EP2041328A1

EP2041328A1 - Aluminum alloy and the utilization thereof for a cast component, in particular a motor vehicle

Info

Publication number: EP2041328A1
Application number: EP07787546A
Authority: EP
Inventors: Jürgen Wüst; Markus Wimmer; Richard Weizenbeck; Dirk E. O. Westerheide
Original assignee: Magna BDW Technologies GmbH
Current assignee: Magna BDW Technologies GmbH
Priority date: 2006-07-14
Filing date: 2007-07-13
Publication date: 2009-04-01
Anticipated expiration: 2027-07-13
Also published as: JP2009543944A; ES2340218T3; DE502007002755D1; SI2041328T1; CA2657731A1; EP2041328B1; DE102006032699A1; WO2008006908A1; ATE456682T1; DE102006032699B4; US20090297393A1

Abstract

The invention relates to an aluminum alloy, in particular a pressure casting alloy, preferably for a cast component of a motor vehicle, with the following alloy elements: 6.5 to <9.5% by weight of silicon, 0.3 to 0.6% by weight of manganese, 0.15 to 0.35% by weight of iron, 0.02 to 0.6% by weight of magnesium, a maximum of 0.1% by weight of titanium, 90 to 180 ppm strontium and aluminum as the remainder, with a maximum of 0.05% by weight, and a total maximum of 0.2% by weight of production-related contaminants. The alloy is particularly suitable for the pressure casting of the cast components of a motor vehicle such as oil pans, for example.

Description

Aluminum alloy and its use for a cast component, in particular a motor vehicle

DESCRIPTION :

The invention relates to an aluminum alloy, in particular a die-cast alloy and its use in a cast component, in particular for a motor vehicle. Moreover, the invention relates to a cast component, in particular for a motor vehicle made of such an aluminum alloy.

In the production of cast components made of aluminum-silicon casting alloys, in particular for use in the automotive industry, basically two paths are taken today.

One way describes the use of relatively inexpensive secondary alloys, for example of the type AISiI OMg, which, however, a relatively high iron content of about 0.5 to 1, 2 wt .-% Fe and a low manganese content of about 0.1 wt .-% Mn exhibit. The high iron content is required, inter alia, against the background of the relatively low addition of manganese, so that the tendency of the aluminum alloy to adhere within the die is reduced and the finished cast component can be reliably removed from the mold.

A problem with such secondary alloys, however, is the fact that due to the high iron content an intermetallic AlFeSi phase forms in the microstructure, which is an extremely large needle-shaped structure Consequently, and gives the cast component extremely brittle material properties. Furthermore, in such high-silicon aluminum casting alloy, a relatively coarse and needle-shaped formation of silicon within the AISi eutectic, by which the ductility of the cast component is reduced to a considerable extent. Therefore, such secondary alloys must be heat-treated following removal from the mold in order to be able to achieve adequate mechanical properties, for example with regard to their hardness and ductility. However, this may possibly lead to a delay of the cast components.

A cast component produced from such a secondary alloy in the form of an oil pan for a motor vehicle can be taken as known from EP 0 61 1 832 B1, in which a local heat treatment is carried out at a corresponding temperature or a corresponding period of time, so that component regions differ Set hardness. In particular, it is provided that the oil sump in the region of a flange remains largely untreated and accordingly has a hardness of 85 to 110 HB and a ductility of 0.5 to 2.5%, while this is heat treated in a bottom area accordingly, so that it has a hardness of 55 to 80 HB and a ductility of above 4%. In other words, this is to be achieved that in the region of the flange existing in the cast state high hardness or low ductility is maintained, whereas in the bottom area reduces the hardness and ductility is increased to the risk of rockfall caused by cracks or the like Damage to the oil sump to reduce. However, such a heat treatment is time-consuming and therefore expensive, so that the cost savings made possible by the use of a secondary alloy are more than consumed.

The alternative to the above-described secondary alloy walkable way describes the use of primary alloys, for example, also of the type AISiI O, in addition to the alloying elements present residual aluminum individually a maximum of 0.05 wt .-% and a maximum of 0.2 wt .-% production-related impurities.

