TECHNICAL FIELD
[0001]
The present invention relates to a processed product formed from a plated steel
sheet including a plating layer on its surface which includes a cut end and to a processed
product producing method for producing the processed product.
BACKGROUND ART
[0002]
In recent years, usage of a processed product for which a plated steel sheet
including a plating layer on its surface is used as a starting material, as a component of
an automobile and equipment such as a household appliance, has increased. Using a
plated steel sheet as a starting material enables the omission of surface treatment after
forming a processed product, keeping production costs low. Further, by the omission
of surface treatment after the forming, the deterioration in dimensional accuracy of a
component due to the surface treatment after the forming can be avoided. The
omission of the surface treatment after the forming is studied particularly for a
component that is required to have high dimensional accuracy, such as a motor frame.
[0003]
When the surface treatment after the forming is omitted, a region where a base
metal of the steel sheet is exposed appears at a cut end of the processed product. In
some environments in which the processed product is placed, red rust may form in the
region where the base metal of the steel sheet is exposed. Red rust degrades the
appearance of the processed product. Further, a red rust formation region spreads with
time, and there is thus a concern about a decrease in strength of the processed product
due to the red rust. In particular, in a case of a household appliance, there is also a
concern about an electrical short circuit due to falling off of the rust.
1
[0004]
Some products of motor frames or the like have shapes without a flange.
Such a motor frame is used in such a manner that a motor is inserted through an opening
portion of the motor frame, and the opening portion is enclosed with another component
called a base plate. If moisture enters the inside of the motor frame, the moisture
causes a malfunction or performance degradation of the motor, and thus a high
gastightness is needed between the opening portion and the base plate. To ensure a
high gastightness, a prescribed flat portion is needed at the opening portion.
[0005]
As a method for improving the antirust capability of a cut end of a processed
product, for example, Patent Document 1 proposes a method in which stamping
processing is performed on a Zn-base plated steel sheet having a sheet thickness of 2 = or less using press tooling that has a curvature radius of a size 0.1 to 0.5 times the
sheet thickness of the Zn-base plated steel sheet in a shoulder portion of a punch or a
die, so that a shear surface ratio of a stamped end surface after the stamping processing
is set to 90% or more, and a zinc coverage of a shear surface is set to 50% or more.
[0006]
Patent Document 2 proposes a method in which a stamping clearance is set to 1
to 20% of a sheet thickness of a Zn-base plated steel sheet irrespective of the sheet
thickness, and the Zn-base plated steel sheet is cut using press tooling that has a
curvature radius of a size 0.12 times or more the sheet thickness of the Zn-base plated
steel sheet in a shoulder portion of a punch or a die, so that a processed product in
which a shear droop Z of its cut end surface is 0.10 x sheet thickness or more, and a
shear droop X of the cut end surface is 0.45 x sheet thickness or more is provided.
[0007]
Patent Document 3 proposes a method in which half die cutting is performed
on a plated steel sheet by 60 to 95% of a sheet thickness with a negative clearance, and
shearing is performed by push-back blanking from an opposite side to that of half die
cutting, so that a product having corrosion resistance of its end surface is provided.
[0008]
2
Patent Document 4 discloses a press processing method for a metal sheet
material that includes a first process in which the metal sheet material is subjected to
half die cutting processing using a first punch and a first die, with a shaving margin
being provided on a fmal processed surface of a stamping processed portion of the metal
plate material, and a second process in which shaving processing mainly constituted by
shearing processing is further performed on a portion subjected to the half die cutting
processing using a second punch and a second die, by which 70% or more of a shearing
processed surface is secured on the final processed surface of the stamping processed
portion.
LIST OF PRIOR ART DOCUMENTS
PATENT DOCUMENT
[0009]
Patent Document 1: JP5272518B
Patent Document 2: JP6073025B
Patent Document 3: JP2002-321021A
Patent Document 4: JP2004-174542A
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0010]
However, a steel sheet intended in the method according to Patent Document 1
is a steel sheet having a sheet thickness of 2 mm or less; if a steel sheet having a sheet
thickness of more than 2 mm is used as a starting material, the zinc coverage of the
shear surface is insufficient, which arises the possibility that the formation of red rust is
difficult to prevent. Further, it is difficult to apply the method to a drawn part such as a
motor frame in which thickening occurs at an end portion of its flange.
[0011]
In the method according to Patent Document 2, since the stamping clearance is
set to a positive clearance, a rupture surface that is more than 0.5 mm tends to be
3
formed in the latter stage of the cutting. Further, by setting the stamping clearance to
the positive clearance, an interfacial pressure between a die and a surface of a plating
layer does not increase, as a result of which the plating layer does not follow an
elongated material but rupture, and a steel base metal tends to be exposed.
[0012]
In the method according to Patent Document 3, the plated steel sheet is
subjected to the half die cutting with a negative clearance and sheared by the push-back
blanking from the opposite side to that of the half die cutting. This may form a rupture
surface at an intermediate position of a cut end of the plated steel sheet in a sheet
thickness direction and may form hair-like burrs in the push-back blanking, degrading
shape quality.
[0013]
The method according to Patent Document 4 is a technique relating to a
shaving processing, and the final processed surface of the metal sheet material is made
favorable by forming a large shearing processed surface. When a metal sheet material
including a plating layer on its surfaces is subjected to shaving processing by the
method according to Patent Document 4, the plating layer on the surface remains little
on the final processed surface, and thus corrosion resistance of the final processed
surface is low.
