FRICTION STIR WELDING TOOL, FRICTION STIR WELDING DEVICE, AND FRICTION STIR WELDING METHOD

Abstract

A friction stir welding tool includes: a first face which is rotated about an axis relative to a joined portion in a state in which the first face comes into contact with the joined portion of a workpiece and in which an arithmetic mean roughness Ra value is greater than or equal to 0.8 μm and less than or equal to 25 μm; and a second face which is formed to continue to the first face, which is rotated about the axis relative to the joined portion in a state in which the second face comes into contact with the joined portion, and in which an arithmetic mean roughness Ra value is smaller than that of the first face.

Claims

1. A friction stir welding tool comprising: a first face which is rotated about an axis relative to a joined portion in a state in which the first face comes into contact with the joined portion of a workpiece and in which an arithmetic mean roughness Ra value is greater than or equal to 0.8 μm and less than or equal to 25 μm; and a second face which is formed to continue to the first face, which is rotated about the axis relative to the joined portion in a state in which the second face comes into contact with the joined portion, and in which an arithmetic mean roughness Ra value is smaller than that of the first face.

2. The friction stir welding tool according to claim 1, wherein the arithmetic mean roughness Ra value of the first face is greater than or equal to 1.6 μm and less than or equal to 25 μm.

3. The friction stir welding tool according to claim 1, wherein the arithmetic mean roughness Ra value of the first face is greater than or equal to 3.2 μm and less than or equal to 25 μm.

4. The friction stir welding tool according to claim 1, further comprising: a probe inserted into the joined portion of the workpiece at a time of joining, having a columnar shape formed about an axis, and rotating about the axis; and a shoulder with a columnar shape formed about the axis, rotated together with the probe, and having a shoulder surface pressed against a surface of the workpiece at the time of joining, wherein the first face and the second face are formed in an outer circumferential surface of the probe to be adjacent to each other in the circumferential direction.

5. The friction stir welding tool according to claim 1, wherein a spiral groove with a spiral shape extending to one direction along the axis as going toward the circumferential direction of the probe is formed in the second face.

6. The friction stir welding tool according to claim 1, comprising: a probe inserted into the joined portion of the workpiece at a time of joining, having a columnar shape formed about an axis, and rotating about the axis; and a shoulder with a columnar shape formed about the axis, rotated together with the probe, and having a shoulder surface pressed against a surface of the workpiece at the time of joining, wherein the first face and the second face are formed in the shoulder surface to be adjacent to each other in the circumferential direction.

7. The friction stir welding tool according to claim 6, wherein a spiral groove with a spiral shape is formed extending outward in a radial direction of the axis as going toward the front of a direction of rotation of the shoulder in the circumferential direction in the shoulder surface, the first face is a surface of the shoulder surface other than a position at which the spiral groove is formed, and the second face is an inner surface of the spiral groove.

8. A friction stir welding device comprising: the friction stir welding tool according to claim 1; and a device main body configured to hold the friction stir welding tool and to rotate the friction stir welding tool relative to the workpiece.

9. A friction stir welding method comprising: a tool contact step of bringing a first face of a friction stir welding tool of which an arithmetic mean roughness Ra value is greater than or equal to 0.8 μm and less than or equal to 25 μm into contact with a joined portion of a workpiece and bringing a second face of the friction stir welding tool, which continues to the first face and of which an arithmetic mean roughness Ra value is smaller than that of the first face, into contact with the joined portion; and a rotating step of rotating the first face and the second face relative to the joined portion.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0030] FIG. 1 is a front view showing a state in which a friction stir welding device according to a first embodiment of the present invention is installed at a workpiece.

[0031] FIG. 2 is an enlarged diagram of a probe of a tool of the friction stir welding device according to the first embodiment of the present invention, showing a perspective view when diagonally viewed from a lower side.

