Method and apparatus for friction stir welding

ES 2 275 813 T3

DESCRIPTION

Method and apparatus for friction stir welding.

Scope of the invention

The present invention relates to a friction stir welding method, and especially relates to a desirably applied welding method for making railway car bodies.

Description of Related Art

Friction stir welding is a method that is performed by inserting a rotating circular shaft (called rotary tool) in the joint area between the members to be welded and moving it along the joint line, thereby heating, softening and plasticizing the material of the members near the tool so that solid phase welding of the members is performed.

The gap between the butt members is an important factor in friction stir welding. If the gap is too large it is difficult to obtain a good friction stir weld. However, when manufacturing a box for a railway car and the like, where the members to be welded together are up to 20 m long and approximately 3 m wide, the manufacturing error of the members is somewhat excessive and, as a consequence , the interspace may be too large.

According to the Provisional Publication of Japanese Patent No. 2000-233285, which represents the closest state of the art, when performing friction stir welding a filler member is arranged in the interspace that is formed in the stop zone between the two members to be welded together.

In addition, Japanese Patent No. 3014654 (USP 6,050,474) describes that projections are arranged in the members near the stop zone, respectively, and that when friction and stir welding is carried out, the interspace is filled using as material of I fill the metal that constitutes the projections.

When inserting a filler member into the gap that is formed between the members to be welded together, it is important that this filler member is firmly fixed in position so that it does not deviate from the gap during friction stir welding.

It is possible to weld the filler member to the butt members, but the large amount of heat that is supplied during welding can cause deformation of the members. Furthermore, if the friction stir welded surface is to be used without any coating applied thereon, the welded part may become discolored and the appearance of the welded surface worsens.

Summary of the invention

The object of the present invention is to provide a friction stir welding method which enables a good weld with an attractive appearance to be achieved.

The above object is achieved with the method according to claim 1.

Brief description of the drawings

Fig. 1 is a perspective typified view illustrating the process according to an embodiment of the present invention;

Fig. 2 is a side simplified view of the process according to an embodiment of the present invention, especially illustrating the filling member feed unit;

Fig. 3 is a cross-sectional view according to the line III-III of Fig. 1;

Fig. 4 is a cross-sectional view according to line IV-IV of Figs. 1 and 2;

Fig. 5 is a cross-sectional view taken along line VV of Figs. 1 and 2;

Fig. 6 is a cross-sectional view according to line VI-VI of Figs. 1 and 2;

Fig. 7 is a cross-sectional view according to line VII-VII of Figs. 1 and 2;

Fig. 8 is a cross-sectional view on the line VIII-VIII of Fig. 1;

Fig. 9 is a cross-sectional view illustrating the welded joint of the members in which the friction stir welded butt joint has been smoothed;

ES 2 275 813 T3 Fig. 10 is a view according to arrow X in Fig. 2; and Fig. 11 is a simplified side view illustrating the process according to another embodiment of the present invention, especially illustrating the filling member feed unit.

Detailed description of the preferred embodiment

The preferred embodiment of the present invention will now be explained with reference to Figs. 1 to 10. However, the technical scope of the present invention is not limited to the values ​​described in the embodiments of the present invention.

Two plate-shaped members 10 and 20 are mounted on a base 25 and abut each other so that their edges are opposed to each other. The limbs are fixed in this position. An interspace usually forms between the butt members. Props 12 and 22 are provided on the upper surface of the butt-abutting opposing portions of the members 10 and 20. Furthermore, on the lower surface of the abutted area of ​​the member 20 is provided a projecting block 23 which projects towards the lower surface of the abutted area of ​​the member 10.

The two members 10 and 20 are pressed against each other and fixed to the base 25 so that the gap 40 between the members 10 and 20 is minimized or decreased, the gap being at least less than a predetermined gap size. The predetermined gap size is equal to or substantially less than a gap 41 mentioned later.

Members 10 and 20 are members with an extruded shape made of an aluminum alloy. The abutting parts (surfaces) of the two members 10, 20 form what is called a bond line. As mentioned later, the material of the filler member 30 is the same as the material of the members 10, 20.

