AND METHOD OF MANUFACTURING SAME
[Technical Field of the Invention]
[000 I]
The present invention relates to a metal pipe having a thickened end portion
and a method of manufacturing the same.
Priority is claimed on Japanese Patent Application No. 2015-29643, filed on
February 18,2015, the content of which is incorporated herein by reference.
[Related Art]
[0002]
From the viewpoint of improving fuel consumption and safety of an
automobile, improvements on weight saving, strength, and rigidity are required for a
vehicle body component and a mounted part (hereinafter, simply referred to as a
"part") of an automobile. In order to realize these, it is effective to increase a
thickness of a member at only a portion which contributes strength or rigidity and
decrease the thickness of the member at the other portions.
Moreover, in order to prevent a portion of a part which is welded to other
parts or members by arc welding or the like from melting down during welding, it is
sometimes necessary to increase a thickness of the member. Accordingly, the
thickness of the member being not increased over the entire part and the thickness of
the member being increased only in the portion in which welding is performed are
effective for weight saving of the part.
[0003]
As a part of an automobile which uses a metal pipe as a material, there is a
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suspension member, a torsion beam, or a shaft part (drive shaft, half shaft, or the like)
of a power transmission system. When the above-described part of an automobile is
manufactured, in upsetting processing which is performed in the related art, the
thickness of a portion of a metal pipe in a longitudinal direction is increased by
applying a pressure to the metal pipe in the longitudinal direction.
Non-Patent Document 1 discloses a technology which partially thickens a
steel plate although it is not a metal pipe.
[Prior Art Document]
[Patent Document]
[0004]
[Non-Patent Document 1] Norihiko MIURA, Munenori ONO: The
Proceedings of the 2001 Japanese Spring Conference for the Technology of Plasticity
(2001), pages 39-40
[Disclosure of the Invention]
[Problems to be Solved by the Invention J
[0005]
In the technology disclosed in Non-Patent Document I, in a case where T/t0
which is a ratio (hereinafter, referred to as a thickness increase ratio) which is obtained
by dividing a thickness T after the thickening by a thickness to before the thickening is
a predetermined value (for example, 1.4) or more, buckling may occur during the
thickening. Also when the metal pipe is thickened, in a case where the thickness
increase ratio increases, buckling occurs, and it is difficult to perform desired
thickening.
[0006]
The present invention is made in consideration of the above-described
- 2 -
circumstances, and an object thereof is to provide a metal pipe having a thickened end
portion in which at least one end is thickened at a large thickness increase ratio in a
longitudinal direction without having a buckling portion, and a method of
manufacturing the same.
[Means for Solving the Problem]
[0007]
The present invention adopts the following means so as to solve the abovedescribed
problems and attain the object.
(1) According to an aspect of the present invention, there is provided a
metal pipe having a thickened end portion, the metal pipe includes: when viewed in a
longitudinal direction of the metal pipe, a thin portion which has a thickness t 0 ; a first
thickened portion which is provided on one end and has a thickness T which is larger
than the thickness t0; and a first taper portion which is provided between the thin
portion and the first thickened portion and has the thickness which gradually increases
from to to T; in which, when a hardness of an inner surface of the first thickened
portion is measured in a circumferential direction and the hardness is plotted with
respect to a position in the circumferential direction, a waveform representing a high
hardness portion having a hardness which is 95% or more of a maximum hardness in
the circumferential direction and a waveform representing a low hardness portion
having a hardness which is less than 95% of the maximum hardness alternately appear,
and a plurality of combinations of the waveform representing the high hardness portion
and the waveform representing the low hardness portion appear.
[0008]
(2) In the metal pipe having a thickened end portion according to (1 ), the
thickness T of the first thickened portion may be 1.2 times or more than the thickness
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to of the thin portion.
[0009]
(3) In the metal pipe having a thickened end portion according to (I) or (2),
a length ofthe first thickened portion in the longitudinal direction may be 3 times or
less than an outer circumferential length of the first thickened portion.
[0010]
(4) In the metal pipe having a thickened end portion according to any one
aspect of (I) to (3), the metal pipe may further include: when viewed in the
longitudinal direction of the metal pipe, a second thickened portion which is provided
on the other end and has a thickness Ta which is larger than to; and a second taper
portion which is provided between the thin portion and the second thickened portion
and has the thickness which gradually increases from to to T a·
[0011]
(5) In the metal pipe having a thickened end portion according to (4), the
thickness T a of the second thickened portion may be 1.2 times or more than the
thickness to of the thin portion.
[0012]
(6) In the metal pipe having a thickened end portion according to (4) or (5),
a length of the second thickened portion in the longitudinal direction may be 3 times or
less than an outer circumferential length of the second thickened portion.
[0013]
(7) According to an aspect of the present invention, there is provided a
method of manufacturing a metal pipe having a thickened end portion by axially
pressing one end of the metal pipe toward the other end, the method includes: when the
metal pipe is viewed in a longitudinal direction, a first process of thickening a die non-
- 4 -
abutting portion by axially pressing a first axial press punch toward the other end side
of the metal pipe; in which the first process is performed: on the one erid side of the
metal pipe in a state where the first axial press punch having an outer circumferential
shape corresponding to an inner circumferential shape of the metal pipe is inserted, an
outer circumferential surface of the metal pipe abuts on an inner surface of a first die in
the die abutting portion on the outer circumferential surface of the metal pipe, and the
outer circumferential surface of the metal pipe does not come into contact with the
inner surface of the first die in the die non-abutting portion on the outer circumferential
surface of the metal pipe; and on the other end side of the metal pipe in a state where
the metal pipe is disposed in the first die such that the outer circumferential surface of
the metal pipe abuts on the inner surface of the first die.
In addition, according to an aspect of the present invention, there is provided a
method of manufacturing a metal pipe having a thickened end portion by axially
pressing one end of the metal pipe toward the other end, the method includes: a second
process of thickening a die abutting portion by axially pressing a second axial press
punch toward the other end side of the metal pipe; in which the second process is
performed: on the one end side of the metal pipe in a state where the second axial press
punch is inserted, and the outer circumferential surface of the metal pipe does not
come into contact with an inner surface of a second die in the die abutting portion of
the metal pipe while the outer circumferential surface of the metal pipe abuts on the
inner surface of the second die in the die non-abutting portion of the metal pipe; and on
the other end side of the metal pipe in a state where the metal pipe is disposed in the
second die such that the outer circumferential surface of the metal pipe abuts on the
inner surface of the second die.
[00 14]
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(8) In the method of manufacturing a metal pipe having a thickened end
portion according to (7), an entire of the outer circumferential surface of the metal pipe
may abut on the inner surface of the first die at the other end side of the metal pipe in
the first process.
[0015]
(9) In the method of manufacturing a metal pipe having a thickened end
portion according to (7) or (8), the other end of the metal pipe may be positioned with
respect to the first die in the first process.
[0016]
(I 0) In the method of manufacturing a metal pipe having a thickened end
portion according to any one aspect of (7) to (9), the entire of the outer circumferential
surface of the metal pipe may abut on the inner surface of the second die at the other
end side of the metal pipe in the second process.
[0017]
(II) In the method of manufacturing a metal pipe having a thickened end
portion according to any one aspect of (7) to (I 0), the other end of the metal pipe may
be positioned with respect to the second die in the second process.
[0018]
(12) In the method of manufacturing a metal pipe having a thickened end
portion according to any one aspect of (7) to (1 1 ), in the first process: a third axial
press punch having an outer circumferential shape corresponding to the inner
circumferential shape of the metal pipe may be inserted; the outer circumferential
surface of the metal pipe may abut on the inner surface of the first die in the die
abutting portion on the outer circumferential surface of the metal pipe; the outer
circumferential surface of the metal pipe may not come into contact with the inner
- 6 -
surface of the first die in the die non-abutting portion on the outer circumferential
surface of the metal pipe; and the third axial press punch may be further axially
pressed toward the one end side of the metal pipe when the first axial press punch is
axially pressed toward the other end side of the metal pipe.
In addition, in the method of manufacturing a metal pipe having a thickened
end portion according to any one aspect of (7) to (II), in the second process: a fourth
axial press punch having an outer circumferential shape corresponding to the inner
circumferential shape of the metal pipe may be inserted; the outer circumferential
surface of the metal pipe may not come into contact with the inner surface of the
second die in the die abutting portion on the outer circumferential surface of the metal
pipe; the outer circumferential surface of the metal pipe may abut on the inner surface
of the second die in the die non-abutting portion on the outer circumferential surface of
the metal pipe; and the fourth axial press punch may be further axially pressed toward
the one end side ofthe metal pipe when the second axial press punch is axially pressed
toward the other end side of the metal pipe.
[0019]
(1 3) According to another aspect of the present invention, there is provided
a method of manufacturing a metal pipe having a thickened end portion by axially
pressing one end of the metal pipe toward the other end in a state where the metal pipe
is disposed in a die such that an entire of an outer circumferential surface of the metal
pipe abuts on an inner surface: of the die, the method includes: when the metal pipe is
viewed in a longitudinal direction, a first process of thickening of an axial press punch
noncabutting portion by axially pressing a first axial press punch toward the other end
side of the metal pipe; in which the first process is performed: on the one end side of
the metal pipe in a state where an inner circumferential surface of the metal pipe abuts
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on an outer surface of the first axial press punch in the axial press punch abutting
portion on the inner circumferential surface of the metal pipe and the inner
circumferential surface of the metal pipe does not come into contact with the outer
surface of the first axial press punch in the axial press punch non-abutting portion on
the inner circumferential surface of the metal pipe.
In addition, according to another aspect of the present invention, there is
provided a method of manufacturing a metal pipe having a thickened end portion by
axially pressing one end of the metal pipe toward the other end in a state where the
metal pipe is disposed in a die such that an entire of an outer circumferential surface of
the metal pipe abuts on an inner surface of the die, the method includes: a second
process of thickening an axial press punch abutting portion by axially pressing a
second axial press punch toward the other end side of the metal pipe; in which the
second process is performed: on the one end side of the metal pipe in a state where the
inner circumferential surface of the metal pipe does not come into contact with an
outer surface of the second axial press punch in the axial press punch abutting portion
of the metal pipe and the inner circumferential surface of the metal pipe abuts on the
outer surface of the second axial press punch in the axial press punch non-abutting
portion of the metal pipe.
[0020]
(14) In the method of manufacturing a metal pipe having a thickened end
portion according to (13), the other end of the metal pipe may be positioned with
respect to the die in the first process.
[0021]
(15) In the method of manufacturing a metal pipe having a thickened end
portion according to (13) or (14), the other end of the metal pipe may be positioned
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with respect to the die in the second process.
[0022]
(16) In the method of manufacturing a metal pipe having a thickened end
portion according to any one aspect of (13) to (15), in which in the first process: the
inner circumferential surface of the metal pipe may abut on an outer surface of a third
axial press punch in the axial press punch abutting portion of the inner circumferential
surface of the metal pipe; the inner circumferential surface of the metal pipe may not
come into contact with the outer surface of the third axial press punch in the axial press
punch non-abutting portion on the inner circumferential surface of the metal pipe; and
the third axial press punch may be further axially pressed toward the one end side of
the metal pipe when the first axial press punch is axially pressed toward the other end
side ofthe metal pipe.
Moreover, in the method of manufacturing a metal pipe having a thickened
end portion according to any one aspect of (13) to (15), in which in the second process:
the inner circumferential surface of the metal pipe may not come into contact with an
outer surface of a fourth axial press punch in the axial press punch abutting portion on
the inner circumferential surface ofthe metal pipe; the inner circumferential surface of
the metal pipe may abuton the outer surface of the fourth axial press punch in the axial
press punch non-abutting portion of the inner circumferential surface ofthe metal pipe;
and the fourth axial press punch may be further axially pressed toward the one end side
o:f'the metal pipP when the second axial press punch is axially pressed towftrd the other
end side ofthe metal pipe.
[0023]
(17) According to still another aspect of the present invention, there is
provided a method of manufacturing a metal pipe having a thickened end portion by
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axially pressing one end of a metal pipe toward the other end, the method includes:
when the metal pipe is viewed in a longitudinal direction, a first process of thickening
an axial press punch non-abutting portion and a die non-abutting portion by axially
pressing a first axial press punch toward the other end side of the metal pipe; in which
the first process is performed: on the one end side of the metal pipe in a state where an
inner circumferential surface of the metal pipe abuts on an outer surface of the first
axial press punch in the axial press punch abutting portion on the inner circumferential
surface of the metal pipe, the inner circumferential surface of the metal pipe does not
come into,contact with the outer surface of the first axial press punch in the axial press
punch nott-abutting portion on the inner circumferential surface of the metal pipe, an
outer circumferential surface of the metal pipe abuts on an inner surface of a first die in
the die abutting portion on the outer circumferential surface of the metal pipe, and the
outer circumferential surface of the metal pipe does not come into contact with the
inner surface of the first die in the die non-abutting portion on the outer circumferential
surface of the metal pipe; on the other end ofthe metal pipe in a state where the metal
pipe is disposed in the first die such that the entire of the outer circumferential surface
of the metal pipe abuts on the inner surface of the first die.
