JP5091303B2 - Friction stir welding method - Google Patents

Description

  The present invention relates to a friction stir welding method in which contact portions of two metal workpieces are joined by friction stir welding.

  Friction stir welding is a kind of joining method in which the abutted workpieces are solid-phase joined and has been widely adopted. In the friction stir welding, the friction stir welding tool is rotated, and the probe provided at the tip of the friction stir welding tool is buried in the contact position between the workpieces. Along with this, frictional heat is generated in the vicinity of the contact portion, and the meat between the end portions including the end face causes plastic flow by this frictional heat, so that the workpieces are joined and integrated.

As shown in FIG. 9 , the probe 502 of the conventional friction stir welding tool 500 may be provided with a threaded portion 508 to promote plastic flow with respect to the workpieces 504 and 506. By the action of the screw portion 508, plastic flow of the workpieces 504 and 506 is promoted, and the probe 502 can be easily inserted into the workpieces 504 and 506.

  By the way, when the screw part 508 is provided in the probe 502, the workpieces 504 and 506 are directed upward and cause plastic flow as schematically shown by cross-hatching. As a result, the work piece 504 on the front side is thinned, and the connection height C, which is important in terms of strength, is reduced. According to the tensile test and shear test results, stress concentration is likely to occur in this part, and the bonding strength is reduced. There is. In addition, a part of the structure in which the plastic flow of the workpiece 504 on the front side is caused may become a burr 510 and appear on the surface.

  From such a viewpoint, a tool has been proposed in which a number of flat rhombus bosses are provided on a probe to generate a uniform plastic flow (for example, see Patent Document 1).

JP 2002-514512 A

  When performing friction stir welding using the tool disclosed in Patent Document 1 described above, the work on the front side is prevented from being thinned and the bonding strength is greater than that having a helical screw shape, Generation of burrs can be suppressed.

However, since this tool does not have the screw portion 508 like the friction stir welding tool 500 (see FIG. 9 ), it is difficult to insert the tool into the workpiece.

  In addition, since there are many rhombus bosses, the forward screw portion and the reverse screw portion are mixed. Therefore, the direction of the plastic flow of the workpiece becomes irregular and uneven, the bonding strength is insufficient, and the friction stir welding tool capable of bonding the workpiece with a larger bonding strength from the viewpoint of improving the bonding quality. Development is desired.

  The present invention has been made in consideration of such problems, and an object thereof is to provide a friction stir welding method capable of uniforming the direction of plastic flow in a workpiece and joining the workpiece with higher joining strength. And

  The present invention relates to a friction stir welding method in which the first and second metal workpieces are joined by friction stir welding by rotating a friction stir welding tool having a probe, and the probes are mutually connected along an axial direction. A first step of having first and second screw portions that are screwed in opposite directions, and inserting the probe to a predetermined position while generating a plastic flow by rotating the probe at the time of joining the first and second workpieces; The first and second workpieces are joined while maintaining the rotation of the probe at the predetermined position and balancing the plastic flow caused by the rotation of the first screw portion and the plastic flow caused by the rotation of the second screw portion. And a second step.

  Thus, by rotating the probe having the first and second screw portions that are spirally wound in the opposite directions along the axial direction, the workpiece can be joined with a greater joining strength.

  In this case, the first and second workpieces are stacked and joined to each other, and a boundary portion between the first screw portion and the second screw portion overlaps the first and second workpieces. It is preferable to maintain the rotation of the probe at a predetermined position coinciding with the mating surface.

  Thus, the rotation of the probe is maintained at a predetermined position where the boundary between the first screw portion and the second screw portion coincides with the overlapping surface of the first and second workpieces, so that the first screw portion is The force that moves downward and the drag generated by the second screw portion are balanced. This is because the probe is prevented from descending unnecessarily.

  Further, the first fluid that plastically flows in the first direction by the first screw portion and the second fluid that plastically flows in the direction opposite to the first direction by the second screw portion are the first and second fluids. The joints are joined at the boundary between the first screw portion and the second screw portion, and pushed out in the outer diameter direction of the probe along the overlapping surface.

  As a result, the first fluid and the second fluid merge at the boundary between the first screw portion and the second screw portion, and are pushed out in the outer diameter direction along the overlapping surface. The portion is agitated mainly, and the first and second workpieces are not thinned, and a large area is reliably joined.

  According to the friction stir welding method of the present invention, the direction of the plastic flow in the workpiece is made uniform by rotating the probe having the first and second screw portions that are spirally wound in the opposite directions along the axial direction. In addition, the workpieces can be bonded with higher bonding strength. Moreover, the effect which can suppress generation | occurrence | production of the burr | flash from the workpiece | work to join is acquired.