[0014]
The present invention is therefore made in view of the problems described
above, and an objective of the present invention is to provide a processed product that is
favorable in corrosion resistance and shape quality even when a plated steel sheet
having a sheet thickness of more than 2.0 = is used as starting material, and to
provide a processed product producing method for producing the processed product.
SOLUTION TO PROBLEM
[0015]
According to an aspect of the present invention, to solve the problems, there is
provided a processed product formed from a plated steel sheet including a plating layer
4
on a surface of the plated steel sheet which includes a cut end on a side wall of the
processed product, the side wall being in a hollow-shell cylindrical shape, wherein the
cut end is flush with an exterior of the side wall of the processed product, and includes a
shear surface, or the shear surface and a rupture surface in this order in a sheet thickness
direction of the cut end, and a ratio Lit! between a plating component remaining length
L by which the shear surface is covered with the plating layer on the surface and a sheet
thickness tl of the cut end of the processed product is 0.70 or more.
[0016]
A length Wl of the rupture surface in the sheet thickness direction of the cut
end may be more than 0 mm to 1.0 mm or less.
[0017]
The length Wl of the rupture surface in the sheet thickness direction of the cut
end may be 0.5 mm or less.
[0018]
A ratio Lt/t between a length Lt of a flat surface of an end surface of the
processed product perpendicular to the side wall and a sheet thickness t of the side wall
of the processed product may be 0.35 or more.
[0019]
A length of a burr on the cut end may be less than 0.2 mm.
[0020]
The cut end may include the shear surface, the rupture surface, and a coined
surface in this order, or the shear surface and a coined surface in this order in the sheet
thickness direction of the cut end, and a length W2 of the rupture surface between the
shear surface and the coined surface in the sheet thickness direction of the cut end may
be more than 0 mm to 0.5 mm or less.
[0021]
According to another aspect of the present invention, to solve the problems,
there is provided a processed product producing method for producing a processed
product for which a plated steel sheet including a plating layer on a surface of the plated
steel sheet is used as a starting material and that includes a cut end on a side wall of the
5
processed product, the side wall being in a hollow-shell cylindrical shape, the processed
product producing method including: a semi-cutting process of subjecting a cut portion
of a first base body to semi-cutting in a sheet thickness direction using a first die and a
first punch, the first base body being formed from the starting material, a clearance
between the first die and the first punch being set to a negative clearance; and a fmish
cutting process of subjecting the first base body subjected to the semi-cutting to finish
cutting in a direction identical to a direction of the semi -cutting using a second die and a
second punch, to thereby obtain the processed product including the cut endthat is flush
with an exterior of the side wall of the processed product, wherein an inner diameter D32
of the second die is made not less than an inner diameter D31 of the fust die, wherein
when t1 denotes a sheet thickness of a cut portion of the first base body, and t2 denotes
a remaining sheet thickness of the cut portion after the semi-cutting process, in the
semi-cutting process, a clearance C31-41 between the first die and the first punch satisfies
Formula (a!) shown below, a curvature radius R 1 of an edge of the first die satisfies
Formula (a2) shown below, a pressing depth D of the fust die or the first punch into the
cut portion of the first base body satisfies Formula ( a3) shown below, and a clearance
CP-D between the frrst die and the first punch at a bottom dead center satisfies Formula
(a4) shown below, and in the finish cutting process, a clearance C32-42 between the
second die and the second punch satisfies Formula (aS) shown below, and a curvature
radius R2 of an edge of the second die satisfies Formula (a6) shown below:
[0022]
-035 x t1 s; C31-41 s; -0.01 (al)
0.10 X t1 s; Rl s; 0.50 X t1 (a2)
D ~ 0.70 X t1
CP-D ~ 0.20
(a3)
(a4)
0.01 s; C32 -42 s; 0.2 X t2
0.25 :S; R2 :S; 1.50 X t2
(aS)
(a6)
where a unit of C31-41, CP-D, C32-42, and R2 is mm.
According to still another aspect of the present invention, to solve the
problems, there is provided a processed product producing method for producing a
6
processed product for which a plated steel sheet including a plating layer on a surface of
the plated steel sheet is used as a starting material and that includes a cut end on a side
wall of the processed product, the side wall being in a hollow-shell cylindrical shape,
the processed product producing method including: a semi-cutting process of subjecting
a cut portion of a first base body to semi-cutting in a sheet thickness direction using a
first die and a first punch, the first base body being formed from the starting material, a
clearance between the first die and the first punch being set to a negative clearance; and
a fmish cutting process of subjecting the first base body subjected to the semi-cutting to
finish cutting in a direction identical to a direction of the semi-cutting using a second
die and a second punch, to thereby obtain the processed product including the cut end
that is flush with an exterior of the side wall of the processed product, wherein an inner
diameter D32 of the second die is made not less than an inner diameter D31 of the first
die, wherein when tl denotes a sheet thickness of a cut portion of the first base body,
and t2 denotes a remaining sheet thickness of the cut portion after the semi -cutting
process, in the semi-cutting process, a clearance C31-41 between the first die and the first
punch satisfies Formula (b1) shown below, a curvature radius Rll of an edge of the first
die satisfies Formula (b2-1) shown below, a curvature radius R12 of an edge of the first
punch satisfies Formula (b2-2) shown below, a pressing depth D of the first die or the
first punch into the cut portion of the first base body satisfies Formula (b3) shown
below, and a clearance CP-D between the first die and the first punch at a bottom dead
center satisfies Formula (b4) shown below, and in the finish cutting process, a clearance
C32-42 between the second die and the second punch satisfies Formula (b5) shown below,
and a curvature radius R2 of an edge of the second die satisfies Formula (b6) shown
below:
-OA5 X tl ~ C31-41 ~ -0.10 X t1
0.10 X tl ~ Rll ~ 0.65 X t1
0.10 X tl ~ R12 ~ 0.65 X t1
D ~ 0.70 X tl
CP-D ~ 0.20
(b3)
(b4)
(bl)
(b2-1)
(b2-2)
O.Ql ~ C32 -42 ~ 0.2 X t2 (b5)
7
0.25 ::; R2 ::; 1.50 X t2 (b6)
where a unit of C31-41, CP-D, C32-42, and R2 is mm.
