FRICTION STIR WELDING TOOL AND FRICTION STIR WELDING METHOD

Abstract

A friction stir welding device and a friction stir welding method provide that an additional material is introduced into the gap between a rotating pin and a fixed shoulder. The pin and/or the shoulder includes a conveyor worm structure by which the additional material is transported to the workpiece.

Claims

1-21 (canceled)

22: A friction stir welding tool comprising a non-rotating shoulder having a first workpiece contact surface for contacting a workpiece to be welded, and at least one rotating pin, a gap delimited between the pin and the shoulder, and the wall of the pin and/or of the shoulder which delimits the gap having a first axially acting conveyor worm structure, and the friction stir welding tool having a material supply opening which is spaced apart from the first workpiece contact surface and leads into the gap.

23: The friction stir welding tool according to claim 22, wherein the at least one pin is configured as a conveyor worm at its outer envelope.

24: The friction stir welding tool according to claim 22, wherein the shoulder has a lateral material supply opening.

25: The friction stir welding tool according to claim 22, wherein in the region of the material supply opening, the pin includes a cutting edge for cutting the supplied material.

26: The friction stir welding tool according to claim 22, wherein the supplied material is a solid material.

27: The friction stir welding tool according to claim 22, wherein at least one of the shoulder and the pin are shiftable with respect to each other in the axial direction of the pin and/or wherein the shoulder is prestressed axially towards the workpiece and is spring-mounted.

28: The friction stir welding tool according to claim 22, wherein the first workpiece contact surface of the shoulder has portions which are inclined with respect to each other for welding corner connections, or portions which are axially offset with respect to each other for deposition welding.

29: The friction stir welding tool according to claim 22, wherein the pin is axially shiftable with respect to the shoulder or the shoulder relative to the pin.

30: The friction stir welding tool according to claim 22, wherein a second shoulder having a second workpiece contact surface opposite the first workpiece contact surface of the first shoulder, the workpiece being located between the two workpiece contact surfaces.

31: The friction stir welding tool according to claim 30, wherein at least one of the pin and the second shoulder comprises a second axial conveyor worm structure which has an axial conveying direction opposite the first conveyor worm structure.

32: The friction stir welding tool according to claim 22, wherein the tool includes a heater.

33: The friction stir welding tool according to claim 22, wherein an axially movable control sleeve is provided between the shoulder and the pin in a region spaced from the first workpiece contact surface, which at least partially delimits the gap axially and makes the axial length thereof variable.

34: The friction stir welding tool according to claim 22, wherein a control/regulating unit is provided which controls or regulates the feed rate, the speed of the pin and/or the quantity of supplied material as a function of at least one of the following parameters: torque of the pin, feed force to be applied for the tool, pressure force of the shoulder in the axial direction, temperature of the shoulder, the pin and/or the supplied material and/or the required force for supplying wire as supplied material.

35: A friction stir welding tool comprising a non-rotating shoulder having a first workpiece contact surface for contacting a workpiece to be welded, and at least one rotating pin, a pin postprocessing unit having a machining cutting tool which can be moved against the pin to machine the latter, the cutting tool being configured in a non-rotating manner, and the rotational movement during machining being carried out by the rotation of the pin.

36: A friction stir welding method, wherein an additional material is introduced into a gap between a non-rotating shoulder contacting the workpiece with a first workpiece contact surface and a rotating pin and is transported to the workpiece.

37: The method according to claim 36, wherein the additional supplied material is softened before reaching the workpiece.

38: The method according to claim 36, wherein the method is used to close a defective spot in a workpiece, to weld a two-part workpiece by joint or lap welding, to weld a corner connection or for deposition welding.

39: The method according to claim 36, wherein additional material is still conveyed to the workpiece at the end of the welding process upon pulling the pin out of the workpiece during rotation of the pin.

40: The method according to claim 36, wherein the lateral feed rate of the tool, the speed of the pin and/or the quantity of supplied material are regulated such that the weld seam is not deepened with respect to the portion of the workpiece contact surface of the shoulder which is opposite the feed direction and/or has no cavities or shrink holes.

