EP4130306A1 - Method for producing an alloy strip made of recycled aluminium, method for producing a slug made of recycled aluminium, and recycled aluminium alloy - Google Patents

Abstract

The present invention provides a method for producing alloy strip from recycled aluminum in which up to 100% PCR aluminum can be used as secondary aluminum, resulting in a CO₂ saving of at least 89% compared to Use of primary aluminum is achieved and thus an important contribution to sustainability can be made. Furthermore, the present invention provides an alloy of recycled aluminum which has higher strength compared to the prior art, thereby enabling reduced wall thicknesses and thus significant savings in material and costs can be achieved through lighter end products.

Description

technical field

The present invention relates to a method for producing an alloy strip with a recycled aluminum content of up to 100%. In particular, the recycled aluminum is "post consumer recycled" (PCR) aluminum (according to DIN EN ISO 14021:2016). The alloy strip produced with a proportion of recycled aluminum is suitable for the production of slugs.

State of the art

A " slug " is a base material for the packaging industry, which is processed into tubes, cans (e.g. aerosol cans), bottles, but also a base material for the accessories industry, which is used for electronic housings, fuel filter housings, capacitor cups, heat sinks and the like is processed, and consists mainly of aluminum (according to DIN EN 570:2007). Slugs are manufactured in the desired shape, wall thickness and strength by strip casting and stamping. The further processing into cans, tubes, bottles, etc. takes place from slugs by cold extrusion. In most cases, slugs are stamped from pure aluminum or sawn from rods, but aluminum alloys with other alloying elements such as silicon and magnesium are sometimes also used (see Literature-1).

Depending on the area of application, slugs are divided into " packaging slugs " and " technical slugs ". Packaging slugs for tubes and cans, for example, are made exclusively from certain aluminum alloys (alloys of the 1000 and 3000 standards, eg EN AW 1050, EN AW 1070, EN AW 3102 and EN AW 3207) by strip casting and stamping. Technical slugs for, for example, electronics housings, fuel filter housings, condenser cups and heat sinks can be made from a wide variety of alloys (including alloys of the 1000, 3000 and 6000 standards).

When using pure aluminium, alloys with an aluminum content of at least 99.5% (EN AW 1050) or with an aluminum content of at least 99.7% (EN AW 1070) are mainly used (according to European standard EN 573-3). Materials of this type can easily be formed by extrusion and experience an increase in strength through cold forming during an extrusion process. Due to these advantageous properties, these alloys cover the majority of the total requirement in the area of packaging slugs and partly also in the area of technical slugs.

• Legierungen der 1000er Normen (z.B. EN AW 1050 und EN AW 1070) umfassen Legierungen aus Reinaluminium mit mindestens 99% Aluminium, wobei einige Legierungen dieser Gruppe für Verpackungsbutzen eingesetzt werden.
• Unter Legierungen der 2000er Normen werden Legierungen aus Aluminium und Kupfer, aber auch Legierungen, welche Mn und Mg enthalten, zusammengefasst.
• Legierungen der 3000er Normen (z.B. EN AW 3102) umfassen Legierungen aus Aluminium und Mangan.
• Legierungen aus Aluminium und Silizium werden als Legierungen der 4000er Normen bezeichnet. Aus diesen Legierungen werden zum Teil Getränkedosen hergestellt.
• Legierungen der 5000er Normen umfassen Legierungen aus Aluminium und Magnesium. Auch aus diesen Legierungen werden zum Teil Getränkedosen hergestellt.
• Legierungen aus Aluminium, Magnesium und Silizium werden als Legierungen der 6000er Normen bezeichnet. Diese Legierungen werden industriell am häufigsten (u.a. aufgrund der guten Umformbarkeit und Aushärtbarkeit) verwendet, aber sind jedoch für die Herstellung von Butzen nur bedingt geeignet.
• Legierungen der 7000er Normen umfassen Legierungen aus Aluminium und Zink. Diese Legierungen weisen jedoch eine schlechte Umformbarkeit und eine hohe Festigkeit, welche teilweise höher als Stahl ist, auf.
• Legierungen aus Aluminium und Eisen werden als Legierungen der 8000er Normen bezeichnet.
• Legierungen der 9000er Normen umfassen Sonderlegierungen, welche nicht unter die Definition einer der vorstehend genannten Gruppen fallen.

In general, aluminum alloys are divided into 9 groups.

• Alloys of the 1000 standards (e.g. EN AW 1050 and EN AW 1070) include alloys of pure aluminum with at least 99% aluminum, with some alloys of this group being used for packaging slugs.
• Alloys of the 2000 standards include alloys made of aluminum and copper, but also alloys containing Mn and Mg.
• Alloys of the 3000 standards (e.g. EN AW 3102) include alloys of aluminum and manganese.
• Alloys of aluminum and silicon are referred to as 4000 standard alloys. Some beverage cans are made from these alloys.
• Alloys of the 5000 standards include alloys of aluminum and magnesium. Some beverage cans are also made from these alloys.
• Alloys of aluminum, magnesium and silicon are referred to as 6000 standard alloys. These alloys are the most commonly used industrially (among other things because of their good formability and hardenability), but they are only conditionally suitable for the production of slugs.
• Alloys of the 7000 standards include alloys of aluminum and zinc. However, these alloys have poor formability and high strength, which is sometimes higher than steel.
• Alloys of aluminum and iron are referred to as 8000 standard alloys.
• 9000 standard alloys include special alloys that do not fall under the definition of any of the above groups.

A typical example of so-called "alloy slugs" are slugs made from aluminum alloys with a manganese content of 0.2% (EN AW 3102) or with a manganese content of 0.6% (EN AW 3207). Alloys of this type have a significantly higher basic hardness and are therefore more likely to be used for more special products that have to withstand higher internal pressure. Due to the higher strength of these alloys, thinner wall thicknesses can be achieved in aerosol cans and housings for technical applications.

The alloys are first produced in strips, which serve as the starting material for the production of slugs, for example. A typical process flow in the production of cast strip includes charging a furnace with feedstock, melting the material, alloying the melt, treating the melt, casting as strip, hot rolling the strip, cold rolling the strip, and coiling the strip.

