FIELD OF THE INVENTION
[0001] The field of the invention is related to aluminium casting alloys. Specifically,
the present invention relates to a hypoeutectic secondary aluminum-silicon alloy,
useful to produce, by high pressure die casting, components which have to fulfill
premium abrasion resistance requirements in as-cast condition at room temperature.
BACKGROUND OF THE INVENTION
[0002] Aluminum casting alloys have not been traditionally well suited for abrasion applications
in which, among others, high hardness properties must be present.
[0003] Regarding the automotive sector, in which most of the aluminum castings are consumed,
some well-known parts that must fulfill abrasion requirements are, among other, piston
cylinders, brake discs or steering boxes. Brake discs and piston cylinders must support
not only abrasion but also thermal fatigue resistance, and if aluminium is employed
instead of steel, hypereutectic alloys have been traditionally applied to produce
automotive components by gravity die casting (GC). Hypereutectic alloys present primary
silicon grains that are normally refined with phosporous and T5 thermal treatment
to resist abrasion. Nickel is the most important alloying element, with also Copper
and dissoluted Zinc, to keep mechanical properties at high temperatures.
[0004] For room temperature applications (i.e. steering boxes) hypereutectic alloys are
not so well suited. They do not fulfill the required hardness (above 115-120HB), Nickel
is superfluous and Phosphorous is so volatile that requires skilled technicians to
melt the alloy, which must be hold at temperatures above 750°C. Only high hardness
and high strength are the objective properties, which opens the door to components
produced by high pressure die casting (HPDC) with hypoeutectic aluminum.
[0005] HPDC process has been widely employed to new applications in the last twenty years,
due to its low cost for big series, a high component reproducibility and reliability
and it is hence mostly preferred when compared with GC.
[0006] Unfortunately, typical hardnesses of hypoeutectic alloys lie on values around 80-100
HB, what is still below the required 120HB. Therefore, when producing steering boxes,
a steel sleeve is placed in the internal surface of the box to accommodate the steering
shaft. Both shaft and box are typically AlSi
9Cu
3 as cast components produced by HPDC, and even the addition of a new step (sleeve
placement) is worth when compared with expensive GC production with hypereutectic
alloy with a T5 thermal treatment.
[0007] Some other new alloys have been later developed to eliminate the thermal treatments,
as those belonging to the AlZn families, which after 1 week of natural aging reach
hardness values close to 120 HB. Unfortunately, the main disadvantage of these alloys
is that quality requirements are only achievable by primary alloys. Primary alloys
means mainly Iron content below 0.15% by weight, Copper content below 0.03% by weight
and Zinc content below 0.1% by weight, being those contents only achievable if Aluminium
is produced by electrolysis smelting from raw alumina. All refined aluminium alloys
produced from scraps, drosses and swarfs coming from post-processing operations and
end of life products is hence limited to low mechanical secondary alloy applications,
what is a large limitation for industry sustainability and for the aluminum recycling
sector.
[0008] Alloys of primary quality with a Fe/Mn ratio of ½ has been disclosed in the prior
art, and decrease die soldering and reduce as much as possible the negative effect
of Al
5FeSi intermetallics on the elongation values.
[0009] WO2006/066314 discloses an aluminium-based high pressure die casting comprising (in wt.%): 4 to
4.9% Cu; 0.09-0.7% Mg; 0.19-0.21% Mn; 0.1-0.12% Ni; 8.3-9.2% Si ; 0.98-1% Fe; 0.5-0.56
Zn; <0.1% Sn; <0.1% Pb; <0.1% Ti, <0.1 % Cr, and the remainder consisting of aluminium
and incidental impurities.
[0010] The problem to be solved is the provision of a novel alloy of secondary quality produced
for HPDC which can be used in as-cast condition and that presents the following values
of elongation and mechanical properties: elongation (A) equal to or more than 1%,
yield strength (Rp0.2) equal to or more than 200 MPa, ultimate tensile strength (Rm)
equal to or more than 300 MPa and Brinell Hardness (HB) equal to or more than 120
HB. Said values of elongation and mechanical properties are required for components
designed to support simultaneously high abrasion and high static bending/torsion loads,
maintaining a minimal ductility and other processing properties as alloy fluidity,
low die soldering, easy welding or high machinability, among others.
