Indian Patents
Title of Invention

A METHOD OF PRODUCTION OF A HIGH-STRENGTH PART AND PART PRODUCED THEREOF
Abstract high-strength part that excels in hydrogen embrittlement resistance and strength after high-temperature forming; and a process for producing the same. The atmosphere in a heating furnace before forming is regulated to one of 10% hydrogen volume fraction and 30°C dew point. As a result the amount of hydrogen penetrating in a steel sheet during heating is reduced. After forming there are sequentially carried out quench hardening in die assembly and post-working. As the method of post-working there can be mentioned shearing followed by re-shearing or compression forming of sheared edge portion; punching with a cutting blade having a gradient portion at which the width of blade base is continuously reduced; punching with a punching tool having a curved blade with a protrudent configuration at the tip of cutting blade part the curved blade having a shoulder portion of given curvature radius and/or given angle; fusion cutting; etc. Consequently the tensile residual stress after punching is reduced and the performance of hydrogen embrittlement resistance is improved.
Full Text DESCRIPTION
HUGH STRENGTH PART AND METHOD OF PRODUCTION OF THE SAME
TECHNICAL FIELD
The present invention relates to a member in which
strength is required such as used for a structural member
and reinforcing member of an automobile more
particularly relates to a part superior in strength after
high temperature shaping and a method of production of
the same
BACKGROUND ART
To lighten the weight of automobiles a need
originating in global environmental problems it is
necessary to make the steel used in automobiles as high
in strength as possible but in general if making steel
sheet high in strength the elongation or r value falls
and the shapeability deteriorates To solve this problem
technology for hot shaping steel and utilizing the heat
at that time to raise the strength is disclosed in
Japanese Patent Publication (A) No 2000-234153 This
technology aims to suitably control the steel
composition heat the steel in the ferrite temperature
region and utilize the precipitation hardening in that
temperature region so as to raise the strength
Further Japanese Patent Publication (A) No 2000-
87183 proposes high strength steel sheet greatly reduced
in yield strength at the shaping temperature to much
lower than the yield strength at ordinary temperature for
the purpose of improving the precision of press-forming
However in these technologies there may be limits to
the strength obtained On the other hand technology for
heating to the high temperature single-phase austenite
region after shaping and in the subsequent cooling
process transforming the steel to a hard phase for the
purpose of obtaining high strength is proposed in
Japanese Patent Publication (A) No 2000-38640
However if heating and rapidly cooling after
shaping problems may arise in the shape precision As
technology for overcoming this defect technology for
heating steel sheet to the single-phase austenite region
and in the subsequent press-forming process cooling the
steel is disclosed in SAE 2001-01-0078 and Japanese
Patent -Publication (A) No 2001-181833
In this way in high strength steel sheet used for
automobiles etc the higher the strength made the
greater the above-mentioned problem of shapeability In
particular in a high strength member of over 1000 MPa
as known in the past there is the basic problem of
hydrogen embrittlement (also called season cracking or
delayed fracture) When used as hot press steel sheet
while there is little residual stress due to the high
temperature pressing hydrogen enters the steel at the
time of heating before pressing Further the residual
stress of the subsequent working causes greater
susceptibility to hydrogen embrittlement Therefore with
just pressing at a high temperature the inherent problem
is not solved It is necessary to optimize the process
conditions in the heating process and the integrated
processes to the post-processing
To reduce the residual stress at the shearing and
the other post-processing it is sufficient that the
strength at the parts to be post-processed fall
Technology lowering the cooling rate at portions to be
post-processed so as to make the hardening insufficient
and thereby lowering the strength at those portions is
disclosed in Japanese Patent Publication (A) No 2003-
328031 According to this method it is considered that
the strength of part of the part falls and enables easy
shearing or other post-processing However when using
this method the mold structure becomes complicated -
which is disadvantangeous economically Further in this
method hydrogen embrittlement is not alluded to at all
By this method even if the steel sheet strength falls
somewhat and the residual stress after the postprocessing
falls to a certain extent if hydrogen remains
in the steel hydrogen embrittlement may undeniably
occur
DISCLOSURE OF THE INVENTION
The present invention was made to solve this problem
and provides a high strength part superior in resistance
to hydrogen embrittlement able to give a strength of 1200
MPa or more after high temperature shaping and method of
production of the same
The inventors conducted various studies to solve
this problem As a result they discovered that to
suppress hydrogen embrittlement it is effective to
control the atmosphere in the heating furnace before
shaping so as to reduce the amount of hydrogen in the
steel and then reduce or eliminate the residual stress by
the post-processing method That is the present
invention has the following as its gists:
(1) A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
005 to 055% and Mn: 01 to 3% in chemical composition
heating the steel sheet in an atmosphere of by volume
percent hydrogen in an amount of 10% or less (including
0%) and of a dew point of 30°C or less until the Ac3 to
the melting point then starting the shaping at a
temperature higher than the temperature at which ferrite
pearlite bainite and martensite transformation occurs
cooling and hardening after shaping in the mold to
produce a high strength part then further performing
post-processing
(2) A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
005 to 055% and Mn: 01 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere of by volume
percent hydrogen in an amount of 10% or less (including
0%)'and of a dew point of 30°C or less to the Acs to the
melting point then starting the shaping at a temperature
higher than the temperature where ferrite pearlite
bainite and martensite transformation occurs cooling
and hardening after shaping in the mold to produce a high
strength part shearing it then shearing again 1 to 2000
pm from the worked end
(3) A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
005 to 055% and Mn: 01 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere with an amount
of hydrogen by volume percent of 10% or less (including
0%) and of a dew point of 30°C or less to the Aca to the
melting point then starting the shaping at a temperature
higher than the temperature where ferrite pearlite
bainite and martensite transformation occurs cooling
and hardening after shaping in the mold to produce a high
strength part then shearing and pressing the sheared end
face
(4) A method of production of a high strength part
as set forth in (3) characterized by using coining as
the method of press working
(5) A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
005 to 055% and Mn: 01 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere of by volume
percent hydrogen in an amount of 10% or less (including
0%) and of a dew point of 30°C or less to the Acs to the
melting point then starting the shaping at a temperature
higher than the temperature where ferrite pearlite
bainite and martensite transformation occurs and
cooling and hardening after shaping in the mold to
produce a high strength part and punching or cutting this
during which using a cutting blade having a step
difference continuously decreasing from the radius of
curvature or width of the blade base by 001 to 30 mm in
the direction from the blade base to the blade tip and
having a height of 1/2 the thickness of the steel sheet
to 100 mm for the punching or cutting
(6) A method of production of a high strength part
as set forth in (5) characterized by having a step
difference continuously decreasing from the radius of
curvature or width of the blade base by 001 to 30 mm in
the direction from the blade base to the blade tip and by
D/H being 05 or less when a height of said step
difference of H (mm) and a difference of the radius of
curvature or width of the blade base and blade tip is D
(mm)
(7) A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
005 to 055% and Mn: 01 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere having an amount
of hydrogen by volume percent of 10% or less (including
0%) and of a dew point of 30°C or less to the Ac3 to the
melting point then starting shaping at a temperature
higher than the temperature where ferrite pearlite
bainite and martensite transformation occurs cooling
and hardening after shaping in the mold to produce a high
strength part then punching the steel sheet forming the
worked material using a die and punch to cut it to
shearing and sheared parts to form the worked material to
a predetermined shape during which using a punching tool
having a bending blade having a shape projecting out at
the front of the punch and/or die and having a radius of
curvature of the shoulder of the bending blade of 02 mm
or more to make the clearance 25% or less
(8) A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
005 to 055% and Mn: 01 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere by volume
percent of hydrogen in an amount of 10% or less
(including 0%) and of a dew point of 30°C or less to the
Ac3 to the melting point then starting the shaping at a
temperature higher than the temperature where ferrite
pearlite bainite and martensite transformation occurs
cooling and hardening after shaping in the mold to
produce a high strength part then punching the steel
sheet forming the worked material using a die and punch
to cut it to shearing and sheared parts to form the
worked material to a predetermined shape during which
using a punching tool having a shape projecting out at
the front of the punch and/or die and having an angle of
the shoulder of the bending blade of 100° to 170° to make
the clearance 25% or less
(9) A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
005 to 055% and Mn: 01 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere by volume
percent of hydrogen in an amount of 10% or less
(including 0%) and of a dew point of 30°C or less to the
Ac3 to the melting point then starting the shaping at a
temperature higher than the temperature where ferrite
pearlite bainite and martensite transformation occurs
cooling and hardening after shaping in the mold to
produce a high strength part then punching the steel
sheet forming the worked material using a die and punch
to cut it into a shearing part and a sheared part and
make the worked material a predetermined shape during
which using a punching tool having a bending blade having
a shape projecting out at the front of the punch and/or
die and having a radius of curvature of the shoulder of
the bending blade of 02 mm or more and an angle of the
shoulder of the bending blade of 100° to 170° to make the
clearance 25% or less
(10) A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
005 to 055% and Mn: 01 to 3% and having a balance of Fe and unavoidable impurities in
chemical composition heating the steel sheet in an atmosphere of by volume percent
hydrogen in an amount of 10% or less (including 0%) and of a dew point of 30°C or less to
the Ac3 to the melting point then starting the press—forming at a temperature higher than
the temperature where ferrite pearlite bainite and martensite transformation occurs and
cooling and hardening after shaping in the mold to produce a high strength part during
which applying the shearing near bottom dead point
(11) A method of production of a high strength part by using steel sheet containing by wt%
C:
005 to 055% and Mn: 01 to 3% and having a balance of Fe and unavoidable impurities in
chemical composition heating the steel sheet in an atmosphere of by volume percent
hydrogen in an amount of 10% or less and having a dew point of 30°C or less to the Ac3 to
the melting point starting the shaping at a temperature higher than the temperature where
feirite pearlite bainite and martensite transformation occurs cooling and hardening after
shaping in the mold to produce a high strength part then melting part of the part to cut it
(12) A method of production of a high strength part by using laser working as the method of
working for melting and cutting part of the part
(13) A method of production of a high strength part in (11) by using plasma cutting as the
method of working for melting and cutting part of the part
(14) A method of production of a high strength part by using steel sheet containing by wt%
C:
0 05 to 055% and Mn: 01 to 3% and having a balance of Fe and unavoidable impurities in
chemical composition heating the steel sheet in an atmosphere of by volume
percent hydrogen in an amount of 10% or less and of a dew point of 30°C or less to the Ac3
to the melting point then starting the shaping at a temperature higher than the temperature
where ferrite pearlite bainite and martensite transformation occurs cooling and hardening
after shaping in the mold to produce a high strength part then machining this to perforate it
or cut around the part
(15) A method of production of a high strength part by using steel sheet containing by wt%
C:
005 to 055% and Mn: 01 to 3% and having a balance of Fe and unavoidable impurities in
chemical composition heating the steel sheet in an atmosphere of by volume percent
hydrogen in an amount of 10% or less and of a dew point of 30°C or less to the Ac3 to the
melting point then starting the shaping at a temperature higher than the temperature where
ferrite pearlite bainite and martensite transformation occurs cooling and hardening after
shaping in the mold to produce a high strength part then shearing and mechanically cutting
the cut surface of the sheared part to remove a thickness of 005 mm or more
(16) A method of production of a high strength part in that the chemical composition of
said steel sheet is by wt% C: 005 to 055% Mn: 01 to 3% Al: 0005 to 01% S: 002% or
less F: 003% or less and N: 001% or less and the balance of Fe and unavoidable
impurities
(17) A method of production of a high strength part in that the chemical composition of said
steel sheet is by wt% C: 005 to 055% Mn: 01 to 3% Si: 10% or less Al: 0005 to 01%
S : 002% or less P: 003% or less Cr: 001 to 10% and N: 001% or less and the balance of
Feand unavoidable impurities
(1 S) A method of production of a high strength part
in that the chemical composition of said steel sheet is by wt% C: 005 to 055% Mn: 01 to
3% Si: 10% or less Al: 0005 to 01% S: 002% or less P: 003% or less Cr: 001 to 10%
B: 00002% to 00050% Ti: (342 x N + 0001)% or more {399 x (C—005) + (342 x
