U.S. patent application number 10/086694 was filed with the patent office on 2002-08-29 for method of friction stir welding structural body, structural body, and extruded material.
Invention is credited to Kawasaki, Takeshi, Sagawa, Toshiaki.
Application Number | 20020119336 10/086694 |
Document ID | / |
Family ID | 25154858 |
Filed Date | 2002-08-29 |
United States Patent
Application |
20020119336 |
Kind Code |
A1 |
Kawasaki, Takeshi ; et
al. |
August 29, 2002 |
Method of friction stir welding structural body, structural body,
and extruded material
Abstract
The object of the present invention is to weld a hollow-shaped
material from one side, regardless of the size accuracy of the
hollow-shaped material or the like, and to form the joint with
higher strength. Projecting segments 12b, 22b of face plates of
hollow-shaped materials 10, 20 are friction stir welded from above.
Next, a connecting material 30 is placed on the upper face plates
11, 21 of the hollow-shaped materials 10, 20, and is friction stir
welded from above. The welding region exists at the node between a
rib connecting the two face plates 11, 12 (21, 22) and the face
plate 11 (21,). The joint of the connecting material 30 and the
face plates 11, 21 are lap joint. Not butt joint. Therefore, the
hollow-shaped materials could be welded with ease, even though
there exists manufacturing tolerance, or tolerance in arrangement
of the hollow-shaped materials 10, 20.
Inventors: |
Kawasaki, Takeshi;
(Kudamatsu, JP) ; Sagawa, Toshiaki; (Kudamatsu,
JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
25154858 |
Appl. No.: |
10/086694 |
Filed: |
March 4, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10086694 |
Mar 4, 2002 |
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09791812 |
Feb 26, 2001 |
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6386425 |
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Current U.S.
Class: |
428/544 ;
228/112.1 |
Current CPC
Class: |
B23K 20/122 20130101;
B23K 33/00 20130101; Y10T 428/12 20150115; B23K 2101/045
20180801 |
Class at
Publication: |
428/544 ;
228/112.1 |
International
Class: |
B21C 001/00 |
Claims
We claim:
1. A structural body, comprising two hollow-shaped materials welded
together; each of said hollow-shaped materials includes two face
plates which are connected by a plurality of ribs, and an end
portion of one of said face plates is projected further than an end
portion of the other of said face plates; the projected end
portions are friction stir welded together; a connecting material
which is substantially parallel to said projected one of said face
plates overlaps an end portion of each of said other face plates of
said hollow-shaped materials, with the overlap being friction stir
welded; and an external surface of said other face plate is
provided with a convex portion along the end portion of said
connecting material.
2. A structural body, comprising: two hollow-shaped materials
welded together; each of said hollow-shaped materials includes two
face plates which are connected by a plurality of ribs, and an end
portion of one of said face plates is projected further than an end
portion of the other of said face plates; the projected end
portions are friction stir welded together; a connecting material
which is substantially parallel to said projected one of said face
plates overlaps an end portion of each of said other face plates of
said hollow-shaped materials, with the overlap being friction stir
welded; and a surface of said connecting material facing said
projected face plate is provided with a convex portion, and said
convex portion is positioned in the vicinity of said other face
plate.
3. A structural body, comprising: two members having overlapping
surfaces, the overlapping surfaces being friction stir welded; and
a convex portion is provided to a surface of one of the two members
adjacent an end portion of the other of the two members, said
surface from which the convex portion extends being adjacent the
other member.
4. An extruded material for friction stir welding, comprising: two
face plates connected by a plurality of ribs; an end portion of one
of said face plates is positioned near a rib at an end portion of
said one of said face plates; an end portion of the other face
plate is projected further than an end portion of said one of said
face plates; and a convex portion is provided to a surface of said
other face plate, closest to said one of said face plates, along
the end portion of said other face plate.
