DESCRIPTION
HYBRID WELDING METHOD AND HYBRID WELDING APPARATUS
TECHNICAL FIELD
The present invention relates to a hybrid welding method
and a hybrid welding apparatus that radiate laser beams to a
welding object and perform arc welding.
BACKGROUND ART
Laser welding has high energy density and can be
performed in a narrow heat-affected zone at a high speed.
However, when there is a gap on a welding object, there is a
concern that a laser beam will leak from the gap, which makes
it difficult to perform welding. In order to solve this problem,
many hybrid welding methods using consumable-electrode-type
arc welding have been proposed.
For example, Fig. 13 is a block diagram illustrating the
structure of a hybrid welding apparatus according to the
related art. Laser generating unit 1 includes laser
oscillator 2, laser transmitting unit 3, and focusing optical
system 4. Focusing optical system 4 radiates laser beam 5 to
the welding position of welding object 6. For example, an
optical fiber or a combination of lenses is used as laser
transmitting unit 3. Focusing optical system 4 includes one
lens or a plurality of lenses. Wire 7 is fed to the welding
position of welding object 6 through torch 9 by wire feeding
unit 8. Arc generating unit 10 controls wire feeding unit 8.
Arc generating unit 10 controls the wire feeding unit to feed
wire 7 to the welding position of welding object 6 through torch
9 such that welding arc 11 is generated or stops between wire
7 and welding object 6. Control unit 12 controls laser
generating unit 1 and arc generating unit 10. Although not
shown in the drawings, laser oscillator 2 outputs a
predetermined output value. In addition, laser oscillator 2
receives a signal of the output value set by control unit 12
and outputs a laser beam corresponding to the signal. Similar
to laser generating unit 1, the output of arc generating unit
10 is controlled by control unit 12.
The operation of the hybrid welding apparatus having the
above-mentioned structure according to the related art will
be described below. When welding starts, although not shown
in the drawings, control unit 12 receiving a welding start
command transmits a laser welding start signal to laser
generating unit 1 to start the radiation of laser beam 5. In
addition, control unit 12 transmits an arc welding start signal
to arc generating unit 10 to start arc discharge. In this way,
welding starts. When welding ends, control unit 12 receiving
a welding end command transmits a laser welding end signal to
laser generating unit 1 to end the radiation of laser beam 5.
In addition, control unit 12 transmits an arc welding end signal
to arc generating unit 10 to end arc discharge. In this way,
welding ends.
Various improvements of the above-mentioned hybrid
welding method have been proposed. For example, PTL 1
discloses a technique in which the gap between laser radiation
and arc discharge is set to a predetermined value at which arc
does not interfere with laser, thereby improving the melting
rate of a welding object. In the above-mentioned case, the
laser beam does not directly irradiate to the wire and a welding
current is almost used for arc welding. NPL 1 discloses a
technique in which the size of a molten pool is substantially
determined by the size of the molten pool formed by arc welding.
PTL 2 discloses a technique that radiates the laser beam
to the wire to reduce the arc current and the size of the molten
pool formed by arc welding. PTL 3 discloses a technique in
which pulsed arc welding is used as arc welding and the pulse
frequency of pulsed arc welding is controlled according to a
laser-wire distance at the radiation point of the welding
object, thereby improving the gap tolerance.
However, the related art does not disclose a hybrid
welding method and a hybrid welding apparatus having all of
the above-mentioned advantages. That is, in the related art,
it is difficult to reduce arc energy or arc current required
to melt the wire and reduce the size of the molten pool formed
by welding arc. In addition, it is difficult to prevent the
generation of spatter involving the rapid evaporation of a
molten droplet formed at the end of the wire. It is also
difficult to supply a high laser output to the welding position
to obtain a high welding rate.
[PTL 1] Japanese Patent Unexamined Publication No.
2002-346777
[PTL 2] Japanese Patent Unexamined Publication No.
2008-93718
[PTL 3] Japanese Patent Unexamined Publication No.
2008-229631
[NPL 1] Seiji Katayama, Satoru Uchiumi, Masami Mizutani,
Jing-Bo Wang, Koji Fujii, Penetration Characteristics and
Porosity Prevention Mechanism in YAG Laser-MIG Hybrid Welding
of Aluminum Alloy, Light Metal Welding, 44, 3 (2006)
DISCLOSURE OF THE INVENTION
An object of the invention is to provide a hybrid welding
method and a hybrid welding apparatus capable of reducing arc
energy or arc current required to melt a wire and the size of
a molten pool formed by welding arc, preventing the generation
of spatter involving the rapid evaporation of a molten droplet
formed at the end of the wire, and supplying a high laser output
to a welding position to obtain a high welding rate.
According to an aspect of the invention, there is
provided a hybrid welding method of feeding a wire to a welding
position of a welding object while radiating a first laser beam
and a second laser beam to the welding position, thereby
performing arc welding between the welding object and the wire.
The hybrid welding method includes: radiating the first laser
beam to a first radiation point of the welding object through
the wire such that an optical axis of the first laser beam
intersects a central axis of the wire; and radiating the second
laser beam to a second radiation point of the welding object
that is spaced a predetermined distance from a target position
where the central axis of the wire intersects the welding object.
The first radiation position, the second radiation position,
and the target position are disposed on a welding line of the
welding object.
According to the above-mentioned structure, it is
possible to reduce arc energy or arc current required to melt
a wire and the size of a molten pool formed by welding arc.
In addition, it is possible to prevent the generation of spatter
involving the rapid evaporation of a molten droplet formed at
the end of the wire. It is also possible to supply a high laser
output to the welding position using the second laser beam to
obtain a high welding rate.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a diagram schematically illustrating a hybrid
welding apparatus according to a first embodiment of the
invention.
Fig. 2 is a diagram schematically illustrating the
correlation between a laser radiation position and a wire
target position in a hybrid welding method according to the
first embodiment.
Fig. 3 is a diagram illustrating the operation timing
of welding arc, a first laser beam, and a second laser beam
in the first embodiment.
