EP4275812A1 - Aluminum alloy structural components, precursor material and method of manufacturing the same - Google Patents

Abstract

The invention relates to a method for producing raw material for forged structural components made of aluminum. The process includes producing an aluminum alloy with 0.7 to 1.8 wt% silicon, 0.5 to 1.4 wt% magnesium, 0.3 to 1.2 wt% manganese, 0.005 to 0 .5% by weight of zirconium, 0.001 to 0.1% by weight of titanium and max. 0.3% by weight of iron using direct quenching continuous casting. The melt is guided in such a way that it does not come into contact with a solid surface during quenching.

Description

The invention relates to structural components made of an aluminum alloy, in particular structural components for automobiles, a raw material for such structural components and associated methods for producing the same.

It is known to produce ingots from aluminum alloys, which are used, for example, to produce structural components for vehicles, using the continuous casting process.

In a continuous casting process, a material - for example an aluminum alloy - is transferred from the molten state to the solidified state by continuously feeding the alloyed or unalloyed melt into a short, water-cooled ring mold. The ring mold is closed off by a lowerable foot block on a casting table. By lowering the casting table, the cast ingot is produced with continuous replenishment of the mold space. The ring mold and the solidified cast product are cooled using water. In addition to ring molds, molds with a ceramic structure on the mold ("hot top") are also used, which reduces the temperature gradient in the solidifying melt, resulting in a more uniform structure in the mold Bar cross-section and a thinner edge shell with increased surface quality. Casting lengths are usually between 3 and 7 meters. ( F. Ostermann "Aluminum Application Technology", Springer, 2007, 2nd edition, p. 419f .).

Prematerial produced in continuous casting is usually brought to suitable preliminary dimensions by extrusion before the actual forming step to the final contour. In addition to changing the dimensions of the forging raw material produced in this way, the grain structure of the material also changes. If there is a more globulitic grain structure in the cast state, this changes through the extrusion process to a fiber structure oriented in the pressing direction ( F. Ostermann "Aluminum Application Technology", Springer, 2007, 2nd edition, p. 482 ).

Extrusion and forging are two of the most economical forming processes for aluminum. The design limits in extrusion and forging are influenced, among other things, by the alloy and the available process forces. In addition to the machine settings and tool design, the quality of a formed part largely depends on the alloy system chosen. AIMn(Cu) and AlMgSi alloy systems are particularly widely used for extruded products. ( F. Ostermann "Aluminum Application Technology", Springer, 2007, 2nd edition, pp. 435-444 ). In principle, all wrought aluminum alloys and cast alloys can be used for hot forming by forging. However, for technical and economic reasons, selected wrought alloys from the 2xxx, 5xxx, 6xxx and 7xxx series in accordance with DIN EN 573-4 and DIN EN 586-3 are used ( F. Ostermann “Aluminum Application Technology”, Springer, 2007, 2nd edition, p. 481f .).

The general heat treatment cycle for age-hardenable wrought aluminum alloys is in Figure 1 shown and consists of the steps solution annealing, quenching and hardening.

Since the hot deformation temperatures during forming are in the range of the solution annealing temperature, solution annealing can be dispensed with for low to medium strength materials. For high-strength materials, the forging material is subjected to solution annealing after forming in order to exploit the full potential of the alloys. Too short a solution heat treatment causes reduced strength levels and reduced ductility after hardening. Re-annealing after forming serves to homogenize the forged structure. Precise control of the quenching speed is not insignificant when it comes to high-alloy materials after the solution annealing process in order to counteract premature segregation processes. An example of this is in Figure 2 the C-curve of a pressed profile from EN AW-6060 is listed.

Following the quenching of the structural component after hot forming, an alloy-specific single or multi-stage cold and/or hot aging usually takes place on the formed component. This serves to set the required mechanical properties ( Source: F. Ostermann "Aluminum Application Technology", Springer, 2007, 2nd edition, pp. 157-166 ).

In the past, increased attention has been paid to the development of aluminum alloys with improved corrosion resistance while increasing mechanical properties. This is happening above all against the background that the demand for materials is increasing, especially in the automotive industry, which enable an advantage in the CO ₂ balance during a vehicle life cycle by saving weight by reducing wall thickness.

At the same time, there are requirements for wear resistance, low density and thermal expansion as well as good formability. These requirements have so far mainly been met by alloys from the 6xxx series according to DIN EN 573-4, for example 6082 alloys.

The demands for the highest mechanical properties can so far only be met by precipitation sequences with copper additions (Cu additions) to the alloy. However, this increasingly leads to a conflict of objectives, as Cu-containing 6xxx alloys reach their limits in terms of corrosion resistance, especially with regard to intergranular corrosion.

Efforts to substitute Cu additives through the use of alloying elements from the group of rare earth metals are partly showing positive results. However, the poor availability of alloying elements from the group of rare earth metals and the associated price situation make such variants less attractive in the industrial environment.

Aluminum alloys for manufacturing structural components are in EP 2 644 727 A2 or EP 2 811 042 B1 described.

Known aluminum alloys according to AA 6182 have the following composition: Aluminum, Al 95 - 97.85% Chromium, Cr <= 0.25% Copper, Cu <= 0.10% Iron, Fe <= 0.50% Magnesium, Mg 0.70 - 1.2% Manganese, Mn 0.50 - 1.0% Silicon, Si 0.90 - 1.3% Titanium, Ti <= 0.10% Zinc, Zn <= 0.20% Zircon, Zr 0.05 - 0.20% others, respectively <= 0.05% others, altogether <= 0.15%

The invention is based on the object of creating a structural component that has both high strength and good corrosion resistance and is economical to produce, as well as an associated manufacturing process.

