JP2009543944A - Aluminum alloy and its use especially for automotive casting parts - Google Patents

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

Detailed Description of the Invention

[Explanation]
The present invention relates to an aluminum alloy, in particular a pressure casting alloy, and its use, in particular in automotive casting parts. The invention also relates to cast parts, especially for automobiles, made of this type of aluminum alloy.

  Currently, there are generally two options for producing cast parts from aluminum-silicon pressure cast alloys, particularly for use in the automotive industry.

  One option includes the use of a relatively inexpensive secondary alloy of the AlSi10Mg type, for example, which alloy has a relatively high iron content of about 0.5 to 1.2 wt% Fe and a Mn of about 0. It has a low manganese content of 1% by weight. In this case, in particular, a relatively small amount of manganese is added to reduce the tendency of the aluminum alloy to adhere to the pressure casting mold and to ensure that the cast part produced can be removed from the mold. In view of the above, a high iron content is required.

  However, the disadvantage of this type of secondary alloy is that an intermetallic AlFeSi phase is formed in the material structure due to the high content of iron, and this phase has an extremely large needle-like structure, so that the cast part is It is to exhibit extremely brittle material properties. Furthermore, the formation of relatively coarse needle-like silicon occurs within the AlSi eutectic in this type of aluminum cast alloy with a high silicon content, resulting in a substantial reduction in the ductility of the cast part. Thus, for example, to obtain a reasonably sufficient mechanical property with respect to its hardness and ductility, it is necessary to heat-treat this type of secondary alloy after removing it from the mold. However, this may cause distortion of the cast part.

  Cast parts made from this type of secondary alloy in the form of automotive oil pans are disclosed in EP 0611832 B1, in which various local heat treatment steps at different temperatures and for different periods of time are disclosed. This is done to produce cast parts with a certain hardness. In this case, the oil pan is properly heat treated in the base region, resulting in a hardness of 55-80 HB and a ductility of over 4%, but the oil pan remains as untreated as possible in the flange region. It is specifically specified that it exhibits a hardness of 85-110 HB and a ductility of 0.5-2.5%. In other words, this reduces the risk of this type of cracking or damage in the oil pan due to stone impact, while reducing the hardness and increasing the ductility in the base region. It is intended to ensure that it retains a high level of hardness and a low level of ductility, respectively, already shown in the flange region. However, this type of heat treatment is time consuming and therefore expensive, so that all the cost savings made by the use of secondary alloys may not be used up in this process.

  Alternative options for the aforementioned secondary alloys include, for example, the use of primary alloys of AlSi10 as well, and this type of residual aluminum, in addition to the alloy elements, individually can be up to 0.05% by weight, or up to a total Contains 0.2% by weight manufacturing related contaminants.

A primary alloy of this type is disclosed for example in EP 0 997 550 B1 and, unlike the aforementioned secondary alloy, has a low iron content of 0.15 to 0.35% by weight of Fe and 0.3 to 0.6% by weight of Mn. Has a relatively high manganese content. In addition to the fact that primary alloys of this type have a reduced tendency to adhere to pressure casting molds and can therefore be easily removed from the mold, the intermetallic AlFeSi phase common to secondary alloys is It does not occur in types of primary alloys. Instead, for example, an intermetallic Al ₁₂ (Mn, Fe) Si- ₂ phase is produced that is more nearly circular in shape, and therefore exhibits no or no significant acicular formation. This results in a considerably improved form, so that it is possible to produce a material having a hardness of about 80-100 HB when cast. Strontium, which stops the acicular growth of silicon inside the AlSi-based eutectic, is preferably added to the above primary alloy in order to reduce silicon coarseness or acicular formation in the AlSi-based eutectic.

However, at least some of the cast component is formed from this type of primary alloy, after disconnecting from the time and the mold was cast, since only shows the elongation at break A ₅ of <5%, the safety in the automotive industry parts For use as these, these cast parts are first partly solution heat treated in a subsequent heat treatment step at a temperature of 400 to 490 ° C. for a period of 20 to 120 minutes and then air cooled. Since this increases the ductility of the cast component considerably, it is possible to obtain an elongation at break A ₅ of> 12%. The heat treatment reduces the hardness of the cast part to a value of about 60-65 HB.

