Extrusion billet and method for the production thereof, and method for producing an extruded part

Abstract

The invention relates to an extrusion billet comprising a billet casing (10) and a billet filling (20), wherein: the billet casing (10) is made of an aluminum material and has a hollow-cylinder-shaped casing wall (11), a bottom casing cap (12) and a top casing cap (13); the bottom casing cap (12) is disposed at a bottom end of the casing wall (11) and the top casing cap (13) is disposed at a top end of the casing wall (11); the billet casing (10) forms a cylindrical interior (14); the billet filling (20) is disposed in the interior (14) and is in the form of aluminum powder comprising compressed powder particles. The invention also relates to a method for producing an extrusion billet of this type and to an extrusion method using a billet of this type.

Description

[0001] Extruded blank and method for its production and method for producing an extruded part

[0002] The invention relates to an aluminum extrusion blank, a method for producing such an extrusion blank and a method for producing an extruded part.

[0003] Extrusion processes and the extrusion blanks used for this purpose, as well as processes for their production, are known in principle from the state of the art.

[0004] Extrusion is a pressure forming process that has become widely used, particularly for the production of profiles or wires as so-called continuous material. Extrusion is used to produce extruded profiles, particularly aluminum profiles. The starting material is pressed into a die, which determines the cross-section of the extruded profile to be produced.

[0005] According to the state of the art, the starting material is provided as an ingot. This is usually a homogeneous casting, also referred to as a slab or billet. To improve the mechanical properties, particularly the strength of the final extruded profile, it is known to alloy the aluminum ingot with other elements such as magnesium, manganese, or silicon, or combinations thereof. A disadvantage of such alloys is the sometimes high cost and the limited availability of the alloying elements.

[0006] The object of the invention is to provide an extruded blank that can be produced cost-effectively and enables the production of an extruded part with particularly high strength. Furthermore, the object of the invention is to provide a method for producing

[0007] Confirmation copying of such an extrusion blank and a method for producing an extrusion.

[0008] The problem is solved with respect to the extruded blank by the features listed in claim 1, with respect to the method for producing the extruded blank by the features listed in claim 7, and with respect to the method for producing the extruded part by the features listed in claim 9. Preferred developments are set out in the subclaims.

[0009] For the purposes of the present invention, an extrusion blank is understood to be a starting material for an extrusion process that is arranged in a dimensionally stable body shape.

[0010] For the purposes of the present invention, an extruded part is understood to mean a workpiece produced by extrusion, for example in the form of an extruded profile or a wire.

[0011] The extrusion blank according to the invention has as basic components a blank shell and a blank filling.

[0012] The blank shell is made of an aluminum material and has a hollow cylindrical shell, a bottom shell cap, and a top shell cap. The bottom shell cap is arranged at a bottom end of the shell, and the top shell cap is arranged at a top end of the shell. The shell caps are preferably initially designed as separate components in the form of an insertable lid. However, it is also possible to form the end sections of the shell as a shell cap, for example by folding them in, so that the entire shell is present as a monolithic component. The blank shell is very thin and preferably has a thickness of less than one millimeter, particularly preferably less than 0.2 mm. The proportion of the blank shell in the total amount of starting material for extrusion provided by the extrusion blank is thus negligible.

[0013] The blank shell forms a cylindrical interior. Cylindrical is not to be understood as a geometric category in the narrow sense, but rather describes a shape defined by a roughly circular cross-section and an axial extension perpendicular to it.

[0014] According to the invention, the blank filling is arranged in the interior space. The blank filling is formed as an aluminum powder comprising compacted powder particles.

[0015] The aluminum powder is formed by a multitude of powder particles. They have a particle size of preferably 10 pm to 200 pm, and particularly preferably 75 pm to 125 pm.

[0016] Compacted powder particles are defined as a structure in which the powder particles are interlocked in such a way that they have a fixed spatial relationship to one another and, in particular, that free-flowing properties are eliminated. Compaction can be achieved, in particular, by axial vibration. Compaction is defined as the powder particles having a positional orientation, compared to a loose bed, that reduces air inclusions between the powder particles, so that the compacted powder particles have a bulk density of preferably 50% or higher.

[0017] The blank shell surrounds the blank filling and further stabilizes it, although the dimensional stability of the extruded blank is already largely provided by the compacted powder particles. Both the blank shell and the blank filling are made of aluminum, and the blank shell acts as a permanent formwork. According to a further development, the extruded blank is characterized by the powder particles having a spattered shape. A spattered shape is a well-established technical term that describes an irregular and jagged shape of the powder particles. The spattered shape can also be described as the opposite of a spherical shape.

