U.S. patent application number 15/336322 was filed with the patent office on 2017-05-04 for aluminum alloy sheet for vehicle structural component and method of manufacturing the aluminum alloy sheet.
This patent application is currently assigned to Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.). The applicant listed for this patent is Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.). Invention is credited to Takahiro HASHIMOTO, Takahiko NAKAMURA, Yasuo TAKAKI.
Application Number | 20170121801 15/336322 |
Document ID | / |
Family ID | 58634540 |
Filed Date | 2017-05-04 |
United States Patent
Application |
20170121801 |
Kind Code |
A1 |
HASHIMOTO; Takahiro ; et
al. |
May 4, 2017 |
ALUMINUM ALLOY SHEET FOR VEHICLE STRUCTURAL COMPONENT AND METHOD OF
MANUFACTURING THE ALUMINUM ALLOY SHEET
Abstract
Provided is a 6000-series aluminum alloy sheet suitable for a
vehicle structural component. The Mg content and the Si content of
an Al--Mg--Si aluminum alloy sheet are balanced in a special
relationship, particularly cube orientation is increased as a
texture in a surface region of the sheet, and the yield ratio of
the sheet is reduced, thereby high strength of 0.2% proof stress of
220 MPa or more required for the vehicle structural component is
ensured, and crashworthiness evaluated by a VDA bending test is
improved.
Inventors: |
HASHIMOTO; Takahiro;
(Moka-shi, JP) ; NAKAMURA; Takahiko; (Moka-shi,
JP) ; TAKAKI; Yasuo; (Moka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) |
Kobe-shi |
|
JP |
|
|
Assignee: |
Kabushiki Kaisha Kobe Seiko Sho
(Kobe Steel, Ltd.)
Kobe-shi
JP
|
Family ID: |
58634540 |
Appl. No.: |
15/336322 |
Filed: |
October 27, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22F 1/047 20130101;
C22C 21/08 20130101; C22C 21/02 20130101; C22F 1/043 20130101 |
International
Class: |
C22F 1/047 20060101
C22F001/047; C22C 21/02 20060101 C22C021/02; C22F 1/043 20060101
C22F001/043; C22C 21/08 20060101 C22C021/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 2, 2015 |
JP |
2015-215541 |
Claims
1. An aluminum alloy sheet for a vehicle structural component,
comprising an Al--Mg--Si aluminum alloy sheet that contains, by
mass percent, Mg: 0.3 to 1.0%, Si: 0.5 to 1.2%, and Cu: 0.08 to
0.20%, content [Mg] of Mg and content [Si] of Si satisfying a
relationship [Si]/[Mg].gtoreq.0.7 and a relationship
1.4%.ltoreq.1.3 [Mg]+[Si].ltoreq.1.9%, the remainder consisting of
Al and inevitable impurities, and has a thickness of 2.0 mm or
more, wherein an average area ratio of cube orientation is 22% or
more in a surface region from a surface of the sheet to a depth of
10% in the thickness direction, an yield ratio of the sheet is 0.63
or less, and when the aluminum alloy sheet is stretched by 2% and
then subjected to artificial aging for 20 min at 180.degree. C.,
the aluminum alloy sheet has properties including 0.2% proof stress
of 220 MPa or more and crashworthiness showing a bending angle of
60.degree. or more at a VDA bending test.
2. The aluminum alloy sheet according to claim 1, wherein the
content [Mg] of Mg and the content [Si] of Si further satisfy a
relationship [Si]/[Mg].gtoreq.1.8 and a relationship
1.6%.ltoreq.1.3 [Mg]+[Si].ltoreq.1.9%.
3. The aluminum alloy sheet according to claim 1, wherein the
aluminum alloy sheet has the average area ratio of cube orientation
of 35% or more, and crashworthiness showing the bending angle of
90.degree. or more at the VDA bending test.
4. The aluminum alloy sheet according to claim 2, wherein the
aluminum alloy sheet has the average area ratio of cube orientation
of 35% or more, and crashworthiness showing the bending angle of
90.degree. or more at the VDA bending test.
5. A method of manufacturing an aluminum alloy sheet for a vehicle
structural component, wherein an Al--Mg--Si aluminum alloy slab
containing, by mass percent, Mg: 0.3 to 1.0%, Si: 0.5 to 1.2%, and
Cu: 0.08 to 0.20%, content [Mg] of Mg and content [Si] of Si
satisfying a relationship [Si]/[Mg].gtoreq.0.7 and a relationship
1.4%.ltoreq.1.3 [Mg]+[Si].ltoreq.1.9%, the remainder consisting of
Al and inevitable impurities is subjected to homogenization and
then rolled into a rolled sheet having a thickness of 2.0 mm or
more, the rolled sheet is subjected to solution treatment in which
the rolled sheet is held for 0.1 to 30 sec within a range from 540
to 570.degree. C., and is successively subjected to quenching, and
is reheated within 10 min after finish of the quenching in such a
manner that the rolled sheet is held for 3 to 20 hr within a
material temperature range from 60 to 90.degree. C. so as to be
formed into an aluminum alloy sheet for a vehicle structural
component, and the aluminum alloy sheet has a microstructure and
properties, the microstructure including an average area ratio of
cube orientation of 22% or more in a surface region from a surface
of the sheet to a depth of 10% in the thickness direction, the
properties including a yield ratio of 0.63 or less, and including
0.2% proof stress of 220 MPa or more and crashworthiness showing a
bending angle of 60.degree. or more at a VDA bending test when the
aluminum alloy sheet is stretched by 2% and then subjected to
artificial aging for 20 min at 180.degree. C.
Description
BACKGROUND
[0001] The present invention relates to a 6000-series aluminum
alloy sheet for a vehicle structural component, which is
manufactured by common rolling (common method) and has high
strength and good crashworthiness, and a method of manufacturing
the aluminum alloy sheet.
[0002] The aluminum alloy sheet described in the present invention
refers to a material aluminum alloy sheet including a rolled sheet
such as a hot-rolled sheet or a cold-rolled sheet, which has been
subjected to tempering such as solution treatment and quenching,
but has not been formed into a vehicle structural component to be
used and has not been subjected to artificial aging such as
paint-bake hardening. Hereinafter, aluminum may be referred to as
Al.
[0003] Recently, a social demand for weight saving of a vehicle
body has increased more and more out of consideration for the
global environment. To meet such a demand, aluminum alloy materials
are used in place of previous steel materials such as steel sheets
for some parts of a vehicle body, such as panels (outer panels such
as a hood, a door, and a roof, and inner panels), and
reinforcements such as a bumper reinforcement (bumper R/F) and a
door beam.
[0004] For further weight reduction of the vehicle body, the
aluminum alloy materials are necessary to be extensively used for
vehicle components, particularly vehicle structural components that
contribute to weight saving, such as members including a side
member, frames, and pillars. However, compared with the vehicle
panel materials, such vehicle structural components are necessary
to be further increased in strength of a material sheet and have an
additional property, i.e., crashworthiness, which leads to shock
absorption or passenger protection at vehicle collision.
