WO2023007343A1

WO2023007343A1 - Friction welding machine and procedure

Info

Publication number: WO2023007343A1
Application number: PCT/IB2022/056832
Authority: WO
Inventors: Roger Bracher; Jean Louis SCHAFER
Original assignee: Esatechnologies Ag
Priority date: 2021-07-29
Filing date: 2022-07-25
Publication date: 2023-02-02
Also published as: CN117999144A; IT202100020342A1; EP4377041A1

Abstract

The invention concerns a machine for friction stir welding of tubes or elements having axial or radial symmetry, comprising one or more welding stations (1) each equipped with a support (3) in turn comprising a chuck (2) for fixing and centering a tube (5) relative to a central axis (X) of symmetry thereof, a housing (31), contiguous to the chuck (2), for fixing and centering an element or part (6) to be welded to the tube (5), so that one end of the tube (5) and the part (6) are contiguous and side by side at an interface (9) to be welded, wherein each station comprises a welding head (7) provided with a rotating welding tool (71) configured to position itself in contact with the interface (9), the welding head (7) is movable along a first angular direction about the axis (X) and along a second radial direction perpendicular to the axis (X), such that the welding tool (71) friction welds the tube (5) and the part (6) along the interface (9). Also object of the invention is a process for friction stir welding performed by means of a machine of the type described.

Description

FRICTION WELDING MACHINE AND PROCEDURE

The present invention relates to a machine for friction stir welding, and a related process for friction stir welding.

More in detail, the invention concerns a machine and a process for making welded connections of metal tube sections or connection elements, such as flanges.

Friction stir welding is a welding method for achieving a union between two metals, even dissimilar metals, by exploiting the heat generated by the friction of a rotating tool placed in contact with the metals themselves.

The heat generated by the tool is sufficient to plasticize the amount of the two materials located in the immediate vicinity of their interface. This type of welding is particularly suitable for those materials that suffer from the high thermal shocks resulting from traditional fusion welding techniques, such as aluminum alloys, copper, magnesium, and even polymeric materials.

Today, known friction stir welding machines include a welding head, on which a rotating tool is mounted equipped with a conical tip and a shoulder.

The tool is positioned at the interface between the two materials to be welded so that the tip penetrates in the space between them, while the shoulder is positioned in contact with the surfaces of the two materials adjacent to the interface itself.

The rotating tool moves along the interface mechanically mixing the two materials while they are in a plastic state, and in addition imparts a shape to the weld bead by applying pressure during the movement.

Before beginning its movement, the tool is kept in contact with the interface in its initial position for some time in order to transfer sufficient heat to soften the adjacent region of material, and then moves at a constant and well-defined speed, depending on the nature and size of the material to be welded. The welding of metal tubes, and more generally of profiles endowed with radial or axial symmetry, presents inherent problems due to the geometry of the parts and the movements that the weld head must make to achieve an adequate result. Usually, tube friction stir welding machines involve attaching the tube itself and the part to be connected to a rotating chuck, such as by means of bolted flanges, jaws, or other known systems.

The chuck rotates the tube and the element to which it is to be connected around the central axis of the tube itself, so that a welding head, coupled with a fixed frame, moves relative to the two pieces to be welded along the interface between the two materials.

For reasons of economy and timing, many machines usually incorporate two heads, and as many chucks, one for each end of the tube to be welded. The drawbacks encountered in the use of such machines may list:

- the impossibility of making welds on beads at different speeds, being the chucks and the tube rigidly and integrally connected; the speed of rotation of the two must necessarily be identical so as not to damage the tube and/or the chucks themselves; - the impossibility of making non-continuous weld beads or starting from different positions at the interfaces between the materials of the two ends; this is because of the minimum time of contact of the tools with the metals to be welded before they begin to move. It is not possible to start welding at first on the first end by means of the first weld head, and then approach and maintain contact with the other head at a later time at the interface on the second end, as the tube continues to move to finish processing on the first end. In other words, the welds of the two ends must necessarily be simultaneous, starting and ending at the same time, respectively; - further, for the same reason, it is not possible for the welds on the ends of the tube to proceed at different speeds from each other, as they are constrained by the rotational speed of the tube being dragged by the chucks;

- inevitably, it is also impossible to weld tubes with interfaces at the two ends having different diameters, because the head operating on the larger diameter would proceed at a greater tangential speed than the head operating on the smaller diameter.

