Method and apparatus for performing double-sided refill friction stir spot welding

Abstract

To provide a method for performing simultaneous double-sided refill friction stir spot welding.SOLUTION: A method includes: providing a first welding head (110) having a first probe member (102) and a first tubular shoulder (104); providing a second welding head (210) having a second probe member (202) and a second tubular shoulder (204); arranging the first welding head (110) on a first surface, so that the first probe member (102) and the first tubular shoulder (104) are brought into contact with a first surface of a welding object; and arranging the second welding head (210) on a second surface of a welding object (112), which faces the first surface.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for performing refill friction stir spot welding. [Background technology]

[0002] Joining two components together by welding is a widely known process. Typically, the method of welding involves clamping two metals in contact and applying heat to a consumable material (e.g., in the form of a consumable electrode) to melt the consumable material, as well as a portion of the material to be welded, which is then often cooled to form a weld.

[0003] While this traditional welding technique is an effective way to create a robust joint between two materials, it does have drawbacks. For example, it requires the use of a consumable material, which means that in order to weld continuously, there must be an equally continuous supply of consumable material. Additionally, the introduction of a second material into the welding process can introduce opportunities for impurities and weak spots to form in the components of the weld, for example, if the consumable material is not manufactured to a high enough quality.

[0004] A way to overcome the need for consumable materials has been provided by the British Welding Institute with the invention of friction stir welding. Friction stir welding is a solid-state joining process that uses frictional heat generated by a rotating tool to join materials, and does not require the use of consumable materials.

[0005] Friction stir spot welding (FSSW) is a solid-state joining technique derived from friction stir welding (FSW). Unlike FSW, FSSW does not involve linear motion of the tool and results in a specific "spot" weld. The technique has attracted interest in many industries, but industrial adoption is limited, mainly because termination holes are produced.

[0006] In response to these concerns, a further technique known as Refill Friction Stir Spot Welding (Refill FSSW) was developed. This innovative technique, outlined in WO 01 / 36144, utilizes a redesigned tool to achieve a spot weld without a termination hole by advancing the probe into the workpiece while rotating both the probe and shoulder, simultaneously retracting the tubular shoulder surrounding the probe. During this motion, material that is plasticized by friction between the probe and the workpiece and is pressed by the advancing probe is received in the space between the probe and the tubular shoulder. When the probe has advanced into the workpiece to a certain depth, the combined motion is reversed, so that the probe retracts while the shoulder advances toward the workpiece, forcing the displaced material back into the recess created by the probe.

[0007] Although this conventional method of refill FSSW avoids the use of consumable materials and termination holes, it still has certain limitations. For example, the weld depth is constrained by the plunge depth of the refill FSSW machine. This limitation results in thick joints not being able to be welded or in long welding times that cause degradation of the previous weld when performing one weld after another.

[0008] Additionally, challenges with welding multi-stack joints such as Al-Ti-Al or Al-St-Al arise due to the high melting temperatures of the intermediate materials. This elevated melting point makes fusion welding or traditional refill FSSW impractical in such applications. Summary of the Invention [Problem to be solved by the invention]

[0009] It is an object of the present invention, as described herein, to overcome the aforementioned drawbacks while providing further advantages. [Means for solving the problem]

[0010] One aspect of the invention relates to a method for performing refill friction stir spot welding, the method including the steps of: providing a first welding head comprising a first probe member and a first tubular shoulder, the first probe member being disposed inside the first tubular shoulder and axially aligned with the first tubular shoulder along a first head axis; and providing a second welding head comprising a second probe member and a second tubular shoulder, the second probe member being disposed inside the second tubular shoulder and axially aligned with the second tubular shoulder along a second head axis. The method includes positioning a first welding head on a first surface of a workpiece such that a first probe member and a first tubular shoulder contact the first surface, and positioning a second welding head on a second surface opposite the first surface such that a second probe member and a second tubular shoulder contact the second surface of the workpiece and the first head axis is aligned with the second head axis. The method includes simultaneously rotating the first and second welding heads to form an increased plastic volume in the welded workpiece in proximity to (and in contact with) the first and second welding heads, and simultaneously advancing one of the first probe member and the first tubular shoulder and one of the second probe member and the second tubular shoulder from an initial position along the respective first and second head axes toward the respective first and second surfaces of the welded workpiece, while retracting (e.g., in the opposite direction) the other of the first probe member and the first tubular shoulder and the second probe member and the second tubular shoulder from the initial position along the respective first and second head axes. The method includes returning each of the first and second probe members and the first and second tubular shoulders toward their initial positions, and removing the first and second welding heads from the respective first and second surfaces of the welded workpiece.