5. An extruded material for friction stir welding according to
claim 4, wherein: said rib at an end portion and a rib adjacent
thereto are substantially connected to one point of said other face
plate.
6. An extruded material for friction stir welding according to
claim 4, wherein: said rib at an end portion of said one of said
face plates is substantially perpendicular to said other face
plate.
7. An extruded material for friction stir welding, comprising: a
first convex portion provided to one of the surfaces at both ends
of a plate; and a pair of second convex portions having narrower
width than that of said first convex portion, provided to the
opposite surface of the plate to that provided with said first
convex portion at both ends.
8. An extruded material for friction stir welding, comprising: a
convex portion provided to one of the surfaces at both ends of a
plate; and a pair of concave portions provided to the surface of
the plate opposite to the surface having said convex portion, the
width of each of said concave portions being narrower than the
width of said convex portion.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a structural body made of
hollow-shaped material and a method of manufacturing the same. For
example, the present invention is preferably applied to
manufacturing of structural bodies formed from hollow extruded
materials made of aluminum alloy which are used in a railway car, a
building structure, and the like.
DESCRIPTION OF THE RELATED ART
[0002] A friction stir welding method is a technique using a round
shaft (called a rotary tool) being inserted into the welding region
of members and moving the rotating rotary tool along the joint
line, thereby heating, mobilizing, fluidizing and plasticising the
welding region, and realizing a solid-phase welding of the members.
The rotary tool is comprised of a small-diameter portion to be
inserted into the welding region, and a large-diameter portion
positioned at the outer side thereof. The small-diameter portion
and the large-diameter portion are coaxial. The boundary between
the small-diameter portion and the large-diameter portion is
slightly inserted into the welding region. This technique is
disclosed in Japanese Patent Laid-Open No. H9-309164
(EP0797043A2).
[0003] FIG. 9 of the literature discloses welding two faces of the
hollow extruded materials from one side. Also, the same discloses a
joint which prevents deformation of the hollow-shaped material.
SUMMARY OF THE INVENTION
[0004] The case where a hollow-shaped material is friction stir
welded from one side, as is disclosed in FIG. 9 of the
above-mentioned Japanese Patent Laid-Open No. H9-309164
(EP0797043A2) will be considered. In such case, the interval
between the upper plates 33, 33 of the two hollow-shaped materials
31, 32 (that is, the interval between the concave portions 39, 39),
and the accuracy of the width of the joint 60 being arranged to the
region are important. If the interval between the upper plates 33,
33 is smaller than the width of the joint 60, then the joint 60
cannot be arranged thereto. On the other hand, if the interval
between the upper plates 33, 33 is larger than the width of the
joint 60, it is difficult to perform friction stir welding. That
is, it is important to maintain the gap in the butted region
between the plate 33 and the joint 60 small.
[0005] However, there tends to be formed a large gap in the butted
region due to the manufacturing tolerance in the extrusion of
hollow-shaped materials 31, 32 or the joint 60. This becomes
noticeable in the case where many hollow-shaped materials are
juxtaposed and welded, as is in the case of welding a car body of a
railway car.
[0006] On the other hand, welding the joint 60 to the concave
portion 39 by lap joint is possible. By doing so, the interval
between the concave portions 39, 39 (interval between the plates
33, 33) could be formed sufficiently larger than the joint 60, and
the materials 31, 32 could be manufactured with ease.
[0007] However, in such case, the material bends at the connecting
region between the plate 33 and the concave portion 39. Therefore,
stress concentrates at this region, and the generated stress is
increased. Moreover, friction stir welding is performed at the
vicinity of the flexure, so that the strength is deteriorated due
to the heat effect generated by the welding. As a result of the
synergy of these strength deteriorating factors, the allowable
stress is greatly deteriorated.
[0008] The object of the present invention is to enable welding of
the hollow-shaped material from one side, regardless of the size
accuracy of the hollow-shaped material and the like.