41: The method according to claim 36, wherein the shoulder is caused to oscillate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0080] FIG. 1 a schematic view in longitudinal section through an embodiment of the friction stir welding tool according to the invention in the region of the tip of the pin,

[0081] FIG. 2 a view in longitudinal section through a variant of the friction stir welding tool according to the invention,

[0082] FIG. 3 the friction stir welding tool according to the invention applied in a hollow profile,

[0083] FIGS. 4a to 4d consecutive steps upon withdrawal of the pin at the end of the friction stir welding method according to the invention,

[0084] FIG. 5 a schematic view in longitudinal section through a further embodiment of the friction stir welding tool according to the invention,

[0085] FIG. 6 a variant of the friction stir welding tool according to the invention upon welding of a corner connection,

[0086] FIG. 7 a schematic sectional view through the friction stir welding tool according to the invention in accordance with a variant in the region of the material supply opening,

[0087] FIG. 8 a view in longitudinal section through a further variant of the friction stir welding tool according to the invention which is used for deposition welding,

[0088] FIG. 9 a bottom view of the tip of the pin and the shoulder of the friction stir welding tool of FIG. 8,

[0089] FIG. 10 a schematic top view onto the friction stir welding tool of FIG. 8 and the workpiece upon friction stir welding,

[0090] FIG. 11 a view in longitudinal section through a variant of the friction stir welding tool according to the invention having a heating system,

[0091] FIG. 12 a schematic view in longitudinal section through a friction stir welding tool according to the invention having a double shoulder,

[0092] FIG. 13 a schematic view in longitudinal section through a friction stir welding tool according to the invention having a variable reservoir of additional material,

[0093] FIG. 14 a view in longitudinal section through the friction stir welding tool of FIG. 13 according to a variant, and

[0094] FIG. 15 a view in longitudinal section through the friction stir welding tools according to the invention upon welding of a lap connection.

DETAILED DESCRIPTION

[0095] FIG. 1 illustrates a friction stir welding tool by means of which a workpiece 14 initially composed of two parts 10, 12 is welding together.

[0096] In the present case, the parts 10, 12 configured as metal sheets are arranged side by side spaced apart from each other with a regular or non-regular gap S.

[0097] The friction stir welding tool comprises a so-called shoulder 16 which is for example a circular cylindrical part. The end face facing the workpiece 14 which in this concrete case is configured in a plane manner, forms a first workpiece contact surface 18 via which the shoulder 16 rests on the upper side of the workplace 14 upon welding.

[0098] A preferably cylindrical opening 20 in the shoulder 16, which is not to be interpreted in a limiting manner, serves to receive a pin 22. This pin 22 is set into a rotary motion by an engine 24. The shoulder 16 does not rotate and is configured as a fixed shoulder.

[0099] A gap 28 is formed between the wall 26 of the shoulder 16 delimiting the opening 20 and the exterior side, more specifically the envelope surface of the pin 22.

[0100] This ring gap 28 has the purpose that the pin 22 does not rub against the shoulder 16. The gap 28 is however used for the supply of material and the processing of material since the gap S between the parts 10 and 12 has to be filled with material to avoid a deepened seam.

[0101] To this end, the shoulder 16 comprises one or several material supply openings 30 which extend laterally in an oblique manner in the present case.

[0102] Additional material 32, here in the form of a solid material such as wire or granular material is supplied to the gap 28 via this material supply opening 30. As an alternative to a wire, it is also possible to supply a granular material as material, or also a pasty or liquid material.

[0103] An axially acting conveyor worm structure 34 ensures the transport of the additional material 32 to the workpiece 14. This conveyor worm structure 34 is provided by an appropriate structures of one or both of the wall(s) which delimit the gap 38, i.e. the envelope surface of the pin 22 and/or the wall 26 of the shoulder 16.

