JP5490076B2 - Friction stir welding method, friction stir weld, and friction stir welding tool - Google Patents

Description

  The present invention relates to a friction stir welding method, a friction stir welded article, and a friction stir welding tool for friction stir welding of an overlapped portion where two workpieces are overlapped.

  In general, friction stir welding is a technique in which two identical or different materials are butted together, and a pin of a friction stir welding tool is inserted between the butted end surfaces while rotating, and the butted end surfaces are joined by friction stirring. In this butt welding, tool insertion / friction stir welding is performed from one side for materials with a thin plate thickness or welding depth, and tool insertion / friction stir welding is similarly performed from the back side for thick materials. Yes. In addition, in the case of superposition, there is what is called friction stir spot welding in which friction stir is performed by inserting and holding a tool like spot welding.

  In the case of joining an overlapped portion in which two workpieces are overlapped by friction stir welding, a tool is inserted and joined from one surface of the overlapped workpieces. In this case, a tool is used in which a shoulder is provided on the end face of the tool body and a pin having a thread formed on the tool rotation axis of the shoulder is provided.

  By the way, when the linear joining is performed continuously while rotating the tool to the overlapped part of two workpieces, it is parallel to either the left or right of the linear joining part depending on the direction of the tool rotation and screw part. As a result, AS (advancing side), which is considered to have a high strength, and RS (retreating side), which has a low strength, are generated. AS is a side where the rotation direction of the tool and the traveling direction of the tool coincide with each other, and RS is a side where the rotation direction of the tool and the traveling direction of the tool are opposite to each other. In RS, the relative speed of rotation of the tool is reduced, resulting in insufficient stirring. As a result, an oxide layer on each material surface at the overlapping interface between the two workpieces remains, resulting in weak joint strength. Therefore, conventionally, a joint portion is provided with a circle or a corner so as to cover the RS, or a portion having inferior strength is overlapped by re-joining the RS generated in the first joining in a direction opposite to the first joining progress direction. Thus, a method for covering a portion having a low bonding strength has been proposed (Patent Document 1). However, in these joining methods, the joining area increases, the joining distance also increases, that is, the processing time is greatly increased, the improvement in productivity is hindered, and the shape of the work material is also secured to secure the joining part area. I had to create constraints.

  Therefore, there has been a friction stir welding method in which AS and RS characteristics do not occur or an equivalent level of joint strength can be obtained, and the tool shape used for the friction stir welding method has been reviewed. If the winding direction of the screw portion and the tool rotation direction are opposite, generally plastic flow occurs downward, and if the winding direction of the screw portion and the tool rotation direction are the same, plastic flow occurs upward. If it is only the latter, the front side plate material, that is, the tool insertion side surface can be restrained by the shoulder, but it causes extra space in the outer peripheral part and the material that should be inside is lost, so it is called a tunnel defect etc. There was a tendency to cause poor bonding. Each of them has a shape having some kind of defect if it is a simple substance, but all have different characteristics. By combining these, a tool shape that covers the defects was researched and developed.

  In view of this, it has been proposed that two workpieces are superposed and joined by generating plastic flow in any of the vertical directions by combining left and right screws in a cylindrical pin (Patent Document 2). In this case, in the plastic flow region around the pin, the direction of the plastic flow is made to flow irregularly and non-uniformly by a plurality of bosses generated in overlapping portions of the left and right screws so as to suppress the movement of the overlapping interface. However, in this Patent Document 2, it is difficult for the plastic flow of the material in the plastic flow region to be sufficiently performed in the plate thickness direction, and it is therefore difficult to join the two workpieces with sufficiently high bonding strength. . Furthermore, since the tip surface of the pin is a simple arc plane, insufficient stirring of the material occurs near the tip of the pin, resulting in insufficient joining.

  Further, in the cylindrical pin, a first screw portion that is a spiral shape of a right-hand screw is provided on the distal end side, and a second screw portion that is a spiral shape of a left-hand screw that is a spiral shape of a left-hand screw is provided on the proximal end side. Has been proposed to perform friction stir welding with the boundary portion of the first and second screw portions aligned with the overlapping interface of the two workpieces (Patent Document 3). In this case, in the plastic flow region around the pin, the first screw portion includes the first fluid that plastically flows upward by the first screw portion and the second fluid that plastically flows downward by the second screw portion. And the second screw portion are joined together and extruded along the overlap interface in the outer diameter direction so that the overlap interface portion is intensively stirred. However, in this patent document 3, it is a tool shape suitable for spot friction stir welding to the last. If the rotation is performed at one point, the upward plastic flow to be generated in the back side plate portion can be sufficiently performed. However, if the lateral movement, that is, continuous joining in a linear form is performed, the upward plastic flow is not improved. It tends to be sufficient, and the extrusion in the outer direction that can be realized at the time of spotting becomes insufficient, and the bonding strength cannot be improved. Furthermore, also in spot friction stir welding, the overlapping interface is moved up and down by the fluid extruded to the overlapping interface in the outer periphery of the plastic flow region, and the upper and lower workpieces are both thinned to increase the bonding height. There was a possibility that high bonding strength could not be obtained due to the decrease in size. Furthermore, since the pin tip surface is a simple flat surface, insufficient stirring of the material occurs near the pin tip, resulting in insufficient joining.

JP 2010-137274 A Special Table 2002-514512 JP 2005-205423 A

The present invention has been made in view of the above circumstances, and when the overlapping portions of two workpieces are subjected to friction stir welding, the materials are sufficiently stirred and overlapped at the outer peripheral portion of the plastic flow region. It is an object of the present invention to provide a friction stir welding method capable of suppressing the movement of the mating interface and performing bonding with high bonding strength.
Another object of the present invention is to provide a friction stir welded product that has been joined with high joining strength by the friction stir welding method.
Moreover, the objective of this invention provides the friction stir welding tool for implement | achieving the said friction stir welding method.