For example, such a primary alloy can already be taken from EP 0 997 550 B1 as known, which - in contrast to the previously described Secondary alloys - a lower iron content of 0.15 to 0.35 wt .-% Fe and a contrast high manganese content of 0.3 to 0.6 wt .-% Mn. In addition to the fact that such a primary alloy has a reduced tendency to stick in the die casting mold and is therefore correspondingly easy to demold, the intermetallic AlFeSi phases customary with secondary alloys do not exist in such a primary alloy. For example, this results in a rather roundish in cross-section, intermetallic Al ₁₂ (Mn, Fe) Si ₂ phase, which accordingly has no or no pronounced needle-shaped training. This results in a significantly improved morphology, so that a material with a hardness of about 80 - 100 HB can be realized in the cast state. In order to reduce the coarse or needle-shaped formation of silicon in the AISi eutectic, strontium is preferably added to the above-described primary alloy, which stops the needle-shaped growth of the silicon within the AISi eutectic.

However, since at least some of the cast components produced by such a primary alloy have only an elongation at break of A ₅ of <5% after demoulding, they are first used as safety components in the automotive industry in a subsequent heat treatment process at a temperature of 400 to 490 ° C partially solution-annealed for a period of 20 to 120 min and then cooled in air. As a result, a significant increase in the ductility of the cast component is achieved, so that sets an elongation at break of A ₅ > 12%. With the heat treatment, the hardness of the cast component drops to a value of about 60 to 65 HB.

Object of the present invention is therefore to provide an aluminum alloy and their use for a cast component in particular a motor vehicle of the type mentioned, with which the production of such a cast component can be realized much easier and therefore cheaper. Moreover, it is an object of the invention to produce a cast component made of such an aluminum alloy in particular for the motor vehicle industry with correspondingly high mechanical requirements in a simpler and more cost-effective manner. This object is achieved by an aluminum alloy with the features of claim 1, with their use in a cast component in particular a motor vehicle with the features of claim 6 and by a cast component of such an aluminum alloy in particular for a motor vehicle with the features of claim 10. Advantageous embodiments with expedient and non-trivial developments of the invention are specified in the dependent claims.

To achieve the object according to the invention, the aluminum alloy, which is to be used in particular as a die-cast alloy, comprises the following alloying elements:

6.5 to <9.5 wt .-% silicon

0.3 to 0.6% by weight of manganese

0.15 to 0.35% by weight of iron 0.02 to 0.6% by weight of magnesium max. 0.1% by weight of titanium

90 to 180 ppm strontium

and the balance aluminum with individually at most 0.05 wt .-% and a maximum of 0.2 wt .-% of production-related impurities.

By reduced compared to the previously known primary alloy according to EP 0 997 550 Bl content of silicon, the proportion of AISi eutectic is significantly reduced and contrast, the proportion of aluminum mixed crystals significantly increased. Thus, it is possible with the aluminum-silicon alloy according to the invention to combine two mutually opposite properties with each other. On the one hand cast components can be created with the aluminum alloy according to the invention, which have a hardness of> 80 HB, and preferably between 84 HB and 88 HB already in the cast state - ie without additional heat treatment after demoulding. It should be noted that these values are measured inside the cast component, ie below the casting skin of the component. On the other hand, with the aluminum alloy according to the invention it is possible, despite the relatively high hardness, to achieve a very high ductility of the cast component, whose elongation at break is determined by the Removal - ie in the cast state and without further heat treatment - has a value of A ₅ > 5%, and preferably 8% to 12%.

Thus, while in a casting made of an aluminum alloy according to EP 0 997 550 B1 cast component, which may have a relatively low elongation at break of A ₅ at about 4% in the cast state, a heat treatment is required to achieve the required in particular in motor vehicle mechanical characteristics, can be dispensed with in such a subsequent treatment in cast components created from the aluminum alloy according to the invention. Rather, a sufficient ductility is ensured with the aluminum alloy according to the invention, in which the breaking elongation A _{5 of} the cast component is greater than 5%. Equally, it is ensured that the hardness of the cast component with> 80 HB is sufficiently high. As a result, an alloy is thus created, with which cast components can be produced, in particular for motor vehicle construction, which already have a very good mechanical properties without heat post-treatment and are therefore extremely easy and inexpensive to produce.

In one embodiment of the invention, the aluminum alloy according to the invention has a selected range of between 0.22 and 0.4% by weight of magnesium compared to that according to EP 0 997 550 B1, since the hardness of the cast component produced from the aluminum alloy is not limited to Eutectic, but also depends on the resulting outsourcing. Due to the specially selected magnesium content, Mg ₂ Si ultrafine precipitates are formed by which the strength or hardness of the cast component can be adjusted. In other words, the hardness of the cast component produced from the aluminum alloy according to the invention is also dependent on the magnesium content. Here, while ensuring an elongation at break A ₅ of> 5%, a particularly high hardness of the cast component of the aluminum alloy according to the invention can be achieved if the magnesium content is in a selected range of 0.3 to 0.4% by weight, and preferably 0 , 32 to 0.36 wt .-% is.

