DE102021126767A1 - friction stir welding device - Google Patents

Abstract

The invention relates to a friction stir welding device (1) for friction stir welding the ends of a workpiece (12) to an upper and lower side by forming a weld seam (10), in particular for welding the ends of the overlap seam of a hollow body, e.g. B. to form a tube or a profile, with an inner wall surface as the underside and an outer wall surface as the upper side, the friction stir welding device (1) having a stirring pin (4), a friction shoulder (8a, 8b) fixedly arranged on the stirring pin (4) and a counter bearing (9, 19, 20 21, 22), wherein the friction shoulder (8a, 8b) is pulled towards the underside by the stirring pin (4) during the rotation of the friction shoulder (8a, 8b) for friction welding, that the counter bearing (9, 19, 20, 21, 22) in the area of the friction shoulder (8a, 8b) rests on the upper side of the workpiece (12).

Description

The invention relates to a friction stir welding device for friction stir welding the ends of a workpiece with an upper side and a lower side by forming a weld seam, in particular for welding the ends of a preformed hollow body, e.g. B. to form a tube or a profile, with an inner wall surface as the bottom and an outer wall surface as the top, wherein the friction stir welding device has a stirring pin, a stirring pin firmly arranged friction shoulder and a counter bearing.

The term "ends" is then also understood to mean the ends of two overlapping workpiece ends, for example in the case of a pipe as a so-called lap joint.

The principle of friction stir welding is well known. In friction stir welding, a rotating tool is placed at the start of a joint seam. The material is plasticized by the friction, with the tool being pressed into or against the material until the friction shoulder touches the surface. The rotating tool then moves through the workpiece along the seam until it exits the workpiece again at the end of the seam.

Furthermore, friction stir welding tools with vertical friction shoulders are known. This is a so-called two-part tool in which the pin rotates and the friction shoulder is stationary, i.e. the pin rotates in the shoulder. The energy for plasticizing the material of the workpiece is introduced through the pin.

In addition, there are tools without a stirrer pin, whereby the advantage of this friction welding process is that thin foils can also be welded.

The use of friction stir welding for pipes and profiles is problematic. In particular, the welding of longitudinal seams of long or endless tubes or profiles has so far not been possible using friction stir welding. Although it is known to connect short pieces of pipe by means of conventional friction stir welding, there are limits to the length of the pipe or the circumference of the pipe, as already stated. This is because the friction stir welding process requires a counter bearing to be provided on the inside of a tube or profile that is not geometrically sufficiently rigid during the welding process, since the compressive force acting on the tube from the outside can be suppressed by the friction shoulder using appropriate means or tools must be included. In this context, it is known to insert a core or a device into the interior of a pipe, which forms the counter bearing during the welding process with the tool of a friction stir welder.

In addition, a so-called "bobbin tool" is known ( US20170304934A1 ), wherein such a bobbin tool comprises a stirring pin, the stirring pin having two friction shoulders spaced apart from one another, the distance between the two friction shoulders correlating with the material thickness of the parts to be welded, in particular pipes to be welded. First of all, it should be noted as a disadvantage of such a bobbin tool that for every material thickness of a workpiece to be welded, e.g. B. a tube or a profile, a separate tool must be provided because, as already stated, the distance between the two friction shoulders is fixed or rigid. In addition, it has been found to be disadvantageous that a flawless seam cannot be produced with fluctuations in material thickness, since the energy input in the form of heat into the workpieces to be welded varies due to the fluctuations in material thickness. Another disadvantage is that no angle of attack can be realized with a bobbin tool; rather, the friction surfaces run parallel to the workpiece surface. This means that compaction of the weld seam occurs only to a small extent, if at all. The use of a bobbin tool to weld the longitudinal or circumferential seams of long pipes has not become established in this respect.

The invention is therefore based on the object of providing a friction stir welding device, with which essentially flawless seams can be produced with the friction stir welding device, with the longitudinal seam of long profiles or tubes or also the longitudinal seam of endless tubes being able to be welded reliably and essentially flawlessly with the friction stir welding device.

The object is achieved according to the invention in that the friction shoulder is under a tensile force in the direction of the workpiece due to the stirring pin on the underside, ie the inner lateral surface of a tube, during the rotation of the friction shoulder for friction welding. In this respect, the friction shoulder forms one part with the stirring pin.

