U.S. patent application number 14/040630 was filed with the patent office on 2014-04-10 for high-strength aluminum alloy extruded material and method for manufacturing the same.
This patent application is currently assigned to SUMITOMO LIGHT METAL INDUSTRIES, LTD.. The applicant listed for this patent is SUMITOMO LIGHT METAL INDUSTRIES, LTD.. Invention is credited to Hidenori HATTA, Takero WATANABE.
Application Number | 20140096878 14/040630 |
Document ID | / |
Family ID | 50403925 |
Filed Date | 2014-04-10 |
United States Patent
Application |
20140096878 |
Kind Code |
A1 |
HATTA; Hidenori ; et
al. |
April 10, 2014 |
HIGH-STRENGTH ALUMINUM ALLOY EXTRUDED MATERIAL AND METHOD FOR
MANUFACTURING THE SAME
Abstract
A high-strength aluminum alloy extruded material contains Si:
0.70 to 1.3 mass %; Mg: 0.45 to 1.2 mass %; Cu: 0.15 to less than
0.40 mass %; Mn: 0.10 to 0.40 mass %; Cr: more than 0 to 0.06 mass
%; Zr: 0.05 to 0.20 mass %; Ti: 0.005 to 0.15 mass %, Fe: 0.30 mass
% or less; V: 0.01 mass % or less; the balance being Al and
unavoidable impurities Crystallized products in the alloy have a
particle diameter of a is 5 .mu.m or less. Furthermore, an area
ratio of a fibrous structure in a cross section parallel to an
extruding direction during hot extrusion is 95% or more.
Inventors: |
HATTA; Hidenori; (Aichi,
JP) ; WATANABE; Takero; (Aichi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUMITOMO LIGHT METAL INDUSTRIES, LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
SUMITOMO LIGHT METAL INDUSTRIES,
LTD.
Tokyo
JP
|
Family ID: |
50403925 |
Appl. No.: |
14/040630 |
Filed: |
September 28, 2013 |
Current U.S.
Class: |
148/690 ;
148/418 |
Current CPC
Class: |
C22F 1/043 20130101;
C22F 1/047 20130101; C22F 1/05 20130101 |
Class at
Publication: |
148/690 ;
148/418 |
International
Class: |
C22F 1/05 20060101
C22F001/05; C22F 1/047 20060101 C22F001/047; C22F 1/043 20060101
C22F001/043 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 5, 2012 |
JP |
2012-222943 |
Claims
1. A high-strength aluminum alloy extruded material comprising: Si:
0.70 to 1.3 mass %; Mg: 0.45 to 1.2 mass %; Cu: 0.15 to less than
0.40 mass %; Mn: 0.10 to 0.40 mass %; Cr: more than 0 to 0.06 mass
%; Zr: 0.05 to 0.20 mass %; Ti: 0.005 to 0.15 mass %, Fe: 0.30 mass
% or less; V: 0.01 mass % or less; and the balance being Al and
unavoidable impurities, wherein crystallized products in the alloy
have a particle diameter of 5 .mu.m or less, and wherein an area
ratio of a fibrous structure in a cross section parallel to an
extruding direction during hot extrusion is 95% or more.
2. A structural member for vehicle comprising the high-strength
aluminum alloy extruded material according to claim 1.
3. A method for manufacturing a high-strength aluminum alloy
extruded material, comprising: producing an ingot which comprises:
Si: 0.70 to 1.3 mass %; Mg: 0.45 to 1.2 mass %; Cu: 0.15 to less
than 0.40 mass %; Mn: 0.10 to 0.40 mass %; Cr: more than 0 to 0.06
mass %; Zr: 0.05 to 0.20 mass %; Ti: 0.005 to 0.15 mass %, Fe: 0.30
mass % or less; V: 0.01 mass % or less; and the balance being Al
and unavoidable impurities; subjecting the ingot to a
homogenization treatment that includes holding the ingot at a
temperature of not lower than 450.degree. C. and lower than
500.degree. C. for 2 to 30 hours; subjecting the homogenized ingot
to hot extrusion in a state where the temperature of the ingot at
the start of the hot extrusion is held at 480.degree. C. to
540.degree. C. so as to form an extruded material; quenching the
extruded material to 150.degree. C. or lower at a cooling rate of
2.degree. C./sec. to 100.degree. C./sec. while the temperature of
the extruded material is held at 480.degree. C. or higher; and
thereafter, subjecting the extruded material to an aging treatment
that includes heating the extruded material at a temperature of
150.degree. C. to 200.degree. C. for 1 to 24 hours.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority under 35 U.S.C.
.sctn.119 to Japanese Application No. 2012-222943, filed on Oct. 5,
2012, entitled "HIGH-STRENGTH ALUMINUM ALLOY EXTRUDED MATERIAL AND
METHOD FOR MANUFACTURING THE SAME". The contents of this
application are incorporated herein by reference in their
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an extruded material formed
of a high-strength aluminum alloy.
[0004] 2. Description of Related Art
[0005] A 6000 series aluminum alloy material has excellent strength
and corrosion resistance, and is used in applications such as
mechanical components, structural members and the like. In recent
years, the application of a 6000 series aluminum alloy material to
frames, etc. of transportation machines such as automobiles has
been considered to reduce the weight of the frames, etc.