Moreover, according to still another aspect of the present invention, there is
provided a method of manufacturing a metal pipe having a thickened end portion by
axially pressing one end of a metal pipe toward the other end, the method includes: a
second process of thickening an axial press punch abutting portion end a die abutting
portion by axially pressing a second axial press punch toward the other end side of the
metal pipe, in which the second process is performed: on the one end side of the metal
pipe in a state where the inner circumferential surface of the metal pipe abuts on an
outer surface of the second axial press punch in the axial press punch non-abutting
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portion on the inner circumferential surface of the metal pipe, the inner circumferential
surface of the metal pipe does not come into contact with the outer surface of the
second axial press punch in the axial press punch abutting portion on the inner
circumferential surface of the metal pipe, the outer circumferential surface of the metal
pipe abuts on an inner surface of a second die in the die non-abutting portion on the
outer circumferential surface of the metal pipe, and the outer circumferential surface of
the metal pipe does not come into contact with the inner surface of the second die in
the die abutting portion on the outer circumferential surface of the metal pipe; and on
the other end of the metal pipe in a state where the metal pipe is disposed in the second
die such that the entire of the outer circumferential surface of the metal pipe abuts on
the inner surface of the second die.
[0024]
(18) In the method of manufacturing a metal pipe having a thickened end
portion according to any one aspect of (7) to (17), the first process may be performed
in a state where a pressure medium is injected inside the metal pipe.
[0025]
(19) In the method of manufacturing a metal pipe having a thickened end
portion according to any one aspect of (7) to (18), the second process may be
performed in a state where a pressure medium is injected inside the metal pipe.
[Effects of the Invention]
[0026]
According to the aspects, it is possible to provide a metal pipe having a
thickened end pmtion in which at least one end is thickened at a large thickness
increase ratio in a longitudinal direction without having a buckling portion, and a
method of manufacturing the same.
- II -
[Brief Description of the Drawings]
[0027]
FIG. 1 is a schematic view showing a metal pipe which is used in a metal pipe
having a thickened end portion when viewed in a longitudinal direction.
FIG. 2 is a schematic view showing a metal pipe having a thickened end
portion according to a first embodiment when viewed in the longitudinal direction.
FIG. 3A is a schematic view showing a metal pipe having a thickened end
portion used in simulation of FIG. 3C.
FIG. 3B is a sectional view taken along line A-A of FIG. 3A.
FIG. 3C is a graph showing a hardness distribution of the metal pipe having a
thickened end portion according to the present embodiment which is obtained by
simulation.
FIG. 4 is an explanatory view showing a state where a first process starts, (a)
is a longitudinal sectional view on one end of a manufacturing device of a metal pipe
having a thickened end portion, and (b) is a sectional view taken along line B-B in (a).
FIG. 5 is an explanatory view showing a state of the manufacturing device of
the metal pipe having a thickened end portion when the first process ends, (a) is a
longitudinal sectional view on one end side, and (b) is a sectional view taken along line
C-C in (a).
FIG. 6 is an explanatory view showing a state of the manufacturing device of
the metal pipe having a thickened end portion before~ second process starts, (a) is a
longitudinal sectional view on one end side, and (b) is a sectional view taken along line
D-D in (a).
FIG. 7 is an explanatory view showing a state of the manufacturing device of
the metal pipe having a thickened end portion when the second process ends, (a) is a
- 12 -
longitudinal sectional view on one end side, and (b) is a sectional view taken along line
E-E in (a).
FIG. 8 is a schematic view showing a metal pipe having a thickened end
portion according to a second embodiment when viewed in a longitudinal direction.
FIG. 9 is an explanatory view showing a state of a manufacturing device of
the metal pipe having a thickened end portion according to the second embodiment
before thickening is performed, (a) is a longitudinal sectional view on one end side,
and (b) is a sectional view taken along line F-F in (a).
FIG. 10 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion when a first process ends, (a) is a
longitudinal sectional view on one end side, and (b) is a sectional view taken along line
G-G in (a).
FIG. II is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion before a second process starts, (a) is a
longitudinal sectional view on one end side, and (b) is a sectional view taken along line
H-H in (a).
FIG. 12 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion when the second process ends, (a) is a
longitudinal sectional view on one end side, and (b) is a sectional view taken along line
I-I in (a).
FIG. 13 is an explanatory view showing a positional relationship between a
manufacturing device of a metal pipe having a thickened end portion according to a
modification example of the second embodiment and a metal pipe before thickening is
performed, (a) is a longitudinal sectional view on one end side, and (b) is a sectional
view taken along line J-J in (a).
- 13 -
FIG. 14 is a schematic view showing a metal pipe having a thickened end
portion according to a third embodiment when viewed in a longitudinal direction.
FIG. 15 is an explanatory view showing a state of a manufacturing device of
the metal pipe having a thickened end portion according to the third embodiment
before thickening is performed, (a) is a longitudinal sectional view on the other end
side of a metal pipe, and (b) is a sectional view taken along line K-K in (a).
FIG. 16 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion when a first process ends, (a) is a
longitudinal sectional view on the other end side, and (b) is a sectional view taken
along line L-L in (a).
FIG. 17 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion before a second process starts, (a) is a
cross sectional view in a longitudinal direction on the other end side, and (b) is a
sectional view taken along line M-M in (a).
FIG. 18 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion when the second process ends, (a) is a
longitudinal sectional view on the other end side, and (b) is a sectional view taken
along line N-N in (a).
FIG. 19 is a schematic view showing a metal pipe having a thickened end
portion according to a fourth embodiment when viewed in a longitudinal direction.
FIG. 20 is an explanatory view showing a state of a manufacturing device of
the metal pipe having a thickened end portion according to the fourth embodiment
before thickening is performed, (a) is a longitudinal sectional view on the other end
side, and (b) is a sectional view taken along line 0-0 in (a).
FIG. 21 is an explanatory view showing the state of the manufacturing device
- 14 -
of the metal pipe having a thickened end portion when a first process ends, (a) is a
longitudinal sectional view on the other end side, and (h) is a sectional view taken
along line P-P in (a).
FIG. 22 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion before a second process starts, (a) is a
longitudinal sectional view on the other end side, and (b) is a sectional view taken
along line Q-Q in (a).
FIG. 23 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion when the second process ends, (a) is a
longitudinal sectional view on the other end side, and (b) is a sectional view taken
along line R-R in (a).
FIG. 24 is a schematic view showing a metal pipe having a thickened end
portion according to a fifth embodiment when viewed in a longitudinal direction.
FIG. 25 is an explanatory view showing a state of a manufacturing device of
the metal pipe having a thickened end portion according to the fifth embodiment
before thickening is performed, (a) is a longitudinal sectional view on one end side,
and (b) is a sectional view taken along lineS-Sin (a).
FIG. 26 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion when a first process ends, (a) is a
longitudinal sectional view on one end side, and (b) is a sectional view taken along line
T-T in (a).
FIG. 27 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion before a second process starts, (a) is a
longitudinal sectional view on one end side, and (b) is a sectional view taken along line
U-U in (a).
- 15 -
FIG. 28 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion when the second process ends, (a) is a
longitudinal sectional view on one end side, and (b) is a sectional view taken along line
V-V in (a).
FIG. 29 is an explanatory view showing tbe state of the manufacturing device
ofthe metal pipe having a thickened end portion before the first process is performed
in a case where a first die having four thickening prevention portions and four
thickening formation portions is used, (a) is a longitudinal sectional view on one end
I b side, and (b) is a sectional view taken along line W-W in (a).
FIG. 30 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion when the first process ends in the case
where the first die having the four thickening prevention portions and tbe four
thickening formation portions is used, (a) is a longitudinal sectional view on one end
lb side, and (b) is a sectional view taken along line X-X in (a).
FIG. 31 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion before the second process is
performed in the case where the first die having the four thickening prevention
portions and the four thickening formation portions is used, (a) is a longitudinal
sectional view on one end I b side, and (b) is a sectional view taken along line Y-Yin
(a).
FIG. 32 is an explanatory view showing the sta, te of the manufacturing device
of the metal pipe having a thickened end portion when the second process ends in the
case where a die having the four thickening prevention portions and the four
thickening formation portions is used, (a) is a longitudinal sectional view on one end
I b side, and (b) is a sectional view taken along line Z-Z in (a).
- 16 -
FIG. 33 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion before the first process is performed
in the case where an axial press punch having the four thickening prevention portions
and the four thickening formation portions is used, (a) is a longitudinal sectional view
on one end side, and (b) is a sectional view taken along lineA'-A' in (a).
FIG. 34 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion when the first process ends in the case
where an axial press punch having the four thickening prevention portions and the four
thickening formation portions is used, (a) is a longitudinal sectional view on one· end
side, and (b) is a sectional view taken along line B'-B' in (a).
FIG. 35 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion before the second process is
performed in the case where the axial press punch having the four thickening
prevention portions and the four thickening formation portions is used, (a) is a
longitudinal sectional view on one end side, and (b) is a sectional view taken along line
C'-C' in (a).
FIG. 36 is an explanatory view showing the state of the manufacturing device
of the metal pipe having a thickened end portion when the second process ends in the
case where the axial press punch having the four thickening prevention portions and
the four thickening formation portions is used, (a) is a longitudinal sectional view, and
(b) is a sectional view taken along line D'-D' in (a).
[Embodiments of the Invention]
[0028]
Hereinafter, a metal pipe having a thickened end portion according to an
embodiment and a method of manufacturing the same will be described with reference
- 17 -
to the drawings.
(First Embodiment, Metal Pipe 1' Having Thickened End Portion)
First, a metal pipe 1' having a thickened end portion according to a first
embodiment will be described.
FIG. I is a schematic view showing a metal pipe 1 which is used in the metal
pipe 1' having a thickened end portion when viewed in a longitudinal direction. FIG.
2 is a schematic view showing the metal pipe 1' having a thickened end portion
according to the first embodiment when viewed in the longitudinal direction.
[0029]
As shown in FIG. 1, the metal pipe 1 which is used in the metal pipe 1' having
a thickened end portion has the same thickness t 0, the outer diameter d0, and an inner
diameter io in the entire longitudinal direction. The metal pipe 1 is not particularly
limited as long as a ratio t0/d 0 which is obtained by dividing the thickness to by the
outer diameter d0 is 0.01 to 0.2. In addition, preferably, the thickness t0 is 1.2 to 15
mm, and preferably, the outer diameter do is 12 mm to 120 mm.
In addition, a material of the metal pipe 1 is not particularly limited, aud
includes steel, stainless steel, aluminum, titanium, or the like. A specific example in a
case where steel is used as the material of the metal pipe 1 includes a carbon steel pipe
for machine structure STKMllA (defined by JIS G3445) having tensile strength of
290 MPa or more.
[0030]
As shown in FIG. 2, in the metal pipe 1' having a thickened end portion
according to the present embodiment, a thickness on one end I b is T while a thickness
on the other end Ia is to similarly to the metal pipe 1. In the present embodiment, Tis
a larger value than t0 . That is, in the metal pipe 1' having a thickened end portion of
- 18 -
the present embodiment, one end 1b is thickened over a longitudinal length E1 so as to
form an one end side thickened portion (first thickened portion) 1c. In addition, in
the metal pipe 1' having a thickened end portion, a portion having the thickness to of
the metal pipe I is referred to as a thin portion 1e. The thin portion leis a portion
which has the thinnest thickness when viewed in the longitudinal direction and has a
longitudinal length E3• A taper portion (first taper portion) lfwhich has a
longitudinal length E2 is formed between the one end side thickened portion 1 c and the
thin portion I e.
As shown in FIG. 1, the metal pipe 1 has the thickness t0 in the longitudinal
direction of the metal pipe 1. However, by performing a method of manufacturing a
metal pipe 1' having a thickened end portion described below on the metal pipe 1, the
thickness of the other end 1a is stayed as to and is not changed, and the thickness of the
one end 1 b is changed from to to T. That is, by performing the method of
manufacturing a metal pipe 1' having a thickened end portion on the metal pipe !, the
other end I a of the metal pipe 1 is not thickened, and the one end 1 b of the metal pipe
1 is thickened. Moreovet~ in the taper portion lf, the thickness gradually increases
fi·om t0 to T from the thin pmiion I e toward the one end side thickened portion 1 c.