0001)}% or less and N: 001% or less and the balance of Fe and unavoidable impurities
(19) A method of production of a high strength in that the chemical composition of said steel
sheet is by wt% C: 005 to 055% Mn: 01 to 3% Si: 10% or less Al: 0005 to 01% S:
002% or less P: 003% or less Cr: 001 to 10% B: 00002% to 00050% Ti: (342 x N -+
0001)% or more {399 x (C—005) + (342 x N + 0001) }% or less N: 001% or less and
0: 0015% or less and the balance of Fe and unavoidable impurities
(20) A method of production of a high strength part in that said steel sheet is treated by any
of aluminum plating aluminum-zinc plating and zinc plating
(21) A high strength part by being produced by a method as set forth in any one of (1) to
(20)
BRIEF DESCRIPTION OF THE DRAWINGS
FIG 1 is a view of the concept of generation of tensile residual stress due to punching
FIG 2 is a view of the concept of removal of a plastic worked layer or other affected parts
FIG 3 is a view of the cut state by a cutting blade having a blade tip shape where a step
difference forms the blade tip
FIG 4 is a view of the cut state by a cutting blade having a blade tip shape having a tip
parallel part at the tip of the step difference
FIG 5 is a view of a conventional punching method
FIG 6 is a view of the cut state by a punch having a two-step structure
FIG 7 is a view of the material deformation
behavior in the case where there is a bending blade
FIG 8 is a view of the relationship of the radius
of curvature Rp of the bending blade and the residual
stress
FIG 9 is a view of the relationship of the angle 0p
of the vertical wall of the bending blade A and the
residual stress
FIG 10 is a view of the relationship of the height
of the bending blade and the residual stress
FIG 11 is a view of the relationship between the
clearance and residual stress
FIG 12 is a view of a piercing test piece
FIG 13 is a view of a shearing test piece
FIG 14 is a view of a tool cross-sectional shape
FIG 15 is a view of a shape of a punch
FIG 16 is a view of a shape of a die
FIG 17 is a view of a shape of a shaped article
FIG 18 is a view of the state of a shearing
position
FIG 19 is a view of the cross-secti'onal shape of a
coining tool
FIG 20 is a view of the cross-sectional shape of a
mold of Example 4
FIG 21 is a view of the cross-sectional shape of a
tool of Example 5
FIG 22 is a view of a shaping punch of Example 5
FIG 23 is a view of a shaping die of Example 5
FIG 24 is a view of a shaped part of Example 5
FIG 25 is a view of the state of a post-processing
position of Example 6
BEST MODE FOR WORKING THE INVENTION
The present invention provides a high strength part
superior in resistance to hydrogen embrittlement by
controlling the atmosphere in the heating furnace when
heating steel sheet before shaping to obtain a high
strength part so as to reduce the amount of hydrogen in
11
the steel and by reducing the residual stress by the
post-processing method and a method of production of the
same
Below the present invention will be explained in
more detail First the reasons for limitation of the
conditions in the present invention will be explained
The amount of hydrogen at the time of heating was
made by volume percent 10% or less because when the
amount of hydrogen is over the limit the amount of
hydrogen entering the steel sheet during heating becomes
great and the resistance to hydrogen embrittlement falls
Further the dew point in the atmosphere was made 30°C or
less because with a dew point greater than this the
amount of hydrogen entering the steel sheet during
heating becomes greater and the resistance to hydrogen
embrittlement falls
The heating temperature of the steel sheet is made
the Acs to the melting point so as to make the structure
of the steel sheet austenite for hardening and
strengthening after shaping Further if the heating
temperature is higher than the melting point pressforming
becomes impossible
The heating temperature of the steel sheet is made
the Acs to the melting point so as to make the structure
of the steel sheet austenite for hardening and
strengthening after shaping Further if the heating
temperature is higher than the melting point pressforming
becomes impossible
The shaping starting temperature is made a
temperature higher than the temperature where ferrite
pearlite bainite and martensite transformation occurs
because if shaped at a temperature lower than this the
hardness after shaping is insufficient
By heating steel sheet under the above conditions
and using the press method to shape it cooling and
hardening after shaping in the mold then post-processing
it it is possible to produce a high strength part The
12
the steel and by reducing the residual stress by the
post-processing method and a method of production of the
same
Below the present invention will be explained in
more detail First the reasons for limitation of the
conditions in the present invention will be explained
The amount of hydrogen at the time of heating was
made by volume percent 10% or less because when the
amount of hydrogen is over the limit the amount of
hydrogen entering the steel sheet during heating becomes
great and the resistance to hydrogen embrittlement falls
Further the dew point in the atmosphere was made 30°C or
less because with a dew point greater than this the
amount of hydrogen entering the steel sheet during
heating becomes greater and the resistance to hydrogen
embrittlement falls
The heating temperature of the steel sheet is made
the Acs to the melting point so as to make the structure
of the steel sheet austenite for hardening and
strengthening after shaping Further if the heating
temperature is higher than the melting point pressforming
becomes impossible
The heating temperature of the steel sheet is made
the Acs to the melting point so as to make the structure
of the steel sheet austenite for hardening and
strengthening after shaping Further if the heating
temperature is higher than the melting point pressforming
becomes impossible
The shaping starting temperature is made a
temperature higher than the temperature where ferrite
pearlite bainite and martensite transformation occurs
because if shaped at a temperature lower than this the
hardness after shaping is insufficient
By heating steel sheet under the above conditions
and using the press method to shape it cooling and
hardening after shaping in the mold then post-processing
it it is possible to produce a high strength part The
12
"hardening" is the method of strengthening steel by
cooling by a cooling rate faster than the critical
cooling rate determined by the composition so as to cause
a martensite transformation
Next a different method of working by the above
post-processing will be explained
The method of working of claim 2 will be explained
The inventors investigated in detail the plastic
worked layer and residual stress affected zone at the
worked end face of the shearing such as the punch
piercing and cutting and as a result learned that there
is a plastic worked layer etc present over about 2000 jam
from the worked end As shown in FIG 1 at the time of
shearing the steel sheet is worked in a compressed
state After working the compressed state is released
so it is believed that residual stress of tension occurs
Therefore as shown in FIG 2 in the plastic worked
layer or other affected zone the partial rise in
strength due to the plastic working or the resistance to
the compression force due to the tensile residual stress
due to the second working causes the amount of
compression at the time of working to become smaller and
the amount of deformation of the opening after cutting to
become smaller so the residual stress can be reduced
Therefore if working the part of over 2000 |4m of the
worked end in range again there is no plastic worked
layer or other affected zone so the part is worked while
again receiving a large compression force When this is
released after working the residual stress is not
reduced and the cracking resistance is not improved so
the upper limit was made 2000 ^m Further the lower
limit was set to I (am since working while controlling
this to a range of less than 1 nm is difficult The most
preferable range of working is 200 to 1000 (Jin
Further the residual stress at the cross-section of
the worked part is measured by an X-ray residual stress
13
measurement apparatus according to the method described
in "X-Ray Stress Measurement Method Standard (2002
Edition)- Ferrous Metal Section" Japan Society of
Materials Science March 2002 The details are as
follows The parallel tilt method is used to measure 20-
sin2v|/ using the reflection X-rays of the 211 plane of a
body centered cubic lattice The 26 measurement range at
this time is about 150 to 162° Cr-Ka was used as the Xray
target the tube current and tube voltage were made
30 kV/10 mA and the X-ray incidence slit was made 1 mm
square The value obtained by multiplying the stress
constant K with the inclination of the 20-sin2vy curve was
made the residual stress At this time the stress
constant K was made -3244 kgf/deg
Under the above conditions in the case of a pierced
hole cross-section X|/(mm)=20 25 30 35 40 45 is
measured while in the case of a cut surface V|/(mm) =0 20
25 30 35 40 45 is measured The measurement was
conducted in a thickness direction of 0° and directions
inclined by 23° and 45° from that for a total of three
measurements The average value was used as the residual
stress
The method of shearing such as punching or cutting
is not particularly limited It is possible to use any
known method Regarding the working temperature the
effect of the present invention is obtained from room
temperature to 1000°C in range
By the above post-processing the residual stress of
the tension at the worked end face becomes 600 MPa or
less so in general when assuming steel sheet of 980 MPa
or more the residual stress becomes less than the yield
stress and cracks no longer occur Further when the
residual stress of compression basically stress does not
act in a direction where cracks form in the steel sheet
at the ends so cracks no longer occur For this reason
14
the residual stress of tension at the end face in
shearing such as punching or cutting preferably is made
600 MPa or less or the residual stress of compression
Next the methods of working of claims 3 and 4 will
be explained
To suppress hydrogen embrittlement in addition to
press working the parts where there is residual stress
arising due to shearing it is effective to impart
residual stress of compression The end faces which were
sheared are press worked because the residual stress of
tension believed to cause hydrogen embrittlement after
shearing is high at sheared ends and if press working
such locations the residual stress of tension falls and
the resistance to hydrogen embrittlement is improved As
the method for press working the sheared end faces any
method may be used but industrially the method of using
coining as shown in claim 5 is economically superior
Next the methods of working shown in claims 5 and 6
will be explained
The sheared end faces are worked in the state with
the steel sheet compressed when working them as shown in
FIG 1 After working the compressed state is released
so residual stress of tension is believed to arise
Therefore the inventors discovered that by widening
holes or pressing the front surfaces of the end faces at
the entire cross-section of the plastic worked layer or
other affected zone the partial rise in strength due to
plastic working or the resistance to the compression
force due to the residual stress of tension enables
control so that the release displacement after complete
cutting becomes the compression side ie a single-step
working method That is if enlarging a hole or pressing
over a part in a range over 2000 pm from the worked end
the hole is widened and the end face is pressed at one
time Since this is released after working the residual
stress ends up at the compression side at the end face
To be able to obtain this by a single working operation
15
using a die and punch the shape of the blade tip as
shown in FIGS 3 4 is important FIG 3 has a step
difference forming the blade tip while FIG 4 has a tip
parallel part at the tip of the step difference
When providing a step difference continuously
decreasing from the radius of curvature or width of the
blade base in the direction from the blade base to the
blade tip if the reduction in the radius of curvature or
width is less than 001 mm the situation ends up
becoming no different from ordinary punching or cutting
so a large tensile stress ends up remaining at the end
face On the other hand if the amount of reduction of
the radius of curvature or width is over 30 mm the de
facto clearance becomes large so the burring of the
worked end face ends up becoming larger
Further if the height of the blade vertical wall
(height of step difference) is less than 1/2 of the
thickness of the worked steel sheet after punching once
it is no longer possible to press the worked end face
from the side face of the step difference so the
situation becomes no different from ordinary punching or
cutting and a large tensile stress ends up remaining at
the worked end face On the other hand if the height is
over 100 mm the stroke becomes larger or shorter
lifetime of the blade itself is a concern
Further the angle formed by the parallel part of
the cutting blade and the step difference (blade vertical
wall angle 0) is preferably 95° to 179° more preferably
at least 140°
In FIG 3 and FIG 4 the step difference is shaped
having a radius of curvature but a blade linearly
reduced in width from the blade base is also included in
the scope of the invention
Further regarding the shape of the cutting blade
D/H is important when the difference of the radius of
curvature or width of the blade base and blade tip is D
(mm) and the height of the step difference is H (mm) If
16
the value is less than 05 the drop in blade life or
burring is suppressed so the value is preferably made
05 or less
On the other hand chamfering of the blade tip such
as disclosed in Japanese Patent Publication (A) No 5-
23755 and Japanese Patent Publication (A) No 8-57557 is
effective for reducing burring prolonging blade life
and preventing cracking of relatively low strength steel
sheet but in the present invention it is most important
that the steel sheet be shaped under predetermined
conditions then the once punched end face or cut end
face be again pushed apart so it is not particularly
necessary to chamber the blade tip in order to reduce the
residual stress or make it the compression side
Further the residual stress at the worked end face
is measured under the above-mentioned conditions by an Xray
residual stress measurement apparatus according to
the method described in "X-Ray Stress Measurement Method
Standards (2002 edition)- Ferrous Metal Section" Japan
Society of Materials Science March 2002
The method of shearing such as punching or cutting
is not particularly limited Any known method may be
used For the working temperature the effect of the
present invention is obtained in the range of room
temperature to 1000°C
Further regarding the residual stress if zero or
the compression side basically no reaction acts at the