[0104] In the example embodiment of FIG. 1, the pin 22 is provided with the conveyor worm structure 34 on the envelope side. The conveyor worm structure 34 extends from the region of Pie shoulder 16 up to the free end of the pin 22 and thus into the workpiece 14.

[0105] As can be seen in FIG. 1, the conveyor worm structure 34 need not necessarily be present at the upper end of the gap 28 to be able to here realize a sealing possibility more easily.

[0106] As can be seen in FIG. 1, the pin 22 penetrates into the workpiece 14, i.e. it is heated by the friction of the edges of the parts 10, 12 occurring upon rotation so as to be able to plunge therein on the side of the edges. Due to the rotation, the materials ore stirred such that an intermaterial bond is generated. This method may also be applied to parts 10, 12 having different materials, for example light metals such as aluminum on the one hand and steel on the other hand. However, in this case, the pin 22 will mainly plunge into the softer material and heat the latter.

[0107] If the workpiece 14 consists of parts 10, 12 of different materials, it may be advantageous to use the material of the softer part of the two parts 10, 12 as additional material 32.

[0108] The additionally supplied material 32 is sheared in the gap 26 and highly heated by the shearing and flexing process and transported to and into the workpiece 14 via the conveyor worm structure 34.

[0109] The additional material 32 preferably reaches the workpiece 14 in a softened, for example pasty state, which is not to be interpreted in a limiting manner.

[0110] Due to the conveyor worm structure, pressure is generated in the workpiece 14 for the material of the workplace 14 softened upon stirring in such an amount that the material softened upon stirring does not penetrate into the gap 28. The shoulder 16 may rest on the workpiece surface in a plane manner or can be slightly angled.

[0111] The delivery rate of supplied material 32 can be controlled or regulated by varying the speed of the pin 22 and of the supplied material 32 and the geometry of the conveyor worm structure 34.

[0112] The tracking portion of the shoulder 16 planishes the top side of the weld seam and of the workpiece such that the two parts 10, 12 can be well connected to each other so that so step and not depression is formed on the workpiece surface and the latter can be painted without further processing.

[0113] The alignment of the material supply opening 30 may be arbitrary. It must not necessarily lead laterally into the gap 28; rather, it can also open into the gap from the top.

[0114] In the embodiment illustrated in FIG. 7, one or more culling edges 36 are formed or fastened to the pin 22 on the axial height of the outlet of the material supply opening 32 which cut the supplied wire in the gap 28 in single parts.

[0115] FIG. 7 also shows irrespective of the cutting edges 36 that a radial offset V may be present between the rotary axis of the pin 22 and the center axis of the (in this case circular cylindrical) opening 26 in the shoulder 16. This results in a gap 28 having radially differing widths and which in the region of the outlet of the material supply opening 30 is larger than on another side. This counteracts a plugging of the wire supply opening 30. The material is scraped from the pin at the narrowest point.

[0116] As already mentioned above, the conveyor worm structure 34 can alternatively or additionally also be configured on the wall 26 of the shoulder 16. This is shown in FIG. 2. Here, the shoulder 16 is also non-rotating. In this case, the pin 22 is furthermore configured in a circular cylindrical manner and has no conveyor worm structure. Due to the friction on the surface of the pin 22, the latter however moves the supplied material 32 in the gap 28 such that it is also displaced in the axial direction towards the workpiece 14 by the stationary conveyor worm structure 34.

[0117] Alternatively, a combination of the conveyor worm structures 34 in FIG. 1 and FIG. 2 on the pin 22 and on the shoulder 16 may be present.

[0118] In the embodiment of FIG. 2, the supplied material 32 is also introduced into the gap 28 via a material supply opening 30, the material supply opening 30 being adapted to be configured like in FIG. 1 also in this case.

