EP1917372B1 - Aluminium casting alloy - Google Patents

Description

The invention relates to aluminum casting alloys, in particular for chassis applications. For this purpose, generally primarily melted hypoeutectic AlSi alloys are used, which are alloyed with low levels of Mg for strength enhancement, e.g. AlSi7Mg or AlSi11 Mg. Occasionally AlSi (Mg, Cu) alloys are also used, but due to their corrosive properties they can only find niche applications. The same applies to the family of AlCu (Ti, Mg) alloys, which offer the highest strengths among common alloys. Also niche applications in the chassis area are the AlMg alloys. Other alloy families, such as AlZn or AlLi, play no role in the chassis.

Usually, the components made from the above alloys are subjected to a two-stage heat treatment to obtain the desired properties.

In general, the existing alloy families have the disadvantage that only a limited strength-strain ratio can be achieved. The above-mentioned high-strength alloys with Cu addition are often eliminated due to the corrosive properties. AlMg alloys are significantly heavier castable and therefore limited in application (component geometry).

From the summary of JP 0710953T A is an Al-Si alloy with a chemical composition in wt.% 3.3-5.5 Si, 0.2-0.7% Mg, 0.01-0.2% Ti, 0.0001-0.01% B, max. 0.2% Fe, max. 0.005% P, max. 0.005% Ca, optionally one or several of the elements 0.02-0.5% Mn, 0.01-0.3% Cr, 0.01-0.2% Zr and 0.2-0.5% Cu and furthermore optionally max. 0.03% Sb, 0.001-0.01% Na and 0.001-0.05% Sr.

Accordingly, it was the object of the invention to develop an alloy which has properties which still have sufficiently high elongation at fracture values, in particular for automotive applications. This combination of properties is necessary, for example, in chassis applications, in order to be able to survive cases of abuse. At the same time, the alloy has to be sufficiently castable and, owing to its composition, should not impose excessive demands on the melting process and the metal circulation.

This is achieved according to the invention in that Al casting alloys contain alloy components listed below: Si: 2.7 to 3.1% by weight mg: 0.3 to 0.6% by weight Fe: 0.05 to 0.16% by weight Mn: <0.5, preferably 0.05 to 0.4 wt .-% Ti: 0.01 to 0.08% by weight Sr: 0.01 to 0.03% by weight other: <0.1% by weight and in each case added to 100 wt .-% with Al.

Optionally, production-related impurities, for example Pb, Ni, Zn, etc., are included, as are generally known to the person skilled in the art.

The alloys of the present invention have a strength-strain ratio that is not achievable with conventional Al casting alloys under the requirement of Cu freedom. Especially in pressure-assisted casting processes, e.g. Low pressure - back pressure - Kogillenguss - result from the good cast structure better mechanical technological properties.

It may also be advantageous if the alloy is grain-fined.

In order to achieve or further develop the advantages mentioned above, it is advantageous if the cast components are heat-treated, in particular with the following parameters: solution annealing 490 to 540 ° C for 1 to 10h start 150 to 200 ° C for 1 to 10h

For some applications, however, it may also be advantageous to carry out only one-stage tempering treatment, generally known as T4, T5 or 0, for example

In addition to the advantages already mentioned, which have components made of alloys according to the invention, there is also the fact that, because of the missing alloy constituents Cu and Zn, the corrosion resistance is significantly increased. The product is also relatively inexpensive because no use is made of the same expensive alloying additives, such as SE metals, the usual melt treatment can be used, and there is no need for a special separation process.

There is also an excellent strength-elongation ratio with excellent castability. On the one hand, the castability allows one of large defects, known as voids, to be free cast, and on the other hand, the microstructure is positively influenced in such a manner that the number of internal grooves which reduce the elongation at break is minimized.

As example values are to be stated: R _m [MPa] R _{p 0.2} [MPa] A ₅ [%] Gravity chill casting casting condition 250 140 13 Gravity chill casting heat treatment T6 (540 ° C, 7h, 160 ° C, 8h) 320 260 5 Pressure assisted chill casting heat treatment T6 (540 ° C, 7h / 160 ° C, 6h) 370 300 11

Claims (7)

1. An Al casting alloy, containing the alloy components listed hereafter: Si: 2.7 to 3.1 wt% Mg: 0.3 to 0.6 wt% Fe: 0.05 to 0.16 wt% Mn: < 0.5, preferably 0.05 to 0.4 wt% Ti: 0.01 to 0.08 wt% Sr: 0.01 to 0.03 wt% other: < 0.1 wt% and in each case completed with Al to 100 wt%.
2. The Al casting alloy according to Claim 1, characterised in that the alloy is grain-refined.
3. A use of Al casting alloys according to one of the preceding claims for work pieces, component parts or parts for or of chassis parts of motor vehicles.
4. A cast part made from an Al casting alloy according to claim 1 or 2.
5. The cast part according to claim 4, characterised in that the cast part is solution-annealed between 490 to 540°C for 1 to 10h.
6. The cast part according to claim 4 or 5, characterised in that the cast part is tempered between 150 to 200°C for 1 to 10h.
7. A use of cast parts according to one of claims 4 to 6 for work pieces, component parts or parts for or of chassis parts of motor vehicles.