[0018] Powder particles in a spiky shape advantageously improve compactability and increase the dimensional stability of the extruded blank. Furthermore, aluminum powder with spiky powder particles is more cost-effective to produce than with spherical powder particles.

[0019] According to a further development, the extruded blank is characterized in that the powder particles have an aluminum metallic phase and an aluminum oxide phase, that the aluminum metallic phase has aluminum and / or an aluminum alloy and forms a particle core, and that the aluminum oxide phase has AI2O3 and forms a particle shell that surrounds the particle core.

[0020] For the use of the extrusion blank in an extrusion process, the properties and interaction of the two phases are decisive for the advantageous process properties and for the properties of the extruded part to be produced.

[0021] The aluminum metallic phase is preferably formed by aluminum without the addition of alloying elements. It is preferably 99.5% to 99.9% aluminum, hereinafter also referred to as pure aluminum. Such pure aluminum is the commercially available base material for aluminum alloys.

[0022] For the purposes of the present invention, the aluminum metallic phase is also understood to mean an aluminum with a higher proportion of accompanying elements or an aluminum alloy with alloying elements such as silicon, magnesium, manganese, copper and zinc.

[0023] For the sake of simplicity, pure aluminum, aluminum with a higher proportion of accompanying elements, and aluminum alloy are collectively referred to as aluminum below, unless expressly stated otherwise.

[0024] The aluminum metallic phase forms the basic body of the powder particles, hereinafter also referred to as the particle core.

[0025] The aluminum-based metal powder for use according to the invention is further characterized by an aluminum oxide phase.

[0026] According to the invention, the aluminum oxide phase is formed by an aluminum oxide layer that surrounds the particle core on the outside as a particle shell. This is, in particular, a particle shell with a predominant proportion of Al2O3. The mass fraction of Al2O3 based on the total mass of the aluminum powder is preferably a maximum of 5%.

[0027] The aluminum oxide phase is therefore not distributed homogeneously throughout the volume of the particle bodies, but rather exhibits a region of higher concentration in the particle shell. The aluminum oxide phase advantageously forms a support structure in an extruded part produced from the extruded blank by extrusion due to its arrangement in the particle shell.

[0028] This is based on the discovery that, as a result of the forces acting on the extrusion blank during pressure forming by extrusion, the powder particles are pressed against each other and deformed. While the aluminum metal body of the particle core undergoes plastic deformation due to its good flowability, the aluminum oxide shell of the particle shell is broken up and shattered due to the low ductility of the aluminum oxide, forming aluminum oxide particle shell fragments. The particle shell fragments are irregularly shaped and also warp due to the movements during pressure forming.Thus, the particle shell fragments do not form a closed plane between the adjacent aluminum-metallic zones of the previous particle cores; rather, there are points of penetration where the aluminum of the particle cores of adjacent particle cores directly meets and forms a cohesive bond, creating a lattice structure. As a result, the particle shell fragments are enclosed by the aluminum of the particle cores. In the zones of the former particle shells, there is a higher concentration and thus a higher mass fraction of aluminum oxide particle shell fragments than in the zones that emerged from the particle cores. The particle shell fragments thus form support structures. Support structures are understood to be linear or, preferably, planar zones in which a higher concentration of particle shell fragments is present than in other zones.

[0029] The particle shell fragments are highly rigid and embedded in the aluminum's metal lattice. Due to their size, typically in the micrometer range, they create higher-strength bodies in the surrounding metal lattice that counteract deformation and thus increase the strength of the aluminum composite material compared to aluminum without an aluminum oxide phase. This is further supported by the relative proximity of the particle shell fragments to one another in the areas of higher concentration. As a result, the particle shell fragments are incorporated as macroscopic, high-strength bodies in the aluminum, which in this respect forms a matrix material. The particle shell fragments therefore do not form closed regions. Rather, the aluminum's metal lattice penetrates the spaces between the aluminum particles without lattice defects necessary for strength.The increase in strength is therefore advantageously not primarily due to solid solution strengthening, but primarily due to the mechanical properties of the particle shell fragments in their mutual support. The greater the degree of deformation and the flow of the material during pressure forming by extrusion, the more the shapes of the zones with a high concentration of aluminum oxide particle fragments deviate from the shapes of the particle shells of the powder particles present before pressure forming. Furthermore, the aluminum oxide particle shell fragments are more widely distributed in the aluminum than in the matrix material.

