TECHNICAL FIELD
[000 r]
The present invention relates to a metal sheet such as a steel sheet suited to be
used in structural components of autornobiles, various kinds of vehicles other than
automobiles, horne appliances, vessels, construction materials and so on. In
particular, the present invention relates to a metal sheet with raised lines, on one of
the upper surface and the lower surf,ace, one or more raised lines extending in the
rolling direction, a method for producing the metal sheet with raised lines, and a
structural component produced by use of the metal sheet with raised lines.
BACKGROUND ART
[0002]
Pressed parts are used in general structural components. The material of a
pressed part is a metal sheet such as a steel sheet. A structural component is formed
from a single pressed part or formed by joining a plurality of pressed parts. For
example, the structural components for automobiles described in Japanese Patent
Application Publication No. 2013-189173 (Pafent Literature 1) and Japanese Patent
Application Publication No. 201 4-91462 (Patent Literature 2) each include a
verlically-long pressed part. The cross section of the pressed part is U-shaped.
[0003]
FIGS. 1A and 1B show an example of a structural component. Of these
drawings, FIG, lA is a perspective view of the structural component, and FIG. 1B is
a cross-sectional view of an end portion of the structural component illustrated in
FIG. lA. The structural component 20 illustrated in FIGS. 1A and 1B includes two
pressed parts2l, each having a U-shaped cross section. Each ofthe pressed parts
2l includes a plate portion 24 and flanges 22 extending from the both sides of the
plate portion 24. By welding the flanges 22 of the two pressed parts 21 together,
the structural component 20 in the shape of a square-pipe is obtained. Reinforcing
plates 40 are welded to the back side of the two plate portion 24 and four ridge
portions 23 of the structural component 20, at both end portions in the longitudinal
direction. In this case, however, the strength of the structural component 20 is
increased only at both end portions in the longitudinal direction. Therefore, it can
be considered that the reinforcement of the structural component 20 is not sufficient.
[0004]
In order to produce a parlly-reinforced structural component such as the
structural component 20 illustrated in FIGS. lA and 18, it is necessary to weld the
reinforcing plates 40 to the portions that need to be reinforced. Accordingly, a
welding process must be separately carried out to partly reinforce the structural
component 20, which results in an increase in manufacturing cost.
CITATION LIST
PATENT LITERATURE
[000s]
Patent Literature 1: Japanese Patent Application Publication No. 2013-189113
Patent Literature 2: Japanese Patent Application Publication No.2014-91462
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0006]
The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a production method that, in
producing a partly-reinforced structural component, facilitates the production of a
metal sheet with raised lines suitable as a material for the structural component. ln
addition, another object of the present invention is to provide a metal sheet with
raised lines suited to be used for the production of the structural component, and a
structural component using the metal sheet with raised lines.
SOLUTION TO PROBLEM
[0007]
(1) A metal sheet production method according to an embodiment of the
present invention is a method for producing a metal sheet by use of a rolling mill
including at least two roll stands, the rnetal sheet including, on an upper surface or a
lower surface, one or ffrore raised lines extending in a rolling direction. The
production method includes a preparing step, a choosing step, an incorporating step,
and a forming step. In the preparing step, a grooved roll is prepared, the grooved
roll including, in an outer peripheral surface, one or more grooves extending in a
circumferential direction. In the choosing step, a roll stand at least one stage before
a last roll stand is chosen from the roll stands.
In the incorporating step, the grooved roll is incorporated in the rolling mill as
an upper roll or a lower roll of the chosen, specifred roll stand. In the forming step,
a workpiece is rolled by the rolling mill incorporating the grooved roll, thereby
forming the workpiece into a metal sheet with raised lines formed corresponding to
the respective grooves of the grooved roll. At this point, in the forming step, until a
leading edge of the workpiece reaches a roll stand next to the specified roll stand, a
maximum rollingreduction achieved by rolls of the specified rollstand is setto a
provisional value that is lower than a required value. Then, after the leading edge
of the workpiece reaches the roll stand next to the specified roll stand, the maximum
rolling reduction achieved by the rolls of the specifred roll stand is changed to the
required value.
[0008]
In the production rnethod (l), the required value is preferably l0 to 80%.
[000e]
In the production method (1), the provisionalvalue is preferably 10 to 90% of
the required value.
[0010]
In the production method (1), it is preferred that, in a longitudinalsection of
the grooved roll, the grooves are in a bilaterally symmetric arrangement.
[00r r ]
ln the production method (1), in a longitudinal section of the grooved roll, the
grooves may be rectangular, trapezoidal or V'shaped.
[00 r 2]
In the production method (1), each of the grooves of the grooved rollrnay
have a width more than 5 mm and less than 2000 mm.
[0013]
In the production method (1), the grooves of the grooved rollmay be at a
pitch more than 15 mm and less than 2000 mm.