[0009] The second object of the present invention is to enable
positioning of the lap joint with ease.
[0010] The above-mentioned objects could be achieved by a method of
friction stir welding a structural body, the method comprising:
[0011] preparing two hollow-shaped materials, each hollow-shaped
material including two face plates which are connected by a
plurality of ribs, and an end portion of one of the face plates
being further projected than an end portion of the other face
plate, in which each face plate at the external side of the
hollow-shaped materials is substantially flat;
[0012] welding the projected face plates together from the other
face plate side with friction stir welding;
[0013] overlapping a connecting material which is substantially
parallel to the projected one of face plates to an end portion of
each other face plate of the hollow-shaped materials, in which the
position of said connecting material relative to the hollow-shaped
materials is determined by a convex portion provided either to the
connecting material or to the other face plate during the
overlapping; and
[0014] friction stir welding said overlap from the external side of
the hollow-shaped material.
[0015] The second object mentioned above could be achieved by a
method of friction stir welding a structural body, comprising:
[0016] overlapping an end portion of a first member on top of an
end portion of a second member, the position of the first member
relative to the second member being determined by a convex portion
provided to the first member or the second member during the
overlapping; and
[0017] friction stir welding the overlap.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a longitudinal cross-sectional view of the feature
of the welding region according to an embodiment of the present
invention;
[0019] FIG. 2 is a longitudinal cross-sectional view of the welding
region according to an embodiment of the present invention;
[0020] FIG. 3 is a longitudinal cross-sectional view of a pair of
hollow-shaped materials according to an embodiment of the present
invention;
[0021] FIG. 4 is a perspective view of a car body of a railway
car;
[0022] FIG. 5 is a longitudinal cross-sectional view of the feature
of another embodiment of the present invention;
[0023] FIG. 6 is a longitudinal cross-sectional view of the feature
of another embodiment of the present invention; and
[0024] FIG. 7 is a longitudinal cross-sectional view of the feature
of another embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0025] A preferred embodiment of the present invention will now be
explained with reference to FIG. 1 through FIG. 4. There will be
cases where reference numbers not indicated in FIG. 1 is used in
the following explanation. In such cases, the reference number
subtracted by 10 corresponds to the reference number of the part in
the left half of the drawings. FIG. 1 is an enlarged view of the
feature of FIG. 2, FIG. 2 is an enlarged view of the feature of
FIG. 3, and FIG. 3 is a longitudinal cross-sectional view of the
feature of the side structure of FIG. 4.
[0026] A car body 200 is comprised of side structures 201
constituting the side surfaces, a roof structure 202 constituting
the roof, an underframe 203 constituting the floor, and end
structures 204 constituting the end portions in the longitudinal
direction. The side structures 201, the roof structure 202 and the
underframe 203 are formed by welding a plurality of extruded
materials together, respectively. The longitudinal direction of the
extruded material is positioned toward the longitudinal direction
of the car body. The extruded material is a hollow-shaped material
made of aluminum alloy.
[0027] The structure and the welding method of the hollow-shaped
materials 10, 20 constituting the side structure 201 will be
explained. The same applies to other regions, and other
structures.
[0028] The hollow-shaped materials 10, 20 are each comprised of two
face plates 11, 12 and 21, 22, and a plurality of ribs 13, 23
arranged in a truss shape. The two face plates 11, 12 (21, 22) are
substantially parallel. The pitch of the trusses by the ribs 13, 23
are uniform. The trusses are constituted by the center lines of the
plate thickness of the face plates 11, 12, 21, 22 and the ribs 13,
23. The apexes are positioned on the face plates 11, 12, 21, 22
side.
[0029] To the vicinity of the apexes of the trusses at the inner
side of the car, there are unitarily provided rails 19, 29 for
mounting equipments thereto. The rails 19, 29 are comprised of two
L-shaped members. The rail becomes a mounting seat for equipments
such as an interior board or a chair and the like.