It is a side view which shows the tool and workpiece | work for implementing the friction stir welding method which concerns on this Embodiment. It is the schematic diagram which expand | deployed the side surface of the probe of the tool for friction stir welding of FIG. It is a partial cross section side view which shows the state by which the front-end | tip part of the probe of the tool for friction stir welding of FIG. 1 was inserted in the workpiece | work. It is a partial cross section side view which shows the initial state in which the probe was inserted in the workpiece | work until the end surface of the cylindrical part of the tool for friction stir welding of FIG. 1 contact | abuts to a workpiece | work. It is a partial cross section side view which shows the state where the probe was inserted in the workpiece | work until the end surface of the cylindrical part of the tool for friction stir welding of FIG. 1 contact | abutted to a workpiece | work, and the plastic flow generate | occur | produced. The first modification of the tool for carrying out the friction stir welding method of the present embodiment and the workpiece It is a partial cross section side view. It is the schematic diagram which expand | deployed the side surface of the probe of the tool for friction stir welding of FIG. The probe according to the second modification of the tool for carrying out the friction stir welding method of the present embodiment FIG. It is a partial cross-section side view of the friction stir welding tool and workpiece according to the prior art.

Hereinafter, DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment in relation to the tool carrying it for FSW method according to the present invention will be described with reference to FIGS. 1-8 of the accompanying drawings.

  As shown in FIG. 1, the friction stir welding tool 10 according to the present embodiment joins the abutting portions of two metal (for example, aluminum) workpieces 12 and 14 that are overlaid by friction stir welding. For this purpose, it has a cylindrical body 16 that holds the workpiece 12 on the front side, and a probe 18 that is coaxially formed at the tip of the cylindrical body 16 and is inserted into the workpieces 12 and 14. The workpieces 12 and 14 have a plate shape and are fixed on a support base 15 having a cylindrical recess 15a. The inner diameter of the cylindrical recess 15a is larger than the outer diameter of the probe 18, and the cylindrical recess 15a and the probe 18 are set coaxially.

  The distal end portion of the probe 18 includes a first screw portion 20 having a right-handed spiral shape and a second screw portion 22 provided on the rear side of the first screw portion 20 and having a left-handed spiral shape. Have. Examples of the material of the friction stir welding tool 10 include high-speed tool steel.

  The friction stir welding tool 10 is driven to rotate clockwise as viewed from above when performing friction stir welding.

  A distance H from the boundary line 24 between the first screw portion 20 and the second screw portion 22 to the end face 16a of the cylindrical body 16 is set equal to a value obtained by subtracting a width H1 described later from the thickness of the work 12 on the front side. . Since the width H1 is a slight value, the distance H may be set equal to the thickness of the workpiece 12 in practice.

  Further, the screw thread 20a of the first screw part 20 and the screw thread 22a of the second screw part 22 are continuous. That is, when the side surface of the probe 18 is developed and schematically shown, the thread 20a and the thread 22a are connected at a point P of the boundary line 24 as shown in FIG. A thin groove or the like may be provided between the screw thread 20a and the screw thread 22b, and the screw thread 20a and the screw thread 22b only need to be substantially connected at the point P.

  The first screw portion 20 and the second screw portion 22 may be provided with screw threads 20b and 22b other than the screw thread 20a and the screw thread 22a to form two screws.

  As apparent from FIGS. 1 and 2, the screw pitches of the first screw portion 20 and the second screw portion 22 are set to be equal, and the axial length H of the first screw portion 20 and the second screw portion 22 is Are set equal. That is, in FIG. 2, the screw thread 20 a and the screw thread 22 a are symmetrical with respect to the boundary line 24.

  In FIGS. 1 and 2, the boundary line 24 is indicated by a one-dot chain line for easy understanding, but the boundary line 24 is a virtual line that does not actually exist.

  Next, a description will be given of a process of performing friction stir welding of the workpiece 12 and the workpiece 14 that are overlapped using the friction stir welding tool 10 configured as described above.

  First, the friction stir welding tool 10 is attached to a drive device (not shown). The drive device has a function of rotating the friction stir welding tool 10 and a function of moving it up and down. When the friction stir welding tool 10 is lowered, it can be rotated clockwise.

  Next, in a state where the workpiece 12 and the workpiece 14 are overlapped with each other, the friction stir welding tool 10 is rotated by the driving device after being fixed at a position below the friction stir welding tool 10.