[00 r 4]
(2) A rnetal sheet with raised lines according to an embodiment of the present
invention is a metal sheet including one or more raised lines on an upper surface or a
lower surface. The raised lines are at a pitch more than l5 mm and less than 2000
mm. A sheet thickness ratio (t / trnin) of a raised*line sheet thickness t to a
minimum sheet thickness tmin is more than 1.0 and less than 10.0, the raised-line
sheet thickness t being expressed as a sum of the minimum sheet thickness tmin and
a height h of the raised lines.
[001s]
In the metal sheet with raised lines (2), each of the raised lines may have a
width rnore than 5 mm and less than 2000 mm.
[00 i 6]
(3) A structural component according to an embodiment of the present
invention including one or more raised lines on a front side or a back side. The
structural component includes a reinforced portion that is increased in strength, and
the raised lines are disposed on the front side or the back side ofthe reinforced
portion.
ADVANTAGEOUS EFFECTS OF INVENTION
[0017]
The production method according to the present invention facilitates the
production of a metal sheet with raised lines. This metal sheet with raised Iines
includes, on one of an upper surface and a lower surface, one or more raised lines
extending in a rolling direction. Accordingly, using the metal sheet with raised
lines as a material to produce a partly-reinforced structural component allows for
production of a structural component including a reinforced portion that is reinforced
in the entire area. Thus, the metal sheet with raised lines according to the present
invention is suitable as a material for a partly-reinforced structural component.
BRIEF DESCRIPTION OF DRAWINGS
[00 r 8]
[FIG. 1A] FIG. 1A is a perspective view of an example of a structural component.
IFIG. i B] FIG. 1B is a cross-sectional view of an end portion of the structural
component illustrated in FIG. lA.
[FIG. 2] FIG. 2 is a schematic diagrarn of an example of a production facility used
for the production of a metal sheet with raised lines according to an embodiment of
the present invention.
[FIG.3] FIG.3 is across-sectionalview of an example of aroll stand incorporatinga
grooved roll according to the embodiment of the present invention.
IFIG. 4] FIG. 4 is a perspective view of a metal sheet with raised lines produced by a
finish-rolling mill including the ro11 stand illustrated in FIG. 3.
[FIG, 5] FIG. 5 is a schematic cross-sectional view of an example of the metal sheet
with raised lines.
[FIG. 6] FIG. 6 is a schematic cross-sectional view of an example of the metal sheet
with raised lines.
[FIG. 7] FIG. 7 is a schematic cross-sectional view of an example of the metal sheet
with raised lines.
[FIG. 8] FIG. 8 is a schematic cross-sectionalview of an example of the metal sheet
with raised lines.
[FlG. 9] FIG. 9 is a cross-sectionalview of an example of a blank cut out from a
metal sheet with raised lines to be used for the production of a structural component
according to an embodiment of the present invention.
[FfG. 104] FIG. 104 is a schematic cross-sectional view of an example of an
apparatus for pressing the blank illustrated in FIG. 9 into a structural component.
IFIG. 108] FIG. 108 is a cross-sectional view of a pressed part formed by the
apparatus illustrate in FIG. 104.
[FIG. 114] FIG, 114 is a schematic cross-sectional view of another example of an
apparatus for pressing the blank illustrated in FIG. 9 into a structural component.
IFIG. 1 1B] FIG. I lB is a cross-sectional view of a pressed part fonned by the device
illustrate in FIG. 1 lA.
[FIG. 12] FIG. 12 is a schematic diagrarn of an example of a structural component.
[FIG. 13] FIG. l3 is a schematic diagram of an example of a structural component.
[FIG. 14] FIG. 14 is a schematic diagram of an example of a structural component.
[FIG. I 5] FIG. I 5 is a schematic diagram of an example of a structural component.
IFIG. 1 6] FIG. I 6 is a schematic diagram of an example of a structural component.
DESCRIPTION OF EMBODIMENTS
[001e]
Some embodiments of the present invention will hereinafter be described with
reference to the drawings.
[0020]
fProducing Metal Sheet with Raised Lines]
FIG. 2 is a schematic diagram of an example of a production facility used for
the production of a metal sheet with raised lines according to an embodiment of the
present invention. The present embodiment describes the production of a steel
sheet I 0 with raised lines as an example of the production of a metal sheet with
raised lines. Specifìcally, in the following, the production of a rnetal sheet with
raised lines with a steel slab 30 used as a material for the metal sheet with raised
lines will be described.
[0021]
The production facility illustrated in FIG. 2 includes a heating furnace 1, a
rough-rollingmill2, a finish-rolling mill 3, a cooling device 4, and a coiler 5 that are
arranged in this order. The heating furnace I heats the slab 30. The heated slab 30
is first fed to the rough-rollingmill2. The rough-rolling mill2 rolls the slab 30 to
form the slab 30 into a longer-length steel plate 3l having a thickness of, for example,
about 50 mm. The steel plate 3l is fed to the frnish-rolling mill 3. The finishrolling
mill3 includes a row of six rollstands Sl to 56 (which may hereinafter be
referred to as simply "stands"). The steel plate 31 is rolled while passing through
the stands S1 to S6 successively, whereby the steel plate 3l is fonned into asteel
sheet 10 having a desired thickness. Thus, the steel plate 31 is a workpiece to be
rolled by the flinish-rolling rnill 3. The steel sheet l0 is cooled while passing
through the cooling device 4, and is wound up into a coil by the coiler 5.
