U.S. patent application number 12/527074 was filed with the patent office on 2010-05-13 for stiffened plate and method of manufacturing the same.
Invention is credited to Koutarou Inose, Junko Kambayashi, Isao Kawaguchi, Shiro Saito, Tomohiro Sugino, Hiroto Yamaoka.
Application Number | 20100115881 12/527074 |
Document ID | / |
Family ID | 39690147 |
Filed Date | 2010-05-13 |
United States Patent
Application |
20100115881 |
Kind Code |
A1 |
Inose; Koutarou ; et
al. |
May 13, 2010 |
STIFFENED PLATE AND METHOD OF MANUFACTURING THE SAME
Abstract
A stiffened plate is formed by welding a plurality of stiffener
materials which, together with a steel plate, form closed
cross-sectional structures onto a surface of the steel plate. The
stiffener materials are joined to the steel plate as a result of
edge portions of the stiffener materials which are in contact with
the steel plate by being laser welded at a predetermined welding
speed as a result of a laser having a predetermined output being
irradiated from a predetermined direction thereon from the external
side of the closed cross-sectional structures. Accordingly, it is
possible to achieve an improvement in the weld quality when welding
stiffener materials onto a steel plate, and to achieve an
improvement in fatigue strength.
Inventors: |
Inose; Koutarou;
(Yokohama-shi, JP) ; Saito; Shiro; (Yokohama-shi,
JP) ; Kambayashi; Junko; (Yokohama-shi, JP) ;
Yamaoka; Hiroto; (Yokohama-shi, JP) ; Sugino;
Tomohiro; (Tokyo, JP) ; Kawaguchi; Isao;
(Yokohama-shi, JP) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
US
|
Family ID: |
39690147 |
Appl. No.: |
12/527074 |
Filed: |
February 15, 2008 |
PCT Filed: |
February 15, 2008 |
PCT NO: |
PCT/JP2008/052531 |
371 Date: |
August 13, 2009 |
Current U.S.
Class: |
52/783.14 ;
219/121.64; 29/897.32 |
Current CPC
Class: |
B23K 26/0626 20130101;
B23K 2103/04 20180801; B23K 33/00 20130101; B23K 26/0884 20130101;
B23K 26/242 20151001; B23K 26/348 20151001; Y10T 29/49629 20150115;
B23K 2101/006 20180801; E04C 2/08 20130101; B23K 28/02 20130101;
B23K 2101/045 20180801; B23K 26/08 20130101 |
Class at
Publication: |
52/783.14 ;
29/897.32; 219/121.64 |
International
Class: |
E04C 2/32 20060101
E04C002/32; B23K 26/20 20060101 B23K026/20; B23K 103/04 20060101
B23K103/04; B21D 47/00 20060101 B21D047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 15, 2007 |
JP |
2007-034826 |
Apr 4, 2007 |
JP |
2007-098323 |
Jan 30, 2008 |
JP |
2008-018968 |
Claims
1. A stiffened plate which is formed by welding a plurality of
stiffener materials which, together with a steel plate, form closed
cross-sectional structures onto a surface of the steel plate,
wherein the stiffener materials are joined to the steel plate as a
result of edge portions of the stiffener materials which are in
contact with the steel plate by being laser welded at a
predetermined welding speed as a result of a laser having a
predetermined output being irradiated from a predetermined
direction thereon from the external side of the closed
cross-sectional structures.
2. The stiffened plate according to claim 1, wherein the edge
portions of the stiffener materials are formed so as to face the
surface of the steel plate substantially parallel therewith, and
are laser welded to the steel plate.
3. The stiffened plate according to claim 1, wherein the stiffener
materials are closed cross section ribs which have a substantially
U-shaped cross section orthogonally to the longitudinal
direction.
4. The stiffened plate according to claim 1, wherein, instead of
laser welding, the stiffener materials are welded to the steel
plate by means of hybrid laser-arc welding in which laser welding
and arc welding are performed in combination.
