ES2954874T3 - Reliable High Extrusion Rate Production Method for Recycling Friendly Soft Aluminum Alloys with High Corrosion Resistance Powder Coating - Google Patents

Abstract

The present invention relates to a reliable high-speed extrusion production method for a recyclable aluminum soft alloy of the 6060X type, which in addition to Al, Mg and Si contains significant amounts of Cu, Zn, Fe and Mn as alloying elements, followed by a pretreatment with an alkaline or acid etching of at least 1.0, preferably 2 grams/m2, resulting in powder coated aluminum profiles with very high corrosion resistance after powder coating for the most common conversion (Ti, Zr, Ti/Zr, pre-anodization, etc.) powder coating systems available on the market. (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

Reliable High Extrusion Rate Production Method for Recycling Friendly Soft Aluminum Alloys with High Corrosion Resistance Powder Coating

field of invention

The present invention relates to a reliable high-speed extrusion production method for the recycling-friendly soft aluminum alloy of type 6060X, which in addition to Al, Mg and Si contains significant quantities of Cu, Zn, Fe and Mn as alloying elements, followed by pretreatment with an alkaline or acid etch of at least 1.0, preferably 2 grams/m2 producing powder coated aluminum profiles with very high corrosion resistance after powder coating for the Most common conversion coating (Ti, Ti,Zr, pre-anodizing, etc.) available on the market.

Background of the invention

Soft aluminum alloys are typically used for the production of components with high surface quality for use in decorative applications, by forming the alloy into a wide variety of shapes through the use of extrusion. Soft aluminum alloys are further suitable for use in a wide variety of non-structural, non-critical applications, such as architectural applications, extrusions such as window and door frames, retaining walls, storefronts, skylight architectural applications, doors, accessories workshop, irrigation pipes, sports equipment, non-structural applications in the aeronautical industry, road transportation, rail transportation, etc. residential buildings and other buildings. Soft aluminum alloys offer good corrosion resistance, good machinability, good weldability, good formability and acceptable strength. They are heat-treatable and can be artificially aged. In many applications, after extrusion, the soft aluminum alloy is subjected to etching and anodizing. Soft aluminum alloys can also be subjected to powder coating or any other suitable surface treatment. Components or parts made of soft aluminum alloys typically take the form of sheets or plates, wires, rods, bars, extrusions, structural shapes, tubes, pipes, liners, sheets, etc.

The main alloying elements contained in soft aluminum alloys can include Mg, Fe, Si, Cu, Mn, Cr, Zn, Ti. The most common soft aluminum alloy in Europe is alloy 6060, which contains Mg and Si as alloying elements and has a minimum tensile strength of 215 MPa. The tensile strength and other mechanical properties to which these 6060 soft alloys must respond are described in Extrusion Norm (EN) EN 755-1 and EN 755-2.

Products made from soft 6060 aluminum alloys currently require strict control of the alloy composition, particularly in relation to the presence of traces of alloying elements. This imposes the incorporation of high amounts of primary aluminum into recycled aluminum in the practical production of aluminum alloys, since the removal of elements from an alloy composition is complicated, expensive and requires a lot of time and risks to increase the costs of use. recycled aluminum to a level that makes it unattractive.

An EN AW 6060 aluminum alloy that meets the European EN 573-3 in relation to its composition may typically contain the following alloying elements in the indicated concentrations (in % by weight with respect to the weight of the alloy composition):

Cu < 0.10

Zn < 0.15

Mn < 0.10

0.10 < Fe < 0.30

0.35 < Mg < 0.60

0.30 < Yes < 0.60

An EN AW 6063 aluminum alloy that meets the European standard in relation to its composition may typically contain the following impurities in the indicated concentrations (in % by weight with respect to the weight of the alloy composition):

Cu < 0.10

Zn < 0.10

Mn < 0.10

Fe < 0.35

0.45 < Mg < 0.60

0.20 < Yes < 0.60

In practice, commercially available primary alloys 6060R and 6063R (R = restrictions) contain the following elements in the indicated concentrations (in % by weight with respect to the weight of the alloy composition):

Cu < 0.02

Zn < 0.02

Mn < 0.04

0.16 < Fe < 0.22

0.45 < Mg and S i < 0.50 for 215 MPa alloys

0.50 < Mg and Si < 0.55 for 245 MPa alloys.

