EP2657360B1 - Pressure cast alloy on an Al-Si basis, comprising secondary aluminium - Google Patents

Description

The invention relates to a die-casting alloy based on Al-Si, comprising in particular secondary aluminum.

Inexpensive die-cast alloys can be obtained, for example, from aluminum scrap, but as a rule they disadvantageously contain undesirably high impurities, in the form of iron, copper and zinc alloy fractions (US Pat. EP1111077A1 ). This not only leads to a reduced ductility potential but can also have negative effects on the strength and quench sensitivity of the diecasting alloy. Various measures for mutual weighting of the alloying elements, as well as various proposals for alloys are known from the prior art - in particular in order to compensate for the negative influences of the impurities.

So is out of the JP9-003610 a die casting alloy containing 5 to 13 wt% Si, containing at most 0.5 wt% Mg, containing 0.1 to 1.0 wt% Mn and containing 0.1 to 2.0 wt% Fe known. Mn is intended to suppress the formation of Al-Fe-Si needle crystals, for example, in order to avoid a reduction in strength. Furthermore, in order to obtain the casting properties, Mg should be kept to a content as low as possible of at most 0.5% by weight. Cu and Zn impurities, such as these usually occur in significant amounts in secondary aluminum, takes into account the die-casting alloy in the JP9-00361 0 Not.

The DE102004013777B4 proposes a casting alloy with 5 to 18 wt .-% Si, with 0.15 to 0.45 wt .-% Mn, with 0.2 to 0.6 wt .-% Fe, with 0.3 to 0.5 wt % Mg, with possibly 0.1 to 0.5% by weight of Cu and with 4 to 5% by weight of Zn. The content of a maximum of 0.5% by weight of magnesium should avoid the formation of Mg-Fe-'pi 'phases in order to obtain the ductility. Cu is said to improve the heat resistance of the alloy, with the content of zinc being limited to 4 to 5% by weight so as to adjust the strength and quenching sensitivity of the alloy. A disadvantage of such a composition of alloying elements, in particular by the comparatively high zinc content, but have a low corrosion resistance, which can lead to safety limitations of die castings produced therefrom.

The farther is from the DE102009012073A1 a die casting alloy with 9 to 11 wt .-% Si, with a maximum of 0.6 wt .-% Fe, with 0.2 to 0.6 wt .-% Mn, with 0.05 to 0.4 wt .-% Cu , with 0.2 to 0.35 wt .-% Mg and with a maximum of 0.35 wt .-% Zn known. Although the DE102009012073A1 with secondary aluminum - due to the comparatively low lower limits of permissible Cu and Zn contents, the range of usable secondary aluminum is comparatively limited. In addition, such a composition can not provide comparatively high strength, ductility and castability, especially since Zn as an impurity should be limited to a small extent. The same is true of the DE102005061668A1 It is known that the Zn content in the diecasting alloy is to be kept below 0.05% by weight.

It is therefore an object of the invention, starting from the above-described prior art, to provide a die-casting alloy based on Al-Si, despite the use of secondary aluminum die castings with high demands in terms of strength, ductility and chemical reaction resistance, especially corrosion resistance. In addition, this die-casting alloy should be able to ensure both die casting and complex demoulding as well as excellent mold release, as well as offering excellent processability in the components produced from it.

The invention solves the task by the fact that the die-cast alloy 6 to 12 % By weight of silicon (Si), at least 0.3 % By weight of iron (Fe), at least 0.25 Wt .-% manganese (Mn), at least 0.1 Wt.% Copper (Cu), 0.24 to 0.8 Wt .-% magnesium (Mg) and 0.40 to 1.5 Wt .-% zinc (Zn) has and that the die-cast alloy 50 to 300 ppm strontium (Sr) and / or 20 to 250 ppm sodium (Na) and / or 20 to 350 ppm antimony (Sb), and at least one of the following components maximum 0.2 % By weight of titanium (Ti); maximum 0.3 % By weight zirconium; maximum 0.3 % By weight of vanadium (V); and the remainder being aluminum and having unavoidable impurities due to production,
the total proportion of Fe and Mn in the die-cast alloy together being a maximum of 1.5% by weight, the quotient of the percentages by weight of Fe and Mn 0.35 to 1.5 and the quotient of the percentages by weight of Cu and Mg 0.2 to 0, 8 amount.

By allowing relatively high wt .-% of impurities, as proposed for iron, copper and zinc according to the invention also, a low-cost die-casting alloy can be provided on Al-Si basis, because essentially reduces the proportion of primary aluminum or . even refrained from it or that secondary aluminum can be used increased for the production of castings. However, this becomes possible only when the alloy constituents of the casting alloy are forced into specific content limits in order to approximate the parameters known from primary aluminum (eg strength values, ductility values, chemical reaction stability, processability and / or castability).