[0032] FIG. 3 is a graph showing a relationship between an arithmetic mean roughness Ra of a first face formed in the probe of the tool of the friction stir welding device and a stirring property of a workpiece according to the first embodiment of the present invention.

[0033] FIG. 4 is a flowchart for describing steps of a friction stir welding method using the tool of the friction stir welding device according to the first embodiment of the present invention.

[0034] FIG. 5 is a front view showing a state in which a friction stir welding device according to a second embodiment of the present invention is installed at a workpiece.

[0035] FIG. 6 is a view showing an upper shoulder surface of a tool of the friction stir welding device according to the second embodiment of the present invention, showing a cross-sectional view taken along line A-A of FIG. 5.

[0036] FIG. 7 is a view showing a lower shoulder surface of the tool of the friction stir welding device according to the second embodiment of the present invention, showing a cross-sectional view taken along line B-B of FIG. 5.

DESCRIPTION OF EMBODIMENTS

First Embodiment

[0037] Hereinafter, a friction stir welding device 1 according to a first embodiment of the present invention will be described.

[0038] As shown in FIG. 1, for example, the friction stir welding device 1 is installed at a joined portion Wa serving as an abutting portion in a workpiece W obtained when two plates (or hollow materials or the like) W1 abut against each other, and the workpiece W is joined by friction stir welding.

[0039] The friction stir welding device 1 includes a friction stir welding tool 12 (hereinafter simply referred to as a “tool 12”) pressed against the joined portion Wa and a device main body 13 configured to hold the tool 12 and to rotate the tool 12 relative to the workpiece W in a state in which the tool 12 is pressed against the workpiece W.

[0040] In this embodiment, the device main body 13 and the tool 12 are installed at the workpiece W from above the workpiece W at a time of joining.

[0041] The tool 12 includes a probe 14 inserted into the joined portion Wa of the workpiece W at the time of joining and a shoulder 18 configured to support the probe 14.

[0042] The probe 14 has a cylindrical shape formed about an axis O and is rotated about the axis O by a power source (not shown) provided in the device main body 13.

[0043] Also, spiral grooves 14a with a spiral shape over the entire region in an axis O direction are formed in an outer circumferential surface of the probe 14. The spiral grooves 14a are formed extending toward one direction along the axis O (an upper side) as going toward a circumferential direction (forward in a direction of rotation R of the tool 12). In other words, the spiral grooves 14a are formed in a right-handed screw shape, and the direction of rotation R of the tool 12 is a clockwise direction when the tool 12 is viewed from a lower side of the probe 14.

[0044] First faces 15 are formed in the probe 14 by cutting a portion of the outer circumferential surface, in which the spiral grooves 14a are formed, at a plurality of places away from each other in the circumferential direction (three places in this embodiment) along the axis O over the entire region in the axis O direction. The first faces 15 have a planar shape along the axis O. The first faces 15 are formed at regular intervals in the circumferential direction in this embodiment.

[0045] An arithmetic mean roughness Ra value of the first faces 15 is greater than or equal to 0.8 μm and less than or equal to 25 μm.

[0046] When an arithmetic mean roughness Ra is larger than 25 μm in the case of Ra as shown in a portion A of FIG. 3, an upper limit of the arithmetic mean roughness Ra is 25 μm because a plastic flow becomes non-uniform. In other words, an upper limit value of Ra in this embodiment is determined so that the stirred workpiece W flows to the joined portion Wa by causing a plastic flow direction not to be non-uniform. When Ra is smaller than 0.8 μm as shown in a portion B of FIG. 3, a lower limit of Ra is 0.8 μm because the amount of heat input from the tool 12 to the workpiece W is insufficient and thus it is difficult for sufficient plastic flow to occur.

[0047] Here, the arithmetic mean roughness Ra value is preferably greater than or equal to 1.6 μm and less than or equal to 25 μm, and the arithmetic mean roughness Ra value is preferably greater than or equal to 3.2 μm and less than or equal to 25 μm.