Through the use of strontium with a content of 90 to 180 ppm is achieved in the aluminum alloy according to the invention beyond that in their Solidification, the needle-shaped silicon growth is stopped within the AISi eutectic, so that the silicon crystals do not adopt extreme needle shape.

As a further advantage, it has been shown to add 0.1 to 0.4 wt .-% copper as a further alloying element of the aluminum alloy according to the invention. As a result, the cold swaging is enhanced, over which the hardness of the cast component produced from the aluminum alloy can be additionally influenced.

Since the aluminum alloy according to the invention or the cast component produced therefrom already has the above-described high hardness or high elongation at break in the cast state, this is particularly suitable for use in motor vehicle construction. The use of the aluminum-silicon alloy according to the invention in oil pans for motor vehicles has proven to be particularly advantageous since it must have a relatively high ductility with an elongation at break A ₅ of> 5% in order to provide adequate protection against crack formation within the oil pan to be able to, which may arise in particular due to falling rocks below the motor vehicle. Since the sumps in the connection or flange area must be sealed with a corresponding motor housing, it is necessary that they have a correspondingly high hardness of> 80 HB. Since a cast component produced from the present aluminum-silicon alloy fulfills these requirements already in the cast state without further heat treatment, it is thus possible to create an oil pan or another component for a motor vehicle that is easy to manufacture and therefore cost-effective.

Since in a variety of cast components used in the automotive industry sufficient in the use of the present aluminum alloy mechanical properties in terms of hardness and ductility, they can now be used without further heat treatment. This not only has the advantage of a simpler and cheaper production, but also can be avoided in the heat treatment optionally accompanying distortion of the cast components in a simple manner that just no aftertreatment is necessary. Particularly advantageously, the aluminum alloy can be used in a die-casting process for the production of cast components, in particular for a motor vehicle, as a result, a particularly fast and cost-effective production of the cast components is possible.

If cast components with respect to their cast state other mechanical properties, in particular with regard to their ductility or hardness required to be used for example in the body, in the chassis or as a component of the powertrain of the motor vehicle, the inventive aluminum-silicon alloy used in the Following the casting process to be subjected to a heat treatment process.

It has proven to be particularly advantageous if the cast component solution-annealed in a temperature range of 400 to 490 ° C, and in particular between 420 to 460 ° C for a period of 20 to 120 min and then cooled in the air. By this extremely gentle heat treatment with the cooling of the cast component in the air is achieved in particular that the castings do not or not excessively forgiven.

To set the desired strength level, the component can additionally be hot-hardened after partial solution annealing in the temperature range of the precipitation hardening of Mg2Si. This thermosetting is preferably carried out in a temperature range of about 190 to 240 ° C, in particular about 190 to 220 ° C.

The casting component produced by the new aluminum-silicon alloy is characterized in particular by the fact that it has an at least approximately uniform hardness of> 80 HB and preferably between 84 and 88 HB in the cast state in all component regions. In addition, the cast component advantageously has an at least approximately uniform elongation at break A ₅ of> 5% and preferably 8% to 12% in all component regions. Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings; these show in:

1 is a process flow diagram of a heat treatment of a component of a motor vehicle; and in

Fig. 2 is another process flow diagram of a heat treatment of a component of a motor vehicle.

Example 1 :

In this case, a plurality of cast components in the form of oil pans for a motor vehicle have been produced in a die casting process from an aluminum-silicon casting alloy, which has the following composition:

6.5 to <9.5 wt .-% silicon

0.3 to 0.6% by weight of manganese

0.15 to 0.35% by weight of iron 0.22 to 0.4% by weight of magnesium max. 0.1% by weight of titanium

90 to 180 ppm strontium

and the remainder being aluminum with a maximum of 0.05% by weight and a maximum of 0.2% by weight in total of production-related impurities, it being possible optionally to provide 0.1 to 0.4% by weight of copper. In the present embodiment, the silicon content is between 7 and 9 wt .-% and the magnesium content between 0.32 and 0.36 wt .-%.

After die casting, tensile specimens from the castings or oil pans were worked out and the mechanical properties ablated in the table below were determined thereon:

It can therefore be seen from the table that all samples have an elongation at break A ₅ between 8 and 12%. Accordingly, the present aluminum alloy is eminently suitable for use in die-casting of oil pans where an elongation at break A ₅ of> 5% has to be achieved, in particular to prevent cracking when rockfall occurs during driving of the motor vehicle.