  The object of the present invention is therefore to provide an aluminum alloy and its use for cast parts, in particular of the type mentioned at the outset, with which this type of cast part It can be manufactured in a simplified manner and thus cost-effective. It is a further object of the present invention to simplify and cost-effectively produce highly mechanical specification cast parts made from this type of aluminum alloy, especially for the automotive industry.

  The present invention is made of an aluminum alloy having the features of claim 1, its use with the features of claim 6, in particular in automotive casting parts, and this type of aluminum alloy with the features of claim 10, especially for automobiles. This is realized in accordance with the present invention by a cast part. Advantageous configurations with appropriate and meaningful development of the invention are specified in the dependent claims.

In order to achieve the object according to the invention, aluminum alloys which are to be used in particular as pressure casting alloys are the following alloy elements:
Silicon 6.5- <9.5% by weight
Manganese 0.3-0.6% by weight
Iron 0.15-0.35 wt%
Magnesium 0.02-0.6% by weight
Titanium up to 0.1% by weight
Strontium 90-180ppm
And other aluminum, production-related contaminants individually up to 0.05% by weight, and in total up to 0.2% by weight.

Due to the lower silicon content than the primary alloys previously known from EP 0997550B1, the proportion of AlSi eutectic is significantly reduced, whereas the proportion of aluminum solid solution is considerably increased. Yes. The aluminum-silicon based alloy according to the present invention enables the coexistence of two kinds of properties which are contradictory to each other. On the one hand, the aluminum alloy according to the invention is used to produce cast parts exhibiting a hardness of> 80 HB, preferably 84 HB to 88 HB, when removed from the cast mold, ie without any additional heat treatment. Is possible. In this regard, it should be noted that these values are measured inside the cast part, i.e. under the cast skin of the part. On the other hand, the aluminum alloy according to the invention makes it possible to obtain a very high level of ductility of the cast part, despite its relatively high hardness, and when it is removed from the mold, i.e. cast, without any further heat treatment. elongation at break of the case is> 5%, preferably it possible to achieve the _{a 5} values of 8% to 12%.

Accordingly, it produced from an aluminum alloy according to EP 09970550B1, cast components which may exhibit relatively low elongation at break A ₅ value of about 4%, in order to obtain the mechanical properties required in particular in the automotive manufacturing industry However, this type of post-treatment can therefore be dispensed with for cast parts made from the aluminum alloy according to the invention. Use an aluminum alloy according to the present invention, the value of elongation at break A ₅ of the cast parts When it is more than 5%, is guaranteed to realize a sufficient level of ductility. With this aluminum alloy, it is likewise ensured that the hardness of the cast part is sufficiently high,> 80 HB. It is therefore possible to produce cast parts that exhibit excellent mechanical properties without heat treatment and are therefore very simple and cost-effective to produce, especially for the automobile manufacturing industry.

In one embodiment of the invention, the aluminum alloy according to the invention is an alloy according to EP 0997550B1, since the hardness of the cast part produced from the aluminum alloy depends not only on the eutectic but also on the precipitates that form. In contrast, it contains 0.22-0.4% by weight of the selected range of magnesium. Fine Mg ₂ Si precipitates that can adjust the strength or hardness of the cast part are formed as a result of a particularly selected magnesium content. In other words, the hardness of the cast part produced from the aluminum alloy according to the invention is also a function of the magnesium content. Accordingly, the magnesium content is 0.3 to 0.4 wt%, preferably if the selected range of 0.32 to 0.36 wt%, still the value of the elongation at break _{A 5} of> 5% It is possible to obtain a particularly high hardness for cast parts made from the aluminum alloy according to the invention while maintaining.

  Moreover, the use of 90-180 ppm amounts of strontium in the aluminum alloy according to the present invention stops the growth of acicular silicon inside the AlSi-based eutectic during solidification of the alloy, so that the silicon crystals are not much needles It is guaranteed that it does not take on the shape of the shape.

  It has further proved advantageous to add 0.1 to 0.4% by weight of copper as a further alloying element to the aluminum alloy according to the invention. This promotes a natural aging process that can also affect the hardness of cast parts made from aluminum alloys.