[0023]
The processed product producing method may further include a coining
process of pressing, with the processed product provided by the finish cutting process
being used as a second base body, a comer portion of the cut end of the second base
body against a pad, to thereby obtain the processed product with a coined surface being
formed at the corner portion.
[0024]
A difference D32-D31 between an inner diameter D31 of the first die and an inner
diameter D32 of the second die may be 1.00 mm or less.
[0025]
The processed product producing method may further include a preparation
process of, before the semi -cutting process, preparing the first base body including a
hollow-shell side wall and a flange portion by subjecting the plated steel sheet being flat
to shape processing.
ADVANTAGEOUS EFFECT OF INVENTION
[0026]
As described above, according to the present invention, even in a case where a
plated steel sheet having a sheet thickness of more than 2.0 mm is used as a starting
material, corrosion resistance and shape quality of the resultant processed product can
be made favorable.
BRIEF DESCRIPTION OF DRAWINGS
[0027]
[Figure 1] Figure 1 is a perspective view illustrating an example of a processed product
produced by a processed product producing method according to a first embodiment of
the present invention.
[Figure 2] Figure 2 illustrates a cut end in a region A of the processed product in Figure
8
1, where the left is a sectional view of the cut end taken along a ZX plane including a
central axis of the processed product, and the right is a diagram illustrating the cut end
in side view in an X direction.
[Figure 3] Figure 3 is a detail view of the sectional view on the left of Figure 2.
[Figure 4] Figure 4 is a schematic diagram for describing gastightness that is changed
with a size of a flat surface of an end portion of a processed product.
[Figure 5] Figure 5 is an explanatory diagram illustrating the processed product
producing method according to the embodiment.
[Figure 6] Figure 6 is an explanatory diagram illustrating a semi-cutting process in a
case where an edge of a die used in the semi-cutting process is formed in an R-shape.
[Figure 7] Figure 7 is an explanatory diagram illustrating a fmish cutting process that is
performed subsequently to the semi-cutting process illustrated in Figure 6.
[Figure 8] Figure 8 is an explanatory diagram illustrating the semi-cutting process in a
case where the edges of the die and the punch used in the semi-cutting process are each
formed in the R-shape.
[Figure 9] Figure 9 is an explanatory diagram illustrating a fmish cutting process that is
performed subsequently to the semi-cutting process illustrated in Figure 8.
[Figure 1 0] Figure 10 is an explanatory diagram illustrating a processed product
producing method according to a second embodiment of the present invention.
[Figure 11] Figure 11 is a schematic diagram illustrating an example of press tooling
used in the coining processing.
[Figure 12] Figure 12 is a partially enlarged view of a region B in Figure 11.
[Figure 13] Figure 13 illustrates a cut end of a processed product after a coining
process, where the left is a sectional view of the cut end portion taken along a ZX plane
including a central axis of the processed product, and the right is a diagram illustrating
the cut end in side view in the X direction.
[Figure 14] Figure 14 is a photograph depicting an example of the cut end of the
processed product after the coining process.
[Figure 15] Figure 15 is an explanatory diagram illustrating a volume of a comer
portion that is crushed by a pad in the coining process.
9
[Figure 16] Figure 16 is a photograph depicting a part produced by drawing of irregular
shape, as an example of a processed product according to the present invention.
[Figure 17] Figure 17 is a photograph depicting a part produced by square cup drawing,
as an example of a processed product according to the present invention.
DESCRIPTION OF EMBODIMENTS
[0028]
A preferred embodiment of the present invention will be described below in
detail with reference to the accompanying drawings. In the present specification and
drawings, components having substantially the same functions and structures are
denoted by the same reference characters, and the repeated description thereof will be
omitted.
[0029]
[1. First Embodiment]
[1-1. Processed Product]
First, with reference to Figure 1, a processed product 1 produced by a
processed product producing method according to a first embodiment of the present
invention will be described. Figure 1 is a perspective view illustrating an example of a
processed product 1 produced by the processed product producing method according to
the first embodiment of the present invention. The processed product 1 illustrated in
Figure 1 is a motor frame for which a plated steel sheet including a plating layer on its
surfaces is used as a starting material. The motor frame illustrated in Figure 1 can be
formed by performing shape processing such as drawing on a flat plated steel sheet.
[0030]
The processed product 1 according to the present embodiment includes, as
illustrated in Figure 1, a barrel portion 10 and a protruding portion 11.