[0119] FIG. 3 shows a possible use of the tool according to the invention, in which a part 12 in the form of a metal sheet is welded to an open hollow profile forming the part 10. The open hollow profile 10 is relatively instable and is supported in the axial direction by a counter support 38. The pin 22 penetrates laterally into the parts 10, 12 and can even possibly project axially through the part 12 and further deeper into the part 10. Using the friction stir welding tool, it is possible to reduce the process forces upon welding in comparison with the prior art, and the missing material volume is compensated due to the use of the supplied material 32. The low process forces permit the use of filigree profiles in the region of the web of the hollow profile.

[0120] To avoid end holes which can be produced upon withdrawal of the pin 22 at the end of the weld seam in the workpiece 14, the invention provides a tracking of the material supply during the extraction of the pin. This is explained in FIGS. 4a to 4d.

[0121] In FIG. 4a, the pin 22 still rotates in the workpiece 14 and has reached its final position in feed direction.

[0122] Upon further rotation of the pin, the latter is pulled axially out of the already welded workpiece 14 (FIG. 4b). In this state, additional material is however still transported to the workpiece 14, as indicated by the arrows in FIG. 4b. The volume of the pin 22 is thus compensated. When it reaches the workpiece surface, the pin 22 can be stopped, see FIG. 4c. The pin 22 and the shoulder 16 are then jointly pulled axially away from the workpiece 14, see FIG. 4d.

[0123] To configure the tool as simple as possible and to permit a method such as in FIGS. 4a to 4d, a parallel guiding may be present along the rotation axis between the shoulder 16 and the non-rotating past of a machine spindle which guides the shoulder 16 in an axially shiftable manner.

[0124] By way of alternative, the pin 22 itself may be axially displaced or the shoulder 16 may be moved relative to the pin 22 by means of an actuator 57.

[0125] A very simple variation of the tool is shown in FIG. 5. The fixed part 40 of the drive engine 24 or of a tool spindle is illustrated here, to which a mounting part 42, here a sleeve having a collar, for example, is screwed. A rotating spindle 44 merges into the pin 22. The mounting part 42 serves as an axial bearing for the shoulder 16 which has a sleeve-shaped portion 46 surrounding the spindle 44. A gap 48 may be formed between the sleeve-shaped portion 46 and the mounting part 42. If necessary, a friction bearing or a coating can here ensure a low friction.

[0126] A spring element 50 ensures an axial prestress of the shoulder 16 in a direction towards the workpiece 14.

[0127] To limit the axial sliding range of the spring-mounted shoulder 16, a stop 52 is provided which acts in two axial directions and comprises a pin 54 which is fastened to the shoulder 16 and projects into an elongated hole 56 in the mounting pad 42.

[0128] In this embodiment of the tool, the tool can generally be axially pulled away from the workpiece 14 when it reaches its final position and when the pin 22 is pulled out. However, since the shoulder 16 presses against the workpiece 14 in a compressed state, see FIG. 5 in the normal welding operation, the shoulder 16 rebounds upon withdrawal of the tool and still remains in contact with the workplace 14.

[0129] The shoulder 16 and/or the pin 22 may be shifted relative to each other in the direction of the pin 22 via the actuator 57 such that the length of the pin 22 projecting from the shoulder 16 can be adjusted actively, more specifically irrespective of the force of the shoulder 16 on the component. The shoulder 16 may alternatively or additionally be prestressed axially in the workpiece direction and can be mounted in a compressed manner.

[0130] The embodiment according to FIG. 5 is furthermore very well suited for the welding of parts 10, 12 having locally different thicknesses such that the shoulder 16 compresses and rebounds upon travelling along the surface of the part(s) 10, 12.

[0131] A further vacant of the friction stir welding tool and a further variant of its applicability are shown in FIG. 6. Here, the pads 10, 12 are configured as corner connection, for example as a T joint of flat metal sheets. In the present friction stir welding methods, wormholes can very easily be produced here.

[0132] The shoulder 16 of the tool according to the invention comprises a first contact surface having a portion 58 and a portion 60 which hath preferably extend parallel to the part 10 or the part 20 and are therefore inclined which respect to each other. The transition between the portions 58, 60 may be configured as a curved portion to generate a uniform hollow weld. In the present case, the pin 22 is also configured with a conveyor worm structure 34 and penetrates in both parts 10, 12 in the region of their joint, as can be seen in FIG. 6 to weld them together. An additional material is also supplied here like in the remaining embodiments.