5. A method of manufacturing a stiffened plate which is formed by
welding a plurality of stiffener materials which, together with a
steel plate, form closed cross-sectional structures onto a surface
of the steel plate, wherein the steel plate and the stiffener
materials are joined together as a result of edge portions of the
stiffener materials which are in contact with the steel plate by
being laser welded at a predetermined welding speed as a result of
a laser having a predetermined output being irradiated from a
predetermined direction thereon from the external side of the
closed cross-sectional structures.
6. The method of manufacturing a steel plate according to claim 5,
wherein, prior to the laser welding, the edge portions of the
stiffener materials are formed so as to face the surface of the
steel plate substantially parallel therewith.
7. The method of manufacturing a steel plate according to claim 5,
wherein, in the laser welding, a refractive laser welding apparatus
which refracts laser light which has been converged by a convex
lens onto a planar mirror is used to irradiate laser light over the
surface of the steel plate so as to join the stiffener materials to
the steel plate.
8. The method of manufacturing a steel plate according to claim 5,
wherein, in the laser welding, a refractive laser welding apparatus
which converges and refracts laser light by using a parabolic
mirror or spherical mirror is used to irradiate laser light over
the surface of the steel plate so as to join the stiffener
materials to the steel plate.
9. The method of manufacturing a steel plate according to claim 5,
wherein the welding is achieved by hybrid laser-arc welding in
which arc welding is performed in a process either simultaneously
with or consecutively to the laser welding.
10. The method of manufacturing a steel plate according to claim 5,
wherein, in the laser welding or in the hybrid laser-arc welding,
filler wire is used.
11. The method of manufacturing a steel plate according to claim 5,
wherein, in the laser welding or in the hybrid laser-arc welding, a
bevel shape in which there is no gap with the skin plate is
used.
12. The method of manufacturing a steel plate according to claim 5,
wherein, in the laser welding or in the hybrid laser-arc welding,
the skin plate is used in a structure having a curved surface.
Description
TECHNICAL FIELD
[0001] The present invention relates to a stiffened plate and to a
method of manufacturing a stiffened plate.
[0002] Priority is claimed on Japanese Patent Application Nos.
2007-034826, filed Feb. 15, 2007, 2007-098323, filed Apr. 4, 2007,
and 2008-018968, filed Jan. 30, 2008, the contents of which are
incorporated herein by reference.
BACKGROUND ART
[0003] Various materials such as concrete materials and the like
are used as the floor material of bridges and the like. Steel floor
plates are known as one of these materials. Steel floor plates are
principally formed by steel plates (i.e., deck plates), however,
deck plates themselves can not satisfactorily guarantee the
necessary strength. Therefore, normally, steel floor plates are
formed as stiffened plates which have stiffener materials (i.e.,
ribs) provided on their bottom surface.
[0004] These stiffener materials may be belt-shaped plate steel, or
may be steel materials having a V-shaped or U-shaped cross section
which are known as closed cross section ribs or the like. These
stiffener materials are joined to the bottom surface of a deck
plate in parallel with each other and at fixed intervals so as to
form a stiffened plate.
[0005] Here, edge portions on both ends of the closed cross section
ribs are joined by arc welding to the deck plate so as to form a
closed cross-sectional structure with the deck plate.
[0006] A variant example of the above described type of stiffened
plate is the sandwich panel shown in Non-patent document 1. This
sandwich panel is manufactured by arranging a number of U-shaped
rib members in parallel with each other on a deck plate so as to
form a closed cross-sectional structure, and by then arc welding
edge portions of the U-shaped rib members onto the deck plate. In
addition, a bottom plate is placed on apex portions of the U-shaped
rib members, and the apex portions of the U-shaped rib members and
the bottom plate are joined together by laser welding.
[0007] Note that Patent document 1 below by the applicants of the
present invention provides documentation for prior art relating to
welding technologies for stiffened plates.