[0030] Particularly advantageously, the extrusion blank according to the invention can achieve a pronounced orientation of the aluminum oxide particle shell fragments as support structures. Due to the mere compaction of the powder particles, which creates dimensional stability, the particle shell remains intact in the extrusion blank. Thus, the arrangement of the aluminum oxide phase is present at the later contact points of the powder particles, so that continuous support structures made of aluminum oxide particle shell fragments can form there. It is advantageous for the support structures to have such a spatial orientation in the extrusion direction. The extruded part to be produced thus exhibits advantageous gradual anisotropy.The support structures oriented in the longitudinal axis of the extruded part result in increased bending strength transverse to the longitudinal axis and, at the same time, increased electrical conductivity in the longitudinal axis, since the aluminum metallic zones are longitudinally extended and fewer zones of aluminum oxide particle shell fragments have to be passed through during a current flow.

[0031] Although aluminum oxide has very low electrical conductivity, the extruded blank according to the invention offers the particular advantage of producing an extruded part whose electrical conductivity is only slightly reduced compared to pure aluminum. It was discovered that the distribution of the aluminum oxide particle shell fragments in perforated support structures only marginally impairs the metal lattice structure. Thus, an extruded part produced exhibits very high conductivity while simultaneously maintaining high strength, something unattainable in aluminum alloys of comparable strength. A shaped body obtained in this way is therefore also advantageously suitable for the production of components for electrical circuits.Components produced in this way are particularly suitable for use in the automotive or aviation sectors, as they offer not only advantageous electrical and mechanical properties but also low weight. Their use is particularly advantageous in the field of electromobility.

[0032] According to a further development, the extruded blank is characterized by the aluminum oxide phase having a mass fraction of 0.1% to 3%. The mass specification according to this development refers to the total mass of the extruded blank without differentiation according to zones of higher and lower concentration, such as the particle shell and the particle core.

[0033] It was found that with such a mass fraction, on the one hand, a significant increase in elongation at break and strength can be achieved, and on the other hand, the electrical conductivity is only slightly reduced compared to aluminum or pure aluminum.

[0034] According to a further development, the extruded blank is characterized in that the aluminum oxide phase has a mass fraction in the particle shell of 10% to 90% and in the particle core of less than 0.3%.

[0035] Advantageously, by having a significantly different concentration of the aluminum oxide phase in the particle core and the particle shell within the specified ranges according to this refinement, a low mass fraction relative to the total mass can be achieved while simultaneously providing high strength and high electrical conductivity. According to a refinement, the extruded blank is characterized in that the shell is designed as a corrugated tube.

[0036] Advantageously, a blank shell with increased strength is provided with minimal material usage. Furthermore, corrugated aluminum tubing is commercially available. Furthermore, the corrugation of the shell, which runs transversely to the longitudinal axis, prevents the vibration impulses from being transmitted within the shell during axial vibration for compaction, allowing the powder particles to adhere undisturbed to the inside of the shell while simultaneously compacting.

[0037] According to a further aspect, the invention relates to a method for producing an extruded blank and a method for producing an extruded part. The descriptions of the extruded blank according to the invention apply correspondingly to the methods according to the invention, taking into account the following aspects.

[0038] The method according to the invention for producing an extruded blank comprises the following process steps: a) Providing an aluminum powder comprising powder particles

[0039] In process step a), the aluminum-based metal powder is provided. Such aluminum-based metal powders are known as such from the prior art and are also referred to herein as aluminum grit. The metal powder is preferably produced according to the process according to the invention with powder particles in the size range from 10 pm to 200 pm and particularly preferably in the size range from 75 pm to 125 pm, which are also referred to as grit particles. To produce the aluminum grit, liquid aluminum is first provided and then sprayed, blown, atomized, stirred, or shaken to form grit particles. The aluminum grit can have different shapes and different size fractions. The shapes and size fractions of the particles influence the properties of the aluminum composite material to be produced and can be determined during production of the aluminum grit and, if necessary, by sieve curves.Preferably, the aluminum grit has a spiky shape. b) Providing a hollow cylindrical shell, a base shell cap, and a cover cap, each formed from an aluminum material.