[0031]
Preferably, T/t0 is 1.2 or more, which is a ratio (hereinafter, referred to as a
thickness increase ratio) obtained by dividing the thickness T of the one end side
thickened portion lc formed on the one end 1 b of the metal pipe I' having a thickened
end portion according to the present embodiment by the thickness t0 of the thin portion
1 e. Since the thickness increase ratio T/t0 is 1.2 or more, fatigue strength becomes
the same as that of a base material when the one end side thickened portion I c is
welded to other members, which is preferable.
- 19 -
More preferably, T/t0 is 1.4 or more, and still more preferably, T/t0 is 2.0 or
more.
In addition, the thickness Tofthe one end side thickened portion lc is an
average of measurement values of the thicknesses which are measured at a plurality of
portions of the one end side thickened portion !c. Similarly, the thickness t0 of the
thin portion leis an average of the thicknesses which are measured at a plurality of
portions of the thin portion 1 e. Moreover, in the calculations of the thickness T and t0,
the thickness of the taper portion 1 f is not considered.
[0032]
In the metal pipe 1' having a thickened end portion. according to the present
embodiment, an outer circumferential surface on the one end lb side of the metal pipe
1 is thickened, and the above-described thickness increase ratio is obtained.
Accordingly, an outer diameter db of the one end I b side of the metal pipe I' having a
thickened end portion is larger than the outer diameter (an outer diameter of the other
end Ia side of the metal pipe 1' having a thickened end portion) do of the metal pipe 1.
Meanwhile, in the metal pipe 1' having a thickened end portion according to
the present embodiment, an inner circumferential surface of the metal pipe 1 is not
thickened. Accordingly, the metal pipe 1' having a thickened end portion according
to the present embodiment has the same inner diameter io as the inner diameter i0 of
the metal pipe 1 in the entire longitudinal direction.
[0033]
Next, a hardness distribution of the metal pipe 1' having a thickened end
portion will be described with reference to FIGS. 3A to 3C.
FIG. 3A is a schematic view showing the metal pipe 1' having a thickened end
pmiion used in simulation ofF! G. 3C. FIG. 3B is a sectional view taken along line A-
- 20 -
A of FIG. 3A. FIG. 3C is a graph showing a hardness distribution of the metal pipe 1'
having a thickened end portion according to the present embodiment which is obtained
by the simulation. Specifically, FIG. 3C is a graph showing a simulation result with
respect to a circumferential distribution of the hardness on the inner surface of the
metal pipe 1' having a thickened end portion in the one end side thickened portion lc
in a case where the metal pipe 1 is processed by the method of manufacturing the metal
pipe 1' having a thickened end portion described below under a condition in which the
thickness increase ratio T Ito is 2.0.
In addition, FIG. 3C shows a simulation result in a case where having a carbon
steel pipe for machine structure (STKMllA) having the outer diameter D of 48.6 mm
and the thickness t0 of 4.0 is used as the metal pipe I. Moreover, in the simulation
shown in FIG. 3C, a method of thickening three circumferential locations of the metal
pipe I at a portion on the one end 1 b side of the metal pipe 1 is used as the method of
manufacturing the metal pipe I' having a thickened end portion.
[0034]
As shown in FIGS. 3A to 3C, a portion (hereinafter, referred to as a high
hardness portion) in which hardness has 95% or more of the maximum hardness in the
circumferential direction of the metal pipe I' having a thickened end portion is formed
at three locations at approximately equal intervals in the circumferential direction of
the one end side thickened portion 1 c.
Moreover, in the metal pipe 1' having a thickened end portion according to the
present embodiment, in a case where center-to-center distances of three high hardness
portions (not shown) are respectively defined as La, Lb, and Lc in a unit of mm, a
difference between the maximum value and the minimum value of La, Lb, and Lc is
0.2 times or less than an outer circumferential length of the other end 1a. Since the
- 21 -
difference between the maximum value and the minimum value of the center-to-center
distances La, Lb, and Lc of the high hardness portion (not shown) is 0.2 times or less
than the outer circumferential length of the other end la, a thickness distribution of the
final product is uniform in the circumferential direction, which is preferable.
[0035]
In FIG. 3C, since the method of manufacturing the metal pipe 1' having a
thickened end portion is the simulation in which the case of using the method of
thickening the three circumferential locations of the metal pipe 1 at a portion on the
one end lb side of the metal pipe 1 is assumed, the high hardness portions (not shown)
are fonned at three locations at approximately equal intervals in the circumferential
direction of the one end side thickened portion !c. However, the number of the high
hardness portions (not shown) formed in the circumferential direction of the one end
side thickened portion lc is not limited to this. The number of the high hardness
portions (not shown) formed in the circumferential direction of the one end side
thickened portion lc is arbitrarily determined according to the usage of the metal pipe
I' having a thickened end portion or the like.
In addition, in the metal pipe I' having a thickened end portion according to
the present embodiment, the longitudinal length E 1 of the one end side thickened
portion lc is 3 times or less than the outer circumferential length (not shown) in the
one end side thickened portion 1 c.
[0036]
In a case hardness on the inner surface of the one end side thickened portion
I c of the metal pipe I' having a thickened end portion according to the present
embodiment is measured in the circumferential direction and the hardness is plotted
with respect to the position in the circumferential direction, a waveform representing
- 22 -
the high hardness portion (not shown) in the circumferential direction and a waveform
representing a portion (hereinafter, referred to as a low hardness portion) in which the
hardness is less than 95% of the maximum hardness on the inner surface of the metal
pipe 1 ' having a thickened end portion alternately appear. In addition, in the case the
hardness on the inner surface of the one end side thickened portion I c of the metal pipe
1' having a thickened end portion is measured in the circumferential direction and the
hardness is plotted with respect to the position in the circumferential direction, a
plurality of combinations of the waveform representing the high hardness portion (not
shown) and the waveform representing the low hardness portion (not shown) appear in
the circumferential direction. In addition, the hardness of the high hardness portion
(not shown) and the hardness of the low hardness portion (not shown) are relatively
different from each other. Accordingly, in a case where the metal pipe 1' having a
thickened end portion according to the present embodiment is applied to automobile
parts such as a suspension member, a torsion beam, or a shaft part (drive shaft, half
shaft, or the like) of a power transmission system, it is possible to dispose the high
hardness portion (not shown) of the metal pipe I' having a thickened end portion to a
portion in which high strength or high rigidity is required. Accordingly, it is possible
to extend fatigue life of the automobile part.
In addition, compared to the metal pipe 1 which is thickened by uniform
defonnation such as simple axial pressing, since the metal pipe I' having a thickened
end portion according to the present embodiment has higher strength, it is possible to
prevent the automobile part from being deformed at the time of collision of an
automobile, and it is possible to extend the fatigue life.
Moreover, when the metal pipe I' having the thickened end portion according
to the present embodiment is secondarily processed, since the low hardness portion
- 23 -
(not shown) is disposed at a portion in which cracks easily occur, cracks are not easily
occurred at the time of the secondary processing, which is preferable.
[0037]
(First Embodiment, Method of Manufacturing Metal Pipe I' Having
Thickened End Portion)
Next, the method of manufacturing the metal pipe 1' having a thickened end
portion according to the first embodiment will be described. Since the method of
manufacturing the metal pipe 1' having a thickened end portion according to the first
embodiment includes a first process and a second process, first, the first process will be
described.
[First Process]
FIG. 4 is an explanatory view showing a state before a manufacturing device 0
of the metal pipe 1' having a thickened end portion, which thickens three locations on
the outer circumferential surface of the metal pipe 1 to manufacture the metal pipe 1'
having a thickened end portion, starts processing, (a) is a longitudinal sectional view
on the one end 1 b side of the manufacturing device 0 of the metal pipe 1' having a
thickened end portion, and (b) is a sectional view taken along line B-B in (a).
[0038]
As shown in FIG. 4, the manufacturing device 0 of the metal pipe 1' having a
thickened end portion includes a die (first die, outer die) 2, an axial press punch (first
axial press punch) 3, and a punch 4.
The metal pipe 1 which is a material of the metal pipe I' having a thickened
end portion is accommodated inside the die 2. The punch 4 positions the other end Ia
of the metal pipe I accommodated in the die 2 with respect to the die 2. The axial
press punch 3 is inseJted into the one end 1 b of the metal pipe 1 accommodated in the
- 24 -
die 2, and axially presses the one end lb of the metal pipe I toward the other end Ia
side.
[0039]
The inner surface shapes and the inner diameters of the die 2 are different
from each other according to the portion in the longitudinal direction of the die 2. In
the inner surface of the die 2, the inner surfaces shape and the inner diameter of the die
2 are determined such that the inner surface of the die 2 abuts on the outer
circumferential surface of the metal pipe I on the other end Ia side of the metal pipe I.
Meanwhile, in the inner surface of the die 2, a thickening prevention portion 2a and a
thickening formation portion 2b are formed on the inner surface of the die 2 on the one
end side lb of the metal pipe I. In the die 2 shown in FIG. 4, three thickening
prevention portions 2a and three thickening formation portions 2b are formed on the
inner surface of the die 2 on the one end 1 b side of the metal pipe I.
In addition, from the viewpoint of reliably preventing buckling, preferably,
the inner surface of the die 2 abuts on the entire of the outer circumferential surface of
the metal pipe I on the other end I a side of the metal pipe I. However, the
configuration of the die 2 of the present embodiment is not limited to this. That is, a
gap between the inner surface of the die 2 and the outer circumferential surface on the
other end Ia side of the metal pipe I may be provided as long as buckling does not
occur.
In the axial press punch 3, the outer surface shape and the outer diameter of
the portion which is inserted into the metal pipe I are determined such that the portion
abuts on the inner circumferential surface of the metal pipe I. Moreover, in the axial
press punch 3, the longitudinal length of the portion which is inserted into the metal
pipe I is determined by the longitudinal length of the one end side thickened portion 1 c
- 25 -
fanned in the metal pipe 1.
[0040]
In each of the thickening prevention portions 2a, the inner surface of the die 2
abuts on a die abutting portion 20 on the outer circumferential surface of the metal pipe
1. Accordingly, in the thickening prevention portion 2a, the die abutting portion 20
on the outer circumferential surface of the metal pipe I is not thickened.
In each of the thickening formation portions 2b, the inner surface of the die 2
and a die non-abutting portion 30 on the outer circumferential surface of the metal pipe
I do not abut on each other. Accordingly, in the thickening formation portion 2b, the
die non-abutting portion 30 on the outer circumferential surface of the metal pipe I is
thickened.
[0041]
In order to prevent buckling, preferably, the minimum distance between the
inner surface of the thickening prevention portion 2a and the die abutting portion 20 on
the outer circumferential surface of the metal pipe 1 exceeds 0 and is 0.1 times or less
than the thickness to of the metal pipe I. Moreover, in order to prevent buckling,
preferably, the minimum distance between the outer surface of the axial press punch 3
and the inner surface of the metal pipe I exceeds 0 and is 0.3 times or less than the
thickness t0 of the metal pipe I.
In a case where a plurality of thickening prevention portions 2a are formed on
the inner surface of the die 2, in order to prevent buckling, preferably, the center-tocenter
distance Lin the circumferential direction of the die inner surface between two
adjacent thickening prevention portions 2a is 3 times or more and 20 times or less than
the thickness to of the metal pipe I.
[0042]
- 26 -
Configurations other than the above-described configurations of each of the
die (outer die) 2, the axial press punch 3, and the punch 4 are not particularly limited.
As described above, the axial press punch 3 is axially pressed toward the other
end l a side of the metal pipe 1 in a state where the metal pipe 1, the die 2, the axial
press punch 3, and the punch 4 are disposed. Accordingly, the metal pipe I is
compressed in the longitudinal direction.
According to the method of manufacturing the metal pipe 1' having a
thickened end portion of the present embodiment, since the die abutting portion 20 on
the outer circumferential surface of the metal pipe I abuts on the thickening prevention
portion 2a of the die 2 so as to be restricted, buckling is prevented.
[0043]
FIG. 5 is an explanatory view showing a state of the manufacturing device 0
of the metal pipe 1' having a thickened end portion when the first process ends, (a) is a
longitudinal sectional view on the one end 1 b side, and (b) is a sectional view taken
along line C-C in (a).
As shown in FIG. 5, in the metal pipe 1 after the first process ends, the die
non-abutting portion 30 on the outer circumferential surface is thickened, and the die
non-abutting portion 30 on the outer circumferential surface of the metal pipe l abuts
on the thickening formation portion 2b of the die 2. In FIG. 5, three die non-abutting
portions 30 formed on the outer circumferential surface of the metal pipe 1 are
thickened.
Moreover, in the present embodiment, the metal pipe 1 after the first process
is performed is referred to as an intermediate metal pipe 1 ".
[0044]
[Second Process]
- 27 -
Next, in the second process, the intermediate metal pipe 1" produced in the
first process is compressed in the longitudinal direction to thicken the die abutting
portion 20, and the metal pipe I' having a thickened end portion is manufactured.
