METHOD FOR ASSEMBLING TWO BARS OF METALLIC MATERIAL BY WELDING
By transversely enlarging the ends of thin metal bars with metallic pellets or folding techniques, the method addresses the issue of excessive molten metal drops during welding, achieving a reliable and high-quality weld for thin bars.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- AMPERE SAS
- Filing Date
- 2024-01-30
- Publication Date
- 2026-05-22
AI Technical Summary
Existing welding processes for thin metal bars, such as those used in electric machine rotors, result in excessive molten metal drops that cause unsightly flows and reliability issues due to limited thickness options and laser welding limitations.
A method involving an additional step to transversely enlarge the ends of the bars before welding, using metallic pellets or folding techniques to contain the molten metal within the bar ends, ensuring the total thickness is sufficient to hold the weld width, thereby preventing metal flow.
The method effectively contains molten metal drops, ensuring a reliable and high-quality weld by maintaining the molten metal within the bar ends, enhancing the strength and appearance of the assembly.
Smart Images
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Abstract
Description
Title of the invention: METHOD FOR ASSEMBLING TWO BARS BY WELDING MADE OF METAL Technical field of the invention
[0001] The invention relates to a method of assembling two bars of metallic material by welding. Technical background
[0002] The prior art includes documents DE-20.2018-006090-U1, US-2013.106231-A1, and DE-10.2016.215031-AL
[0003] In an electrical device or power component, or more generally in a device in which high electrical powers are transmitted, it is common to have to weld conductive metal bars of relatively large dimensions, these bars being made of copper for certain applications.
[0004] For certain applications, such as welding an electric machine rotor to its excitation system, it may be necessary to perform butt welding of two substantially longitudinal metal bars placed parallel to each other. Such bars are generally a few millimeters thick, typically 2 to 4 mm, which allows butt welding to be performed using many welding processes known in the prior art.
[0005] In certain specific applications, however, it may be necessary to use bars of a smaller thickness, typically on the order of 1 mm, which limits the choice of available welding processes and complicates their execution.
[0006] In the context of large-scale production, it is generally preferred to use a laser welding process, which allows the end assembly of the bars to be carried out by a welding robot with high speeds and with high quality.
[0007] However, when assembling bars with a reduced thickness on the order of a millimeter, such as those used for connecting an electric machine rotor with its excitation system, it has been observed that the melting of the metal at the end of the bars under the effect of the laser beam produces a drop of molten metal which is of a dimension much greater than the cumulative thickness of the bars, which results in a flow of metal along the bars and a weld which is on the one hand unsightly and which on the other hand can pose reliability problems in the long term.
[0008] However, in this type of application it is not possible to increase the thickness of the bars so that the drop of molten metal remains contained at the end of the bars, nor is it possible to use a welding process that generates a drop of molten metal of smaller dimensions.
[0009] There is therefore a real need for a welding assembly process for two bars of reduced thickness which makes it possible to avoid any flow of molten metal along said bars. Summary of the invention
[0010] The invention satisfies this need by proposing an assembly method that allows the drop of molten metal to be contained at the end of the two bars.
[0011] To this end, the invention proposes a method for welding together two substantially longitudinal bars of determined first transverse thicknesses made of metallic material, said method comprising the steps of:
[0012] - ET1 place said bars longitudinally side by side with free ends of said bars in the same transverse plane to form a rough part having a transverse thickness comprising the first cumulative transverse thicknesses of said bars,
[0013] - ET2 position a welding tool suitable for performing a weld of width determined at the free end of said bars, and weld said free ends of said bars,
[0014] characterized in that it comprises an additional step ETS during which the blank part is transversely enlarged in end sections of said bars so that its transverse thickness is greater than the width of said weld.
[0015] The widening of the blank in the end sections of said bars advantageously makes it possible to provide a surface at the end of the bars which is suitable for containing the drop of molten metal generated by the welding tool at the end of these bars and to prevent it from flowing down these bars.