The friction stir welding apparatus comprises the units illustrated in Figs. 1 and 2 (not including members 10, 20, and base 25, but including filling member 30 delivery apparatus), which includes a movable body that moves at a specified speed relative to base 25 in which the members 10, 20 are attached. In Fig. 1 the apparatus moves from right to left (in the direction illustrated by the large white arrow). In Fig. 2 the apparatus moves from right to left. In other words, the left side cutting tool 60 cuts the members 10 and 20 first and the machining proceeds in the direction of the friction stir welding tool 81, arranged on the right side.

After fixing the members 10 and 20 on the base 25, the joint line (in which the gap 40 exists) is cut from the upper side using a cutting tool 60 to create a predetermined groove 41. Slot 41 is rectangular. Opposite sides of slot 41 (the ends of members 10 and 20) are parallel.

The width of this cut is at least large enough so that neither of the two side walls that define the gap 40 remain. The depth of the cut is equal to the depth of the upper surface of the protruding block 23. In the cutting process a dry cut is made.

In the figures, cutting tool 60 is illustrated as a circular saw, but other cutting tools, such as a slotting cutter or radial cutter, may also be used, providing the same effect. In conclusion, the depth and width of the cut are required to be uniform.

Then, the metal chips generated by the cutting tool 60 are removed by injecting compressed air, by means of a chip evacuation injector 50, or by drawing them into a dust collector.

Disposed behind the chip evacuation injector 50 is a rubber plate 95 which is in contact with the upper surface of the shoulders 12 and 22, with the upper surface of the members 10 and 20 extending outside the shoulders and with the protruding block 23 inside the slot 41. Consequently, the rubber plate prevents the metal chips from moving further back.

After the slot 41 is made, the filler member 30 is inserted into the slot 41. This is done by removing the filler member 30 from a coil 90, inserting the member 30 into the slot 41, and pressing the member 30 downward by means of of a pressure roller 70 to insert the same in the groove. The pressure roller 70 presses down the upper surface of the filling member 30, against the bottom of the groove 41, by the action of an air cylinder device 71 (or a compression spring).

The height of the filler member 30 is determined so that the upper surface of the filler member 30 protrudes slightly above the upper surfaces of the shoulders 12, 22 when the lower surface of the filler member 30 contacts the surface. top of boss block 23.

The cross-sectional shape of the filler member 30 is substantially the same as that of the slot 41. The width of the filler member 30 is substantially equal to the width of the slot 41. The filler member 30 is relatively easily inserted into groove 41 by pressure roller 70, but no gap is formed

Excessive ES 2 275 813 T3 between filler member 30 and member 10 (20). The difference in width between the filler member 30 and the groove 41 is set to less than 1mm.

The filler member 30 is wound around a rotating spool 90, which extends to the pressure roller 70 through straightening rollers 91a, 91b and 91c and through feed rollers 92a, 92b, 92c, 92d, 92e and 92f in this order. These rollers are brought into contact with the filler member 30.

The straightening rollers 91a, 91b, and 91c squeeze the filler member 30 that has been wound around the coil 90 together, thereby straightening the curvature of the member 30. The straightening rollers 91a and 91c are primarily in contact with the inner surface of the filler member 30 wound around the coil 90. The straightening roller 91b is primarily in contact with the outer surface of the filler member 30 wound around the coil 90. The contact surfaces of the straightening rollers 91a, 91b, and 91c that contact the filler member 30 ( the outer circumference of the rollers) are recessed. The filler member 30 enters the recess.

The feed rollers 92a, 92b, 92c and 92d are rollers that remove the filler member 30 from the coil 90 and feed it into the groove 30. The feed rollers contact the surface of the height sense (the surface oriented according to the height of the groove 41) of the filling member 30. The contact surfaces of the feed rollers that come into contact with the filling member 30 are recessed. The filler member 30 is inserted into the recess. The feed rollers 92a and 92c are driven by a motor through a torque limiter. Accordingly, the filling member 30 is sent towards the longitudinal direction with a predetermined force. The feed rollers 92a and 92c are connected to the feed rollers 92b and 92d, respectively. For example, sprockets are disposed on the outer circumference of feed rollers 92a, 92c, 92b, and 92d, with the sprockets of feed rollers 92a and 92c meshing with the sprockets of feed rollers 92b and 92d.

The feed rollers 92a, 92b, 92c, 92d, 92e, and 92f are guide rollers of the filler member 30. The feed rollers 92e and 92f do not have motors. The feed rollers 92e and 92f are brought into contact with the height sense surface (the surface oriented according to the height of the groove 41) of the filler member 30. The contact surface of the feed roller that comes into contact with the filler member 30 is recessed. The filler member 30 enters the recess.

