METHOD AND APPARATUS FOR INCREASING THE QUALITY OF THE WELD SEAM IN FRICTION STIR WELDING

Abstract

Apparatus and method for increasing the quality of the weld seam in friction stir welding, with the following features: a) a receiving plate (1) with a drive head (2), the latter having a receiving flange (19) for receiving a holding bell (3) connected by means of a union nut (7) to a welding shoe (4) with a welding pin tip (5), b) the welding shoe (4) has a circular basic shape, on which there is a transverse web running over the cross section and rising at a right angle to said basic shape, said transverse web having a width of approximately 1/4 to 1/5 of the diameter of the basic shape and having an arc-shaped shoe sliding surface and shoe smoothing surface (9), c) the welding pin tip (5) has substantially a surface structure in the form of a tapering thread, this thread-like structure not being arranged in a purely circular manner.

Claims

1: A device for increasing the quality of the weld seam in friction stir welding, the device having the following features: d) a receptacle plate (1) having a drive head (2), wherein the latter has a receptacle flange (19) for receiving a mounting bell (3) which by means of a union nut (7) is connected to a welding shoe (4) having a welding pin tip (5); e) the welding shoe (4) has a circular basic shape on which a transverse web, running across the cross section and rising orthogonally to this basic shape, is located which has approximately the width of to of the diameter of the basic shape and has an arcuate shoe sliding face and shoe smooth face (9), wherein a small planar face in the form of a notch-type tapering (16) is located on each side of this face (9) in the region of the periphery of this face (9); f) the welding pin tip (5) has a surface structure which is substantially in the form of a heavily tapered thread, wherein this thread-like structure is not disposed so as to be purely circular but in each thread pitch has three flat spots which are distributed on the circumference, wherein the centers of these flat spots each are mutually placed at an angle of 120 degrees, and wherein the lead of this thread-like structure is 0.5 mm and the flank height varies from 0.25 mm to 0.05 mm.

2: The device as claimed in claim 1, characterized in that each of the notch-type taperings (16) is configured as a step with a height of a plurality of millimeters.

3: The device as claimed in claim 1, characterized in that a positive pressure which ensures that contaminations on the tool are largely removed is generated in the mounting bell (3) by means of a pressure-generating device, wherein by means of this system it may be determined also by measuring the counter-pressure prevailing on the tool whether the exit region 8 on the welding shoe 4 is clogged or free.

4: The device as claimed in claim 1, characterized in that the contact pressure of the shoe sliding face and of the shoe smooth face (9) is adjustable, the respective adjustment being measured and displayed.

5: The device as claimed in claim 1, characterized in that the result of the welding process is optically monitored.

6: A method for increasing the quality of the weld seam in friction stir welding, the method having the following features: e) at the beginning of the welding process a welding pin tip (5) in a welding shoe (4), guided as welding tool by the drive head (2) by means of a mounting bell (3), in a pin plunging path (10) plunges into the component (6) to be joined; f) thereupon the actual welding procedure is performed in a welding path (11) until the planned weld seam has been completely processed, wherein the setting angle (12) of the welding tool in relation to the vertical is maintained up to the end of the welding path (11); g) in the following pin run-out path (13) the welding tool is again withdrawn from the component (6) to be joined, wherein the setting angle (12) slowly and continuously increases up to the end of the pin run-out path (13) up to the pin spin-out angle (15); h) in the following pin spin-out path (14) the welding tool is removed from the component (6) to be joined in such a manner that the spin-out angle (15) in relation to the vertical, which exists at the beginning of the spin-out path (14), increases further, the welding tool continuously moving away from the component (6) to be joined, without forming a hole.

7: The method as claimed in claim 6, characterized in that a positive pressure which ensures that contaminations on the tool are largely removed is generated in the mounting bell (3) by means of a pressure-generating device, wherein by means of this system it may be determined also by measuring the counter-pressure prevailing on the tool whether the exit region (8) on the welding shoe (4) is clogged or free.

8: The method as claimed in claim 5, characterized in that the contact pressure of the shoe sliding face and of the shoe smooth face (9) is adjustable, the respective adjustment being measured, regulated, and displayed.

9: A computer program having a program code for carrying out the method steps as claimed in claim 6, if and when the program is executed in a computer.

10: A machine-readable carrier having the program code of a computer program for carrying out the method as claimed in claim 6, if and when the program is executed in a computer.

Description

[0024] The device according to the invention will be described in more detail hereunder. In the figures and in detail:

[0025] FIG. 1 shows a side view of an assembly for friction stir welding;

[0026] FIG. 2 shows a series of illustrations of the welding procedure;

[0027] FIG. 3 shows the illustration of a preferred welding shoe;

[0028] FIG. 4 shows an illustration of a particular construction mode of the welding shoe as above;

[0029] FIG. 5 shows an illustration of a sealing pack;

[0030] FIG. 6 shows the illustration of the entire mounting of a welding pin tip 5;

[0031] FIG. 7 shows a particular shape of a welding pin tip 5.

