The present disclosure relates to a shearing method for shearing a blank, more
particularly relates to a shearing method able to secure a sheared edge with excellent surface
perpendicularity and surface prope1ties and to suppress tool wear and damage when shearing a
I 0 metal member to be used in automobiles, household electrical appliances, building structures,
ships, bridges, construction machinery, various plants, penstocks, etc.
15
[Background A1t]
[0002]
Shearing is made much use of for manul:1cture of the metal members used in
automobiles, household electrical appliances, building structures, ships, bridges, construction
machinery, various plants, penstocks, etc. FIGS. I and 2 schematically show modes of this
shearing. FIG. I schematically shows the mode of shearing for forming a hole in a blank, while
FIG. 2 schematically shows the mode of shearing for forming an open cross-section in a blank.
20 [0003]
In the shearing shown in FIG. I, a blank 10 is placed on a die 40 (below, also referred to
as a "first blank") and a punch 90 is pushed into the blank I 0 in a sheet thickness direction 90a to
form a hole in the blank I 0. In the shearing shown in FIG. 2, a blank I 0 is placed on a die 40 and
similarly a punch 90 is pushed into the blank I 0 in the sheet thickness direction 90a to form an
25 open cross-section in the blank I 0.
(0004]
Referring to FIG. 3 and FIG. 4, the shape and shaping mechanism of the sheared edge
formed by the mode shown in FIG. I or FIG. 2 are shown. FIG. 3 shows a cross-sectional
schematic view of a sheared edge 19 of a worked material 12 formed by shearing, while FIG. 4
30 shows a cross-sectional schematic view of shearing using a punch 90, die 40, and holder 50 for
obtaining a punched out material II and worked material 12. The sheared edges of the punched
out material II and worked material 12, usually, as shown in FIGS. 3 and 4, are comprised of
shear droops 14, 14', burnished surfaces 15, 15', fi·acture surfaces 16, 16', and burrs 17, 17'. The
shear droop 14 is tormed at the punch side surface 18a of the sheared edge by the blank I 0 being
35 pushed in by the punch 90. As shown in FIGS. I, 2, and 4, a clearance CL is provided between
the punch 90 and die 40 so that the punch 90 and die 40 will not contact when the punch is
:-:';
pushed in the sheet thickness direction 90a. The clearance CL is necessary for seeming a certain
extent of distance for obtaining a contact margin of the punch 90 and die 40. When the punch 90
pushes the blank 10 in the sheet thickne-ss direction' fi.-Ucturcd. A bu1-r 17 is formed at the
. die·side surface 18b of the sheared edge when the blank I 0 drawn. into the clearance CL of the
punch 90 and die 40 fi·actures and separates.
[0005]
A sheared edge generally suffers fi·om the problem of being inferior in surface prope1ties,
lower in fatigue strength, or lower in hydrogen embrittlement resistance compared with a worked
surtace fanned by machining.
[0006]
Numerous techniques have been proposed for solving the problem of a sheared edge.
15 These techniques generally can be divided into ones which specially devise the structures of the
punch and die to tty to improve the surface perpendicularity and surface prope1ties (fatigue
strength etc.) of the sheared edge (for example, see PTLs I to 3) and ones which shave, coin, or
otherwise process the sheared edge to try to improve the surface perpendicularity and surface
prope1ties (fatigue strength, hydrogen embrittlement resistance, etc.) (for example, see PTLs 4 to
20 6).
[0007]
However, in the techniques specially devising the structures of the punch and die, there is
a limit to the improvement of the surface perpendicularity and surface prope1ties of the sheared
edge. Further, in the techniques of processing the sheared edge, the productivity falls and the
25 manufacturing costs rise by the amount of the increase of one step. Fmther, when working a high
strength material, a tool easily suffers fi·om wear, chipping, or other damage.
[0008]
PTL 7 discloses a working method and working apparatus stacking shearing mechanisms
of punches and dies and successively shearing metal sheets placed on the dies by pushing down
30 the punches. In the working method and working apparatus ofPTL 7, the productivity is
improved and the manufacturing costs fall, but it is difficult to raise the surface perpendicularity
and surface propet1ies of the sheared edge of the worked material and the punch and/or die is
damaged when shearing a high strength material.
35
[0009]
NPTL I discloses post processing a punched out material blanked into a predetermined
shape during which placing a blade at the die side and using a punch larger than the die to shave
2
: i'
doubly stacked blanks in an overlaid blanking and shaving method. llowev,er, when blanking
into a predetermined shape, the punch or die is damaged. On top of this, when shaving, the die
with the blade ma)• be danwged.
[0010]
,, In the final analysis, in the prior mt, it is·dimfu'lt'.to shear a material while securing a
sheared edge with excellent surface perpetidictifadiyand surface propetties and suppressing tool
wear and damage.
[Citation List]
I 0 [Patent Literature]
(0011]
15
[PTL I] Japanese Patent Publication No. 2009-051001 A
(PTL 2] Japanese Patent Publication No. 2014-231 094A
[PTL 3] Japanese Patent Publication No. 20 I 0-036195A
[PTL 4] Japanese Patent Publication No. 2008-018481 A
[PTL 5] Japanese Patent Publication No. 20 ll-218373A
[PTL 6] Japanese Patent Publication No. 2006-082099A
[PTL 7] Japanese Patent Publication No. 20 12-115894A
[Nonpatent Literature]
20 [0012]
[NPTL I] Plasticity and Processing, "Research on Shaving and Press Forming"
(Nakamura et al.), Vol. 4, No. 29 (1963), p. 387
[Summary of the Invention]
25 [Problems to be Solved by the Invention]
[0013]
The present disclosure, in view of the current state of the prior mt, has as its technical
problem to manufacture· a worked material (product) having a sheared edge excellent in surface
perpendicularity and surface properties with a good productivity while suppressing wear and
30 damage ofthe tools (punch and die) and has as its object to the provision of a shearing method
and shearing apparatus which solve this problem.
35
(Means for Solving the Problems]
[0014]
The inventors engaged in in-depth studies on techniques for solving the above problem.
