DE102013002632A1 - Aluminum-silicon die casting alloy comprises a specific amount of silicon, zinc, magnesium, manganese, zirconium, contaminants, and aluminum - Google Patents

Abstract

Aluminum-silicon die casting alloy comprises 5-12 mass% silicon, 0.5-3 mass% zinc, 0.1-0.7 mass% magnesium, 0.2-0.8 mass% manganese, 0.05-0.3 mass% zirconium, individually greater than 0.05 mass% and a total of greater than 0.4 mass% contaminants, and the balance amount of aluminum. An independent claim is also included for preparing a die casting component, preferably thin-walled bodywork or a chassis cast component, comprising casting a cast component with evacuated permanent molds made of the above mentioned die casting alloy, and subjecting the cast component to (a) T5 heat treatment, which includes a hot exposure of the cast component at 220[deg] C for 2 hours, (b) T6 heat treatment, which includes a solution heat treatment at 490[deg] C for 1 hour, quenching in air, and hot exposure at 210[deg] C for 3 hours, or (c) T7 heat treatment, which includes a solution heat treatment at 460[deg] C for 1.5 hours, quenching in air, and hot exposure at 230[deg] C for 2.5 hours.

Description

The invention relates to an aluminum-silicon casting alloy and a method for producing a cast component.

Typically, cast components for bodywork and chassis applications are die cast from aluminum-silicon casting alloys, typically containing silicon at a mass fraction of 6 to 12 mass%. Advantages in the use of silicon are the good casting properties, a reduced shrinkage tendency and thus a very low susceptibility to hot cracks and voids. Due to the low shrinkage tendency such cast components can have a very high complexity.

The strength is increased by the addition of typically 0.1 to 0.5 Ma% of magnesium. The increase in strength is caused by the phase Mg ₂ Si, which is mainly formed by a heat treatment. For optimum solubility of magnesium as a prerequisite for the formation of this phase, solution heat treatment usually takes place at temperatures of 450 to 530 ° C. during the heat treatment. However, this phase causes a decrease in the deformability of the alloy, thus acting embrittling and is to limit their content depending on the component requirement.

As a rule, such cast components are subjected to a T5, T6 or T7 heat treatment.

The T5 heat treatment is a heat treatment to the so-called T5 state of the alloy according to DIN EN 515 which describes a cured alloy which has cooled after hot forming and is thermally aged. Usually, the thermal aging takes place at temperatures of 180 to 240 ° C for periods of 1.5 to 4 hours.

The T6 heat treatment is a heat treatment to the so-called T6 state of the alloy according to DIN EN 515 which describes a cured alloy that is solution annealed, quenched, and aged. In this case, the artificial aging is terminated when the maximum strength is reached.

The T7 heat treatment is a heat treatment to the so-called T7 state of the alloy according to DIN EN 515 which describes a cured alloy that is solution annealed, quenched, and aged when hot aging. In this case, the artificial aging is terminated in time only after reaching the maximum strength.

Usually, in the T6 and T7 heat treatment, the solution annealing is carried out at temperatures of 450 to 530 ° C for periods of 1 to 2 hours and aging at temperatures of 180 to 240 ° C for periods of 2 to 5 hours.

The T5 heat treatment is characterized by a very good resulting dimensional stability of the components with high strength. A disadvantage is the low resulting deformation properties.

The T6 and T7 heat treatments, on the other hand, are characterized by high deformation properties and high strength. For high strength to be achieved usually high solution annealing temperatures are used. Due to the reduced strength in the hot state, creep effects, which are responsible for component distortions, occur during solution annealing. For this reason, it is endeavored to choose the lowest possible temperature and the period of solution annealing.

