or more in
view of protection of vehicles upon crashing.
In addition, according to the above conventional techniques, a method
wherein the alloy content of Be, B, or the like is adjusted (JP Patent
Publication
(Kokai) No. 6-2063 A (1994)) requires complicated control of the content.
Also, a method wherein the cooling rate is controlled (JP Patent Publication
3
CA 02628229 2008-05-01
(Kokai) No. 9-176806 A (1997)) comprises complicated steps and causes cost
increases when applied to a thick extruded profile. These conventional
techniques are applied to aluminium rolled plates having a plate thickness of
approximately 1 mm. Thus, if such techniques are directly applied to
aluminium extruded profiles, such aluminium extruded profiles might not
sufficiently exhibit paint-baking hardenability. Further, in the case of a
method wherein working strain is introduced after extrusion (JP Patent
Publication (Kokai) No. 2004-204321 A), it is difficult to control steps of
stretch straightening and it is also difficult to carry out secondary
processing
due to an increase of yield strength as a result of work hardening.
Furthermore,
when stretch straightening is not carried out, it is necessary to carry out
secondary processing. When the above methods are applied to structural
members of automobiles and the like, the application is limited so that the
methods cannot be applied depending on parts of automobiles and the like.
Furthermore, stabilizing treatment must be carried out within 24 hr following
extrusion molding in the case of the method disclosed in JP Patent Publication
(Kokai) No. 2002-23 515 8 A.
In view of the problems of the aforementioned conventional techniques,
it is a technical objective of the present invention to provide an aluminum
extruded profile superior in paint-baking hardenability, the yield strength of
which can be secured to a level applicable to structural members of
automobiles
and the like with the use of a thermal history corresponding to paint baking
(approximately 150 to 200 C x 0.3 to 0.5 hr).
The present inventors have found that the above problems can be solved
with the use of: an aluminium extruded material obtained by retaining a 6000-
series aluminium alloy (Al-Mg-Si alloy) with a specific composition at a
predetermined temperature for a predetermined period of time immediately after
extrusion molding and allowing the alloy to be subjected to a thermal history
corresponding to paint baking; or an aluminium extruded material obtained by
4
CA 02628229 2008-05-01
s
setting a specific billet temperature and a specific cooling rate immediately
after
extrusion in the steps of manufacturing such extruded material with the use of
the above 6000-series aluminium alloy. This has led to the completion of the
present invention.
That is, first, the present invention relates to a 6000-series aluminum
extruded material containing: magnesium (0.3% to 0.7% by mass) and silicon
(0.7% to 1.5% by mass) for the ensuring of strength; copper (0.35% or less by
mass) for the ensuring of elongation; iron (0.35% or less by mass) for the
ensuring of yield strength; titanium (0.005% to 0.1% by mass) for
microcrystallization; and manganese (0.05% to 0.30% by mass), chrome (0.10%
or less by mass), and zirconium (0.10% or less by mass) for tissue
stabilization
upon extrusion (provided that at least one transition element selected from
the
group consisting of manganese, chromium, and zirconium is contained in a total
amount representing 0.05% to 0.40% by mass); with the balance comprising
aluminum with inevitable impurities. Such 6000-series aluminium extruded
material has a predetermined yield strength of 180 MPa or more with an
increase
of 60 MPa as a result of a thermal history corresponding to paint baking. The
6000-series aluminium extruded material of the present invention is an
aluminium extruded material superior in paint-baking hardenability, which can
be improved in terms of yield strength when subjected to a thermal history
corresponding to paint baking as well as when subjected to thermal refining.
The 6000-series aluminium extruded material of the present invention
can be obtained by the steps of:
(1) retaining an aluminium extruded material at 90 50 C for 1 to 24 hr
immediately after extrusion molding; and
(2) setting the billet temperature at 500 C or more and the cooling rate
at not less than 70 C/min for 4 minutes immediately after extrusion during
manufacturing of the extruded material.
Secondly, the present invention relates to a method for manufacturing a
CA 02628229 2008-05-01
6000-series aluminium extruded material, wherein an aluminum alloy ingot
containing magnesium (0.3% to 0.7% by mass), silicon (0.7% to 1.5% by mass),
copper (0.35% or less by mass), iron (0.35% or less by mass), titanium (0.005%
to 0.1% by mass), manganese (0.05% to 0.30% by mass), chrome (0.10% or less
by mass), and zirconium (0.10% or less by mass) (provided that at least one
transition element selected from the group consisting of manganese, chromium,
and zirconium is contained in a total amount representing 0.05% to 0.40% by
mass), with the balance comprising aluminum with inevitable impurities, is
subjected to extrusion molding.
As described above, the 6000-series aluminium extruded material of the
present invention can be obtained by the steps of:
(1) retaining an aluminium extruded material at 90 50 C for 1 to 24 hr
immediately after extrusion molding; and
(2) setting the billet temperature to 500 C or more and the cooling rate
at not less than 70 C/min for 4 minutes immediately after extrusion during
manufacturing of the extruded material.
According to the present invention, a 6000-series extruded profile
superior in paint-baking hardenability that has sufficient yield strength as a
result of a thermal history corresponding to paint baking and a method for
manufacturing the same are provided.
Brief Description of the Drawings
Figs. 1 A to 1C show steps of manufacturing automobile members with
the use of conventional aluminium extruded profiles and the aluminium extruded
profile of the present invention. In the figures, door frames were used as
examples for comparison and explanation. Fig. 1A shows steps of
manufacturing a conventional separate-type door frame. Fig. 1B shows steps of
manufacturing a conventional integrated door frame. Fig. I C shows steps of
manufacturing the integrated door frame of the present invention.