Further problems are encountered in the attachment of tubes to rotating chucks, as the use of flanges or other known fastening systems is not straightforward, given the long time required to assemble and disassemble the flanges and their respective counterflanges and bolts.

In addition, it is possible that, due to the stresses to which the tube is subjected during the welding process, it may become stuck by interference on the supports, causing further delays due to interventions by technical personnel to remove the tube from its seat.

The aim of the present invention is to provide a friction stir welding machine and a process that solves the mentioned drawbacks.

Specifically, it is the aim of the invention to provide a friction stir welding machine and a process that allows to independently adjusted the welding progress parameters on each seam located on the ends of a part to be welded.

Furthermore, it is an aim of the present invention to provide a friction stir welding machine and a related process that are more versatile and flexible than the prior art.

It is also an aim of the invention to provide a friction stir welding machine and a related process that enable welds to be made on the ends of tubes or related items at the same time and with different diameters or progressing speed.

These and other aims are achieved by a friction stir welding machine and a related process according to the attached independent claims 1 and 8.

Further detailed technical features are given in the attached dependent claims. The present invention will now be described, by way of example but not limitation, according to some of its preferred embodiments, and with the aid of the attached figures, wherein:

- figure 1 is a schematic representation of the machine according to the invention in a first resting position before welding;

- figures 2-5 are representations of the machine in figure 1 in different successive positions during and after the execution of the procedure;

- figures 6A and 6B are perspective views of a chuck for clamping tubes or other elements with radial or axial symmetry to the machine;

- figures 7A, 8A and 9 are front, side and rear views of the chuck in Figures 6A and 6B, respectively;

- figure 7B is a cross-sectional front view of the chuck along the A-A line of figure 8A;

- figure 8B is a side sectional view of the chuck along line B-B of figure 7A;

- figure 10 is an exploded perspective view of the chuck from figures

6-9;

- figure 11 is a front view of a machine component according to the invention.

Referring to figure 1 , a preferred embodiment of the friction stir welding machine according to the invention is shown.

The machine is designed to make a weld bead on the surface of a tube, or other part having substantially axial or radial symmetry, which can be attached to supports suitably shaped and placed laterally to it at its two ends.

The machine comprises a plurality of welding stations 1 , preferably one station for each of the two ends to be welded.

Each station 1 , contrary to the prior art, can work independently of the other station, as will become clearer below.

Each station 1 includes a chuck 2 (not visible in figures 1-5 because it is inserted inside the cavity of the part to be welded) attached to a support 3. The supports 3 of stations 1 are in turn coupled to a fixed machine frame 4, and have a housing 31 , wherein the chuck 2 is housed and which is configured to accommodate an element, such as a flange 6, to be welded to an open end of a tube 5. Given the symmetry of the parts on which the machine is set up to operate, the supports 3, thus also chucks 2, are prospettive and facing each other.

In addition, chucks 2 are aligned along an X axis together with supports 3, or are otherwise arranged to keep tube 5 on axis with each flange 6 between the two supports 3.

For attachment to supports 3, flanges 6 are inserted inside housings 31 and secured by counterflanges 32, each bolted to the back wall of housings 31.

The chucks 2 preferably project from the supports 3 onto which the flanges 6 to be welded to the open ends of the tube 5 are attached.

In this way, chucks 2 can adhere to the inner wall of tube 5, securing it in place and ensuring maximum alignment between the profiles to be welded.

Associated with each welding station 1 is a movable welding head 7, comprising a welding tool 71 , comprising a shoulder and a tip, set in rotation by a motor 710.

Specifically, the welding head 7 is configured to move along an angular direction, describing a circular trajectory around the X axis of tube 5, and along a radial direction, along a line intersecting the X axis and perpendicular to it.