• 1) T5-Wärmebehandlung (Warmauslagern bei 220°C für 2 h): Rp0,2 = 150 bis 180 MPa A5 = 4 bis 7%
• 2) T6-Wärmebehandlung (Lösungsglühen bei 490°C für 1 h, Abschrecken in Luft, Warmauslagern bei 210°C für 3 h): Rp0,2 = 150 bis 170 MPa A5 = 7 bis 12%
• 3) T7-Wärmebehandlung (Lösungsglühen bei 460°C für 1,5 h, Abschrecken in Luft, Warmauslagern bei 230°C für 2,5 h): Rp0,2 = 120 bis 140 MPa A5 = 10 bis 15%

In the following, typical resulting mechanical characteristic values for AlSi10Mg0.3 are given, namely the 0.2% yield strength Rp0.2 and the elongation at break A5:

• 1) T5 heat treatment (heat aging at 220 ° C for 2 h): Rp0.2 = 150 to 180 MPa A5 = 4 to 7%
• 2) T6 heat treatment (solution annealing at 490 ° C for 1 h, quenching in air, heat aging at 210 ° C for 3 h): R p 0.2 = 150 to 170 MPa A 5 = 7 to 12%
• 3) T7 heat treatment (solution annealing at 460 ° C for 1.5 hours, quenching in air, heat aging at 230 ° C for 2.5 hours): R p 0.2 = 120 to 140 MPa A 5 = 10 to 15%

Although the alloys of the prior art have a good flowability for components with wall thicknesses greater than 2 mm, so that can be produced in the wall thickness range greater than 2 mm components without cold flow and hot cracks. However, with thinner-walled die-cast components with wall thicknesses of less than 2 mm, mold filling problems in the form of cold flow points and hot cracks due to the tendency to shrink are increasingly occurring.

The object of the invention is to provide an aluminum-silicon casting alloy, which has a high strength and at the same time a good ductility with very good flowability for components with wall thicknesses below 2 mm, and a method for producing a cast component from such an alloy.

This object is achieved by an aluminum-silicon casting alloy according to claim 1 and a method for producing a cast component according to claim 8. Further embodiments are described in the subclaims.

• – 5 bis 12 Ma% Silizium;
• – 0,5 bis 3,0 Ma% Zink;
• – 0,1 bis 0,7 Ma% Magnesium;
• – 0,2 bis 0,8 Ma% Mangan
• – 0,05 bis 0,3 Ma% Zirconium
• – einzeln höchstens 0,05 Ma% und insgesamt höchstens 0,4 Ma% Verunreinigungen;
• – als Rest Aluminium.

The invention proposes, according to a first aspect, an aluminum-silicon casting alloy containing

• - 5 to 12% by mass of silicon;
• 0.5 to 3.0% by mass of zinc;
• 0.1 to 0.7 Ma% magnesium;
• - 0.2 to 0.8 Ma% manganese
• 0.05 to 0.3 Ma% zirconium
• - not more than 0.05% by mass and not more than 0.4% in total of impurities;
• - as the rest aluminum.

Since aluminum has a high affinity for iron, manganese is added to the alloy to reduce the tendency of the cast components to adhere to the die. Furthermore, the plate-shaped iron-containing phases due to the iron impurities of the starting material are converted into a polyhedral morphology via manganese, which increases the ductility of the alloy.

Zirconium serves to grain refine the cast structure and increase strength by forming (AlZr) phases. This alloying element contributes significantly to achieving the mechanical characteristics.

The proposed alloy uses not only the curing over the phase Mg ₂ Si but also a further solidification mechanism, namely a solid solution hardening by the zinc. In particular, the combination of these curing mechanisms offers the advantage of high deformation suitability coupled with high strength of the cast components. Furthermore, the zinc showed a significant improvement in flowability.

The proposed alloy gives the following typical mechanical properties after a T6 or T7 heat treatment, namely the tensile strength Rm, the 0.2% proof stress Rp0.2, the uniform elongation Ag and the elongation at break A5:
Rm = 200 to 300 MPa
Rp0.2 = 120 to 240 MPa
Ag = 6 to 15%
A5 = 10 to 25%

These characteristics depend on the respective heat treatment parameters. Depending on the component requirement, the solution annealing and / or the hot aging can be one or more stages.

It is also advantageous that the proposed alloy shows positive results in the joining techniques of welding and riveting.

In addition, the requirements for long and short-term stability with successful heat treatment are guaranteed even at low storage periods.

Another advantage of the proposed alloy is that no corrosion-prone phases, such as the π-phase, θ-phase or Q-phase form, since copper is not present as an alloying element.