Additional process sequences in the production of slugs from cast strip include stamping the slugs from an uncoiled strip, soft annealing the slugs, treating the surface of the slugs (e.g., blasting, scouring, tumbling, barrel finishing, etc.), packing the slugs, and finally storing the slugs.

For reasons of environmental protection and resource conservation, recycling material can be added to the manufacturing process. In principle, a return material that can be added during the production of an alloy can be divided into two types.

On the one hand there is the so-called " Waste before use " or " Post Industrial Recycled " (abbreviation: PIR). This term includes, for example, pressed screens from slug production with primary aluminum as the starting material.

On the other hand, there is the so-called " waste after use " or " post consumer recycled " (abbreviation: PCR, according to DIN EN ISO 14021:2016). This term includes used beverage cans from collection points (according to EN 13920-10 or waste code 15 01 04 or 19 12 03), sorting scrap containing aluminum from the "yellow bag" (according to EN 13920-9 or waste code 15 01 04 or 19 12 03 ), off-set sheets (according to EN 13920-2 or waste code 19 12 03), wire and cable scrap (according to EN 13920-3 or waste code 19 12 03), profile scrap (according to EN 13920-4 or -5 or Waste code 19 12 03), and processed aluminum dross from our own smelting with a secondary aluminum content > 60% (according to EN 13920-16).

The PCR mainly involves contaminated waste or scrap to which organic substances (e.g. oil, paint, residues from the filling, etc.) adhere. In general, there are two ways to process such material. Processing without pre-treatment is only possible if a melting furnace with the appropriate technology is used. Without using a furnace, a rework step is necessary. Contaminated scrap is remelted in a facility with the appropriate technology. Through the remelting Ingots are formed (so-called "sows "), which can then be used in the melting furnace of the rotary casting plant without any problems.

So far, however, PCR aluminum has hardly been processed as a recycle material. Industrially, alloys are mainly manufactured from PIR aluminum due to the following advantages over the use of PCR aluminum.

One of the most important reasons is formability. Pure aluminum alloys (e.g. EN AW 1050 and EN AW 1070) can be easily formed into cans and tubes. Due to this very good formability, materials made from such alloys are ideal starting materials for further processing for all can and tube manufacturers.

Furthermore, a reproducible process is crucial on an industrial scale. Pure alloys are to be made from primary aluminum of the same degree of purity. Primary metal is used because there are only a very limited number of types of scrap that have the same degree of purity.

Since an average of 40% process scrap is produced during stamping, it makes economic sense to keep the pure alloys in your own material cycle. If pure alloys are added to higher alloys, they are lost to the pure alloy cycle.

Pure alloys such as EN AW 1050 and EN AW 1070 have a similar chemical composition and can also be mixed if necessary, which results in simple logistics.

In general, when producing an alloy without using aluminum scrap, primary aluminum is used as the basis and alloyed with appropriate master alloys. For example, primary aluminum and an AlMn master alloy are used to achieve the EN AW 3102 alloy. If PIR aluminum is used as a return material, the mixture of input materials consists of Primary aluminum and a master alloy (e.g. AlMn to obtain the EN AW 3102 alloy) and, for example, pressed screens made from the same alloy (from a previous production).

In the production of the alloys EN AW 1050 and EN AW 1070, for example, a typical ratio of 60 to 70% primary aluminum (e.g. ingots of quality P1020 according to the DIN EN 576 standard) to 30 to 40% secondary aluminum (PIR Process scrap, e.g. stamped grid scrap from slug production, each made of the same alloy) is used.

In the production of the alloys EN AW 3102 and EN AW 3207, for example, a typical ratio of 60 to 70% primary aluminum (e.g. ingots in quality P1020 according to the DIN EN 576 standard) to 30 to 40% secondary aluminum (master alloys for alloys and PIR process scrap, e.g. lead frame scrap from slug production, each made from the same alloy).

Literature-2 ( EP 3 144 403 B1 ) discloses prior art aluminum alloys made by blending 10 to 60% PIR aluminum alloys (grades: 3105, 3004, 3003, 3103, or 3104) with 40 to 90% pure aluminum (grades 1070 and 1050).

problem

The input material for the production of aluminum alloys largely determines the level of CO ₂ emissions. The primary metal production from bauxite is very energy-intensive due to the electrolysis and therefore causes a high CO ₂ load. The CO ₂ load when using primary metal is therefore significantly higher than when using recycled material.

With regard to primary aluminum, the CO ₂ pollution in Europe in relation to produced primary aluminum is 6.7 kg(CO ₂ )/kg(Al) and primary aluminum used is 8.7 kg(CO ₂ )/kg(Al). Globally, the CO ₂ load from the use of primary aluminum is as high as 18 kg(CO ₂ )/kg(Al) (see Table 1, Literature-3).

In contrast to this, the CO ₂ load with regard to the secondary aluminum by remelting the cycle material is only 0.3 kg(CO ₂ )/kg(Al) (see Table 1, Literature-3). In addition, there are CO ₂ emissions, which arise from processes such as collecting, cleaning, sorting and transporting the cycle material, and can be estimated at approx. 0.625 kg(CO ₂ )/kg(Al) throughout Germany (see Table 1, Literature-4 ). Table 1: Overview of the CO₂ pollution of primary aluminum and secondary aluminum (see Literature-3 and Literature-4). CO ₂ pollution PRIMARY ALUMINUM [kg(CO ₂ )/kg(Al)] primary aluminum used (worldwide) 18 Primary aluminum produced (Europe-wide) 6.7 primary aluminum used (across Europe) 8.7 SECONDARY ALUMINUM Collecting, cleaning, sorting and transporting (throughout Germany) 0.625 possibly reworking the cycle material with organic adhesions; Conversion companies, certified according to ASI (Aluminum Stewardship Initiative)) 0.35

According to Table 1, the CO ₂ load of a starting material that is charged, for example, in a melting/casting furnace of a strip caster, is approx. 0.625 kg(CO ₂ )/kg(Al) in the case of direct use and in the case of an additionally processed material approx. 0.975 kg(CO ₂ )/kg(Al).