In other words, in the preferred embodiment described here, the welding head 7 can move within a plane perpendicular at a given instant to the X axis of tube 5, or of the part, according to a polar coordinate system wherein the pole coincides with the point of intersection between the X axis and the plane wherein lies the tip of the tool 71 of the welding head 7.

Angular motion is realized by means of a ring 8 rotating about the X axis and moved by a motor. Specifically, movement is achieved by a mechanism including gear wheels (not shown) respectively connected to the ring 8 and to the machine frame.

To reduce the torque applied by the motor and to help balance, counterweights 82 are optionally attached to ring 8 in the opposite position from welding head 7.

Welding head 7 is moved in the radial direction by means of sliding a slide 72, integral to welding head 7 itself, on one or more tracks 83, integral to ring 8.

As mentioned, initially, components to be welded to tube 5, such as flanges 6, are attached to supports 3.

Subsequently, tube 5 is fixed and centered by means of expansion chucks 2, visible in figures 6A-10.

Each chuck 2 has a first front surface 20 and a second back surface

21.

There are projecting pins 210 on the back surface 21 that are inserted into appropriate (unseen) slots of the support 3 to couple the two elements.

The chuck 2 comprises a plurality of expandable segments 22 arranged along its periphery in a conventional manner for the industry technique.

These segments 22 are movable in the radial direction, and are configured to expand and contact the inner wall of the tube 5 so as to clamp and center it with respect to the supports 3 of the welding machine.

The movement of segments 22 is achieved by means of moving parts housed inside chuck 2, in the space identified between the front and back faces (figures 7B, 8B, 10).

Each segment 22 is coupled to a runner 23, sliding radially relative to chuck 2 and connected to a first end of a rod 24 via a first hinge 25.

Centrally located in the inner space of chuck 2 is a wheel 26, movable about the central axis of symmetry of chuck 2, and having a gear seat 260, accessible from the back face 21. The second end of each rod 24 is connected to wheel 26 via a second hinge 27.

Wheel 26 is configured to rotate about the central axis of chuck 2, so as to propel the runners 23 outward through the action of rods 24.

The rods 24, in fact, are misaligned with respect to the radial direction, which causes the segments 22 to expand outward, locking the tube 5 in place.

Advantageously, action on wheel 26 can be by automatic means (mechanical or pneumatic actuators integrated with the machine itself) or by manual means (for example, wrenches), in cases where the spindle remains locked by interference to the inner surface of tube 5.

A chuck of the type described provides numerous advantages, such as: greater speed in attachment and replacement to the machine, thanks to attachment via pins 210; greater versatility and ease of use due to the possibility of manual locking or unlocking; improved maneuverability, due to the compact design and lighter weight, for the same benefits achieved, compared with the prior art.

Operationally, after fastening the elements to be welded to the supports at the ends of tube 5, for example., flanges 6, the ends themselves are brought closer to flanges 6 until they are contiguous and flanked by flanges 6 themselves at an interface 9, as shown in figure 1.

The chucks 2, already inserted inside the cavity of the tube 5, are driven and the parts to be welded are thereby mutually clamped and centered.

The welding head 7 is brought closer, by sliding the slide 72 on the trucks 83 of the ring 8, to the line of interface 9 so that the tip of the tool 71 penetrates and positions itself at the interface of the two parts to be welded in an initial position (figure 2).

This interface should be of the smallest possible width, on the order of a tenth of a millimeter. To reduce the interface, the invention uses a system of springs placed inside the housings 31 , allowing an angular oscillation of the part to be welded with respect to the X axis of about 0.3°.

A front view of a housing 31 intended to accommodate the part to be welded at the end of a tube is shown in figure 11.

Blind holes 310 are cut in housing 31, into which elastic means (not shown), such as springs, are placed.

The springs contact the part when the counterflange 32 is coupled to hold the part in place.

This aids alignment and minimizes the possibility of misalignment between each piece and the respective end of the tube to be welded.