[0011] In use, the method may be used to create a weld on a weld object by placing a first welding head on a first surface of the weld object, placing a second welding head on a second surface of the weld object, and simultaneously advancing both the first and second welding heads simultaneously into the weld object to plasticize the volume of the weld object, creating a weld volume of the weld object extending from both the first and second surfaces of the weld object. When performing the described method on both the first and second surfaces of the weld object, heat loss that may normally occur through the back side (e.g., second surface) of the weld object can be avoided, and in fact, for example, heat penetrating the weld object from the first surface to the second surface can increase the efficiency of creating a weld on the second surface, and vice versa. Furthermore, the increased heat provided plasticizes the material that requires more energy, allowing the realization of a deep weld. Thus, a synergistic effect is realized compared to performing welding on a single surface. Additionally, the weld volume may be large and may extend across the entire thickness of the workpiece, thereby increasing the strength of the weld as compared to performing welding on only one surface of the workpiece at a given time. In particular, welding from both sides simultaneously allows for welding in a single step joints twice as thick as is achievable with conventional refill FSSW processes.

[0012] The method may include simultaneously advancing the first and second tubular shoulders from an initial position along the respective first and second head axes into the respective first and second surfaces of the welding workpiece while retracting the first and second probe members from an initial position along the respective first and second head axes. The initial position may correspond to a position of the first and second probe members and the tubular shoulders in contact with the welding workpiece prior to rotation of the first and second probe members and the first and second tubular shoulders. Thus, the method may include placing the first and second probe members and the first and second tubular shoulders in contact with the respective first and second surfaces of the welding workpiece, where the first and second probe members and the first and second tubular shoulders are rotationally stationary (e.g., do not rotate relative to each other or the welding workpiece).

[0013] The welding object may comprise a first and a second component disposed between a first and a second welding head, the first component comprising a first surface and the second component comprising a second surface, the method including advancing the first tubular shoulder into the welding object a distance equal to or less than the thickness of the first component, and advancing the second tubular shoulder into the welding object a distance equal to or less than the thickness of the second component. The first and second components may be in the form of sheets of material to be welded, such as sheets of aluminum. The welding object may be in the form of a weld stack, in which case the resulting weld may be in the form of a multi-stack joint. In particular, the method of the present invention is suitable for spot welding aluminum and aluminum alloys, magnesium and magnesium alloys, and copper and copper alloys, and combinations thereof. Furthermore, spot welds in thermoplastic polymers and polymer matrix composites and combinations of the aforementioned materials may also be created by the method of the present invention. Furthermore, it should be noted that titanium and titanium alloys, as well as steel components may also form part of the welded objects subjected to the method of the present invention, although in the case of these materials it is preferred that the probe member and / or the tubular shoulder do not penetrate the components of these materials. Finally, the present invention is not limited to the examples of materials mentioned above.

[0014] The method may include simultaneously advancing the first tubular shoulder and the second probe member from an initial position along the respective first and second head axes into respective first and second surfaces of a weld workpiece, while retracting the first probe member and the second tubular shoulder from an initial position along the respective first and second head axes. By advancing the probe member of one weld head and the tubular shoulder of the other weld head, a user can obtain a preferred shape and / or configuration of the weld.

[0015] The object to be welded may comprise first and second components arranged between a first and a second welding head, the first component comprising a first surface and the second component comprising a second surface. The method may include advancing a first tubular shoulder into the object to be welded by a distance greater than the thickness of the first component, and advancing a second probe member into the object to be welded by a distance greater than the thickness of the second component. By advancing the first tubular shoulder into the object to be welded by more than the thickness of the first component, a weld with a particularly high mechanical mixing of the first and second components can be created, which can improve the integration of the weld volume into the welded first and second components.

[0016] More preferably, the distance by which the first shoulder advances into the object to be welded need only be slightly greater than the thickness of the first component, such that only the surface area of the second component adjacent to the first component is essentially affected, i.e., the first shoulder merely "scrapes" the second component. Similarly, in this more preferred embodiment, the distance by which the second probe member advances into the object to be welded need only be slightly greater than the thickness of the second component, such that only the surface area of the first component is essentially affected by the second probe member, i.e., the second probe member merely scrapes the first component. This embodiment has proven to result in a particularly stable joint.

[0017] The method may include advancing the first tubular shoulder and the second probe member into the object to be welded such that the second probe member is partially disposed within the first tubular shoulder. Thereby, when the probe member and the tubular shoulder are returned to their original positions, the mixing of the first and second components can be assisted.

[0018] The welding object may include a third component disposed between the first and second components, and the method includes advancing one of the first probe member and the first tubular shoulder along the first head axis into the welding object a distance greater than, equal to, or less than a thickness of the first component, and advancing one of the second probe member and the second tubular shoulder along the second head axis (208) into the welding object a distance greater than, equal to, or less than a thickness of the second component, while retracting the other of the first probe member and the first shoulder and the other of the second probe member and the second shoulder from an initial position along their respective first and second axes. The third component may be less plastic than the first and second components at a given temperature. The third component may have a higher melting point than the first and second components. The first and second components may be made of the same first material, while the third component may be made of a second material. For example, the first and second components may be made of aluminum, while the third component may be made of titanium. The third component may thus be welded to the first and second components, thereby providing a high strength multi-stack joint. More preferably, the distance the first probe member or the first shoulder advances into the welded object may be only slightly greater than the thickness of the first component, such that essentially only the surface area of ​​the third component adjacent to the first component is affected, i.e., the first probe member or the shoulder merely "rubs" the third component. Similarly, in this further preferred embodiment, the distance the second probe member or second shoulder advances into the welded object need only be slightly greater than the thickness of the second component, such that only a surface area of ​​the third component is essentially affected by the second probe member or second shoulder, i.e., the second probe member or second shoulder simply rubs against the third component.