Compared to the primary aluminum used, there is a CO ₂ saving of at least 89% if an aluminum alloy is produced exclusively with secondary aluminium.

For example, the recycling rate for beverage cans containing aluminum is around 72% in Europe and around 99% in Germany. The deposit system introduced in Germany decades ago led to such a high proportion of PCR aluminum being recycled (see Literature-5).

This means that through the targeted use of types of recycling material available on the market, the CO ₂ balance, for example in the production of slugs, which is determined by the CO ₂ value of the primary material used by up to 90%, can be significantly reduced.

The increasing sensitivity of end users with regard to the sustainability of production and material cycles and the resulting CO ₂ balance calls for the increasing use of recycled material, especially PCR aluminum, in the production of aluminum alloys.

In the prior art, however, packaging slugs, which are used, for example, as a starting material for the production of cans and tubes, and technical slugs, which are used, for example, for the production of housings (e.g. fuel filter housings in cars) or similar, are mainly made of pure aluminum (alloys according to EN AW 1050A and EN AW 1070A). Such pure alloys can be produced without any problems using ingots and/or single-variety scrap, for example stamped skeletons. For example, a typical manufacturing process uses 60% primary aluminum and 40% lead frame.

In general, the lower the alloy content (approx. max. 0.5% total), the easier it is to set the standardized chemical composition through the use of primary aluminum. In addition, with such low alloy proportions, there is the advantage that the material can be formed more easily and the required forming force is therefore lower. This has a positive effect on tool wear.

For the reasons mentioned above, little has been changed in the prior art to the previous processes. The increasing environmental awareness and the heightened awareness of the sustainability of society is forcing the aluminum industry to break new ground, that is, for example to produce alloys from various recycling materials (non-standard materials with higher alloy proportions).

Summary of the invention and solution to the problem

The present method was invented in order to use the most sustainable possible material cycles in production and to produce products which are essentially produced from secondary material with minimal CO ₂ emissions.

The present invention solves the above problem and contributes to sustainability by using up to 100% of recyclable material types (secondary aluminium). The present invention advantageously uses types of cycle material that are currently sufficiently available on the market, since they occur as a result of the process and are therefore inevitable or have a short useful life. The present invention enables the use of different types of circuit material in different proportions with a wide tolerance (in terms of weight %).

Alloying elements and in particular the specific manganese content of the alloy according to the invention lead to an increase in strength, which enables new possibilities in the design of the wall thicknesses (in particular a lower wall thickness), and as a result of which considerable savings potential in the use of materials in the impact extrusion process and ultimately lighter end products (e.g. low empty can weight) can be achieved .

In a first aspect of the present invention, there is provided a method of making alloy strip from recycled aluminum or PCR aluminum provided, wherein no alloying elements are added and the method comprises the following steps.

First, the composition of individual batches of the starting materials, consisting of aluminum such as ingots ( "primary aluminum ") and aluminum cycle materials such as scrap before use (PIR) e.g. stamped skeleton and scrap after use (PCR) such as wire scrap or sows from various types of scrap, to achieve an alloy with the desired composition ("RAW-C","Recycled Aluminum Wutöschingen-Container "). The determination is based on a theoretical calculation of the chemical composition of the target alloy, with a mixing ratio being determined on the basis of the respective chemical compositions of the individual input material types used, in particular scrap types such as beverage cans, off-set sheet metal or wire scrap.

PCR aluminum, which is used in the production of an alloy, can be obtained in the form of sows as starting material from reworking foundries. For example, such a starting material can consist of 40% beverage cans and 60% off-set sheet metal, but separate remelting is also possible, so that the starting material in the form of sows consists of 100% beverage cans or 100% off-set sheet metal.

Such a determination or " batching " is calculated for each casting according to the materials used and the desired end product ("RAW" alloy).

Then, a strip casting line with the batches of the starting materials according to the previous step according to the shape of the starting material or input material (first, small-sized scraps such as stamping skeleton or cube-shaped wire scrap, and then the large-sized scraps such as sows (about 800kg/pc) ) loaded. Such a system can, for example consist of a separate melting furnace and a downstream casting furnace, or of a combined melting/casting furnace.

The mixture is then melted in the furnace. The energy can be supplied, for example, by a burner on the furnace roof. During the melting phases, the temperature is monitored and varied. The ceiling temperature before loading may have a temperature in a range of 700°C to 1000°C, preferably in a range of 800°C to 900°C, more preferably in a range of 820°C to 870°C, and in particular has preferably a temperature of 850 °C. The ceiling temperature during melting may have a temperature in a range of 800°C to 1000°C, preferably in a range of 900°C to 1000°C, and more preferably in a range of 950°C to 1000°C a temperature of 990° C. is particularly preferred.

The resulting melt is treated and cleaned, for example, by salt, standing and purge gas treatments to bind non-metallic impurities such as oxides. Molten aluminum is cleaned by ceramic filters on the way to the casting plant.

The resulting melt is analyzed for chemical composition, with a first sample taken after the furnace is fully charged (melt sample) and a second sample taken before pouring (release sample).

The ceiling temperature during casting may be a temperature in a range of 600°C to 900°C, preferably a temperature in a range of 700°C to 800°C, and more preferably a temperature in a range of 700°C to 750°C have, and particularly preferably has a temperature of 720 ° C, the temperature of the metal, depending on the alloy, a temperature in a range from 700 ° C to 800 ° C, preferably a temperature in a range from 710 ° C to 740°C; and more preferably has a temperature of 730°C. The casting temperature depends on the material and is usually above 660 °C. The Casting temperature may have a temperature in a range from 660°C to 900°C, preferably in a range from 660°C to 800°C, more preferably in a range between 690°C and 750°C, and most preferably has a temperature of 730 °C.