• Herstellen einer Aluminiumlegierung mit den Bestandteilen.
  • 1,2 bis 1,4 Gew.-% Silizium,
  • 0,8 bis 1,2 Gew.-% Magnesium,
  • 0,3 bis 1,2 Gew.-% Mangan,
  • 0,1 bis 0,2 Gew.-% Zirkon,
  • 0,01 bis 0,05 Gew.-% Titan,
  • 0,08 bis 0,3 Gew.-% Eisen,
  • 0,08 bis 0,2 Gew. % Chrom
  • max. 0,04 Gew.-% Zink, und
  • max. 0,02 Gew.-% Kupfer
  • wobei das Verhältnis von Silizium zu Magnesium mindestens 1 : 0,8 beträgt,
• Stranggießen der Aluminiumlegierung, bei dem die Schmelze so geführt wird, dass sie beim Erstarren keinen Kontakt zu einer festen Oberfläche hat.

According to a first aspect of the invention, this object is achieved by a method for producing raw material for forged structural components made of aluminum, which comprises the following steps:

• Producing an aluminum alloy with the components.
  • 1.2 to 1.4% by weight of silicon,
  • 0.8 to 1.2% by weight magnesium,
  • 0.3 to 1.2% by weight of manganese,
  • 0.1 to 0.2% by weight zirconium,
  • 0.01 to 0.05% by weight titanium,
  • 0.08 to 0.3% by weight iron,
  • 0.08 to 0.2% by weight of chromium
  • max. 0.04% by weight zinc, and
  • max. 0.02% by weight copper
  • where the ratio of silicon to magnesium is at least 1:0.8,
• Continuous casting of aluminum alloy, in which the melt is guided so that it does not come into contact with a solid surface during solidification.

The melt is preferably liquid-cooled as it passes through a mold so that it solidifies without coming into contact with the wall. Preferably, the coolant temperature and the mass flow of the coolant (e.g. water) are set so that the highest cooling rate of the melt is more than -25 K/s. Suitable cooling speeds are, for example, between -15 K/s and -35 K/s for a bolt with a diameter between 90 mm and 100 mm, measured at a lateral distance of approximately 20 mm from a central longitudinal axis of the bolt. The coolant is preferably water with a maximum temperature of 80°C. At a casting speed between 100 mm/min and 500 mm/min, the cooling water volume flow for a bolt with a diameter between 90 mm and 100 mm is preferably between 40 l/min and 80 l/min. Preferably, the cooling water volume flow is 20 to 50 times larger than that Volume flow of the cast aluminum alloy, wherein the cooling water volume flow for bolt diameters of the order of 50 mm is preferably approximately 25 times greater than the volume flow of the cast aluminum alloy and for bolt diameters of the order of 100 mm is preferably approximately 40 times greater than the volume flow of the cast Aluminum alloy. The cooling capacity can be determined and adjusted as a function of the flow/return temperature and volume flow.

A water-cooled ring mold is preferably used as the mold, which is designed in such a way that the melt of the aluminum alloy is spaced from the solid components of the ring mold by a film of water and therefore does not touch any solid components of the mold during solidification. The water is used for the liquid cooling of the cast strand as described

Preferably, the melt passing through the mold is completely exposed from the outside to a gas mixture containing oxygen, preferably oxygen that is as pure as possible, in order to promote the formation of a solidified surface layer made of oxidized aluminum alloy. The application of oxygen takes place before the application of water for liquid cooling. Only after the solidified surface layer has formed is the cast strand (ingot), which is initially still formed by liquid melt, cooled with water as mentioned above. The water film mentioned does not come into contact with the melt, but rather with the already solidified edge layer of the cast strand. Beforehand, the melt is separated from the mold by the gas mixture during the solidification of the surface layer.

The gas mixture preferably contains between 10% and 80% or between 20% and 70% oxygen (O ₂ ).

• max. 0,2 Gew.-% Chrom
• max. 0,04 Gew.-% Zink
• max. 0,02 Gew.-% Kupfer

In further embodiment variants, the alloy can optionally also contain one or more of the following elements in the proportions specified below:

• max. 0.2% by weight chromium
• max. 0.04% by weight zinc
• max. 0.02% by weight copper

In comparison with standard continuous casting processes, by using a direct quenching continuous casting process while avoiding contact between the melt and solid surfaces (e.g. the mold), a raw material quality that can be directly massively formed can be achieved, which is characterized by a sufficiently homogeneous surface quality, a sufficiently fine structure and a sufficiently low tendency to recrystallization .

The primary material according to the invention has a significantly reduced tendency to secondary recrystallization compared to the prior art, so that, for example, the circumferential coarse grain seam typical of forged parts is eliminated (see also Figures 3 and 4 ). The electrical conductivity is significantly lower than in comparable extruded material, namely around 16 to 18 MS/m compared to approximately 25 MS/m in the prior art. This is advantageous if the raw material according to the invention is used to produce components of electrical machines because the lower conductivity reduces harmful eddy currents.

The primary material according to the invention has increased corrosion resistance compared to the prior art.

