Aluminum alloy extrusion profile and extrusion profile production method

Abstract

The extrusion profile suitable for architectural and construction applications according to the present invention is manufactured from an aluminum alloy having the following composition in weight% (wt.-%): Si 0.20 - 0.38, Mg 0.20 - 0.38, Fe 0.10 - 0.30, Mn 0.02 - 0.10, Cu 0.10 or less, Zn 0.15 or less, Cr 0.05 or less, Ti 0.10 or less, Each impurity is 0.05 wt% or less and the total is 0.15 wt% or less, The remaining part is Al.

Description

Technology Field

[0001] The present invention generally relates to extruded profiles made of aluminum alloy. Additionally, the present invention generally relates to a method for producing such extruded profiles and the use thereof. Background Technology

[0002] Aluminum-based materials are frequently used in the architecture and construction industry today. One reason for this is that a high strength-to-weight ratio can be achieved, which, for instance, makes it possible to reduce the load applied to a building's supporting structure. Aluminum-based materials also enable improved energy efficiency in buildings because they reflect heat rather than absorb energy. Furthermore, aluminum-based materials possess high natural corrosion resistance, allowing for a long service life. These materials can also be anodized or painted as needed to further enhance corrosion resistance and / or achieve a desired aesthetic appearance. Aluminum-based materials also have the advantage of being fully recyclable countless times without any degradation of achievable properties associated with recycling.

[0003] Examples of applications for aluminum-based materials in the architecture and construction industry include architectural profiles, facades, roofing materials, door and window frames, railings, and ladders. In some of these applications, extruded profiles of aluminum-based materials are used. EN AW 6063 and EN AW 6060 are the most frequently used aluminum-based materials for extruded profiles for architecture and construction applications requiring a moderate level of strength. For applications requiring higher strength, EN AW 6106 or even EN AW 6082 may typically be used.

[0004] While aluminum-based materials are an eco-friendly choice that offers a long service life and is fully recyclable, as mentioned above, there are ongoing efforts to further reduce the environmental impact of these products. This can be achieved, for example, by reducing the wall thickness of products such as extruded profiles. Reduced wall thickness directly translates to a corresponding reduction in the carbon dioxide footprint for each component produced from that material. However, this must be balanced with the required (or desired) product characteristics. Furthermore, for profile manufacturers, it is important that such a reduction in wall thickness does not lead to any significant increase in manufacturing costs. The problem to be solved

[0005] The objective of the present invention is to enable the reduction of environmental impact for extrusion profiles used in architecture and construction applications. means of solving the problem

[0006] This objective is achieved by the subject of the appended independent claim(s).

[0007] The extrusion profiles described herein are manufactured from an aluminum alloy having the following composition in weight% (wt.-%):

[0008] Si 0.20 - 0.38,

[0009] Mg 0.20 - 0.38,

[0010] Fe 0.10 - 0.30,

[0011] Mn 0.02 - 0.10,

[0012] Cu 0.10 or less,

[0013] Zn 0.15 or less,

[0014] Cr 0.05 or less,

[0015] Ti 0.10 or less,

[0016] Impurities, each at 0.05 weight% or less and total at 0.15 weight% or less, and

[0017] The remaining part is Al.

[0018] The composition of the aluminum alloy of the extrusion profile described above results in a significant improvement in extrudability when compared, for example, to EN AW 6060, an alloy considered to have high extrudability. The improved extrudability of the aluminum alloy described herein makes it possible to reduce the wall thickness of the profile, thereby also enabling a reduction in the carbon dioxide footprint and the consequent reduction in environmental impact.

[0019] In addition, the composition of the aluminum alloy of the extrusion profile results in improved surface quality in terms of surface roughness and the severity of die lines in the state immediately after extrusion, for example, when compared to EN AW 6060. This reduces the need for etching to remove material from the surface of the extrusion profile to obtain the desired surface quality / appearance after subsequent surface treatments, such as anodizing. The reduction in material to be removed from the surface of the extrusion profile consequently enables a reduction in sludge generated during etching and requiring treatment with various chemicals. This consequently leads to a reduction in environmental impact.

[0020] These improvements in environmental impact are achieved without leading to any significant increase in manufacturing costs. In fact, improved extrudability leads to higher productivity, which in turn makes it possible for profile manufacturers to improve process economics.

[0021] In addition, various surface treatment processes, such as anodizing or painting, can be applied to the extrusion profile, and as a result, a high-quality surface finish can be obtained. In fact, it is possible to achieve a surface finish that is, for example, as good as the surface finish of EN AW 6060. Through this, it is also possible to meet customer expectations in terms of the aesthetic appearance of the surface of the extrusion profile.

[0022] The chemical composition of the aluminum alloy of the extruded profile above results in a reduction in the achievable strength of the extruded profile when compared to the extruded profiles of EN AW 6063 and EN AW 6060. However, extruded profiles provided by profile manufacturers today often have higher mechanical strength than what customers actually require. Therefore, the extruded profile described herein can be advantageously used for applications where the mechanical properties of currently available extruded profiles are superior to the requirements.