6
CA 02628229 2008-05-01
Fig. 2 shows a cross section of a test piece.
Fig. 3 shows a thermal history corresponding to paint baking.
Best Mode for Carrying Out the Invention
Figs. 1 A to I C show steps of manufacturing automobile members with
the use of conventional aluminium extruded profiles and the aluminium extruded
profile of the present invention. In the figures, door frames were used as
examples for comparison and explanation.
Fig. 1 A shows steps of manufacturing a conventional separate-type door
frame. A billet (BLT) consisting of an aluminium member is subjected to
extrusion steps (extrusion molding -> stretch straightening -a cutting),
bending
such as stretch bending, secondary processing involving welding with another
aluminium member, and thermal refining (e.g., T5 (200 C x 3 hr)) in that
order.
Thereafter, a painting step is carried out and then the door frame is
manufactured by paint baking at approximately 170 C x 0.3 hr.
Fig. 1 B shows steps of manufacturing a conventional integrated door
frame. A billet (BLT) consisting of an aluminium member is subjected to
extrusion steps (extrusion molding -> stretch straightening --> cutting),
secondary processing involving bending such as stretch bending, and thermal
refining (e.g., T5 (200 C x 3 hr)) in that order. Thereafter, a painting step
is
carried out and then the door frame is manufactured by paint baking at
approximately 170 C x 0.3 hr.
During the above steps of manufacturing conventional door frames, an
aluminium extruded material is subjected to two different thermal histories
corresponding to thermal refining and paint baking. In addition, when an
aluminium extruded material in the state after secondary processing is
subjected
to thermal refining, the load efficiency deteriorates, resulting in high
product
costs.
Meanwhile, fig. I C shows steps of manufacturing the integrated door
7
CA 02628229 2008-05-01
frame of the present invention. A billet (BLT) consisting of an aluminium
member is subjected to extrusion steps (extrusion molding -> stretch
straightening -> cutting), and secondary processing involving bending such as
stretch bending. Thereafter, a painting step is carried out without thermal
refining and then the door frame is manufactured by paint baking at
approximately 170 C x 0.3 hr. As described above, according to the present
invention, thermal refining is abolished such that the yield strength of an
aluminium extruded material is increased with the use of a single thermal
history
corresponding to paint baking alone.
Unlike thermal refining, in the case of paint baking, a thermal history of
approximately 170 C x 0.3 hr is used. Thus, the aging temperature of paint
baking is lower than that of general thermal refining (e.g., 200 C x 3 hr). In
addition, the retention time for paint baking is shorter than that for general
thermal refining. In order to secure the applicable structural member yield
strength, the density of an Mg2Si precipitate that is deposited upon aging
treatment is preferably equivalent to that obtained upon thermal refining,
even in
a case in which an aluminium extruded profile having paint-baking
hardenability
is treated at a low aging temperature and retained for a short period of time.
The yield strength of a 6000-series aluminium alloy can be improved with the
presence of such Mg2Si precipitate. Therefore, although magnesium and
silicon are contained in the case of the present invention, the upper limits
of the
magnesium and silicon contents are provided. This is because excessive
magnesium and silicon contents can significantly inhibit extrusion
moldability.
Further, the presence of copper results in the improvement of yield strength
and
elongation. However, excessive copper content inhibits extrusion moldability
and corrosion resistance. Furthermore, regarding iron, iron crystal is
obtained
upon casting and a bulky iron precipitate is deposited upon high-temperature
heating, resulting in the decreased density of an Mg2Si precipitate that is
deposited upon aging treatment. Accordingly, inhibition of the increase in
8
CA 02628229 2008-05-01
yield strength occurs upon aging treatment.
According to the present invention, an aluminium extruded profile
having paint-baking hardenability and a method for manufacturing the same are
established. Such aluminium extruded profile satisfies the scope of alloy
contents allowing paint-baking hardenability to be efficiently exhibited
without
the inhibition of extrusion moldability of 6000-series aluminium alloy, and
the
yield strength of such aluminium extruded profile can be secured at 180 MPa or
more with an increase of 60 MPa as a result of a thermal history corresponding
to paint baking in view of protection of vehicles upon crushing.
Alloy contents of the aluminium extruded profile having paint-baking
hardenability and the method for manufacturing of the aluminium extruded
profile of the present invention will be described below.
[Magnesium and silicon]
After extrusion, cooling is carried out such that magnesium and silicon
form a supersaturated solid solution with aluminium. During subsequent aging
treatment, an Mg2Si precipitate is formed, resulting in the improvement of
alloy
strength. In order to secure the necessary yield strength of an aluminium
extruded profile having paint-baking hardenability, the magnesium content is
preferably 0.3% or more. However, excessive magnesium content causes a
significant increase in deformation resistance upon extrusion molding. Thus,
the magnesium content is preferably 0.7% or less. Therefore, the magnesium
content is 0.3% to 0.7% and more preferably 0.4% to 0.6%.
Silicon is less likely to inhibit extrusion productivity even when the
amount thereof is larger than that of magnesium. In addition, in order to
secure
the necessary yield strength of an aluminium extruded profile having paint-
baking hardenability, the silicon content is preferably 0.7% or more. However,
when the silicon content exceeds 1.5%, silicon is less likely to form a solid
solution with aluminium as a result of cooling following extrusion. In
addition,
even with greater silicon content, extrusion productivity tends to be
inhibited as
9
CA 02628229 2008-05-01
with the case of magnesium. In view of the above, the silicon content is
preferably 1.5% or less. Thus, the silicon content is 0.7% to 1.5% and more
preferably 0.8% to 1.3%.