Furthermore, a counter bearing is provided here, which rests on the upper side of the workpiece in the area of the friction shoulder. The counter bearing is not connected to the stirring pin. Rather, it is an independent component of the friction stir welding device. The friction shoulder can be designed in the manner of a disk, which has the stirring pin in the center.

The essence of the invention is therefore the reversal of the position of the counter bearing with the friction shoulder and correspondingly a reversal of force, which in friction stir welding according to the prior art is a compressive force with which the friction shoulder acts on the workpiece, and according to the invention one of the friction shoulder applied traction.

In the prior art, it is the case that the friction shoulder is pressed onto the outer lateral surface, for example of a pipe, whereas the counter bearing is pressed onto the inner lateral surface to form the counterforce. This may still work with pipes up to a length of approx. 1 m, but with longer pipes, and especially with endless pipes, this method does not work. Because the friction shoulder is pulled from the inside against the inner lateral surface, for example of a pipe, and a corresponding counterforce is applied from the outside, i.e. on the outer lateral surface, by a counter bearing placed there, it is possible to weld the longitudinal seams of long pipes and also to weld endless tubes. This means that weld seams of any length in the longitudinal and circumferential direction can be formed by an inverse arrangement of counter bearing and friction shoulder, since the force and counterforce can always lie in one longitudinal axis.

Technologically, friction stir welding has particular advantages; among other things, that the substance-to-substance connection of the joining partners takes place well below the melting temperature. This means that hot cracks and signs of porosity due to gas inclusions do not occur, and component distortions are also minimized. It has also been found that the mechanical-technological properties, for example, of aluminum components connected by friction stir welding are significantly superior to those of fusion-welded aluminum components. In addition, mechanical properties are achieved in the joining zone that almost correspond to those of the base materials and thereby ensure significantly better formability.

It has been found to be particularly advantageous that the device according to the invention can be used to weld a pipe not only in the usual position from above (welding position PA), but also from the side (welding position PC), overhead from below (welding position PE) and in positions in between.

Advantageous features and refinements of the invention result from the dependent claims.

In particular, it is provided that the counter-bearing held by the friction stir welding device exerts pressure on the workpiece in the region of the friction shoulder during the friction stir welding process. The weld seam is smoothed by the counter bearing. In this respect, the weld seam essentially has no cracks or other defects. In this respect, a smooth surface also results on the weld seam, which hardly differs from the surface of the rest of the workpiece.

According to a first embodiment, the counter-bearing, which is held by the friction stir welding device, is designed in the manner of a clamp-like carriage in plan view. Due to the clamp-like or U-shaped design of the carriage as a counter bearing, the stirring pin is guided in the U-shaped recess of the carriage. In detail, it is provided in this connection that the counter bearing designed in the manner of a clamp- or U-shaped carriage has two guide rails which run at a distance from one another over part of the length of the carriage and have a sliding piece at the end or in a sliding piece end up. The sliding piece slides on the fresh, still plasticized weld seam and, in conjunction with the friction shoulder aligned with an angle of attack, ensures that the seam is compacted. This is a further advantage over a bobbin tool, which cannot be used at an angle of attack, which is why the suture material is not compacted. The distance between the two guide rails correlates with the thickness of the stirring pin, which causes the stirring pin to be guided by the clamp-like or U-shaped carriage, as already mentioned.

In order to prevent the clamp-like carriage from dipping into the material, the carriage is bent up in the welding direction over part of its length, in particular in the area of the guide rails. The bending up advantageously continues into the sliding piece, which can also be at least partially bent up. The same can also be achieved if the width of the carriage is greater than the width of the weld seam, so that the carriage can slide on the non-plasticized material of the workpiece, in particular the pipe, ie it is supported there.

According to a second embodiment of the clamp-like carriage, there is the alternative possibility of designing the counter-bearing in the manner of a disk or sleeve or ring. In this case, the side of the disk facing the workpiece can have a smaller thickness towards the edge, starting from the center of the disk. For this purpose, it can be provided that the surface of the disk facing the workpiece has a chamfer at the edge. The chamfer can be formed circumferentially or only partially present on the circumference. Such an embodiment prevents the immersion of the tool into the seam provided that the partial bevel is aligned in the direction of the weld seam.

As another advantageous option for compacting the seam, the side of the disk facing the workpiece is curved towards the center of the disk, ie inwards. Such a disk designed as a counter bearing has the advantage that the side of the disk facing the workpiece provides a higher surface pressure as a counter bearing on the upper side of the workpiece. This achieves a smooth surface free of defects, even if the plasticity of the weld seam material is low.