Fig. 4 is a diagram schematically illustrating the
correlation between a laser radiation position and a wire
target position in a hybrid welding method according to a second
embodiment of the invention.
Fig. 5 is a diagram schematically illustrating a hybrid
welding apparatus according to a third embodiment of the
invention.
Fig. 6 is a diagram illustrating the operation timing
of welding arc, a first laser beam, and a second laser beam
in the third embodiment.
Fig. 7 is a diagram schematically illustrating the
structure of a laser transmitting unit and a focusing optical
system according to the invention.
Fig. 8 is a diagram schematically illustrating the
structure of a hybrid welding apparatus according to a fourth
embodiment of the invention.
Fig. 9A is a diagram schematically illustrating the
arrangement of a first laser beam and a wire in the hybrid
welding apparatus.
Fig. 9B is a diagram schematically illustrating a molten
droplet at the end of the wire in the hybrid welding apparatus.
Fig. 10 is a diagram schematically illustrating the
propagation state of the first laser beam in the hybrid welding
apparatus.
Fig. 11A is a diagram illustrating a state before the
generation of spatter in the hybrid welding apparatus.
Fig. 11B is a diagram illustrating a variation in the
generation of spatter in the hybrid welding apparatus.
Fig. 11C is a diagram illustrating a variation in the
generation of spatter in the hybrid welding apparatus.
Fig. 11D is a diagram illustrating a variation in the
generation of spatter in the hybrid welding apparatus.
Fig. HE is a diagram illustrating a variation in the
generation of spatter in the hybrid welding apparatus.
Fig. 11F is a diagram illustrating a variation in the
generation of spatter in the hybrid welding apparatus.
Fig. 12 is a diagram illustrating the bead appearances
when a laser output is changed in the hybrid welding apparatus.
Fig. 13 is a block diagram illustrating the structure
of a hybrid welding apparatus according to the related art.
DESCRIPTION OF REFERENCE NUMERALS AND SIGNS
6: welding object
7: wire
8: wire feeding unit
9: torch
9a: tip
10: arc generating unit
11: welding arc
15: molten pool
17: control unit
13: first laser beam
14: second laser beam
16: current detecting unit
20: droplet
100: laser generating unit
101, 114: laser oscillator
115: laser output setting unit
102, 102A, 102B: laser transmitting unit
103: focusing optical system
103A, 103B: focusing optical part
113: pulsed arc generating unit
115: laser output setting unit
116: calculating unit
117: maximum power density setting unit
118: display unit
119: pulsed arc
PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION
(First embodiment)
Fig. 1 is a diagram schematically illustrating a hybrid
welding apparatus according to a first embodiment of the
invention. In Fig. 1, laser generating unit 100 includes laser
oscillator 101, laser transmitting unit 102, and focusing
optical system 103. Laser generating unit 100 radiates first
laser beam 13 and second laser beam 14 to the welding position
of welding object 6. Focusing optical system 103 focuses first
laser beam 13 and second laser beam 14 on the welding position
of welding object 6. Laser transmitting unit 102 is, for
example, an optical fiber or a combination of lenses. Focusing
optical system 103 includes one lens or a plurality of lenses.
Wire 7 is fed to the welding position of welding object 6 through
torch 9 by wire feeding unit 8 . Arc generating unit 10 controls
wire feeding unit 8. In addition, arc generating unit 10
controls the wire feeding unit to feed wire 7 to the welding
position of welding object 6 through torch 9 such that welding
arc 11 is generated or stops between wire 7 and welding object
6. Control unit 17 controls laser generating unit 100 and arc
generating unit 10 . For example, control unit 17 is a computer,
a device having a calculation function, or a robot. Although
not shown in the drawings, laser oscillator \j& outputs a
predetermined output value. In addition, laser oscillator lol
receives a signal of the output value set by control unit 17
and outputs the signal. Similar to laser generating unit 100,
the output of arc generating unit 10 is controlled by control
unit 17. As shown in Fig. 1, the hybrid welding apparatus
according to this embodiment differs from the hybrid welding
apparatus according to the related art shown in Fig. 13 in that,
in this embodiment, laser oscillator 101 generates first laser
beam 13 and second laser beam 14, focusing optical system 103
radiates first laser beam 13 and second laser beam 14 to the
welding position of welding object 6, and control unit 17
controls laser oscillator 101 and focusing optical system 103.
Fig. 2 is a diagram schematically illustrating the
correlation between a laser radiation position and a wire
target position in a hybrid welding method according to this
embodiment. In Fig. 2, a side view and a top view are arranged
in the vertical direction. Tip 9a is attached to the torch
9 and supplies power to wire 7. First laser beam 13 is radiated
to first radiation position A on the surface of welding object
6. That is, first radiation position A on the surface of
welding object 6 is disposed on optical axis aa' of first laser
beam 13. Second laser beam 14 is radiated to second radiation
position B on the surface of welding object 6. That is, second
radiation position B on the surface of welding object 6 is
disposed on optical axis bb' of second laser beam 14. Wire
7 is fed to target position C of welding object 6. That is,
target position C on the surface of welding object 6 is disposed
on central cc' of wire 7. First laser beam 13 is radiated to
first radiation position A across wire 7. That is, laser
radiation position D of wire 7 and first radiation position
A on the surface of welding object 6 are disposed on optical
axis aa' of first laser beam 13. In addition, target position
C on the surface of welding object 6 and laser radiation
position D of wire 7 are disposed on central axis cc' of wire
7. In this embodiment, focusing optical system 103 and torch
9 are arranged such that the above-mentioned positional
relationship is established. Welding is performed along
welding line M1M2 on the surface of welding object 6 in the
direction of the bold arrow. In Fig. 2, welding line M1M2 is
a straight line. However, welding line M1M2 may be a curved
line according to the welding position. That is, first
radiation position A, second radiation position B, and target
position C are disposed on welding line M1M2 in this order.