[Copper]
Preferably, copper is contained for the ensuring of strength and
elongation. However, excessive copper content causes a decrease in corrosion
resistance. In addition, deformation resistance upon extrusion increases so
that
productivity tends to be inhibited. In view of the above, the copper content
is
0.35% or less.
[Iron]
Upon casting, an intermetallic compound comprising iron is crystallized
in a large amount, resulting in a decrease in alloy strength. Such
intermetallic
compound is bulky and contains silicon that constitutes an Mg2Si precipitate
which causes the improvement of yield strength upon subsequent aging
treatment. Thus, the density of the precipitate decreases. In addition,
excessive iron content causes a decrease in corrosion resistance. In view of
the
above, the iron content is 0.35% or less.
[Manganese, chrome, and zirconium]
Manganese, chrome, and zirconium have effects of inhibiting
recrystallization upon extrusion and stabilizing the fibrous structure.
However,
chrome and zirconium significantly inhibit quenching sensitivity. With the
presence of chrome and zirconium, a supersaturated solid solution is less
likely
to be formed during fan air cooling following extrusion in the case of an
aluminium extruded profile that constitutes a structural member of automobiles
and the like. During subsequent aging treatment, the density of an MgZSi
precipitate that causes the improvement of yield strength decreases. In
addition,
zirconium is formed into an intermetallic compound with titanium upon casting,
resulting in fewer effects of titanium microcrystallization and the occurrence
of
cracking upon casting.
CA 02628229 2008-05-01
Manganese is relatively less likely to inhibit quenching sensitivity and is
likely to suppress recrystallization. In order to obtain recrystallization
suppression effects, the manganese content must be 0.05% or more. However,
when the manganese content is 0.30% or more, quenching sensitivity is
inhibited,
as with the cases of chrome and zirconium. In addition, a supersaturated solid
solution is less likely to be formed during fan air cooling following
extrusion in
the case of an aluminium extruded profile that constitutes a structural member
of
automobiles and the like. During a subsequent aging treatment, the density of
an Mg2Si precipitate that causes the improvement of yield strength decreases.
In view of the above, the manganese content is 0.05% to 0.30%, the
chrome content is 0.10% or less, and the zirconium content is 0.10% or less.
The total content of at least one transition element selected from the group
consisting of manganese, chrome, and zirconium is 0.05% to 0.40%.
[Titanium]
With the presence of titanium, fine crystals can be obtained upon casting.
However, the addition of titanium at an excessive amount results in saturation
of
effects that are obtained by addition of titanium. In view of the above, the
titanium content can be 0.005% to 0.10%, more preferably 0.005% to 0.05%, and
further preferably 0.005% to 0.03%.
[Inevitable impurities]
Incorporation of inevitable impurities, such as a base metal used for
casting of an aluminium alloy and an intermediate alloy comprising added
elements, occurs via different routes. Different elements are incorporated;
however, they hardly influence alloy properties as long as the content of a
single
element is 0.05% or less and the total content of such elements is 0.15% or
less.
In view of the above, the content of a single inevitable impurity is 0.05% or
less
and the total content of inevitable impurities is 0.15% or less.
[Manufacturing method: (1) Retention at 90 50 C for 1 to 24 hr immediately
after extrusion molding]
11
CA 02628229 2008-05-01
An aluminium extruded material having paint-baking hardenability
refers to an aluminium extruded profile subjected to the manufacturing steps
of:
extrusion molding -> retention at 90 50 C x 1 to 24 hr; painting; and a
thermal
history corresponding to paint baking. As a result of retention at 90 50 C x
1
to 24 hr following extrusion molding, nuclei (i.e., GPzones) of Mg2Si
precipitates are formed, and such precipitates are formed as a result of a
subsequent thermal history corresponding to paint baking. Many GPzones can
be formed as a result of retention at low temperatures. However, in the case
of
retention at less than 50 C, formation of GPzones requires a retention time of
24
hr or more, resulting in the deterioration of production efficiency. Thus, it
is
preferable that an aluminium extruded material having paint-baking
hardenability be retained at 50 C or more. In addition, in the case of
retention
at a temperature of more than 120 C, Mg2Si precipitates excessively grow,
resulting in an increase in yield strength. Thus, upon subsequent secondary
processing, workability tends to be inhibited. Thus, the temperature is
preferably retained at 120 C or less. In view of the above, retention is
carried
out at 90 50 C x 1 to 24 hr and preferably at 70 10 C x l to 12 hr
following
extrusion molding. Such retention step at 90 50 C x 1 to 24 hr may be
carried out in an atmosphere furnace, a water bath, or an oil bath following
extrusion molding and air cooling. Alternatively, such aluminium extruded
material may be allowed to stand to cool at a controlled temperature following
extrusion molding so as to be retained under thermal insulation.
Further, natural aging (causing an increase in strength due to GPzone
formation, which gradually takes place when an extruded profile is allowed to
stand at room temperature following extrusion molding) occurs in conventional
cases in which a step of retention at 90 50 C x 1 to 24 hr is not carried
out.
However, GPzones are formed during retention at 90 50 C x 1 to 24 hr. Thus,
such retention step is also effective for inhibition of subsequent natural
aging.