The aluminum alloy according to the invention or the cast parts produced therefrom are already very suitable for use in the automotive industry, as they already exhibit the above-mentioned high levels of hardness and elongation at break, respectively, during casting. To particularly with sufficient resistance to oil pan inside the crack that might occur by the collision of stone to the bottom of the motor vehicle, the oil pan,> 5% relatively high levels of ductility with elongation at break A ₅ of It has been found to be particularly advantageous to use an aluminum-silicon based alloy according to the present invention in an automotive oil pan. The oil pan must exhibit a reasonably high hardness of> 80 HB, since the oil pan needs to be securely fastened to each corresponding engine housing in the connection area or flange area. Cast parts made from the present aluminum-silicon alloys can meet these requirements at the time of casting without any further heat treatment, and are therefore easy to manufacture and therefore cost effective. It is possible to produce expensive automotive oil pans or other parts.

  The mechanical properties related to hardness and ductility that can be achieved with the use of this aluminum alloy are sufficient for use in many cast parts used in the automotive industry, so these cast parts are currently used without the need for further heat treatment. it can. This is not only advantageous with respect to simpler and more cost-effective manufacturing processes, thus easily avoiding cast part distortion that may occur during heat treatment due to the fact that no post-treatment is required. It is also possible to do.

  Since it is thus possible to produce cast parts particularly quickly and cost-effectively, the aluminum alloys can be used particularly advantageously in pressure casting processes, especially for producing cast parts for automobiles.

  Because casting parts having mechanical properties different from those exhibited by casting parts, particularly those relating to ductility or hardness, are required for use as parts of, for example, vehicle bodies, chassis or power transmission systems of automobiles. If present, the aluminum-silicon alloy according to the present invention used for this purpose can be subjected to a heat treatment after the casting process.

  In this case, it has been found to be particularly advantageous if the cast part is solution treated for a period of 20 to 120 minutes in the temperature range of 400 to 490 ° C., in particular 420 to 460 ° C. and then air cooled. This extremely gentle heat treatment and air cooling of the cast part in particular guarantees that the cast part will not warp or excessively warp.

  To achieve the desired strength level, the part can also be artificially aged in the Mg 2 Si precipitation hardening temperature range after a partial solution treatment. This artificial aging process is preferably performed in a temperature range of about 190-240 ° C, especially about 190-220 ° C.

Cast parts formed from new aluminum-silicon alloys are particularly distinguished by the fact that the entire area of the part during casting exhibits at least approximately uniform hardness of> 80 HB, preferably 84-88 HB. Furthermore, the total area of the parts,> 5%, preferably advantageously to exhibit elongation A ₅ at least substantially uniform at break of 8% to 12%.

  Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments with reference to the drawings.

[Example 1]
In this case, a plurality of cast parts in the form of oil pans for automobiles have the following composition:
Silicon 6.0- <9.5% by weight
Manganese 0.3-0.6% by weight
Iron 0.15-0.35 wt%
Magnesium 0.22-0.4% by weight
Titanium up to 0.1% by weight
Strontium 90-180ppm
And, in addition, aluminum and, individually, up to 0.05% by weight and in total up to 0.2% by weight of production-related contaminants (but in some cases also 0.1 to 0.4% by weight of copper It may be produced by a pressure casting process from an aluminum-silicon casting alloy. In this embodiment, the silicon content is therefore 7-9% by weight and the manganese content is 0.32-0.36% by weight.

  After the pressure casting process, the tensile sample was removed from the cast part or oil pan and found to have the mechanical properties listed in the table below.

Table has been shown that all the samples showed an elongation at break A ₅ of 8% to 12%. Accordingly, the aluminum alloy is particularly to prevent the formation of cracks occurring in the collision of the driver during stone automobile> 5% break oil pan which is the required elongation A _5, be produced by pressure casting Very suitable for use in.

  In further tests, oil pan castings using the present aluminum-silicon alloys exhibit a hardness of> 80 HB, in particular 84-88 HB, so that the connection in the flange area of the oil pan is securely attached to the corresponding engine housing of the vehicle. It was also found that it can be fixed. In order to ensure that the actual hardness value at the time of casting of the oil pan could be determined, the cast skin at the time of casting of the oil pan was appropriately removed by a mechanical operation such as milling.