However, first radiation position A, target position C, and
second radiation position B form a straight line for practical
purposes. Molten pool 15 is formed at the welding position
on the surface of welding object 6 by a welding operation using
first laser beam 13, second laser beam 14, and wire 7.
Therefore, molten pool 15 is formed on welding line M1M2. LI
denotes a laser-arc distance which indicates the distance
between first radiation position A and target position C on
the surface of welding object 6. L2 denotes a laser-arc
distance which indicates the distance between second radiation
position B and target position C on the surface of welding
object 6. That is, second laser beam 14 is radiated to second
radiation position B that is spaced predetermined distance L2
from target position C of wire 7.
In this embodiment, an operation when welding starts and
an operation when welding ends will be described with reference
to Fig. 3. Fig. 3 is a diagram illustrating the operation
timing of welding arc 11, first laser beam 13, and second laser
beam 14 in the hybrid welding method according to this
embodiment. When welding starts, as represented by signal P2,
the output of second laser beam 14 is turned on at time tl.
Then, at time t2 after period Atl has elapsed, as represented
by signal PA, the output of welding arc 11 is turned on. Then,
at time t3 after period At2 has elapsed, as represented by
signal PI, the output of first laser beam 13 is turned on. That
is, welding arc 11 is generated after predetermined period Atl
has elapsed from the start of the radiation of second laser
beam 14. Then, first laser beam 13 is radiated after
predetermined period At2 has elapsed. The reason is as
follows.
During period Atl from the start of the radiation of
second laser beam 14 to the generation of welding arc 11, the
welding position of welding object 6 is heated by second laser
beam 14 and laser-induced plasma or plume is generated. The
laser-induced plasma or plume can make the start of welding
arc 11 easy. Meanwhile, during period At2 from the generation
of welding arc 11 to the radiation of first laser beam 13,
welding arc 11 is generated without any contact between first
laser beam 13 and wire 7. The reason is that, if welding arc
11 is generated after the radiation of first laser beam 13
starts, before contacting welding object 6, the wire 7 directly
receives irradiation of the first laser beam 13, and is melted
before welding arc 11 is generated, which makes it difficult
to normally start arc welding.
Next, the operation when welding ends will be described.
At time t4, as represented by signals PI and P2, the radiation
of first laser beam 13 and second laser beam 14 ends at the
same time. Then, at time t5 after period At3 has elapsed, as
represented by signal PA, the generation of welding arc 11 ends .
In general, in order to end the welding operation, it is
necessary to turn off torch 9 and perform a cratering process.
However, if first laser beam 13 and second laser beam 14 are
radiated for a long time with welding arc 11, the penetration
depth of welding object 6 is too large, which may cause the
occurrence of burn through. Therefore, period At3 makes it
possible to perform a cratering process by welding arc 11
without generating burn through.
However, in the above description, first laser beam 13
radiated to wire 7 is not particularly limited. However, in
order to prevent wire 7 from being evaporated due to the
absorption of an excessive amount of energy from first laser
beam 13, it is preferable that the output value of first laser
beam 13 be set to a predetermined allowable value or less, that
is, a molten droplet formed at the leading end of wire 7 be
not rapidly evaporated even though they absorb the energy of
first laser beam 13. Actually, the absorption of first laser
beam 13 by wire 7 and the evaporation of wire 7 are determined
by the power density of the first laser beam at laser radiation
position D on the surface of wire 7 . It is possible to prevent
the molten droplet formed at the tip of wire 7 from being rapidly
evaporated by setting the output value of first laser beam 13
to a predetermined allowable value or less considering the
above, that is, by setting the power density of first laser
beam 13 at laser radiation position D of wire 7 to a
predetermined allowable value or less. In addition, in the
actual welding operation, the power density of first laser beam
13 radiated to the surface of welding object 6 can be directly
managed. When the arrangement relationship between first
laser beam 13 and wire 7 is determined considering the above,
it is possible to prevent the molten droplet formed at the tip
of wire 7 from being rapidly evaporated by setting the output
value of first laser beam 13 to a predetermined allowable value
or less, that is, by setting the power density of first laser
beam 13 at first laser radiation position A of welding object
6 to a predetermined allowable value or less.
As described above, laser oscillator 101 and torch 9 are
arranged such that optical axis aa' of first laser beam 13
intersects central axis cc' of wire 7. Therefore, it is
possible to directly radiate first laser beam 13 to wire 7.
In this way, it is possible to reduce arc energy or arc current
required to melt wire 7 and thus reduce the size of molten pool
15 formed by welding arc 11. The limitation of the output value
of first laser beam 13 will be described below.
Since second laser beam 14 is not directly radiated to
wire 7, the output value of second laser beam 14 is not limited
by wire 7 . Therefore, it is possible to set the output of second
laser beam 14 according to a material forming welding object
6 to be welded, the thickness of welding object 6, a necessary
welding speed, or a necessary bead shape. For example, it is
possible to perform welding at a high welding speed and with
a large penetration depth by increasing the output value of
second laser beam 14.
As described above, according to this embodiment, it is
possible to reduce arc energy or arc current required to melt
wire 7 and thus reduce the size of molten pool 15 formed by
the welding arc. In addition, it is possible to prevent the
generation of spatter involving the rapid evaporation of the
molten droplet formed at the end of wire 7. It is possible
to obtain a high welding speed by supplying a high laser output
to the welding position using second laser beam 14.
(Second embodiment)
Fig. 4 is a diagram schematically illustrating the
correlation between a laser radiation position and a wire
target position in a hybrid welding method according to a second
embodiment of the invention. Similar to Fig. 2, in Fig. 4,
a side view and a top view are arranged in the vertical direction.
The second embodiment shown in Fig. 4 is similar to the first
embodiment shown in Fig. 2 except for the radiation direction
and the radiation position of second laser beam 14. That is,
in this embodiment, second radiation position B of second laser
beam 14 is spaced predetermined distance L2 from target
position C of wire 7. Target position C, first radiation
position A, and second radiation position B form a straight
line in this order. Target position C, first radiation
position A, and second radiation position B are arranged on
welding line M1M2 in this order from the end to the origin of
the welding direction. In this embodiment, it is practical
that the three positions are arranged in a straight line.