The friction stir welding method according to the present invention is:
A friction stir welding tool provided with a pin on the shoulder portion of the tool body is pressed against the overlapped portion where the two workpieces are overlapped from the surface of the workpiece on the front side while rotating, in the two workpieces In the friction stir welding method for friction stir welding the two workpieces by generating a plastic flow zone and relatively moving the friction stir welding tool along the overlapping portion,
The friction stir welding tool has a large-diameter shoulder provided on the end surface of the rotated tool body, and a small-diameter pin projecting on the tool rotation axis of the shoulder,
The pin has a cylindrical pin base end portion in which a screw portion is formed, and a taper portion formed in a tapered shape from the pin base end portion toward the pin tip end, and is wound in a direction opposite to the screw portion. With a pin tip formed with a spiral groove in the entire area,
The pin tip portion is further configured by a flat portion whose tip portion is parallel to the pin radial direction, and the spiral groove is continuously formed from the tapered portion to the entire flat portion,
During the friction stir welding, while rotating the friction stir welding tool in the direction opposite to the winding direction of the screw portion of the pin, the shoulder is pressed in parallel to the surface of the workpiece on the front side to place the pin into the two workpieces At this time, the taper part of the tip of the pin is arranged at the overlapping interface of the two workpieces,
As the plastic flow region, all of the cylindrical pin base end portions on which the screw portions are formed are arranged in the workpiece on the front side, and the screw portion does not include the overlapping interface of the two workpieces. A first plastic flow region is formed in which a convection in the plate thickness direction is convected with respect to the work material, and a part of the tapered portion of the pin tip portion where the spiral groove is formed is inserted into the work material on the back side. Then, the first plastic flow region in an oblique direction inclined from the plate thickness direction with respect to the overlapping interface and the workpiece on the back side along the tapered portion and the flat portion of the pin tip by the spiral groove. Generates a second plastic flow region that causes plastic flow by convection in the opposite direction, thereby suppressing the movement of the overlapping interface in the plate thickness direction at the outer periphery of the plastic flow region, and Friction stir welding.

In the friction stir welding method,
The shoulder portion has a plane parallel to the radial direction of the tool body, the concave portion is not open to the side surface of the tool body is formed and extends from protruded portion of the pin to the vicinity of the outer diameter of the shoulder portion,
It is preferable that the material on the surface of the workpiece on the front side pressing the shoulder is guided to the center side by the recess as the tool rotates.

In the friction stir welding method,
A pin having a tapered part in which the entire cylindrical pin base end part in which the thread part is formed is inserted into the work piece on the front side in a range of 70% to 95% of the plate thickness and the spiral groove is formed. It is desirable to insert a part of the front end portion into the back side workpiece at a depth of 20% to 70% of the thickness of the front side workpiece plate.

In the friction stir welding method,
And in the final joint joining line terminating the friction stir welding tool are relatively moved along said overlapping portions, by moving the friction stir welding tool so as to surround the tool withdrawing position, about the pin hole of the tool withdrawing position It is desirable to form the joint portion so as to compensate for the above. In this case, it includes various methods such as moving the tool around the pin hole once, moving it in a partial arc shape, or moving it in the direction opposite to the traveling direction.

In the friction stir welding method,
It is desirable to friction stir welding by said friction stir welding tool projecting from the shoulder by tilting the said pin relative to the tool axis of rotation.

In the friction stir welding method,
Bonding defects that are likely to occur around the pin hole at the tool pulling position in the final joint, by cutting through or not including the workpiece on the back side in the form of cutting out the agitated part around the pin hole at the tool pulling position It is desirable to remove.

In the friction stir welding method,
Two plate materials can be arranged on the left and right sides as the work material on the front side and butt, and can be overlapped and joined to the work material on the back side along the butt portion.

A friction stir welded product having a joint obtained by friction stir welding of an overlapped portion obtained by superimposing two work materials by the friction stir welding method is provided on the outer periphery of the joint. It has a cross-sectional shape in which fluctuations in the thickness direction of the overlapping interface are suppressed.
Further, the friction stir welded article can be a vehicle wheel including a joint portion obtained by friction stir welding an overlapping portion in which a rim portion and a disk portion are overlapped. In the case of this vehicle wheel, the non-through hole formed at the tool extraction position is filled with a sealing material such as pressure-resistant silicone resin to prevent air leakage. A configuration in which the hole is a valve hole can be employed.

On the other hand, the friction stir welding tool according to the present invention is
In a friction stir welding tool that friction stir welds an overlapped portion where two workpieces are overlapped,
A shoulder with a large diameter provided on the end surface of the rotated tool body and holding the surface of the workpiece on the front side;
A small-diameter pin that is inclined with respect to the tool rotation axis and protrudes from the shoulder to be inserted into two workpieces;
The pin is
A cylindrical pin base end set to a length of 70% to 95% of the workpiece thickness on the front side;
It is composed of a pin tip to the pin base end flat portion a and the tip portion has a tapered portion formed on the tapered toward the pin tip is formed by a pin radially and parallel to the plane of section, further ,
The pin base end portion is formed with a screw portion whose winding direction is opposite to the tool rotation direction during friction stir welding over the entire length,
Wherein the pin tip is formed continuously said threaded portion and opposite direction of the winding direction and became spiral groove over the entire area of the flat portion from the tapered portion.

In the friction stir welding tool,
It is desirable that the taper angle of the tapered portion is set to 60 degrees or more and 120 degrees or less.

  According to the present invention, when the overlapping portions of two workpieces are subjected to friction stir welding, the materials are sufficiently stirred and the movement of the overlapping interface in the outer peripheral portion of the plastic flow region is suppressed. Bonding with high strength is realized. Therefore, it is possible to prevent breakage starting from the overlapping interface at the joint. In addition, the RS (retreating side) at the linear joint can achieve substantially the same joint strength as the AS (advancing side).