[Example 2]
In this case, a plurality of cast parts in the form of an oil pan for an automobile have the following composition:
Silicon 7.8-8.2% by weight
Manganese 0.5-0.6% by weight
Iron 0.15-0.2% by weight
Magnesium 0.27 to 0.33 wt%
Titanium 0.04-0.08% by weight
Strontium 140-180ppm
And others as aluminum, and individually from aluminum-silicon based casting alloys with production-related contaminants of up to 0.05 wt. In this embodiment, the magnesium content is particularly about 0.3% by weight.

  In this case, the individual oil pans were not heat treated. Therefore, the measured value relates to the part during casting, and the cast skin is also removed from each sample region by a mechanical operation such as milling.

This table, oil pan 250~260N / mm ² greater than the tensile strength _R m in this case, 120 N / mm ² greater proof stress _{R p0.2} and 6.25 to 14.38% in the range elongation at break A of _It shows in particular that a value of ₅ was shown. Accordingly, the aluminum alloy, to be particularly suitable in the production due to the pressure casting of oil pan must achieve an elongation at break A ₅ of> 5% was demonstrated. It was also possible to achieve a hardness of> 80 HB with this alloy composition.

[Example 3]
This embodiment is based on a test program performed on a part in the form of an automobile door pillar or B pillar. These door pillar is therefore should exhibit an elongation at break _{A 5} equals strength _{R p0.2} and 7% 150～180MPa.

In this case, the B pillar has the following composition:
Mutant composition: 1
Silicon 7.8-8.2% by weight
Manganese 0.5-0.6% by weight
Iron 0.15-0.2% by weight
Magnesium 0.27 to 0.33 wt%
Titanium 0.04-0.08% by weight
Strontium 140-180ppm
And, in addition, aluminum, and individually from two variant compositions of aluminum-silicon alloys with production-related contaminants of up to 0.05% by weight and up to 0.2% by weight in total, were produced in a pressure casting process.

Mutant composition: 2
Silicon 7.8-8.2% by weight
Manganese 0.5-0.6% by weight
Iron 0.15-0.2% by weight
Magnesium 0.5-0.6% by weight
Titanium 0.04-0.08% by weight
Strontium 140-180ppm
And aluminum as the other, and manufacturing-related contaminants individually include up to 0.05% by weight, and up to a total of 0.2% by weight.

  The two variant compositions are substantially different with respect to their different magnesium contents, ie 0.27 to 0.33% by weight for variant composition 1 and 0.5 to 0.6% by weight for variant composition 2. Therefore it is clear.

[Heat treatment]
Step 1:
Two variant compositions of aluminum-silicon casting alloy, and more specifically variant composition 2 having a magnesium content of about 0.6% by weight, are described in this case with reference to the flow charts of FIGS. For example, the following heat treatment was performed.

  FIG. 1 shows a method in which a B-pillar (product P) is cast in step 1, subjected to solution treatment in step 2 using some casting heat, and then air-cooled by a fan. In other words, after removal from the mold, the product P is not cooled to, for example, room temperature, but instead is solution treated at a temperature of about 200 ° C. in step 2. Sprue A or other casting residue remains on the product P during the solution treatment in step 2.

  After solution treatment in step 2, this part is still relatively soft or ductile and can therefore be deburred in step 3. In this process, sprue A or other casting residue is removed from the product P. Product P remains soft during this process.

  After the deburring process performed in step 3, the B pillar or product P is defaced in step 4. Product P remains soft for this purpose.

  Finally, in step 5, the product P undergoes precipitation hardening at one of the precipitation hardening temperatures described in more detail below, and more specifically. The product that is soft until after step 4 then obtains its desired material properties.

Step 2:
In particular, the order of steps 2 and 3 has been interchanged, so FIG. 2 shows a different process than FIG. 1 since this process does not use any casting heat.

  After step 1, product P is therefore cooled to room temperature or about 20 ° C. along with gate A or other casting residue. The sprue and casting residue are then deburred 3 or removed and the product is still soft during this process.

  After the deburring step 3, the solution treatment step 2 and air cooling using a fan, for example, are performed thereafter. Product P remains soft during this process.

