U.S. patent application number 10/542929 was filed with the patent office on 2006-07-13 for metal foil tube and method and apparatus for production thereof.
Invention is credited to Atsuhiko Imai, Koki Inada, Kazutoshi Iwami, Hiroki Kobayashi, Tohru Saito, Yasuo Takahashi, Mukio Yamanaka.
Application Number | 20060150388 10/542929 |
Document ID | / |
Family ID | 32775157 |
Filed Date | 2006-07-13 |
United States Patent
Application |
20060150388 |
Kind Code |
A1 |
Inada; Koki ; et
al. |
July 13, 2006 |
Metal foil tube and method and apparatus for production thereof
Abstract
The present invention provides a metal foil tube with a
thickness of 10 to 100 .mu.m and a method and apparatus of
production of the metal foil tube enabling even an extremely thin
metal foil to be reliably finished into a tube, that is, a metal
foil tube comprised of a metal foil sheet W with a thickness t of
10 to 100 .mu.m joined by welding, the method of production of the
metal foil tube shaping the metal foil sheet W to form an overlap
part G, then welding the facing sides and finishing the weld zone
part flat.
Inventors: |
Inada; Koki; (Tokyo, JP)
; Iwami; Kazutoshi; (Tokyo, JP) ; Imai;
Atsuhiko; (Tokyo, JP) ; Kobayashi; Hiroki;
(Tokyo, JP) ; Takahashi; Yasuo; (Osaka, JP)
; Yamanaka; Mukio; (Kanagawa, JP) ; Saito;
Tohru; (Kanagawa, JP) |
Correspondence
Address: |
KENYON & KENYON LLP
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
32775157 |
Appl. No.: |
10/542929 |
Filed: |
January 19, 2004 |
PCT Filed: |
January 19, 2004 |
PCT NO: |
PCT/JP04/00360 |
371 Date: |
July 20, 2005 |
Current U.S.
Class: |
29/516 ;
29/428 |
Current CPC
Class: |
B23K 11/084 20130101;
C22C 38/34 20130101; G03G 2215/20 20130101; B21D 5/015 20130101;
B23K 11/0873 20130101; C22C 38/42 20130101; G03G 2215/0634
20130101; Y10T 29/49826 20150115; C22C 38/44 20130101; B21C 37/0815
20130101; Y10T 29/49927 20150115; C22C 38/58 20130101; B21D 33/00
20130101; G03G 15/2057 20130101; G03G 15/0818 20130101 |
Class at
Publication: |
029/516 ;
029/428 |
International
Class: |
B21D 39/03 20060101
B21D039/03; B21D 39/00 20060101 B21D039/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 20, 2003 |
JP |
2003-011015 |
Jan 12, 2003 |
JP |
2003-401052 |
Claims
1-76. (canceled)
77. A metal foil tube characterized by joining or welding a metal
foil with a thickness of 10 to 100 .mu.m comprised of Fe, Cr, Ni,
Co, Mo, Be, Cu, Ti, Nb, Zr, Ta, or an alloy of the same.
78. A metal foil tube as set forth in claim 77, characterized in
that said metal foil is a stainless steel foil, and said stainless
steel is one of ferritic stainless steel, martensitic stainless
steel, austenitic stainless steel, and precipitation hardened
stainless steel.
79. A metal foil tube as set forth in claim 77 or 78, characterized
by being joined by seam welding or mash seam welding.
80. A metal foil tube as set forth in claim 79, characterized in
that at least part of the joint surface is a solid phase joint.
81. A metal foil tube as set forth in claim 77 or 78, characterized
in that the joint or weld line is arranged in a line or spiral.
82. A metal foil tube as set forth in claim 77 or 78, characterized
in that an absolute value of a hardness difference between the
joint or weld zone and matrix part is, in terms of Vicker's
hardness (Hv), 25% or less of the hardness of the matrix part.
83. A metal foil tube as set forth in claim 77 or 78, characterized
by cold working the metal foil tube to reduce its thickness, smooth
the joint zone, even out the shape and surface roughness of the
joint zone, and work harden the material of at least said joint
zone.
84. A metal foil tube as set forth in claim 78, characterized in
that said metal foil is stainless steel foil, and said stainless
steel foil is an annealed material of an austenitic stainless
steel.
85. A metal foil tube as set forth in claim 78, characterized in
that said stainless steel foil is a high strength austenitic
stainless steel containing C: 0.05 to 0.2 wt %, Si: 0,05 to 3.6 wt
%, Mn: 1.0 to 5.0 wt %, Cr: 15 to 26 wt %, Ni: 5 to 25 wt %, Mo:
5.0 wt % or less, Cu: 4.0 wt % or less, N: over to 0.06 wt % to 0.4
wt %, and a balance of Fe and unavoidable impurities.
86. A metal foil tube as set forth in claim 77 or 78, characterized
in that the Vicker's hardness (Hv) of the matrix part and weld zone
of said metal foil tube is 300 to 600.
87. A metal foil tube as set forth in claim 78, characterized in
that a maximum nitrogen concentration of the surface layer of said
stainless steel foil is 3 wt % or less.
88. A metal foil tube as set forth in claim 85, wherein said
stainless steel foil contains N: over to 0.06 wt % to 0.4 wt %.
89. A metal foil tube as set forth in claim 78, characterized in
that said metal foil is stainless steel as rolled and the weld zone
has a martensite phase precipitated at it.
90. A metal foil tube as set forth in claim 77 or 78, characterized
in that a foil tube obtained by joining and forming metal foil is
surface hardened at least at one of its outside surface and inside
surface by a hard plating layer.
91. A metal foil tube as set forth in claim 90, characterized in
that said hard plating layer is mainly comprised of one or more
metals of chromium, nickel, cobalt, and palladium.
92. A metal foil tube as set forth in claim 90, characterized in
that said hard plating layer is comprised of an Ni--P based
alloy.
93. A metal foil tube as set forth in claim 92, characterized in
that said hard plating layer is comprised of Ni--P alloy
containing, by weight ratio, 1 to 14% of P.
94. A metal foil tube as set forth in claim 90, characterized in
that a metal foil tube obtained by joining or further shaping
stainless steel foil is heat treated at a temperature of 800 to
1100.degree. C., then the foil tube is hard plated at least at one
of its inside and outside surfaces.
95. A metal foil tube as set forth in claim 77 or 78, characterized
in that a metal foil tube obtained by joining or further shaping
stainless steel foil is heat treated at a temperature of 800 to
1100.degree. C.
96. A metal foil tube as set forth in claim 80, characterized in
that a weld zone of said metal foil tube has continuous nuggets
along the weld line or discontinuous nuggets present at least at
50% or more of the weld line.
97. A metal foil tube as set forth in claim 96, characterized in
that the overlap (x) .mu.m of the joint zone of said metal foil
tube satisfies x.ltoreq.40+5 t with respect to the metal foil
thickness (t) .mu.m.
98. A metal foil tube as set forth in claim 77 or 78, characterized
in that a vicinity of the joint zone of at least one of the two
surfaces of the stainless steel foil is plated with a Group X to XI
element or an alloy including such an element or a metal having a
melting point of 1200.degree. C. or less and then the foil is
resistance welded.
99. A metal foil tube as set forth in claim 77 or 78, characterized
in that the ratio of the thickness of said metal foil tube to the
inside diameter of the tube is 1/500 or less.
100. A metal foil tube as set forth in claim 77 or 78,
characterized in that a surface roughness Rz of said metal foil
tube defined by JIS B0601-2001 is 2.0 .mu.m or less.
101. A metal foil tube as set forth in claim 77 or 78,
characterized in that said metal foil tube has a durability of
1.times.10.sup.6 cycles or more in a fatigue test giving a strain
of 0.2% or less at repeated cycles of 60 cycles/min or more.
102. A metal foil tube as set forth in claim 101, characterized in
that it is used for a toner roll and/or development roll of an
image forming device.
103. A method of production of a metal foil tube characterized by
comprising a shaping step of shaping a metal foil sheet with a
thickness of 10 to 100 .mu.m so that its facing sides overlap and a
welding step of welding the overlapped facing sides.
104. A method of production of a metal foil tube as set forth in
claim 103, characterized by further having a finishing step of
finishing said welded part smooth.
105. A method of production of a metal foil tube as set forth in
claim 103, characterized in that said shaping step has a
positioning step of positioning said metal foil sheet at a shaping
use core rod before overlapping the facing sides of said metal foil
sheet.
106. A method of production of a metal foil tube as set forth in
claim 105, characterized in that said positioning step holds the
metal foil sheet at a shaping device approaching and moving away
from said core rod while constantly maintaining a parallel position
with it, bringing said shaping device close to said core rod, and,
when the metal foil sheet and core rod come into line contact,
pressing and positioning said metal foil sheet with respect to the
core rod.
107. A method of production of a metal foil tube as set forth in
claim 106, characterized in that said shaping step has, after said
positioning step, a wrapping step of bringing said shaping device
closer to the core rod, holding said metal foil sheet between the
semicircular cross-sectional recess formed at said shaping device
and said core rod, and wrapping said metal foil sheet around the
core rod.
108. A method of production of a metal foil tube as set forth in
claim 107, characterized in that after said wrapping step, said
shaping step has an overlap adjusting step of adjusting the overlap
by making part of the circumference of said metal foil sheet
displace in the radial direction.
109. A method of production of a metal foil tube as set forth in
claim 103, characterized in that said overlap (x) .mu.m satisfies
x.ltoreq.40+5 t with respect to said thickness (t) .mu.m.
110. A method of production of a metal foil tube as set forth in
claim 103, characterized in that said welding step is electrical
resistance welding.
111. A method of production of a metal foil tube as set forth in
claim 110, characterized in that said electrical resistance welding
is seam welding or mash seam welding.
112. A method of production of a metal foil tube as set forth in
claim 111, characterized in that said electrical resistance welding
uses a pulse power source and sets the ratio of the conduction time
and non-conduction time to 1/15 to 1/7 for seam welding or uses a
pulse power source and sets the ratio of the conduction time and
non-conduction time to 1/3 to 1/1 for mash seam welding.
113. A method of production of a metal foil tube as set forth in
claim 110, characterized in that said welding step is performed by
running a current between a conductive stationary electrode member
provided in a groove formed along the axial direction of the
outside surface of said core rod and a conductive movable electrode
member provided facing said stationary electrode member.
114. A method of production of a metal foil tube as set forth in
claim 117, characterized in that said stationary electrode member
is formed so that part or all of the outside surface is flat.
115. A method of production of a metal foil tube as set forth in
claim 113, characterized in that said stationary electrode member
and/or movable electrode member is comprised at least partially of
molybdenum or alumina-dispersed copper alloy.
116. A method of production of a metal foil tube as set forth in
claim 113, characterized in that the hardness of said stationary
electrode member and/or movable electrode member and the hardness
of said metal foil sheet are substantially the same.
117. A method of production of a metal foil tube as set forth in
claim 105, characterized in that said metal foil tube is separated
and removed from said core rod by ejecting a fluid from the inside
of said core rod toward the radial direction.
118. A method of production of a metal foil tube as set forth in
claim 105, characterized in that said core rod is comprised of a
plurality of members and part is moved in the axial direction to
separate the metal foil tube from said core rod.
119. A method of production of a metal foil tube as set forth in
claim 103, characterized by inserting a metal core into the metal
foil tube and cold working the tube by sedging, split roller
rolling method, drawing, spinning, or a combination of these
methods to reduce the thickness, smooth said weld zone, even out
the shape and surface roughness of the weld zone, and work harden
the material of the weld zone.
120. A method of production of a metal foil tube as set forth in
claim 103, characterized by plating the vicinity of the joint zone
of at least one of the two surfaces of the stainless steel foil by
a Group X to XI element or an alloy containing that element or a
metal with a melting point of 1200.degree. C. or less and then
resistance welding the foil.
121. A method of production of a metal foil tube as set forth in
claim 103, characterized by heat treating a metal foil tube
obtained by joining or further shaping stainless steel foil at a
temperature of 800 to 1100.degree. C.
122. A method of production of a metal foil tube as set forth in
claim 121, characterized by heat treating a metal foil tube
obtained by joining or further shaping stainless steel foil at a
temperature of 800 to 1100.degree. C., then hard plating at least
one of the inside and outside surfaces of the metal foil tube.
123. A method of production of a metal foil tube as set forth in
claim 122, characterized in that the composition of said hard
plating is an Ni--P alloy containing, by weight ratio, 1 to 14% of
P.
124. A production apparatus of a metal foil tube, characterized by
having a shaping unit for shaping a 10 to 1.00 .mu.m thick metal
foil sheet to a predetermined shape and a welding unit for welding
facing sides of said metal foil sheet.
125. A production apparatus of a metal foil tube as set forth in
claim 124, characterized in that said the shaping unit has a core
rod of a circular cross-section perpendicular to the axis, a
shaping device provided to be able to approach and move away from
said core rod and holding the metal foil sheet, and a positioning
member for making said shaping device approach said core rod and
pressing against said metal foil sheet to position it with respect
to said core rod at the time when the metal foil sheet and core rod
come into line contact, and making said shaping device move so as
to make said positioned metal foil sheet approach the core rod and
wrap the metal foil sheet in a U-shape around the core rod.
126. A production apparatus of a metal foil tube as set forth in
claim 125, characterized in that said shaping device has a holding
plate provided so as to approach and move away from said core rod
while constantly maintaining a parallel position with it and having
a semicircular cross-section recess for wrapping said metal foil
sheet in a U-shape with said core rod, a first pressing member for
pressing one side of said U-shaped metal foil sheet so as to
closely contact the circumference of said core rod, and a second
pressing member for pressing the other side of said U-shaped metal
foil sheet toward the circumference of said core rod, and after
said wrapping, overlapping the facing side edges of said metal foil
sheet to form an overlap part.
127. A production apparatus of a metal foil tube as set forth in
claim 126, characterized in that said the shaping unit has an
overlap adjusting means for displacing part of the circumference of
said metal foil sheet in the radial direction so that the overlap
of the overlap part of the facing sides becomes a predetermined
value before the end of the pressing action by said second pressing
member.
128. A production apparatus of a metal foil tube as set forth in
claim 127, characterized in that said overlap adjusting means is
comprised of an offsetting device provided at the inside of said
core rod.
129. A production apparatus of a metal foil tube as set forth in
claim 127, characterized in that said the overlap adjusting means
is comprised of an offsetting device provided at the outside of
said core rod.
130. A production apparatus of a metal foil tube as set forth in
claim 127, characterized in that said the overlap adjusting means
is designed to press a non-contact part where said metal foil sheet
does not closely contact said core rod by a pressing member.
131. A production apparatus of a metal foil tube as set forth in
claim 127, characterized in that said the overlap adjusting means
is designed to press a pressing member provided at the outside of
said core rod into a recess formed in said core rod.
132. A production apparatus of a metal foil tube as set forth in
claim 130 or 131, characterized in that said pressing member is any
of a cam, roll, tube, or rod-shaped member and is provided to
operate separately at each of the two ends in the axial direction
of said core rod.
133. A production apparatus of a metal foil tube as set forth in
claim 124, characterized in that said welding unit is comprised of
a conductive stationary electrode member provided along the axial
direction of the outside surface of said core rod and a movable
electrode member provided facing said stationary electrode member,
grips said overlap part of said metal foil sheet between the two
electrode members, and welds it in that state.
134. A production apparatus of a metal foil tube as set forth in
claim 133, characterized in that said stationary electrode member
is formed so that part or all of its outside surface is flat.
135. A production apparatus of a metal foil tube as set forth in
claim 133, characterized in that said movable electrode member is
an electrode ring pressing against said overlap part and carrying a
current.
136. A production apparatus of a metal foil tube as set forth in
claim 133, characterized in that said stationary electrode member
and/or movable electrode member is comprised at least partially of
molybdenum or alumina-dispersed copper alloy.
137. A production apparatus of a metal foil tube as set forth in
claim 133, characterized in that a hardness of said stationary
electrode member and/or movable electrode member and a hardness of
said metal foil sheet are substantially the same.
138. A production apparatus of a metal foil tube as set forth in
claim 125, characterized in that said metal foil tube is separated
and removed from said core rod by ejecting a fluid from the inside
of said core rod toward the radial direction.
139. A production apparatus of a metal foil tube as set forth in
claim 125, characterized in that said core rod has a fluid passage
for ejecting a fluid for separating the welded metal foil tube from
said core rod.
140. A production apparatus of a metal foil tube as set forth in
claim 125, characterized in that said core rod has grooves at its
outer circumference for preventing said metal foil sheet from
closely contacting the core rod.
141. A production apparatus of a metal foil tube as set forth in
claim 126, characterized in that said core rod is comprised of a
plurality of members and part is made to move in the axial
direction so as to separate the metal foil tube from said core
rod.
142. A metal foil tube characterized by being obtained using a
method of production of the metal foil tube as set forth in claim
103.
143. A metal foil tube characterized by being obtained using a
production apparatus of a metal foil tube as set forth in claim
124.
Description
TECHNICAL FIELD
[0001] The present invention relates to a novel metal foil tube and
a method of production and production apparatus for the same. More
particular, it relates to a novel metal foil tube suitable for use
for a copier, facsimile, etc. of an electronic photo printer, laser
beam printer (LBP), toner roll, development roll, fixing roll, etc.
and a method of production and production apparatus for the
same.