[0023] The present invention also relates to a method for producing an extrusion profile. The method comprises the following steps:

[0024] (a) A step of providing a billet of an aluminum alloy having the following composition in weight% (wt.-%):

[0025] Si 0.20 - 0.38,

[0026] Mg 0.20 - 0.38,

[0027] Fe 0.10 - 0.30,

[0028] Mn 0.02 - 0.10,

[0029] Cu 0.10 or less,

[0030] Zn 0.15 or less,

[0031] Cr 0.05 or less,

[0032] Ti 0.10 or less,

[0033] Impurities, each at 0.05 weight% or less and the total at 0.15 weight% or less,

[0034] Remaining Al;

[0035] (b) a step of homogenizing the billet at a temperature of 480–620°C for 1–5 hours, and then cooling it to room temperature;

[0036] (c) a step of preheating the billet to a billet temperature of 440 - 530°C, preferably 460 - 500°C;

[0037] (d) a step of cooling the preheated billet with air or water after extruding it into an extrusion profile;

[0038] (e) optionally stretching the extrusion profile;

[0039] (f) optionally, a step of quenching the extruded profile after solution heat treatment;

[0040] (g) a step of aging an extrusion profile in a single or multi-step aging process, wherein the aging process comprises maintaining at a peak temperature of 160–200°C for 1–100 hours; and

[0041] (h) Optionally, a step of performing a surface treatment on the extrusion profile, such as anodizing or painting. Brief explanation of the drawing

[0042] FIG. 1 is a graph showing the Mg and Si content of an experimental alloy, respectively, with respect to the Mg-Si range of an aluminum alloy according to the present invention, and FIG. 2 illustrates a portion of the cross-section of an extrusion profile according to an experimental test, FIG. 3 illustrates a graph of extrusion pressure determined at different measurement points as extrusion proceeds for an experimental alloy, and FIG. 4 illustrates the theoretical relative extrudability of experimental alloys 1-5 compared with alloy A, and FIG. 5 illustrates a digital image of the measurement area of ​​each profile, illustrating a recorded depth profile (top) corresponding to a die line (bottom), and FIG. 6 illustrates the surface roughness Ra of the experimental alloy in the state immediately after extrusion, FIG. 7 illustrates a graph showing hardness (HV) as a function of aging time for an experimental alloy when aged at 185°C, and FIG. 8a illustrates the yield strength Rp0.2 of an experimental alloy after aging according to two different procedures, FIG. 8b illustrates the tensile strength Rm of the experimental alloy after aging according to the two different procedures above, and FIG. 8c illustrates the elongation of an experimental alloy after aging according to the two different procedures above. Specific details for implementing the invention

[0043] The present invention will be described in more detail below with reference to exemplary embodiments and the accompanying drawings. However, the present invention is not limited to the exemplary embodiments mentioned and / or illustrated in the drawings, but may vary within the scope of the appended claims.

[0044] Where a range is disclosed herein, such range includes the end value of the range unless otherwise explicitly disclosed. Likewise, where an open range is disclosed, such open range also includes a single end value of the open range unless otherwise explicitly disclosed.

[0045] The extruded profiles described herein have been developed primarily for use in architectural and construction applications, such as building profiles, door and / or window frames (including sliding frames), railings, etc. However, it should be noted that the extruded profiles may also be used in other applications, particularly where reducing environmental impact is desired and only low or moderate strength is required. Examples of other applications for the extruded profiles described herein include, but are not limited to, weathering profiles, frames for solar panels, and decorative trims, for example, for vehicle interiors.

[0046] Furthermore, the present invention is not limited to any specific geometric shape of the extrusion profile, i.e., the cross-sectional shape. Accordingly, the geometric shape of the extrusion profile can be adapted to meet the requirements of its intended use. For example, the extrusion profile may be a solid profile or a hollow profile without departing from the present invention.

[0047] The present invention provides an extrusion profile of an aluminum-based alloy, wherein the aluminum-based alloy has the following composition in weight% (wt.-%):

[0048] Si 0.20 - 0.38,

[0049] Mg 0.20 - 0.38,

[0050] Fe 0.10 - 0.30,

[0051] Mn 0.02 - 0.10,

[0052] Cu 0.10 or less,

[0053] Zn 0.15 or less,

[0054] Cr 0.05 or less,

[0055] Ti 0.10 or less

[0056] Impurities, each at 0.05 weight% or less and the total at 0.15 weight% or less,

[0057] The remainder is made of Al.

[0058] In the following, the importance of the different elements of the alloy composition will be briefly discussed. All percentages of the chemical composition are given in weight percent (wt.-%) unless otherwise specified. Any preferred upper and / or lower limits for the individual elements of the composition given herein may be freely combined within the widest range of each element in the composition as specified above, unless otherwise explicitly disclosed.

[0059] Silicon (Si): 0.20 - 0.38 wt%

[0060] Silicon is an important element of the aluminum alloy described herein because it combines with Mg to form dispersed Mg2Si particles, and these particles eventually contribute to precipitation hardening. Therefore, to obtain sufficient mechanical strength after aging, the aluminum alloy described herein contains at least 0.20% Si. Preferably, Si is present in an amount of 0.22% or more, or even 0.24% or more.

