Welding process for dissimilar sheet metal for motor vehicles

Abstract

The invention relates to a welding method for attaching a first part to a second part. The welding method comprises the steps: a) supplying or manufacturing (100) a first part made of a first material; b) supplying or manufacturing (102) a second part made of a metallic material different from the first material; c) drilling (104) the first part; d) inserting (106) a retaining pin into an opening through the first part; e) fitting (108) an insulating sleeve into the opening through the first part; f) electrically welding (110) the retaining pin to the second part to join the first part to the second part via the retaining pin; the first part is then electrically insulated from the retaining pin by the insulating sleeve. The method is applied to a motor vehicle structure. Figure to be published with the abbreviation: Figure 6

Description

Title of the invention: Welding process for dissimilar sheet metal for motor vehicles

[0001] The invention relates to welds joining parts made of different materials, and more specifically, with widely varying melting temperatures. The invention concerns the fastening of sheet metal using welded retaining pins. The invention relates to a welding process involving a retaining pin for joining two parts made of different materials. The invention also relates to an assembly, and to a motor vehicle with such an assembly.

[0002] A motor vehicle comprises a complex structure, defining cavities and various profiles. In order to achieve these shapes within predefined geometric tolerances, the structure requires the assembly of several sheets of metal. Steel is commonly used due to its mechanical strength and its ability to be shaped by stamping. The various stamped sheets are welded together.

[0003] Due to the electrification of motor vehicles, their mass frequently increases by 200 kg to 500 kg in order to accommodate sufficient electric batteries to extend their driving range. To compensate for this increased weight, the structure must be lightened. This is possible by replacing some steel sheets with aluminum sheets, which must then be welded to the remaining steel sheets. However, these materials have very different melting points, making mass welding, as encountered in the automotive industry, impractical.

[0004] Steel pins can overcome this constraint. These steel pins have the same melting point as the steel sheets. They are inserted into holes in the aluminum sheets and then welded in the same way as electric spot welds. Furthermore, they are configured to ensure retention of the aluminum sheet through which they pass.

[0005] The phenomena of galvanic corrosion are well known. In the presence of a liquid phase forming an electrolyte, two materials with different electrical potentials generate a chemical oxidation-reduction reaction that physically consumes the material with the lower electrical potential. In this particular case, the aluminum sheet dissolves around the pins that pass through it. Despite the pins being held in place by welding them to the steel sheet, the fastening function of the aluminum sheet is no longer ensured.

[0006] Document FR3097456B1 and document US20220355409A1 each present a method for assembling a sheet metal and an iron-based metal part comprising a step of punching through the sheet metal with a hollow cylinder of electrically conductive metal, one end of which has a flare which butts against the surface of the sheet metal once the through punching has been carried out, then a step of welding the hollow metal cylinder to the iron-based metal part by bringing a free end of the hollow metal cylinder opposite the flare into contact with the surface of the iron-based metal part and applying an electrical resistance welding electrode to the mouth of the flare.

[0007] The hollow weld-on pin comprises a first metal part and a second metal part, the shaft of which is positioned externally. These parts are respectively made of low-alloy steel and stainless steel. This solution provides a certain level of protection against galvanic corrosion. However, this solution remains expensive and heavy. There is also a need to further increase protection against the risk of galvanic corrosion.

[0008] The invention aims to address at least one of the problems or drawbacks encountered in the prior art. The invention aims to provide an alternative method of corrosion protection for an assembly. The invention aims to preserve a welded retaining pin fastening between two dissimilar parts. The invention also aims to optimize protection against galvanic corrosion, as well as the mass and cost of an assembly.

[0009] According to a first aspect, the invention provides a welding method for attaching a first part to a second part via a retaining pin; the welding method comprising the following steps: a) supplying or making a first part with a first material; b) supplying or making a second part with a metallic material different from the first material; d) placing a retaining pin in an orifice through the first part; f) electric welding of the retaining pin to the second part in order to join the first part to the second part via the retaining pin; notable in that prior to step f) electric welding the welding method comprises a step: e) arranging an insulating sleeve in the orifice through the first part; in step f) electric welding, the insulating sleeve surrounds the retaining pin in order to electrically insulate the first part from the retaining pin.

