' ORIGINAL
Formed Member and Manufacturing Method Thereof
Technical Field
This invention relates to a formed member and a method for its
5 manufacture. Specifically, the present invention relates to a formed member
which can be manufactured at a low cost and has improved dimensional accuracy,
which has improved axial crushing properties and three-point bending properties or
improved bending stiffness and torsional stiffness? and which is therefore suitable
for use in components of automobiles. It also relates to a method for its
10 manufacture.
Background Art
As is well known, almost all automobile bodies are monocoque bodies
(unit construction bodies) in order to achieve both a lightweight and a high
15 stiffness.
Figure 20 is an explanatory view schematically showing an automobile
body 1.
A monocoque automobile body is usually constructed by assembling a
large number of components which are fabricated by press forming of a steel sheet
20 having a thickness of at most 2.0 mm into a specified shape and connecting them
by spot welding, for example. These many components for an automobile body
(referred to below as automotive components) include, for example, a front side
member 2, a bumper reinforcement 3, a front crash box 4, a front upper rail 5, a
side sill 6, a floor cross member 7, a floor panel 8, a center pillar 9, a roof rail side
25 member 10, a rear side member 11, and a rear crash box 12. In order to guarantee
the required stiffness of the vehicle body, these components are constituted by one
or more formed member body portions such as press-formed member body portions
or roll-formed member body portions.
The term "formed member body portion" used herein means a body portion
:o of a member in which the body portion has a ridge formed by a suitable bending
technique such as press forming or roll forming of a sheet. In this description, it
will be referred to for convenience as simply a formed member.
Figure 21 shows an example of a formed member 13 which was fabricated
by press forming of a flat sheet blank into a hat shape in cross section.
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manner, the width of the welds is preferably a large proportion of the length R8 in
the circumferential direction of a cross section of the ridge portions 28,30, and 33
in order to maintain desired properties of the formed members 20 - 25, and a
plurality of welds are preferably present on each ridge portion.
5 A weld is preferably provided in a region from the center in the
circumferential direction of the cross sections of the ridge portions 28,30, and 33
to a position at a distance of 50% of the circumferential length of the cross sections
of the ridge portions.28,.30,and33. By doing so, it is possible to obtainthe
effects of the present invention with certainty.
10 The entire width of a weld need not be contained in a region for a ridge
portion having a length of R0 in the circumferential direction of a cross section of
the ridge portions 28, 30, and 33. It is sufficient for at least a portion of a weld to
be contained in the region of a ridge portion.
Basically, the greater the width of the reinforcing members 35,35-1, and
15 35-2, the greater is the effect of reinforcing the bent formed members 20 - 25 by the
reinforcing members 35, 35-1, and 35-2. However, as the width of a reinforcing
member increases, an increase in the weight and cost of components of an
automobile cannot be avoided. Therefore, the width of the reinforcing members
i 35,35-1, and 35-2 is preferably slightly larger than the length R0 in the
20 circumferential direction of the cross sections of the ridge portions 28, 30, and 33,
and specifically it is preferably at most R0*5, more preferably at most R-0x4, and
most preferably at most R0x3.
When the cross-sectional shape of the formed members 20 - 25 in the
extending direction of the ridge portions 28, 30, and 33 is constant and does not
25 vary, the effect of the present invention can be obtained by providing the
reinforcing members 35, 35-1, and 35-2 over the entire length in the extending
direction of the ridge portions 28, 30, and 33.
However, many actual formed members have a cross-sectional shape in the
extending direction of the ridge portions 28, 30, and 33 which is not fixed and
30 varies with the location. In this case, the formed members 20 - 25 have a region
where their cross-sectional area is small and where they most easily deform when
bearing a load such as a load in the axial crushing direction. Therefore, it is
effective to provide reinforcing members 35, 35-1, and 35-2 at least in this region.
Even if reinforcing members 35, 35-1, and 35-2 are not provided over the entire
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length in the axial direction of the formed members 20 - 25, it is possible to obtain
the effects of the present invention with greater certainty by providing the
reinforcing members 35, 35-1, and 35-2 in such a region having a small crosssectional
area. Of course, it is possible to obtain a greater effect by providing the
5 reinforcing members 35, 35-1, and 35-2 over the entire length in the axial direction
of the formed members 20-25.