A particular advantage of the proposed alloy is its high crash energy absorption. This can be seen by a pronounced Brucheinschnürung the tensile test. The difference between elongation at break and uniform strain, which characterizes the fracture constriction, is 4 to 8%.

Furthermore, very high 0.2% proof strengths of Rp0.2> 180 MPa could be detected. The high strengths allow a reduction in the wall thickness of the components with the same component function. In order to implement this reduction, the alloy was optimized in terms of flowability in thin wall thickness ranges. Due to the zinc content, the alloy has a much better flowability than the prior art. This can be detected above all in areas of very thin wall thicknesses down to a minimum of 1 mm without cold flow and hot cracks. This means that the cast components show a very high quality with thin wall thicknesses.

The mentioned curing via the zinc-magnesium combination has the advantage that the formation of the eutectic silicon takes place even at low solution annealing temperatures and solution annealing periods, so that due to these gentle solution annealing parameters particularly dimensionally accurate and complex cast components can be manufactured.

Furthermore, all alloying elements of the proposed alloy are very readily available worldwide, whereby the manufacturing costs of this alloy are low.

In the range of "5 to 12 mass% of silicon", 5.0 mass%, 5.5 mass%, 6.0 mass%, 6.5 mass%, 7.0 mass%, 7.5 mass%, 8 , 0 Ma%, 8.5 Ma%, 9.0 Ma%, 9.5 Ma%, 10.0 Ma%, 10.5 Ma%, 11.0 Ma%, 11.5 Ma%, 12.0 Understood Ma% silicon.

The proportion of silicon is preferably 8 to 11.5 Ma%.

Among the range "0.5 to 3.0% by mass of zinc", 0.5% by mass, 0.6% by mass, 0.7% by mass, 0.8% by mass, 0.9% by mass, 1.0 Ma%, 1.1 Ma%, 1.3 Ma%, 1.5 Ma%, 1.8 Ma%, 2.1 Ma%, 2.4 Ma%, 2.7 Ma%, 3.0 Ma% Zinc understood.

The content of zinc is preferably 0.5 to 1.2 mass%

Among the range "0.1 to 0.7% by mass of magnesium", 0.1% by mass, 0.2% by mass, 0.3% by mass, 0.4% by mass, 0.44% by mass, 0.48 Ma%, 0.52 Ma%, 0.56 Ma%, 0.6 Ma%, 0.65 Ma%, 0.7 Ma% magnesium understood.

The proportion of magnesium is preferably 0.35 Ma% to 0.5 Ma%.

In particular, 0.2% by mass or 0.3% by mass or 0.4% by mass or 0.5% by mass or 0.6% by mass or 0.7 is used in the range of "0.2 to 0.8% by mass of manganese" Ma% or 0.8 Ma% manganese understood.

The proportion of manganese is preferably 0.4 to 0.8 mass%.

In the range of "0.05 to 0.3 mass% zirconium", particularly, 0.05 mass% or 0.08 mass% or 0.11 mass% or 0.14 mass% or 0.17 mass% or 0.20 Ma% or 0.23 Ma% or 0.26 Ma% or 0.3 Ma% zirconium understood.

The content of zirconium is preferably 0.1 to 0.25 mass%.

The content of impurities may be, for example, at most 0.05 Ma% or at most 0.045 Ma% or at most 0.040 Ma% or at most 0.035 Ma% or at most 0.030 Ma% or at most 0.025 Ma% or at most 0.020 Ma% or at most 0.015 Ma% or at most 0.010 Ma % and / or a total of at most 0.4 Ma% or at most 0.35 Ma% or at most 0.30 Ma% or at most 0.25 Ma% or at most 0.20 Ma% or at most 0.15 Ma% or at most 0.10 Ma%.

The proportion of impurities is preferably at most 0.01 mass% individually and at most 0.15 mass% at a maximum.

It is envisaged that the casting alloy contains at least 0.5 mass% to 3.0 mass% zinc.