In this embodiment, first radiation point A of first
laser beam 13 and second radiation point B of second laser beam
14 are disposed at different positions. However, first
radiation position A of first laser beam 13 may be the same
as second radiation position B of second laser beam 14. In
this case, second radiation position B of second laser beam
14 is spaced a predetermined distance L£ from target position
C of wire 7. That is, laser-arc distances LI and L2 are equal
to each other.
As such, in this embodiment, it is possible to reduce
arc energy or arc current required to melt wire 7 and thus reduce
the size of molten pool 15 formed by the welding arc. In
addition, it is possible to prevent the generation of spatter
involving the rapid evaporation of the molten droplet formed
at the tip of wire 7. It is possible to obtain a high welding
speed by supplying a high laser output to the welding position
using second laser beam 14.
(Third embodiment)
Fig. 5 is a diagram schematically illustrating a hybrid
welding apparatus according to a third embodiment of the
invention. The basic structure of the welding apparatus
according to this embodiment is the same as that of the welding
apparatus according to the first embodiment shown in Fig. 1.
In Fig. 5, laser generating unit 100 includes laser oscillator
101, laser transmitting unit 102, and focusing optical system
103. Laser generating unit 100 emits first laser beam 13 and
second laser beam 14 to the welding position of welding object
6. Current detecting unit 16 connected between arc generating
unit 10 and welding object 6 detects the timing of a current
flowing through wire 7 and welding object 6 when welding arc
11 is generated. Control unit 17 receives an output signal
from current detecting unit 16 and controls laser generating
unit 100 or arc generating unit 10. Current detecting unit
16 may be incorporated into arc generating unit 10 . A detecting
unit, such as a Hall element, or a shunt may be used as current
detecting unit 16.
The operation of this embodiment will be described below.
First, an operation when current detecting unit 16 is not used
will be described. In this case, the operation is the same
as that in the first embodiment and will be described with
reference to Fig. 3. When welding starts, although not shown
in the drawings, control unit 17 receives a welding start signal
and controls laser generating unit 100 to output only second
laser beam 14 at time tl, as represented by signal P2. Then,
at time t2 after predetermined period Atl has elapsed, control
unit 17 controls arc generating unit 10 to instruct wire feeding
unit 8 to feed wire 7 to welding object 6, as represented by
signal PA, such that welding arc 11 is generated between wire
7 and welding object 6. Then, at time t3 after predetermined
period At2 has elapsed, control unit 17 controls laser
generating unit 100 again to radiate first laser beam 13, as
represented by signal PI. When welding ends, although not
shown in the drawings, control unit 17 receives a welding end
signal and controls laser generating unit 100 to end the
radiation of both first laser beam 13 and second laser beam
14 at a time t4, as represented by signals PI and P2. Then,
at time t5 after period At3 has elapsed, control unit 17
controls arc generating unit 10 to end the generation of the
welding arc, as represented by signal PA.
Next, an operation when current detecting unit 16 is used
will be described with reference to Fig. 6. Fig. 6 is a diagram
illustrating the operation timing of the welding arc, the first
laser beam, and the second laser beam in this embodiment. When
welding starts, although not shown in the drawings, control
unit 17 receives a welding start signal and controls arc
generating unit 10 to instruct wire feeding unit 8 to feed wire
7 to welding object 6 at time t2, as represented by signal PA,
such that welding arc 11 is generated between wire 7 and welding
object 6. In this case, current detecting unit 16 detects
current flowing between wire 7 and welding object 6 and
immediately outputs a current detection signal to control unit
17. control unit 17 receives the current detection signal and
controls laser generating unit 100 to immediately output second
laser beam 14, as represented by signal P2. Then, at time t3
after period At2 has elapsed, control unit 17 controls laser
generating unit 100 to radiate first laser beam 13, as
represented by signal PI. The operation when welding ends is
the same as that described with reference to Fig. 3. As such,
even when welding is performed at the timing shown in Fig. 6,
the same effects as those in Fig. 3 are obtained.
As described in the first to third embodiments, laser
generating unit 100 that outputs two laser beams will be
described. In Figs. 1 and 5, laser generating unit 100 has
the following structure as the simplest structure. Laser
oscillator 101 outputs two laser beams, and the two laser beams
are transmitted to focusing optical system 103 by laser
transmitting unit 102 capable of transmitting the two laser
beams. Focusing optical system 103 focuses the two laser beams
into first laser beam 13 and second laser beam 14 and radiates
the first and second laser beams to welding object 6. The gap
between first and second radiation positions A and B of first
laser beam 13 and second laser beam 14 on welding object 6 can
be adjusted by the gap between two laser beams introduced from
transmitting unit 102 to focusing optical system 103.
This will be described with reference to Fig. 7. Fig.
7 is a diagram schematically illustrating the structure of the
laser transmitting unit and the focusing optical system
according to the invention. Laser transmitting unit 102
includes first and second laser transmitting units 102A and
102B that respectively transmit two first and second laser
beams 13 and 14 generated by laser oscillator 101. First and
second laser transmitting units 102A and 102B are arranged with
laser transmitting unit gap LO therebetween. Focusing optical
system 103 includes focusing optical part 103A that is provided
close to laser transmitting unit 102 and focusing optical part
103B that is provided close to welding object 6. Focusing
optical part 103A makes two first and second laser beams 13
and 14 transmitted from laser transmitting units 102A and 102B
parallel to each other. Focusing optical part 103B focuses
the parallel two first and second laser beams 13 and 14 on first
and second radiation positions A and B, respectively. Laser
transmitting units 102A and 102B are, for example, optical
fibers. Focusing optical parts 103A and 103B are, for example,
convex lenses with the same or different focal lengths. As
shown in Fig. 7, it is possible to adjust gap L1+L2 between
first and second radiation positions A and B of two first and
second laser beams 13 and 14 on the surface of welding object
6 by adjusting laser transmitting unit gap LO. For example,
when first laser beam 13 and second laser beam 14 are vertical
to the surface of welding object 6, LO = L1+L2 is established.