[0010] The invention makes it possible to weld materials of different types, such as steel and aluminum, or aluminum and an organic matrix composite material. It makes it possible to optimize resistance to impact and fatigue.

[0011] Preferably, the insulating sleeve comprises a ceramic material or a plastic material.

[0012] Preferably, the welding process further comprises a step c) drilling of the first piece with the insulating sleeve; preferably, step c) drilling is a punching step of the first piece by the insulating sleeve.

[0013] Preferably, before step d) setting up the retention pin and / or before step e) arranging the insulating sleeve, said retention pin is in the insulating sleeve.

[0014] Preferably, step d) setting up the retention pin and / or step e) arranging the insulating sleeve is carried out with a gripping tool comprising a bearing surface axially pushing the insulating sleeve and / or the gripping tool comprises a cylindrical holding surface holding the retention pin.

[0015] Preferably, the first part comprises: an aluminum alloy, or plastic, or a composite material with fibers and a plastic resin; preferably, the metallic material comprises steel.

[0016] Preferably, in step e) arrangement, the insulating sleeve includes a collar against the first piece; before step f) electrical welding, the collar surrounds the retaining pin and / or a layer of adhesive is at an interface between the first piece and the second piece.

[0017] Preferably, the second part includes a boss in contact with the first part; preferably, step b) supply or production of the second part includes the production of the boss by stamping.

[0018] Preferably, the retention pin includes a retention head.

[0019] Preferably, the retaining pin comprises a cylindrical body with a first outer diameter, and a head with a second outer diameter greater than the first outer diameter.

[0020] Preferably, the insulating sleeve comprises an inner diameter equal to the first outer diameter.

[0021] Preferably, the retaining pin comprises the same metallic material as the second part.

[0022] Preferably, the retention pawl is full.

[0023] Preferably, the boss passes through the adhesive layer.

[0024] Preferably, before step f) electric welding, the first piece and the second piece are placed against each other and present a contact interface.

[0025] Preferably, step e) arrangement is an engagement step of the insulating socket.

[0026] Preferably, in step d) setting up the retention pin and / or in step e) arranging the insulating sleeve, said retention pin is in the insulating sleeve.

[0027] Preferably, the welding process further includes a step c) drilling the first piece in order to form a hole through said first piece.

[0028] Preferably, in step f) electric welding, the electric welding is a Electric resistance welding.

[0029] Preferably, the first material is a different metal from that of the second piece.

[0030] According to another aspect, the invention proposes an assembly comprising a first part with a first material and a second part with a metallic material different from the first material, the first part includes a through hole, the assembly further includes a retaining pin welded to the second part and extending into the through hole of the first part in order to link it to the second part; notable in that the assembly further includes an insulating sleeve in the through hole and surrounding the retaining pin in order to electrically isolate the first part from the retaining pin.

[0031] Preferably, the assembly is produced by the welding process according to the invention.

[0032] Preferably, the retaining pin comprises a head diameter between 9 mm and 19 mm.

[0033] According to another aspect, the invention proposes a motor vehicle comprising at least one assembly, remarkable in that the assembly conforms to the invention.

[0034] Preferably, the motor vehicle includes an electric motor for driving the motor vehicle and an electric battery for powering said electric motor for driving.

[0035] Each feature introduced by the expression "preferably" given in relation to one of the aspects of the invention applies to all other aspects of the invention.

[0036] The invention will be well understood and other aspects and advantages will become clear upon reading the following description, given with reference to the attached figures listed below.

[0037] Fig. 1 is a side view of a motor vehicle according to the invention.

[0038] Figure 2 shows the gripping of a retaining pin and an insulating sleeve by a gripping tool used during a welding process according to the invention.

[0039] Fig. 3 illustrates the beginning of a drilling step of a first part with an insulating sleeve during a welding process according to the invention.

[0040] Fig. 4 illustrates a step in arranging an insulating sleeve in an orifice through a first sheet of a welding process according to the invention.

[0041] Figure 5 represents an electric welding step of a welding process according to the invention.

[0042] The [Fig.6] is a diagram of a welding process according to the invention.