It is a side view which shows the friction stir welding tool by embodiment. It is a bottom view which shows the state which looked at the friction stir welding tool by embodiment from the front end side. It is sectional drawing which shows the state which inserted the friction stir welding tool by embodiment into the workpiece. It is sectional drawing which shows the state which inserted the friction stir welding tool by embodiment into a workpiece, and the plastic flow of material generate | occur | produced. It is an expanded sectional view of a plastic flow area. It is sectional drawing which shows typically the cross-sectional shape of the junction part which carried out friction stir welding. FIG. 3 is a cross-sectional view showing a state in which a rim and a disk are friction stir welded in a vehicle wheel. In a vehicle wheel, it is a front view which shows the site | part which carries out friction stir welding of the window part outer side or spoke part outer side of a disk. FIG. 3 is a side view showing a joint portion obtained by friction stir welding of a rim and a disk in a vehicle wheel. FIG. 6 is a side view showing another example of a joint portion obtained by friction stir welding of a rim and a disk in a vehicle wheel. It is a side view which shows what formed the shoulder part only by the plane as a modification of a friction stir welding tool. It is a side view which shows what provided only the pin inclining as a modification of a friction stir welding tool. As a modification of the friction stir welding tool, FIG. 2 is a side view showing the one shown in FIG. 1 and the screw portion and spiral groove in opposite directions. As a modification of the friction stir welding tool, FIG. 2 is a bottom view showing a state in which the screw of FIG. 1 and the spiral of the screw portion and the spiral groove are reversed from the tip side.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIGS. 1, 2, and 3, the friction stir welding tool 1 according to the embodiment is mounted on a rotation drive device (not shown) and rotated, while being rotated, the two workpieces 61 stacked one above the other. , 62 is pressed against the superposed portion 61 from the surface of the upper workpiece 61 and friction stir welds the superposed portion. This friction stir welding tool (hereinafter referred to as “tool” as appropriate) 1 is formed of a heat-resistant material that is harder than the workpieces 61 and 62 to be joined and can withstand the frictional heat at the time of joining. For example, when the workpieces 61 and 62 are aluminum, magnesium, or an alloy thereof, the tool 1 can be made of a steel material such as SKD.

  The friction stir welding tool 1 is provided on the end surface of a rotating columnar tool body 2 and presses the upper surface (front side) of the workpiece 61 between the two workpieces 61 and 62 that are vertically stacked. A large-diameter shoulder portion 21 and a small-diameter pin 3 protruding straight on the tool rotation axis of the shoulder portion 21 and inserted into the upper and lower workpieces 61 and 62 are provided.

  The shoulder 21 is constituted by a plane 23 parallel to the radial direction of the tool body 2 (see FIG. 2). Thereby, at the time of friction stir welding, the shoulder portion 21 is pressed against the surface of the upper workpiece 61 in a parallel posture, thereby suppressing the lifting of the material accompanying the friction stir and the shoulder portion 21 is brought into contact. It is possible to make the contact surface of the workpiece 61 to be a uniform surface state.

  Further, the shoulder portion 21 is formed with a slit 24 that extends from the projecting portion of the pin 3 to the vicinity of the outer diameter of the shoulder portion 21 on the flat surface 23 and does not open to the side surface of the tool body 2 (see FIG. 2). A plurality of slits 24 are formed extending radially, but the slit 24 is not limited to this, and may be a concave portion such as a continuous spiral groove. By the way, when the material raised on the surface of the work material 61 during the friction stir welding is released to the outside of the shoulder portion by the centrifugal force of the rotation of the friction stir welding tool, a burr is generated and a lack of material due to the released material occurs. The surface condition may be deteriorated. On the other hand, by forming the slits 24 in the shoulder portions 21, each slit 24 is not formed at the outer edge portion of the shoulder portion 21 but is closed at the outer end portion, so that the outer end portion where the slit 24 is closed. Thus, the material that flows outwardly by the centrifugal force of the rotation of the tool 1 can be stopped so that it is not discharged to the outside of the shoulder portion 21. In addition, each slit 24 can level the surface of the workpiece 61 while scraping off the material raised on the surface of the workpiece 61. Therefore, it is possible to suppress the generation of burrs and make the surface state of the workpiece 61 uniform in the joint portion.

  The plurality of radially extending slits 24 are formed so that the outwardly extending direction is inclined toward the tool rotation direction. In this case, the slit 24 may be formed in a curved shape so that the direction extending outward is directed toward the tool rotation direction. As a result, a force that guides the material that has entered the slit 24 toward the center portion with the rotation of the tool 1 acts. Therefore, the material floating on the surface of the workpiece 61 can be pushed back into the workpiece 61 and the plastic flow of the material can be actively performed.

  An outer peripheral portion 22 of the shoulder portion 21 (a portion where the shoulder portion 21 and the side surface of the tool body 2 are continuous) is formed in an R shape. If the outer peripheral portion 22 of the shoulder portion 21 has a corner, the material surface can be scooped at this corner and a burr can be generated like a cutting tool such as an end mill. On the other hand, by forming the outer peripheral portion 22 of the shoulder portion 21 in an R shape, it is possible to prevent the phenomenon of scooping up the material surface at the outer peripheral portion 22 of the shoulder portion 21 and suppress the generation of burrs.

  The pin 3 is a portion that penetrates the upper (front side) workpiece 61 and is inserted shallowly into the lower (back side) workpiece 62, and includes a cylindrical pin base end portion 3a and a tapered portion. 31 and a pin tip portion 3b having a flat surface portion 32.

  On the outer peripheral surface of the pin base end portion 3a, a screw portion 4 is formed over the entire length. The spiral winding direction of the screw portion 4 is opposite to the rotation direction of the tool 1 at the time of friction stir welding defined by the rotary drive device on which the tool 1 is mounted. That is, this tool 1 is used by rotating it in the direction opposite to the winding direction of the screw portion 4 by a rotational drive device at the time of friction stir welding. The tool 1 shown in FIGS. 1 and 2 is rotated clockwise (rotation direction S1) when viewed from above the tool 1 (the base end side of the tool body 2) by a rotary drive device, and the screw portion 4 is spirally wound. The direction is formed in a counterclockwise direction (left-hand thread) from the base end to the tip end of the pin 3.