end in the direction where the steel sheet will crack so
cracks no longer occur Further pressing at not more
than 600 MPa is effective for preventing cracks
Next the methods of working of claims 7 8 and 9
will be explained
The inventors considered the above problems and
discovered that by making the punch shape a two-step
structure of the bending blade A and cutting blade B
shown in FIG 6 it is possible to reduce the residual
stress at the punched end face
17
The reasons are considered to be as follows
In ordinary punching the part deformed by the punch
and die shown in FIG 5 (hardened layer) is subjected to
a large tensile or compressive strain For this reason
the work hardening of that part becomes remarkable so
the ductility of the end face deteriorates However when
making the punch shape the two-step structure comprised
of the cutting blade B and bending blade A such as shown
in the present invention (FIG 6) as shown in FIG 7
when the part cut by the cutting blade B (material cut
part M) is given tensile stress by the bending blade A
the progression of cracks arising due to the cutting
blade B and die shoulder is promoted by the tensile
stress and the material is cut by the cutting blade B
without compression so the residual stress of tension
after punching becomes lower and the drop in the
allowable amount of hydrogen entering from the
environment can be suppressed
Further the inventors conducted detailed studies on
the shape of the bending blade and discovered that unless
making the shape of the bending blade a predetermined
shape a sufficient effect of reduction of the residual
stress cannot be obtained
That is when the shape of the bending blade A is
not the predetermined shape the material is cut by the
bending blade A so the part M cut by the cutting blade B
cannot be given sufficient tensile stress by the bending
However by making the shape of the bending blade a shape
where the material is not cut by the bending blade
itself the residual stress can be reduced
FIG 8 shows the relationship between the radius of
curvature Rp and the residual stress in the case of using
TS1470 MPa grade hardened steel sheet of a thickness of
20 mm under conditions of a height Hp of the bending
blade 03 mm a clearance of 5% a vertical wall angle 0p
of the bending blade of 90° and a predetermined radius of
curvature Rp given to the shoulder of the bending blade
18
A If the radius of curvature is 02 mm or more it is
learned that the residual stress is reduced Here the
residual stress is found by measuring the change in
lattice distance by the X-ray diffraction method at the
cut surface The measurement area is made a 1 mm square
region and the measurement conducted at the center of
thickness at the cut surface When using a punch to make
holes it is not possible to fire X-rays from a direction
vertical to the cutting surface so the angle of emission
of the X-rays is changed for measurement so as to enable
measurement of the residual stress in the thickness
direction Further in this case the clearance is the
punch and die clearance C/thickness t x 100 (%) The
other punching conditions are a punch diameter Ap = 20 mm
and a distance Dp = 10 mm between the cutting blade end
P and the bending blade rising position D
Further FIG 9 shows the relationship between the
angle 6p and the residual stress in the case of using
TS1470 MPa grade hardened steel sheet of a thickness of
18 mm under conditions of a height Hp of the bending
blade of 03 mm a clearance of 56% a radius of
curvature of the bending blade shoulder of 02 mm and a
vertical wall part of the bending blade A of a
predetermined angle 0p Due to this it is learned that by
making the angle 0p of the vertical wall of the bending
blade 100° to 170° the residual stress is reduced The
other punching conditions are a punch diameter Ap = 20 mm
and a distance Dp = 10 mm between the cutting blade end
P and the bending blade rising position D
FIG 10 shows the relationship between the height Hp
of the bending blade and the residual stress in the case
of using TS1470 MPa grade hardened steel sheet of a
thickness of 14 mm under conditions of a radius of
curvature Rp of the shoulder of the bending blade A of
03 mm an angle 6p of the vertical wall of the bending
blade A of 135° a clearance of 71 and a height Hp of
19
the bending blade of 03 to 3 mm Due to this it is
learned that by making the radius of curvature Rp of the
shoulder of the bending blade 02 mm or more or making
the angle 6p of the vertical wall of the bending blade
100° to 170° the residual stress is reduced compared with
the ordinary case of no bending blade that is Hp = 0
The rest of the punching conditions are a punch diameter
of Ap = 20 mm and a distance Dp = 10 mm of the cutting
blade end P and bending blade rising position D
Further FIG 11 shows the effect of punching
clearance on the residual stress when using TS1470 MPa
grade hardened steel sheet of a thickness of 16 mm under
conditions of a radius of curvature Rp of the shoulder of
the bending blade A of 03 mm an angle 6p of the vertical
wall of the bending blade A of 135° and a height Hp of
the bending blade of 03 mm The rest of the punching
conditions are a punch diameter of Ap = 20 mm and a
distance Dp = 10 mm of the cutting blade end P and the
bending blade rising position D The clearance also has
an effect on the residual stress If the clearance
becomes a large one over 25% the residual stress also
becomes larger This is believed to be due to the tensile
effect by the bending blade becoming smaller so the
clearance has to be made 25% or less
The present invention was made based on this study
and has the following requirements
The punching punch or die used in the present
invention has to be made a two-step structure of the
bending blade A and cutting blade B This is so that
before the cutting blade B shears the worked material
the bending blade A gives tensile stress to the cut part
M of the worked material and reduces the residual stress
of the tension remaining at the cut end surface of the
worked material after cutting
The radius of curvature Rp of the bending shoulder
has to be at least 02 mm This is because if the radius
20
of curvature Rp of the shoulder of the bending blade is
not more than 02 mm it is not possible for the worked
material to be sheared by the bending blade A and for the
part M sheared by the cutting blade B to be given
sufficient tensile stress
The angle 0p of the shoulder of the bending blade has
to be made 100° to 170° This is because if the angle 9p
of the shoulder of the bending blade is 100° or less the
material is sheared by the bending blade A so a
sufficient tensile stress cannot be given to the part M
sheared by the cutting blade B Further if the angle 0p
of the shoulder of the bending blade is 170° or more
sufficient tensile stress cannot be given to the part to
be sheared by the cutting blade B
If either of the above conditions relating to the
radius of curvature Rp of the shoulder of the bending
blade and the angle 6p of the shoulder of the bending
blade is met a large effect is obtained but when both
are met the contact pressure of the material contacting
the alloy mold is reduced so the mold wear is
suppressed Therefore for maintenance having both
conditions met is preferred
Further in ordinary punching usually a sheet
holder is used for fastening the material to the die but
it is also possible to suitably use a sheet holder in the
method of punching of the present invention The wrinkle
suppressing load (load applied to material from sheet
holder) does not have a particularly large effect on the
residual stress so may be used in the usually used
range
The punch speed does not have a great effect on the
residual stress even if the changed within the usual
industrially used range for example 001 m/sec to
several m/sec so may be made any value
Further in most cases in the punching process to
21
suppress mold wear the mold or material is coated with
lubrication oil In the present invention as well a
suitable lubrication oil may be used for this purpose
Further to give sufficient tensile stress to the
bending blade A the height Hp of the bending blade is
preferably made at least 10% of the thickness of the
worked material
Further the distance Dp of the cutting blade end P
and the rising position Q of the bending blade is
preferably made at least 01 mm This is because if the
distance is less than this when shearing the worked
material by the cutting blade B the cracks which usually
occur near the shoulder of the cutting blade become
difficult to occur and strain is given to the cutting
position by the cutting blade
Further the part between the cutting blade end P
and rising position Q of the bending blade in the punch
of the present invention the bottom part of the bending
blade A and the vertical wall part of the bending blade
A are preferably flat shapes in terms of the production
of the punch but even if there is some relief shape the
effect is the same even if the above requirements are
satisfied
The present invention reduces the residual stress of
the end face at the time of punching by further adding
the bending blade A to the punch of conventionally only
the cutting blade B By adding the bending blade A and
further making the height Hp of the bending blade higher
the facial pressure where the cutting blade B and worked
material contact each other falls so the amount of wear
of the cutting blade end P is also reduced but if the Hp
is too high before the cutting blade B and worked
material contact the material may break between the
bending blade A and the cutting blade B and the effect
may not be obtained In this case the height Hp of the
bending blade is preferably made about 10 mm or less
In the present invention there is no particular
22
upper limit to the radius of curvature Rp of the shoulder
of the bending blade shoulder but depending on the size
of the punch If the radius of curvature Rp is too large
it becomes difficult to increase the height Hp of the
bending blade so 5 mm or less is preferable
Above the effect in the case of adding a bending
blade to the punch was explained but both when adding
bending blades to both of the punch and die and when
adding a bending blade to only the die since a tensile
stress is given to the material in the same way as when
adding a bending blade to only the punch as explained
above similar effects are obtained The limitations on
the dimensions of the bending blade in this case are the
same as the limitations in the case of adding a bending
blade to only the punch as explained above
Next the method of working of claim 10 will be
explained
As the method of reducing the residual stress it is
necessary to hot shape the steel and then shear it near
bottom dead center The reason is believed to be as
follows In shearing during hot working it is believed
that the shearing tool contacts the steel sheet with a
high facial pressure In this case it is believed that
the cooling rate becomes large and that the steel is
transformed from austenite to a low temperature
transformed structure with a high deformation resistance
At this time it is believed that while smaller than the
case of working hardened material at room temperature
larger residual stress than the case of austenite may
remain Therefore the plate is sheared near bottom dead
center because if during hot shaping the deformation
resistance of the steel sheet is small and the residual
stress after working becomes low Further the reason for
the timing of working being near bottom dead center is
that if not near bottom dead center after shearing the
steel sheet will deform and the shape and positional
precision will drop "Near bottom dead point" means
around the part any method may be used but
industrially drilling or cutting by a saw is good since
it is economically superior
The method of working of claim 15 will be explained
Even in the case of using the prior working for the
post-processing it is sufficient to mechanically cut the
location with the high residual stress at the end face of
the sheared part The cut surface of the sheared part is
removed to a thickness of 005 mm or more because with
removal of thickness less than this the location where
residual stress remains cannot be sufficiently removed
and the resistance to hydrogen embrittlement falls
As the method for removing a thickness of 005 mm or
more from the cut surface of the sheared part by
mechanical cutting any method may be used Industrially
a mechanical cutting method such as reaming is good since
it is economically superior
Below the reasons for limiting the chemical
composition of the steel sheet forming the material will
be explained
C is an element added for making the structure after
cooling martensite and securing the material properties
To secure a strength of 1000 MPa or more it is desirably
added in an amount of 005% or more However if the
amount added is too large it is difficult to secure the
strength at the time of impact deformation so the upper
limit is desirably 055%
Mn is an element for improving the strength and
hardenability If less than 01% sufficient strength is
not obtained at the time of hardening Further even if
added over 3% the effect becomes saturated Therefore
Mn is preferably 01 to 3% in range
Si is a solution hardening type alloy element but
if over 10% the surface scale becomes a problem
Further when plating the surface of steel sheet if the
amount of Si added is large the plateability
deteriorates so the upper limit is preferably made 05%
24
within at least 10 mm preferably within 5 mm of bottom
dead point
Next the methods of working of claims 11 12 and
13 will be explained
To suppress the hydrogen embrittlement it is
effective to control the atmosphere in the heating
furnace before shaping to reduce the amount of hydrogen
in the steel and then post-process it by fusion cutting
with its little residual stress after working
The reason for cooling and hardening the steel after
shaping in the mold to produce a high strength part then
melting part of the part to cut it is that if melting
part of the part to cut it the residual stress after
working is small and the resistance to hydrogen
embrittlement is good
As the method of working to melt part of the part to
cut it any method may be used but industrially laser
working and plasma cutting with small heat affected zones
such as shown in claims 12 13 are preferable Gas
cutting has small residual stress after working but is
disadvantageous in that it requires a large input heat
and has greater parts where the strength of the part
falls
Next the method of working of claim 14 will be
explained
To suppress hydrogen embrittlement it is effective
to control the atmosphere in the heating furnace before
shaping so as to reduce the amount of hydrogen in the
steel and to post-process the steel by machining with a
small residual stress after working
The reason for cooling and hardening the steel after
shaping in the mold to produce a high strength part then
machining it to perforate it or cut around the part is
that with cutting or other machining the residual stress
after working is small and the resistance to hydrogen
embrittlement is good
As the method for machining to perforate it or cut