BACKGROUND ART
[0002] In current electronic photo printers, laser beam printers
(LBP), copiers, facsimiles, and other image forming devices, a
photosensitive drum is exposed by an image signal, a developer
forms a toner image, the toner image formed on this photosensitive
drum is transferred to paper, and a fixer is used to fix it by heat
for output. In such an image forming process, the photosensitive
drum, toner roll, development roll, pressing roll, fixing roll, and
various other roll members are used. Normally, these roll members
are formed into tubular or cylindrical shapes and are designed to
be driven by drive devices (motors etc.)
[0003] The tubular thin metal tube able to be used as a toner roll,
development roll, fixing roll, etc. of such an electronic photo
printer, laser beam printer (LBP), copier, facsimile, or other
image forming device is required to exhibit the high elasticity,
high rigidity, and high heat conductivity of the metal. Further, it
is required to be made light in weight through ultra-thinning
technology and to be smooth on the surface as a whole in order to
achieve a high rotational precision free from vibration, uneven
rotation, etc. having a detrimental effect on the desired sharp
full color image quality and to be superior in durability.
Therefore, such a thin metal tube is obtained by shaping and
welding a stainless steel sheet etc. into a tubular shape by press
working, laser welding, plasma welding, etc. to fabricate a tube
blank (thick metal tube) and working this to an extremely thin
thickness by ironing, spinning, drawing, bulging, or other thinning
technology (for example, see Japanese Unexamined Patent Publication
(Kokai) No. 2002-55557).
[0004] Further, as a method able to produce a thin metal tube able
to be used as a toner roll, development roll, fixing roll, etc. of
an electronic photo printer, laser beam printer (LBP), copier,
facsimile, or other image forming device, the method of joining the
end faces of a metal thin film sheet by a thermoplastic resin has
been proposed (for example, see Japanese Unexamined Patent
Publication (Kokai) No. 2000-280339).
[0005] However, with a thin metal tube obtained by working a tube
blank (thick metal tube) fabricated by press working, laser
welding, plasma welding, etc. by thinning technology, the structure
of the weld zone melts once due to the laser welding or plasma
welding, its hardness (Hv) falls to about half, and the strength
also declines. Further, when thinning the tube blank, the surface
becomes coarser compared with a metal rolled material (for example,
stainless steel foil) (orange peel surface). For example, when
spinning to work it by about 90%, there are the problems that the
surface roughness (Rz) is about 3 .mu.m and surface flaws occur
along with the thinning. Therefore, there is the problem that a
sufficient rotational precision is hard to obtain due to the
vibration or uneven rotation having a detrimental effect on the
desired sharp full color image. Further, in these thinning
technologies, the process of production is complicated and the
production cost tends to rise.
[0006] Further, with the method of joining the end faces of a metal
thin film sheet by a thermoplastic resin, the resin film covering
the metal thin film has to be a thermoplastic resin. With a
non-thermoplastic or heat curing polyimide or other resin, shaping
is not possible. Further, compared with joining metal, when joining
resin, the joint strength is weak and imparting long term
durability is difficult. In particular, when used at a high
temperature, heat embrittlement is seen in which the load applied
to the joint zone causes separation at the joint zone etc.
Therefore, this is not suitable for a toner roll etc. Further, the
metal thin film has to be uniformly covered with another resin.
There was therefore the problem of swelling production costs.
[0007] Therefore, an object of the present invention is to provide
a novel thin metal tube having an extremely smooth surface, having
the high elasticity, high rigidity, and high heat conductivity of
the metal, extremely thin and light in weight, having a high
rotational precision free from the vibration, uneven rotation, etc.
having a detrimental effect on the desired sharp full color image,
and excellent in durability without using press working, laser
welding, plasma welding, thinning technology, or a resin material
etc. and a method of production and production apparatus for the
same.
[0008] To achieve the above object, the inventors engaged in
intensive study of a novel thin metal tube and a method of
production and production apparatus for the same and as a result
discovered a method of production and production apparatus of a
novel thin metal tube with almost no melted parts at all or a very
small part and therefore free from a drop in hardness, high in
durability, and enabling the weld zone to be finished smooth,
through welding and/or crimping stainless steel foil or another
metal foil substantially in a non-molten state without using the
conventional press working, laser welding, plasma welding, thinning
technology, or resin material. Due to this, they discovered it is
possible to remarkably lower the production costs and obtain a
metal foil tube which, compared with the conventional thin metal
tube obtained using thinning technology or a resin material, has
the high elasticity, high rigidity, and high heat conductivity of
the metal, is extremely thin and light in weight, is superior in
surface smoothness, has a high rotational precision free from the
vibration or uneven rotation etc. having a detrimental effect on
the desired sharp full color image quality, and is excellent in
durability and thereby completed the present invention.
[0009] Further, the inventors were not satisfied with the novel
metal foil tube obtained by the novel method of production and
production apparatus and engaged in intensive efforts to make
further improvements. As a result, they obtained the following
discoveries and made the further improvements of the present
invention.
[0010] That is, in general, the weld zone becomes somewhat
irregular in shape compared with the matrix of the metal foil and
tends to become greater in surface roughness as well. The present
invention welds and/or crimps the metal foil in the substantially
non-molten state. Therefore, it is possible to finish the weld zone
smooth, prevent the weld zone from becoming irregular in shape
compared with the foil matrix, and further reduce the surface
roughness. However, in the midsts of subsequent further research
and improvements, the inventors learned that when welding and/or
crimping metal foil in the substantially non-molten state, when
using a soft foil material, the parts where the two sections are
superposed can be easily crushed and further electrode flaws can be
reduced, while on the other hand there are often cases where the
material of the tube is desirably hard in order to increase the
high-cycle fatigue life from the viewpoint of the performance in
use. Therefore, as a means for dealing with this contradiction and
further improving the metal foil tube of the present invention,
they discovered that by welding and/or crimping annealed foil in
the substantially non-molten state and suitably thereafter cold
working it by sedging, split roller rolling, drawing, spinning, or
a combination of these methods so as to reduce the thickness,
smooth the weld zone, even out the shape and surface roughness of
the weld zone, and simultaneously work harden the material, it is
possible to increase the fatigue life of the metal foil tube. Here,
with SUS301, SUS304, or other metastable austenite steel, cold
working causes a martensite phase to be formed. The work hardening
is remarkable and hardening up to a Vicker's hardness of about 600
is possible. Further, while not to this extent, even with SUS304N1,
SUS304N2, SUS316N, SUS836L, and other high nitrogen stainless steel
or SUS201, SUS202, or other high Mn stainless steel, there is large
work hardening and a Vicker's hardness of up to about 500 is
possible. They learned that with other ordinary austenitic
stainless steel, work hardening is possible up to about a Vicker's
hardness of 430 and thereby further improved the present
invention.
[0011] Further, in the present invention, the inventors discovered
welding and/or crimping metal foil in the substantially non-molten
state by joining by seam welding or mash seam welding or other
electrical resistance welding, but later engaged in further
research and improvements and during this discovered that a weld
zone obtained by seam welding can be stably raised in the strength
of the weld zone by the presence of continuous nuggets along the
weld line (melted and solidified parts) or discontinuous nuggets
along 50% or more of the weld line. That is, in seam welding for
welding and/or crimping with substantially no melting, once nuggets
are formed, even if the electrode wheel (see reference notation 32
in FIG. 6) proceeds to turn, most of the current flows to the
nugget parts with the small electrical resistance (invalid
current). Since the interface to be newly joined has a large
electrical resistance, only a small amount of current flow to it.
Therefore, this part does not reach the welding temperature and is
crimped. Once such a crimped part is formed, since this part also
becomes small in electrical resistance, like with the nuggets, the
formation of nuggets ahead of it is inhibited. To avoid this
vicious cycle, the inventors used a pulse power source for seam
welding, provided a short conduction time followed by a relatively
long non-conduction time, and repeated this cycle and thereby
succeeded in obtain continuous nuggets. The optimum ratio of the
conduction time and non-conduction time at this time is 1/12 to
1/8. If less than 1/12 or over 1/8 to 1/6, discontinuous nuggets
are formed. Experiments of the inventors revealed that even with
discontinuous nuggets, if the weld line is covered 50% or more by
the nuggets, there is no problem strengthwise. From the above, they
learned that to obtain nuggets covering 50% or more of the weld
length, it is necessary to use a pulse power source and set the
ratio of the conduction time and non-conduction time to 1/15 to 1/7
for seam welding and thereby further improved the present
invention.
[0012] On the other hand, even in mash seam welding able to weld
and/or crimp in the non-molten state (due to the non-molten state,
there are no melted parts, so there is the advantage that the
hardness of the weld zone does not fall), to more stably improve
the strength of the weld zone, it is possible to use a pulse power
source for mash seam welding. At this time as well, the inventors
discovered that there is an optimal ratio of the conduction time
and non-conduction time. That is, they learned that with mash seam
welding, it is preferable to use a pulse power source and set the
ratio of the conduction time and non-conduction time to 1/3 to 1/1
for welding and thereby further improved the present invention.
[0013] Further, the fixing roll of a printer sometimes becomes
flawed at the surface due to the entry of foreign matter. Once
flawed, this has a detrimental effect on the later printing
results.
[0014] Further, in the novel metal foil tube discovered by the
inventors, when seam welding the metal foil, quite often the
nuggets formed by melting and solidification are not formed
continuously. This part becomes relatively low in weld strength in
the crimped state. It was learned that there is room for
improvement. Therefore, it was learned that it was necessary to
improve on these points to improve the yield and quality of the
products.
[0015] Therefore, a further improvement of the present invention
enables even these problems to be solved and provides, as a first
aspect, a metal foil tube comprised of a metal foil joined and
shaped by resistance welding etc. with at least one of its outside
surface and inside surface hardened by a hard plating layer.
[0016] Further, it provides, as a second aspect, a metal foil tube
where the plating layer is mainly comprised of one or two or more
metals selected from chromium, nickel, cobalt, and palladium.
[0017] Further, it provides, as a third aspect, a metal foil tube
where the plating layer is comprised of a Ni--P-based alloy.
[0018] Further, it provides, as a fourth aspect, a metal foil tube
wherein the vicinity of the joint zone of at least one of the two
surfaces of the stainless steel foil is plated with a Group X to XI
element or an alloy containing at least one of these elements or a
metal with a melting point of 1200.degree. C. or less and then the
foil is resistance welded and a method of production of the
same.
[0019] Further, it provides, as a fifth aspect, a metal foil tube
where the plating layer is comprised of a Ni--P alloy containing by
weight ratio 1 to 14% of P and a method of production of the
same.
[0020] Further, it provides, as a sixth aspect, a metal foil tube
comprised of a foil tube made of stainless steel foil joined by
resistance welding etc. or further shaped and heat treated at a
temperature of 800 to 1100.degree. C. and a method of production of
the same.
[0021] Further, it provides, as a seventh aspect, a metal foil tube
comprised of a foil tube made of stainless steel foil joined by
resistance welding etc. or further shaped and heat treated at a
temperature of 800 to 1100.degree. C., then hard plated at least at
one of the inside and outside surfaces of the foil tube and a
method of production of the same.
[0022] The object of the present invention is achieved by the
following means.
[0023] (1) A metal foil tube characterized by joining or welding a
metal foil with a thickness of 10 to 100 .mu.m.
[0024] (2) A metal foil tube as set forth in (1), characterized in
that the metal foil is a stainless steel foil, and the stainless
steel is one of ferritic stainless steel, martensitic stainless
steel, austenitic stainless steel, and precipitation hardened
stainless steel.
[0025] (3) A metal foil tube as set forth in (1) or (2),
characterized by being joined by electrical resistance welding.
[0026] (4) A metal foil tube as set forth in (3), characterized in
that the electrical resistance welding is seam welding.
[0027] (5) A metal foil tube as set forth in (4), characterized in
that the seam welding is performed using a pulse power source and
setting a ratio of the conduction time and non-conduction time to
1/15 to 1/7.
[0028] (6) A metal foil tube as set forth in (3), characterized in
that the electrical resistance welding is mash seam welding.
[0029] (7) A metal foil tube as set forth in (6), characterized in
that the mash seam welding is performed using a pulse power source
and setting a ratio of the conduction time and non-conduction time
to 1/3 to 1/1.
[0030] (8) A metal foil tube as set forth in any one of (1) to (7),
characterized in that at least part of the joint surface is a solid
phase joint.
[0031] (9) A metal foil tube as set forth in any one of (1) to (8),
characterized in that the joint or joint line is arranged in a line
or spiral.
[0032] (10) A metal foil tube as set forth in any one of (1) to
(9), characterized in that an absolute value of a hardness
difference between the joint or weld zone and matrix part is, in
terms of Vicker's hardness (Hv), 25% or less of the hardness of the
matrix part.
[0033] (11) A metal foil tube as set forth in any one of (1) to
(10), characterized by cold working the metal foil tube to reduce
its thickness, smooth the joint zone or weld zone, even out the
shape and surface roughness of the joint zone or weld zone, and
work harden the material of at least the joint zone.
[0034] (12) A metal foil tube as set forth in any of (2) to (11),
characterized in that the metal foil is a stainless steel foil, and
the stainless steel foil is an annealed material of an austenitic
stainless steel.
[0035] (13) A metal foil tube as set forth in any of (1) to (12),
characterized in that the Vicker's hardness of the matrix part of
the metal foil tube is 180 or less.
[0036] (14) A metal foil tube as set forth in any of (1) to (12),
characterized in that the Vicker's hardness of the matrix part and
weld zone of the metal foil tube is 300 to 600.
[0037] (15) A metal foil tube as set forth in any of (11) to (14),
characterized in that a maximum nitrogen concentration of the
surface layer of the stainless steel foil is 3 wt % or less.
[0038] (16) A metal foil tube as set forth in any of (2) to (15),
characterized in that the stainless steel foil is a soft austenitic
stainless steel containing [0039] C: 0.05 wt % or less, [0040] Si:
0.05 to 3.6 wt %, [0041] Mn: 0.05 to 1.0 wt %, [0042] Cr: 15 to 26
wt %, [0043] Ni: 5 to 25 wt %, [0044] Mo: 2.5 wt % or less, [0045]
Cu: 2.5 wt % or less, and [0046] N: 0.06 wt % or less, and a
balance of Fe and unavoidable impurities.
[0047] (17) A metal foil tube as set forth in any one of (2) to
(11), characterized in that the stainless steel foil is a high
strength austenitic stainless steel containing [0048] C: 0.05 to
0.2 wt %, [0049] Si: 0.05 to 3.6 wt %, [0050] Mn: 1.0 to 5.0 wt %,
[0051] Cr: 15 to 26 wt %, [0052] Ni: 5 to 25 wt %, [0053] Mo: 5.0
wt % or less, [0054] Cu: 4.0 wt % or less, [0055] N: over to 0.06
wt % to 0.4 wt %, and a balance of Fe and unavoidable
impurities.
[0056] (18) A metal foil tube as set forth in any one of (2) to
(12), characterized in that the metal foil is a stainless steel as
rolled and the weld zone has a martensite phase precipitated at
it.
[0057] (19) A metal foil tube as set forth in any one of (1) to
(18), characterized in that a foil tube obtained by joining and
shaping metal foil is surface hardened at least at one of its
outside surface and inside surface by a hard plating layer.
[0058] (20) A welded metal foil tube as set forth in (19),
characterized in that the hard plating layer is mainly comprised of
one or more metals of chromium, nickel, cobalt, and palladium.
[0059] (21) A welded metal foil tube as set forth in (19),
characterized in that the hard plating layer is comprised of an
Ni--P-based alloy.
[0060] (22) A welded metal foil tube as set forth in (21),
characterized in that the hard plating layer is comprised of an
Ni--P alloy containing, by weight ratio, 1 to 14% of P.
[0061] (23) A metal foil tube as set forth in any one of (1) to
(22), characterized in that a vicinity of the joint zone of at
least one of the two surfaces of the stainless steel foil is plated
with a Group X to XI element or an alloy including such an element
or a metal having a melting point of 1200.degree. C. or less and
then the foil is resistance welded.
[0062] (24) A metal foil tube as set forth in any one of (1) to
(18), characterized in that a metal foil tube obtained by joining
or further shaping a stainless steel foil is heat treated at a
temperature of 800 to 1100.degree. C.
[0063] (25) A metal foil tube as set forth in any one of (1) to
(18), characterized in that a metal foil tube obtained by joining
or further shaping a stainless steel foil is heat treated at a
temperature of 800 to 1100.degree. C., then the foil tube is hard
plated at least at one of the inside and outside surface.
[0064] (26) A metal foil tube as set forth in any one of (1) to
(25), characterized in that a weld zone of the metal foil tube has
continuous nuggets along the weld line or discontinuous nuggets
present at least at 50% or more of the weld line.
[0065] (27) A metal foil tube as set forth in any one of (1) to
(26), characterized in that an overlap (x) .mu.m of the joint zone
of the metal foil tube satisfies x.ltoreq.40+5 t with respect to
the metal foil thickness (t) .mu.m.
[0066] (28) A metal foil tube as set forth in any one of (1) to
(27), characterized in that the ratio of the inside diameter of the
metal foil tube to the thickness of the tube is 1/500 or less.
[0067] (29) A metal foil tube as set forth in any one of (1) to
(28), characterized in that a surface roughness Rz of the metal
foil tube defined by JIS B0601-2001 is 2.0 .mu.m or less.
[0068] (30) A metal foil tube as set forth in any one of (1) to
(29), characterized in that the metal foil tube has a durability of
1.times.10.sup.6 cycles or more in a fatigue test giving a strain
of 0.2% or less at repeated cycles of 60 cycles/min or more.
