JP3285015B2 - Friction stir welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction stir welding method suitable for joining long structural members such as automobiles, railway vehicles, and buildings.

[0002]

2. Description of the Related Art Thermal distortion generated at the time of joining is small, and after joining.
As a solid-phase joining method that maintains good shape accuracy, friction
Attention has been paid to the stir welding method. In the case of friction stir welding,
Rotation with a pin 1 on the same axis as shown in Fig. 1
Use child 2. Material W to be joined while rotating pin 1
₁ , W_Two And along the butt line WL
The pin 1 is moved (joining direction D). Workpiece W ₁ , W
_Two Is heated by the frictional heat generated by the pin 1 and is rotated by the rotation of the pin 1.
Stirred. Metal that plastically flows by heating and stirring
Workpiece W₁ , W_Two Intermingle with each other, heat is rapid
Is solidified by being taken away by the
WB is formed. Friction stir welding has good
Utilizing the advantage that shape accuracy is maintained, automobiles and railway cars
Applications to various components such as vehicles and building structures are being promoted.
You.

[0003]

In the fields of automobiles, railway vehicles, building structures, and the like, long structural members are often used. In the case of the long structural member, the joint WB is long, and the relative movement of the pin 1 along the long butting line WL is required. The relative movement of the pin 1 includes a method of moving the pin 1 with respect to the workpieces W ₁ and W ₂ , and a method of moving the pin 1 with respect to the pin ₁ .
There is a method of moving the W _2. The method of moving the workpieces W ₁ and W ₂ requires only a small-scale friction stirrer, but it is difficult to accurately move the long workpieces W ₁ and W ₂ . When the workpieces W ₁ and W ₂ move while being displaced, the pins 1 are displaced in the height direction or the width direction with respect to the butting line WL, and defects such as poor stirring are likely to occur in the bonding portion WB. In the method in which the pin 1 is moved, the workpieces W ₁ ,
Butt line WL for W ₂ is fixed are secured in position, it is possible to bond with good accuracy. However, since the movable distance of the pin 1 is restricted by the size of the friction stirrer equipment, there is a disadvantage that the equipment becomes larger when trying to join a long structural member having a long butt line WL.

[0004]

SUMMARY OF THE INVENTION The present invention has been devised in order to solve such a problem, and when joining a long material to be joined by joining a plurality of joints. The holes created in the trace of pulling out the pin in the friction stir welding process are opened to the downstream side in the welding direction to prevent air from getting into the joint and even when using small-scale equipment An object of the present invention is to precisely join a long member by friction stir welding.

According to the friction stir welding method of the present invention, in order to achieve the object, a pin is inserted into a butt portion of two materials to be welded to each other, and the butt line between the materials to be welded is rotated while rotating the pin. The material to be welded is friction stir welded by moving the pin along, and the pin running in the middle of the butt line is raised, and then the pin is inserted again into the butt portion on the already-joined side from the rising start position of the pin. And moving the pin to the unjoined side of the butt line while rotating the pin. In the subsequent friction stir welding step, a pin which is shorter than the pin used in the preceding friction stir welding step by the amount of the shoulder pushing may be used, and the shoulder may be pushed into the material to be joined when joining the joint portions. By properly adjusting the amount of pushing of the shoulder, the necessary metal is secured even in the portion thinned in the preceding friction stir welding step, and the occurrence of hollow defects due to insufficient metal supply is prevented. The pin may be raised continuously, intermittently, swirled, or a combination thereof.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, for example, a friction stir welding apparatus whose equipment configuration is schematically shown in FIG. 2 is used. In this friction stir welding apparatus, an X-axis drive motor 13 is provided on a beam 12 extending over an upper part of a portal frame 11, and a movable gantry 14 is arranged so as to be able to travel. The movable gantry 14 can be moved up and down by a Z-axis drive motor 15 and has a main shaft motor 16. The output of the spindle motor 16 is transmitted to the rotor 2 via the belt 17. Pin 1 at the tip of rotor 2 (Fig. 1)
Are mounted coaxially, and the pin 1 is directed to a material to be joined (not shown) arranged on the table 20. Since the material to be joined is inclined such that the pin 1 is directed in the forward direction at an angle of about 3 degrees toward the joint WB,
It is placed on the gantry 19 with the inclination angle adjusted by the joining jig 18.