As a result, they discovered that if using a punched out material obtained by punching a blank as
3
-', '
10
a punch and/or using the punched worked material as the die, it is possible to manufacture a
worked material (product) having a sheared edge excellent in surface· perpendicularity and
. SUrk1Ce· prop.erties With a good productivity while suppressing tool \vear iuid damage .. "
[0015]
The present invention was made based ci,;:ihe above findings and has as its gist the
following:
[0016]
(I) A shearing method of shearing a blank by a die and a punch, characterized by
comprising:
a first shearing step of placing, on a first die, a first blank having a first surface and a
second surface on an opposite side to the first surt;1cc so that said second surface is arranged on
said first die side, and shearing said first blank fi·01n said tirst surface toward said second surface
in a sheet thickness direction of said first blank by a first punch arranged at said first surface side
to obtain a first punched out material and a first worked material each having a first surface and a
15 second surface corresponding to the first surface and the second surface of said first blank; and
20
a second shearing step of placing a second blank and shearing said second blank to obtain
a second punched out material and a second worked material by (x) using said first punched out
material as a second punch, (i) using said first worked material as a second die, or (z) using said
first punched out material as a second punch and using said first worked material as a second die.
(2) The shearing method according to (I) characterized in that, in said second shearing step,
said first punched out material is placed so that the second surface of said first punched out
material faces said second blank and so that the first surface of said first punched out material is
arranged at said first punch side, and said first punched out material is used as said second punch
to shear said second blank to obtain the second punched out material and the second worked
25 materiaL
(3) The shearing method according to (I) characterized in that, in said second shearing step,
said first punched out material is placed so that the first surface of said first punched out material
faces said second ·blank and so that the second surface of said first punched 'OUt material is
arranged at said first punch side, and said first punched out material is used as said second punch
30 to shear said second blank to obtain the second punched out material and the second worked
material.
( 4) The shearing method according to any one of (I) to (3) characterized in that, in said
second shearing step, said first worked material is placed so that the first surface of said first
worked material faces said second blank and so that the second surt;1ce of said first worked
35 material is arranged at said first die side, and said first worked material is used as said second die
to shear said second blank to obtain the second punched out material and the second worked
4
material.
·(5). "The shearing method according to any one of (I) to (3}characterized in that, in said
second shearing step, said first worked material is placed sd thatthe· second surfa~.:e of said fi•'s1
worked material faces said second blank and so that the first surface of said first worked material
is arranged at said first die side, and;sald·firshvorked material is used as said second die to shcm'· '~
said second blank to obtain the second punched out material and the second worked materiaL
(6) The shearing method according to any one of (I) to (5) characterized in that, in said
second shearing step, a clearance between the punch'used for said second blank and the die used
for said second blank in a direction perpendicular to a sheet thickness direction of said second
I 0 blank is about 0 nun.
(7) The shearing method according to any one of(l) to (6) characterized by further
comprising a third shearing step of shearing a third blank to obtain a third punched out material
and a third worked material by (x) using said second punched out material as a third punch, (y)
using said second worked material as a third die, or (z) using said second punched out material
15 as a third punch and using said second worked material as a third die.
(8) A shearing apparatus having a punch and a die for shearing a blank and shearing said
blank to obtain a punched out material and a worked material, the shearing apparatus comprising
a first punch and a first die, characterized in that said shearing apparatus finiher comprises:
a punched out material reutilization mechanism using a first punched out material
20 obtained by shearing a first blank by said first punch and first die as a second punch when
shearing a second blank,
25
30
a worked material reutilization mechanism using a first worked material obtained
by shearing a first blank by said first punch and first die as a second die when shearing a second
blank, or
a punched out material reutilization mechanism using a first punched out material
obtained by shearing a first blank by said first punch and first die as a second punch when
shearing a second blank and a worked material reutilizationmechanism using a fu·st worked
material·obtained by shearing a first blank by said first punch and first die as a second die when
shearing a second blank.
[Effect of the Invention]
[0017]
According to the present disclosure, it becomes possible to produce a worked material
.(product) having a sheared edge excellent in surface perpendicularity and surf:1ce propctiies with
35 a good productivity while suppressing tool wear and damage.
5
5
10
[Brief Description of the Drawings]
[0018]
_ [FIG:_ I] FIG. I is ·a c•'oss-sectionai schematic vie\\" showing a mode.of sheariiig'tor
·forming a hole in a blank ..
[FIG. 2] FIG. 2 is across"ieCtional schematic view showing a mode of shearing fon"--:i:··· ..
forming an open cross-seetiori in a blank:
[FIG. 3] FIG. 3 is a cross-sectional schematic view of a sheared edge of a blank.
[FIG. 4] FIG. 4 is a cross-sectional schematic. view of shearing for obtaining a punched
out material and worked material.
[FIG. 5] FIG. 5 is a cross-sectional schematic view showing an Embodiment I of
shearing of the present disclosure for obtaining a first punched out material and a first worked
material.
[FIG. 6] FIG. 6 is a cross-sectional schematic view showing an Embodiment I of
shearing of the present disclosure for obtaining a first punched out material and a first worked
15 material.
[FIG. 7] FIG. 7 is a cross-sectional schematic view showing an Embodiment I of
shearing ofthe present disclosure for obtaining a second punched out material and a second
worked material.
[FIG. 8] FIG. 8 is a cross-sectional schematic view showing an Embodiment 1 of
20 shearing of the present disclosure for obtaining a second punched out material and a second
worked material.
[FIG. 9] FIG. 9 is a cross-sectional schematic view showing an Embodiment 2 of the
present method.
[FIG. 10] FIG. 10 is a cross-sectional schematic view showing an Embodiment 2 ofthe
25 present method.
[FIG. 11] FIG. II is a cross-sectional schematic view showing an Embodiment 3 of the
present method.
-- [FIG. 12] FIG. 12 is a cross-sectional schematic view-showing an Embodiment 3 ofthe
present method.
30 [FIG. 13] FIG. 13 is a cross-sectional schematic view showing an Embodiment 4 of the
present method.
[FIG. 14] FIG. 14 is a cross-sectional schematic view showing an Embodiment 4 of the
present method.
[FIG. 15] FIG. 15 is a cross-sectional schematic view showing an Embodiment 5 of the
35 present method.
[FIG. 16] FIG. 16 is a cross-sectional schematic view showing an Embodiment 5 of the
6
',,.
5
10
present method.
[FIG. 17] FIG. 17 is a cross-sectional schematic view showing an Embodiment 6 of the
.present. 111ethod. .,,· .. :· ...
[FIG. 18] FIG. ·18 is a cross-sectional schematic view showing an Embodilhent 6 of the
present method.
[FIG. 19] FIG. 19.is. a· cross-sectional schematic view showing an Embod il\lent Tofthc
present method.
[FIG. 20] FIG. 20 is a cross-sectional schematic view showing an Embodiment 7 of the
present method.
[FIG. 21] FIG. 21 is a cross-sectional schematic view showing an Embodiment 8 of the
present method.