[0005] In this regard, an extrusion, which is manufactured by hot
extruding of JIS or AA 7000-series aluminum alloy, has been
generally used as a material for the reinforcement in the vehicle
structural components. On the other hand, the large vehicle
structural components such as the member, the frame, and the pillar
are each preferably formed of a rolled sheet as a material, which
is produced by hot rolling or hot rolling followed by cold rolling
of a homogenized slab. However, the 7000-series aluminum alloy has
not been actively put to practical use in a form of a rolled sheet
because of its high strength and low formability.
[0006] Hence, JIS or AA 6000-series aluminum alloy, which is
Al--Mg--Si aluminum alloy having lower strength and better
formability than the 7000-series aluminum alloy, attracts attention
as alloy for a rolled sheet manufactured by common rolling (common
method).
[0007] The 6000-series aluminum alloy extrusion has been provided
and practically used as the reinforcement, but has been rarely
provided as a rolled sheet.
[0008] Japanese Unexamined Patent Application Publication No.
JP2001-294965 barely describes a 6000-series aluminum alloy sheet
having improved crashworthiness, which has a sheet microstructure
controlled in size and aspect ratio of a grain and has a proof
stress of 230 MPa or more after artificial aging.
[0009] On the other hand, the 6000-series aluminum alloy sheet is
already used for the large body panels (outer panels such as a
hood, a fender, a door, a roof, and a trunk lid, and inner panels)
of a vehicle.
[0010] Hence, many metallurgical remedies including a composition,
a microstructure, and a texture have been provided in order to
combine or improve press formability and bake hardenability (BH)
required for such large body panels of a vehicle.
[0011] For example, Japanese Patent No. 5148930 describes a
material as the panel material, in which the intensity of cube
orientation is increased to 20 or more in order to improve
bendability in flat hemming or the like during press forming.
SUMMARY
[0012] However, the existing 6000-series aluminum alloy sheet, in
which an intensity or an average area ratio of cube orientation is
increased, is a material for the vehicle panels.
[0013] On the other hand, unlike such vehicle panel applications,
the vehicle structural components such as the members, the frames,
and the pillars, to which the present invention is intended to be
applied, are required to have properties specific to such
applications as described above, such as increased strength,
crashworthiness as an additional property, press formability, and
corrosion resistance.
[0014] For example, in Europe, along with recent raising the level
(tightening) of the collision safety standards of vehicles, the
vehicle structural components such as the frames and the pillars
are required to satisfy the crashworthiness evaluated by
"VDA238-100 Plate bending test for metallic materials (hereinafter,
referred to as VDA bending test)" standardized by German
Association of the Automotive Industry (Verb and der
Automobilindustrie (VDA)).
[0015] However, unclear is whether it is effective in improving
crashworthiness to increase the intensity or the area ratio of cube
orientation in the sheet surface in order to improve bendability of
the existing 6000-series aluminum alloy sheet for the vehicle
panels during press forming.
[0016] In Japanese Unexamined Patent Application Publication No.
JP2001-294965 that aims to improve crashworthiness, crashworthiness
is evaluated based on whether a crack occurs after a 180.degree.
bending test. The VDA bending test as an evaluation test of
crashworthiness of a sheet is known to correlate with the
crashworthiness at vehicle collision. The VDA bending test that
allows superiority of the crashworthiness to be represented by a
bending angle is a quantitative evaluation test, and appropriately
represents the crashworthiness.
[0017] In light of such a circumstance, an object of the present
invention is to allow a 6000-series aluminum alloy sheet
manufactured by common rolling to have properties specific to the
vehicle structural component application, such as increased
strength, crashworthiness as an additional property, press
formability, and corrosion resistance.
[0018] To achieve the object, an aluminum alloy sheet for a vehicle
structural component having good crashworthiness of the present
invention is summarized by an Al--Mg--Si aluminum alloy sheet that
contains, by mass percent, Mg: 0.3 to 1.0%, Si: 0.5 to 1.2%, and
Cu: 0.08 to 0.20%, the content [Mg] of Mg and the content [Si] of
Si satisfying a relationship [Si]/[Mg].gtoreq.0.7 and a
relationship 1.4%.ltoreq.1.3 [Mg]+[Si].ltoreq.1.9%, the remainder
consisting of Al and inevitable impurities, and has a thickness of
2.0 mm or more, in which an average area ratio of cube orientation
is 22% or more in a surface region from a surface of the sheet to a
depth of 10% in the thickness direction, an yield ratio of the
sheet is 0.63 or less, and when the aluminum alloy sheet is
stretched by 2% and then subjected to artificial aging for 20 min
at 180.degree. C., the aluminum alloy sheet has properties
including 0.2% proof stress of 220 MPa or more and crashworthiness
showing a bending angle of 60.degree. or more at a VDA bending
test.
[0019] Furthermore, to achieve the object, a method of
manufacturing an aluminum alloy sheet for a vehicle structural
component having good crashworthiness of the present invention is
summarized in that an Al--Mg--Si aluminum alloy slab, which
contains, by mass percent, Mg: 0.3 to 1.0%, Si: 0.5 to 1.2%, and
Cu: 0.08 to 0.20%, the content [Mg] of Mg and the content [Si] of
Si satisfying a relationship [Si]/[Mg].gtoreq.0.7 and a
relationship 1.4%.ltoreq.1.3 [Mg]+[Si].ltoreq.1.9%, the remainder
consisting of Al and inevitable impurities, is subjected to
homogenization and then rolled into a rolled sheet having a
thickness of 2.0 mm or more, the rolled sheet is subjected to
solution treatment in which the rolled sheet is held for 0.1 to 30
sec within a range from 540 to 570.degree. C., and is successively
subjected to quenching, and is reheated within 10 min after finish
of the quenching in such a manner that the rolled sheet is held for
3 to 20 hr within a material temperature range from 60 to
90.degree. C. so as to be formed into an aluminum alloy sheet for a
vehicle structural component, and the aluminum alloy sheet has a
microstructure and properties, the microstructure including an
average area ratio of cube orientation of 22% or more in a surface
region from a surface of the sheet to a depth of 10% in the
thickness direction, the properties including a yield ratio of 0.63
or less, and including 0.2% proof stress of 220 MPa or more and
crashworthiness showing a bending angle of 60.degree. or more at a
VDA bending test when the aluminum alloy sheet is stretched by 2%
and then subjected to artificial aging for 20 min at 180.degree.
C.
[0020] In the present invention, the alloy composition of the
6000-series aluminum alloy sheet is reviewed in light of a
relationship between the content balance between Mg and Si or the
texture and the properties specific to the applications of the
vehicle structural component.
[0021] As a result, it has been found that while the aluminum alloy
sheet has increased strength and crashworthiness as an additional
property by balancing the content between Mg and Si and increasing
the area ratio of cube orientation, the alloy sheet can have the
properties specific to that applications, such as press formability
and corrosion resistance. According to the present invention, the
6000-series aluminum alloy sheet suitable for the vehicle
structural components can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a perspective view illustrating an aspect of a VDA
bending test that evaluates crashworthiness.
