FR3141359A1 - Friction stir welding process and associated welding assembly - Google Patents

Abstract

This method of friction stir welding of a first part (8) on a second part (9), the first part (8) being arranged on the second part (9), comprises the following steps: Machining (E1) of means for positioning and holding the first part on the second part (13, 16, 17) on the first and second parts (8 and 9), the machined positioning and holding means (13, 16, 17) comprising at least one projecting part (13a, 16a, 17a) and at least one groove (13b, 16b, 17b) intended to receive the at least one projecting part (13a, 16a, 17a) for positioning and maintaining the first part (8) on the second part (9), the at least one projecting part (13a, 16a, 17a) being machined on the first part (8) and the at least one groove (13b, 16b, 17b) being machined in the second part (9), Activation (E2) of the positioning and holding means (13, 16, 17), Welding (E3) by friction stir of a first welding zone (10) of the first part ( 8) and a second welding zone (11) of the second part (9). Figure for abstract: Fig 4

Description

Friction stir welding process and associated welding assembly

The present invention relates to friction stir assembly devices and processes, also called “friction stir welding” in English terms.

In particular, the invention relates to a process for welding two parts by friction stir and an associated welding assembly.

In general, the invention applies to any type of field requiring assembly by friction kneading of two elements to be assembled.

Previous techniques

In industry, and particularly in the aeronautics industry, it is common to have to assemble several elements together. This may involve, for example, the assembly of a stiffener on a structural panel of an aircraft in order to stiffen said structural panel.

Among the different assembly processes, friction stir welding is an assembly process allowing, using welding tools including a rotating tip of less than five millimeters in diameter, to mix together the materials of the elements to be assembled and thus create a weld. Friction stir welding is particularly suitable for aluminum alloys.

To weld two parts together, the parts must be positioned relative to each other and held in position during welding. For this, one of the existing solutions is illustrated on the , and consists of positioning and holding the parts using a system of pins.

More particularly, with reference to the , a welding assembly 1 comprises a first part 2 and a second part 3. Pre-drillings are made in the parts 2 and 3, into which pins 4 are inserted. Thanks to the pins 4, the first part 2 is positioned and maintained on the second part 3, allowing friction stir welding to be carried out using welding tools 5. On the , welding is in progress, and a weld bead 6 is produced where the tooling 5 has already passed.

However, this solution has many disadvantages. First of all, the pin and pre-drilling system is bulky, and is detrimental to welding paths and the machine environment. In addition, this solution blocks the passage of the welding tool 5, which cannot be used too close to the pins 4. This results in a limitation of the weld bead 6 in the vicinity of the pins 4. Generally speaking, it is not possible, by the conventional friction stir welding process, to obtain a continuous trajectory of the weld bead 6 between the two parts to be welded. Also, the pins must be removed once the welding has been completed, and then leave the pre-drilled holes free, which must be filled with standard riveting in order to ensure watertightness and aerodynamics. Finally, due to a slight movement of the two parts 2 and 3 relative to each other during welding, the pre-drillings present and aligned on the two parts 2 and 3 may end up offset, which causes tightening and blocking of the pins 4 in the pre-drilled holes.

The present invention therefore aims to overcome the aforementioned drawbacks.

• Usinage d’un moyen de positionnement et de maintien de la première pièce sur la deuxième pièce sur les première et deuxième pièces, le moyen de positionnement et de maintien usiné comprenant au moins une partie saillante et au moins une rainure destinée à recevoir l'au moins une partie saillante pour le positionnement et le maintien de la première pièce sur la deuxième pièce, l’au moins une partie saillante étant usinée sur la première pièce et l’au moins une rainure étant usinée dans la deuxième pièce,
• Activation du moyen de positionnement et de maintien,
• Soudage par friction malaxage d’une première zone de soudage de la première pièce et d’une deuxième zone de soudage de la deuxième pièce.

The subject of the present invention is therefore a process for friction stir welding of a first part onto a second part, the first part being placed on the second part, comprising the following steps:

• Machining of a means for positioning and holding the first part on the second part on the first and second parts, the machined positioning and holding means comprising at least one projecting part and at least one groove intended to receive the at at least one protruding part for positioning and holding the first part on the second part, the at least one protruding part being machined on the first part and the at least one groove being machined in the second part,
• Activation of the positioning and holding means,
• Friction stir welding of a first welding zone of the first part and a second welding zone of the second part.