According to a particularly advantageous feature, the friction shoulder bears against the underside of the workpiece at an angle of attack, the angle of attack being open in the direction of welding. Since the friction shoulder in particular is connected in one piece to the stirring pin, the angle of attack continues in the position of the stirring pin. Due to the open angle of attack, there is no risk of the friction shoulder digging into the plasticized weld metal, regardless of the angle of attack. This means that if the direction of the weld seam changes, the position of the friction shoulder does not have to be changed. This is in complete contrast to the counter bearing designed as a carriage, which has to be aligned with a change of direction according to the changed welding direction.

The friction shoulder is advantageously designed as a disk which has the stirring pin in the center. The friction shoulder designed as a disc can be designed to be arched on its side facing the workpiece.

The setting angle α of the friction shoulder is advantageously between 2° and 4°, in particular 2°. If these angles are observed, the weld seam can be compacted in such a way that essentially no cracks or other intolerable faults occur.

It was already mentioned at the outset that if the thickness of the workpiece varies, the welding parameters can be adapted to the instantaneous thickness of the workpiece by means of regulation. The parameters that are adapted to the different thicknesses of the workpiece are, in particular, the contact pressure and/or the speed and/or the tool feed of the friction shoulder. This means that the force and/or the speed and/or the tool feed of the friction shoulder can be regulated with varying thickness of the workpiece when the friction shoulder is in contact with the workpiece. The aim is that the energy input into the weld seam remains constant over the height of the weld seam. This can be accomplished by displacing the tool shank, which is in force-transmitting connection with the stirring pin, in the direction of the workpiece or away from the workpiece, or by increasing or decreasing the speed and/or the tool feed of the friction shoulder, for example. The energy input can thus be influenced not only by the contact pressure, but also by the speed and/or the tool feed of the friction shoulder.

It is also provided that when the thickness of the workpiece varies, the position of the counter bearing can also be adapted to the current thickness of the workpiece by means of a regulation (double arrow 7).

• 1 zeigt eine schematische, perspektivische Darstellung der Rührreibschweißvorrichtung mit einem Schlitten als Gegenlager;
• 2 zeigt eines Seitenansicht gemäß 1;
• 3 zeigt eine Ansicht von oben auf die Rührreibschweißvorrichtung;
• 4 zeigt eine weitere Ausführungsform der Rührreibschweißvorrichtung in perspektivischer Darstellung mit einem als Scheibe ausgebildeten Gegenlager;
• 5 zeigt eine Seitenansicht gemäß 4;
• 6 zeigt eine Ansicht von oben auf die Rührreibschweißvorrichtung gemäß 4;
• 7a, 7b zeigen zwei Ausführungsformen einer Reibschulter mit zentrisch an der Reibschulter angeordnetem Rührstift;
• 8a, 8b zeigen eine Draufsicht auf die Darstellungen der Reibschulter gemäß den 7a, 7b;
• 9a - 9d zeigen unterschiedliche Ausführungsformen eines Gegenlagers schematisch in perspektivischer Darstellung;
• 10a -10dzeigen die entsprechenden Schnittdarstellungen der in den 9a-9d perspektivisch dargestellten Gegenlagern.

In the appended drawings, the invention is explained below by way of example.

• 1 shows a schematic, perspective view of the friction stir welding device with a carriage as a counter bearing;
• 2 shows a side view according to FIG 1 ;
• 3 shows a view from above of the friction stir welding device;
• 4 shows a further embodiment of the friction stir welding device in a perspective view with a counter bearing designed as a disk;
• 5 shows a side view according to FIG 4 ;
• 6 shows a view from above of the friction stir welding device according to FIG 4 ;
• 7a , 7b show two embodiments of a friction shoulder with a stirring pin arranged centrally on the friction shoulder;
• 8a , 8b show a top view of the illustrations of the friction shoulder according to FIGS 7a , 7b ;
• 9a - 9d show different embodiments of a counter bearing schematically in a perspective view;
• 10a - 10 dshow the corresponding sectional views of the 9a-9d counter bearings shown in perspective.