[0006] Examples of high-strength aluminum alloy materials suitably
used in automobiles, etc. include the aluminum alloy extruded
material described in Patent Document 1 listed below and the
aluminum alloy forged material described in Patent Document 2
listed below. The aluminum alloy extruded material described in
Patent Document 1 is comprised of a fibrous central structure with
a recrystallized surface structure on both sides thereof; it was
alleged to have excellent impact absorption properties. Further,
the aluminum alloy forged material described in Patent Document 2
is intended to have increased strength due to the addition of 0.4%
to 1.2% by weight of Cu in addition to Mg and Si.
PATENT DOCUMENTS
[0007] Patent Document 1: JP-A 2001-355032 [0008] Patent Document
2: JP-A 06-330264
SUMMARY OF THE INVENTION
[0009] A 6000 series aluminum alloy manufactured within
conventional elemental ranges and by a conventional manufacturing
method generally has low strength as compared to iron-based
materials commonly used in frames. Therefore, it has been required
to increase the plate thickness and to impart a shape for
reinforcement, for example, by forging, which disadvantageously
results in low productivity. Therefore, there is a need in the art
to produce a high-strength aluminum alloy material having a proof
stress of 350 MPa or more by high productivity extrusion.
[0010] However, the aluminum alloy extruded material described in
Patent Document 1 has a tensile strength of about 300 MPa, which is
an insufficient strength for use in place of iron-based
materials.
[0011] The aluminum alloy described in Patent Document 2 has higher
strength than conventional 6000 series aluminum alloys, but is a
forged material that involves the following problem when carrying
out the extrusion. Specifically, when the aluminum alloy described
in Patent Document 2 is extruded at a high speed, defects may occur
on its surface in association with the extrusion, such as surface
exfoliation, due to friction against the die, etc., which results
in a reduction of the surface quality.
[0012] Also, the aluminum alloy forged material described in Patent
Document 2 has a relatively high Cu content for 6000 series
aluminum alloys, and thus has poor corrosion resistance.
[0013] Therefore, in one aspect of the present teachings, a
high-strength aluminum alloy extruded material is provided that
preferably has excellent corrosion resistance, excellent extrusion
productivity and/or an excellent surface quality after
extrusion.
[0014] In another aspect of the present teachings, a high-strength
aluminum alloy extruded material contains Si: 0.70 to 1.3 mass %;
Mg: 0.45 to 1.2 mass %; Cu: 0.15 to less than 0.40 mass %; Mn: 0.10
to 0.40 mass %; Cr: more than 0 to 0.06 mass %; Zr: 0.05 to 0.20
mass %; Ti: 0.005 to 0.15 mass %, Fe: 0.30 mass % or less; V: 0.01
mass % or less; and the balance being Al and unavoidable
impurities. Crystallized products in the alloy have a particle
diameter of 5 .mu.m or less. Furthermore, an area ratio of a
fibrous structure in a cross section parallel to an extruding
direction during hot extrusion is 95% or more.
[0015] In another aspect of the present teachings, a method for
manufacturing a high-strength aluminum alloy extruded material,
includes producing an ingot which includes Si: 0.70 to 1.3 mass %;
Mg: 0.45 to 1.2 mass %; Cu: 0.15 to less than 0.40 mass %; Mn: 0.10
to 0.40 mass %; Cr: more than 0 to 0.06 mass %; Zr: 0.05 to 0.20
mass %; Ti: 0.005 to 0.15 mass %, Fe: 0.30 mass % or less; V: 0.01
mass % or less; and the balance being Al and unavoidable
impurities; subjecting the ingot to an homogenization treatment
that includes holding the ingot at a temperature of not lower than
450.degree. C. and lower than 500.degree. C. for 2 to 30 hours;
subjecting the ingot to hot extrusion in a state where the
temperature of the ingot at the start of the hot extrusion is held
at 480.degree. C. to 540.degree. C. so as to form an extruded
material; quenching the extruded material to 150.degree. C. or
lower at a cooling rate of 2.degree. C./sec. to 100.degree. C./sec.
while the temperature of the extruded material is held at
480.degree. C. or higher; and thereafter, subjecting the extruded
material to an aging treatment that includes heating the extruded
material at a temperature of 150.degree. C. to 200.degree. C. for 1
to 24 hours.
[0016] The above-described high-strength aluminum alloy extruded
material contains the above-specified elements in the
above-specified amounts. Therefore, the above-described
high-strength aluminum alloy extruded material exhibits excellent
corrosion resistance and excellent extrusion productivity, and can
easily serve as a high-strength extruded material.
[0017] Further, for the above-described high-strength aluminum
alloy extruded material, the particle diameter of the crystallized
products is restricted to 5 .mu.m or less. Therefore, the
high-strength aluminum alloy extruded material is not likely to
experience surface exfoliation during the extrusion, and thus can
easily exhibit an excellent surface quality after the
extrusion.
[0018] Furthermore, in the above-described high-strength aluminum
alloy extruded material, the area ratio of the fibrous structure in
the cross section parallel to the extruding direction during the
hot extrusion is 95% or more. Therefore, the high-strength aluminum
alloy extruded material can exhibit a proof stress of 350 MPa or
more.