  Steps 4 and 5, i.e. one of the precipitation hardening temperatures that will be described in greater detail below, allow the B pillar or product P to be combed and precipitation hardened in a manner similar to the process of FIG. After that. After step 5, the product that is soft until after step 4 again achieves its desired material properties.

  A common feature of both methods according to FIGS. 1 and 2 is that in both steps, a dimensional test is performed at point Q1, and a strength test or tensile test is performed at point Q2.

  In each of the two steps shown in FIGS. 1 and 2, the solution treatment performed in Step 2 was performed in various tests at different temperatures of 460 to 490 ° C. and different treatment periods of 15 to 120 minutes.

  In each of the two steps according to FIG. 1 and FIG. 2, the precipitation treatment performed in step 5 was also performed in different tests at different temperatures of 160-240 ° C. and different precipitation periods of 20-240 minutes.

By heat treatment, proof stress _R p0.2 of 90～180MPa, for example in a vehicle body, a chassis or a power transmission system of an automobile showing the value of elongation at break _{A 5} of the tensile strength _{R m} and the range from 8 to 22% of the 180~250MPa Used parts were manufactured. The aluminum alloy is therefore particularly well suited for use in motor vehicles.

[Example 4]
This example is based on a test program, in which a high-strength automobile part having an alloy composition with a mutation composition 1 (Mg 0.27 to 0.33% by weight) is 180 MPa after the heat treatment described below. It is processed in such a way as to have an equal yield strength R _p0.2 .

  For this purpose, the high-strength parts were subjected to a T5 heat treatment at different temperatures of 160-240 ° C. and different periods of 20-240 minutes.

It is process drawing of the heat processing of a motor vehicle part. It is a further process figure of heat processing of a motor vehicle part.

Claims (14)

The following alloying elements:
Silicon 6.5- <9.5% by weight
Manganese 0.3-0.6% by weight
Iron 0.15-0.35 wt%
Magnesium 0.02-0.6% by weight
Titanium up to 0.1% by weight
Strontium 90-180ppm
And, in particular, aluminum, production-related contaminants individually comprising up to 0.05% by weight, and in total up to 0.2% by weight, preferably for automotive casting parts, in particular pressure cast alloys Is an aluminum alloy.   2. Aluminum alloy according to claim 1, characterized in that the alloy exhibits a hardness of> 80 HB, preferably 84 HB to 88 HB, when cast. Wherein the alloy is, at the time of> 5% casting preferably characterized by showing an elongation at break A ₅ of 8% to 12%, aluminum alloy according to claim 1 or claim 2.   4. The aluminum alloy according to claim 1, wherein the alloy contains 0.1 to 0.4% by weight of copper as a further alloy element.   Aluminum according to any one of claims 1 to 4, characterized in that the alloy contains 0.22 to 0.4 wt% magnesium, preferably 0.32 to 0.36 wt%. alloy.   Use of the aluminum alloy according to any one of claims 1 to 5, particularly in a cast part of an oil pan of an automobile.   Use according to claim 6, characterized in that the cast part is produced in a pressure casting process.   Use according to any of claims 6 or 7, characterized in that the cast part undergoes a heat treatment step after the casting step.   The cast part is partially solution-treated for a period of 20 to 120 minutes in a temperature range of 400 to 490 ° C, particularly 420 to 460 ° C, and then air-cooled. Use as described in.   Cast parts, in particular for automobiles, produced from the aluminum alloy according to any one of claims 1-5.   The cast part according to claim 10, wherein the part is formed as an oil pan for an automobile.   12. Cast part according to claim 10 or 11, characterized in that the entire area of the part exhibits at least a substantially uniform hardness of> 80HB, preferably 84HB to 88HB, when cast. All regions of the part, when the> 5% casting preferably characterized by showing an elongation A ₅ at least substantially uniform at break of 8% to 12%, according to any one of claims 10 to 12 Casting parts.   The cast part is at least partially solution treated for a period of 20 to 120 minutes in a temperature range of 400 to 490 ° C, in particular in a temperature range of 420 to 460 ° C, and then air cooled. Item 14. A cast part according to Item 13.

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