[0043] In the following description, the term "include" is synonymous with "include" and is not limiting in that it permits the presence of other elements in the vehicle automotive, assembly, or other stages in the welding process to which it relates. It is understood that the term "include" includes the terms "consist of." The terms "external" and "internal" will respectively refer to what is oriented towards the outside of the vehicle and towards the inside of the vehicle.

[0044] In this description, the terms "longitudinal," "longitudinally," "transverse," and "transversely" are used with respect to the vehicle's frame of reference in the mounting configuration. The term "longitudinal" refers to the principal direction of travel of the vehicle. The term "transverse" refers to a direction perpendicular to the principal direction of travel of the vehicle. The term "front" refers to the principal direction of travel of the vehicle. The term "rear" refers to the opposite of the front of the vehicle.

[0045] The X-axis represents the longitudinal direction, the Y-axis represents the transverse direction, and the Z-axis represents the vertical direction of the motor vehicle. These three axes define a right-handed trihedron.

[0046] In this description, the ranges of values ​​include the bounds that delimit them.

[0047] In the present description, equality between values ​​is not to be understood in the strict sense insofar as each equality allows a variation of at most 10%, preferably at most 5%, more preferably at most 2%, between these values.

[0048] In this description, the terms "vertical" and "horizontal" are not to be understood in their strict sense. Indeed, they allow an inclination of at most 20°, preferably at most 10°, more preferably at most 5°, and even more preferably at most 2°; with respect to the strict meaning of these terms.

[0049] Throughout the description, the different figures use the same reference signs to designate identical or similar entities.

[0050] In general, the invention proposes a method for welding dissimilar sheet metal using at least one retaining pin with an insulating spacer, preferably for the construction of a motor vehicle structure

[0051] Figure 1 represents a motor vehicle 10, according to an embodiment of the invention. The motor vehicle 10 comprises energy storage means and at least one motor (not shown) adapted to drive said motor vehicle 10. The motor is preferably an electric drive motor 14, and the storage means preferably comprise an electric battery 16 suitable for driving the motor vehicle 10. The electric battery 16 has a mass of at least 250 kg, preferably of at least 400 kg.

[0052] The motor vehicle 10 comprises a structure 12. The structure 12 forms an outer body, or the main frame of the motor vehicle. The structure 12 delimits different compartments of the motor vehicle 10, including The passenger compartment. Structure 12 forms the roof and underbody; it extends from the front to the rear of the motor vehicle. Structure 12 provides a mounting support for the powertrain, suspension systems, steering system, braking systems, and doors.

[0053] The structure 12 comprises at least one assembly 18 of stamped and welded sheet metal parts. The sheets are metallic. According to one embodiment of the invention, the assembly 18 also comprises one or more cast parts. According to one embodiment of the invention, the assembly 18 comprises at least one part made of plastic material, for example, a plastic matrix composite part. The composite part comprises reinforcing fibers, for example, glass fibers or carbon fibers. The assembly 18 comprises two parts made of two different materials, for example, of different types and / or different properties, which are secured by means of retaining pins.

[0054] The motor vehicle can, for example, be a private motor vehicle or a commercial motor vehicle.

[0055] Figure 2 shows the gripping of an assembly including a retaining pin 20 and an insulating sleeve 22. The gripping is carried out using a gripping tool 24. The retaining pin 20 and the insulating sleeve 22 are pre-assembled. Their tight fit ensures retention.

[0056] The retaining pin 20 may be a welding pin. The retaining pin 20 comprises a head 26 and a cylindrical body 28. The cylindrical body 28 is also called the foot of the pin. The head 26 is chamfered. An axial direction 30 is defined in relation to the retaining pin 20. The axial direction 30 is along the axis of the cylindrical body 28. The retaining pin 20 is made of a metallic material, for example, steel.

[0057] The insulating sleeve 22 is generally an insulating tube. The insulating sleeve 22 may be an insulating sleeve. The insulating sleeve 22 forms an insulating sheath, such as a jacket or sleeve, around the retaining pin. It is an electrically insulating sleeve. The insulating sleeve 22 comprises a tubular portion 32 and optionally a collar 34 at one axial end of the tubular portion 32. The tubular portion 32 is hollow, with the cylindrical body 28 being partially housed within it.