[0008] Non-patent document 1: "Strength Characteristics of Laser
Lap Welded Joins in Medium Thickness Plates and Panel
Manufacturing", by Shoichi Kitagawa, Hitachi Zosen Corporation in
"Laser Symposium: Applications of Laser Welding to Medium Thickness
Plate manufactured Bodies" Corporation: Japan Welding Engineering
Society, LMP Committee, convoked Aug. 22 (Th) to 23 (We), 2002
[0009] Patent document 1: Japanese Unexamined Patent Application,
Publication No. 2006-224137
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0010] In arc welding, since a welded metal experiences thermal
contraction after welding, tensile residual stress (i.e., welding
residual stress) is generated within the deck plate and closed
cross section ribs. This welding residual stress causes the
assembly accuracy of the components to deteriorate, giving rise to
problems such as deteriorated tensile strength, compressive
strength, or fatigue strength in the components.
[0011] Moreover, in the welding of the closed cross-sectional
structure portion of a closed cross section rib, it is only
possible to perform the welding operation from the external side of
the closed cross-sectional structure portion. However, when this
type of closed cross-sectional structure portion is arc welded, if
an attempt is made to prevent melt-through (i.e., over-welding),
the problem exists that partially unwelded portions (i.e., welding
residue portions) occur in the distal end of a single bevel or
single-J bevel, namely, in a root portion on the internal side of
the closed cross-sectional structure. Namely, in arc welding,
because it is not possible to accurately control the melt range, if
an attempt is made to prevent melt-through, then welding residue
portions end up being generated.
[0012] In this manner, if welding residual stress is generated
within a deck plate and closed cross section ribs, and if welding
residue portions are present in root portions on the internal side
of the closed cross-sectional structures, then stress is
concentrated in an area directly above the welding residue portions
of the deck plate. Because of this, cracks are easily generated in
areas directly above the welding residue portions of the deck
plate. If cracks are generated in a deck plate, the problems arise
that there is an abrupt drop in fatigue strength and that this
might easily lead to fatigue failure. Moreover, because
melt-through causes the weld quality to deteriorate, this is not
preferable.
[0013] Furthermore, although the laser lap welding described in the
aforementioned Non-patent document 1 in which welding is performed
so as to penetrate two components in a sandwich panel is the method
used for the laser welding in order to manufacture a stiffened
plate, laser welding is not used conventionally for joining edge
portions of the closed cross section ribs to the deck plate.
DISCLOSURE OF THE INVENTION
[0014] The present invention was conceived in view of the above
described circumstances and it is an object thereof to achieve an
improvement in weld quality when welding stiffener materials onto a
steel plate, and to achieve an improvement in fatigue strength.
Means for Solving the Problem
[0015] In order to achieve the above described object, a first
aspect of the present invention is a stiffened plate which is
formed by welding a plurality of stiffener materials which,
together with a steel plate, form closed cross-sectional structures
onto a surface of the steel plate, wherein the stiffener materials
are joined to the steel plate as a result of edge portions of the
stiffener materials which are in contact with the steel plate by
being laser welded at a predetermined welding speed as a result of
a laser having a predetermined output being irradiated from a
predetermined direction thereon from the external side of the
closed cross-sectional structures.
[0016] A second aspect of the present invention is the stiffened
plate according to the first aspect, wherein the edge portions of
the stiffener materials are formed so as to face the surface of the
steel plate substantially parallel therewith, and are laser welded
to the steel plate.
[0017] A third aspect of the present invention is the stiffened
plate according to the first or second aspects, wherein the
stiffener materials are closed cross section ribs which have a
substantially U-shaped cross section orthogonally to the
longitudinal direction.
[0018] A fourth aspect of the present invention is the stiffened
plate according to any one of the first through third aspects,
wherein instead of laser welding, the stiffener materials are
welded to the steel plate by means of hybrid laser-arc welding in
which laser welding and arc welding are performed in
combination.
[0019] A fifth aspect of the present invention is a method of
manufacturing a stiffened plate which is formed by welding a
plurality of stiffener materials which, together with a steel
plate, form closed cross-sectional structures onto a surface of the
steel plate, wherein the steel plate and the stiffener materials
are joined together as a result of edge portions of the stiffener
materials which are in contact with the steel plate being laser
welded at a predetermined welding speed as a result of a laser
having a predetermined output being irradiated from a predetermined
direction thereon from the external side of the closed
cross-sectional structures.