[FIG. 22] FIG. 22 is a cross-sectional schematic view showing an Embodiment 8 of the
present method.
[FIG. 23] FIG. 23 is a cross-sectional schematic view showing an Embodiment 9 of the
15 present method.
[FIG. 24] FIG. 24 is a cross-sectional schematic view showing an Embodiment 9 of the
present method.
[FIG. 25]FIG: 25 is a cross-sectional schematic view showing an Embodiment 9 of the
present method.
20 [FIG. 26] FIG. 26 is a cross-sectional schematic view showing an Embodiment 9 of the
present method.
[FIG. 27] FIG. 27 is a cross-sectional schematic view showing an Embodiment I 0 of the
present method.
[FIG. 28] FIG. 28 is a cross-sectional schematic view showing an Embodiment I 0 of the
25 present method.
[FIG. 29] FIG. 29 is a cross-sectional schematic view showing an Embodiment II of the
present method.
[FIG. 30]FIG. 30 is a cross-sectional schematic·view showing an Embodiment II of the
present method.
30 [FIG. 31] FIG. 31 is a cross-sectional schematic view showing an Embodiment 12 of the
present method.
[FIG. 32] FIG. 32 is a cross-sectional schematic view showing an Embodiment 12 ofthc
present method.
[FIG. 33] FIG. 33 is a cross-sectional schematic view showing an Embodiment 12 of the
35 present method.
[FIG. 34] FIG. 34 is a cross-sectional schematic view showing an Embodiment 12 of the
7
present method.
[FIG. 35] FIG. 35 is a cross-sectional schematic view showing an Embodiment 13 ofthe
. present method,::·' __ ·,_. :_:
[FIG.36JFIG.36 is a cross-sectional schematic view showing an E1i1bodiment 14 of the
5 present method.·· /·"· ·: · ,.,,,:,:._.,_.· ·
[FIG. 37] FIG .. J7 is'a cross-sectional schematic view showing an Eiribodili1ent 14 of the
present method.
[FIG. 38] FIG. 38 is a cros·s-scctional schematic view showing an Embodiment 14 of the
present method.
10 [FIG. 39] FIG. 39 is a cross-sectional schematic view showing an Embodiment 14 of the
present method.
[FIG. 40] FIG. 40 is a cross-sectional schematic view showing an Embodiment 15 of the
present method.
[FIG. 41] FIG. 41 is a cross-sectional schematic view of a punch provided with an
15 electromagnet.
20
[FIG. 42] FIG. 42 is a cross-sectional schematic view of a punch provided with
electro magnets.
[FIG. 43] FIG.ATis a Ci·oss-sectional schematic view of a punch provided with a suction
part.
[FIG. 44] FIG. 44 is a cross-sectional schematic view of a punch provided with suction
.parts.
[FIG. 45] FIG. 45 is a schematic view showing a measurement position of residual stress
at a sheared edge.
[FIG. 46] FIG. 46 is a cross-sectional photograph of a first worked material obtained by
25 shearing by the prior mi.
' 30
[FIG. 47] FIG. 47 is a cross-sectional photograph of a second worked material obtained
by shearing by an Embodiment I.
[FIG. 48] FIG. 48 is a cross-sectional photograph of a second worked material obtained
by shearing by an Embodiment 2.
[FIG: 49] FIG. 49 is a cross-sectional photograph of a second worked material obtained
by shearing by an Embodiment 5.
[FIG. 50] FIG. 50 is a cross-sectional photograph of a second worked material obtained
by shearing by an Embodiment 6.
[FIG. 51] FIG. 51 is a graph measuring the average residual stress of a sheared edge of a
35 second worked material.
8
[Description of Embodiments]
[0019]
The• shearing method of the present disclostJre{below, also referred to as "the present
method") and shearing apparatus of the same (below, also referred.ti:i as "the present apparatus")
5 have as.theit,basic itlea to use at least one of the punched out material and worked material
obtairied by shcat'iitg a blank as at least one tool among the punch and die iti the shearing of the
next blank.
[0020]
The present method is a shearing method for shearing a blank by a die and a punch, and
I 0 comprises a first shearing step and a second shearing step. In the first shearing step, a first blank
having a first surface and a second surface at the opposite side to the first surface is placed on a
first die so that the second surface is placed on the first die side. Next, the first blank is sheared
fi·orn the first surface toward the second surface in the sheet thickness direction of the first blank
by a first punch arranged at the first surface side to obtain a first punched out material and a first
15 worked material each having a first surface and a second surface corresponding to the first
surface and the second surface of the first blank. At the second shearing step, a second blank is
placed and (x) the first punched out material is used as a second punch, (y) the fu·st worked
material is used as a secoitif die, or (z) the first punched out material is used as a second punch
and the first worked material is used as a second die, to shear a second blank to obtain a second
20 punched out material and a second worked material.
[0021]
Below, the present method will be suitably explained based on the drawings.
[0022]
In the present method, the first and second blanks are usually metal blanks able to be
25 sheared. The first and second blanks may include nonmetallic blanks if able to be sheared. For
example, they may also be laminated steel sheets including resin layers. The metal blanks able to
be sheared may be ferrous or ferrous alloy metal sheets or nonferrous or nonferrous alloy metal
sheets. The first and second blanks are preferably ferrous or ferrous alloy metal sheets, more ,. ·
preferably metal sheets having a 340 MPa class or more, more preferably 980 MPa class or more
30 tensile· strengths, stillmore preferably steel materials having the above tensile strengths. In metal
sheets having 340 MPa class or more tensile strengths, in particular measures against fatigue
fi·acture become necessary. In metal sheets having 980 MPa class or more tensile strengths,
measures against hydrogen embrittlement cracks also become necessary. In particular, when the
blank is a steel material, measures against hydrogen cmbrittlement cracks and fatigue fi·acture
35 become important. The present method can be similarly used for shearing a third blank as
explained later. The material of the third blank is similar to the materials of the first and second
9
,.--· -. -··
blanks.
[0023]
(Embodiment I)
. PIGS. 5 to 8 show one embodiment of the shearingofthe present method. In the one
5 embodiniei1tofthe shearing of the present method, the first sheacingshown in FIGS. 5 and 6
(conveiltiot\al shearing) is performed, then the second slieariiig show1i in FIGS. 7 and 8 is
performed.