[0058] The retaining pin 20 is solid. The cylindrical body 28 has a first outer diameter, and the head 26 has a second outer diameter that is larger than the first outer diameter. The diameters are maximum diameters. The head 26 is chamfered. The insulating sleeve 22 has an inner diameter equal to the first outer diameter. This feature optimizes mass and retention.

[0059] The gripping tool 24 comprises a bearing surface 36 adapted to push the insulating sleeve 22; and a retaining surface 38 adapted to retain the retaining pin 20. The retaining surface 38 is preferably perpendicular to the bearing surface 36. The bearing surface 36 is flat, and the retaining surface 38 is cylindrical. The bearing surface 36 and the retaining surface 38 are each split and formed on two movable arms 40 of the gripping tool 24. The gripping tool 24 is capable of rotating. The movable arms 40 are capable of moving apart and together in order to grasp and then release the retaining pin 20.

[0060] Figure 3 shows a drilling step in a first part 42 with an insulating sleeve 22. The insulating sleeve 22 is held by the gripping tool 24 via a retaining pin 20 which it surrounds. The gripping tool 24, the insulating sleeve 22 and the retaining pin 20 can correspond to those shown in relation to Figure 2.

[0061] The gripping tool 24 is here in a closed configuration. Its movable arms 40 are tightened, and the retaining surfaces 38 position the retaining pin 20 relative to the first part 42.

[0062] Drilling is carried out by pressing the insulating sleeve 22 against the first part 42 via the gripping tool 24. The force is transmitted by the movable arms 40, at the level of the bearing surface 36 which is in contact with the collar 34. It is understood that the extent of the collar 34 makes it possible to reduce the mechanical stress at its interface with the movable arms 40.

[0063] A concentration of stress is observed at the level of the first part 42 in contact with the tubular portion 32. When the force exceeds the resistance of the first part 42, it is pierced and presents a through orifice.

[0064] Figure 4 shows the result of a fitting step of an insulating sleeve 22 in a through hole 48. The fitting is a drilling which is carried out by punching with the help of an insulating sleeve 22 pushed by a gripping tool 24. The gripping tool 24, the insulating sleeve 22 and the retaining pin 20 correspond to those shown in relation to one of Figures 2 to 3. The first part 42 corresponds to that shown in relation to one of the preceding figures.

[0065] By increasing the pressing force 44 transmitted by the gripping tool 24, the insulating sleeve 22 punches the first part 42. It is remarkable that the drilling is carried out without mechanically stressing the retaining pin 20. The latter is preserved.

[0066] A drop 46 detaches from the first part 42. It exits the through-hole 48. The through-hole 48 forms a passage between the opposite faces of the first part 42. The drop 46 is cut by the insulating sleeve 22. A die, with an orifice of complementary shape to the insulating sleeve 22, is arranged under the first part 42. The first part 42 rests horizontally on said die when the insulating sleeve 22 acts as a punch.

[0067] According to one embodiment of the invention, the drilling step and the arrangement step are carried out at the same time.

[0068] Figure 5 shows a welding step for attaching a first part 42 to a second part 50 via a retaining pin. The insulating sleeve 22, the retaining pin 20, and the first part 42 correspond to those shown in relation to the preceding figures. Prior to this, the gripping tool is released from the retaining pin.

[0069] At their interface, the first part 42 and the second part 50 are separated by a layer of adhesive 52. The adhesive layer 52 allows them to be held together temporarily. It is also capable of forming a watertight barrier. Thus, it eliminates the possible presence of an electrolyte involved in galvanic corrosion. It is present before welding. The adhesive layer 52 is an adhesive film. It has a thickness of at most 1.00 mm; preferably at most 0.10 mm.

[0070] The retaining pin 20 and the second part 50 comprise materials of the same type. They comprise metallic materials of the same nature. They may comprise similar alloys. By similar alloys is meant variations in grade that remain compatible for welding.

[0071] To maintain the gap between the first part 42 and the second part 50, the latter has raised sections 54. The adhesive layer 52 surrounds each raised section 54 to create a watertight seal. In turn, the presence of the raised sections 54 helps to maintain a minimum thickness for the adhesive layer 52.