[0023] FIG. 2 includes front and side views of a punch in FIG.
1.
DETAILED DESCRIPTION
[0024] Hereinafter, an embodiment of the present invention is
specifically described for each of requirements.
[0025] As a prerequisite, the Al--Mg--Si (hereinafter, also
referred to as 6000-series) aluminum alloy sheet of the present
invention is used for the vehicle structural components rather than
the vehicle panel materials as in the previous case.
[0026] Hence, such vehicle structural components (hereinafter, may
be simply described as structural components) are required to
satisfactorily have properties that are not provided in the
existing vehicle panel materials, including good crashworthiness, a
low yield ratio that allows the aluminum alloy sheet to be formed
into a complicated shape, high post-baking proof stress, and high
grain-boundary corrosion resistance. If any one of such properties
is lacked, the aluminum alloy sheet cannot be used as the
structural component.
[0027] More specifically, the properties required for the
structural component can be defined to include press formability
with a yield ratio of 0.63 or less, and include properties
including BH showing 0.2% proof stress of 220 MPa or more and
crashworthiness showing a bending angle of 60.degree. or more at
the VDA bending test when the aluminum alloy sheet is stretched by
2% and then subjected to artificial aging for 20 min at 180.degree.
C.
[0028] More preferably, the aluminum alloy sheet has the average
area ratio of cube orientation of 35% or more, and crashworthiness
showing a bending angle of 90.degree. or more at the VDA bending
test.
[0029] Hence, the requirements of the present invention described
below are on the aluminum alloy sheet for the structural
components, the meanings of which are to satisfactorily provide the
specifically required properties.
Chemical (Alloy) Composition:
[0030] In the present invention, to satisfy the properties required
for the structural components in terms of a composition, the
Al--Mg--Si (hereinafter, also referred to as 6000-series) aluminum
alloy sheet has a composition including, by mass percent, Mg: 0.3
to 1.0%, Si: 0.5 to 1.2%, and Cu: 0.08 to 0.20%, the content [Mg]
of Mg and the content [Si] of Si satisfying a relationship
[Si]/[Mg].gtoreq.0.7 and a relationship 1.4%.ltoreq.1.3
[Mg]+[Si].ltoreq.1.9%, the remainder consisting of Al and
inevitable impurities.
[0031] The content range and the meaning or the tolerance of each
element of the 6000-series aluminum alloy sheet are now described.
The percentage representing the content of each element refers to
mass percent.
Mg: 0.3 to 1.0%
[0032] Mg forms a compound phase such as Mg.sub.2Si with Si during
artificial aging such as paint-bake cycle, and increases strength
through precipitation of the compound phase. An excessively small
content of Mg, less than 0.3%, does not ensure sufficient
strength.
[0033] If the Mg content exceeds 1.0%, the compound phase such as
Mg.sub.2Si is crystallized or precipitated as a coarse particle
during casting or solution treatment, and acts as an origin of a
small crack. This promotes the destruction and thus increases the
yield ratio, leading to deterioration of press formability.
Consequently, the Mg content is 0.3 to 1.0%.
Si: 0.5 to 1.2%
[0034] Si also forms the compound phase such as Mg.sub.2Si with Mg
during artificial aging such as paint-bake cycle, and increases
strength through precipitation of the compound phase.
[0035] An excessively small content of Si, less than 0.5%, does not
ensure sufficient strength.
[0036] If the Si content exceeds 1.2%, the compound phase such as
Mg.sub.2Si is crystallized or precipitated as a coarse particle
during casting or solution treatment, and acts as an origin of a
small crack. This promotes the destruction and thus increases the
yield ratio, leading to deterioration of press formability.
Consequently, the Si content is 0.5 to 1.2%.
Content [Mg] of Mg and Content [Si] of Si
[0037] The Mg content and the Si content [Si] are importantly
balanced to improve press formability and crashworthiness in terms
of the composition in addition to the content of each element.
[0038] In this regard, the content [Mg] of Mg and the content [Si]
of Si are adjusted to satisfy a relationship [Si]/[Mg].gtoreq.0.7
and a relationship 1.4%.ltoreq.1.3 [Mg]+[Si].ltoreq.1.9%.
[Si]/[Mg].gtoreq.0.7
[0039] A larger Si content or a smaller Mg content improves work
hardenability through solid-solution strengthening caused by solid
solution of Si into a matrix, and thus decreases the yield ratio,
leading to improvement in press formability.
[0040] If [Si]/[Mg] is less than 0.7, sufficient work hardenability
is not ensured, and the yield ratio is increased, leading to
deterioration of press formability.
[0041] Consequently, [Si]/[Mg] is 0.7 or more. If [Si]/[Mg] is 1.8
or more, the yield ratio is further decreased, and press
formability is further improved. Hence, [Si]/[Mg] is preferably 1.8
or more.
1.4%.ltoreq.1.3 [Mg]+[Si].ltoreq.1.9%
[0042] Si and Mg form a .beta.'' phase as a reinforcement phase
after bake hard (artificial aging), and increases strength through
precipitation of such a compound phase.
[0043] However, if Mg or Si is excessively contained, the compound
phase such as Mg.sub.2Si is crystallized or precipitated as a
coarse particle during casting or solution treatment, and acts as
an origin of a small crack, which greatly deteriorates
crashworthiness. Such a crystallized or precipitated state depends
on the content of each of Si and Mg.
[0044] If 1.3 [Mg]+[Si] is less than 1.4%, sufficient BH
characteristics (post-baking proof stress) are not ensured.
[0045] If 1.3 [Mg]+[Si] exceeds 1.9%, the compound phase is
crystallized or precipitated as a coarse particle during casting or
quenching, which extremely deteriorates crashworthiness.
[0046] Consequently, 1.3 [Mg] (which means 1.3.times.Mg
content)+[Si] (which means Si content) is within a range from 1.4
to 1.9%, preferably 1.6 to 1.9%.
Cu: 0.08 to 0.20%
[0047] Cu is solid-solutionized in a matrix and improves work
hardenability through solid-solution strengthening, and thus
decreases the yield ratio, leading to improvement in press
formability.
[0048] However, if the Cu content is excessive, more than 0.20%, a
PFZ (precipitate free zone) of Cu is formed in the vicinity of a
grain boundary along with age precipitation, and the zone, which is
potentially baser than the inside of a grain, is selectively
dissolved in a corrosion environment, leading to deterioration of
grain-boundary corrosion resistance.
[0049] If the Cu content is less than 0.08%, sufficient work
hardenability is not provided, and thus the yield ratio is not
decreased, leading to deterioration of press formability.
[0050] Consequently, the Cu content is within a range from 0.08 to
0.20%.
Other Elements
[0051] Other elements are essentially impurities in the present
invention. The following upper limit is given as a tolerance for
each element when the element is contaminated from a melting
material for a slab, such as a scrap. The upper limit includes
0%.