100221
Each of the stands Sl to S6 of the finish-rolling mill3 includes an upper roll 6
and a lower roll 7 (work rolls), and further includes back-r"rp rolls paired with the
rolls 6 and 7 respectively. Each of the stands Sl to 56 is provided with an interroll-
axis distance adjustment mechanism (not shown in the drawings). Each interroll-
axis distance adjustment mechanism adjusts the distance between the axis of the
upper roll 6 and the axis of the lower roll 7. The inter-roll-axis distance adjr"rstment
mechanism allows for adjustment of the rolling reduction achieved by the upper roll
6 and the lower rollT in each of the stands Sl to 56.
[00231
Each of the stands S1 to 56 is provided with a load cell(not shown in the
drawings). The load cell measures the rolling load applied by the upper roll 6 and
the lower roll 7. The load cell allows for monitoring of the rolling load in each of
the stands S 1 to 56. The load cell also allows for detection of a time point at which
the leading edge of the steelplate 31 reaches each of the stands Sl to 56 (atime
point at which the leading edge of the steel plate 3 1 is pinched in a gap between the
upper roll 6 atld a lower roll 7).
[00241
However, in a case where any of the stands S1 to 36 does not perform to
roll the steel plate 31, no rolling load occurs in the non-rolling-performing stand. In
this case, detection as to whether the leading edge of the steel plate 31 has reached
the non-rolling-performing stand can be carried out by use of the output from the
load cell provided in a rolling-perfonning stand that is one stage before the nonrolling-
performing stand. Specifically, the load cell detects the leading edge of the
steel plate 31 reaching the rolling-performing stand, and an elapsed time from a time
point of the detection is measured. Based on the elapsed time, a theoretical running
speed of the workpiece due to rolling by the rolling-performing stand, and a distance
between a roll axis of the rolling-performing stand and a roll axis of the next nonrolling-
perfonning stand, it is possible to calculate the time point at which the
leading edge of the steel plate 3l has reached the non-rolling-perfoming stand.
However, each of the stands S1 to S6 may be provided with a sensor that detects
passing of the leading edge of the steel plate 31.
[002s]
In the present embodiment, in order to produce the steel sheet 10 with raised
Iines, a grooved roll, which will be described later, is incorporated in one specified
rollstand that is selected from amongthe roll stands S1 to S6 of the finish-rolling
mill 3. The specifìed stand is chosen according to rolling capabilities (e.g., rolling
loads, rolling reductions, etc.) of the stands S1 to 56. For example, in the finishrolling
mill 3 illLrstrated in FIG. 2, the fourth stand 54, which is two stages before the
last sixth stand 56, incorporates the grooved rol1. There is no particular limit to the
stand to incorporate the grooved roll. It is noted that the grooved roll should not be
incorporated in the last stand 56 in the present embodiment because of a reason to be
described later. In other words, the grooved roll is incorporated in a stand at least
one stage before the last stand 56. One or more stands in stages subsequent to the
stand including the grooved roll incorporated therein each serve as a non-rollingperforming
stand, which does not substantially roll, and rolls incorporated in the nonrolling-
performing stand function as rolls for conveyance.
100261
FIG. 3 is a cross-sectionalview of an example of a rollstand incorporating a
grooved roll according to the enbodiment of the present invention. FIG. 4 is a
perspective view of a metal sheet with raised lines produced by the finish-rolling mill
including the roll stand illustrated in FIG. 3. In the present embodiment, as shown
in FIG. 3, a grooved roll 8 is incorporated in as the upper roll 6, of the upper roll 6
and the lower roll 7 of the specified stand (the fourth stand 54 illustrated in FIG. 2).
As the lower roll 7, a nonnal flat roll is incorporated in. In other words, the
grooved roll 8 is incorporated in as one of the upper roll6 and the lower roll7. ln
the stands other than the specified stand, nonnal flat rolls are incorporated.
100271
In the outer peripheral surface ofthe grooved roll 8, one or more grooves 9
(hereinafter, also referred to as "roll grooves") are made to extend in the
circumferential direction, FIG. 3 illustrates how eight roll grooves 9 are provided at
regular intervals. By the finish-rolling mill 3 including the grooved roll I
incorporated therein, the steel plate 31 is rolled. Thereby, raised lines 1 i are
fonned corresponding to the respective roll grooves 9, and a steel sheet 10 with
raised lines 1 1 is produced (see FIG. 4). The raised lines 1l extend in the rolling
direction of the steelsheet 10. As shown in FIGS. 3 and4, since the grooved roll 8
is incorporated in as the upper roll 6, the raised lines I I are formed on the upper
surface of the steel sheet 10. In other words, the raised lines 11 are fonned on one
of the r"rpper surface and the lower surface of the steel sheet 10.