[0020] A sixth aspect of the present invention is the method of
manufacturing a stiffened plate according to the fifth aspect in
which, prior to the laser welding, the edge portions of the
stiffener materials are formed so as to face the surface of the
steel plate substantially parallel therewith.
[0021] A seventh aspect of the present invention is the method of
manufacturing a stiffened plate according to the fifth or sixth
aspects, wherein in the laser welding, a refractive laser welding
apparatus which refracts laser light which has been converged by a
convex lens onto a planar mirror is used to irradiate laser light
over the surface of the steel plate so as to join the stiffener
materials to the steel plate.
[0022] An eighth aspect of the present invention is the method of
manufacturing a stiffened plate according to any one of the fifth
through seventh aspects, wherein in the laser welding, a refractive
laser welding apparatus which converges and refracts laser light
using a parabolic mirror or spherical mirror is used to irradiate
laser light over the surface of the steel plate so as to join the
stiffener materials to the steel plate.
[0023] A ninth aspect of the present invention is the method of
manufacturing a stiffened plate according to any one of the fifth
through seventh aspects, wherein, the welding is achieved by means
of hybrid laser-arc welding in which arc welding is performed in a
process either simultaneously with or consecutively to the laser
welding.
[0024] A tenth aspect of the present invention is the method of
manufacturing a stiffened plate according to any one of the fifth
through ninth aspects, wherein in the laser welding or in the
hybrid laser-arc welding, filler wire is used.
[0025] An eleventh aspect of the present invention is the method of
manufacturing a stiffened plate according to any one of the fifth
through tenth aspects, wherein in the laser welding or in the
hybrid laser-arc welding, a bevel shape in which there is no gap
with the skin plate is used.
[0026] A twelfth aspect of the present invention is the method of
manufacturing a stiffened plate according to any one of the fifth
through eleventh aspects, wherein in the laser welding or in the
hybrid laser-arc welding, the skin plate is used in a structure
having a curved surface.
EFFECT OF THE INVENTION
[0027] According to the present invention, because edge portions of
stiffener materials are joined to a steel plate by laser welding or
by hybrid laser-arc welding, for example, by appropriately setting
the laser output, the irradiation direction, and the welding speed,
it is possible to eliminate the occurrence of melt-through and
welding residue portions. Accordingly, it is possible to achieve an
improvement in the weld quality when welding stiffener materials
onto a steel plate, and to achieve an improvement in fatigue
strength.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a perspective view showing the structure of a
stiffened plate in an embodiment of the present invention.
[0029] FIG. 2 is a perspective view showing a portion of the
stiffened plate shown in FIG. 1 which has been enlarged and
vertically inverted.
[0030] FIG. 3 is a cross-sectional view taken along a line A-A in
FIG. 2.
[0031] FIG. 4 is a typical view showing the structure of a
refractive laser welding apparatus which is used for the laser
welding in an embodiment of the present invention, and also shows a
state in which this refractive laser welding apparatus is in
use.
[0032] FIG. 5 is a typical view showing a configuration of an edge
portion of a closed cross section rib in an embodiment of the
present invention.
[0033] FIG. 6 is an explanatory view showing a manufacturing
process for a steel floor plate in an embodiment of the present
invention.
[0034] FIG. 7 is a typical view showing the structure of a
refractive laser welding apparatus which is used in another
embodiment of the present invention, and also shows a state in
which this refractive laser welding apparatus is in use.
[0035] FIG. 8A is a perspective view showing an outer appearance of
a closed cross section rib in another embodiment of the present
invention.
[0036] FIG. 8B is a perspective view showing an outer appearance of
a closed cross section rib in another embodiment of the present
invention.
[0037] FIG. 8C is a perspective view showing an outer appearance of
a closed cross section rib in another embodiment of the present
invention.
[0038] FIG. 8D is a perspective view showing an outer appearance of
a closed cross section rib in another embodiment of the present
invention.
[0039] FIG. 9A is a cross-sectional view illustrating hybrid
laser-arc welding in another embodiment of the present
invention.
