WO2021105229A1

WO2021105229A1 - Die casting part, body component having said die casting part, vehicle having said body component and method for producing said die casting part

Info

Publication number: WO2021105229A1
Application number: PCT/EP2020/083393
Authority: WO
Inventors: Marc Hummel; Marius KOHLHEPP; Robin Müller; Heinz Werner HÖPPEL; Werner FRAGNER
Original assignee: Amag Casting Gmbh; Audi Ag; Friedrich-Alexander-Universität Erlangen-Nürnberg
Priority date: 2019-11-25
Filing date: 2020-11-25
Publication date: 2021-06-03
Also published as: HUE061156T4; CN115279931A; US20230008295A1; PL3825428T3; HUE061156T2; EP3825428B1; EP3825428A1; MX2022006232A

Abstract

The invention relates to a method for producing a die casting part and a die casting part produced with said method. According to the invention, an excellent punch-riveting suitability is achieved when the die casting part has a curable aluminium alloy with the following alloy constituents: 5.0 to 9.0 wt.-% silicon (Si), 0.25 to 0.5 wt.-% magnesium (Mg) and as the remainder aluminium and unavoidable impurities caused by production each with max. 0.05 wt.-% and in total at most 0.15 wt.-%, wherein the die casting part has a yield point (Rp0.2) of greater than 190 MPa and an elongation at break (A5) of greater than or equal to 7 %, and uniform strain (Ag) and necking strain (Az) meet the condition Az ≥ Ag/2.

Description

Die-cast component, body component with this die-cast component, motor vehicle with this body component and method for producing this die-cast component

Technical area

The invention relates to a die-cast component and a method for producing this die-cast component.

State of the art

_{In order to bring the strength (R P} o, 2, Rm) and the ductility (or elongation at break As) into a desired ratio in a thin-walled die-cast component, for example in structural components for motor vehicles - thus, for example, crash-relevant FDI values [FDI = strength -Ductility index, which is _{calculated from material characteristics R m} , R _P o, 2 and As, namely FDI = (R _m +3 ^* R _P o, 2) / 4 ^* A5 / 100] must be met in the automotive sector -, EP3176275A1 proposes a heat treatment of an Al-Si-aluminum alloy with a two-stage annealing, quenching and three-stage artificial aging process. This method also leads to good punch riveting suitability - that is, joining by forming - which is essentially dependent on the ductility of the die-cast component. In particular, punch riveting using a dome die requires the highest deformability on the die-cast component compared to other dies (flat die, ball die, etc.). If the deformability of the material is not sufficient, cracks occur in the die-cast component on the die side. A further improvement of the punch riveting suitability by increasing the ductility in turn causes losses in strength - which disadvantageously reduces crash-relevant FDI values.

Presentation of the invention On the basis of the prior art described at the outset, the invention has also set itself the task of creating a die-cast component which, compared to known die-cast components, is characterized by improved punch rivet suitability with the same elongation at break and strength.

The invention solves the problem posed by the features of claim 1.

By making the die-cast component a hardenable aluminum alloy with 5.0 to 9.0% by weight silicon (Si) and from 0.25 to 0.5% by weight magnesium (Mg) and the remainder aluminum as well as unavoidable impurities due to the manufacturing process, each with a maximum 0.05% by weight and a total of at most 0.15% by weight, a comparatively high yield point (R _P o, 2) of greater than 190 MPa and also an elongation at break As of greater than or equal to 7% can be made possible.

Si: 5.0 to 9.0% by weight silicon (Si), which represents a reduced proportion compared with the prior art, can significantly reduce the proportion of primary phases that cause cracks (namely eutectic silicon particles). This reduces their negative influence when joining by forming.

Mg: 0.25 to 0.5% by weight of magnesium (Mg) can _{enable a yield point (R P} o.2) of greater than 190 MPa.

However, it is particularly improved by the punch rivet suitability of the die-cast component, because uniform elongation (A _g ) and constricting _{elongation (A z} ) meet the condition A _z > A _g / 2. As a result, this high-strength die-cast component can be subjected to joining by reshaping, for example punch riveting or clinching, without cracking, even with a thin-walled design.

In addition to Si and Mg, the aluminum alloy can optionally have one or more alloy elements of the group: up to 0.8% by weight manganese (Mn), from 0.08 to 0.35% by weight zinc (Zn), from 0 , 08 to 0.35% by weight chromium (Cr), up to 0.30% by weight zirconium (Zr), up to 0.25% by weight iron (Fe), up to 0.15% by weight Titanium (Ti), up to 0.20% by weight copper (Cu), up to 0.025% by weight strontium (Sr), up to 0.2% by weight vanadium (V) and / or up to 0.2% by weight % Molybdenum (Mo). The aforementioned punch rivet suitability can be further improved if the die-cast component has a uniform elongation (A _g ) of at least 6% and a neck _{elongation (A z} ) of at least 4%.