The concentration of Fe in soft alloys of these types is restricted to a maximum of 0.22% by weight, preferably less than 0.19% by weight, due to its negative impact on the extrusion rate or speed and negative impact on the surface quality of extruded products due to the presence of heavy buildups at higher iron levels. The concentration of Mn is generally restricted to a maximum of 0.04 wt%, preferably below 0.01 wt%, because Mn is known to interfere with the recrystallization of aluminum during extrusion, and lead to the formation of large grains with an irregular shape and/or a fiber structure and a dull surface after anodization. Furthermore, it has been found that the presence of too high amounts of Mn increases the cooling rate and the formation of large Mg ² Si precipitates, which have an adverse effect on the mechanical properties of the extruded product. The Cu concentration is generally limited to a maximum of 0.02 wt%, preferably below 0.01 wt% to minimize the risk of corrosion problems occurring, which can deteriorate surface quality and give lead to color or gloss problems after anodizing. Cu is also known to have a negative impact on extrusion speed. The concentration of Zn is generally limited to a maximum of 0.02 wt%, preferably below 0.01%, in view of its negative impact on the anodizing behavior of soft alloys due to preferential grain etching.

In addition to these problems mentioned, there is a great fear in the market of using soft alloys with a greater amount of these elements, and then in particular concentrations of Zn and Cu. Cu should be absolutely less than 0.02% by weight, considering the fact that all known wrought aluminum copper (2XXX) alloys have serious corrosion problems.

The reason for these restrictions dates back to 1990, in this period a large amount of Russian aluminum entered the Western European market with higher trace elements, such as Cu, Zn and Fe. In this period there were a large number of claims on the market of buildings with filiform corrosion. Research at the University of Gent, Professor Defrcq, showed a clear relationship between these trace elements and the appearance of filiform corrosion. Since that period, 6060R alloys with restricted trace elements and close tolerances in chemical composition were used as described above. After introducing these 6060R restricted soft alloys, the problematic filiform corrosion completely disappeared.

In the prior art, JP H10 306336 describes the extrusion of a 6-series Al alloy comprising 0.45 to 0.9% Mg, 0.2 to 0.6% Si, <= 0.1 % Cu, <= 0.35 % Fe as impurities, the rest Al. This alloy billet is heated to 500 to 590 °C for 2 to 24 h, cooled to <= 250 °C, reheated and subsequently extruded from a way to regulate the temperature of the material, from 560 to 590 °C at the exit of the extrusion dies. D2 further describes etching and neutralization or peeling.

The growing demand for aluminum-based products and the increasing globalization of the aluminum industry have contributed to increasing aluminum alloy consumption. In view of this, and in view of the remarkable ability of aluminum and its alloys to be recycled repeatedly with minimal risk of loss of product integrity and loss of material through oxidation, additional growing demand for the use recycled aluminum in the future. The use of recycled aluminum allows savings in the exploitation of virgin aluminum sources, significant energy savings can be achieved, as well as emission reductions compared to the production of primary aluminum. European estimates suggest that the mass of solid waste generated per ton of recycled aluminum is approximately 95% lower than that of the primary metal. Therefore, the secondary aluminum stream from recycled aluminum has been identified as an attractive source for the production of aluminum alloys.

Recycled aluminum can originate from a variety of alloys, which in turn can originate from a fairly wide variety of applications. Recycled aluminum can originate, for example, from cast products typically made of 4XXX-alloys which generally have a high Si content, from rolling products typically made from 5XXX alloys which generally contain a fairly high percentage of Mg, from extruded profiles made of other alloys such as 2XXX-alloys with a high Cu content, 3XXX alloys with a high Mn content or 7XXX alloys that generally contain high percentages of Mg and Zn. Often, at the end of their life cycle, these products are collected together and a detailed classification of different aluminum alloys is usually carried out. Therefore, recycling can lead to higher levels of certain elements in recycled aluminum, such as Mg, Si, Zn, Cu, Fe, Mn, etc. Additionally, when recycling demolished products containing aluminum parts, such as parts taken from buildings or vehicles, the recycled parts may show increased levels of Fe, Mn, Cu and Zn. As a result, these elements are at risk of ending up in applications that make use of recycled aluminum, even when performance grading techniques are employed.

Following European legislation in 2017, it is no longer permitted to use a stable Cr®+ conversion layer for powder coating, which today requires strict control of the alloy composition, in particular in relation to the presence of traces. of alloying elements Fe, Mn, Zn and Cu. This imposes the incorporation of high amounts of primary aluminum into recycled aluminum in the practical production of aluminum alloys, since the removal of elements from an alloy composition is complicated, expensive and requires a lot of time and risks to increase the costs of use. recycled aluminum to a level that makes it unattractive. Additionally, in 2018 and 2019, some cases of filiform corrosion were observed on the market with a recycled aluminum diluted from primary aluminum. The actual cause of the return of filiform corrosion is not clear, but as a consequence the use of recycled aluminum is under severe pressure.

It is an object of the present invention to provide a method of producing extruded soft alloys possessing the presence of higher concentrations of these elements and the absence of the prohibited Cr 6+ conversion layer without scarifying corrosion behavior in particular filiform corrosion. .

Brief description of the figures

With specific reference now to the figures, it is emphasized that the details shown are by way of example and for purposes of illustrative discussion of the different embodiments of the present invention only. They are presented in order to provide what is considered the most useful and simple description of the principles and conceptual aspects of the invention. In this regard no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention. The description taken with the drawings makes it apparent to those skilled in the art how the various forms of the invention can be incorporated into practice.