[0069] (31) A metal foil tube as set forth in any one of (1) to
(30), characterized in that it is used for a toner roll and/or
development roll of an image forming device.
[0070] (32) A method of production of a metal foil tube
characterized by comprising a shaping step of shaping a metal foil
sheet with a thickness of 10 to 100 .mu.m so that its facing sides
overlap and a welding step of welding the overlapped facing
sides.
[0071] (33) A method of production of a metal foil tube as set
forth in (32), characterized by further having a finishing step of
finishing the welded part smooth.
[0072] (34) A method of production of a metal foil tube as set
forth in (32) or (33), characterized in that the shaping step has a
positioning step of positioning the metal foil sheet at a shaping
use core rod before overlapping the facing sides of the metal foil
sheet.
[0073] (35) A method of production of a metal foil tube as set
forth in (34), characterized in that the positioning step holds the
metal foil sheet at a shaping device approaching and moving away
from the core rod while constantly maintaining a parallel position
with it, bringing the shaping device close to the core rod, and,
when the metal foil sheet and core rod come into line contact,
pressing and positioning the metal foil sheet with respect to the
core rod.
[0074] (36) A method of production of a metal foil tube as set
forth in (34) or (35), characterized in that the shaping step has,
after the positioning step, a wrapping step of bringing the shaping
device closer to the core rod, holding the metal foil sheet between
a semicircular cross-sectional recess formed at the shaping device
and the core rod, and wrapping the metal foil sheet around the core
rod.
[0075] (37) A method of production of a metal foil tube as set
forth in (36), characterized in that after the wrapping step, the
shaping step has an overlap adjusting step of adjusting the overlap
by making part of the circumference of the metal foil sheet
displace in the radial direction.
[0076] (38) A method of production of a metal foil tube as set
forth in (36) or (37), characterized in that an overlap (x) .mu.m
satisfies x.ltoreq.40+5 t with respect to the thickness (t)
.mu.m.
[0077] (39) A method of production of a metal foil tube as set
forth in (32) or (33), characterized in that the welding step is
electrical resistance welding.
[0078] (40) A method of production of a metal foil tube as set
forth in (39), characterized in that the electrical resistance
welding is seam welding or mash seam welding.
[0079] (41) A method of production of a metal foil tube as set
forth in (40), characterized in that the electrical resistance
welding uses a pulse power source and sets the ratio of the
conduction time and non-conduction time to 1/15 to 1/7 for seam
welding or uses a pulse power source and sets the ratio of the
conduction time and non-conduction time to 1/3 to 1/1 for mash seam
welding.
[0080] (42) A method of production of a metal foil tube as set
forth in any one of (32), (33), or (39) to (41), characterized in
that the welding step is performed by running a current between a
conductive stationary electrode member provided in a groove formed
along the axial direction of the outside surface of the core rod
and a conductive movable electrode member provided facing the
stationary electrode member.
[0081] (43) A method of production of a metal foil tube as set
forth in (42), characterized in that the stationary electrode
member is formed so that part or all of the outside surface is
flat.
[0082] (44) A method of production of a metal foil tube as set
forth in (42) or (43), characterized in that the stationary
electrode member and/or movable electrode member is comprised at
least partially of molybdenum or alumina-dispersed copper
alloy.
[0083] (45) A method of production of a metal foil tube as set
forth in any one of (42) to (44), characterized in that the
hardness of the stationary electrode member and/or movable
electrode member and the hardness of the metal foil sheet are
substantially the same.
[0084] (46) A method of production of a metal foil tube as set
forth in any one of (34) to (36) and (42), characterized in that
the metal foil tube is designed to be separated and removed from
the core rod by ejecting a fluid from the inside of the core rod
toward the radial direction.
[0085] (47) A method of production of a metal foil tube as set
forth in any one of (34) to (37) and (42), characterized in that
the core rod is comprised of a plurality of members and part is
moved in the axial direction to separate the metal foil tube from
the core rod.
[0086] (48) A method of production of a metal foil tube as set
forth in any one of (32) to (47), characterized in that a ratio of
the inside diameter of the metal foil tube to the thickness of the
metal foil sheet is 1/500 or less.
[0087] (49) A method of production of a metal foil tube as set
forth in any one of (32) to (48), characterized by inserting a
metal core into the metal foil tube and cold working the tube by
sedging, split roller rolling, drawing, spinning, or a combination
of these methods to reduce the thickness, smooth the joint zone or
weld zone to even out the shape and surface roughness of the joint
zone or weld zone, and work harden the material of the joint zone
or weld zone.
[0088] (50) A method of production of a metal foil tube as set
forth in any one of (32) to (49), characterized by plating the
vicinity of the joint zone of at least one of the two surfaces of
the stainless steel foil by a Group X to XI element or an alloy
containing that element or a metal with a melting point of
1200.degree. C. or less and then resistance welding the foil.
[0089] (51) A method of production of a metal foil tube as set
forth in any one of (32) to (50), characterized by heat treating a
metal foil tube obtained by joining or further shaping a stainless
steel foil at a temperature of 800 to 1100.degree. C.
[0090] (52) A method of production of a metal foil tube as set
forth in any one of (32) to (51), characterized by heat treating a
metal foil tube obtained by joining or further shaping a stainless
steel foil at a temperature of 800 to 1100.degree. C., then hard
plating at least one of the inside and outside surfaces of the
metal foil tube.
[0091] (53) A method of production of a metal foil tube as set
forth in (50) or (52), characterized in that the composition of the
hard plating is an Ni--P alloy containing 1 to 14% of P by weight
ratio.
[0092] (54) A method of production of a metal foil tube as set
forth in any one of (32) to (53), characterized in that due to the
welding of the metal foil tube, the weld zone has continuous
nuggets along the weld line or discontinuous nuggets along 50% or
more of the weld line.
[0093] (55) A production apparatus of a metal foil tube,
characterized by having a shaping unit for shaping a 10 to 100
.mu.m thick metal foil sheet to a predetermined shape and a welding
unit for welding facing sides of the metal foil sheet.
[0094] (56) A production apparatus of a metal foil tube as set
forth in (55), characterized in that the shaping unit has a core
rod of a circular cross-section perpendicular to the axis, a
shaping device provided to be able to approach and move away from
the core rod and holding the metal foil sheet, and a positioning
member for making the shaping device approach the core rod and
pressing against the metal foil sheet to position it with respect
to the core rod at the time when the metal foil sheet and core rod
come into line contact, and
[0095] making the shaping device move so as to make the positioned
metal foil sheet approach the core rod and wrap the metal foil
sheet in a U-shape around the core rod.
[0096] (57) A production apparatus of a metal foil tube as set
forth in (56),characterized in that the shaping device has a
holding plate provided so as to approach and move away from the
core rod while constantly maintaining a parallel position with it
and having a semicircular cross-section recess for wrapping the
metal foil sheet in a U-shape with the core rod, a first pressing
member for pressing one side of the U-shaped metal foil sheet so as
to contact the circumference of the core rod, and a second pressing
member for pressing the other side of the U-shaped metal foil sheet
toward the circumference of the core rod, and
[0097] after the wrapping, overlapping the facing side edges of the
metal foil sheet to form an overlap part.
[0098] (58) A production apparatus of a metal foil tube as set
forth in (56) or (57),characterized in that the shaping unit has an
overlap adjusting means for displacing part of the circumference of
the metal foil sheet in the radial direction so that the overlap of
the overlap part of the facing sides becomes a predetermined value
before the end of the pressing action by the second pressing
member.
[0099] (59) A production apparatus of a metal foil tube as set
forth in (58),characterized in that the overlap adjusting means is
comprised of offsetting devices provided at the inside of the core
rod.
[0100] (60) A production apparatus of a metal foil tube as set
forth in (58),characterized in that the overlap adjusting means is
comprised of offsetting devices provided at the outside of the core
rod.
[0101] (61) A production apparatus of a metal foil tube as set
forth in (58),characterized in that the overlap adjusting means is
designed to press a non-contact part where the metal foil sheet
does not contact the core rod by a pressing member.
[0102] (62) A production apparatus of a metal foil tube as set
forth in (58),characterized in that the overlap adjusting means is
designed to press a pressing member provided at the outside of the
core rod into a recess formed in the core rod.
[0103] (63) A production apparatus of a metal foil tube as set
forth in (61) or (62),characterized in that the pressing member is
any of a cam, roll, tube, or rod-shaped member and is provided to
operate separately at each of the two ends in the axial direction
of the core rod.
[0104] (64) A production apparatus of a metal foil tube as set
forth in (57) or (58),characterized in that the overlap (x) .mu.m
satisfies x.ltoreq.40+5 t with respect to the thickness (t)
.mu.m.
[0105] (65) A production apparatus of a metal foil tube as set
forth in (55), characterized in that the welding is an electrical
resistance welding.
[0106] (66) A production apparatus of a metal foil tube as set
forth in (55), characterized in that the welding unit is comprised
of a conductive stationary electrode member provided along the
axial direction of the outside surface of the core rod and a
movable electrode member provided facing the stationary electrode
member, grips the overlap part of the metal foil sheet between the
two electrode members, and welds it in that state.
[0107] (67) A production apparatus of a metal foil tube as set
forth in (66), characterized in that the stationary electrode
member is formed so that part or all of its outside surface is
flat.
[0108] (68) A production apparatus of a metal foil tube as set
forth in (66), characterized in that the movable electrode member
is an electrode ring pressing against the overlap part and carrying
a current.
[0109] (69) A production apparatus of a metal foil tube as set
forth in any of (66) to (68), characterized in that the stationary
electrode member and/or movable electrode member is comprised at
least partially of molybdenum or an alumina-dispersed copper
alloy.
[0110] (70) A production apparatus of a metal foil tube as set
forth in any of (66) to (68), characterized in that a hardness of
the stationary electrode member and/or movable electrode member and
a hardness of the metal foil sheet are substantially the same.
[0111] (71) A production apparatus of a metal foil tube as set
forth in any of (56), (57), or (66), characterized in that the
metal foil tube is designed to be separated and removed from the
core rod by ejecting a fluid from the inside of the core rod toward
the radial direction.
[0112] (72) A production apparatus of a metal foil tube as set
forth in any of (56), (57), or (66), characterized in that the core
rod has a fluid passage for ejecting a fluid for separating the
welded metal foil tube from the core rod.
[0113] (73) A production apparatus of a metal foil tube as set
forth in any of (56), (57), or (66), characterized in that the core
rod has grooves at its outer circumference for preventing the metal
foil sheet from closely contacting the core rod.
[0114] (74) A production apparatus of a metal foil tube as set
forth in any of (56), (57), or (66), characterized in that the core
rod is comprised of a plurality of members and part is made to move
in the axial direction so as to separate the metal foil tube from
the core rod.
[0115] (75) A production apparatus of a metal foil tube as set
forth in any of (55) to (74), characterized in that a ratio of an
inside diameter of the metal foil tube to a thickness of the metal
foil sheet is designed to be 1/500 or less.
[0116] (76) A metal foil tube characterized by being obtained using
a method of production of the metal foil tube as set forth in (32)
to (54) or a production apparatus of a metal foil tube as set forth
in (55) to (75).
BRIEF DESCRIPTION OF THE DRAWINGS
[0117] FIG. 1(A) is a plan view of a metal foil sheet for forming a
metal foil tube.
[0118] FIG. 1(B) is a sectional view of a metal foil tube before
welding.
[0119] FIG. 1(C) is a perspective view of a metal foil tube with a
straight joint zone.
[0120] FIG. 1(D) is a perspective view of a metal foil tube with a
spiral joint zone.
[0121] FIG. 2 is a schematic side view of a metal foil tube
production apparatus according to an embodiment of the present
invention.
[0122] FIG. 3 is a plan view of FIG. 2.
[0123] FIG. 4 is a sectional view along the line 4-4 of FIG. 3.
[0124] FIG. 5 is an enlarged sectional view of principal parts of
FIG. 4.
[0125] FIG. 6 is an enlarged sectional view showing a state of
welding of a metal foil tube production apparatus of an embodiment
of the present invention.
[0126] FIG. 7 is a schematic sectional view along the axis of the
core rod of a metal foil tube production apparatus of an embodiment
of the present invention.
[0127] FIG. 8 is a schematic view of another example of a core rod
of a metal foil tube production apparatus of an embodiment of the
present invention.
BEST MODE FOR WORKING THE INVENTION
[0128] Below, embodiments of the present invention will be
explained with reference to the attached drawings.
[0129] Metal Foil Tube
[0130] The present invention is a metal foil tube characterized by
joining or welding metal foil of a thickness of 10 to 100 .mu.m,
preferably 20 to 50 .mu.m. The metal foil tube of the present
invention, as explained below, has the high elasticity and high
rigidity characteristic of a metal, is thin, light in weight, and
excellent in durability, has a high heat conductivity, and can be
used for a toner roll, development roll, etc. of an electronic
photo printer, laser beam printer (LBP), copier, facsimile, or
other image forming device where a high rotational precision free
of the vibration or uneven rotation having a detrimental effect on
the desired sharp full color image quality is desired. In the
conventional thinning technology, the surface inevitably ends up
rough and smoothing is difficult. Only a surface with a surface
roughness Rz of 3 .mu.m or less could be obtained. With the metal
foil as in the present invention, however, for example, when
joining or welding a rolled stainless steel foil, the surface is
smooth and a tube with a surface roughness of 2 .mu.m or less can
be provided. As a result, it is possible to provide a metal foil
tube having a high rotational precision free from the vibration or
uneven rotation having a detrimental effect on the desired sharp
full color image quality. Further, with the conventional method of
joining by a thermoplastic resin, a sufficient joint strength
cannot be obtained and the durability becomes inferior, but with
the present invention, since metal is joined, the joint strength is
sufficient and the durability is superior. Further, with the
conventional method of joining by a thermoplastic resin, it is
necessary to coat thermoplastic resin to a uniform thickness on the
surface of the metal foil and therefore the cost becomes high, but
in the present invention, this step is not required, productivity
is excellent, and low cost metal foil tubes can be provided.
Further, it is possible to provide a metal foil tube with a small
power consumption, excellent in repeated mechanical stress,
excellent in durability in a fatigue test etc., long in product
life, free from heat embrittlement even in a temperature region of
a high temperature of 200 to 400.degree. C. or so, suitable for use
even for a toner roll etc., and enabling use of an alloy such as
stainless steel. Further, it is possible to reduce the size and
lighten the weight of the electronic photo printer, laser beam
printer (LBP), copier, facsimile, or other image forming device and
further save on energy.
[0131] Here, when the thickness of the metal foil tube of the
present invention is over 100 .mu.m, the heat conductivity becomes
poor, so startup from the energy saving mode takes time. Further,
the weight increases and the foil becomes thicker, so reduction of
thickness and weight becomes difficult. Therefore, the demands from
users and manufacturers for smaller size and lighter weight may not
be able to be sufficiently met. On the other hand, the thinner the
stainless steel foil, the better, but if less than 10 .mu.m, the
strength and rigidity are low and handling is difficult.
[0132] Note that, in the present invention, since the metal foil
tube is comprised of the metal foil joined together as is, the
surface roughness Rz can be made 2 .mu.m or less, preferably 0.1 to
1 .mu.m. This is because, as explained above, it is possible to
obtain a metal foil tube by joining without detracting from the
surface roughness of the rolled metal foil. Note that, in
accordance with need, it is also possible to finish the surface
after rolling. Further, if making the surface roughness Rz of the
rolled metal foil less than 0.1 .mu.m, the cost becomes high, so it
is desirable to make the surface roughness Rz of the metal foil 0.1
.mu.m or more. Due to this, as a metal foil tube able to be used
for the toner roll, development roll, etc. of an electronic photo
printer, laser beam printer (LBP), copier, facsimile, or other
image forming device, it is possible to provide a tube with
excellent surface properties having a high elasticity and high
rigidity, extremely thin, light in weight, excellent in durability,
and having a high rotational precision free from vibration or
uneven rotation having a detrimental effect on the desired sharp
full color image quality.
[0133] Note that the surface roughness Rz may be measured by the
measurement method defined in JIS B0601-2001 (maximum height
roughness), but the invention is not limited to this.
[0134] Next, the metal foil material used for the metal foil tube
of the present invention is not particularly limited. The optimal
material may be suitably selected in accordance with the
application. In the case of a fixing roll, development roll,
heating roll, etc. of an electronic photo printer, laser beam
printer (LBP), copier, facsimile, or other image forming device or
other application, from the viewpoint of the ability to provide a
tube having a high elasticity and high rigidity, extremely thin,
light in weight, excellent in durability, and having a high
rotational precision free from vibration or uneven rotation having
a detrimental effect on the desired sharp full color image quality,
a stainless steel foil is desirable. Specifically the material is
any one of ferritic stainless steel, martensitic stainless steel,
austenitic stainless steel, and precipitation hardened stainless
steel. Note that, the precipitation hardened stainless steel, as
shown in the later explained Example 7, is advantageous in the
point of enabling electrical resistance welding or the like to be
used for joining the foil to prepare a metal foil tube, polishing
or otherwise finishing, then performing solid solution heat
treatment along with the characteristics of stainless steel for
example and, in accordance with need, intermediate treatment,
precipitation hardening heat treatment, etc. to cause precipitation
hardening and obtain a high yield and further make the hardnesses
of the matrix part and weld zone substantially the same and greatly
improve the durability. The conditions for the solid solution heat
treatment at this time and, if necessary, the intermediate
treatment, precipitation hardening heat treatment, etc. may be
optimally selected in accordance with the type of the stainless
steel.