Preferably, the step of activating the positioning means comprises assembling the at least one protruding part with the at least one groove intended to receive the at least one protruding part.

Advantageously, the at least one protruding part is machined on a lower surface of the first part, and the at least one groove is machined in an upper surface of the second part.

Preferably, the at least one protruding part is machined from an aluminum alloy.

Advantageously, the at least one protruding part is machined in the material of the first welding zone.

Advantageously, the at least one protruding part is machined on the first welding zone of the first part and the at least one groove is machined in a portion of the second welding zone intended to be in contact with the at least one protruding part.

In one embodiment, the at least one groove is machined in a portion of the second welding zone intended to be in contact with the first welding zone.

In this embodiment, during the welding step, at least a portion of the positioning and holding means is welded by friction stir to the first and second welding zones.

In one embodiment, the method comprises a step of applying an insulating element in the at least one groove, prior to the step of activating the positioning and holding means.

Preferably, the insulating element is putty.

The invention also relates to a weld obtained from the implementation of a friction stir welding process as defined above on a welding assembly comprising a first part arranged on a second part.

Other purposes, characteristics and advantages will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

illustrates an example of implementation of a friction stir welding process known from the state of the art on a welding assembly. ;

illustrates an initial welding assembly in cross section before implementation of the method according to the invention;

illustrates an example of a friction stir welding process according to the present disclosure;

illustrates a first example of implementation of the method of conforming to this disclosure on the welding assembly of the , illustrated in longitudinal section;

illustrates the example of the in cross section;

illustrates the example of the seen from above;

illustrates a second example of implementation of the method of conforming to this disclosure on the welding assembly of the , shown in cross section;

illustrates the example of the seen from above;

illustrates a third example of implementation of the method of conforming to this disclosure on the welding assembly of the , shown in cross section.

detailed description

We have shown schematically on the an initial welding assembly 7 before the application of a friction stir welding process according to the invention represented in . The welding assembly 7 comprises a first part 8 and a second part 9, illustrated schematically in cross section.

For the purposes of the description, we refer to a direct orthonormal reference, in which the X axis designates the longitudinal direction of the welding assembly 7, the Y axis designates the direction along the width of the welding assembly 7, and the Z axis denotes the vertical direction, facing upwards.

There therefore illustrates a cross section along a plane parallel to the Y axis of the welding assembly 7.

For example, the first part 8 is a stiffener and the second part 9 is an aircraft structure panel.

The first part 8 and the second part 9 are intended to be welded together by friction kneading in transparency, that is to say one on top of the other. Thus, the first part 8 comprises a lower surface 8a preferably resting entirely on an upper surface 9a of the second part 9.

More precisely, the first part 8 comprises a first welding zone 10 and the second part 9 comprises a second welding zone 11, which define respective parts of the parts 8 and 9 intended to be mixed together during friction stir welding.

The first welding zone 10 thus comprises at least a portion of the lower surface 8a and the second welding zone 11 comprises at least a portion of the upper surface 9a which is intended to be in contact with the first welding zone 10. Thus , the first welding zone 10 and the second welding zone 11 are in fact positioned in contact with each other.

By way of non-limiting example in the context of the present disclosure, the first part 8 illustrated on the is an L-shaped stiffener, comprising a base 12a and a shoulder 12b.

The first part 8 and the second part 9 are made of materials suitable for friction stir welding. In particular, the first part 8 and the second part 9 are made from aluminum alloys, possibly different from each other.

There illustrates a friction stir welding process of the first part 8 on the second part 9 capable of being implemented on the welding assembly 7. The steps of the process are described below.

In a first step E1, a positioning and holding means is machined on the first and second parts 8 and 9, the positioning and holding means comprising at least one projecting part and at least one groove intended to receive the projecting part, the at least one projecting part being machined on the lower surface 8a of the first part 8 and the at least one groove being machined in the upper surface 9a of the second part 9.

Once the holding and positioning means have been machined, a step E2 includes the installation of the first part 8 on the second part 9, and the activation of the positioning and holding means to guarantee the correct positioning and holding of the first piece 8 on the second piece 9. Activation of the positioning and holding means consists of inserting the at least one projecting part into the at least one corresponding groove. In this way, the first part 8 is correctly positioned and held on the second part 9, allowing in a third step E3 to carry out friction stir welding of the first welding zone 10 and the second welding zone 11.