As described above, LI denotes the gap between first radiation
position A of first laser beam 13 on the surface of welding
object 6 and target position C of wire 7 on the surface of welding
object 6. L2 denotes the gap between second radiation position
B of second laser beam 14 on welding object 6 and target position
C of wire 7 on the surface of welding object 6. When first
and second laser beams 13 and 14 are not vertical to the surface
of welding object 6, it is possible to calculate laser
transmitting unit gap LO when L1+L2 is known.
As another structure, laser generating unit 100 may-
include two laser generating units 1 used in the hybrid welding
apparatus according to the related art shown in Fig. 13 and
use two laser beams generated by the two laser generating units
as first laser beam 13 and second laser beam 14.
In the above-described first to third embodiments, the
arc welding and arc generating unit 10 have been used. However,
pulsed arc welding or pulsed MIG arc welding may be used instead
of the arc welding and a pulsed arc generating unit may be used
instead of arc generating unit 10. In this case, it is possible
to obtain the same effects as those in the first to third
embodiments and reduce the generation of spatter during
welding.
In the first to third embodiments, the materials forming
welding object 6 and wire 7 are not particularly designated.
However, both the welding object and the wire may be made of
an aluminum alloy.
(Fourth embodiment)
In this embodiment, the limitation of the output value
of first laser beam 13 in the first to third embodiments will
be described in detail. In this embodiment, the limitation
of the power density of first laser beam 13 at radiation
position D of wire 7 to a power density allowable value or less
will be described.
Fig. 8 is a diagram schematically illustrating the
structure of a hybrid welding apparatus according to a fourth
embodiment of the invention. The same structure and operation
as those in the first to third embodiments are denoted by the
same reference numerals and a detailed description thereof will
be omitted. The description is focused on the difference
between this embodiment and the first to third embodiments.
In Fig. 8, in this embodiment, pulsed arc generating unit
113 is used instead of arc generating unit 10 shown in Fig.
1, and laser oscillator 114 is used instead of laser oscillator
101. Output calculating unit 130 including laser output
setting unit 115, maximum power density setting unit 117,
calculating unit 116, and display unit 118 is added. Laser
output setting unit 115 sets the laser output value of laser
oscillator 114. Maximum power density setting unit 117 sets
the power density allowable value of the first laser beam at
a predetermined position. Calculating unit 116 calculates the
laser output value of laser oscillator 114 using parameters,
which will be described below. Display unit 118 displays the
laser output value calculated by calculating unit 116.
Although not shown in the drawings, pulsed arc generating
unit 113 outputs pulse-shaped welding power including a pulse
current, a base current, a pulse width, and a base width to
perform pulsed arc welding while generating pulsed arc 119
between wire 7 and welding object 6. Pulsed arc generating
unit 113 is used because it is possible to reliably transfer
the molten droplet to the welding position of welding object
6 using a pulsed arc without contacting one molten droplet with
the molten pool with one pulse and it is possible to effectively
prevent the generation of spatter.
Although not shown in the drawings, when the signal from
calculating unit 116 is not connected, laser oscillator 114
outputs output set value PS set by laser output setting unit
115 without any change. When the signal from calculating unit
116 is connected, laser oscillator 114 preferentially outputs
output calculation value PC input from calculating unit 116.
In the above-mentioned structure, control unit 17 may
also serve as laser output setting unit 115. In this case,
the signal of control unit 17 is input to calculating unit 116.
As described in the first to third embodiments, laser
oscillator 114 radiates first laser beam 13 and second laser
beam 14 to welding object 6. However, as described in the first
to third embodiments, since second laser beam 14 is not directly
radiated to wire 7, the output value of second laser beam 14
is not limited by wire 7. Therefore, in this embodiment, the
control of the calculation of the output value of first laser
beam 13 will be described.
Before the calculation method and the operation
principle of calculating unit 116 are described, the
arrangement of first laser beam 13 and wire 7 will be described
with reference to Figs. 9A and 9B in order to describe, for
example, parameters required for calculation. In addition,
the propagation of the radiation direction of first laser beam
13 will be described with reference to Fig. 10. Fig. 9A is
a diagram schematically illustrating the arrangement of first
laser beam 13 and wire 7. Fig. 9B is a diagram schematically
illustrating a droplet. Fig. 10 is a side view schematically
illustrating the propagation of the radiation direction of
first laser beam 13 to the surface of welding object 6. In
Fig. 10, the left side indicates the radiation source of optical
axis aa' and the right side indicates the radiation destination.