The content of zinc may be, for example, at least 0.5 mass% or at least 0.6 mass% or at least 0.7 mass% or at least 0.8 mass% or at least 0.9 mass% or at least 1.0 mass% or at least 1 , 1 Ma% or at least 1.2 Ma% or at least 1.3 Ma% or at least 1.4 Ma% or at least 1.5 Ma% or at least 1.6 Ma% or at least 1.7 Ma% or at least 1, 8 mass% or at least 1.9 mass% or at least 2.0 mass% or at least 2.1 mass% or at least 2.2 mass% or at least 2.3 mass% or at least 2.4 mass% or at least 2.5 Ma% or at least 2.6 Ma% or at least 2.7 Ma% or at least 2.8 Ma% or at least 2.9 Ma% or at least 3.0 Ma%.

The range "0.5 to 3.0% by mass of zinc" is understood to mean, in particular, 0.5% by mass to 1.2% by mass of zinc.

It may be provided that the casting alloy contains at most 0.3 mass% or at most 0.24 mass% or 0.05 to 0.30 mass% or 0.1 to 0.2 mass% iron.

While it is desirable to have as little iron as possible, it is not possible, or particularly with regard to production, to avoid, for example when heating the melt, or only with great effort. The ranges given are especially tolerable for the proposed alloy.

The content of iron may be, for example, at most 0.3 mass% or at most 0.25 mass% or at most 0.20 mass% or at most 0.15 mass% or at most 0.10 mass% or at most 0.05 mass%.

Particularly, in the range of "0.05 to 0.30 mass% of iron", 0.05 mass% or 0.10 mass% or 0.15 mass% or 0.20 mass% or 0.25 mass% or 0.30 Ma% iron understood.

Desirable is as little copper as possible, but it can not be avoided completely or only with great effort, since it is present as an impurity element in aluminum alloys.

• – 0,005 bis 0,03 Ma% Strontium und/oder 0,002 bis 0,025 Ma% Natrium; oder
• – 0,002 bis 0,035 Ma% Antimon enthält.

It can be provided that the casting alloy

• 0.005 to 0.03 Ma% strontium and / or 0.002 to 0.025 Ma% sodium; or
• Contains 0.002 to 0.035% by mass of antimony.

As a result, a refinement of the proposed alloy can be achieved.

The range "0.005 to 0.03% by weight of strontium" is understood to mean in particular 0.005% by mass or 0.010% by mass or 0.015% by mass or 0.020% by mass or 0.025% by mass or 0.03% by mass strontium.

More specifically, in the range of "0.002 to 0.025% by mass of sodium", 0.002% by mass or 0.004% by mass or 0.006% by mass or 0.008% by mass or 0.010% by mass or 0.013% by mass or 0.016% by mass or 0.019% by mass or 0.022% by mass or 0.025 Ma% sodium understood.

More specifically, in the range of "0.002 to 0.035% by mass of antimony", 0.002% by mass or 0.004% by mass or 0.006% by mass or 0.008% by mass or 0.010% by mass or 0.013% by mass or 0.016% by mass or 0.019% by mass or 0.023% by mass or 0.027 Ma% or 0.031 Ma% or 0.035 Ma% antimony understood.

It may be provided that the casting alloy contains at most 0.2% by mass of titanium and / or at most 0.3% by mass of vanadium.

In this way, a further grain refinement of the proposed alloy can be achieved.

The content of titanium may, for example, be at most 0.16 Ma% or at most 0.12 Ma% or at most 0.08 Ma% or at most 0.04 Ma%.

The content of vanadium may be, for example, at most 0.24 Ma% or at most 0.18 Ma% or at most 0.12 Ma% or at most 0.06 Ma%.

• – ein Gussbauteil aus einer Gusslegierung gemäß der vorherigen Ansprüche gegossen wird., insbesondere mit evakuierten Dauerformen;
• – das Gussbauteil nach dem Gießen einer Wärmebehandlung auf den Zustand T5, T6 oder T7 unterworfen wird.

According to a second aspect, the invention proposes a method for producing a die-cast component, in particular a thin-walled body or chassis casting component, with the steps of

• - A cast component is cast from a casting alloy according to the preceding claims, in particular with evacuated permanent molds;
• - The cast component after casting a heat treatment to the state T5, T6 or T7 is subjected.