Fe, Mn:

Thus, a quotient of the weight percentages of Fe and Mn 0.35 to 1.5 can lead to the formation of the β-phase (eg: Al ₅ FeSilAl _8.9 Fe ₂ Si ₂ ) in the microstructure, which results in a comparatively high iron content Form of fine needles excretes, can be significantly reduced. With an increased occurrence of the α-phase can be expected, which may be present as Al ₁₅ (FeMn) ₃ Si ₂ due to the manganese content of at least 0.25 wt .-% according to the invention. This α-phase crystallizes in globulitic form and, due to its compact structure, can have a significantly more favorable influence on the ductility than is known from the acicular β-phases. A diecasting alloy with a comparatively high ductility can thus be ensured. In general, it is also mentioned that through this ratio of Fe / Mn in combination with high cooling rates (eg: by accelerated cooling), their phases and thus their influence on the microstructure can be kept comparatively low. In addition, if the total content of Fe and Mn on the die casting alloy is limited to a maximum of 1.5% by weight, the formation of coarse α phases can be further reduced, even if the high cooling rates usually used in die casting processes are used. The concentration requirements for Fe and Mn can therefore be particularly beneficial to the ductility of the diecasting alloy.

Cu, Mg:

By introducing and / or adjusting an excess of magnesium in that the quotient of the weight percent of Cu and Mg is 0.2 to 0.8, and taking into account that at least 0.1 wt .-% Cu and 0.24 to 0.8 Wt .-% Mg can be substantially, the existing copper in the preferably forming Q phase (Al ₅ Cu ₂ Mg ₈ Si ₆ ) are bound. This concentration rule can therefore prevent the formation of corrosion-prone phases, such as the Tao phase (Al ₅ Cu ₄ Zn) or the theta phase (Al ₂ Cu) in the microstructure, so that despite comparatively high weight percent of Cu, which according to the invention is used to improve the hot curing of the diecasting alloy, also a high corrosion resistance can be maintained. In addition, this excess magnesium can improve the curing mechanism of the alloy because part of the Mg is bound in the Q phase (Al ₅ Cu ₂ M ₉₈ Si ₆ ) and thus overcome known limitations due to excessive precipitation of Set Mg ₂ Si pre-phases. The concentration requirements for Cu and Mg can therefore satisfy particularly high demands of the diecasting alloy in terms of strength and chemical reaction resistance. In addition, the proposed concentration ratio of Cu and Mg improved the processability, for example with regard to the weldability and rivability of components made from this diecasting alloy.

Mg, Fe, Mn:

In addition, it has been found that the introduction and / or adjustment of the aforementioned magnesium excess over Cu can also be used to bind the increased Fe content of the diecasting alloy in a pi phase (Al ₈ FeMg ₃ Si ₆ ). Thus, on the one hand, the ductility affecting β-phase (eg: Al ₅ FeSi / Al _8.9 Fe ₂ Si ₂ ) can be reduced because less Fe is available for the formation of this β-phase, but in particular could on the On the other hand, the Mn content in the diecasting alloy can also be reduced because the pi phase (eg: Al ₈ FeMg ₃ Si ₆ ) can be used to take up Fe. Die casting problems, usually to be accepted due to an increased Mn content to compensate for Fe effects, can thus be reduced. A complex deformation as well as an excellent releasability can be ensured by the special content limits of Mg, Fe, Mn in connection with their concentration requirements.

Zn:

The strength of the alloy, for example coined by an interaction of the pre-phases Mg ₂ Si and Q-phase (Al ₅ Cu ₂ Mg ₈ Si ₆ ), can be determined by solid-solution hardening be further improved with the help of a zinc deposit. For this purpose, zinc should be adjusted in the content limits of 0.40 to 1.5 wt .-%. In addition, this may be beneficial to the ductility of the diecasting alloy. In the case of the diecasting alloy, it is thus possible to reduce a possible negative influence of a comparatively high Mg content on its ductility. In addition, the content limits of Zn according to the invention may be distinguished in improving the castability of the die-cast alloy, whereby adverse effects due to the proposed content limits of Mn in the diecasting alloy can be largely compensated.

Therefore, the Al-Si-based die-casting alloy balanced in the alloy components Fe, Mn, Cu, Mg and Zn can combine a comparatively high ductility, corrosion resistance, strength, castability and processability, thus overcoming parameter boundaries known from the prior art even if the die-cast alloy has secondary aluminum and / or is added to it or thereby leads to comparatively high levels of impurities.