The workpieces W ₁ and W ₂ are fixed to the gantry 19 via their own weights or appropriate fixing means via a joining jig 18, and a butt line WL between the workpieces W ₁ and W ₂ is fixed to the movable pedestal 14. It extends in the running direction (FIG. 3). The pin 1 is inserted between the workpieces W ₁ and W ₂ at one end position (starting point P _1S ) of the butt line WL, and the pin 1 is rotated to travel toward the other end of the butt line WL. The workpieces W ₁ and W ₂ are heated and stirred by the rotational friction of the pin ₁ , and the workpieces W ₁ and W ₂ are stirred.
_The metal flows plastically over ₁ and W ₂ . After the pin 1 passes, the materials W ₁ and W ₂ to be joined are rapidly cooled by losing the heat source, so that the plastically flowing metal solidifies and the joint W
B are sequentially formed.

The movable range length ML of the pin 1 which can move along the direction of the butting line WL is restricted by the size of the friction stir welding apparatus including the portal frame 11 and the like. Therefore, when joining the long joining materials W ₁ and W ₂ , the movable range length ML may be shorter than the butting line WL (FIG. 4). When such a long butt line WL is subjected to friction stir welding, the starting point P _1S on one end side of the workpieces W ₁ and W _2.
Then, the pin 1 is moved along the butt line WL toward the other end by the movable range length ML, and the pin 1 is pulled out of the workpieces W ₁ and W ₂ at the end point P _1E .

Next, the end point P which is an unjoined portion_1EFrom the other
To be joined so that the end of the workpiece 1 is within the movable range of the pin 1.
₁ , W_Two Is moved, and the workpiece W₁ , W_Two To
It is fixed on a gantry 19 via a joining jig 18. And
End point P in preceding friction stir welding process_1EStarting point P_1S
Starting point P at the position slightly returned to the side_2SAnd set the starting point P
_2SThe pin 1 is inserted into the₁ , W_Two To the other end of
And set pin 1 to the end point P_2ERun until Like this
And the material W to be joined extends over the entire length of the long butt line WL. ₁ , W
_Two Is subjected to friction stir welding. Longer workpiece W₁ , W_Two To
When joining, the length of the butt line WL and the movable range of the pin 1
Three or more friction stir welding processes were performed in the same manner due to the relationship with the length ML.
Repeat as above.

In the friction stir welding, the metal located forward in the traveling direction is supplied rearward by the stirring force of the pin 1 so as to fill the trace of the passage of the pin 1. At this time, if the amount of metal supply to the rear is small, a hollow defect occurs at the joint WB. If friction stir welding the extruded material or the like, since there is a generation of a gap in the abutting surface and matching the welded material W _1, W ₂ to each other (bonding surface), the welded material shoulder W _1, W ₂ in The gap between the joining surfaces is filled with the pushed metal slightly to prevent the occurrence of hollow defects. Since the shoulder in the prior friction stir welding process is pushed slightly shoulder into the welded material W _1, W ₂ (specifically about 0.1~0.4mm is), only pushing portion of the shoulder material to be joined W _1, W ₂
Becomes thinner. When the subsequent friction stir welding step is performed in this state, it is necessary to slightly push the shoulder in the subsequent friction stir welding step. However, if the pin 1 used in the preceding friction stir welding process is used as it is, a shoulder is required to avoid interference between the joining jig 18 located on the P back surface of the workpieces W ₁ and W ₂ and the tip of the pin 1. I can't push it. Even if the shoulder is pushed in, a sufficient pushing amount cannot be secured, and a cavity-like defect is likely to occur. When the joining jig 18 and the tip of the pin 1 interfere with each other, the workpiece W
₁ , the joining quality of the joining jig 18 side of W ₂ is impaired. Therefore, in order to secure a sufficient pushing amount of the shoulder in the subsequent friction stir welding step, it is necessary to use a pin 1 shorter than the pin 1 used in the preceding friction stir welding step in the subsequent friction stir welding step. preferable. The difference between the lengths of the pins 1 used in the preceding and subsequent friction stir welding steps corresponds to the reduction in the thickness of the workpieces W ₁ and W ₂ , which are thinned when the shoulder is pushed in and friction stir welding is performed.

Also, by using a pin 1 having a larger diameter than the pin 1 used in the preceding friction stir welding step in the subsequent friction stir welding step, the entrainment of air into the joint WB can be effectively performed. Can be prevented. That is, when using the pins 1 of the same diameter in the preceding and succeeding steps to fill the voids V generated in the trace of removing the pins 1 in the preceding friction stir welding step in the subsequent friction stir welding step, Pin 1 in the process
Is required to set the passing locus right above the hole V with high accuracy. On the other hand, in the subsequent friction stir welding process using the pin 1 having a large diameter, the positional deviation can be tolerated by an amount corresponding to the increase in the diameter of the pin 1, and the condition regarding accuracy is relaxed.

