JP6739171B2 - Friction stir welding method - Google Patents

Description

The present invention relates to a friction stir welding method.

In recent years, friction stir welding has been used as a material joining method (see Patent Document 1).
In friction stir welding, a rotating welding tool is pressed against an object to be welded, and the object to be welded is fluidized by friction heat and welded.
In friction stir welding, a welding tool is mounted on a main shaft of a friction stir welding apparatus, and is rotationally driven about a rotation axis that intersects with the surface of an object to be welded. Then, it is translated along the joining portion on the surface of the article to be joined while being rotated.

As a friction stir welding device, a high torque is required for rotating the welding tool in order to obtain sufficient friction heat, and a dedicated device is often used. On the other hand, if the torque is high, a general-purpose machine tool is also used.
As the joining tool, for example, a tool in which a conical pin that is coaxial and downward is formed on the lower end surface of a cylindrical holder is used. A stepped shoulder is formed around the pin.
During the friction stir welding operation, the pin is introduced inside the object to be welded, and the shoulder is maintained to face the surface of the object to be welded.

JP, 2005-177844, A

When performing friction stir welding, the objects to be welded are fluidized by the welding tool. The fluidization is remarkable around the pin, and the upper surface side of the fluidized portion is covered with a shoulder.
However, depending on the situation, the fluidized portion of the article to be welded may overflow from around the pin. Then, when the overflowed fluidized part has spread to the peripheral surface of the object to be welded, it cannot return to the original fluidized part, and the welding trace of the object to be welded after the welding tool has passed through is filled. If not, the joining result may be poor.

As a cause of such overflow, the fluidization of the article to be welded is based on the temperature rise due to frictional heat to the rotating pin, and the temperature changes depending on the friction state between the pin and the article to be welded and the heat radiation state due to the surrounding air flow. However, it is conceivable that the movement of the welding tool and the fluidization around the pin do not always proceed in a constant state. However, it is difficult to measure these changes with high precision, and it is practically difficult to precisely control the rotating state and moving state of the welding tool.Therefore, it is necessary to develop a method that can prevent overflow of the fluidized part. It was being done.

Further, in the friction stir welding described above, it is necessary to strongly press the welding tool against the object to be welded in order to generate sufficient friction on the object. If the objects to be joined have high rigidity, they can withstand strong pressing. However, when the object to be welded has a thin plate shape, the object to be welded may be deformed and escape due to strong pressing of the welding tool, and the desired friction stir may not be obtained. Conventionally, in order to prevent such deformation, a support is also provided on the lower surface side (back surface side) of the thin objects to be joined. However, the support may not be installed depending on the equipment space and the shape of the article to be joined. Therefore, improvement has also been demanded for the problem of escape in thin objects to be joined.

A main object of the present invention is to provide a friction stir welding method capable of preventing overflow of a fluidized portion with a simple auxiliary operation.
Another object of the present invention is to provide a friction stir welding method in which deformation is small even for thin objects to be welded.

The present invention is a friction stir welding method for welding a pair of objects to be welded using a welding tool having a downward pin and a shoulder,
While rotating the pin in the object to be joined, to fluidize the object to be joined around the pin,
While horizontally moving the welding tool along the surface of the object to be welded, the welding tool is periodically moved up and down with respect to the surface of the object to be welded,
When the welding tool is raised, the shoulder raises the fluidized portion of the welded object,
During lowering of the bonding tool, characterized in that for pressing the pre-Symbol flow if part the shoulder.

According to the present invention as described above, even if the fluidized portion around the pin is about to overflow on the front side in the moving direction of the welding tool, it is pressed by the shoulder and pushed back around the pin. As a result, a sufficient amount of the fluidized portion is pushed back to the rear side in the moving direction of the welding tool and solidified again. As a result, the welding marks of the objects to be welded after passing through the welding tool are in a good state.
As described above, according to the present invention, the overflow of the fluidized portion can be prevented by a simple auxiliary operation, and the joining result can be improved.

