U.S. patent application number 10/497168 was filed with the patent office on 2006-08-03 for pressure-cast component made of highly ductile and resilient aluminium alloy.
Invention is credited to Stig Brusethaug, Francois Cosse, Jorunn Snoan Maeland, Gisele Perrier, Jean-Jacques Perrier, Nicole Perrier, Willi Schneider, Lutz Storsberg.
Application Number | 20060169371 10/497168 |
Document ID | / |
Family ID | 8870569 |
Filed Date | 2006-08-03 |
United States Patent
Application |
20060169371 |
Kind Code |
A1 |
Cosse; Francois ; et
al. |
August 3, 2006 |
Pressure-cast component made of highly ductile and resilient
aluminium alloy
Abstract
A component, in particular a safety, structural or ground
connection component for a motor vehicle, cast under pressure, and
made of an aluminum alloy with the following composition (in wt.
%): Mg: 1.0-4.5; Si: 0.2-1.3; Cu<0.3; Zn<0.1; Fe<0.3,
Ti<0.3 and at least one element for reducing adherence to the
mold which is Mn (0.3-1), Cr (0.1-0.4), Co (0.1-0.4), V (0.1-0.4)
and Mo (0.1-0.4), other elements<0.05 each and 0.15 in total,
the remainder being aluminum.
Inventors: |
Cosse; Francois; (Grenoble,
FR) ; Perrier; Jean-Jacques; (Paris, FR) ;
Brusethaug; Stig; (Sunndalsora, NO) ; Maeland; Jorunn
Snoan; (Sunndalsora, NO) ; Storsberg; Lutz;
(Offenau, DE) ; Schneider; Willi; (Titting,
DE) ; Perrier; Gisele; (Paris, FR) ; Perrier;
Nicole; (Paris, FR) |
Correspondence
Address: |
DENNISON, SCHULTZ, DOUGHERTY & MACDONALD
1727 KING STREET
SUITE 105
ALEXANDRIA
VA
22314
US
|
Family ID: |
8870569 |
Appl. No.: |
10/497168 |
Filed: |
December 17, 2002 |
PCT Filed: |
December 17, 2002 |
PCT NO: |
PCT/FR02/04364 |
371 Date: |
September 27, 2005 |
Current U.S.
Class: |
148/439 |
Current CPC
Class: |
C22F 1/047 20130101;
C22C 21/08 20130101 |
Class at
Publication: |
148/439 |
International
Class: |
C22C 21/06 20060101
C22C021/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2001 |
FR |
0116300 |
Claims
1. Die-cast component, particularly a safety, structural or
suspension component of a motor vehicle, made of an aluminum alloy
having a composition (% by weight): Mg 1.0-4.5; Si 0.2-1.3;
Cu<0.3; Zn<0.1; Fe<0.3; Ti<0.3, and at least one
element for reducing adherence to the selected from the group
consisting of Mn (0.3-1), Cr (0.1-0.4); Co (0.1-0.4); V (0.1-0.4)
and Mo (0.1-0.4), other elements<0.05 each and 0.15 in total,
the remainder being aluminum.
2. Component according to claim 1, characterised in that the Mg
content is between 2.0 and 4.0%.
3. Component according to claim 1, characterised in that the Si
content is between 0.4 and 1.0%.
4. Component according to claim 1, characterised in that the Cu
content is less than 0.10%.
5. Component according to claim 1, characterised in that the Fe
content is less than 0.2%.
6. Component according to claim 1, characterised in that the Ti
content is between 0.05 and 0.25%.
7. Component according to claim 1, characterised in that the alloy
contains Be with a content of not more than 50 ppm.
8. Die-cast component according to claim 1, having a yield strength
in the T5 temper (aged at a temperature of between 150 and
200.degree. C.), equal to more than 100 MPa and elongation at
rupture equal to more than 15%.
Description
FIELD OF THE INVENTION
[0001] The invention relates to the field of Al--Mg--Si alloys
intended for the manufacture of relatively thin die-cast
components, particularly of structural and safety components of a
motor vehicle.
STATE OF THE ART
[0002] The need to reduce vehicle weight has encouraged an increase
in the development of complex-shaped cast safety components in
which several functions are integrated and that have to satisfy the
different deformation tests used by automobile manufacturers such
as the "crash test" or the "body block", and requirements of
different assembly methods.