[0016] According to other features of the invention:
[0017] - the additional step ETS is a prerequisite step to the ET2 step during to which is added, transversely on each side of the blank on each of the said end sections, a pellet of said metallic material, each pellet being flush in said transverse plane and a second determined thickness of each pellet being chosen so that the sum of the first two thicknesses and the second two thicknesses is of transverse thickness at least equal to the width of the weld,
[0018] - during the additional ETS step, each pellet is welded onto one of the bars of the draft,
[0019] - during the additional ETS step, the pads are welded onto the bars through resistance,
[0020] - the additional step ETS is a prerequisite step to step ET1,
[0021] - during the additional ETS step, the sections are sintered end of said bars, so that the total thickness of each bar is at least equal to half the width of the weld,
[0022] - during step ET1, said bars are placed longitudinally side by side with their end sections transversely opposed to each other, to form a basin between the two bars, the bottom of said basin defining the free ends of said bars,
[0023] - during step ET2, the free ends of the bars are welded into said basin,
[0024] - during the additional ETS step, the end sections of said bars folded over themselves so that a total thickness of each bar at its folded end section is at least equal to half the width of the weld, each folded section defining a main branch and a folded branch joined by a bend forming the free end of said bar,
[0025] - during step ET1, said bars are placed longitudinally side by side with the folded branches of their end sections turned towards each other,
[0026] - during step ET1, said bars are placed longitudinally side by side with the folded branches of their end sections transversely opposed to each other,
[0027] - during step ET2, the ends of said bars are welded in the plane transverse, passing through the elbows,
[0028] - the welding tool is a laser welding tool.
[0029] The invention finally relates to a part made by assembling two bars according to the assembly process described above, comprising the blank of the part enlarged transversely in the end sections of the bars. Brief description of the figures
[0030] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the accompanying drawings in which:
[0031] [Fig. 1] the [Fig. 1] is an assembly of two bars according to a state-of-the-art process;
[0032] [Fig.2] the [Fig.2] is an assembly of two bars according to a first embodiment of a process which is the subject of the invention;
[0033] [Fig.3] the [Fig.3] is an assembly of two bars according to a second embodiment of a process which is the subject of the invention;
[0034] [Fig.4] the [Fig.4] is an assembly of two bars according to a third embodiment of a process which is the subject of the invention;
[0035] [Fig.5] the [Fig.5] is an assembly of two bars according to a fourth embodiment of a process which is the subject of the invention;
[0036] [Fig.6] [Fig.6] is a block diagram illustrating the steps of an assembly process according to the state of the art;
[0037] [Fig.7] [Fig.7] is a block diagram illustrating the steps of an assembly process according to the first embodiment of the invention;
[0038] [Fig. 8] [Fig. 8] is a block diagram illustrating the steps of an assembly process according to the first to fourth embodiment of the invention. Detailed description of the invention
[0039] An assembly 10 is schematically represented in [Fig.1], this assembly being produced by a laser welding process.
[0040] The two bars 12 are substantially longitudinal and each has a first transverse thickness determined.
[0041] This is, for example, an assembly for the electrical connection of an electric machine rotor with its electrical excitation system. Thus, the first bar 12 belongs to the rotor, while the second bar 12 belongs to the electrical excitation system. For this purpose, the bars 12 must be able to conduct electricity. They are, for example, made of copper.
[0042] According to the prior art process, during a step ET1, which has been represented in the block diagram of [Fig. 6], the bars 12 are placed longitudinally side by side with their free ends 14 in the same transverse plane P. This forms a rough part 16 having a transverse thickness El, which is the sum of the first transverse thicknesses el of the bars 12.
[0043] Then, during a step ET2, a welding tool 18 suitable for welding is positioned at the free end 14 of the bars 12, and the free ends 14 of the bars 12 of determined width 11 are welded. A drop of molten metal 19 forms at the free ends 14 of the bars 12.
[0044] The molten metal droplet 19, upon solidifying, transforms into a weld 20, which will be represented by dotted lines in the remainder of this description.
[0045] In the context of high-volume production, and in order to obtain high-quality welds that can be executed at high rates by a welding robot, a welding tool 18, which is a laser welding tool, is generally used.
[0046] Currently, as illustrated in [Fig. 1], such a laser welding tool causes the metal of the bars 12 to melt in such a way that the droplet 19 of molten metal that forms at the ends 14 of the bars 12 has a width E2 that is greater than the width of the blank 16. For example, each bar 12 has a thickness el of 1 mm, the blank 16 thus having a width El of 2 mm. This configuration is detrimental because it risks causing drips 21 of molten metal (represented by dashed lines in [Fig. 1]) along the bars 12, these drips 21 being both unsightly and potentially preventing the bars 12 from being placed in a housing provided for this purpose. In addition, the deficit of molten metal at the ends of the bars 12 can lead to a weakness of the weld 20 after the solidification of the drop 19 of molten metal, which goes against the desired reliability.