Further, when the friction stir welding method of the present invention is applied to a thin object to be welded, deformation after welding can be suppressed even without a support on the lower surface side. That is, in the present invention, since the welding tool is moved up and down, even if the object to be welded is deformed downward by being pushed down when it is lowered, the deformation of the base material is recovered within the elastic limit when the welding tool is raised, and the original material is restored when the welding tool is lowered next time. Can be pressed at the position. As a result, according to the present invention, it is possible to reliably perform friction stir with less deformation even on a thin object to be joined.

According to the friction stir welding method of the present invention, overflow of the fluidized portion can be prevented with a simple auxiliary operation, and the welding result can be improved. Further, even if the object to be welded is thin, frictional stirring can be reliably performed.

The perspective view showing the outline of one embodiment of the present invention. Sectional drawing which shows the principal part of the said embodiment. Sectional drawing which shows operation|movement of the said embodiment. Sectional drawing which shows the raising operation of the said embodiment. Sectional drawing which shows the lowering operation of the said embodiment. The graph which shows the other raising/lowering operation which can be utilized for the said embodiment. The graph which shows the other raising/lowering operation which can be utilized for the said embodiment. The graph which shows the other raising/lowering operation which can be utilized for the said embodiment. Sectional drawing which shows other embodiment of this invention. Sectional drawing which shows other embodiment of this invention.

An embodiment of the present invention will be described below with reference to the drawings.
In FIG. 1, in the present embodiment, a pair of thin plates 11 and 12 made of a metal material are used as objects to be joined, and friction stir welding is performed based on the present invention.
The thin plates 11 and 12 are fixed to the friction stir welding apparatus such that the edges 11A and 12A of the thin plates 11 and 12 are butted against each other at the joining line 13 and the surfaces thereof are horizontal.

In this embodiment, a machine tool (not shown) is used as the friction stir welding apparatus. As this machine tool, one having a sufficiently high torque for friction stir welding is selected.
A welding tool 20 for friction stir welding is attached to the main shaft of the machine tool.

The welding tool 20 has a cylindrical holder 21 and has a coaxial downward pin 22 on its lower end surface. Although the pin 22 has a conical shape, the outer diameter of the holder 21 is smaller than the outer diameter of the upper portion having the largest diameter. Therefore, the lower end surface of the holder 21 appears in a step shape around the pin 22, and the shoulder 23 is formed by the step.

The welding tool 20 is applied to the thin plates 11 and 12 in a state in which the pin 22 is directed downward and the rotation axis is vertical due to each axis movement of the machine tool which is a friction stir welding apparatus.
That is, in the thin plates 11 and 12, the respective edges 11A and 12A are butted along the joining line 13. The welding tool 20 is disposed at one end (lower side in FIG. 1) of the welding line 13 while being rotationally driven, and the pin 22 at the tip thereof is pressed horizontally from the end faces of the thin plates 11 and 12.
When the pin 22 is pressed in a rotating state, friction heat is generated in the thin plates 11 and 12, and the thin plates 11 and 12 are fluidized along the joining line 13. Then, by moving the welding tool 20 horizontally along the welding line 13, the fluidized portion advances along the welding line 13.

As shown in FIG. 2, when the pin 22 is pressed in a rotating state, the thin plates 11 and 12 are fluidized by frictional heat on the front side in the moving direction of the pin 22. That is, in the thin plates 11 and 12, a temperature rising range A1 due to frictional heat is formed. Then, a fluidized region A2 is formed in the vicinity of the pin 22 having a high temperature.

On the other hand, on the rear side in the moving direction of the pin 22, the fluidized region A2 in which the fluidized portions of the thin plates 11 and 12 are mixed remains. However, as the pin 22 separates, the fluidized portion cools and solidifies again. Then, the fluidized portions of the thin plates 11 and 12 are integrally solidified to form the fusion bonded area A3.
As a result, on the joining line 13 after the joining tool 20 has passed, joining marks 14 are formed in which the fluidized portions of the thin plates 11 and 12 are integrally solidified. By forming the joining mark 14 over the entire length of the joining line 13, the thin plates 11 and 12 are joined together.