That is, the die non-abutting portion 30 thickened in the first process and the die
abutting portion 20 thickened in the second process form the one end side thickened
portion lc, and the metal pipe 1' having a thickened end portion is manufactured.
[0045]
FIG 6 is an explanatory view showing a state of the manufacturing device 0'
of the metal pipe 1' having a thickened end portion before the second process starts, (a)
is a longitudinal sectional view on the one end I b side, and (b) is a sectional view
taken along lineD-Din (a).
As shown in FIG 6, in the second process, the die 2 used in the first process is
replaced with a die (second die) 2', and the axial press punch 3 is replaced with an
axial press punch (second axial press punch) 3'. The axial press punch 3' has an outer
circumferential shape corresponding to the inner circumferential shape of the
intermediate metal pipe 1 ".
[0046]
Similarly to the first die 2, the inner surface shapes and the inner diameters of
the second die 2 are different from each other according to the portion in the
longitudinal direction of the second die 2'.
Similarly to the first die, in the inner surface of the secnnd die 2', the inner
surfaces shape and the inner diameter of the die 2' are determined such that the inner
surface of the die 2' abuts on the outer circumferential surface of the intermediate
metal pipe 1" on the other end Ia side of the intermediate metal pipe I".
Meanwhile, in the im1er surface of the second die 2', a thickening prevention
- 28 -
portion 2a' and a thickening formation portion 2b' are formed on the inner surface of
the die 2' on the one end side lb of the intermediate metal pipe 1 ". In the second die
2' shown in FIG. 6, three thickening prevention portions 2a' and three thickening
formation portions 2b' are formed on the inner surface of the second die 2' on the one
end I b side of the intermediate metal pipe I".
[0047]
In each of the thickening prevention portions 2a', the inner surface of the
second die 2' abuts on the die non-abutting portion 30 on the outer circumferential
surface of the intermediate metal pipe 1" thickened in the first process. Accordingly,
in the second process, it is possible to prevent the die non~abutting portion 30 on the
outer circumferential surface of the intermediate metal pipe 1" from being thickened.
In addition, in each of the thickening formation portions 2b', the inner surface
of the second die 2' does not abut on the die abutting portion 20 on the outer
circumferential surface ofthe intermediate metal pipe I". Accordingly, in the second
process, it is possible to thicken the die abutting portion 20 on the outer circumferential
surface of the metal pipe L
[0048]
In this way, in the second process, the die abutting portion 20 which is not
thickened in the first process is thickened. At this time, since the die non-abutting
portion 30 thickened in the first process abuts on the thickening prevention pmiion 2a'
of the second die 2', it is possible to prevent buckling of the intermediate metal pipe
' 1" .
In addition, the die non-abutting portion 30 thickened in the first process
corresponds to the low hardness portion (not shown) of the metal pipe 1' having a
thickened end portion, and the die abutting portion 20 thickened in the second process
- 29 -
corresponds to the high hardness portion (not shown) of the metal pipe I' having a
thickened end portion. The die abutting portion 20 is not thickened in the first
process. However, it is considered that the nature of the die abutting portion 20 is
changed by a force generated when the axial press punch 3 is axially pressed and the
hardness of the die abutting portion 20 when the die abutting portion 20 is thickened in
the second process is increased by the change of the nature.
(0049]
FIG. 7 is an explanatory view showing a state of the manufacturing device 0'
of the metal pipe I' having a thickened end portion when the second process ends, (a)
is a longitudinal sectional view on one end 1 b side, and (b) is a sectional view taken
along line E-E in (a).
As shown in FIG. 7, the second process is performed on the intermediate
metal pipe 1 ", and it is possible to manufacture the metal pipe 1' having a thickened
end portion in which the one end I b side is thickened.
[0050]
When the metal pipe I' having a thickened end portion was manufactured in
the related art, in a case where the thickness increase ratio was 1.4 or more, buckling
occurred. Meanwhile, according to the method of manufacturing the metal pipe I'
having a thickened end portion of the present embodiment, even in a case where the
thickness increase ratio is 1.4 or more, it is possible to manufacture the metal pipe 1'
having a thickened end portion without occurring J,uckling. According to the method
of manufacturing the metal pipe I' having a thickened end portion of the present
embodiment, even when the thickness increase ratio is 2.0 or more, it is possible to
manufacture the metal pipe 1' having a thickened end portion without occurring
buckling.
- 30 -
Moreover, the method of manufacturing the metal pipe I' having a thickened
end portion of the present embodiment, the first process and the second process are
performed in cold.
[0051]
(Second Embodiment, Metal Pipe 201' Having Thickened End Portion)
Next, a metal pipe 201' having a thickened end portion according to a second
embodiment will be described.
FIG. 8 is a schematic view showing the metal pipe 201' having a thickened
end portion according to the second embodiment In the metal pipe 201' having a
thickened end portion shown in FIG. 2, the outer diameter Db on the one end I b side of
the metal pipe I' having a thickened end portion is larger than the outer diameter do on
the other end Ia side while the inner diameter i0 of the metal pipe 1' having a
thickened end portion in the entire longitudinal direction is constant Meanwhile, in
the metal pipe 20 I' having a thickened end portion according to the second
embodiment shown in FIG. 8, an inner diameter lb on the one end I b side of the metal
pipe 20 I' having a thickened end portion is smaller than an inner diameter i0 on the
other end Ia side while an outer diameter do of the metal pipe 201' having a thickened
end portion in the entire longitudinal direction is constant, and the thickness Ton the
one end lb side is configured to be larger than the thickness t0 on the other end Ia side.
That is, the metal pipe 20 I' having a thickened end portion has one end side thickened
portion 20 I c in which the thickness is T.
Moreover, detail descriptions with respect to portions having configurations
similar to those of the metal pipe I' having a thickened end portion according to the
first embodiment are omitted.
[0052]
- 31 -
Similarly to the metal pipe l' having a thickened end portion, the metal pipe
201' having a thickened end portion is manufactured with the metal pipe l as a
material. Since the metal pipe I is similar to that of the first embodiment,
descriptions thereof are omitted.
The thickness T of the metal pipe 201' having a thickened end portion on the
one end I b side is larger than the thickness t0 on the other end l a side. Moreover, the
inner diameter Ib of the metal pipe 201' having a thickened end portion on the one end
1 h side is smaller than the inner diameter i0 on the other end 1a side. Moreover, the
outer diameter do of the metal pipe 201' having a thickened end portion is constant in
the entire longitudinal direction of the metal pipe 201' having a thickened end portion.
In addition, the metal pipe 201' having a thickened end portion has a taper
portion 201 fin which the thickness gradually increases from to to Ta between the one
end side thickened portion 201 c and the thin portion I e.
[0053]
(Second Embodiment, Method of Manufacturing Metal Pipe 201' Having
T11ickened End Portion)
Next, a method of manufacturing the metal pipe 201' having a thickened end
portion according to the second embodiment will be described. Since the method of
manufacturing the metal pipe 201' having a thickened end portion according to the
second embodiment includes a first process and a second process, first, the first
process will be described.
[First Process]
FIG. 9 is an explanatory view showing a state of a manufacturing device 200
ofthe metal pipe 201' having a thickened end portion according to the second
embodiment before thickening is performed, (a) is a longitudinal sectional view on one
- 32 -
end 1 b side, and (b) is a sectional view taken along line F-F in (a).
[0054]
As shown in FIG. 9, the manufacturing device 200 of the metal pipe 201'
having a thickened end portion includes a die (outer die) 202, an axial press punch
(first axial press punch) 203, and the punch 4.
In the die 2 according to the first embodiment, the inner surface shape and the
inner diameter are determined such that the inner surface of the metal pipe I on the
other end Ia side abuts on the outer circumferential surface of the metal pipe 1, and the
thickening prevention portion 2a and the thickening formation portion 2b are formed
on the inner surface on the one end 1 b side. Meanwhile, in the die 202 according to
the second embodiment, the thickening prevention portion 2a and the thickening
formation portion 2b are not formed, and the inner surface shape and the inner
diameter are determined such that the inner surface abuts on the outer circumferential
surface of the metal pipe 1 in the entire longitudinal direction of the die 202.
[0055]
In the axial press punch 3 according to the first embodiment, the outer surface
shape and the outer diameter of the portion which is inserted into the metal pipe I are
determined such that the portion abuts on the inner circumferential surface of the metal
pipe I, and the longitudinal length of the portion which is inserted into the metal pipe 1
is determined by the longitudinal length of the one end side thickened portion lc
formed in the metal pipe I.
Meanwhile, the axial press punch (first axial press punch) 203 according to
the second embodiment is similar to the axial press punch 3 according to the first
embodiment in that the longitudinal length ofthe portion which is inserted into the
metal pipe I is determined by the longitudinal length of the one end side thickened
- 33 -
portion 20lc formed in the metal pipe I. However, the axial press punch 203
according to the second embodiment is different from the axial press punch 3
according to the first embodiment in that a thickening prevention portion 203a and a
thickening formation portion 203b are fonned on the outer surface of the portion of the
axial press punch 203 according to the second embodiment which is inserted into the
metal pipe I.
[0056]
The axial press punch 203 abuts on the inside of the one end lb ofthe metal
pipe 1 accommodated inside the die 202 to be inserted into the metal pipe 1, and
axially presses the one end 1 b of the metal pipe 1 toward the other end 1 a. In this
way, the manufacturing device 200 of the metal pipe 201' having a thickened end
portion compress the metal pipe 1 in the longitudinal direction, and one end side
thickened portion 20 I c is formed on the inner circumferential surface of the metal pipe
1 in a portion on the one end 1 b side of the metal pipe 1.
The axial press punch 203 shown in FIG. 9 includes three thickening
prevention portions 203a and three thickening formation portions 203b on the inner
surface of a portion inserted into the metal pipe 1.
[0057]
In each of the thickening prevention portions 203a, the outer circumferential
surface of the axial press punch 203 abuts on an axial press punch abutting portion 220
on the inr1er circumferential surface of the metal pipe 1. Accordingly, in the
thickening prevention portion 203a, the inner circumferential surface of the metal pipe
1 is not thickened.
Meanwhile, in each of the thickening formation portions 203b, the outer
circumferential surface of the axial press punch 203 does not abut on an axial press
- 34 -
punch non-abutting portion 230 on the inner circumferential surface of the metal pipe I.
Accordingly, in the thickening formation portion 203b, the axial press punch nonabutting
portion 230 on the inner circumferential surface of the metal pipe I is
thickened.
[0058]
In order to prevent buckling, preferably, the minimum distance between the
inner circumferential surface of the die 202 and the outer circumferential surface of the
metal pipe 1 exceeds 0 and is 0.1 times or less than the thickness t0 of the metal pipe I.
Moreover, in order to prevent buckling, preferably, the minimum distance between the
outer circumferential surface ofthe axial press punch 203 and the inner circumferential
surface of the metal pipe 1 exceeds 0 and is 0.3 times or less than the thickness t0 of
the metal pipe I.
In order to prevent buckling, preferably, a distance Lin the circumferential
direction of the outer surface of the axial press punch between two adjacent thickening
prevention portions 203a is 3 times or more and 20 times or less than the thickness t0
of the metal pipe I.
[0059]
Configurations other than the above-described configurations of each of the
die (outer die) 202, the axial press punch 203, and the punch 4 are not particularly
limited.
As described above, the axial press punch 203 is axially pressed toward the
other end I a side of the metal pipe 1 in a state where the metal pipe 1, the die 202, the
axial press punch 203, and the punch 4 are disposed. Accordingly, the metal pipe 1 is
compressed in the longitudinal direction.
According to the method of manufacturing the metal pipe 20 I' having a
- 35 -
thickened end portion of the present embodiment, since the axial press punch abutting
portion 220 on the inner circumferential surface of the metal pipe I abuts on the
thickening prevention portion 203a of the axial press punch 203 so as to be restricted,
buckling is prevented.
[0060]
FIG. 10 is an explanatory view showing a state of the manufacturing device
200 of the metal pipe 20 1' having a thickened end portion when the first process ends,
(a) is a longitudinal sectional view on the one end lb side, and (b) is a sectional view
taken along line G-G in (a).
As shown in FIG. 10, in the metal pipe 1 after the first process ends, the axial
press punch non-abutting portion 230 is thickened, and the axial press punch nonabutting
portion 230 on the inner circumferential surface of the metal pipe I abuts on
the thickening formation portion 203b of the axial press punch 203. In FIG. 10, three
axial press punch non-abutting portions 230 formed on the inner circumferential
surface of the metal pipe 1 are thickened.
Moreover, the metal pipe 1 after the first process is performed is referred to as
an intermediate metal pipe 201 ".