[0048] As described above, the probe 14 includes, on the outer circumferential surface thereof, the first faces 15 and a plurality of (three in this embodiment) second faces 16 which are adjacent to the first faces 15 in the circumferential direction, which are separated from each other at regular intervals in the circumferential direction, and in which the spiral grooves 14a are formed. The arithmetic mean roughness Ra value of the second faces 16 is smaller than that of the first faces 15. Thus, the second faces 16 are smoother than the first faces 15.

[0049] The first faces 15 and the second faces 16 may not be formed at regular intervals in the circumferential direction. Furthermore, the number of first faces 15 and the number of second faces 16 may be any number, but are preferably odd numbers.

[0050] The shoulder 18 has a cylindrical shape formed about the axis O coaxially with the probe 14. Furthermore, the shoulder 18 is disposed to face one surface (an upper surface) of the workpiece W and supports the probe 14. The shoulder 18 rotates about the axis O together with the probe 14. The shoulder 18 has a shoulder surface 18a pressed against the surface of the workpiece W at the time of joining.

[0051] At the time of joining, first, the tool 12 rotates about the axis O (refer to a rotating step S1: FIG. 4), and then the first faces 15 and the second faces 16 are brought into contact with the joined portion Wa of the workpiece W (refer to a tool contact step S2: FIG. 4) while the workpiece W is pressed by the shoulder surface 18a so that such a friction stir welding tool 12 can increase frictional heat using the relatively coarse first faces 15 of which the arithmetic mean roughness Ra is greater than or equal to 0.8 μm and less than or equal to 25 μm. As a result, the workpiece W stirred by the first faces 15 moves to be widened on the outer circumferential surface of the probe 14 in the circumferential direction so that the plastic flow of the workpiece W is promoted. For this reason, more stirred workpieces W are allowed to flow into the joined portion Wa, and thus satisfactory joining can be performed.

[0052] Also, a material of the workpiece W stirred by the first faces 15 is allowed to flow into the joined portion Wa while adhesion of the workpiece W plastically flowing using the second faces 16 smoother than the first faces 15 is reduced.

[0053] The spiral grooves 14a are formed in the second faces 16. For this reason, the plastic flow of the workpiece W from the first faces 15 is guided through the spiral grooves 14a of the second faces 16 along with the rotation of the tool 12 and is guided to a distal end side of the probe 14. Therefore, more stirred workpieces W are allowed to flow into the joined portion Wa, and thus the workpiece W can be joined satisfactorily.

[0054] When the arithmetic mean roughness Ra value of the first faces 15 is greater than or equal to 1.6 μm and less than or equal to 25 μm and preferably greater than or equal to 3.2 μm and less than or equal to 25 μm, frictional heat is further increased by the first faces 15 and thus an amount of stirring of the workpiece W can be further increased. Thus, the plastic flow of the workpiece W using the first faces 15 can be further promoted, the amount of plastic flow of the workpiece W to the joined portion Wa is increased, and thus the workpiece W can be joined satisfactorily.

[0055] Also, the arithmetic mean roughness Ra value of the first faces 15 is greater than or equal to 0.8 μm and less than or equal to 25 μm. Thus, a surface of the probe 14 is relatively coarse. Therefore, precise machining in which the first faces 15 are smoothened is not needed. As a result, costs can be reduced.

[0056] Here, in this embodiment, the spiral grooves 14a are not necessarily formed in the second faces 16.

Second Embodiment

[0057] Hereinafter, a friction stir welding device 21 of a second embodiment of the present invention will be described with reference to FIG. 5.

[0058] Constituent elements which are the same as those of the first embodiment are denoted with the same reference numerals, and detailed descriptions thereof will be omitted.

[0059] This embodiment and the first embodiment differ in view of a tool 22.

[0060] In other words, in this embodiment, the tool 22 includes a probe 24 inserted into a joined portion Wa of a workpiece W at a time of joining, an upper shoulder 25 configured to support the probe 24 from above, and a lower shoulder 27 configured to support the probe 24 from below.

