U.S. patent application number 10/085090 was filed with the patent office on 2002-06-27 for friction stir welding method.
Invention is credited to Ezumi, Masakuni, Fukuyori, Kazushige, Mizusaki, Tsuyoshi.
Application Number | 20020079347 10/085090 |
Document ID | / |
Family ID | 26586831 |
Filed Date | 2002-06-27 |
United States Patent
Application |
20020079347 |
Kind Code |
A1 |
Ezumi, Masakuni ; et
al. |
June 27, 2002 |
Friction stir welding method
Abstract
On a main shaft 30 of a numeric control type machine tool, a
rotary tool 50 is installed. The main shaft 30 is not inclined in
the machine tool. A first member 70 and a second member 76 to be
subjected to friction stir welding are fixed on a table 20.
Relative to an axial center of the rotary tool 50, a non-linear
welding portion of the first member 70 and the second member 76 is
inclined by inclining the table 20. Then, by rotating the table 20
and relatively moving the portion to be welded into contact with
the rotary tool 50, welding of the first member to the second
member is carried out according to friction stir welding. The
above-stated inclination is the inclination required for the
friction stir welding. In this way, welding along a path of ring
shape or circular shape (including a circular arc) using friction
stir welding can be carried out easily.
Inventors: |
Ezumi, Masakuni; (Kudamatsu,
JP) ; Fukuyori, Kazushige; (Kudamatsu, JP) ;
Mizusaki, Tsuyoshi; (Kudamatsu, JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
26586831 |
Appl. No.: |
10/085090 |
Filed: |
March 1, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10085090 |
Mar 1, 2002 |
|
|
|
09781289 |
Feb 13, 2001 |
|
|
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Current U.S.
Class: |
228/2.1 ;
228/112.1 |
Current CPC
Class: |
B23K 20/122 20130101;
B23K 20/123 20130101; B23K 20/1235 20130101; B23K 20/124
20130101 |
Class at
Publication: |
228/2.1 ;
228/112.1 |
International
Class: |
B23K 020/12; B23K
037/00; B23K 031/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 2000 |
JP |
2000-060202 |
Oct 19, 2000 |
JP |
2000-318730 |
Claims
What is claimed is:
1. A machine tool, comprising: a table adapted to have a face
thereof rotate, said face being adapted to fix a pair of members
vertically or horizontally; and a main shaft opposed to said face
and having an axis center along to a horizontal direction or a
vertical direction, and further adapted to rotate under a state in
which a friction stir welding use rotary tool is installed to a tip
end thereof, wherein, a side of small diameter portion of an axis
center of said rotary tool is positioned in a rear portion from a
side of a large diameter portion of said rotary tool, said small
diameter portion being closer to said table than said large
diameter portion, and the end of the main shaft installs the
friction stir welding use rotary tool such that said axis center of
said rotary tool is adapted to incline relative to said pair of
members.
2. A machine toolaccording to claim 1, wherein the tip end of said
main shaft is adapted to move along said axis center of said main
shaft.
3. A machine tool according to claim 1, wherein said main shaft is
adapted to move in a radial direction of said main shaft during the
rotation of the table.
4. A machine took according to claim 1, wherein said table is
adapted to move in a radial direction of an axis center thereof
during the rotation of said table.
5. A machine tool, comprising: a table adapted to have a face
thereof rotate, said face being adapted to fix a pair of members;
and a main shaft having an axis center which is inclined to a
horizontal face or a vertical face of said table and being adapted
to rotate under a state in which a friction stir welding use rotary
tool is installed to a tip end thereof, wherein as to an
inclination of said main shaft, a side of a small diameter portion
of an axis center to said rotary tool is positioned in a rear
portion from a large diameter portion of said rotary tool, said
small diameter portion being closer to said table than said large
diameter portion, and an axis center of said rotary tool is adapted
to incline.
6. A machine tool according to claim 5, wherein a tip end of said
main shaft is adapted to move along said axis center of said main
shaft.
7. A machine tool according to claim 5, wherein said main shaft is
adapted to move in a radial direction of said main shaft during
rotation of the table.
8. A machine tool according to claim 5, wherein said table is
adapted to move in a radial direction of said axis center of the
main shaft during the rotation of said table.
Description
[0001] This application is a Divisional application of application
Ser. No. 09/781,289, filed Feb. 13, 2001.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to friction stir welding along
a non-linear path, for example, a circular-shaped path.