Hereinafter, the same reference numerals as those in the first
to third embodiments have the same meaning as that in the first
to third embodiments. In Figs. 9A and 10, Fi indicates a first
radiation point (radiation position A), which is an
intersection point between optical axis aa1 of first laser beam
13 and welding object 6. In Fig. 9A, F2 indicates a radiation
point (laser radiation position D), which is an intersection
point between optical axis aa' of first laser beam 13 and
central axis cc' of wire 7 . F3 indicates a target point (target
position C), which is an intersection point between central
axis cc ' of wire 7 and welding object 6 . LI denotes a laser-wire
distance indicating the distance between radiation position
Fi and target position F3. ccL denotes a laser inclination angle
indicating the inclination of optical axis aa' with respect
to welding object 6. aw denotes a wire inclination angle
indicating the inclination of central axis cc' with respect
to welding object 6. As shown in Fig. 9B, wire 7 is irradiated
with first laser beam 13 or is heated by pulsed arc 119 and
droplet 20 is formed at the tip of wire 7. In Fig. 10, F0
indicates a focal point obtained when first laser beam 13 is
focused by focusing optical system 103. Z indicates a
coordinate axis that is aligned with optical axis aa' , has focal
point F0 as the origin, and has the propagation direction
(radiation destination direction) of first laser beam 13 as
a positive direction, or the coordinate value of the coordinate
axis. <|)o denotes a focused beam diameter indicating the
diameter of first laser beam 13 at focal point F0 (or the origin
of coordinate axis Z) . (|>(Z) indicates the diameter of first
laser beam 13 at arbitrary coordinate value Z. It has been
known that beam diameter <|>(Z) has the relationship between
focused beam §0 and coordinate value Z represented by
(Expression 1):
(Expression 1)
<|>(Z) = (|)o-(i+yz2)1/2
Where y indicates a constant that is determined by the
beam quality of first laser beam 13 and focusing optical system
103. AZ indicates the distance between focal point F0 and
radiation point Fi and also indicates the amount of defocus
of first laser beam 13. Therefore, the beam diameter at
radiation point Fi is represented by (j)(AZ) . However, for the
sign of the amount AZ of defocus, when coordinate value Z of
radiation point Fi is positive, AZ has a positive value, and
when coordinate value Z is negative, AZ has a negative value.
For example, in Fig. 10, AZ has a positive value.
The calculation method and the operation principle of
calculating unit 116 will be described with reference to Figs.
8 to 10. Calculating unit 116 receives the following
parameters, performs calculation, and outputs the calculation
result as output calculation value PC to laser oscillator 114
and display unit 118. Two kinds of parameters are provided,
one of which is output set value PS set by laser output setting
unit 115 and power density allowable value WO set by maximum
power density setting unit 117. In this embodiment, output
set value PS is the output power of laser oscillator 101 that
is set by the user according to the kind of welding object 6
or the welding speed. Power density allowable value WO is the
allowable value of power density at radiation position D that
is determined by the user. In this embodiment, power density
allowable value WO is a function that is determined by a
material of wire 7 and the feed rate of wire 7.
The other kind of parameter is focused light diameter
<|>o, beam diameter <|>(Z), the amount AZ of defocus, laser-wire
distance LI, laser inclination angle ocL, and wire inclination
angle ocw obtained from welding position neighborhood 131.
Although not shown in the drawings, the parameter obtained from
welding position neighborhood 131 may be measured in advance
according to the welding apparatus used.
In order to prevent the rapid evaporation of droplet 20
as shown in Fig. 9B, power density calculation value WC (which
is calculated by (Expression 3) , which will be described below)
at radiation point F2 of wire 7 may be equal to or less than
power density allowable value WO. First, when beam diameter
(j)(F2) at radiation point F2 is calculated by (Expression 1),
the following (Expression 2) is obtained:
(Expression 2)
(F2) = (F2) ]2/sin(aL+a„) } .
Then, calculating unit 116 compares power density
allowable value WO with power density calculation value WC.
As a result, when power density calculation value WC is smaller
than power density allowable value WO, calculating unit 116
outputs output set value PS as output calculation value PC to
laser oscillator J.14 and display unit 118 without any change.
On the other hand, when power density calculation value WC is
greater than power density allowable value WO, calculating unit
116 can calculate output calculation value PC from power
density allowable value WO and beam diameter <|> (F2) at radiation
point F2 using the following (Expression 4):
(Expression 4)
PC = WO-{7u-[4>(F2) ]2/sin(aL+aw) }/4.
Calculating unit 116 outputs calculated output
calculation value PC to laser oscillator 114 and display unit
118.
During welding, laser oscillator 114 outputs calculated
output value PC, and display unit 118 displays calculated
output value PC. During the actual welding, display unit 118
may be omitted.
It has been described above that it is preferable that
power density calculation value WC at radiation point F2 of
wire 7 be equal to or less than power density allowable value
WO. The reason is as follows. As shown in Fig. 9B, even after
droplet 20 is formed at the tip of wire 7, wire 7 is continuously
irradiated with first laser beam 13 or it is continuously heated
by pulsed arc 119. Therefore, the size of droplet 20 increases .
When the subsequent pulse period starts, constriction occurs
at the boundary between droplet 20 and a solid portion of wire
7. During the pulse period, constriction is grown, and droplet
20 is separated from the tip of wire 7 and is then moved to
the welding position of welding object 6 immediately before
or after the pulse period ends. Droplet 20 is continuously
irradiated with first laser beam 13 until it is separated from
the tip of wire 7 and passes through the radiation range of
first laser beam 13. Therefore, when the power density of first
laser beam 13 on the surface of droplet 20 is too high, the
temperature of droplet 20 is too high and reaches a boiling
point. Then, droplet 20 is rapidly evaporated, which causes
spatter. Therefore, in order to prevent the generation of
spatter due to the rapid evaporation of droplet 20, it is
necessary to limit the power density at radiation point F2 of
wire 7. In Fig. 10, radiation point Fi and focal point F0 are
disposed at different positions, but they may be disposed at
the same position. In this case, AZ is 0.
Figs. 11A to 11F are diagrams illustrating a variation
in the state of spatter when power density is too high and the
wire end molten droplet is rapidly evaporated during the pulsed
MIG arc welding of aluminum alloy. That is, Figs. 11A to 11F
show a variation in the state of spatter at an interval of 1
ms from Fig. 11A. Fig. 11A shows the actual relative positional
relationship between droplet 20 and laser beam 5 at an arbitrary
timing during welding. In this state, droplet 20 is irradiated
with first laser beam 13, but droplet 20 is not rapidly-
evaporated. As shown in Figs. 11B to 11F, droplet 20 is
irradiated with first laser beam 13, the evaporation rate of
droplet 20 is gradually increased, and droplet 20 is scattered
as spatter S.