According to 1 the friction stir welding device is denoted by 1 as a whole. The friction stir welding device 1 forms a weld seam 10 for connecting the metal sheets 13 and 14 forming a workpiece 12. The friction stir welding device 1 comprises the tool shank 2, through which the stirring pin 4 is to be set in rotation on the one hand, and on the other hand the stirring pin 4 according to the double arrow 6 for varying the contact pressure of the friction shoulder 8 ( 2 ) towards the workpiece 12 is movable. The friction shoulder 8 lies on the underside of the workpiece 12 with an open angle of attack α (in the direction of welding (arrow 16) 5 ) at. On the one hand, this results in a good compaction of the weld seam material and, on the other hand, that the rear side of the friction shoulder 8 can dip into the seam material. The angle of attack α is approx. 2°.

In alignment with the friction shoulder 8, as part of the friction welding device 1, the carriage 9 is located on the upper side of the workpiece 12 as a counter bearing. The carriage 9 comprises the slider 9a and the two guide rails 9b and 9c, which run parallel to one another to form a distance 9d and have the said slider 9a at the end, which rests on the weld seam 10. The weld seam 10 is produced by the friction stir welding device 1 in the direction of the arrow 16 (welding direction).

The 4 until 6 show a further embodiment of the friction stir welding device 1, the difference from that in FIGS 1 until 3 shown friction stir welding device consists in the formation of the disc 19, 20, 21, 22 as a counter bearing. Otherwise, the parts forming the friction stir welding device are the same and in this respect have the same reference numbers as in FIGS 1 until 3 .

The counter bearing is formed here by a disk 19 . Depending on the proportions of the counter bearing, in particular with regard to the height, one also speaks of a sleeve or of a ring. The counter bearing can be adjusted according to the double arrow 7 in order to ensure a constant energy input into the workpiece when the thickness of the workpiece varies. A regulation can be provided for this.

The 7a , 8a and 7b, 8b show two different embodiments for the stirring pin 4 with the friction shoulder 8a, 8b arranged at the end and firmly connected to the stirring pin 4. The friction shoulder 8a shows the convex curvature 8c, which, alternatively or in addition to the angle of incidence α, prevents the friction shoulder from dipping into the plasticized weld seam material during the welding process.

However, it is also conceivable for the friction shoulder designed as a disc not only to have a convex curvature, but also to have a concave curvature, with the surface pressure being somewhat higher when a concave curvature is used, which benefits compaction.

Finally, there is also the possibility of providing a thread on the upper side of the friction shoulder, which promotes stirring of the plasticized suture material.

In the representation according to the 7b , 8b the only difference is that there the friction shoulder 8b has no bulge 8c. Otherwise, the stirring pin 4 forms a one-piece component with the respective friction shoulder 8a, 8b. That is, the stirring pin 4 and the friction shoulder 8a, 8b can, for example, be welded or made in one piece, e.g. B. by turning.

The in the 9a until 9d as well as the 10a until 10d variants of a disc as a counter bearing shown are explained below as follows.

In the representation according to 9a and 10a the disc 19 is provided as an abutment on its side facing the workpiece 12 with a concave curvature 19a and an edge 19b. The disc 19 has a continuous opening 19c tapering conically towards the bulge 19a. The conical opening 19c allows an angle of attack α to be set.

The abutment designed as a disk 20 according to FIG 9b and 10b has a flat underside 20a and a bevel 20b in the edge region which extends only partially over part of the circumference. The central opening for the stirring pin 4 is in turn conical and has the reference number 20c.

The in the 9c and 10c illustrated further embodiment of a disc 21 as a counter bearing has the peripheral chamfer 21a on the edge, which finally forms a flat bottom 21b. The central, conical opening has the reference number 21c.

The abutment designed as a disk 22 has a flat surface 22b on its side facing the workpiece, with a conical opening 22c also being discernible in the center here.