Al is a required element used as a material for
deoxidizing molten steel and further is an element fixing
N Its amount has an effect on the crystal grain size or
mechanical properties To have such an effect a content
of 0005% or more is required but if over 01% there
are large nonmetallic inclusions and surface flaws easily
occur at the product For this reason Al is preferably
0005 to 01% in range
S has an effect on the nonmetallic inclusions in the
steel It causes deterioration of the workability and
becomes a cause of deterioration of the toughness and
increase of the anisotropy and susceptibility to repeat
heat cracking For this reason S is preferably 002% or
less Note that more preferably it is 001% or less
Further by limiting the S to 0005% or less the impact
characteristics are strikingly improved
P is an element having a detrimental effect on the
weld cracking and toughness so P is preferably 003% or
less Note that preferably it is 002% or less Further
more preferably it is 0015% or less
If N exceeds 001% the coarsening of the nitrides
and the age hardening by the solute N causes the
toughness to deteriorate as a trend For this reason N
is preferably contained in an amount of 001% or less
0 is not particularly limited but excessive
addition becomes a cause of formation of oxides having a
detrimental effect on the toughness To suppress oxides
becoming the starting point of fatigue fracture
preferably the content is 0015% or less
Cr is an element for improving the hardenability
Further it has the effect of causing the precipitation
of M23C6 type carbides in the matrix It has the action of
raising the strength and making the carbides finer It is
added to obtain these effects If less than 001% these
effects cannot be sufficiently expected Further if over
12% the yield strength tends to excessively rise so Cr
is preferably 001 to 10% in range More preferably it
is 005 to 1%
B may be added for the purpose of improving the
hardenability during the press-forming or in the cooling
after press-forming To achieve this effect addition of
00002% or more is necessary However if this amount of
addition is increased too much there is a concern of hot
cracking and the effect is saturated so the upper limit
is desirably made 00050%
Ti may be added for the purpose of fastening the N
forming a compound with B for effectively bringing out
the effect of B To bring out this effect (Ti - 342 x
N) has to be at least 0001% but if overly increasing
the amount of Ti the amount of C not bonding with Ti
decreases and after cooling a sufficient strength can no
longer be obtained As the upper limit the Ti equivalent
enabling an amount of C not bound with Ti of at least
01% that is {399 x (C-005) + (342 x N + 0001)}%
is preferable
Ni Cu Sn and other elements probably entering
from the scrap may also be included Further from the
viewpoint of control of the shape of the inclusions Ca
Mg Y As Sb and REM may also be added Further to
improve the strength it is also possible to add Ti Nb
Zr Mo or V In particular Mo improves the
hardenability as well so may also be added for this
purpose but if these elements are overly increased the
amount of C not bonding with these elements will decrease
and a sufficient strength will no longer be obtained
after cooling so addition of not more than 1% or each is
preferable
The above Cr B Ti and Mo are elements having an
effect on the hardenability The amounts of these
elements added may be optimized considering the required
hardenability the cost at the time of production etc
For example it is possible to optimize the above
elements Mn etc to reduce the alloy cost reduce the
number of steel types to reduce the cost even if the
alloy cost does not become the minimum or use other
various combinations of elements in accordance with the
circumstances at the time of production
In addition there is no particular problem even if
inevitably included impurities are included
The steel sheet of the above composition may also be
treated by aluminum plating aluminum-zinc plating or
zinc plating In the method of production of the same
the pickling and cold rolling may be performed by
ordinary methods There is also no problem even if the
aluminum plating process or aluminum-zinc plating process
and zinc plating are also performed by ordinary methods
That is with aluminum plating an Si concentration in
the bath of 5 to 12% is suitable while with aluminumzinc
plating a Zn concentration in the bath of 40 to 50%
is suitable Further there is no particular problem even
if the aluminum plating layer includes Mg or Zn or the
aluminum-zinc plating layer includes Mg It is possible
to produce steel sheet of similar characteristics
Note that regarding the atmosphere of the plating
process plating is possible by ordinary conditions both
in a continuous plating facility having a nonoxidizing
furnace and in a not continuous plating facility having a
nonoxidizing furnace Since with this steel sheet alone
no special control is required the productivity is not
inhibited either Further if the zinc plating method
hot dip galvanization electrolytic zinc coating
alloying hot dip galvanization or another method may be
used Under the above production conditions the surface
of the steel sheet is not pre-plated with metal before
the plating but there is no particular problem
preplating the steel sheet with nickel preplating it
with iron or preplating it with another metal to improve
the platability Further there is no particular problem
even if treating the surface of the plated layer by
plating by a different metal or coating it by an
inorganic or organic compound Next examples will be
used to explain the present invention in more detail
EXAMPLES
(Example 1)
Slabs of the chemical compositions shown in Table 1
were cast These slabs were heated to 1050 to 1350°C and
hot rolled at a finishing temperature of 800 to 900°C and
a coiling temperature of 450 to 680°C to obtain hot rolled
steel sheets of a thickness of 4 mm Next these were
pickled then cold rolled to obtain cold rolled steel
sheets of a thickness of 16 mm After this these were
heated to the austenite region of 950°C above the Ac3
point then were hot shaped The atmosphere of the
heating furnace was changed in the amount of hydrogen and
dew point The conditions are shown in Table 2 and Table
3 The tensile strengths were 1523 MPa and 1751 MPa
When evaluating the punch pieced parts 100 mm x 100
mm size pieces were cut from these shaped parts to obtain
test pieces The center parts were punched out by a O10
mm punch at a clearance of 15% then the pieces were
secondarily worked under various conditions Further
when evaluating cut parts the secondarily worked test
pieces were cut to sizes of 314 mm x 314 mm by primary
working at a clearance of 15% then were secondarily
worked under various conditions in the same way as punch
piercing The shape of the test piece at this time is
shown in FIGS 12 13 The range of working when
performing this secondary working was also noted The
mechanical grinding was performed by a reamer for the
punch pierced hole and by a milling machine for the cut
end To evaluate the resistance to cracks of these test
pieces the test pieces were allowed to stand after
secondary working for 24 hours at room temperature then
the number of cracks at the worked ends and the residual
stress at the punched ends and cut ends were measured by
X-rays The number of cracks was measured for the entire
circumference of the hole for a punch pierced hole For
cut ends one side was measured
As a result of the study under both the conditions
of punch piercing and cutting cracking frequently
occurred under the production condition nos 1 2 3 5
6 7 8 and 10 where the amount of hydrogen of the
heating atmosphere is 30% or the dew point is 50°C the
primary working is left as it is or after the primary
working secondary working is performed over 3 mm from
the worked end while cracking did not occur under the
secondary working production condition nos 4 and 9 where
the amount of hydrogen of the heating atmosphere is 10%
or less the dew point is 30°C or less and 1000 Jim from
the worked end is secondarily worked after the primary
working Further the trends in the number of cracks
occurring under production conditions of an amount of
hydrogen in the heating atmosphere of 10% or less and of
a dew point of 30°C or less and the results of measurement
of the residual stress by X rays match well Therefore
for improvement of the crack resistance of worked ends
it can be said to be effective to rework the part of 1 to
2000 urn from the worked ends after primary working
(Example 2)
Slabs of the chemical compositions shown in Table 4
were cast These slabs were heated to 1050 to 1350°C and
hot rolled at a finishing temperature of 800 to 900°C and
a coiling temperature of 450 to 680°C to obtain hot rolled
steel sheets of a thickness of 4 mm Next these were
pickled then cold rolled to obtain steel sheets of a
thickness of 16 mm Further parts of the cold rolled
plates were treated by hot dip aluminum coating hot dip
aluminum-zinc coating alloying hot dip galvanization
and hot dip galvanization Table 5 shows the legend of
the plating type After this these cold rolled steel
sheets and surface treated steel sheets were heated by
furnace heating to the austenite region of the Acs point
to 950°C then were hot shaped The atmosphere of the
heating furnace was changed in the amount of hydrogen and
dew point The conditions are shown in Table 6
A cross-section of the mold shape is shown in FIG
14 The legend in FIG 14 is shown here (1: die 2:
punch) The shape of the punch as seen from above is
shown in FIG 15 The legend in FIG 15 is shown here (2:
punch) The shape of the die as seen from below is shown
in FIG 16 The legend in FIG 16 is shown here (1: die)
The mold followed the shape of the punch The shape of
the die was determined by a clearance of a thickness of
16 mm The blank size was made (mm) 16 thickness x 300
x 500 As the shaping conditions the punch speed was
made 10 mm/s the pressing force was made 200 tons and
the holding time until the bottom dead point was made 5
seconds A schematic view of the shaped part is shown in
FIG 17 A tensile test piece was cut out from the shaped
part The tensile strength of the shaped part was 1470
MPa or more The shearing conducted was piercing The
position shown in FIG 18 was pierced using a punch of a
diameter of 10 mm(j and using a die of a diameter of 105
mm FIG 18 shows the shape of the part as seen from
34
above The legend in FIG 18 is shown here (1: part 2:
center of pieced hole) The piercing was performed within
30 minutes after the hot shaping After the piercing
shaping was performed The working methods are also shown
in Table 6 For the legend the case of shaping is shown
by "S" while the case of no working is shown by "N" At
this time the finished hole diameter was changed and the
effect of the removed thickness was studied The
conditions are shown together in Table 6 The shaping was
performed within 30 minutes after the piercing The
resistance to hydrogen embrittlement was evaluated by
examining the entire circumference of the hole one week
after the shaping so as to judge the presence of any
cracks The examination was performed using a loupe or
electron microscope The results of judgment are shown
together in Table 6 Note that the press used was a
general crank press
Experiment Nos 1 to 249 show the results of
consideration of the effects of the steel type plating
type concentration of hydrogen in the atmosphere and
dew point for the case of working by shaping If in the
scope of the invention no cracks occurred after
piercing Experiment Nos 250 to 277 are comparative
cases of no working In all cases no cracks occurred
(Example 3)
Slabs of the chemical compositions shown in Table 4
were cast These slabs were heated to 1050 to 1350°C and
hot rolled at a finishing temperature of 800 to 900°C and
a coiling temperature of 450 to 680°C to obtain hot rolled
steel sheets of a thickness of 4 mm Next these were
pickled then cold rolled to obtain cold rolled steel
sheets of a thickness of 16 mm Further parts of these
cold rolled sheets were treated by hot dip aluminum
coating hot dip aluminum-zinc coating alloying hot dip
galvanization and hot dip galvanization Table 5 shows
the legends of the plating types After this these cold
rolled steel sheets and surface treated steel sheets were
heated by furnace heating to more than the Ac3 point that
is the 950°C austenite region then hot shaped The
atmosphere of the heating furnace was changed in the
amount of hydrogen and the dew point The conditions are
shown in Table 7
A cross-section of the shape of the mold is shown in
FIG 14 The legend in FIG 14 is shown here (1: die 2:
punch) The shape of the punch as seen from above is
shown in FIG 15 FIG 15 shows the legend (2: punch)
The shape of the die as seen from the bottom is shown in
FIG 16 The legend in FIG 16 is shown here (1: die)
The mold followed the shape of the punch The shape of
the die was determined by a clearance of a thickness of
16 mm The blank size (mm) was made 16 thickness x 300
x 500 The shaping conditions were a punch speed of 10
mm/s a pressing force of 200 ton and a holding time at
bottom dead center of 5 second A schematic view of the
shaped part is shown in FIG 17 From a tensile test
piece cut out from the shaped part the tensile strength
of the shaped part was shown as being 1470 MPa or more
The shearing performed was piercing The position
shown in FIG 18 was pierced using a punch of a diameter
of 10 mm 18 shows the shape of the part as seen from above The
legend in FIG 18 is shown here (1: part 2: center of
pierce hole) The piercing was performed within 30
minutes after hot shaping After the piercing coining
was performed The coining was performed by sandwiching a
plate to be worked between a conical punch having an
angle of 45° with respect to the plate surface and a die
having a flat surface FIG 19 shows the tool The legend
in FIG 19 is shown here (I: punch 2: die 3: blank
after piercing) The coining was performed within 30
seconds after piercing The resistance to hydrogen
embrittlement was evaluated one week after coining by
observing the entire circumference of the hole and
judging the presence of cracks The cracks were observed
by a loupe or electron microscope The results of
judgment are shown together in Table 7
Experiment Nos I to 249 show the results of
consideration of the effects of the steel type plating
type concentration of hydrogen in the atmosphere and
dew point for the case of coining If in the scope of the
invention no cracks occurred after piercing Experiment
Nos 250 to 277 are comparative examples in the case of
no coining Since these are outside of the scope of the
(Example 4)
Slabs of the chemical compositions shown in Table 1
were cast These slabs were heated to 1050 to 1350°C and
hot rolled at a finishing temperature of 800 to 900°C and
coiling temperature of 450 to 680°C to obtain hot rolled
steel sheets of a thickness of 4 mm Next these were
pickled then cold rolled to obtain cold rolled steel
sheets of a thickness of 16 mm After this the sheets
were heated to the Ac3 point to the 950°C austenite