In addition, products made from the raw material according to the invention offer, for example, a higher pressure tightness compared to cast aluminum, which results from the absence of porosity.

The aluminum alloy used according to the invention is easy to cast and form and has good mechanical properties. The mechanical properties achieved are, for example, a tensile strength Rm>375 MPa, a yield strength Rp02>345 MPA, an elongation A>10% and a hardness>100 HB. In addition, the aluminum alloy has good machinability and high corrosion resistance.

The components made from aluminum alloy are characterized by high strength and elongation properties combined with excellent corrosion resistance.

The aluminum alloy used according to the invention is particularly suitable for producing structural components, in particular automotive components, by means of forming processes.

Preferably, the weight ratio of titanium to zirconium (Ti:Zr) in the aluminum alloy is between 1:4 and 1:6, particularly preferably at least approximately 1:5.

Preferably the weight ratio of iron to chromium to manganese (Fe:Cr:Mn) in the aluminum alloy is at least approximately 1:1:4.

To form further finely divided dispersoids, the aluminum alloy preferably contains up to a maximum of 0.3% by weight of one or more elements of the so-called rare earths, preferably Sc, Er, La, Ce, Y and/or Yb.

Grain refinement is preferably carried out in the aluminum alloy according to the invention.

For this purpose, the alloy for grain refinement can contain Ti and B, with the addition of titanium and boron via a master alloy with 2.7 to 3.2% by weight of Ti and 0.6 to 1.1% by weight of B, the balance being aluminum , he follows. According to a variant, the aluminum master alloy contains 2.9 to 3.1% by weight of Ti and 0.8 to 0.9% by weight of B and has a Ti-B weight ratio Ti:B of approximately 3:1 .

A master alloy that has a Ti-B weight ratio Ti:B between approximately 5:1 and 5:0.6 is preferred. In this case, the titanium content is preferably between 4.5 and 5.5% by weight, for example between 4.8 and 5.2% by weight.

The content of the master alloy in the alloy according to the invention is preferably set to 0.02 to 0.3% by weight.

• Herstellen einer Aluminium-Vorlegierung mit 4,8 bis 5,2 Gew.-% Ti und 0,8 bis 1,2 Gew.-% B und als Rest Aluminium und unvermeidbare Verunreinigungen und
• Zufügen der Aluminium-Vorlegierung zu der Aluminiumlegierung mit den Bestandteilen:
  • 1,2 bis 1,4 Gew.-% Silizium,
  • 0,8 bis 1,2 Gew.-% Magnesium,
  • 0,3 bis 1,2 Gew.-% Mangan,
  • 0,1 bis 0,2 Gew.-% Zirkon,
  • 0,01 bis 0,05 Gew.-% Titan,
  • 0,08 bis 0,3 Gew.-% Eisen,
  • 0,08 bis 0,2 Gew. % Chrom,
  • max. 0,04 Gew.-% Zink, und
  • max. 0,02 Gew.-% Kupfer.

The production method according to the invention accordingly preferably additionally includes the following steps:

• Produce an aluminum master alloy with 4.8 to 5.2% by weight of Ti and 0.8 to 1.2% by weight of B and the balance aluminum and unavoidable impurities and
• Adding the aluminum master alloy to the aluminum alloy with the components:
  • 1.2 to 1.4% by weight of silicon,
  • 0.8 to 1.2% by weight magnesium,
  • 0.3 to 1.2% by weight of manganese,
  • 0.1 to 0.2% by weight zirconium,
  • 0.01 to 0.05% by weight titanium,
  • 0.08 to 0.3% by weight iron,
  • 0.08 to 0.2% by weight of chromium,
  • max. 0.04% by weight zinc, and
  • max. 0.02% by weight copper.

Using the aluminum master alloy, Ti and B are added to the aluminum alloy for grain refinement.

In the preferred production process for a starting material made of the aluminum alloy, the aluminum master alloy containing titanium and boron is preferably added to the melt in the form of a wire immediately before the mold.

The primary material produced using the method according to the invention is preferably forged into a structural component immediately after continuous casting.

Another aspect of the invention is a manufacturing process for the aluminum alloy according to the invention, through which the required component properties are obtained.

Another aspect is a structural component made of the aluminum alloy according to the invention, in particular a structural component for a vehicle, for example an aircraft or an automobile.

Another aspect is a method for producing a structural component in which the primary material produced as described above is hot-formed, in particular forged, into a structural component immediately after continuous casting, without any treatment to homogenize the primary material taking place between continuous casting and hot forming.

The forged structural component can be quenched directly after hot forming, without the hot-formed structural component being solution annealed again beforehand. The forged structural component can then be subjected to heat aging.

Alternatively, the forged structural component can be solution annealed, quenched and aged after hot forming. The temperature during solution annealing approximately corresponds to the forming temperature for forging, i.e. between 400°C and 570°C.

After hot forming, in particular after forging, the structural component is preferably subjected to hot aging and subsequent air cooling. The aging process is preferably carried out for 2 hours to 7 hours at 180°C to 210°C.

Due to the material properties, crash or deformation-relevant parts or fail-safe parts that are made from the raw material according to the invention are particularly preferred. Examples of preferred structural components are the following vehicle parts: skid wedges, battery boxes, junction points, engine mounts, pivot bearings and wishbones.