The location of welds in the extending direction of the ridge portions 28,
........... 30,. and33. can. be suitably set in accordance with formability at the time of forming
and the properties required of the formed member. The shape of welds such as
10 dots, straight lines, or curves, the number of welds, and the dimensions (length) of
the welds can be suitably set. It is possible to provide both dot-shaped welds and
elongated welds and to provide both linear welds and curved welds.
The term "extending direction" of a ridge portion used herein means the ' -
lengthwise direction, namely, the axial direction of the ridge portion because the
15 ridge portion is provided in the lengthwise direction of a formed member. The
term "cross-sectional shape of a ridge portion" means the shape of a ridge portion
in a cross section perpendicular to the lengthwise direction.
Figures 3(a) - 3(d) are perspective views partially showing the installation
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| positions of welds 40 in the extending direction of a ridge portion 28 for the case in
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| 20 which the welds 40 are dot-shaped spot welds. The circles in Figures 3(a) - 3(d)
I show the welds 40. In the illustrated examples, the case will be explained in
j which a reinforcing member 35 on the outer peripheral surface of a ridge portion 28
j provided on a formed member 20 shown in Figure 2 is joined to the ridge portion
28 by welding. For convenience, the ridge portion 28 is shown as the ridge
j 25 portion of the reinforcing member 35. The same is the case with respect to belowdescribed
Figures 4-7.
Figure 3(a) shows the case in which the welds 40 are disposed in the same
| cross sections in the extending direction of the ridge portion 28. This arrangement
has the effect of making it easy to control formability and deformation in one
30 direction.
Figure 3(b) shows the case in which welds 40 are staggered in the
extending direction of the ridge portion 28. This arrangement can increase the
number of welds 40 per unit area and so can improve the properties of the formed
member.
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Figure 3(c) shows the case in which the locations where the welds 40 are
formed vary in accordance with their positions in the extending direction of the
ridge portion 28. For example, by having different locations where the welds 40
are formed in a portion 28-1 of the ridge portion 28 which requires resistance to
5 axial crushing and a portion 28-2 which requires resistance to bending deformation,
the resistance to axial crushing and the resistance to bending deformation of the
i formed member can both be increased In this manner, by varying the location
-—where welds 40 are formed m accordance with the location hr the extending
direction of the ridge portion 28, it is possible to flexibly cope with various
10 demands made of a formed member.
Figure 3(d) shows the case in which the pitch of the welds 40 varies in the
extending direction of the ridge portion 28. In the same manner as in Figure 3(c),
this arrangement can flexibly xope with various demands of a formed member.
Figures 4(a) - 4(h) are explanatory views schematically showing the
15 positions of welds 41 in the extending direction of a ridge portion 28 for the case in
which each weld is an elongated weld 41.
Figure 4(a) shows the case in which a weld 41 is formed with a linear shape
extending continuously in the extending direction of a ridge portion 28.
Figure 4(b) shows the case in which welds 41 are formed as intermittent
20 linear portions extending in the extending direction of a ridge portion 28.
Figure 4(c) shows the case in which a weld 41 is formed with a linear shape
which is continuous in the extending direction of a ridge portion 28 and which ' '
changes its position along the way.
Figure 4(d) shows the case in which a weld 41 is formed as a continuous
25 curve generally extending in the extending direction of the ridge portion 28.
Figure 4(e) shows the case in which welds 41 having the shape of a C are
spaced from each other and continuously arranged in the extending direction of a
ridge portion 28.
Figure 4(f) shows the case in which welds 41 having the shape of a C are
30 continuously arranged in the extending direction of the ridge portion 28 so as to
cross each other in portions.
Figure 4(g) shows the case in which welds 41 having the shape of stitches
in the cross-sectional direction are sequentially spaced in the extending direction of
the ridge portion 28.
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Figure 4(h) shows the case in which continuous welds 41 in the crosssectional
direction are sequentially spaced in the extending direction of the ridge
portion 28.
Figures 5(a) - 5(d) are explanatory views schematically showing the case in
5 which welds are a combination of elongated welds and dot-shaped welds. The
dot-shaped welds may be formed by spot welding or by laser welding. The
elongated welds may be formed byjaser welding or by seam welding.