[0061]
[Second Process]
Next, in the second process, the intermediate metal pipe 201" produced by the
first process is compressed in the longitudinal direction to thicken the axial press
punch abutting portion 220, and the metal pipe 201' having a thickened end portion is
manufactured. That is, the axial press punch non-abutting portion 230 thickened by
the first process and the axial press punch abutting portion 220 thickened in the second
process form the one end side thickened portion 201c, and the metal pipe 201' having a
- 36 -
thickened end portion is manufactured.
[0062]
FIG. 11 is an explanatory view showing a state of the manufacturing device
200' of the metal pipe 201' having a thickened end portion before the second process
starts, (a) is a longitudinal sectional view on the one end lb side, and (b) is a sectional
view taken along line H-H in (a).
As shown in FIG. II, the second process is similar to tbe first process in that
the die 202 is used. However, the axial press punch 203 used in the first process is
replaced with an axial press punch (second axial press punch) 203'.
The intermediate metal pipe 201" is disposed in the die 202 such that the
entire of the outer circumferential surface of the intermediate metal pipe 201" abuts on
the inner surface of the die 202.
[0063]
The second axial press punch 203 includes a thickening prevention portion
203a' and a thickening formation portions 203b' on the inner surface of a portion
inserted into the metal pipe 1. The thickening prevention portion 203a' of the second
axial press punch 203' abuts on the axial press punch non-abutting portion 230 of the
intermediate metal pipe 20 I". Accordingly, in the second process, it is possible to
prevent the axial press punch non-abutting portion 230 on the inner circumferential
surface of the intermediate metal pipe 20 I" from being thickened.
In addition, the thickening formation portion 203b' of the second axial press
punch 203' does not abut on the axial press punch abutting portion 220 of the
intennediate metal pipe 20 I". Accordingly, in the second process, it is possible to
thicken the axial press punch abutting portion 220 on tbe inner circumferential surface
of the intermediate metal pipe 201 ".
- 37 -
[0064]
In this way, in the second process, the axial press punch abutting portion 220
which is not thickened in the first process is thickened. At this time, since the axial
press punch non-abutting portion 230 thickened in the first process abuts on the
thickening prevention portion 203a' of the second axial press punch 203', it is possible
to prevent buckling of the intermediate metal pipe 201 ".
[0065]
FIG. 12 is an explanatory view showing a state of the manufacturing device
200' of the metal pipe 201' having a thickened end portion when the second process
ends, (a) is a longitudinal sectional view on one end 1b side, and (b) is a sectional view
taken along line I-1 in (a).
As shown in FIG. 12, the second process is performed on the intermediate
metal pipe 201 ", and it is possible to manufacture the metal pipe 201' having a
thickened end portion in which the one end 1 b side is thickened.
[0066]
When the metal pipe 201' having a thickened end portion was manufactured
in the related art, in a case where the thickness increase ratio was 1.4 or more, buckling
occurred. Meanwhile, according to the method of manufacturing the metal pipe 20 I'
having a thickened end portion of the present embodiment, even in a case where the
thickness increase ratio is 1.4 or more, it is possible to manufacture the metal pipe 20 I'
having a thickened end portion without occurring buckling. According to the method
of manufacturing the metal pipe 201' having a thickened end portion ofthe present
embodiment, even when the thickness increase ratio is 2.0 or more, it is possible to
manufacture the metal pipe 201' having a thickened end portion without occurring
buckling.
- 38 -
[0067]
(Second Embodiment, Modification Example)
In the method of manufacturing the metal pipe 20 I' having a thickened end
portion according to the present embodiment, the metal pipe 201' having a thickened
end portion may be manufactured in a state where an internal pressure is applied to the
metal pipe I.
FIG 13 is an explanatory view showing a manufacturing device 200" of
manufacturing the metal pipe 20 I ' having a thickened end portion in a state where an
internal pressure is applied to the metal pipe 1, (a) is a longitudinal sectional view of
the manufacturing device 200" of the metal pipe 201' having a thickened end portion,
and (b) is a sectional view taken along line J-J in (a).
[0068]
As shown in FIG. 13, in manufacturing device 200" of the metal pipe 201'
having a thickened end portion, water paths 12 through which a pressure medium is
injected into the metal pipe I are formed in a punch 204' and an axial press punch
203". In the punch 203", an inner surface of the pipe end is sealed by a seal member
13. It is possible to use an 0-ring, a metal seal, or the like as the seal member 13.
As shown in FIG. 13, an internal pressure is applied to the metal pipe 1 by
injecting the pressure medium into the metal pipe I. Accordingly, when the metal
pipe I is axially pressed from the one end 1 b side toward the other end !a side using
the axial press punch 203 ", it is possible to prevent buckling on the inner
circumferential surface side of the metal pipe I.
Preferably, as the pressure medium, a liquid is used, and for example, water is
used.
[0069]
- 39 -
(Third Embodiment, Metal Pipe 301' Having Thickened End Portion)
Next, a metal pipe 301' having a thickened end portion according to a third
embodiment will be described.
FIG. I 4 is a schematic view showing the metal pipe 301' having a thickened
end portion according to the third embodiment. In the metal pipe I' having a
thickened end portion shown in FIG. 2, the outer diameter Db on the one end I b side is
larger than the outer diameter do on the other end I a side. In the metal pipe 30 I'
having a thickened end portion shown in FIG. 14, the configuration on the one end 1b
side is similar to that of the metal pipe I' having a thickened end portion. Meanwhile,
in the metal pipe 301' having a thickened end portion, the configuration on the other
end 1a side is different from that of the metal pipe I' having a thickened end portion,
and an outer diameter Da on the other end Ia side is larger than an outer diameter do of
a center portion ld in the longitudinal direction. That is, the metal pipe 301' having a
thickened end portion includes the other end side thickened portion (second thickened
portion) 301c on the other end Ia side in addition to the one end side thickened portion
1c.
In addition, the metal pipe 301' having a thickened end portion includes a
taper portion (second taper portion) 30lf, in which the thickness gradually increases
from to to Ta is formed, between the thin portion I e and the other end side thickened
portion 30lc.
Moreover, detail descriptions with respect to portions having configurations
similar to those of the metal pipe I' having a thickened end portion according to the
first embodiment and the metal pipe 20 I' having a thickened end portion according to
a second embodiment are omitted.
[0070]
- 40 -
Similarly to the metal pipe 1' having a thickened end portion and the metal
pipe 201' having a thickened end portion, the metal pipe 301' having a thickened end
portion is manufactured with the metal pipe 1 as a material. Since the metal pipe 1 is
similar to those of the first embodiment and the second embodiment, descriptions
thereof are omitted.
The thickness T of the one end side thickened portion lc and the thickness Ta
of the other end side thickened portion 301c in the metal pipe 301' having a thickened
end portion are larger than the thickness t0 of the center portion 1 d (thin portion 1 e).
In addition, as described above, the outer diameter Db of the one end side thickened
portion lc and the outer diameter Da of the other end side thickened portion 301c in
the metal pipe 301' having a thickened end portion are larger than the outer diameter
do in the center portion 1d (thin portion le). Meanwhile, in the metal pipe 301'
having a thickened end portion, the inner diameter of the one end side thickened
portion 1 c, the inner diameter of the other end side thickened portion 301 c, and the
inner diameter of the center portion 1d (thin portion le) are i0, and have the same size
as each other.
Preferably, Talt0 is 1.2 or more, which is a ratio (the thickness increase ratio)
obtained by dividing the thickness Ta of the other end side thickened portion 301c by
the thickness t0 of the center portion 1 d (the thin portion le).
More preferably, Tallo is 1.4 or more, and still more preferably, T alto is 2.0 or
more.
[0071]
In the metal pipe 301' having a thickened end portion, the thickness T of the
one end side thickened portion lc and the thickness Ta of the other end side thickened
portion 30lc may be the same as each other, or may be different from each other.
- 41 -
That is, in the metal pipe 301' having a thickened end portion, the outer diameter Db of
the one end side thickened portion lc and the outer diameter Da of the other end side
thickened portion 301c may be the same as each other, or may be different from each
other.
Moreover, in the metal pipe 301' having a thickened end portion, the
longitudinal length E1 of the one end side thickened portion lc and the longitudinal
length Ea of the other end side thickened portion 30lc may be the same as each other,
or may be different from each other.
In the metal pipe 301' having a thickened end portion, the longitudinal length
E1 of the one end side thickened portion lc is 3 times or less than the outer
circumferential length (not shown) of the one end side thickened portion Jc.
Moreover, in the metal pipe 301' having a thickened end portion, the longitudinal
length Ea of the other end side thickened portion 301 c is 3 times or less than the outer
circumferential length (not shown) of the other end side thickened portion 301c.
[0072]
The other end side thickened portion 30lc is similar to the one end side
thickened portion 1c in that the high hardness portion (not shown) and the low
hardness portion (not shown) are alternately provided in the circumferential direction.
[0073]
(Third Embodiment, Method of Manufacturing Metal Pipe 301' Having
Thickened End Portion)
Next, a method of manufacturing the metal pipe 301' having a thickened end
portion according to the third embodiment will be described. Since the method of
manufacturing the metal pipe 301' having a thickened end portion according to the
third embodiment includes a first process and a second process, first, the first process
- 42 -
will be described.
[First Process]
FIG. 15 is an explanatory view showing a state of a manufacturing device 300
of the metal pipe 301' having a thickened end portion according to the third
embodiment before thickening is performed, (a) is a longitudinal sectional view on the
other end Ia side of the metal pipe I, and (b) is a sectional view taken along line K-K
in (a).
[0074]
As shown in FIG. 15, the manufacturing device 300 of the metal pipe 30 I'
having a thickened end portion includes a die (outer die) 302, an axial press punch
(first axial press punch) 3 which is used on the one end lb side of the metal pipe I, and
an axial press punch (third axial press punch) 303 which is used on the other end la
side of the metal pipe 1.
[0075]
In the manufacturing device 0 of the metal pipe I' having a thickened end
portion according to the first embodiment, the axial press punch 3 is inserted into the
inner surface on the one end lb side of the metal pipe I, and the punch 4 is inserted
into the inner surface on the other end Ia side. Meanwhile, in the manufacturing
device 300 of the metal pipe 301' having a thickened end portion according to the third
embodiment, the axial press punch 3 is inserted into the inner surface on the one end
lb side of the metalnipe I, and the axial press punch 303 is inserted into the other end
Ia side.
In addition, in the die 2 according to the first embodiment, the thickening
prevention portion 2a and the thickening formation portion 2b are formed on only the
one end I b side of the metal pipe I. Meanwhile, in the die (first die) 302 according to
- 43 -
the third embodiment, in addition to the thickening prevention portion 2a and the
thickening fonnation portion 2b being formed on the one end lb side of the metal pipe
1, the thickening prevention portion 312a and the thickening formation portion 312b
are formed on the other end I a side.
[0076]
The configuration on the one end I b side of the die 302 according to the third
embodiment is similar to the configuration on the one end lb side of the die 2
according to the first embodiment.
Meanwhile, the configuration on the other end Ia side of the die 302 is
different from the configuration on the one end lb side ofthe die 2, and a thickening
prevention portion 302a and a thickening formation portion 302b are formed.
In the die 302 shown in FIG. 15, three thickening prevention portions 2a and
three thickening formation portions 2b are formed on the one end lb side of the metal
pipe 1, and three thickening prevention portions 302a and three thickening formation
portions 302b are formed on the other end Ia side.
[0077]
In the axial press punches 3 and 303 according to the third embodiment, the
outer surface shape and the outer diameter of the portion inserted into the metal pipe I
are determined such that the portion abuts on the inner circumferential surface of the
metal pipe I.
[0078]
As described above, the axial press punch 3 is axially pressed toward the other
end la side of the metal pipe 1 and the axial press punch 303 is axially pressed toward
the one end lb side of the metal pipe I in a state where the metal pipe I, the die 302,
the axial press punches 3 and 303 are disposed. Accordingly, the metal pipe 1 is
- 44 -
compressed in the longitudinal direction.
[0079]
FIG. 16 is an explanatory view showing the state of the manufacturing device
300 of the metal pipe 301' having a thickened end portion when the first process ends,
FIG. 16 is a longitudinal sectional view on the other end I a side, and (b) is a sectional
view taken along line L-L in (a).
Similarly to the first embodiment, as shown in FIG. 16, it is possible to
thicken the die non-abutting portion 30 of the metal pipe I on the one end I b side of
the metal pipe I by the first process of the present embodiment. Moreover, it is
possible to thicken the die non-abutting portion 30 of the metal pipe I on the other end
!a side of the metal pipe I by the first process of the present embodiment. That is, it
is possible to form the one end side thickened portion lc on the one end lb side of the
metal pipe I and form the other end side thickened portion 301 c on the other end I a
side by the first process of the present embodiment.
[0080]
In this case, since the die abutting portions 20 on the one end I b side and the
other end Ia side of the metal pipe I abut on the thickening prevention portion 2a of
the die 2 and the thickening prevention portion 302a of the die 302 so as to be
restricted, buckling is prevented.