region then were hot shaped The atmosphere of the
heating furnace was changed in the amount of hydrogen and
the dew point The conditions are shown in Table 8 The
tensile strengths were 1525 MPa and 1785 MPa
When evaluating the punch pieced parts 100 mm x 100
mm size pieces were cut from these shaped parts to obtain
test pieces The centers were punched out in the shapes
shown in FIGS 3 4 by a punch with a parallel part of
O10 mm and 20 mm and a tip of 5 to 13 mm by a clearance
of 43 to 25% To evaluate these test pieces for
resistance to cracking the number of cracks at the
secondarily worked ends were measured and the residual
stress at the punched ends and cut ends was measured by
X-rays The number of cracks were measured for the entire
circumference of the punch pieced holes For the cut
ends single sides were measured The working conditions
and results are also shown in Table 8
The result of the above study is that under both
punch piercing and cutting conditions cracks frequently
occurred at samples outside of the scope of the present
invention while no cracks occurred at samples inside the
scope of the present invention
(Note) Underlines indicate conditions outside range of invention
(Example 5)
Aluminum plated steel sheets of the compositions
shown in Table 9 (thickness 16 mm) were held at 950°C for
1 minute then hardened at 800°C by a sheet mold to
prepare test samples The test samples had strengths of
TS=1540 MPa YP=1120 MPa and T-E1=6% Holes were made in
the steel sheets using molds of the types shown in FIG
20A FIG 20B FIG 20C and FIG 20D under the
conditions of Table 10 The punching clearance was
adjusted to 5 to 40% in range The resistance to hydrogen
embrittlement was evaluated by examining the entire
circumference of the holes one week after working to
judge for the presence of cracks The observation was
performed using a loupe or electron microscope The
results of judgment are shown together in Table 10
Level 1 is the level serving as the reference for
the residual stress resulting from punching by the
present invention in a conventional punching test using
an A type mold Cracks occurred due to hydrogen
embrittlement
In a test using a B type mold level 2 had a large
angle 9p of the shoulder of the bending blade shoulder a
small radius of curvature Rp of the shoulder of the
bending blade a small effect of reduction of the
residual stress and cracks due to hydrogen
embrittlement Level 3 had a large clearance a small
effect of reduction of the residual stress and cracks
due to hydrogen embrittlement Level 4 had a small
shoulder angle 0p of the bending blade and a small radius
of curvature Rp of the shoulder of the bending blade For
this reason the widening value obtained by this punching
was not improved over the prior art method so cracks
occurred due to hydrogen embrittlement
In a test using a C type mold level 11 had a punch
constituted by an ordinary punch and a shoulder angle 6d
of the projection of the die and a radius of curvature Rd
of the shoulder satisfying predetermined conditions so
there was a small effect of reduction of the residual
stress and cracks occurred due to hydrogen embrittlement
Level 12 had a large clearance and a small effect of
reduction of the residual stress so cracks occurred due
to hydrogen embrittlement
In a test using a D type mold level 18 did not meet
the predetermined conditions in the angle 0p of the
shoulder of the projection of the punch the radius of
curvature Rp of the shoulder the angle 0d of the shoulder
of the projection of the die and the radius of curvature
Rd of the shoulder so no effect of reduction of the
residual stress could be seen and no cracks occurred due
to hydrogen embrittlement Further level 15 had a large
clearance and a small effect of reduction of residual
stress so cracks occurred due to hydrogen embrittlement
Levels 8 9 14 15 21 22 have heating atmospheres
over the limited range so cracks occurred due to
hydrogen embrittlement
The other levels satisfied the conditions of the
present invention The residual stresses at the punched
cross-sections were reduced and no cracks occurred due to
hydrogen embrittlement
(Example 6)
Slabs of the chemical compositions shown in Table 4
were cast These slabs were heated to 1050 to 1350°C and
hot rolled at a finishing temperature of 800 to 900°C and
a coiling temperature of 450 to 680°C to obtain hot rolled
steel sheets of a thickness of 4 mm After this the
steel sheets were pickled then cold rolled to obtain
cold rolled steel sheets of a thickness of 16 mm
Further part of these cold rolled steel sheets were
treated by hot dip aluminum coating hot dip aluminumzinc
coating alloying hot dip galvanization and hot dip
galvanization Table 5 shows the legends of the plating
types After this these cold rolled steel sheets and
surface treated steel sheets were heated by furnace
heating to above the Ac3 point that is the 950°C
austenite region then were hot shaped The atmosphere of
the heating furnace was changed in the amount of hydrogen
and the dew point The conditions are shown in Table 11
The cross-sectional shape of the mold is shown in
FIG 21 The legend in FIG 21 is shown here (1: pressforming
die 2: press-forming punch 3: piercing punch
4: button die) The shape of the punch as seen from above
is shown in FIG 22 The legend in FIG 22 is shown here
(2: press-forming punch 4: button die) The shape of the
die as seen from the bottom is shown in FIG 23 The
legend in FIG 23 is shown here (1: press-forming die 3:
piercing punch) The mold followed the shape of the
punch The shape of the die was determined by a clearance
of a thickness of 16 mm The piercing was performed
using a punch of a diameter of 20 mm and a die of a
diameter of 205 mm The blank size was made 16 mm
thickness x 300 x 500 The shaping conditions were made a
punch speed of 10 mm/s a pressing force of 200 ton and
a holding time at bottom dead center of 5 seconds A
schematic view of the shaped part is shown in FIG 24
From a tensile test piece cut out from the shaped part
54
the tensile strength of the shaped part was shown as
being 1470 MPa or more
The effect of the timing of the start of piercing
was studied by changing the length of the piercing punch
Table 11 shows the depth of shaping where the piercing is
started by the distance from bottom dead center as the
shearing timing To hold the shape after working this
value is within 10 mm preferably within 5 mm
The resistance to hydrogen embrittlement was
evaluated by observing the entire circumference of the
pieced holes one week after shaping to judge the presence
of cracks The observation was performed using a loupe or
electron microscope The results of judgment are shown
together in Table 11 Further the precision of the hole
shape was measured by a caliper and the difference from a
reference shape was found A difference of not more than
10 mm was considered good The results of judgment were
shown together in Table 11 Further the legend is shown
in Table 12
Experiment Nos 1 to 249 show the results of
consideration of the effects of the steel type plating
type concentration of hydrogen in the atmosphere and
dew point If in the scope of the invention no cracks
occurred Experiment Nos 250 to 277 show the results of
consideration of the timing of start of the shearing If
in the scope of the invention no cracks occurred and the
shape precision was also good
(Example 7)
Slabs of the chemical compositions shown in Table 4
were cast These slabs were heated to 1050 to 1350°C then
hot rolled at a finishing temperature of 800 to 900°C and
a coiling temperature of 450 to 680°C to obtain hot rolled
steel sheets of a thickness of 4 mm After this the
steel sheets were pickled then cold rolled to obtain
cold rolled steel sheets of a thickness of 16 mm
Further part of the cold rolled plates were treated by
hot dip aluminum coating hot dip aluminum-zinc coating
alloying hot dip galvanization and hot dip
galvanization Table 5 shows the legend of the plating
type After this these cold rolled steel sheets and
surface treated steel sheets were heated by furnace
heating to the above the Ac3 point that is the 950°C
austenite region then hot shaped The atmosphere of the
heating furnace was changed in the amount of hydrogen and
the dew point The conditions are shown in Table 13
A cross-section of the shape of the mold is shown in
FIG 14 The legend in FIG 14 is shown here (1: die 2:
punch) The shape of the punch as seen from above is
shown in FIG 15 The legend in FIG 15 is shown here (2:
punch) The shape of the die as seen from below is shown
in FIG 16 The legend in FIG 16 is shown here (1: die)
The mold followed the shape of the punch The shape of
the die was determined by a clearance of a thickness of
16 mm The blank size (mm) was made 16 thickness x 300
x 500 The shaping conditions were a punch speed of 10
mm/s a pressing force of 200 tons and a holding time at
bottom dead center of 5 seconds A schematic view of the
shaped part is shown in FIG 17 From a tensile test
piece cut out from the shaped part the tensile strength
of the shaped part was shown as being 1470 MPa or more
After hot shaping a hole of a diameter of 10 mm made at the position shown in FIG 25 FIG 25 shows the
shape of the part as seen from above The legend in FIG
25 is shown here (1: part 2: hole part) As the working
method laser working plasma cutting drilling and
cutting by sawing by a counter machine were performed
The working methods are shown together in Table 13 The
legend in the table is shown next: laser working: "L"
plasma cutting: "P" gas fusion cutting "G" drilling:
"D" and sawing: "S" The above working was performed
within 30 minutes after the hot shaping The resistance
to hydrogen embrittlement was evaluated by examining the
entire circumference of the holes one week after the
working so as to judge the presence of any cracking The
observation was performed using a loupe or electron
microscope The results of judgment are shown together in
Table 3
Further the heat effect near the cut surface was
examined for laser working plasma cutting and gas
fusion cutting The cross-sectional hardness at a
position 3 mm from the cut surface was examined by
Vicker's hardness of a load of 10 kgf and compared with
the hardness of a location 100 mm from the cut surface
where it is believed there is no heat effect The results
are shown as the hardness reduction rate below This is
shown together in Table 13
Hardness reduction rate = (hardness at position 100
mm from cut surface) - (hardness of position 3 mm from
the cut surface)/(hardness at position 100 mm from cut
surface) x 100 (%)
The legend at that time is as follows: Hardness
61
reduction rate less than 10%: VG hardness reduction rate
10% to less than 30%: G hardness reduction rate 30% to
less than 50%: F hardness reduction rate 50% or more: P
Experiment Nos 1 to 249 show the results of
consideration of the effects of the steel type plating
type concentration of hydrogen in the atmosphere and
dew point for the case of laser working If in the scope
of the invention no cracks occurred after piercing
Experiment Nos 250 to 277 show the results of plasma
working as the effect of the working method If in the
scope of the invention no cracks occurred after
piercing Experiment Nos 278 to 526 show the results of
consideration of the effects of the steel type plating
type concentration of hydrogen in the atmosphere and
dew point in the case of drilling If in the scope of the
invention no cracks occurred after piercing Experiment
Nos 527 to 558 show the results of sawing as the effect
of the method of working If in the scope of the
invention no cracks occurred after piercing
Experiment Nos 559 to 564 are experiments changing
the fusion cutting method Since the atmospheres are in
the scopes of the invention and the methods are fusion
cutting cracking does not occur but it is learned that
in Experiment Nos 561 and 564 the hardness near the cut
parts falls From this it is learned that the fusion
cutting method shown in claims 2 and 3 are superior in
that the heat affected zones are small
Slabs of the chemical compositions shown in Table 4
were cast These slabs were heated to 1050 to 1350°C and
hot rolled at a finishing temperature of 800 to 900°C and
a coiling temperature of 450 to 680°C to obtain hot rolled
steel sheets of a thickness of 4 mm After this the
steel sheets were pickled then cold rolled to obtain
cold rolled steel sheets of a thickness of 16 mm
Further parts of the cold rolled plates were treated by
hot dip aluminum coating hot dip aluminum-zinc coating
alloying hot dip galvanization and hot dip
galvanization Table 5 shows the legends of the plating
types After this these cold rolled steel sheets and
surface treated steel sheets were heated by furnace
heating to more than the Acs point that is the 950°C
austenite region then hot shaped The atmosphere of the
heating furnace was changed in the amount of hydrogen and
the dew point The conditions are shown in Table 14
A cross-section of the shape of the mold is shown in
FIG 14 The legend in FIG 14 is shown here (1: die 2:
punch) The shape of the punch as seen from above is
shown in FIG 15 The legend in FIG 15 is shown here (2:
punch) The shape of the die as seen from below is shown
in FIG 16 The legend in FIG 16 is shown here (1: die)
The mold followed the shape of the punch The shape of
the die was determined by a clearance of a thickness of
16 mm The blank size (mm) was 16 thickness x 300 x
500 The shaping conditions were a punch speed of 10
mm/s a pressing force of 200 tons and a holding time at
bottom dead center of 5 seconds A schematic view of the
shaped part is shown in FIG 17 From a tensile test
piece cut out from the shaped part the tensile strength
of the shaped part was shown as being 1470 MPa or more
The shearing performed was piercing The position
shown in FIG 18 was pierced using a punch of a diameter
of 10 mmcj) and using a die of a diameter of 105 mm FIG 5
shows the shape of the part as seen from above The
legend in FIG 18 is shown here (1: part 2: center of
pierce hole) The piercing was performed within 30
minutes after the hot shaping After piercing reaming
was performed The working method is shown together in
Table 14 For the legend the case of reaming is shown by
"R" while the case of no working is shown by "N" At
that time the finished hole diameter was changed and the
effect on the thickness removed was studied The
conditions are shown together in Table 14 The reaming
was performed within 30 minutes after the piercing The
resistance to hydrogen embrittlement was evaluated after
one week from reaming by observing the entire
circumference of the hole to judge for the presence of
cracking The observation was performed by a loupe or
electron microscope The results of judgment are shown
together in Table 4
Experiment Nos 1 to 277 show results of
consideration of the effects of the steel type plating
type concentration of hydrogen in the atmosphere and
dew point in the case of reaming If in the scope of the
invention no cracks occurred after the piercing
Experiment Nos 278 to 289 show the results of
consideration of the effects of the amount of working In
the scope of the invention no cracks occurred after the
piercing