Further in the aluminum alloy according to the invention for silicon (Si) and / or zinc (Zn) and / or magnesium (Mg) and / or manganese (Mn) and / or copper (Cu) and / or iron (Fe) and / or Titanium (Ti) and / or Strontium (Sr) the following content or the following content is conceivable:

• from more than 6.5 to 9.0% by weight silicon (Si), in particular from more than 6.5 to 8% by weight silicon (Si)

• from 0.3 to 0.5% by weight magnesium (Mg)

• from 0.3 to 0.6% by weight manganese (Mn)

• from 0.15 to 0.3% by weight zinc (Zn), in particular from 0.15 to 0.25% by weight zinc (Zn)

• from 0.10 to 0.20% by weight copper (Cu)

• from 0.10 to 0.25% by weight iron (Fe), in particular from 0.15 to 0.25% by weight iron (Fe)

• from 0.05 to 0.15% by weight titanium (Ti)

• from 0.015 to 0.025% by weight strontium (Sr)

Particularly high FDI values can be achieved if the hardenable aluminum alloy contains more than 6.5 to 9.0% by weight silicon (Si), in particular more than 6.5 to 8% by weight silicon (Si), having.

Si: 6.5 <wt .-% silicon (Si) <9.0 can, for example, with sufficiently good

The castability of the alloy also reduces the primary phases that cause cracks, which can further improve joining by forming - all the more if the condition 6.5 <wt.% Silicon (Si) <8.0 is met.

Strength and ductility can be further improved if the aluminum alloy contains from 0.15 to 0.3% by weight of zinc (Zn) and / or from 0.3 to 0.5% by weight of magnesium (Mg). Zn: A zinc (Zn) content of 0.15 to 0.3% by weight can further improve the ductility of the die-cast component. Zinc (Zn) preferably has a content of 0.15 to 0.25% by weight.

Mg: A content of 0.3 to 0.5% by weight of magnesium (Mg) can _{further increase the yield strength (R P} o.2).

The castability of the die-cast alloy can be further improved if the aluminum alloy contains from 0.3 to 0.6% by weight of manganese (Mn).

The strength of the aluminum alloy can be further increased with a copper (Cu) content of 0.10 to 0.20% by weight.

In addition, because of this copper content, the aluminum alloy can have a higher content of secondary aluminum, which can be increased further if the aluminum alloy has 0.15 to 0.25% by weight of iron (Fe). This is particularly the case when the aluminum alloy has from 0.15 to 0.25% by weight of iron (Fe).

The ductility and strength of the aluminum alloy can be improved with 0.05 to 0.15% by weight of titanium (Ti), whereas from 0.015 to 0.025% by weight of strontium (Sr) the ductility can be further optimized.

It is also conceivable that the aluminum alloy has up to 0.05% by weight of manganese (Mn) and / or up to 0.05% by weight of copper (Cu).

Mn: A manganese (Mn) content of up to 0.05% by weight can lead to a significant increase in ductility. Such a limitation of the manganese content can in fact further reduce the proportion of crack-inducing primary phases (manganese-containing intermetallic phases), which would structurally weaken the cast component, in particular when joining by forming.

Cu: A copper (Cu) content of up to 0.05% by weight can further reduce the tendency to crack, which can further facilitate joining by forming or further improve punch riveting. The die-cast component according to the invention is particularly suitable as a body component for a motor vehicle. The die-cast component is preferably firmly connected to the other component via a punch rivet. The die-cast component is preferably part of a motor vehicle as a body component.

On the basis of the prior art described at the beginning, the invention has set itself the task of changing the method in order to further improve the punch riveting suitability with almost constant FDI values on the die-cast component. In addition, the method should be easy to handle and reproducible.

The invention solves the problem set with regard to the method by the features of claim 9.

If a hardenable aluminum alloy with 5.0 to 9.0% by weight silicon (Si) and from 0.25 to 0.5% by weight magnesium (Mg) and the remainder aluminum as well as unavoidable impurities with a maximum of 0 0.05 wt% and a total of 0.15 wt% or less is used, a special heat treatment can be carried out.