[0040] In process step b), the blank casing is prepared. The casing is preferably a commercially available, very thin-walled aluminum tube or hose. The casing caps can also be formed from thin-walled aluminum sheet. c) The bottom casing cap is arranged at a bottom end of the casing, forming an interior space open on the lid side, and placed vertically on a vibrating table.

[0041] In process step c), the bottom shell cap is positioned so that a blank shell is still open on one side, the interior of which is accessible via an opening in the lid. The open blank shell is placed upright on a vibrating table with the bottom cap; placing it on the vibrating table can also be done after process step d). d) The aluminum powder is poured into the interior via one end on the lid.

[0042] In process step d), the aluminum powder is poured into the interior through the opening on the lid. This can preferably be done mechanically and automatically. e) The aluminum powder is compacted using the vibrating table through axial vibrations.

[0043] In process step e), which is particularly important for the process according to the invention, vibratory compaction is carried out. The vibrating table introduces axial impact pulses into the aluminum powder, causing the powder particles to align, gaps to be filled and reduced, and the powder particles to interlock, increasing the bulk density compared to loose bulk. At the same time, the powder particles adhere more intensively to the inside of the casing, supporting it and thus increasing its dimensional stability. The filling and the casing thus support each other. Optionally, additional aluminum powder can be added to compensate for any volume released in the interior due to settlement. Furthermore, process steps d) and e) can also be carried out entirely or partially simultaneously. f) Positioning the cover casing cap on the cover-side end

[0044] The lid cover cap is arranged to close the interior.

[0045] The result of the process is an extrusion blank that is sufficiently dimensionally stable to be transported manually or mechanically and is available for use in an extrusion device.

[0046] Particularly advantageously, the process can be used to obtain an extruded blank cost-effectively and with low energy expenditure, which enables the production of an extruded part with the particularly advantageous properties described.

[0047] According to a further development, the method for producing an extruded blank is characterized in that the powder particles are formed according to one of claims 2 to 5. This advantageously results in an extruded blank which has the production of an extruded part with the particular properties according to the description sections of claims 2 to 5.

[0048] The method according to the invention for producing an extruded part comprises the following method steps.

[0049] Process steps a) to f) according to one of the preceding claims 7 or 8

[0050] First, the described process steps a) to f) of the process for producing an extruded blank are carried out. g) Inserting the extruded blank obtained by process steps a) to f) of claims 7 or 8, or an extruded blank according to one of claims 1 to 6, into an extrusion device and extruding the extruded blank into an extruded part.

[0051] In process step g), the resulting extruded blank is placed in an extrusion device, and extrusion is carried out. Extrusion devices and the extrusion process are known in the art.

[0052] Advantageously, an extruded part with the particularly advantageous properties described above is obtained.

[0053] The invention is illustrated by way of example with reference to

[0054] Fig. 1 Schematic representation of an extrusion blank Fig. 2 Schematic representation of a blank shell without blank filling explained in more detail.

[0055] Identical reference symbols in the various figures refer to identical features or components. These reference symbols are used in the description even if they are not shown in the respective figure.

[0056] Fig. 1 shows an exemplary embodiment of an extruded blank. The blank casing 10 has a casing jacket 11, which here is designed as a corrugated aluminum tube. The wall thickness of the corrugated aluminum tube in this exemplary embodiment is 0.15 mm. Attached to a bottom end of the casing jacket 11 is the bottom casing cap 12, which in this exemplary embodiment is a round aluminum sheet with a rim for flanging with the casing jacket.

[0057] In Fig. 1, the blank shell 10 is already provided with the blank filling 20, which almost lies against the lid-side end of the shell 10. The lid shell cap 13 is shown still open here.

[0058] Fig. 2 shows the blank casing 10 without the lid casing cap 13 and without the blank filling 20, with the concealed bottom casing cap 12 represented by the dashed line. Fig. 2 also shows the interior 14.

[0059] Furthermore, an extrusion blank, a method for producing it and a method for producing an extrusion part are described in one embodiment as follows.

[0060] An aluminum powder based on 99.7% aluminum is supplied as a spray grit with a grain size of 75 pm to 125 pm. Due to its production by spraying in an oxygen-containing atmosphere, it contains an aluminum oxide-containing particle shell and has a total mass fraction of Al2O3 of approximately 3%.