[0019] The method may also include advancing the first probe member and the second probe member from an initial position into respective first and second surfaces of the object to be welded along respective first and second head axes, while retreating the first tubular shoulder and the second tubular shoulder from an initial position along respective first and second head axes. By advancing the probe members of the welding heads in parallel, the user can provide a specific shape and / or structure of the weld. In particular, the mutual mixing of the materials of the object to be welded can be improved.

[0020] The volume with increased plasticity extends across the entire width of the object to be welded and may, for example, extend through both the first and second components.

[0021] The first welding head and the second welding head may be structurally identical, which may facilitate providing a weld with consistent quality and strength across the entire width of the object to be welded.

[0022] The first welding head and the second welding head may be structurally different. For example, the diameter of the first probe member may be larger or smaller than the diameter of the second probe member. The inner diameter of the first tubular shoulder may be larger or smaller than the inner diameter of the second tubular shoulder. The outer diameter of the first tubular shoulder may be larger or smaller than the outer diameter of the second tubular shoulder. In this way, an asymmetric weld can be formed on the object to be welded.

[0023] The first welding head may include a first clamp and the second welding head may include a second clamp. The method may include clamping the welding object between the first clamp and the second clamp before rotating the first and second welding heads. In this way, the welding object can be fixed before welding, ensuring precision of the weld and alignment of both sides of the welding object. Furthermore, the clamp surrounding the tubular shoulder prevents the plasticized material from squeezing laterally outward, thereby ensuring that as the probe and / or shoulder advances into the object, the entire material is forced into the welding object and into the recess created by the forward movement.

[0024] The method may include simultaneously rotating the first shoulder and the first probe member in the same direction and simultaneously rotating the second shoulder and the second probe member in the same direction. Alternatively, the method may include simultaneously rotating the first shoulder and the first probe member in opposite directions and simultaneously rotating the second shoulder and the second probe member in opposite directions. In this way, the introduction and mixing of heat in the area affected by the welding head may be further tailored to the specific requirements of the components involved. In addition to selecting the rotational direction in which the probe member and the tubular shoulder rotate, the respective rotational speeds may also be adjusted according to the needs of the material and dimensions of the welded objects.

[0025] Additionally, the method may include rotating the first probe member and the second probe member in the same direction. Alternatively, the method may include rotating the first probe member and the second probe member in opposite directions. This provides further options for optimizing mixing and heat introduction in the weld zone.

[0026] A second aspect relates to an apparatus for providing refill friction stir spot welding, the apparatus comprising: a first welding head comprising a first probe member and a first tubular shoulder, the first probe member disposed inside the first tubular shoulder and axially aligned with the first tubular shoulder along a first head axis, the first probe member being rotatable relative to the first tubular shoulder, and a second welding head comprising a second probe member and a second tubular member, the second probe member disposed inside the second tubular shoulder and axially aligned with the second tubular shoulder along a second head axis, the second probe member being rotatable relative to the second tubular shoulder. The apparatus further includes a recess for positioning a welding object therein, the recess being disposed between the first welding head and the second welding head, the first welding head being disposed opposite to the second welding head, and the first welding head and the second welding head being axially movable along respective first and second head axes to selectively engage a welding object positioned within the recess.

[0027] The apparatus may be configured such that the first welding head includes a first clamp and the second welding head includes a second clamp that clamps the welding object between the first clamp and the second clamp, thereby enabling the welding object to be fixed in a clearly defined position relative to the welding head. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 illustrates an example of refill friction stir spot welding according to known methods. [Diagram 2] FIG. 1 illustrates an example of a refill friction stir spot weld according to the present disclosure. [Diagram 3] FIG. 13 is a further example of refill friction stir spot welding illustrating alternative advancement and retraction of the probe member and tubular shoulder relative to the weld workpiece. [Figure 4]FIG. 13 is a further example of refill friction stir spot welding illustrating alternative advancement and retraction of the probe member and tubular shoulder relative to the weld workpiece. [Diagram 5] 11A-11C are diagrams of the described method with alternative welding objects. [Figure 6] 11A-11C are diagrams of the described method with further alternative welding objects. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] FIG. 1 shows an example of a refill friction stir spot welding process according to known methods. Here, a welding head 10 comprises a probe member 2 and a tubular shoulder 4. A clamp 6 may also be considered as optionally part of the welding head 10. The probe member 2 is cylindrical in shape, while the tubular shoulder 4 is in the form of a cylindrical sleeve with a central recess. As shown in FIG. 1, the probe member 2 is disposed in the central recess of the tubular shoulder 4, and both the probe member 2 and the tubular shoulder 4 are positioned about a central axis 8 of the welding head 10. Although not shown, both the probe member 2 and the tubular shoulder 4 are connected to a drive member configured to rotate both the probe member 2 and the tubular shoulder 4 about the central axis 8 and to move both in a translational direction along the central axis.