[0072] The welding of the retaining pin 20 to the adhesive layer 52 is carried out using a welding clamp 56. Initially, the welding clamp 56 pushes the retaining pin 20 into the insulating sleeve 22 until it reaches the adhesive layer 52. The retaining pin 20 enters and slides into the insulating sleeve 22. The welding clamp 56 exerts a force of between 300 N and 400 N. It can be deduced that the presence of the bosses 54 limits the crushing of the adhesive layer 52 despite the clamping force of the welding clamp 56.

[0073] An electric current is applied via the electrodes 58 of the welding clamp 56. The electrical resistance at the point of contact increases the temperature. This electrical current generates a melting of the metal at the tip of the retaining pin 20, which is in contact with the adhesive layer 52, particularly through the adhesive layer 52. A weld point 60 is formed. The weld point 60 creates a continuous bond between the retaining pin 20 and the adhesive layer 52, which become integral. The bosses 54 are positioned away from the weld point 60. Thus, during the temperature increase, the adhesive layer 52 in contact with the bosses 54 is preserved.

[0074] The weld point 60 is vertically aligned with the adhesive layer 52. It is surrounded by the insulating sleeve 22. The weld point 60 has a heat-affected zone. It exhibits crystallographic heterogeneity at the interface of welding.

[0075] It is noted that the insulating sleeve 22 forms an electrical insulation barrier between the first part 42 and the second part 50. This feature limits galvanic corrosion. Consequently, it is possible to fix a first aluminum part to a second steel part. The invention also limits corrosion of parts with different electrical potentials.

[0076] According to one option, the insulating sleeve 22 provides thermal protection for the first part 42 during welding. Thus, the first part can be made of a plastic material and the second part can be made of metal despite the difference in melting temperatures. The material of the insulating sleeve 22 has a lower thermal conductivity coefficient than that of the retaining pin.

[0077] In the present embodiment, the first part 42 and the second part 50 are sheet metal. They each have a constant thickness. Their thicknesses can be between 0.50 mm and 3.00 mm; preferably between 0.65 mm and 1.50 mm.

[0078] In the present embodiment illustrated in the preceding figures, the assembly 18 comprises two parts. However, the invention applies to an assembly of three or more parts. These parts are stacked and joined by the retaining pin 20. The first part is stacked with the second part, a third part, and the subsequent parts. The insulating sleeve 22 passes through the stack. For example, the first part is made of steel, and the second and third parts are made of aluminum. Alternatively, the third part is made of steel, with its face against the second aluminum part being coated with a layer of adhesive.

[0079] According to one embodiment of the invention, the insulating sleeve is hybrid. It comprises a tube made of ceramic material and a collar made of plastic, or vice versa. The plastic collar may be a plastic washer. The plastic washer surrounds the ceramic tube or is axially positioned against the ceramic tube.

[0080] The present embodiment describes a fastening of an assembly 18 with a pin-and-socket assembly. However, the invention applies to an assembly in which two parts are fastened by several pin-and-socket assemblies. It is interesting to note that the invention avoids the short-circuit effect, also known as the "shunt" effect, which occurs when two parts are fastened by several retaining pins close to each other.

[0081] Figure 6 shows a diagram of a welding process for two parts made of different materials, one of the parts being made of a metallic material. These two parts can form an assembly for a motor vehicle structure. The motor vehicle can correspond to the one shown in relation to Figure 1. The assembly corresponds to one of the preceding figures.

[0082] The welding process comprising the following steps:

[0083] a) supply or production of a first part with a first material;

[0084] b) supplying or producing 102 a second part with a metallic material different from the first material;

[0085] c) drilling 104 of the first part with the insulating sleeve, in order to make a through hole;

[0086] d) installation 106 of a retention pin in the orifice passing through the first part

[0087] e) arrangement 108 of an insulating sleeve in the orifice passing through the first part;

[0088] f) electric welding 110 of the retaining pin to the second part in order to join the The first piece is connected to the second piece via the retaining pin. The first piece is then electrically isolated from the retaining pin by the insulating sleeve that covers it.

[0089] Step b) supplying or manufacturing 102 of the second part includes creating a boss by stamping. A layer of adhesive is intended to form a contact interface with the first part. When the first part covers the second part, they remain separated. This improves the insulation between these two parts via the adhesive layer.