DESCRIPTION OF THE INVENTION
[0011] A preferred embodiment of the present invention is an aluminium casting alloy, wherein
said alloy consists of:
7-11% by weight of silicon,
0.6-1% by weight of iron,
4-5% by weight of copper,
0.05-0.5% by weight of manganese,
0.05-1.2% by weight of zinc,
0.56-0.9% by weight of magnesium,
0.01-0.15% by weight of titanium,
0.01-0.1% by weight of chrome,
0.01-0.1% by weight of nickel,
0.01-0.1 % by weight of lead and
0.01-0.1% by weight of tin,
herewith aluminium casting alloy of the invention.
[0012] Silicon content has been set into a wide range between 7-11% by weight to guarantee
high fluidity, especially for thin wall castings.
[0013] Copper content has been set at values above 4% as it is required to get hardness
above 125 HB and high strength.
[0014] Magnesium content is also a key element to maximize the hardness and mechanical properties,
whose content must be coupled with the copper content, showing best performance when
both set above 0.5% by weight and 4% by weight, respectively.
[0015] Iron content plays a key role into the mechanical properties and hence it has been
limited to 0.6-1% by weight to guarantee both low mold soldering and small volume
fraction of Al
5FeSi intermetallics, which are minimized by the manganese content, implying an elongation
above 1%.
[0016] The manganese content helps to transform the Al
5FeSi intermetallics into Al
12(Mn,Fe)Si
2 and to reduce as much as possible the negative effect of those intermetallics. Values
of manganese above 0.3% by weight were not found to be useful in terms of Al
5FeSi intermetallics transformation.
[0017] A further embodiment of the invention is the aluminium casting alloy of the invention,
wherein said alloy comprises 8-9% by weight of silicon.
[0018] A further embodiment of the invention is the aluminium casting alloy of the invention,
wherein said alloy comprises 0.8-1 % by weight of iron.
[0019] A further embodiment of the invention is the aluminium casting alloy of the invention,
wherein said alloy comprises 4-4.5% by weight of copper.
[0020] A further embodiment of the invention is the aluminium casting alloy of the invention,
wherein said alloy comprises 0.05-0.3% by weight of manganese.
[0021] A further embodiment of the invention is the aluminium casting alloy of the invention,
wherein said alloy comprises 0.6-0.7% by weight of magnesium.
EXAMPLES OF THE INVENTION
Example 1. Aluminium casting alloys (prepararation, composition and mechanical properties)
[0022] Aluminium compositions have been prepared by melting a standard EN-AC 46500 alloy
in a holding furnace at 690°C and later poured into the injection vessel, being injected
into the mold cavity of a 950 tonnes closing force HPDC machine at 685°C. No vacuum
conditions were applied.
[0023] A serial of 30 specimens were produced, for each composition. Casted specimens were
cooled down in air. Specimens dimensions and later mechanical characterization were
set and carried out following, respectively, UNE-EN ISO 6892-1 B:2010 standards. For
the hardness determination, plate specimens with 5 mm thickness have been casted and
tested.
[0024] Several compositions were tested, the content of the content if specified in Table
1. The obtained results are also specified in Table 1.
Table 1
|
Alloy 1 (comparative composition, not according to the invention) |
Alloy 2 (comparative composition, not according to the invention) |
Alloy 3 |
Alloy 4 |
Si (% by weight) |
8.68 |
9.08 |
8.9 |
10.41 |
Fe (% by weight) |
0.95 |
1.07 |
1.32 |
1.32 |
Cu (% by weight) |
1.78 |
3.1 |
4.33 |
3.97 |
Mn (% by weight) |
0.33 |
0.272 |
0.272 |
0.54 |
Mg (% by weight) |
0.046 |
0.62 |
0.56 |
0.54 |
Zn (% by weight) |
1.74 |
1.23 |
1.19 |
1.14 |
Ti (% by weight) |
0.023 |
0.188 |
0.225 |
0.272 |
Cr (% by weight) |
0.018 |
0.195 |
0.198 |
0.189 |
Ni (% by weight) |
0.062 |
0.099 |
0.106 |
0.102 |
Pb (% by weight) |
0.051 |
0.091 |
0.092 |
0.087 |
Sn (% by weight) |
0.018 |
0.034 |
0.036 |
0.035 |
Rp0.2 (MPa) |
150 |
208 |
227 |
218 |
Rm (MPa) |
290 |
300 |
305 |
290 |
A (%) |
4.5 |
1.75 |
1.2 |
1.1 |
Brinell Hardness (HB) |
- |
116 |
125 |
122 |
[0025] The values obtained after one month of natural aging is shown in Table 2.