Optionally, the method comprises a step E4 between the first and second steps E1 and E2, in which an insulating element is applied in the at least one groove.

Different examples of implementation of this process of on the initial welding assembly 7 of the will be described in what follows. In particular, Figures 4, 5 and 6 illustrate a first example of implementation of the method of , Figures 7 and 8 illustrate a second example and the illustrates a third example.

Only the third example includes optional step E4.

The first example of implementation of the process of on the welding assembly 7 of the is illustrated in Figures 4, 5 and 6.

In particular, the illustrates a longitudinal section along a plane parallel to the axis X of the welding assembly 7 during step E3 of the first example of implementation of the welding process of the , there illustrates a section along a plane parallel to the Y axis of the welding assembly 7 of the , and the illustrates a top view along a plane perpendicular to the axis Z of the welding assembly 7 at the end of step E2 of the first example of implementation of the welding process of the .

During the first step E1 of this first example of implementation of the method of , a positioning and holding means 13 is machined on the first and second parts 8 and 9. More precisely, the positioning and holding means 13 comprises at least one projecting part 13a machined on the first part 8 and at least one groove corresponding 13b made on the second part 9 and intended to receive and cooperate with the projecting part 13a. The projecting part 13a can thus be described as the male portion of the first part 8 cooperating with the groove 13b of the second part 9 which can be described as the female portion.

The projecting part 13a is machined on the lower surface 8a of the first part 8, and more particularly on the portion of the lower surface 8a included in the first welding zone 10 of the first part 8. The projecting part therefore extends towards the bottom when the lower surface 8a is placed on the upper surface 9a.

Correspondingly, the groove 13b corresponding to said projecting part 13a is machined in the upper surface 9a of the second part 9, and more particularly in the portion of the upper surface 9a included in the second welding zone 11 and which is intended to be in contact with the first welding zone 10. This portion of the upper surface 9a on which the groove 13b is machined is also intended so as to be in contact with the projecting part 13a.

On the illustrating a top view of the welding assembly 7, the base 12a is shown in transparency so as to reveal the projecting part 13a and the groove 13b.

In this first example shown in Figures 4,5 and 6, the projecting part 13a extends over the entire length along the axis correspondingly over the entire length along the axis X of the upper surface 9a of the second part 9 in contact with the lower surface 8a. The dimension of the projecting part 13a along the Y axis is less than 30% of the dimension along the Y axis of the first part 8. The groove 13b likewise extends along the Y axis over a distance less than 30 % of the dimension along the Y axis of the first part 8, this distance being nevertheless greater by a few millimeters than the dimension along the Y axis of the projecting part 13a, so that the groove 13b is configured to receive and grip the projecting part 13a.

Thus, the projecting part 13a and the groove 13b are well configured to cooperate so that the groove is able to receive the projecting part 13a when the lower surface 8a of the first part 8 is correctly arranged on the upper surface 9a of the second piece 9.

The holding and positioning means 13 is machined from an aluminum alloy, possibly identical to the alloy used to manufacture one of the welding zones 10 and 11. For example, the projecting part 13a is machined from the same material than the first welding zone 10.

The holding and positioning means 13 is dimensioned to be included in the first and second welding zones 10 and 11. Thus, the holding and positioning means 13 is configured to be welded by friction stir at least partially to the first and second 9 pieces and 10, and therefore to the first and second welding zones 10 and 11.

During step E2, the first part 8 is positioned on the part 9 and the positioning and holding means 13 is activated. More precisely, the activation of the positioning and holding means 13 comprises a phase of assembling the protruding part 13a with the corresponding groove 13b. The projecting part 13a is thus inserted into the corresponding groove 13b. In this way, the first part 8 is correctly positioned and held on the second part 9.

During the third step E3, friction stir welding of the first welding zone 10 and the second welding zone 11 is carried out.

In particular, the welding step E3 is carried out using friction stir welding tools 14, and consists of a first phase of setting up the friction stir welding tools for welding the first part 8 on the second part 9. The installation consists of positioning the assembly 7 of the two parts 8 and 9 assembled and secured by the positioning and holding means 13 on a welding frame of the welding tool intended to support the lower surface 9b of the second part 9.