[0090] Step c) drilling 104 is a punching step of the first part by the insulating sleeve. According to an alternative of the invention, the through hole is made by molding, so that step c) drilling is optional. According to another alternative of the invention, the through hole is made by machining with a rotating tool, or by cutting during a stamping step. For example, the retaining pin is inserted from one face of the first part, then the insulating sleeve is inserted from the other face, in the opposite direction.

[0091] Before step d) installation 106 of the retaining pin and / or before step e) arrangement 108 of the insulating sleeve, said retaining pin is in the insulating sleeve. Step e) arrangement 108 is a step of inserting the insulating sleeve into the through-hole, while simultaneously forming said through-hole. Step c) drilling 104 and step d) installation 106 are performed at the same time.

[0092] Step d) installation 106 of the retention pin and step e) arrangement 108 of the insulating sleeve are carried out using a tool for gripping the retention pin. The gripping tool includes a bearing surface that axially pushes the insulating sleeve. The gripping tool also includes a cylindrical holding surface that secures the retention pin. The retention pin has a head diameter ranging from 9 mm to 19 mm. This diameter range allows for positioning variations with the welding pliers, while maintaining the compactness of the retention pin.

[0093] Steps d) placement 106 of the retention pin and step e) arrangement 108 of The insulating sleeves are made at the same time. According to an alternative of the invention, step e) arrangement of the insulating sleeve is carried out before step d) placement of the retention pin.

[0094] According to an alternative embodiment of the invention, step d) setup is a roughing step of the through-hole using the retaining pin. Step e) arrangement is a finishing step of the through-hole.

[0095] In step e) arrangement 108, the insulating sleeve includes a collar against the first part; the collar surrounds the retaining pin. The collar is located between the first part and the retaining head of the retaining pin. According to an alternative embodiment of the invention, the retaining head includes a washer made of insulating material against the first part. According to another alternative embodiment of the invention, the first part includes a layer of insulation on top of it, opposite the second part; the retaining head being against said layer of insulation. Thus, the first part is electrically insulated from the retaining pin, which prevents the risk of galvanic corrosion.

[0096] According to one embodiment of the invention, before step d) installation of the retaining pin 106 and step e) arrangement 108 of the insulating sleeve, and before the optional step c) drilling 104, the welding process includes an assembly step 112 of the retaining pin and the insulating sleeve. During assembly step 112, the stem of the retaining pin is inserted into the insulating sleeve. The retaining pin has an axial orientation along the through hole and / or along the insulating sleeve. The welding process includes a step of translating the retaining pin within the insulating sleeve.

[0097] Before step f) electric welding 110 the first piece and the second piece are placed against each other and present a contact interface.

[0098] Before step f) electric welding 110, a layer of adhesive is applied to the interface between the first part and the second part. Preferably, the insulating sleeve is in contact with the adhesive layer during said step f) electric welding 110. According to one embodiment, during step b) supplying or manufacturing 102 of the second part, said second part is coated with the adhesive layer.

[0099] According to one alternative of the invention, the adhesive layer is arranged against the first part during step a) supply or fabrication of the first part. According to another alternative of the invention, the adhesive layer is placed at the interface of the first part and the second part after steps a) supply or fabrication of the first part and b) supply or fabrication of the second part; and before step f) electric welding.

[0100] In step f) electric welding 110, an electric current is applied between the second part and the retaining pin. Since their contact is point-like, a temperature rise occurs, causing localized melting and thus fixation when The molten pool solidifies as it cools. The molten pool is surrounded by the insulating sleeve.

[0101] In step f) electric welding 110, the first part is electrically and thermally isolated from the retaining pin by the insulating sleeve. The insulating sleeve is a drilling tool and forms an intermediate piece in the through-hole. In addition to providing physical separation, the insulating sleeve acts as electrical insulation, optionally combined with thermal insulation. Thus, the invention manages to preserve the fastening formed by the retaining pin. It preserves it during welding and throughout the vehicle's service life. This allows it to withstand impacts and contributes to fatigue resistance.

[0102] According to a preferred embodiment, the insulating sleeve is made of a plastic or ceramic material.

[0103] The plastic material may include a thermoplastic material or a thermosetting material. The ceramic material may include alumina or silicon nitride.