Figure 1: Typical Mg and Si contents of soft aluminum (6060X, 6060 6063), medium 6005A, 6101) and hard alloys (6061, 6082).

Figure 2: Schematic cross-sectional view of a device for manufacturing a soft extruded aluminum alloy (100) using the method according to the invention.

Figure 3A: Schematic cross-sectional view of an extruded façade profile, indicating where the temperature was measured and maintained at 559°C, in this case near the hottest point of the profile (roof zone), (dashed area is hot spot (hottest area of the profile)

Figure 3B: Schematic cross-sectional view of an extruded window profile, indicating where the temperature was measured and maintained at 550 °C, in this case most distant from the hottest point of the profile (shaded area) (dashed area is dot hot (hottest area of the profile)

Detailed description of the invention

Typical recyclable friendly soft alloys contain alloying elements in the following exemplified ranges, especially the trace element at the upper end of the tolerance field (in weight % with respect to the weight of the alloy composition) compared to restricted alloys ( supra ):

Trace Alloy Elements

Min 0.015 - 0.15

Cu 0.015 - 0.25

Zn 0.015 - 0.25

Faith 0.18 - 0.35

Main alloy elements

Yes 0.40 - 0.60

Mg 0.25 - 0.45

Others up to 0.03 and a total of 0.15, the rest Al

The first large deviation in the trace alloying elements is iron. Due to recycling, these values can be much higher than 0.22 wt% and as a result expect a very negative impact on extrusion speed. It is also known if the iron is in the alpha condition (round shape) and not in the beta condition (needle), the negative impact on the extrusion speed is negligible. As known in document WO 98/42884 dated October 1, 1998. It is recommended that Mn be optimally 0.04 - 0.07% by weight to achieve optimal beta-alpha conversion during the homogenization process for Avoid tearing or reduction in extrusion speed during extrusion. With these Mn values, the negative impact of Fe is of minor importance.

The second large deviation in trace alloy elements is Zn. Due to recycling, these values are well above 0.02 and as a result there is a negative impact on anodizing behavior due to preferential grain etching. As known in document US-3594133 of publication date 20/ H 1971, it is recommended that Cu = 0.97 Zn to avoid PGE during alkaline etching. Recent research has confirmed this theory in document WO2017 /093304 A1 dated 6/8/2017. However, higher levels of Cu can result in filiform corrosion of coated profiles.

As a result, all these additional alloying elements in recycling friendly soft alloys give a higher amount of surface problems during extrusion and as a result a lower extrusion speed and a lower reliable extrusion process compared to available primary soft alloys. in practice. The most well-known surface defects are, for example, pick-up (hard inclusions in the extrudate), cracks or tears (interruptions in the extrudate), rough surface (scratches in the extrudate with Rt more than 9 μm) and filiform corrosion.

Currently, all methods for evaluating surface quality are based on the press operator's controls at the exit of the die. To produce high quality surfaces, it is a very complex and difficult process. In case of poor surface quality operator will reduce the extrusion speed or lower billet temperature. Very often the problem is not solved, and production stops. Often the reason is not clear, and multiple restarts are needed.

One of the parameters controlled by the press operator is the temperature of the extruded aluminum part that has left the extrusion die. This temperature control is absolutely necessary given the fact that, due to the higher concentrations of trace elements, there are a large amount of intermetallic particles in these recyclable friendly alloys, particularly low fusion particles, which can cause melting. incipient and can lead to a sharp drop in extrusion speed. Measuring the temperature of the extruded aluminum part that has left the extrusion die is quite complex. Temperature measurements by mechanical contact are very cumbersome and are not possible without damaging the profile. Theoretical temperature calculations using finite element process energy input, such as SMS's CADEX system, are unreliable and were not satisfactory. Non-contact infrared measurements are very difficult due to the high emissivity of aluminums, although there has been much progress in recent years, making this innovative new solution possible. Additionally, you need to find the hottest point (hot spot) of the profile which is very often on the inside of the profile where it is impossible to measure. It is the main reason that today it is still the operator who is responsible for setting the most important pressure parameters.

All of these issues result in the industry hesitant to use recycling-friendly aluminum alloys if high surface quality is needed.

By making use of this state-of-the-art non-contact infrared temperature measurement equipment and measuring the temperature to an easy-to-measure area and determining the correlation between this area and the hottest area of the profile (hot spot), it has been discovered which is capable of producing 6060X type aluminum soft alloy profiles which have very high alloying elements and trace elements, with very high extrusion speed and high surface quality. (See extrusion test runs).

Using the method of the present application, regardless of the pretreatment solutions used in the industry before aluminum coating, surface problems such as filiform corrosion of this type of pre-treated extruded recyclable friendly type soft alloys 6060X were solved with the presence of higher concentrations of trace elements and the absence of the prohibited Cr 6+ conversion layer.