Accordingly, a further aspect is the use of the aluminum alloy according to the invention for producing a structural component for a vehicle, for example an aircraft or an automobile, in particular for producing deformation-relevant parts or fail-safe parts, especially for producing sliding wedges, battery boxes, body nodes , engine mounts, pivot bearings and wishbones for vehicles.

The invention includes the knowledge that in order to achieve the required mechanical properties, in particular a high yield strength Rp0.2, copper or zinc usually has to be added to a 6xxx alloy. However, this approach conflicts with the corrosion resistance that is also required. In order to achieve this, the permissible Cu and Zn proportions in the alloy must be severely limited, otherwise precipitation will occur, particularly on the grain boundaries, which will have a negative impact affect the corrosion resistance of the alloy. The required properties are therefore achieved by other suitable measures, such as setting the Si:Mg ratio of at least 1:0.8 and preferably the Fe:Mn:Cr ratio of at least approximately 1:1:4 or the addition of dispersoid formers to realize. In addition, a suitable heat treatment strategy is an effective means of achieving the required goals. Phases such as these must be formed which counteract the dislocation movements when force is applied.

The invention also includes the knowledge that known EN AW-6082 aluminum alloys do not have sufficient strength with sufficient corrosion resistance. On the other hand, known EN AW-6056 aluminum alloys offer sufficient mechanical properties, but fail when it comes to the required corrosion properties. Other alloys of EN AW-6xxx and the other wrought alloy groups also do not meet the required properties.

Furthermore, the invention includes the knowledge that only a few wrought alloys are actually used for forging, although in principle all aluminum and wrought alloys can be formed using hot solid forming. The reason for this is the high demands in terms of strength and component safety in the typical areas of application for forged aluminum parts, namely vehicle construction and mechanical engineering. A common area of application for aluminum forgings is chassis safety parts, which can be permanently exposed to corrosion attack due to their exposed location; cf. F. Ostermann, Application Technology Aluminum, London, Heidelberg: Springer, 2007 .

It is generally known that pure aluminum has a high resistance to corrosion. Susceptibility only arises through the addition of appropriate alloying elements. F. Uyma writes that increasing magnesium contents improve corrosion properties. Manganese influences the recrystallization and precipitation behavior, which leads to the increased occurrence of the so-called "Chinese writing" (binary eutectic made of Al and Mg ₂ Si), which in turn causes intergranular corrosion. Zinc and scandium additions are intended to increase resistance to intergranular corrosion; cf. F. Uyma, Investigations in the field of Al-Mg-Si and Al/Mg2Si in-situ alloys, Freiberg: Technical University of Bergakademie Freiberg, 2007 . JP Wloka states that a continuous corrosive active path through the metal is responsible for the occurrence of intergranular corrosion. This occurs especially with materials that have been subjected to heat aging which have pearl-string-like grain boundary precipitates. This phenomenon cannot be observed in aging structures; cf. JP Wloka, Corrosion studies on scandium-containing AlZnMgCu alloys with special consideration of the influence of intermetallic phases, Erlangen: University of Erlangen-Nuremberg, 2007 . It is also known that sensitivity to intergranular corrosion is increased by insufficient quenching rates after solution annealing. This is particularly true for age-hardenable alloys. In the case of thick-walled semi-finished products, intergranular corrosion can hardly be avoided; cf. F. Ostermann, Application Technology Aluminum, London, Heidelberg: Springer, 2007 . G. Svenningsen et al. have investigated the influence of copper content in AlMgSi alloys. The susceptibility to intergranular corrosion is therefore largely based on the copper content of an alloy. In addition, the quenching rate has a significant influence on the intergranular corrosion resistance of an alloy. Cooling with water is therefore preferable to cooling in air. Finally, as in also in JP Wloka, Corrosion studies on scandium-containing AlZnMgCu alloys with special consideration of the influence of intermetallic phases, Erlangen: University of Erlangen-Nuremberg, 2007 described, it can be shown that overaging has a positive influence on the resistance with regard to intergranular corrosion. The so-called Q phase (Al4Mg8Si7Cu2) was identified as the phase primarily responsible for intercrystalline corrosion ( G. Svenningsen et al., "Effect of low copper content and heat treatment on intergranular corrosion of model AlMgSi alloys," Corrosion Science, Vol. 1, No. 48, p. 226-242, 2006 ). In this context, the proportion of magnesium to silicon is heavily discussed. However, there is no consensus about the best ratio, partly because no direct evidence of the influence has yet been provided. G. Svennigsen et al. set the ratio to Mg/Si ~ 0.87. Altenpohl suggests a ratio of Mg/Si ~ 1 ( G. Svenningsen et al., "Effect of low copper content and heat treatment on intergranular corrosion of model AlMgSi alloys," Corrosion Science, Vol. 1, No. 48, p. 226-242, 2006 ), ( D. Altenpohl, Aluminum and Aluminum Alloys, London, Heidelberg: Springer, 1965 ).

With the alloy composition according to the invention, significantly improved corrosion properties can be achieved in massively formed components with at least the same high strength values and at least the same low recrystallization tendency. Surprisingly, it has been shown that a more stable casting process and a more moderate use of grain refiners are also possible.