When performing such a joining operation, in the present embodiment, an auxiliary operation based on the present invention is performed.
That is, the welding tool 20 is moved horizontally along the surfaces of the thin plates 11 and 12, and the welding tool 20 is moved up and down in accordance with a predetermined pattern P with respect to the surfaces of the thin plates 11 and 12.
When the welding tool 20 descends, the shoulder 23 presses the fluidized portions of the thin plates 11 and 12.
In this embodiment, the pattern P is a sine wave vibration with a period of about 1 Hz.

3 to 5 show the lifting operation of the welding tool 20 according to the present invention and its operation.
In FIG. 3, when the welding tool 20 is horizontally moved while being rotated, in the thin plates 11 and 12, the temperature rising range A1 and the fluidized region A2 are formed on the front side of the pin 22, and the fluidized region A2 is formed on the rear side. And the fusion bonding area A3 is formed.
At this time, by adjusting the rotation state of the welding tool 20, the temperature rising range A1 reaches the lower surface side of the thin plates 11 and 12, but the fluidized region A2 does not appear on the lower surface side of the thin plates 11 and 12.

In FIG. 3, in the fluidized region A2, the material of the thin plates 11 and 12 is fluidized, and overflow 15 may occur in a part of the fluidized portion particularly on the front side of the pin 22.
However, in the present embodiment, since the welding tool 20 is moved up and down in the predetermined pattern P, the shoulder 23 presses the welding tool 20 when the welding tool 20 is lowered, and the overflow 15 of the fluidized portion can be pushed back.

In FIG. 4, first, when the welding tool 20 is raised, the lower surface of the shoulder 23 is also raised, the fluidized portion of the fluidized region A2 is pulled up, and the overflow 15 protruding to the surroundings is pulled inward to flow. It is merged with the conversion area A2.
In FIG. 5, when the welding tool 20 is lowered next, the fluidized portion and the overflow 15 of the fluidized area A2 that have been once pulled up are pressed downward by the lower surface of the shoulder 23, and the thin plate 11 and the thin plate 12 are sandwiched. Pushed back.

In this way, as the welding tool 20 moves up and down, so-called pumping of the fluidized portion of the fluidized region A2 is performed, and the overflow 15 is collected at that time.
As a result, it is possible to prevent the overflow 15 from remaining around the thin plates 11 and 12. Further, the material corresponding to the overflow 15 is returned to the fusion-bonding area A3 on the rear side of the pin 22, so that the lack of the material in the fusion-bonding area A3 is avoided, and the bonding trace 14 formed over the entire length of the bonding line 13 is formed. Can be good without defects.

Further, the thin plates 11 and 12 are pushed down when the welding tool 20 descends and tend to deform downward. However, since the welding tool 20 moves up and down, the deformation of the base material recovers within the elastic limit when the welding tool 20 is subsequently raised. Then, when the welding tool 20 is lowered next time, the thin plates 11 and 12 can be pressed by the welding tool 20 at their original positions.
In this way, by raising and lowering the welding tool 20, even if the thin plates 11 and 12 are easily deformed, it is possible to surely perform friction stir with less deformation.

As described above, according to the present embodiment, even if the fluidized portion around the pin 22 is about to overflow on the front side in the moving direction of the welding tool 20, the shoulder 23 pushes the fluidized portion around the pin 22 to the periphery of the pin 22. Can be pushed back. As a result, a sufficient amount of the fluidized portion is pushed back to the rear side in the moving direction of the welding tool 20, and is solidified again. As a result, the joining marks 14 of the thin plates 11 and 12 which are the objects to be joined after the joining tool 20 has passed are in a good state.
Therefore, according to the present embodiment, the overflow of the fluidized portion can be prevented and the welding result can be improved by a simple auxiliary operation of raising and lowering the welding tool 20 by the pattern P.