[0030] The end portion of the face plates 12, 22 positioned to the
outer surface side of the car body is projected further towards the
adjacent hollow-shaped materials 20, 10 side than the end portion
of the face plates 11, 21 at the inner side of the car. The
projected face plates are called 12b, 22b. Friction stir welding is
performed by butting the end portion of the face plates 12b, 22b
against each other. The end portions are abutted against each other
in order to minimize the gap in the butted region. The plate
thickness of the face plates 12b, 22b are thicker than the plate
thickness of the face plates 12, 22 at other regions.
[0031] The hollow-shaped materials 10, 20 are placed on a bed 240
with the face plates 12, 22 downward. The face plates 11, 21 side
are positioned upward. Friction stir welding is performed by
inserting a rotary tool 250 into the welding region from above. It
may be said that the friction stir welding is performed from the
inner side of the car.
[0032] The end portion of the face plates 12b, 22b are provided
with convex portions 16, 26 projecting towards the inner side of
the car (that is, toward the face plates 11, 21 side). The width
and height of the convex portions 16, 26 are substantially the
same.
[0033] The end portion of the face plate 11 and the end portion of
the face plate 21 at the inner side of the car are welded through a
connecting material 30. The connecting material 30 is placed on
(overlaps) the face plates 11, 21. The welding region is at the
node between the rib 23A (13A) and the rib 23B (13B).
[0034] A convex portion 35 projecting upwardly is provided to each
end of the connecting material 30. The upper surface of the convex
portion 35 is provided with a V-shaped groove 36. The groove 36 is
positioned at the center of width of the convex portion 35. The
width of the convex portion 35 is larger than the diameter of a
large-diameter portion 252 of the rotary tool 250. The groove 36
acts as the object of position detection for guiding the rotary
tool 250. The groove 36 is detected with the use of a laser sensor,
so that the axial center of the rotary tool 250 coincides with the
groove 36. The node between the two ribs 13A (23A) and 13B (23B)
exists on the extension of the groove 36, that is, on the axial
center of the rotary tool 250.
[0035] To the surface opposite to the convex portions 35, 35, there
are provided convex portions 37, 37. The interval of the convex
portions 37, 37 is smaller than the interval between the end
portion of the face plates 11, 21. The width of the convex portion
37 is narrower than that of the convex portion 35.
[0036] The overlapping surfaces between the connecting material 30
and the face plates 11, 21 are flat without any inequality, so that
they are in contact with each other. The connecting material 30 is
an extruded material made of the same material with the
hollow-shaped materials 10, 20. The length of the connecting plate
30 is the same as the length of the hollow-shaped materials 10,
20.
[0037] The distance P from the end portion of the face plate 11 to
the end portion of the face plate 21 (distance from the apex of the
truss at the end portion of the hollow-shaped material 10 to the
apex of the truss at the end portion of the hollow-shaped material
20) is the same as the pitch P of the trusses at other
locations.
[0038] The trusses of the hollow-shaped material are isosceles
triangles, when setting the apexes on the face plates 11, 12, 21,
22 side. However, the truss at the end portion of the hollow-shaped
materials 10, 20 is not an isosceles triangle. The ribs 13A, 23A
constituting the truss at the end portion of the hollow-shaped
materials 10, 20 are at an angle of 1 to the vertical line. The
ribs 13B, 23B constituting the truss of the end portion mentioned
above are at an angle of 2 to the vertical line. The angle 1 is
smaller than the angle 2.
[0039] Therefore, the rib 13A (23A) is connected to the
intermediate point of the face plate 12 (22). A space for inserting
the friction stir welding device is formed at the interval between
the connecting region of the rib 13A and the face plate 12 and the
connecting region of the rib 23A and the face plate 22.