Figur 1:

den allgemeinen Wärmebehandlungszyklus für aushärtbare Aluminiumknetlegierungen;

Figur 2:

C-Kurven für Profile aus Legierung EN AW-6060 (AlMgSi);

Figur 3:

eine schematische Darstellung der Grobkornentwicklung an einem Schmiedeteil unter Verwendung des üblichen stranggepressten Materials;

Figur 4:

eine schematische Darstellung der Grobkornentwicklung an einem Schmiedeteil unter Verwendung des erfindungsgemäßen Materials; und

Figur 5:

eine schematische Skizze zur Erläuterung der Herstellung des erfindungsgemäßen Vorprodukts.

The invention will now be explained in more detail using exemplary embodiments and in comparison to other aluminum alloys. Of the figures shows:

Figure 1:

the general heat treatment cycle for age-hardenable wrought aluminum alloys;

Figure 2:

C-curves for profiles made of alloy EN AW-6060 (AlMgSi);

Figure 3:

a schematic representation of coarse grain development on a forging using the usual extruded material;

Figure 4:

a schematic representation of the coarse grain development on a forged part using the material according to the invention; and

Figure 5:

a schematic sketch to explain the production of the preliminary product according to the invention.

The one already mentioned in the introduction to the description Figure 1 (Source: F. Ostermann "Aluminum Application Technology", Springer, 2007, 2nd edition, p. 174 ) shows the schematic of the general heat treatment cycle for age-hardenable aluminum alloys. I illustrates the non-critical heating rate during solution annealing, II illustrates the critical cooling rate during quenching after solution annealing, III illustrates the critical heating rate during aging (this depends on the alloy) and IV illustrates the non-critical cooling rate after aging. “RT” denotes the room temperature.

For the process presented in this description, compared to the general presentation in Figure 1 The following deviations: explicit cold aging is not required. Rather, there is only interim storage until hot aging. Hot aging is a one-stage process. It is precisely an advantage of the process described here that the bolts produced using the continuous casting process can be cold-formed after continuous casting without prolonged aging. After continuous casting, after cooling, aging can be carried out for a period of 2h to 7h at 180°C to 210°C.

In the Figure 2 The C curves shown illustrate the influence of the quenching speed on the formation of phases or undesirable precipitates for extrusion. The quenching speed must be chosen so that undesirable precipitation does not occur. The principles applicable to extrusion are intended to illustrate the influence that quenching speed has on the formation of precipitates. According to the method described here, the bolts are preferably not strand pressed, but rather forged. After forging, solution annealing can optionally be carried out.

An advantage of the aluminum alloy according to the invention, which is explained in more detail below, is that it does not require any heat treatment or only a short hot aging if a preliminary product is produced in the manner described here in the direct quenching continuous casting process.

An aluminum alloy preferred for this has the following components:
The preferred silicon content is 0.7 to 1.8% by weight, particularly preferably 1.0 to 1.6% by weight, especially 1.2 to 1.4% by weight.

The preferred magnesium content is 0.5 to 1.4% by weight, particularly preferably 0.6 to 1.2% by weight, especially 0.8 to 1.0% by weight.

The preferred copper content is a maximum of 0.1% by weight.

The preferred manganese content is 0.4 to 0.8% by weight, particularly preferably 0.5 to 0.7% by weight.

The preferred zirconium content is 0.005 to 0.5% by weight, particularly preferably 0.005 to 0.1% by weight.

In addition, the alloy can optionally contain one or more of the following elements in the proportions specified below:
The preferred chromium content is a maximum of 0.2% by weight.

The preferred iron content is a maximum of 0.3% by weight.

The preferred titanium content is 0.001 to 0.05% by weight.

The preferred zinc content is a maximum of 0.04% by weight, preferably a maximum of 0.01% by weight.

• Si:Mg - zwischen 1:0,5 und 1:0,75
  Ein entsprechend eingestellter Silizium-Überschuss bewirkt, dass die Festigkeit signifikant steigt
• Fe:Cr:Mn - zwischen etwa 1:1:4 und 1:1:5
  wobei das Verhältnis von Eisen zu Chrom Fe:Cr vorzugsweise 1:1 beträgt und zwischen 0,8:1 und 1:0,8 liegt. Das bevorzugte Verhältnis von Eisen zu Chrom zu Mangan dient zum Vermeiden von nadeligen AlFeSi-Phasen, welche sich negativ auf die Duktilität auswirken. Mangan formt diese Phasen zu weniger problematischen Al-FeMnSi-Phasen ein. Der Chrom-Gehalt wird wegen der hohen Affinität zu freiem Silizium beschränkt, was sich ebenfalls negativ auf die mechanischen Eigenschaften auswirken kann.
• Ti:Zr - 1:5 (TiZr-Verbindung/Thema Rekristallisation, auch RE-Metals s.u., Kornfeinung)
  Das Verhältnis von Titan zu Zirkonium dient zur Bildung von ausreichend vieler Al3Zr Phasen mit einer L12 Struktur, welche als Dispersoide die mechanischen Eigenschaften und das Rekristallisationsverhalten positiv beeinflussen.
• Cu<0,02, bevorzugt Cu<0,01
  Kupfer dient zur Hemmung der Korrosionsneigung, insbesondere in Hinblick auf interkristalline Korrosion
• Zn<0,04, bevorzugt Zn<0,01
  Zink dient zur Hemmung der Korrosionsneigung, insbesondere in Hinblick auf Spannungs-Riss-Korrosion
• Seltene Erden
  Seltene Erden wirken als zusätzliche Dispersoid-Bildner zu Steigerung der mechanischen Eigenschaften, insbesondere der Härte, und zur Beeinflussung der Rekristallisationsneigung beim Warmumformen.