1. A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
0.05 to 0.55% and Mn: 0.1 to 3% in chemical composition
heating the steel sheet in an atmosphere of by volume
percent hydrogen in an amount of 10% or less (including
0%) and of a dew point of 30°C or less until the Ac3 to
the melting point then starting the shaping at a
temperature higher than the temperature at which ferrite
pearlite bainite and martensite transformation occurs
cooling and hardening after shaping in the mold to
produce a high strength part then further performing
post-processing.
2. A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
0.05 to 0.55% and Mn: 0.1 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere of by volume
percent hydrogen in an amount of 10% or less (including
0%) and of a dew point of 30°C or less to the Ac3 to the
melting point then starting the shaping at a temperature
higher than the temperature where ferrite pearlite
bainite and martensite transformation occurs cooling
and hardening after shaping in the mold to produce a high
strength part shearing it then shearing again 1 to 2000
urn from the worked end.
3. A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
0.05 to 0.55% and Mn: 0.1 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere with an amount
of hydrogen by volume percent of 10% or less (including
0%) and of a dew point of 30°C or less to the Ac3 to the
melting point then starting the shaping at a temperature
higher than the temperature where ferrite pearlite
bainite and martensite transformation occurs cooling
and hardening after shaping in the mold to produce a high strength part then shearing and pressing the sheared end face.
4. A method of production of a high strength part
as set forth in claim 3 characterized by using coining
as the method of press working.
5. A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
0.05 to 0.55% and Mn: 0.1 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere of by volume
percent hydrogen in an amount of 10% or less (including
0%) and of a dew point of 30°C or less to the Acs to the
melting point then starting the shaping at a temperature
higher than the temperature where ferrite pearlite
bainite and martensite transformation occurs and
cooling and hardening after shaping in the mold to
produce a high strength part and punching or cutting this
during which using a cutting blade having a step
difference continuously decreasing from the radius of
curvature or width of the blade base by 0.01 to 3.0 mm in
the direction from the blade base to the blade tip and
having a height of 1/2 the thickness of the steel sheet
to 100 mm for the punching or cutting.
6. A method of production of a high strength part
as set forth in claim 5 characterized by having a step
difference continuously decreasing from the radius of
curvature or width of the blade base by 0.01 to 3.0 mm in
the direction from the blade base to the blade tip and by
D/H being 0.5 or less when a height of said step
difference of H (mm) and a difference of the radius of
curvature or width of the blade base and blade tip is D
(mm) .
7. A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
0.05 to 0.55% and Mn: 0.1 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere having an amount of hydrogen by volume percent of 10% or less (including 0%) and of a dew point of 30°C or less to the Acs to the melting point then starting shaping at a temperature higher than the temperature where ferrite pearlite bainite and martensite transformation occurs cooling and hardening after shaping in the mold to produce a high strength part then punching the steel sheet forming the worked material using a die and punch to cut it to shearing and sheared parts to form the worked material to a predetermined shape during which using a punching tool having a bending blade having a shape projecting out at the front of the punch and/or die and having a radius of curvature of the shoulder of the bending blade of 0.2 mm or more to make the clearance 25% or less.
8. A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
0.05 to 0.55% and Mn: 0.1 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere of by volume
percent hydrogen in an amount of 10% or less (including
0%) and of a dew point of 30°C or less to the Acs to the
melting point then starting the shaping at a temperature
higher than the temperature where ferrite pearlite
bainite and martensite transformation occurs cooling
and hardening after shaping in the mold to produce a high
strength part then punching the steel sheet forming the
worked material using a die and punch to cut it to
shearing and sheared parts to form the worked material to
a predetermined shape during which using a punching tool
having a shape projecting out at the front of the punch
and/or die and having an angle of the shoulder of the
bending blade of 100° to 170° to make the clearance 25% or
less.
9. A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
0.05 to 0.55% and Mn: 0.1 to 3% and having a balance of Fe and unavoidable impurities in chemical composition heating the steel sheet in an atmosphere of by volume percent hydrogen in an amount of 10% or less (including 0%) and of a dew point of 30°C or less to the Ac^ to the melting point then starting the shaping at a temperature higher than the temperature where ferrite pearlite bainite and martensite transformation occurs cooling and hardening after shaping in the mold to produce a high strength part then punching the steel sheet forming the worked material using a die and punch to cut it into a shearing part and a sheared part and make the worked material a predetermined shape during which using a punching tool having a bending blade having a shape projecting out at the front of the punch and/or die and having a radius of curvature of the shoulder of the bending blade of 0.2 mm or more and an angle of the shoulder of the bending blade of 100° to 170° to make the clearance 25% or less.
10. A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
0.05 to 0.55% and Mn: 0.1 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere of by volume
percent hydrogen in an amount of 10% or less (including
0%) and of a dew point of 30°C or less to the Ac3 to the
melting point then starting the press-forming at a
temperature higher than the temperature where ferrite
pearlite bainite and martensite transformation occurs
and cooling and hardening after shaping in the mold to
produce a high strength part during which applying the
shearing near bottom dead point.
11. A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
0.05 to 0.55% and Mn: 0.1 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere of by volume percent hydrogen in an amount of 10% or less and having a dew point of 30°C or less to the Acs to the melting point starting the shaping at a temperature higher than the temperature where ferrite pearlite bainite and martensite transformation occurs cooling and hardening after shaping in the mold to produce a high strength part then melting part of the part to cut it.
12. A method of production of a high strength part
as set forth in claim 11 characterized by using laser
working as the method of working for melting and cutting
part of the part.
13. A method of production of a high strength part
as set forth in claim 11 characterized by using plasma
cutting as the method of working for melting and cutting
part of the part.
14. A method of production of a high strength part
characterized by using steel sheet containing by wt% C:
0.05 to 0.55% and Mn: 0.1 to 3% and having a balance of
Fe and unavoidable impurities in chemical composition
heating the steel sheet in an atmosphere of by volume
percent hydrogen in an amount of 10% or less and of a
dew point of 30°C or less to the Aca to the melting point
then starting the shaping at a temperature higher than
the temperature where ferrite pearlite bainite and
martensite transformation occurs cooling and hardening
after shaping in the mold to produce a high strength
part then machining this to perforate it or cut around
the part.
15. (Amended) A method of production of a high
strength part characterized by using steel sheet
containing by wt% C: 0.05 to 0.55% and Mn: 0.1 to 3%
and having a balance of Fe and unavoidable impurities in
chemical composition heating the steel sheet in an
atmosphere of by volume percent hydrogen in an amount
of 10% or less and of a dew point of 30°C or less to the
Ac3 to the melting point
then starting the shaping at a temperature higher than the temperature where ferrite pearlite bainite and martensite transformation occurs cooling and hardening after shaping in the mold to produce a high strength part then shearing and mechanically differentially cut surface of the sheared part to remove a thickness of 0.05 mm or more.
16. A method of production of a high strength part
as set forth in any one of claims 1 to 15 characterized
in that the chemical composition of said steel sheet is
by wt% C: 0.05 to 0.55% Mn: 0.1 to 3% Al: 0.005 to
0.1% S: 0.02% or less P: 0.03% or less and N: 0.01% or
less and the balance of Fe and unavoidable impurities.
17. A method of production of a high strength part
as set forth in any one of claims 1 to 15 characterized
in that the chemical composition of said steel sheet is
by wt% C: 0.05 to 0.55% Mn: 0.1 to 3% Si: 1.0% or
less Al: 0.005 to 0.1% S: 0.02% or less P: 0.03% or
less Cr: 0.01 to 1.0% and N: 0.01% or less and the
balance of Fe and unavoidable impurities.