The liquid mixture is preferably cast into a tape by rotary casting. Casting takes place continuously via a casting wheel. A casting wheel can be made of steel or copper, for example, and have a diameter of 1000 to 1800 mm. The temperature of the strip emerging from the plant depends, inter alia, on the strip cross-section and the type of casting wheel, and can be a temperature in a range from 400 °C to 600 °C, preferably a temperature in a range from 450 °C to 550 °C, more preferably a temperature in a range from 470°C to 530°C, and particularly preferably has a temperature of 500°C. A strip with a thickness of 16 to 32 mm, for example, is formed from liquid aluminum in the casting gap between the casting strip and the casting wheel.

Subsequent hot rolling of the strip occurs above the recrystallization temperature of the composition. The recrystallization temperature depends on the material, and thus a temperature during hot rolling can be in a range of 300°C to 600°C, preferably a temperature in a range of 320°C to 500°C, more preferably a temperature in a range of 370° C to 470 °C can be selected. A temperature of 440° C. is particularly preferably selected during hot rolling. This step reduces the initial thickness by 25% to 50%.

After hot rolling, the strip must be cooled to a maximum of 50°C, more preferably to a temperature not higher than 40°C, and most preferably to a temperature not higher than 30°C, by suitable cooling. The cooling gradient is preferably between 800° C. and 1200° C./min, more preferably between 850° C. and 1150° C., particularly preferably between 900° C. and 1100° C.

After the strip has been cold-rolled, a thickness of between 5 mm and 12 mm is achieved, for example.

In a second aspect of the present invention, there is provided a method of producing a recycled aluminum or PCR aluminum slug, wherein no alloying elements are added separately, the method comprising the steps of the first aspect described above and the steps below.

"Added separately" in this context means that, apart from the types of aluminum pre-material used, which already have alloying elements, no elementary elements of the Al alloy are added. In the case of old beverage cans, for example, the types of primary material used have a total alloy content of approx. 2% to 3%. Since the primary material types bring sufficient alloying elements into the melt, additional alloying by adding alloying elements is not necessary.

The slugs are produced by stamping the cast strip produced using a suitable stamping tool.

In addition, the slugs are heat treated to remove work hardening caused by rolling and stamping. In the heat treatment, a temperature in a range of 400 °C to 600 °C, preferably a temperature in a range of 420 °C to 580 °C, more preferably a temperature in a range of 450 °C to 550 °C can be selected, and most preferably the temperature is 520°C.

After the slugs have cooled to room temperature, the slug surface is roughened, for example by blasting, scouring and tumbling, in order to enable the slugs to absorb sufficient lubricant for the cold extrusion process.

In a third aspect of the present invention there is provided a "RAW" alloy produced by the method according to the first or second aspect. This alloy has the following composition: Si: 0.05 to 0.40% by weight, Fe: 0.20 to 0.60% by weight, Cu: 0.03 to 0.20% by weight, Mn: 0.16 to 0.50% by weight, Mg: 0.03 to 0.20% by weight, Cr: 0.01 to 0.03% by weight, Zn: 0.01 to 0.06% by weight, Ti: 0.01 to 0.03% by weight, Zr: ≤ 0.03% by weight, Pb: ≤ 0.005% by weight, Al: Rest.

In a fourth aspect of the present invention, there is provided an alloy "RAW-C25" according to the third aspect. This alloy has the following composition: Si: 0.05 to 0.12% by weight, Fe: 0.20 to 0.30% by weight, Cu: 0.03 to 0.07% by weight, Mn: 0.16 to 0.22% by weight, Mg: 0.03 to 0.07% by weight, Cr 0.005 to 0.03% by weight, Zn 0.01 to 0.04% by weight, Ti 0.005 to 0.03 wt%, Zr: ≤ 0.03% by weight, Pb: ≤ 0.005% by weight, and Al: balance.

In a fifth aspect of the present invention, there is provided a specific alloy "RAW-C25" according to the fourth aspect. This alloy has the following composition: Si: 0.12% by weight, Fe: 0.24% by weight, Cu: 0.05% by weight, Mn: 0.21% by weight, Mg: 0.06% by weight, Cr: 0.005% by weight, Zn: 0.0325% by weight, Ti: 0.01% by weight, Zr: 0.00% by weight, Pb: 0.0005% by weight, Al: Rest.

In a sixth aspect of the present invention, there is provided an alloy "RAW-C50" according to the third aspect. This alloy has the following composition: Si: 0.10 to 0.20% by weight, Fe: 0.28 to 0.40% by weight, Cu: 0.05 to 0.10% by weight, Mn: 0.20 to 0.30% by weight, Mg: 0.05 to 0.10% by weight, Cr: 0.005 to 0.03% by weight, Zn: 0.01 to 0.05% by weight, Ti: 0.005 to 0.03% by weight, Zr: ≤ 0.03% by weight, Pb: ≤ 0.005% by weight, and Al: balance.

In a seventh aspect of the present invention, there is provided a specific alloy "RAW-C50" according to the sixth aspect. This alloy has the following composition: Si: 0.14% by weight, Fe: 0.32% by weight, Cu: 0.07% by weight, Mn: 0.30% by weight, Mg: 0.10% by weight, Cr: 0.01% by weight, Zn: 0.03% by weight, Ti: 0.01% by weight, Zr: 0.00% by weight, Pb: 0.001% by weight, Al: Rest.

In an eighth aspect of the present invention, there is provided an alloy "RAW-C95" according to the third aspect. This alloy has the following composition: Si: 0.15 to 0.40% by weight, Fe: 0.35 to 0.60% by weight, Cu: 0.10 to 0.20% by weight, Mn: 0.25 to 0.50% by weight, Mg: 0.08 to 0.20% by weight, Cr: 0.005 to 0.03% by weight, Zn: 0.01 to 0.06% by weight, Ti: 0.01 to 0.03% by weight, Zr: ≤ 0.03% by weight, Pb: ≤ 0.005% by weight, and Al: balance.

In a ninth aspect of the present invention, there is provided a specific alloy "RAW-C95" according to the eighth aspect. This alloy has the following composition: Si: 0.16% by weight, Fe: 0.45% by weight, Cu: 0.10% by weight, Mn: 0.43% by weight, Mg: 0.15% by weight, Cr: 0.01% by weight, Zn: 0.03% by weight, Ti: 0.02% by weight, Zr: 0.00% by weight, Pb: 0.002% by weight, Al: Rest.