[0019] Specifically, the above-described high-strength aluminum
alloy extruded material can be made as a high-strength extruded
material that exhibits excellent corrosion resistance, excellent
extrusion productivity and excellent surface quality after
extrusion. Furthermore, it can achieve a proof stress of 350 MPa or
more due to the synergistic effects of the above specified elements
and the metallographic structure constituted in the above
manner.
[0020] In addition, in a method for manufacturing the
above-described high-strength aluminum alloy extruded material, the
above-described high-strength aluminum alloy extruded material is
manufactured by employing the above-specified processing
temperatures, processing times and processing procedures.
Consequently, the above high-strength aluminum alloy extruded
material can be easily obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 shows a photograph of a metallographic structure of
Sample No. 1 having a high area ratio of a fibrous structure in
Example 1.
[0022] FIG. 2 shows a photograph of the metallographic structure of
Sample No. 10 having a low area ratio of a fibrous structure in
Example 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The above-described high-strength aluminum alloy extruded
material includes 0.70% or more and 1.3% or less of Si and 0.45% or
more and 1.2% or less of Mg. When Si and Mg coexist in an alloy,
they cause precipitation of Mg.sub.2Si particles during an aging
treatment (also known as precipitation hardening or age hardening).
Such enhancement of the precipitation increases the (yield)
strength of the extrusion material. Further, excess Si that does
not precipitate in Mg.sub.2Si particles, for example, makes the
Mg.sub.2Si particles fine, and contributes to the improvement of
the strength of the above-described extruded material.
[0024] If the Si content is less than 0.7%, the amount of
precipitated Mg.sub.2Si particles will be relatively low, thereby
resulting in a relatively low strength of the resulting extruded
material. Therefore, the Si content is preferably 0.7% or more,
more preferably 0.85% or more. On the other hand, if the Si content
exceeds 1.3%, defects such as exfoliation tend to occur on the
surface of the extruded material during extrusion, which may tend
to reduce the surface quality of the resulting extruded material.
Therefore, the Si content is preferably 1.3% or less, more
preferably 1.2% or less.
[0025] If the Mg content is less than 0.45%, the amount of
precipitated Mg.sub.2Si particles will be relatively low, thereby
resulting in a relatively low strength of the resulting extruded
material. Therefore, the Mg content is preferably 0.45% or more,
more preferably 0.6% or more. On the other hand, if the Mg content
exceeds 1.2%, the extrusion productivity deteriorates. For example,
the extrusion pressure during extrusion will be increased.
Consequently, the surface quality of the resulting extruded
material and the productivity of the extruded material are prone to
be reduced. Therefore, the Mg content is preferably 1.2% or less,
more preferably 0.9% or less.
[0026] The Cu content is not less than 0.15% and less than 0.40%.
Cu is dissolved in a solid state in an alloy, resulting in
enhancement of solid solution. Such enhancement increases the
strength of the extruded material. If the Cu content is less than
0.15%, the strength of the resulting extruded material is reduced
because the Cu content is insufficient. Therefore, the Cu content
is preferably 0.15% or more, more preferably 0.20% or more. On the
other hand, if the Cu content is 0.40% or more, the extrusion
productivity deteriorates, so that the surface quality and the
productivity of the resulting extruded material are prone to be
reduced. Furthermore, in this case, the corrosion resistance tends
to deteriorate. Therefore, the Cu content is preferably less than
0.40%, more preferably 0.38% or less.
[0027] The Mn content is 0.10% or more and 0.40% or less, the Cr
content is 0.06% or less (but greater than 0%), and the Zr content
is 0.05% or more and 0.20% or less.
[0028] Mn, Cr and Zr form Al--Mn based, Al--Mn--Si based, Al--Cr
based and Al--Zr based fine intermetallic compounds in combination
with Al. The intermetallic compounds, when precipitated in an
alloy, suppress recrystallization and thereby increase the ratio or
percentage of the fibrous structure in the extruded material.
Therefore, if the contents of these three elements are too low, the
ratio or percentage of the fibrous structure in the resulting
extruded material becomes lower and the strength of the extruded
material may be reduced. On the other hand, if the Mn, Cr and Zr
contents are too high, the intermetallic compounds become coarse
and thereby cause defects such as exfoliation on the surface of the
extruded material during the extrusion; consequently, the surface
quality of the resulting extruded material is prone to be
reduced.
[0029] Each of Mn, Cr and Zr suppresses recrystallization
independently, and their effects on the suppression of the
recrystallization can be further increased by adding these three
elements in combination. Therefore, by adjusting (setting)
respective the Mn, Cr and Zr contents within the above-specified
ranges, the precipitation of coarse intermetallic compounds can be
suppressed while increasing the ratio or percentage of the fibrous
structure in the extruded material.
[0030] The Ti content is 0.005% or more and 0.15% or less. Ti makes
the ingot structure fine and increases the ratio or percentage of
the fibrous structure in the extruded material. If the Ti content
is less than 0.005%, the ingot structure will not be sufficiently
fine, such that the ratio or percentage of the fibrous structure
will be too low. This tends to reduce the strength and surface
quality of the resulting extruded material. On the other hand, if
the Ti content exceeds 0.15%, Al--Ti based coarse crystallized
products are likely to form with Al. Therefore, defects such as
exfoliation tend to occur on the surface of the extruded material
during the extrusion, which tends to reduce the surface quality of
the resulting extruded material.
