Title of Invention

HEAT-RESISTANT ALUMINIUM ALLOY

Abstract A cold-hardening aluminium casting alloy with good thermal stability for the production of thermally and mechanically stressed cast components contains from 11.0 to 12.0 wt% silicon from 0.7 to 2.0 wt% magnesium from 0.1 to 1 wt% manganese at most 1 wt% iron at most 2 wt% copper at most 2 wt% nickel at most 1 wt% chromium at most 1 wt% cobalt at most 2 wt% zinc at most 0.25 wt% titanium 40 ppm boron optionally from 80 to 300 ppm strontium and aluminium as the remainder with further elements and impurities due to production individually at most 0.05 wt%, in total at most 0.2 wt%. The alloy is suitable in particular for the production of cylinder crank cases by the die-casting method.
Full Text Heat-resistant Aluminium Alloy
The invention relates to a cold-hardening aluminium
5 casting alloy with good thermal stability for the
production of thermally and mechanically stressed cast
components.
The further development of diesel engines with the aim
10 of improved combustion of the diesel fuel and a higher
specific power is leading inter alia to an increased
explosion pressure and consequently to a mechanical
stress, acting in a pulsating fashion on the cylinder
crank case, which places the most stringent of
15 requirements on the material. Besides a high
durability, a high-temperature cycling strength of the
material is a further requisite for its use in the
production of cylinder crank cases.
20 AlSi alloys are normally used at present for thermally
stressed components, the thermal stability being
increased by alloying them with Cu. Copper, however,
increases the hot cracking susceptibility and has a
detrimental effect on the castability. Applications in
25 which thermal stability is required in particular are
encountered primarily in the field of cylinder heads in
automotive manufacturing, see for example F. J. Feikus
"Optimierung von Aluminium-Silicium-Gusslegierungen fur
Zylinderkopfe" [Optimization of aluminium-silicon
30 casting alloys for cylinder heads], Giesserei-Praxis,
1999, volume 2, pp. 50-57.
US-A-3 868 250 discloses a heat-resistant AlMgSi alloy
for the production of cylinder heads. Besides the usual
35 additives, the alloy contains from 0.6 to 4.5 wt% Si,
from 2.5 to 11 wt% Mg, of which from 1 to 4.5 wt% free
Mg, and from 0.6 to 1.8 wt% Mn.

WO-A-9615281 discloses an aluminium alloy having from
3.0 to 6.0 wt% Mg, from 1.4 to 3.5 wt% Si, from 0.5 to
2.0 wt% Mn, at most 0.15 wt% Fe, at most 0.2 wt% Ti,
and aluminium as the remainder with further impurities
5 individually at most 0.02 wt%, in total at most 0.2
wt%. The alloy is suitable for components with
stringent requirements on the mechanical properties.
The alloy is preferably processed by die-casting,
thixocasting or thixoforging.
10
WO-A-0043560 discloses a similar aluminium alloy for
the production of safety components by the die-casting,
squeeze casting, thixoforming or thixoforging method.
The alloy contains 2.5 - 7.0 wt% Mg, 1.0 - 3.0 wt% Si,
15 0.3 - 0.49 wt% Mn, 0.1 - 0.3 wt% Cr, at most 0.15 wt%
Ti, at most 0.15 wt% Fe, at most 0.00005 wt% Ca, at
most 0.00005 wt% Na, at most 0.0002 wt% P, other
impurities individually at most 0.02 wt%, and aluminium
as the remainder.
20
A casting alloy of the AlMgSi type known from EP-A-1
234 893 contains from 3.0 to 7.0 wt% Mg, from 1.7 to
3.0 wt% Si, from 0.2 to 0.48 wt% Mn, from 0.15 to 0.35
wt% Fe, at most 0.2 wt% Ti, optionally also from 0.1 to
25 0.4 wt% Ni and aluminium as the remainder, and
impurities due to production individually at most 0.02
wt%, in total at most 0.2 wt%, with the further proviso
that magnesium and silicon are present in the alloy
essentially in an Mg:Si weight ratio of 1.7:1
30 corresponding to the composition of the quasi-binary
eutectic with the solid phases Al and Mg2Si. The alloy
is suitable for the production of safety parts in a
vehicle manufacturing by die-casting, rheo- and
thixocasting.
35
EP-A-1 645 647 discloses a cold-hardening casting
alloy. The alloy, based on foundry metal with 99.9 Al
purity, contains 6-11 wt% Si, 2.0 - 4.0 wt% Cu, 0.65
- 1.0 wt% Mn, 0.5 - 3.5 wt% Zn, at most 0.55 wt% Mg,