In a tenth aspect of the present invention, PCR aluminum is used to produce an alloy according to any aspect of the third to ninth aspects produced by the method according to the first or second aspect. PCR aluminum includes aluminum scrap, and/or used beverage cans, and/or sorting scrap containing aluminum, and/or offset sheet metal, and/or wire and cable scrap, and/or profile scrap, and/or reworked aluminum dross your own melt.

In an eleventh aspect, the proportion of the PCR aluminum according to the tenth aspect is between 10% and 100%, between 20% and 100%, between 30% and 100%, between 40% and 100%, between 50% and 100%, between 60% and 100%, between 70% and 100%, between 80% and 100%, between 90% and 100%, or between 95% and 100%.

Detailed description of the invention

The present method was invented in order to use the most sustainable possible material cycles in production and to produce products which are essentially produced from secondary material with minimal CO ₂ emissions.

The method and the alloys produced thereby ("RAW-C" alloys) of the present invention have advantageous effects in that a proportion of up to 100% of the PCR aluminum can be used and good availability for the continuous supply of the recycle types the market exists. The alloys of the present invention result in higher strength in the case of thin-walled housings and variable, good formability in the cold forging process, as a result of which tool wear during stamping remains within an economically justifiable range.

In the conventional process for manufacturing the slugs (according to EN AW 1050A and EN AW 1070A), the average material flow consists of ingots (quality: P1020) and stamped skeleton (according to EN AW 1050A and EN AW 1070A), with the stamped skeleton going to the furnace after the stamping process is supplied again during charging ("charging") (see Fig. 1).

The general chemical composition of mainly used aluminum alloys EN AW 1050A, EN AW 1070A, and EN AW 3102 (according to EN 573-3) is as follows:
- Aluminum alloy according to EN AW 1050A: Si: ≤ 0.25% by weight, Fe: ≤ 0.40% by weight, Cu: ≤ 0.05% by weight, Mn: ≤ 0.05% by weight, Zn: ≤ 0.07% by weight, Ti: ≤ 0.05% by weight, and Al: balance. - Aluminum alloy according to EN AW 1070A: Si: ≤ 0.20% by weight, Fe: ≤ 0.25% by weight, Cu: ≤ 0.03% by weight, Mn: ≤ 0.03% by weight, Zn: ≤ 0.07% by weight, Ti: ≤ 0.05% by weight, and Al: balance. - Aluminum alloy according to EN AW 3102: Si: ≤ 0.40% by weight, Fe: ≤ 0.70% by weight, Cu: ≤ 0.10% by weight, Mn: 0.05 to 0.40% by weight, Zn: ≤ 0.03% by weight, Ti: ≤ 0.10 wt%, and Al: balance.

A typical chemical composition of EN AW 1050A alloy is: Si: 0.079% by weight, Fe: 0.258% by weight, Cu: 0.001% by weight, Mn: 0.001% by weight, Mg: 0.001% by weight; Zn: 0.005% by weight; Ti: 0.011% by weight, Cr: 0.001% by weight; Zr: 0.002% by weight; Pb: 0.002% by weight; and Al: 99.62% by weight

A typical chemical composition of EN AW 1070A alloy is: Si: 0.048% by weight, Fe: 0.161% by weight, Cu: 0.001% by weight, Mn: 0.001% by weight, Mg: 0.001% by weight, Zn: 0.003% by weight, Ti: 0.015% by weight, Cr: 0.001% by weight, Zr: 0.001% by weight, Pb: 0.002% by weight, and Al: 99.74% by weight

A typical chemical composition of alloy EN AW 3102 is: Si: 0.058% by weight, Fe: 0.180% by weight, Cu: 0.001% by weight, Mn: 0.245% by weight, Mg: 0.000% by weight, Zn: 0.007% by weight, Ti: 0.013% by weight, Cr: 0.001% by weight, Zr: 0.001% by weight, Pb: 0.002% by weight, and Al: 99.47% by weight

In the process according to the invention for producing slugs, an average material flow consists of stamped skeleton, scrap beverage cans, offset sheet metal and other types of scrap, with the stamped skeleton being returned to the furnace during charging ("charging") after the stamping process. It is particularly advantageous that the production method according to the invention can be used to produce an aluminum alloy which consists of up to 100% recycled material (see FIG. 2).

• Exemplary embodiments of a material flow

In a material flow of the first embodiment ("RAW-C-I"), mixed, old beverage cans (according to EN 13920-10) and mixed stamped scrap from EN AW 1050A and 1070A (according to EN 13920-2) are supplied as circulating materials.

In a material flow of the second embodiment ("RAW-C-II"), mixed, old beverage cans (according to EN 13920-10), offset sheet metal (according to EN 13920-2), wire and cable scrap (according to EN 13920- 3), and mixed lead frame scrap from EN AW 1050A and 1070A (according to EN 13920-2) fed in as circulating materials.

The chemical composition of the alloy produced by this material flow according to the first embodiment is outside the composition according to the EN 573-3 standard.

The chemical composition of an alloy resulting from the material flow of the first embodiment ("RAW-CI") is as follows (determined by optical emission spectroscopy or by means of a spark spectrometer): Si: 0.203% by weight, Fe: 0.320% by weight, Cu: 0.067% by weight, Mn: 0.344% by weight, Mg: 0.081% by weight, Zn: 0.020% by weight, Ti: 0.02% by weight, Cr: 0.011% by weight, Zr: 0.002% by weight, Pb: 0.002% by weight, and Al: 98.89% by weight.

The chemical composition of an alloy resulting from the material flow of the second embodiment ("RAW-C-II") is as follows (determined by optical emission spectroscopy): Si: 0.187% by weight, Fe: 0.479% by weight, Cu: 0.102% by weight, Mn: 0.414% by weight, Mg: 0.076% by weight, Zn: 0.057% by weight, Ti: 0.02% by weight, Cr: 0.011% by weight, Zr: 0.003% by weight, Pb: 0.003% by weight, and Al: 98.61% by weight.