[0047] To remedy this drawback, the invention proposes a method comprising, as illustrated in Figures 2 to 5, an additional step ETS during which the blank 16 of the part is transversely widened in end sections 24 of the bars 16 so that its transverse thickness E3 is greater than the width E2 of said weld 20.
[0048] According to a first embodiment of the process which is the subject of the invention, which has been shown in Figures 2, 7 and 8, the additional step ETS is a step prior to step ET2, this step being able to take place between step ET1 and step ET2 as shown in [Fig.7], or prior to step ET1 as shown in [Fig.8].
[0049] During this ETS step, a pad 22 of the same metallic material as the bars 12 is added transversely on each side of the blank 16 on each of these end sections 24. As can be seen in [Fig.2], each pad 22 is flush in the transverse plane P and a second determined thickness e2 of each pad 22 is chosen so that the sum E3 of the first two thicknesses e1 and the two second thicknesses e2 is at least equal to the width E2 of the weld 20.
[0050] Thus, the weld 20, of the same width as the drop of molten metal 19, does not extend beyond the bars 12.
[0051] Without limiting the invention, during this additional step ETS, each pad 22 is welded onto each of the end sections 24 of the bars 12 of the blank 16. This configuration is not limiting the invention, and the pads 22 could be held by clamping onto the bars 12, the pads 22 then being finally assembled during step ET2 during the laser welding operation.
[0052] Preferably, the pellets 22 are however previously resistance-welded to the bars 12, in order not to cause deformation of the bars 12.
[0053] In second, third, and fourth embodiments of the process of the invention, which have been shown in [Fig. 8], the additional step ETS is a prerequisite to the step EET
[0054] According to the second embodiment of the process illustrated in [Fig.3], during the additional step ETS, the end sections 24 of the bars 12 are sintered.
[0055] For the record, it is recalled that soyage is a double-folding operation of a flat sheet, at the end of which two parallel planes are obtained, offset by a distance of the same order of magnitude as the thickness of the sheet.
[0056] Thus a total thickness e3 of each bar 12, including the end sections 24, is at least equal to half the width E2 of the weld 20 once the drop of molten metal 19 has solidified, so that the total thickness E3 of the two bars 12 with their end sections 24 is greater than the width of the weld 20.
[0057] Then, having done this, during the following step ET1, the bars 12 are placed longitudinally side by side with their end sections 24 transversely opposed to each other, to form a bowl 26 between the two bars 12. A bottom of this bowl 26 thus determines the free ends 14 of the bars 12.
[0058] Finally, during the next step ET2, the free ends 14 of the bars 12 are welded into the bowl 26 so that the drop 19 of molten metal forms at the ends 14 of the bars 12. As it solidifies, the drop 19 forms the weld 20 of width E2.
[0059] This configuration is particularly advantageous because the molten metal droplet 19 is contained by the end sections 24 of the bars 12, which ensures that the molten metal droplet 19 is of a width less than the thickness E3 of the blank 16.
[0060] According to the third and fourth embodiments of the process, as shown in Figures 4 and 5, during the additional step ETS, the end sections 24 of said bars are folded back on themselves so that a total thickness e4 of each bar 12 at the level of its folded end section 24 is at least equal to half the width E2 of the weld 20.
[0061] Each folded section 24 of the bar 12 determines a main branch 12a and a folded branch 12b joined by an elbow forming the free end 14 of the bar 12.
[0062] Then, in the third embodiment of the invention, as shown in [Fig. 4], during step ET1, the bars 12 are placed longitudinally side by side with the folded branches 12b of their end sections 24 transversely opposed to each other. This yields a blank 16 of thickness E4 greater than the width of the molten metal droplet 19, and therefore to the width E2 of the corresponding weld 20 once the molten metal droplet 19 has solidified.
[0063] In the fourth embodiment of the invention, as shown in [Fig.5], during step ET1 the bars 12 are placed longitudinally side by side with the branches 12b folded from their end sections 24b turned in the opposite direction towards each other.
[0064] In both cases, it is therefore the bends forming the free end 14 of the bar 12 that determine the plane P in which the weld 20 will be carried out.