[0061] To produce the extrusion blank, a thin-walled corrugated aluminum tube with a wall thickness of 0.15 mm and a diameter of approximately 50 mm is placed on a vibrating table as a casing. The corrugated aluminum tube is tightly sealed at the end resting on the vibrating table with an aluminum sheet cover, which forms the bottom closure cap.

[0062] The described spray grit is poured loosely into the corrugated aluminum pipe, resulting in a bulk density of approximately 42%. The corrugated aluminum pipe, with its aluminum powder filling, is then vibrated using the vibrating table, aligning the powder particles and reducing the total volume of air inclusions to such an extent that a bulk density of approximately 55% is achieved. During vibration, the corrugated aluminum pipe is supported along its circumference to prevent it from tipping over or changing position. After vibratory compaction is complete, an aluminum sheet cover is placed on top as a cover shell cap, and the extrusion blank is finished. In the example shown, it has a height of 220 mm. It can now be removed.

[0063] To produce an extruded part, which in this example is a wire with a diameter of 1 mm, the extruded blank is placed in an 8 MN extrusion press. (The 8 MN (meganewton) refers to the extrusion system and not the actual applied force.) The extruded blank is heated to approximately 300 °C, and then extrusion is performed at a pressing force of approximately 2.2 MN.

[0064] The wire, as the extruded part, exhibits advantageous mechanical and electrical properties. The yield strength was determined to be 15%. In comparison, the yield strength of 99.7% aluminum is approximately 3% to 5%. Furthermore, the produced wire exhibited advantageously low resistivity and, conversely, advantageously good electrical conductivity of 32.4 x 10 6S / m. In comparison, the conductivity of aluminum, depending on the degree of purity, is 28 x 10 6 S / m up to 37 x 10 6 S / m. Thus, despite the significantly improved mechanical properties compared to pure aluminum, the conductivity has not significantly deteriorated.

[0065] Reference symbols used

[0066] 10 blank sleeves

[0067] 11 Sheath

[0068] 12 bottom cover cap

[0069] 13 Ceiling cover cap

[0070] 14 Interior

[0071] 20 blank filling

Claims

Patent claims 1. Extruded blank, comprising a blank shell 10 and a blank filling 20, wherein the blank shell 10 is formed from an aluminum material and has a hollow cylindrical shell 11, a bottom shell cap 12 and a cover shell cap 13, wherein the bottom shell cap 12 is arranged at a bottom end of the shell 11 and the top shell cap 13 is arranged at a cover end of the shell 11 and wherein the blank shell 10 forms a cylindrical interior 14, wherein the blank filling 20 is arranged in the interior 14 and is formed as aluminum powder having compacted powder particles.

2. Extruded blank according to claim 1, characterized in that the powder particles have a spattered shape.

3. Extruded blank according to one of the preceding claims, characterized in that the powder particles have an aluminum metallic phase and an aluminum oxide phase, that the aluminum metallic phase has aluminum and / or an aluminum alloy and forms a particle core and that the aluminum oxide phase has Al2O3 and forms a particle shell which surrounds the particle core.

4. Extruded blank according to one of the preceding claims, characterized in that the aluminum oxide phase has a mass fraction of 0.1% to 3%.

5. Extruded blank according to one of the preceding claims, characterized in that the aluminum oxide phase has a mass fraction in the particle shell of 10% to 90% and in the particle core of less than 0.3%.

6. Extruded blank according to one of the preceding claims, characterized in that the enveloping jacket is designed as a corrugated tube.

7. A method for producing an extruded blank, comprising the following method steps: a) providing an aluminum powder comprising powder particles, b) providing a hollow cylindrical shell, a bottom shell cap and a lid cap, each formed from an aluminum material, c) arranging the bottom shell cap at a bottom end of the shell and forming an interior space open on the lid side and placing it vertically on a vibrating table, d) filling the aluminum powder into the interior space via a lid-side end, e) vibratory compacting the aluminum powder by means of the vibrating table through axial vibrations, f) arranging the lid shell cap at the lid-side end.

8. A method for producing an extruded blank according to claim 7, characterized in that the powder particles are formed according to one of claims 2 to 5.

9. A method for producing an extruded part, comprising the following method steps: Process steps a) to f) according to one of the preceding claims 7 or 8, g) inserting the extrusion blank obtained by process steps a) to f) or an extrusion blank according to one of claims 1 to 6 into an extrusion device and extruding the extrusion blank to form an extruded part. HERE IS A PAGE OF DRAWINGS

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