[0032] FIG. 1 shows a side view of an assembly for friction stir welding. A receptacle plate 1 which may be guided by a robotic arm carries a drive head 2 having a mounting bell 3 which by means of a receptacle flange 19 is fastened to the drive head 2. The mounting bell 3 serves for receiving a welding shoe 4 having a pin mounting for a welding pin, wherein the welding shoe 4 by means of a union nut 7 is fastened to the mounting bell 3 and is secured against being inadvertently twisted. The component 6 to be joined is processed by a welding pin tip 5.

[0033] FIG. 2 shows a series of illustrations of the welding procedure. The welding shoe 4 shown herein is shown in five different positions a) to e) during the welding procedure, so as to correspond to the progress of the process. A pin plunging path 10, in which a welding pin tip 5 plunges into the component 6 to be joined, commences in the position 2a). The plunging path 10 may also be omitted, that is to say that the entire plunging procedure is performed at a specific point. The welding pin tip 5 typically penetrates so as to be perpendicular to the upper side of the workpiece, and is then adjusted to the setting angle 12. The pin plunging path 10 is followed by the actual welding path 11. The shoe sliding face and the shoe smooth face 9 and the exit region for welding material 8 are particularly identified here. The welding shoe 4 is located at the beginning of the welding path 11 in the position 2b), wherein the welding shoe 4 plunges into the component 6 to be joined at a setting angle 12, the latter being in relation to the vertical for the entire welding tool.

[0034] The reference signs 5 and 9 are known from the position 2a. The welding path 11 is followed by a pin run-out path 13.

[0035] The welding shoe 4 is shown at the beginning of the pin run-out path 13 in the position 2c), said pin run-out path 13 being followed by a pin spin-out path 14. It can be derived from the position 2d) that the welding shoe at the beginning of the pin spin-out path 14 has a pin spin-out angle 15 (measured in relation to the vertical) which slightly increases up to the end of the pin spin-out path 14, wherein the welding shoe at the end of the spin-out path 14 moves farther, while the pin spin-out angle 15 steadily increases, and compresses plasticized material and is then lifted from the component 6 to be joined. This condition is shown in the position 2e). It is important herein that the welding shoe travels across all regions of the weld seam that have previously been stirred by the welding pin tip 5. This corresponds to a cold compression of the spin-out path.

[0036] FIG. 3 shows the illustration of a preferred welding shoe.

[0037] This welding shoe 4 may be seen in FIG. 3a. A notch-type tapering 16 in the shoe sliding face and the shoe smooth face 9 is particularly identified herein on the right side, wherein this welding shoe 4 in this view can be seen from the broad side thereof. The notch-type tapering 16 on both sides of the welding shoe 4 leads to an aerodynamic or bow-like shape, on account of which the welding shoe 4 becomes less sensitive to being oriented in a sub-optimal manner toward the so-called welding impact and may thus be more readily guided around radii which are to be welded. In this context, this may be referred to as self-centering of the welding shoe 4.

[0038] The same welding shoe is illustrated in FIG. 3b, rotated by 90 degrees and viewed from the narrow side thereof, wherein the notch-type tapering 16 which has been shown in FIG. 3a can be seen from the front in this view.

[0039] FIG. 3c shows the welding shoe 4 of FIG. 3a in section. The pin mounting 18 may be seen here in particular, the cross-sectional profile of said pin mounting 18 following an approximately trumpet-shaped curve. The tolerance in the pin mounting 18, between the pin shaft 17 and the welding shoe 4, is approximately 100 m.

[0040] FIG. 3d shows this special welding shoe 4 as viewed from below. Herein, the show sliding face and the shoe smooth face 9, together with a referenced notch-type tapering 16 and the pin shaft 17, are particularly identified. The welding pin tip 5 can be seen as being central, in the center of the welding shoe 4. The welding shoe 4 shown here has a substantially circular basic shape on which a transverse web rises, running across the cross section and rising orthogonally, and extends across a width of approximately to of the diameter, having an arcuate delimitation face which functions as the shoe sliding face and the shoe smooth face 9, and having a contour of the type of a bell-crank lever or of a rolling curve. A small planar face, which in each case acts like a notch-type tapering in the shoe sliding face and the shoe smooth face 9, is respectively located on each side of this arcuate delimitation face, in the region of the periphery to the circular basic shape. FIG. 3e imparts a spatial illustration of the described welding shoe 4.