[0135] In the past, no technology had been established for directly
joining metal foil, but the joining technology of the present
invention enables use, in accordance with the purpose, for a broad
range of materials from soft stainless steel foil to hard stainless
steel foil. There is no limitation on the material used. It is
possible to provide a metal foil tube able to be used for a broad
range of applications. Note that the material of the metal foil
tube of the present invention is not limited to these. For example,
ultra-high purity Fe alloy, Ni and Ni alloy, Co and Co alloy, Ti
and Ti alloy, Nb and Nb alloy, Zr and Zr alloy, Ta and Ta alloy,
etc. may be used.
[0136] The material of the metal foil of the metal foil tube of the
present invention is suitably a rolled material obtained by rolling
a sheet of a stainless steel of any of ferritic stainless steel,
martensitic stainless steel, austenitic stainless steel, or
precipitation hardened stainless steel, an annealed material
obtained by annealing this after rolling, or a tension annealed
material etc., but the invention is not limited to these.
Specifically, a rolled material obtained by rolling a sheet of any
stainless steel of ferritic stainless steel foil of the JIS SUS400
series, SUSXM27, Tp.409, or other ferritic stainless steel foil,
martensitic stainless steel foil of the JIS SUS400 series,
austenitic stainless steel foil of the JIS SUS200 series and 300
series, SUSXM7, SUSXM15J1, Tp.302B, Tp.314, and other austenitic
stainless steel, or SUS630, SUS631, or other precipitation hardened
stainless steel, an annealed material or precipitation hardened
material obtained by annealing this after rolling, etc. may be
mentioned.
[0137] Further, the metal foil tube of the present invention is
preferably joined by electrical resistance welding. Specifically,
the electrical resistance welding is seam welding, preferably mash
seam welding. Further, the metal foil tube of the present invention
is better in surface smoothness compared with the conventional
thinning technologies, but to achieve this surface smoothness, it
is necessary to join the joint zone and matrix part to be superior
in surface smoothness as well and further make the hardness
difference between the joint zone and matrix part 25% or less of
the hardness of the matrix part in terms of Vicker's hardness (Hv).
For this purpose, the joint is preferably joined by electrical
resistance welding. Specifically, the electrical resistance welding
is seam welding, preferably mash seam welding. In a metal foil tube
using such a joining means, by employing a resistance welding
method applying electrode pressure, that is, seam welding, and
further a welding method welding while crushing the joint zone
under the strong pressure of an electrode wheel to obtain a joint
zone close to a butt joint, that is, mash seam welding, it is
possible to continuously crush together the overlapping foil of the
joint zone by a suitable electrode pressure to form a joint zone
close to a butt joint. Therefore, the weld zone is flattened in
thickness. At the time of the subsequent surface finishing, simple
smoothing is sufficient without requiring an excessive load to be
placed on the joint zone of the parts of the foil, therefore the
production costs can be suppressed. As a result, it is possible to
finish this to a smooth surface (joint zone) with a low surface
roughness Rz.
[0138] Further, in the metal foil tube of the present invention,
the weld zone of the metal foil tube preferably has continuous
nuggets (melted and solidified parts) along the weld line or
discontinuous nuggets along at least 50% of the weld line. This is
because when joining by seam welding etc. enabling welding and/or
crimping in the substantially non-molten state, the weld zone has
continuous nuggets (melted and solidified parts) along the weld
line or discontinuous nuggets along at least 50% of the weld line
and therefore the strength of the weld zone can be kept stably
high.
[0139] That is, in ordinary seam welding, once nuggets are formed,
even when the electrode wheel (see reference numeral 32 of FIG. 6)
proceeds to rotate, most of the current flows to the small
electrical resistance nugget parts (invalid current). Since the
interface to be newly joined has a large electrical resistance,
only a small amount of current flows to it. Therefore, this part
does not reach the welding temperature and is crimped in state.
Once such a crimped part is formed, since this part also becomes
small in electrical resistance, like with the nuggets, the
formation of nuggets ahead of it is inhibited. To avoid this
vicious cycle, the inventors used a pulse power source for seam
welding, provided a short conduction time followed by a relatively
long non-conduction time, and repeated this cycle and thereby
succeeded in obtain continuous nuggets. The optimum ratio of the
conduction time and non-conduction time at this time is 1/12 to
1/8. If less than 1/12 or more than 1/8 to 1/6, discontinuous
nuggets are formed. However, experiments of the inventors revealed
that even with discontinuous nuggets, if the nuggets can cover 50%
or more of the weld line, there is no problem strength-wise. To
obtain nuggets covering 50% or more of the weld length, the ratio
of the conduction time and non-conduction time has to be set to
1/15 to 1/7. From the above viewpoint, in the metal foil tube of
the present invention, using a pulse power source and setting the
ratio of the conduction time and non-conduction time to 1/15 to 1/7
for seam welding can be said to be preferable.
[0140] Further, mash seam welding enables welding and/or crimping
in a non-molten state. This mash seam welding has the advantage
that it is non-melting, so no melted parts are formed and therefore
the hardness does not fall. In this as well, to more stably raise
the strength of the weld zone, the inventors discovered that it is
preferable to use a pulse power source for mash seam welding. At
this time as well, there is an optimal ratio of the conduction time
and non-conduction time. That is, in the metal foil tube of the
present invention, using a pulse power source and setting the ratio
of the conduction time and non-conduction time to 1/3 to 1/1 for
mash seam welding can also be said to be a preferable
embodiment.
[0141] Further, the weld zone of the metal foil tube of the present
invention is a solid phase joint with no molten phase remaining
except at the parts of the nuggets formed along the joint surface.
Therefore, compared with laser welding or plasma welding where the
molten phase remains extending across the entire thickness of the
weld zone, it is possible to suppress a drop in strength due to a
change in composition at the joint zone (change in crystal
structure). Further, since the joint zone and non-joint zone
(matrix part) are substantially the same in hardness and other
mechanical properties, there is little cracking or joint separation
due to sudden metal fatigue due to concentration of stress at the
interface or joint surface between the joint zone and matrix part,
and the durability becomes excellent. Therefore, when using the
metal foil tube for the toner roll, development roll, etc. of an
image forming device, it is possible to increase the service life.
However, when the material used is a soft material, it is possible
to reduce the pressing force at the time of welding, leave the
molten phase at the weld zone, and reduce the hardness difference
from the matrix. From the above, it is preferable that at least
part of the joint surface of the weld zone of the metal foil tube
according to the present invention be a solid phase joint. In this
case, the solid phase joint may be part or all of the joint
surface. Note that if using mash seam welding enabling welding
and/or crimping in the non-molten state, no nuggets are formed and
the entire joint surface of the weld zone can be made a solid phase
joint. This is preferable in that since no molten phase is formed,
there is no drop in strength due to the change in composition of
that joint zone (change in crystal structure).
[0142] By the electrical resistance welding (including seam welding
and mash seam welding) or other welding in a substantially
non-molten state and/or crimping, preferably the overlap (x) of the
joint zone preferably satisfies x.ltoreq.40+5 t with respect to the
thickness (t) of the metal foil in the foil tube. Here, when the
overlap (x) is larger than 40+5 t, surface finishing should be
performed. Note that here, the units of the overlap (x) and the
thickness (t) of the metal foil are both .mu.m.
[0143] In the metal foil tube of the present invention, it is
preferable that the absolute value of the hardness difference
(Vicker's hardness) of the weld zone and matrix part (non-weld
zone) be 25% or less of the hardness of the matrix part in terms of
Vicker's hardness (Hv). If the absolute value of the hardness
difference of the weld zone and matrix part (non-weld zone) is over
25% of the hardness of the matrix part in terms of Vicker's
hardness (Hv), at the interface between the weld zone and matrix
part (non-weld zone), the metallurgical notch effect due to the
hardness difference causes metal fatigue etc. and as a result
susceptibility to cracks and fractures. Note that with the
conventional laser welding method, the weld zone melts and the
hardness remains declined. The method of measurement of the
Vicker's hardness (Hv) is based on JIS Z 2244 (1998). In the
present invention, by suitably selecting the welding method,
material, and heat treatment method, it is possible to suppress the
hardness difference of the weld zone and matrix part (non-weld
zone), possible to improve the durability of the metal foil tube as
a whole, and possible to realize a high rotational precision with
no uneven rotation or vibration due to its mechanical strength
(hardness difference).
[0144] Further, in the metal foil tube of the present invention, as
the stainless steel foil, ferritic stainless steel or martensitic
stainless steel as rolled with a martensite phase precipitated at
the weld zone preferably can be used. Specifically, SUS410L or
another ferritic stainless steel, SUS403, SUS410, SUS420, SUS431,
SUS440, or another martensitic stainless steel etc. may be
mentioned as steels where the martensite phase precipitates at the
weld zone. In the case of these steels, the weld zone is hardened
by the precipitation of martensite due to the welding heat, the
matrix part is hardened utilizing the work hardening due to
rolling, and the hardness difference between the weld zone and
matrix part is made smaller.
[0145] Further, with martensitic stainless steel, by heat treatment
at a suitable temperature after welding, it is possible to adjust
the hardness to a broad range of Hv300 to 600.
[0146] A metal foil tube using a hard material as the stainless
steel foil may be suitably utilized for applications of a metal
foil tube of for example, 30 .mu.m or less thickness. In
particular, when using a hard material as the stainless steel foil,
the mechanical properties of the weld zone can be raised.
Therefore, it is possible to extend the fatigue life and contribute
to improvement of the durability. Further, it is possible to
shorten the startup time from the energy saving mode.
[0147] Further, in the metal foil tube of the present invention, as
the stainless steel foil, an annealed material obtained by rolling
and annealing SUS304 or another JIS SUS 300 series austenitic
stainless steel may be mentioned. The metal foil tube obtained by
using a soft material as the stainless steel foil does not harden
that much in the weld zone. Since the matrix part is a soft
material, overall a soft tube can be obtained. In this case, by
using an electrode material of a hardness substantially the same as
the hardness of the metal foil, joining is possible without
damaging either the electrode material and metal foil. In
particular, when using an annealed material of austenitic stainless
steel for the metal foil, this is advantageous also in the point of
enabling combination of copper or another material excellent in
electrical conductivity for the electrode material.
[0148] When using an annealed material of austenitic stainless
steel as the metal foil, one with a Vicker's hardness (Hv) of the
matrix part of 180 or less is preferable. This has the feature of
excellent workability in the production stage and ease of shaping
into a tube. Further, this is also superior in the point that even
when precisely cutting out (punching) the metal foil, warping or
strain of the edges etc. does not easily occur. Further, as an
electrode material with a hardness substantially the same as the
hardness of the metal foil, for example there are molybdenum,
alumina-dispersed copper alloy, etc. Since these electrode
materials can be used, damage to the electrode material or tube at
the production stage can be suppressed.
[0149] In the above metal foil tube, from the viewpoint of
excellent durability and wear resistance and longer high-cycle
fatigue life, the Vicker's hardness (Hv) of the material, that is,
the material of the matrix part and joint zone (weld zone) of the
metal foil tube, is 300 to 600, preferably 400 to 500. That is,
from the viewpoint of excellent workability at the production stage
and ease of shaping to a tube, the Vicker's hardness of the matrix
part is preferably 180 or less. However, from the viewpoint of the
performance in use, a hard tube material is preferable in many
cases for increasing the high-cycle fatigue life. Therefore, it is
also possible to cold work the metal foil tube obtained by joining
or welding metal foil to reduce the thickness, smooth the joint
zone, even out the shape and surface roughness of the joint zone,
and work harden at least the material of the joint zone. Due to
this, it is possible to raise the Vicker's hardness (Hv) of the
material including the joint zone to a range defined above and
possible to improve aspects of performance in use such as
durability and wear resistance. As a result, it is possible to
simultaneously achieve both workability at the welding stage and
high high-cycle fatigue life from the aspect of performance in
use.
[0150] In the present invention, it is also possible to work the
entire metal foil tube including the weld zone to thin it, smooth
the weld zone, even out the shape and surface roughness of the weld
zone, and work harden the material of the entire tube including the
weld zone. This is because, as explained above, in the case, as in
the present invention, when welding and/or crimping metal foil in
the substantially non-molten state, when using a soft foil
material, the parts where the two sections are superposed can be
easily crushed and further electrode flaws can be reduced, while on
the other hand there are often cases where the material of the tube
is desirably hard in order to increase the high-cycle fatigue life
from the viewpoint of the performance in use. To eliminate this
contradiction, in a further improvement of the present invention,
it is possible to weld an annealed foil, then suitably thereafter
cold work this by sedging, split roller rolling, drawing, spinning,
or a combination of these methods to reduce the thickness, smooth
the weld zone, even out the shape and surface roughness of the weld
zone, and simultaneously work harden the material. Due to this, it
is possible to increase the fatigue life of the metal foil
tube.
[0151] That is, as the metal foil tube suitable for the working
method, one obtained by welding annealed foil in the above way is
preferable, but the invention does not exclude one obtained by
welding unannealed foil. That is, if it is possible to cold work a
metal foil tube comprised of a metal foil joined or welded together
to reduce the thickness, smooth the weld zone, even out the shape
and surface roughness of the weld zone, and simultaneously work
harden the material so as to increase the fatigue life of the metal
foil tube, even welded unannealed foil is included in the technical
scope of the present invention.
[0152] As the method for working the weld zone of the metal foil
tube, for example, it is possible to cold work the weld zone by
sedging, split roller rolling, drawing, spinning, or a combination
of these methods. However, so long as it is possible to smooth the
weld zone, even out the shape and surface roughness of the weld
zone, and work harden the material of at least the weld zone, the
invention is not limited to these cold working methods.
[0153] It is preferable to use the above working method for cold
working to smooth the weld zone and even out the weld zone in
appearance, shape, surface roughness, and hardness so as to be
indistinguishable from the matrix part. Due to this, it is possible
to provide a metal foil tube which can achieve a high rotational
precision free from vibration or uneven rotation having a
detrimental effect on the desired sharp full color image quality,
has a smooth surface of the tube as a whole, and is excellent in
durability.
[0154] Similarly, by smoothing the weld zone, the surface roughness
is preferably leveled to a surface roughness Rz defined by JIS
B0601-2001 (maximum height roughness) of 2.0 .mu.m or less,
preferably 0.1 to 1 .mu.m. In particular, cold working by the
working method is suitable for evening out the surface roughness
and is extremely effective in terms of enabling adjustment to a
value close to the lower limit of the preferable range (see later
explained Table 1 of Example 9).
[0155] Further, it is preferable to cold work the metal fail tube
and work harden the material and the material of the matrix part
and joint zone (weld zone) of the metal foil tube to obtain a
Vicker's hardness (Hv) of the material of 300 to 600, preferably
400 to 600, more preferably 450 to 550. Due to this, as explained
above, it is possible to provide a welded metal foil tube suitable
for use as a toner roll, development roll, etc. of an image forming
device, excellent in durability and wear resistance, and having a
hardness effective for increasing the high-cycle fatigue life.
[0156] Further, when using as the metal foil an annealed material
of austenitic stainless steel, to prevent wrinkles, cracks, etc.
when cutting out (punching) the metal foil at a high precision, the
content of the nitrogen element in the stainless steel foil as a
whole (bulk) is preferably 0.06 wt % or less, more preferably 0.03
wt % or less. Further, simultaneously, the maximum nitrogen
concentration of the surface layer of the stainless steel foil is
preferably 3 wt % or less. Here, the "surface layer of the
stainless steel foil" means the oxide film formed on the surface
due to the annealing. In general, the "oxide film" indicates the
part of a depth from the surface-most layer down to where the
oxygen concentration becomes 50% of the peak. If the content of
nitrogen of the stainless steel foil exceeds 0.06 wt %, the
stainless steel foil becomes hard, so easily fractures when the
metal foil is cut out (punched) to a high precision and therefore
is liable to easily crack. This is because with ordinary stainless
steel sheet or just rolled stainless steel foil, the nitrogen
content does not remarkably increase, but if annealing this at the
production stage, the N.sub.2 gas in the atmosphere is taken into
the stainless steel foil and remarkable nitridation occurs.
Therefore, the nitrogen content of the bulk increases and
simultaneously the nitrogen content in the oxide film at the
surface layer remarkably increases. The nitrogen content of the
surface layer increases relatively from that of the inside of the
bulk, so the hardness becomes even higher than the inside of the
bulk. As a result, when cutting out (punching) the metal foil with
a high precision, shallow cracks occur in the surface layer and
proceed in the thickness direction to lead to fractures.
[0157] Further, when using as the metal foil an annealed material
of austenitic stainless steel, the material is specifically a sheet
of stainless steel, in the SUS series, of SUS304, SUS304L, SUS304J1
(Cu added), SUS304J2 (17% Cr-7% Ni-4% Mn-2% Cu), SUS316 (Mo added),
SUS316L (Mo added), SUS305, SUSXM7 (Cu added), SUS317, SUS317L,
SUS309S, etc. and, in Nippon Steel Corporation's own steel of the
YUS series, YUS304UL, YUS316UL (Mo added), YUS27A (Cu added),
YUS110M (Cu, Si, and Mo added), YUS170, or other stainless steel,
which is then rolled and annealed, but the invention is not limited
to these. Sheets of SUS316, SUS304, or other stainless steel used
most widely as stainless steel, already inexpensively and cheaply
available as stainless steel sheet used for rolling, for which
technology has been established for rolling to stainless steel
foil, and suitable for annealing as well, which are then rolled and
annealed are more preferable. In particular, sheets of SUS304J1
(17% Cr-7% Ni-2% Cu) and SUS304J2 (17% Cr-7% Ni-4% Mn-2% Cu) are
large in effect of improvement of the shapeability and improvement
of the age cracking due to the drop in C and N and addition of Cu.