Reference List

1

friction stir welding device

2

tool shank

4

stir stick

6

Tool shank double arrow

7

Double arrow of the counter bearing

8a

friction shoulder

8b

friction shoulder

8c

curvature of the friction shoulder

9

slide as a counter bearing

9a

slider

9b

guide rail (carriage)

9c

guide rail (carriage)

9d

Distance between the guide rails

10

Weld

12

workpiece

13

sheet

14

sheet

16

arrow (welding direction)

19

disc as a counter bearing

19a

concave curvature

19b

edge

19c

centric, through and conical opening

20

disc as a counter bearing

20a

flat underside

20b

partial chamfer extending over part of the circumference

20c

centric, through and conical opening

21

disc as a counter bearing

21a

circumferential chamfer

21b

level ground

21c

centric, through and conical opening

22

disc as a counter bearing

22b

flat surface

22c

centric, through and conical opening

a

angle of attack (friction shoulder)

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US20170304934A1 [0007]

Claims (19)

Friction stir welding device (1) for friction stir welding the ends of a workpiece (12) to an upper and lower side by forming a weld seam (10), in particular for welding the ends of the overlap seam of a preformed hollow body, e.g. B. to form a tube or a profile, with an inner wall surface as the underside and an outer wall surface as the upper side, the friction stir welding device (1) having a stirring pin (4), a friction shoulder (8a, 8b) fixedly arranged on the stirring pin (4) and a counter bearing (9, 19, 20, 21, 22), characterized in that the friction shoulder (8a, 8b) is pulled onto the underside by the stirring pin (4) during the rotation of the friction shoulder (8a, 8b) for friction welding, that the Counter bearing (8, 19, 20, 21, 22) in the area of the friction shoulder (8a, 8b) rests on the upper side of the workpiece (12). Friction stir welding device (1) after claim 1 , characterized in that the counter bearing (9, 19, 20, 21, 22) is designed in the manner of a clamp-like carriage (9) in plan view. Friction stir welding device (1) after claim 1 or 2 , characterized in that the weld seam (10) is a longitudinal seam in a hollow body. Friction stir welding device (1) after claim 1 or 2 , characterized in that the weld seam (10) is a peripheral seam in a hollow body. Friction stir welding device (1) according to one of claims 2 until 4 , characterized in that the abutment designed in the manner of a clamp-like carriage (9) has two guide rails (9b, 9c) which extend over part of the length of the clamp-like carriage (9) at a distance (9d) from one another. Friction stir welding device (1) after claim 5 , characterized in that the distance (9d) between the two guide rails (9b, 9c) correlates with the thickness of the stirring pin (4). Friction stir welding device (1) after claim 5 or 6 , characterized in that the guide rails (9b, 9c) have a sliding piece (9a) at the end, which rests on the weld seam (10). Friction stir welding device (1) after claim 1 , characterized in that the counter bearing is designed in the manner of a disk (19, 20, 21, 22). Friction stir welding device (1) after claim 8 , characterized in that the disc (20, 21) at least partially on its circumference in the edge area has a smaller thickness than in the middle area. Friction stir welding device (1) after claim 9 , characterized in that the workpiece (12) facing surface of the disc (20, 21) has a chamfer (20b, 21a) at least on part of its circumference. Friction stir welding device (1) after claim 8 or 9 , characterized in that the workpiece (12) facing side of the disc (19) is curved (19a) at least on part of the circumference such that the thickness in the edge area is less than in the central area. Friction stir welding device (1) according to one of the preceding claims, characterized in that the friction shoulder (8a, 8b) bears against the underside of the workpiece (12) at an angle (α), the angle (α) being open in the welding direction (arrow 16). is. Friction stir welding device (1) according to one of the preceding claims, characterized in that when the thickness of the workpiece (12) varies, the welding parameters can be adapted to the instantaneous thickness of the workpiece (12) by regulation. Friction stir welding device (1) after Claim 13 , characterized in that the compressive force and/or the rotational speed and/or the tool feed of the friction shoulder (8a, 8b) can be changed by the regulation as the thickness of the workpiece (12) varies. Friction stir welding device (1) according to one of the preceding claims, characterized in that the workpiece (12) and/or friction stir welding device (1) can be moved during the welding process. Friction stir welding device (1) according to one of the preceding claims, characterized in that the counter bearing (9, 19, 20, 21, 22) rests under pressure on the workpiece (12) in the region of the friction shoulder (8a, 8b). Friction stir welding device (1) according to one of claims 2 until 7 characterized , that the guide rails (9b, 9c) of the carriage (9) designed as a counter bearing are bent up in order to prevent digging into the plasticized weld seam (10). Friction stir welding device (1) after Claim 17 , characterized in that the slider (9a) is bent over part of its length. Friction stir welding device (1) according to one of the preceding claims, characterized in that when the thickness of the workpiece (12) varies, the position of the counter bearing designed as a carriage (9) or disc (19, 20, 21, 22) also adapts to the current thickness of the workpiece (12) is adjustable by regulation.

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