To achieve such an excellent surface quality and to allow parts to be produced with the desired high extrusion speed or speed, the process of the present invention comprises the steps of creating an inert atmosphere at the die outlet and to control and maintain the temperature of the extruded aluminum. at the output of the matrix in an interval of temperature between 500 and 600 °C, preferably between 550 and 59 °C, followed by etching pretreatment with an alkali or acid. Surprisingly, using such conditions, only a low grade etch of at least 1.0, preferably 2 grams/mm2 is already sufficient to obtain a soft aluminum alloy with excellent surface qualities and free of surface problems such as filiform corrosion in the coating. of dust.

The present invention relates to a process for producing an extruded part, wherein a quantity of a recyclable friendly 6060X aluminum alloy having a composition as described in the present description above, is heated to a softening temperature that is below of the melting temperature of the soft aluminum alloy in order to soften the alloy, after which the softened alloy is forced through an extrusion die at an extrusion temperature until it exits the extrusion die at a extrusion die output so that an extruded alloy part is produced. The process of the present invention is characterized in that the extruded alloy part is brought into contact with a flow of an inert gas at the position where it exits the die, and maintains the temperature at the die exit within the range prescribed in the present memory.

The inert gas used in the process of the present invention may be any inert gas considered suitable by the person skilled in the art, for example nitrogen, helium, argon, etc. or mixtures of two or more thereof. More preferably, liquid nitrogen is used given the massive expansion of liquid nitrogen when it comes into contact with the extrudate.

Contact of the extruded alloy with a flow of inert gas has the effect that the surface of the extruded part exiting the die becomes inert while still hot. Bringing the extruded alloy into contact with a flow of an inert gas as it exits the extrusion die makes it possible to minimize the risk of unwanted oxidation of the extruded alloy that is still at a high temperature. A further improvement of this invention is to force the flow of the inert gas as close as possible to the outlet by drilling holes or slots in the die support plate and to force the inert gas in the immediate vicinity of the die outlet. Using this technique, the consumption of this expensive gas could be greatly reduced. Introducing the inert gas as close as possible to the outlet also helps control the temperature of the extrudate with a cooling effect on the extrudate. It has been observed that the presence of additional elements such as Fe, Mn, Zn and Cu in soft aluminum alloys of Fe, Mn, Zn and Cu has an impact on the solidification temperature of the extruded material. The solidification temperature is the temperature at which the first liquid phase is observed in the material, and in recyclable friendly 6060X soft aluminum alloys this temperature is reduced. Near the solidification temperature, the material cannot withstand active shear forces in the matrix and begins to crack. The recyclable friendly aluminum alloy starts cracking much earlier due to its lower solidification temperature. The injection of the inert gas, the immediate proximity of the die outlet will result in a local cooling effect, and prevents the cracks caused by the lower solidification temperature of the recyclable friendly 6060XS aluminum soft alloys.

The present invention enables products to be produced from aluminum alloys with the conventional mechanical properties required by the intended applications, for example, the building or construction industry, regardless of the presence of unwanted elements, such as Fe, Mn, Zn and Cu , which are supposed to negatively affect visual quality and extrusion speed. By strictly controlling the temperature of the extruded part at the die outlet, extruded parts with a desired surface quality and desired mechanical properties can be produced. Thus, the high extrusion speeds conventionally used in the art can be maintained, regardless of the presence of high trace alloying elements in the soft aluminum alloy composition of this invention. The surface quality obtained from these soft aluminum alloys that may contain recycled aluminum, having a chemical composition as described above and executed with production methods as described above, is completely within the standards as described in Qualanod (2017 ) and Qualcoat (2013).

As detailed below, in a preferred embodiment, the die surfaces in the profile forming (bearing) area should comprise a white or composite layer (such as a gas nitride die with a nitride layer or dies coated with CrN with a hard Cr-N layer) of minimum 5 μm, preferably about 8 μm with a diffusion layer of about 0.15 to about 0.30 mm. Other parameters that could influence the surface quality of the extruded alloy are the quality of the billet and the temperature and time treatment (TTT) after extrusion.

The billet preferably has a beta-alpha iron conversion of at least 90%, and is free of hard particle inclusions, such as AhO ₃ , TiB, Fe2O3, AhO ₃ , SiO ² , etc., with a maximum particle size 50 μm.

To ensure that small precipitates below 1 μm after aging the TTT after extrusion preferably comprise a one- or two-stage aging protocol, comprising a cooling rate of approximately 3 °C/s and maintaining the extruded profile at a temperature of about 160 to about 180 °C for at least 8 h; in one embodiment at about 175°C for about 8 hours; in another embodiment at approximately 165 ° C for approximately 12 hours. Together with the aforementioned control of temperature with an inert atmosphere in the die exiting these TTTs after extrusion treatments, it results in an extruded 6060X type soft aluminum alloy with a minimum tensile strength of 215 N/ mm2 with hardening precipitates that are less than 1 μm.