The press workability is highest among the steels illustrated
above. Further, sheets of austenite stabilized steel such as SUS316
or SUS305 are free from formation of work-induced martensite and
the risk of age cracking. Note that the Ti added steel of SUS316Ti,
SUS321, and the high Ni steels of SUS310S (25% Cr-20% Ni),
SUS317J5L (21% Cr-24% Ni-4.5% Mo-1.5% Cu-low C), SUS384 (16% Cr-18%
Ni), and SUSXM15Jl (18% Cr-13% Ni-4% Si) can also be used as the
toner rolls, development rolls, etc. of electronic photo printers,
laser beam printers (LBP), copiers, facsimiles, and other image
forming devices.
[0158] Further, when using as the metal foil a soft austenitic
stainless steel (soft material) or high strength austenitic
stainless steel (hard material) such as an annealed material of
austenitic stainless steel, the preferable ranges of the
ingredients of the stainless steel are as follows:
[0159] C: C is an element stabilizing austenite, but when slightly
high in content, the material becomes hard, so to obtain a soft
material, the content is made 0.05 wt % or less, while to obtain a
hard material, the content is made 0.05 to 0.2 wt %.
[0160] Si: Si has to be contained in an amount of 0.05 wt % for
deoxidation. Further, it works effectively for oxidation
resistance, but is a powerful ferrite forming element. If over 3.6
wt %, the workability is impaired, while simultaneously the
descaling at the time of hot rolling becomes difficult, so the
upper limit is made 3.6 wt %.
[0161] Mn: Mn is effective as an element stabilizing austenite and
simultaneously fixes S to improve the hot workability. However, if
the content is less than 0.05 wt %, the effect is small, while if
over 1.0 wt %, the material becomes hard, so to obtain a soft
material, the content is made 0.05 to 1.0 wt %, while to obtain a
hard material, the content is made 1.0 to 5.0 wt.
[0162] Cr: Cr is a basic ingredient of stainless steel. To obtain
excellent corrosion resistance, a minimum of 15 wt % is required.
On the other hand, if over 26 wt %, the steel becomes brittle and
the workability deteriorates, so the upper limit is made 26 wt %.
The preferable range is 17 to 19 wt %.
[0163] Ni: Ni is one of the basic ingredients of austenite
stainless steel. It is an element effective for workability and
corrosion resistance and is added in an amount of 5 wt % or more.
However, even if added in an amount exceeding 25 wt %, these
effects become saturated, so 5 to 25 wt % in range is
preferable.
[0164] Mo: Mo is an element improving the corrosion resistance and
is added in accordance with need. However, if the content is over
2.5 wt %, the steel hardens, while if over 5.0 wt %, the steel
becomes brittle, so to obtain a soft material, the upper limit is
made 2.5 wt %, while to obtain a hard material, the upper limit is
made 5.0 wt %.
[0165] Cu: Cu is an element stabilizing austenite and improving the
workability and corrosion resistance and is added in accordance
with need. However, even if the content is added in an amount over
2.5 wt % with a soft material or over 4.0 wt % with a hard
material, the effect becomes saturated, so to obtain a soft
material, the upper limit is made 2.5 wt % and to obtain a hard
material, the upper limit is made 4.0 wt %.
[0166] N: N is an element strongly stabilizing austenite and
simultaneously improving the corrosion resistance and is added in
an amount of at least 0.005 wt %. With a soft material, if
contained in an amount over 0.06 wt %, the workability of the foil
material after bright annealing (high precision cutting or punching
and pressing) deteriorates and fractures or cracks easily occur. On
the other hand, with a hard material, with a content of 0.06 wt %
or less, a sufficient strength is difficult to obtain, while if
contained over 0.4 wt %, the workability of the foil material (high
precision cuttability or punch pressability) deteriorates and
fractures or cracks easily occur. From the above, to obtain a soft
material, the content is 0.06 wt % or less, more preferably 0.007
to 0.03 wt % in range, while to obtain a hard material, the content
is over 0.06 wt % to 0.4 wt %.
[0167] Further, the stainless steel may also contain fine amounts
of additional elements of Ti, Ca, etc.
[0168] Further, the stainless steel may contain the above
ingredients (including the above additional trace elements) in the
above ranges (the amounts of the additional trace elements may be
the suitable amounts in accordance with the purpose of use
(normally Ti: 0.2 wt % or less, Ca: 0.0050 wt % or less), but the
invention is not in particular limited to these) and a balance of
Fe and unavoidable impurities. As unavoidable impurity elements, P,
S, Al, O, etc. may be mentioned. The amounts of the unavoidable
impurities are usually P: 0.045 wt % or less, Al: 0.05 wt % or
less, S: 0.030 wt % or less, O: 0.01 wt % or less.
[0169] Further, in the metal foil tube of the present invention, at
least one of the outside surface and inside surface of the foil
tube joined by resistance welding of the metal foil and shaped is
hardened by a hard plating layer. Below, a metal foil tube
comprised of the foil tube of the present invention with an outside
surface and inside surface hardened by a hard plating layer will be
explained in detail.
[0170] The fixing roll of a printer sometimes is contaminated by
foreign matter carried in along with the paper. Sometimes the roll
becomes flawed as a result. This sometimes has a detrimental effect
on the printing. Therefore, the surface hardness of the roll is
preferably a Vicker's hardness of 400 or more. When not working the
tube much after welding, this is achieved by hard plating the
inside surface and outside surface of the metal foil tube. As the
metal for plating, one mainly comprised of chromium, nickel,
cobalt, palladium, or another metal is possible. To harden these,
it is effective to add some P or other additive. In the case of
plating by an Ni--P-based alloy, a concentration of P of a weight
ratio of 1 to 14% is preferable. The reason is that if less than
1%, the hardening effect is small, while if over 14%, the plating
layer is brittle and cracks easily occur. The plating method may be
electroless plating or electroplating, but to plate the inside
(inner surface) of the foil tube, electroless plating is more
convenient. The present invention is not limited in any way to the
case of providing a hard plating layer on both the outside surface
and inside surface of such a foil tube. It is also possible to
provide just one with a hard plating layer. That is, when used for
a toner roll, development roll, fixing roll, etc., it is effective
to harden the surface (outside surface) of the foil tube contacting
the photosensitive drum or other roll or paper etc. On the other
hand, sometimes a heater is provided in the roll, so in this case,
it is effective to harden the inside surface of the foil tube in
advance. In this way, in accordance with the application of the
metal foil tube, it is sufficient to provide a hard plating layer
at the inside and/or outside surface of the foil tube.
[0171] Further, the metal foil tube of the present invention is
obtained by heat treating a foil tube comprised of a stainless
steel foil joined by resistance welding etc. or further shaped at a
temperature of 800 to 1100.degree. C.
[0172] When seam welding stainless steel, since the surface passive
film of the stainless steel is strong, in order to completely break
this and obtain a strong metal bond along the entire length of the
weld line, welding within considerably narrow range of welding
conditions obtained by detailed study on the current, voltage
welding speed, conduction ratio etc. is required. In particular, in
the case of mash seam welding for completely crushing two
superposed layers of foil to reduce them to a thickness of a single
layer, the current-carrying density to the part where the end faces
of the foil are buried, that is, the part where the crimping
crushes the end faces of the superposed two sections of the foil to
make them substantially integral, is low. Therefore, the bonding
strength at this part is insufficient, and if repeatedly worked,
sometimes the part will open up along the joint line. To solve this
problem, the inventors discovered that two methods were
effective.
[0173] One is to heat treat the foil tube comprised of stainless
steel foil joined by resistance welding or further shaped so as to
diffusion bond the joint line to increase the joint strength. In
this case, the heat treatment may be vacuum heat treatment or heat
treatment in an inert atmosphere. The heat treatment temperature is
suitably 800 to 1100.degree. C. When the stainless steel is
ferritic or martensitic, a slightly lower temperature is also
possible, while when it is austenitic, a slightly higher
temperature is necessary. However, if less than 800.degree. C., the
diffusion bonding is insufficient. Further if over 1100.degree. C.,
there is large deformation during heat treatment and the crystal
grains also become coarser, so this is not preferable. Further, due
to the heat treatment, there is the effect that the thermal stress
around the weld zone is released and the stiffness often seen
around the weld zone is eliminated. Further, if hard plating after
the heat treatment, the small uneven parts of the weld zone are
also concealed and the position of the weld zone can no longer even
be discerned. Therefore, in the metal foil tube of the present
invention, it is preferable to heat treat a foil tube comprised of
stainless steel foil joined by resistance welding etc. or shaped at
a temperature of 800 to 1100.degree. C., then hard plate at least
one of the inside and outside surfaces of the foil tube. The hard
plating was explained above, so the explanation will be omitted
here.
[0174] The second method is to plate the metal foil before welding
in advance with Au, Ag, Cu, Ni, or another Group X to XI element or
an alloy containing the same (for example, an Ni--P-based alloy
etc.) or Al or another metal with a melting point of 1200.degree.
C. or less and resistance weld this to obtain a metal foil tube.
With this method, even without the joint line part reaching the
melting point of the stainless steel or other metal foil, so long
as the temperature is higher than the melting point of the plating
layer, the plating layer will melt and the majority will be pushed
outside of the joint zone along the joint line along with the
passive film at the surface of the stainless steel or other metal
foil. Therefore, a complete metal bond is obtained along the weld
line. Further, the part of the foil where the end faces are buried
sometimes has small grooves, but this is also buried by the plated
molten metal, so there is the advantage that no notches occur at
the joint zone. Therefore, in the metal foil tube of the present
invention, it is preferable to plate the vicinity of the joint zone
of at least one surface of the metal foil with Au, Ag, Cu, Ni, or
another Group X to XI element or alloy containing one or more of
these elements (for example an Ni--P-based alloy etc.) or Al or
other metal (including alloy) with a melting point lower than the
melting point of the metal foil, preferably a metal (including
alloy) with a melting point of 1200.degree. C. or less, then
resistance weld the foil.
[0175] Further, in the metal foil tube of the present invention,
the ratio of the inside diameter of the tube to the thickness of
the tube (thickness/inside diameter ratio) is 1/300 or less,
preferably 1/500 or less. Note that the thickness and the inside
diameter of the tube spoken of here are in the allowable range, so
the average of a plurality of locations (for example 5 to 10
locations or so) is used.
[0176] Further, the inside diameter of the metal foil tube is not
particularly limited and may be suitably determined in accordance
with the application, but for example for a toner roll or
development roll of an electronic photo printer, laser beam printer
(LBP), copier, facsimile, or other image forming device, due to the
strong demands for smaller size and lighter weight, a length able
to match the currently used lengths of 50 mm or less is sufficient.
In particular, in the later explained method of production and
production apparatus of the present invention, it is possible to
sufficiently meet this demand for smaller size. Even when the
reduction of size results in a larger curvature of the tube and
workability is required when shaping the tube, by using an annealed
material of an austenitic stainless steel among the above stainless
steel foils, it is possible to sufficiently handle small diameters
of inside diameters of 10 to 15 mm.
[0177] Similarly, the length of the metal foil tube is not
particularly limited and may be suitably determined in accordance
with the application, but for example for a toner roll or
development roll of an electronic photo printer, laser beam printer
(LBP), copier, facsimile, or other image forming device, due to the
strong demands for smaller size and lighter weight, a length able
to match the currently used lengths of 500 mm or less is
sufficient. In particular, in the later explained method of
production and production apparatus of the present invention, it is
possible to sufficiently meet this demand for smaller size. As the
size becomes smaller, the contribution of the allowable error to
the precision increases, but in the present invention, by using an
annealed material of the austenitic stainless steel, strain does
not easily arise when cutting out (punching) the foil to
predetermined dimensions, so it is possible to obtain extremely
high dimensional precision in punching and possible to sufficiently
handle short tubes.
[0178] Further, the metal foil tube of the present invention
preferably has a durability of 1.times.10.sup.6 cycles or more,
more preferably 2.times.10.sup.6 cycles or more, in a fatigue test
giving 0.2% or less strain by a repeated cycle of 60 cycles/min or
more. In the present invention, when utilized for a toner roll or
development roll etc. for the following electronic photo printer,
laser beam printer (LBP), copier, facsimile, or other image forming
device, the fatigue test described above is generally used as the
fatigue test. If the durability in this case is about 1 or 2
million cycles, it is possible to obtain an extremely high
durability sufficiently higher than the durability of the current
used parts. When the results of the fatigue test of the metal foil
tube is less than 1 to 2 million cycles, it is not possible to
strikingly improve the durability of the thin metal tube. Regarding
the "durability" referred to here, when there are no cracks or
fractures or other abnormalities in surface properties and further
no joint separation or other abnormalities can be recognized in the
joint zone, the state is deemed good and it is deemed that there is
durability, while conversely when abnormalities are recognized, it
is deemed that there is no durability. However, in the present
invention, depending on the application, a result of the fatigue
test of the metal foil tube of 500,000 cycles or more is sufficient
for use.
[0179] Further, the applications of the metal foil tube of the
present invention are not particularly limited, but for example it
may be used for a toner roll or development roll etc. of an
electronic photo printer, laser beam printer (LBP), copier,
facsimile, or other image forming device, but the invention is not
limited to these.
[0180] Metal Foil Tube Production Apparatus
[0181] Next, the production apparatus of the metal foil tube of the
present embodiment will be explained. FIG. 1(A) is a plan view of a
metal foil sheet for forming a metal foil tube, FIG. 1(B) is a
sectional view of a metal foil tube before welding, FIG. 1(C) is a
perspective view of a metal foil tube obtained by welding so that
the joint zone becomes straight, and FIG. 1(D) is a perspective
view of a metal foil tube obtained by welding so that the joint
zone becomes spiral. FIG. 2 is a schematic side view of a metal
foil tube production apparatus according to an embodiment of the
present invention, FIG. 3 is a plan view of FIG. 2, and FIG. 4 is a
sectional view along line 4-4 of FIG. 3.
[0182] The metal foil sheet W used in the present embodiment, as
shown in FIG. 1(A) and FIG. 1(B), is rectangular in overall shape,
for example, has a length S.sub.1 of 1 m and a width S.sub.2 of 100
mm or so, while the thickness t is an extremely thin one of 10 to
100 .mu.m. In the present embodiment, this metal foil sheet W is
rounded to a circle in cross-section, the facing side ends are
overlapped, and the overlap part G is welded to form a metal foil
tube P. This metal foil tube P can be used, for example, for a
fixing roll of a copier or other devices.
[0183] The metal foil tube production apparatus according to the
present embodiment, roughly speaking, has a shaping unit 10 and
welding unit 30. The shaping unit 10 does not round the rectangular
metal foil sheet W all at once into a tube, but uses a shaping
device 15 serving as an external die around the core rod 13 serving
as an internal die to press it in stages and form it into a tube,
while the welding unit 30 welds the overlapped part G of the facing
side ends of the metal foil sheet W.
[0184] First, the shaping unit 10 will be explained. In FIGS. 2 and
3, the shaping unit 10 has a cylindrical core rod 13 supported in a
cantilever fashion at a support part 12 projected on a base 11, a
shaping device 15 positioned under the core rod 13, holding the
metal foil sheet W, and wrapping it around the circumference of the
core rod 13, and a positioning member 16 for positioning the metal
foil sheet W with respect to the core rod 13.
[0185] The core rod 13 is somewhat longer than the length direction
length S.sub.1 of the metal foil sheet W and has a thickness of
about one turn of the length S.sub.2 in the width direction of the
metal foil sheet W. This core rod 13 will be explained in detail
later.
[0186] The shaping device 15, as shown in FIG. 4, has a positioning
member 16, holding plate 17, first pressing member 18, and second
pressing member 19. The positioning member 16 is a member
positioned at the approximate center of W and the center of the
bottom surface of the core rod 13. The holding plate 17 is
positioned below the core rod 13 and is connected with the cylinder
C.sub.1 provided on the base 11 so as to approach or move away from
the core rod 13 while maintaining a parallel state with it at all
times. This holding plate 17 has a flat top surface and is formed
at its center with a semicircular cross-section recess 20 of an
extent enabling the core rod 13 to be fit in it. The mating of this
recess 20 and core rod 13 enables deformation of the metal foil
sheet W and its being wrapped in a U-shape at the bottom part of
the core rod 13.
[0187] The first pressing member 18 presses a side of U-shaped
deformed metal foil sheet W rising up from the side faces of the
core rod 13 against the circumference of the core rod 13 for close
contact. This first pressing member 18, as shown in FIG. 4, is
positioned at the left of the core rod 13 on the holding plate 17
and is designed to be moved by the cylinder C.sub.2 to approach or
move away from the rod in a direction perpendicular to the axis of
the core rod 13.
[0188] The second pressing member 19 is also configured in the same
way as the first pressing member 18, is provided at position
symmetric with the first pressing member 18 across the core rod 13,
is moved by the cylinder C.sub.3 to approach and move away from the
core rod 13, and presses the other side of the U-shaped metal foil
sheet W toward the circumference of the core rod 13.