[Manufacturing method: (2) Setting of the billet temperature at 500 C or more
12
CA 02628229 2008-05-01
and setting the cooling rate at not less than 70 C/min for 4 minutes
immediately
after extrusion during manufacturing of an extruded material]
In the case of an aluminium extruded material having paint-baking
hardenability, the billet temperature is set at 500 C or more and the cooling
rate
is set at not less than 70 C/min for 4 minutes immediately after extrusion
during
manufacturing. Further, such aluminium extruded material having paint-baking
hardenability refers to an aluminium extruded profile retained at 90 50 C x
1
to 24 hr immediately after extrusion molding and subjected to painting and a
thermal history corresponding to paint baking. In general extrusion steps, the
billet temperature must be retained at 600 C or less so that the upper limit
of the
temperature is not predetermined. The billet heating temperature is set at
500 C or more and the cooling rate is set at not less than 70 C/min for 4
minutes
immediately after extrusion. Accordingly, a supersaturated solid solution,
which is necessary for formation of nuclei (i.e., GPzones) of Mgz-Si
precipitates
that are formed as a result of subsequent retention at 90 50 C x 1 to 24 hr,
can
be obtained. When the billet temperature is less than 500 C, a vacancy that is
necessary for GPzone formation cannot be formed inside an aluminium matrix.
In addition, when the cooling rate is less than 70 C/min, a vacancy disappears
during cooling, or solute atoms in a solid solution are deposited in the form
of
precipitates. In such case, GPzones cannot be formed by subsequent retention
at 90 50 C x 1 to 24 hr. Thus, the billet heating temperature is set at 500
C
or more and the cooling rate is set at not less than 70 C/min for 4 minutes
immediately after extrusion. Accordingly, nuclei (i.e., GPzones) of MgZSi
precipitates that are formed after retention at 90 50 C x 1 to 24 hr can be
formed. Further, a greater number of GPzones can be formed by retention at
low temperatures. However, in the case of retention at less than 50 C, GPzone
formation requires a retention time of 24 hr or more, resulting in the
deterioration of production efficiency. Thus, an aluminium extruded material
having paint-baking hardenability is preferably retained at 50 C or more. In
13
CA 02628229 2008-05-01
addition, in the case of retention at temperatures above 120 C, MgZSi
precipitates grow excessively, resulting in an increase in yield strength.
Thus,
upon subsequent secondary processing, workability tends to be inhibited. Thus,
the temperature is preferably retained at 120 C or less. In view of the above,
retention is carried out at 90 50 C x 1 to 24 hr and preferably at 70 10 C
xl
to 12 hr following extrusion molding. Such retention step at 90 50 C x 1 to
24 hr may be carried out in an atmosphere furnace, a water bath, or an oil
bath
following extrusion molding and air cooling. Alternatively, such aluminium
extruded material may be allowed to stand to cool at a controlled temperature
following extrusion molding so as to be retained under thermal insulation.
The aluminium extruded profile having paint-baking hardenability of the
present invention is preferably used as a solid-core or hollow profile. It may
be in a rectangular tube form, a cylindrical form, or an irregular form.
Examples
Hereafter, Examples and Comparative examples of the present invention
will be described.
[Manufacturing method: (1) Retention at 90 50 C for 1 to 24 hr immediately
after extrusion molding]
First, starting material contents were adjusted so as to achieve
compositions of 6000-series aluminium alloys shown as test samples Nos. 1 and
2 listed in table 1. The starting materials were dissolved and melted into
cylindrical ingots (diameter: 204 mm x length: 700 mm) having a size
appropriate for extrusion. In addition, alloy contents listed in table 1 are
expressed in analytical values. The value "0.00%" is shown for the effective
digit. Subsequently, ingots were subjected to homogenization treatment at
560 C x 4 hr.
Next, extrusion molding of ingots (billets) subjected to homogenization
treatment was carried out using an extrusion molding die at predetermined
14
CA 02628229 2008-05-01
extrusion temperatures (billet heating temperatures) under cooling conditions
listed in table 2. Thus, aluminium extruded profiles each having a cross
section of a frame structural member shown in fig. 2 were formed.
Table 1
o 0
0 0
o 0
N o 0
0 0
o 0
U o 0
,~ o 0
3 rn o ~ o 0
00 00
o 0
~, o 0
0
o 0
U N N
O O
00 00
O O
O O
--01
--O
--N
N N
Q. R.,
CA 02628229 2008-05-01
Table 2
aa aa
.~
o N N
õ ~.. '.
a~ r
bp E "O
0 3
-'
to
E
F" w
3 ~
p N N
~ } CL
o p
~ s-p ~
+
w cc
p * O O
F-bA p
p q
3 Y
o ~
.~ p Q p
cz 3 N ~ N ~ N N N N N ~ N ~ N N N N
N r-
c~ G1 ~
--N M V ~n ~p l~ 00 ,--~ N c+i ~ ~n ~O l~ 00
a o a 4~" o
x x x x ~
W o ' w W o ' W
U U
p -" N
16
CA 02628229 2008-05-01
The obtained aluminium extruded profiles having paint-baking
hardenability were evaluated by tensile experiments regarding yield strength,
strength, and breaking elongation. Tensile properties were determined by
collecting flat test pieces from the extruded profiles having paint-baking
hardenability and examining the test pieces using a tensile tester (complying
with the JIS standards) according to JIS-Z 2241. Regarding criteria, a yield
strength of 180 MPa or more was designated with "0" in view of protection of
vehicles upon crushing. A yield strength of 180 to 150 MPa was designated
with "A," because application is possible depending on sectional design. In
addition, a yield strength of less than 150 MPa was designated with "x."