For duration refinement purposes, the die casting alloy may have 50 to 300 ppm strontium (Sr) and / or 20 to 250 ppm sodium (Na) and / or 20 to 350 ppm antimony (Sb). Optionally, for grain refining of the diecasting alloy, at most 0.2% by weight of titanium (Ti) and / or at most 0.3% by weight of zirconium and / or at most 0.3% by weight of vanadium (V) may prove to be advantageous. The die-cast alloy can be supplemented in each case to 100% by weight with Al, and this die-casting alloy can also lead to unavoidable impurities due to its production. In general, it is mentioned that the die-cast alloy can have impurities of not more than 0.1% by weight and not more than 1% by weight in total.

For the sake of completeness, it is mentioned that as secondary aluminum aluminum or an aluminum alloy, obtained from aluminum scrap, can be understood.

Strength, ductility, processability, and chemical reaction resistance of the die-cast alloy can be further improved when they contain 0.3 to 1.0 wt% Fe (Fe), 0.25 to 1.0 wt% Manganese (Mn), and 0 , 1 to 0.6 wt .-% copper (Cu).

kann eine einfache Verfahrensvorschrift zur Erhöhung des Anteils an pi-Phase (z.B.: Al₈FeMg₃Si₆) im Gefüge der Druckgusslegierung gegeben werden. Erhöhte Fe-Anteile können so kompensiert werden, wodurch mit vermindertem Mn-Anteil beste Gießbarkeit der Druckgusslegierung gewahrt bleiben kann. Außerdem kann diese pi-Phase mit einem Lösungsglühen in eine für die geforderten Eigenschaften der Druckgusslegierung harmlose α-Phase umgewandelt werden.If the diecast alloy meets the order relation in its composition $$\mathrm{weight}\mathrm{,}-\%\mathrm{mg}>0.2+0.12\times \left(\mathrm{weight}\mathrm{,}-\%\mathrm{Fe}/\mathrm{weight}\mathrm{,}-\%\mathrm{Mn}\right)$$

a simple procedure for increasing the proportion of pi-phase (eg: Al ₈ FeMg ₃ Si ₆ ) in the structure of the die-cast alloy can be given. Increased Fe contents can thus be compensated, whereby the best castability of the die-cast alloy can be maintained with a reduced Mn content. In addition, this pi-phase can be converted with a solution annealing into a harmless for the required properties of the die-cast alloy α-phase.

The die cast alloy can be further improved in terms of achievable ductility, strength and corrosion resistance, if the total content of Fe and Mn together on the die-cast alloy together maximally 1.2 wt .-%, the quotient of the weight percentages of Fe and Mn 0.5 to 1 , 25 and the quotient of the weight percent of Cu and Mg is 0.2 to 0.5.

If the die casting alloy has 9.5 to 11.5 wt.% Silicon (Si) and / or 0.35 to 0.6 wt.% Iron (Fe) and / or 0.3 to 0.75 wt. Manganese (Mn) and / or 0.1 to 0.4% by weight of copper (Cu) and / or 0.24 to 0.5% by weight of magnesium (Mg) and / or 0.40 to 1.0 Zinc (Zn) results in narrower limits for an improved Al-Si based through-casting alloy in its mechanical and / or chemical resistance. In general, it is mentioned that the proposed content of Si improves the flow properties of the melt and that brittle primary silicon phases can be avoided. This also makes it possible to pressure-mold even comparatively thin-walled components. 9.5 to 11.5% by weight of silicon (Si) may prove to be particularly advantageous for this purpose.

• Zum Nachweis der erzielten Effekte wurden aus verschiedenen Druckgusslegierungen dünnwandige Gussbauteile im Druckgussverfahren hergestellt. Die Zusammensetzungen der untersuchten Legierungen sind in der Tabelle 1 angeführt.

Tabelle 1: Übersicht zu den untersuchten Legierungen Legierungs-Nr. Zusammensetzung Fe/Mn Cu/Mg 1 AlSi10Mn0,5Fe0,1Mg0,4 0,2 0 2 AlSi10Mn0,5Fe0,5Mg0,4Cu0,25Zn0,75 1 0,63 In the following, the invention will be explained in more detail by way of example with reference to exemplary embodiments:

• To demonstrate the effects achieved, thin-walled cast components were produced by die casting from various die cast alloys. The compositions of the alloys studied are listed in Table 1.

Table 1: Overview of the investigated alloys Alloy no. composition Fe / Mn Cu / Mg 1 AlSi10Mn0,5Fe0,1Mg0,4 0.2 0 2 AlSi10Mn0,5Fe0,5Mg0,4Cu0,25Zn0,75 1 0.63

Alloy 1 is a die cast alloy of low contamination primary aluminum. Alloy 2, on the other hand, shows a considerable degree of impurities in iron and copper alloy fractions, which can be introduced, for example, by secondary aluminum.