The following ratios of the alloy components to one another are preferred:

• Si:Mg - between 1:0.5 and 1:0.75
  An appropriately adjusted excess of silicon causes the strength to increase significantly
• Fe:Cr:Mn - between about 1:1:4 and 1:1:5
  where the ratio of iron to chromium Fe:Cr is preferably 1:1 and is between 0.8:1 and 1:0.8. The preferred ratio of iron to chromium to manganese serves to avoid needle-like AlFeSi phases, which have a negative effect on ductility. Manganese forms these phases into less problematic Al-FeMnSi phases. The chromium content is limited due to the high affinity for free silicon, which can also have a negative effect on the mechanical properties.
• Ti:Zr - 1:5 (TiZr compound/topic of recrystallization, also RE-Metals see below, grain refinement)
  The ratio of titanium to zirconium serves to form a sufficient number of Al3Zr phases with an L12 structure, which, as dispersoids, positively influence the mechanical properties and recrystallization behavior.
• Cu<0.02, preferably Cu<0.01
  Copper serves to inhibit the tendency to corrosion, especially with regard to intergranular corrosion
• Zn<0.04, preferably Zn<0.01
  Zinc serves to inhibit the tendency to corrosion, especially with regard to stress-crack corrosion
• Rare earth
  Rare earths act as additional dispersoid formers to increase mechanical properties, especially hardness, and to influence the tendency to recrystallization during hot forming.

Description of an exemplary embodiment:

The aluminum alloy can be produced using methods known to those skilled in the art, usually by producing a melt which has a composition which corresponds to the alloy composition specified above.

The alloying elements Ti and B are preferably added in the form of a master alloy in the production of the alloy, as explained above.

The raw material made from the aluminum alloy according to the invention is preferably produced using a horizontal continuous casting process (horizontal casting, HCM). A prior gas treatment of the melt with a suitable inert gas or several inert gases ensures sufficient melt quality and produces a low-H ₂ cast product, which represents an important step in achieving the required properties in the end product. Methods for treating metal melts with inert gases are known to those skilled in the art. In order to obtain a cast product low in H ₂ , the maximum value for hydrogen (H ₂ ) in the melt is preferably between 0.05 and 0.5 ml of H ₂ per 100 g of aluminum. A maximum value for hydrogen of less than 0.25 ml H ₂ /100g Al and in particular less than 0.15 ml H ₂ /100g Al is particularly preferred

The production of structural components using the aluminum alloy according to the invention is carried out by means of hot forming, preferably by means of drop forging of primary material preferably produced as described here. Heating to a forming temperature between 400°C and 570°C can be carried out in any way, preferably by means of a heating furnace or induction. Intermediate heating steps can take place between individual forming steps.

The forged structural component can be quenched directly from the forming heat - i.e. immediately after hot forming. The forged structural component can then be subjected to heat aging.

Alternatively, the forged structural component can be solution annealed, quenched and aged. The temperature during solution annealing approximately corresponds to the forming temperature for forging, i.e. between 400°C and 570°C.

Depending on the area of application or requirement profile, the raw material can be subjected to heat treatment before hot forming or the structural component obtained through hot forming. However, heat treatment is not absolutely necessary because the continuously cast raw material already has excellent properties for producing structural components using the forging process. The aluminum alloy according to the invention can, for example, be heat treated for 0.25 hours to 24 hours at 150 ° C to 260 ° C and then quenched in a suitable gaseous medium, for example air or inert gas, or in a suitable liquid medium, for example water or oil. The preferred heat treatment takes place at 1h to 10h and 170°C to 220°C, particularly preferably 2h to 7h at 180°C to 210°C with subsequent air cooling.

However, homogenization and/or extrusion of the raw material is not necessary. In particular, the primary material can be hot-formed, for example forged, immediately after continuous casting. Otherwise common process steps such as homogenization following continuous casting and extrusion following homogenization can be omitted

The heat-treated raw material is suitable for producing structural components that are used in heavily stressed and safety-relevant areas, e.g. vehicle construction. In addition to high strength, high ductility is required.

• Schmelzen der Legierungsbestandteile
• Einstellen der Legierung
• Schmelezreinigung
• direktabschreckendes Stranggießen eines Barrens
• Herstellen von Bolzen als Vormaterial durch Sägen des Barrens

Producing the raw material includes, for example, the following process steps:

• Melting of the alloy components
• Setting the alloy
• Melt cleaning
• direct quenching continuous casting of an ingot
• Producing bolts as raw material by sawing the billet

• Erwärmen des Bolzens
• Vorformen
• optional: Zwischenerwärmen
• Schmieden
• optional: Lösungsglühen
• Abschrecken
• Warmauslagern

The subsequent forging of a structural component includes, for example, the following process steps:

• Heating the bolt
• preforms
• optional: intermediate heating
• Forge
• optional: solution annealing
• Scare off
• Hot aging

It has been shown that forged parts made from the raw material according to the invention have a significantly reduced formation of coarse grains. This is in the Figures 3 and 4 shown.

Figure 3 shows a schematic representation of a cross section through a hot-formed structural component 30, which is made from a conventional raw material. A pronounced coarse-grain seam 32 and a likewise pronounced ridge area 34 can be seen.