[0030] In operation, the welding head 10 may be positioned near the workpiece 12, as shown in the leftmost view of Fig. 1. The workpiece 12 may be provided on a support 14, as shown in Fig. 1. The welding head 10 may then be moved axially to contact the workpiece 12, and may be pressed against the workpiece 12 with a predetermined force to apply pressure from the welding head 10 to the workpiece 12, as shown in the second view from the left in Fig. 1.

[0031] While maintaining pressure against the workpiece 12, both the probe member 2 and the tubular shoulder 4 may be rotated, thereby creating friction between the weld head 10, i.e., the probe member 2 and / or shoulder 4, and the weld workpiece 12, generating heat therebetween. The generated heat penetrates the material as the tubular shoulder 4 advances from its initial position in contact with the weld workpiece 12 into the weld workpiece 12, and the probe member 2 is withdrawn from its initial position in contact with the weld workpiece 12. The heat generated from the rotation of the probe member 2 and tubular shoulder 4 in contact with the weld workpiece 12 increases the temperature of the weld workpiece 12 proximate the weld head 10, creating a plasticized volume 16 in the weld workpiece that becomes more malleable than the surrounding weld workpiece.

[0032] When the tubular shoulder 4 is driven into the plasticized volume 16 of the workpiece 12 and the probe member 2 is withdrawn from its initial position, the plasticized volume 16 moves upwardly toward the probe member 2 as it is displaced by the tubular shoulder 4 being driven into the workpiece 12.

[0033] After a predetermined length of time and displacement of the probe member 2 and tubular shoulder 4, both the probe member 2 and tubular shoulder 4 are moved back towards their initial positions, forcing the displaced plasticized material in the plasticized volume 16 back towards the work piece 12, as shown in the second-from-the-right diagram of Figure 1. Finally, rotation of the probe member 2 and tubular shoulder 4 is stopped and the welding head 10 is removed from the surface of the work piece 12 to allow the plasticized volume to cool and the weld to harden.

[0034] Figure 2 shows the steps in a method and apparatus for providing refill friction stir spot welding according to the present invention. Here, a first welding head 110 and a second welding head 210 are shown. Each of the first and second welding heads 110, 210 includes a first probe member 102 and a second probe member 202, and first and second tubular shoulders 104, 204. In this example, the first and second probe members 102, 202 are each cylindrical in shape and are positioned inside recesses formed in the respective first and second tubular shoulders 104, 204. The tubular shoulders 104, 204 have the shape of cylindrical sleeves, but it should be noted that the central recess of the tubular shoulder needs to extend over its entire length. The first probe member 102 and the first tubular shoulder 104 are positioned such that their longitudinal axes are aligned with the first head axis 108 of the first welding head 110. The second probe member 202 and the second tubular shoulder 204 are positioned such that their longitudinal axes are aligned with the second head axis 208 of the second welding head 210. While the first welding head 110 includes a first clamp 106, the second welding head 210 includes a second clamp 206. In this example, the first and second clamps 106, 206 form part of their respective welding heads 110, 210 and are disposed radially outside the respective first and second tubular shoulders 104, 204. The first and second clamps 106, 206 may be in the form of cylindrical clamp members having recesses in which the respective first and second probe members 102, 202 and tubular shoulders 104, 204 are positioned.

[0035] The clamps 106, 206 function to hold the respective probe members 102, 202 and tubular shoulders 104, 204 in place while forming a weld in the weld object 112. Further, the clamps 106, 206 prevent the plasticized material from escaping from the area under the shoulders 104, 204.

[0036] Although not shown, the first probe member 102 and the first tubular shoulder 104 may be coupled to a rotation device to enable rotation thereof. The first probe member 102 and the first tubular shoulder 104 may be rotatable relative to one another and thus may be coupled to a rotation device that enables independent rotation of each, or each may be coupled to a separate rotation device. Similarly, the second probe member 202 and the second tubular shoulder 204 may be coupled to a rotation device to enable rotation thereof, may be rotatable relative to one another and may be coupled to separate rotation devices to enable independent rotation thereof, or to a single rotation device that enables such independent rotation.

[0037] 2, the first welding head 110 and the second welding head 210 are positioned on either side of the welding workpiece 112 such that the first head axis 108 of the first welding head 110 is aligned with the second head axis 208 of the second welding head 210. In this example, since the first welding head 110 and the second welding head 210 are geometrically identical, aligning the first welding head 110 with the second welding head 210 can ensure a balanced application of force, and therefore a balanced weld, on either side of the welding workpiece 112.