[0133] Counter supports 62, 64 may also be provided for supporting the parts 10, 12.

[0134] The new method may also be used for deposition welding, for example using the tool according to FIGS. 8 and 9. The pin 22, which is not obligatorily the case, can penetrate to a minimum into a lower layer 66 of the produced workplace 14, and additional material 32 in the form of a trace 68 is simultaneously deposited. To this end, the shoulder 16 is not flush with a first workpiece contact surface 18 located in a plane. Rather, it has a lateral outlet in the region of that end which is located opposite the feed direction X such that the softened, for example pasty material can exit as a trace 68 via an lateral outlet 70. Here, a variant consists in that two portions 72, 74 of the workpiece contact surface 16 are arranged axially offset with respect to each other, the two portions 72, 74 being separated from each other by two steps 76 which extend in feed direction X and are parallel to each other. As can be seen in FIG. 10, the portion 74 arranged further away from the workpiece surface rests on a previously produced parallel trace 68 and on the adjacent trace 68 which is just to be produced. The pin 22 can also penetrate into the previously produced trace 68 upon rotation to again softened and plasticize the latter. The deepened portion 72 rests on the lower layer 66 and delimits the trace 68 just being produced laterally to the feed direction X (see FIG. 10).

[0135] By tempering the tool, in particular the shoulder 16, it is possible to avoid a clogging of the pin 22 and the shoulder 16 by cooled material. By increasing the temperature, it is however also possible the make the additional material 32 softer or at least to pre-heat the latter. To this end, a heating system 78, see FIG. 11, is for example integrated into the shoulder 16. The shoulder 16 can then include a channel through which heated oil flows. Alternatively, it is also possible to integrate a heating system, for example an inductive heating means into the shoulder 16. The shoulder 16 is for example made of ceramics, which is advantageous for an inductive heating by means of introduced coils. To increase the concentration of the magnetic field, it is optionally possible to use diamagnetic, paramagnetic or ferromagnetic materials in the tool, for example in the pin 22 or in the shoulder 16 or in the region of the support of the parts 10, 12.

[0136] FIG. 12 shows a friction stir welding tool having a so-called double shoulder. In addition to the shoulder 16 which constitutes a first shoulder, a second shoulder 80 is used which comes to rest on the face of the workpiece 14 which is opposite the shoulder 16 and contacts the workpiece 14 and thus acts as an counter-support. The shoulder 80 can rotate or can also be stationary as in the example embodiment of FIG. 12 in which the shoulder 80 rests on the widened end 84 of the continuous pin 22 via a pivot bearing 82.

[0137] The pin 22 preferably comprises a first conveyor worm structure 34 in the region of the shoulder 16, which is not to be interpreted in a limiting manner, the structure being configured such that the supplied material 32 is transported to the workpiece 14. However, the pin 22 furthermore includes an opposite second conveyor worm structure 86 in the region of the shoulder 80 which in turn is oriented such that the material is also conveyed in a direction towards the workpiece 14 upon rotation of the pin 22.

[0138] The conveyor worm structures 34, 86 may extend up to the interior of the workpiece 14 and directly adjoin each other. Additional material 32 is thus preferably also supplied in the region of the shoulder 80, which is not to be understood in a limiting manner.

[0139] In this embodiment, the workpiece 14 rests on the first workpiece contact surface 18 of the first shoulder 16 and the oppositely aligned second workpiece contact surface 88 of the second shoulder 80.

[0140] The non-rotating shoulder 16 (alternatively of course also additionally the shoulder 80) can include a reservoir 90 in the form of an extra wide portion of the gap 28. This is illustrated in FIGS. 13 and 14. It is possible to temporarily store supplied additional material 32 or to receive released material upon penetration of the pin 22 into the workpiece 14 in this reservoir 90.