[0040] FIG. 9B is a plan view illustrating hybrid laser-arc welding
in another embodiment of the present invention.
[0041] FIG. 10 is an explanatory view illustrating hybrid laser-arc
welding in another embodiment of the present invention, and is an
enlargement of a principal portion of FIG. 9A.
[0042] FIG. 11A shows a state of a melt portion which corresponds
to an irradiation angle .theta. of a laser L in FIG. 10, and shows
a case in which the irradiation angle .theta. of the laser L is not
less than 10.degree..
[0043] FIG. 11B shows a state of a melt portion which corresponds
to an irradiation angle .theta. of a laser L in FIG. 10, and shows
a case in which the irradiation angle .theta. of the laser L is
less than 10.degree..
[0044] FIG. 12A shows a state of a melt portion in FIG. 10 when a Z
target position is not more than 5 mm (i.e., low).
[0045] FIG. 12B shows a state of a melt portion in FIG. 10 when a Z
target position is greater than 5 mm (i.e., high).
[0046] FIG. 13 is an explanatory view illustrating hybrid laser-arc
welding in another embodiment of the present invention, and is an
enlargement of a principal portion of FIG. 9B.
DESCRIPTION OF THE REFERENCE NUMERALS
[0047] 10 Deck plate [0048] 20 Closed cross section rib [0049] 20
Rib [0050] 21 Edge portion [0051] 22 Edge portion [0052] 22 Laser
welding apparatus [0053] 31 Light source [0054] 32 Convex lens
[0055] 33 Planar mirror [0056] 34 Laser emission port [0057] 35
Housing [0058] 40 Laser welding apparatus [0059] 41 Light source
[0060] 43 Curved mirror [0061] 44 Laser emission port [0062] 45
Housing a: arrow [0063] L Laser [0064] M Torch [0065] t1
Predetermined plate thickness [0066] t2 Predetermined plate
thickness [0067] W Filler wire [0068] X Distance from head [0069] Y
Welding direction [0070] .theta. Irradiation angle
BEST MODE FOR CARRYING OUT THE INVENTION
[0071] Hereinafter, an embodiment of the present invention will be
described with reference made to the drawings. Firstly, FIG. 1 is a
perspective view showing the structure of a stiffened plate in the
present embodiment. FIG. 2 is a perspective view showing a portion
of the stiffened plate shown in FIG. 1 which has been enlarged and
vertically inverted. FIG. 3 is a cross-sectional view taken along a
line A-A in FIG. 2.
[0072] Note that stiffened plates are used in a variety of
applications such as the decking and structural components of ships
and the like, however, here, an example is described in which
stiffened plates are used, for example, for the steel floor plates
of a bridge.
[0073] Steel floor plates (i.e., stiffened plates) are formed by
placing a plurality of closed cross section ribs 20 (i.e.,
stiffener materials) at fixed intervals on one surface of a deck
plate 10 (i.e., a steel plate). The deck plate 10 is a flat plate
made from steel having a predetermined thickness of t1 (for
example, 12 mm). The closed cross section ribs 20 are made of shape
steel having a U-shaped cross-section and are formed by bending a
flat plate made from steel having a predetermined thickness of t2
(for example, 6 to 8 mm).
[0074] FIG. 4 is a typical view showing the structure of a laser
welding apparatus 30 (i.e., a refractive laser welding apparatus),
and also shows a state in which the laser welding apparatus 30 is
in use. As shown in this drawing, the laser welding apparatus 30
has a light source 31, a convex lens 32, a planar mirror 33, and a
housing 35 which houses the components 31 through 33 and in which
is formed a laser emission port 34. The light source 31 emits a
laser L. The convex lens 32 converges the laser L. The planar
mirror 33 reflects the laser L.
[0075] FIG. 5 is a typical view showing the shape of a pair of edge
portions 21 and 22 of a closed cross section rib 20. FIG. 6 is an
explanatory view showing a process to manufacture a steel floor
plate. A description will now be given in detail of a process to
manufacture a steel floor plate with reference made to these
drawings.