[0024]
In the first shearing shown in FIGS. 5 and 6, a first blank 10 having a first surface 101
I 0 and a second surface I 02 on the opposite side is placed between a first die 40 and a tirst punch
90 so that the first surface is arranged on the first punch 90 side and the second surface I 02 is
arranged on the first die 40 side. The first punch 90 punches the first blank I 0 fi·om the first
surface 101 toward the second surJ:1ce 102 of the first blank 10 to thereby obtain a first punched
out material II and a first worked material 12. The first punched out material I I has a first
15 surface Ill and a second surface 112 corresponding to the first surface I 0 I and the second
surface 102 of the first blank 10. The first worked materiall2 also has a first surface 121 and a
second surJ:1ce 122 corresponding to the first surface I 0 I and the second surface I 02 of the first
blank. A holder 50 holds down the first blank 10 fi·om the first surface I 0 I side toward the first
die 40 side to fasten the first blank 10 at the time of punching by the first punch 90. FIGS. 5 and
20 6 show the holder 50, but the holder 50 can be configured in any way. In the following
explanation, the same is true unless particularly indicated otherwise.
[0025]
In the second shearing shown in FIGS. 7 and 8, the first punched out material II punched
out in the first shearing step is used as a second punch in the punched out state without changing
25 its orientation. In more detail, the first punched out material II is placed between the first punch
90 and the second blank 20 so that the second surface 112 of the first punched out material II
faces a predetermined punching location at the second blank 20 and the first surface Ill faces
· the tirst punch 90. From this state, the first punch 90 pushes down the first punched out material
II as the second punch and punches the second blank 20 fi·om the first surface 20 I toward the
30 ·· second surface 202 of the second blank 20 to thereby obtain the second punched out material21
and the second worked material 22. Here, the first punched out material having the second
surtace 112 at the second blank 20 side and having the first surface !! l at the tirst punch 90 side,
that is, "the first punched our material in the punched out state", will also be referred to ·as the
first punched out material !! or the first non in vetted punched out material II.
35 [0026]
In the second shearing step shown in FIGS. 7 and 8, when shearing the second blank 20
!0
placed on the first die 40, the first non inverted punched out material II is placed at the scheduled
punching location and used as a second punch to shear the second blank 20 and obtain a second
-_ punched out material 21 and a second worked material2-2: The first non inverted punched out
-- .material II is work hardet\ed when punching it by the first shearing step. Fut1her, it is pushed in
5 -·.b~·,thd1rst punch 90, so even if the second blank 20isthe'cand-.7, means the clearance in the direction perpenditt>lal:·td'the sheet thickness direction of the
blahk between the punched out material used astheJirsLpunch or the second punch and the
·worked material used as the first die or the second die:· The clearance CL being about 0 n11n
means the clearance between the punch and die is preferably within ±I% ofthe sheet thickness,
more preferably within ±0.5% of the sheet thickness, still more preferably within ±0.1% of the
l 0 sheet thickness, stillmore preferably substantially 0.
(0031]
Normally, as shown in FIG. 5, if the clearance CL is large, during shearing, tensile stress
is generated at the location being sheared and a fi·acture surface (see numerals "16" and "16"' in
FIGS. 3 and 4) where voids causing ductile fi·acture easily occur is formed.
15 [0032]
On the other hand, as shown in FIG. 7, if the clearance CL is small, preferably if it is
about 0 mm, during shearing, it becomes difficult for tensile stress to form at the location being
sheared, formation of a fi·acture surface where voids causing ductile fi·acture easily occur is
suppressed, and shearing becomes possible. The thus formed sheared edge has excellent surface
20 perpendicularity, has excellent surface prope1ties with suppressed residual tensile stress, and is
excellent in hydrogen embrittlement resistance and fatigue characteristics.
[0033]
Below, other embodiments will be explained. In the following explanations of the
embodiments, common explanations of the first shearing will be omitted.
25 [0034]
(Embodiment 2)
FIGS. 9 and I 0 show another embodiment of the second shearing step in the shearing of
the present method. The first punched out material II punched out at the first shearing step
shown in FIG. 6 may be inverted fi·om the punched out state and used as the second punch in the
30 second shearing step. Here, the first punched out material having the first surface Ill at the
second blank 20 side and the second surface l 12 at the first punch 90 side, that is, the "tirst
punched out material inve1ted fi·om the punched out state", will also be referred to as the "tirst
punched out material II"' or the "first inve1ted punched out material II'". In the second shearing
step shown in FIGS. 9 and l 0, the first punched out material II punched out in the first shearing
35 step is inverted fi·om the punched out state and used as the second punch. In more detail, the first
inverted punched out material ll' is placed between the tirst punch 90 and the second blank 20
12
so that the first surface Ill faces the scheduled punching location at the second blank 20 and so
·that the second surface 112 faces the first punch 90. From this state, the first punch 90 pushes
down the first inverted punched .out mated~ I II' as the second. punch and punches the. second
blank 20 fi·om the first surface 20 I to the second surf:~ce 202 of the second blank 20 to thereby
·.. ·.,·,.:•·• 5•?'··· • . obtain the second punched out material 21. ana·i·lr0•S<''1il.m··:'':ix'·.-
The present method includes any one of the E1ribodi1i1ents I to 8. The Embodiments I, 3,
5, and 6 to 8 arc preferable, while the Embodiments I and 6 to 8 are more preferable. In the
Embodiments I to 8, the average residual stress at the sheared edge can be made smaller than the
past, while in the Embodiments I, 3, 5, and 6 to 8, it may be made even smaller. In particular, in
I 0 the Embodiments I and 6 to 8, it is possible to make the average residual stress at the sheared
edge the compression side.
[0052]
(Embodiment 9)
The present method preferably comprises a third shearing step of shearing a third blank
15 to obtain a third punched out material and a third worked material by (x) using the second
punched out material as a third punch, (y) using the second worked material as a third die, or (z)
using the second punched out material as a third punch and using the second worked material as
a third die.
20
[0053]
The second punched out material and the second worked material, in the same way as the
first punched out material and the first worked material, can be used as the third punch and the
third die in the noninve1ted or inverted state. The second punched out material used as the third
punch and the first worked material used as the second die or the first die may be combined for
use, while the second worked material used as a third die and the first punched out material used
25 as the second punch or the first punch may be combined for use. The combination is not
pmticularly limited so long as a combination where the clearance between the first punch or the
punched out material used as the second or later punches and the first die or the worked material
used as the second or later dies becomes smaller compared with the conventional shearing shown
in FIG. 5.