Furthermore, according to the present embodiment, even if the work piece is a thin plate 11 or 12 that is easily deformed, the deformation due to the pressing force at the time of lowering can be alleviated at the time of ascending by raising and lowering the welding tool 20. It is possible to surely perform friction stirring. Therefore, it is not necessary to provide a support on the lower surface side of the thin plates 11 and 12 to support the thin plates 11, 12, so that the facility can be simplified and the objects to be joined having a shape difficult to be supported by the support can be easily joined.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications and the like within a range in which the object of the present invention can be achieved are included in the present invention.
The pattern P for raising and lowering the welding tool 20 has a cycle of about 1 Hz. However, depending on conditions such as the material of the thin plates 11 and 12 which are the objects to be welded, the temperature of the working environment, and the state in which the overflow 15 actually occurs. , May be changed as appropriate.
The change of the cycle may be adjusted at the start of the work, or may be changed during the work while observing the state of the overflow 15.

The raising and lowering of the welding tool 20 is not limited to the sinusoidal pattern P as in the above-described embodiment, but may be another waveform.
For example, as shown in FIG. 6, the pattern P may have a triangular wave shape that linearly moves up and down.
The raising and lowering of the welding tool 20 is not limited to the continuous movement, and may be a stepwise change in height due to intermittent movement.
For example, as shown in FIG. 7, the pattern P may be a triangular wave due to a step change.

The raising and lowering of the welding tool 20 is not limited to the one in which the rising time and the falling time are the same (the ratio is 1:1), and may be, for example, one in which the rising time is short and the falling time is long.
For example, as shown in FIG. 8, the pattern P may have a rise time of 30% and a fall time of 70% in a cycle.
When the rising time is short, the pullback of the overflow 15 can be strengthened by the rapid rising. Further, since the descending is gentle, it is possible to prevent the fluidized portion of the lower surface of the shoulder 23 from overflowing again.
On the other hand, depending on the conditions such as materials, it may be preferable to increase the rising time to gently pull back the overflow 15 and to make the falling rapid to strengthen the pushing down by the shoulder 23.

In the above-described embodiment, as the friction stir welding apparatus, a machine tool having a sufficiently high torque for friction stir welding is used, but a dedicated machine for friction stir welding may be used. In this case, in addition to the rotational drive of the welding tool 20, the horizontal movement of the welding tool 20 (X-axis or Y-axis in the machine tool), a mechanism (Z-axis in the machine tool) that can raise and lower the welding tool according to the present invention is provided. It must be

Although the thin plates 11 and 12 are used as the objects to be bonded in the above-described embodiment, a pair of block-shaped objects and other objects to be bonded may be used.
As shown in FIG. 9, the thin plate 12 may be used for the block 11B having a large thickness as the object to be bonded. In this case as well, by moving the welding tool 20 that moves up and down while rotating along the welding line 13 between the block 11B and the thin plate 12, it is possible to form the ordered welding mark 14 according to the present invention.
As shown in FIG. 10, a pair of thick blocks 11B and 12B may be used as the objects to be bonded. In this case as well, by moving the welding tool 20 that moves up and down while rotating along the welding line 13 of the blocks 11B and 12B, it is possible to form the ordered welding mark 14 according to the present invention.

The present invention relates to a friction stir welding method, and can be used when joining metal materials and the like.

11, 12... Thin plates to be joined, 11B, 12B... Blocks to be joined, 11A, 12A... Edges, 13... Joining lines, 14... Joining marks, 20... Joining tools, 21... Holders, 22... Pins, 23... Shoulder, A1... Temperature rising range, A2... Fluidization area, A3... Fusion area, P... Pattern.

Claims (1)

A friction stir welding method for joining a pair of objects by using a friction stir welding apparatus equipped with a welding tool having a downward pin and a shoulder,
While rotating the pin in the object to be welded by the friction stir welding device , while fluidizing the object to be welded around the pin,
While horizontally moving the welding tool along the surface of the object to be welded by the friction stir welding apparatus , the friction stir welding apparatus periodically moves the welding tool up and down with respect to the surface of the object to be welded.
When the welding tool is raised, the shoulder raises the fluidized portion of the welded object,
The friction stir welding method characterized in that the fluidized portion is pressed by the shoulder when the welding tool is lowered.

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