[0104] The first part comprises at least 10% by weight of recycled material based on the total weight of said material; preferably from 10 to 80% by weight; more preferably from 20 to 60% by weight or from 30 to 40% by weight. The use of recycled material reduces the environmental footprint of the motor vehicle.

[0105] For example, the composite material comprises a matrix of a plastic material as described above with a reinforcement. For example, the reinforcement comprises glass or carbon fibers.

[0106] The first part comprises an aluminum alloy, copper, a composite material with fibers, and a plastic resin. The fibers may be carbon or graphite fibers. Being electrically conductive, they are susceptible to galvanic corrosion due to contact with a third metallic part.

[0107] Preferably, the metallic material of the second part comprises steel. Alternatively, it comprises aluminum and is different from the material of the first part. The retaining pin is then made of aluminum.

[0108] The invention comprises the combination of all the embodiments illustrated by all the figures.

Claims

Demands

1. A welding method for attaching a first part (42) to a second part (50) via a retaining pin (20); the welding method comprising the following steps: • a) supplying or making (100) a first part (42) with a first material; • b) supplying or making (102) a second part (50) with a metallic material different from the first material; • d) placing (106) a retaining pin (20) in a through hole (48) in the first part (42); • f) electric welding (110) of the retaining pin (20) to the second part (50) in order to join the first part (42) to the second part (50) via the retaining pin (20); characterized in that before step f) electric welding (110) the welding process includes a step: • e) arrangement (108) of an insulating sleeve (22) in the orifice passing through (48) the first piece (42);in step f) electric welding (110), the insulating sleeve (22) surrounds the retaining pin (20) in order to electrically isolate the first piece (42) from the retaining pin (20).;

2. Welding method according to claim 1, characterized in that the insulating sleeve (22) comprises a ceramic material or a plastic material.

3. Welding method according to any one of claims 1 to 2, characterized in that the welding method further comprises a step c) drilling (104) of the first piece (42) with the insulating sleeve (22); preferably, the step c) drilling (104) is a punching step of the first piece (42) by the insulating sleeve (22).

4. Welding method according to any one of claims 1 to 3, characterized in that before step d) setting (106) of the retaining pin (20) and / or before step e) arrangement (108) of the insulating sleeve (22), said retaining pin (20) is in the insulating sleeve (22).

5. Welding method according to claim 4, characterized in that step d) placement (106) of the retaining pin (20) and / or step e) arrangement (108) of the insulating sleeve (22) is made with a gripping tool (24) comprising a bearing surface (36) axially pushing the insulating sleeve (22) and / or the gripping tool (24) comprises a cylindrical holding surface (38) holding the retaining pin (20).

6. A welding method according to any one of claims 1 to 5, characterized in that the first part (42) comprises: an aluminum alloy, or plastic, or a composite material with fibers and a plastic resin; preferably, the metallic material comprises steel.

7. Welding method according to any one of claims 1 to 6, characterized in that at step e) arrangement (108), the insulating sleeve (22) includes a collar (34) against the first part (42); before step f) electric welding (110), the collar (34) surrounds the retaining pin (20) and / or a layer of adhesive (52) is at an interface between the first part (42) and the second part (50).

8. Welding method according to any one of claims 1 to 7, characterized in that the second part (50) comprises a boss (54) in contact with the first part (42); preferably, step b) supply or production (102) of the second part (50) comprises the production of the boss (54) by stamping.

9. Assembly (18) comprising a first part (42) with a first material and a second part (50) with a metallic material different from the first material, the first part (42) comprising a through hole (48), the assembly (18) further comprising a retaining pin (20) welded to the second part (50) and extending into the through hole (48) of the first part (42) in order to connect it to the second part (50); characterized in that the assembly (18) further comprises an insulating sleeve (22) in the through hole (48) and surrounding the retaining pin (20) in order to electrically insulate the first part (42) from the retaining pin (20); preferably, the assembly (18) is produced by the welding process according to any one of claims 1 to 8; and the retention pin (20) includes a head diameter between 9 mm and 19 mm.

10. A motor vehicle (10) comprising at least one assembly (18), characterized in that the assembly (18) conforms to claim 9; preferably the motor vehicle (10) comprises an electric drive motor (14) for the motor vehicle (10) and a electric battery (16) intended to power said electric drive motor (14).

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