30 [0054]
The sheared edges of the second punched out material and the second worked material
are excellent in surface perpendicularity and surface properties as explained above. Therefore,
the third worked material can be given a sheared edge more excellent in surface pe.l'pendicularity
and surface properties .. The third punched out material similarly can also be given a sheared edge
35 more excellent in surface perpendicularity and surface properties. Further, since the second
punched out material is used as the third punch and/or the second worked material is used as the
20
.:...:.1''
third die, it is possible to manufacture a worked material (product) with a good productivity
while suppressing wear and damage of the tool (the first punch and/or the first· die);
[0055]
FIGS. 23 to 26·illustrate two embodiments ofthethird shearing with respect to the third
· 5.•.'.fH\l,jj)a'ilk{ but the invention is not limited to these combinat'iotisr HIGS. 23 and 24 show an
.eihbodiment placing the second worked material22 obtained in the Embodiment I shown in
· · FIGS .. 7 and 8 between the first die 40 and the third blank 30 and using it as the third die. In
FIGS. 23 m1d 24, the first punched out material II used in the Embodiment I shown in FIGS. 7
and 8 is again used as the second punch to shear the third blank 30 and obtain the third punched
I 0 out material 31 and worked material 32. FIGS. 25 and 26 show an embodiment arranging the
second worked materia122 obtained in the Embodiment I shown in FIGS. 7 and 8 between the
first die 40 and the third blank 30 and using it as the third die. In FIGS. 25 and 26, the first
punched out material used in the Embodiment I shown in FIGS. 7 and 8 is inve1ted to obtain the
first inve1ted punched out material II' for use again as the second punch to shear the third blank
15 30 and obtain the third punched out material 31 and the third worked material32.
[0056]
In the third shearing step illustrated in FIGS. 23 to 26 as well, as shown by the broken
lines in FIGS. 23 and 25, it is possible to make the clearance CL between the outside diameter of
any of the first punched out material II or the first inverted punched out material II' used again
20 as the second punch and the inside diameter of the first die 40 smaller than the clearance CL
between the outer shape of the first punch 90 and the inside diameter of the first die 40,
preferably make it about 0 mm. Therefore, in the same way as the Embodiments I to 8, the third
worked materia132 can be formed with a sheared edge having excellent surface perpendicularity,
having excellent smface propetties with suppressed residual tensile stress, and excellent in
25 hydrogen embrittlement resistance and fatigue characteristics.
[0057]
In the third shearing step illustrated in FIGS. 23 to 26, the first punched out material used
again as the second punch and the second worked material used as the third die have·sheared
edges excellent in surface perpendicularity and surface properties as explained above. For this
30 reason, the third worked material 32 can be given a sheared edge more excellent in surface
perpendicularity and surface properties. The third punched out material 31 as well can similarly
be given a sheared edge better in surface perpendicularity and surface prope1ties. Flllther, if
using the first punched out material as the second punch and using the second worked material as
the third die, it is possible to manufacture worked materials (products) with a good productivity
35 while suppressing wear and damage of the tools (first die 40 and first punch 90).
[0058]
21
In the same way as the Embodiment 9, it is possible to shear a fourth and later blanks.
That is, it .isvossible to use the punched out material as a punch or use the worked material as a
die .10~: repeated reuse. !fa p11nched out material and worked material are used a larger.nnmbqr of ""';
times, the end face prope1ties deteriorate, so the upper limit of the number oftimes of repeated
; ·;\,,,s. ·.;c·. use can be made within 100 times or within JO·tilli::".c';i· ... ,.,.
it is preferable to not separate the fii·st punched out material I I, first worked material 12, and ·
fastening jig 60 but to use them to shear the second blank while maintaining the assembled state
after shearing. !fusing the invet1ed worked materiall2' as the positioning member ofthe
punched out material, the punched out material is preferably used as an inverted punched out
I 0 material II'. The fit between the shear droop of the punched out material and the shear droop of
15
the worked material is high, so positioning the punched out material used as the second punch
and suppressing deviation of the punched out material in the direction perpendicular to the
punching direction become easier.
[0063]
(Embodiment II)
FIGS. 29 and 30 show another embodiment of the shearing of the present method. As the
positioning jig of the punched out material used as the second punch, it is possible to use the
worked materiai.'FIG. 29 shows an embodiment in which in the second shearing step shown in
FIGS. 7 and 8, the fastening jig 60 is arranged at the outer circumference of the second blank to
20 fasten the second blank while shearing the second blank to obtain the second punched out
material21 and the second worked material 22.
[0064]
FIG. 30 shows an embodiment using the second punched out material 21 obtained in the
second shearing step as the third punch to shear the third blank 30 in the third shearing step
25 while fastening the outer circumference of the third blank 30 and the outer circumference of the
second worked material 22 obtained in the second shearing step shown in FIG. 29 by the
fastening jig 60 arranged at the same position as the second shearing step.
[0065]
The fastening jig 60 can fasten the outer circumference of the second worked material22
30 at the same position as the second shearing step. For this reason, the relative position of the
second worked material22 with respect to the inside diameter of the first die 40 in the direction
perpendicular to the punching direction becomes the same at the time of the second shearing and
the time of the third shearing. For this reason, it is possible to arrange the second punched out
materia121 at the center position of the punched hole of the second worked material 22 in the
35 direction perpendicular to the punching direction. Therefore, it is possible to accmately position
the second punched out material2l with respect to the inside diameter of the fu·st die 40 in the
23
,,' ,., 5
. direction perpendicular to the punching direction and possible to perform the third shearing of
.the,third blank 30 while suppressing deviation of the second punched out material21 in the
· dircctioil perpendic..ular to the punching direction .. The second worked material.22 can also.8.ct as
a holder for holding down the. third blank 30 at the time of shearing.
[0066]
The second punched out n\aterialmay be used as a non inverted punched out materia121
or inve1ted punched out material21 '. Instead of the second punched out material, the first
punched out material may also be used. In each combination, it is possible to accurately position
the punched out material with respect to the inside diameter of the first die 40 in the direction
I 0 perpendicular to the punching direction and possible to perform shearing while suppressing
deviation of the punched out material in the direction perpendicular to the punching direction.
[0067]
In the shearing of the Embodiments I 0 and II shown in FIGS. 27 to 30, the clearance CL
between the inside diameter of the first die 40 and the outside diameter of the first punched out
15 material II used as the second punch or the outside diameter of the second punched out material
21 used as the third punch can be made smaller, preferably can be made about 0 mm. Therefore,
it is possible to form at the worked material (product) a sheared edge having excellent surface
perpendicularity, "having excellent surface properties with suppressed residual tensile stress, and
excellent in hydrogen embrittlement resistance or fatigue characteristics.