[0003] As disclosed in Japanese application patent laid-open
publication No. Hei 9-309164 (EP 0797043 A2), friction stir welding
is a method in which, by rotating a round rod (hereinafter called
"a rotary tool"), inserting the rotary tool into a welding joint
and moving the rotary tool along to the welding line, the welding
portion is heated, softened and plastically fluidized and is
solid-stately welded.
[0004] The rotary tool is comprised of a small diameter portion
(called "a pin"), which is inserted into the welding joint, and a
large diameter portion (called "a shoulder"), which is positioned
adjacent the small diameter portion of the rotary tool. The small
diameter portion and the large diameter portion of the rotary tool
have the same axis. The large diameter portion of the rotary tool
is driven so that the rotary tool is rotated.
[0005] Japanese application patent laid-open publication No. Hei
11-197855, discloses a welding method for use a case in which a
welding line between two members has a ring shape (a circular
shape). After a start end and a finish end of the welding have
overlapped, the finish end is finished in a ring-shaped inner
portion or a ring-shaped outer portion of the welding line.
Accordingly, after the friction stir welding has been completed and
the rotary tool is withdrawn from the welded member, a hole
corresponding to the small diameter portion (the pin) of the rotary
tool is left in the welded member. When a drawing position is a
ring-shaped position to be welded, a problem in the strength of the
weld results.
[0006] Further, the rotary tool, which comprises a small diameter
portion that is inserted into the welding portion and a large
diameter portion that is positioned adjacent to and outside of the
small diameter portion, is inserted at an angle so s to be inclined
relative to the member to be welded. The direction of inclination
is such that, in a moving direction (a direction to be welded) of
the rotary tool, the small diameter portion of the rotary tool is
positioned in front of and leads the large diameter portion of the
rotary tool. In other words, the rotary tool is inclined to the
rear relative to the direction of movement. The above fact is
disclosed also in Japanese patent laid-announcement No. Hei
9-508073 (EP 0752926 B1).
[0007] In Japanese application patent laid-open publication No. Hei
11-197855, the inclined rotary tool is moved along a circular path.
However, it is extremely difficult to move an inclined rotary tool
along a path having a circular shape. To accommodate various kinds
of circular shapes, it has been suggested that the welding should
be carried out using a numeric control type machine tool. In this
type of machine tool, the member to be subjected to welding is
fixed to a table, the rotary tool is installed on a main shaft of
the machine tool, the main shaft is inclined relative to the table,
and the main shaft is moved along a path having a circular shape.
However, to maintain a predetermined inclination angle of the main
shaft in a circular moving direction, it is necessary to vary the
inclination angle with movement along the circular path; and, as a
result, the preparation of programs to control such movements is
not easily carried out.
SUMMARY OF THE INVENTION
[0008] An object of the present invention is provide to a friction
stir welding method in which welding along a path having a ring
shape or a circular shape (a circular arc is included) during the
friction stir welding can be carried out easily.
[0009] The above-stated object can be attained by a friction stir
welding method, characterized in that a first member and a second
member are fixed on a table of a machine tool having a main shaft
onto which a rotary tool is installed; and then, the table is
rotated relative to an axial center of the desired non-linear
welding line, and also relative to the direction in which the first
member and the second member are to be welded, under a state in
which the table is inclined, so as to effect relative movement
between the members to be welded and the rotary tool, thereby
carrying out friction stir welding of the first and second
members.
BRIEF DESCRIPTION OF DRAWING
[0010] FIG. 1 is a side view of an object to be subjected to
friction stir welding according to one embodiment of the present
invention;
[0011] FIG. 2 is a flow chart of a friction stir welding process
according to one embodiment of the present invention;
[0012] FIG. 3 is a plane view of an object before welding;
[0013] FIG. 4 is a longitudinal cross-sectional view taken along
line IV-IV in FIG. 3;
[0014] FIG. 5 is a plane view of the object after welding;
[0015] FIG. 6 is a cross-sectional view taken along line VI-VI in
FIG. 5; and
[0016] FIG. 7 is a longitudinal cross-sectional view of the welded
members of FIG. 6 after the outer periphery has been cut off
DESCRIPTION OF THE INVENTION
[0017] A friction stir welding method according to one embodiment
of the present invention will be explained with reference to FIG. 1
to FIG. 7. FIG. 4 is a cross-sectional view taken along line IV-IV
in FIG. 3. The reference numeral 10 in FIG. 1 generally refers to
elements of a numeric control type machine tool, which typically
comprises a machining center. The machine tool has a table 20 for
mounting an object to be subjected to processing (in this case to
be subjected to welding), and a main shaft 30 for processing the
object to be subjected to welding. The main shaft 30 carries a
welding tool 50 and can be rotated to carry out friction stir
welding. The machine tool of this embodiment according to the
present invention is of the lateral axis type, in which the axis of
the main shaft 30 is oriented in a horizontal direction. The
surface of the table 20 for mounting (fixing) the object to be
subjected to welding is oriented substantially in the vertical
direction, with the center axis thereof being slightly inclined to
the horizontal by an angle .theta., as seen in FIG. 1. The table 20
is mounted so that it can be rotated about its center axis, which
is inclined to the horizontal.