[0052] Mn: 1.0% or less, Fe: 0.5% or less, Cr: 0.3% or less, Zr:
0.2% or less, V: 0.2% or less, Ti: 0.1% or less, Zn: 0.5% or less,
Ag: 0.1% or less, and Sn: 0.15% or less.
BH (Bake Hardenability, Artificial Aging Hardenability):
[0053] In order to ensure strength and stiffness necessary for the
vehicle structural component, BH is defined after the aluminum
alloy sheet is stretched by 2% and then subjected to artificial
aging (hereinafter, may be simply referred to as aging) under a
special condition of 180.degree. C..times.20 min for better
reproducibility.
[0054] Higher BH is better for the vehicle structural component,
and an aluminum alloy sheet having BH providing 0.2% proof stress
of 220 MPa or more is defined to be acceptable in the present
invention.
Yield Ratio:
[0055] A low yield ratio means a low proof stress to tensile
strength. A breaking limit is higher with higher tensile strength
to a proof stress. A lower proof stress to a tensile strength leads
to a smaller springback amount, leading to improvement in press
formability. Consequently, the yield ratio is defined to be 0.63 or
less to ensure press formability that allows the aluminum alloy
sheet to be formed into a structural component having a complicated
shape.
Thickness:
[0056] Thickness of the aluminum alloy sheet is necessary to be 2.0
mm or more to ensure the strength and the stiffness necessary for
the vehicle structural component. Although the upper limit of the
thickness is not specifically defined, the upper limit is about 4.0
mm in consideration of the limit of forming such as press forming,
and of a weight increase range in which the effect of weight
reduction is not effectively reduced compared with a steel sheet as
a comparative material. One of a hot-rolled sheet and a cold-rolled
sheet is appropriately selectively formed based on such a preferred
thickness range (2.0 to 4.0 mm).
Area Ratio of Cube Orientation:
[0057] In the present invention, the area ratio of cube orientation
in an appropriate surface region from the sheet surface to the
depth of 10% in the thickness direction is defined to be 22% or
more in order to improve crashworthiness of the sheet.
[0058] The meaning of "sheet surface" in the present invention is a
surface of a natural oxide film (having a thickness level of tens
to hundreds nanometers) formed on (the surface of) an aluminum
alloy matrix.
[0059] A larger area ratio of cube orientation in the surface
region from the sheet surface to the depth of 10% of the thickness
in the thickness (depth) direction more suppresses formation of a
shear band on a bending outside, leading to improvement in crash
properties of the sheet.
[0060] If the area ratio of cube orientation in the surface region
from the sheet surface to the depth of 10% of the thickness in the
thickness direction is smaller than 22%, crashworthiness is
extremely deteriorated. Consequently, the area ratio of cube
orientation is 22% or more in the surface region. Furthermore,
since the area ratio of cube orientation of more than 35% leads to
good crashworthiness, the area ratio of cube orientation in the
surface region is preferably 35% or more.
Measurement of Area Ratio of Cube Orientation:
[0061] For the average area ratio of cube orientation of a grain of
the sheet, the sheet surface is polished by mechanical polishing or
buff polishing such that an observation surface at an appropriate
depth position in the surface region from the sheet surface to the
depth of 10% in the thickness direction appears as the observation
surface extending parallel to a rolling plane (rolling surface) in
plan view of the sheet (test specimen) of each of (three) test
specimens each being taken from the appropriate depth position in
the surface region from the sheet surface to the depth of 10% of
the thickness in a depth direction.
[0062] The test specimen obtained in this way is irradiated with an
electron beam at a pitch of 5 .mu.m with SEM-EBSD over a
rectangular measurement area with a length of 1000 .mu.m of a side
in a rolling direction of the sheet and a length of 320 .mu.m of a
side in a sheet width direction in the observation surface.
[0063] For example, SEM (JEOLJSM5410) from JEOL Ltd. and an EBSD
measurement/analysis system: OIM (Orientation Imaging Macrograph,
analysis software "OIM Analysis") from TSL Solutions are used as
the SEM system to determine whether each grain shows cube
orientation (within 15.degree. from an ideal orientation), and
obtain area of each crystal orientation in a measured view.
[0064] For example, such measurement is performed by electron beam
scan at a step interval of 5 .mu.m. Crystal orientation of an
individual grain is measured at each measurement point, and is
analyzed in combination with positional data of the measurement
point, thereby crystal orientation of the individual grain is
determined in the measurement area.
[0065] For each test specimen, an average area ratio (%) of grains
having cube orientation to area (320000 .mu.m.sup.2) of the
measurement area as the total measurement area is determined, and
the measured average area ratios for the three test specimens are
averaged.
[0066] The SEM-EBSD (EBSP) method is a general crystal orientation
analyzing method with a field emission scanning electron microscope
(FESEM) equipped with an electron back scattering (scattered)
diffraction pattern (EBSD) system.
[0067] Specifically, the observation specimen for SEM-EBSD is
prepared by mirror-finishing the observation specimen (sectional
microstructure) through mechanical polishing. The specimen is
placed in a bodytube of the FESEM, and the mirror-finished surface
of the specimen is irradiated with an electron beam to project EBSD
(EBSP) onto a screen. The projected EBSD (EBSP) is photographed by
a highly sensitive camera, and is loaded as an image into a
computer. The computer analyzes the image and determines crystal
orientation through comparison with a pattern obtained by
simulation using known crystal systems. The calculated crystal
orientation is registered as a three-dimensional Euler angle
together with a position coordinate (x, y). This process is
automatically performed on all measurement points; hence, tens of
thousands to hundreds of thousands of crystal orientation data on a
sheet section are obtained at the end of the measurement.
[0068] Hence, an observation field is wide, and information on a
large number of grains, including a distribution state, average
grain size, standard deviation of the average grain size, and
orientation analysis, is advantageously obtained within several
hours. Hence, the SEM-EBSD (EBSP) method is most suitable for a
case where a texture including the area ratio of cube orientation
is accurately determined as in the present invention.
[0069] An aluminum alloy sheet typically has a texture including
the following many orientation factors (grains having such
orientations), and has corresponding crystal planes. In general, a
texture of a rolled recrystallized sheet of aluminum alloy mainly
includes Cube orientation, Goss orientation, Brass orientation, S
orientation, and Copper orientation. For a texture of a rolled
sheet, the texture is represented by a rolling plane and a rolling
direction, while the rolling plane is expressed by {hkl} and the
rolling direction is expressed by <uvw>. According to such
expression, each orientation is expressed as follows.
[0070] Cube orientation {001}<100>
[0071] Goss orientation {011}<100>
[0072] Brass orientation (B orientation) {011}<211>
[0073] Cu orientation (copper orientation) {112}<111>
[0074] S orientation {123}<634>
Crashworthiness:
[0075] Crashworthiness refers to the following property: When a
structural component receives an impact load at vehicle collision
or the like, the structural component deforms to the last without
cracking or crush (or even if cracking or crush occurs) in an early
stage or in a process of deformation. That is, a component having a
good crashworthiness bending-deforms into concertinas without
cracking or crush (or even if cracking or crush occurs).