[0061] However, the amount of Si also affects the extrudability of the aluminum alloy. Therefore, in order to achieve improved extrudability compared to previously known aluminum alloys for architectural and construction applications, thereby enabling a reduction in the wall thickness of extruded profiles, the aluminum alloy described herein contains up to 0.38% Si. Preferably, Si is present in an amount of 0.36% or less.

[0062] Magnesium (Mg): 0.20 - 0.38 wt%

[0063] As previously mentioned, Mg is combined with Si to form Mg2Si, which is important for obtaining the desired mechanical strength. Therefore, Mg is an essential element of the aluminum alloy described herein. To obtain sufficient mechanical strength after aging, the aluminum alloy contains at least 0.20% Mg. Preferably, Mg is present in an amount of 0.22% or more, or even 0.24% or more.

[0064] However, as the amount of Mg increases, the extrudability of the aluminum alloy decreases. Therefore, to ensure improved extrudability compared to previously known aluminum alloys for architectural and construction applications, the aluminum alloy described herein contains up to 0.38% Mg. Preferably, Mg is present in an amount of 0.36% or less.

[0065] Preferably, Mg and Si may be present in the aluminum alloy in amounts that satisfy Equation (1). This allows the extrudability of the aluminum alloy to be further improved.

[0066] [Wt% Mg] ≤ 0.48 - 0.48 * [Wt% Si] Formula 1

[0067] Iron (Fe): 0.10 - 0.30 wt%

[0068] Iron is an element that enables the anodizing of extruded profiles. Furthermore, reducing the iron content to less than 0.10 weight percent would require replacing a large amount of recycled scrap with primary aluminum in the raw materials used to produce the aluminum alloy, which would consequently increase not only the CO2 footprint but also the cost of raw materials. Therefore, the aluminum alloy described herein contains at least 0.10% Fe. Preferably, Fe is present in an amount of 0.15% or more, or even 0.18% or more. By increasing the amount of Fe, it becomes generally easier to obtain the matte surface appearance typically sought in architectural and construction applications, which is possible after anodizing.

[0069] However, an excessively high Fe content can lead to a decrease in extrudability as well as a decrease in surface quality immediately after extrusion. Accordingly, the aluminum alloy described herein contains up to 0.30% Fe. Preferably, Fe may be present in an amount of 0.26% or less, or even 0.24% or less.

[0070] Preferably, Fe and Si may be present in the aluminum alloy in amounts that satisfy Equation (2). This allows the surface quality of the profile to be improved immediately after extrusion, which consequently results in a reduction of etching required prior to possible surface treatments such as anodizing or painting.

[0071] [wt% Fe] / [wt% Si]≥0.55 Equation 2

[0072] Copper (Cu): 0.10 wt% or less

[0073] Copper is not an essential element of the aluminum alloy described herein, but may be present in an amount of up to 0.10% without negatively affecting the desired properties. For example, too high a Cu content may pose a risk of causing a decrease in corrosion resistance, undesirable reactions during etching, and an undesirable increase in gloss on the anodic surface of the extrusion profile. Preferably, Cu may be present in an amount of 0.05% or less.

[0074] However, copper is an element that can enhance mechanical properties by contributing to solid solution strengthening.

[0075] Manganese (Mn): 0.02 - 0.10 wt%

[0076] The addition of a small amount of Mn can have the advantageous effect of lowering the stability of β-AlFeSi, thereby facilitating the transformation to α-AlFeSi during homogenization. This can consequently improve the surface quality in the state immediately after extrusion. The reduction of β-AlFeSi can also be beneficial for the finish of the anodic surface, as the phase has an undesirable tendency to be embedded in the anodic surface layer. Accordingly, the aluminum alloy described herein advantageously contains 0.02% or more of Mn. Preferably, Mn is present in an amount of 0.03% or more.

[0077] However, an excessively high Mn content can lead to the formation of undesirable dispersions. Therefore, the Mn content of the aluminum alloy described herein is limited to a maximum of 0.10%. Preferably, Mn may be present in an amount of 0.08% or less.

[0078] Zinc (Zn): 0.15 wt% or less

[0079] Although zinc is not an essential element of the aluminum alloy described herein, it may be present in an amount up to 0.15% without adversely affecting the desired properties. When present, Zn may contribute to strength, for example, through solid solution strengthening. Preferably, Zn is present in an amount of 0.10% or less, or even 0.05% or less.

[0080] Chromium (Cr): 0.05 wt% or less

[0081] Chromium is not an essential element of the aluminum alloy described herein. However, if necessary, it may be present in an amount of up to 0.05% without degrading the desired properties. The addition of a small amount of Cr can have a beneficial effect, for example, in facilitating the achievement of a matte appearance on the anodized surface of an extrusion profile. Preferably, Cr may be present in an amount of 0.03% or less.

[0082] Titanium (Ti): 0.10 wt% or less

[0083] Titanium is not an essential element of the aluminum alloy described herein, but may be present in an amount up to 0.10%. For example, titanium may be added as needed to act as a grain refiner. Preferably, Ti is present in an amount of 0.05% or less, or 0.04% or less.