  Next, as shown in FIG. 3, the friction stir welding tool 10 is lowered while maintaining the rotation, and the probe 18 is pressurized and inserted into the work 12 on the front side. At this time, since the first screw portion 20 provided at the tip of the probe 18 is a right-hand thread, the first screw portion 20 is inserted smoothly into the work 12 as if a bolt is inserted (or a tap is cut).

  In the friction stir welding, when a friction stir welding tool 10 is first brought into contact with the surface of the workpiece 12 and insertion is started, a predetermined pressure is required. Thus, the probe 18 is smoothly inserted, so that the pressing force required for the friction stir welding tool 10 is small, and the life of the friction stir welding tool 10 can be increased.

  As shown in FIG. 4, the friction stir welding tool 10 is further lowered until the end surface 16 a of the cylindrical body 16 bites into the surface of the work 12 by a slight width H <b> 1. At this time, although the friction stir welding tool 10 is rotating in the clockwise direction, the second screw portion 22 is a left-hand screw, so that the second screw portion 22 has a drag that prevents insertion of the workpiece 12. Occur. This drag force increases as the second screw portion 22 is inserted into the workpiece 12.

  On the other hand, since the first screw portion 20 is a right-hand screw as described above, the first screw portion 20 generates a force that moves downward by rotating the friction stir welding tool 10 clockwise. Since the screw pitch of the first screw portion 20 and the second screw portion 22 is set equal, and the axial length H of the first screw portion 20 and the second screw portion 22 is set equal, the first screw The force that the portion 20 moves downward and the drag generated by the second screw portion 22 will eventually balance.

  At least until the boundary line 24 reaches the surface of the workpiece 12, the probe 18 is smoothly inserted into the workpiece 12 and the workpiece 14 by the action of the first screw portion 20, and the pressure applied by the driving device is small.

  Further, when the probe 18 is rotated and lowered, the workpiece 12 and the workpiece 14 receive a force that lifts upward by the first screw portion 20, and are pressed downward by the second screw portion 22. Thereby, the floating of the workpiece | work 12 and the workpiece | work 14 can be prevented.

  Next, after the end surface 16a is lowered until the end face 16a bites into the workpiece 12 by the width H1, only the lowering operation is stopped while the rotation of the friction stir welding tool 10 is maintained. At this time, the force by which the first screw portion 20 moves downward and the drag force generated by the second screw portion 22 are balanced, thereby preventing the probe 18 from being lowered unnecessarily. At this time, the boundary line 24 between the first screw portion 20 and the second screw portion 22 in the probe 18 coincides with the overlapping surface 26 of the workpiece 12 and the workpiece 14. The boundary line 24 and the overlapping surface 26 only need to substantially coincide.

  At this time, since the plastically flowed meat of the workpiece 14 is caused to flow into the cylindrical recess 15a of the support base 15, the stirring region in the stacked portion becomes large. For this reason, since the contact site | part of each workpiece | work 12 and 14 is stirred a lot and it solidifies by cooling, a friction stir joint part member with favorable joining strength can be obtained.

  Furthermore, as schematically shown by arrows A1 and A2 in FIG. 4, the vicinity of the probe 18 in the work piece 14 on the back side is wound upward by the first screw portion 20. On the other hand, as schematically shown by the arrows B <b> 1 and B <b> 2, the vicinity of the probe 18 in the work 12 on the front side is pushed downward by the second screw portion 22.

Next, as shown in FIG. 5, plastic flow occurs in the direction of arrows B <b> 1 and B <b> 2 in the workpiece 12, and in the directions of arrows A <b> 1 and A <b> 2 in the workpiece 14. These plastic flows become uniform plastic flows along the directions of arrows A1, A2, B1, and B2. In addition, the cross hatching part in FIG. 5 (and FIG. 6 mentioned later) shows the location where plastic flow generate | occur | produces typically.

  The fluid wound upward by the first screw portion 20 and the fluid pushed down by the second screw portion 22 merge in the vicinity of the boundary line 24 and are pushed out in the outer diameter direction along the overlapping surface 26.

  As described above, the screw pitches of the first screw portion 20 and the second screw portion 22 are set to be equal, and the axial lengths H of the first screw portion 20 and the second screw portion 22 are set to be equal. Therefore, the plastic flow caused by the first screw portion 20 and the plastic flow caused by the second screw portion 22 occur in a well-balanced manner, and the plastic flow near the boundary line 24 is promoted.

