Welding method for a motor vehicle body

Abstract

The invention relates to a welding method for a motor vehicle body comprising a welding device. The method comprises the steps of: bringing a first part (22), a second part (23) and a third part into contact; the first part comprising a cavity; installing a pin (24) in the cavity, thereby forming a first contact region with the first part (22) and a second contact surface with the second part or the third part (23); positioning a first electrode and a second electrode of the welding device in the first contact region or the second contact surface; welding the first contact region and the second contact surface using the first electrode and the second electrode; and sub-steps comprising: generating a first pulse for a first duration; generating a second pulse at the end of the first duration for a second duration.

Description

[0001] Description

[0002] Title of the invention: Welding process for automobile bodywork

[0003] Technical field of the invention

[0004] The present invention claims priority from French application 2408738 filed on August 7, 2024, the content of which (text, drawings, and claims) is incorporated herein by reference. The present invention relates to a welding method for automotive bodywork. It is applicable in the field of automotive bodywork.

[0005] Previous technique

[0006] Welding is an assembly process that involves melting base materials and adding a filler metal, which forms a permanent bond after cooling and solidification.

[0007] An example of a prior art realization of such a device is shown in Figure 1.

[0008] Figure 1 represents a graph defining a single-pulse welding process.

[0009] In this figure, an initial pulse is applied to a surface area between a stud and two steel sheets. The welding energy with a single pulse and a single current value is too high, and also generates material ejection at the joint between the stud and the steel sheet; this causes large shrinkage cavities.

[0010] By applying an initial pulse with a higher welding current, the bond between the pin and the aluminum sheet is weakened. The heat generated melts the aluminum around the periphery of the pin head.

[0011] Presentation of the invention

[0012] The present invention aims to remedy these drawbacks with a completely innovative approach.

[0013] More specifically, the invention aims to provide a welding process for automotive bodywork.

[0014] In particular, one objective of the invention is to provide such a method as to eliminate the need for any other complex adjustment system. These objectives, as well as others that will emerge subsequently, are achieved, in a first aspect, using a welding process for automotive bodies comprising a welding apparatus remarkable in that the process includes the following successive steps:

[0015] -a) to connect a first room with a second room and a third room; the first room contains a dwelling;

[0016] -b) install a pawn in said housing forming a first contact area with said first room and a second contact area with said second or third room;

[0017] -c) placement of a first electrode and a second electrode of said welding apparatus on said first contact surface or said second contact surface;

[0018] -d) weld said first contact area and said second contact surface with said first electrode and said second electrode; this step comprises the following substeps:

[0019] -1) generate a first pulse for a first duration with the welding device;

[0020] -2) generate a second pulse at the end of said first duration for a second duration with the welding device.

[0021] Thanks to these provisions, welding will prevent the parts from melting under the pin, and without causing material to be expelled at the fusion core between the pin and the first and / or second part.

[0022] This allows the fusion core to be increased between the two steel sheets, without melting the aluminum under the head of the pin and without degrading the bond between the pin and the first steel sheet by ejection of material.

[0023] Generating a first pulse followed by a second pulse of specific durations optimizes weld quality. The first pulse heats and prepares the contact surfaces, while the second pulse finalizes the weld, ensuring complete and uniform fusion of the materials. Furthermore, this method reduces the risk of defects such as cracks or weak spots in the weld.

[0024] The invention is advantageously implemented according to the embodiments and variants described below, which may be considered individually or in any technically feasible combination. In one embodiment, the pawl from step b) has a "T" shape. In one embodiment, during the substep of generating the first pulse, the first duration is between 20 ms and 300 ms.

[0025] In one embodiment, during the substep of generating the second pulse, the second duration is between 100 ms and 800 ms.

[0026] In one embodiment, during substeps 1) and 2), the first pulse and the second pulse are current pulses.

[0027] In one embodiment, the first pulse is a current pulse between 1 kA and 7 kA.

[0028] In one embodiment, the second pulse carries a current between 4 kA and 15 kA.

[0029] In one embodiment, the process includes a welding force during step c); this force is between 50 daN and 500 daN.

[0030] In one embodiment, the first electrode is mobile and the second electrode is stationary.

[0031] In one embodiment, the method further comprises a bonding element positioned on the first contact surface and on the second contact surface.

[0032] Brief description of the figures

[0033] Other advantages, purposes and features of the present invention will become apparent from the following description, given for explanatory purposes only and not as a limitation, with reference to the accompanying drawings, in which:

[0034] Figure 1 (relating to the prior art) represents a graph defining a single-pulse welding process;

[0035] Figure 2 represents the welding process for vehicle bodywork.

[0036] Figure 3 represents a graph depicting the welding during the process.

[0037] Description of the implementation methods

[0038] Figure 1 shows a graph defining a single-pulse welding process.

[0039] Naturally, the invention described above is by way of example. It is understood that a person skilled in the art is capable of carrying out different embodiments of the invention without departing from its scope.

[0040] Figure 2 shows the welding process for vehicle bodywork. The process includes a first part 22, a second part 23, and a third part and a T-shaped pin 24.

[0041] The first part 22, the second part 23, and the third part are assembled together. The first part 22, the second part 23, and the third part are sheet metal.