The friction stir welding tool 14 comprises a rotating tip 14a for friction stir welding and a shoulder 14b carrying the tip 14a at one of its ends. The thickness of the tip 14a conditions the size of the welding zones 10 and 11, and therefore the dimensions of the projecting part 13a perpendicular to the surface 8a.

As part of a second phase of step E3, the welding tool 14 is inserted into the first part 8 up to the welding zones 10 and 11, as illustrated in the . The welding tool 14 is inserted so as to be in contact with the positioning means 13 and the welding zones 10 and 11. The third phase of step E3, which is welding, then begins, and a weld bead 15 is formed in the welding zones 10 and 11 as the tooling 14 advances and the local heating of the welding zones 10 and 11 due to the action of the rotating tip 14a. The direction of advancement of the welding tool 14 on the is from right to left. In the first example of implementation, the positioning and holding means 13 is thus welded at least partially to the first and second parts 8 and 9.

The welding path followed by the welding tool 14 then follows the positioning means 13, as illustrated in the , and is not limited by a pin. The positioning and welding means 13 is completely welded to the first and second welding zones 10 and 11 of the parts 8 and 9 at the end of stage E3.

We therefore understand that the holding and positioning means 13 has the function of holding the first and second parts 8 and 9 together, which makes it possible to dispense with the use of pins, and consequently, to limit pre-drilling and the subsequent use of rivets or other solutions for blocking these drillings. The holding and positioning means 13 thus eliminates the obstacles to obtaining a continuous weld bead 15. More generally, it is thus possible to use the welding tool 14 in all the required areas between the two parts without accessibility and bulk problems. It is therefore not necessary to adapt the trajectory of the weld beads nor to have to stop the bead before the pin areas. In addition, no element needs to be removed after welding, and no element such as riveting needs to be added.

The second example of implementation of the process of on the welding assembly 7 of the is illustrated in Figures 7 and 8. More precisely, like the , there illustrates a longitudinal section along a plane parallel to the axis X of the welding assembly 7 during step E3 of the second example of implementation of the welding process of the . Likewise, like the , there illustrates a top view along a plane perpendicular to the axis Z of the welding assembly 7 at the end of step E2 of the second example of implementation of the welding process of the .

As for the first example, a positioning and holding means 16 is machined during step E1 on the first and second parts 8 and 9.

The positioning means 16 differs from the first example in that it comprises several projecting parts 16a and several corresponding grooves 16b intended to each receive one of the projecting parts 16a for positioning and maintaining the first part 8 on the second part 9. In the example illustrated in Figures 7 and 8, two projecting parts 16a are machined on the portion of the lower surface 8a included in the first welding zone 10, and two grooves 16b are made in the portion of the upper surface 9a included in the second welding zone 11 intended to be in contact with the protruding parts 16a.

The positioning means 16 also differs from the first example in that the corresponding projecting parts 16a and grooves 16b do not have the same dimension along the axis a dimension along the axis X between 5% and 15% of the dimension along the axis .

In addition, one of the two groove parts 16b has a dimension along the axis The axis In the example illustrated in Figures 7 and 8, the groove 16b allowing an additional degree of freedom is the right groove.

Steps E2 and E3 are carried out in the same way as for the first implementation example.

The third example of implementation of the process of on the welding assembly 7 of the is illustrated on the . More precisely, like the , there illustrates a section along a plane parallel to the axis Y of the welding assembly 7 at the end of step E3 of the third example of implementation of the welding process of the .

As for the first two examples, a positioning and holding means 17 is machined during step E1 on the first and second parts 8 and 9. The positioning means 17 comprises two projecting parts 17a and two grooves 17b configured to receive and grip the protruding parts 17a.

The dimensions along the axis

The two projecting parts 17a are machined parallel on the lower surface 8a of the first part 8, outside and on either side of the first welding zone 10. Likewise, the two grooves 17b are machined parallel on the upper surface 9a of the second part 9, outside and on either side of the second welding zone 11. The positioning and holding means 17 is thus not intended to be welded during step E3, at the difference from the first two examples.

The third example is the only example described in which the optional step E4 is carried out. Thus, at the end of step E1, an insulating element 18 is applied in the grooves 17b. The insulating element is for example putty.