Si: With 5.0 to 9.0% by weight of silicon (Si), the castability of the aluminum alloy can initially be ensured even with complex contours due to the lower limit of 5.0% by weight. In addition, due to the upper limit of 9.0% by weight silicon (Si), the aluminum alloy can be prepared for an annealing treatment at higher temperatures.

Mg: The aluminum alloy can be prepared with 0.25 to 0.5% by weight of magnesium (Mg) in order to achieve increased strength, in particular yield point (R _P o, 2).

On the basis of these Si and Mg contents, the Al-Si alloy is prepared for increased strength with reduced ductility - namely by first annealing at a temperature in the range from 320 ° C (degrees Celsius) to 450 ° C a period of 20 to 75 minutes and a second annealing at a temperature in the range from 510 ° C. to 540 ° C. for a period of 5 to 35 minutes, ie at increased temperatures compared to the prior art. The quenching after annealing with a temperature gradient in the range of greater than 4 K / s adjusts the properties (increased strength with reduced ductility) on the die-cast component.

A shift in the mechanical properties from ductility towards strength can subsequently be compensated for by overaging the die-cast component with the help of at least three-stage artificial aging.

Flierzu has proven to be advantageous if a first artificial aging at a temperature in the range from 100 ° C to 180 ° C over a period of 40 minutes to 150 minutes, a second artificial aging at a temperature in the range from 180 ° C to 300 ° C for a period of 30 minutes to 100 minutes and a third artificial aging at a temperature in the range of 230 ° C to 300 ° C for a period of 5 minutes to 120 minutes. A T7 state can thus be achieved on the die-cast component, which not only fulfills the specified FDI values for strength (Rp02, Rm) and ductility or elongation at break As, but surprisingly also has a significant increase in the suitability for punch riveting. Investigations have shown that the method according to the invention has a particular influence on the ratio between constriction _{elongation (A z} ) and uniform elongation (A _g ), which constriction _{elongation A z} is determined by the equation A _z = A (or As) -A _g . According to the invention, a comparatively high-strength Al-Si-aluminum alloy in the T7 condition thus results in a constriction A _z that is greater than _{or equal to A g} / 2 - which ensures crack-free punch riveting, in particular also punch riveting using a dome die, which on the die side has a particularly high deformability from the die-cast component.

This can also be achieved in the case of a thin-walled die-cast component, for example for body construction, which was currently not reliably accessible to joining by forming, especially by punch riveting.

In addition, compared to other known methods, the method according to the invention only requires an adaptation in terms of temperature and holding time - which is comparatively easy to handle and thus improves the reproducibility of the method. The method according to the invention can thus ensure the production of a die-cast component that has a yield point (R _P o, 2) of greater than 190 MPa and an elongation at break (As) of greater than or equal to 7% and its uniform elongation (A _g ) and constriction elongation (A _z ) the condition A _z > A _g / 2 is fulfilled.

The die-cast component produced can preferably have a uniform elongation (A _g ) of at least 6% and a neck _{elongation (A z} ) of at least 4%. In addition to Si and Mg, the aluminum alloy can optionally have the following further alloy elements, namely up to 0.8% by weight of manganese (Mn), from 0.08 to 0.35% by weight of zinc (Zn), from 0.08 up to 0.35% by weight chromium (Cr), up to 0.30% by weight zirconium (Zr), up to 0.25% by weight iron (Fe), up to 0.15% by weight titanium ( Ti), up to 0.20% by weight copper (Cu), up to 0.025% by weight strontium (Sr), up to 0.2% by weight vanadium (V) and / or up to 0.2% by weight % Molybdenum (Mo).

The constricting elongation A _z can be further improved if the first annealing takes place at a temperature in the range from 390 ° C. to 410 ° C. and / or over a period of 50 minutes to 70 minutes. In addition, through this comparatively narrow temperature and time range, the mechanical properties of the finished die-cast component can be influenced more reproducibly.

If the second annealing takes place at a temperature in the range from 520 ° C. to 535 ° C., in particular from 525 ° C. to 535 ° C., and / or over a period of 25 to 30 minutes, there is a delay, for example due to the comparatively short holding time avoidable on the die-cast component. This also improves the reproducibility of the process.

The strength values can be set within comparatively narrow limits if the quenching is carried out with a temperature gradient in the range from 7 K / s to 20 K / s. This accelerated cooling can take place, for example, by cooling in moving air, etc. The first artificial aging is preferably carried out at a temperature in the range from 140 ° C. to 160 ° C. and / or over a period of 110 minutes to 130 minutes in order to initially put the die-cast component in a T64 state.