Table 2 shows the mechanical properties of slugs produced from the above starting materials under the same conditions. Table 2: Comparison of the mechanical properties of the alloys from the material flows of the first and second embodiment (RAW-CI and RAW-C-II) with the base alloys EN AW 1050A and 1070A and 3102, where Rp0.2 is the yield strength and Rm is the tensile strength (Tensile test according to DIN EN ISO 6892 and hardness test according to DIN EN ISO 6506). alloy Condition Rp0.2 [MPa] Rm [MPa] hardness EN AW 1050A (according to EN 485) O (soft) min 20 65 - 95 20 HBW EN AW 1050A (typical values) O (soft) 52 75 22 EN AW 1070A (according to EN 485) O (soft) min 15 60 - 90 18 HBW EN AW 1070A (typical values) O (soft) 40 70 20 EN AW 3102 (according to EN 570) O (soft) - - 23 EN AW 3102 (typical values) O (soft) 52 73 22 RAW CI O (soft) 62 98 27 RAW-C-II O (soft) 67 106 35

The results shown in Table 2 show that the hardness of the slugs in the annealed condition in the case of the first embodiment heats (RAW-CI) compared to EN AW 1050A decreased by 23% and 35% respectively compared to EN AW 10170A 35% and 50% higher, respectively, and compared to EN AW 3102 is 17% and 23% higher, respectively. In addition, the yield strength of the RAW-CI alloy is at least 10 MPa or 19% higher and the yield strength at least 23 MPa or 31% higher than the typical values of the base alloys.

Furthermore, the results of Table 2 show that the hardness of the slugs in the annealed condition in the case of the heats of the second embodiment (RAW-C-II) compared to EN AW 1050A by 59 and 75% respectively, compared to EN AW 1070A 75 and 94% higher, and compared to EN AW 3102 is 52 and 59% higher. In addition, the yield strength of the RAW-C-II alloy is at least 15 MPa or 29% higher and the yield strength at least 31 MPa or 41% higher than the typical values of the base alloys.

Due to the higher strength and associated higher resistance to internal pressure, the wall thicknesses of cans can be reduced by the alloys of the present invention. A lower wall thickness brings the advantage of weight savings, which leads to a reduction in CO ₂ during transport. Less CO ₂ is already emitted during the production of the primary material due to a reduced use of material, which is a further significant advantage of the present invention with regard to environmental pollution.

The increased strength of RAW-C alloys is due to the higher Mn content, which has a recrystallization-inhibiting effect. Since the content of the strength-enhancing alloying element Mn in old beverage cans is 0.8 wt% to 1.0 wt%, those according to the invention have a higher Mn content than alloys of standards EN AW 1050 and EN AW 1070, and even partially has a higher Mn content than the EN AW 3102 alloy, which has a Mn content of approx. 0.3% by weight.)

The chemical composition results from the proportions of different types of cycle material and their chemical composition. The availability of a recycle material depends on the production volume, the useful life, and the return rate in the material cycle.

The mechanical properties of the alloy, such as formability, depend primarily on the chemical composition. The limits of individual alloying elements are selected in such a way that a composition suitable for the respective application can be selected in accordance with the requirements for mechanical properties.

In general, an alloy of the present invention has the chemical composition: Si: 0.05 to 0.40% by weight, Fe: 0.20 to 0.60% by weight, Cu: 0.03 to 0.20% by weight, Mn: 0.16 to 0.50% by weight, Mg: 0.03 to 0.20% by weight, Cr 0.01 to 0.03% by weight, Zn 0.01 to 0.06% by weight, Ti 0.01 to 0.03% by weight, Zr: ≤ 0.03% by weight, Pb: ≤ 0.005% by weight, and Al: Rest.

• Exemplary embodiments of an alloy First embodiment of an alloy ("RAW-C25")

In general, an alloy of the first embodiment ("RAW-C25") has a post-anneal hardness of 24+3 HB and the following composition: Si: 0.05 to 0.12% by weight, Fe: 0.20 to 0.30% by weight, Cu: 0.03 to 0.07% by weight, Mn: 0.16 to 0.22% by weight, Mg: 0.03 to 0.07% by weight, Cr 0.005 to 0.03% by weight, Zn 0.01 to 0.04% by weight, Ti 0.005 to 0.03 wt%, Zr: ≤ 0.03% by weight, Pb: ≤ 0.005% by weight, and Al: balance.

A specific example of an alloy of the first embodiment ("RAW-C25") has the following composition of starting materials:
- 75% ingots (P1020A according to DIN EN 576) with the composition: Si: 0.08% by weight, Fe: 0.15% by weight, Cu: 0.00% by weight, Mn: 0.00% by weight, Mg: 0.00% by weight, Cr: 0.00% by weight, Zn: 0.03% by weight, Ti: 0.00% by weight, Zr: 0.00% by weight, Pb: 0.00% by weight, and Al: remainder; and
- 25% beverage can scrap with the composition: Si: 0.24% by weight, Fe: 0.52% by weight, Cu: 0.19% by weight, Mn: 0.84% by weight, Mg: 0.32% by weight, Cr: 0.02% by weight, Zn: 0.04% by weight, Ti: 0.02% by weight, Zr: 0.00% by weight, Pb: 0.002% by weight, and Al: rest.

The alloy of the first embodiment ("RAW-C25") resulting from this specific composition has the following composition (determined by optical emission spectroscopy): Si: 0.12% by weight, Fe: 0.24% by weight, Cu: 0.05% by weight, Mn: 0.21% by weight, Mg: 0.06% by weight (taking into account the burn-up), Cr: 0.005% by weight, Zn: 0.0325% by weight, Ti: 0.01% by weight, Zr: 0.00% by weight, Pb: 0.0005% by weight, and Al: rest.