[0076] For the crashworthiness in the present invention, a
structural component having a crashworthiness showing a bending
angle of 60.degree. or more at the VDA bending test is defined to
be acceptable for the vehicle structural component. The larger the
bending angle, the better the crashworthiness, and a bending angle
of 90.degree. or more is more preferable. A structural component
having a crashworthiness showing a bending angle of less than
60.degree. cannot be used for the vehicle structural component.
[0077] The bending test evaluating the crashworthiness is performed
as the VDA bending test in accordance with "VDA238-100 Plate
bending test for metallic materials" in the standard of German
Association of the Automotive Industry (Verband der
Automobilindustrie (VDA)).
[0078] The test method is shown by a perspective view of FIG. 1.
FIG. 2 illustrates a punch to be used by front and side views.
[0079] First, a sheet-like test specimen is horizontally placed
with an equal length on both sides as illustrated by a dot line in
FIG. 1 on two rolls disposed parallel to each other with a roll
gap.
[0080] Specifically, the sheet-like test specimen is horizontally
placed with an equal length on both sides on the two rolls so that
its central portion is located in the middle of the roll gap such
that the rolling direction of the test specimen is perpendicular to
an extending direction of a sheet-like pressing bend tool
vertically disposed on an upper side.
[0081] The pressing bend tool is pressed from the upper side to the
central portion of the sheet-like test specimen to exert a load to
the test specimen, so that the test specimen is press-bent
(push-bent) toward the narrow roll gap, and the central portion of
the bending-deformed sheet-like test specimen is forced into the
narrow roll gap.
[0082] When the load F from the upper pressing bend tool is
maximized (immediately before a bending end of the central portion
of the sheet-like test specimen is cracked), an angle on a bending
outside of the central portion of the sheet-like test specimen is
measured as the bending angle (.degree.), and the crashworthiness
is evaluated by measure of the bending angle. As the bending angle
is larger, bending deformation of the sheet-like test specimen
continues longer without crush halfway, i.e., crashworthiness is
better.
[0083] The test condition of the VDA bending test is described
below using signs shown in FIG. 1. That is, the sheet-like test
specimen has a square shape having a width b of 60 mm and a length
1 of 60 mm, the two rolls each have a diameter D of 30 mm, and the
roll gap L is two times as large as the thickness of the sheet-like
test specimen (two times as large as the thickness 2.5 mm of a
cold-rolled sheet, i.e., 5 mm, in Example as described later). S is
the forced depth of the central portion of the sheet-like test
specimen into the roll gap when the load F is maximized.
[0084] As shown in FIG. 2, the punch as a sheet-like pressing bend
tool has a tapered shape in such a manner that a sheeted blade
(thickness 2 mm) on the lower side of the punch, which is to be
pressed to the central portion of the sheet-like test specimen, has
a pointed end (lower end) having a radius r of 0.2 mm.
Manufacturing Method:
[0085] A method of manufacturing the aluminum alloy sheet of the
present invention is now described. The aluminum alloy sheet of the
present invention is manufactured, in which a casted aluminum alloy
slab having the 6000-series composition is subjected to
homogenization, and is then subjected to hot rolling and cold
rolling so as have a predetermined thickness, and is further
subjected to tempering such as solution treatment.
[0086] During such a manufacturing process, a reduction condition
of cold rolling is adjusted to be within a preferred range, and the
conditions of the solution treatment and the following pre-aging
treatment are also adjusted to be within preferred ranges as
described later in order to ensure the microstructure and texture
defined in the present invention.
(Cooling Rate in Melting and Casting)
[0087] In a melting-and-casting step, molten metal of aluminum
alloy, which is melted and adjusted to be within the 6000-series
composition range, is casted by an appropriately selected common
melting-and-casting process such as a continuous casting process
and a semi-continuous casting process (DC casting process)
(Homogenization)
[0088] Subsequently, the casted aluminum alloy slab is subjected to
homogenization prior to hot rolling. The homogenization (soaking)
is important for sufficient solid solution of Si and Mg in addition
to eliminating segregation in a microstructure of a slab as a
common purpose. Any homogenization condition including common
onetime or one-stage treatment may be used without limitation as
long as the purpose is achieved.
[0089] Homogenization temperature is 500 to 560.degree. C., and
homogenization (holding) time is appropriately selected from a
range of 1 hr or more. If the homogenization temperature is low,
segregation in the grain cannot be sufficiently eliminated, and
acts as an origin of fracture; hence, crashworthiness may be
deteriorated.
(Hot Rolling)
[0090] After the homogenization, the slab is hot-rolled so as to be
formed into a hot-rolled sheet. Hot rolling includes a rough
rolling step for the slab and a finish rolling step depending on
thickness of the sheet to be rolled.
[0091] A reverse-type or tandem-type rolling mill is appropriately
used for the rough rolling step or the finish rolling step.
[0092] The hot-rolled sheet has a worked structure remaining after
the hot rolling and a high integration of cube orientation, and
thus has a preferred average area ratio of cube orientation of 35%
or more in the surface region from the sheet surface to the depth
of 10% in the thickness direction, and consequently has an
extremely improved crashworthiness. Hence, the hot-rolled sheet may
be used as a product sheet having a final thickness of 2.0 mm or
more while being not subjected to cold rolling.
(Cold Rolling)
[0093] When the hot-rolled sheet is cold-rolled into a desired
thickness, cold reduction is adjusted to be 70% or less, preferably
small as much as possible so that the worked structure caused by
the hot rolling still remains, integration of cube orientation is
increased, and an average area ratio of cube orientation is 22% or
more, preferably 35% or more, in the surface region from the sheet
surface to the depth of 10% in the thickness direction.
[0094] If the cold reduction exceeds 70%, uniform strain in a
thickness direction is introduced after the cold rolling, and
uniform and fine isometric grains are given during the solution
heat treatment. However, since an area ratio of a crystal
orientation other than the cube orientation increases, the area
ratio of cube orientation in the surface region from the sheet
surface to the depth of 10% in the thickness direction necessarily
becomes smaller than 22%, and thus crashworthiness may be
deteriorated.
[0095] In this regard, the cold reduction is preferably further
smaller, less than 5%. If the cold reduction is less than 5%,
substantially no strain is introduced by the cold rolling, so that,
as with the hot-rolled sheet, a microstructure caused by the hot
rolling still remains, integration of cube orientation is high, and
an area ratio of cube orientation is 35% or more in the surface
region from the sheet surface to the depth of 10% in the thickness
direction, leading to significant improvement in
crashworthiness.
[0096] Consequently, the cold reduction is desirably less than 5%.
Intermediate annealing may be appropriately performed between cold
rolling passes.
(Solution treatment and Quenching)
[0097] The cold-rolled sheet is subjected to solution treatment and
subsequent quenching to room temperature. The solution treatment
may be performed using a common continuous heat treatment line.