[0028]
In longitudinalsections of the grooved roll 8, each of the rollgrooves 9 is
rectangular, trapezoidal or V-shaped. Here, being rectangular,trapezoidal or Vshaped
includes being in a shape varying a little from these shapes and in a cornbined
shape ofcurved lines.
[002e]
It is preferred that, in a longitudinal section of each of the grooved roll 8, the
arrangement of the roll grooves 9 is bilaterally symmetric as shown in FIG. 3, Here,
bilaterally means in a direction along the axial direction of the grooved roll 8 and in a
width direction that is perpendicular to the rolling direction of the steel sheet 10. If
the arrangement of the roll grooves 9 is bilaterally asymmetric, the rolling performed
by the grooved rolls 8 willbe bilaterally uneven. In this case, the steel sheet 10 is
likely to move obliquely, and trouble may occur during operation. On the other
hand, when the arrangement of the roll grooves 9 is bilaterally syrnmetric, the rolling
performed by the grooved rolls 8 is bilaterally even. Then, the steel sheet 10 moves
straight in the rolling direction, and any trouble due to oblique movement of the steel
sheet l0 will not occur during operation.
[0030]
The width w1 of the roll grooves 9 corresponds to the width of the raised lines
1l of the steelsheet 10. The pitch of the rollgrooves 9 corresponds to the pitch p
ofthe raised lines I 1 ofthe steel sheet 10. The depth ofthe roll grooves 9
corresponds to the height h ofthe raised lines I I ofthe steel sheet 10. In the steel
sheet 10, the portion with the minimum sheet thickness tmin is formed by the rolling
l0
of the portion of the grooved rollwith no rollgrooves 9 (the portion hereinafter
referred to as "non-grooved pofiion") and the flat rolls. The minimum sheet
thickness tmin of the steel sheet i0 is the minimum sheet thickness of the portion
with no raised lines I 1. The width w2 of the non-grooved poftion corresponds to
thewidthof arecessedportion 12betweentwoadjacentraisedlines iI (therecessed
portion hereinafter referred to as "inter-raised-line recessed portion"). The
dimensions regarding the roll grooves 9 and the raised lines 1 I (including the
numbers and the cross-sectionalshapes of these members 9 and 11) are determined
basically by the designed dimensions of a structural component (pressed part) to be
produced by use of the steel sheet 10 with raised lines. The determination is made
in consideration of the capability of the finish-rolling mill 3, the effective length of
the roll (practically 2000 mm at rnost) and so on. Further, the determination is
made in consideration of the formability of the steelsheet l0 with raised lines into
the pressed part.
[0031]
For example, the width wl of the roll grooves 9 (that is, the width of the
raised lines I 1) can be set to a value more than 5 mm and less than 2000 mm. In
this regard, however, the width of the roll grooves 9 is desirably equal to or greater
than 10 mm, and more desirably equal to or greater than 20 mm. This is to secure a
suffrcient width for a reinforced portion of a structural component to be produced by
use of the steel sheet 10 with raised lines, thereby ensuring the strength of the
structural component. Also, the width of the roll grooves 9 is desirably equal to or
less than 1000 rnm, and more desirably equal to or less than 500 mm. This is to
reduce the weight ofa structural component to be produced by use ofthe steel sheet
l0 with raised lines.
[0032]
The pitch of the roll grooves 9 (that is, the pitch p of the raised lines 11) can
be set to a value more than 15 mm and less than 2000 mrn, ln this regard, however,
the pitch of the roll grooves 9 is desirably more than 20 mm. This is to ensure the
width wl of the rollgrooves 9 (that is, the rvidth of the raised lines 11), thereby
ensuring the strength of a structural component to be produced by r.rse of the steel
sheet 10 with raised lines. Also, the pitch ofthe roll grooves 9 is desirably equal to
11
or less than 500 mrn, and more desirably equalto or less than 200 mm. The reason
is as follows. If the pitch of the roll grooves 9 is too large, in a case where the
width of the rollgrooves 9 (thar" is, the width of the raised lines l1) is small, the
width w2 of the non-grooved portion (that is, the width of the inter-raised-line
recessed portion l2) will be large. Then, the portion with the minimum sheet
thickness tmin of the steel sheet 10 willhave a large width. In this case, the portior"r
with the minimum sheet thickness tmin will deform easily, and the quality of the
steel sheet 10 will be degraded.
[0033]
The sheet thickness ratio (t / tmin¡ of the raised line sheet thickness t (tmin +
h), which is the sum of the minimum sheet thickness tmin of the steel sheet 10 and
the height h of the raised lines 11 (that is, the depth of the roll grooves 9), to the
minimum sheet thickness tmin can be set to a value more than 1.0 and less than 10.0.