Second embodiment of the alloy ("RAW-C50")

In general, an alloy of the second embodiment ("RAW-C50") has a hardness of 28+2 HB and the following composition: Si: 0.10 to 0.20% by weight, Fe: 0.28 to 0.40% by weight, Cu: 0.05 to 0.10% by weight, Mn: 0.20 to 0.30% by weight, Mg: 0.05 to 0.10% by weight, Cr: 0.005 to 0.03% by weight, Zn: 0.01 to 0.05% by weight, Ti: 0.005 to 0.03% by weight, Zr: ≤ 0.03% by weight, Pb: ≤ 0.005% by weight, and Al: rest.

A specific example of an alloy of the second embodiment ("RAW-C50") has the following composition of starting materials:
- 50% ingots (P1020A according to DIN EN 576) with the composition: Si: 0.08% by weight, Fe: 0.15% by weight, Cu: 0.00% by weight, Mn: 0.00% by weight, Mg: 0.00% by weight, Cr: 0.00% by weight, Zn: 0.03% by weight, Ti: 0.00% by weight, Zr: 0.00% by weight, Pb: 0.00% by weight, and Al: remainder; - 35% beverage can scrap with the composition: Si: 0.24% by weight, Fe: 0.52% by weight, Cu: 0.19% by weight, Mn: 0.84% by weight, Mg: 0.32% by weight, Cr: 0.02% by weight, Zn: 0.04% by weight, Ti: 0.02% by weight, Zr: 0.00% by weight, Pb: 0.002% by weight, and Al: remainder; and
- 15% off-set sheets with the composition Si: 0.08% by weight, Fe: 0.45% by weight, Cu: 0.001% by weight, Mn: 0.03% by weight, Mg: 0.01% by weight, Cr: 0.001% by weight, Zn: 0.019% by weight, Ti: 0.01% by weight, Zr: ≤ 0.00% by weight, Pb: 0.002% by weight, and Al: rest.

The alloy of the second embodiment ("RAW-C50") resulting from this specific composition has the following composition (determined by optical emission spectroscopy): Si: 0.14% by weight, Fe: 0.32% by weight, Cu: 0.07% by weight, Mn: 0.30% by weight, Mg: 0.10% by weight (taking into account the burn-up), Cr: 0.01% by weight, Zn: 0.03% by weight, Ti: 0.01% by weight, Zr: 0.00% by weight, Pb: 0.001% by weight, and Al: rest.

Third embodiment of the alloy ("RAW-C95")

In general, an alloy of the third embodiment ("RAW-C95") has a hardness of 32+4 HB and the following composition: Si: 0.15 to 0.40% by weight, Fe: 0.35 to 0.60% by weight, Cu: 0.10 to 0.20% by weight, Mn: 0.25 to 0.50% by weight, Mg: 0.08 to 0.20% by weight, Cr: 0.005 to 0.03% by weight, Zn: 0.01 to 0.06% by weight, Ti: 0.01 to 0.03% by weight, Zr: ≤ 0.03% by weight, Pb: ≤ 0.005% by weight, and Al: balance.

A specific example of an alloy of the third embodiment ("RAW-C95") has the following composition of starting materials (composition: 95% recycle and 5% primary metal):
- 5% ingots (P1020A according to DIN EN 576) with the composition: Si: 0.08% by weight, Fe: 0.15% by weight, Cu: 0.00% by weight, Mn: 0.00% by weight, Mg: 0.00% by weight, Cr: 0.00% by weight, Zn: 0.03% by weight, Ti 0.00% by weight, Zr: 0.00% by weight, Pb: 0.00% by weight, and Al: remainder; - 50% beverage can scrap with the composition: Si: 0.24% by weight, Fe: 0.52% by weight, Cu: 0.19% by weight, Mn: 0.84% by weight, Mg: 0.32% by weight, Cr: 0.02% by weight, Zn: 0.04% by weight, Ti: 0.02% by weight, Zr: 0.00% by weight, Pb: 0.002% by weight, and Al: remainder; - 35% off-set sheets with the composition: Si: 0.08% by weight, Fe: 0.45% by weight, Cu: 0.001% by weight, Mn: 0.03% by weight, Mg: 0.01% by weight, Cr: 0.001% by weight, Zn: 0.019% by weight, Ti: 0.01% by weight, Zr: ≤ 0.00% by weight, Pb: 0.002% by weight, and Al: remainder; and
- 10% wire scrap with the composition: Si: 0.11% by weight, Fe: 0.25% by weight, Cu: 0.03% by weight, Mn: 0.03% by weight, Mg: 0.03% by weight, Cr: 0.03% by weight, Zn: 0.03% by weight, Ti: 0.03% by weight, Zr: 0.00% by weight, Pb: 0.003% by weight, and Al: rest.

The alloy of the third embodiment ("RAW-C95") resulting from this specific composition has the following composition (determined by optical emission spectroscopy): Si: 0.16% by weight, Fe: 0.45% by weight, Cu: 0.10% by weight, Mn: 0.43% by weight, Mg: 0.15% by weight (taking into account the burn-up), Cr: 0.01% by weight, Zn: 0.03% by weight, Ti: 0.02% by weight, Zr: 0.00% by weight, Pb: 0.002% by weight, and Al: rest.

With the method of the present invention, up to 100% of different types of cycle material or recycling waste (see § 1 Recycling Management Act), which are currently sufficiently available on the market, can inevitably occur or have a short useful life, an important one, by using different proportions contribution to sustainability can be made.