After inserting into slot 41 the filler member 30, a rotary tool 80 is used to temporarily weld the filler member 30 to the members 10 and 20 in a position that is behind the pressure roll 70. This weld is a weld by friction and agitation that is done using the rotary tool 80.

Generally a rotary tool used to effect friction stir welding has a small diameter part disposed at the tip of a large diameter part, but according to this embodiment the rotary tool 80 has no small diameter part. The tip of the rotary tool 80 is flat. Rotary tool 80 is inserted from above into members 10, 20, and filler member 30. The axis of the rotary tool 80 is inclined similar to a normal rotary tool. The direction of inclination is also the same as in a typical friction stir welding. Rotary tool 80 is rotated.

The diameter of the rotary tool 80 is somewhat larger than the width of the slot 41. For example, if the width of the slot 41 is 3mm, the diameter of the rotary tool 80 is set to 6mm. The insertion depth of the rotary tool 80 with respect to the shoulders 12 and 22 is very small because this weld is only temporary. For example, the weld depth is 1.0mm from the top surface of shoulders 12 and 22. The weld strength of the temporary weld must be sufficient to prevent the filler member 30 from coming out of the groove 41 during the friction stir welding treatment that is performed using the rotary tool 81. In other words, the depth of insertion is determined so that such weld strength is obtained.

The upper end of the filler member 30 is higher than the upper surfaces of the bosses 12 and 22. The filler member 30 protrudes from the bosses 12 and 22. Consequently, even if an interspace is formed between the filler member 30 and the groove 41 due to manufacturing errors, the gap can be filled with the protruding part of the filling member 30. Thus, the filling member 30 can be firmly attached to the members 10 and 20. Furthermore, by squeezing and inserting the filler member 30 into the groove using the pressure roll 70 the filler member 30 can come into close contact with the protruding block 23, thereby allowing a strong weld to be made.

When friction stir welding is performed using the rotary tool 80, the upper surface of the weld joint becomes somewhat jagged. In Figs. 7 and 8 the upper surface of the weld joint is illustrated as being flat.

Since no thread is provided on the outer circumference of the large diameter portion of the rotary tool 80, there is no fear that the filler member 30 and the shoulders 12, 22 will be pushed out in the axial direction of the rotary tool. rotary tool 80 during friction stir welding.

ES 2 275 813 T3

It is preferable that the position of the rotary tool 80 is arranged as close as possible to the pressure roller 70.

The three members, which are shoulders 12, 22 and filler member 30, are then friction stir welded using rotary tool 81. This welding is performed to firmly weld members 10 and 20 together.

The rotary tool 81 comprises a small diameter part arranged at the tip of a large diameter part. The diameter of the small diameter portion is somewhat greater than the width of the filler member 30 and the width of the groove 41. During friction stir welding, the lower front of the dividing surface between the large diameter portion and the small diameter portion of the rotary tool 81 is disposed above the upper surface of the members 12 and 22 excluding the shoulders 12 and 22, but below the top of ribs 12 and 22. Similarly, the tip of the small diameter portion of the rotary tool 81 is disposed near the top surface of the boss block 23 or within the boss block 23.

As mentioned above, if an interspace is formed between the filler member 30 and the members 10, 20, the interspace is filled using as the material the filler member 30 and the projections 12 and 22 arranged on the upper surface of the members. 10, 20 (eliminating highlights 12, 22). The upper surface of the weld joint is slightly jagged.

After this and if necessary, the filler member 30 and the shoulders 12 and 22 (which form the welded joint part) located above the upper surface of the members 10 and 20 are cut and eliminated, eliminating the shoulders 12 and 22. so that a flat smooth surface is obtained.

Fig. 9 illustrates the cross section of the friction stir welded joint, having a flattened upper surface by elimination of the projections 12, 22 and the weld joint disposed above the upper surface of the members 10, 20. The area designated by reference numeral 43 is the friction stir welded joint.

The cutting tool 60 and the rotary tools 80 and 81 are designed, respectively, so that they can move independently in the direction orthogonal to the bond line, in other words, in the direction of the width of the gap 40 (groove 41) . This serves to detect the position of the bond line (gap 40, slot 41) and to position the cutting tool 60 and rotary tools 80 and 81 in the center of the bond line. In addition, the cutting tool 60 and the rotary tools 80 and 81 can move independently in the vertical direction, respectively. This serves to control, up to a specified depth, the depth of cut of the cutting tool 60 (depth of groove 41) and the depth of welding of the rotary tools 80 and 81.