[0038] The first and second welding heads are also translatable, for example, toward or away from each other, in this case in the direction of or parallel to the respective head axes 108,208.

[0039] Here, the welding workpiece 112 is composed of a first component 112a and a second component 112b. Note that in this example, both the first and second components 112a, 112b are made from the same material, but this is not necessarily the case and the first and second components 112a, 112b may be made from different materials. The welding workpiece 112 may have an overall thickness of 6-8 mm, which means that each component 112a, 112b may be 3-4 mm thick. The welding workpiece 112 is positioned in a recess 118 between the first welding head 110 and the second welding head 210. The welding workpiece 112 may be held in place by any suitable means, such as an external arm, clamp, etc., not shown in FIG. 2 for clarity.

[0040] As shown in the leftmost view of FIG. 2, when the welding workpiece 112 is placed in the recess 118 between the first welding head 110 and the second welding head 210, the first and second welding heads advance toward each other in a direction aligned with their respective head axes 108, 208 until both the first and second welding heads 110, 210 contact the welding workpiece 112. In particular, the tip faces of the probe members 102, 202, the tubular shoulders 104, 204, and in this example the clamps 106, 206 are also aligned with the surface of the welding workpiece 112 to assume an "initial position" in contact with the welding workpiece 112. Pressure is then applied to the welding workpiece 112 via the first and second welding heads 110, 210 as indicated by the arrows 120, 220 on the second leftmost view of FIG. 2.

[0041] Turning now to the central view of FIG. 2, the probe members 102,202 and tubular shoulders 104,204 are rotated simultaneously about their respective head axes 108,208, as indicated by arrows 122,222.

[0042] The first shoulder 104 and the first probe member 102 may rotate in the same direction, and similarly the second shoulder 204 and the second probe member 202 may rotate in the same direction. Alternatively, the first shoulder 104 and the first probe member 102 may rotate in the opposite direction, and the second shoulder 204 and the second probe member 202 may rotate in the opposite direction. In this way, the heat introduction and mixing in the area affected by the welding head 110, 210 may be further tailored to the specific requirements of the welding workpiece 112. Furthermore, in any of the aforementioned options, the first probe member 102 and the second probe member 202 may rotate in the same direction or in the opposite direction. In addition to selecting the rotational direction in which the probe members 102, 202 and the tubular shoulders 104, 204 rotate, the respective rotational speeds may also be adjusted according to the needs of the material and dimensions of the welding workpiece 112.

[0043] Upon rotation of both the probe member 102, 202 and the tubular shoulder 104, 204 in contact with the work piece 112, friction is generated between the tip surface of the rotating probe member 102, 202 and the tubular shoulder 104, 204, generating heat therebetween. The heat propagates through the work piece, heating it and creating an increased plastic volume 124 within the work piece. The increased plastic volume may be more malleable than the surrounding work piece. The speed of rotation, the direction of rotation, and the force with which the weld head 110, 210 (in this case the tubular shoulder 104, 204) is pressed into the work piece 112 may all be varied to vary the amount of heat generated. This may vary, for example, depending on the energy input required to plasticize the particular material of the work piece 112 and / or the melting point of the material of the work piece 112.

[0044] As the first and second probe members 102, 202, and the first and second tubular shoulders 104, 204 rotate, at the same time, the tubular shoulders 104, 204 advance (e.g., are driven) into the weld object 112 and into the volume 124 with increased plasticity, as shown in the central view of FIG. 2, while the probe members 102, 202 are withdrawn from their initial positions in a direction away from the weld object 112. As shown in the central view of FIG. 2, this has the effect of aligning with the head axes 108, 208 and forming a recess 126 (in this case, a cylindrical recess) that is partially defined by each central recess of the tubular shoulders 104, 204. To avoid damage to any of the tubular members 104, 204, contact between the operating tubular members 104, 204 may be avoided.

[0045] The probe members 102, 202, and the tubular shoulders 104, 204 are shown as rotating in the same direction, but they may rotate in different directions as already described above, which provides a change in heat generation and thus may provide another variable for the user to control the welding method. Note that this is possible.

[0046] As shown, the volume 124 with increased plasticity extends across the entire thickness of the weld object 112. This is due to the heat generated on both sides of the weld object 112, and each welding head 110, 210 benefits from the heat generated by the other welding head 210, 110, thus creating a synergistic effect between the welding heads 110, 210. In addition, this means that it may not be necessary to provide the same level of pressure and / or the same degree of rotation, which means that the life of the welding heads is extended.