In addition, in the present embodiment, the metal pipe I after the first process
is perfqrmed is referred to as an intermediate metal pipe 30 I".
[0081]
[Second Process]
Next, in the second process, the intermediate metal pipe 301" produced in the
first process is compressed in the longitudinal direction from the one end I b side and
- 45 -
the other end 1 a side to thicken the die abutting portion 20, and the metal pipe 301'
having a thickened end portion is manufactured. That is, the die non-abutting portion
30 thickened in the first process and the die abutting portion 20 thickened in the second
process form on the one end side thickened portion 1 c and the other end side thickened
portion 301c, and the metal pipe 301' having a thickened end portion is manufactured.
[0082]
FIG. 17 is an explanatory view showing the state of a manufacturing device
300' of the metal pipe 301' having a thickened end portion before the second process
starts, (a) is a cross sectional view in a longitudinal direction on the other end la side,
and (b) is a sectional view taken along line M-M in (a).
In the second process of the first embodiment, the die 2', the axial press punch
3', and the punch 4 are used. However, in the second process of the present
embodiment, as shown in FIG. 17, a die (second die) 302', an axial press punch
(second axial press punch) 3' and an axial press punch (fourth axial press punch) 303'
are used.
[0083]
The die 302' according to the present embodiment and the die 2' according to
the first embodiment have the same configuration as each other on the one end I b side.
Meanwhile, the die 302' according to the present embodiment is different from the die
2' according to the first embodiment, and a thickening prevention portion 302a' and a
thickening fonnation portion 302b' are also formed on theother end la side.
In the thickening prevention portion 302a', the inner surface of the die 302'
abuts on the die non-abutting portion 30 on the outer circumferential surface of the
intermediate metal pipe 301 ". Meanwhile, in the thickening formation portion 302b',
the inner surface ofthe die 302' does not abut on the die abutting portion 20 on the
- 46 -
outer circumferential surface of the intennediate metal pipe 301 ".
[0084]
FIG. 18 is an explanatory view showing the state of the manufacturing device
300' of the metal pipe 301' having a thickened end portion when the second process
ends, (a) is a longitudinal sectional view on the other end 1a side, and (b) is a sectional
view taken along line N-N in (a).
As shown in FIG. 18, it is possible to thicken not only the die abutting portion
20 on the one end 1 b side of the metal pipe 1 but also the die abutting portion 20 on the
other end 1a side by the second process of the present embodiment. Accordingly, the
metal pipe 301' having a thickened end portion is manufactured, in which not only the
one end 1 b side but also the other end I a side are thickened.
[0085]
In addition, in the first process, the case where the axial press punch 3 is used
on the one end 1b side of the metal pipe 1 and the axial press punch 303 is used on the
other end Ia side is described. However, in a case where the one end side thickened
portion lc (or the other end side thickened portion 30lc) is fanned on both ends of the
metal pipe 1, the axial press punches 3 (or axial press punches 303) may be used on
both the one end 1 b side and the other end Ia side. Moreover, in the die 302 which is
used in the first process, the case where the thickening prevention portion 2a and the
thickening fom1ation portion 2b are formed on the one end 1 b side and the thickening
prevention portion 302a and the thickening formati<:>n portion 302b are formed on the
other end 1a side is described. However, the thickening prevention portion 2a and the
thickening formation portion 2b (or the thickening prevention portion 302a and the
thickening formation portion 302b) may be formed on both the one end 1 b side and the
other end 1 a side.
- 47 -
Similarly, when the one end side thickened portion I c (or the other end side
thickened portion 301c) is formed on both ends of the metal pipe I, in the second
process, the case where the axial press punch 3' is used on the one end I b side of the
metal pipe I and the axial press punch 303' is used on the other end Ia side is
described. However, the axial press punch 3' (or axial press punch 303') may be used
on both the one end I b side and the other end Ia side. In addition, in the die 302'
which is used in the second process, the case where the thickening prevention portion
2a' and the thickening formation portion 2b' are formed on the one end I b side and the
thickening prevention portion 302a' and the thickening formation portion 302b' are
formed on the other end Ia side is described. · However, the thickening prevention
portion 2a' and the thickening formation portion 2b' (or the thickening prevention
portion 302a' and the thickening formation portion 302b') may be formed on both the
one end 1 b side and the other end I a side.
£0086]
(Fourth Embodiment, Metal Pipe 401' Having Thickened End Portion)
Next, a metal pipe 401' having a thickened end portion according to a fourth
embodiment will be described.
FIG. 19 is a schematic view showing the metal pipe 401' having a thickened
end portion according to the fourth embodiment. In the metal pipe 20 I' having a
thickened end portion shown in FIG. 8, the inner diameter Ib on the one end I b side is
smaller than the inner diameter io on the other end 1 a side. In the metal pipe 401'
having a thickened end portion shown in FIG. 19, the configuration on the one end 1 b
side is similar to that ofthe metal pipe 201' having a thickened end portion.
Meanwhile, the configuration on the other end Ia side of the metal pipe 401' having a
thickened end portion is different from that of the metal pipe 201' having a thickened
- 48 -
end portion, and the inner diameter I a on the other end I a side is smaller than the inner
diameter io of the center portion I d. That is, the metal pipe 40 I' having a thickened
end portion includes the other end side thickened portion (second thickened portion)
401c on the other end Ia side in addition to the one end side thickened portion 201c.
In addition, the metal pipe 401' having a thickened end portion includes a
taper portion (second taper portion) 40 If in which the thickness. gradually increases
from to to T a between the thin portion I e and the other end side thickened portion 40 I c.
Moreover, detail descriptions with respect to portions having configurations
similar to those of the metal pipe 1' having a thickened end portion according to the
first embodiment, the metal pipe 201' having a thickened end portion according to the
second embodiment, and the metal pipe 30 I' having a thickened end portion according
to the third embodiment are omitted.
[0087]
Similarly to the metal pipe 1' having a thickened end portion, the metal pipe
201' having a thickened end portion, and the metal pipe 301' having a thickened end
portion, the metal pipe 40 I' having a thickened end portion is manufactured with the
metal pipe I as a material. Since the metal pipe I is similar to those of the first to
third embodiments, descriptions thereof are omitted.
The thickness T of the one end side thickened portion 20lc and the thickness
Ta of the other end side thickened portion 40lc in the metal pipe 401' having a
thickened end portion are larger than the thickness t0 of the center portion ld (thin
portion !e). In addition, as described above, the inner diameter It of the one end side
thickened portion 201c and the inner diameter I a of the other end side thickened
portion 40lc in the metal pipe 401' having a thickened end portion are smaller than the
inner diameter i0 in the center portion ld (thin portion !e). Meanwhile, in the metal
- 49 -
pipe 401' having a thickened end portion, the outer diameter of the one end side
thickened portion 20lc, the outer diameter of the other end side thickened portion 40lc,
and the outer diameter of the center portion ld (thin portion I e) are d0, and have the
same size as each other.
[0088]
In the metal pipe 40 I' having a thickened end portion, the thickness T of the
one end side thickened portion 20 I c and the thickness T a of the other end side
thickened portion 40 I c may be the same as each other, or may be different from each
other. That is, in the metal pipe 401' having a thickened end portion, the inner
diameter h of the one end side thickened portion 201 c and the inner diameter Ia of the
other end side thickened portion 401c may be the same as each other, or may be
different from each other.
Moreover, in the metal pipe 40 I' having a thickened end portion, the
longitudinal length Eb of the one end side thickened portion 201 c and the longitudinal
length Ea of the other end side thickened portion 401c may be the same as each other,
or may be different from each other.
[0089]
The other end side thickened portion 401 c is similar to the one end side
thickened portion 201c in that the high hardness portion (not shown) and the low
hardness portion (not shown) are alternately provided in the circumferential direction.
[0090]
(Fourth Embodiment, Method of Manufacturing Metal Pipe 401' Having
Thickened End Portion)
Next, a method of manufacturing the metal pipe 401' having a thickened end
portion according to the fourth embodiment will be described. Since the method of
- 50 -
manufacturing the metal pipe 401' having a thickened end portion according to the
fourth embodiment includes a first process and a second process, first, the first process
will be described.
[First Process]
FIG. 20 is an explanatory view showing a state of a manufacturing device 400
of the metal pipe 40 I' having a thickened end portion according to the fourth
embodiment before thickening is performed, (a) is a longitudinal sectional view on the
other end la side, and (b) is a sectional view taken along line 0-0 in (a).
[0091]
As shown in FIG. 20, the manufacturing device 400 of the metal pipe 401'
having a thickened end portion includes a die 402, the axial press punch (first axial
press punch) 203, and an axial press punch (third axial press punch) 403.
The configuration on the one end lb side of the die 402 according to the
present embodiment is similar to the configuration on the one end lb side of the die
202 according to the second embodiment. Meanwhile, the configuration on the other
end Ia side of the die 402 according to the present embodiment is different from the
configuration on the other end Ia side of the die 202 according to the second
embodiment, and the other end I a side is configured to be fitted to the axial press
punch403.
[0092]
The axial press Dunch 403 includes a thickening prevention portion 403-a and
a thickening formation portion 403b. The thickening prevention portion 403a of the
axial press punch 403 abuts on the axial press punch abutting pmiion 220 of the metal
pipe 1. Meanwhile, the thickening formation portion 403b of the axial press punch
403 does not abut on the axial press punch non-abutting pmiion 230 of the metal pipe 1.
- 51 -
The axial press punch 403 shown in FIG. 20 includes three thickening
prevention portions 403a and three thickening formation portion 403b.
[0093]
In this way, in a state where the metal pipe 1 and the manufacturing device
400 of the metal pipe 401' having a thickened end portion are disposed, the axial press
punch 203 is axially pressed toward the other end Ia side, and the axial press punch
403 is axially pressed toward the one end I b side.
[0094]
FIG. 21 is an explanatory view showing the state of the manufacturing device
400 of the metal pipe 40 I' having a thickened end portion when the first process ends,
(a) is a longitudinal sectional view on the other end Ia side, and (b) is a sectional view
taken along line P-P in (a).
As shown in FIG. 21, according to the first process of the method of
manufacturing the metal pipe 40 I' having a thickened end portion according to the
present embodiment, it is possible to thicken not only the axial press punch nonabutting
portion 230 on the one end lb side of the metal pipe I but also the axial press
punch non-abutting portion 230 on the other end 1 a side. That is, not only the one
end side thickened portion 201 c is formed on the one end 1 b side of the metal pipe I,
but the other end side thickened portion 401c is also formed on the other end la side.
In addition, the metal pipe 1 after the first process is performed is referred to
as an intermediate. metal pipe 40 I".
[0095]
[Second Process]
Next, in the second process, the intermediate metal pipe 401" produced in the
first process is compressed in the longitudinal direction to thicken the axial press
- 52 -
punch abutting portion 220, and the metal pipe 40 I' having a thickened end portion is
manufactured.
FIG. 22 is an explanatory view showing the state of a manufacturing device
400' of the metal pipe 401' having a thickened end portion before the second process
starts, (a) is a longitudinal sectional view on the other end Ia side, and (b) is a sectional
view taken along line Q-Q in (a).
[0096]
As shown in FIG. 22, the second process is similar to the first process in that
the die 402 is used. However, the second process is different from the first process in
that the axial press punch (second axial press punch) 203' is used on the one end I b
side of the metal pipe I and the axial press punch (fourth axial press punch) 403' is
used on the other end 1 a side. The axial press punch 403' includes a thickening
prevention portion 403a' and a thickening formation portion 403b'. The thickening
prevention portion 403a' abuts on the axial press punch non-abutting portion 230 of the
intermediate metal pipe 401 ". Meanwhile, the thickening formation portion 403b'
does not abut on the axial press punch abutting portion 220 of the intermediate metal
pipe 401 ".
[0097]
In the state of being disposed as described above, the axial press punch 203' is
axially pressed toward the other end Ia side, and the axial press punch 403' is axially
pressed towrrrd the one end I b side.
[0098]
FIG. 23 is an explanatory view showing the state of the manufacturing device
400' of the metal pipe 401' having a thickened end portion when the second process
ends, (a) is a longitudinal sectional view on the other end I a side, and (b) is a sectional
- 53 -
view taken along line R-R in (a).
As shown in FIG. 23, the second process is performed, and the axial press
punch abutting portions 220 on the one end 1 b side and the other end !a side of the
metal pipe I are thickened. Accordingly, it is possible to manufacture the metal pipe
401' having a thickened end portion in which the one end lb side and the other end Ia
side are thickened.
[0099]
In addition, when the one end side thickened portion 201 c (or other end side
thickened portion 401 c) is formed on both ends of the metal pipe 1, in the first process,
the case where the axial press punch 203 is used on the one end.! b side of the metal
pipe 1 and the axial press punch 403 is used on the other end 1 a side is described.