  The tapered portion 31 is formed in a tapered shape from the pin base end portion 3a to the pin tip. A taper angle α (see FIG. 3) of the taper portion 31 is set within a range of 60 degrees to 120 degrees. By setting the taper angle α to 60 ° or more, chipping or pin breakage due to excessive standing of the taper portion 31 can be prevented, and by setting the taper angle α to be within 120 °, the necessary taper portion 31 is required. The axial length can be easily secured. Further, the flat portion 32 at the tip of the pin is formed by a surface parallel to the pin radial direction. The diameter W2 of the flat portion 32 is set to about 50% of the shaft diameter W1 of the pin base end portion 3a (see FIG. 1).

  A spiral groove 5 starting from the center point of the flat portion 32 is continuously formed from the taper portion 31 to the entire flat portion 32 (see FIG. 2). The spiral groove 5 is formed such that the winding direction from the tapered portion 31 side (the outer peripheral side of the spiral groove 5) toward the center of the flat portion 32 (the center of the spiral groove 5) is opposite to the screw portion 4 (clockwise). . That is, the winding direction of the spiral groove 5 is the same direction as the rotation direction S1 of the tool 1 at the time of friction stir welding defined by the rotary drive device on which the tool 1 is mounted. In the tool 1 shown in FIGS. 1 to 3, the spiral winding direction of the screw portion 4 is counterclockwise (left screw) when viewed from the top of the tool 1, so that the spiral groove 5 extending from the tapered portion 31 to the flat portion 32 is formed. The winding direction is formed in the clockwise direction when viewed from above the tool 1. 2 is a view seen from the bottom of the tool 1 on the pin tip side, the winding direction of the spiral groove 5 is shown counterclockwise from the outer peripheral side toward the center, and the rotation direction of the tool 1 S1 is also shown in the counterclockwise direction.

  The total length of the pin 3 is set to a length at which the tapered portion 31 is disposed at the overlapping interface 60 between the upper and lower workpieces 61 and 62 when the pin 3 is inserted into the upper and lower workpieces 61 and 62. (See FIG. 3). In this case, the vertical positional relationship of the tapered portion 31 with respect to the overlapping interface 60 can be set to an arbitrary position as long as the tapered portion 31 is disposed on the overlapping interface 60. That is, the length L1 of the pin base end portion 3a in which the screw portion 4 on the pin base end side is formed is set to a length shorter than the plate thickness t1 of the upper workpiece 61 on the pin insertion side (FIG. 3). Specifically, the length is set to 70% to 95% of the upper workpiece 61 thickness t1. Further, the axial length L2 of the taper portion 31 on the pin tip side is 20% to 70% of the plate thickness of the upper workpiece 61 when the insertion length L3 into the lower workpiece 62 is at the time of friction stir welding. % Is set so as to ensure the length (see FIGS. 1 and 3). In this case, the pin tip 3b is set within a range not penetrating the lower workpiece 62. In addition, it is preferable that the full length (L1 + L2) of the pin 3 is below the shaft diameter W1 of the pin base end part 3a, and thereby, breakage of the pin 3 at the time of friction stir welding can be suppressed.

  On the other hand, during the friction stir welding, the shoulder portion 21 of the tool 1 presses the surface of the upper workpiece 61 so that no gap is formed at the overlapping interface 60 between the upper and lower workpieces 61 and 62. Therefore, the shoulder portion 21 is buried at a certain depth from the surface of the upper workpiece 61. The burying amount L4 of the shoulder portion 21 is set to 1% to 20% of the upper workpiece 61 plate thickness t1 (see FIG. 3), but the tapered portion 31 of the pin 3 has upper and lower workpieces 61, 20% to 70% of the thickness of the upper workpiece 61 as an insertion length L3 in which the tapered portion 31 is inserted into the lower workpiece 62 within a range where the taper portion 31 is disposed in the overlapping interface 60 of 62. It is limited within the range.

  For example, when the length L1 of the pin base end portion 3a in which the screw portion 4 of the pin 3 is formed is 95% of the upper workpiece 61 plate thickness t1, the burying amount L4 of the shoulder portion 21 is When the workpiece 61 is limited to 1% or more and less than 5% of the plate thickness t1, and the length L1 of the pin base end portion 3a is 70% of the upper workpiece 61 plate thickness t1, the shoulder portion 21 is limited to 1% or more and 20% or less of the upper workpiece 61 plate thickness t1. The insertion depth of the pin 3 is such that the lower end position of the pin base end portion 3a (the boundary position between the pin base end portion 3a and the taper portion 31) on which the screw portion 4 is formed from the surface of the upper workpiece 61. The position is preferably 80% to 95% of the plate thickness t1. Further, the amount of burying L4 of the shoulder portion 21 is an insertion length at which the tapered portion 31 is inserted into the lower workpiece 62 in addition to the limitation due to the relationship with the length L1 of the pin base end portion 3a. The length L3 is limited within the range of 20% to 70% of the thickness of the upper workpiece 61 without depending on the thickness 62 of the lower workpiece 62.

  Further, the pin 3 is provided so that the shaft portion 30 connected to the pin base end portion 3 a is press-fitted into a hole portion provided in the shoulder portion 21 and can be detached from the shoulder portion 21. Accordingly, the pin 3 having an appropriate pin length (L1 + L2) can be mounted and used according to the plate thickness t1, t2 of the two workpieces 61, 62 to be joined. Further, when the screw portion 4 of the pin 3 is worn or the pin 3 is broken, only the pin 3 can be replaced and reused. Accordingly, it is possible to prevent a change / decrease in bonding strength due to wear of the pins 3. In addition to the configuration in which the shaft portion 30 is press-fitted into the shoulder portion 21, the pin 3 may be provided with a tapped hole in the shoulder portion 21 to screw the shaft portion 30, or the hole portion of the shoulder portion 21. The shaft portion 30 inserted into the shoulder portion 21 can be attached to and detached from the shoulder portion 21 by various fixing means such as bolting from a screw hole provided on the side surface of the tool body 2. Further, the pin 3 may be integrally formed with the shoulder portion 21 without being detachable from the shoulder portion 21 as described above.

  Next, a method of friction stir welding the two overlapped workpieces 61 and 62 at the overlapping portion using the friction stir welding tool 1 having the above-described configuration will be described with reference to FIGS. explain. The friction stir welding tool 1 is mounted on a rotation drive device (not shown) and rotated in one direction and can be moved up and down.