[0031]
The barrel portion 10 includes a side wall 101 in a hollow-shell cylindrical
shape and a top walll03 that is formed such that one end of the side walllOl is covered
with the top wall 103. The top wall 103 may be called differently, for example, a
10
bottom wall, depending on an orientation in which the processed product 1 is used.
The barrel portion I 0 of the processed product I illustrated in Figure I has a perfectly
circular sectional shape on an XY plane, but the present invention is not limited to such
an example. The sectional shape of the barrel portion 10 on the XY plane may be, for
example, another shape such as ellipse and polygon. The barrel portion 10 has an
opening portion on a side opposite to the top wall 103. Through the opening portion, a
motor is inserted.
[0032]
The protruding portion 11 is a protrusion that protrudes from the top wall 103
outward in a central-axis direction of the barrel portion 10 (Z direction). Note that the
protruding portion 11 need not necessarily be formed, and thus the top wall 103 may be
flat.
[0033]
The barrel portion 10 according to the present embodiment includes a cut
end13 on an outer surface of its end portion on an opening portion side. The cut end
13 is formed by performing cutting processing on a base body that is to be processed
into the processed product 1. The cut end 13 is formed in such a manner as to be flush
with an exterior of the barrel portion 10.
[0034]
The cutting processing includes types of processing such as cutting, stamping,
and punching. The cutting is processing in which a cutting object is cut along a
prescribed straight line or curve. The stamping is processing in which a product is
stamped out from a cutting object. The punching is processing in which a portion of a
non-product portion is punched out from a cutting object, thereby providing a product
with an opening. The barrel portion 10 including the cut end 13 illustrated in Figure 1
can be provided by stamping from a base body.
[0035]
As the plated steel sheet, a plated steel sheet including any of various types of
plating layers is preferably used. Although various steel sheets can be used as the
plated steel sheet, a Zn-base plated steel sheet is preferably used. Zn-based plating
11
includes Zn plating, Zn-Al-base alloy plating, Zn-Al-Mg-base alloy plating, and
Zn-Al-Mg-Si-base alloy plating. It is particularly preferable that a steel sheet
subjected to the Zn-Al-Mg-base alloy plating be used as the plated steel sheet. Here,
for the alloy plating, 80 mass% or more of Zn is preferably contained with respect to a
total number of moles of plating, and 90 mass% or more of Zn is more preferably
contained.
[0036]
A base steel sheet of the plated steel sheet may be any base steel sheet and can
be, for example, an ultra-low carbon steel.
[0037]
A lower limit of a coating weight of the plated steel sheet is preferably set to 30
g/m2, and more preferably, the lower limit may be set to 45 g/m2· In addition, an upper
limit of the coating weight of the plated steel sheet is preferably set to 450 glm2
, and
more preferably, the upper limit may be set to 190 glm2· In particular, by setting the
coating weight to 45 glm2 or more, plating metal tends to extend to a shear surface of
the cut end 13 (a shear surface 13c in Figure 2), which enables improvement in
corrosion resistance after the cutting processing.
[0038]
A sheet thickness of the plated steel sheet (a sheet thickness of the base steel
sheet + a thickness of the plating layer) may be any sheet thickness, and the sheet
thickness may be 2.0 mm or less or may be more than 2.0 mm. The sheet thickness of
the plated steel sheet can be, for example, 0.8 mm or more to 6.0 mm or less, and more
preferably 2.0 mm or more to 4.5 mm or less.
[0039]
[1-2. Cut End of Processed Product]
Next, with reference to Figure 2 and Figure 3, the cut end 13 of the processed
product 1 according to the present embodiment will be described. Figure 2 illustrates
the cut end 13 in a region A of the processed product I in Figure 1, where the left is a
sectional view of the cut end 13 taken along a ZX plane including a central axis of the
processed product 1, and the right is a diagram illustrating the cut end 13 in side view in
12
an X direction. Figure 3 is a detail view of the sectional view on the left of Figure 2.
Note that, in Figure 2, the illustration of plating layers 13fl and 13f2 is omitted.
[0040]
As illustrated in Figure 2 and Figure 3, the cut end 13 of the processed product
1 is formed in such a manner as to be flush with an exterior of the processed product 1,
for example, an outer surface 1 01 a of the side wall 1 01, in the Z direction. Further, the
cut end 13 is formed along a direction T2 (hereinafter, also referred to as a "second
direction"), which is parallel to the central axis of the processed product 1 and
perpendicular to a sheet thickness direction T1 of the side wall 101 (hereinafter, also
referred to as a "first direction"). In the second direction T2, the cut end 13 includes
the shear surface 13c and a rupture surface 13d in this order as illustrated in, for
example, Figure 2 and Figure 3.
[0041]
Note that, in Figure 2, a curved surface Rd is illustrated at a boundary between
the outer surface lOla and the cut end 13 of the processed product as being so
exaggerated that the curved surface Rd is slightly present, but the curved surface Rd is
not supposed to form a large step at the boundary between the outer surface lOla and
the cut end 13, and the outer surface lOla and the cut end 13 can be regarded as being
flush with each other. Here, when a step between a surface of the cut end 13 and the
outer surface lOla of the side wall 101 is 0.5 mm or less, it is determined that the step is
not large, and the outer surface 1 Ola and the cut end 13 are regarded as being flush with
each other. As necessary, an upper limit of the step may be set to 0.4 mm, 0.3 mm, 0.2
mm, or 0.1 mm. Note that a sheet thickness of a lowermost part of the side wall 101 of
the processed product 1 is determined to be a sheet thickness t of the processed product
1. That is, a sheet thickness of the side wall 101 directly above the curved surface Rd
at the boundary between the outer surface 101 a of the side wall 1 01 and the cut end 13
is defined as the sheet thickness t of the processed product 1.