[0084] impurities

[0085] The above aluminum alloy may also contain impurities that occur conventionally. Without departing from the scope of the present invention, such impurities may be present as a result of the raw materials used (e.g., the composition of recycled scrap used in the production of aluminum alloys) or as a result of the process of producing the aluminum alloy. However, the total content of impurities in the aluminum alloy is limited to a maximum of 0.15 weight% to reduce the risk of degradation of the desired properties. Additionally, each impurity element is permitted to be present only in an amount of a maximum of 0.05 weight%. Examples of impurity elements include, but are not limited to, Ca, Sn, Sb, Pb, Zr, and B.

[0086] Method for producing extrusion profiles

[0087] The extrusion profile according to the present invention can be produced by providing a billet of the aforementioned aluminum alloy. This can be made, for example, by DC casting of a melt having the aforementioned composition.

[0088] Subsequently, homogenization is performed on the billet. The purpose of the homogenization is to reduce micro-segregation and dissolve the Mg2Si formed during casting, thereby facilitating subsequent extrusion. The homogenization also serves the purpose of transforming the plate-shaped β-phase AlFeSi particles formed during casting into the rounder α-phase AlFeSi as much as possible. This is because β-AlFeSi is associated with poor hot workability due to its shape as well as its brittleness, which consequently negatively affects extrudability. Homogenization can be performed at a temperature of 480–620°C for 1–5 hours. Optionally, homogenization can be performed at a temperature of 540–600°C, preferably 560–590°C, for 1–5 hours, preferably 2–4 hours. Afterward, the billet is cooled to room temperature. The above cooling can be carried out, for example, at an average cooling rate of 300 to 500°C / h. However, it should be noted that a lower cooling rate, such as about 1°C / min, is also possible, as any Mg2Si precipitated during cooling will be relatively small and evenly distributed and can be easily dissolved during subsequent processing steps. An average cooling rate higher than 500°C / h is also possible, but is not essential and can be avoided for reasons of process economics.

[0089] After homogenization, the billet is preheated to a billet temperature of 420–530°C, preferably 460–500°C, and then extrusion is performed in a conventional extrusion press to obtain an extrusion profile of the desired cross-section. Afterward, the extrusion profile is cooled, which can be carried out by cooling with air or water. At least, in the case of a profile having a thin wall cross-section, such as a wall thickness of about 2 mm or less, it is not necessary to use any forced cooling, but it may be used if necessary. In order to achieve the desired reaction during subsequent aging, a sufficient amount of Mg and Si will still remain in the solid solution.

[0090] Extruded profiles may be solid or hollow profiles depending on their intended use. To reduce environmental impact, extruded profiles may suitably be thin-walled extruded profiles. The thickest wall portion of the profile cross-section may have a thickness of, for example, 1.5 mm or less, or even 1.3 mm or less. In practice, the high extrudability of the aluminum alloys described herein makes it possible to produce profiles with a wall thickness of 1.0 mm or less without any specific measures being taken.

[0091] The extrusion profile of the aforementioned aluminum alloy generally has a fully recrystallized grain structure. The low content of dispersion-forming elements, Mn and Cr, in the aluminum alloy promotes the recrystallized grain structure.

[0092] Therefore, after extrusion, the extrusion profile can be appropriately woven according to a conventional process. Such weaving can be carried out, for example, by stretching the extrusion profile. Stretching can be performed to cause plastic deformation of the extrusion profile of, for example, 5% or less, e.g. 1-5%, but is not limited thereto.

[0093] If required or desired for practical reasons, the extruded profile may be stored immediately after extrusion (and optionally elongated) at room temperature, for example, before subsequent processing steps. Such storage may typically lead to natural aging for aluminum alloys belonging to the 6xxx series. Generally, clustering of Mg and Si occurs during the natural aging of 6xxx aluminum alloys, which may consequently lead to an increase in the mechanical strength of the extruded profile. This increase in mechanical strength may have a negative effect on the increase in strength during subsequent artificial aging for high-alloy 6xxx aluminum alloys. However, considering the low content of Mg and Si in the alloys described herein, it is believed that there will be no negative effect of possible natural aging on subsequent artificial aging. Instead, natural aging may have a positive effect on mechanical properties. Accordingly, the method described herein may also include a natural aging step for, for example, 1 to 100 hours (e.g., 2 to 48 hours).

[0094] Although not essential, solution heat treatment may be performed on the extrusion profile as needed prior to artificial aging. Solution heat treatment may be performed, for example, at a temperature of 460 to 580°C for 20 minutes to 2 hours. Preferably, solution heat treatment may be performed at a temperature of 540 to 560°C for 0.5 to 1 hour. To fully utilize the possible solution heat treatment, cooling from the solution heat treatment temperature may be appropriately carried out by forced cooling, for example, by forced air cooling or water quenching.

[0095] Afterward, artificial aging is performed on the extrusion profile, which can be carried out as a single-step aging process or a multi-step aging process (e.g., a dual-step aging process). The aging process may appropriately include a step of maintaining the extrusion profile at a peak temperature of at least 160 to 200°C for 1 to 100 hours. Here, the peak temperature is intended to mean the highest temperature at which the extrusion profile is aged.