  Then, while rotating the tool 1 as the rotation direction S1 in the direction opposite to the winding direction of the screw portion 4 of the pin 3 (clockwise), the pin 3 is caused to penetrate the workpiece 61 from the surface of the upper workpiece 61. Then, the shoulder 21 is pressed in parallel with the surface of the upper workpiece 61 in a manner straddling the upper and lower workpieces 61, 62, and a predetermined burying amount L4 (upper workpiece 61 plate thickness t1). 1% to 20% deep). Thereafter, when the tool 1 is moved along the overlapping portion, the overlapping portion of the two workpieces 61 and 62 is overlapped and joined by friction stir along the joining line (tool movement trajectory) of the tool 1. In addition, as joining conditions, for example, the tool rotation is set to 2000 to 3000 rpm, and the advance speed is set to 500 to 1000 mm / min. Further, the tool 1 moves the shoulder portion 21 in parallel with the surface of the workpiece 61 without providing an advance angle. In addition, in the friction stir welding operation, the joining operation is performed while cooling by cooling a coolant such as water or cooling air from the front side or the back side of the overlapped workpieces 61 and 62 toward the joint. May be.

  By the above-described tool insertion operation, as shown in FIG. 3, the pin 3 has the entire pin base end portion 3 a forming the pin base end screw portion 4 embedded in the upper workpiece 61, The tip end portion of the taper portion 31 on the tip end side of the pin has a predetermined insertion depth L3 in the lower workpiece 62 (not affected by the plate thickness of the lower workpiece 62, the upper workpiece 61 plate). The taper portion 31 is disposed at the overlapping interface 60 between the upper and lower workpieces 61 and 62, with a depth of 20% to 70% of the thickness t1). As a result, the workpieces 61 and 62 around the pin 3 are heated and softened by frictional heat generated by the rotation of the pin 3 to generate a plastic flow region 7 in which plastic flow occurs.

  Specifically, referring to FIG. 4 and FIG. 5, the softened upper workpiece 61 around the pin base end portion 3 a is lowered around the screw portion 4 toward the plate thickness direction. A first plastic flow region 71 is generated that plastically flows by convection (A1) so as to rise outside. At this time, the material that has risen on the surface of the workpiece 61 is forcibly guided toward the center by the plurality of slits 24 of the shoulder 21 and is pushed back downward by the shoulder 21. As a result, the convection phenomenon of A1 is satisfactorily performed, the plastic flow in the first plastic flow region 71 is actively performed, and the stirring of the material is enhanced.

  On the other hand, with respect to the upper and lower workpieces 61 and 62 softened including the overlapping interface 60 around the taper portion 31 and the flat portion 32, the spiral groove is directed in an oblique direction inclined from the plate thickness direction. A second plastic flow region 72 is generated which flows by convection (A2) so as to rise around 5 and to fall outside. The direction of convection (A2) in the second plastic flow region 72 is opposite to the direction of convection (A1) in the first plastic flow region 71. In the second plastic flow region 72, since the taper portion 31 has a smaller shaft diameter toward the tip, the peripheral speed of the taper portion 31 due to the tool rotation is the cylindrical pin base on which the screw portion 4 is formed. The speed is lower than the peripheral speed of the end 3a. Therefore, the plastic flow in the second plastic flow region 72 is considered to be lower than that in the first plastic flow region 71.

  As described above, the first plastic flow region 71 and the second plastic flow region 72 in the plastic flow region 7 have the directions of the convections (A1) and (A2) of the respective plastic flows opposite to each other. It is considered that the plastic flow at the boundary portion P (see FIG. 5) between the flow region 71 and the second plastic flow region 72 is suppressed. Accordingly, the movement of the work materials 61 and 62 in the periphery (B) of the boundary portion P at the outer peripheral portion of the plastic flow region 7 is suppressed. The boundary portion P corresponds to the boundary between the pin base end portion 3a and the pin tip end portion 3b, and is close to the overlapping interface 60 between the two workpieces 61 and 62 (from the overlapping interface in the upper workpiece 61). Therefore, the movement of the overlapping interface 60b in the outer peripheral portion of the plastic flow region 7 is suppressed.

  Further, even if the force of colliding each other's plastic flow acts at the boundary portion P between the first plastic flow region 71 and the second plastic flow region 72, the boundary portion P is located slightly off the overlap interface 60. Therefore, the intrusion of the colliding material into the overlapping interface 60 is prevented. Further, the plastic flow in the second plastic flow region 72 with respect to the overlapping interface 60 and the lower workpiece 62 occurs in an oblique direction inclined from the plate thickness direction. These also suppress the movement of the overlapping interface 60b in the plate thickness direction in the outer peripheral portion of the plastic flow region 7.

  Therefore, as shown in FIG. 6, the friction stir welded product has a cross-sectional shape in which the movement of the overlapping interface 60 b in the outer peripheral portion of the joint portion J in the thickness direction is hardly seen. As a result of the above, friction stir of the material around the pin 3 can be sufficiently performed, and the movement of the overlapping interface 60b in the outer peripheral portion of the plastic flow region 7 can be suppressed. Can be realized.

  Further, since the tapered portion 31 on the tip side is disposed at the overlapping interface 60 between the two workpieces 61 and 62, the oxide layer 60 a of the overlapping interface 60 is slanted of the softening material around the tapered portion 31. Along with the upward plastic flow, it is pushed upward in the workpiece thickness direction (see FIG. 4). The oxide layer 60a is well dispersed by the plastic flow of the softening material that convects up and down. As a result, the remaining of the oxide layer 60a at the overlapping interface 60 is suppressed, so that the remaining oxide layer 60a is prevented from being broken and the bonding strength can be improved. When the rotating friction stir welding tool 1 is translated in the lateral direction with respect to the workpiece and joined linearly, the oxide layer 60a remains even in the RS (retreating side). Suppressed, it is possible to obtain a bonding strength substantially equivalent to AS (advancing side). Here, RS is a side where the rotation direction of the tool 1 and the traveling direction of the tool 1 are opposite to each other, and the relative speed of rotation becomes small and the stirring tends to be insufficient. AS is a side where the rotation direction of the tool 1 and the traveling direction of the tool 1 coincide with each other, and a good relative stirring speed is achieved.