Figure 5(a).shows the case in which dot-shaped welds 40 and elongated
welds 41 are combined. Figure 5(b) shows the case in which elongated welds 41
10 are combined with an elongated weld 42 extending in a different direction. Figure
5(c) shows the case in which C-shaped welds 41 are combined With dot-shaped
welds 40. Figure 5(d) shows the case in which elongated welds 40 in the direction
perpendicular to the extending direction of the ridge portion are combined with dotshaped
welds 40.
15 In this manner, a reinforcing member 35 may extend over all or a portion of
the extending direction of a ridge portion 28, and it may be a single member or may
be divided into two or more pieces in the extending direction of a ridge portion 28.
The welds 40 - 42 for welding the reinforcing member 35 to the ridge
portion 28 prevent gaps from developing between the reinforcing member 35 and
20 the formed member 20 when an external force is applied to the formed member 20,
thereby providing the effect of improving the performance under a stress which
causes axial crushing or bending deformation or the effect of markedly increasing
bending stiffness and torsional stiffness. Therefore, it is most preferable for the
welds 40 - 42 to be continuously formed along the extending direction of the ridge
25 portions 28. However, it is possible to form them intermittently in the extending
direction of the ridge portion 28 such as is the case with spot welding. When
welds 40 - 42 are intermittently formed in the extending direction of a ridge portion
j 28, the spacing between adjoining welds is suitably set so that the reinforcing
member 35 does not detach from the ridge portion 28 at the time of deformation.
30 When a component of an automobile made from a formed member is a
lloor panel, for example, there is a tendency for the length R9 in the circumferential
direction of across section of the ridge portion to be long. In this case, it is not
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| necessary for the weld to extend linearly in the extending direction of the ridge
portion, and it can have a curved shape such as an S shape, or it can be in the form
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of staggered short lines or dots. Namely, the welds can be suitably formed so that
the reinforcing member does not detach from the ridge portion when the formed
member receives an external force.
When the reinforcing member 35 covers not just the ridge portion 28 but
5 also a surface contiguous to the ridge portion 28 (such as a vertical wall portion of
a member with a hat-shaped cross section), not only the ridge portion 28 but this
surface as well may of course be welded.
Whenthe formed member. 2.0. undergoes axial crushing deformation, if the ..
cross-sectional shape does not change in the extending direction of the ridge
l o portion 28,. deformation at the time of axial crushing is concentrated at the ends of
the formed member 20. Therefore, in order to prevent the materials from sliding
between the formed member 28 and the reinforcing member 35 at the ridge portion
at the time of press forming or to prevent the materials from undergoing different
deformation from each other, welds are more densely provided at the end portions
15 and particularly in the portions where the cross-sectional shape varies. In this
manner, it is important to reduce by means of welding the area of gaps between the
ridge portion 28 and the reinforcing member 35 at both ends of the formed member
20 and, when the cross-sectional shape varies, to reduce by means of welding the
area of gaps between the ridge portion 28 and the reinforcing member 35 in the
20 vicinity of the region where the cross-sectional shape varies. When welds are
discontinuously formed such as with spot welding, the spacing between adjoining
welds 40 - 42 in these portions is preferably set to a small value.
There are no particular limitations on the welding method. For example,
spot welding, seam welding, laser welding, or plasma welding can be used. As
25 stated below, any welding method capable of welding between a flat reinforcing
member and a flat sheet blank in a state that the reinforcing member is superposed
i on a portion of the blank is equally applicable.
Figures 6(a) - 6(c) are explanatory views schematically showing an
i example of a welding method for the case in which welds 40 - 42 are formed in a
30 portion where external appearance with good quality is required.
When a good quality external appearance is required on a whole or portion
of a surface of a formed member after assembly, namely, when it is required to
have a clean external appearance in which surface irregularities such as weld beads
or electrode marks produced by resistance welding do not remain, the methods
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shown in Figure 6(a) - 6(c) are preferred.
Referential number 70 in Figure 6(a) indicates a laser welding machine.
As shown in Figure 6(a), by carrying out laser welding so that the resulting weld
bead 41 does not reach the surface a which becomes the outer surface of a ridge
5 portion, a good quality external appearance of surface a can be maintained when
carrying out laser welding of a reinforcing member 35 to a ridge portion 28.
Referential numbers 71 and 72 in Figure 6(b) indicate electrodes for seam
_ welding. As shown in Figure 6(b)riri seam welding, a good quality external
appearance of surface a can be maintained by disposing a disc-shaped electrode 72
10 for seam welding having a-larger contact surface on the side of surface a and
carrying out Welding while rotating the electrodes.