[0042] The first piece 22 is an aluminum sheet and the second piece 23 and the third piece are two steel sheets.

[0043] The third one is positioned below the second piece 23. According to a variant, the third one is positioned above the second piece 23.

[0044] According to one variant, the second room 23 or the first room 22 contains a dwelling.

[0045] This housing allows the pin 24 to be assembled with the second part 23 and the first part 22 defining a welded assembly.

[0046] The process involves a welding apparatus comprising a first electrode and a second electrode.

[0047] The first electrode is mobile and the second electrode is stationary. The assembly to be welded has a longitudinal plane.

[0048] The first electrode and the second electrode being arranged on either side of said assembly to be welded along the longitudinal plane.

[0049] According to one embodiment, the first electrode and the second electrode are on a part of pin 24.

[0050] According to one variant, the first part 22 or the second part 23 includes a gluing element.

[0051] This bonding agent is adhesive or glue.

[0052] According to an example embodiment, the first part 22 is made of aluminium or composite, and the second part 23 is made of steel.

[0053] Figure 3 shows a graph representing the welding during the process.

[0054] The graph shows two curves A and B, two ordinate axes x and z, and one abscissa axis y.

[0055] The letter x indicates the current emitted by the welding in kA or kiloamperes.

[0056] The ampere is the base unit of electric current intensity in the International System of Units.

[0057] The letter there indicates the welding time in ms, or milliseconds.

[0058] The second is the base unit of time in the International System of Units. The letter z indicates the force exerted by the welding equipment during the process in daN, or decanewtons.

[0059] The newton is the unit of measurement for force in the International System of Units. Curve A represents the current generated by the welding process.

[0060] This curve A is supported by the ordinate axis represented by the letter x. According to an example carried out during welding, the curve A has a first pulse 20 and a second pulse 21.

[0061] The first pulse 20 is represented on the graph by a square located in a first duration between 80 ms and 270 ms.

[0062] During the first pulse 20, the current is between 0.1 kA and 5 kA.

[0063] The second pulse 21 is represented on the graph by a rectangle located in a second duration between 271 ms and 600 ms.

[0064] The sequence of the first pulse 20 and the second pulse 21 makes it possible to increase the fusion core between the two steel sheets, without melting the aluminum under the head of the pin and without degrading the bond between the pin and the first steel sheet by ejection of material.

[0065] During the second pulse 21, the current is between 5 kA and 10 kA.

[0066] According to an example, the second pulse 21 starts at the end of the first duration of the first pulse 20.

[0067] Curve B represents the welding force applied to the first piece, the second piece and the pin during welding.

[0068] This welding force is supported by the ordinate axis represented by the letter z.

[0069] The curve is increasing between 0 ms and 50 ms, then straight between 51 ms and 730 ms. This increasing curve indicates the start of welding with the welding machine.

[0070] During the first pulse 20 and the second pulse 21, the welding force has a force between 400 daN and 320 daN.

[0071] It is emphasized that all features, as they are apparent to a person skilled in the art from this description, drawings and attached features, even if in practice they have only been described in relation to other specific features, both individually and in any combinations, may be combined with other features or groups of features disclosed herein, provided that this has not been expressly excluded or that technical circumstances render such combinations impossible or meaningless.

[0072] LIST OF REFERENCE SIGNS

[0073]

[0001] [Table 1]

Claims

Demands Claim 1. A welding process for automobile bodies comprising a welding apparatus characterized in that the process comprises the following successive steps: -a) to connect a first room (22) with a second room (23) and a third room; the first room includes a dwelling; -b) install a pawl (24) in said housing forming a first contact area with said first part (22) and a second contact surface with said second or third part (23); -c) placement of a first electrode and a second electrode of said welding apparatus on said first contact surface or said second contact surface; -d) weld said first contact area and said second contact surface with said first electrode and said second electrode; this step comprises the following substeps: -1) generate a first pulse (20) for a first duration with the welding device; -2) generate a second pulse (21) at the end of said first duration for a second duration with the welding device. Claim 2. A method according to claim 1, wherein the pin (24) from step b) has a "T" shape. Claim 3. A method according to any one of claims 1 to 2, wherein during the substep of generating the first pulse (20), the first duration is between 20 ms and 300 ms. Claim 4. A method according to any one of claims 1 to 3, wherein during the substep of generating the second pulse (21), the second duration is between 100 ms and 800 ms. Claim 5. A method according to any one of claims 1 to 4, wherein in substeps 1) and 2), the first pulse (20) and the second pulse (21) are current pulses. Claim 6. A method according to any one of claims 1 to 5, wherein the first pulse (20) is a current pulse of between 1 kA and 7 kA. Claim 7. A method according to any one of claims 1 to 6, wherein the second pulse (21) has a current between 4 kA and 15 kA. Claim 8. A method according to any one of claims 1 to 7, wherein the method includes a welding force during step c); this force is between 50 daN and 500 daN. Claim 9. A method according to any one of claims 1 to 8, wherein the first electrode is mobile and the second electrode is immobile. Claim 10. A method according to any one of claims 1 to 9, wherein the method further comprises a bonding element positioned on the first contact surface and on the second contact surface.

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