  In addition, since the tip of the pin is a flat portion 32, the pressing pressure of the tool 1 is less concentrated locally on the tip of the pin than when the tip of the pin is sharpened. Deformation on the back surface of the workpiece 62 can be prevented. In addition, the insertion depth of the pin 3 into the lower workpiece 62 can be reduced, and the thermal influence on the back surface of the lower workpiece 62 can be suppressed. Then, the softened lower workpiece 62 around the flat portion 32 is plastically flowed outward (laterally) along the flat portion 32 by the spiral groove 5 of the flat portion 32, and the downward plastic flow is generated. It is suppressed. Therefore, even if the workpiece is a thin plate (including the case where the thickness of the lower workpiece 62 is thinner than the thickness of the upper workpiece 61), the back surface of the lower workpiece 62 is included. Deformation and heat effects can be prevented.

  As described above, the softened material in the overlapped portion where the two workpieces 61 and 62 are overlapped is plastically flowed up and down so as to convect and is well stirred, and the oxide layer 60a at the overlap interface 60 is favorable. And the remaining oxide layer 60a is suppressed. Therefore, it is possible to obtain a good bond without causing a tunnel-like defect in the bonded portion, and to prevent the remaining oxide layer 60a from being broken as a starting point, thereby improving the bonding strength. Moreover, when joined in a linear form, even if it is RS (retreating side), the remaining oxide layer 60a is suppressed, and a joining strength substantially equivalent to that of AS (advancing side) can be obtained. Furthermore, deformation of the back surface of the lower workpiece 62 and thermal effects can be prevented, and the back side of the joint can be in a good surface state.

  Incidentally, by using the friction stir welding method (FIGS. 3 and 4) of the embodiment described above using the friction stir welding tool 1 having the configuration of the embodiment shown in FIGS. When a bending test was performed on a joining sample of a joining material in which the overlapped portion was linearly friction stir welded, a conventional tool (a screw in the direction opposite to the pin rotation direction was formed on a cylindrical pin) It was confirmed that no breakage occurred from the overlapping interface 60 as occurred at the RS of the joint part. Moreover, when the back surface (surface on the opposite side of tool insertion) of the said joining sample was visually observed, it was also confirmed that there was no deformation | transformation and the burning by a heat influence, etc., and it was a beautiful surface state almost unchanged before joining. Furthermore, it was also confirmed that the bonding surface state on the surface of the bonding sample (surface on the tool insertion side) had no burrs and was a uniform surface state. In the joined sample (friction stir welded product), it was also confirmed that the cross-sectional shape of the joint J was suppressed from moving the overlapping interface 60b at the outer periphery of the joint J as shown in FIG.

  By the way, if the friction stir welding is performed in a linear shape, a pin hole remains at the tool drawing position at the final joint at the end of the joint line. Therefore, the pin hole part of the final joint part has a joint cross-sectional area that is not only the cross-sectional area of the pin is lost compared to other joint parts, but there is no lateral tool or material movement, and it depends only on the tool rotation under a fixed point stop. For this reason, a large variation in conditions is caused from the continuous bonding, so that bonding defects are likely to occur. For this reason, since joint strength can fall, this pin hole can become a starting point of fatigue fracture of a joined part.

Therefore, before the tool 1 is pulled out, the tool 1 is drawn around the tool pulling position continuously around the tool pulling position before the tool 1 is pulled out, and then the tool 1 is pulled out. Then, a joint portion is formed around the pin hole at the tool extraction position (see FIG. 9. In FIG. 9, J represents the joint portion, h represents the pin hole, and e represents the final joint portion). As a result, the area of the joint portion is formed widely around the pin hole of the final joint portion, so that the lack of joint strength due to the pin hole dropout is reinforced, and fatigue failure of the joint portion starting from the pin hole can be prevented. it can. When the final joint e is formed so as to supplement the periphery of the pin hole at such a tool extraction position, in addition to moving the tool 1 around the pin hole h once, the tool 1 may be moved in a partial arc shape. Various methods such as parallel movement in the direction opposite to the traveling direction are included.
Regardless of whether this is used together or not, the friction stir affected part formed around the pin hole in the final joint part is cut out regardless of whether the lower workpiece 62 is penetrated or not penetrated. Thus, it may be possible to prevent a breakage starting point by removing a defective portion that is likely to occur in the final joint.

(Application example for vehicle wheels)
In the friction stir welding method and the friction stir welding tool 1 described above, in a vehicle wheel, a disk-shaped disc is fitted to the inner peripheral portion of a cylindrical rim, and the overlapping portion of the rim and the disc is friction stir welded. It can be applied when manufacturing a vehicle wheel. In this case, as shown in FIG. 7, in the overlapping portion T of the rim 8 and the disk 9, the pin 3 is inserted from the outer peripheral surface of the rim 8 while rotating the friction stir tool 1, and the pin 3 penetrates the rim 8. Then, the disc 9 is inserted so as to reach the outer peripheral portion of the disk 9 and the shoulder portion 21 is pressed substantially parallel to the outer peripheral surface of the rim 8. At this time, as described above, the taper portion 31 of the pin 3 is set to a height at which it is disposed at the overlapping interface (60) between the rim 8 and the disk 9. Then, the friction stir welding tool 1 is relatively moved in the circumferential direction of the rim 8, and the overlapping portion of the rim 8 and the disk 9 is friction stir welded (see FIG. 9).

  For example, as shown in FIG. 8A, this friction stir welding operation may be performed only on the outer peripheral portion J2 of each spoke portion 92 of the disk 9, or each window portion 91 of the disk 9 may be operated. It may be performed only on the outer peripheral portion J1, or may be performed on the entire circumference of the disk 9. As shown in FIG. 8B, in the case where the outer peripheral portion of the window portion 91 is not formed as the disk 9 and only the outer peripheral portion J2 of the spoke portion 92 is in contact with the inner peripheral surface of the rim 8, The friction stir welding may be performed at the position of the outer peripheral portion J2 of 92.