20 [0068]
(Embodiment 12)
A first punch provided with projecting pmts at the punching surface can be used to shear
the first blank (first shearing) while making the projecting parts bite into the first surface of the
first blank to obtain a punched out material and worked material. Next, the punched out material
25 fastened to the punching surface of the first punch by engagement of the projecting parts can be
used as a second punch to shear the second blank (second shearing). FIGS. 31 to 34 show
another embodiment of shearing of the present method.
[0069]·
In FIGS. 31 and 32, the fu·st punch 90 provided with the projecting pmts 80 at the
30 · punching. surface is used to shear the first blank 10 (first shearing) while making the projecting
parts 80 bite into the first surface 101 ofthe first blank 10 to obtain the tirst punched out material
II and the first worked material 12. By the projecting parts 80 biting into the first surface Ill of
the first punched out material II, the first punched out material II is fastened to the punching
surf:~ce of the first punch 90.
35 [0070]
In FIGS. 33 and 34, the first punched out material II t:~stened to the punching surface of
24
the first punch 90 by engagement of the projecting parts 80 is used as a second punch to shear
"' "'' , ... - the second blank 20 (second shearing) to obtain the second punched out material 21 and the
5
second. "~otked,matei'iUI22•t ··'·-·
[0071]
If providing the projecrlng;pmis 80 at the punching surface of the first punch 90;•the·lirst· "
punched out material"ll i"s tasteiH~d at the punching surface of the first punch 90; so iftlsitig'the
first punched out material II as the second punch, it is possible to easily position the first
punched out material II with respect to the inside diameter of the first die 40 in the direction
perpendicular to the punching direction.
I 0 [0072]
(Embodiment 13)
A first punch provided with projecting pmis and a back holder arranged at the second
surface side of the first blank so as to face the first punch can be used to sandwich and fasten the
first blank while shearing it to obtain the first punched out material and the first worked material.
15 FIG. 35 shows another embodiment of shearing of the present method.
[0073]
In FIG. 35, the first blank I 0 is sandwiched by the first punch 90 provided with the
projecting patis 80 at the punching surface and the back holder 70 arranged at the second surface
I 02 side of the first blank I 0 so as to face the first punch 90. The first blank I 0 is sheared (first
20 shearing) while making the projecting patis 80 bite into the first surface 101 of the first blank 10
to obtain the first punched out material and the first worked material." The back holder 70 is
preferably held by an elastic member 71.
[0074]
FIG. 35 shows an embodiment additionally using the back holder 70 for the shearing
25 shown in FIG. 31, Due to the back holder 70, it is possible to sandwich and fasten the first blank
I 0 by the punching surface of the first punch 90 provided with the projecting patis 80 and the
back holder 70, so even after punching, the first punched out material can be sandwiched and
"·fastened. For this reason, it is possible to prevent the first vunched out material from being
detached from the punching surface of the first punch 90 provided with the projecting patis 80.
30 After the shearing shown in FIG. 35, the first punched out· material can be fastened sandwiched
by the punching surface of the first punch 90 provided with the projecting parts 80 and the back
holder 70 while, in the same way as the embodiment shown in FIGS. 32 to 34, the first blank 10
and the second blank 20 arc sheared (second shearing).
[0075]
35 (Embodiment 14)
A first die provided with projecting parts at the surf:~ce contacting the second surf:~ce of
25
the blank (below, also referred to as the "holding surface") can be used to shear the first blank
. -.-.·. while making the projecting parts bite into the second surface of the first blank so as to obtain a
punckd.outniatediil·and worked materiaL Next, the worked.mateJ:.ial fastened:~o the holding
surface of the first die· by the engagement of the projecting parts can be used as the second die to
5 shear the second blankt0sccond.shearing) to obtain a second punched out material"ahrl'second
worked materiaL FIGS. 36_ to 39 show another embodiment of shearing of the pi·eseilt ·method.
[0076]
In FIGS. 36 and 37, the first die 40 provided with projecting pmts 80 at the holding
surface is used to shear the first blank (first shearing) while making the projecting pa1ts 80 bite
I 0 into the second surface of the first blank to obtain the first punched out material II and the first
worked material 12 fastened to the holding surface of the first die 40 by the engagement of the
projecting pmts 80.
[0077]
FIGS. 38 and 39 show using the worked material 12 fastened to the holding surface of the
15 first die 40 by engagement of the projecting pa1ts 80 as the second die to shear the second blank
20 (second shearing) to obtain the second punched out material2l and the second worked
material 22.
[0078]
If providing the projecting pmts 80 at the holding surface of the first die 40, the first
20 worked material 12 is fastened to the fu·st die 40, so if using the first worked material 12 as the
second die, it is possible to easily position the first worked material 12 with respect to the first
punch 90.
[0079]
In the embodiments illustrated in FIGS. 36 to 39, a holder 50 may be used or may not be
25 used, but preferably a holder 50 is used. It is possible to sandwich and fasten the first blank 10
between the holder 50 and the first die 40 and sandwich and fasten the first worked material 12
even after being punched. For this reason, it is possible to prevent the first worked material 12
fi·om detaching or deviating in position fi·om the holding surface of the first die 40 provided with
the projecting pmts 80.
30 [0080]
The embodiment illustrated in FIGS. 31 to 35 and the embodiment illustrated in FIGS. 36
to 39 may be combined.
]0081 1
The shape of the projecting pmts may be any one which can restrain the blank. It may be
35 a projection, relief, surface treated surface, or other shape increasing the fi·ictional resistance.
The method of forming the projection, relief, or surface treated surface is not particularly limited,
26
5
but for example can be made as follows: A projection can be formed by embedding a pin having.
a projecting shape at its tip. The relief cmrbc formed by cutting to form I 0 f.!m to 500 f.!m
grooves in tlie'surface contacting the steel sheet. The.surface . treated surface can be formed by
sandblasting or another method of increasing the fi·ictionalresistance;
[0082]
The heighfofthe projecting parts in the sheet thickness direCtion of the. blank is
preferably I 0 to 500 f.!m. The circle equivalent diameter of the projecting parts in the direction
perpendicular to the sheet thickness direction of the blank is preferably 10 to 500 f.!m. The higher
the height of the projecting parts, the stronger the restraining force can be made, but the
I 0 projecting parts easily become greater in wear. Further, the load necessary for biting into the
blank becomes greater. The smaller the circle equivalent diameter of the projecting pmts, the
smaller the load necessary for making the projecting pmts bite into the blank, but the projecting
parts easily become greater in wear. The smaller the number of the projecting parts (density), the
smaller the load necessary for making them bite into the blank, but the restraining force is
15 weakened.