In Figure 6(c), referential number 73 indicates an electrode for one-sided
seam welding and referential number 74 indicates a flat back electrode. As shown
in Figure 6(c), in one-sided seam welding, a good quality external appearance of
15 surface a can be maintained by disposing the flat back electrode 74 on the side of
surface a and performing welding while rotating the electrode 73 on surface b (socalled
one-sided seam welding).
In spot welding, a good quality external appearance can be maintained
without leaving electrode marks on surface a by using a flat back electrode or an
20 electrode having a tip with a large radius of curvature.
A formed member according to the present invention can be preferably
used either by itself or in combination with other member or members in a
component for an automobile such as a front side member, a bumper reinforcement,
a front crash box, a front upper rail, a side sill, a floor cross member, a floor panel,
25 a center pillar, a roof rail side, a rear side member, or a rear crash box.
Alternatively, a formed member according to the present invention may constitute a
portion of such a component for an automobile. Namely, a reinforcing member
according to the present invention may be secured to portions of the abovedescribed
components for automobiles by a weld provided on a ridge portion of a
30 component.
In this description, in order to simplify the explanation, a component for an
automobile like those described above will sometimes itself be referred to as a
formed member according to the present invention.
When, for example, the present invention is applied to a floor panel having
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a tunnel portion (a front floor panel), of the ridge portions in the tunnel portion, a
reinforcing member is preferably positioned on a ridge portion on the side closer to
the dashboard lower panel (the front side), which is the portion where an impact
load is first applied at the time of a front end collision. In this manner, it is not
5 only possible to increase the bending stiffness and the torsional stiffness of the
front floor panel but it is also possible to increase its impact absorbing properties.
Aformed member according tothe present invention has a reinforcing
member welded to a ridge portion of the formed member. Therefore, at the time
of axial crushing, for example, (i) deformation tending to open the outer wall
10 portion of the formed member towards the outer side of the cross section (referred
to below as outward deformation) is suppressed by the reinforcing member with
certainty, thereby increasing the buckling load of the formed member, and (ii) if the
formed member has a reinforcing member welded to the ridge portion having the
greatest effect on properties, it is possible to increase the single buckling load and
15 diminish the buckling wavelength of the formed member. As a result, the present
invention improves the ability of the formed member to absorb impact energy.
In addition, with a formed member according to the present invention, due
to the provision of a reinforcing member welded to a ridge portion of the formed
member, at the time of three-point bending, for example, the reinforced ridge
20 portion has a higher stiffness and a higher strength compared to a conventional case
in which a reinforcing member is not joined to a ridge portion. Therefore, the
formed member according to the present invention exhibits a high bending strength
from the initial stage of deformation, and the amount of deformation of the ridge
portion is smaller than for a conventional formed member. As a result, a side wall
25 portion can effectively bear a load which produces a bending stress, and a high
buckling load when bending is applied is obtained. Therefore, the present
invention improves the ability of a formed member to absorb impact energy.
Furthermore, due to the provision of a reinforcing member welded to a
ridge portion in a formed member according to the present invention, when the
30 formed member is applied to a floor panel, for example, the resistance of the floor
panel to bending deformation and torsional deformation is increased, and the
I bending stiffness and the torsional stiffness of the formed member can be
increased.
Therefore, by fabricating a component for an automobile using a formed
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member according to the present invention, any of the following is possible
(A) increasing the ability to absorb impact energy at the time of axial
crushing when the formed member is a tubular component for an automobile which
bears an impact load applied in the axial direction (such as a front side member, a
5 front crash box, a front upper rail, a floor cross member, a rear side member, or a
rear crash box),
(B) increasing the ability to absorb impact energy at the time of three-point
bending.when..the formed member is a-tubular component for -an- automobile- which
bears an impact load applied in a direction perpendicular to the axial direction
10 (such as a bumper reinforcement, a side sill, a center pillar, or a roof rail side)? and
(C) increasing the bending stiffness and torsional stiffness when the formed
member is a flat component for an automobile (such as a floor panel).
Figures 7(a) - 7(d) are explanatory views schematically showing suitable
positions for forming welds 40 - 42 in a portion of a cross section of formed
15 members 44 - 47.