Figure 3 illustrates the typical coarse grain development on a forged part using the usual extruded material.

Figure 4 In contrast, shows the significantly lower coarse grain development on a forged part 30 'using the raw material according to the invention, because the tendency to secondary recrystallization is significantly reduced with the raw material according to the invention. The all-round coarse grain seam 32 (see Figure 3 ) is omitted (see Figure 4 ). This results in a high surface quality of the forged parts.

The tables below show examples of various alloys examined for comparison with the claimed alloy. Si Fe Cu Mn Mg Cr Zn Ti Zr 6082 BFATmod. 0.91 0.12 0.45 0.46 0.78 0.17 <0.01 0.03 0.02 6082 default 0.98 0.17 0.08 0.52 0.83 0.16 <0.01 0.03 <0.01 6182 default see below see below see below see below see below see below see below see below see below V0a 0.94 0.15 <0.01 0.29 1.19 0.09 <0.01 0.03 0.08 V0b 0.95 0.14 0.09 0.29 1.18 0.09 <0.01 0.04 0.07 V0c 1.34 0.07 <0.01 0.49 1.19 0.11 <0.01 0.03 0.12 V0d 1.06 0.10 <0.01 0.58 1.23 0.15 <0.01 0.03 0.12 V0e 1.07 0.11 <0.01 0.82 1.25 0.15 <0.01 0.03 0.12 6182-A 1.27 0.11 <0.01 0.72 0.94 0.13 0.02 0.03 0.15 6182-B 1.28 0.12 <0.01 0.71 0.93 0.12 0.12 0.03 0.16 6182-C 1.26 0.27 <0.01 0.59 0.94 0.11 <0.01 0.03 0.14 6182-D 1.27 0.11 <0.01 0.62 0.97 0.13 <0.01 0.03 0.14 6182-E 1.27 0.12 <0.01 0.61 0.96 0.08 <0.01 0.04 0.15 Hot-formed chill casting Hot-formed HCM casting HBW5/250 T6 Rm Mpa Rp02 Mpa A% Rm Mpa Rp02 Mpa A% 6082 BFAT mod. 125 387 359 7.5 406 380 12.8 6082 default 101 V0a 101 311 278 5.1 V0b 110 307 291 2.5 342 320 12.5 V0c 117 V0d 114 v0e 114 6182-A 121 6182-B 121 6182-C 121 6182-D 125 367 342 6.2 391 366 11.4 6182-E 125

By definition, AA6182 alloys have the following composition: Al Cr Cu Fe Mg Mn Si Ti Zn Zr others, respectively others, altogether 95 - 97.85% <= 0.25% <= 0.10% <= 0.50% 0.70 - 1.2% 0.50 - 1.0% 0.90 - 1.3% <= 0.10% <= 0.20% 0.05 - 0.20% <= 0.05% <= 0.15%

• 1,2 bis 1,4 Gew.-% Silizium,
• 0,8 bis 1,2 Gew.-% Magnesium,
• 0,3 bis 1,2 Gew.-% Mangan,
• 0,1 bis 0,2 Gew.-% Zirkon,
• 0,01 bis 0,05 Gew.-% Titan,
• 0,08 bis 0,3 Gew.-% Eisen,
• 0,08 bis 0,2 Gew. % Chrom,
• max. 0,04 Gew.-% Zink, und
• max. 0,02 Gew.-% Kupfer.

The primary material, which is suitable for forging, for example, is produced from the aluminum alloy according to the invention, in which a melt 10 is produced with the following components:

• 1.2 to 1.4% by weight of silicon,
• 0.8 to 1.2% by weight magnesium,
• 0.3 to 1.2% by weight of manganese,
• 0.1 to 0.2% by weight zirconium,
• 0.01 to 0.05% by weight titanium,
• 0.08 to 0.3% by weight iron,
• 0.08 to 0.2% by weight of chromium,
• max. 0.04% by weight zinc, and
• max. 0.02% by weight copper.

In addition, a wire 12 made of an aluminum master alloy with 4.8 to 5.2% by weight of Ti and 0.8 to 1.2% by weight of B and the balance aluminum and unavoidable impurities is provided and immediately before the melt this passes through a water-cooled ring mold 14, added; please refer Figure 5 . The ring mold 14 is designed in such a way that the melt of the aluminum alloy is spaced from the solid components of the ring mold by a film of water and therefore does not touch any solid components of the mold during solidification. In addition, the melt passing through the ring mold 14 is completely exposed to the purest possible oxygen O ₂ from the outside in order to promote the formation of an edge layer made of oxidized aluminum alloy. The application of oxygen takes place before the application of water for liquid cooling.

When continuously casting an ingot with a diameter between 90 mm and 100 mm, the casting speed is, for example, between 150 mm/min and 200 mm/min.

The cooling water 16 for cooling the melt 10 as it passes through the ring mold 14 is guided in the circuit 18 in such a way that the temperature and the volume flow of the cooling water cause a maximum cooling rate of the melt when it solidifies of more than -25 K/s. Suitable cooling speeds are, for example, between -15 K/s and -35 K/s for a billet with a diameter between 90 mm and 100 mm, measured at a lateral distance of approximately 20 mm from a central longitudinal axis of the billet.

The water 16 used as coolant has a temperature between 20°C and 80°C. When continuously casting an ingot with a diameter between 90 mm and 100 mm at a casting speed between 150 mm/min and 200 mm/min, the cooling water volume flow is, for example, between 40 l/min and 80 l/min.