[0040] Because the ribs 13A, 23A are more vertical than the ribs
13B, 23B (1 is smaller), the plate thickness of the ribs 13A, 23A
are thicker than the plate thickness of the ribs 13B, 23B. The
plate thickness of the ribs 13B, 23B are thicker than that of the
other ribs 13. The connecting regions between ribs 13A, 13B, 13 and
the face plates 11, 12, 21, 22 are arcuate. The thickness of the
connecting region is determined in light of strength.
[0041] The method of producing the structural body will be
explained. The hollow-shaped materials 10, 20 are placed on the bed
240, and are fixed thereto. The butted region at the end portion of
the face plates 12b, 22b are either in contact with each other, or
positioned close by. The convex portions 16, 26 of the butted
region between the face plates 12, 22 are temporarily joined by arc
welding from above. The temporarily welding is carried out
intermittently.
[0042] The upper surface of the bed 240 for placing the butted
region between the face plates 12b, 22b is flat. The vicinity of
the butted region between the face plates 12b, 22b, the vicinity of
the node between the ribs 13A, 23A and the face plates 12b, 22b,
and the vicinity of the node between the ribs 13B, 23B and the face
plates 12, 22 are all placed on the bed 240 having the same
height.
[0043] In such state, the rotary tool 250 of the friction stir
welding device is inserted to the butted region between the convex
portions 16, 26 from above, and is moved along the joint line, so
as to perform friction stir welding. The axial center of the rotary
tool 250 is vertical (direction along the normal of the welding
region). However, the axial center of the rotary tool is inclined
relative to the moving direction of the rotary tool 250, as is
known in the art. The butted region between the two convex portions
16, 26 is detected with the aforementioned sensor, in order to
determine the position of the gap. The axial center of the rotary
tool 250 is positioned at the gap.
[0044] The rotary tool 250 is comprised of a large-diameter portion
252 and a small-diameter portion 251 at the leading end thereof.
The leading end of the small-diameter portion 251 is positioned at
the vicinity of the lower surface of the face plates 12b, 22b. The
lower end of the large-diameter portion 252 is positioned between
the peak of the convex portions 16, 26 and the surface of the face
plates 12b, 22b at the inner side of the car (surface at the face
plates 11, 21 side). The diameter of the large-diameter portion 252
is smaller than the sum width of the two convex portions 16, 26.
The small-diameter portion 251 is a screw portion.
[0045] As a result of the friction stir welding, the gap existing
at the butted region between the face plates 12b, 22b is infilled
and welded. The outer surface side (outer side of the car) of the
butted region is welded evenly. There exists no concave portion of
the joint line at the external side of the face plates 12b,
22b.
[0046] The upper surfaces of the convex portions 16, 26 are
concaved by the large-diameter portion 252 of the rotary tool 250.
The non-welded region remains at both sides of the concave
portion.
[0047] Next, the connecting material 30 is placed on the face
plates 11, 21. The overlap between the connecting material 30 and
the face plates 11, 21 becomes the predetermined size by the convex
portions 37, 37. The end portions of the connecting material 30 are
temporarily fixed against the face plates 11, 21 by arc welding.
The temporary welding is performed intermittently. The welding is
fillet welding.
[0048] Subsequently, the lap welding between the connecting
material 30 and the face plates 11, 21 are performed using the
friction stir welding device used in the friction stir welding of
the butted region between the face plates 12b, 22b. The rotary tool
250 is inserted to the overlap between the connecting material 30
and the face plate 21 (11) from above, and is moved along the joint
line (that is, along the groove 36), so as to perform friction stir
welding. The joint line is positioned toward the longitudinal
direction of the material.
[0049] The width of the convex portion 35 is larger than the
diameter of the large-diameter portion 252 of the rotary tool 250.