Figure 7(a) shows a formed member 44 which bears an impact load applied
in its axial direction. A weld 40 - 42 is preferably located at least in a region
which is included in 50% of the circumferential length R9 of the cross section of a
ridge portion (shown as 1/2R9 in the figure).
20 Figure 7(b) shows a formed member 45 which bears an impact load applied
in a direction perpendicular to the axial direction (this load a is indicated by a
hollow arrow in the figure). A portion of a weld 40 - 42 is preferably located at
the end of the ridge position where a ridge portion is connected to a side Wall.
Figure 7(c) shows a formed member 46 in which a single weld bears
25 impact loads applied in two directions, i.e., in the axial direction and in a direction
perpendicular to the axial direction.
Figure 7(d) shows a formed member 47 which has a plurality of welds
which individually correspond to different load directions in the same cross section.
Figure 8 gives explanatory views showing an example of an embodiment in
30 which the present invention is applied to a center pillar (a B-pillar) 48. Figure
8(a) is an overall view, Figure 8(b) is a cross-sectional view of a conventional
center pillar for comparison taken along line XIII - XIII of Figure 8(a), and Figure
I 8(c) is a cross-sectional view of an example of a center pillar according to the
j present invention, also taken along line VIII-VIII of Figure 8(a). In the figures,
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the locations of welds are shown by circles. The same applies to Figure 9.
When the present invention is applied to a B-pillar 48, a B-pillar
reinforcement 50 which is provided between a B-pillar outer member 49 and a Bpillar
inner member 51 is constituted by a formed member according to the present
5 invention. The B-pillar reinforcement 50, which is a formed member having a
reinforcing member, is usually disposed in the upper portion of the B-pillar 48.
By applying the present invention to a B-pillar reinforcement 5,0 and providing
reinforcing members .(not shown) andwelds 40 - 42 on its ridge-portions, the
resistance to impacts of the B-pillar outer member 49 is greatly improved. The
10 exact structure of the B-pillar reinforcement 50 which is the formed member in
Figure 8(c) can be any of the specific shapes shown in Figure 2, for example.
There are no particular limitations on the materials of the B-pillar
reinforcement 50 and the reinforcing member, and they may be high tensile
strength steel sheets or hot press-formed materials.
15 The welds shown in Figure 8(c) are spot welds 40, but they need not be
spot welds 40 and may be laser welds 41 or seam welds 42.
More preferably, the performance of the B-pillar 48 with respect to bending
load can be further increased by forming a plurality of ridge portions in the B-pillar
! outer member 49 and the B-pillar inner member 51 and suitably disposing
20 reinforcing members and welds 40 - 42 on these ridge portions.
Figure 9 gives explanatory views showing an example of an embodiment in
which the present invention is applied to a front pillar (an A-pillar). Figure 9(a) is
an overall view, Figure 9(b) is a cross-sectional view of a conventional front pillar
for comparison taken along line XI - XI of Figure 9(a), and Figure 9(c) is a cross-
25 sectional view of an example of a front pillar according to the present invention,
also taken along line XI - XI of Figure 9(a).
An A-pillar inner reinforcement 54 and an A-pillar outer reinforcement 53
are provided between an A-pillar outer member 57 and an A-pillar inner member
i 56 of an A-pillar 52. When the present invention is applied to an A-pillar 52, a
I 30 reinforcing member is preferably disposed on a ridge portion of the outer
| reinforcement 53 and secured by a weld 40 - 42 provided on the ridge portion.
Namely, the outer reinforcement 53 is constituted by a formed member according
to the present invention.
| Alternatively, a reinforcing member and a weld 40 - 42 may be disposed on
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a ridge portion of the inner reinforcement 54 of the A-pillar.
As a result, the crushing load by bending of the A-pillar 52 at the time of a
front-end collision can be greatly increased.
In Figures 8 and 9, in order to simplify the explanation, reinforcing
5 members are not shown, but in an actual embodiment, the various types shown in
Figure 2, for example, can be employed in accordance with the shape of the inner
reinforcement 54 and the outer reinforcement 53, namely, in accordance with the
shape of.the formed, member. ~~ —
There is no particular limitation on the material used for the outer
i o reinforcement 53 and the inner reinforcement 54 of the A-pillar or the reinforcing
' •'. members provided on their ridge portions, and they may be high tensile strength
steel sheets or hot press-formed materials.
