EP1564308B1 - Casting of an aluminium alloy - Google Patents

Abstract

A casting process for producing a cast product comprises providing an aluminum alloy comprising (wt.%) magnesium (2-4), silicon (0.9-1.5), manganese (0.1-0.4), chromium (0.1-0.4), iron (=0.2), copper (=0.1), zinc (=0.2), titanium (=0.2), zirconium (=0.3), beryllium (=0.008), vanadium (=0.5), and aluminum (balance), with further elements and production-induced contaminants (=0.2); and casting the aluminum alloy to produce a cast product. An independent claim is also included for an aluminum alloy with good heat resistance, comprising (wt.%) magnesium (2-4), silicon (0.9-1.5), manganese (0.1-0.4), chromium (0.1-0.4), iron (=0.2), copper (=0.1), zinc (=0.2), titanium (=0.2), zirconium (=0.3), beryllium (=0.008), vanadium (=0.5), and aluminum (balance), with further elements and production-induced contaminants (=0.2).

Description

The invention relates to a cast component made of an aluminum alloy with good heat resistance.

For thermally stressed components today AlSi alloys are commonly used, the hot strength is achieved by alloying of Cu. However, copper also increases the tendency of hot cracking and has a negative effect on the castability. Applications in which hot strength in particular is required are found mainly in the field of cylinder heads in the automotive industry, see e.g. F. J. Feikus, "Optimization of aluminum-silicon casting alloys for cylinder heads", foundry practice, 1999, No. 2, pp. 50-57.

From WO-A-0043560 is an aluminum alloy with 2.5 to 7.0 wt.% Mg, 1.0 to 3.0 wt.% Si, 0.3 to 0.49 wt.% Mn, 0.1-0.3% by weight Cr, max. 0.15% by weight of Ti, max. 0.15% by weight of Ti, max. 0.15 wt.% Fe, max. 0.00005 wt.% Ca, max. 0.00005 wt.% Na, max. 0.0002 wt.% P, other impurities individually max. 0.02 wt .-% and aluminum as the remainder for the production of security components in the die-casting, squeeze casting, thixoforming or thixoforging process known.

The invention has for its object to provide a suitable for the production of thermally stressed components aluminum alloy with good heat resistance. The alloy should be particularly suitable for gravity die casting, low pressure die casting and sand casting.

The components cast from the alloy should have a high strength combined with high ductility. The mechanical properties sought in the component are defined as follows: yield strength Rp0.2> 170 MPa tensile strenght Rm> 230 MPa elongation A5> 6%

Due to the applications, the corrosion tendency of the alloy should be kept as low as possible, and the alloy must also have a correspondingly good fatigue strength. The castability of the alloy should be better than that of currently used AlSiCu casting alloys, and the alloy should show no tendency to crack.

The term cast component includes in addition to the pure, manufactured only by casting components and those that are cast as a preform and subsequently formed by kneading cold or warm to final dimensions.

Examples of pure cast components are those which are produced exclusively by sand casting, gravity die casting, low pressure die casting, die casting, thixocasting or squeeze casting.

Forming operations performed on a cast preform by kneading include, for example, forging and thixoforging.

For the inventive solution of the problem leads with an aluminum alloy
2 to 4 wt .-% magnesium
0.9 to 1.5 wt .-% silicon
0.1 to 0.4% by weight of manganese
0.1 to 0.4% by weight of chromium
Max. 0.2% by weight of iron
Max. 0.1% by weight of copper
Max. 0.2% by weight of zinc
Max. 0.2% by weight of titanium
Max. 0.3% by weight zirconium
Max. 0.008% by weight of beryllium
Max. 0.5% by weight of vanadium
as well as aluminum as balance with production-related impurities individually max. 0.02 wt .-%, a total of max. 0.2% by weight.

For the individual alloying elements, the following content ranges are preferred: mg 2.5 to 3.5% by weight, in particular 2.7 to 3.3% by weight Si 0.9 to 1.3% by weight Mn 0.15 to 0.3% by weight Cr 0.15 to 0.3% by weight Ti 0.05 to 0.15% by weight Fe Max. 0.15% by weight Cu Max. 0.05% by weight Be 0.002 to 0.005% by weight V 0.01 to 0.1% by weight Zr 0.1 to 0.2% by weight

The effect of the alloying elements can be characterized approximately as follows:

Silicon in conjunction with magnesium leads to a corresponding curing, in particular, the hot curing is of interest. A heat treatment to the condition T6, e.g. a solution annealing at 550 ° C for 12 h with subsequent hot aging at 160-170 ° C for 8 - 10 h.

The combination of manganese and chromium leads to a good heat resistance at a continuous temperature of up to 180 ° C.

Titanium and zirconium are used for grain refining. A good grain refinement contributes significantly to improve the casting properties.

Beryllium in combination with vanadium reduces dandruff.