[0042]
The shear surface 13c is a surface formed by shearing the base body of the
processed product 1 with an edge of a cutting die. The rupture surface 13d is a surface
13
formed by a rupture caused by coalescence of cracks that form in the base body from
the edge of the cutting die. The rupture surface 13d is adjacent to the shear surface 13c
in the second direction 1'2. On a lower side of the rupture surface 13d (i.e., on an
opposite side of the rupture surface 13d from the shear surface 13c ), burrs may be
formed. The burrs are portions formed by stretching or tearing off the base body when
the rupture surface 13d is formed.
[0043]
In the processed product 1 produced by the processed product producing
method according to the present embodiment, a part of the shear surface 13c of the cut
end 13 is covered with the plating layer 13fl as illustrated in Figure 3. When the edge
of the cutting die goes into the base body, the cutting die stretches the plating layer 13fl,
by which the plating layer 13fl extends to the shear surface 13c. The extension of the
plating layer 13fl, at least a part of the shear surface 13c is covered with the plating
layer 13fl. At the part of the shear surface 13c covered with the plating layer 13fl, the
formation of red rust can be prevented. Further, in a case where the plating layer 13fl
is a Zn-based plating layer, the formation of red rust can be prevented also in the
vicinity of the part covered with the plating layer 13fl by sacrificial protection action of
the Zn-based plating layer. Note that the processed product 1 illustrated in Figure 3 is
a processed product 1 having a negligible step at the boundary between the outer surface
1 Ola and the cut end 13, and thus the illustration of the curved surface Rd is omitted in
Figure 3.
[0044]
In the processed product 1 at this time, a length L of the plating layer 13 fl with
which at least the part of the shear surface 13c of the cut end 13 is covered is 0. 70 times
or more of a sheet thickness t1 of the cut end 13 of the processed product 1 (hereinafter,
also referred to as a "length tl of the cut end 13"). That is, a ratio Lltl between a
plating component remaining length L by which the shear surface 13c is covered with
the plating layer 13 fl and the sheet thickness t1 of the cut end 13 of the processed
product 1 is 0.70 or more. The larger the ratio Lltl, the more preferable it is. Note
that a lower limit of the ratio Lltl may be set to 0.75, 0.78, 0.81, 0.83, 0.85, or 0.88.
14
An upper limit of the ratio Lltl is 1.00. Note that the sheet thickness t1 of the cut end
13 is, as illustrated in Figure 2, a length from a lower end of the curved surface Rd to an
end surface of the barrel portion 10 (an end surface 14a in Figure 3) in the second
direction 1'2.
[0045]
The rupture surface 13d is formed as a result of the coalescence of cracks that
form in the base body, and the rupture surface 13d is a rough surface that is formed
anew. At the rupture surface 13d, a metallic component in a steel base metal is
exposed. For the plating layer 13 f1 with which the shear surface 13 c is covered, it is
difficult to extend up to the rupture surface 13d. For that reason, the rupture surface
13d is more susceptible to the formation of red rust than the other surface of the cut end
13.
[0046]
The present inventors conducted an experiment in which the sheet thickness t1
of the cut end 13 of the processed product 1, conditions for the cutting processing,
conditions for surface treatment, and the like were changed within their respective
ranges, to investigate how red rust forms. The sheet thickness t1 of the cut end 13 of
the processed product 1 was changed by changing a sheet thickness of a flange portion
20 illustrated on the left of Figure 5 described later (i.e., a sheet thickness of a plated
steel sheet). As a result, the present inventors conceived the provision of a processed
product 1 having a ratio Lltl of 0. 70 or more by causing a plating layer 13fl to extend
to shear surface 13c when a plated steel sheet is subjected to the cutting processing.
The present inventors found that this enables the formation of red rust to be prevented at
the cut end 13 with time after the cutting processing.
[0047]
In addition, a length Wl of the rupture surface 13d in a sheet thickness
direction of the cut end 13 of the processed product 1 (i.e., the second direction T2)
(hereinafter, also referred to as a "rupture surface length") is preferably more than 0 =
to 1.0 = or less. With the rupture surface length Wl of the processed product 1
being set to 1.0 = or less, even when red rust forms at the rupture surface 13d, the red
15
rust is inconspicuous and can be determined to be practically unproblematic. The
shorter the rupture surface length Wl of the processed product 1, the more preferable it
is, and thus the rupture surface length W1 may be set to 0.8 = or less or 0.6 = or
less. It is more preferable that the rupture surface length W1 of the processed product
1 is set to 0.5 = or less, 0.3 = or less, or 0.2 = or less. Further, a ratio Wllt1
between the rupture surface length W1 and the sheet thickness t1 of the cut end 13 of
the processed product 1 may be less than 0.15, less than 0.10, less than 0.08, less than
0.06, or less than 0.04. Note that the rupture surface length W1 of the processed
product 1 may be 0 =· That is, the cut end 13 of the processed product 1 need not
include the rupture surface 13d. In this case, the cut end 13 includes only the shear
surface 13c in the second direction T2.