In this regard, however, the sheet thickness ratio (t / trnin) is desirably equal to or
rnore than 1,2. This is to ensure the height h of the raised lines 11, thereby ensuring
the strength ofa structural component to be produced by use ofthe steel sheet l0
with raised lines. Also, the sheet thickness ratio (t / tmin) is desirably less than 4.0.
If the sheet thickness ratio (t / tmin) is too large, the rolling reduction achieved by the
grooved roll I will be excessively large.
[0034]
There is no particular limit to the minimum sheet thickness tmin of the steel
sheet 10. However, the minimum sheet thickness tmin is practically about 0.6 to 10
mlr.
[003s]
FIGS. 5 to 8 are schematic cross-sectional views of other examples of a metal
sheet with raised lines. Each of the steel sheets 10 illustrated in FIGS. 5 to 7
includes a plurality of raised lines 11 on its upper surface. The steel sheet l0
illustrated in FIG. 8 includes one raised line 11 on its uppersurface. In any of FIGS,
5, 6 and 8, the raised lines are in a bilateral symmetric arrangement, and in FIG. 7,
the raised lines are in a bilaterally asymrnetric arrangement.
[0036]
l2
Here, as ilh"rstrated in FIGS. 2 and3,when the steel plate 31 is rolled by the
finish-rolling mill 3 inclLrding the grooved roll 8 incorporated as the upper roll 6 of
the specified stand (the fourlh stand 54 illustrated in FIG. 2),tlte following trouble
will occur, and the process to produce a steel sheet with raised lines will not go
smoothly. In the specified stand, the steel plate 31 immediately after subjected to
the rolling by the rolls is rnore likely to stick to the grooved roll 8 as the upper roll 6
than to stick to the flat roll as the Iower roll 7. This is because the steel plate 31
gets stuck in the roll grooves 9. This provides upward force to the steel plate 3 i
that has passed through the specified stand. Therefore, if the maxirnum rolling
reduction achieved by the rolls of the specified stand is initially set to a required
value, the leading end portion of the steel plate 31 will warp upward greatly. The
greatly warping leading end portion of the steel plate 31 will wind around the
grooved roll 8 or collide against the next stand without coming into the gap between
the rolls of the stand.
[0037]
To deal with such a trouble in operation, in the present embodiment, control
described below is performed at the beginning of rolling by the finish-rolling mill3.
Until the leading edge of the steel plate 31 reaches a roll stand next to the specifred
stand, a maximum rolling reduction achieved by the rolls of the specified stand is set
to a provisional value that is less than a required value. Then, after the leading edge
of the steel plate 3 I reaches the stand next to the specified stand, the maximum
rolling reduction achieved by the rolls of the specified stand is changed to the
required value. The setting and adjustment of the maximum rolling reduction are
carried out by the inter-roll-axis distance adjustment mechanism provided for the
specified stand. The maximum rolling reduction A herein is expressed by the
following Formula (1).
A:(t0-tl)/t0x 100[%] .,.(1)
In the Formula ( 1 ), t0 denotes the sheet thickness of the steel plate 3 1 before
subjected to the rolling in the specified stand, and tl denotes a minimum sheet
thickness ofinter-raised-line recessed portions l2 in the steel sheet 10 after subjected
to the rolling in the specified stand.
[003 8]
t3
By perforrning such control, the upward force acting on the leading end
portion of tlie steel plate 3 I is reduced until the leading edge of the steel plate 3 I
reaches the stand next to the specified stand. Thus, warping of the leading end
portion of the steel plate 3 1 is suppressed, and the leading edge of the steel plate 3 1
srnoothly comes into the gap between the rolls of the next stand. Therefore, any
trouble due to warping of the leading end portion of the steelplate 31 willnot occur.
[003e]
A timing of changing the maximurn rolling reduction of the specifìed stand to
the reqr.rired value is not limited in pafticular, as long as tlie timing is a1Ìer the
leading edge ofthe steel plate 3 1 reaches the stand next to the specified stand.
However, unless the maximurn rolling reduction of the specified stand is not changed
to the required value, a desired steel sheet 10 with raised lines cannot be produced.
For this reason, in terms of yield, the timing of changing is preferably set at a timing
immediately after the leading edge of the steel plate 31 comes into the gap between
the rolls of the stand next to the specified stand.
[0040]
Actually, in the present embodiment, the stand next to the specifìed stand is a
non-rolling-performing stand for conveyance. Therefore, detection as to whether
the leading edge of the steel plate 3 I has reached the non-rolling-performing stand,
for example, can be carried out by use of the output from the load cell provided in
the specified stand, as described above. Specifrcally, the load cell detects the
leading edge of the steel plate 31 reaching the specified stand, and an elapsed tirne
from a tirne point of the detection is measured. Based on the elapsed time, a
theoretical running speed of the workpiece due to rolling by the specified stand, and
a distance between the rollaxis of the specifìed stand and the roll axis of the next
non-rolling-performing stand, it is possible to calculate the time point at which the
leading edge of the steel plate 31 has reached the non-rolling-perfonning stand.
