WO2010057562A1

WO2010057562A1 - Hollow profiles made of aluminium alloy

Info

Publication number: WO2010057562A1
Application number: PCT/EP2009/007640
Authority: WO
Inventors: Jérôme PIGNATEL
Original assignee: Alcan Rhenalu
Priority date: 2008-11-21
Filing date: 2009-10-26
Publication date: 2010-05-27
Also published as: EP2358546B1; FR2938790B1; EP2358546B2; ES2524436T3; ES2524436T5; FR2938790A1; EP2358546A1

Abstract

The invention relates to a hollow profile formed by assembling at least a first solid profile (1) made of aluminium alloy with at least a second solid profile (2) made of aluminium alloy, said first and second profiles being obtained by extrusion and each having a yield strength of at least 350 MPa and preferably of at least 400 MPa. Typically at least one of said solid profiles is made of an aluminium alloy of the 2xxx, 6xxx or 7xxx series, and is preferably selected in the group comprising the 6082, 6056, 6013, 7108, 7020, 7022, 7075, 7349, 7449, 2017, 2014, 2196 and 2195 alloys. The hollow profiles of the invention are advantageously used for making rims of cycle wheels.

Description

Aluminum alloy hollow sections

Field of the invention

The invention relates to the field of aluminum profiles and more particularly the hollow profile especially for the manufacture of crazy bike.

State of the art

The hollow aluminum profiles are wrought products, generally spun, of uniform cross section over their entire length and whose cross section comprises at least one inner hole. Solid sections, on the other hand, have a section with no internal holes.

The manufacture of aluminum alloy hollow sections by spinning is known to those skilled in the art. For the simplest forms, it is possible to carry out the needle or needle threading of a hollow billet. However, in general, and in any case for forms without axis symmetry, the spinning is carried out using bridge dies to obtain hollow sections. These spinning techniques are generally used for alloys such as 6060, 6061, 6106 or 6005 and can be difficult to implement for harder alloys, typically aluminum alloys whose yield strength at 0.2% elongation is greater than 350 MPa. In particular the production of hollow sections whose inner walls have low thicknesses, typically of the order of mm, proves delicate for these hard alloys. Similarly, the service life of the tools used is low for the realization of hollow monobloc hollow alloy profiles.

The aluminum hollow profiles are particularly useful for the manufacture of rims for bicycle wheels.

A bicycle wheel generally comprises a central hub connected to a circular rim by spokes. The rim may be formed of an aluminum alloy profile comprising two coaxial circular bridges connected by two lateral flanks so as to form a box. The lateral flanks extend radially outwards by two wings, so as to form with the outer bridge an annular groove provided to receive a tire. For certain rims that are provided to receive a hose, the groove is a simple groove formed by a sagging of the outer bridge radially inwardly. The spokes are connected to the rim by nuts screwed to the end of the spokes. These nuts also make it possible to adjust the tension of the spokes. To receive the spoke nuts, in the usual way, the two rim bridges are usually pierced with orifices distributed around the circumference of the rim. The inner bridge openings are designed to serve as seating for the nut heads. The outside deck openings, of outside diameter, are provided to allow the installation of the radius nut from the outside and / or to strengthen the attachment of the spokes. It is also possible to drill only the inner bridge and avoid drilling the outer deck so as to obtain a gas-tight outer deck, however this configuration requires a large thickness of the inner bridge so that it has sufficient rigidity .

Rims must combine two characteristics that often prove to be antithetical: the lightness, so as to improve the comfort of the users, and the mechanical resistance so as to ensure the safety and the lifetime of the products. In the prior art, additional steps to the rim manufacturing method have been proposed to reconcile these antinomic characteristics.

Patent Application FR 2,727,355 A1 describes a method of manufacturing a cycle rim consisting in bending a hollow section in which, in a complementary stage, a chemical machining is carried out, which consists in removing the metal by dissolving in an aggressive chemical bath in order to reduce the thickness of the walls and the weight of the rim. This chemical machining step can be difficult to implement and results in a loss of metal. The patent application FR 2 897 013 A1 describes a method of manufacturing an aluminum alloy bicycle rim comprising a hollow section comprising a lower bridge pierced by rack orifices in which a cold deformation step in the vicinity. racking holes locally increase the hardness of aluminum. The hardness increase by work hardening, however, remains very limited.