A manufacturing method according to the present invention will be
explained.
15 According to one embodiment, a formed member according to the present
invention is manufactured by providing a formed member body portion and a
reinforcing member each having a ridge portion, which is formed by bending by
previously carrying out press forming or roll forming. The press forming or roll
forming which is previously carried out may be performed in a hot state or a cold
20 state. On the ridge portion of the formed member body portion which has
previously been formed, a reinforcing member which has previously bent to the
same shape is disposed and is welded in the ridge portion to secure the two
members to each other. When the reinforcing member is disposed on the ridge
portion of the body portion, gaps between the two members are made as small as
25 possible. The location of welds at this time is as already described in detail. A
welding means can be suitably selected from the above-described various means.
In this manner, according to the present invention, a formed member can be
manufactured by simple means. If a reinforcing member is provided on a ridge
portion, the impact resistance of the ridge portion can be greatly improved locally
30 just by locally providing the reinforcing member in a desired location, and if such a
formed member is used as a component tor an automobile, it is possible to
simultaneously decrease the vehicle weight and improve impact resistance, which
are by nature mutually conflicting properties.
According to another embodiment of the present invention, a formed
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member according to the present invention is manufactured by superposing a flat
sheet blank and a flat sheet reinforcing member 35, 35-1, or 35-2. The
superposing position becomes the location at which a ridge portion is to be formed
on the blank.
5 The blank and the reinforcing member 35, 35-1, or 35-2 are welded at this
location by any of the above-described welding methods to provide a flat welded
member. The location of the welds and the method of forming the welds at this
time are as described above. -
Press forming or roll forming is carried out on this flat welded member
10 such that a ridge portion 28, 30, or 33 is formed in the region where the reinforcing
member 35,35-1, or 35-2 is present. In this manner, a formed member according
to the present invention having a reinforcing member on the press-formed or rollformed
portion, namely, on the ridge portion is manufactured. Forming at this
time can be carried out in either a cold state or a hot state. It can be suitably
15 determined whether to use hot or cold forming in accordance with the type of
material and the welding means.
The present inventors carried out a large number of times a press forming
test in which superposed two high-strength steel sheets (sheet thickness of 0.7 - 2.0
! mm) of the grade of 440 - 980 MPa were welded by spot welding and then
20 subjected to 90-degree bending in such a manner that that the center of the spot
welds which were formed became the apex of a ridge portion having a bending
radius of 3 mm, and they ascertained whether the spot welds fractured as a result of
i the bending. It was confirmed that there was no occurrence of weld cracking in
j any of these tests.
25 In the present invention, a sufficient effect is obtained even when press
| forming (or roll forming) is carried out after a flat welded material is heated to a
I temperature of at least the Ac3 point, namely, even when the press forming is socalled
hot press forming. As a result, a hot press-formed member having a higher
strength can be manufactured while increasing press formability.
30 When a hot press-formed member is made from a high strength material,
so-called HAZ softening sometimes occurs in the welds. However, by performing
hot press forming on a flat welded material, quench hardening takes place even in
the portions which were softened at the time of welding. As a result, HAZ
softened portions no longer exist, and a formed member in which the base metal
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and the welds have the same strength (hardness) is obtained.
There are no particular limitations on the material of a steel sheet used in
the present invention as long as it can be heated to at least the Ac3 point and
undergo hot press forming or hot roll forming. However, HAZ softening of welds
5 is due to martensite strengthening of steel, which greatly contributes to the
strengthening mechanism of steel. Therefore, a steel type having a strength of at
least 590 MPa which produces HAZ softening (particularly a dual-phase (DP)
steel) is preferred, and a steel having a strength of at least 1500 MPa is.more.-
preferred.
10 In this manner, according to the present invention, it is possible to provide
a formed member suitable for use in-a component for an automobile or as a
component for an automobile itself which can be inexpensively manufactured and
has excellent dimensional accuracy, which has excellent axial crushing properties
and three-point bending properties, or which has excellent bending stiffness and
15 torsional stiffness.
Example 1
Figure 10(a) is an explanatory view schematically showing the crosssectional
shape of a reinforcing member 35 used in this example, and Figure 10(b)
20 is an explanatory view showing the shape and location of reinforcing members 35
on the ridge portions 28 of a formed member 21.