[0047] Once the tubular shoulder 104, 204 has advanced a predetermined distance into the workpiece (once the probe member 102, 202 has been withdrawn a predetermined distance), the probe member 102, 202 and tubular shoulder 104, 204 may return to their original positions (e.g., initial positions) after a predetermined length of time. The time length may vary depending, for example, on the stiffness of the material of the workpiece 112 and the melting point of that material. The predetermined distance may be equal between the tubular shoulder 104, 204 and the probe member 102, 202 or may be based on the thickness of the first and second components 112a, 112b, which may or may not be equal. For example, the predetermined distance for each tubular shoulder 104, 204 may be 50%, 45%, 40%, etc., of the thickness of the workpiece 112 to be welded, or may be the total thickness of the respective first or second component 112a, 112b, or 95% of the thickness, 90% of the thickness, etc. of the respective component 112a, 112b.

[0048] As the probe members 102, 202 and tubular shoulders 104, 204 are returned to their original positions, the increased plastic volume 124 is forced back into the original volume of the weld workpiece 112. Rotation of the probe members 112 continues during the return of the probe members 102, 202 and tubular shoulders 104, 204 is maintained until the probe members 102, 202 and tubular shoulders 202, 204 return to their initial positions. The described movements of the probe members 102, 202 and tubular shoulders 202, 204 may have the effect of mixing together the plasticized volumes spanning both components 112a, 112b of the weld workpiece.

[0049] The weld head 110, 210 may then be withdrawn from the work piece 112 and the plasticized volumes may be allowed to cool, thus solidifying them together to form a weld volume.

[0050] Although the first and second probe members 102, 202 and the first and second tubular shoulders 104, 204 are shown to be of the same dimensions, this need not be the case. For example, one of the first and second probe members 102, 202 may be of a larger or smaller diameter than the other, and thus the corresponding inner diameter of the tubular shoulders 104, 204 may also be different. Additionally, the outer diameter of one tubular shoulder 104, 204 may be larger or smaller than the other. Thus, the shape and strength of the plasticized volume may vary based thereon.

[0051] Another example of a method for providing a refill friction stir spot weld is shown in Figure 3. Many of the features of Figure 3 are common to those described in Figure 2 and therefore will not be repeated.

[0052] As previously mentioned, there are shown first and second welding heads 110, 210 with respective first and second probe members 102, 202, first and second tubular shoulders 104, 204, and first and second clamps 106, 206. As is evident from Fig. 3, only the central view differs from the view of Fig. 2.

[0053] According to the method shown in Figure 3, the first probe member 102 is rotated and advanced into the workpiece 112 while the second probe member 202 is also advanced from its initial position into the workpiece 112. In parallel, the first and second tubular shoulders 104, 204 are withdrawn from the workpiece 112, in contrast to the illustration of Figure 2. In this example, the first and second probe members 102, 202 are advanced into the weld material.

[0054] As shown, one recess defined by the probe members 102, 202 is formed containing a volume of plasticized material. This volume 126 is defined by the first and second probe members 102, 202. To form this volume, the first tubular shoulder 102 and the second probe member 202 may be advanced into the weld workpiece 112 by less than 50% of the width or thickness of the weld workpiece. Here, a single volume may improve mixing of the material in the plasticized volume and may result in preferred weld strength for some applications compared to the view of FIG.

[0055] A further example of a method for providing a refill friction stir spot weld is shown in Figure 4. Many of the features of Figure 4 are common to those described in Figures 2 and 3 and therefore will not be repeated.

[0056] As previously mentioned, there are shown first and second welding heads 110, 210 with respective first and second probe members 102, 202, first and second tubular shoulders 104, 204, and first and second clamps 106, 206. As is evident from Fig. 4, only the central view differs from the views of Figs.

[0057] According to the method shown in Figure 4, the first tubular shoulder 104 is rotated and advanced into the welding workpiece 112 as in Figure 2, and the second probe member 202 is advanced into the welding workpiece 112 from its initial position while the second tubular shoulder 204 is withdrawn from the welding workpiece 112 in contrast to the illustration of Figure 2. It should be noted that in this example, the second probe member 202 is advanced into the weld material such that the second probe member 202 is partially disposed within the recess of the first tubular member 104, however, in some other examples, the second probe member 202 and the first tubular shoulder 104 may be advanced a lesser distance into the welding workpiece 112 such that the second probe member 202 is not disposed within the first tubular shoulder 104.

[0058] Instead of forming one recess defined by the tubular shoulder 104, 204 (e.g., the inner surface of the tubular shoulder) and the probe member 102, 202 (e.g., the tip surface of the probe member 102, 202) as shown, now two recesses containing volumes of plasticized material are formed. A first of these volumes, volume 126a, is defined by the inner surface of the first tubular shoulder 104 and the tip surfaces of the first and second probe members 102, 202, while a second volume 126b is defined by the outer surface of the second probe member 202, the tip surfaces of the tubular shoulder 104, 204, and the second clamp 206. To form these volumes, the first tubular shoulder 104 and the second probe member 202 may be advanced into the weld workpiece 112 beyond 50% of the width of the weld workpiece. The presence of two separate volumes allows for improved mixing of the materials in the plasticized volume and may result in preferred weld strength for some applications compared to the diagram of FIG.