It may be contemplated that the T6 / T7 heat treatment includes solution annealing at 450 to 530 ° C for 1 to 2 hours, then quenching and then aging at 180 to 240 ° C for 2 to 5 hours.

It may be provided that the T5 heat treatment includes aging at 150-320 ° C for 0.5-5 hours.

The term "450 to 530 ° C" is understood in particular 450 ° C, 460 ° C, 470 ° C, 480 ° C, 490 ° C, 500 ° C, 510 ° C, 520 ° C, 530 ° C.

In particular, 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h are in the range "1 to 2 h" , 1.8 hours, 1.9 hours, 2.0 hours.

Under the range "180 to 240 ° C" in particular 180 ° C, 190 ° C, 200 ° C, 210 ° C, 220 ° C, 230 ° C, 240 ° C understood.

In particular, 2.00 hours, 2.25 hours, 2.50 hours, 2.75 hours, 3.00 hours, 3.25 hours, 3.50 hours, 3.75 hours are included under the range "2 to 5 hours" , 4.00 h, 4.25 h, 4.50 h, 4.75 h, 5.00 h.

In particular, 150 ° C, 160 ° C, 170 ° C, 180 ° C, 190 ° C, 200 ° C, 210 ° C, 220 ° C, 230 ° C, 240 ° are used as the "150-320 ° C" range C, 250 ° C, 260 ° C, 270 ° C, 280 ° C, 290 ° C, 300 ° C, 310 ° C, 320 ° C understood.

In particular, 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h are used under the range "0.5-5 h". 5 h understood.

The solution annealing and / or the aging can be done in one or more stages as needed.

It can be provided that the quenching takes place in moving or stationary air or in a moving or stationary inert gas or in water or in oil or in a combination of said media.

The statements relating to one of the aspects of the invention, in particular to individual features of this aspect, also apply analogously to the other aspects of the invention.

Embodiments of the invention will be explained in greater detail below by way of example. However, the individual features resulting therefrom are not limited to the individual embodiments, but can be combined with individual features described above and / or with individual features of other embodiments.

Comparative test

The following five aluminum-silicon casting alloys were each tested for their performance by casting and sampling thin-walled castings from them by die casting: Alloy 1: AlSi10Mn0.6Mg0.3, ie aluminum with 10 mass% silicon, 0.6 mass% manganese, 0.3 mass% magnesium. Alloy 2: AlSi10Mn0.6Mg0.5, ie aluminum with 10 mass% silicon, 0.6 mass% manganese, 0.5 mass% magnesium. Alloy 3: AlSi10Mn0.6Cu0.5Mg0.5, ie aluminum with 10 mass% silicon, 0.6 mass% manganese, 0.5 mass% copper, 0.5 mass% magnesium. Alloy 4: AlSi10Mn0.6Zn1.0Mg0.3Zr0.12, that is aluminum with 10 mass% silicon, 0.6 mass% manganese, 1.0 mass% zinc, 0.3 mass% magnesium 0.12 mass% zirconium. Alloy 5: AlSi10 Mn0.6 Zn0.74 Mg0.42 Zr0.12, that is aluminum with 10 mass% silicon, 0.6 mass% manganese, 0.74 mass% zinc, 0.4 mass% magnesium, 0.12 mass% zirconium.

Alloy 1 is a typical prior art alloy. Alloys 2 and 3 are attempts at improvement by increasing the magnesium content or adding copper in comparison to alloy 1. Alloys 4 and 5 are exemplary embodiments of the proposed alloy.

After a T6 heat treatment with the following parameters: Solution annealing: at 470 ° C for 1 h Deterrence: in moving air outsourcing: at 200 ° C for 2.5 h The following mechanical characteristics and quality characteristics were obtained on a component with wall thicknesses of 2 mm: Rp0.2 / MPa Rm / MPa Ag /% A5 /% hot cracks Cold Water leaks Alloy 1 166 235 7.5 12.1 + 0 Alloy 2 185 257 7.9 9.3 + 0 Alloy 3 198 274 7.1 8.6 - - Alloy 4 173 250 11.2 16.6 + + Alloy 5 202 276 8.0 12.7 + +

In this table, "+" stands for "nonexistent", "0" for "slightly present" and "-" for "existent".