Expressed differently, in a preferred embodiment the method of the present application allows through it;

- Strict control of the temperature at the exit of the extrusion press after an inert atmosphere;

- The TTT mentioned above after the extrusion process; and

- in particular when using nitrided dies, to produce defect-free surfaces after pretreatment by extrusion and etching even when

- 6060X alloy composition is used with trace elements of higher amounts of Fe, Mn, Cu and Zn,

As further detailed in the examples hereinafter, the appropriate pretreatment of the soft 6060X alloy thus obtained, such as a state-of-the-art acid etching or alkaline etching (at least 1.0 or preferably 2 grams/m2) , and in case of alkaline etching followed by a standard acid peeling to avoid enrichments of Zn, Cu, Mn on the surface. This step of etching the inerted extruded alloy is preferably followed by the deposition of a good stable conversion layer on Ti, Zr, Ti/Zr base or an anodization layer of at least 4 μm is also used. As a final stage, a single or two-layer powder coating (very popular in the Netherlands) is placed of typical 70 μm.

After all these standard and popular pretreatments for powder coating, only the A rate results for FFC (FiliForme Corrosion Test, a specially developed test to see how resistant powder coated aluminum profiles are against filiform corrosion or filamentary corrosion after powder coating) and A s S tests (Saline Spray Test with Acetic Acid: a general test developed to test the corrosion behavior of powder-coated aluminum profiles is obtained (very popular in automotive).

The present invention further provides a device 100 for manufacturing a recycling-friendly soft alloy having a composition as described above 10. A preferred embodiment of a device suitable for producing an extruded part of a soft aluminum alloy obtainable using the method as described above, is shown in Figure 2. The device comprises a container 8, with container liners 7 into which the aluminum alloy or billet 2 to be extruded is pushed. Often the vessel 8 will be heated to maintain the temperature of the soft aluminum alloy or billet 2 at a desired level. The soft aluminum alloy or billet has been heated to softening temperature by a billet furnace. The device also comprises a forwarding system 1 for forwarding the softened aluminum alloy or billet 2 of the container into, through and out of an extrusion die 3. The forwarding systems used in this type of devices are generally known to the expert and generally comprise a hydraulic system with a hydraulic press 50. As pressure is applied, the billet 2 is crushed against the die 3, becoming shorter and wider until its expansion is restricted by full contact with the walls casing of the vessel 7 where the billet 2 is contained. Then, as the pressure increases, the soft (but still solid) metal 2 has no place to go and begins to squeeze through the formed hole or die opening 33 of the die 3 to emerge on the other side from the exit of the die 23 as a fully formed profile 10. The front part of the hydraulic system will usually comprise a ram 9 or a pusher, which forces the aluminum alloy or billet 2 through the die opening 33 into the die cavity 43.

The extrusion die 3 comprises a die opening 33 in the shape of the part 10 to be extruded. The extrusion die 3 may also comprise a die cavity 43 bounded by the die backs 12 and die support parts 13. Depending on the size of the billet and the die opening 33, a continuous extrusion of / - 50 meters with each press stroke. The newly formed extruded part 10 is supported on a runout conveyor or table 4 as it exits the die 3.

As close as possible to the die opening 33 of the extrusion die 3, preferably within the die cavity 43 delimited by the die backs 12 and the die support parts 13 of the extrusion die 3, a gas Inert gas 15 is supplied from an inert gas supply 5 such that the extruded aluminum alloy portion 10 exiting the die opening 33 is contacted or surrounded by an inert gas 15 to create an inert atmosphere in the die cavity 43, at least at the position where the newly extruded hot aluminum alloy leaves the extrusion die 3. Suitable inert gases are well known to the skilled person and include nitrogen, helium, argon, etc., but preferably used nitrogen. More preferably, a flow of nitrogen obtained from the expansion of liquid nitrogen is made, so that in addition to providing an inert atmosphere, a cooling effect can also be achieved. In an alternative embodiment, CO ² gas that originates from the expansion of solid CO ² can be used. The person skilled in the art will be able to adapt the flow of inert gas so that a desired inerting and, if possible, cooling is achieved at the position where the aluminum alloy emerges from the opening of the die 33. In this way , the risk of unwanted oxidation of the extruded metal alloy can be reduced, and extruded aluminum parts can be obtained whose surface quality can be improved. Therefore, the device of this invention also comprises a device 5 for supplying an inert gas to the die opening 33. This can be achieved in various ways, for example by supplying inert gas at the position of the die opening. matrix 33. In an alternative embodiment, Inert gas may be supplied along holes or slots in the support plate 13 and/or the die backs 12 present behind the die opening (33) of the die 3 towards and to the outlet of the die 23.