[0018] On a tip end of the main shaft 30, a cutting rotary tool
operating as a machine tool or a friction stir welding rotary tool
50 can be installed. Herein, the friction stir welding rotary tool
50 is installed so that the tip end 51 of the rotary tool 50 is
directed toward the table 20. The axial center of the main shaft 30
and the rotary tool 50 is oriented in the horizontal direction. The
rotary tool 50 is rotated by rotation of the main shaft 30. The
main shaft 30 is mounted so as to be able to move in an axial
direction, as well as in a radial direction.
[0019] The machine tool has a tool stocking device comprised of
plural cutting rotary tools and plural friction stir welding rotary
tools, and an automatic exchange device is provided for exchanging
a desirable rotary tool between the tool stocking device and the
main shaft.
[0020] A member 70 to be subjected to welding is fixed to the table
20 using known means. As seen in FIG. 4, a circular-shaped recess
71 is provided in the member 70 on the side of the main shaft 30.
In an outer peripheral portion of the circular-shaped recess 71, an
annular step 72 is provided. The step 72 and the outer face of the
member 70 form substantially flat parallel planar surfaces. This
flat face of the step 72 is oriented in a rectangular direction
relative to the axial direction of the circular shape recess.
[0021] In the recess formed by the step 72, a circular-shaped plate
cover 76 is inserted. The outer surface of the member 70 and the
outer surface of the cover 76 are disposed in the same plane. The
butted portion between the circular periphery of the cover 76 and
the circular periphery of the step 72 is subjected to friction stir
welding. Accordingly, the portion 79 to be welded (the welding
line) has the form of a ring of circular shape. The reference
numeral 79b in FIG. 5 indicates the welding bead which is produced
by the welding.
[0022] The butted portion between the member 70 and the cover 76 is
first temporarily welded at intermittent portions by arc welding to
hold the cover 76 in position. After the temporary arc welding, the
member 70 is fixed to the table 20 and friction stir welding is
carried out. When the members 70 and 76 are joined by friction stir
welding, a space is formed by the recessed portion 71 and the cover
76 which serves as a cooling passage. An inlet and an outlet of the
cooling passage are not shown in the figure. The member 70 and the
cover 76 form a part of a cooling machine. The member 70 and the
cover 76 are made of aluminum alloys.
[0023] The table 20 can be rotated about the center of the
circular-shaped welding line 79 as a rotation center. In this
regard, the member 70 is mounted on the table 20 so that the
rotation center of the table 20 and the center of the
circular-shaped welding line 79 are coincident. The rotary tool 50,
fixed to the main shaft 30, is held stationary at first, so that it
can not move in the circumferential direction of the welding line
79; it can only be rotated with the rotation of the main shaft 30.
However, by rotation of the table 20, the rotary tool 50 is moved
relatively along the welding line 79.
[0024] The rotary tool 50, fixed to the main shaft 30, is
positioned at a position 50S, which is a position on the horizontal
plane through the axial center of the welding line 79. With the
rotary tool 50 at this position 50S, the table 20 is inclined away
with respect to the relative moving direction of the rotary tool 50
during the friction stir welding. Due to the inclination of the
table 20 in the above-stated moving direction (the direction to be
welded), the small diameter portion 51 of the rotary tool 50 is
positioned in front of the large diameter portion 52 of the rotary
tool 50 in the welding direction.
[0025] When the table is operated in the standard manner, and the
rotation direction of the table 20 is counter-clockwise, the small
diameter portion 57 of the rotary tool will be positioned to the
rear of the large diameter portion 52 of the rotary tool 50 in the
direction of rotation. The inclination angle .theta. of the table
20 is three (3) degrees, for example. In FIG. 3 and FIG. 5, the
rotary tool 50 is positioned at point 50S on the circular-shaped
welding line 79; and, since the table 20 is rotated in a clockwise
direction, an upper side of the table 20 (the member 70) is
inclined away relative to the lower side so as to separate from the
rotary tool 50.