The experiment shown in Figs. 11A to 11F was conducted
under the following conditions. Welding object 6 is an A5052
aluminum alloy with a thickness of 2 mm and wire 7 is an A5356
aluminum alloy with a diameter of 1.2 mm. First laser beam
13 is a fiber laser with a focused light diameter of 0.2 mm
and has an output of 4.0 kW, a fiber diameter of 0.1 mm, a
collimator lens focal length of 125 mm, a focusing lens focal
length of 250 mm, and a defocused beam diameter of 0.9 mm.
Laser-wire distance LI is 2 mm and the welding speed is 4 m/min.
In order to check the effects of the embodiments of the
invention, hybrid welding was performed using an A5356 wire
(diameter: 1.2 mm) for an A5052 aluminum alloy with a thickness
of 2 mm while fixing the beam diameter on the surface of the
welding object and changing only the laser output. Fig. 12
is a diagram illustrating the outward appearance of beads when
the laser output is changed. As can be seen from columns a
to d in Fig. 12, when the laser output was equal to or less
than 3.0 kW (the calculated value of the power density at
radiation point F2 of wire 7 is 2.33 kW/mm2) , the bead surface
including a cleaning region in the vicinity of the welding
position (in Fig. 12, the upper and lower sides in the vicinity
of the welding position) was good. Meanwhile, as can be seen
from column e in Fig. 12, when the laser output was 4.0 kW (the
calculated value of the power density at radiation point F2
of wire 7 is 3.11 kW/mm2) , the cleaning region was narrowed
and the bead surface was darkened. In addition, a lot of small
spatters were adhered to the vicinity of the bead. The black
contaminants on the bead surface or a lot of small spatters
in the vicinity of the surface of the bead are caused by the
rapid evaporation of the droplet irradiated with the laser beam
during welding. The aspect was as shown in Figs. 11B to 11F.
The conditions of the experiment shown in Fig. 12 are the same
as those in Figs. 11A to 11F; except the laser power.
As such, according to this embodiment, first laser beam
13 and wire 7 are arranged such that first laser beam 13 is
directly radiated to wire 7 supplied to welding object 6, that
is, optical axis aa' of first laser beam 13 intersects central
axis cc' of wire 7. In addition, welding is performed such
that the power density of first laser beam 13 at laser radiation
point F2 of wire 7 is equal to or less than a predetermined
value. In this way, it is possible to prevent the generation
of spatter due to the rapid evaporation of droplet 20.
In the above description, the pulsed MIG arc welding is
given as an example of the pulsed arc welding, but the invention
is not limited thereto.
In this embodiment, both the welding object and the wire
are made of an aluminum alloy, but the invention is not limited
thereto.
In the above description, welding was performed such that
the power density of first laser beam 13 at laser radiation
point F2 of wire 7 was equal to or less than a predetermined
value. In this embodiment, the predetermined value was
calculated and set by a function that was determined by the
material forming wire 7 and the feed rate of wire 7. The reason
is as follows. For the material of wire 7, when the material
is changed, the boiling point of droplet 20 formed at the tip
of wire 7 is changed and the absorptance of the material with
respect to first laser beam 13 is also changed. Meanwhile,
for the feed rate of wire 7, when the feed rate of wire 7 is
changed, the interaction time between first laser beam 13 and
wire 7 is changed. Therefore, the heating time until wire 7
is melted and reaches the boiling point is also changed.
In particular, when wire 7 made of an aluminum alloy is
used, the boiling point of wire 7 varies greatly depending on
the amount of Mg (magnesium) included in wire 7. Therefore,
the predetermined value may be a function of the amount of Mg
included in wire 7.
Specifically, when a wire made of a 5000-series aluminum
alloy was used, the predetermined value was set in the range
of 0.5 kW/mm2 to 3 kW/mm2 and the welding result was good. When
a wire made of a 4000-series aluminum alloy was used, the
predetermined value was set in the range of 0.5 kW/mm2 to 5
kW/mm2 and the welding result was good.
In this embodiment, welding was performed such that the
power density of first laser beam 13 at laser radiation point
F2 of wire 7 was equal to or less than a predetermined value.
However, the output value of first laser beam 13 may be limited
such that the power density of first laser beam 13 at radiation
point Fi (first radiation position A) of first laser beam 13
on the surface of welding object 6 is equal to or less than
a predetermined allowable value. In this case, similar to the
fourth embodiment, it is possible to calculate the power
density of first laser beam 13 using Expressions 1 to 4.
That is, in the invention, the output value of first laser
beam 13 may be limited such that the power density of first
laser beam 13 at an arbitrary radiation point other than laser
radiation point F2 or radiation point Fi is equal to or less
than a predetermined value. Therefore, in the invention, it
is possible to prevent the generation of spatter involving the
rapid evaporation of droplet 20 by setting the output value
of first laser beam 13 to be equal to or less than a predetermined
allowable value.
INDUSTRIAL APPLICABILITY
As described above, according to the invention, it is
possible to prevent the generation of spatter involving the
rapid evaporation of a wire end molten droplet. The invention
is useful, for example, as a hybrid welding method using the
radiation of two laser beams and arc welding.

WE CLAIM:
1. A composite welding method of feeding a
wire to a welding position of a welding object while radiating
a first laser beam and a second laser beam to the welding
position, thereby performing arc welding between the welding
object and the wire, comprising:
radiating the first laser beam to a first radiation
position of the welding object through the wire such that an
optical axis of the first laser beam intersects a central axis
of the wire; and
radiating the second laser beam to a second radiation
position of the welding object that is spaced a predetermined
distance from a target position where the central axis of the
wire intersects the welding object,
wherein the first radiation position, the second
radiation position, and the target position are disposed on
a welding line of the welding object,
an arc is generated between the wire and the welding
object after a predetermined time has elapsed from the
radiation of the second laser beam, and
the first laser beam is radiated after the generation
of the arc is detected.
2. The composite welding method of Claim 1,
wherein an output value of the first laser beam is set
to a predetermined allowable value or less.
3. The composite welding method of Claim 1,
wherein an output value of the first laser beam is set
such that the power density of the first laser beam at the first
radiation position of the welding object is equal to or less
than a predetermined allowable value.