The present invention seeks to solve the aforementioned problem of manufacturing hard alloy hollow profiles, and in particular to improve the production of hollow profiles intended for the manufacture of a bicycle. Description of figures

Figure 1 illustrates a profile according to the invention.

FIG. 2 illustrates the second profile used to produce the profile according to the invention of FIG.

FIG. 3 illustrates the first profile used to make the profile according to the invention of FIG. 1. FIG. 4 illustrates another profile according to the invention.

Objects of the invention

A first object of the invention is a hollow profile formed by assembling at least a first solid section (1) of aluminum alloy with at least a second solid section (2) of aluminum alloy, said first and second profiles being obtained by spinning and each having a yield strength of at least 350 MPa and preferably at least 400 MPa. A second object of the invention is a wheel rim for a cycle comprising a hollow section according to the invention, said section having been bent before or after assembly. Yet another object of the invention is a bicycle wheel comprising a hub, a rim according to the invention and spokes stretched between the hub and the rim. Yet another object of the invention is a method of manufacturing a hollow section according to the invention in which:

(i) supplying at least a first solid section (1) of aluminum alloy and at least a second solid section (2) of aluminum alloy, said first and second sections being obtained by spinning and each having a limit of elasticity of at least 350 MPa and preferably at least 400 MPa; (ii) said solid sections are assembled so as to form a hollow section

Detailed description of the invention

Unless stated otherwise, all the information concerning the chemical composition of the alloys is expressed as a percentage by weight based on the total weight of the alloy. The designation of alloys is in accordance with the regulations of The Aluminum Association, known to those skilled in the art. The definitions of the metallurgical states are given in the European standard EN 515. Unless otherwise stated, the static mechanical characteristics, in other words the tensile strength R _m , the conventional yield stress at 0.2% elongation R _p o, ₂ ("yield strength") and the elongation at break A%, are determined by a tensile test according to EN 10002-1, the sampling and the direction of the test being defined by the EN 485-1 standard.

Unless otherwise specified, the definitions of EN 12258 apply. The thickness of the solid profiles is defined according to EN 2066: 2001: the cross section is divided into elementary rectangles of dimensions A and B; A being always the largest dimension of the elementary rectangle and B can be considered as the thickness of the elementary rectangle.

According to the invention a hollow profile is formed by assembling at least one first solid section (1) of aluminum alloy with at least one second solid section (2) of aluminum alloy, said first and second sections being obtained by spinning and each having a yield strength of at least 350 MPa and preferably at least 400 MPa. Obtaining a single-piece hollow profile of identical geometry by spinning on a needle or spinning with a bridge die would be very difficult. The advantage of the process according to the invention is that it makes it possible to obtain hard alloy profile shapes that would have been very difficult to obtain with a bridge die, because of their shape, their thickness and the nature of the alloy. alloy to spin. Indeed, when the metal must flow along the supply channels of a bushing die, it undergoes intense shear stresses related to the proximity of the walls of said feed channels. The mechanical energy required to overcome these shears and to make the flow of the metal possible is largely transformed into heating, so that locally the metal leaving the die can quickly reach a dangerous temperature, for example vis-à-vis vis the risk of burns. In addition, the bridge tools, in particular the needles which form the "cover" making it possible to obtain the cavity of the hollow profile, are inherently very fragile because they undergo very high stresses due to the friction of the metal on their flanks. and, because of the difficulty of their cooling, they heat up progressively and deform by creep. With the method for obtaining the profile according to the invention, it avoids the constraints related to the use of die bridge: can spin faster profiles with lower thicknesses while controlling much more easily the regime thermal spun metal. The invention is particularly advantageous for hollow sections in which at least one of the solid sections has a thickness of less than 2 mm and preferably less than 1 mm, ie a solid section whose thickness B d is less than 1 mm. at least one elementary rectangle is less than 2 mm and preferably less than 1 mm. The zone of small thickness is preferably part of the walls of the peripheral box formed by the assembly of the solid sections. It is no longer necessary to obtain these profiles to perform mechanical or chemical machining steps as in the prior art.