[0041] FIG. 4 shows an illustration of a particular construction mode of the welding shoe as above. This welding shoe 4 here is shown having the welding pin tip 5 thereof and the pin shaft 17 thereof, when processing a component 6 to be joined. Herein, the shoe sliding face and the shoe smooth face 9 are characterized in that the notch-type tapering 16 is configured as a step with a height of a plurality of millimeters. In this sense, this here is a so-called relief groove which significantly reduces any compression and compacting of the component to be joined when the latter impacts the welding shoe 4. Moreover, better free-running properties result, that is to say that excess material is more readily conveyed away. This is expressed in an improved configuration of the seam surface of the welded joints and in reduced clogging of the welding shoe 4. In the illustration shown, the entire welding shoe 4 is heavily highlighted as being engaged in the component 6 to be joined.

[0042] FIG. 5 shows an illustration of three design embodiments of a sealing pack. In this context, reference is not made to a mounting since, apart from adequate guiding, defined sealing in relation to the welding process must also be guaranteed. It is preferable herein that the pin neck 26 in the cross section thereof has the shape of the end piece of a trumpet, as is shown on the right of the figure.

[0043] FIG. 6 shows the illustration of the entire mounting of a welding pin tip 5. As a base, the receptacle flange 19 for the mounting bell 3 can be seen here, wherein a mounting screw 20 having a conus serves for mounting the mounting bell 3 on the receptacle flange 19. A welding pin mounting conus 24 which encloses a pin shaft 17 which by way of an adjustment element 22 is connected to a welding pin counter-bearing 25 is mounted so as to be central in the mounting bell 3. The welding pin counter-bearing 25 is secured by means of a mounting screw 21. A rough adjustment of the effective length of the welding pin tip 5 may be performed by way of the welding pin counter-bearing 25, wherein said rough adjustment may be performed by means of a respective fine pitch thread (not referenced in more detail). A fine adjustment of the effective length of the welding pin tip 5 may be performed by means of a piezo element (likewise not referenced in more detail) which is electronically variable in terms of length.

[0044] Herein, 9 again references the shoe sliding face and the shoe smooth face 9 of the welding shoe 4, wherein the welding shoe 4 by means of a lock 23 is secured against being twisted and by means of a union nut 7 is fastened to the mounting bell 3. The exit region 8 for the welding material of the welding shoe 4 is likewise visible here. It is preferably provided here by way of the visible gap which exists on either side between the welding pin mounting conus 24 and the mounting bell 3, that a positive pressure which ensures that contaminations on the tool are largely removed is generated by means of a pressure-generating device (not referenced in more detail here). This procedure may also be facilitated by adding a cleaning liquid based on nano technology. By way of this system it may also be determined by measuring the counter-pressure prevailing on the tool whether the exit region 8 on the welding shoe 4 is clogged or free. It is furthermore preferably provided that a respective cleaning cycle using ionized air and/or suitable cleaning liquids is carried out at specific intervals. Furthermore, it is provided by means of a device (not referenced in more detail) that excess material which is created during the welding process is likewise suctioned off.

[0045] FIG. 7 shows a particular shape of a welding pin tip 5. An enlarged side view of a preferred construction mode of a welding pin tip can be seen herein in FIG. 7a. This construction mode has a surface structure which is substantially in the form of a heavily tapered thread.

[0046] However, this thread-like structure is not disposed so as to be purely circular, but in each thread pitch 3 has flat spots which are distributed on the circumference, wherein the centers of these flat spots are mutually placed at an angle of 120 degrees, as is shown in FIG. 7b. The lead of this thread-like structure is 0.5 mm and the flank height varies from 0.25 mm to 0.05 mm.

[0047] The tool parts that are in engagement preferably have a coating with ZrCrN or CrN.

[0048] The complex controller of the motion sequences described requires a special control program.

LIST OF REFERENCE SIGNS

[0049] 1 Receptacle plate (robotic arm) [0050] 2 Drive head [0051] 3 Mounting bell for the tool [0052] 4 Welding shoe [0053] 5 Welding pin tip [0054] 6 Component to be joined [0055] 7 Union nut as mounting for a welding shoe [0056] 8 Exit region for welding material [0057] 9 Shoe sliding face and shoe smooth face [0058] 10 Pin plunging path [0059] 11 Welding path (seam) [0060] 12 Setting angle of the welding tool [0061] 13 Pin run-out path [0062] 14 Pin spin-out path (increase in angle of setting angle) [0063] 15 Pin spin-out angle [0064] 16 Notch-type tapering of the shoe smooth face [0065] 17 Pin shaft [0066] 18 Sealing pack in the welding shoe [0067] 19 Receptacle flange for the mounting bell 3 [0068] 20 Mounting screw having a cone for the mounting bell 3 [0069] 21 Mounting screw for the pin stop [0070] 22 Adjustment element for the pin length [0071] 23 Welding shoe lock preventing twisting [0072] 24 Welding pin mounting conus [0073] 25 Welding pin counter-bearing [0074] 26 Pin neck