[0026] The welding process of this embodiment according to the
present invention will be explained. With the table 20 inclined
with respect to the vertical by the above-stated three (3) degrees,
the cover 76 is fixed to the member 70 by temporary arc welding.
The rotary tool 50 is then positioned at the predetermined position
50S. In this state, by rotating (rotating on its own axis) the main
shaft 30, the rotary tool 50 is rotated, and then it is moved in
the axial direction, so that the small diameter portion 51 of the
rotary tool 50 is inserted into the butted portion 79. When the
rotary tool 50 has been inserted to a predetermined depth; the
axial movement of the rotary tool 50 is stopped. The insertion
position of the rotary tool 50 is the position 50S in FIG. 3, which
is a start point of the welding (step S11).
[0027] Next, under the state in which the inclination angle of
three (3) degrees is maintained, the table 20 is rotated. The
rotation direction of the table 20 is the left-rotation (step S13).
The center of rotation of the table 20 is the center of the
circular welding line 79. Accordingly, the rotary tool 50 is moved
relatively along to the welding line 79 and the circular-shaped
butted portion is subjected to friction stir welding. The reference
numeral 79b indicates a welding bead produced by the friction stir
welding operation.
[0028] When by rotation of the table 20 the table again reaches a
state where the tool 50 reaches the position 50S at which the
rotary tool 50 was originally inserted, namely when the table 20
has rotated through 360 degrees, the rotation of the table 20 is
continued. Accordingly, from the start point 50S of the friction
stir welding, the welding is carried out again.
[0029] Next, when the table 20 has rotated through a predetermined
angle of 360 degrees+.alpha., the main shaft 30 is moved in the
radial direction (step S15). Herein, the main shaft 30 is moved
outwardly from the circular-shaped welding line 79 as the table 20
is made to continue its rotation. The inclination angle .theta. of
the table is not varied. Accordingly, outside of the circular
welding line 79, an arc-shaped welding bead 79c is formed, as seen
in FIG. 5. The inclination angle .theta. of the rotary tool 50 with
respect to the relative direction of movement of the rotary tool 50
from the point at the angle 360 degrees+.alpha. (the point from
which the main shaft 30 is started to move in the radial direction)
must be the above stated three (3) degrees to effect a proper weld.
However, since this portion of the member 70 is not normally a
portion to be subjected to friction stir welding, this requirement
of the regular friction stir welding can be dispensed with.
[0030] When the rotary tool 50 has moved to a predetermined
position 50E, the main shaft 30 (namely, the rotary tool 50) is
withdrawn from the member 70 at the end of the welding line 79c
(step S17). The position of withdrawal of the main shaft 30 is
determined by the extent of radial movement of the main shaft 30.
The withdrawal position of the main shaft 30 is located just inside
of the outer diameter of the member 70. At the position (the finish
point of the welding) where the rotary tool 50 is withdrawn from
the member 70, a hole 55, which corresponds to the outer diameter
of the small diameter portion 51 of the rotary tool 50,
remains.
[0031] After the friction stir welding has been completed, the
member 70 is removed from the table 20, and using another machine
tool, the unnecessary peripheral portion of the member 70 is cut
off. Herein, the portion of the member 74 outside of the
circular-shaped welding line 79 is cut off to leave a circular
shape (step S21). The reference numeral 74 in FIG. 5 and FIG. 6
indicates the cut-off position. Since the hole 55 remains at the
finish point of the welding, the portion with this hole 55 is
removed by cutting off an outer peripheral portion of the member 70
according to a machine processing. Further, since burrs and
recessed portions often remain in the welded portion, the face that
has been welded (an upper face in FIG. 6) is machined, if
necessary. As a result, the hole 55 in the welding portion is
removed, and the side that has been welded becomes flat, so that a
good product appearance can be obtained.
[0032] Accordingly, it is unnecessary to incline the rotary tool 50
and to move the rotary tool 50 along the circular shape. Using a
machine tool in which the main shaft 30 (the rotary tool 50) is not
inclined, friction stir welding can be effectively carried out.