0.01 - 0.04 wt% Sr, at most 0.2 wt% Ti, at most 0.2 wt%
Fe and optionally at least one of the elements silver
0.01 - 0.08, samarium 0.01 - 1.0, nickel 0.01 - 0.40,
cadmium 0.01 - 0.30, indium 0.01 - 0.20 and beryllium
5 up to 0.001 wt%. An alloy specified by way of example
has the following composition: Si 9%, Cu 2.7%, Mn 1%,
Zn 2%, Sr 0.02%, Mg 0.5%, Fe 0.1%, Ti 0.1%, Ag 0.1%, Ni
0.45 %, In 0.1%, Be 0.0005%.
10 A standardized casting alloy of the type AlSi9Cu3(Fe)
is known as alloy 226 (EN AC - 46000) with 8-11 wt%
Si, at most 1.30 wt% Fe, 2-4 wt% Cu, at most 0.55 wt%
Mn, 0.05 - 0.55 wt% Mg, at most 0.015 wt% Cr, at most
0.55 wt% Ni, at most 1.20 wt% Zn, at most 0.35 wt% Pb,
15 at most 0.25 wt% Sn, at most 0.25 wt% Ti, others
individually at most 0.05 wt%, in total at most 0.25
wt%, remainder aluminium.
It is an object of the invention to provide an
20 aluminium alloy having good thermal stability for the
production of thermally and mechanically stressed cast
components. The alloy is intended to be suitable
primarily for die-casting, but also for gravity mould
casting, low-pressure mould casting and sand casting.
25
It is a particular object of the invention to provide
an aluminium alloy for cylinder crank cases of
combustion engines, in particular diesel engines,
produced by the die-casting method.
30
The components cast from the alloy are intended to have
a high strength after cold hardening.
The object is achieved according to the invention in
35 that the alloy contains
from 11.0 to 12.0 wt% silicon
from 0.7 to 2.0 wt% magnesium
from 0.1 to 1 wt% manganese

at most 1 wt% iron
at most 2 wt% copper
at most 2 wt% nickel
at most 1 wt% chromium
5 at most 1 wt% cobalt
at most 2 wt% zinc
at most 0.25 wt% titanium
4 0 ppm boron
optionally from 80 to 300 ppm strontium
10 and aluminium as the remainder with further elements
and impurities due to production individually at most
0.05 wt%, in total at most 0.2 wt%.
A first preferred variant of the alloy according to the
15 invention has the following preferred content ranges
for the alloy elements listed below:
from 11.2 to 11.8 wt% silicon
from 0.6 to 0.9 wt% manganese
20 at most 0.15 wt% iron
from 1.8 to 2.0 wt% magnesium
from 1.8 to 2.0 wt% copper
from 1.8 to 2.0 wt% nickel
from 0.08 to 0.25 wt% titanium
25 from 20 to 30 ppm boron.
A second preferred variant of the alloy according to
the invention has the following preferred content
ranges for the alloy elements listed below:
30
from 11.2 to 11.8 wt% silicon
from 0.6 to 0.9 wt% manganese
at most 0.15 wt% iron
from 1.8 to 2.0 wt% magnesium
35 from 1.8 to 2.0 wt% copper
from 1.8 to 2.0 wt% nickel
from 0.6 to 1.0 wt% cobalt
from 0.08 to 0.25 wt% titanium
from 20 to 3 0 ppm boron.

A third preferred variant of the alloy according to the
invention has the following preferred content ranges
for the alloy elements listed below:
5
from 11.2 to 11.8 wt% silicon
from 0.6 to 0.9 wt% manganese
at most 0.15 wt% iron
from 0.7 to 1.0 wt% magnesium
10 from 1.8 to 2.0 wt% copper
from 0.5 to 1.0 wt% chromium
from 1.7 to 2.0 wt% zinc
from 0.08 to 0.25 wt% titanium
from 20 to 30 ppm boron.
15
The addition of manganese can prevent adhesion of the
cast parts in the mould. Manganese also contributes
substantially to the thermal hardening. A lower iron
content leads to a high elongation and reduces the risk
20 of creating platelets containing Fe, which lead to
increased cavitation and impair the mechanical
processability.
The high Si content leads to a very good castability
25 and to reduction of the cavitation. The near-eutectic
Al-Si composition also makes it possible to reduce the
casting temperature and therefore extend the lifetime
of a metal mould. The hypo-eutectic Si level has been
selected so that no primary Si crystals occur.
30
By adding chromium, the mould release behaviour of the
alloy can be improved further and the strength values
can be increased. Cobalt serves to increase the thermal
stability. Titanium and boron serve for grain refining.
35 Good grain refining contributes substantially to
improving the casting properties and the mechanical
properties.