[0096] In the case of a multi-step aging process (e.g., a dual-step aging process), the aging process may suitably include a first aging step in which the extrusion profile is maintained at a temperature lower than the peak temperature; suitably at 100–160°C or preferably at 120–160°C. The first aging step may suitably be performed prior to the step in which the extrusion profile is maintained at the peak temperature, and may be performed primarily to achieve the nucleation of the desired Mg2Si precipitates. This first aging step may be performed for, for example, 0.5–3 hours, preferably 1–2 hours. In the case of a multi-step aging process, the extrusion profile is typically not cooled between individual steps of the process.

[0097] The upper limit of 100 hours for the aging step in which the extrusion profile is maintained at the peak temperature is not a critical upper limit for the duration of the aging, but is selected primarily for reasons of process economics. Here, it is necessary to note that to achieve a similar aging response in terms of increasing mechanical strength, a lower peak aging temperature typically requires a longer duration, and vice versa. Additionally, depending on the desired mechanical strength, aging can be performed in an under-aged condition or a peak aged condition. Preferably, the aging of the extrusion profile can be performed in a single or multi-step aging process, said aging process comprising maintaining at a peak temperature of 180–195°C for at least 5 hours. A peak aged condition can be achieved, for example, by performing aging for 10–25 hours at a peak temperature of 185–190°C.

[0098] Depending on its intended use, the extrusion profile may be surface-treated to obtain a desired aesthetic appearance and / or further improve corrosion resistance. Examples of such surface treatments include anodizing and painting. Regardless of whether the extrusion profile is to be anodized or painted, etching may be performed on the extrusion profile after artificial aging to remove small surface defects and expose the metal surface. Accordingly, such etching may be performed according to previously known methods, and the etchant may be corrosive or acidic.

[0099] Therefore, the anodic oxidation treatment can be performed according to previously known methods. For example, the anodic oxidation treatment can be performed using a sulfuric acid electrolyte. The anodic oxidation treatment can be appropriately performed with an anodic surface layer thickness of 8 to 12 μm, but other thicknesses are also possible. If necessary, the anodic surface may be colored using a suitable dye that penetrates into the pores of the anodic surface layer. Regardless of whether additional coloring is performed, the extrusion profile may be sealed after the anodic oxidation treatment as known in the art. This may be performed, for example, using nickel acetate.

[0100] characteristic

[0101] As would be well understood by those skilled in the art, the characteristics of the extrusion profiles described herein will depend on the condition of the extrusion profiles. Here, a distinction is made between the condition immediately after extrusion and various aging conditions.

[0102] The composition of the aluminum alloy described herein makes it possible to obtain an extrusion profile having a surface roughness Ra of less than 0.42 μm in the state immediately after extrusion (i.e., without any surface etching being performed). Surface roughness can be determined according to ISO 3274:1996 using a BFW probe arm A 10-45-2 / 90°.

[0103] In addition, the aluminum alloy described herein makes it possible to obtain an extrusion profile having a tensile strength Rm of 100 to 180 MPa and a yield strength Rp0.2 of 80 to 150 MPa when the extrusion profile is in a fully aged state. In addition, in the above state, the elongation A50 may be 4.5 to 8.5%. The tensile strength, yield strength, and elongation may be determined in accordance with ISO 6982-1 when a tensile load is applied in the extrusion direction.

[0104] In addition, when fully aged, the extrusion profile can obtain a hardness of 40 to 65 Hv as determined according to ISO 6507-1.

[0105] The extrusion profile can also be aged in an unaged state as needed. For example, as a result of aging at 190°C for 2 hours, a tensile strength Rm of 90-120 MPa, a yield strength Rp0.2 of 40-70 MPa, and an elongation A50 of 14-20% can be obtained.

[0106] As described above, the extrusion profiles described herein may also be subjected to, for example, anodizing or painting after aging. Such processes do not affect the mechanical strength of the extrusion profiles, and accordingly, the mechanical strength achieved during aging will also be maintained even after the extrusion profiles are anodized or painted.

[0107] As a result of anodizing an extrusion profile with an anodic surface layer thickness of 8 to 12 μm, the average specular gloss at 60° determined according to ISO 7668 can be 8.5 to 11.5 GU. The thickness of the anodic surface layer can be determined by cross-sectional inspection using a microscope according to ISO 1463.

[0108] Experimental test

[0109] After remelting the EN AW 6060 alloy billet, multiple experimental alloys were produced by alloying each melt to reach a different chemical composition. Melting was carried out in a resistance furnace with a capacity of 500 kg. After alloying, the melt was cast into a billet with a diameter of 203 mm by DC (direct-chill) casting.

[0110] The composition of the experimental alloy, determined by optical emission spectroscopy (OES) analysis, is specified in Table 1. Alloy A constitutes a reference alloy whose composition was selected to target the composition of a commercially available aluminum alloy known for having high extrudability.