[0189] These positioning member 16, holding plate 17, first
pressing member 18, and second pressing member 19 operate together
to wrap the metal foil sheet W around the circumference of the core
rod 13 and form an overlap part G comprised of the superposed
facing side ends of the metal foil sheet W, that is, the two ends
in the width direction, on the top surface of the core rod 13.
[0190] Note that the metal foil sheet W is loaded onto the holding
plate 17 of the shaping device 15 for example by a suitable
conveyance means such as a vacuum suction means (not shown).
[0191] The positioning member 16 is a rod 21 passing through a
through hole 21 formed in a semicircular cross-section recess 20
formed at the center of the shaping device 15 and is positioned
below the core rod 13 at the base end, center, and front end in the
axial direction. It is provided so as to approach and move way from
the bottom surface of the core rod 13 by the cylinder C.sub.4.
[0192] The positioning member 16 abuts against the bottom surface
of the core rod 13 at the time of approach and presses against the
metal foil sheet W so as to hold the metal foil sheet W at a fixed
position. The timing when the positioning member 16 is actuated is
the time when the metal foil sheet W placed on the top surface of
the holding plate 17 is pushed up by upward movement of the holding
plate 17 and comes into line contact with the core rod 13.
[0193] However, even if using the positioning member 16 for
positioning, an overlap part G of a uniform width from the bottom
end to front end of the core rod 13 is not necessarily formed.
Therefore, in the shaping unit 10 of the present embodiment, an
overlap adjusting means 22 for adjusting the overlap x of the
overlap part G (see FIG. 1B) is provided (see FIG. 5). Here, FIG. 5
is an enlarged sectional view of principal parts of FIG. 4.
[0194] The overlap adjusting means 22 makes part of the
circumference of the metal foil sheet W displace in the radial
direction so that the overlap x of the overlap part of the facing
sides becomes a predetermined value, for example, about 0.1 mm,
before the completion of the pressing action by the second pressing
member 19.
[0195] Explaining this more specifically, the overlap adjusting
means 22, as shown in FIG. 5, is provided inside the core rod 13
with offsetting devices (cams, rollers, etc.) 23 at least at the
base end and front end of the core rod 13, drives the offsetting
devices (cams, rollers, etc.) 23 by a drive device (motor etc.)
M.sub.1, and makes part of the circumference of the metal foil
sheet W displace in the radial direction.
[0196] The amount of rotation of the offsetting devices (cams,
rollers, etc.) 23 is controlled by a signal from the controller 24
so that the overlap x becomes a predetermined value. The controller
24 has a detection device for detecting the overlap x of the
overlap part G (CCD camera etc.) 25 and a processor 26 for
monitoring this, comparing it with the predetermined value, and
determining the control amount.
[0197] Note that the drive device (motor etc.) M.sub.1 may be
provided at the base end of the core rod 13 and make a plurality of
offsetting devices (cams, rollers, etc.) 23 provided at the base
end, center, and front end operate all together, but it is also
possible to make the offsetting devices (cams, rollers, etc.) 23
individually operate to adjust the overlap x.
[0198] However, the present invention is not limited to this. For
example, as another overlap adjusting means 22, as shown by the
dot-dash line in FIG. 5, it is also possible to provide the
offsetting devices (cams, rollers, etc.) 23 at the outside of the
core rod 13. Further, it is possible to provide them at the
circumference of the core rod 13 so as to form non-contact parts
where the metal foil sheet W does not closely contact the core rod
13 and press the sheet by a pressing member so as to make part of
the circumference of the metal foil sheet W displace in the radial
direction.
[0199] Further, as schematically shown in FIG. 6, it is also
possible to use a pressing member 28 provided at the outside of the
core rod 13 facing the recess 27 formed in the core rod 13 to press
the sheet so that part of the circumference of the metal foil sheet
W displaces in the radial direction as shown by the broken line in
the figure. The pressing member may be any of a cam, roll,
cylinder, or rod member.
[0200] Experiments revealed that the overlap (x) preferably
satisfies x.ltoreq.40+5 t (unit .mu.m) with respect to the
thickness (t).
[0201] Next, the welding unit 30 will be explained. The welding in
the present embodiment is a resistance welding method. Since an
extremely thin metal foil sheet W is welded, an easily controllable
welding method is necessary. In particular, among the resistance
welding methods, seam welding is preferable, more preferably mash
seam welding. If using this welding, the hardness difference
between the weld zone and the other parts becomes small, whereby
preferable results are obtained. Note that if using laser welding,
plasma welding, etc., the hardness difference becomes 30% or more.
It was learned that this was not practical.
[0202] FIG. 6 is an enlarged cross-sectional view showing the state
of welding of the present embodiment. The welding unit 30, as shown
in FIG. 6, is comprised of a conductive stationary electrode member
31 provided at the outside surface of the core rod 13 along the
axial direction and a conductive movable electrode member 32
provided facing the stationary electrode member 31 and grips the
overlap part G of the metal foil sheet W between the two electrode
members for welding.
[0203] The stationary electrode member 31 is a conductive member
provided in a groove 33 formed along the axial direction of the
outer surface of a core rod 13. On the other hand, the movable
electrode member 33 is a conductive electrode ring 32 which rotates
and moves while pressing against the overlap part G.
[0204] This stationary electrode member 31 is comprised of a copper
material provided in a groove 33 provided in the top part of the
core rod 13, but the electrode ring 32 performs welding while
rotating on this, so the top surface of the stationary electrode
member 31 is preferably formed flat overall. Therefore, as the
stationary electrode member 31, for example, flat copper wire is
used. However, there is no need for the top surface as a whole to
be flat. Just part may also be flat. On the other hand, the
electrode ring 32 preferably also has a flat circumference if the
top surface of the stationary electrode member 31 is flat, but if
the top surface of the stationary electrode member 31 is arc
shaped, the circumference is preferably made recessed at the
center, that is, hourglass shaped. The radius of curvature in this
case is preferably larger than the radius of curvature of the
arc-shaped surface of the stationary electrode member 31.
[0205] The electrode ring 32, as shown in FIG. 4, is connected
through a conductive flanged-shaped rotational member 34 to the
power supply member 35, but the power supply member 35 is supported
by a non-conductive bracket 36. This bracket 36 is connected to be
able to be elevated and lowered by the cylinder C.sub.5. The
cylinder C.sub.5 is attached to a moving block 37, but this moving
block 37 is supported slidably by a pair of guide rods 38 (see FIG.
3) and designed to move along the axis of the core rod 13 by a
screw shaft 39 provided passing through the center. The screw shaft
39 is supported by bearings 42 provided on the support tables 40
and 41 and rotated by a drive device (motor etc.) M.sub.2 connected
through a coupling 43. That is, the electrode ring 32 is designed
to be raised and lowered and moved by the cylinder C.sub.5 and
moved from the base end to the front end of the core rod 13 by the
screw shaft 39 and drive device (motor etc.) M.sub.2.
[0206] The hardness of the electrode members 31 and 32 is
preferably made substantially the same as the hardness of the metal
foil sheet W so as to prevent uneven contact or uneven wear and to
enable reliable welding over a long period. The fact that if the
Vicker's hardness HV is 180 or less, there is little electrode
damage was found by experiments. To raise the high temperature
strength or creep strength, the stationary electrode member 31 and
movable electrode member 33 may be comprised at least in part by
molybdenum or alumina-dispersed copper alloy.
[0207] In the present embodiment, since the overlap part G of the
small overlap x of 0.1 mm of the extremely thin 10 to 100 .mu.m
metal foil sheet W is welded, the current value and feed rate
become issues, but experiments showed that a current value of 700
to 1500 amperes or so, a voltage of 0.5 to 2.0V, and a feed rate of
0.3 to 1.5 m/min or so gave the best results.
[0208] However, if passing a current, the welding unit 30 is
heated. If performing welding work over a long period of time, the
heat causes the thin metal foil sheet W to deform and is liable to
make good welding impossible. Further, since the metal foil sheet
is wrapped around the circumference of a relatively long core rod
13 to form the metal foil tube P, separation and removal of this
metal foil tube P also become an issue.
[0209] Here, in the present embodiment, as a means for solving all
at once the problem of cooling (surface deformation) and the
problem of removal, the core rod 13 itself is modified in various
ways.
[0210] First, the core rod 13 functions as a die material for
shaping the metal foil sheet W into a circular cross-section, so
overall has a circular cross-section, but as shown in FIG. 6, the
center part is provided with a core 13a comprised of ordinary
mechanical structural use carbon steel having a Y-shaped
cross-section. This core 13a has an electrode support 13b made of
chromium steel superior in strength attached on it to hold the
stationary electrode member 31, while the side part of the core 13a
is provided with a side plate 13c for finishing the entire part to
a circular cross-section.
[0211] By doing this, even if the stationary electrode member 31
becomes worn, it is easily replaced. Shaping is also easy when
shaping the whole into a circular cross-section.
[0212] Further, the core rod 13 is formed inside it, as shown in
FIGS. 6 and 7, with a fluid passage 45. The fluid passage 40 is
comprised of a center passage 45a formed in the center part along
the axis of the core rod 13 and branch passages 45b formed in the
radial direction from the center passage 40a. Note that FIG. 7 is a
schematic sectional view along the axis of the core rod.
[0213] The fluid passage 45 is filled with air from a pipe 47
connected to one end of the core rod 13 through a rotary joint 46
(see FIG. 2). This air cools the core rod 13. Along with this, air
is ejected from the branch passages 45b. Due to this, the metal
foil tube P is lifted from the surface of the core rod 13 and made
easy to detach.
[0214] If using air, there are the effects that the work efficiency
is good and the work environment becomes clean, but the invention
is not limited to this. Another fluid, for example, water, a
cutting oil, etc. may also be used.
[0215] Further, to facilitate the detachment of the metal foil tube
P from the core rod 13, the core rod 13 may be provided at its
circumference with grooves R formed so as to extend in the axial
direction (see FIG. 6). Due to this, the contact area between the
metal foil sheet W and core rod 13 is reduced and the handling of
the metal foil tube P becomes much easier.
[0216] Regarding the handling, the core rod 13 itself may also be
comprised of a plurality of members which may be disassembled after
formation of the metal foil tube P. FIG. 8 is a schematic sectional
view showing another example of a core rod. For example, as shown
in FIG. 8, the core rod 13 is split at the taper surface 50
intersecting the axis into the two core rod members 13d and 13e.
After shaping the metal foil tube, it is possible to slide one core
rod member 13e in the axial direction with respect to the other
core rod member 13d to separate the metal foil tube P from the core
rod 13. However, when using this split core rod 13 for detachment,
the core rod 13 is preferably supported at its two ends with one
being designed to be able to move in the axial direction.
[0217] The metal foil tube obtained by the embodiment, as shown in
FIG. 1(C), can give a metal foil tube having a joint zone with an
overlap part G welded in a straight line. However, the present
invention is not limited to these. For example, as shown in FIG.
1(D), it is possible to obtain a metal foil tube having a joint
zone with an overlap part G' welded in a spiral. In this case, for
example, a suitable thickness of metal foil is slit to a suitable
width which is then wound around a copper alloy electrode rod in a
spiral. At this time, the overlap x between the parts of the foil
is adjusted by the detector to about 0.1 mm. Further, it is
possible to rotate the electrode rod and make it slide to the left
and right and roll over the overlap part by another copper alloy or
other rolling electrode roller and pass current with the electrode
rod for electrical resistance welding (preferably seam welding,
more preferably mash seam welding). After this, it is possible to
cut this tube to a suitable length and, in accordance with need,
polish the inside and outside surfaces near the joint zone to
obtain the desired metal foil tube.
[0218] Further, the ratio of the inside diameter of the metal foil
tube with respect to the thickness of the metal foil sheet is 1/300
or less, preferably 1/500 or less. Note that the thickness of the
metal foil sheet and inside diameter of the metal foil tube spoken
of here are in the allowable range of error, so the average value
of a plurality of locations (for example, 5 to 10 locations or so)
is used.
[0219] Note that when passing current to the electrode rod for seam
welding, the weld zone can be stably increased in strength by the
presence of the continuous nuggets (molten and solidified parts)
along the weld line or the discontinuous nuggests along 50% or more
of the weld line. That is, in seam welding, once nuggets are
formed, even if the electrode wheel (see reference notation 32 in
FIG. 6) proceeds to turn, most of the current flows to the nugget
parts with the small electrical resistance (invalid current). Since
the interface to be newly joined has a large electrical resistance,
only a small amount of current flows to it. Therefore, this part
does not reach the welding temperature and is crimped. Once such a
crimped part is formed, since this part also becomes small in
electrical resistance, like with the nuggets, the formation of
nuggets ahead of it is,inhibited. To avoid this vicious cycle, the
inventors used a pulse power source for seam welding, provided a
short conduction time followed by a relatively long non-conduction
time, and repeated this cycle and thereby succeeded in obtain
continuous nuggets. The optimum ratio of the conduction time and
non-conduction time at this time is 1/12 to 1/8. If less than 1/12
or over 1/8 to 1/6, discontinuous nuggets are formed. Further,
experiments of the inventors revealed that even with discontinuous
nuggets, if the weld line is covered 50% or more by the nuggets,
there is no problem strengthwise, so it is preferable to use a
pulse power source and set the ratio of the conduction time and
non-conduction time to 1/15 to 1/7 for seam welding. Due to this,
it is possible to obtain nuggets covering 50% or more of the weld
length.
[0220] Similarly, they discovered that even if using a pulse power
source for mash seam welding, there is an optimal ratio of the
conduction time and non-conduction time for stably increasing the
strength of the weld zone. That is, in mash seam welding, it is
preferable to use a pulse power source and set the ratio of the
conduction time and non-conduction time to 1/3 to 1/1 for
welding.
[0221] Method of Production of Metal Foil Tube
[0222] The action of the apparatus for production of a metal foil
tube configured in this way and the method of production of the
metal foil tube will be explained next.
[0223] Shaping Step
[0224] A 10 to 100 .mu.m thick metal foil sheet W is placed by a
vacuum suction means or other conveying means on the holding plate
17 of the shaping device 15. The metal foil sheet W is held by a
not shown guide member and set so that its center line matches the
center axis of the core rod 13 and the center axis of the recess 20
formed in the holding plate 17.
[0225] From this state, the holding plate 17 starts to rise by the
cylinder C.sub.1, but the holding plate 17 holds a position
parallel with the core rod 13 at all times. Therefore, when the
metal foil sheet W contacts the core rod 13, the metal foil sheet W
becomes substantially the same width centered about the core rod
13. When the metal foil sheet W contacts the core rod 13, the
positioning member 16 operates.
[0226] The positioning member 16 is operated by the cylinder
C.sub.4, abuts against the center of the core rod 13 from the
bottom, and grips the metal foil sheet W between the core rod 13
and the front end of the rod. This gripping action is performed by
the base end, center, and front end of the core rod 13, so the
metal foil sheet W contacts the core rod 13 along its entire
length. Due to this, the metal foil sheet W is positioned at the
substantial center in the width direction.
[0227] After this positioning, if the cylinder C.sub.1 is further
operated, the holding plate 17 rises and the core rod 13 starts to
enter the recess 20 of the holding plate 17. As a result, the metal
foil sheet W is gradually deformed to a U-shape. Further, when the
core rod 13 enters the recess 20, the metal foil sheet W is wrapped
at the circumference of the bottom half of the core rod 13 and
deformed to a pair of sides rising up from the sides.
[0228] The first pressing member 18 is made to project out toward
one side by the operation of the cylinder C.sub.3. This projection
action is performed by the arc-shaped part 18a of the front end
contacting the circumference of the core rod 13. This arc shaped
part 18a presses one side of the metal foil sheet W against the
circumference of the core rod 13 for contact.
[0229] Next, the second pressing member 19 is similarly operated by
the cylinder C.sub.3 and presses the other side of the metal foil
sheet W until the arc-shaped part 19a of the front end contacts the
circumference of the core rod 13, but this pressing action stops
right before the final stage and therefore the metal foil sheet W
is not completely in contact with the core rod 13.
[0230] That is, the metal foil sheet W is wrapped around the core
rod 13 and the facing side ends of are superposed at the top of the
core rod 13 to form an overlap part G. The other side is however
not completely fixed in position and is made displaceable in
state.
[0231] This displaceable state is used to adjust the overlap x of
the overlap part G. This adjustment is performed by a detector (CCD
camera etc.) 25 of the controller 24 detecting the amount of
overlap x, the processor 26 comparing this with a predetermined
value, judging whether it is normal, and, when not normal, driving
the drive device (motor etc.) M.sub.1 to make the offsetting
devices (cams, rollers, etc.) 23 rotate and make the metal foil
sheet W displace to the radial direction.
[0232] When the overlap (x) at the overlap part G satisfies
x.ltoreq.40+5 t (unit: .mu.m) with respect to the thickness (t),
the adjustment of the overlap x ends. In this state, the second
pressing member 19 operates by the cylinder C.sub.3 and completely
presses the other side of the metal foil sheet W into contact with
the core rod 13. Due to this, the metal foil sheet W is held fixed
in position on the core rod 13.
[0233] Welding Step
[0234] When the metal foil sheet W finishes being held, the overlap
part G is positioned between the front end of the first pressing
member 18 and the front end of the second pressing member 19 and
directly above the stationary electrode member 31, and the
electrode ring 32 can be raised and lowered between the first
pressing member 18 and second pressing member 19, so welding can be
started.
[0235] At the time of start of the welding, if positioning the
electrode ring 32 at the base end of the core rod 13 and welding
the entirety, good precision welding becomes possible.