[0031] The contents of Fe and V are restricted to be 0.30% or less
and 0.01% or less, respectively. If the contents of Fe and V are
too high, coarse crystallized products are prone to be formed.
Therefore, defects such as exfoliation tend to occur on the surface
of the extruded material during the extrusion, which tends to
reduce the surface quality of the resulting extruded material. Such
a reduction in surface quality can be avoided by restricting the
contents of Fe and V to 0.30% or less and 0.01% or less,
respectively. On the other hand, there are no lower limits of the
Fe and V contents. However, to significantly reduce the Fe and V
contents, a high-purity aluminum metal must be used, which
increases costs without substantial additional benefits. Therefore,
in order to avoid excessive material cost increases, the Fe content
may be, e.g., 0.05% or more.
[0032] The above-described high-strength aluminum alloy extruded
material may contain 0.20% or less of Zn. Zn is an impurity mixed,
for example, when a recycled material is used, but does not
adversely affect the performance of the extruded material when the
content thereof is 0.20% or less. On the other hand, if the Zn
content exceeds 0.20%, the corrosion resistance of the resulting
extruded material may be reduced in some cases.
[0033] Further, for the above-described high-strength aluminum
alloy extruded material, the particle diameter of crystallized
products is restricted to 5 .mu.m or less. During the extrusion, it
is highly likely that exfoliation will begin at the crystallized
products present in the metallographic structure of the extruded
material. However, by restricting the particle diameter of
crystallized products to 5 .mu.m or less, defects generated during
the extrusion can be suppressed, which improves the surface quality
of the extruded material.
[0034] The particle diameter of the crystallized products can be
measured, for example, by the following method. First, the extruded
material is cut to expose its cross section, and the cross section
is polished to obtain a smooth surface. Thereafter, the smooth
surface is observed with an optical microscope, and the
crystallized products in the resulting microscopic image are
approximated with an ellipse. The length of the ellipse in the long
axis direction is utilized as the particle diameter.
[0035] The surface quality of the above-described high-strength
aluminum alloy extruded material can be further improved by
reducing the content of the crystallized products. For example, the
content of the crystallized products is preferably 1% or less. The
content of the crystallized products can be determined by obtaining
a microscopic image in a manner similar to the above-described
particle diameter measuring method, and thereafter, calculating the
area ratio of the crystallized products in the microscopic image by
means of image processing. This area ratio is utilized as the
content of the crystallized products.
[0036] In the above-described high-strength aluminum alloy extruded
material, the area ratio of the fibrous structure in the cross
section parallel to the extruding direction during hot extrusion is
preferably 95% or more. The fibrous structure included in the
metallographic structure of the extruded material improves the
mechanical properties such as tensile strength and proof stress in
the extruding direction. Therefore, a high-strength extruded
material can be achieved by adjusting the area ratio of the fibrous
structure to be 95% or more. The metallographic structure of the
extruded material can be confirmed, for example, by performing
electrolytic polishing on the cross section of the extruded
material, carrying out electrolytic etching for 1 minute at
20.degree. C. and 20 V using a Barker liquid, and then observing
the etched cross section using a polarization microscope. Further,
the method for calculating the area ratio of the fibrous structure
will be explained in further detail in Examples.
[0037] As the above-described cross section parallel to the
extruding direction during hot extrusion, the cross section that
represents the ratio of the fibrous structure present in the
metallographic structure can be arbitrarily selected from various
cross sections parallel to the extruding direction. Specifically,
the cross section parallel to the extruding direction during hot
extrusion can be appropriately selected depending on the shape of
the extruded material. For example, when the extruded material has
a round-bar shape, a cross section passing through the central axis
can be selected. When the extruded material has a square-bar shape,
a cross section passing through the central axis and vertical to
either one of the width and thickness directions can be selected.
Further, when the extruded material, for example, is molded into an
approximately L-shape as viewed from the extruding direction so as
to have a shape with a plate-like portion, a cross section parallel
to the thickness (depth) direction of the plate-like portion can be
selected. However, the above-described methods for selecting the
cross section are merely representative examples, and the
cross-section selecting method is not limited thereto.
[0038] As was described above, the above-described high-strength
aluminum alloy extruded material having the above-specified
chemical components (elements) and the above-specified
metallographic structure has higher strength than 6000 series
aluminum alloy materials produced within conventional elemental
ranges and by conventional manufacturing processes and also has
excellent corrosion resistance and surface quality. Therefore, the
above-described high-strength aluminum alloy extruded material can
be suitably and advantageously used as a structural member for
vehicles, e.g., as a frame.
[0039] Specifically, the above-described high-strength aluminum
alloy extruded material can exhibit advantageous properties even in
harsh environments, such as vibration and corrosion, and can be
suitably used, for example, in a side frame and a door sash of an
automobile. Additionally, the high-strength aluminum alloy extruded
material exhibiting a proof stress of 350 MPa or more, is suitable
for use in a structural member for a vehicle.