[0061] The probe 24 has a cylindrical shape formed about an axis O. The probe 24 is rotated about the axis O by a power source (not shown) provided in a device main body 13.

[0062] A probe groove 24a with a spiral shape over the entire region in an axis O direction is formed in an outer circumferential surface of the probe 24. As the probe groove 24a, a first groove 24a1 formed at the upper shoulder 25 side in the probe 24 and a second groove 24a2 formed at the lower shoulder 27 side in the probe 24 are formed using a central position of the probe 24 in the axis O direction as a boundary.

[0063] The first groove 24a1 is formed extending toward one side of the axis O (an upper side) as going toward one side in a circumferential direction (a front of a direction of rotation R of the tool 22). In other words, the first groove 24a1 is formed in a left screw shape. Furthermore, the direction of rotation R of the tool 22 is a counterclockwise direction when the tool 22 is viewed from a lower side of the probe 24.

[0064] The second groove 24a2 is formed extending toward the other direction along the axis O (a lower side) as going toward the circumferential direction (the front of the direction of rotation R of the tool 22). In other words, the second groove 24a2 is formed in a right screw shape.

[0065] As described above, the left-screw-shaped groove and the right-screw-shaped groove are formed in the outer circumferential surface of the probe 24 using the central position of the probe 24 in the axis O direction as the boundary.

[0066] The upper shoulder 25 has a cylindrical shape formed about the axis O coaxially with the probe 24. The upper shoulder 25 is disposed to face an upper surface serving as one surface of the workpiece W. Furthermore, the upper shoulder 25 supports the probe 24 and rotates together with the probe 24. The upper shoulder 25 has an upper shoulder surface 26 pressed against the upper surface of the workpiece W at the time of joining.

[0067] As shown in FIG. 6, a first spiral-shaped groove 26a with a spiral shape is formed extending outward in a radial direction of the axis O as going toward the front of the direction of rotation R of the tool 22 in the circumferential direction in the upper shoulder surface 26. In other words, the first spiral-shaped groove 26a is formed in a helical shape when viewed from below.

[0068] The first spiral-shaped groove 26a is open in the outer circumferential surface, that is, an outer-circumferential-side edge, of the upper shoulder 25 at a position of an outside in the radial direction of the upper shoulder surface 26, and continues to the outer circumferential surface of the probe 24 at a position of an inside in the radial direction thereof.

[0069] The lower shoulder 27 has a cylindrical shape formed about the axis O coaxially with the probe 24. The lower shoulder 27 is disposed to face a lower surface serving as the other surface of the workpiece W. Furthermore, the lower shoulder 27 supports the probe 24 and rotates together with the probe 24. The lower shoulder 27 has a lower shoulder surface 28 pressed against a lower surface of the workpiece W at the time of joining.

[0070] As shown in FIG. 7, a second spiral-shaped groove 28a with a spiral shape outward in a Radial direction of the axis O is formed in the lower shoulder surface 28 toward the front of the direction of rotation R of the tool 22 in the circumferential direction. In other words, the second spiral-shaped groove 28a is formed in a helical shape when viewed from above.

[0071] The second spiral-shaped groove 28a is open in the outer circumferential surface, that is, an outer-circumferential-side edge, of the lower shoulder 27 at a position of an outside in the radial direction of the lower shoulder surface 28, and continues to the outer circumferential surface of the probe 24 at a position of an inside in the radial direction thereof.

[0072] Surfaces of other portions (hereinafter referred to as “mountain portions”) of the upper shoulder surface 26 and the lower shoulder surface 28, in which the first spiral-shaped groove 26a and the second spiral-shaped groove 28a in the upper shoulder surface 26 and the lower shoulder surface 28 are not formed, are first faces 35 which are the same as the first faces 15 of the first embodiment. In other words, an arithmetic mean roughness Ra value at surfaces of the mountain portions is greater than or equal to 0.8 μm and less than or equal to 25 μm, is preferably greater than or equal to 1.6 μm and less than or equal to 25 μm, and is more preferably greater than or equal to 3.2 μm and less than or equal to 25 μm.