[0111] Figure 1 shows a graph showing the Mg-Si content of the experimental alloy with respect to the Mg-Si range of 0.20 - 0.38 wt% Mg and 0.20 - 0.38 wt% Si of the aluminum alloy according to the present invention.

[0112] Table 1. Chemical composition of experimental alloy, remainder is Al

[0113]

[0114] * Comparison, outside the claimed scope

[0115] The obtained billet was homogenized at a uniform temperature of 585°C for 2 hours, and then cooled at a cooling rate of approximately 400°C / h. Afterward, the homogenized billet was machined to a billet diameter of 178 mm and a billet length of 662 mm prior to extrusion.

[0116] The extrusion of the experimental alloy was performed using a solid profile (1) having a cross-section as partially illustrated in FIG. 2. Parts of the profile not illustrated in the drawings relate to specific details of the intended final product, such as various flanges. The aforementioned details regarding the cross-sectional shape of the profile are not critical for the tests described below and have therefore been omitted for clarity and brevity. The cross-section of the profile (1) can be described as comprising two straight leg sections (2, 4) connected by a curved section (3). The wall thickness (t) of each leg section (2, 4) is 1.25 mm. The leg sections (2, 4) are oriented at an angle α of 96.5° relative to each other. The curved section has substantially the same wall thickness as the leg sections (2, 4).

[0117] The billet temperature used for extrusion was 480°C, and the extrusion speed was set to 41 m / min. The profile was cooled in air after extrusion. The same die was used for all experimental alloys. Alloy A was extruded first, and then billets of the other experimental alloys were extruded in numerical order.

[0118] Figure 3 illustrates a graph of extrusion pressure determined at different measurement points as extrusion proceeds for the experimental alloys. As illustrated by the arrows in Figure 3, a low extrusion pressure indicates high extrudability. From the above results, it can be confirmed that Alloy 1 has slightly better extrudability than Alloy A, and Alloys 2 through 5 each exhibit much higher extrudability. The highest extrudability was achieved in the case of Alloys 3 through 5. All of these experimental alloys satisfy the criteria given by the aforementioned Equation 1. The criteria of Equation 1 are schematically represented by a dotted line in Figure 1.

[0119] The extrudability of experimental alloys can also be compared through theoretical calculations based on their respective compositions. Models that can be used for these calculations are described, for example, in "Modeling of Recrystallization, Quenching Sensitivity, and Surface Tear of 6xxx-Series Alloys" by Ole Runar Myhr, Rune Østhus, Anders Nesse, and Trond Furu, ET2022 Conference, 2022, and in "Modeling Framework for Rapid Evaluation of Rate Limitation During Extrusion of Aluminum Profiles" by Mads Iddberg, Ole Runar Myhr, Anders Nesse, and Trond Furu, Aluminium 2000 Conference, 2023.

[0120] Figure 4 shows the PRO, a digital twin developed by Norsk Hydro. 3The relative extrudability of alloys 1–5 with respect to alloy A, determined by theoretical calculations performed using the ™ software, is illustrated. For the results shown in Fig. 4, the relative extrudability of the materials was calculated by comparing the maximum extrudability of a 9 mm cylindrical profile from a 100 mm billet for each experimental alloy. Furthermore, the calculation was based on experimental alloys that were industrially cooled in air after homogenization at 585°C for 2 hours.

[0121] Here, it is necessary to note that theoretical extrudability can be calculated using different models and based on different estimations, and thus yield different results. However, by comparing the theoretical extrudability of different alloys with the theoretical extrudability of a reference alloy (here, Alloy A), the same trend will be observed regardless of the model used to determine the theoretical extrudability. Therefore, the results presented in Figure 4 will be regarded merely as a method of theoretically comparing the extrudability of different experimental alloys.

[0122] Evaluation of surface quality after extrusion

[0123] After extrusion, a sample was taken from the leg portion (2) (see FIG. 2) of the profile of each experimental alloy, and the surface quality of the profile in the state immediately after extrusion was investigated. More specifically, surface roughness was determined according to ISO 3274:1996 using a BFW probe arm A 10-45-2- / 90°. In addition, the severity of die lines was investigated by recording a depth profile over a linear distance of 45 mm in the transverse direction relative to the extrusion direction using a MHAR surface measuring device MarSurf M 400 equipped with drive unit SD26.

[0124] The surface quality of the profile of Alloy A was found to be consistent with expectations based on previous experience with commercially available aluminum alloys of that composition, and is generally considered to be of good surface quality for intended use. However, the profiles of Alloys 1–5 were found to possess much better surface quality immediately after extrusion.

[0125] Figure 5 illustrates an image taken with a digital camera of the measurement area, showing the die line before background filtering (at the bottom) and the corresponding recorded depth profile (at the top). In the case of Alloys 2-5, it can be seen in Figure 5 that the severity of the die line is significantly reduced compared to Alloys A and 1. In contrast to Alloys A and 1, each of Alloys 2-5 satisfies the criteria of Equation 2 as described above. Unless constrained by theory, the ratio of Fe to Si is believed to affect the composition and / or morphology of iron-containing precipitates, which consequently affects the severity of the die line formed during extrusion. As can be seen from the figure, the best results were obtained in the case of Alloys 3-5.