[0048]
The end surface 14a of the opening portion (an opening portion 14 in Figure 4)
of the processed product 1 according to the present embodiment includes a flat surface
13k. In a product without a flange as illustrated in Figure 1, the end surface 14a of the
barrel portion 10 usually serves as a mounting surface for another component. For
example, in the example of the motor frame in Figure 1, a base plate 15 is fixed to the
end surface 14a of the barrel portion 10, by which the opening portion is sealed, as
illustrated in Figure 4. At this time, the longer a length Lt of the flat surface 13k of the
end surface 14a of the barrel portion 10, the larger a contact area between the flat
surface 13k and a mounting surface 15a of the base plate 15, which enables an increase
of gastightness. To provide such an effect, a ratio Lt/t between the length Lt of the flat
surface 13k and the sheet thickness t of the side wall 101 of the processed product 1 is
preferably 0.35 or more, 0.40 or more, or 0.50 or more, more preferably 0.60 or more,
0.70 or more, 0.80 or more, or 0.85 or more.
[0049]
In addition, lengths of burrs that are formed on a lower side of the rupture
surface 13d of the cut end 13 of the processed product 1 may be set to less than 0.2 =·
The burrs can cause a dent, an electrical short circuit, or the like. By setting the
lengths of the burrs to less than 0.2 = so as to make the burrs not remain on the
16
processed product 1 as much as possible, the occurrence of a dent, an electrical short
circuit, or the like can be prevented. It is more preferable that the lengths of the burrs
are less than 0.1 mm.
[0050]
The processed product according to the present embodiment is produced not by
cutting a plated steel sheet in one process but by cutting a plated steel sheet in two
processes: a semi-cutting process and a fmish cutting process. This enables the
provision of a processed product 1 in which its plating layer 13fl is made to extend to
its shear surface 13c in a larger amount. The processed product producing method
according to the present embodiment will be described below.
[0051]
[1-3. Processed Product Producing Method]
First, with reference to Figure 5, the processed product producing method
according to the present embodiment will be described. Figure 5 is an explanatory
diagram illustrating the processed product producing method according to the present
embodiment. As illustrated in Figure 5, the processed product producing method
according to the present embodiment includes a preparation process, the semi-cutting
process, and the finish cutting process.
[0052]
The preparation process is a process of preparing a first base body 2. The first
base body 2 can be provided by performing shape processing such as drawing on a flat
plated steel sheet. That is, a starting material of the first base body 2 is a plated steel
sheet as with the processed product 1. The first base body 2 includes a flange portion
20 at a position reserved for the cut end 13 illustrated in Figure 1. In plan view, an
external shape of the flange portion 20 may be circular or may be noncircular. A
portion of the first base body 2 other than the flange portion 20 can have the same shape
as with the processed product 1. Note that the preparation process is not an
indispensable part for carrying out the present invention. The preparation process can
be omitted in a case where a base body processed by a third party in some way is
available.
17
[0053]
The semi-cutting process is a process in which semi-cutting is performed on
the first base body 2. In the semi -cutting process, semi -cutting is performed on the
flange portion 20. The semi-cutting is processing in which the flange portion 20 is cut
up to an intermediate position in a direction of cutting the flange portion 20. In the
present embodiment, the flange portion 20 is to be a removed portion 20a that is a
non-product portion in the end, and the flange portion 20 is cut at a boundary position
between the flange portion 20 and a portion reserved for a side wall 1 01 of a barrel
portion 10 of a processed product 1. The direction of cutting the flange portion 20 is a
sheet thickness direction of the flange portion 20.
[0054]
The fmish cutting process is a process in which finish cutting is performed on
the first base body 2. In the fmish cutting process, the flange portion 20 subjected to
semi-cutting is cut and separated from the portion reserved for the side wall!Ol of the
barrel portion 10 of the processed product I. By the cutting of the flange portion 20,
the processed product I in which its cut end 13 is formed to be flush with the side wall
101 is provided. An end surface 14a of an opening portion 14 of the processed product
1 is covered with a plating layer 13 f2 on an inside surface 101 b side of the barrel
portion 10 as illustrated in Figure 3. Further, the end surface 14a of the opening
portion 14 of the processed product 1 is formed to have a flat surface 13k.
[0055]
In the semi-cutting process and the fmish cutting process of the processed
product producing method according to the present embodiment, the first base body 2 is
processed with a die and a punch. The semi-cutting process and the finish cutting
process will be described below in detail along with two forms in relation to shapes of
edges of the die and punch used in the semi-cutting process. The edges of the die and
the punch may be each referred to as a "shoulder portion". Note that, in the following
description, regarding press tooling used to provide a processed product 1, an upper
piece of the press tooling (an upper die) will be referred to as a die, and a lower piece of
the press tooling (a lower die) will be referred to as a punch, for the sake of
18
convenience. Therefore, this technique is naturally applicable to a case where the die
on the upper side (upper die) is referred to as a punch, and the die on the lower side
(lower die) is referred to as a die. Further, moving directions of the die and the punch
are determined depending on their placement condition; the die and the punch may be
moved in a vertical direction or may be moved in a horizontal direction.
[0056]
(a. Case Where Only Edge of Die Used in Semi-Cutting Process Is Formed in R-Shape)
First, with reference to Figure 6 and Figure 7, the semi-cutting process and the
finish cutting process in a case where only the edge of the die used in the semi-cutting
process is formed in an R-shape will be described. Figure 6 is an explanatory diagram
illustrating the semi-cutting process in a case where the edge of the die used in the
semi-cutting process is formed in the R-shape. Figure 7 is an explanatory diagram
illustrating the finish cutting process that is performed subsequently to the semi -cutting
process in Figure 6.