The cooling water volume flow is preferably 20 to 50 times larger than the volume flow of the cast aluminum alloy, with the cooling water volume flow for ingot diameters of the order of 50 mm preferably being approximately 25 times larger than the volume flow of the cast aluminum alloy and for ingot diameters in of the order of 100 mm is preferably about 40 times larger than the volume flow of the cast aluminum alloy. With a ring mold 14, for example, a cast strand 20 for ingots 22 with an outer diameter of 60 mm to 110 mm can be produced. At a melt temperature of approximately 650 ° C and a continuous casting speed v _G between 150 mm / min and 200 mm / min, the cooling water temperature T _K is preferably between 20 ° C and 80 ° C and the cooling water flow is preferably greater than 30 l / min.

After solidification, the billet 20 is separated into individual bolts 22, which can then be cold-formed or forged. Preferably, the diameter and cross-sectional shape - for example circular or oval - of the billet 20 is selected so that bolts obtained from the billet 20 have a volume that exceeds the volume of the cold-formed finished part as little as possible. The diameter and cross-sectional shape of the billet 20 can be adjusted by selecting a suitable ring mold 14.

A bolt 22 made from the aluminum alloy described here using the continuous casting process also described here has properties that make the bolt 22 suitable as a starting material for forging resilient structural components with high strength, a low tendency to corrosion and a high surface quality. Values typically achieved from this raw material are a tensile strength Rm>375 MPa, a yield strength Rp02>345 MPA, an elongation A>10% and a hardness>100 HB.

Structural components forged from the raw material can be deformation-relevant parts or fail-safe parts for motor vehicles, for example slip wedges, battery boxes, junction points, engine mounts, pivot bearings or wishbones.

Because of its reduced electrical conductivity, the primary material is also suitable for components of electrical machines in which eddy currents and the associated losses are to be reduced.

Reference symbol list

10

melt

12

wire

14

Ring mold

16

cooling water

18

Circulation

20

Ingots

22

bolt

30

Structural component

32

Coarse grain hem

34

Ridge area

Claims (15)

Process for producing raw material for forged structural components made of aluminum, comprising the steps: Producing an aluminum alloy with the components. 0.7 to 1.8% by weight, preferably 1.2 to 1.4% by weight, of silicon, 0.5 to 1.4% by weight, preferably 0.8 to 1.2% by weight, of magnesium, 0.3 to 1.2% by weight, preferably 0.4 to 0.8% by weight of manganese, 0.005 to 0.2% by weight, preferably 0.05 to 0.2% by weight of zirconium, 0.01 to 0.05% by weight titanium, 0.08 to 0.3% by weight iron, 0.08 to 0.2% by weight of chromium, max. 0.04% by weight zinc, and max. 0.1% by weight, preferably max. 0.02% by weight of copper where the ratio of silicon to magnesium is at least 1:0.8, by means of continuous casting, in which the melt is guided so that it has no contact with a solid surface when it solidifies. The method of claim 1, wherein producing the aluminum alloy comprises adding a titanium and boron containing master alloy for grain refinement. The method according to claim 2, wherein the aluminum master alloy contains 4.5 to 5.5% by weight of titanium and 0.8 to 1.2% by weight of boron and the balance aluminum and unavoidable impurities. Method according to at least one of claims 1 to 3, wherein the weight ratio of titanium to zirconium (Ti:Zr) in the aluminum alloy is between 1:4 and 1:6, preferably at least approximately 1:5. A method according to at least one of claims 1 to 4, wherein the weight ratio of iron to chromium to manganese (Fe:Cr:Mn) in the aluminum alloy is at least approximately 1:1:4. Method according to at least one of claims 1 to 5, wherein the aluminum alloy to form further finely divided dispersoids contains between 0.05 and 0.3% by weight of one or more elements of the so-called rare earths, preferably Sc, Er, La, Ce, Y and /or Yb, contains. Method according to at least one of claims 1 to 6, wherein the weight ratio of silicon to magnesium (Si:Mg) in the aluminum alloy is between 1:0.7 and 1:0.8, preferably at least approximately 1:0.75. Method according to at least one of claims 1 to 7, wherein during the solidification of the melt during continuous casting, contact of the melt and a solidified surface layer with a solid surface of the mold is prevented and liquid cooling of the melt is effected as it passes through a mold. Method according to claim 8, wherein the melt is liquid-cooled during its passage through the mold in such a way that the cooling rate of the solidifying aluminum alloy is greater than 25 Kelvin per second. Method according to claim 8 or 9, wherein the melt is exposed to an oxygen-containing gas mixture as it passes through the mold before and during the solidification of the surface layer. Method for producing a structural component, in which the primary material produced by the method according to one of claims 1 to 10 is hot-formed, in particular forged, into a structural component immediately after continuous casting, without any treatment for homogenizing the primary material between continuous casting and hot forming takes place. Method for producing a structural component according to claim 11, comprising hot aging and subsequent air cooling of the hot-formed structural component. Method according to claim 12, in which the aging takes place at 180°C to 210°C for 2h to 7h. Use of a raw material produced using a method according to at least one of claims 1 to 10 for extruding forging raw material for the vehicle industry. Use of a raw material produced using a method according to at least one of claims 1 to 10 for forging components for the vehicle industry.

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