Further, considering the cases involving secondary processing, differences in
terms of yield strength before and after a thermal history corresponding paint
baking of 60 MPa or more and of less than 60 MPa were designated with "0"
and "x," respectively. Then, comprehensive judgment was carried out. Table
3 shows the evaluation results.
17
CA 02628229 2008-05-01
Table 3
~
E O O O x O O O O O d a x O O O O
a o
O O O X0000000 x O O O O
~~ a'd x N ~O --l~ ~t N o0 M N ~O O v'~ O~ [~ l~ N
"O kn O~ Q~ 00 Oll O,\ ~D ~ M 00 00 00 01
L W
~
~
~ O O O O O O O O O 4 a a O O O O
~
~
ti
x o
cq ~ o t~ t~ ~O t~ ~ t~ ~ t~ o0 00 0o a, ~ oo t~ o0
.-. ,-, - - r. - - ... r, - - - - - - -
~ o ~ ~1 --cl ~D ~ ~ O 01 N N ~O M O ~t M ~ ~n
~ N a~ ~ a+ r. O O O --~ '--~ O ~ 00 [~ t~ ~ 00 00 00 00
N N N N N N N N - -
~
U
d ~~'d O l~ ~O ~O O ~ N Q N M ~ Q N ~ ~ M
~ 0= O O~ O~ O~ O O O O~ ~O V-) kn \~O ~o ~D "D
a~ O y~ M N N N M M M N N N N N N N N N
~ o
y to '~ N N N N N N N N N N N N N N N N
1-I W
~
~
~
r ~+
Ly ~ a O cC v' O 00 i/ ) ~O d M
* Ø ~
~
U
bA 00 l- M ~ 00 01 O l~ N V'1 00 N V') M N
.~r --i --i
=~ rn p,"
V k/'1 l~ 00 00 V') l!1 V') M M ~ N N --~
u O* J., ~ N N N N N N N N N N N N N N
N M ~ N M kn l0 l- 00
a~ y
. + .-. .--
O ~ N N a) ~ y O
U, ~ t]., Q Ct., RS p, f1õ
~ O, cd c~C ~ p, c~d c~d
W O ' W W O a~ W
U U
18
CA 02628229 2008-05-01
[Evaluation]
Test sample No. 1 is an aluminium extruded profile containing Si
(1.10%), Cu (0.20%), Mg (0.59%), and Mn (0.08%). Test samples Nos. 1-1 to
1-3 corresponding to the Examples and a test sample No. 1-4 corresponding to
the Comparative example were allowed to stand at room temperature for 12 to
168 hr following extrusion molding and retained at 70 C x 12 hr. Then, the
samples were compared in terms of yield strength before and after bake
hardening (hereafter abbreviated as "B. H.") treatment. In addition, test
samples Nos. 1-5 to 1-8 corresponding to the Examples were allowed to stand
for 12 hr following extrusion molding, treated at 70 C x 12 hr, and further
allowed to stand at room temperature for 12 to 168 hr. Then, the samples were
compared in terms of yield strength before and after B. H. treatment.
As a result, in the cases of test samples Nos. 1-1 to 1-4, the yield
strength after B. H. treatment became lower in inverse proportion to the
length
of time during which the relevant sample was allowed to stand at room
temperature following extrusion molding. Yield strengths after B. H. treatment
were 211 MPa, 204 MPa, 206 MPa, and 204 MPa, respectively. The results
were judged as corresponding to "0." However, yield strength increases as a
result of B. H were 92 MPa, 66 MPa, 61 MPa, and 57 MPa, respectively. The
yield strength became lower in inverse proportion to the length of time during
which the relevant sample was allowed to stand at room temperature. In the
case of test sample No. 1-4 corresponding to the Comparative example, which
had been allowed to stand at room temperature for 168 hr, the result was
judged
as corresponding to "x." In the cases of the other samples, yield strength
increases were 60 MPa or more as a result of B. H., and thus the results were
judged as corresponding to "0." Accordingly, upon comprehensive judgment
of test samples Nos. 1-1 to 1-4 corresponding to the Examples, in the cases of
the samples that had been allowed to stand at room temperature for less than
168
hr following extrusion molding (test samples Nos. 1-1, 1-2, and 1-3), the
results
19
CA 02628229 2008-05-01
were judged as corresponding to "0." Meanwhile, in the case of the sample
that had been allowed to stand at room temperature for 169 hr or more
following
extrusion molding (test sample No. 1-4), the result was judged as
corresponding
x.
to " "
Further, test samples Nos. 1-5 to 1-8 corresponding to the Examples
were allowed to stand for 12 hr following extrusion molding, retained at 70 C
x
12 hr, and further allowed to stand at room temperature for 12 to 168 hr,
followed by B. H. treatment. Yield strengths after B. H. treatment were 214
MPa, 210 MPa, 209 MPa, and 212 MPa, respectively. Thus, the samples were
not affected as a result of being allowed to stand at room temperature after
retention at 70 C x 12 hr. Therefore, the results were all judged as
corresponding to "0." In addition, yield strength increases as a result of B.
H.
were 94 MPa, 92 MPa, 88 MPa, and 93 MPa, respectively. Thus, the samples
were not affected as a result of being allowed to stand at room temperature
after
retention at 70 C x 12 hr. Therefore, the results were all judged as
corresponding to "0." Accordingly, in the cases of test samples Nos. 1-5 to 1-
8
corresponding to the Examples, the results were all judged as corresponding to
"0" upon comprehensive judgment.