A preferred field of application for the aluminium
alloy according to the invention is the production of
thermally and mechanically stressed cast components as
die, mould or sand castings, in particular for cylinder
5 crank cases in automotive manufacturing produced by the
die-casting method.
Other advantages, features and details of the invention
may be found in the following description of preferred
10 exemplary embodiments.
The alloys according to the invention were cast by the
die-casting method to form flat tensile specimens with
a wall thickness of 3 mm. After removal from the die-
15 casting mould, the specimens were cooled in still air.
The mechanical properties yield point (Rp0.2), tensile
strength (Rm) and elongation at break (A) were
determined for the tensile specimens in the cast state
20 at room temperature (RT) , 150°C, 225°C and 300°C, and
also at room temperature (RT) and at the heat treatment
temperature (HTT) after various one-stage heat
treatments respectively for 500 hours at 150°C, 225°C
and 300°C.
25
The alloys studied are collated in Table 1.
Tables 2, 3 and 4 report the results of the mechanical
properties determined for tensile specimens of the
30 alloys of Table 1 in the cast state at various
temperatures.
Tables 5, 6 and 7 report the results of the mechanical
properties determined at room temperature (RT) and at
35 the heat treatment temperature (HTT) for tensile
specimens of the alloys of Table 1 after a heat
treatment for 500 hours at various temperatures.

The results of the long-term tests confirm the good
thermal stability of the alloy according to the
invention.




Patent Claims
1. Cold-hardening aluminium casting alloy with
5 good thermal stability for the production of thermally
and mechanically stressed cast components,
characterized in that the alloy contains
from 11.0 to 12.0 wt% silicon
10 from 0.7 to 2.0 wt% magnesium
from 0.1 to 1 wt% manganese
at most 1 wt% iron
at most 2 wt% copper
at most 2 wt% nickel
15 at most 1 wt% chromium
at most 1 wt% cobalt
at most 2 wt% zinc
at most 0.25 wt% titanium
40 ppm boron
20 optionally from 80 to 300 ppm strontium
and aluminium as the remainder with further elements
and impurities due to production individually at most
0.05 wt%, in total at most 0.2 wt%.
25 2. Aluminium alloy according to Claim 1,
characterized by
from 11.2 to 11.8 wt% silicon
from 0.6 to 0.9 wt% manganese
at most 0.15 wt% iron
30 from 1.8 to 2.0 wt% magnesium
from 1.8 to 2.0 wt% copper
from 1.8 to 2.0 wt% nickel
from 0.08 to 0.25 wt% titanium
from 20 to 30 ppm boron.
35
3. Aluminium alloy according to Claim 1,
characterized by
from 11.2 to 11.8 wt% silicon

from 0.6 to 0.9 wt% manganese
at most 0.15 wt% iron
from 1.8 to 2.0 wt% magnesium
from 1.8 to 2.0 wt% copper
5 from 1.8 to 2.0 wt% nickel
from 0.6 to 1.0 wt% cobalt
from 0.08 to 0.25 wt% titanium
from 20 to 3 0 ppm boron.
10 4. Aluminium alloy according to Claim 1,
characterized by
from 11.2 to 11.8 wt% silicon
from 0.6 to 0.9 wt% manganese
at most 0.15 wt% iron
15 from 0.7 to 1.0 wt% magnesium
from 1.8 to 2.0 wt% copper
from 0.5 to 1.0 wt% chromium
from 1.7 to 2.0 wt% zinc
from 0.08 to 0.25 wt% titanium
20 from 20 to 30 ppm boron.
5. Use of an aluminium alloy according to one of
Claims 1 to 4 for thermally and mechanically stressed
cast components produced by the die-casting, mould
25 casting or sand casting method.
6. Use according to Claim 5 for cylinder crank
cases in automotive manufacturing produced by the die-
casting method.
30
7. Use of an aluminium alloy according to one of
Claims 1 to 4 for safety parts in automotive
manufacturing produced by the die-casting method.
35 8. Cast component made of a cold-hardening
aluminium casting alloy with good thermal stability
according to one of Claims 1 to 4.

A cold-hardening aluminium casting alloy with good
thermal stability for the production of thermally and
mechanically stressed cast components contains
from 11.0 to 12.0 wt% silicon
from 0.7 to 2.0 wt% magnesium
from 0.1 to 1 wt% manganese
at most 1 wt% iron
at most 2 wt% copper
at most 2 wt% nickel
at most 1 wt% chromium
at most 1 wt% cobalt
at most 2 wt% zinc
at most 0.25 wt% titanium
40 ppm boron
optionally from 80 to 300 ppm strontium
and aluminium as the remainder with further elements
and impurities due to production individually at most
0.05 wt%, in total at most 0.2 wt%. The alloy is
suitable in particular for the production of cylinder
crank cases by the die-casting method.

Documents:

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Patent Number 268351
Indian Patent Application Number 924/KOL/2008
PG Journal Number 35/2015
Publication Date 28-Aug-2015
Grant Date 27-Aug-2015
Date of Filing 22-May-2008
Name of Patentee ALUMINIUM RHEINFELDEN GMBH
Applicant Address FRIEDRICHSTRASSE 80 7961 RHEINFELDEN
Inventors:
# Inventor's Name Inventor's Address
1 DAN DRAGULIN ELSA-BRANDSTROM-STRASSE 8 79618 RHEINFELDEN
2 RUDIGER FRANKE THEODOR-HEUSS-STRASSE 70 79539 LORRACH
PCT International Classification Number C22C 21/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 07 405 150.9 2007-05-24 EUROPEAN UNION