In order to realize the above advantage, optical sensors (not shown) are provided in the apparatus to detect the position of the shoulders 12 and 22. The optical sensors detect the position in width of the two shoulders 12 and 22 in order to position the cutting tool 60 and rotary tools 80 and 81 in the center of the width thereof. In addition, the optical sensors detect the position in height of the upper surfaces of the shoulders 12 and 22 in order to insert the cutting tool 60 and the rotary tools 80 and 81 to a predetermined depth.

The drag force applied to the filler member 30 by the feed rollers 92a, 92b, 92c, and 92d must be great enough to oppose the backward driving force acting on the filler member 30 during friction stir welding performed by the rotary tool 81.

The distance between the feed rollers 92e and 92f and the pressure roller 70, the distance between the pressure roller 70 and the rotary tool 80, and the distance between the rotary tool 80 and the rotary tool 81 should be respectively set to a distance that does not cause the filler member 30 to warp, in the respective positions, by the rearwardly urging force of the filler member 30.

According to this embodiment, even if there is an interspace along the joint line when butting and welding the two members, the joint line can be cut in order to form an interspace having a predetermined size into which it is inserted. a filler member to substantially eliminate the gap formed in the bond line prior to friction stir welding, thereby allowing a good weld to be achieved.

If the joint part is to be smoothed after friction stir welding and a very fine finish is to be made on it, a good appearance is achieved because the material of the filler member 30 is the same as the receptor material (members 10 and 20), so there is little discoloration.

Furthermore, the rotary tool 80 may have a small diameter part disposed at the tip of a large diameter part, similar to the rotary tool 81.

Another preferred embodiment of the present invention will be explained with reference to Fig. 11. The reference numerals in Fig. 11 which are the same as those used in Figs. 1 to 10 refer to substantially the same members. This embodiment is primarily concerned with an example where temporary welding is eliminated.

ES 2 275 813 T3

The feed rollers 92a, 92b, 92c and 92d are positioned at an angular difference of 90 degrees from the example illustrated in Fig. 2. A guide roller may be arranged between the straightening rollers 91a-91c and the feed rollers 93a- 93d, which is not arranged according to the present embodiment, but instead a guide tube 94 is arranged. The guide tube 94 is abrasion resistant, rigid and flexible. It can be, for example, a Teflon tube (registered trademark). There is adequate clearance between the inner diameter of the guide tube 94 and the filler member 30. The two ends of the guide tube 94 are attached to the movable body (not shown) on which the present friction stir welding apparatus is mounted. In FIG. 11 the filler member 30 is illustrated with a solid line within the guide tube 94. A pressure roll 70 can be used, but is not used in the illustrated embodiment. The rotary tool 80 for temporary welding is eliminated.

The drag force applied by the feed rollers 92a-92d is sufficient to feed the filler member 30 overcoming the resistance of the back drive force applied by the rotary tool 81. The distance between the feed rollers 93a-93d and the tool Rotary 81 is set so that the backdrive force does not cause the filler member 30 to warp. Therefore, the temporary welding performed with the rotary tool 80 can be omitted.

When using the supply rollers 92a-92f, the rollers must be arranged movably relative to the moving body, but the structure can be simplified by using the guide tube 94 instead.

An example of the sizes, etc., of the members used in the present invention will now be explained.

Material of members 10, 20 and filler material 30: aluminum alloy.

Thickness of the plate of the members 10, 20 (excluding the thickness of the projections 12, 22): 4 mm.

Rib width 12, 22: 8 mm

Height of the projections 12, 22 (excluding the thickness of the plate of the members 10, 20): 2 mm.

Groove width 41: 3 mm.

Groove depth 41: 6mm.

Width of filling member 30: 3 mm.

Height of filling member 30: 6.5mm.

Rotary tool diameter 80: 6 mm.

Rotary tool 80 friction stir welding depth: 1.0 mm from surface of shoulders 12, 22.

In accordance with the present invention, good friction stir welding can be achieved by cutting and forming a predetermined gap between the two butt members, filling the gap with a filler member, so that the gap between the butt members is substantially eliminated. stop, and performing friction and stir welding in it.