However, the axial press punch 203 (or the axial press punch 403) may be used on both
the one end lb side and the other end Ia side.
Similarly, when the one end side thickened portion 201 c (or the other end side
thickened portion 401 c) is formed on both ends of the metal pipe 1, in the second
process, the case where the axial press punch 203' is used on the one end 1 b side of the
metal pipe 1 and the axial press punch 403' is used on the other end Ia side is
described. However, the axial press punch 203' (or axial press punch 403') may be
used on both the one end 1 b side and the other end Ia side.
(0 1 00]
(Fifth Embodiment, Metal Pipe 501' Having Thickened End Portion)
Next, a metal pipe 501' having a thickened end portion according to a fifth
embodiment will be described.
FIG. 24 is a schematic view showing the metal pipe 501' having a thickened
end portion according to the fifth embodiment. In the metal pipe I' having a
- 54 -
thickened end portion shown in FIG. 2, the inner diameter io on the one end 1 b side is
the same as the inner diameter i0 on the other end Ia side while the outer diameter Db
on the one end 1 b side is larger than the outer diameter do on the other end Ia side. 1n
addition, in the metal pipe 201' having a thickened end portion shown in FIG. 8, the
outer diameter do on the one end 1 b side is the same as the onter diameter do on the
other end Ia side while the inner diameter h on the one end I b side is smaller than the
inner diameter i0 on the other end Ia side. Meanwhile, in the metal pipe 501' having
a thickened end portion according to the present embodiment, the outer diameter Db on
. the one end 1 b side is larger than the outer diameter do on the other end Ia side, and
the inner diameter Ib on the one end 1 b side is larger than the inner diameter i0 on the
other end Ia side. That is, the metal pipe 501' having a thickened end portion
includes the one end side thickened portion SOle on the one end lb side.
In addition, detail descriptions with respect to portions having configurations
similar to those of the metal pipe 1' having a thickened end portion according to the
first embodiment, the metal pipe 201' having a thickened end portion according to the
second embodiment, the metal pipe 301' having a thickened end portion according to
the third embodiment, and the metal pipe 401' having a thickened end portion
according to the fourth embodiment are omitted.
[0101]
Similarly to the metal pipe 1' having a thickened end pmtion, the metal pipe
201' having a thickened end portion, the metal pipe 301 ~having a thickened end
portion, and the metal pipe 401' having a thickened end portion, the metal pipe 501'
having a thickened end portion is manufactured with the metal pipe 1 as a material.
Since the metal pipe 1 is similar to those of the first to fourth embodiments,
descriptions thereof are omitted.
- 55 -
As described above, in the metal pipe 501' having a thickened end portion
according to the present embodiment, the outer diameter Dt of the one end side
thickened portion 50 I c is larger than the outer diameter Da on the other end Ia (thin
portion !e) side, and the inner diameter lb of the one end side thickened portion SOle is
smaller than the inner diameter i0 on the other end Ia (thin portion !e) side. That is,
in the metal pipe 50 I' having a thickened end portion according to the present
embodiment, the inner circumferential surface and the outer circumferential surface of
the metal pipe 1 on the one end 1 b side are thickened. Accordingly, a thickness T b of
the one end side thickened portion 501 c of the metal pipe 50 I' having a thickened end
portion is larger than the thickness to on the other end Ia (thin portion 1 e) side.
In addition, the metal pipe 501' having a thickened end portion has a taper
portion SOl fin which the thickness gradually increases from to to Tt between the one
end side thickened portion 501c and the thin portion 1e.
[0102]
Preferably, T b/t0 is 1.2 or more, which is a ratio (the thickness increase ratio)
obtained by dividing the thickness Tb of the one end side thickened portion SOle by the
thickness t0 of the thin portion 1e. More preferably, Tb/t0 is 1.4 or more, and still
more preferably, T b/t0 is 2.0 or more.
Similarly to the one end side thickened portion lc, the one end side thickened
portion 50lc alternately includes the high hardness portion (not shown) and the low
hardness portion (not shown) in the circumferential direction.
[0103]
(Fifth Embodiment, Method of Manufacturing Metal Pipe 501' Having
Thickened End Portion)
Next, a method of manufacturing the metal pipe 501' having a thickened end
- 56 -
portion according to the fifth embodiment will be described. Since the method of
manufacturing the metal pipe 501' having a thickened end portion according to the
fifth embodiment includes a first process and a second process, first, the first process
will be described.
[First Process]
FIG. 25 is an explanatory view showing a state of a manufacturing device 500
of the metal pipe 501' having a thickened end portion according to the fifth
embodiment before thickening is performed, (a) is a longitudinal sectional view on the
one end lb side, and (b) is a sectional view taken along line S-S in (a).
[0104]
As shown in FIG. 25, the manufacturing device 500 of the metal pipe 501'
having a thickened end portion includes a die 502, an axial press punch 503, and the
punch 4.
The die (first die) 502 according to the fifth embodiment includes a thickening
prevention portion 502a and a thickening fonnation portion 502h on the one end 1 b
side. The thickening prevention portion 502a abuts on the die abutting portion 20.
The thickening fom1ation portion 502b does not abut on the die non-abutting portion
30. The die 502 shown in FIG. 25 includes three thickening prevention portions 502a
and three thickening formation portions 502b.
[0105]
The axial press punch (first axial n.ress punch) 503 according to the fifth
embodiment includes a thickening prevention portion 503a and a thickening formation
portion 503b on the one end I b side. TI1e thickening prevention portion 503a abuts
on the axial press punch abutting portion 220. The thickening formation portion 503b
does not abut on the axial press punch non-abutting portion 230. The axial press
- 57 -
punch 503 shown in FIG. 25 includes three thickening prevention portions 503a and
three thickening formation portions 503b.
Since the punch 4 configuring the manufacturing device 500 of the metal pipe
501' having a thickened end portion is similar to the punch 4 according to the first
embodiment, detail descriptions thereof is omitted.
[0106]
In the state where the metal pipe I, the die 502, the axial press punch 503, and
the punch 4 are disposed as described above, the axial press punch 503 is axially
pressed toward the other end la side.
[0107]
FIG. 26 is an explanatory view showing the state of the manufacturing device
500 of the metal pipe 501' having a thickened end portion when the first process ends,
(a) is a longitudinal sectional view on the one end lb side, and (b) is a sectional view
taken along line T-T in (a).
As shown in FIG. 26, according to the first process of the present embodiment,
the die abutting portion 20 and the axial press punch abutting portion 220 are not
thickened while the die non-abutting portion 30 and the axial press punch non-abutting
portion 230 are thickened on the one end lb side of the metal pipe 1.
In addition, the metal pipe 1 after the first process is performed is referred to
as an intermediate metal pipe 501 ".
[0108]
[Second Process]
Next, in the second process, the intermediate metal pipe 501" produced by the
first process is compressed in the longitudinal direction to thicken the die abutting
portion 20 and the axial press punch abutting portion 220, and the metal pipe 50 I'
- 58 -
having a thickened end portion is manufactured.
[0 I 09]
FIG. 27 is an explanatory view showing a state of the manufacturing device
500' of the metal pipe 501' having a thickened end portion before the second process
starts, (a) is a longitudinal sectional view on the one end I b side, and (b) is a sectional
view taken along line U-U in (a).
As shown in FIG. 27, the manufacturing device 500' of the metal pipe 501'
having a thickened end portion includes a die (second die) 502', an axial press punch
(second axial press punch) 503', and the punch 4.
[OliO]
The die 502' includes a thickening prevention portion 502a' and a thickening
formation portion 502b' on the one end lb side. The thickening prevention portion
502a' abuts on the die non-abutting portion 30. The thickening formation portion
502b' does not abut on the die abutting portion 20.
The axial press punch 503' includes a thickening prevention portion 503a' and
a thickening formation portion 503b' on the one end 1 b side. The thickening
prevention portion 503a' abuts on the axial press punch non-abutting portion 230.
The thickening formation portion 503b' does not abut on the axial press punch abutting
portion 220.
Since the configuration of the punch 4 is similar to that of the punch 4
according to the first embodiment, detail descriptions thereof are omitted.
[0 Ill J
In the state where the metal pipe 1, the die 502', the axial press punch 503',
and the punch 4 are disposed as described above, the axial press punch 503' is axially
pressed toward the other end 1 a side.
- 59 -
[0112]
FIG. 28 is an explanatory view showing the state of the manufacturing device
500' of the metal pipe 501' having a thickened end portion when the second process
ends, (a) is a longitudinal sectional view on the one end lb side, and (b) is a sectional
view taken along line V-V in (a).
As shown in FIG. 28, the second process is performed, and the die abutting
portion 20 and the axial press punch abutting portion 220 are thickened and the die
non-abutting portion 30 and the axial press punch non-abutting portion 230 are not
thickened on the one end side 1 b of the intermediate metal pipe 50 I". Accordingly,
the metal pipe 501' having a thickened end portion is manufactured.
[0113]
According to the method of manufacturing the metal pipe 50 I' having a
thickened end portion according to the present embodiment, the inner surface side and
the outer surface side are thickened on the one end I b side of the metal pipe without
occurring buckling, and it is possible to manufacture the metal pipe 501' having a
thickened end portion.
[0114]
In addition, the present invention is not limited to the above-described
embodiments. The present invention includes modifications, combinations, or the
like of the configurations within a scope which does not depart from the gist of the
present invention. In addition, it is needless to say that appropriate combinations of
the configurations shown in respective embodiments can be used.
For example, in the first process of the method of manufacturing the metal
pipe I' having a thickened end portion according to the first embodiment, the die 2
which includes three thickening prevention portions 2a and three thickening formation
- 60 -
portions 2b are formed on the inner surface is used. However, the die 2 which is used
in the first process of the method of manufacturing the metal pipe I' having a
thickened end portion according to the first embodiment is not limited to this. For
example, a manufacturing device 600 of the metal pipe having a thickened end portion
shown in FIG. 29 includes a die 602 in which four thickening prevention portions 602a
and four thickening formation portions 602b are formed on the inner surface.
FIG. 30 shows a state where the first process is performed on the metal pipe 1
using the die 602. As shown in FIG. 30, in an intermediate metal pipe 601 ", four die
non-abutting portions 30 which are provided in the circumferential direction are
thickened. Meanwhile, in an intermediate metal pipe 60 I", four die abutting portions
20 which are provided in the circumferential direction are not thickened.
[0115]
FIG. 31 is an explanatory view showing the state of a manufacturing device
600' of the metal pipe 60 1' having a thickened end portion before the second process is
performed, (a) is a longitudinal sectional view on one end I b side, and (b) is a sectional
view taken along line Y-Yin (a).
As shown in FIG. 31, a die (second die) 602' includes four thickening
prevention portions 602a' and four thickening formation portions 602b' on the one end
lb side of the intermediate metal pipe 601 ". From the state shown in FIG. 31, the
axial press punch 3' is axially pressed toward the other end 1 a side.
[0 116]
FIG. 32 is an explanatory view showing the state of the manufacturing device
600' of the metal pipe 601' having a thickened end portion after the second process is
performed, (a) is a longitudinal sectional view on one end 1b side, and (b) is a sectional
view taken along line Z-Z in (a).
- 61 -
As shown in FIG. 32, according to the second process, the die abutting portion
20 of the intermediate metal pipe 601" is thickened, and the metal pipe 601' having a
thickened end portion is manufactured.
[0117]
In the first process of the method of manufacturing the metal pipe 201' having
a thickened end portion according to the second embodiment, the axial press punch
(first axial press punch) 203 which includes three thickening prevention portions 203a
and three thickening formation portions 203b are used on the inner surface of the
portion inserted into the metal pipe 1. However, the first axial press punch 203 which
is used in the first process of the method of manufacturing the metal pipe 201' having a
thickened end portion according to the second embodiment is not limited to this. For
example, as shown in FIG. 33, it is possible to use a first axial press punch 703 which
includes four thickening prevention portions 703a and four thickening formation
portions 703b on the inner surface on the portion inserted into the metal pipe I.
FIGS. 34 shows a state after the first process is performed using the first axial
press punch 703. As shown in FIG. 34, the first process is performed on the metal
pipe 1, four axial press punch non-abutting portions 230 on the one end 1 b side are
thickened, and the intermediate metal pipe 70 I" is manufactured.
[0118]
FIG. 35 is an explanatory view showing a state of a manufacturing device 700'
of a met0l pipe 701' having a thickened end portion before the seco11d process is
performed, (a) is a longitudinal sectional view on the one end side I b, and (b) is a
sectional view taken along line C'-C' in (a).
As shown in FIG. 35, an axial press punch (second axial press punch) 703'
includes four thickening prevention portions 703a' and four thickening formation
- 62 -
portions 703b' on the one end lb side of the intennediate metal pipe 701". From the
state shown in FIG. 35, the axial press punch 703' is axially pressed toward the other
end Ia side.