A T6 state on the die-cast component is achieved in that the second artificial aging takes place at a temperature in the range from 190 ° C to 210 ° C and / or over a period of 50 minutes to 70 minutes.

If the third artificial aging takes place at a temperature in the range from 230 ° C to 270 ° C and / or over a period of 10 minutes to 30 minutes, the strength and ductility of the die-cast component can be set even more precisely. In particular, however, a comparatively high constriction _{elongation (A z} ) can thus be achieved, which can further reduce the risk of cracks when punch riveting the die-cast component.

Brief description of the drawings

To prove the effects achieved, thin-walled cast components were produced from various cast alloys using the die-casting process. The subject matter of the invention is shown in the figures, for example. 1 shows a view of the course of the heat treatment according to the invention,

2a shows a broken cross-section of two punch-riveted components, the lower component being a die-cast component according to the prior art,

FIG. 2b shows a three-dimensional, die-side view of FIG. 2a,

3a shows a broken cross-section of two punch-riveted components, the lower component being the die-cast component according to the invention, and

FIG. 3b shows a three-dimensional, die-side view of FIG. 3a.

Ways of Carrying Out the Invention The compositions of the alloys examined are listed in Table 1, with the alloy elements listed in this table as the remainder aluminum and unavoidable impurities due to production, each with a maximum of 0.05% by weight and a maximum of 0.15% by weight in total to be added.

Table 1: Overview of the aluminum alloys

The alloys AISi7MgO, 4 moves within the content limits according to the invention according to the independent claims. Alloy AISi10Mg0.4Mn has a significantly higher Si content compared to alloy AISi7MgO.4 - and in this regard is therefore outside the content limits according to the invention.

The die-cast components P1 (prior art) and 11 (according to the invention) with the related Al-Si-aluminum alloys were subjected to the following heat treatment according to Table 2:

Table 2: Overview of the heat treatment

In Fig. 1, the process of the heat treatment according to the invention is shown in more detail: First, a two-stage annealing, namely a first annealing 1.1 and a Subsequent second annealing 1.2, then quenching 2 and, after a certain storage time, three-stage artificial aging with a first heating 3.1, a subsequent second heating 3.2 and a subsequent third heating 3.3. During this heat treatment, the cast component 11 passes through a wide variety of states from T4, T6x, T6 to T7, as can be seen in FIG. 1.

The difference in the second annealing 1.2 between the invention 11 and the prior art P1 can also be seen in FIG. 1. The second annealing in the prior art P1 thus takes place at a significantly lower temperature than in the invention 11.

In contrast to the invention, the cast component P1 lacks a third artificial aging. Significant differences can also be found in the parameters of the second annealing - these differences lead overall to the fact that the cast component P1 is in the T6 state after the heat treatment.

The two die-cast parts P1 and 11 were finally examined for their mechanical properties. For this purpose, the yield point R _P o, 2, tensile strength R _m , elongation at break As and the uniform elongation A _{g were} determined. The measured values obtained are summarized in Table 3. The constricting _{elongation A z} was calculated from the elongation at break As and the uniform elongation A _g.

Table 3: mechanical parameters

According to Table 3, the die-cast component 11 according to the invention has a significantly higher constriction elongation (A _z ) - which means that the die-cast component 11 is particularly suitable for punch riveting or is generally particularly suitable for joining by forming. This suitability was tested by punch riveting using a dome die - namely, an aluminum sheet A of the 6xxx series was punch riveted on the die side with the die-cast component P1 or with the die-cast component 11 on the die side using a rivet element N. The results of this punch riveting can be seen in FIGS. 2a, 2b and 3a, 3b.

Thus, several cracks R can be seen in the cross-section according to FIG. 2a for the AISi10Mg0.4Mn in the T6 state, whereas no cracks can be seen in the cross-section according to FIG. In addition, the AISi10Mg0.4Mn T6 according to FIG. 2b shows numerous deep cracks on the die side, whereas the cracks in the case of Al-Si7MgO.4 T7 are significantly finer. Their number is higher, but they are not critical due to their small width and depth. According to the invention, a riveting result is significantly improved compared to the prior art.

For this reason, the die-cast component 11 according to the invention also has, for example, particularly good suitability for thin-walled molded parts on a body of a vehicle, preferably a motor vehicle.