[0236] The welding is first performed after actuation of the
cylinder C.sub.5. When the cylinder C.sub.5 is actuated, the piston
rod descends and the electrode ring 32 descends through the bracket
36, power supply member 35, and flange-like rotational member 34.
The electrode ring 32 enters the space between the front end of the
first pressing member 18 and the front end of the second pressing
member 19 and grips the overlap part G with the stationary
electrode member 31.
[0237] If running current through the stationary electrode member
31 and electrode ring 32 along with this gripping action, the
overlap part G is welded together, simultaneously the drive device
(motor etc.) M.sub.2 also operates, the screw shaft 39 rotates, and
the moving block 37 starts to move. Due to this, the electrode ring
32 moves over the overlap part G by 0.3 to 1.5 m/min or so and
welds up to the end of the metal foil sheet W.
[0238] Further, in some cases, it is possible to position the
electrode ring 32 at the front end of the core rod 13 and pull out
the metal foil tube P while welding. If doing this, fast, good work
efficiency welding becomes possible.
[0239] Finishing Step
[0240] When the welding is completed, the welded part is finished
smooth. This finishing is performed by polishing or lapping by a
grindstone, crushing by roller burnishing, etc. until the surface
of the metal foil tube P becomes a smooth surface, but known art is
used, so explanations will be omitted.
[0241] Further, the metal foil tube P is detached from the core rod
13. This detachment action comprises supplying air from the end of
the core rod 13 to the fluid passage 45 and ejecting air from the
center passage 45a along the axis of the core rod 13 through the
branch passages 45b toward the radial direction so as to separate
the metal foil tube P from the core rod 13. If even a small amount
of air flows between the core rod 13 and the metal foil tube P, the
metal foil tube P can be easily detached from the core rod 13. Note
that after detachment, the tube may also be finished.
[0242] In the above embodiment, the movable electrode member runs
on the stationary electrode member or the metal foil tube P is made
to move over it, but the present invention is not limited to this.
The two electrode members may also be moved relative to each other
or the two electrode members and the metal foil tube P may also be
moved relative to each other.
[0243] The welded metal foil tube obtained by the above welding
method may be used as is as the welded metal foil tube of the
present invention for a broad range of applications, but, further,
in accordance with need, it is also possible to insert a metal core
into the welded metal foil tube obtained by the welding method and
cold work it by sedging, split roller rolling, drawing, spinning,
or a combination of these methods to reduce the thickness, smooth
the weld zone to even out the shape and surface roughness of the
weld zone, and work harden the material.
[0244] The weld zone of the metal foil tube may be worked by the
above-mentioned sedging, split roller rolling, drawing, spinning,
or a combination of these methods. These sedging, split roller
rolling, drawing, and spinning are known cold working technologies,
so the explanations of these working methods will be omitted
here.
[0245] The present invention covers the weld zone of a welded metal
foil tube. Since handling is difficult in that state, it is
possible to insert a metal core into the metal foil tube in advance
to place it in a state enabling cold working (mainly plastic
working) and to work it in that state.
[0246] As the metal core, it is preferable to use one made of a
quenched material with a high hardness such as for example S45C and
an outside diameter matching the inside diameter of the welded
tube. When the working would change the inside diameter of the
tube, it is preferable to change the metal cores to ones with
outside diameters matching the same.
[0247] Further, with sedging, the metal core is inserted into the
welded tube, then three or four tools arranged at the outside of
the tube are used to strike the surface of the tube and reduce the
tube thickness.
[0248] Further, with split roller rolling, the metal core is
inserted into the welded tube, then a plurality of small diameter
rollers arranged at the outside of the tube are pressed by separate
fixtures or a backup roll and the tube and plurality of small
diameter rollers are made to rotate relative to each other to
reduce the thickness of the tube.
[0249] Further, drawing is a method of passing a somewhat thick
material (here the welded foil tube with the metal core inserted in
it) through a conical hole (die). If using a suitable lubricant, it
is possible to reduce the thickness without changing the diameter
of the tube.
[0250] Further, with spinning, the welded foil tube with the metal
core inserted in it is rotated and one or more flat tools are
pressed against the outside surface of the tube to reduce its
thickness.
[0251] In these cold working, when the tube is brought close to the
finished dimensions, it is possible to switch to sufficiently small
work tools or rollers with sufficiently small surface roughnesses
so as to shape the weld zone to an uneven thickness and smoothness.
In the metal foil tube of the present invention, it is preferable
to cold work it to thin it until a surface roughness Rz defined by
JIS B0601-2001 (maximum height roughness) of 2.0 .mu.m or less,
preferably 0.1 to 1 .mu.m and smoothly even out the weld zone.
[0252] Further, the tube is preferably cold worked to thin it and
work harden the material so as to make the Vicker's hardness (Hv)
of the material 300 to 600, preferably 400 to 600, more preferably
450 to 550. Due to this, as explained above, it is possible to
provide a welded metal foil tube excellent in durability and wear
resistance, increased in high-cycle fatigue life, and having
effective hardness. Note that, the "Vicker's hardness" of the
material referred to here includes the hardness of both the matrix
part and weld zone of the metal foil tube.
[0253] Further, in the method of production of the metal foil tube
of the present invention, when seam welding the stainless steel,
since the surface passive film of the stainless steel is strong, in
order to completely break this and obtain a strong metal bond along
the entire length of the weld line, welding within considerably
narrow range of welding conditions obtained by detailed study on
the current, voltage welding speed, conduction ratio etc. is
required. In particular, in the case of mash seam welding for
completely crushing two superposed layers of foil to reduce them to
a thickness of a single layer, the current-carrying density to the
part where the end faces of the foil are buried, that is, the part
where the crimping crushes the end faces of the superposed two
sections of the foil to make them substantially integral, is low.
Therefore, the joint strength at this part is insufficient, and if
repeatedly worked, sometimes the part will open up along the joint
line. To solve this problem, the inventors discovered that two
methods were effective. The first method is to heat treat the foil
tube comprised of stainless steel foil joined by resistance welding
etc. or further shaped for diffusion bonding and increasing the
strength. In this case, the heat treatment is conducted by vacuum
heat treatment or in an inert atmosphere. The heat treatment
temperature is suitably 800 to 1100.degree. C. When the stainless
steel foil is ferritic or martensitic, a slightly lower temperature
may be used, while when austenitic, a slightly high temperature is
necessary. However, if less than 800.degree. C., the diffusion
bonding is insufficient, while if over 1100.degree. C., there is
large deformation during the heat treatment and the crystal grains
become coarse, so this is not preferred. Further, due to the heat
treatment, there is the effect that the thermal stress around the
weld zone is released and the stiffness often seen around the weld
zone is eliminated. Further, if hard plating after the heat
treatment, the small uneven parts of the weld zone are also
concealed and the position of the weld zone can no longer even be
discerned. As the metal for hard plating, one mainly comprised of
chromium, nickel, cobalt, palladium, or another metal may be used.
To cause these to harden, it is effective to add slight amounts of
P or other additives. In the case of plating by a Ni--P-based
alloy, the concentration of P is preferably 1 to 14%. The reason is
that if less than 1%, there is little effect of hardening, while if
over 14%, the plating layer becomes brittle and easily cracks. As
the plating method, electroless plating or electroplating is
possible, but electroless plating is convenient for plating the
inside of the tube.
[0254] The second method is to plate the metal foil before welding
in advance with Au, Ag, Cu, Ni, or another Group X to XI element or
alloy containing such an element (for example, Ni--P-based alloys
etc.) or Al or another metal (including alloy) with a melting point
lower than the melting point of the metal foil, preferably a metal
(including alloy) with a melting point of 1200.degree. C. or less,
and to resistance weld this to obtain a metal foil tube. With this
method, even without the joint line part reaching the melting point
of the stainless steel or other metal foil, so long as the
temperature is higher than the melting point of the plating layer,
the plating layer will melt and the majority will be pushed outside
of the joint zone along the joint line along with the passive film
at the surface of the stainless steel or other metal foil.
Therefore, a complete metal bond is obtained along the weld line.
Further, the part of the foil where the end faces are buried
sometimes has small grooves, but this is also buried by the plated
molten metal, so there is the advantage that no notches occur at
the joint zone.
[0255] Further, in the method of production of the metal foil tube
of the present invention, due to the welding of the metal foil
tube, the weld zone preferably has continuous nuggets (melted and
solidified parts) along the weld line or discontinuous nuggets
along 50% or more of the weld line. This is because if the seam
welded or other weld zone has continuous nuggets (melted and
solidified parts) along the weld line or discontinuous nuggets
along 50% or more of the weld line, it is possible to stably raise
the joint strength of the weld zone.
[0256] Further, in seam welding, once nuggets are produced, even if
the electrode wheel (see reference notation 32 in FIG. 6) proceeds
to turn, most of the current will flow to the small electrical
resistance nugget parts (invalid current). Since the interface to
be newly joined has a large electrical resistance, only a small
amount of current will flow to it. Therefore, this portion will not
reach the welding temperature and will be crimped. Once such a
crimped part is formed, since this part will also be small in
electrical resistance, like nuggets, formation of nuggets ahead of
it will be inhibited. To avoid this vicious cycle, the inventors
used a pulse power source for seam welding, provided a short
conduction time followed by a relatively long non-conduction time,
and repeated this cycle to thereby succeed in obtaining continuous
nuggets. The optimum ratio of the conduction time and
non-conduction time at this time is 1/12 to 1/8. If less than 1/12
or over 1/8 to 1/6, discontinuous nuggets are produced. Experiment
by the inventors revealed that even with discontinuous nugget, if
covering the weld line over 50% or more by nuggets, there is no
problem strengthwise. To obtain nuggets covering 50% or more of the
weld length, the ratio of the conduction time and non-conduction
time has to be set to 1/15 to 1/7. From the above, in the method of
production of the metal foil tube of the present invention, it is
preferable to use a pulse power source and set the ratio of the
conduction time and non-conduction time to 1/15 to 1/7 for seam
welding.
[0257] Further, the inventors discovered that even when using a
pulse power source for mash seam welding, there is an optimal ratio
of conduction time and non-conduction time for more stably raising
the strength of the weld zone. That is, in the method of production
of the metal foil tube of the present invention, it is preferable
to use a pulse power source and to set the ratio of the conduction
time and nonconduction time to 1/3 to 1/1 for the mash seam
welding.
EXAMPLES
[0258] The effects of the present invention will be explained using
the following examples and comparative examples. However, the
technical scope of the present invention is not limited to the
following examples. Note that the units of dimensions not
particularly indicated are "mm" units.
Example 1
[0259] Stainless steel foils made of SUS410L (11% Cr-0.02% C) were
rolled to thicknesses of 40 .mu.m while suitably controlling the
rolled surface roughnesses to give surface roughnesses Rz of 1.5
.mu.m and 0.8 .mu.m. The rolled materials were cut to 94.3
mmL.times.250 mmW. The foils having the two types of surface
roughnesses were wrapped around 30 mm.phi. copper alloy tools and
joined at the 100 .mu.m overlap parts by mash seam welding. At this
time, the vicinities of the joint zones of both tubes ((a) tube
having a surface roughness Rz of 1.5 .mu.m and (b) tube having a
surface roughness Rz of 0.8 .mu.m) were cut out, buried, and
polished. In both cases, it was confirmed that the hardness of the
matrix part was, in Hv, around 270, while the hardness of the joint
zone was, in Hv, around 230. The two polishing samples were etched
and examined for metal structure. As a result, in both cases, there
was no melted and solidified phase at the joint zone, the joint
surface was a solid phase in state, and a low carbon martensite
phase was seen here. Note that the thickness of the joint zone was
55 .mu.m in both cases. The two tubes (see FIG. 1(C)) were cut to
lengths of 50 mm, the inside and outside surfaces near the joint
zones were polished, and the thicknesses of the two joint zones
were made 42 .mu.m or so. In both cases, a hard sponge tube was
inserted. This was rotated while pressed against the surface of a
120 mm.phi..times.80 mmL steel roller to investigate the fatigue
life. The rotational speed of the tested tube at this time was 120
rpm. In the state most pressed against the steel roller, the tested
tube was crushed to about 4 mm. The strain applied to the surfaces
of the tested tubes at this time was 0.17%. As a result of the
test, both tubes (a) and (b) did not exhibited any abnormality in
the tested tube even after over 1 million cycles.
Example 2
[0260] Annealed foils having surface roughnesses Rz of 1.0 .mu.m
and 0.5 .mu.m, made of SUS316L (16% Cr-12% Ni-2% Mo), and having
thicknesses of 30 .mu.m were slit to 60 mm widths. These were
wrapped in spirals around the above 30 mm.phi. copper alloy
electrode rods. At this time as well, the foil with the surface
roughness Rz of 1.0 .mu.m and the foil with the surface roughness
Rz of 0.5 .mu.m were adjusted so that the overlap between sections
of the foil became 100 .mu.m. Further, it is possible to rotate the
electrode rod and make it slide to the left and right and to roll
over the overlap part by another copper alloy or other rolling
electrode roller and pass current with the electrode rod for mash
seam welding. The same procedure was followed as in Example 1 to
investigate the hardnesses of the vicinities of the joint zones of
the two tubes ((c) tube having a surface roughness Rz of 1.0 .mu.m
and (d) tube having a surface roughness Rz of 0.5 .mu.m). As a
result, in both tubes, the matrix part had a hardness Hv of around
200 and the joint zone a hardness of around 245. Further, the
inventors investigated the metal structures and confirmed that
there were no melted and solidified phases in both tubes. The two
tubes (see FIG. 1(D)) were cut to lengths of 50 mm, the inside and
outside parts near the joint zones were polished, and the same
procedure was used as in Example 1 for a fatigue test.
[0261] Note that the strain applied to the surface of the tested
tubes in the test was 0.13%. The result was that the two tubes (c)
and (d) withstood the fatigue test for 1 million cycles or
more.
Example 3
[0262] Completely annealed foils having surface roughnesses Rz of
0.3 .mu.m and 0.8 .mu.m, made of SUS304 (18% Cr-8% Ni), and having
thicknesses of 50 .mu.m were used by the same method as in Example
1 to prepare two types of foil tubes. Note that the stainless steel
foils were annealed in an Ar--H.sub.2 atmosphere. The nitrogen
concentrations of the surfaces were 1.2%. In both cases ((e) tube
having surface roughness Rz of 0.3 .mu.m and (f) tube having
surface roughness Rz of 0.8 .mu.m), the joint zones had thicknesses
of 75 .mu.m. The inside and outside surfaces were polished to 60
.mu.m. In this case, with both tubes, the hardness of the matrix
part was about, in terms of Hv, 178, while that of the joint zone
was, in Hv, around 220. The same procedure was followed as in
Example 1 for a fatigue test. The result was that both tubes (e)
and (f) withstood the fatigue test for 1 million cycles or
more.
Example 4
[0263] A completely annealed foil having a surface roughness Rz of
0.34 .mu.m, made of SUS304 (18% Cr-8% Ni), and having a thickness
of 50 .mu.m was used by the same method as in Example 1 to prepare
a foil tube. Note that this stainless steel foil was annealed in
ammonia decomposition gas and the nitrogen concentration at the
surface was 4.4%. The thickness of the joint zone was 77 .mu.m.
This was reduced by polishing the inside and outside surfaces to 60
.mu.m. The hardness of the matrix part in this case was, in terms
of Hv, around 190, while the hardness of the joint zone was, in
terms of Hv, around 230. The same procedure was followed as in
Example 1 for a fatigue test. As a result, the tube developed fine
cracks in the surface of the matrix at the time of 500,000 cycles,
so the fatigue test was suspended, but depending on the
application, the tube had durability up to 500,000 cycles.
Depending on the application, this was sufficient for use.
Example 5
[0264] A hard material having a surface roughness Rz of 0.5 .mu.m,
made of SUS304 (18% Cr-8% Ni), and having a thickness of 50 .mu.m
was used by the same method as in Example 1 to prepare a foil tube.
The joint zone had a thickness of 90 .mu.m. This was polished at
the inside and outside surfaces to 60 .mu.m. The hardness of the
matrix part in this case was, in terms of Hv, around 410, the
hardness of the joint zone was, in terms of Hv, around 230, and the
hardness difference of the joint zone and matrix part was 43% of
the hardness of the matrix part. The same procedure was followed as
in Example 1 for a fatigue test. As a result, this tube cracked and
broke at the interface between the joint zone and matrix at 500,000
cycles. In this case as well, depending on the application, the
tube had a durability of up to 500,000 cycles. Depending on the
application, this was sufficient for use.
Example 6
[0265] A rolled foil having a surface roughness Rz of 0.7 .mu.m,
made of SUS42OJ1 (13% Cr-0.18% C), and having a thickness of 20
.mu.m was used by the same method as in Example 1 to prepare a foil
tube. The joint zone had a thickness of 32 .mu.m. The inside and
outside surfaces were polished to 23 .mu.m. The hardness of the
matrix part in this case was, in terms of Hv, around 340, while the
hardness of the joint zone was, in terms of Hv, around 315. The
same procedure was followed as in Example 1 for a fatigue test. The
result was that this tube withstood the fatigue test for 2 million
cycles or more.
Example 7
[0266] A rolled foil having a surface roughness Rz of 0.9 .mu.m,
made of SUS630 (17% Cr-4% Ni-4% Cu-0.2% Nb-0.1% Ta), and having a
thickness of 20 .mu.m was worked by the same method as in Example 1
to prepare a foil tube. The joint zone had a thickness of 35 .mu.m.