[0040] Next, a representative method for manufacturing the
above-described high-strength aluminum alloy extruded material will
be explained. In such a method, an aluminum alloy ingot having the
above-specified chemical components (elemental composition) is
first produced. During the production of this ingot, the cooling
rate during a period of time from tapping to the completion of
solidification is preferably controlled to be 0.2.degree. C./sec.
or higher. The particle diameter of the crystallized products
formed in the ingot can be easily reduced by controlling the
cooling rate during casting as described above.
[0041] Next, the ingot is subjected to a homogenization treatment
that involves holding the ingot at a temperature of not lower than
450.degree. C. and lower than 500.degree. C. for 2 to 30 hours. If
the temperature during the homogenization treatment is lower than
450.degree. C., the homogenization of the ingot segregation layer
in the metallographic structure of the ingot will be insufficient.
As a result, coarsening of crystal grains, formation of an uneven
crystal structure, etc. are likely to occur, which may cause a
deterioration of the surface quality of the extruded material as
the final product. On the other hand, if the temperature during
homogenization exceeds 500.degree. C., the AlZr based precipitated
product will be transformed, resulting in a reduction of the
recrystallization suppressing effect. In this case, the ratio
(percentage) of the fibrous structure in the resulting extruded
material may be decreased. Thus, the (holding) temperature during
the above-described homogenization treatment is preferably not
lower than 450.degree. C. and lower than 500.degree. C.
[0042] Further, the holding time in the above-described
homogenization treatment is preferably 2 hours or longer. If the
above holding time is less than 2 hours, the surface quality of the
extruded material as the final product is prone to be reduced in a
manner similar to as described above due to insufficient
homogenization of the ingot segregated layer in the ingot
structure. On the other hand, if the holding time in the
homogenization treatment exceeds 30 hours, the homogenization of
the ingot segregated layer will have been sufficiently achieved and
no additional effects can be expected. Thus, the holding time in
the homogenization treatment is preferably 2 hours or more and 30
hours or less.
[0043] After the homogenization treatment, the ingot is hot
extruded in a state where the temperature of the ingot is held at
480.degree. C. to 540.degree. C., thereby resulting in an extruded
material. If the temperature of the ingot before extrusion is lower
than 480.degree. C., the strength of the resulting extruded
material is likely to be reduced due to insufficient dissolution of
the added elements. On the other hand, when the temperature of the
ingot before extrusion exceeds 540.degree. C., working heat
generation during the extruding may locally cause eutectic melting.
Therefore, the surface quality of the resulting extruded material
may be reduced.
[0044] Further, the above-described hot extrusion is preferably
carried out within 5 hours from the time when the temperature of
the ingot has reached the range of from 480.degree. C. to
540.degree. C. If the hot extrusion is not carried out within 5
hours, the AlZr based precipitated products may be transformed,
resulting in a reduction of the recrystallization suppressing
effect.
[0045] The extruded material obtained by the above-described hot
extrusion is quenched to 150.degree. C. or lower at a cooling rate
of 2.degree. C./sec. to 100.degree. C./sec. while the temperature
is 480.degree. C. or higher. (Hereinafter the "quenching of the
extruded material" is referred to as the "quenching treatment" in
some cases.) If the temperature of the above-described extruded
material before quenching is lower than 480.degree. C., the quench
hardening will be insufficient and the strength of the resulting
extruded material may be reduced. Furthermore, if the temperature
of the extruded material after quenching exceeds 150.degree. C.,
the quench hardening will be insufficient and the strength of the
resulting extruded material may be reduced.
[0046] If the above-described cooling rate exceeds 100.degree.
C./sec., no commensurate effect can be obtained. On the other hand,
if the cooling rate is lower than 2.degree. C./sec., the quench
hardening will be insufficient and the strength of the resulting
extruded material may be reduced.
[0047] It is noted that a forced or active cooling means may be
utilized in the quenching of the extruded material. For example,
fan air cooling, mist cooling, shower cooling or water cooling can
be employed during the quenching step.
[0048] The quenched extruded material is then subjected to an aging
(precipitation hardening) treatment that involves heating the
extruded material at a temperature of 150.degree. C. to 200.degree.
C. for 1 to 24 hours. If the temperature during the aging treatment
is lower than 150.degree. C., the effects obtained by the aging
treatment will be insufficient and the strength of the resulting
extruded material may be reduced. On the other hand, if the
temperature during the aging treatment exceeds 200.degree. C.,
over-aging results and the strength of the resulting extruded
material may be reduced.
[0049] If the heating time during the aging treatment is less than
1 hour, under-aging results and the strength of the resulting
extruded material may be reduced. On the other hand, if the heating
time during the aging treatment exceeds 24 hours, over-aging
results and the strength of the resulting extruded material may be
reduced.
EXAMPLES
Example 1
[0050] This is an Example for investigating the chemical components
(elemental composition) of the above-described high-strength
aluminum alloy extruded material. In this Example, alloys (Alloys
Nos. A to M) comprising the elements in various amounts as
indicated in Table 1 were used to produce samples (Samples Nos. 1
to 13) according to the manufacturing conditions indicated in Table
2, and then strength measurements, metallographic structure
observations, surface quality evaluations and corrosion resistance
evaluations were carried out on the respective samples.
Hereinafter, the conditions for manufacturing the respective
samples and the methods for measuring their strength, observing
their metallographic structure, evaluating their surface quality
and evaluating their corrosion resistance will be explained in
further detail.