Test sample No. 2 is an aluminium extruded profile containing Si
(0.90%), Cu (0.20%), Mg (0.40%), and Mn (0.08%). Test samples Nos. 2-1 to
2-3 corresponding to the Examples and test sample No. 2-4 corresponding to the
Comparative example were allowed to stand at room temperature for 12 to 168
hr following extrusion molding and retained at 70 C x 12 hr. Then, the
samples were compared in terms of yield strength before and after B. H.
treatment. In addition, test samples Nos. 2-5 to 2-8 corresponding to the
Examples were allowed to stand for 12 hr following extrusion molding, treated
at 70 C x 12 hr, and further allowed to stand at room temperature for 12 to
168
hr. Then, the samples were compared in terms of yield strength before and
after B. H. treatment.
CA 02628229 2008-05-01
As a result, in the cases of test samples Nos. 2-1 to 2-4, the yield
strength after B. H. treatment became lower in inverse proportion to the
length
of time during which the relevant sample was allowed to stand at room
temperature following extrusion molding. Yield strengths after B. H. treatment
were 182 MPa, 176 MPa, 176 MPa, and 170 MPa, respectively. In the case of
the test sample No. 2-1, the result was judged as corresponding to "0," and in
the cases of test samples Nos. 2-2 to 2-4, the results were judged as
corresponding to "A." Further, yield strength increases as a result of B. H.
were 92 MPa, 66 MPa, 60 MPa, and 35 MPa, respectively. The yield strength
became lower in inverse proportion to the length of time during which the
relevant sample was allowed to stand at room temperature. In the case of test
sample No. 2-4 corresponding to the Comparative example, which had been
allowed to stand at room temperature for 168 hr or more, the result was judged
as corresponding to "x." In the cases of the other samples (test samples Nos.
2-
1 and 2-3), yield strength increases as a result of B. H. were 60 MPa or more,
and thus the results were judged as corresponding to "0."
Thus, upon comprehensive judgment, in the case of test sample No. 2-1
corresponding to the Example, which had been allowed to stand at room
temperature for 12 hr following extrusion molding, the result was judged as
corresponding to "0." Also, in the cases of test samples No. 2-2 and 2-3 that
had been allowed to stand at room temperature for 24 to 72 hr following
extrusion molding, the results were judged as corresponding to "A" because
application is possible depending on sectional design although low yield
strengths were exhibited after B. H. treatment. Meanwhile, in the case of the
sample that had been allowed to stand at room temperature for 168 hr or more
following extrusion molding (test sample No. 2-4), the result was judged as
corresponding to "x."
Further, test samples No. 2-5 to 2-8 corresponding to the Examples were
allowed to stand for 12 hr following extrusion molding, retained at 70 C x 12
hr,
21
CA 02628229 2008-05-01
and further allowed to stand at room temperature for 12 to 168 hr, followed by
B.
H. treatment. Yield strengths after B. H. treatment were 184 MPa, 183 MPa,
181 MPa, and 185 MPa, respectively. Thus, the samples were not affected as a
result of being allowed to stand at room temperature after retention at 70 C x
12
hr. Therefore, the results were all judged as corresponding to "0." In
addition, yield strength increases as a result of B. H. were 89 MPa, 87 MPa,
87
MPa, and 92 MPa, respectively. Thus, the samples were not affected by as a
result of being allowed to stand at room temperature after retention at 70 C x
12
hr. Therefore, the results were all judged as corresponding to "O."
Accordingly, in the cases of test samples No. 2-5 to 2-8 corresponding to the
Examples, the results were all judged as corresponding to "0" upon
comprehensive judgment.
[Manufacturing method: (2) Setting of the billet temperature at 500 C or more
and setting the cooling rate at not less than 70 C/min for 4 minutes
immediately
after extrusion during manufacturing of an extruded material]
First, starting material contents were adjusted so as to achieve the
compositions of 6000-series aluminium alloys shown in table 4 (test samples
Nos. 1 to 4). The starting materials were dissolved and melted into
cylindrical
ingots (diameter: 204 mm x length: 700 mm) having a size appropriate for
extrusion. In addition, alloy contents listed in table 4 are expressed in
analytical values. The value "0.00%" is shown for the effective digit.
Subsequently, the ingots were subjected to a homogenization treatment at 560 C
x 4 hr.
22
CA 02628229 2008-05-01
Table 4
~, o 0 0 0
0 0 0 0
O O M O
N O O O O
O O O O
O o N O
U O O o O
~ O O o O
+' 01 O O O~
O O O O
N
00 00 O O
O O O N O
v O O O O
O
O O O O
U N N N O
O O O O
00 00 00 00
~ ----=--~ =--~
Lz=~
O O O O
O O O~ ~
.. ~ 41 I:
~ O O
N G~
03 cz
N ~ k
R. A
E > >
ct Lt =~ ...
~ ~
W W C3 ct
O O
U U
-- N M ~t
O N O N
O c~3 cd cd cC
z cn V) cn cn
cn cn
23
CA 02628229 2008-05-01
Next, extrusion molding of ingots (billets) subjected to a
homogenization treatment was carried out using an extrusion molding die at
predetermined billet heating temperatures under cooling conditions listed in
table 5. Thus, aluminium extruded profiles each having a cross section of a
frame structural member shown in fig. 2 were formed. Herein, under general
cooling fan conditions listed in table 5, a 45-cm fan was set to rotate at
1680
rpm.