[0083]
(Embodiment 15)
Part of the 'first punch may also be provided with electromagnets. FIG. 40 shows another
embodiment of shearing of the present method. FIG. 40 shows a mode of shearing using a first
20 punch 90 provided with an electromagnet 92 at patt. By arranging the electromagnet 92 inside
the first punch 90, it is possible to draw the first blank and the first punched out material together
by the electromagnetic force and, in the same way as the case of providing the projecting parts at
the first punch, possible to easily position the first punched out material used as the second
punch.
25 [0084]
The electromagnet 92 in the first punch 90 may be arranged at a desired position other
than the blade 91. FIGS. 41 and 42 show cross-sectional schematic views of the first punch 90
with different arrangements of electromagnets 92. The first punch 90 is preferably provided with
two or more electromagnets 92. By the first punch 90 being provided with two or more
. 30 electromagnets 92, it is possible to suppress more the drop off or deviation of the blank and
punched out material due to the eftect of momentum. The first punch 90 of FIG. 41 includes one
electromagnet 92 inside it, while the tirst punch 90 of FIG. 42 includes two electromagnets 92
inside it. For this reason, the first punch 90 ofF! G. 42 suppresses drop-off and deviation of the
blank and punched out material more than the first punch 90 ofF! G. 41. However, the first
35 punch 90 should be small in dimension in the direction perpendicular to the punching direction
so as to reduce the scrap and improve the yield. The number of the electromagnets 92 is
27
preferably two to four.
[0085] ,-,• .
. . The material of the electromagnets is not .pmticularly limited so long as one able to tasten
the blank and punched out material, but the electromagnets preferably have a maximum
5 attraction foroo_,)f50N or more per I kg weight of punched out.materialj:morc preferably SOON
or mot·c per I kg weight of punched out material. The shapes of the electr;oinagnets are not
particularlydimited·so long as ones arranged at the inside ofthe first punch and able to fasten the
blank, but preferably they have substantially columnar shapes concentric with the first punch.
For example, it is possible to use round electromagnets FSGP® made by Fujita.
I 0 [0086]
The first punch may be provided with electromagnets and have the above projecting parts
at the punching surface and may be combined with the above back holder.
[0087]
The first die may be provided with electromagnets. Even in this case, it is possible to use
15 the magnetic force to pull together the blank and worked material and, in the same way as the
case of providing the projecting parts at the first die, possible to easily position the worked
material used as the second die.
20
[0088]
(Embodiment 16)
Part of the first punch may also be provided with suction parts. FIGS. 43 and 44 show
cross-sectional schematic views of the first punch 90 provided with suction parts 94 inside it. By
arranging the suction paris 94 at the inside of the first punch 90, it is possible to pull against the
blank by suction. In the same way as the case of providing projecting parts at the first punch or
the first die, it is possible to easily position the first punched out material used as the second
25 punch.
[0089]
The suction part 94 in the first punch 90 can be placed at a desired position other than the
blade 91. The first punch 90 is preferably provided with two or more suction parts 94. By the
first punch 90 being provided with two or more suction parts 94, it is possible to suppress more
30 the drop off or deviation of the blank and punched out material due to the effect of momentum.
The first punch 90 ofF1G. 43 includes one suction part 94 at the inside, while the first punch 90
ofF! G. 44 includes two suction parts at the inside. For this reason, the first punch 90 ofF! G. 44
can suppress drop off or deviation of the blank and punched out material more than the first
punch 90 ofFlG. 43. However, the first punch 90 should be small in dimension in the direction
35 perpendicular to the punching direction so as to reduce the scrap and improve the yield. The
number oft he suction parts 94 is preferably two to four.
28
[0090]
The configuration of the suction parts 94 is not pmiicularly limited so long as able·to
fasten the blank·and punched out material, .. buLthc suction p~rts 94 preferably have a maximunL
suction -force of SON or more per I kg weight of punched' oi1t material, more preferably SOON or
S . ·.Inore·j).enhkg weight of punched out material. The shape.nf th'iin;uation .. pmts 94 is not
· particula'rly limited so long as the pmts arc arranged at the ilisioc of the first punch 90 and can
· fastewthe blank, but, for example, it is possible to use Freeholder® made· by Nihon Pisco.
[0091]
The first punch may be provided with suction parts at pmi and have projecting parts on
I 0 the punching surface. It may also be combined with the above back holder.
(0092]
The first die may be provided with suction parts. In this case as well, the blank and
worked material can by pulled against by suction force. In the same way as when providing the
projecting pmts at the first die, it is possible to easily position the worked material used as the
IS second die.
[0093]
The present method can be performed by combining as desired embodiments selected
fi·mn at least one of the E1nbodiments 10 to 16, any one of the Embodiments I to 8, and the
Embodiment 9.
20 [0094]
The blank has a hole expansion rate/, of preferably over I%, more preferably overS%,
stillmore preferably over I 0%. By having the above range of hole expansion rate/,, a longer
burnished surface can be obtained. !fusing a first punch including electromagnets, the blank is a
material attracted by electromagnetic force.
2S [0095]
30
As explained above, the present method has as its basic idea to use the punched out
material as a punch in the punched out state or inve1tcd fi·om the punched out state and/or to use
the worked material as a die in the punched state or inverted fi·om the punched state.
[0096]
In the present method, in this way, the punched out material is used as a punch and/or the
worked material is used as a die, so the wear and damage of the first punch and/or the first die
can be reduced and the clearance CL can be reduced. Preferably it can be made about 0 mm, so it
is possible to form a sheared edge excellent in surface perpendicularity and surface propc1ties at
the worked material.
3S (0097]
The present disclosure lint her covers a shearing apparatus. The present apparatus is a
29
.........
shearing apparatus having a punch and a die for shearing a blank and shearing the blank to obtain
a punched·out material and a wor·ked material. The shearing apparatus is provided with a first
· .. ; punch and a first die. Th~ shcaring.appllxatm has a prinched mit material reutilizatiqn
·mechanism, a worked riiaterial reutilization mechanis1i1, or both mechanisms. The punched out
- .5 -c:<:•:•:malcrial reutilization mechanism is a mechanism using a•.first,pimched out material obtained by
-sh'earilig a first blank by the first punch and a first die as' the secoiid punch when shearing the
· .~;secondblank. The worked material reutilization mechanism is·a mechanism using a first worked
material obtained by shearing the first blank by the first punch and the first die as a second die
when shearing the second blank.