[0076] Firstly, as is shown in FIG. 5, the pair of edge portions 21
and 22 of the closed cross section rib 20 are formed at an angle
which enables them to face the surface of the deck plate 10 against
which they are abutted substantially parallel therewith. The pair
of edge portions 21 and 22 of the closed cross section rib 20 are
then abutted on the surface of the deck plate 10 (see the arrow a
in FIG. 6).
[0077] Next, the laser welding apparatus 30 irradiates a laser (see
c in FIG. 6) over the entire length of the closed cross section rib
20 (see the arrow b in FIG. 6) from the external side of the closed
cross sectional structure which is formed by the deck plate 10 and
the closed cross section rib 20. As a result, the respective edge
portions 21 and 22 of the closed cross section rib 20 are laser
welded to the surface of the deck plate. As a result of laser
welding being performed on the two edge portions 21 and 22 of the
closed cross section rib 20, the closed cross section rib 20 is
joined to the deck plate 10 and a steel floor plate is thereby
produced.
[0078] As shown in FIG. 4, the laser welding apparatus 30 converges
the laser L emitted by the light source 31 by means of the convex
lens 32, and then reflects the laser L which has been converged by
the convex lens 32 by means of the planar mirror 33 so as to
refract the direction of travel of the laser L. The laser welding
apparatus 30 then emits the laser L through the laser emission port
34. The laser L which has been emitted by the laser welding
apparatus 30 is irradiated onto the deck plate 10 adjacent to the
edge portions 21 and 22 of the closed cross section rib 20. As a
result, the closed cross section rib 20 is joined to the deck plate
10. Note that, if necessary, it is possible to supply a wire W to
the vicinity of the edge portions 21 and 22 of the closed cross
section rib 20 together with the laser L.
[0079] When laser welding is being performed by the laser welding
apparatus 30, the output of the laser L, the irradiation position,
the irradiation direction, the welding speed, and the supply speed
of the wire W are appropriately set. As a result, it is possible to
prevent the occurrence of melt-through, and to reduce welding
residue portions to approximately 0.5 mm.
[0080] Moreover, by using the laser welding apparatus 30 which is a
refractive laser welding apparatus, it is possible to freely
refract the laser L to a desired angle (for example, approximately
90.degree.), and then irradiate it across the surface of the deck
plate 10. Herewith, it is possible to irradiate easily the laser L
onto the deck plate 10 adjacent to the edge portions 21 and 22 of
the closed cross section rib 20.
[0081] Furthermore, since the weld of the present embodiment is not
achieved by arc welding, there are no effects from welding residual
stress which is caused by thermal contraction of the welded metal
after arc welding has ended. Accordingly, there is no reduction in
the assembly accuracy of the components, and no reduction in the
tensile strength, the compression strength, or the fatigue strength
of the components due to the effects of welding residual
stress.
[0082] In addition, if, as in the present embodiment, the closed
cross section ribs 20 are welded onto the deck plate 10 without
welding residual stress being generated and with only a minimal
amount of welding residue portions, then stress concentration in
the welding residue portions is decreased. As a result, it is
possible to reduce the extent to which cracks are generated in an
area directly above welding residue portions in the deck plate 10.
Accordingly, according to the present embodiment, it is possible to
eliminate the occurrence of melt-through when welding the edge
portions 21 and 22 of a closed cross section rib 20 onto the deck
plate 10, and to achieve an improvement in the weld quality by
reducing welding residue portions to an absolute minimum. In
addition to this, it is possible to suppress the occurrence of
cracks in the deck plate 10 and thereby improve the fatigue
strength.
[0083] Note that in the above described embodiment the laser
welding apparatus 30 shown in FIG. 6 has been used, however, when
implementing the present invention, it is also possible to use the
laser welding apparatus 40 (i.e., a refractive laser welding
apparatus) shown in FIG. 7. The laser welding apparatus 40 has a
light source 41, a curved mirror 43 having a paraboloidal or
spherical reflective surface, and a housing 45 which houses the
portions 41 and 43 and in which a laser emission port 44 is
formed.