Figure 11 (a) is a perspective view of a formed member 21 after spot
welding of reinforcing members, and Figures 11(b) and 11(c) are explanatory
views showing the location of spot welding of reinforcing members to a ridge
25 portion 28 in an example of the present invention and Comparative Example 2,
respectively In Comparative Example 2, no spot welds were present on the ridge
portion 28.
The formed members 21 used in this example had nearly the same crosssectional
shape as the formed member 21 shown in Figure 1(a), so the same
30 portions are indicated by the same referential numbers. In Figures I Kb) and
11(c), spot welds are shown by solid circles, (he formed member 21 and the
reinforcing members 35 both had a sheet thickness of 0.7 mm.
Figure 12 is an explanatory view showing the specification of the formed
members and the test conditions. Figure 13 is an explanatory view showing the
test method. In Figure 12, the locations shown by the hollow arrows in the
column labeled "Cross-sectional view of formed member" are the locations of spot
welds.
The test shown in Figure 13 was carried out on the formed members
5 obtained in Comparative Examples 1 and 2 and Examples 1 and 2 shown in Figure
12. Namely, as shown in Figure 13, a drop-weight body 36 which was dropped at
a speed of 64 km/hour was allowed to impinge on the upper end of a vertically
.djsposed.formed.member sampleiiavjng its lower end totally secured and
restrained, and the load at which the amount of deformation in the axial direction
10 became 20 mm was measured. As shown in Figure 12, spot welds were not
present on the ridge portions 28 of Comparative Examples 1 and 2, but spot welds
were present on the ridge portions 28 of Examples 1 and 2 according to the present
invention.
Figure 14(a) is a graph showing the relationship between the displacement
15 and the load for formed members made from a steel sheet having a tensile strength
of 270 MPa (Comparative Example 1 and Example 1 of the present invention), and
Figure 14(b) is a graph showing the relationship between the displacement and the
absorbed energy for formed members made from a steel sheet having a tensile
strength of 270 MPa (Comparative Example 1 and Example 1 of the present
20 invention).
Similarly, Figure 15(a) is a graph showing the relationship between the
displacement and the load for formed members when the tensile strength was 980
MPa (Comparative Example 2 and Example 2 of the present invention), and Figure
15(b) is a graph showing the relationship between the displacement and the
25 absorbed energy for specimens having a tensile strength of 980 MPa (Comparative
Example 2 and Example 2 of the present invention).
As is clear from the graphs in Figures 14(a), 14(b), 15(a), and 15(b),
Examples 1 and 2 according to the present invention had higher load properties and
greater ability to absorb impact energy than Comparative Examples 1 and 2.
:>o Figures 16(a) and 16(b) are explanatory views showing the distribution of
stresses in the axial direction of formed members which had a deformation of 8 mm
and were made of a material having a tensile strength of 980 MPa (Comparative
Example 2 and Example 2 of the present invention, respectively). The reinforcing
members 35 have been omitted from Figure 16.
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As shown in Figure 16(a), in the case of Comparative Example 2, stress
concentrations developed in portions A and B in the axial direction, whereas in the
case of Example 2 of the present invention shown in Figure 16(b), outward
deformation of the ridge portion was more restrained than in Comparative Example
5 2. As a result, stresses in the axial direction increased, and the stress distribution
uniformly spread over the entirety of region C in the axial direction.
Example 2
A hat body portion having a hat-shaped cross section, namely, a hat-shaped
10 formed member was manufactured by hot press forming and was tested by a threepoint
bending test. This example illustrates an embodiment in which a reinforcing
member 60 was provided on the inner side of ridge portions of the hat-shaped
formed member.
Figure 17(a) is an explanatory view showing the state during the three-
15 point bending test, and Figure 17(b) is an explanatory view showing the crosssectional
shape of the hat-shaped formed member 58.
As shown in Figure 17(b), the hat-shaped formed member 58 comprises a
hat body portion 59, a reinforcing member 60, and a hat bottom plate 61. The
j specifications of these components 59-61 are given below.
I 20 Hat body portion 59: a galvannealed steel sheet for hot press forming
having a sheet thickness of 1.2 mm, a width of 240 mm, and a length of 600 mm.