  As described above, the workpiece 12 and the workpiece 14 are agitated mainly at the overlapping surface 26, and the workpiece 12 and the workpiece 14 are not thinned, and a large area is reliably joined. The In particular, since the screw threads 20a and 22a of the first screw portion 20 and the second screw portion 22 in the probe 18 are connected at a point P (see FIG. 2), plastic flow in the vicinity of the overlapping surface 26 is promoted. And the fluid is pushed further outward.

  Since the thinning of the workpiece 12 is prevented, the height H2 of the joining portion is substantially equal to the plate thickness of the workpiece 12. Accordingly, the load is distributed over a wide area, and the bonding strength is improved. Further, since the overlapping surface 26 is agitated and bonded over a wide area, the tensile strength is increased in addition to the shearing force.

  Furthermore, since the vicinity of the probe 18 in the workpiece 12 on the front side plastically flows so as to be pushed downward by the second screw portion 22, the fluid does not bulge to the surface of the workpiece 12, and burrs are generated. Can be suppressed.

  After joining the workpiece 12 and the workpiece 14 in this manner, the friction stir welding tool 10 is pulled upward by the driving device to finish the friction stir welding. In this case, the workpiece 12 and the workpiece 14 are joined at a point where the friction stir welding tool 10 is inserted, and are joined as so-called spot joining.

If the friction stir welding tool 10 is rotated in the counterclockwise direction, the stir welding generated on the overlapping surface 26 has a small area, and burrs may be generated on the surface of the workpiece 12. . That is, the above-described effect can be obtained by rotating the friction stir welding tool 10 clockwise. When the rotation direction is counterclockwise, it is preferable to use a friction stir welding tool 10a (see FIG. 6 ) having a reverse screw direction.

In the above description, the friction stir welding tool 10 has been described as being rotated clockwise by the driving device, when the driving device is intended to rotate in the counterclockwise direction, shown in FIG. 6 Like the friction stir welding tool 10a, the first screw portion 30 corresponding to the first screw portion 20 may be a left screw, and the second screw portion 32 corresponding to the second screw portion 22 may be a right screw. In this way, the direction of the screw is reversed with respect to the friction stir welding tool 10 and rotated counterclockwise, so that the friction stir welding tool 10a has the same effect as the friction stir welding tool 10. Play.

Further, in the above description, the screw thread 20a of the first screw part 20 and the screw thread 22a of the second screw part 22 have been described as being connected at a point P (see FIG. 2). As shown in FIG. 7 , the tip of the screw thread 20a and the tip of the screw thread 22a may be spaced apart in the circumferential direction. Furthermore, as shown in FIG. 8 , the tip of the screw thread 20a and the tip of the screw thread 22a, and the tip of the screw thread 20b and the tip of the screw thread 22b may be slightly separated in the axial direction.

  In the above description, for convenience, notation in the vertical direction is described according to the drawings. However, the direction of the workpiece can be set in an arbitrary direction, and the friction stir welding tools 10 and 10a are substantially perpendicular to the workpiece. It may be pressed and inserted like this.

  Of course, the friction stir welding method according to the present invention is not limited to the above-described embodiment, and various configurations can be adopted without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10, 10a ... Friction stir welding tool 12, 12a, 14, 14a ... Workpiece 16 ... Cylindrical body 16a ... End surface 18 ... Probe 20, 30 ... 1st thread part 20a, 20b, 22a, 22b ... Screw thread 22, 32 ... Second screw part 24 ... boundary line 26 ... overlapping surface

Claims (3)

First and arranged on the second metal workpiece by a laminated together on a support table, by friction stir welding said first and second word over click by rotating the friction stir welding tool having a probe In the friction stir welding method for joining,
The probe has first and second screw portions that are screwed in opposite directions along the axial direction,
A first step of inserting the probe to a predetermined position while rotating the probe at the time of joining the first and second workpieces to generate plastic flow;
While maintaining the rotation of the probe at the predetermined position to balance the plastic flow caused by the rotation of the first screw portion and the plastic flow caused by the rotation of the second screw portion, the recess is formed in the recess formed on the support base. A friction stir welding method, comprising: a second step of joining the first and second workpieces by flowing in fluidized meat . In the friction stir welding method according to claim 1 ,
Friction stir, characterized in that rotation of said probe at a predetermined position where the boundary coincides with the first and superposed surfaces of the second work with the previous SL said second threaded portion and the first threaded portion is maintained Joining method. In the friction stir welding method according to claim 2,
The first fluid that plastically flows in the first direction by the first screw portion and the second fluid that plastically flows in the direction opposite to the first direction by the second screw portion are the first screw. The friction stir welding method is characterized by joining at a boundary portion between the first screw portion and the second screw portion and pushing out in the outer diameter direction of the probe along the overlapping surface.

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