[0057]
(Semi-Cutting Process)
In the semi-cutting process, as illustrated in Figure 6, semi-cutting is performed
on a flange portion 20 of a first base body 2 with a first die 31 and a first punch 41.
Figure 6 illustrates, as a mode of the semi-cutting, how the flange portion 20 is
subjected to half die cutting from the first base body 2 with a portion reserved for a side
wall 101 of a barrel portion 10 clamped between the first punch 41 and a first guide 51.
In the semi-cutting, the first die 31 constitutes a cutting die that is to be pressed into the
flange portion 20. In the present embodiment, a die that holds a portion reserved for
an end surface of the side wall 1 01 of the barrel portion 10 (the end surface 14a in
Figure 3) is defined as the first punch 41, and a die that holds the flange portion 20 (i.e.,
the removed portion 20a) is defmed as the first die 31.
[0058]
Here, a clearance C31-41 between the first die 31 and the first punch 41 is set to
a negative clearance. The clearance C31-41 represents a gap between the first die 31 and
the first punch 41; specifically, as illustrated in Figure 6, the clearance C31-41 is given by
19
a distance between a lateral surface 31 a of the first die 31 and a lateral surface 41 a of a
first punch 41. With respect to a state where there is no clearance (i.e., when C31-41 is
zero), a clearance in a state where the first die 31 and the first punch 41 are separated
from each other as viewed in a direction of pressing the first die 31 (i.e., a sheet
thickness direction of the flange portion 20, the Z direction) is called a positive
clearance, and a clearance in a state where the first die 31 and the first punch 41 overlap
is called a negative clearance. Regarding the clearance between the die and the punch,
a positive clearance will be herein expressed as a positive value, and a negative
clearance will be herein expressed as a negative value.
[0059]
As illustrated in Figure 6, the frrst die 31 and the frrst punch 41 with which
semi-cutting is performed on the frrst base body 2 are placed such that the fust die 31
and the frrst punch 41 overlap as viewed in the direction of pressing the frrst die 31. If
the clearance C31-41 is set as a positive clearance, cracks that form from edges of the frrst
die 31 and the frrst punch 41 coalesce as with stamping processing in which stamping is
performed once, which raises the possibility that the removed portion 20a is completely
cut from the flange portion 20. Further, a cutting position of the flange portion 20 is
away from the side wa11101 of the barrel portion 10, as a result of which the cut end 13
is not flush with the side wall 1 01, and a step is formed on an exterior of the resultant
processed product 1. By setting the clearance C31-41 to a negative clearance, the
complete cutting of the flange portion 20 (i.e., the removed portion 20a) from the frrst
base body 2 in the semi-cutting process is avoided, so that the cut end 13 and the side
wall1 01 can be made flush with each other.
[0060]
In addition, by setting the clearance C31-41 to a negative clearance, a great
hydrostatic stress is produced in a region that is clamped between the frrst die 31 and
the first punch 41. In stresses produced when the first die 31 is pressed into the flange
portion 20, this decreases a proportion accounted for by a tensile stress that is produced
between a material to be a scrap after cutting processing (i.e., the removed portion 20a)
and a side wall material reserved for the side wall 101 of the barrel portion 10. As a
20
result, a material in contact with an end of an edge of the first die 31, which is to be a
scrap after the cutting processing, tends to move from the end of the edge of the first die
31 to the lateral surface 31 a side of the first die 31, which can increase the extension of
a plating layer 13fl to the shear surface 13c. Further, the reduction in the proportion
of the tensile stress increases a compressive stress, which causes a material that should
otherwise move to a side intended for a scrap to be brought back to a side intended for
the side wall 1 01. As a result, after the cutting processing, a portion reserved for an
end surface 14a of an opening portion 14 is compressed to be flattened.

CLAIMS
[Claim 1]
A processed product formed from a plated steel sheet including a plating layer
on a surface of the plated steel sheet which includes a cut end on a side wall of the
processed product, the side wall being in a hollow-shell cylindrical shape, wherein
the cut end
is flush with an exterior of the side wall of the processed product, and
includes a shear surface, or the shear surface and a rupture surface in
this order in a sheet thickness direction of the cut end, and
a ratio Lltl between a plating component remaining length L by which the
shear surface is covered with the plating layer on the surface and a sheet thickness tl of
the cut end of the processed product is 0. 70 or more.
[Claim 2]
The processed product according to claim 1, wherein a length Wl of the
rupture surface in the sheet thickness direction of the cut end is more than 0 mm to 1.0
mmorless.
[Claim 3]
The processed product according to claim 2, wherein the length Wl of the
rupture surface in the sheet thickness direction of the cut end is 0.5 mm or less.
[Claim 4]
The processed product according to any one of claims 1 to 3, wherein a ratio
Lt/t between a length Lt of a flat surface of an end surface of the processed product
perpendicular to the side wall and a sheet thickness t of the side wall of the processed
product is 0.35 or more.
[Claim 5]
The processed product according to any one of claims 1 to 4, wherein a length
of a burr on the cut end is less than 0.2 mm.