Further, in a case where the main shaft 30 is inclined, the design
of a program for maintaining the predetermined angle .theta. of the
rotary tool along the entire length of the path of circular shape
is troublesome and expensive. However, according to the
above-stated embodiment, since the required inclination is provided
by the table 20, the design of high cost programs becomes
unnecessary. Accordingly, according to the present invention,
friction stir welding can be carried out in a low cost and simple
way using an existing machine tool.
[0033] The cut-off processing is carried out according to demand.
The hole 55 at the finish point of the welding can be bored out by
a drill machine and the like, and the hole can be used as a bolt
hole and the like. Further, the hole 55 can be buried using TIG
(Tungsten Inert Gas) welding, and the welded surface can be
machined. As a welding rod for the TIG welding, the same material
as that of the member 70 is used. Accordingly, the welding portion
where the hole is formed will be hardly seen even in the case where
no coating is applied.
[0034] At the side of the main shaft 30, an optical type sensor for
detecting the position of the butted portion is provided, and,
based on the output of this optical type sensor, the position of
the main shaft 30 can be moved. The moving direction of the main
shaft 30 is a rectangular direction with respect to the relative
direction of movement due to the rotation of the table 20.
Accordingly, even when the accuracy of a first member (70) and the
accuracy of a second member (76) in the butted portion (the joining
line 79) are inferior, the axial center of the rotary tool 50 can
be positioned at the center of the circular butted portion.
[0035] Further, the welding lines of the object to be welded may be
a circular path, a ring-shaped free curved line, a non-ring-shaped
circular line, and a non-ring-shaped free curved line. In the case
of the free curved line, the table 20 can be rotated around the
center of the circular arc of the welding portion as a center while
the table 20 as a whole is moved in a linear direction. Since the
machine tool is of the numeric control type, the welding can be
carried out easily along welding lines having the form of various
curved lines. The hole 55 at the finish point of the welding, in
the case of a circular arc-shaped line, will be buried using
welding or soldering. Further, it is possible to carry out friction
stir welding along a welding line which comprises four (4) linear
sides. In this case, to achieve welding along a path having four
(4) linear sides, the table is moved linearly. At the time of
welding the intersecting portions of the sides or the circular arc
portions in the vicinity of the corners, the table 20 is
rotated.
[0036] Further, not only the welding of a butted portion, but also
a portion in which two members are overlapped can be welded.
Further, it is possible to use a longitudinal type machine
tool.
[0037] When the welding has been completed in an inner side of the
circular welding line, for example, the inner side member is
removed according to a counter boring processing.
[0038] The rotary tool 50 is inclined relative to the moving
direction, and the rotation for effecting relative movement is
carried out by the table 20. Since the inclination of the rotary
tool 50 and the circular movement of the rotary tool 50 are
independent, the welding can be carried out at a low cost and
easily.
[0039] Further, after the friction stir welding has been carried
out, under the state where the member 70 is fixed to the table 20,
the rotary tool 50 on the main shaft 30 is exchanged for a cutting
rotary tool. The exchange is carried out using an automatic
exchanging device disposed between the main shaft 30 and a tool
stocking device. After that, by rotating the main shaft, the
cutting tool is rotated, and an unnecessary portion of the member
70 is cut off However, when friction stir welding has been carried
out, the oil used for the cutting and the oil for cleaning after
the cut-off processing exert a bad influence on the friction stir
welding joint. Further, depending on the residual stock removal,
the combination accuracy in the two members may become bad.
However, after friction stir welding has been carried out, since
the unnecessary portion is cut off, the above-stated problems can
be eliminated. Before the friction stir welding, the cut-off of the
two members may be carried out, however the removal of the cutting
oil is to be carried out sufficiently using another machine. As
cut-off processes, for example, there are an enlargement with a
desirable diameter of the hole 55 at the time of withdrawal of the
rotary tool 50, as well as a screw cutting process.
[0040] Further, friction stir welding of a pair of members to be
subjected to welding may be carried out in a first welding portion
of the members using a first rotary tool; next, between the main
shaft and the tool stocking device, the first rotary tool is
exchanged for a second rotary tool; and then, friction stir welding
of a second welding portion of the above-stated members to be
subjected to welding is carried out using the second rotary
tool.
[0041] The technical range of the present invention is not limited
by the foregoing embodiments or the described means for solving the
problems of the prior art, but also includes a range in which one
of ordinary skill in this technical field would recognize obvious
equivalents.
[0042] According to the present invention, friction stir welding
can be carried out along a path having a ring shape, circular
shape, free curved line shape, and a circular arc shape easily and
at low cost.
* * * * *