This was polished at the inside and outside surfaces to 26 .mu.m.
After this, a vacuum heat treatment furnace was used to heat this
to 1040.degree. C. This was soaked in a cooling process at
480.degree. C. for 1 hour to precipitation harden it. The
hardnesses of the matrix part and weld zone were substantially the
same or, in terms of Hv, around 380. The same procedure was
followed as in Example 1 for a fatigue test. The result was that
this tube withstood the fatigue test for 2 million cycles or
more.
Example 8
[0267] A rolled foil having a surface roughness Rz of 0.85 .mu.m,
made of YUS170 (Nippon Steel Corporation's specification: 24%
Cr-12% Ni-0.7% Mo-0.35% N), and having a thickness of 25 .mu.m
thickness was worked by the same method as in Example 1 to prepare
a foil tube. The joint zone had a thickness of 30 .mu.m. This was
polished at the inside and outside surfaces to 22 .mu.m. The
hardness of the matrix part in this case was, in terms of Hv,
around 290, while that of the joint zone was, in Hv, around 220.
The same procedure was followed as in Example 1 for a fatigue test.
The result was that this tube withstood the fatigue test for 1
million cycles or more.
Comparative Example 1
[0268] The same procedure was followed as in Examples 1 to 8 except
that the stainless steel foils were joined by laser welding instead
of the electrical resistance welding (mash seam welding) in
Examples 1 to 8 to prepare foil tubes of the stainless steel foil
materials for use in a fatigue test. In each case, the boundaries
of the joint zones and matrixes cracked and broke at 100,000 to
300,000 cycles.
Comparative Example 2
[0269] The same procedure was followed as in Examples 1 to 8 except
that the stainless steel foils were joined by plasma welding
instead of the electrical resistance welding (mash seam welding) in
Examples 1 to 8 to prepare foil tubes of the stainless steel foil
materials for use in a fatigue test. In each case, the boundaries
of the joint zones and matrixes cracked and broke at 100,000 to
300,000 cycles.
Example 9
[0270] A 0.9 .mu.m surface roughness Rz, SUS304, 60 .mu.m thick
fully annealed foil (nitrogen concentration of surface of 1.2%)
annealed in an Ar--H.sub.2 atmosphere was used by the same method
as in Example 1 to fabricate seven 24 to 30 mm.phi..times.250 mmL
tubes by mash seam welding. After this, six of these were worked by
inserting quenched S45C metal cores into the tubes, cold working
them by sedging, split roller rolling, drawing, spinning, or a
combination of the same to reduce the thicknesses, smooth the weld
zones, even out the shapes and surface roughnesses of the weld
zones, and simultaneously work harden the materials to thereby
obtain around 30 .mu.m thick foil tubes. These foil tubes were
measured before and after cold working (that is, unworked and
worked) for dimensions, materials, fatigue life, etc. The results
are summarized in Table 1. TABLE-US-00001 TABLE 1 Working method
Dimensions, (1) as (2) (3) 3-split- (4) (5) (6); (7); materials,
etc. welded sedging roller rolling drawing spinning (2) + (3) (5) +
(4) Tube 60 28 32 34 30 29 30 thickness (.mu.m) Hardness 220 467
423 396 448 454 445 (Hv) Weld zone 0.62 0.33 0.18 0.12 0.29 0.19
0.12 surface roughness Ra (.mu.m) Weld zone 5.22 1.96 1.36 0.99
1.91 1.58 0.91 surface roughness Rz (.mu.m) Fatigue 456 818 732 701
763 774 753 life (hr)
[0271] In Table 1, the tube thickness is the thickness of the
non-joint zone (matrix part), the hardness is the Vicker's hardness
of the matrix part, the surface roughness Ra of the weld zone is
the value measured by (JIS B0601 2001 arithmetic average
roughness), and the surface roughness Rz of the weld zone is the
value measured by JIS B0601-2001 (maximum height roughness) of the
metal foil.
[0272] Further, the fatigue life of Table 1, like in Example 1, is
the value found by inserting a hard sponge cylinder into each foil
tube and rotating this while pressing against the surface of a 120
mm.phi..times.80 mmL steel roller so as to investigate the fatigue
life. The rotational speed of the tested tube at this time is 360
rpm. In the state pressed most against the steel roller, the tested
tube is collapsed to about 4 mm. The strain applied to the surface
of the tested tube at this time was successively (1) 0.34, (2)
0.16, (3) 0.18, (4) 0.19, (5) 0.17, (6) 0.16, and (7) 0.17%. The
test was conducted until cracks or other abnormalities could be
confirmed in the foil tube. The fatigue time (hr) during this time
was designated the fatigue life.
[0273] Note that, the cold workings of (2) to (7) of Table 1 were
performed starting from welded tubes with the following inside
diameters before cold working by the respective cold working
methods.
[0274] That is, (2) sedging; 26 mm.phi. welded tube, (3)
three-piece roller rolling; 24 mm.phi. welded tube, (4) drawing; 30
mm.phi. welded tube, (5) spinning; 24 mm.phi. welded tube, (6):
(2)+(3); 24 mm.phi. welded tube, (7): (5)+(4); 26 mm.phi. welded
tube.
Example 10
[0275] Completely annealed foils annealed in an Ar--H.sub.2
atmosphere, having surface roughnesses Rz of 1.2 .mu.m, made of
SUS301, SUS201, SUS316N, and YUS170 (24% Cr-12% Ni-0.3% N), and
having thicknesses of 25 .mu.m (nitrogen concentrations of surfaces
of 1.7 to 2.4%) were used by the same method as in Example 1 to
prepare 30 mm.phi..times.250 mmL tubes by mash seam welding. After
this, these tubes were worked in the same way as in Example 9 by
sedging+split roller rolling (the (6): (2)+(3) cold working) to
obtain around 25 .mu.m thick foil tubes. The dimensions, materials,
fatigue life, etc. of the foil tubes before and after cold working
are shown in Table 2. TABLE-US-00002 TABLE 2 Material SUS301 SUS201
SUS316N YUS170 (8) (9) (10) (11) (12) (13) (14) (15) Material as
after as after as after as after etc. welded working welded working
welded working welded working Tube 50 27 50 25 50 24 50 25
thickness (.mu.m) Hardness 251 608 235 512 198 497 211 511 (Hv)
Weld zone 0.42 0.29 0.51 0.18 0.55 0.17 0.45 0.20 surface roughness
Ra (.mu.m) Weld zone 3.45 1.96 2.73 1.32 3.72 1.45 2.57 1.42
surface roughness Rz (.mu.m) Fatigue 328 857 228 723 208 785 325
817 life (hr)
[0276] Note that the tube thickness (.mu.m), hardness (Hv), weld
zone surface roughness Ra (.mu.m), weld zone surface roughness Rz
(.mu.m), and fatigue life (hr) of Table 2 are as explained in Table
1.
[0277] Note that the strains given to the surface of the tested
tubes in the fatigue life were, in order (8) 0.28, (9) 0.15, (10)
0.28, (11) 0.14, (12) 0.28, (13) 0.14, (14) 0.28, and (15)
0.14%.
Example 11
[0278] 25 .mu.m thick SUS316 foil was seam welded by the same
method as in Example 1 method to obtain a 30 mm.phi..times.250 mmL
foil tube. This was plated with hard Cr to a target thickness of 2
.mu.m. The foil tube had a rod-shaped Cr electrode inserted inside
it and was plated with Cr over its inside and outside surface.
Further, another SUS316 foil tube welded in the same way was
electrolessly plated by Ni-8% P, Co, Pd respectively to a target
thickness of 2 .mu.m. These tubes were cut at their ends, the
cross-sections were buried and polished, and the thicknesses of the
plating films (layers) were investigated. Separate from these, for
measurement of the hardness of the plating layer, iron sheets were
plated with the same materials to thicknesses of about 30 .mu.m,
buried in resin, polished, then measured for hardness. As a
comparison with the plated foil tubes, an unplated foil tube was
attached as a fixing roll of a printer, half a pinch's worth of
iron powder was sprinkled on the inside surface of the tube, then
the tube was rotated for 10 minutes. After this, the tube was
detached and cut open to investigate the state of formation of
flaws at the inside surface. The results are summarized in Table 3.
TABLE-US-00003 TABLE 3 Plating Plating layer State of layer
hardness formation of thickness Hv flaws Unplated foil -- -- Tens
of stripe- tube shaped flaws Ni-8% P plated 2 .mu.m 562 No flaws
foil tube Co plated foil 3 .mu.m 432 No flaws tube Pd plated foil 2
.mu.m 481 No flaws tube
[0279] As shown in Table 3, the hardnesses of the plating layers
were all, in terms of Hv, 400 or more. These foil tubes did not
become flawed even in an adverse environment with iron powder
sprinkled on the inside surfaces of the fixing rolls. As opposed to
this, the unplated foil tube exhibited several stripe-shaped
flaws.
Example 12
[0280] 30 .mu.m thick SUS316 foils were electrolessly plated on
their two surfaces with Ni-2% P, Ni-8% P, and Ni-12% P to
thicknesses of about 2 .mu.m. Further, separate from these, the
vicinities of the foils forming the weld zones, that is, the 2 to 3
mm distances from the cut edges, at the two sides were
electroplated with Al and Ag to thicknesses of about 2 .mu.m. These
foils were welded by mash seam welding to form 30 mm.phi..times.250
mmL tubes. The weld zones were cut out, buried, and polished, then
the cross-sections and metal structures of the weld zones were
examined. As a result, the thicknesses of the matrix parts,
including the plating layers, were 34 .mu.m, while the thicknesses
of the weld zones where the two sides of the foil were superposed
were 35 to 37 .mu.m or substantially the same thicknesses as the
matrix parts. Further, the weld zones were tightly bent, buried in
resin, and examined for the metal structure at the bent parts. As a
comparative material, unplated SUS316 foil of a thickness of 40
.mu.m was mash seam welded in the same way as the above SUS 316
foil, the weld zone was cut out, and that part was tightly bent.
Further, this part was buried in resin, polished, and examined for
metal structure. As a result, the weld zone of the unplated foil
opened slightly at the part where the joint line reached the foil
surface due to the tight bending, but the tightly bent part of the
weld zone of the plated foil did not open at all.
Example 13
[0281] 40 .mu.m thick SUS304 and SUS420J2 foils were welded by mash
seam welding to form 30 mm.phi..times.250 mmL tubes. After welding,
the SUS304 tube was vacuum heat treated at 1030.degree. C. for 3
minutes, while the SUS420J2 tube was vacuum heat treated at
880.degree. C..times.10 minutes. The vicinities of the weld zones
of the tubes after heat treatment were cut out, were tight bent
about the weld zones, and were buried, polished, etched, and
examined for the structures of the weld zones. As a result, the
weld zones did not open at all and could withstand tight
bending.
Example 14
[0282] The SUS304 and SUS420J2 foil tubes prepared in Example 13
were electrolessly plated at the inside and outside surfaces by
Ni-8% P. These tubes were tested for flaws by iron powder similar
to Example 11, but no stripe-shaped flaws were caused. Further,
these tubes were used for the above fatigue tests. With both, no
destruction of the weld zone could be found even after the elapse
of 7.5 million cycles.
Example 15
[0283] A 40 .mu.m thick SUS316 foil was used to form a 30
mm.phi..times.250 mmL tube by seam welding. At that time, the
welding power source used was a pulse power source, the ratio of
the conduction time and non-conduction time was changed in various
ways, the metal structure of the weld zone was examined, and the
state of formation of the nuggets was examined. The results are
shown in Table 4. TABLE-US-00004 TABLE 4 Conduction
time/non-conduction time 1/20 1/15 1/14 1/12 1/10 1/8 1/7 1/6 1/5
Ratio of nugget 36 52 63 100 100 100 54 18 0 length (%) Remarks
Comp. Inv. Inv. Inv. Inv. Inv. Inv. Comp. Comp. ex. ex . ex. ex.
ex. ex. ex. ex. ex.
[0284] As shown in Table 4, with the conduction time/non-conduction
time set to 1/15 to 1/7, the nugget length became 50% or more along
the weld line. It was learned that good welding was performed.
INDUSTRIAL APPLICABILITY
[0285] In the metal foil tube of the present invention, compared
with the prior art of joining sections of a metal sheet by press
working, laser welding, plasma welding, etc. to form a tube blank
and working this tube blank by for example ironing, spinning,
drawing, bulging, or other thinning technology to form a thin tube,
by rolling the metal sheet and, in accordance with need, annealing
or heat treating it to reduce its thickness, it is possible to mass
produce metal foil or tubes of the desired thickness, so it is
possible to remarkably lower the production costs compared with the
case of thinning individual tube blanks.
[0286] Further, in the prior art, when thinning a tube blank formed
into a tubular shape by press working, laser welding, plasma
welding, etc., the surface of the tube blank is subjected to strong
mechanical stress, so an orange peel surface (drop in surface
smoothness) is inevitable, but in the present invention, it is
possible to obtain metal foil excellent in surface smoothness by
rolling, possible to use this metal foil to form a finished metal
foil tube, and possible to use the metal foil as it is without
thinning, so the superior surface smoothness can be held.
[0287] Further, in the present invention, since the metal foil is
welded by electrical resistance welding to form a tube, control of
the joining process is simple and it is possible to produce an
extremely thin metal foil tube well. Therefore, compared with the
conventional practice of laser welding, plasma welding, etc. to
form a tube blank and thin this to form a thin tube, it is possible
to reduce the difference in hardness between the joint zone and
non-joint zone and possible to suppress the drop in durability due
to the metal fatigue at the boundary between the joint zone and
non-joint zone. Further, regarding the problem of weld separation
at the weld zone as well, with a thin tube obtained by forming a
tube blank by conventional laser welding, plasma welding, etc. and
thinning it, at the time of thinning, the weld zone is subjected to
large working of about 90%, so weld separation easily occurs due to
later use, but in the present invention, no large working is
applied after welding, so the problem of weld separation of the
weld zone etc. does not easily occur.
[0288] Further, the present invention is advantageous in the point
that it is possible to select any material as the metal foil in
accordance with the application. That is, in the present invention,
it is possible to use an existing material, from hard materials to
soft materials, and possible to suitably select a material
satisfying the high elasticity, high rigidity, light weight,
thinness, high heat conductivity, and other performance
requirements in accordance with the application.
[0289] Further, in the present invention, by hard plating the
inside and outside surfaces of the tube, even if foreign matter is
carried in along with the paper, it is possible to suppress flaws
in the roller and possible to suppress the detrimental effect on
the results of printing. Further, by hard plating, at the time of
seam welding, even if nuggets formed by melting and solidification
are not continuously formed, the plating layer will melt and a
complete metal bond will be obtained along the weld line.
Therefore, this part can give a sufficient joint strength in the
crimped state and the product yield and quality can be
improved.
[0290] The method of production of the metal foil tube of the
present invention can shape even a metal foil sheet having a
thickness of 10 to 100 .mu.m to form an overlap part, then weld the
facing sides and finish this weld zone part smooth, so can reliably
finish even extremely thin metal foil into a tube shape.
[0291] This shaping does not round the metal foil all at once. It
positions the foil, then wraps it around a core rod having an
electrode, forms an overlap part, then welds it, so extremely
precision shaping is possible and welding is also easy. This
overlap part is also formed while adjusting the overlap, so greater
precision shaping becomes possible. If the overlap (x) satisfies
x.ltoreq.40+5 t (unit .mu.m) with respect to the thickness (t), it
is possible to weld together the two ends even with an extremely
thin metal foil.
[0292] The welding is electrical resistance welding, so control of
the welding is simple and extremely thin metal foil can be produced
well. Further, by providing the core rod serving as the inside die
with a stationary electrode member, providing a movable electrode
member facing this stationary electrode member, and running current
across the two over the metal foil, it is possible to join the two
ends of the metal foil with a good precision.
[0293] The production apparatus of the present invention is
provided with a shaping device for holding a metal foil sheet to be
able to approach or move away from the circumference of a core rod
with a circular cross-section perpendicular to the axis, so even
with an extremely thin metal foil with a thickness of 10 to 100
.mu.m, it is possible to shape the foil to form the overlap part,
then weld the facing sides and reliably finish the foil into a tube
shape.
[0294] The tube is shaped by wrapping and positioning the foil
against the core rod by a holding plate for bending the metal foil
sheet into a U-shape and for a first pressing member and second
pressing member pressing the sides against the circumference of the
core rod and overlapping the facing side ends, so it is possible to
shape the tube extremely precisely and later weld it easily as
well.
[0295] The overlap of the overlap part is adjusted by using
offsetting devices (cams, rollers, etc.) provided at the inside or
outside of the core rod to press against the non-contact parts of
the metal foil sheet or by a pressing member for pressing the metal
foil sheet toward a recess formed in the core rod, so more precise
shaping becomes possible.
[0296] The welding is performed by providing the core rod serving
as the internal die with a stationary electrode member, providing a
movable electrode member facing this stationary electrode member,
and running current across the two over the metal foil, so it is
possible to connect the two ends of the metal foil with a good
precision. Further, if making the movable electrode member an
electrode ring, smooth, good precision welding becomes possible. If
making the hardness of the electrode member and the hardness of the
metal foil sheet substantially the same, good precision welding
over a long period becomes possible.
[0297] After shaping the metal foil tube, if ejecting a fluid from
the core rod in the radial direction or using a split core rod, the
metal foil tube can be easily separated from the core rod and even
an extremely thin metal foil tube can be easily detached.
* * * * *