Further, in the final joint at the end of the joint line, in order to prevent fatigue fracture of the joint starting from the pin hole, as shown in FIG. 9, the tool is preceded by the tool 1 before the tool 1 is pulled out at the final joint e. The tool 1 is withdrawn after the tool 1 is continuously rotated around the tool extraction position so as to surround the extraction position (for example, moved in a circular arc shape, parallel movement in the direction opposite to the tool traveling direction). Thus, the final joint e may be formed so as to supplement the periphery of the pin hole h at the tool extraction position. Furthermore, in any of the methods of reinforcing or not reinforcing the periphery of the pin hole h, the disk side member that serves as the lower plate member is applied to the friction stir affected portion formed around the pin hole h of the final joint portion. It is also effective to remove the friction stir defect that is likely to occur at the tool extraction position by cutting regardless of whether it is penetrated or not penetrated.
In addition, it is preferable to fill the pin hole h with a sealing material such as a pressure-resistant silicone resin. In that case, the sealing material can surely prevent the tire from leaking air from the pin hole h portion. . Further, when a through hole is provided, the through hole can be used as an air valve hole.

According to the friction stir welding described above, it is possible to increase the joint strength of the joint portion between the rim 8 and the disk 9 and to avoid deterioration due to high-temperature heat effects unlike the case of welding. Accordingly, a vehicle wheel having high bonding strength between the rim 8 and the disk 9 and excellent quality can be obtained.
In the friction stir welding operation, the cooling operation is performed by spraying a coolant such as water or cooling air from the outer peripheral surface side or the inner peripheral surface side of the rim 8 toward the joints (J1) and (J2). May be performed. In this case, since the thermal influence on the disk 9 can be reliably prevented, the coating film of the disk 9 and the disk surface can be prevented from being burned or discolored, and a high-quality vehicle wheel can be obtained.

  In addition, when performing cylindrical joining by continuously making a round of the tool 1 in the circumferential direction with respect to the cylindrical object including the vehicle wheel, the start point and the end point of the movement of the tool 1 are set to the same position, or the end point May be slightly overlapped from the starting point (see FIG. 10A). In this case, a wide bonding area can be secured at the final bonding portion, and a high bonding strength can be ensured. Note that an end point of the tool movement may be provided near the movement start point of the tool 1 so that the start point and the end point do not overlap (see FIG. 10B).

  Further, in the vehicle wheel, when the tool 1 is made to make one round continuously in the circumferential direction of the rim 8 and the overlapping portion of the rim 8 and the disk 9 is joined, the pin hole h at the tool extraction position of the final joint e. On the other hand, a through hole larger than the pin hole h may be provided, and this through hole may be used as an air valve hole of a tire to be attached to the rim 8. As a result, the pin hole h of the final joint e can be eliminated to prevent fatigue failure of the joint J starting from the pin hole h, and the pin hole h can be effectively used as an air valve hole for vehicles. A wheel can be manufactured efficiently.

In addition, this invention is not limited only to the said embodiment, In the range of the summary of this invention, it can change suitably.
In the present invention, two plate members may be arranged on the left and right sides as the workpiece 61 on the front side and butt, and overlapped and joined to the workpiece 62 on the back side along the butt portion. That is, on the back side work material 62, by placing two plate materials as a work material 61 on the front side, but by relatively moving the tool 1 along a butt portion where the two plate materials are butted, The two workpieces 61 of the front side plate material are butt-joined and overlapped with the workpiece 62 on the back side at the same time.
As shown in FIG. 11, the shoulder 21 of the friction stir welding tool 1 </ b> A may be only the flat surface 23 without forming a recess such as the slit 24.

  Also, as shown in FIG. 12, the pin 3 of the friction stir welding tool 1B may be inclined from the tool rotation axis at a predetermined inclination angle C and protruded from the shoulder portion 21. Thereby, stirring of the material of the plastic flow region 7 can be further increased, and the bonding strength can be further increased. In other words, if the tool is given a forward angle during friction stir welding, the rear side of the tool in the direction of travel of the tool will float and the surface of the workpiece will not be pressed sufficiently, and plastic flow (first plastic flow region 71) due to material convection will be suppressed. Can be done. On the other hand, since only the pin 3 is provided to be inclined with respect to the shoulder portion 21, the tool 1 can be advanced with the shoulder portion 21 parallel to the surface of the workpiece, so that the entire surface of the shoulder portion 21 is provided. Friction stirring can be enhanced by pressing the surface of the workpiece and actively performing plastic flow (first plastic flow region 71) by convection of the material. In this case, for example, the inclination angle C of the pin 3 is preferably set to be greater than 0 degree and less than or equal to 10 degrees with respect to the tool rotation axis, but is not limited thereto and can be inclined more than 10 degrees. It is. Thereby, the pin insertion to a workpiece can be performed without trouble, and the load increase to the pin 3 at the time of a tool advance can be suppressed, and the breakage of the pin 3 can be prevented. As in the case where the advance angle is given, the effect of increasing the agitation of the material can be surely obtained by increasing the pin inclination angle C.

  Moreover, although the friction stir welding tool 1 of the said embodiment was demonstrated as what is rotated clockwise (rotation direction S1) by a rotation drive device, when rotating counterclockwise (rotation direction S2), FIG. 13, as the friction stir welding tool 1C, the spiral winding direction of the screw portion 4 of the pin base end portion 3a of the pin 3 is formed in the clockwise direction (right screw) when viewed from above the tool 1C. The winding direction of the spiral groove 5 from the tapered portion 31 to the flat portion 32 of the pin 3 is assumed to be counterclockwise.