[0084] This laser welding apparatus 40 causes a laser L which has
been emitted by the light source 41 to be converged and reflected
by the curved mirror 43, and is thus able to refract the direction
of travel of the laser L. The laser L is then emitted from the
laser emission port 44.
[0085] Moreover, in the above described embodiment, shaped steel
having a U-shaped cross-section is used for the closed cross
section ribs 20. However, when implementing the present invention,
it is also possible for the closed cross section ribs to have a
cross section of another shape such as a V-shaped cross section, a
semicircular cross section, a trapezoidal cross section, or a
quadrangular cross section such as those shown in FIG. 8.
Furthermore, in the above described embodiment, the stiffener
materials were provided by the closed cross section ribs 20.
However, when implementing the present invention, it is not
essential for a closed cross-sectional structure to be formed
together with the deck plate 10, and for example, even when I-steel
or the like is joined to the deck plate 10, the present invention
can be applied with superior results.
[0086] In addition, in the above described embodiment, a
description is given in which steel plate is used for the deck
plate 10 and in which a steel floor plate is used as an example of
a stiffened plate. However, when implementing the present
invention, the steel plate is not limited to being the deck plate
10 and the stiffened plate is not limited to being a steel floor
plate. If it is provided that the stiffened plate is formed by
arranging stiffener materials on a steel plate, then the present
invention can be applied with superior results.
[0087] Next, a description will be given using FIG. 9 through FIG.
11B of a case in which the welding is achieved by means of hybrid
laser-arc welding in which arc welding is performed in a process
either simultaneously with or consecutively to the laser welding.
As described below, in a hybrid laser-arc welding apparatus, a
laser L and an arc welding torch M target substantially the same
spot. Note that, in the drawings, the same functional portions are
given the same descriptive symbols and any duplicated description
thereof is avoided.
[0088] FIG. 9 is an explanatory view showing hybrid laser-arc
welding in another embodiment of the present invention with (a)
being a cross-sectional view thereof and (b) being a plan view
thereof. As shown in FIG. 9 (a) and FIG. 9 (b), when joining a
closed cross section rib (may also be referred to below simply as a
`rib` or `stiffened plate`) 20 to a deck plate (may also be
referred to below simply as a `skin plate` or `steel material`) 10
by means of hybrid laser-arc welding, the laser L is irradiated
with a distance of X from a head of the laser welding apparatus 30
onto a weld spot. While an arc welding torch is then applied to a
position close to this irradiated portion, hybrid laser-arc welding
is then performed in a welding direction Y at a predetermined
welding speed. Note that it is possible for either the laser
welding or the arc welding to be given precedence.
[0089] FIG. 10 is an explanatory view showing hybrid laser-arc
welding in another embodiment of the present invention, and is an
enlarged view of a principal portion H in FIG. 9A. As shown in FIG.
10, it is preferable for the irradiation angle .theta. of the laser
L to be not less than 10 degrees. It is also preferable for the Z
target position to be set somewhat low (for example, 5 mm or
less).
[0090] When the predetermined output is less than 4 kW, it is
difficult for melt-through to occur but easy for welding residue to
be generated so that the welding quality required from the present
system cannot be achieved. Moreover, if the predetermined output is
greater than 10 kW, since the output is large relative to the rib
thickness of the steel floor plate, there is a concern that
melt-through will be generated.
[0091] On the other hand, when the predetermined welding speed is
less than 50 cm/min, the advantage of laser welding that is fast
welding speeds is lost. However, if the predetermined welding speed
is greater than 200 cm/min, there is a concern that welding residue
will be generated.
[0092] FIG. 11A shows a state of a melt portion which corresponds
to the aforementioned irradiation angle .theta., and shows a melt
portion Y1 when the irradiation angle .theta. of the laser L is not
less than 10.degree.. FIG. 11B shows a melt portion Y2 when the
irradiation angle .theta. of the laser L is less than 10.degree..