[0041]
In consideration of the capability of the finish-rolling mill 3, the required
value of the maximum rolling reduction of the specified stand is preferably l0 to
80%. More preferably, the required value is 20 to 60%.
100421
14
To suppress the warping of the leading end portion of the steel plate 31
suffìciently, the provisional value of the maximum rolling reduction of the specified
stand is preferably 10 to 900/o of the required value. The provisional value is more
preferably 40 to 80o/o ofthe required value.
[0043]
[Production of Structural Component (Pressed Part) by use of Metal Sheet with
Raised linesl
The above-described steel sheet 10 with raised lines is used as a blank for a
structural component to be produced by press working. At the time of production
of a structural component, the steel sheet 10 is cut into a shape fit for a pressed part
to be used in the structural component. Before cutting, the steel sheet 10 is
subjected to hot-dip galvanizing, hot-dip galvannealing, electrogalvanizing,
aluminum plating or the like. Before such a plating process, the oxidized film on
the surface of the steel sheet 10 is removed by pickling, shot blasting or the like.
The pickling, the shot blasting, and the plating only need to be performed before the
press working, and these processes may be perfonned toward the blank cut out from
the steel sheet 10. Depending on the specification of the structural component, the
plating may be omitted.
[0044]
FIG. 9 is a cross-sectional view of an example of a blank cut out from a metal
sheet with raised lines to be used for the production of a structural component
according to an embodiment of the present invention. FIGS. 1 0A and 108 are
sectional views schematically showing an example of pressing to form the blank
illustrated in FIG. 9 into a structural component. FIG. l0A shows a pressing
machine, and FtG. 108 shows a pressed part for a structural component. FIGS.
114 and 118 show another example of pressing of the blank illustrated in FIG. 9 into
a structural component. FIG. 1 1A shows a pressing machine, and FIG. I I B shows
a pressed part for a structural component. The present embodiment describes a case
where the above-described steel sheet 10 with raised lines is used as the metal sheet
with raised lines as an example.
[004s]
15
As shown in FIG. 9, a blank 15 is cut out from the steel sheet 10. In this
regard, the steel sheet l0 is cut along the longitudinal direction (the extending
direction of the raised lines l1) and alongthe lateraldirection (direction
perpendicular to the extending direction of the raised lines 11). The cut position is
determined depending on the specifìcation of the structural component.
[0046]
For example, the pressed part21 shown in FIG, 10B and FIG. I 1B has a Ushaped
cross section. By joining two pressed parts 21, a structural component in
the shape of a square pipe is produced (see FIGS. I A and 1 B). In the pressed part
2l,the portion that needs to have strength is a portion from the plate portion 24 to
the ridge portions 23. Therefore, when the blank 1 5 fit for the pressed part 21 is cut
out from the steel sheet 1 0, the steel sheet 1 0 is cut at the inter-raised-line recessed
portions 12 such that one of the raised lines i I can be formed into the plate portion
24 and the ridge portions 23 of the pressed parf 21.
[0047]
As shown in FIG. I 04, the bank I 5 can be pressed into the pressed part 21 by
use of a sirnple set of a punch 5l and adie 52. In this case, however, as shown in
FIG. 108, since the raised line 1l with agreatersheetthickness is bent, spring-back
is likely to occur. Therefore, it is preferred that a segmented punch 53 is used as
illustrated in FIG. 1 14. In the segmented punch 53, a shoulder portion is separated.
At the time of pressing, by applying a greater load to the raised line 1 1 from the
shoulder portion ofthe punch 53, it is possible to suppress the spring-back.
[0048]
FIGS. I 2 to l6 are schematic views showing other examples of structural
components. Any of tlie structural components 20 (pressed parts 21) illustrated in
FIGS. 12 to 16 is formed from the blank 15 cut out from the above-described steel
sheet 10 with raised lines, and has one or more raised lines 1 1 on the front side or on
the back side. These structural components formed from a steel sheet with raised
lines have the following advantages over structural components formed from a steel
sheet having an even sheet thickness: ofhaving high performance as a structural
component; and of being produced in a simple method. For example, no separate
reinforcing member is necessary, thereby resulting in a reduction in the number of
t6
members, Integration of a reinforcing member into a structural component allows
for improvernents in strength and rigidity and a reduction in weight. Integration of
a reinforcing member also eliminates the need to carry out a jointing process by
welding, screwing and the like. Further, such a structural conlponent including an
integrated reinforcing member has a smaller overall surface area than a structural
component including a separate reinforcing member, and thus, integration of a
reinforcing member also results in an improvement in antirust capability.