In the preceding friction stir welding process, the end point P_1E
A hole V (FIG. 5) is formed in the trace where the pin 1 is pulled out by
ing. The holes V are used at the beginning of the subsequent friction stir welding process.
Point P _2STo the end point P_1EStarting point P_1SSet to the side, leading and
The joint WB formed in the subsequent friction stir welding process is
It is closed by wrapping. However,
In the friction stir welding process, a direction perpendicular to the joining direction D,
Joining material W₁ , W_Two Pull out pin 1 in the direction perpendicular to the surface of
Specifically, the inside of the hole V located on the downstream side with respect to the joining direction D
The wall S is substantially perpendicular to the joining direction D. Orthogonal to joining direction D
Inner wall S is formed with a hole V in a subsequent friction stir welding step.
Makes it difficult for air to escape, and the residual air gets caught in the joint WB
It can cause you to get tired

The entrapment of residual air is eliminated by inclining the inner wall S with respect to the joining direction D and opening the holes V downstream in the joining direction D. When the pin 1 is pulled up in the preceding friction stir welding step, the inclined inner wall S
The pin 1 is formed by raising the pin 1 continuously or intermittently while running the pin 1 or by rotating the pin 1 around the spindle motor 16 (FIG. 2), the rotor 2 and the like. For example, when the pin 1 is raised in the pull-out direction U while traveling in the bonding direction D, the motion components in the bonding direction D and the pull-out direction U are combined, and the lower end of the pin 1 along the inclined line I at the predetermined rising angle θ. Moves diagonally upward (Fig. 6
a). Therefore, the void V formed at the position of the end point P _1E
The wall surface on the downstream side with respect to the joining direction D is an inclined surface VI following the movement locus of the lower end of the pin 1. The hole V is opened toward the downstream side in the joining direction D by the inclined surface VI.
The distance from the start point P _1S to the end point P _1E is set to an appropriate value within the range of the movable range length ML of the pin 1.

In the subsequent friction stir welding step, a start point P _2S is set at a position on the start point P _1S side from the end point P _1E, and the start point P _2S
The pin 1 is inserted into the joint WB (FIG. 6B). The inserted pin 1 travels in the joining direction D while rotating as in the preceding friction stir welding step. At this time, since the holes V are open on the downstream side in the joining direction D, air can easily escape from the holes V. Therefore, entrainment of residual air is prevented in the process of forming the joint WB in the joining direction D due to the rotational friction of the pin 1, and the joint WB in the subsequent friction stir welding process overlaps the preceding joint WB. (FIG. 6c). In this way, a healthy joint WB free from hollow defects and entrainment of residual air is formed over the entire length of the butt line WL. In order to smoothly discharge the air from the holes V, it is preferable that the rising angle θ is larger than the angle α between the tip of the pin 1 of the welding tool and the outer periphery of the shoulder. If the rising angle θ is smaller than the angle α between the tip of the pin 1 and the outer periphery of the shoulder, it is difficult for the lower surface of the shoulder to slip out of the hole V due to interference by the lower surface of the shoulder, and the residual air is likely to be caught in the joint.

When the moving pin 1 is continuously raised,
An inclined surface VI having a constant rising angle θ is formed.
a). When the pin 1 is raised intermittently, a step-like inclined surface VI is formed (FIG. 7B). When the pin 1 is turned around the spindle motor 16 (FIG. 2), the rotor 2 and the like, an inclined surface VI curved in an arc shape is formed (FIG. 7).
c). Regardless of the inclined surface VI, the holes V are open downstream in the joining direction D, so that the air in the holes V is removed in the process of forming the joining portions WB in the joining direction D. A joint portion WB that is smoothly discharged and has no entrainment of residual air is formed.

[0016]

[Example] (Example) 500 mm in width and 5000 m in length
Extruded members of JIS 6N01 alloy having a thickness of 4 mm and a plate thickness of 4 mm are prepared as materials to be joined W ₁ and W ₂ , and the gantry 1 is connected via a joining jig 18 in a parallel state where both sides are butted against each other.
9 on. As the friction stir welding apparatus, an apparatus (FIG. 2) incorporating a rotary tool having a shoulder diameter of 15 mm, a pin diameter of 5.0 mm, and a pin length of 3.6 mm was used. In this case, the movable range length ML of the pin 1 was 4000 mm.