However, to ensure a sufficient solid-solution amount of each
element such as Mg or Si, it is preferred that the cold-rolled
sheet is heated to a solution treatment temperature (achieving
temperature) of 540 to 570.degree. C. and held at the temperature
for 0.1 to 60 sec, and is then successively subjected to
quenching.
[0098] If the solution temperature is lower than 540.degree. C.,
sufficient solid solubility of each of Mg and Si is not ensured,
and sufficient post-baking strength may not be provided. If the
solution treatment temperature exceeds 570.degree. C., the sheet
may be melted because such temperature is close to the melting
point. If the holding time of the solution treatment is longer than
60 sec, initial strength is high, and the yield ratio may be
increased. Consequently, the solution treatment temperature is
preferably 540 to 570.degree. C., and the holding time of the
solution treatment is preferably 0.1 to 60 sec.
[0099] The quenching subsequent to the solution treatment is
conducted while cooling methods such as air cooling with a fan and
water cooling with mist, spray, or immersion, and cooling
conditions are selectively used to ensure a cooling rate such that
the solid-solutionized Mg amount and the solid-solutionized Si
amount are each not decreased by formation of precipitates mainly
including Mg--Si during cooling.
(Reheating; Preliminary Aging)
[0100] The cold-rolled sheet is preferably reheated within 10 min
after the cold-rolled sheet is thus subjected to quenching
subsequent to solution treatment and thus cooled to room
temperature (when the quenching has been finished), so that the
sheet is held for 3 to 20 hr within a range of material temperature
from 60 to 90.degree. C.
[0101] If the room-temperature holding time before start of the
reheating (start of the heating) is too long, a Si-rich Mg--Si
cluster is formed due to room-temperature aging, and an Mg--Si
cluster having a good balance between Mg and Si is less likely to
be increased; hence, BH may be deteriorated. Hence, a shorter
room-temperature holding time is better. The quenching subsequent
to the solution treatment may be followed by the reheating with
substantially no interval, and no lower limit interval is set.
[0102] The sheet is held for 3 to 20 hr at 60 to 90.degree. C. in
the reheating, thereby the Mg--Si cluster having a good balance
between Mg and Si is formed, and thus BH is improved.
[0103] The reheating temperature of less than 60.degree. C. or the
holding time of less than 3 hr leads to a state similar to the
state without reheating, in which the Mg--Si cluster having a good
balance between Mg and Si is less likely to be increased, and thus
post-paint-bake proof stress (BH) is easily reduced.
[0104] The reheating temperature of more than 90.degree. C. or the
holding time of more than 20 hr may provide a high initial strength
and an increase in yield ratio.
[0105] Although the present invention is now described in detail
with Example, the present invention should not be limited thereto,
and modifications or alterations thereof may be made within the
scope without departing from the gist described before and later,
all of which are included in the technical scope of the present
invention.
Example
[0106] 6000-Series aluminum alloy cold-rolled sheets having
compositions shown in Table 1 were produced at different
manufacturing conditions as in Table 2 so as to have different
textures. The sheets were subjected to BH and evaluated in
mechanical properties such as a yield ratio and strength,
crashworthiness evaluated by the VDA bending test, and
grain-boundary corrosion resistance as the corrosion resistance
necessary for the structural component. Table 2 also shows results
of such evaluation.
[0107] Aluminum alloys having the compositions shown in Table 1
were melted and casted. Each of the produced slabs was homogenized
under a condition of 540.degree. C..times.4 hr, and was
successively hot-rolled with a finish temperature of 260 to
350.degree. C. Subsequently, the slabs were cold-rolled with
reductions shown in Table 2 so as to have a final thickness of 2.5
mm, and were thus formed into cold-rolled sheets.
[0108] Subsequently, each of the cold-rolled sheets was heated at a
heating rate of 100.degree. C./min or more, and was subjected to
solution treatment under a condition of temperature and holding
time shown in Table 2, and was then successively subjected to
solution treatment in which the cold-rolled sheet was dipped in
water so as to be cooled to room temperature. Subsequently, sheets
to be reheated were reheated into temperature regions shown in
Table 2 and were held at 60.degree. C. or more under conditions of
time shown in Table 2, and were then natural-cooled to room
temperature.
[0109] Test samples were taken from the aluminum alloy sheets. For
each test sample, a texture in the surface region of a section and
a yield ratio were measured. The test sample was then subjected to
BH, and was then subjected to examination of mechanical properties
and crashworthiness, and subjected to examination of grain-boundary
corrosion resistance typically required for the vehicle structural
component.
Average Area Ratio of Cube Orientation:
[0110] For the area ratio (%) of cube orientation, a section
orthogonal to a sheet width direction of the reheated test sample
was mechanically polished and electro-polished. Subsequently,
crystal orientation in the normal direction to the section along
the sheet width in the surface region was measured by the SEM-EBSD
method.
[0111] Shift in crystal orientation within .+-.5.degree. is defined
to be contained in one crystal orientation. Table 2 shows average
area ratios of cube orientation in the surface region from the
sheet surface to the depth of 10% in the thickness direction.
Mechanical Properties:
[0112] The mechanical properties were determined through a tensile
test under the following condition. The yield ratio was obtained
for a test sample after a lapse of six months (after
room-temperature aging) after the reheating, and the yield ratio
was evaluated such that 0.63 or less was good, 0.60 or less was
further good, and 0.64 or more was bad for the structural
component.
[0113] For the post-BH proof stress, a test sample after a lapse of
six months (after room-temperature aging) after the reheating was
allowed to have a pre-strain of 2% as simulated press forming of a
sheet by a tensile tester, and was then subjected to artificial
aging under a heat treatment condition of 180.degree. C..times.20
min, and proof stress of such a test sample (AB material) was
measured. The proof stress was evaluated such that 220 MPa or more
was acceptable, and 230 MPa or more was good for the structural
component.
[0114] The tensile test was performed at room temperature with a
JIS Z2201 No. 5 test specimen (25 mm.times.50 mm gage length
(GL).times.thickness) taken from each test sample. The tensile
direction of the test specimen was perpendicular to the rolling
direction. The tensile speed was 5 mm/min below the 0.2% proof
stress, and was 20 mm/min at or above the 0.2% proof stress. The
number N of times of measurement of each of the mechanical
properties was five, and an average of the measured values was
calculated for each property.
Crashworthiness:
[0115] With the crashworthiness, a test sample after a lapse of six
months (after room-temperature aging) after the reheating was
allowed to have a pre-strain of 2% by a tensile tester, and was
then subjected to artificial aging under a heat treatment condition
of 180.degree. C..times.20 min so as to be formed as a measuring
object of the VDA bending test.
[0116] Each test sample was stretched by 2% in a direction
perpendicular to the rolling direction, and was then cut into a
square test specimen having a thickness of 2.5 mm, a width b of 60
mm, and a length 1 of 60 mm.