The groove 36 is provided at the center of the width of the convex
portion 35. The axis of rotation of the rotary tool 250 is
coincided with the groove 36. That is, the rotary tool 250 is
positioned to the inner side of the end portion of the connecting
material 30 which will not be friction stir welded. Also, the
leading end of the small-diameter portion 251 of the rotary tool
250 is inserted deeper than the external surface of the face plates
11, 21. The lap welding is thus carried out. The lower end of the
large-diameter portion 252 is positioned between the upper surface
of the connecting material 30 other than the convex portion and the
peak of the convex portion 35.
[0050] The upper surface of the convex portion 35 is concaved by
the large-diameter portion 252 of the rotary tool 250. The
non-welded region remains at both sides of the concave portion.
[0051] The aforementioned sensor of the friction stir welding
device detects the groove 36, and moves the rotary tool 250 along
the groove 36. Therefore, the positional relationship between the
rotary tool 250 and the sensor, which is used during welding of the
butted region between the face plates 12b, 22b, may entirely be
used herein. The other relationship between the rotary tool and the
welding region are the same as those mentioned before.
[0052] The axial center of the rotary tool 250 is positioned on the
vertical line passing through the apex of the truss by the two ribs
13A, 13B (23A, 23B), or through the vicinity thereof. In order to
prevent defects caused by deflection, measures such as the increase
of the plate thickness of the ribs 13A, 13B (23A, 23B), the shape
of the arc connecting the rib and the face plate, and the thickness
of the connecting region, and the like are taken.
[0053] The welding of the connecting material 30 is performed first
with the face plate 11, then with the face plate 21. The welding of
both ends of the connecting material 30 may be performed
simultaneously by using two rotary tools.
[0054] With such method, the welding of the connecting material 30
is a lap joint and not butt joint. Therefore, the connecting
material 30 could be welded, even when the gap between the two
hollow-shaped materials 10, 20 changes due to the manufacturing
tolerance of the two hollow-shaped materials 10, 20, or the
tolerance in the interval of arrangement of the two hollow-shaped
materials. In particular, error is increased in the case where many
hollow-shaped materials are juxtaposed and welded simultaneously.
In such case, the welding could be performed with ease, since the
welding is a lap joint.
[0055] Also, because the connecting material 30 is welded
overlapping the face plates 11, 21, the flexuous regions at the
face plate side of the hollow-shaped materials 10, 20 are
eliminated, resulting in eliminating stress concentration.
[0056] Moreover, the welding of both surfaces of the hollow-shaped
material could be performed from one side. Therefore, there is no
need to turn over the structural body after completing welding of
one of the surfaces. Accordingly, the structural body could be
manufactured inexpensively as well as highly precisely.
[0057] Furthermore, the external surface of the welding region
between the face plates 12b, 22b is flat. The convex portions 16,
26, 35 are positioned inside the structural body or to the inner
side of the car, and not at the region where flat surface is
required (external surface side, outer side of the car). Also,
there exists no concave portion at the outer side of the car, which
is formed by being cut with the rotary tool. Therefore, there is no
need to cut the convex portion and the like, enabling inexpensive
manufacturing of a car body.
[0058] Still further, the inserting strength during welding of the
connecting material 30 is borne by the two ribs 13A, 13B (23A, 23B)
arranged towards the axial center of the rotary tool 250.
Therefore, bending of the ribs 13A, 13B (23A, 23B) could be
restrained. Also, the plate thickness of the ribs 13A, 13B (23A,
23B) could be thinned, achieving reduction in weight. Needless to
say, bending of the face plates 11, 21, 30 could also be
restrained.
[0059] The height of the bed 240 for supporting the ribs 13A, 13B
(23A, 23B) is uniform, so that bending of the face plates 12, 22
could be prevented.
[0060] Moreover, considering the case where the materials after
welding are used as a structural body, substantially all parts are
constituted from the truss structure. The welding region between
the hollow-shaped materials 10, 20 is also the truss structure.
Therefore, outward shearing rigidity is improved, resulting in
reduction in weight.