In further experiments, it has also been found that the oil pans cast by means of the above aluminum-silicon alloy have a hardness of> 80 HB, and in particular between 84 and 88 HB, so that the oil pans in the connection or flange area correspond to one another Motor housing of the motor vehicle can be tightly closed. The casting skin of the as-cast condition The existing oil pans were correspondingly removed by a machining process, for example by milling, so that realistic hardness values of the oil pans in the cast state could be determined.

Example 2:

In the present case, in turn, a plurality of cast components in the form of oil pans for a motor vehicle have been produced in a die casting process from an aluminum-silicon casting alloy, which has the following composition:

7.8 to 8.2 wt .-% silicon

0.5 to 0.6% by weight of manganese

0.15 to 0.2% by weight of iron

0.27 to 0.33 wt .-% magnesium

0.04 to 0.08% by weight of titanium 140 to 180 ppm of strontium

and the balance aluminum with individually at most 0.05 wt .-% and a maximum of 0.2 wt .-% of production-related impurities. In the present embodiment, the magnesium content is in particular about 0.3 wt .-%.

The individual oil pans have not been heat treated. Consequently, the measured values relate to the casting state of the components, wherein the casting skin in the respective test area has in turn been correspondingly removed by a machining method, for example by milling.

It can be seen in particular from the table that in the present oil sumps the tensile strength Fy _{n is} above 250-260 N / mm ² , the yield strength F 1 above 120 N / mm ² and the elongation at break A ₅ in the range between 6.25 and 14 , 38% lies. Accordingly, the present aluminum alloy, in turn, is particularly well suited for use in die casting of oil pans where an elongation at break A ₅ of> 5% must be achieved. Also in this alloy composition, a hardness of> 80 HB could be achieved.

Example 3:

The present example is based on a test program which has been carried out on components in the form of door pillars or B pillars of passenger cars. These door _pillars should have a yield strength R _p0.2 of 150 to 180 MPa and an elongation at break A ₅ of = 7%.

The B-pillars have been produced in a die casting process from an aluminum-silicon casting alloy in two variants, which have the following compositions:

Variant 1: 7.8 to 8.2% by weight of silicon 0.5 to 0.6% by weight of manganese 0.15 to 0.2% by weight of iron 0.27 to 0.33% by weight of magnesium 0.04 to 0.08% by weight of titanium 140 to 180 ppm of strontium

Variant 2:

7.8 to 8.2% by weight of silicon 0.5 to 0.6% by weight of manganese

0.15 to 0.2% by weight of iron

0.5 to 0.6 wt .-% magnesium

0.04 to 0.08% by weight of titanium

140 to 180 ppm strontium

and the balance aluminum with individually at most 0.05 wt .-% and a total of maximum

0.2 wt .-% production-related impurities.

Thus, it can be seen that the two variants essentially by the different contents of magnesium, namely in the variant 1 with 0.27 to 0.33 wt .-% and in the variant 2 with 0.5 to 0.6 wt. -%, different.

Heat treatment: Process 1: The two variants of the aluminum-silicon casting alloy - in particular variant 2 with a content of about 0.6 wt .-% magnesium - were, for example, the following, in FIGS. 1 and 2 using flowcharts explained heat treatments, subjected to:

1 shows a method in which the B-pillars (product P) after casting in a step 1 - using a portion of the casting heat - are solution-annealed in a step 2 and quenched in the air by means of a fan. In other words, in the present case, the product P is not cooled to room temperature, for example, after demolding from the casting tool, but rather solution-annealed at a temperature of about 200 ° C in step 2. During the solution annealing in step 2, a sprue A or other casting residues remain on the product P.

After the solution heat treatment in step 2, the component is still relatively soft or ductile and can therefore be deburred in step 3. In this case, the sprue A or other casting residues are removed from the product P. The product P remains soft.

Following the deburring carried out in step 3, the B-pillar or product P is straightened in step 4. The product P is further soft for this purpose.

Finally, the product P is removed in step 5, specifically at one of the aging temperatures which will be described in more detail below. Thereafter, the product which is soft until after step 4 is adjusted according to its desired material properties.

Process flow 2:

FIG. 2 shows a method which differs from that according to FIG. 1 in particular in that the steps 2 and 3 are reversed in their sequence and therefore no utilization of part of the casting heat takes place in the present case.