[0003] With known alloys such as the Al--Si9Cu3Mg alloy, it is
possible to obtain a tensile strength R.sub.m in the non-treated
temper F equal to at least 300 MPa and a yield strength R.sub.p0.2
equal to at least 230 MPa. However, the elongation at rupture A
does not exceed 2%. But structural and safety components of a motor
vehicle require sufficient ductility to absorb energy and prevent
rupture in case of shock, and to adapt to different assembly
modes.
[0004] Moreover, the high content of copper may have a favourable
influence for the mechanical strength, but it makes the alloy
sensitive to corrosion. Yet good resistance to corrosion is
necessary to avoid deterioration of the component in a corrosive
environment such as de-icing salt, to prevent deterioration of the
component.
[0005] Various alloy formulations have been proposed to satisfy
these requirements. Patent EP 0792380 filed by Aluminium
Rheinfelden in 1994 describes the use for casting of an alloy with
the following composition (% by weight) in the semi-solid
state:
[0006] Mg 3.0-6.0; Si 1.4-3.5; Mn 0.5-2.0; Fe<0.15; Ti 0.2.
[0007] The divisional application EP 0853133 derived from the
previous patent application applies to an alloy for die casting
with the following composition:
[0008] Mg 4.6-5.8; Si 1.8-2.5; Mn 0.5-0.9; Fe<0.15;
Ti<0.2
[0009] for which heat treatment of the cast components is not
essential to obtain good mechanical properties.
[0010] U.S. Pat. No. 5,667,602 filed by Alcoa in 1995, describes an
alloy for die casting, intended particularly for structural nodes
of a "space frame" type automobile bodywork structure with
composition Si<0.30; Fe<1.00; Mg 2.00-5.00; Mn 0.20-1.60; Zr
0.10-0.30. Good mechanical properties are obtained without heat
treatment of cast components. U.S. Pat. No. 6,132,531, also filed
by Alcoa in 1997, applies to an alloy of the same type, for the
same application, with composition Si<0.20; Fe<0.20; Mg
2.80-3.60; Mn 1.10-1.40; Ti<0.15; Be 0.0005-0.0015.
[0011] AlMgMn alloys were also used for making die-cast vehicle
steering wheels. Patent DE 3827794 (Toyoda Gosei) applies to the
use firstly of an alloy with composition Mg 1.5-2.5; Si 0.2-0.4; Fe
0.4-1.0; Mn 0.4-0.6, and secondly an alloy with composition Mg
1.5-2.4 Si<1.0; Fe 0.3-0.8; Mn 0.2-0.4, for a special shaped
steering wheel.
[0012] Patent EP 0412605 (Kolbenschmidt) describes the use of an
alloy with composition Mg 2.5-3.5; Si 0.10-0.30; Fe 0.40-0.60; Mn
0.25-0.45; Cu 0.015-0.05; Sn 0.035-0.065, for the same
application.
[0013] Patent application EP 0911420 (Aluminium Rheinfelden)
describes a casting alloy with composition Mg 2.0-3.5; Si
0.15-0.35; Mn 0.2-1.2; Fe<0.40; Cu<0.10; Zn<0.10;
Cr<0.05; Co<0.60; Ce<0.80.
[0014] Patent application EP 1138794 (Corus Aluminium) describes an
alloy for die casting with the following composition Mg 2.7-6.0;
Si<1.4; Mn 0.4-1.4; Zn 0.10-1.5; Fe<1.0; Sr<0.3; V<0.3;
Sc<0.3.
PURPOSE AND SUBJECT OF THE INVENTION
[0015] The purpose of the invention is to provide die-cast
structural, ground connection and safety components of a motor
vehicle, with good mechanical strength, high ductility and a good
energy absorption capacity, very resistant to corrosion and with
good castability that can be manufactured in large series under
acceptable economic conditions.
[0016] The subject of the invention is a die-cast component,
particularly a safety, structural or suspension component of a
motor vehicle, made of an aluminium alloy with the following
composition (% by weight):
[0017] Mg 1.0-4.5; Si 0.2-1.3; Cu<0.3; Zn<0.1; Fe<0.3;
Ti<0.3, and at least one element for reducing adherence to the
mould: Mn (0.3-1); Cr (0.1-0.4); Co (0.1-0.4); V (0.1-0.4) and Mo
(0.1-0.4), other elements<0.05 each and 0.15 in total, the
remainder being aluminium.