[0061] The connecting material 30, the face plates 12b, 22b between
the ribs 13A, 23A, and the ribs 13A, 23A substantially constitute a
truss, so that this region is not particularly weak. However, the
plate thickness should be considered.
[0062] Still further, the tilt angle 1 of the ribs 13A, 23A may be
formed larger than the tilt angle 2 of the ribs 13B, 23B. By doing
so, the width of the connecting material 30 is enlarged, so that it
is necessary to thicken the plate thickness thereof, resulting in
increase in overall weight. However, it is useful in the case where
large opening is needed to insert the friction stir welding
device.
[0063] The tilt angles 1, 2 may be formed the same to obtain an
isosceles triangle. By doing so, the plate thickness of the ribs
13A, 13B (23A, 23B) could be formed the same. Moreover, the plate
thickness of the ribs 13A, 23A may be thinner than in the case
shown in FIG. 1. However, when the size of the truss of the
isosceles triangle is identical to the size of the truss in other
regions, the width of the connecting material 30 is increased.
[0064] When the tilt angles 1, 2 of the two ribs 13A, 13B (23A,
23B) are set at tilt angle 1 in FIG. 1, the truss at the end
portion could be formed in a small isosceles triangle. The length
of the base of the truss at the end portion is smaller than the
length of the base of the truss in other regions. By doing so, the
distance between the node of the rib 13B (23B) and the face plate
12 (22) and the end portion of the hollow-shaped material 10
(20)could be shortened. Therefore, the width of the connecting
material 30 may be formed the same as the width of the connecting
material 30 in FIG. 1.
[0065] Every pitch of the trusses is identical, including the
region with the connecting material 30. The size of the trusses is
identical, excluding the truss at the end portion. Therefore, the
design of the hollow-shaped material could be standardized.
[0066] The node between the two ribs 13A, 13B (23A, 23B) may be
formed to the external side than the face plates 11, 21.
[0067] Moreover, the rotary tool 250 may be inserted at an angle
toward the middle of the angle formed by the two ribs 13A, 13B
(23A, 23B). In this case, the axial center is positioned toward the
apex of the truss.
[0068] The welding of the connecting material 30 in the
above-mentioned embodiment is performed by friction stir welding.
However, it may be combined with arc welding. The above-mentioned
friction stir welding is a lap joint, so that welding strength is
weak compared to the case of a butt joint. Therefore, the butted
regions between the end portions of the connecting material 30 and
the face plates 11, 21 are arc welded. The arc welding is performed
to the region with inferior strength and the like. Also, arc
welding may be used for repairing.
[0069] In the above-mentioned embodiment, both ends of the
connecting material 30 are welded by friction stir welding.
However, one end may be performed with friction stir welding and
the other end may be performed with arc welding. In such case,
friction stir welding is performed first, because arc welding
deforms more than friction stir welding.
[0070] In the above-mentioned embodiment, the face plates 11, 12,
21, 22 are parallel. However, the present invention could be
applied to the case where one of the face plates is inclined
relative to the other face plate.
[0071] The plate thickness of the ribs 13A, 13B (23A, 23B) is
thicker towards the face plates 11, 21 side than the face plate 12,
22 side. The plate thickness is thickened towards the face plates
11, 21 side because the region tends to be exposed to high
temperature during welding.
[0072] In the above-mentioned embodiment, the face plates at the
welding region are horizontal. However, welding may be performed
even in the case where the normal of the face plates at the welding
region are inclined. This tends to happen in the joint line at the
end portion of the side structure 201. In this case, the axial
center of the rotary body is positioned along the normal of the
face plate.
[0073] The groove 36 may be changed to a convex portion.
[0074] The embodiment shown in FIG. 5 will be explained. The convex
portions 37, 37 of the connecting material 30 are taken away, and
are replaced with a triangular convex portion 28 at the upper
surface of the face plate 21. Similar convex portion is formed to
the face plate 11. The distance between a pair of convex portions
28 is larger than the width of the connecting material 30. By doing
so, the interval between the convex portion 28 and the end portion
of the connecting material 30 could easily be confirmed visually.