[004e]
The structural component 20 illustrated in FIG. 12 has an L-shaped cross
section, and has a raised line 1i on the back side of the ridge portion 23. In this
case, the ridge portion 23 is reinforced throughout the whole length, and the strength
of the structural component20 is improved.
[00s0]
The structural component 20 illustrated in FIG, l3 is substantially planar, and
has a wide raised line I 1 on the front side, in the center. In this case, the central
portion is reinforced over a wide range throughout the whole length, and the strength
of the structural component 20 is improved.
[00s 1]
The structural component 20 illustrated in FIG. l4 has a U-shaped cross
section, and has a raised line 11 on the back side of the ridge portions 23 andthe
plate portion24. In this case, the plate portion 24 and the ridge portions 23 are
reinforced throughout the whole length, and the strength of the structural component
20 is improved. Further, by locating the raised line 1 I at a distance from the axis of
bending (neutral axis), it is possible to minimize an increase in weight, thereby
resulting in a great enhancement of the second moment of area,
[00s2]
The structural component 20 illustrated in FIG. 17 has a U-shaped cross
section, and has raised lines 11 on the back side of the portions near the ridge
portions 23. ln this case, the portions of the plate portion 24 near the ridge portions
23 and the portions of the flanges 22 near the ridge portions 23 are reinforced
throughout the whole length, and the strength of the structural component 20 is
improved. With regard to the structural compon ent 20 shown in FIG. 16, not the
17
raised lines 11 but the portions near the raised lines 11 is bent at the time of press
working, and the forrnability is good. Specifically, the steel sheet with raised lines
has in-plane anisotropy because of the presence of raised lines. Utilization of this
characteristic allows for both a reduction in the pressing load at the time of press
working and enhancements of the pressed part in strength and rigidity.
[0053]
The structural component 20 illustrated in FIG. 16 is shaped like a square pipe.
This structural component 20 is a combination of a pressed part having a U-shaped
cross section and a metal sheet. In the square-pipe-like structural component 20,
the raised lines I 1 are arranged to extend in the circumferential direction.
Accordingly, the inter-raised-line recessed portion l2 extends in the circumferential
direction of the square-pipe-like structuralcomponent 20. In this case, the portions
where the raised lines 1 1 are located are reinforced throughout the whole
circumference, and the strength of the structural component20 is irnproved.
Therefore, even if another component is welded to any of the portions where the
raised lines 1 I are located, the structural component 20 maintains strength.
Accordingly, the structural component 20 is effectively used as a component
required to be welded to another component. The structural component 20 is
effectively used especially as a welded component of which thickening is restricted
for the reason of constraints on weight and space. With regard to the structural
component 20 illustrated in FIG. 16, the portion where the inter-raised-line recessed
portion 12 is located is fragile throughout the whole circumference. Accordingly,
the portion where the inter-raised-line recessed portion 12 is located is more
breakable than the portions where the raised lines I I are located. Therefore, the
structural component 20 is effectively used as a component of which breakdown
region is intentionally specified.
[00s4]
In the above-described embodiment, the steel sheet 10 with raised lines is
produced by hot working by use of the finish-rolling mill 3. Therefore, in the thick
portions where the raised lines I 1 are located, the cooling rate is slow, and the
hardness is likely to become low, as compared with those in the other portions (the
inter-raised-line recessed porlions i2). Utilizing this characteristic of the raised
l8
lines 11, it is possible to improve the formability by using the portions where the
raised lines I 1 are located as the portions of a structural component to be shaped with
difficulty.
[00ss]
TABLE I below shows examples of a strength difference between a portion
where a raised line is located and another portion. As is clear from TABLE 1, the
strength difference varies depending on the material of the workpiece (whether highcarbon
steel or low-carbon steel), the difference between the raised-line sheet
thickness and the minimum sheet thickness, the cooling rate and the like. The
portion where the raised line is located always has higher hardness than any other
portion,
[00s6]
ITABLE 1l
TABLE I
Test
No.
Material
Raised-line
sheet thickness
[mm]
Minimum
sheet
thickness
lmml
Cooling rate
["C/sec]
Steel sheet
running speed
[m/min]
Strength
difference
IMPa]
A
High-carbon
steel
3.0 1.0 50 300 300
B
Low-carbon
steel
3.0 1.0 20 300 t00
C
High-carbon
steel
3.0 2.0 50 300 250
D
Low-carbon
steel
3.0 2.0 20 300 50
E
High-carbon
steel
4.0 1.0 50 300 400
F
Low-carbon
steel
4.0 r.0 20 300 200
[00s7]
As thus far described, the metal sheet production rnethod according to the
present embodiment facilitates the production of a metal sheet with raised lines.
The metal sheet with raised lines has, one of the upper surface and the lower surface,
one or more raised lines extending in the rolling direction. Accordingly, when the
metal sheet is used as a material for a partly-reinforced structural component, it is
l9
possible to obtain a structural component including a reinforced portion that is
reinforced in the entire area. Thus, the metal sheet with raised lines is suited to be
used as a material for a partly-reinforced structural component. The Lrse of the
metal sheet with raised lines eliminates the need to weld a separate reinforcing plate
to partly reinforce the structural component. This allows for a reduction in
manufacturing cost.