[0059] In this example, the distance the first shoulder 104 advances into the welding workpiece 112 need only be slightly greater than the thickness of the first component 112a, and therefore only the surface area of ​​the second component 112b adjacent to the first component 112a is essentially affected, i.e., the first shoulder 104 merely "rubs" the second component 112b. Similarly, the distance the second probe member 202 advances into the welding workpiece 112 need only be slightly greater than the thickness of the second component 112b, and therefore only the surface area of ​​the first component 112a is essentially affected, i.e., the second probe member 202 merely rubs against the first component 112a.

[0060] Further, FIG. 5 shows a fourth example of a method for providing a refill friction stir spot weld. In this example, the same movement of the welding head 110, 210 as in FIG. 2 is performed, but the welding object is composed of first, second and third components 112a, 112b, 112c, and the third component 112c is positioned between the first and second components 112a, 112b. Here, the first and second components 112a, 112b are of the same material, e.g., aluminum, while the third component 112c is of a different material, e.g., titanium. In this example, two plasticized volumes 124a, 124b are present in the first and second components 112a, 112b of the welding object 112. The melting point of the third component 112c may be higher than the melting points of the first and second components 112a, 112b, and therefore a plasticized volume may not be formed in the third component 112c, or a plasticized volume may be formed that is less plastic compared to the plasticized volumes of the first and second components 112a, 112b. It should be noted here that the first and second components 112a, 112b may be different materials, such as magnesium and copper.

[0061] According to the method, the tubular shoulders 104, 204 may advance into the workpiece 112 a distance equal to or less than the thickness of the respective first or second components 112a, 112b, and the plasticized volumes 124a, 124b may form two welds on the surface of the third component 112c. However, it is also contemplated that the distance that the first and second shoulders 104, 204 advance into the first and second components 112a, 112b is slightly greater than the respective thicknesses of the components, and thus the surface area of ​​the third component 112c is also affected by the first and second shoulders 104, 204.

[0062] Further, FIG. 6 shows a fifth example of a method for providing a refill friction stir spot weld. In this example, the same movement of the welding head 110, 210 is performed as in FIG. 2. However, the welded object 112 is composed of multiple components formed as a multi-layer arrangement. Here, the components may be of the same material or may be of alternating materials, for example aluminum and copper, as used in battery technology. In this example, it can be seen that a single continuous plasticized volume 126 exists within the multiple components, and that the method of the present invention can be used to form stir spot welds in a multi-layer structure.

[0063] Although described separately above, it should be noted that these are merely illustrative examples of possible methods and steps described in connection with one method may be applicable to another method. For example, the movement of the probe members 102, 202 and tubular shoulders 104, 204 described in Figures 3 and 4 may be applicable to the method having three or more component welding workpieces 112 of Figures 5 and 6.

Claims

1. 1. A method of performing refill friction stir spot welding, comprising: providing a first weld head (110) comprising a first probe member (102) and a first tubular shoulder (104), said first probe member (102) disposed inside said first tubular shoulder (104) and axially aligned with said first tubular shoulder (104) along a first head axis (108); providing a second weld head (210) comprising a second probe member (202) and a second tubular shoulder (204), said second probe member (202) disposed inside said second tubular shoulder (204) and axially aligned with said second tubular shoulder (204) along a second head axis (208); positioning the first welding head (110) on a first surface of a workpiece such that the first probe member (102) and the first tubular shoulder (104) are in contact with the first surface; positioning the second welding head (210) on a second surface opposite the first surface such that the second probe member (202) and the second tubular shoulder (204) contact a second surface of the workpiece (112) and the first head axis (108) is aligned with the second head axis (208); simultaneously rotating the first and second weld heads to form a volume of increased plasticity in the weld workpiece adjacent the first and second weld heads; simultaneously advancing one of the first probe member (102) and the first tubular shoulder (104) and one of the second probe member (202) and the second tubular shoulder (204) from an initial position along the respective first and second head axes (108, 208) toward the respective first and second surfaces of the welding workpiece (112), while retracting the other of the first probe member (102) and the first tubular shoulder (104) and the second probe member (202) and the second tubular shoulder (204) from an initial position along the respective first and second head axes (108, 208); returning each of the first and second probe members (102, 202) and the first and second tubular shoulders (104, 204) towards the initial position; removing the first and second welding heads (110, 210) from the first and second surfaces, respectively, of the work piece (112); 16. A method for performing refill friction stir spot welding comprising:

2. 2. The method for performing refill friction stir spot welding of claim 1, comprising simultaneously advancing the first tubular shoulder (104) and the second tubular shoulder (204) from the initial position along the respective first and second head axes (108, 208) into the respective first and second surfaces of the workpiece (112) while retracting the first and second probe members (102, 202) from the initial position along the respective first and second head axes (108, 208).