Reinforcing member 60: a galvannealed steel sheet for hot press forming
having a sheet thickness of 1.4 mm, a width of 180 mm, and length of 600 mm
Hat bottom plate 61: a galvannealed steel sheet of 780 MPa grade having a
25 sheet thickness of 1.8 mm, a width of 150 mm, and length of 600 mm
The flat sheets (blanks) for the hat body portion 59 and the reinforcing
member 60 were welded by the welding methods shown in below-described Figure
19 to obtain a welded blank for hot press forming. The welded blank was
• subjected to hot press forming (heating at 900° C for 4 minutes) to form a hat body
30 member, and then the hat bottom plate 61 was spot welded to the hat body member
I to manufacture a hat-shaped formed member 8 for a bending test. I
| As shown in Figure 17(a), the hat-shaped formed member 58 which was
obtained in this manner was supported at two points 62 and 63 separated by 500
i mm, and an impactor 64 having a radius of 150 mm was lowered at a speed of 2
.-_C
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mm/second to impact the center in the lengthwise direction of the hat-shaped
formed member 58 to produce bending deformation.
Figure 18 is a graph showing the result of bending tests for Nos. 1-3, and
Figure 19 is an explanatory view compiling the test conditions and the test results
5 (maximum load) for Nos. 1-6.
In Figure 19, HP forming means hot press forming, and TWB means tailor
welded blank. The circles in the column labeled "Shape in batch TWB" and in the
column labeled "Cross-sectional shape" indicate the location of spot welds, and the — -
straight lines in the column labeled "Shape in batch TWB" indicate continuous
10 welds (seam welds or laser welds).
Nos. 1 and 2 in Figures 18 and 19 are comparative examples not having
welds on the ridge portions, and Nos. 3 - 6 are examples of the present invention
having welds on the ridge portions.
Spot welding was carried out with a pitch of 40 mm in the extending
15 direction of the ridge line. The seam welds for No. 5 (perpendicular to the ridge
lines) had a length of 40 mm and a pitch of 40 mm. The curved laser welds for
No. 6 had sine wave curves with an amplitude of 20 mm and a period of 40 mm.
From the results shown in Figures 18 and 19, it can be seen that the
! examples of the present invention had a greatly increased maximum load compared
J 20 to the comparative examples, and in particular, the load was increased compared to
the comparative examples for the entire range of displacement indicating that the
amount of absorbed impact energy was greatly increased.
I 2-1-
|

We claim:
1. A formed member having at least one ridge portion connecting one
surface and another surface characterized by having a reinforcing member which is
5 joined to at least the ridge portion of the formed member by a weld provided on the
ridge portion.
2. A formed member as set forth in claim 1 wherein the reinforcing
member has a widthwise dimension which can cover at least the entirety of the
10 ridge portion in a cross section perpendicular to the extending direction of the ridge
portion.
3. A formed member as set forth in claim 1 or claim 2 wherein the weld
is provided continuously or intermittently in the extending direction of the ridge
15 portion.
4. A formed member as set forth in any one of claims 1-3 wherein the
weld has a linear shape or a curved shape in the extending direction of the ridge
portion.
20
5. A formed member as set forth in any one of claims 1 - 4 wherein the
weld is provided in a region from the center in the circumferential direction of the
cross section of the ridge portion to a distance of 50% of the circumference of the^
cross section of the ridge portion.
25
6. A formed member as set forth in any one of claims 1-5 wherein the
weld is a spot weld, a seam weld, a laser weld, or a plasma weld.
7. A formed member as set forth in any one of claims 1-6 wherein the
30 reinforcing member extends over all or a portion of the extending direction of the
ridge portion.
8. A formed member as set forth in any one of claims 1-7 wherein a
single reinforcing member or two or more reinforcing members are provided in the
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extending direction of the ridge portion.
9. A formed member as set forth in any one of claims 1 - 8 wherein the
reinforcing member is provided on the outer peripheral surface or the inner
5 peripheral surface of the ridge portion,
10. A method of manufacturing a formed member comprising welding a
flat sheet reinforcing member to a flat sheet blank by forming a weld in a location
which becomes a ridge portion of the blank, and carrying out press forming or roll
10 forming on the blank having the reinforcing member welded thereto to manufacture
a formed member as set forth in any one of claims 1-9.
11. A method of manufacturing a formed member as set forth in claim 10
wherein the press forming is carried out after the blank having the reinforcing
15 member welded thereto is heated to a temperature of at least the Acs point.