[0018] The preferred contents are Mg: 2.0-4.0; Si 0.4-1.0;
Cu<0.1; Fe<0.2; Ti: 0.005-0.25.
[0019] The alloy may possibly contain Be to a content of not more
than 50 ppm.
[0020] Another subject of the invention is a die-cast component
with the indicated composition, with a yield strength in the T5
temper (aged at a temperature of between 150 and 200.degree. C.),
equal to more than 100 MPa and elongation at rupture equal to more
than 15%.
DESCRIPTION OF THE INVENTION
[0021] The invention is based on the applicant's observation that
by reducing the content of magnesium and silicon compared with
alloys according to prior art to be used for the manufacture of
die-cast safety components, a useful compromise can be obtained
between usage properties, particularly between the yield strength
in the F temper (as-cast structure) and ductility, while
maintaining an acceptable castability. The magnesium content is at
least 4.5% so that the alloy remains castable and must not exceed
4.5% if a high ductility is required even in the T5 temper, in
other words in the aged temper at a temperature of between 100 and
200.degree. C. corresponding to the baking temperature of a paint
for a motor vehicle. The preferred content is between 2 and 4%.
[0022] The silicon content is equal to at least 0.2% to obtain a
sufficient tensile strength and yield strength, while maintaining
high ductility. It is preferably between 0.4 and 1%. Magnesium and
silicon combine together to form Mg.sub.2Si which is in the form of
a very fine eutectic at die casting solidification rates. The
presence of a eutectic fraction, in non-negligible quantities,
contributes to improving the usage properties while reducing the
formation of cracks when hot. Furthermore, a certain quantity of
magnesium remains in the solid aluminium solution due to the fast
cooling rate in the mould, and the aluminium solution is thus
supersaturated.
[0023] The applicant has observed that elongation at rupture for a
given content of silicon within the limits according to the
invention, increases quickly when the magnesium content reduces.
Conversely, for a given content of magnesium, a reduction in the
silicon content increases elongation at rupture, while keeping the
yield strength above 100 MPa.
[0024] Copper must be kept below 0.3%, and preferably below 0.1%,
to obtain sufficient resistance to atmospheric corrosion and stress
corrosion.
[0025] Iron, manganese, chromium, cobalt, molybdenum and nickel
form intermetallic compounds either individually or in combination
with aluminium, that cause embrittlement in the case of sand
casting or permanent mould gravity casting. However, in
die-casting, considering cooling rates in the mould, these
compounds are small and their morphology is such that the
mechanical strength is not affected. On the other hand, the
presence of these elements provides a means of limiting adherence
of components in the mould, by reducing the chemical potential of
the alloy with respect to steel in the mould. Since the iron
content has a bad influence on the elongation and must be limited
to 0.5% and preferably to 0.2%, the presence of at least one of the
other elements mentioned above in addition to iron is
essential.
[0026] Thorough refining of primary grains in the solid aluminium
solution by a master alloy or a salt containing titanium or boron,
for example a mix of fluoborate and potassium fluotitanate,
provides a means of almost completely eliminating the tendency to
the formation of cracks when hot, and contributes to reducing the
size of microporosities resulting from contraction during
solidification, which improves the compactness of components. The
refined alloy then contains between 0.05 and 0.25% of titanium and
between 10 and 30 ppm of residual boron.
[0027] Alkaline elements such as sodium, calcium and strontium,
must be kept at a very low content, preferably below 10 ppm, since
they have an unfavourable influence on the mechanical properties.
An addition of beryllium, limited to 50 and preferably 30 ppm, is
advantageous to limit the tendency of alloys to oxidise in the
liquid state.
[0028] Die-cast components, with or without vacuum assistance, are
preferably used in the as-cast structure state, to prevent
deformations in quenching and subsequent extensive straightening.
They are not very sensitive to ageing resulting from the baking of
paint performed in the automobile industry. The typical duration of
this treatment is between fifteen minutes and one hour at a
temperature of between 150 and 200.degree. C.
[0029] Components according to the invention have a yield strength
that is always more than 100 MPa, or even 120 MPa, in the F temper
or the T5 temper, with an elongation of more than 15%, which
improves energy absorption capacity under shock and makes it
possible to use assembly techniques requiring good ductility, such
as hemming or riveting.