As mentioned above, and attributing to the inerting of the environment at the position where the aluminum alloy exits the die opening 33, in a preferred embodiment the die surfaces in the profile forming area (bearings) should comprise a white compound or layer (such as a gas nitride matrix or CrN-coated matrices that permanently produce a nitride layer or a Cr-N hard coating) of at least 5 μm, preferably about 8 μm with a layer diffusion of approximately 0.15 to approximately 0.30 mm.

Depending on the nature and composition of the alloy, the extruded part 10 may be cooled after it has left the die 3, either by natural cooling in the environment or by the use of air or water cooling, to ensure that the properties Desired metallurgical properties are obtained after aging.

The device of this invention may further preferably comprise a temperature sensor 6 to measure the temperature of the extruded part 10 that has left the extrusion die 3 and determine that the temperature of the extruded part is maintained in the range between 500 and 600 °C; in particular between 550 °C and 595 °C. To measure temperature, various devices known to those skilled in the art can be used, for example, an infrared camera. After being subjected to the extrusion process, the extruded part is transferred to a cooling table for time temperature treatment (TTT) after extrusion treatment.

The present invention further relates to a device for producing an extruded part of a soft aluminum alloy composition as described above, wherein the device may comprise a heating device 11 known in the art (such as a heating coil that surrounds the container) to heat the container and maintain the pre-softened and preheated soft aluminum alloy at its elevated temperature, a pusher for pushing the softened alloy into an extrusion die to extrude the alloy into a desired shape, a device for supplying a inert gas at the exit of the die, a device for measuring the temperature of the die, a device for measuring the temperature of the extruded part, a device for measuring the temperature of the extruded part that has left the extrusion die, and controlling the temperature of the extruded part in the range between 500 and 600 °C; in particular between 550 °C and 595 °C.

Examples

Extrusion test operations

The table below (Table 1) provides a comparison between the extrusion operations of a series of tested alloys (Table 1A) including a primary classical aluminum soft alloy (Alloy 1) with two typical environmentally friendly soft alloys (Alloy 2 & 3 ) used in the method according to the invention. For each material, two test operating conditions were compared (Table 1B), respectively applying on one side a temperature control according to the method of the present invention and, on the other hand, omitting this temperature control during the extrusion process. . Three parameters were monitored during these operations. Two of them related to surface problems that cause production to stop immediately (Direct surface problems) or before the target volume for surface problems is reached (Indirect surface problems). The last parameter is the average ram speed that can be maintained without affecting the quality of the extruded soft aluminum alloy.

These test operations show that for classical alloys the need for temperature control for an experienced operator is not really necessary. These alloys have a wide stable process window showing an acceptable ram speed of at least 8 mm/s, with a small number of surface problems regardless of the operating conditions used.

Table 1A - Composition of the alloys tested

eaco is from e sayo Mn Mg Zn

Extrusion conditions

The billets were pressed through a die cavity as shown schematically in Figure 2, comprising dies (3) having a Nitride layer with the following characteristics; - a layer of compound or white layer of 5 μm, preferably 8 μm; and - a diffusion layer of 0.15 mm preferably 0.30 mm.

In these experiments, the temperature measurement of the extruded profiles is always performed at the same location on the top of the profile where a stable temperature measurement is possible. In these tests, the AMETEK Land SPOT AL EQS pyrometer and SPOT actuator were used. The equipment temperatures (maximum outlet temperature) were 5-55 °C. Figure 3 A - near the hot spot and the set temperature (maximum outlet temperature) was 550 °C - far from the hot spot, as indicated in Figure 3B.

The maximum outlet temperature of the extruded profiles was determined after wrapping with liquid nitrogen at 1 m from the die outlet (Max. Ex.Temp.)

Table 1B - Results of extrusion tests

Contrary to classical alloys with low concentrations of trace elements, where temperature control at the exit of the die is apparently not required, for soft recycling-friendly alloys (Alloy 2 & 3), the counter ram speed is reduced with more than 10% and stops caused by superficial problems more than double.

For these recyclable soft alloys, the process window is small, showing a clear effect of temperature on each of the parameters mentioned above as evident from the following table (Table 1C). In a series of test operations, extrusion was performed under an inert atmosphere and only the set temperature was changed, processing respectively 15 °C below the set temperature or 15 °C above the set temperature. At lower temperatures there is a clear impact on ram speed, but at higher temperatures, there is a drastic increase in both direct and indirect surface problems.

From the above experiments, it follows that for recyclable-friendly alloys, good temperature control is absolutely recommended to achieve good results. To a certain extent, this requirement for good temperature control can be explained by the difference in solidification temperature between classical alloy 1 and the recyclable friendly alloys 2 and 3 (Table 2).

Table 1C-of alloys tested during production under different temperature control conditions

Table 2. Solidification temperature of the tested alloys.