The alloys and die castings or specimens produced therefrom were subjected to T7 heat treatment for 1 hour at 460 ° C solution annealing, quenching with water and 2 hours aging at 220 ° C. The finished test specimens were finally examined for their mechanical properties. For this purpose, the tensile strength R _m , the yield strength R _p0.2 and the elongation at break A _{5 were determined} in a tensile test. The measured values obtained are summarized in Table 2. Table 2: Mechanical characteristics of the alloys investigated Alloy no. R _p0.2 [MPa] R _m [MPa] A ₅ [%] 1 155 230 14.3 2 160 240 13.8

Investigations on die casting alloy no. 2 showed that the formation of an undesirable beta phase during solidification can be avoided by the iron content and manganese content set. The proportion of copper can be completely bound by a magnesium content in the Q phase, whereby comparatively high corrosion resistance is achieved. Due to these element combinations, an increased strength and elongation at break of 13.8% can be achieved despite an iron content of 0.5 wt .-%. The comparatively high zinc content leads to an increase in strength without negatively influencing the mechanical properties.

As can now be seen in the comparison of the two die-cast alloys 1 and 2 according to Table 2, these two alloys show similar mechanical properties, although Alloy 2 has a significantly higher iron and copper content compared to Alloy 1.

It is thus shown that the concentration ratios for a diecasting alloy proposed according to the invention make it possible to ensure comparatively high ductility, corrosion resistance, strength, castability and processability.

Claims (10)

1. Al-Si based die-casting alloy comprising in particular secondary aluminium, characterized in that
   the die-casting alloy comprises 6 to 12 wt. % silicon (Si), at least 0.3 wt. % iron (Fe), at least 0.25 wt. % manganese (Mn), at least 0.1 wt. % copper (Cu), 0.24 to 0.8 wt. % magnesium (Mg) and 0.40 to 1.5 wt. % zinc (Zn) and that the die-casting alloy comprises 50 to 300 ppm strontium (Sr) and/or 20 to 250 ppm sodium (Na) and/or 20 to 350 ppm antimony (Sb), as well as at least one of the following components maximum 0.2 wt. % titanium (Ti); maximum 0.3 wt. % zirconium; maximum 0.3 wt. % vanadium (V); and as the remainder, aluminium as well as unavoidable impurities caused by production,
   wherein the total fraction of Fe and Mn in the die-casting alloy together is a maximum of 1.5 wt.%, the quotient of the percentage weights of Fe and Mn is 0.35 to 1.5 and the quotient of the percentage weights of Cu and Mg is 0.2 to 0.8.
2. Die-casting alloy according to claim 1, characterized in that the die-casting alloy comprises 0.3 to 1.0 wt. % iron (Fe), 0.25 to 1.0 wt. % manganese (Mn) and 0.1 to 0.6 wt. % copper (Cu).
3. Die-casting alloy according to claim 1 or 2 characterized in that the die-casting alloy in its composition satisfies the order relationship $$\mathrm{wt}\mathrm{.}\%\mathrm{Mg}>0.2+0.12\times \left(\mathrm{wt}\mathrm{.}\%\mathrm{Fe}/\mathrm{wt}\mathrm{.}\%\mathrm{Mn}\right)\mathrm{.}$$

   
4. Die-casting alloy according to claim 1, 2 or 3 characterized in that the total fraction of Fe and Mn in the die-casting alloy together is a maximum of 1.2 wt. %, the quotient of the percentage weights of Fe and Mn is 0.5 to 1.25 and the quotient of the percentage weights of Cu and Mg is 0.2 to 0.5.
5. Die-casting alloy according to one of claims 1 to 4, characterized in that the die-casting alloy comprises 9.5 to 11.5 wt. % silicon (Si).
6. Die-casting alloy according to one of claims 1 to 5, characterized in that the die-casting alloy comprises 0.35 to 0.6 wt. % iron (Fe).
7. Die-casting alloy according to one of claims 1 to 6, characterized in that the die-casting alloy comprises 0.3 to 0.75 wt. % manganese (Mn).
8. Die-casting alloy according to one of claims 1 to 7, characterized in that the die-casting alloy comprises 0.1 to 0.4 wt. % copper (Cu).
9. Die-casting alloy according to one of claims 1 to 8, characterized in that the die-casting alloy comprises 0.24 to 0.5 wt. % magnesium (Mg).
10. Die-casting alloy according to one of claims 1 to 9, characterized in that the die-casting alloy comprises 0.40 to 1.0 wt. % zinc (Zn).