[00s 8]
The present invention is not limited to the above-described embodiment, and
various changes are possible without departing frorn the gist and scope of the present
invention. For example, the grooved roll may be incorporated in as the lower roll of
the specified stand. In addition, the metal sheet with raised lines, the material of the
metal sheet, the material of the structural component formed from the metal sheet are
not limited to steel, such as ordinary carbon steel, high-tensile steel, stainless steel
and the like, and aluminum, copper-and the like may be used.
[005e]
In the rolling mill including grooved roll, the total number of stands is not
limited, However, since the grooved roll is incorporated in a stand at least one
stage before the last stand, the total number of stands is at least two.
[0060]
The method for pressing a blank cut out from the metal sheet with raised lines
into a structural component is not particularly limited. As the method, for example,
it is possible to adopt a hot stamping method in which forming and quenching are
carried out in a mold.
REFERENCE SIGNS LIST
[0061]
1: heating furnace
2: rough-rolling mill
3: finish-rolling mil
4: cooling device
5: coiler
S1 to 56: roll stand
20
6: upper roll
7: lower roll
8: grooved roll
9: groove
10: steel sheet
1 1: raised line
I 2: inter-raised-line recessed portion
15: blank
20: structural component
2l : pressed part
22: flange
23: ridge portion
24: plate porlion
30: slab
3 1: steel sheet
5 1: punch
52: die
53: segmented punch
w I : width of roll groove
w2: width of non-grooved region
p: pitch of raised Iine
tmin: minimum sheet thickness
h: height of raised lines
t: raised-line sheet thickness

We claim:
l. A method for producing a tnetal sheet by use of a rolling rnill i¡cluding at
least two roll stands, the metal sheet inclLrding, on an upper surface or a lower
surface, one or more raised lines extending in a rolling direction, the method
comprising:
a preparing step of preparing a grooved roll, the grooved roll including, in an
oute| peripheral surface, orìe or lnore grooves extencling in a circumferential
direction;
a choosing step of cltoosing a roll stand at least one stage before a last roll
stand, frorn the roll stands;
an incorporating step of incorporating the grooved roll in the rollìng mill as an
upper roll or a lower roll of the chose', specified roll stand; and
a lorrning step of rolling a w'orkpiece by the rolling mill incorporating the
grooved roll, thereby forming the workpiece into a metal sheet with raised lines
formecl corresponding to the respective grooves of the grooved roll, wherein
in the forming step, until a leacling edge of the workpiece reac6es a roll stand
next to the specified rollstarrd, a nlaximu¡n rolling reduction achieved by rolls of the
specifìed roll stand is set to a provisional value that is less than a required value, a¡d
after the leadir-rg eclge of the workpiece reaches the roll stand next to the specified
roll stand, the maximurn rolling rlecluction achieved by the rolls of t¡e specifìed roll
stand is changed to the required value.
2' The method for producing a metal sheet with raised lines according to claim 1,
wherein
the required value is l0 to B0%.
3' The method fol prodLrcing a rnetal sheet with raised Iines according to clairn I
or 2, wherein
the provisional value is l0 to 90% of the required value.
22
4. The method for producing a metal sheet with raised lines according to any one
of claim I to claim 3, wherein
in a longitudinal section of the grooved roll, the grooves are in a bilaterally
symmetric arrangement.
5. The method for producing a rnetal sheet with raised lines according to any one
of claim 1 to claim 4, wherein
in a longitudinal section of the grooved roll, the grooves is rectangular,
trapezoidal o r V-shaped.
6. The method for producing a metal sheet with raised lines according to any one
of claim I to claim 5, wherein
each of the grooves in the grooved roll has a width more than 5 mm and less
than 2000 mm.
7. The method for producing a metal sheet with raised lines according to any one
of claim i to claim 6, wherein
the grooves of the grooved roll are at a pitch more than l5 mm and less than
2000 mm.
8. A metal sheet with raised lines including one or more raised lines on an upper
surface or a lower surface, wherein:
the raised lines are at a pitch more than 15 mm and less than 2000 mm; and
a sheet thickness ratio (t / tmin) of a raised-line sheet thickness t to a
minimum sheet thickness tmin is more than 1 0 and less than 10.0, the raised-line
sheet thickness t being expressed as a sum of the rninimum sheet thickness tmin and
a height h of the raised lines.
9. The metal sheet with raised lines according to claim 8, wherein
each of the raised lines has a width more than 5 mm and less than 2000 mm.
23
10. A structural component comprising one or more raised lines on a front side or
a back side, wherein
the structural component includes a reinforced poftion that is increased in
strength, and the raised lines are disposed on the front side or the back side ofthe
reinforced portion.