DESCRIPTION OF SYMBOLS 1 Friction stir welding tool 2 Tool main body 3 Pin 3a Pin base end part 3b Pin front end part 4 Screw part 5 Spiral groove 7 Plastic flow area 8 Rim 9 Disc 21 Shoulder part 22 Outer peripheral part 23 of shoulder part 21 Plane 24 of shoulder part 21 Slit (concave)
30 Shaft portion 31 Tapered portion 32 Plane portion 60 Overlap interface 60a Oxide layer 60b Overlap interface 61 at the outer periphery of the plastic flow region Upper workpiece (front side)
62 Lower workpiece (back side)
71 First plastic flow region 72 Second plastic flow region α Taper angle C Pin inclination angle

Claims (12)

A friction stir welding tool provided with a pin on the shoulder portion of the tool body is pressed against the overlapped portion where the two workpieces are overlapped from the surface of the workpiece on the front side while rotating, in the two workpieces In the friction stir welding method for friction stir welding the two workpieces by generating a plastic flow zone and relatively moving the friction stir welding tool along the overlapping portion,
The friction stir welding tool has a large-diameter shoulder provided on the end surface of the rotated tool body, and a small-diameter pin projecting on the tool rotation axis of the shoulder,
The pin has a cylindrical pin base end portion in which a screw portion is formed, and a taper portion formed in a tapered shape from the pin base end portion toward the pin tip end, and is wound in a direction opposite to the screw portion. With a pin tip formed with a spiral groove in the entire area,
The pin tip portion is further configured by a flat portion whose tip portion is parallel to the pin radial direction, and the spiral groove is continuously formed from the tapered portion to the entire flat portion,
During the friction stir welding, while rotating the friction stir welding tool in the direction opposite to the winding direction of the screw portion of the pin, the shoulder is pressed in parallel to the surface of the workpiece on the front side to place the pin into the two workpieces At this time, the taper part of the tip of the pin is arranged at the overlapping interface of the two workpieces,
As the plastic flow region, all of the cylindrical pin base end portions on which the screw portions are formed are arranged in the workpiece on the front side, and the screw portion does not include the overlapping interface of the two workpieces. A first plastic flow region is formed in which a convection in the plate thickness direction is convected with respect to the work material, and a part of the tapered portion of the pin tip portion where the spiral groove is formed is inserted into the work material on the back side. Then, the first plastic flow region in an oblique direction inclined from the plate thickness direction with respect to the overlapping interface and the workpiece on the back side along the tapered portion and the flat portion of the pin tip by the spiral groove. Generates a second plastic flow region that causes plastic flow by convection in the opposite direction, thereby suppressing the movement of the overlapping interface in the plate thickness direction at the outer periphery of the plastic flow region, and Friction stir welding method for friction stir welding. In the friction stir welding method according to claim 1,
The shoulder portion has a plane parallel to the radial direction of the tool body, the concave portion is not open to the side surface of the tool body is formed and extends from protruded portion of the pin to the vicinity of the outer diameter of the shoulder portion,
A friction stir welding method in which the material on the surface of the workpiece on the front side pressing the shoulder is guided to the center by the recess as the tool rotates. In the friction stir welding method according to claim 1 or 2,
A pin having a tapered part in which the entire cylindrical pin base end part in which the thread part is formed is inserted into the work piece on the front side in a range of 70% to 95% of the plate thickness and the spiral groove is formed. A friction stir welding method in which a part of the front end is inserted into a workpiece on the back side at a depth of 20% to 70% of the thickness of the workpiece on the front side. In the friction stir welding method according to any one of claims 1 to 3,
And in the final joint joining line terminating the friction stir welding tool are relatively moved along said overlapping portions, by moving the friction stir welding tool so as to surround the tool withdrawing position, about the pin hole of the tool withdrawing position Friction stir welding method for forming joints in a form that compensates for. In the friction stir welding method according to any one of claims 1 to 4,
Friction stir welding method for friction stir welding by the friction stir welding tool projecting from the shoulder by tilting the said pin relative to the tool axis of rotation. In the friction stir welding method according to any one of claims 1 to 5,
Bonding defects that are likely to occur around the pin hole at the tool pulling position in the final joint, by cutting through or not including the workpiece on the back side in the form of cutting out the agitated part around the pin hole at the tool pulling position Friction stir welding method to remove. In the friction stir welding method according to any one of claims 1 to 6,
A friction stir welding method in which two plate materials are arranged on the left and right sides as a workpiece on the front side and butt-joined, and overlapped and joined to the workpiece on the back side along the butt portion. A friction stir welded article comprising a joint part obtained by friction stir welding a superposed part obtained by superposing two workpieces by the friction stir welding method according to any one of claims 1 to 7,
A friction stir welded article having a cross-sectional shape in which fluctuations in the thickness direction of the overlapping interface of the two workpieces at the outer periphery of the joint are suppressed. The friction stir welded product according to claim 8,
A vehicle wheel provided with a joint portion obtained by friction stir welding of an overlapping portion in which a rim portion and a disk portion are overlapped. The vehicle wheel according to claim 9, which cites claim 8 which cites claim 6,
The non-through hole formed at the tool extraction position is filled with a sealing material such as pressure-resistant silicone resin to prevent air leakage, while in the case of a through hole, the through hole is a valve hole. Vehicle wheels. In a friction stir welding tool that friction stir welds an overlapped portion where two workpieces are overlapped,
A shoulder with a large diameter provided on the end surface of the rotated tool body and holding the surface of the workpiece on the front side;
A small-diameter pin that is inclined with respect to the tool rotation axis and protrudes from the shoulder to be inserted into two workpieces;
The pin is
A cylindrical pin base end set to a length of 70% to 95% of the workpiece thickness on the front side;
It is composed of a pin tip to the pin base end flat portion a and the tip portion has a tapered portion formed on the tapered toward the pin tip is formed by a pin radially and parallel to the plane of section, further ,
The pin base end portion is formed with a screw portion whose winding direction is opposite to the tool rotation direction during friction stir welding over the entire length,
The pin tip friction stir welding tool wherein the threaded portion and the opposite direction of the winding direction and became spiral groove over the entire area of the flat portion from the tapered portion is formed continuously in the unit. The friction stir welding tool according to claim 11,
The friction stir welding tool in which the taper angle of the tapered portion is set to 60 degrees or more and 120 degrees or less.