[0141] In the embodiment according to FIG. 13, the reservoir 90 is open towards the workpiece 14 without any constriction, whereas in the embodiment according FIG. 14, a constriction 92 is additionally present in the shoulder such that the reservoir 90 is in fluidic communication with the workpiece 14 only via the narrow part of the gap 28.

[0142] A control sleeve 94 forms the axial upper wall portion which delimits the reservoir 90 at least essentially axially upwards. The control sleeve 94 is adapted to be axially shifted in a controlled or regulated manner to change the volume of the reservoir 90, i.e. if necessary to receive or suck material or to press material out.

[0143] FIG. 15 shows a lap connection having a first softer part 10 and a harder part 12 arranged therebelow, for example the pair aluminum and steel. The pin 22 preferably slightly penetrates into the lower part 12 and extends through the part 10. Additional material 32 is also supplied in the present case. Incidentally, this of course also applies to the embodiment according to all previous figures in which the workpiece supply opening 30 is partially not represented in an explicit manner.

[0144] It is true for all embodiments that they can be combined with other embodiments and the features of these embodiments as mentioned above. This is for example the case for the shape of the shoulder, the heating means, the reservoir and also for the double shoulder as well as for the conveyor worm structure 34 which can be provided on the pin 22 and/or on the shoulders) 16, 80. As also already explained above, the supplied material 32 can be composed of the same material as one of the parts 10, 12 or also have a higher or lower solidity than one of the parts 10, 12.

[0145] The number of pins 22 per tool is not limited, it is possible to realize several pins side by side like a double screw-type extruder. It is thus possible to increase the ability of bridging the gap as well the delivery rate.

[0146] Irrespective of the embodiment or the combinations thereof, the tool may be provided with a control/regulation unit 96 which is represented only as an example in FIG. 1. This unit 96 ensures a perfect welding process without the formation of pores, for example by determining the cross-section of the missing material in the gap between the pads 10, 12 using a laser scanner and by calculating the missing weld volume. The supplied quantity of material 32 is accurately controlled or regulated via a supply unit 98, in the specific example using two or at least one driven roller for the conveyance of wire.

[0147] The lateral feed rate of the tool, the speed of the pin 22 and/or the quantity of supplied material 32 is controlled or regulated as a function of at least one of the following parameters via the unit 96: [0148] torque of the pin 22, [0149] feed force to be applied for the tool, [0150] pressure force of the shoulder 16 in the axial direction, [0151] temperature of the shoulder 16, of the pin 22 and/or of the supplied material 32, and/or [0152] the required force for supplying wire as supplied material 32.

[0153] Furthermore, a direct or indirect regulation can be carried out, for example via the torque and/or the feed force and/or the axial force of the tool from which it is possible to draw conclusions as to necessity of changing the material supply. This has already been explained above in the present introductory part of the specification to which reference is made.

[0154] The friction stir welding tool can comprise a pin postprocessing unit 100 (see FIG. 1), having a machining cutting tool 102 (for example a grinding means or a cutting edge) which can be moved laterally against the pin 22 to machine the latter in a chip-forming manner. The cutting tool 102 may be non-rotating and merely be fed laterally by means of an actuator 104. The rotary motion in machining is carried out by the rotation of the pin 22. An axial motion of the pin 22 can be realized by the actuator 57. The friction stir welding tool thus has an integrated pin postprocessing unit 100, and it is no longer necessary to dismount the pin 22 when it has first signs of wear. A tool-integrated pin postprocessing unit 100 is not limited to the fact that the friction stir welding tool has a material supply. Rather, it can be used in any friction stir welding tool.

[0155] Finally, it can also be mentioned that the shoulder 16 or both shoulders 16, 18 can be caused to make an oscillating movement so as to reduce the friction on the workpiece 14.

[0156] The tool and the method are in particular provided for the welding of light metals together or of light metals with steel or with steel alloys. Particularly aluminum and the alloys thereof are used therefor.