24
CA 02628229 2008-05-01
Table 5
.~
~...
x~ x x x i x
a~ a cQ c~ aa
~~~ o N N N I N
3 0
~ ~ ~ I I I
L
0 ~
~
y N N
L
oY' ~o O O I I I I
E-~
~ ~= U o0 ~O l~ O O O~ 00 Q1 ~ ~ l~ -+ O
Ci. >
~" =--= >>
o 0 o0 Ln c+1 00 tn O t~
w Q o w ~ o 00 l- N M C~ O ~O N N 00 - O I-
00 O M vl N 01 O M V'1 N M M M N
a x '~ ~/ Vl vl kn V) tn v1 V't v"t kn tn
~-+
Q Q 'O 00 N l~ 'O \C M V1 01 O1 00 ~
O~E
Ln v') l~ O O M O a1 01 O~
~ U o oe 00 00 p\ D\ I- p\ 00 00 00
~
~
YC
W a0 bD o' a a~ o
u V) V) z
~
~
U o 0 0 0 0 0 0 0 0 0 0 0 0 0
00 O N O 'O 00
o O N O O O O O
o., =~ Ct ~ Ln V) W) v'~ v') V) tn tn
Vl
~ N M d ~n ~ N c*M ~ v'~ ~ N ~ N
iE ~ cE ~~ E 'aE ~E cz E
c~.cl ct aCd aca ro rsca a ro acz
o ' 0 ' o J o ' J
U U U U U U
N cn ~
CA 02628229 2008-05-01
Thereafter, the aluminium extruded material was retained at 70 C x 12
hr, allowed to stand at room temperature for 1 week, and subjected to a
thermal
history (B. H. treatment) corresponding to paint baking shown in fig. 2. In
this
case, heat treatment corresponding to general thermal refining was not carried
out.
The obtained aluminium extruded profiles having paint-baking
hardenability were evaluated by tensile experiments regarding yield strength,
strength, and breaking elongation. Tensile properties were determined by
collecting flat test pieces from the extruded profiles having paint-baking
hardenability and examining the test pieces using a tensile tester (complying
with the JIS standards) according to JIS-Z 2241. Regarding criteria, a yield
strength of 180 MPa or more was designated with "0" in view of protection of
vehicles upon crushing. A yield strength of 180 to 150 MPa was designated
with "A" because application is possible depending on sectional design. In
addition, a yield strength of less than 150 MPa with designated with "x."
Further, considering the cases involving secondary processing, differences in
terms of yield strength before and after a thermal history corresponding paint
baking of 60 MPa or more and of less than 60 MPa were designated with "0"
and "x," respectively. Then, comprehensive judgment was carried out. Table
6 shows the evaluation results.
26
CA 02628229 2008-05-01
Table 6
>
x x O O x x x d O d x ~ x
a o
0
x x O O x x O O O O x ~ x ~
ti
.6 C~t~~ x M l N [~ O N M v'~ et O O d
a~ q a~
Y ~~~ aa ~~n o~ oo ~n v~ ~o 00 0~ ~o r. I
o s. w
~ .., o
~
~ d d O O 4 x x d O 4 x I x
on
~
0
ti
x o
0. t~ t~ oo ~ o0 00 0~ oo t~ ~O ~t ~
o b ~~ N ~ ~ 01 l~ M l~ 00 ~ V1 V1 [~ M
Q" N u t!) l- O l~ M ~t ~ 00 V'~ O 01 M
~ O > w =--~ ,--~ N N ,--~ , ,--~ .-+ .-. N
a, ~...
ro
.~ U y
't to Cd M M M ~ N W) O O ~ ~
c~ N N M N N N N N N N N N N
1" o
W o N N N N N ~ ~n ~ v~ ~ O O
y N N N N N N N N N N N N
w W
~
oq
O O T~~" ~ N ~ N~ 00 00 O1\ 01 01 O1,
Cd
U
CQ cz N O ~ v'
kn ~O v'
N N N N N N N N N --~
~ N M v) .-N M d v)
> ai > a> > a~ a> >
~ a a ~ a ~ a ia ~ a. ~ a ~ a
E E ct 6 m m E cz a
acs a. cz aca cz aCd o. cc a a
o '
U U U U U U
27
CA 02628229 2008-05-01
Test sample No. 1 is an aluminium extruded profile containing Si
(1.10%), Cu (0.20%), Mg (0.59%), and Mn (0.08%). Test samples Nos. 1-1 to
1-4 were heated at different billet temperatures of 460 C, 480 C, 500 C, and
520 C, respectively, upon extrusion. The samples were compared in terms of
yield strength before and after B. H. treatment. In addition, a sample heated
at
a billet temperature of 500 C upon extrusion and treated at a cooling rate of
less
than 70 C/min for 4 minutes immediately after extrusion (test sample No. 1-5)
was compared with the above samples. As a result, yield strengths after B. H.
treatment were 152 MPa, 171 MPa, 213 MPa, 209 MPa, and 177 MPa,
respectively. The samples treated at billet temperatures of less than 500 C
(test samples Nos. 1-1 and 1-2) and the sample treated at a cooling rate of
less
than 70 C/min for 4 minutes immediately after extrusion (test sample No. 1-5)
had low yield strengths after B. H. treatment, and thus the results were
judged as
corresponding to "A." In the cases of the other samples, yield strengths after
B.
H. treatment were 180 MPa or more, and thus the results were judged as
corresponding to "0." In addition, yield strength increases as a result of B.