Table 2
|
Alloy 2 (comparative composition, not according to the invention) |
Alloy 3 |
Alloy 4 |
Rp0.2 (MPa) |
220 |
241.5 |
230 |
Rm (MPa) |
317 |
324 |
300 |
A (%) |
2.2 |
2.4 |
2 |
Brinell Hardness (HB) |
120 |
135 |
130 |
1. Aluminium casting alloy,
characterized in that said alloy is consisting of:
7-11% by weight of silicon,
0.6-1 % by weight of iron,
4-5% by weight of copper,
0.05-0.5% by weight of manganese,
0.05-1.2% by weight of zinc,
0.56-0.9% by weight of magnesium,
0.01-0.15% by weight of titanium,
0.01-0.1 % by weight of chrome,
0.01-0.1% by weight of nickel,
0.01-0.1% by weight of lead,
0.01-0.1 % by weight of tin,
and aluminium as the remainder.
2. Aluminium casting alloy according to claim 1, characterized in that said alloy is consisting of 8-9% by weight of silicon.
3. Aluminium casting alloy according to claim 1 or claim 2, characterized in that said alloy is consisting of 0.8-1% by weight of iron.
4. Aluminium casting alloy according to any one of claims 1 to 3, characterized in that said alloy is consisting of 4-4.5% by weight of copper.
5. Aluminium casting alloy according to any one of claims 1 to 4, characterized in that said alloy is consisting of 0.05-0.3% by weight of manganese.
6. Aluminium casting alloy according to any one of claims 1 to 5, characterized in that said alloy is consisting of 0.6-0.7% by weight of magnesium.
1. Aluminiumgusslegierung,
dadurch gekennzeichnet, dass die genannte Legierung aus Folgendem besteht:
7-11 Gew.-% Silicium,
0,6-1 Gew.-% Eisen,
4-5 Gew.-% Kupfer,
0,05-0,5 Gew.-% Mangan,
0,05-1,2 Gew.-% Zink,
0,56-0,9 Gew.-% Magnesium,
0,01-0,15 Gew.-% Titan,
0,01-0,1 Gew.-% Chrom,
0,01-0,1 Gew.-% Nickel,
0,01-0,1 Gew.-% Blei,
0,01-0,1 Gew.-% Zinn,
und Aluminium als Rest.
2. Aluminiumgusslegierung nach Anspruch 1, dadurch gekennzeichnet, dass die genannte Legierung aus 8-9 Gew.-% Silicium besteht.
3. Aluminiumgusslegierung nach Anspruch 1 oder Anspruch 2, dadurch gekennzeichnet, dass die genannte Legierung aus 0,8-1 Gew.-% Eisen besteht.
4. Aluminiumgusslegierung nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass die genannte Legierung aus 4-4,5 Gew.-% Kupfer besteht.
5. Aluminiumgusslegierung nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die genannte Legierung aus 0,05-0,3 Gew.-% Mangan besteht.
6. Aluminiumgusslegierung nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass die genannte Legierung aus 0,6-0,7 Gew.-% Magnesium besteht.
1. Alliage de fonderie d'aluminium,
caractérisé en ce que ledit alliage est constitué de :
7-11% en poids de silicium,
0,6-1% en poids de fer,
4-5% en poids de cuivre,
0,05-0,5% en poids de manganèse,
0,05-1,2% en poids de zinc,
0,56-0,9% en poids de magnésium,
0,01-0,15% en poids de titane,
0,01-0,1% en poids de chrome,
0,01-0,1% en poids de nickel,
0,01-0,1% en poids de plomb,
0,01-0,1% en poids d'étain
et le reste est de l'aluminium.
2. Alliage de fonderie d'aluminium selon la revendication 1, caractérisé en ce que ledit alliage est constitué de 8-9% en poids de silicium.
3. Alliage de fonderie d'aluminium selon la revendication 1 ou la revendication 2, caractérisé en ce que ledit alliage est constitué de 0,8-1% en poids de fer.
4. Alliage de fonderie d'aluminium selon l'une quelconque des revendications 1 à 3, caractérisé en ce que ledit alliage est constitué de 4-4,5% en poids de cuivre.
5. Alliage de fonderie d'aluminium selon l'une quelconque des revendications 1 à 4, caractérisé en ce que ledit alliage est constitué de 0,05-0,3% en poids de manganèse.
6. Alliage de fonderie d'aluminium selon l'une quelconque des revendications 1 à 5, caractérisé en ce que ledit alliage est constitué de 0,6-0,7% en poids de magnésium.