[0030] This reduction in the magnesium content compared with alloys
according to prior art intended for use in similar components
improves the suitability for TIG, MIG or laser welding, and
achieves excellent compatibility with aluminium alloys in the 6000
series used for bodywork plates.
EXAMPLES
Example 1
[0031] The influence of the composition and the Mg/Si ratio on
static mechanical properties of die-cast components was studied.
Test plates made of 9 different alloys A to I with the composition
given in table 1 were produced by vacuum assisted die-casting
(residual pressure in the mould 80 hPa). The size of the plates was
120.times.220 mm and their thickness was 2.5 mm. Casting was done
on a press with a closing force of 3200 kN at a piston injection
velocity of 0.7 m/s. The metal temperature in the furnace was
780.degree. C. TABLE-US-00001 TABLE 1 Alloy Si Fe Mg Ti Mg/Si A 0.3
0.12 3 0.15 10 B 0.3 0.12 4 0.15 13.3 C 0.3 0.12 5 0.15 16.2 D 0.8
0.12 3 0.15 3.7 E 0.8 0.12 4 0.15 5 F 0.8 0.12 5 0.15 6.2 G 1.4
0.12 3 0.15 2.1 H 1.4 0.12 4 0.15 2.8 I 1.4 0.12 5 0.15 3.6
[0032] Tensile test specimens, taken from areas of these plates
that had not received any heat treatment and in which there are no
faults visible in radiography, were machined, and the tensile
strength R.sub.m (in MPa), the conventional yield strength at 0.2%
elongation Rp0.2 (in MPa) and the elongation at rupture A (in %)
were all measured. The results (averages of 10 test specimens) are
included in table 2. TABLE-US-00002 TABLE 2 Alloy R.sub.m
R.sub.p0.2 A average A max A 240 124 20.9 25.3 B 266 140 21.2 26.4
C 270 154 9.6 15.7 D 242 128 15.8 20.7 E 269 143 15.3 20.3 F 277
158 9.3 16.1 G 263 163 7.8 12.9 H 273 146 12.6 20.3 I 287 158 9.8
15.6
[0033] The results show that the elongation for alloys with 3 and
4% Mg increases significantly when the Si content reduces from 1.4
to 0.3%. This tendency is not continued for alloys with 5% Mg, for
which the elongation remains close to 10%. For a Si content equal
to 1.4%, alloys with 3, 4 or 5% Mg have similar values for R.sub.m,
R.sub.p0.2 and A. For Si contents of less than 1%, alloys with 3
and 4% Mg have a yield strength of more than 120 MPa and an
elongation of more than 15%.
Example 2
[0034] The effect of a paint baking treatment on the hardness of
components was studied in comparison with the as-cast temper
naturally aged at ambient temperature. The hardnesses Hv 5/30 in
the naturally aged temper and in the T5 temper were measured after
20 minutes ageing at 190.degree. C. on tensile test specimens
similar to those in example 1, for alloys B, D, E and H. The
results are given in table 3. TABLE-US-00003 TABLE 3 Alloy Aged as
cast temper T5 temper B 80.8 80.8 D 80.8 82.4 E 84.0 84.4 H 88.4
89.6
[0035] It can be seen that the T5 treatment gives a slightly higher
hardness for alloys for which the Mg/Si ratio is low, and the
hardness can be kept constant for alloys with a higher Mg/Si
ratio.
[0036] The effect of the treatment duration on the mechanical
properties of alloy A with 0.5% Mn was studied by comparing them
with the F temper and with two T5 tempers, one with 20 minutes
ageing, the other 60 minutes ageing at 190.degree. C. The results
are given in table 4: TABLE-US-00004 TABLE 4 State R.sub.m (MPa)
R.sub.p0.2 (MPa) A (%) F 246 129 22.2 20 min. at 190.degree. C. 244
125 20.2 60 min. at 190.degree. C. 249 141 20.4
[0037] It can be seen that this type of treatment hardly affects
the mechanical properties, which is an advantage since the energy
absorption properties for safety component with a high deformation
capacity are maintained in assemblies. Furthermore, there is no
risk that machined dimensions of components will be modified by
this treatment.
* * * * *