By means of motor 710 (controlled by a PLC), the tip of the tool 71 is set into rotation and held in its initial position, at a certain depth in the material, for a predetermined time that varies according to the type of material to be welded and/or its thickness, so as to bring the region surrounding the interface to temperature.

At this point, the ring 8 begins to rotate about the X axis, through the action of the motor, dragging the welding head 7 and bringing the tip of the tool 71 to describe a circular trajectory along the interface 9 (figure 3).

Once interface 9 is fully welded (figure 4), first the tip of the tool 71 is removed from the interface, then the movement of slide 72 ends, and then the rotation of ring 8 ends.

The welding head 7 is returned to its initial position, and the tube 5 can be removed from the holder of chucks 2.

Next, the means of locking flanges 6 (in this case they also lock counterflanges 32) are removed from supports 3, allowing the flanges 6 themselves to be removed from housings 31 , along with tube 5.

More precisely, the flange is unlocked with respect to the counterflange seat, which is not removed.

The machine further includes a control logic unit, which is connected to all the moving components of the machine itself and configured to control its movements. The invention thus conceived and illustrated herein is susceptible to numerous modifications and variations, all within the scope of the inventive concept.

Furthermore, all details may be replaced by other technically equivalent elements.

Finally, the components used, provided they are compatible with the specific use, as well as the dimensions, may be any according to the needs and state of the art.

Where features and techniques mentioned in any claim are followed by reference marks, such reference marks have been appended for the sole purpose of increasing the intelligibility of the claims and, accordingly, such reference marks have no limiting effect on the interpretation of each element identified by way of example by such reference marks.

Claims

1. Machine for friction stir welding of tubes or elements having axial or radial symmetry, comprising one or more welding stations (1) each equipped with a support (3) in turn comprising a chuck (2) for fixing and centering a tube (5) relative to a central axis (X) of symmetry thereof, a housing (31), contiguous to the chuck (2), for fixing and centering an element or part (6) to be welded to the tube (5), so that one end of the tube (5) and the part (6) are contiguous and side by side at an interface (9) to be welded, wherein each station comprises a welding head (7) provided with a rotating welding tool (71) configured to position itself in contact with the interface (9), characterized in that the welding head (7) is movable along a first angular direction about the axis (X) and along a second radial direction perpendicular to the axis (X), such that the welding tool (71) friction welds the tube (5) and the part (6) along the interface (9).

2. Welding machine according to claim 1 , characterized in comprising a ring (8) rotating about the axis (X) of the tube (5) and provided with tracks (83) oriented perpendicularly with respect to the axis (X), wherein the welding head (7) is coupled to a slide (72) sliding with respect to the tracks (83).

3. Welding machine according to claim 2, characterized in that the ring (8) comprises counterweights (82).

4. Welding machine according to any one of claims 1-3, characterized in that the chuck (2) is of the expanding type and includes a plurality of segments (22) on its periphery, configured to contact the inner surface of the tube (5).

5. Welding machine according to claim 4, characterized in that the chuck (2) includes a wheel (26), connected to each segment (22) by a rod (24), and operable by a user to move away and expand each segment (22).

6. Welding machine according to claim 4 or 5, characterized in that the chuck (2) includes pins (210) for attachment to the support (3) of the machine.

7. Welding machine according to any one of claims 1-6, characterized in comprising a logical control unit or PLC for moving the welding head (7).

8. A welding machine according to any one of claims 1-7, characterized in that said housing (31 ) has blind holes (310) wherein elastic means are positioned to facilitate alignment of the part (6) to be welded with the end of the tube (5).

9. A process for friction stir welding using a machine according to any one of claims 1-8, comprising the following successive steps:

- securing and centering a tube (5) and a part (6) to be welded so that one end of the tube (5) and the part (6) are contiguous and side-by-side at an interface (9) to be welded;

- positioning of a rotating welding tool (71 ) in contact with the tube (5) and part (6) at the interface (9);

- moving the welding tool (71) along the interface so as to weld the tube (5) and the part (6) together.