Filiform corrosion test - Test 1

For soft aluminum alloys, high trace concentrations of alloying elements such as Cu are not recommended. For example, in certain countries, Cu concentrations above 0.02 are prohibited and etch rates below 2.0 grams/m ² are not permitted following qualicoat specifications, particularly for quality near the sea. It is generally accepted that these criteria regarding the presence of trace alloying elements and the amount of etch rates are necessary to prevent filiform corrosion of soft aluminum alloys. The extruded profiles obtained using the extrusion method exemplified above according to the invention were tested to determine their resistance to filiform corrosion. The most common pretreatments on the market were used and tested, namely;

• Alkaline / acid etching - Alkaline etching (minimum 1 gram/m ² ), Acid flaking (HNO ³ solution) and as a conversion of an ALFICOAT Ti conversion layer (Alufinisch);

• Alkaline / acid etching with high etching rates (50-70 grams/m ² ) and as conversion preanodization 4-10 μm (Preano); and

• Double acid etching with etching speed 2 grams/m ² and as a conversion layer Precoat Ti - conversion layer Zr (Precoat)

Table 3: Pretreated soft aluminum alloy samples tested

The previously treated materials (summarized in Table 3 above) were subsequently exposed in triplicate to the filiform corrosion (FFC) test (Qualicoat, modified ISO 4623-2).

- The samples were scratched in 2 directions of length 10 or 2 x 5 cm;

- HCl (37%, 1.19 g/cm3) is dripped along the scratches for ±1 min;

- The acid is removed with a piece of cloth;

- After 1 h at room temperature, samples were applied in a Climate Controlled chamber and exposed to 82% ±5% humidity and 40°C ±2°C temperature using the following test cycle.

Pretreatment of samples : Exposed after scratch application and HCl treatment Scratch application: 2 scratches on each sample (w: 1 mm, crf. QC FFC test) Relevant test surface : Plate surface, excl. edges

Exposure Angle: Horizontal Position

Test Program: Specific

Evaluation type: Final evaluations only

Surprisingly, and as summarized in Table 4 below, even at a low etch rate, even recycle alloys with high concentrations of alloy trace elements pass the entire filiform corrosion test and receive the highest A rating.

Table 4: Filiform Corrosion Test Results

Acetic Acid Salt Spray Test - Test 2

To confirm the corrosion resistance observed for the extruded recycle and soft 6060X alloys obtained using the extrusion method according to the invention, additional testing has been performed on a further series of test alloys with even higher Cu concentrations (Table 5)

Table 5 - Compositions of tested alloys

Extrusion conditions

The extrusion conditions were the same as above, billets were pressed briefly with an average ram speed of 8 mm/s through a die cavity as shown schematically in Figure 2, comprising the dies (3) that They have a Nitride layer with the following characteristics; - a layer of compound or white layer of 5 μm, preferably 8 μm; and - a diffusion layer of 0.15 mm preferably 0.30 mm. In these experiments, the temperature measurement of the extruded profiles is always performed at the same location on the top of the profile where a stable temperature measurement is possible. In these tests, the AMETEK Land SPOT AL EQS pyrometer and SPOT actuator were used. The temperatures set at these locations were 550 °C in case of a window profile and 595 °C in case of a façade profile. See Figures 3A and 3B Temperature time treatment after extrusion to ensure small precipitates after aging:

Max.Ex.Temp. always above 500 °C

Cooling speed 3 °C/s

Aging 8 h at 175 °C

Pretreatments

The pretreatment conditions were the same as before.

Corrosion tests

In addition to the filiform corrosion (FFC) test (same as above), the pretreated materials were also exposed in triplicate to the acetic acid salt spray test (AASS), a general test developed to test the corrosion behavior of materials. materials after powder coating (very popular in automotive). In this sample test, the samples are placed in a closed chamber and exposed to a Continuous indirect spray of salt water solution, prepared in accordance with the requirements of the test standard (Annex 1 ASTM G85) and acidified (pH 3.1 - 3.3) by the addition of acetic acid. This spray is established on the samples at a rate of 1 -2 ml/80 cm2 / hour, at a chamber temperature of 35 °C. Test results

The results are summarized below for the different pretreatment methods and both the FCC and AASS tests, where an A rate indicates that all three samples pass the test.

All samples tested received an A grade in the FCC test as well as the AASS test.

All samples tested received an A grade in the FCC test as well as the AASS test.

All samples tested received an A grade in both the FCC test and the AASS test.

This additional test confirms that 6060X alloys as defined herein and extruded by using the method according to the invention, result in extruded profiles with high corrosion resistance, even in the absence of the conversion layer. Cr 6+ prohibited.

It is also important to mention that in all the previous tests the final powder coating was executed with two different types of powder coatings, Interpon Akzo Noble and Axalta, and that no significant differences were observed during all the corrosion tests between both powder coatings. , indicating that the positive effect on surface problems is independent of the powder coating used, and dictated by the extrusion and pretreatment method used.