All five alloys tested met the requirements for long-term and short-term thermal stability.

For Alloys 1 and 2, the mechanical characteristics are adjusted mainly by the formation of Mg ₂ Si phases. Depending on the amount of Mg ₂ Si phases formed, the strength Rm or elongation at break A5 can be adjusted. A large increase in strength, however, causes an embrittlement of the material, which is recognizable by the decrease of the elongation at break A5 and the fracture constriction A5-Ag. Due to this reduced deformability, the rivet suitability is reduced. Due to the relationship between strength Rm and elongation at break A5, the potential for increasing strength has been exhausted. Problems with susceptibility to corrosion do not exist. Furthermore, the sweat tendency is guaranteed. No hot cracks can be detected over the entire component. Occasionally cold flow points occur on the component surface.

To achieve a further increase in strength, additional hardening effects must be taken into account. Here comes above all copper in question.

If copper is added as in the case of the alloy 3, then the strength Rm can be further increased. This increase is due to copper-containing phases, which, however, may be susceptible to corrosion depending on the Cu-Mg ratio. In addition, the elongation at break A5 is greatly reduced compared to alloys 1 and 2. A pronounced fracture constriction A5-Ag is not present here. Consequently, the rivet suitability is limited. Due to the increased copper content, the weldability is limited. There are increasingly hot cracks as well as cold flow points.

Surprisingly, it has been found that another way to increase strength is to add zinc instead of copper as in alloys 4 and 5. Here, the increase in strength is achieved by a combination of different curing mechanisms. On the one hand, the strength is raised by the already known Mg ₂ Si phases. However, their content is limited to avoid embrittlement. Due to the zinc present in the solution in the alpha solid solution, the further increase in strength due to solid solution hardening takes place here. This combination appears to be particularly advantageous, since in this case an increase in strength Rm occurs without noticeable drop in the elongation at break A5. Furthermore, there is a pronounced A5-Ag breakage in the order of 4 to 6%, which promotes crash energy absorption. After a salt spray test, the resistance to corrosion could be detected. Furthermore, a good weldability and rivet suitability has been demonstrated in these alloys. Due to the good flowability and the good mold filling capacity, hot cracks and cold flow points could not be determined for any component.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• DIN EN 515 [0005]
• DIN EN 515 [0006]
• DIN EN 515 [0007]

Claims (8)

Aluminum-silicon die cast alloy containing - 5 to 12% by mass of silicon; 0.5 to 3.0% by mass of zinc; 0.1 to 0.7 Ma% magnesium; - 0.2 to 0.8 Ma% manganese; 0.05 to 0.3 Ma% zirconium; - not more than 0.05% by mass and not more than 0.4% in total of impurities; - as the rest aluminum. Casting alloy according to claim 1, comprising - 0.5 Ma% to 1.2 Ma% zinc. Casting alloy according to one of the preceding claims, further containing 0.005 to 0.03 Ma% strontium and / or 0.002 to 0.025 Ma% sodium; or - 0.002 to 0.035 Ma% antimony. Casting alloy according to one of the preceding claims, further containing - not more than 0.2% titanium by weight and / or not more than 0.3% ma vanadium. Method for producing a die-cast component, in particular a thin-walled bodywork or chassis casting component, with the steps of A cast component, in particular with evacuated permanent molds, is cast from a casting alloy according to the preceding claims; - The cast component after casting a heat treatment to the state T5, T6 or T7 is subjected. The method of claim 5, wherein The T6 / T7 heat treatment comprises solution annealing at 450 to 530 ° C for 1 to 2 hours, quenching and aging at 180 to 240 ° C for 2 to 5 hours. The method of claim 5, wherein - Quenching in moving or still air or in a moving or stationary inert gas or in water or in oil or in a combination of said media takes place. The method of claim 5 wherein - The T5 heat treatment involves aging at 150 to 320 ° C for 0.5 to 5 h.