Claims

Patent claims:

1. Die-cast component made from a hardenable aluminum alloy with the following alloy components: from 5.0 to 9.0% by weight silicon (Si), from 0.25 to 0.5% by weight magnesium (Mg) and optionally up to 0.8 % By weight of manganese (Mn), from 0.08 to 0.35% by weight of zinc (Zn), from 0.08 to 0.35% by weight of chromium (Cr), to 0.30% by weight % Zirconium (Zr), up to 0.25% by weight iron (Fe), up to 0.15% by weight titanium (Ti), up to 0.20% by weight copper (Cu), up to 0.025% by weight % Strontium (Sr), up to 0.2% by weight vanadium (V), up to 0.2% by weight molybdenum (Mo) and the remainder aluminum as well as impurities that are unavoidable due to production, each with a maximum of 0.05% by weight and total at most 0.15% by weight, with the die-cast component having a yield point (R _P o, 2) of greater than 190 MPa and an elongation at break (As) of greater than or equal to 7% and uniform elongation (A _g ) and constriction _{elongation (A z} ) the condition A _z > A _g / 2 is met.

2. Die-cast component according to claim 1, characterized in that this die-cast component has a uniform elongation (A _g ) of at least 6% and a constricting _{elongation (A z} ) of at least 4%. 3. Die-cast component according to claim 1 or 2, characterized in that the hardenable aluminum alloy contains more than 6.5 to 9.0% by weight of silicon (Si) and / or from 0.3 to 0.5% by weight Magnesium (Mg), and / or from 0.3 to 0.6% by weight of manganese (Mn), and / or from 0.15 to 0,

3% by weight zinc (Zn), and / or from 0.10 to 0.20% by weight copper (Cu), and / or from 0.10 to 0.25% by weight iron (Fe), and / or from 0.05 to 0.15% by weight of titanium (Ti), and / or from 0.015 to 0.025% by weight of strontium (Sr).

4. Die-cast component according to claim 3, characterized in that the hardenable aluminum alloy contains more than 6.5 to 8% by weight of silicon (Si) and / or from 0.15 to 0.25% by weight of zinc (Zn ), and / or from 0.15 to 0.25% by weight of iron (Fe).

5. Die-cast component according to claim 1 or 2, characterized in that the hardenable aluminum alloy up to 0.05 wt .-% manganese (Mn) and / or up to 0.05% by weight of copper (Cu).

6. Body component for a motor vehicle with a die-cast component (11) according to one of claims 1 to 5.

7. Body component according to claim 6, with at least one punch rivet (N) and with another component (A), wherein the die-cast component (11) is firmly connected to the other component (A) via the punch rivet (N).

8. Motor vehicle with a body component according to Claim 6 or 7.

9. The method for producing a die-cast component according to one of claims 1 to 5, wherein the method comprises a heat treatment with the following steps in the specified order: at least two-stage annealing, comprising at least a first annealing at a temperature in the range from 320 ° C to 450 ° C for a period of 20 minutes to 75 minutes, and a second anneal at a temperature in the range of 510 ° C to 540 ° C for a period of 5 minutes to 35 minutes,

Quenching with a temperature gradient in the range of greater than 4 K / s and at least three-stage artificial aging, comprising at least a first artificial aging at a temperature in the range from 100 ° C to 180 ° C over a period of 40 minutes to 150 minutes, a second artificial aging at a Temperature in the range from 180 ° C to 300 ° C for a period of 30 minutes to 100 minutes and a third artificial aging at a temperature in the range of 230 ° C to 300 ° C for a period of 5 minutes to 120 minutes.

10. The method according to claim 9, characterized in that the first annealing takes place at a temperature in the range from 390 ° C to 410 ° C and / or over a period of 50 minutes to 70 minutes

11. The method according to claim 9 or 10, characterized in that the second annealing takes place at a temperature in the range from 520 ° C to 535 ° C and / or over a period of 25 to 30 minutes.

12. The method according to claim 11, characterized in that the second annealing takes place at a temperature in the range from 525 ° C to 535 ° C.

13. The method according to any one of claims 9 to 12, characterized in that the quenching takes place with a temperature gradient in the range from 7 K / s to 20 K / s.

14. The method according to any one of claims 9 to 13, characterized in that the first artificial aging takes place at a temperature in the range from 140 ° C to 160 ° C and / or over a period of 110 minutes to 130 minutes.

15. The method according to any one of claims 9 to 14, characterized in that the second artificial aging takes place at a temperature in the range from 190 ° C to 210 ° C and / or over a period of 50 minutes to 70 minutes.

16. The method according to any one of claims 9 to 15, characterized in that the third artificial aging takes place at a temperature in the range from 230 ° C to 270 ° C and / or over a period of 10 minutes to 30 minutes.