18. (Amended) A method of production of a high
strength part as set forth in any one of claims 1 to 15
characterized in that the chemical composition of said
steel sheet is by wt% C: 0.05 to 0.55% Mn: 0.1 to 3%
Si: 1.0% or less Al: 0.005 to 0.1% S: 0.02% or less P:
0.03% or less Cr: 0.01 to 1.0% B: 0.0002% to 0.0050%
Ti: (3.42 x N + 0.001)% or more {3.99 x (C-0.05) + (3.42
x N + 0.001)}% or less and N: 0.01% or less and the
balance of Fe and unavoidable impurities.
19. (Amended) A method of production of a high
strength part as set forth in any one of claims 1 to 15
characterized in that the chemical composition of said
steel sheet is by wt% C: 0.05 to 0.55% Mn: 0.1 to 3%
Si: 1.0% or less Al: 0.005 to 0.1% S: 0.02% or less P:
0.03% or less Cr: 0.01 to 1.0% B: 0.0002% to 0.0050%
Ti: (3.42 x N + 0.001)% or more {3.99 x (C-0.05) + (3.42
x N -I- 0.001)}% or less N: 0.01% or less and 0: 0.015%
or less and the balance of Fe and unavoidable impurities .
20. A method of production of a high strength
part as set forth in any one of claims I to 15
characterized in that said steel sheet is treated by
any of aluminum plating aluminum-zinc plating and
zinc plating.
21. A high strength part characterized by being
produced by a method as set forth in any one of claims
1 to 20.
22. A method of production of a high strength
part substantially as herein described with reference
to foregoing examples illustrations and accompanying
drawings.