[0117] A three-point bend test, in which the bending line was
parallel to the rolling direction, was performed using the test
specimen in accordance with the VDA238-100. The testing rate was 10
mm/min below a load of 30 N, and was 20 mm/min at or above the
load. The bending test was set such that bending was stopped when
the load was decreased by 60 N from the maximum load due to
cracking or a decrease in thickness.
[0118] The bending test was performed on three sheet-like test
specimens (three times) for each sample, and an average of the
three measured angles was used as the bending angle (.degree.).
[0119] The maximum bending angle (bending angle when the load F
from the pressing bend tool is maximized, i.e., a bending angle
immediately before a bending end of the central portion of the
sheet-like test specimen is cracked) of the sheet-like test
specimen subjected to the bending test was evaluated in such a
manner that 90.degree. or large was good, 60.degree. or larger was
acceptable, and less than 60.degree. was unacceptable for the
structural component.
Grain-Boundary Corrosion Resistance:
[0120] The evaluation test of the grain-boundary corrosion
resistance was conducted in accordance with ISO11846 Method B.
After a lapse of six months (after room-temperature aging) after
the reheating, a test sample was allowed to have a pre-strain of 2%
by a tensile tester and then subjected to artificial aging under a
heat treatment condition of 180.degree. C..times.20 min. The test
sample was then dipped in 5% NaOH (60.degree. C.) to remove a
surface coating, and was then rinsed and dipped in 70% HNO.sub.3
for 1 min, and was then rinsed again and dried at room
temperature.
[0121] An aqueous solution containing HCl and NaCl (containing 30
g/l of NaCl and 10.+-.1 ml/l of 36% concentrated hydrochloric acid)
was used as an etchant, and the test sample was dipped for 24 hr at
25.degree. C. in the etchant of 5 ml per surface area 1 cm.sup.2 of
a material. Subsequently, corrosion products were removed by
dipping in 70% HNO.sub.3 and brushing using a plastic brush, and
then the test sample was rinsed and dried at room temperature.
[0122] Three regions that were determined to be deeply corroded
were selected by a focal depth method, and each region was buried
to show a cross section, and a depth of a deepest grain-boundary
corrosion in each section was measured by a light microscope.
[0123] Three test samples taken from three appropriate places of a
sheet were used as the test samples. Among the measurements of the
three test samples, a test sample having a largest grain-boundary
corrosion depth of less than 300 .mu.m was defined to be
acceptable, and a test sample having that of 300 .mu.m or more was
defined to be unacceptable for the structural component.
[0124] As clear from Tables 1 and 2, each inventive example is
within a range of the aluminum alloy composition of the present
invention, and is manufactured within the range of the preferred
condition.
[0125] As a result, as shown in Table 2, inventive examples Nos. 1
to 11 each show an average area ratio of cube orientation of 22% or
more in a surface region from the surface of the sheet to the depth
of 10% in the thickness direction, an yield ratio of 0.63 or less,
and properties including 0.2% proof stress of 220 MPa or more and
crashworthiness showing a bending angle of 60.degree. or more at
the VDA bending test when the aluminum alloy sheet is stretched by
2% and then subjected to artificial aging for 20 min at 180.degree.
C.
[0126] In particular, the inventive examples Nos. 1 and 2 each show
a further good crashworthiness because the cube area ratio is 35%
or more in the surface region from the sheet surface to the depth
of 10% in the thickness direction.
[0127] The inventive example No. 3 shows a further good yield ratio
and a further good post-BH proof stress because the content [Mg] of
Mg and the content [Si] of Si satisfy a relationship
[Si]/[Mg].gtoreq.1.8 and a relationship 1.6%.ltoreq.1.3
[Mg]+[Si].ltoreq.1.9%.
[0128] In contrast, as shown in Table 1, each comparative example
is manufactured with an alloy composition out of the range of the
present invention, or manufactured with a hot rolling condition out
of the preferred range of the hot rolling condition while having an
alloy composition within the range of the present invention. As a
result, as shown in Table 2, the average area ratio of cube
orientation or the yield ratio does not satisfy the requirement,
and post-BH strength, crashworthiness, or grain-boundary corrosion
resistance is bad.
[0129] Comparative examples Nos. 12 to 23 each have an alloy
composition out of the range of the present invention.
[0130] The comparative examples Nos. 12 and 13, which correspond to
alloy numbers 6 and 7, respectively, in Table 1, are each bad in
post-baking proof stress because the Mg content is less than the
lower limit (1.3[Mg]+[Si] is also less than the lower limit in the
comparative example No. 12).
[0131] The comparative example No. 14 corresponds to alloy number 8
in Table 1, in which the yield ratio exceeds 0.63 because the Mg
content exceeds the upper limit. In addition, since 1.3 [Mg]+[Si]
exceeds the upper limit of the present invention, crashworthiness
is bad.
[0132] The comparative example No. 15 corresponds to alloy number 9
in Table 1, in which crashworthiness is bad because 1.3 [Mg]+[Si]
exceeds the upper limit.
[0133] The comparative example No. 16 corresponds to alloy number
10 in Table 1, in which post-BH proof stress is bad because the Si
content is less than the lower limit. In addition, since [Si]/[Mg]
is less than the lower limit, the yield ratio exceeds 0.63.
[0134] The comparative example No. 17 corresponds to alloy number
11 in Table 1, in which the yield ratio exceeds 0.63 because the Si
content exceeds the upper limit. In addition, since 1.3 [Mg]+[Si]
exceeds the upper limit, crashworthiness is bad.
[0135] The comparative example No. 18 corresponds to alloy number
12 in Table 1, in which crashworthiness is bad because 1.3
[Mg]+[Si] exceeds the upper limit.
[0136] The comparative example No. 19 corresponds to alloy number
13 in Table 1, in which the yield ratio exceeds 0.63 because the
content of Cu is less than the lower limit. In addition,
post-baking proof stress is bad.
[0137] The comparative example No. 20 corresponds to alloy number
14 in Table 1, in which grain-boundary corrosion resistance is bad
because the content of Cu exceeds the upper limit.
[0138] The comparative example No. 21 corresponds to alloy number
15 in Table 1, in which the yield ratio exceeds 0.63 because the
content of Mg is less than the lower limit and [Si]/[Mg] is less
than the lower limit of the present invention. In addition, since
1.3 [Mg]+[Si] is less than the lower limit of the present
invention, post-BH proof stress is bad.
[0139] The comparative example No. 22 corresponds to alloy number
16 in Table 1, in which post-BH proof stress is bad because 1.3
[Mg]+[Si] is less than the lower limit.
[0140] The comparative example No. 23 corresponds to alloy number
17 in Table 1, in which crashworthiness is bad because 1.3
[Mg]+[Si] exceeds the upper limit.
[0141] The comparative examples Nos. 24 to 35 each correspond to
alloy number 1 or 2 in Table 1, in each of which although the alloy
composition is within the range of the present invention, a
manufacturing method is out of the preferred range.
[0142] The comparative examples Nos. 24 and 25 are each bad in
crashworthiness because cold reduction is too high, and the average
area ratio of cube orientation in the surface region of the sheet
is less than 22%.