10 [0098]
The configuration of the punched out material reutilization mechanism is not limited so
long as having a mechanism for using the first punched out material as the second punch when
shearing the second blank. Similarly, the configuration of the worked material reutilization
mechanism is not limited so long as having a mechanism for using the first worked material as
15 the second die when shearing the second blank. The configurations of the punched out material
reutilization mechanism and worked material reutilization mechanism preferably may have
configurations selected fi·01n a configuration corresponding to at least one of the Embodiments
1 0 to 16 of the sheai·ing method, a configuration corresponding to any one of the Embodiments l
to 8, and a configuration corresponding to the Embodiment 9 in the desired combination.
20 [0099]
The shearing apparatus can be provided with a first punch, a first die, a blank placement
mechanism able to automatically place the first blank at the shearing pari, a punched out material
rcutilization mechanism placing the first punched out material obtained by the first shearing at a
scheduled punching location at the first punch side of the second shearing performed next, and a
25 worked material reutilization mechanism placing the first worked material obtained by the first
shearing at a scheduled punching location at the first die side of the second shearing performed
next.
[0100[
The shearing apparatus preferably is provided with a first punch and back holder able to
30 sandwich and fasten the first blank and a first die and holder.
[0101]
The punched out material reutilization mechanism preferably is provided with a robot
arm for placing the first punched out material obtained in the first shearing at a scheduled
punching location. of the first punch side of the second shearing performed next.
35 [0102[
The punched out material reutilizationmechanism preferably includes at least one of a
30
first punch having projecting parts at the punching surface and a first punch provided with
electromagnets or· suction pmts. The first punch having projecting pmts-at-the punching surface
can bite into the first blank ancUh.e first punclie.d out material by.the projeCting pmts to holrl.the · ......
first punched out material at the punching surface of the first punch. The first punch provided
.... ·i;c!i\><"-''"·' .with electromagnets or suction parts can pull.the first-blank-and the first punched out material to ·'. ·,_,.
the punching surface of the first punch to hold them.
. . . [0103)
·The \Vorked material reutilization mechanism is preferably provided with a robot ann for
placing the first worked material obtained by the first shearing at the scheduled punching
10 location of the first die side of the second shearing performed next.
[0104)
The worked material reutilization mechanism preferably includes at least one of a first
die having projecting patts at a holding surface and a first die provided with electromagnets or
suction parts.
15 [0105)
The worked material reutilization mechanism ftnther can place the first worked material
obtained by the first shearing as a holder for the second shearing to be performed next. The
worked material reutilization mechanism is preferably provided with a robot arm for placing the
first worked material at the holder pmt.
20 [0106)
The punched out material reutilization mechanism and worked material reutilization
mechanism preferably can place the first punched out material and the fu·st worked material afier
the first shearing, without separating them, at the scheduled punching location and holder
location of the fu·st punch side of the second shearing performed next.
25 [0107)
The shearing apparatus may be provided with a punched out material takeout mechanism
for removing the first punched out material instead of a punched out material reutilization
mechanism. The punched out material takeout mechanism has a configuration similar to the
punched out material reutilization mechanism except for taking out and ejecting the first punched
30 out material. The shearing apparatus may be further provided with a worked material takeout
mechanism for taking out the first worked material instead of the worked material rcutilization
mechanism. The worked material takeout mechanism has a configuration similar to the worked
material reutilization mechanism except for taking out and ejecting the tirst worked material.
35
[01 08)
In addition, the above description explaining the configuration of the shearing method
can also be applied to the configuration of the present apparatus.
31
'.:·
[Examplesl· ·
. . [0109) . '·'
Next, examples of the presentinvention will be explained. The conditions in the
examples are an illustration ofconditiom;:emplo·ycd for confirming the workability and effects of. < '.'otira"''il''
the present invention. The present in\'ention is not limited to this illustration of conditions. The
10
··.: · present invention can employ various conditions without depmting fimn the gist of the present
invention so long as achieving the object of the present invention.
(OliO]
A diameter I 0.00 mm first punch and inside diameter 10.32 mm first die were used to
shear a first steel sheet having a 1.6 nnn thickness and having a tensile strength of 1180 MPa to
obtain a first punched out material and first worked material. The obtained first punched out
material was used as a second punch and/or the obtained first worked material was used as a
second die to shear a second steel sheet having a 1.6 mm thickness and having a tensile strength
15 of 1180 MPa to obtain a second punched out material and second worked material.
[0111]
Specifically, in the first shearing method (conventional shearing method) shown in FIGS.
5 and 6, the first steel sheet was sheared to obtain the first worked material. Fmther, after the
first steel sheet was sheared to obtain the first worked material, the second shearing method
20 shown in the Embodiments I to 8 shown in FIGS. 7 and 8, FIGS. 9 and 10, FIGS. II and 12,
FIGS. 13 and 14, FIGS .. 15 and 16, FIGS. 17 and 18, FIGS. 19 and 20, and FIGS. 2land 22 was
used to shear the second steel sheet to obtain the second worked material. The first worked
material and the second worked material were cut on the line passing through the centers ofthe
punched holes in parallel in the sheet thickness direction to observe the surface perpendicularity
25 of the sheared edge. The average tensile residual stresses of the sheared edges ofthe first worked
material and the second worked material were measured by firing spot diameter 500 ~lm X-rays.
using the sin21J1method. FIG. 45 shows the measurement locations of the average residual stress
of the first worked materiall2. There are three measurement locations of the average residual
stress ofS I (burnished surface side), S2 (sheet thickness center), and S3 (burr side) along the
3 0 sheet thickness direction of the first worked materia I 12 fi·om the top of Fl G. 45. For the second
worked material as well, the average residual stress of the three locations ofSI (burnished
surf:~cc side), S2 (sheet thickness center), and S3 (burr side) was measured in the same way.
[0112]
FIG. 46 shows a cross-sectional photograph of the first worked material 12 obtained by
35 shearing the first steel sheet by the mode shown in FIGS. 5 and 6 (first shearing, prior art). FIGS.
47 to 50 shows cross-sectional photographs of second worked materials 22 obtained by shearing
32
5
the second steel sheets by the methods shown in the Embodiments I, 2, 5, and 6.
[Ol13] •-.: -:
As shown. inJ':lG. 46, the sheared edge 19a.ofthe fi1'st worked.matcdal.l2.sheared by,thc
c01iVentional method was slanted, while as shown in FIGS. 47to 50, the surface
perpendicularities of the sheared .edgos