[0073] Inner surfaces of the first spiral-shaped groove 26a and the second spiral-shaped groove 28a are second faces 36 which are the same as the second faces 16 of the first embodiment.

[0074] According to the friction stir welding device 21 in this embodiment, when the friction stir welding tool 22 rotates about the axis O, frictional heat can be increased by the relatively coarse first faces 35 in the upper shoulder surface 26 and the lower shoulder surface 28. Thus, the amount of stirring of the workpiece W is increased, and thus the plastic flow of the workpiece W is promoted.

[0075] The workpiece W is guided using the first spiral-shaped groove 26a and the second spiral-shaped groove 28a serving as the second faces 36 of which the inner surfaces are smoother than the first faces 35. For this reason, a material of the workpiece W plastically flows toward the inside in the radial direction of the probe 24 side along with the rotation of the upper shoulder surface 26 and the lower shoulder surface 28. Therefore, stirred workpieces W are further allowed to flow into the joined portion Wa, and thus the workpiece W can be joined satisfactorily.

[0076] The first groove 24a1 and the second groove 24a2 having screw shapes with different directions are formed in the probe 24 as the probe groove 24a. For this reason, the plastically flowing workpiece W guided by the first spiral-shaped groove 26a and the second spiral-shaped groove 28a is fed into the joined portion Wa along the rotation of the tool 22 (refer to arrows of FIG. 5). Therefore, satisfactory joining can be performed while occurrence of joining defects inside the joined portion Wa is reduced.

[0077] Here, although a bobbin tool including the probe 24, the upper shoulder 25, and the lower shoulder 27 is used as the tool 22 in this embodiment, the present invention can also be applied to, for example, a case in which a tool like the tool 12 of the first embodiment having the upper shoulder 25 (or the lower shoulder 27) and the probe 14 is used.

[0078] Although the embodiments of the present invention have been described in detail above, some changes in design are also possible without departing from the technical idea of the present invention.

[0079] For example, a groove which is the same as the first spiral-shaped groove 26a of the tool 22 in the second embodiment may be formed in the tool 12 in the first embodiment.

[0080] For example, although a case in which two plates W1, which abut against each other, as the workpiece W are joined has been described in the above-described embodiments, two plates W1, which are overlapped with each other, as the workpiece W can also be joined using the tool 12 or 22 in the above-described embodiments.

INDUSTRIAL APPLICABILITY

[0081] According to the friction stir welding tool, the friction stir welding device using the friction stir welding tool, and the friction stir welding method which have been described above, a workpiece is caused to sufficiently plastically flow and thus the workpiece can be joined satisfactorily.

REFERENCE SIGNS LIST

[0082] 1 Friction stir welding device [0083] 12 Tool (for friction stir welding) [0084] 13 Device main body [0085] 14 Probe [0086] 14a Spiral groove [0087] 15 First face [0088] 16 Second face [0089] 18 Shoulder [0090] 18a Shoulder surface [0091] 21 Friction stir welding device [0092] 22 Tool (for friction welding) [0093] 24 Probe [0094] 24a Probe groove [0095] 24a1 First groove [0096] 24a2 Second groove [0097] 25 Upper shoulder [0098] 26 Upper shoulder surface [0099] 26a First spiral-shaped groove [0100] 27 Lower shoulder [0101] 28 Lower shoulder surface [0102] 28a Second spiral-shaped groove [0103] 35 First face [0104] 36 Second face [0105] W Workpiece [0106] Wa Joined portion [0107] W1 Plate [0108] O Axis [0109] R Direction of rotation [0110] S1 Rotating step [0111] S2 Tool contact step