<Manufacturing Conditions for the Samples>
[0051] Ingots having a diameter of 90 mm and containing the
elements indicated in Table 1 were cast using a continuous casting
technique. Thereafter, the ingots were subjected to a
homogenization treatment that involved holding them at a
temperature of 480.degree. C. for 10 hours. Then, the ingots were
subjected to hot extrusion at an extruding rate of 10 m/min. in a
state where the temperatures of the ingots were maintained at the
temperatures indicated in Table 2, thereby producing extruded
materials having a flat bar shape with a width of 35 mm and a
thickness of 3 mm. Then, the extruded materials were subjected to a
quenching treatment that involved cooling them to the temperatures
indicated in Table 2 at a cooling rate of 10.degree. C./sec. in a
state where the temperatures of the extruded materials were
maintained at the temperatures indicated in Table 2. The quenched
extruded materials were then subjected to an aging treatment that
involved heating them at 180.degree. C. for 6 hours, thereby
producing the samples (Samples Nos. 1 to 13).
<Strength Measuring Method>
[0052] Test pieces (tensile test pieces of metal materials, No. 5
test pieces) were collected from the samples by a method in
accordance with JIS 22241 (1506892-1) to measure the proof stress.
As a result, the test pieces exhibiting a proof stress of 350 MPa
or more were judged to be acceptable.
<Method for Observing Metallographic Structure>
[0053] After the samples were cut such that the dimension in the
width direction was halved, the measurement of the particle
diameter of the crystallized product in the cut surface and the
calculation of the area ratio of the fibrous structure were carried
out by the following methods.
[0054] In the measurement of the particle diameter of the
crystallized products, the above-described cut surface was first
polished to obtain a smooth surface. Five places on the smooth
surface were randomly selected, and microscopic images of these
five places were obtained at 500-times magnification using an
optical microscope. Thereafter, image analysis was performed on the
microscopic images, thereby obtaining a maximum value among the
particle diameters of the crystallized products calculated using
the above-described ellipse approximation method. The samples in
which the thus-obtained maximum particle diameter of the
crystallized products was 5 .mu.m or less were judged to be
acceptable.
[0055] In the calculation of the area ratio of the fibrous
structure, the cut surface was subjected to electrolytic polishing
and etching by the above-described method, and then a microscopic
image of the above cut surface was obtained using an optical
microscope so as to bring the entire range in the thickness
direction into view. Thereafter, image analysis was performed on
the resulting microscopic image to calculate the area ratio of the
fibrous structure relative to the entire metallographic structure.
The samples in which the thus-obtained area ratio of the fibrous
structure was 95% or more were judged to be favorable.
<Method for Evaluating Surface Quality>
[0056] The surfaces of the samples were visually observed to
confirm the presence or absence of defects such as surface
exfoliation or streaky scratchs formed in the extruding direction.
The samples having no such defects were judged to be
acceptable.
<Method for Evaluating Corrosion Resistance>
[0057] Salt spray testing was performed on the respective samples
by a method in accordance with JIS 22371 to measure the maximum
corrosion depth after a 1000-hour testing time. As a result, those
samples exhibiting a maximum corrosion depth of 200 .mu.m or less
were judged to be acceptable.
[0058] The evaluation results for each of the samples are indicated
in Table 3. The evaluation results for the samples which were not
judged as being acceptable or favorable are underlined in Table
3.
[0059] As can be seen from Table 3, Samples Nos. 1 to 3 were judged
as being acceptable in terms of all the evaluation criteria and
exhibited excellent properties in strength, corrosion resistance,
extrusion productivity and surface quality properties. FIG. 1 shows
a microscopic image used in the calculation of the area ratio of
the fibrous structure of Sample No. 1 as one typical example having
excellent properties. As shown in FIG. 1, the samples having
excellent properties exhibit a metallographic structure, in which a
recrystallized structure is generated only very near the surface;
the insides of these samples are mostly comprised of a fibrous
structure oriented in parallel to the extrusion direction.
[0060] Sample No. 4, the Si content of which was too low, was
judged as being unacceptable in terms of proof stress.
[0061] Sample No. 5, the Si content of which was too high, was
judged as being unacceptable because surface exfoliation was
observed after the extrusion.
[0062] Sample No. 6, the Mg content of which was too low, was
judged as being unacceptable in terms of proof stress.
[0063] Sample No. 7, the Mg content of which was high, was judged
as being unacceptable because surface exfoliation was observed
after the extrusion.
[0064] Sample No. 8, the Cu content of which was too low, was
judged as being unacceptable in terms of proof stress.
[0065] Sample No. 9, the Cu content of which was too high, was
judged as being unacceptable because surface exfoliation was
observed after the extrusion and the corrosion resistance was
poor.
[0066] Sample No. 10, the Mn, Cr and Zr contents of which were too
low, was judged as being unacceptable due to the reduced proof
stress that resulted from the low area ratio of the fibrous
structure. FIG. 2 shows a microscopic image used in the calculation
of the area ratio of the fibrous structure of Sample No. 10 as a
typical example of samples having a low area ratio of the fibrous
structure. As shown in FIG. 2, the metallographic structure of this
sample having a low area ratio of the fibrous structure had a thick
recrystallized structure generated on the surface as compared with
that shown in FIG. 1, and a layer (recrystallized structure) having
no streaky pattern and different in color hue from the fibrous
structure was clearly observed near the surface.