During step E2 of activating the positioning and holding means 17, the insertion of the protruding parts 17a into the grooves 17b causes the insulating element 18 to flow back into a free space 19 between the walls of the grooves 17b and the walls of the protruding parts 17a, this free space resulting from the difference in dimension of a few millimeters between the grooves 17b and the protruding parts 17a. In this way, the insulating element 18 makes it possible to seal the positioning and holding means 17 by filling the free space.

During the last step E3, the first welding zone 10 is welded to the second welding zone 11 by friction stir, so that the welding path is traced between the two protruding parts 17a inserted in the grooves 17b. In this way, the positioning and holding means 17 is not welded to the first and second part, unlike the first two examples described. A welding bead 20 is therefore formed between the two protruding parts 17a inserted in the grooves 17b during step E3.

Step E4 is optional and makes it possible to overcome cases, as illustrated in the first two examples described, where the welding trajectory does not allow the entire positioning and holding means machined in step E1 to be welded to the zones welding 10 and 11. Indeed, when the positioning and holding means is not completely welded to the welding zones 10 and 11, the difference between the dimensions of the protruding parts and the grooves causes the presence of free spaces between the walls of the protruding parts and grooves, resulting in a lack of tightness of the welded assembly.

Conversely, when the positioning and holding means machined in step E1 is completely welded with the welding zones 10 and 11 during step E3, the mixing of the materials welded by friction stir makes it possible to fill the initial free space and to seal the welded assembly.

Claims (11)

Friction stir welding process of a first part (8) on a second part (9), the first part (8) being placed on the second part (9), comprising the following steps:

• Machining (E1) of a means for positioning and holding the first part on the second part (13, 16, 17) on the first and second parts (8 and 9), the means (13, 16, 17) for machined positioning and holding device comprising at least one protruding part (13a, 16a, 17a) and at least one groove (13b, 16b, 17b) intended to receive the at least one protruding part (13a, 16a, 17a) for positioning and maintaining the first part (8) on the second part (9), the at least one projecting part (13a, 16a, 17a) being machined on the first part (8) and the at least one groove (13b , 16b, 17b) being machined in the second part (9),
• Activation (E2) of the positioning and holding means (13, 16, 17),
• Welding (E3) by friction stir of a first welding zone (10) of the first part (8) and a second welding zone (11) of the second part (9).

Welding method according to claim 1, in which the step of activating (E2) the positioning and holding means (13, 16, 17) comprises the assembly of the at least one projecting part (13a, 16a, 17a) with the at least one groove (13b, 16b, 17b) intended to receive the at least one projecting part (13a, 16b, 17b). Welding method according to one of claims 1 or 2, in which the at least one projecting part (13a, 16a, 17a) is machined on a lower surface (8a) of the first part (8), and the at at least one groove (13b, 16b, 17b) is machined in an upper surface (9a) of the second part (9). Welding method according to any one of claims 1 to 3, in which the at least one projecting part (13a, 16a, 17a) is machined from an aluminum alloy. Welding method according to any one of claims 1 to 4, in which the at least one projecting part (13a, 16a, 17a) is machined from the material of the first welding zone (10). Welding method according to any one of claims 1 to 5, in which the at least one projecting part (13a, 16a, 17a) is machined on the first welding zone (10) of the first part (8) and the at least one groove (13b, 16b, 17b) is machined in a portion of the second welding zone (11) intended to be in contact with the at least one projecting part (13a, 16a, 17a). Welding method according to any one of claims 1 to 6, in which the at least one groove (13b, 16b) is machined in a portion of the second welding zone (11) intended to be in contact with the first zone welding (10). Welding method according to any one of claims 1 to 7, in which during the welding step (E3), at least a portion of the positioning and holding means (13, 16) is welded by friction stir to the first and second welding zones (10 and 11). Welding method according to any one of claims 1 to 7, comprising a step (E4) of applying an insulating element (18) in the at least one groove (17b), prior to step (E2) activation of the positioning and holding means (17). Method according to claim 8, wherein the insulating element (18) is putty. Weld obtained from the implementation of a friction stir welding process according to any one of claims 1 to 10 on a welding assembly (7) comprising a first part (8) arranged on a second part (9).