[0119]
FIG. 36 is an explanatory view showing the state of the manufacturing device
700' of the metal pipe 701' having a thickened end portion after the second process is
performed, (a) is a longitudinal sectional view on one end lb side, and (b) is a sectional
view taken along lineD' -D' in (a).
As shown in FIG. 36, according to the second process, the axial press punch
abutting portion 220 of the intermediate metal pipe 701" is thickened, and the metal
pipe 701' having a thickened end portion is manufactured.
[Industrial Applicability]
[0120]
According to the embodiments, it is possible to provide a metal pipe having a
thickened end portion in which at least one end is thickened at a large thickness
increase ratio in a longitudinal direction without having a buckling portion, and a
method of manufacturing the same.
[Brief Description of the Reference Symbols]
[0121]
0, 0', 200, 200', 300, 300', 400, 400', 500, 500': MANUFACTURING
DBVICE OF METAL PIPE HAVING THICKENED END PORTION
1: METAL PIPE
lc, 20lc, SOle: ONE END SIDE THICKENED PORTION (FIRST
THICKENED PORTION)
30lc, 40lc: OTHER END SIDE THICKENED PORTION (SECOND
- 63 -
THICKENED PORTION)
1', 201 ', 301', 401', 501': METAL PIPE HAVING THICKENED END
PORTION
le: THIN PORTION
If: TAPER PORTION (FIRST TAPER PORTION)
30lf, 40lf: TAPER PORTION (SECOND TAPER PORTION)
2, 202, 302, 402, 502, 602: DIE (FIRST DIE)
2', 302', 502', 602': DIE (SECOND DIE)
4:PUNCH
3, 203, 403, 403', 503, 503', 603, 603', 703: AXIAL PRESS PUNCH (FIRST
AXIAL PRESS PUNCH)
3', 203', 503', 703': AXIAL PRESS PUNCH (SECOND

[Document Type] CLAIMS
1. A metal pipe having a thickened end portion, the metal pipe comprising:
when viewed in a longitudinal direction of the metal pipe,
a thin portion which has a thickness t 0 ;
a first thickened portion which is provided on one end and has a thickness T
which is larger than the thickness t0; and
a first taper portion which is provided between the thin portion and the first
thickened portion and has the thickness which gradually increases from to toT,
wherein
when a hardness of an inner surface of the first thickened portion is measured
in a circumferential direction and the hardness is plotted with respect to a position in
the circumferential direction,
a waveform representing a high hardness portion having a hardness
which is 95% or more of a maximum hardness in the circumferential direction and a
waveform representing a low hardness portion having a hardness which is less than
95% of the maximum hardness altemately appear, and
a plurality of combinations of the waveform representing the high
hardness portion and the waveform representing the low hardness portion appear.
2. The metal pipe having a thickened end portion according to claim 1,
wherein the thickness T of the first thi.ckened portion is I .2 times or more than
the thickness to of the thin portion.
3. The metal pipe having a thickened end portion according to claim I or 2,
wherein a length of the first thickened portion in the longitudinal direction is 3
- 65 -
times or less than an outer circumferential length of the first thickened portion.
4. The metal pipe having a thickened end portion according to any one of
claims 1 to 3, the metal pipe further comprising:
when viewed in the longitudinal direction of the metal pipe,
a second thickened portion which is provided on the other end and has a
thickness T a which is larger than to; and
a second taper portion which is provided between the thin portion and the
second thickened portion aud has the thickness which gradually increases from to toT a·
5. The metal pipe having a thickened end portion according to claim 4,
wherein the thickness T a of the second thickened portion is 1.2 times or more
than the thickness to of the thin portion.
6. The metal pipe having a thickened end portion according to claim 4 or 5,
wherein a length ofthe second thickened portion in the longitudinal direction
is 3 times or less than an outer circumferential length of the second thickened portion.
7. A method of manufacturing a metal pipe having a thickened end portion
by axially pressing one end ofthe metal pipe toward the other end, the method
comprising:
when the metal pipe is viewed in a longitudinal direction,
a first process of thickening a die non-abutting portion by axially pressing a
first axial press punch toward the other end side of the metal pipe; and
a second process of thickening a die abutting portion by axially pressing a
- 66 -
second axial press punch toward the other end side of the metal pipe,
wherein the first process is performed:
on the one end side of the metal pipe in a state where the first axial
press punch having an outer circumferential shape corresponding to an inner
circumferential shape of the metal pipe is inserted, an outer circumferential surface of
the metal pipe abuts on an inner surface of a first die in the die abutting portion on the
outer circumferential surface of the metal pipe, and the outer circumferential surface of
the metal pipe does not come into contact with the inner surface of the first die in the
die non-abutting portion on the outer circumferential surface of the metal pipe; and
on the other end side of the metal pipe in a state where the metal pipe
is disposed in the first die such that the outer circumferential surface of the metal pipe
abuts on the inner surface of the first die,
wherein the second process is performed:
on the one end side of the metal pipe in a state where the second
axial press punch is inserted, and the outer circumferential surface of the metal pipe
does not come into contact with an inner surface of a second die in the die abutting
portion of the metal pipe while the outer circumferential surface of the metal pipe abuts
on the inner surface ofthe second die in the die non-abutting portion ofthe metal pipe;
and
on the other end side of the metal pipe in a state where the metal pipe
is disposed in the second die such that the outer circumferential surface of the metal
pipe abuts on the inner surface of the second die.
8. The method of manufacturing a metal pipe having a thickened end
portion according to claim 7,
- 67 -
wherein an entire of the outer circumferential surface of the metal pipe abuts
on the inner surface of the first die at the other end side of the metal pipe in the first
process.
9. The method of manufacturing a metal pipe having a thickened end
portion according to claim 7 or 8,
wherein the other end of the metal pipe is positioned with respect to the first
die in the first process.
10. The method of manufacturing a metal pipe having a thickened end
portion according to any one of claims 7 to 9,
wherein the entire of the outer circumferential surface of the metal pipe abuts
on the inner surface of the second die at the other end side of the metal pipe in the
second process.
11. The method of manufacturing a metal pipe having a thickened end
portion according to any one of claims 7 to 10,
wherein the other end of the metal pipe is positioned with respect to the
second die in the second process.
12. The method of manufacturing a metal pipe having a thickened end
portion according to any one of claims 7 to 11, wherein
in the first process:
a third axial press punch having an outer circumferential shape
corresponding to the inner circumferential shape of the metal pipe is inserted;
- 68 -
the outer circumferential surface of the metal pipe abuts on the inner
surface of the first die in the die abutting portion on the outer circumferential surface
of the metal pipe;
the outer circumferential surface of the metal pipe does not come into
contact with the inner surface of the first die in the die non-abutting portion on the
outer circumferential surface of the metal pipe; and
the third axial press punch is further axially pressed toward the one
end side of the metal pipe when the first axial press punch is axially pressed toward the
other end side of the metal pipe, and
in the second process:
a fourth axial press punch having an outer circumferential shape
corresponding to the inner circumferential shape of the metal pipe is inserted;
the outer circumferential surface of the metal pipe does not come into
contact with the inner surface of the second die in the die abutting portion on the outer
circumferential surface of the metal pipe;
the outer circumferential surface of the metal pipe abuts on the inner
surface of the second die in the die non-abutting portion on the outer circumferential
surface of the metal pipe; and
the fourth axial press punch is further axially pressed toward the one
end side of the metal pipe when the second axial press punch is axially pressed toward
the other end side of the metal pipe.
13. A method of manufacturing a metal pipe having a thickened end portion
by axially pressing one end of the metal pipe toward the other end in a state where the
metal pipe is disposed in a die such that an entire of an outer circumferential surface of
- 69 -
the metal pipe abuts on an inner surface of the die, the method comprising:
when the metal pipe is viewed in a longitudinal direction,
a first process of thickening of an axial press punch non-abutting portion by
axially pressing a first axial press punch toward the other end side of the metal pipe;
and
a second process of thickening an axial press punch abutting portion by
axially pressing a second axial press punch toward the other end side of the metal pipe,
wherein the first process is performed:
on the one end side of the metal pipe in a state where an inner
circumferential surface of the metal pipe abuts on an outer surface of the first axial
press punch in the axial press punch abutting portion on the inner circumferential
surface of the metal pipe and the inner circumferential surface ofthe metal pipe does
not come into contact with the outer surface ofthe first axial press punch in the axial
press punch non-abutting portion on the inner circumferential surface of the metal
pipe; and
wherein the second process is performed:
on the one end side of the metal pipe in a state where the inner
circumferential surface of the metal pipe does not come into contact with an outer
surface of the second axial press punch in the axial press punch abutting portion of the
metal pipe and the inner circumferential surface of the metal pipe abuts on the outer
surface ofth~ second axial press punch in the axial press punch non-abutting portion of
the metal pipe.
14. The method of manufacturing a metal pipe having a thickened end
pmiion according to claim 13,
- 70 -
wherein the other end of the metal pipe is positioned with respect to the die in
the first process.
15. The method of manufacturing a metal pipe having a thickened end
portion according to claim 13 or 14,
wherein the other end of the metal pipe is positioned with respect to the die in
the second process.
16. The method of manufacturing a metal pipe having a thickened end
portion according to any one of claims 13 to 15, wherein
in the first process:
the inner circumferential surface of the metal pipe abuts on an outer
surface of a third axial press punch in the axial press punch abutting portion of the
inner circumferential surface of the metal pipe;
the inner circumferential surface of the metal pipe does not come into
contact with the outer surface of the third axial press punch in the axial press punch
non-abutting portion on the inner circumferential surface of the metal pipe; and
the third axial press punch is further axially pressed toward the one
end side of the metal pipe when the first axial press punch is axially pressed toward the
other end side of the metal pipe, and
in the second process:
the inner circumferential surface of the metal pipe does not come into
contact with an outer surface of a fourth axial press punch in the axial press punch
abutting portion on the inner circumferential surface of the metal pipe;
the inner circumferential surface of the metal pipe abuts on the outer
- 71 -
surface of the fourth axial press punch in the axial press punch non-abutting portion of
the inner circumferential surface of the metal pipe; and
the fourth axial press punch is further axially pressed toward the one
end side of the metal pipe when the second axial press punch is axially pressed toward
the other end side of the metal pipe.
17. A method of manufacturing a metal pipe having a thickened end portion
by axially pressing one end of a metal pipe toward the other end, the method
comprising:
when the metal pipe is viewed in a longitudinal direction,
a first process of thickening an axial press punch non-abutting portion and a
die non-abutting portion by axially pressing a first axial press punch toward the other
end side of the metal pipe; and
a second process of thickening an axial press punch abutting portion and a die
abutting portion by axially pressing a second axial press punch toward the other end
side of the metal pipe,
wherein the first process is performed:
on the one end side of the metal pipe in a state where an inner
circumferential surface of the metal pipe abuts on an outer surface of the first axial
press punch in the axial press punch abutting portion on the inner circumferential
surface of the metal pipe, the inner circumferential surface of the metal pipe does not
come into contact with the outer surface ofthe first axial press punch in the axial press
punch non-abutting portion on the inner circumferential surface of the metal pipe, an
outer circumferential surface of the metal pipe abuts on an inner surface of a first die in
the die abutting portion on the outer circumferential surface of the metal pipe, and the
- 72 -
outer circumferential surface of the metal pipe does not come into contact with the
inner surface of the first die in the die non-abutting portion on the outer circumferential
surface of the metal pipe;
on the other end of the metal pipe in a state where the metal pipe is
disposed in the first die such that the entire of the outer circumferential surface of the
metal pipe abuts on the inner surface of the first die, and
the second process is performed:
on the one end side of the metal pipe in a state where the inner
circumferential surface of the metal pipe abuts on an outer surface of the second axial
press punch in the axial press punch non-abutting portion on the inner circumferential
surface of the metal pipe, the inner circumferential surface of the metal pipe does not
come into contact with the outer surface of the second axial press punch in the axial
press punch abutting portion on the inner circumferential surface of the metal pipe, the
outer circumferential surface of the metal pipe abuts on an inner surface of a second
die in the die non-abutting portion on the outer circumferential surface of the metal
pipe, and the outer circumferential surface of the metal pipe does not come into contact
with the inner surface ofthe second die in the die abutting portion on the outer
circumferential surface of the metal pipe; and
on the other end of the metal pipe in a state where the metal pipe is
disposed in the second die such that the entire of the outer circumferential surface of
the metal pipe abuts on the inner surface of the second die.
18. The method of manufacturing a metal pipe having a thickened end
portion according to any one of claims 7 to 17,
wherein the first process is performed in a state where a pressure medium is
- 73 -
I
i11jected inside the metal pipe.
19. The method of manufacturing a metal pipe having a thickened end
portion according to any one of claims 7 to 18,
wherein the second process is performed in a state where a pressure medium
is injected inside the metal pipe.