The pin 1 and the tip of the shoulder 0.2 mm
Starting point P located at one end of butt line WL_1STo be joined W
₁ , W_Two Insert it inside and rotate it at 1500 rpm
Pin 1 toward the other end of the butt line WL at 500 mm / min.
It was run at the speed of. Start point P _1S3000mm away from
End point P at position_1EAnd set the end point P_1EPin 1 has reached
From the time point, ascending speed 50 while running Pin 1 at the same speed
Raised at 0 mm / min. End point where pin 1 ascent started
P_1E3.7 mm away from the pin 1
₁ , W_Two Completely inclined from the slope surface with an inclination angle θ = 45 degrees
Voids V having VI were formed.

Next, the rotary tool was replaced with a rotary tool having the same shoulder diameter and pin diameter and a pin length of 3.4 mm, and the starting point P set at a position 200 mm back from the end point P _1E to the starting point P _1S side.
Pin 2 and shoulder tip 0.2mm at joint WB with _2S
And the pin 1 was run toward the other end of the butt line WL at a speed of 500 mm / min while rotating the pin 1 at 1500 rpm. When the pin 1 reached the other end of the butt line WL, the movement of the pin 1 was stopped, and the pin 1 was pulled vertically upward. In this manner, the total length 500 of the workpieces W ₁ and W ₂
A joint WB having no hollow defect and no air entrainment was formed over 0 mm, and the joint strength also showed a high value of 60 N / mm ² or more.

(Comparative Example) When the pin 1 reached the end point P _1E , the running of the pin 1 was stopped, and the extruded sections were friction stir welded under the same conditions as in the example except that the pin 1 was pulled vertically upward. . Observing the joint WB obtained in this case, air entrapment is detected in the joint WB corresponding to the seam between the preceding and subsequent friction stir welding processes, and the joint strength at this portion is 40 N / mm ² . Had dropped significantly.

[0020]

As described above, according to the present invention, when a long member is friction stir welded in the longitudinal direction, holes formed in the trace where a pin has been pulled out in the preceding friction stir welding step are formed in the downstream in the welding direction. By forming the shape open toward the side, air is smoothly discharged from the holes when forming a joint in the subsequent friction stir welding process, forming a healthy joint without entrapment of residual air Is done. By joining a plurality of joints formed by moving the pins within the movable range limited by the size of the friction stir welding apparatus in this way, a long member through a healthy and high-quality joint is joined. Joining becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a friction stir welding method.

FIG. 2 is a schematic view of a friction stir welding apparatus used in the present invention.

FIG. 3 is an explanatory view in which long members are joined by friction stir welding.

FIG. 4 is an explanatory view of forming a joining portion over a long butt line while overlapping in a plurality of friction stir welding processes.

FIG. 5 is a joint in which a hole is formed in the trace of a pin pulled vertically upward.

FIG. 6 is an explanatory view in which a hole whose downstream side in the joining direction is opened is formed by raising a running pin.

FIG. 7 is a view showing that the shape of the open side wall surface of the hole changes depending on the ascending form of the pin;

[Explanation of symbols]

1: Pin 2: rotor theta: the pin lower end rising angle W _1, W _2: the welded material WL: butt line WB: junction D: welding direction U: pin withdrawing direction ML: movable range Length P _{1S: Start} point of the preceding friction stir welding step P _1E : End point of the preceding friction stir welding step P _2S : Start point of the subsequent friction stir welding step P _2E : End point of the subsequent friction stir welding step Void V: S: Inner wall of the hole VI: Empty Hole slope

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2000-3344583 (JP, A) JP-A-2000-42781 (JP, A) JP-A-11-197856 (JP, A) JP-A-10-52771 ( JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B23K 20/12

Claims (2)

(57) [Claims] 1. A pin is inserted into a butted portion of two workpieces butted against each other, and the pins are rotated and moved along a butting line between the workpieces to friction stir weld the workpieces. Then, the running pin is lifted in the middle of the butt line, and then the pin is reinserted from the rising start position of the pin into the butt portion on the already-joined portion side, and the pin is rotated while the pin is rotated to the unjoined side of the butt line. Friction stir welding. 2. A pin which is shorter than the pin used in the preceding friction stir welding by an amount corresponding to the shoulder push- in is used in the subsequent friction stir welding, and when joining the joint portion in the subsequent friction stir welding, the shoulder is used as a material to be joined. The friction stir welding method according to claim 1, wherein the pressing is performed.