The alloys of the present invention offer the advantage of higher strength compared to the prior art. Due to the possibility of low wall thicknesses or higher possible internal pressures with the same wall thickness and the associated lower use of materials, considerable savings can be achieved in production and ultimately in the end products.

bibliography

Literature-1:

Horst Häusler, "The aluminum industry - formative industrial power of the municipality of Wutöschingen" in "Wutöschingen - then and now", local administration Wutöschingen, 2006, page 235, note 6 ;

Literature-2:

EP 3 144 403 B1 ;

Literature-3:

Environmental Profile Report, Life-Cycle inventory data for Aluminum Production and Transformation Process in Europe, EAA, February 2018 ;

Literature-4:

" Life cycle assessment of various packaging systems for beer IFEU", Institute for Energy and Environmental Research Heidelberg GmbH, 2010

Literature-5:

Association of the Aluminum Industry eV; FS7: aluminum beverage can, GDA, 2017, homepage: http://www.aluinfo.de/download.html?did=105 (accessed on July 29, 2021 )

Claims (11)

Process for producing an alloy strip from recycled aluminum, in particular PCR aluminum, with no alloying elements being added separately and the process comprising the following steps: a) Determining the respective chemical composition of individual batches of starting materials, which include pure aluminum and/or aluminum cycle materials such as process scrap, sows and wire scrap, in order to achieve an alloy with the desired chemical composition, based on the respective chemical compositions of the starting materials by theoretical calculating the composition of the target alloy, a mixing ratio is determined; b) charging a strip casting furnace with the charges of the starting materials in a mixing ratio determined by the previous step, the roof temperature of the furnace prior to charging preferably being between 700°C and 1000°C; c) melting the mixture in the furnace, wherein the roof temperature of the furnace during the melting is preferably between 800°C and 1000°C; d) treating and purifying the melt, preferably by filtration, salt, standing and purge gas treatments, to remove non-metallic impurities; e) casting the liquid mixture into a strip, preferably by rotary casting, the casting temperature preferably being greater than 660°C; f) hot rolling of the strip above the recrystallization temperature of the composition, preferably in a temperature range between 300°C and 600°C, whereby the thickness of the strip is preferably reduced by 25 to 50%; g) cooling the strip, preferably to a temperature not higher than 50°C with a cooling gradient preferably between 800°C and 1200°C/min; and h) cold rolling the strip, preferably to a strip thickness of between 5 and 12 mm. Method for producing a slug from recycled aluminum, in particular PCR aluminum, wherein no alloying elements are added separately and the method comprises the following steps in addition to steps a) to h) according to claim 1: i) stamping the ribbon to produce a slug; j) heat treating the slug, preferably in a temperature range between 400°C and 600°C, to relieve work hardening; k) cooling the slug; and 1) Treating the surface of the slug, preferably by blasting, scrubbing and tumbling, to roughen the slug surface and allow the slugs to absorb adequate lubricant. Alloy "RAW" produced by the method according to claim 1 or 2, wherein the alloy has the following composition: Si: 0.05 to 0.40% by weight, Fe: 0.20 to 0.60% by weight, Cu: 0.03 to 0.20% by weight, Mn: 0.16 to 0.50% by weight, Mg: 0.03 to 0.20% by weight, Cr: 0.01 to 0.03% by weight, Zn: 0.01 to 0.06% by weight, Ti: 0.01 to 0.03% by weight, Zr: ≤ 0.03% by weight, Pb: ≤ 0.005% by weight, Al: Rest. Alloy "RAW-C25" according to claim 3, wherein the alloy has the following composition: Si: 0.05 to 0.12% by weight, Fe: 0.20 to 0.30% by weight, Cu: 0.03 to 0.07% by weight, Mn: 0.16 to 0.22% by weight, Mg: 0.03 to 0.07% by weight, Cr 0.005 to 0.03% by weight, Zn 0.01 to 0.04% by weight, Ti 0.005 to 0.03 wt%, Zr: ≤ 0.03% by weight, Pb: ≤ 0.005% by weight, and Al: balance. Alloy "RAW-C25" according to claim 4, wherein the alloy has the following composition: Si: 0.12% by weight, Fe: 0.24% by weight, Cu: 0.05% by weight, Mn: 0.21% by weight, Mg: 0.06% by weight, Cr: 0.005% by weight, Zn: 0.0325% by weight, Ti: 0.01% by weight, Zr: 0.00% by weight, Pb: 0.0005% by weight, Al: Rest. Alloy "RAW-C50" according to claim 3, wherein the alloy has the following composition: Si: 0.10 to 0.20% by weight, Fe: 0.28 to 0.40% by weight, Cu: 0.05 to 0.10% by weight, Mn: 0.20 to 0.30% by weight, Mg: 0.05 to 0.10% by weight, Cr: 0.005 to 0.03% by weight, Zn: 0.01 to 0.05% by weight, Ti: 0.005 to 0.03% by weight, Zr: ≤ 0.03% by weight, Pb: ≤ 0.005% by weight, and Al: balance. Alloy "RAW-C50" according to claim 6, wherein the alloy has the following composition: Si: 0.14% by weight, Fe: 0.32% by weight, Cu: 0.07% by weight, Mn: 0.30% by weight, Mg: 0.10% by weight, Cr: 0.01% by weight, Zn: 0.03% by weight, Ti: 0.01% by weight, Zr: 0.00% by weight, Pb: 0.001% by weight, Al: Rest. Alloy "RAW-C95" according to claim 3, wherein the alloy has the following composition: Si: 0.15 to 0.40% by weight, Fe: 0.35 to 0.60% by weight, Cu: 0.10 to 0.20% by weight, Mn: 0.25 to 0.50% by weight, Mg: 0.08 to 0.20% by weight, Cr: 0.005 to 0.03% by weight, Zn: 0.01 to 0.06% by weight, Ti: 0.01 to 0.03% by weight, Zr: ≤ 0.03% by weight, Pb: ≤ 0.005% by weight, and Al: balance. Alloy "RAW-C95" according to claim 8, wherein the alloy has the following composition: Si: 0.16% by weight, Fe: 0.45% by weight, Cu: 0.10% by weight, Mn: 0.43% by weight, Mg: 0.15% by weight, Cr: 0.01% by weight, Zn: 0.03% by weight, Ti: 0.02% by weight, Zr: 0.00% by weight, Pb: 0.002% by weight, Al: Rest. Use of PCR aluminum to produce an alloy according to any one of claims 3 to 9 prepared by the method of claim 1 or 2, wherein the PCR aluminum comprises one or more selected from: used beverage cans, sorting scrap containing aluminum, off-set sheets, wire and cable scrap, profile scraps, and reworked aluminum dross from our own melt. Use of PCR aluminum according to claim 10, wherein the proportion of the PCR aluminum is between 10% and 100%.