A preferred area of application of the cast components according to the invention are thermally stressed components, in particular pressure vessels, compressor housings and engine components such as cylinder heads in the automotive industry. The components are preferably produced by sand or Kokillengiessverfahren.

Fig. 1 - 3

Zugfestigkeit, Dehngrenze und Bruchdehnung in Abhängigkeit von der Temperatur nach 500 h Dauertemperaturbeanspruchung für eine erfindungsgemässe Legierung und eine Vergleichslegierung nach dem Stand der Technik.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing; this shows in

Fig. 1-3

Tensile strength, yield strength and elongation at break as a function of the temperature after 500 hours of continuous temperature stress for an alloy according to the invention and a comparison alloy according to the prior art.

An inventive alloy with the name AlMg3Si1MnCr and a comparative alloy with the name AlSi7MgCu1 from FJ Feikus, "Optimization of aluminum-silicon casting alloys for cylinder heads", foundry practice, 1999, No. 2, pp. 50-57 with those given in Table 1 Compositions were compared with each other in terms of their long-term behavior under constant temperature load. Table 1: Chemical composition of the alloys (in% by weight) alloy Si Fe Cu Mn mg Cr Zn Ti Be V Zr AlSi7MgCu1 6.97 00:11 0.94 0005 00:38 0008 00:03 AlMg3Si1MnCr 1.10 00:07 0001 00:20 3.2 00:21 0002 00:12 0003 00:03 0.0005

The alloy according to the invention was cast in a sample mold according to Diez into round rods of 16 mm diameter. On the test bars the mechanical properties yield strength (Rp0.2), tensile strength (Rm) and elongation at break (A5) in state T6 (165 ° C / 6h) after a continuous temperature load of 500 h at different temperatures. The corresponding values for the comparative alloy were taken from the above article by FJ Feikus. The results are shown in Fig. 1 in diagram form.

Although the AlMg3Si1MnCr alloy according to the invention does not reach the peak values of the comparative alloy AlSi7MgCu1 in terms of yield strength and tensile strength, it is "less changeable" in its temperature behavior. This changeability is distracting in operation insofar as slight changes in temperature can cause large changes in the mechanical properties. The yield strength of the inventive alloy remains at about 180 ° C at a nearly same level, gradually falls to 200 ° C and begins to fall off only from about 200 ° C continuously. The continuous waste occurs in comparison with the alloy AlSi7MgCu1 with a lower inclination.

With regard to the elongation at break, the alloy according to the invention is distinguished by an almost constant value up to 180 ° C. High elongation values provide favorable fracture / failure behavior. The breakage of the component is preceded by a visible deformation. Above 180 ° C, the strain increases continuously. In the case of the comparative AlSi7MgCu1 alloy, the clear hardening effect is recognized here. Low elongation values cause unfavorable failure behavior, i. the component deforms only slightly or not at all. At load peaks, the component breaks without warning.

Claims (13)

1. Casting of an aluminium alloy with good heat resistance, characterised in that the alloy contains
   2 to 4 w.% magnesium
   0.9 to 1.5 w.% silicon
   0.1 to 0.4 w.% manganese
   0.1 to 0.4 w.% chromium
   max. 0.2 w.% iron
   max. 0.1 w.% copper
   max. 0.2 w.% zinc
   max. 0.2 w.% titanium
   max. 0.3 w.% zirconium
   max. 0.008 w.% beryllium
   max. 0.5 w.% vanadium
   with aluminium as the remainder, with production-induced contaminants individually max. 0.02 w.%, total max. 0.2 w.%.
2. Casting according to claim 1, characterised in that the alloy contains 2.5 to 3.5 w.% Mg, in particular 2.7 to 3.3 w.% Mg.
3. Casting according to claim 1 or 2, characterised in that the alloy contains 0.9 to 1.3 w.% Si.
4. Casting according to any of claims 1 to 3, characterised in that the alloy contains 0.15 to 0.3 w.% Mn.
5. Casting according to any of claims 1 to 4, characterised in that the alloy contains 0.15 to 0.3 w.% Cr.
6. Casting according to any of claims 1 to 5, characterised in that the alloy contains 0.05 to 0.15 w.% Ti.
7. Casting according to any of claims 1 to 6, characterised in that the alloy contains max. 0.15 w.% Fe.
8. Casting according to any of claims 1 to 7, characterised in that the alloy contains max. 0.05 w.% Cu.
9. Casting according to any of claims 1 to 8, characterised in that the alloy contains 0.002 to 0.005 w.% Be.
10. Casting according to any of claims 1 to 9, characterised in that the alloy contains 0.01 to 0.1 w.% V.
11. Casting according to any of claims 1 to 10, characterised in that the alloy contains 0.1 to 0.2 w.% Zr.
12. Casting according to any of claims 1 to 11, produced in the sand casting or chilled casting process.
13. Use of a casting according to any of claims 1 to 12 for pressure vessels, compressor housings and engine components such as cylinder heads in automobile construction.

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