In a first embodiment, a hollow profile according to the invention has, in cross-section, two lateral wings (3, 4) forming the two lateral flanks of said profile, joined at their base by a lower bridge (5) and in their central part by an upper bridge (6) so as to produce towards the top of the wings a groove characterized in that said upper bridge is part of said first solid profile and said lower bridge is part of said second solid profile. An advantageous example of hollow section according to the invention of this first embodiment is illustrated in FIG.

The hollow profile according to the invention of this embodiment is of general plane of symmetry (P) and has a section having the general shape of a U open towards the outer periphery. The hollow section is formed by assembling a first solid section (1) illustrated in FIG. 3 and a second solid section (2) illustrated in FIG. 2. The profile has two advantageously symmetrical lateral wings (3, 4). relative to the plane (P) connected by two transverse bridges (5, 6) spaced from one another: a lower bridge (5) from the second section and an upper bridge (6) from the first section, both bridges (5, 6) being preferably slightly curved and forming with lateral wings (3, 4) a peripheral box (7) intended in particular to ensure the mechanical strength and rigidity of the hollow profile thus formed. The minimum thickness B is typically less than 1 mm, for example of the order of 0.75 mm.

Furthermore, advantageously, the end of each of the wings (3, 4) comprises a local projection (8, 9) intended in particular to retain a tire when this profile is used as a bicycle wheel rim. Advantageously, at least one of said solid profile is aluminum alloy series 2xxx, 6xxx or 7xxx.

Preferably, at least one solid section is aluminum alloy selected from the group consisting of alloys 6082, 6056, 6013, 7108, 7020, 7022, 7075, 7349, 7449, 2017, 2014, 2196 and 2195. In a preferred embodiment, said first solid profile and second solid section are aluminum alloy of the 2xxx, 6xxx or 7xxx series. and preferentially are selected from the group consisting of alloys 6082, 6056, 6013, 7108, 7020, 7022, 7075, 7349, 7449, 2017, 2014, 2196 and 2195. Alloys 7108, 7020, 7022, 7075, 7349, 7449 have in particular the advantage of a high hardness. In particular, alloys 2195 and 2196 which contain lithium have the advantage of low density. The alloy 6056 is preferred for the production of solid profiles according to the invention because it has a good compromise between all the desired properties: spinnability, hardness and resistance to corrosion. In an advantageous embodiment of the invention the first solid section is made of a first aluminum alloy and the second solid section is made of a second aluminum alloy different from the first alloy. Advantageously, the first alloy is selected from the group consisting of alloys 6082, 6056, 6013, 2017, 2014, 2196 and 2195 and the second alloy is selected from the group consisting of alloys 7108, 7020, 7022, 7075, 7349, 7449. first and second profiles can be assembled by any means to achieve the desired mechanical characteristics for the intended application. In one embodiment illustrated in FIG. 4, the profiles are assembled by cooperation of shapes (12, 13). This embodiment by clipping can be consolidated by structural bonding. In a preferred embodiment illustrated in Figure 1, the contact between the profiles is typically made on flat-shaped areas (10, 11) and the assembly is performed by welding or gluing. This embodiment makes it possible to achieve greater mechanical strength of the assembly than that obtained by simple clipping. Advantageously, the welding when it is chosen is performed by friction stir welding, laser welding or arc welding. Advantageously, the hollow sections according to the first embodiment are used for the manufacture of wheel rims for cycling the profiles that have been bent before or after assembly. In this embodiment, the lower bridge of the hollow section becomes the inner bridge of the rim and the upper bridge of the hollow section becomes the outer bridge of the rim. The first section and the second profile can be bent after assembly. This embodiment has the advantage of allowing a direct substitution of the profiles currently used with existing methods: the hollow profile according to the invention can be directly substituted for the one-piece hollow profiles according to the prior art. In some cases, however, the present inventors have found that the bending of the assembled section could weaken the assembly area. One solution that can be advantageous is to move the area welding so that it is closer to the neutral fiber during bending, so as to minimize mechanical stresses on said area during bending. In another embodiment allowing a second solution to solve this problem when it occurs, the first and second profiles are bent in a first step and then assembled in a second step.