[0067] Sample No. 11, the Mn, Cr and Zr contents of which were too
high, was judged as being unacceptable because the particle
diameter of the crystallized product was excessively large and
surface exfoliation was observed after the extrusion.
[0068] Sample No. 12, the Ti content of which was too low, was
judged as being unacceptable due to the reduced proof stress that
resulted from the low area ratio of the fibrous structure.
[0069] Sample No. 13, the Ti, V and Fe contents of which were too
high, was judged as being unacceptable because the particle
diameter of the crystallized product was excessively large and
surface exfoliation was observed after the extrusion.
Example 2
[0070] This is an Example for investigating methods for
manufacturing the above-described high-strength aluminum alloy
extruded material. In this Example, alloy No. A indicated in Table
1 was used to produce samples (Samples Nos. 21 to 39) according to
the manufacturing conditions that varied as indicated in Table 4,
and then the strength measurements, metallographic structure
observations, surface quality evaluations and corrosion resistance
evaluations were carried out on the respective samples. In this
respect, it is noted that the details of the conditions for
manufacturing the respective samples and the methods for measuring
their strength, observing their metallographic structure,
evaluating their surface quality and evaluating their corrosion
resistance are the same as described above in Example 1.
[0071] The evaluation results for the respective samples are
indicated in Table 5. It is noted that the evaluation results for
the samples that were not judged as being acceptable or favorable
are underlined in Table 5.
[0072] As can be seen from Table 5, Samples Nos. 21 to 30 were
judged as being acceptable in terms of all the evaluation criteria,
and exhibited excellent properties in strength, corrosion
resistance, extrusion productivity and surface quality.
[0073] Sample No. 31, prepared at a too low holding temperature
during the homogenization treatment, was judged as being
unacceptable because the proof stress was low and surface
exfoliation was observed after the extrusion.
[0074] Sample No. 32, prepared at a too high holding temperature
during the homogenization treatment, was judged as being
unacceptable due to the reduced proof stress that resulted from the
low area ratio of the fibrous structure.
[0075] Sample No. 33, prepared at a too short holding temperature
during the homogenization treatment, was judged as being
unacceptable because the proof stress was low and surface
exfoliation was observed after the extrusion.
[0076] Sample No. 34, prepared at a too low ingot temperature
before hot extrusion, was judged as being unacceptable in terms of
proof stress.
[0077] Sample No. 35, prepared at a too high ingot temperature
before hot extrusion, was judged as being unacceptable because
surface exfoliation was observed after the extrusion.
[0078] Sample No. 36, prepared at a too low cooling rate during the
quenching treatment, was judged as being unacceptable in terms of
proof stress.
[0079] Sample No. 37, prepared at a too high extruded material
temperature after completion of the quenching treatment, was judged
as being unacceptable in terms of proof stress.
[0080] Samples Nos. 38 and 39, prepared at an aging treatment time
and temperature that fall outside the above-specified ranges, were
judged as being unacceptable in terms of proof stress.
TABLE-US-00001 TABLE 1 Alloy Si Mg Cu Mn Cr Zr Ti V Fe Zn Al No.
(%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) A 1.00 0.80 0.35 0.30
0.05 0.15 0.020 0.005 0.20 0.01 bal B 0.70 1.20 0.15 0.10 0.01 0.05
0.005 0.005 0.06 0.15 bal C 1.30 0.45 0.39 0.40 0.06 0.20 0.140
0.008 0.30 0.01 bal D 0.65 0.80 0.35 0.30 0.05 0.15 0.020 0.005
0.20 0.01 bal E 1.34 0.80 0.35 0.30 0.05 0.15 0.020 0.005 0.20 0.01
bal F 1.00 0.42 0.35 0.30 0.05 0.15 0.020 0.005 0.20 0.01 bal G
1.00 1.30 0.35 0.30 0.05 0.15 0.020 0.005 0.20 0.01 bal H 1.00 0.80
0.12 0.30 0.05 0.15 0.020 0.005 0.20 0.01 bal I 1.00 0.80 0.45 0.30
0.05 0.15 0.020 0.005 0.20 0.01 bal J 1.00 0.80 0.35 0.07 0.00 0.03
0.020 0.005 0.20 0.01 bal K 1.00 0.80 0.35 0.45 0.10 0.24 0.020
0.005 0.20 0.01 bal L 1.00 0.80 0.35 0.30 0.05 0.15 0.003 0.005
0.20 0.01 bal M 1.00 0.80 0.35 0.30 0.05 0.15 0.170 0.015 0.36 0.01
bal
TABLE-US-00002 TABLE 2 Hot Extruding Homogenization Ingot Quenching
Aging Treatment Temperature Temperature Temperature Treatment
Retaining Retaining before before Cooling immediately Treatment
Treatment Sample Alloy Temperature Time extruding quenching Rate
after quenching Temperature Time No. No. (.degree. C.) (Hour)
(.degree. C.) (.degree. C.) (.degree. C./sec.) (.degree. C.)