[0143] The comparative example No. 26 is not reheated and thus bad
in post-baking proof stress.
[0144] The comparative examples Nos. 27 and 28 are not reheated and
thus bad in post-baking proof stress. In addition, crashworthiness
is bad because cold reduction is too high, and the average area
ratio of cube orientation in the surface region of the sheet is
less than 22%.
[0145] The comparative example No. 29 is bad in post-BH proof
stress because solution temperature is less than the preferred
lower limit.
[0146] The comparative example No. 30 has a yield ratio of more
than 0.63 because solution holding time exceeds the preferred upper
limit.
[0147] The comparative example No. 31 is bad in post-BH proof
stress because time required before reheating exceeds 10 min.
[0148] The comparative example No. 32 is bad in post-BH proof
stress because reheating temperature is less than the preferred
lower limit.
[0149] The comparative example No. 33 shows a yield ratio of more
than 0.63 because reheating temperature exceeds the preferred upper
limit.
[0150] The comparative example No. 34 is bad in post-BH proof
stress because holding time at 60.degree. C. or more after
reheating is less than the preferred lower limit.
[0151] The comparative example No. 35 shows a yield ratio of more
than 0.63 because holding time at 60.degree. C. or more after
reheating exceeds the preferred upper limit.
[0152] These results of the Example support the meaning of
satisfying the composition and the microstructure defined in the
present invention for the vehicle structural component.
TABLE-US-00001 TABLE 1 Chemical composition of aluminum alloy sheet
Alloy (mass %, the remainder: Al) No. Si Mg Cu [Si]/[Mg] 1.3[Mg] +
[Si] Fe Mn Ti 1 0.6 0.7 0.10 0.9 1.5 0.20 0.10 0.01 2 1 0.4 0.17
2.5 1.5 0.20 0.10 0.01 3 1 0.5 0.10 2 1.7 0.20 0.10 0.01 4 1 0.4
0.10 2.5 1.5 0.20 0.10 0.01 5 0.9 0.7 0.10 1.3 1.8 0.20 0.10 0.01 6
1 0.2 0.10 5 1.3 0.20 0.10 0.01 7 1.2 0.2 0.10 6 1.5 0.20 0.10 0.01
8 1 1.1 0.10 0.9 2.4 0.20 0.10 0.01 9 1 0.9 0.10 1.1 2.2 0.20 0.10
0.01 10 0.4 0.9 0.10 0.4 1.6 0.20 0.10 0.01 11 1.3 0.7 0.10 1.9 2.2
0.20 0.10 0.01 12 1.1 0.7 0.10 1.6 2 0.20 0.10 0.01 13 0.6 0.7 0.04
0.9 1.5 0.20 0.10 0.01 14 1 0.4 0.23 2.5 1.5 0.20 0.10 0.01 15 0.4
0.7 0.10 0.6 1.3 0.20 0.10 0.01 16 0.8 0.4 0.17 2.0 1.3 0.20 0.10
0.01 17 1.1 0.7 0.10 1.6 2 0.20 0.10 0.01
TABLE-US-00002 TABLE 2 Time from Reheating Reheated aluminum
Solution solution Holding alloy sheet Aluminum alloy sheet
subjected treatment treatment time Average to artificial aging
Achieving to Achieving from area ratio of cube Crashworthiness
Grain-Boundary Alloy number Cold temperature Holding reheating
temperature 60 to orientation in 0.2% Proof evaluated by Corrosion
Classification No. in Table 1 reduction % .degree. C. time s min
.degree. C. 90.degree. C. h sheet surface % Yield ratio stress MPa
VDA test Resistance Inventive 1 1 3 560 10 5 80 5 46 0.62 222 Good
Acceptable example 2 2 3 550 10 5 80 5 39 0.59 228 Good Acceptable
3 3 60 550 10 5 70 5 28 0.58 255 Acceptable Acceptable 4 2 60 550
10 5 80 5 25 0.59 236 Acceptable Acceptable 5 4 60 550 10 5 70 5 24
0.59 230 Acceptable Acceptable 6 5 60 550 10 5 70 5 27 0.62 242
Acceptable Acceptable 7 1 60 550 1 5 70 5 25 0.61 222 Acceptable
Acceptable 8 1 50 550 10 5 70 5 26 0.62 225 Acceptable Acceptable 9
1 60 550 30 5 70 5 24 0.62 230 Acceptable Acceptable 10 1 60 550 10
5 70 5 24 0.62 232 Acceptable Acceptable 11 1 60 550 10 5 70 15 28
0.62 225 Acceptable Acceptable Comparative 12 6 60 550 10 5 70 5 25
0.57 204 Acceptable Acceptable example 13 7 60 550 10 5 70 5 26
0.63 217 Acceptable Acceptable 14 8 60 550 10 5 70 5 25 0.64 279
Unacceptable Acceptable 15 9 60 550 10 5 70 5 26 0.62 262
Unacceptable Acceptable 16 10 60 550 10 5 70 5 25 0.65 217
Acceptable Acceptable 17 11 60 550 10 5 70 5 28 0.64 265
Unacceptable Acceptable 18 12 60 550 10 5 70 5 27 0.62 262
Unacceptable Acceptable 19 13 60 550 10 5 70 5 24 0.64 213
Acceptable Acceptable 20 14 60 550 10 5 70 5 25 0.58 234 Acceptable
Unacceptable 21 15 60 560 10 5 70 5 25 0.64 206 Acceptable
Acceptable 22 16 60 550 10 5 80 5 24 0.58 215 Acceptable Acceptable
23 17 60 550 10 5 80 5 26 0.61 252 Unacceptable Acceptable 24 2 80
550 10 5 70 5 20 0.59 227 Unacceptable Acceptable 25 2 90 550 10 5
70 5 18 0.59 230 Unacceptable Acceptable 26 1 58 550 10 5 Not 25
0.61 183 Good Acceptable reheated 27 1 80 550 10 5 Not 20 0.61 180
Unacceptable Acceptable reheated 28 1 90 550 10 5 Not 17 0.60 180
Unacceptable Acceptable reheated 29 1 60 530 10 5 70 5 24 0.61 215
Acceptable Acceptable 30 1 60 550 90 5 70 5 28 0.64 236 Acceptable
Acceptable 31 1 60 550 10 15 70 5 28 0.61 214 Acceptable Acceptable
32 1 60 550 10 5 50 -- 25 0.58 205 Acceptable Acceptable 33 1 60
550 10 5 100 5 26 0.65 235 Acceptable Acceptable 34 1 60 550 10 5
70 1 27 0.61 201 Acceptable Acceptable 35 1 60 550 10 5 70 25 27
0.64 230 Acceptable Acceptable
[0153] According to the present invention, a 6000-series aluminum
alloy sheet manufactured by common rolling can be allowed to have
properties specific to the vehicle structural component
application, such as increased strength, crashworthiness as an
additional property, press formability, and corrosion resistance.
Hence, the 6000-series aluminum alloy sheet can be extensively used
for the vehicle structural component.
* * * * *