In particular, when the hollow profiles according to the invention are used for the manufacture of wheel rims, it is advantageous to use a second hollow section of harder alloy than that of the first hollow profile and preferably having a yield strength of at least 400 MPa and preferably at least 450 MPa. In fact, the second hollow section comprises the inner bridge of the rim which must be drilled for fixing the spokes; the use of a hard alloy makes it possible to obtain a satisfactory fixation without having to pierce the outer bridge as well. Thus, it is no longer necessary to perform a cold deformation step in the vicinity of the hole so as to locally increase the hardness of the aluminum as in the prior art. An alloy of the 7xxx family such as 7108, 7020, 7022, 7075, 7349, 7449 may advantageously be used for the production of the second profile while an alloy of the 2xxx or 6xxx family such as 6082, 6056, 6013, 2017, 2014, 2196 and 2195 is advantageous for the production of the first section. In such a case, it is preferable to bend each section separately and then assemble them. In known manner, the two ends are assembled end to end after bending so as to form a wheel, typically by welding.

A bicycle wheel comprising a hub, a rim according to the invention and spokes stretched between the hub and the rim, has improved characteristics in terms of lightness and mechanical strength.

The invention also relates to the method of manufacturing the profiles according to the invention in which:

(i) supplying at least a first solid section (1) of aluminum alloy and at least a second solid section (2) of aluminum alloy, said first and second sections being obtained by spinning and each having a limit of elasticity of at least 350 MPa and preferably at least 400 MPa;

(ii) assembling said solid sections to form a hollow section. Advantageously, the assembly is made by welding.

Claims

claims

A hollow profile formed by assembling at least a first solid section (1) of aluminum alloy with at least a second solid section (2) of aluminum alloy, said first and second sections being obtained by spinning and having each has a yield strength of at least 350 MPa and preferably at least 400 MPa.

2. Hollow section according to claim 1 wherein at least one of said solid profiles locally has a thickness of less than 2 mm and preferably less than 1 mm.

3. Hollow section according to claim 1 or claim 2 having in cross section two lateral wings (3,4) forming the two lateral flanks of said profile, joined at their base by a lower bridge (5) and in their middle part by a upper bridge (6) so as to produce towards the top of the wings a groove characterized in that said upper bridge (6) is part of said first solid profile and said lower bridge (5) is part of said second solid profile.

4. hollow profile according to any one of claims 1 to 3 characterized in that at least one of said solid profile is aluminum alloy series 2xxx, 6xxx or

7xxx. and preferentially is selected from the group consisting of alloys 6082, 6056, 6013, 7108, 7020, 7022, 7075, 7349, 7449, 2017, 2014, 2196 and 2195.

5. hollow profile according to any one of claims 1 to 4 characterized in that said first solid section is made of a first aluminum alloy and said second solid section is a second aluminum alloy different from said first alloy.

6. hollow profile according to claim 5 characterized in that said first alloy is selected from the group consisting of alloys 6082, 6056, 6013, 2017, 2014, 2196 and 2195 and said second alloy is selected from the group consisting of alloys

7108, 7020, 7022, 7075, 7349, 7449.

7. hollow profile according to any one of claims 1 to 6 wherein the assembly is performed by welding or gluing.

8. Hollow section according to claim 7 wherein the assembly is performed by friction stir welding, laser welding or arc welding.

9. A cycle wheel rim comprising a hollow section according to any one of claims 3 to 8, said section having been bent before or after assembly.

The cycle wheel rim of claim 9 wherein said second hollow section has a yield strength greater than that of the first hollow section.

A wheel rim according to claim 9 or claim 10 wherein an alloy of the 7xxx family is used for producing said second section.

Bicycle wheel comprising a hub, a rim and spokes stretched between the hub and the rim, characterized in that the wheel comprises a rim according to any one of claims 9 to 11.

13. A method of manufacturing a hollow section according to any one of claims 1 to 8 wherein (i) supplying at least a first solid section (1) of aluminum alloy and at least a second solid section (2). in aluminum alloy, said first and second sections being obtained by spinning and each having a yield strength of at least 350 MPa and preferably at least 400 MPa; (ii) assembling said solid sections to form a hollow section.

14. The method of claim 13 wherein the assembly is performed by welding.