Claims (11)

1. A method for manufacturing a flexible pretreated 6060X type aluminum alloy (10) comprising, in addition to Mg and Si, in an amount between 0.2 and 0.6% by weight, also Fe, Mn, Zn and Cu as alloying elements each independently in an amount of between 0.015 and 0.35% by weight of the total weight; said method comprises; Yo. heating said soft aluminum alloy of type 6060X to extrude at a softening temperature and ii. forcing the thus softened 6060X type aluminum alloy (2) through the die opening (33) of an extrusion die (3) with a ram speed of at least 7 mm/s; iii. collecting the extruded flexible type 6060X aluminum alloy (10) emerging from the die opening (33) through the die outlet (23); iv. inerting the flexible extruded type 6060X aluminum alloy (10) at the position where the soft extruded aluminum alloy (10) emerges from the opening of the die (33) with a flow of an inert gas (15), in particular nitrogen liquid; v. maintaining the extruded 6060X type flexible aluminum alloy (10) in the position where it exits the die and after inerting at a temperature in the range of 500-600 ° C; in particular, in the range from 550 °C to 595 °C; and characterized in that the method also includes the step of saw. subjecting the soft inert extruded type aluminum alloy 6060X to etching pretreatment with an alkali or acid of at least 1.0, preferably 2 grams/m2 followed by acid peeling to avoid enrichment of Cu, Zn, Mn that are leaves on the surface in case of alkaline etching; to produce the pre-treated extruded 6060X type soft aluminum alloy (10). 2. The method according to claim 1, further comprising the step of; i.installation of a layer of Ti, Zr, Ti/Zr or preferably a pre-anodization layer of at least 4 μm on the etched inert extruded type aluminum soft alloy 6060X to produce the pretreated extruded extruded type 6060X soft aluminum alloy ( 10). 3. The method according to claims 1 or 2, wherein the soft aluminum alloy of type 6060X contains the following alloying elements (in % by weight): i.Yes 0.20 0.60; preferably 0.40-0.50; ii.Mg 0.20 0.60; preferably 0.35-0.45; iii. Mn 0.015 - 0.15; preferably 0.03-0.10; iv. Cu 0.015 - 0.25; preferably 0.03 - 0.10; v. Zn 0.015 - 0.15; preferably 0.03-0.10; saw. Faith 0.18 - 0.35; preferably 0.20 - 0.30 vii. Another s up to 0.03 and in total equilibrium of 0.15 of Al. 4. The method according to any one of the preceding claims, wherein the softened aluminum alloy (2) is forced through the die opening (33) with a ram speed of 7 mm/s to 12 mm/s; in particular at a ram speed of approximately 8 mm/s. 5. The method according to any one of the preceding claims, wherein the soft extruded aluminum alloy (10) has a minimum tensile strength of 215 MPa. 6. A pretreated extruded 6060X type soft aluminum alloy (10) comprising Mg and Si, in an amount between 0.2 and 0.6% by weight; further comprising Fe, Mn, Zn and Cu as alloying elements, said Fe, Mn, Zn and Cu each independently present in an amount of between 0.015 and 0.35% by weight of the total weight and characterized in that said soft alloy pre-treated extruded 6060X type aluminum (10) is obtained by the method according to any one of the preceding claims. 7. The pretreated extruded aluminum soft alloy (10) according to claim 6, wherein the direct surface defects of said pretreated extruded aluminum soft alloy (10) are less than or equal to 3.0%, in particular less than or equal to 2.5%. 8. The soft pretreated extruded aluminum alloy (10) according to claims 5 or 6, wherein the indirect defects of said soft pretreated extruded aluminum alloy (10) are less than or equal to 4.0%, in particular less or equal to 3.5%. 9. A powder coated extruded aluminum soft alloy obtained by powder coating the pretreated extruded aluminum soft alloy (10) according to any one of claims 7 to 8. 10. The powder coated extruded aluminum soft alloy according to claim 9 having a rating of A in either the filiform corrosion test (FFC) or the acetic acid salt spray test (AASS). 11. A device for manufacturing an extruded 6060X type soft aluminum alloy (100) according to the method of any one of claims 1-6, wherein the device comprises; to. a container (8) for a preheated softened soft aluminum alloy (2), b. a pusher or ram (9) for pushing the softened alloy from the container through a die opening (33) to extrude the alloy into a desired shape, c. a supply of an inert gas (15) in a position where the extruded part leaves the outlet of the die (23), and characterized in that it comprises d. a device (6) for measuring the temperature of the extruded soft aluminum alloy (10), preferably an infrared camera, in the position where it exits the die and after inerting, and where the device is configured to maintain the soft aluminum alloy extruded in the position where it comes out of the die and after inerting in the range of 500 - 600 °C; in particular in the range of 550 ° C to 559 ° C, and because the surfaces of the matrix in the area of profile formation (bearings) comprise a compound or white layer of 5 |jm minimum, preferably of approximately 8 μm with a diffusion layer of about 0.15 to about 0.30 mm.