Melt-through is not generated in the melt portion Y1 in which the
irradiation angle .theta. of the laser L is 10.degree. or more,
however, melt-through is generated in the melt portion Y2 in which
the irradiation angle .theta. of the laser L is less than
10.degree.. When the irradiation angle .theta. of the laser L is
10.degree. or greater, as shown in the drawing, since the distal
end of the weld penetration is inside the deck plate 10, it is
difficult for melt-through to be generated. However, when the
irradiation angle .theta. of the laser L is less than 10.degree.,
since the distal end of the weld penetration is positioned between
the deck plate 10 and the rib 20, it is easy for melt-through to be
generated.
[0093] FIG. 12A and FIG. 12B show states of a melt portion
corresponding to the aforementioned Z target position. FIG. 12A
shows a melt portion Y3 in which the Z target position is 5 mm or
less (i.e., low), while FIG. 12B shows a melt portion Y4 in which
the Z target position is greater than 5 mm (i.e., high). In the
melt portion Y3 in which the Z target position has been set low,
melt-through is not generated, however, in the melt portion Y4 in
which the Z target position has been set high, melt-through is
generated. When the Z target position has been set low, as shown in
the drawing, since the distal end of the weld penetration is inside
the deck plate 10, it is difficult for melt-through to be
generated, however, when the Z target position has been set high,
because the distal end of the weld penetration is positioned
between the deck plate 10 and the rib 20, it is easy for
melt-through to be generated.
[0094] FIG. 13 is an explanatory view showing hybrid laser-arc
welding in another embodiment of the present invention, and is an
enlarged view of a principal portion K in FIG. 9B. As shown in FIG.
11A and FIG. 11B, in a hybrid laser-arc welding apparatus, the
laser L and the arc welding torch M as a rule aim for substantially
the same spot, however, preferably, the welds of the laser L and
the arc welding torch M are at a distance of 0 to 5 mm from each
other. By using this hybrid laser-arc welding, the following two
advantages are obtained.
[0095] The first advantage is that hybrid laser-arc welding makes
it possible to fill the gap between the rib 20 and the deck plate
10. The gap margins at this time are as follows.
(a) In laser welding, if there is no filler wire W, this gap margin
is limited to approximately 0.5 mm. (b) In laser welding, if there
is filler wire W, this gap margin is limited to approximately 1 mm.
(c) In hybrid laser-arc welding, the gap may be as much as 3
mm.
[0096] The second advantage is that, compared with when only laser
welding is used, because there is also heat input from the arc
welding, rapid heating and rapid cooling can be avoided. Because of
this, the hardness of the welding metal is less than when laser
welding (i.e., using filler wire W) is used.
[0097] Moreover, in electronic beam welding and laser welding,
fundamentally, a join is achieved by only welding the base
materials without adding any welding material, however, in cases
such as those described below, it is preferable to add welding
material (referred to below as `filler wire` or `wire`) W.
(a) When there is a gap in the weld portion in a piece of work and
it is necessary to provide a supplementary material in order to
achieve consistent bead formation. (b) When it is necessary to
improve the cleanliness and mechanical properties of a weld metal.
(c) When weld reinforcement is being formed in a material whose
nature is such that surface beads are easily hollowed out therein
(such as aluminum alloy and the like) when performing complete-melt
welding.
[0098] Moreover, in laser welding, the greatest advantage in using
the filler wire W is that it is possible to fill the gap between
the stiffened plate (i.e., rib) 20 and the steel plate (i.e., skin
plate or deck plate) 10. Note that the present invention can also
be applied to a deck plate 10 having a curved surface structure
(not shown). It is also possible for the present invention to be
applied to a bevel shape in which there is no gap with the deck
plate 10 (see FIG. 5 and FIG. 7).
[0099] In addition, the method which is most commonly used to add a
welding material in laser welding is to gradually feed out the
filler wire W, as partially shown in FIG. 7. Because both an
electron beam and a laser beam which are converged on a weld
portion have extremely small diameters, it is common that a wire
having a narrow diameter of 1 mm or less is used for the wire W.
This filler wire W is fed precisely via a wire guide (not shown) to
the beam irradiation point where it is then melted.
[0100] Note that the present invention can be applied to a wide
range of cross-sectional shapes for the ribs 20 such as U-shapes
and circular shapes and the like.
* * * * *