[Claim 6]
The processed product according to any one of claims 1 to 5, wherein
the cut end includes the shear surface, the rupture surface, and a coined surface
58
in this order, or the shear surface and the coined surface in this order in the sheet
thickness direction of the cut end, and
a length W2 of the rupture surface between the shear surface and the coined
surface in the sheet thickness direction of the cut end is more than 0 mm to 0.5 mm or
less.
[Claim 7]
A processed product producing method for producing a processed product for
which a plated steel sheet including a plating layer on a surface of the plated steel sheet
is used as a starting material and that includes a cut end on a side wall of the processed
product, the side wall being in a hollow-shell cylindrical shape, the processed product
producing method comprising:
a semi -cutting process of subjecting a cut portion of a first base body to
semi-cutting in a sheet thickness direction using a first die and a fust punch, the first
base body being formed from the starting material, a clearance between the first die and
the first punch being set to a negative clearance; and
a finish cutting process of subjecting the first base body subjected to the
semi-cutting to finish cutting in a direction identical to a direction of the semi-cutting
using a second die and a second punch, to thereby obtain the processed product
including the cut end that is flush with an exterior of the side wall of the processed
product, wherein
an inner diameter D32 of the second die is made not less than an inner diameter
D31 of the fust die, and
when t1 denotes a sheet thickness of a cut portion of the frrst base body, and t2
denotes a remaining sheet thickness of the cut portion after the semi-cutting process,
in the semi -cutting process,
a clearance C31-41 between the first die and the first punch satisfies
Formula (al) shown below,
a curvature radius Rl of an edge of the first die satisfies Formula (a2)
shown below,
a pressing depth D of the frrst die or the first punch into the cut
59
portion of the first base body satisfies Formula ( a3) shown below, and
a clearance CP-D between the first die and the first punch at a bottom
dead center satisfies Formula (a4) shown below, and
in the fmish cutting process,
a clearance C32-42 between the second die and the second punch
satisfies Formula (aS) shown below, and
a curvature radius R2 of an edge of the second die satisfies Formula
(a6) shown below:
-035 x t1 :s; C31-41 :s; -0.01 (al)
0.10 X t1 :s; Rl :s; 0.50 X t1 (a2)
D <:: 0.70 X t1
CP-D <:: 0.20
(a3)
(a4)
0.01 :s; C32 -42 :s; 0.2 X t2
0.25 :S; R2 :S; 1.50 X t2
(aS)
(a6)
where a unit of C31-41, CP-D, C32-42, and R2 is mm.
[Claim 8]
A processed product producing method for producing a processed product for
which a plated steel sheet including a plating layer on a surface of the plated steel sheet
is used as a starting material and that includes a cut end on a side wall of the processed
product, the side wall being in a hollow-shell cylindrical shape, the processed product
producing method comprising:
a semi -cutting process of subjecting a cut portion of a first base body to
semi-cutting in a sheet thickness direction using a first die and a first punch, the first
base body being formed from the starting material, a clearance between the first die and
the first punch being set to a negative clearance; and
a finish cutting process of subjecting the first base body subjected to the
semi-cutting to finish cutting in a direction identical to a direction of the semi-cutting
using a second die and a second punch, to thereby obtain the processed product
including the cut end that is flush with an exterior of the side wall of the processed
product, wherein
60
an inner diameter D32 of the second die is made not less than an inner diameter
D31 of the first die, and
when t1 denotes a sheet thickness of a cut portion of the first base body, and t2
denotes a remaining sheet thickness of the cut portion after the semi-cutting process,
in the semi -cutting process,
a clearance C31-41 between the first die and the first punch satisfies
Formula (bl) shown below,
a curvature radius Rll of an edge of the first die satisfies Formula
(b2-1) shown below,
a curvature radius R12 of an edge of the first punch satisfies Formula
(b2-2) shown below,
a pressing depth D of the first die or the first punch into the cut
portion of the first base body satisfies Formula (b3) shown below, and
a clearance CP-D between the first die and the first punch at a bottom
dead center satisfies Formula (b4) shown below, and
in the fmish cutting process,
a clearance C32-42 between the second die and the second punch
satisfies Formula (b5) shown below, and
a curvature radius R2 of an edge of the second die satisfies Formula
(b6) shown below:
-OA5 X t1 s; C31-41 s; -0.10 X t1
0.10 X t1 s; Rll s; 0.65 X t1
0.10 X t1 s; Rl2 s; 0.65 X t1
D ~ 0.70 X t1
CP-D ~ 0.20
(b3)
(b4)
(bl)
(b2-1)
(b2-2)
0.01 s; C32 -42 s; 0.2 X t2
0.25 :S; R2 :S; 1.50 X t2
(b5)
(b6)
where a unit of C31-41, CP-D, C32-42, and R2 is mm.
[Claim 9]
The processed product producing method according to claim 7 or 8, further
61
comprising a coining process of pressing, with the processed product provided by the
finish cutting process being used as a second base body, a comer portion of the cut end
of the second base body against a pad, to thereby obtain the processed product with a
coined surface being formed at the comer portion.
[Claim 10]
The processed product producing method according to any one of claims 7 to
9, wherein a difference D32-D31 between an inner diameter D31 of the first die and an
inner diameter D32 of the second die is 1.00 mm or less.
[Claim 11]
The processed product producing method according to any one of claims 7 to
10, further comprising a preparation process of, before the semi-cutting process,
preparing the first base body including a hollow-shell side wall and a flange portion by
subjecting the plated steel sheet being flat to shape processing.