Therefore, it is easy to confirm that the connecting material 30 is
overlapped against the face plates 11, 21 at the predetermined
position.
[0075] The embodiment shown in FIG. 6 will be explained. A convex
portion 29 is provided at the upper surface of the face plate 21
(11) at the place where the rotary tool 250 is to be inserted (at
the vicinity of the node between the two ribs 23A, 23B). The lower
surface of the connecting material 30 is provided with concave
portions 39 for engaging with the convex portions 29. The width of
the concave portion 39 is sufficiently larger than the width of the
convex portion 29, taking into consideration the tolerance of the
interval between the pair of convex portions 29. The width of the
concave portion 39 is smaller than the diameter of the
small-diameter portion 251 of the rotary tool 250. The rotary tool
250 is inserted until the lower end of the small-diameter portion
251 reaches below the base of the convex portion 29 (lower than the
upper surface of the face plate 21). The width of the concave
portion 39 and the convex portion 29 are smaller than the width of
the convex portion 35.
[0076] By doing so, the space between the concave portion 39 and
the convex portion 29 is filled using the material of the convex
portion 35 as the source. The space is filled because the material
of the corresponding member is forced downward by the
large-diameter portion 252 of the rotary tool. The material of the
convex portion 30 does not always moves to the above-mentioned
space.
[0077] In the case where the connecting material 30 and the
hollow-shaped material 20 are welded by friction stir welding, the
two members are connected against each other so that there exists
as little space as possible therebetween. However, there exists a
space between the concave portion 39 and the convex portion 29 for
absorbing the manufacturing tolerance. When friction stir welding
is performed while the above-mentioned space still exists, the
material for filling the space tends to fall short. Therefore,
defects tend to occur at interior or exterior of the welding
region.
[0078] Thus, friction stir welding is performed after filling
powdery or fibrous filler to the space between the concave portion
39 and the convex portion 29. The material used herein is an
identical material or a material of the same group with the
connecting material 30 or the hollow-shaped material 20. Powdery or
fibrous material deforms easily, so that they could absorb the
tolerance and fill the space regardless of the positional
relationship between the concave portion 39 and the convex portion
29.
[0079] The upper surface of the face plate 31 may be provided with
a concave portion, and the lower surface of the connecting material
30 may be provided with a convex portion for engaging with the
above-mentioned concave portion. In this case, the thickness of the
welding region at the hollow-shaped material 20 side is
thickened.
[0080] The embodiment shown in FIG. 7 will now be explained. The
rib 13C at the end portion of the hollow-shaped material 10C is
perpendicular to the face plates 11C, 12C (along the normal of the
face plate). The axis of rotation of the rotary tool 250, the
groove 36, the concave portion 39, and the convex portion 19 are
all provided within the range of the plate thickness of the rib
13C. The convex portion 19 corresponds to the convex portion 29. In
this embodiment, the inserting force during friction stir welding
is borne by the rib. Reference number 17Cb denotes a projecting
segment for placing the connecting material 30. The rib at the end
portion of the other hollow-shaped material may be formed the
same.
[0081] The convex portion 37, the convex portion 28, the concave
portion 39, and the convex portion 29 are explained as the
positioning means. However, they are not only applicable to
friction stir welding of the hollow-shaped materials, but also to
the lap joint of the members.
[0082] The technical scope of the present invention is not limited
to the terms used in the claims or in the summary of the present
invention, but is extended to the range in which a person skilled
in the art could easily substitute based on the present
disclosure.
[0083] According to the present invention, the hollow-shaped
material could be welded from one side, regardless of the size
accuracy of the hollow-shaped material or the like. Moreover, the
joint could be formed with higher strength.
[0084] Still more, positioning is made simple in friction stir
welding.
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