3. the welding object (112) comprises first and second components (112a, 112b) disposed between the first and second welding heads (110, 210), the first component (112a) comprising the first surface and the second component (112b) comprising the second surface; 3. The method for performing refill friction stir spot welding of claim 2, wherein the method includes advancing the first tubular shoulder (104) into the workpiece (112) a distance equal to or less than a thickness of the first component (112a) and advancing the second tubular shoulder (204) into the workpiece (112) a distance equal to or less than a thickness of the second component (112b).

4. 2. The method for performing refill friction stir spot welding of claim 1, comprising simultaneously advancing the first tubular shoulder (104) and the second probe member (202) from the initial position along the respective first and second head axes (108, 208) into the respective first and second surfaces of the welded workpiece (112) while retracting the first probe member (102) and the second tubular shoulder (204) from the initial position along the respective first and second head axes (108, 208).

5. the welding object (112) comprises first and second components (112a, 112b) disposed between the first and second welding heads (110, 210), the first component (112a) comprising the first surface and the second component comprising the second surface; 5. The method for performing refill friction stir spot welding of claim 4, wherein the method includes advancing the first tubular shoulder (104) into the weld workpiece a distance greater than a thickness of the first component (112a) and advancing the second probe member (202) into the weld workpiece (112) a distance greater than a thickness of the second component (112b).

6. 6. The method for performing refill friction stir spot welding as recited in claim 4 or 5, comprising advancing the first tubular shoulder (104) and the second probe member (202) into the weld workpiece (112) to partially position the second probe member (202) within the first tubular shoulder (104).

7. the welding object (112) comprises first and second components (112a, 112b) disposed between the first and second welding heads (110, 210), the first component (112a) comprising the first surface and the second component (112b) comprising the second surface, and a third component (112c) disposed between the first and second components (112a, 112b); 2. The method for performing a refill friction stir spot welding as recited in claim 1, comprising: advancing one of the first probe member and the first tubular shoulder along the first head axis into the welded workpiece a distance greater than, equal to, or less than a thickness of the first component; and advancing one of the second probe member and the second tubular shoulder along the second head axis into the welded workpiece a distance greater than, equal to, or less than a thickness of the second component while retracting the other of the first probe member and the first shoulder, and the other of the second probe member and the second shoulder from the initial position along their respective first and second axes.

8. 2. The method for performing refill friction stir spot welding of claim 1, comprising advancing the first and second probe members (102) and (202) from the initial position along the respective first and second head axes (108, 208) into the respective first and second surfaces of the workpiece (112) while retracting the first and second tubular shoulders (104) and (204) from the initial position along the respective first and second head axes (108, 208).

9. 9. The method for performing refill friction stir spot welding of any one of claims 1 to 8, wherein the first welding head (110) comprises a first clamp (106) and the second welding head (210) comprises a second clamp (206), and the method includes clamping the welded workpiece (112) between the first clamp (106) and the second clamp (206) prior to rotating the first and second welding heads (110, 210).

10. simultaneously rotating said first tubular shoulder (104) and said first probe member (102) in the same direction; 10. The method for performing refill friction stir spot welding according to any one of claims 1 to 9, comprising simultaneously rotating the second tubular shoulder (204) and the second probe member (202) in the same direction.

11. simultaneously rotating said first tubular shoulder (104) and said first probe member (102) in opposite directions; 10. The method for performing refill friction stir spot welding according to any one of claims 1 to 9, comprising simultaneously rotating the second tubular shoulder (204) and the second probe member (202) in opposite directions.

12. 12. The method for performing refill friction stir spot welding as recited in claim 10 or 11, comprising rotating the first probe member (102) and the second probe member (202) in the same direction.

13. 12. The method for performing refill friction stir spot welding as recited in claim 10 or 11, comprising rotating the first probe member (102) and the second probe member (202) in opposite directions.

14. 1. An apparatus for providing refill friction stir spot welding, comprising: a first welding head (110) comprising a first probe member (102) and a first tubular shoulder (104), said first probe member (102) disposed inside said first tubular shoulder (104) and axially aligned with said first tubular shoulder (104) along a first head axis (108), said first probe member (102) being rotatable relative to said first tubular shoulder (104); a second welding head (210) comprising a second probe member (202) and a second tubular member (204), said second probe member (202) disposed inside said second tubular shoulder (204) and axially aligned with said second tubular shoulder (204) along a second head axis (208), said second probe member (202) being rotatable relative to said second tubular shoulder (204); a recess for positioning a workpiece (112) therein, said recess being disposed between said first welding head (110) and said second welding head (210); Equipped with 1. An apparatus for providing refill friction stir spot welding, wherein the first welding head (110) is positioned opposite the second welding head (210), and the first welding head (110) and the second welding head (210) are axially movable along respective first and second head axes (108, 208) to selectively engage a welding workpiece (112) positioned within the recess.

15. 15. The apparatus for providing a refill friction stir spot weld as recited in claim 14, wherein the first welding head (110) comprises a first clamp (106) and the second welding head (210) comprises a second clamp (206) that clamps the weld workpiece (112) between the first clamp (106) and the second clamp (206).

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