[0126] FIG. 6 illustrates the surface roughness Ra of the experimental alloys in the state immediately after extrusion. As is evident from the figure, the surface roughness of alloys 1-5 is significantly lower than that of alloy A.

[0127] To demonstrate that the improved surface quality of the profiles of Alloys 1–5 was not merely the result of extrusion using the same die as Alloy A, already available billets of the aforementioned commercial aluminum alloys were also extruded after the experimental alloys. The same processing conditions regarding homogenization and extrusion as described above were applied to the commercial aluminum alloys. The resulting surface quality was, at best, only slightly better than that of the profile of Alloy A. More specifically, the surface roughness Ra was approximately 0.45 μm, which is comparable to approximately 0.46 μm in the case of Alloy A and may be lower than 0.40 μm in the case of Alloys 1–5. Additionally, the depth profile, which indicates the severity of die lines, was similar to that of Alloy A.

[0128] statute of limitations test

[0129] Laboratory aging tests were performed to investigate the dependence of material hardness on aging time. Prior to aging, the extrusion profiles of the experimental alloy were solution heat-treated at 545°C for 30 minutes and then quenched with water. Aging was carried out according to a dual-step (i.e., multi-step) aging procedure comprising a first step of holding at 130°C for 1 hour and a subsequent second step of holding at a peak temperature of 185°C. Hardness was determined according to ISO 6507-1.

[0130] The results are illustrated in Fig. 7, which illustrates a graph showing hardness (HV) as a function of aging time (in hours) at the peak temperature. It can be clearly seen from the graph that, compared to alloys A and 1, alloys 2-5 require a longer aging time to reach peak hardness. Additionally, the peak hardness of alloys 2-5 is significantly lower than that of alloy A. The difference in material hardness between the different experimental alloys is mainly a result of the difference in Mg and Si content of the experimental alloys.

[0131] Tensile test

[0132] Here, two different dual-stem aging procedures, designated DSA190 and DSA185 respectively, were performed on extrusion profiles. According to the DSA190 procedure, after storage at room temperature for about 2 hours, a first aging step was performed in a full-scale production furnace at a temperature of 130°C for 30 minutes, followed by a second aging step performed at a peak temperature of 190°C for 2 hours on the extrusion profiles. Based on the results shown in FIG. 7, it can be expected that the aging procedure will lead to a substantially fully aged state for Alloy A, whereas at least Alloys 2-5 will be expected to remain in an underaged state.

[0133] According to the DSA185 procedure, a first aging step was performed on the extrusion profile, comprising solution heat treatment at 545°C for 30 minutes followed by quenching with water, followed by holding at 130°C for 1 hour to achieve a fully aged state, and then holding at a peak temperature of 185°C. The DSA185 was performed in a laboratory furnace. The aging times for different experimental alloys were selected based on the results shown in Fig. 7, namely the period required to reach peak hardness.

[0134] Afterwards, a sample for tensile testing was taken from the aged profile. Tensile testing was performed according to ISO 6982-1 with a tensile load applied in the extrusion direction. The results are specified in Table 2 and are also illustrated in Figures 8a–8c.

[0135] Table 2. Tensile properties after aging

[0136]

[0137] * Comparison, outside the claimed scope

[0138] Surface appearance after anodizing treatment

[0139] After aging according to the aforementioned procedure DSA190, the extrusion profile was etched using a caustic etchant, and then anodizing treatment using a sulfuric acid electrolyte and subsequent conventional sealing were performed on the extrusion profile (no coloring of the anodized surface layer was performed). The duration of the anodizing treatment was selected to aim for a thickness of 10 μm of the resulting oxide layer, which is a typical thickness for anodized aluminum profiles for architectural and construction applications.

[0140] The surface appearance and surface anodic oxidation coating after anodizing treatment were evaluated according to EN ISO 7599. More specifically, oxide thickness was determined by cross-sectional inspection using a microscope according to ISO 1463. Mirror gloss was determined according to ISO 7668.

[0141] Table 3 lists the results of oxide thickness measurements, and Table 4 lists the results of mirror gloss measurements.

[0142] Table 3. Oxide thickness

[0143]

[0144] * Comparison, outside the claimed scope

[0145] Table 4. Glossiness at a 60° measurement angle

[0146]

[0147] * Comparison, outside the claimed scope

[0148] Overall, good surface appearances similar to the surface appearance of reference alloy A were confirmed for all alloys 1 to 5. This demonstrates that it is possible to meet customer expectations for architectural and construction applications in terms of anodized surface appearance, despite changes in the chemical composition of the alloys of the extruded profiles compared to the conventional EN AW 6060 alloy.