Thus, the product P in the present case after step 1 is cooled together with the sprue A or other casting residues to room temperature or to about 20 ° C. Thereafter, the deburring 3 and the removal of the sprue and the casting remains, wherein the product is still soft.

After the deburring 3, the solution annealing 2 and the subsequent cooling takes place for example in the air by means of a fan. The product P remains soft.

Steps 4 and 5, so the straightening of the B-pillar or the product P and the outsourcing in one of the hereinafter described in more detail Auslageremperaturen, then again take place analogously to the method according to Fig.1. After step 5, the product which is soft until after step 4 is in turn adjusted in accordance with its desired material properties.

It is common to both methods according to FIG. 1 and FIG. 2 that in the respective method sequence at the points Q1 a dimensional check at the point Q2 has a strength test. Tensile test is made.

The solution annealing carried out in the respective step 2 of the two methods according to FIGS. 1 and 2 was carried out in different tests at different temperatures between 460 and 490 ° C. and during different annealing times of 15 to 120 minutes.

The removal performed in the respective step 5 of the two methods according to FIGS. 1 and 2 likewise took place in different tests at different temperatures between 160 and 240 ° C. and during different removal times of 20 to 240 minutes.

The heat treatment components were created for use, for example, in the body, in the chassis or in the drive train of the motor vehicle, which has a yield strength R _p0,2 between 90 and 180 MPa, a tensile strength R _m between 180 and 250 MPa and an elongation at break A ₅ in the range between 8 and 22%.

Consequently, the present aluminum alloy is again particularly good for

Suitable for use in motor vehicles.

Example 4:

The present example is based on a test program in which high-strength components of passenger cars with an alloy composition according to Variant 1 (0.27 to 0.33 wt .-% Mg) are processed accordingly, that these after the heat treatment described below, a yield strength Rp _{O, 2} of = 180 MPa. For this purpose, the high-strength components of a T5 annealing were subjected to different temperatures between 160 and 240 ° C and for different times from 20 to 240 min.

Claims

Aluminum alloy and its use for a cast component, in particular a motor vehicle CLAIMS

1. aluminum alloy, in particular die-cast alloy preferably for a cast component of a motor vehicle characterized by the following alloying elements:

6.5 to <9.5 wt .-% silicon 0.3 to 0.6 wt .-% manganese

0.15 to 0.35% by weight of iron

0.02 to 0.6% by weight of magnesium max. 0.1% by weight of titanium

90 to 180 ppm strontium

2. Aluminum alloy according to claim 1, characterized in that it has a hardness of> 80 HB, and preferably between 84 HB and 88 HB in the cast state.

3. Aluminum alloy according to claim 1 or 2, characterized in that it has a breaking elongation A ₅ of> 5%, and preferably 8% to 12% in the cast state.

4. Aluminum alloy according to one of claims 1 to 3, characterized in that it comprises 0.1 to 0.4 wt .-% copper as a further alloying element.

5. Aluminum alloy according to one of claims 1 to 4, characterized in that it comprises 0.22 to 0.4 wt .-%, and preferably 0.32 to 0.36 wt .-% magnesium.

6. Use of an aluminum alloy according to one of claims 1 to 5 in a cast component, in particular an oil pan of a motor vehicle.

7. Use according to claim 6, characterized in that the cast component is produced in a die-casting process.

8. Use according to claim 6 or 7, characterized in that the cast component after the casting process a

Heat treatment process is subjected.

9. Use according to claim 8, characterized in that the cast component in a temperature range of 400 to 490 ° C, in particular in a temperature range of 420 to 460 ° C for a period of 20 to 120 min partially solution-annealed and then cooled in air.

10. cast component, in particular for a motor vehicle made of an aluminum alloy according to one of claims 1 to 5.

11. Cast component according to claim 10, characterized in that this is designed as an oil pan of a motor vehicle.

12. Cast component according to claim 10 or 11, characterized in that this has in the cast state in all component areas an at least approximately uniform hardness of> 80 HB, and preferably between 84 HB and 88 HB.

13. Cast component according to one of claims 10 to 12, characterized in that this has in the cast state in all component areas an at least approximately uniform elongation at break A ₅ of> 5%, and preferably 8% to 12%.

14. Cast component according to claim 13, characterized in that it is at least partially partially solution-annealed in a temperature range of 400 to 490 ° C, in particular in a temperature range of 420 to 460 ° C for a period of 20 to 120 min and then cooled in air ,