(.degree. C.) (Hour) 1 A 480 10 480 481 10 140 180 6 2 B 480 10 520
523 10 25 180 6 3 C 480 10 520 524 10 25 180 6 4 D 480 10 520 523
10 140 180 6 5 E 480 10 520 526 10 140 180 6 6 F 480 10 520 523 10
140 180 6 7 G 480 10 520 523 10 140 180 6 8 H 480 10 520 524 10 140
180 6 9 I 480 10 520 523 10 140 180 6 10 J 480 10 520 524 10 140
180 6 11 K 480 10 520 524 10 140 180 6 12 L 480 10 520 524 10 140
180 6 13 M 480 10 520 523 10 140 180 6
TABLE-US-00003 TABLE 3 Strength Observation of Evaluation of
Evaluation of Test Metallographic Structure Surface Quality
Corrosion Resistance Proof Maximun Area Ratio of Result of Maximum
Sample Alloy Stress Particle Diameter Fibrous Structure Visual
Corrosion Depth No. No. (MPa) (.mu.m) (%) Observation (.mu.m) 1 A
350 2 98 nondefective 65 2 B 356 2 95 nondefective 160 3 C 360 5 99
nondefective 150 4 D 330 2 98 nondefective 55 5 E 360 2 98
exfoliated 160 6 F 326 2 98 nondefective 60 7 G 382 2 98 exfoliated
70 8 H 318 2 98 nondefective 60 9 I 360 2 98 exfoliated 230 10 J
290 2 78 nondefective 180 11 K 380 6 99 exfoliated 100 12 L 348 2
93 nondefective 80 13 M 385 7 98 exfoliated 150
TABLE-US-00004 TABLE 4 Hot Extruding Homogenization Ingot Quenching
Aging Treatment Temperature Temperature Temperature Treatment
Retaining Retaining before before Cooling immediately Treatment
Treatment Sample Temperature Time extruding quenching Rate after
quenching Temperature Time No. (.degree. C.) (Hour) (.degree. C.)
(.degree. C.) (.degree. C./sec.) (.degree. C.) (.degree. C.)
(Hour)) 21 455 10 520 524 10 140 180 6 22 495 10 520 524 10 140 180
6 23 480 2 520 523 10 140 180 6 24 480 30 520 524 10 140 180 6 25
480 10 480 481 10 140 180 6 26 480 10 540 541 10 140 180 6 27 480
10 520 523 2 140 180 6 28 480 10 520 523 100 140 180 6 29 480 10
520 524 10 30 150 24 30 480 10 520 524 10 25 200 1 31 440 10 520
524 10 140 180 6 32 530 10 520 523 10 140 180 6 33 480 1 520 523 10
140 180 6 34 480 10 460 463 10 140 180 6 35 480 10 550 552 10 140
180 6 36 480 10 520 524 1 140 180 6 37 480 10 520 524 10 200 180 6
38 480 10 520 524 10 30 130 30 39 480 10 520 523 10 25 220 0.5
TABLE-US-00005 TABLE 5 Observation of Metallographic Evaluation
Structure Evaluation of Corrosion Strength Area of Surface
Resistance Test Maximun Ratio of Quality Maximum Proof Particle
Fibrous Result of Corrosion Sample Stress Diameter Structure Visual
Depth No. (MPa) (.mu.m) (%) Observation (.mu.m) 21 351 2 98
nondefective 60 22 375 2 98 nondefective 120 23 372 2 98
nondefective 150 24 373 2 98 nondefective 80 25 350 2 98
nondefective 65 26 384 2 98 nondefective 120 27 351 2 98
nondefective 155 28 374 2 98 nondefective 50 29 380 2 98
nondefective 70 30 351 2 98 nondefective 75 31 346 2 99 exfoliated
70 32 330 2 70 nondefective 110 33 342 2 98 exfoliated 150 34 312 2
98 nondefective 60 35 389 2 98 exfoliated 110 36 290 2 98
nondefective 170 37 285 2 98 nondefective 90 38 290 2 98
nondefective 65 39 330 2 98 nondefective 85
[0081] Representative, non-limiting examples of the present
invention were described above in detail with reference to the
attached drawings. This detailed description is merely intended to
teach a person of skill in the art further details for practicing
preferred aspects of the present teachings and is not intended to
limit the scope of the invention. Furthermore, each of the
additional features and teachings disclosed above may be utilized
separately or in conjunction with other features and teachings to
provide improved aluminum alloys and methods for manufacturing and
using the same.
[0082] Moreover, combinations of features and steps disclosed in
the above detailed description may not be necessary to practice the
invention in the broadest sense, and are instead taught merely to
particularly describe representative examples of the invention.
Furthermore, various features of the above-described representative
examples, as well as the various independent and dependent claims
below, may be combined in ways that are not specifically and
explicitly enumerated in order to provide additional useful
embodiments of the present teachings.
[0083] All features disclosed in the description and/or the claims
are intended to be disclosed separately and independently from each
other for the purpose of original written disclosure, as well as
for the purpose of restricting the claimed subject matter,
independent of the compositions of the features in the embodiments
and/or the claims. In addition, all value ranges or indications of
groups of entities are intended to disclose every possible
intermediate value or intermediate entity for the purpose of
original written disclosure, as well as for the purpose of
restricting the claimed subject matter.
* * * * *