Claims

Claim 1 Extruded profile made of an aluminum alloy having the following composition in wt.% (wt.-%): Si 0.20 - 0.38, Mg 0.20 - 0.38, Fe 0.10 - 0.30, Mn 0.02 - 0.10, Cu 0.10 or less, Zn 0.15 or less, Cr 0.05 or less, Ti 0.10 or less, impurities each 0.05 wt% or less and the total sum 0.15 wt% or less, remainder Al. Claim 2 An extrusion profile according to claim 1, wherein the aluminum alloy comprises 0.22 weight% or more of Si; preferably 0.24 weight% or more of Si. Claim 3 An extrusion profile according to claim 1 or 2, wherein the aluminum alloy contains 0.36 weight% or less of Si. Claim 4 An extrusion profile according to any one of claims 1 to 3, wherein the aluminum alloy comprises 0.22 weight% or more of Mg; preferably 0.24 weight% or more of Mg. Claim 5 An extrusion profile according to any one of claims 1 to 4, wherein the aluminum alloy comprises 0.36 weight% or less of Mg. Claim 6 An extrusion profile according to any one of claims 1 to 5, wherein the aluminum alloy comprises 0.15 weight% or more of Fe; preferably 0.18 weight% or more of Fe. Claim 7 An extrusion profile according to any one of claims 1 to 6, wherein the aluminum alloy comprises 0.26 weight% or less of Fe; preferably 0.24 weight% or less of Fe. Claim 8 An extrusion profile according to any one of claims 1 to 7, wherein the aluminum alloy comprises 0.03 weight% or more of Mn. Claim 9 In any one of claims 1 to 8, the extrusion profile wherein the composition of the aluminum alloy satisfies the criterion given by Formula 1: [W / L Mg] ≤ 0.48 - 0.48 * [W / L Si] Formula 1 Claim 10 In any one of claims 1 to 9, the extrusion profile wherein the composition of the aluminum alloy satisfies the criterion given by Formula 2: [wt% Fe] / [wt% Si]≥0.55 Formula 2 Claim 11 An extrusion profile according to any one of claims 1 to 10, wherein the thickest wall portion of the extrusion profile has a wall thickness of 1.5 mm or less, preferably 1.3 mm or less. Claim 12 An extrusion profile according to any one of claims 1 to 11, wherein, in the state immediately after extrusion, the surface roughness determined using a BFW probe arm A 10-45-2 / 90° in accordance with ISO 3274:1996 is less than 0.42 μm. Claim 13 An extrusion profile according to any one of claims 1 to 12, wherein, when fully aged, the tensile strength Rm determined according to ISO 6982-1 is 100 to 180 MPa and the yield strength Rp0.2 is 80 to 150 MPa. Claim 14 An extrusion profile according to any one of claims 1 to 13, comprising a surface anodic oxidation coating, preferably wherein the surface anodic oxidation coating has an average thickness of 8 to 12 μm as determined by cross-sectional inspection using a microscope in accordance with ISO 1463. Claim 15 In claim 14, the surface of the extrusion profile is an extrusion profile having an average specular gloss of 8.5 - 11.5 GU at 60° as determined according to ISO 7668. Claim 16 A method for producing an extrusion profile: (a) providing a billet of an aluminum alloy having the following composition in weight% (wt.-%): Si 0.20 - 0.38, Mg 0.20 - 0.38, Fe 0.10 - 0.30, Mn 0.02 - 0.10, Cu 0.10 or less, Zn 0.15 or less, Cr 0.05 or less, Ti 0.10 or less, Impurities, each at 0.05 weight% or less and the total at 0.15 weight% or less, A method comprising: (b) homogenizing the billet at a temperature of 480–620°C for 1–5 hours, and then cooling it to room temperature; (c) preheating the billet to a billet temperature of 420–530°C, preferably 460–500°C; (d) extruding the preheated billet into an extrusion profile and then cooling it with air or water; (e) optionally stretching the extrusion profile; (f) optionally heat-treating the extrusion profile with a solution heat treatment; (g) aging the extrusion profile in a single or multi-step aging process, wherein the aging process comprises maintaining the extrusion profile at a peak temperature of 160–220°C for 1–100 hours; and (h) optionally performing a surface treatment on the extrusion profile, such as anodizing or coating. Claim 17 A method according to claim 16, wherein step (d) comprises extruding the preheated extrusion profile into an extrusion profile having a wall thickness of 1.5 mm or less, or 1.3 mm or less, at the thickest part of the extrusion profile. Claim 18 A method according to claim 16 or 17, wherein step (g) comprises aging in a single or multi-step aging process comprising maintaining the extrusion profile at a peak temperature of 180-195°C for at least 5 hours. Claim 19 A method according to any one of claims 16 to 18, wherein step (f) comprises solution heat treatment of the extrusion profile at a temperature of 460 to 580°C for 20 minutes to 2 hours, followed by forced cooling. Claim 20 A method according to any one of claims 16 to 19, wherein step (b) comprises homogenizing the billet at a temperature of 560 to 590°C for 2 to 4 hours, and then cooling to room temperature; optionally, the cooling is performed at an average cooling rate of 300 to 500°C / h. Claim 21 A method according to any one of claims 16 to 20, wherein step (e) comprises stretching the extrusion profile to cause plastic deformation of the extrusion profile of up to 5%, preferably 1-5%. Claim 22 Use of an extruded profile according to any one of claims 1 to 15 in architectural and construction applications, for example, in producing architectural profiles, door or window frames, railings, or ladders, or in producing frames for solar panels.

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