[0065] Then, whether in the third or fourth embodiment of the invention, during step ET2 the ends 14 of the bars 12 are welded in the transverse plane P which passes through the bends. The molten metal droplet 19 occupies a width E2 corresponding to the width E2 of the weld 20 once the molten metal droplet 19 has solidified.
[0066] Other embodiments of the process which have not been described more explicitly in the present description may be considered for the proper implementation of the process of the invention, as long as it includes an ETS step consisting of widening the blank 16. For example, instead of the pellets 22 described with reference to the first embodiment of the process, it could be envisaged to cap the ends 14 of the bars 12 with a cap of the same material, of adequate width, which would allow the blank 16 to be widened.
[0067] The invention makes it possible to considerably improve the laser welding operation of two bars of reduced thickness metallic materials, and to make the weld 20 thus obtained reliable during the solidification of the molten metal droplet 19. It makes it possible to obtain a part of great strength from a blank of part 16 previously widened transversely in the end sections 24 of the bars 12.
Claims
Demands
1. A method for joining two substantially longitudinal bars (12) of metallic material, the two bars (12) being substantially longitudinal and each having a first determined transverse thickness (el), said method comprising the steps of: - (ET1) placing said bars (12) longitudinally side by side with free ends (14) of said bars (12) in the same transverse plane (P) to form a rough part (16) having a transverse thickness (El) comprising the first cumulative transverse thicknesses (el) of said bars (12), - (ET2) positioning a welding tool (18) capable of making a weld (20) of determined width (E2) at the free end (14) of said bars (12), and welding said free ends (14) of said bars (12),characterized in that it comprises an additional step (ETS) during which the blank part (16) is transversely enlarged in end sections (24) of said bars (12) so that its transverse thickness (E3) is greater than the width (E2) of said weld (20).
2. Assembly method according to the preceding claim, characterized in that the additional step (ETS) is a pre-step to step (ET2) in which a pellet (22) of said metallic material is added transversely on each side of the blank (16) on each of said end sections (24), each pellet (22) being flush in said transverse plane (P) and a second determined thickness (e2) of each pellet being chosen so that the sum (E3) of the first two thicknesses (el) and the second two thicknesses (e2) is at least equal to the width (E2) of the weld (20).
3. Assembly method according to the preceding claim, characterized in that, during the additional step (ETS), each pellet (22) is welded onto one of the bars (16) of the blank (12).
4. Assembly method according to the preceding claim, characterized in that, during the additional step (ETS), the pellets (22) are resistance welded onto the bars (12).
5. Assembly method according to claim 1, characterized in that the additional step (ETS) is a prerequisite step to step (ET1).
6. Assembly method according to the preceding claim, characterized in that during the additional step (ETS), the end sections (24) of said bars (12) are swaged so that a total thickness (e3) of each bar (12) is at least equal to half the width (E2) of the weld (20).
7. Assembly method according to the preceding claim, characterized in that, during step (ET1) said bars (12) are placed longitudinally side by side with their end sections (24) transversely opposed to each other, to form a cup (26) between the two bars (12), a bottom of said cup (26) determining the free ends (14) of said bars (12).
8. Assembly method according to the preceding claim, characterized in that, during step (ET2) said free ends (14) of said bars (12) are welded into said bowl (26).
9. Assembly method according to claim 5, characterized in that during the additional step (ETS), the end sections (24) of said bars are folded back on themselves so that a total thickness (e4) of each bar (12) at the level of its folded end section (24) is at least equal to half the width (E2) of the weld (20), each folded section (24) determining a main branch (12a) and a folded branch (12b) joined by a bend forming the free end (14) of said bar (12).
10. Assembly method according to the preceding claim, characterized in that, during step (ET1) said bars (12) are placed longitudinally side by side with the folded branches (12b) of their end sections (24) turned towards each other.
11. Assembly method according to the preceding claim, characterized in that, during step (ET1) said bars (12) are placed longitudinally side by side with the folded branches (12b) of their end sections transversely opposed to each other.
12. Assembly method according to any one of claims 10 or 11, characterized in that, during step (ET2) said ends (14) of said bars are welded in the transverse plane (P) which passes through the bends.
13. Assembly method according to any one of the preceding claims, characterized in that the welding tool is a laser welding tool. 10
14. Part made by assembling two bars according to the assembly method of any one of the preceding claims, characterized in that it comprises the blank part (16) enlarged transversely in the end sections (24) of the bars (12).