H.
were 43 MPa, 57 MPa, 92 MPa, 87 MPa, and 50 MPa, respectively. In the
cases of the samples treated at billet temperatures of less than 500 C (test
samples No. 1-1 and 1-2) and the sample treated at a cooling rate of less than
70 C/min for 4 minutes immediately after extrusion (test sample No. 1-5), the
yield strength slightly increased as a result of B. H. Thus, the results were
judged as corresponding to "x." In the cases of the other samples, yield
strength increases as a result of B. H. were 60 MPa or more, and thus the
results
were judged as corresponding to "0." Accordingly, upon comprehensive
judgmerit of test sample No. 1, in the cases of the test samples (Nos. 1-3 and
1-
4) corresponding to the Examples, which had been heated at billet temperatures
of 500 C or more, the results were judged as corresponding to "0." Also, in
the cases of the other samples, the results were judged as corresponding to
"x."
Test sample No. 2 is an aluminium extruded profile containing Si
28
CA 02628229 2008-05-01
(0.90%), Cu (0.20%), Mg (0.40%), and Mn (0.09%). Test samples No. 2-1 to
2-4 were heated at different billet temperatures of 460 C, 480 C, 500 C, and
520 C, respectively, upon extrusion. The samples were compared in terms of
yield strength before and after B. H. treatment. Further, a sample heated at
billet temperature of 500 C upon extrusion and treated at a cooling rate of
less
than 70 C/min for 4 minutes immediately after extrusion (test sample No. 2-5)
was compared with the above samples. As a result, the yield strengths after B.
H. treatment were 133 MPa, 147 MPa, 178 MPa, 184 MPa, and 155 MPa,
respectively. The samples treated at billet temperatures of less than 500 C
(test samples No. 2-1 and 2-2) had low yield strengths after B. H. treatment,
and
thus the results were judged as corresponding to "x." The sample treated at a
billet temperature of 500 C (test sample 2-3) had a low but acceptable yield
strength value of 150 MPa or more, and thus the result was judged as
corresponding to "A." The sample treated at a billet temperature of 520 C
(test
sample No. 2-4) had a sufficiently high yield strength after B. H. treatment,
and
thus the result was judged as corresponding to "0." In addition, yield
strength
increases as a result of B. H. were 52 MPa, 63 MPa, 85 MPa, 94 MPa, and 60
MPa, respectively. In the case of the sample treated at a billet temperature
of
460 C or less (test sample No. 2-1), the yield strength increase as a result
of B.
H. was less than 60 MPa, and thus the result was judged as corresponding to
"x."
In the cases of the other samples (test samples Nos. 2-2, 2-3, 2-4, and 2-5),
yield
strength increases as a result of B. H. were 60 MPa or more, and thus the
results
were judged as corresponding to "0." Accordingly, upon comprehensive
judgment of test sample No. 2, in the cases of the samples (Nos. 2-1 and 2-2)
corresponding to the Examples, which had been heated at billet temperatures of
480 C or less, the results were judged as corresponding to "x." In the cases
of
the samples that had been heated at a billet temperature of 500 C (test
samples
No. 2-3 and 2-5), the results were judged as corresponding to "A" because
application is possible depending on sectional design although low yield
29
CA 02628229 2008-05-01
strengths were exhibited after B. H. treatment. Also, in the case of the
sample
that had been heated at a billet temperature of 520 C (test sample No. 2-4),
the
result was judged as corresponding to "O."
Test sample No. 3 corresponding to the Comparative example 1 is an
aluminium extruded profile containing Si (0.59%), Cu (0.20%), Mn (0.20%), Mg
(0.60%), and Cr (0.02%). The Si content does not fall within the scope of the
present invention. The material was subjected to extrusion at a billet
temperature of 500 C and a cooling rate of not less than 70 C/min for 4
minutes
immediately after extrusion, followed by B. H. treatment without treatment at
70 C x 2 h. The yield strength was 105 MPa and the yield strength increase as
a result of B. H. was 10 MPa, and thus the results were judged as
corresponding
to "x." When such material was subjected to general thermal refining, the
yield
strength was 197 MPa. Thus, the material can be applied depending on type of
structural member used in automobiles and the like. However, such material
might have poor paint-baking hardenability, resulting in cost increase.
Test sample No. 4 corresponding to the Comparative example is an
aluminium extruded profile containing Si (0.44%) and Mg (0.49%). The Si
content does not fall within the scope of the present invention. The material
was subjected to extrusion at a billet temperature of 500 C and a cooling rate
of
not less than 70 C/min for 4 minutes immediately after extrusion, followed by
B.
H. treatment without treatment at 70 C x 2 h. The yield strength was 85 MPa
and the yield strength increase as a result of B. H. was 14 MPa, and thus the
results were judged as corresponding to "x." When such material was subjected
to general thermal refining, the yield strength was 233 MPa. Thus, the
material
can be applied depending on type of structural member used in automobiles and
the like. However, such material might have poor paint-baking hardenability,
resulting in cost increase.
Industrial Applicability
CA 02628229 2008-05-01
According to the present invention, it is possible to provide a 6000-
series aluminium extruded profile superior in paint-baking hardenability, the
yield strength of which can be secured to a level applicable to structural
members of automobiles and the like with the use of a thermal history
corresponding to paint baking. The aluminium extruded profile of the present
invention can be applied to members that are subjected to a thermal history
corresponding to paint baking, such as structural members of vehicles (e.g.,
automobiles), including frame structural members such as a side sill, a side
member, a cross member, and a door frame.
31