Documents:

2015-delnp-2007-Abstract (20-04-2011).pdf

2015-delnp-2007-abstract.pdf

2015-delnp-2007-Claims (20-04-2011).pdf

2015-delnp-2007-claims.pdf

2015-delnp-2007-Correspondence Others-(27-11-2013).pdf

2015-delnp-2007-Correspondence-others (20-04-2011).pdf

2015-delnp-2007-Correspondence-Others-(10-06-2013).pdf

2015-delnp-2007-correspondence-others-1.pdf

2015-delnp-2007-correspondence-others.pdf

2015-delnp-2007-description (complete).pdf

2015-delnp-2007-Drawings (20-04-2011).pdf

2015-delnp-2007-drawings.pdf

2015-delnp-2007-Form-1 (20-04-2011).pdf

2015-delnp-2007-form-1.pdf

2015-delnp-2007-Form-13 (20-04-2011).pdf

2015-delnp-2007-form-18.pdf

2015-delnp-2007-Form-2 (20-04-2011).pdf

2015-delnp-2007-form-2.pdf

2015-delnp-2007-form-26.pdf

2015-delnp-2007-Form-3 (20-04-2011).pdf

2015-delnp-2007-form-3.pdf

2015-delnp-2007-form-5.pdf

2015-delnp-2007-GPA (20-04-2011).pdf

2015-delnp-2007-pct-210.pdf

2015-delnp-2007-pct-304.pdf

2015-delnp-2007-pct-308.pdf


« Previous Patent
Next Patent »
Patent Number 260099
Indian Patent Application Number 2015/DELNP/2007
PG Journal Number 14/2014
Publication Date 04-Apr-2014
Grant Date 31-Mar-2014
Date of Filing 15-Mar-2007
Name of Patentee NIPPON STEEL CORPORATION
Applicant Address 6-3, OTEMACHI 2-CHOME, CHIYODA-KU, TOKYO 100-8071, JAPAN
Inventors:
# Inventor's Name Inventor's Address
1 NOBUHIRO FUJITA C/O NIPPON STEEL CORPORATION NAGOYA WORKS, 5-3, TOKAIMACHI, TOKAI-SHI, AICHI 476-8686, JAPAN
2 NORIYUKI SUZUKI C/O NIPPON STEEL CORPORATION TECHNICAL DEVELOPMENT BUREAU, 20-1, SHINTOMI, FUTTSU-SHI, CHIBA 293-8511, JAPAN
3 KUNIO HAYASHI C/O NIPPON STEEL CORPORATION TECHNICAL DEVELOPMENT BUREAU, 20-1, SHINTOMI, FUTTSU-SHI, CHIBA 293-8511, JAPAN
4 JUN MAKI C/O NIPPON STEEL CORPORATION YAWATA WORKS, 1-1, TOBIHATACHO, TOBATA-KU, KITAKYUSHU-SHI, FUKUOKA 804-8501, JAPAN
5 MANABU TAKAHASHI C/O NIPPON STEEL CORPORATION TECHNICAL DEVELOPMENT BUREAU, 20-1, SHINTOMI, FUTTSU-SHI, CHIBA 293-8511, JAPAN
6 KAZUHISA KUSUMI C/O NIPPON STEEL CORPORATION YAWATA WORKS, 1-1, TOBIHATACHO, TOBATA-KU, KITAKYUSHU-SHI, FUKUOKA 804-8501, JAPAN
7 HIRONORI SATO C/O NIPPON STEEL CORPORATION TECHNICAL DEVELOPMENT BUREAU, 20-1, SHINTOMI, FUTTSU-SHI, CHIBA 293-8511, JAPAN
8 MASAYUKI ABE C/O NIPPON STEEL CORPORATION YAWATA WORKS, 1-1, TOBIHATACHO, TOBATA-KU, KITAKYUSHU-SHI, FUKUOKA 804-8501, JAPAN
9 SHINYA NAKAJIMA C/O NIPPON STEEL CORPORATION YAWATA WORKS, 1-1, TOBIHATACHO, TOBATA-KU, KITAKYUSHU-SHI, FUKUOKA 804-8501, JAPAN
10 MASAHIRO OOGAMI C/O NIPPON STEEL CORPORATION YAWATA WORKS, 1-1, TOBIHATACHO, TOBATA-KU, KITAKYUSHU-SHI, FUKUOKA 804-8501, JAPAN
11 TOSHIYUKI KANDA C/O NIPPON STEEL CORPORATION TECHNICAL DEVELOPMENT BUREAU, 20-1, SHINTOMI, FUTTSU-SHI, CHIBA 293-8511, JAPAN
12 YUZO TAKAHASHI C/O NIPPON STEEL CORPORATION OITA WORKS, 1-OAZA-NISHINOSU, OITA-SHI,OITA 870-8566,JAPAN
PCT International Classification Number B21D 28/00
PCT International Application Number PCT/JP2005/017441
PCT International Filing date 2005-09-15
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2004-309779 2004-10-25 Japan
2 2004-267792 2004-09-15 Japan
3 2004-267795 2004-09-15 Japan
4 2004-267797 2004-09-15 Japan