4. The composite welding method of Claim 1,
wherein an output value of the first laser beam is set
such that the power density of the first laser beam at the
radiation position of the wire where the optical axis of the
first laser beam intersects the central axis of the wire is
equal to or less than a predetermined allowable value.
5. The composite welding method of Claim 1,
wherein an arc is generated between the wire and the
welding object, and
both the first laser beam and the second laser beam are
radiated after the generation of the arc is detected.
6. The composite welding method of Claim 1,
wherein the target position is disposed ahead of the
first radiation position in the movement direction of the
welding position, and
the second radiation position is spaced the
predetermined distance from the target position in the movement
direction of the welding position.
^f. The composite welding method of Claim 1,
wherein the target position is disposed ahead of the
first radiation position in the movement direction of the
welding position, and
the second radiation position is spaced the
predetermined distance from the target position in a direction
opposite to the movement direction of the welding position.
£". The composite welding method of Claim 1,
wherein only the optical axis of the first laser beam
intersects the central axis of the wire.
9", The composite welding method of Claim 1,
wherein the arc welding is pulsed MIG arc welding.
10. The composite welding method of Claim 1,
wherein both the welding object and the wire are made
of an aluminum alloy.
11. The composite welding method of Claim 2,
wherein the predetermined value is determined by a
material of the wire and the wire feed rate.
12. The composite welding method of Claim 10.,
wherein the predetermined value is determined by the
amount of magnesium included in the wire made of the aluminum
alloy.
13 . The composite welding method of Claim 4,
wherein, when the wire is made of a 5000-series aluminum
alloy, the predetermined value is set such that the power
density of the first laser beam is in the range of 0.5 kW/mm2
to 3 kW/mm2.
14 . The composite welding method of Claim 4,
wherein, when the wire is made of a 4000-series aluminum
alloy, the predetermined value is set such that the power
density of the first laser beam is in the range of 0.5 kW/mm2
to 5 kW/mm2.
15" A composite welding apparatus
comprising:
a laser generating unit that radiates a first laser beam
and a second laser beam to a welding position of a welding
object;
a wire feeding unit that feeds a wire to the welding
position through a torch;
an arc generating unit that supplies power for arc
welding to the wire and the welding object; and
. a control unit that controls the laser generating unit
and the arc generating unit,
wherein the laser generating unit is arranged so as to
radiate the first laser beam to a first radiation position of
the welding object through the wire such that an optical axis
of the first laser beam intersects a central axis of the wire,
the laser generating unit is arranged such that the
second laser beam is radiated to a second radiation position
of the welding object that is spaced a predetermined distance
from a target position where the central axis of the wire
intersects the welding object, and
the first radiation position, the second radiation
position, and the target position are arranged so as to be
disposed on a welding line of the welding object,
the control unit generates an arc between the wire and
the welding object after a predetermined time has elapsed from
the radiation of the second laser beam, and
the control unit radiates the first laser beam after the
generation of the arc is detected.
16 . The composite welding apparatus of Claim 15",
wherein the control unit sets an output value of the first
laser beam to a predetermined allowable value or less.
17 . The composite welding apparatus of Claim 15,
. wherein the control unit sets an output value of the first
laser beam such that the power density of the first laser beam
at the first radiation position of the welding object is equal
to or less than a predetermined allowable value.
18. The composite welding apparatus of Claim 15",
wherein the control unit sets an output value of the first
laser beam such that the power density of the first laser beam
at the radiation position of the wire where the optical axis
of the first laser beam intersects the central axis of the wire
is equal to or less than a predetermined allowable value.
19. The composite welding apparatus of Claim 15",
wherein the control unit generates an arc between the
wire and the welding object, and
the control unit radiates both the first laser beam and
the second laser beam after the generation of the arc is
detected.
20. The composite welding apparatus of Claim 15,
wherein the target position is disposed ahead of the
first radiation position in the movement direction of the
welding position, and
, the second radiation position is spaced the
predetermined distance from the target position in the movement
direction of the welding position.
21. The composite welding apparatus of Claim l5,
wherein the target position is disposed ahead of the
first radiation position in the movement direction of the
welding position, and
the second radiation position is spaced the
predetermined distance from the first radiation position in
a direction opposite to the movement direction of the welding
position.
22. The composite welding apparatus of Claim 15,
wherein the laser generating unit is arranged such that
only the optical axis of the first laser beam intersects the
central axis of the wire.
23. The composite welding apparatus of Claim 15,
wherein the arc welding is pulsed MIG arc welding.
24. The composite welding apparatus of Claim 15",
wherein both the welding object and the wire are made
of an aluminum alloy.
25. The composite welding apparatus of Claim l£,
wherein the predetermined value is determined by a
material of the wire and the wire feed rate.
26. The composite welding apparatus of Claim 1%,.
wherein the predetermined value is determined by the
amount of magnesium included in the wire made of the aluminum
alloy.
27. The composite welding apparatus of Claim 1%,
wherein, when the wire is made of a 5000-series aluminum
alloy, the predetermined value is set such that the power
density of the first laser beam is in the range of 0.5 kW/mm2
to 3 kW/mm2.
28. The composite welding apparatus of Claim 18,
wherein, when the wire is made of a 4000-series aluminum
alloy, the predetermined value is set such that the power
density of the first laser beam is in the range of 0.5 kW/mm2
to 5 kW/mm2.
29, A composite welding apparatus comprising:
a laser generating unit that radiates a first laser beam
and a second laser beam to a welding position of a welding
object;
, a wire feeding unit that feeds a wire to the welding
position through a torch;
a pulsed arc generating unit that supplies power for arc
welding to the wire and the welding object;
a control unit that controls the laser generating unit
and the pulsed arc generating unit;
a laser output setting unit that sets the output of the
first laser beam of the laser generating unit;
a maximum power density setting unit that sets a maximum
power density allowable value of the first laser beam at a
predetermined position; and
a calculating unit that calculates a power density
calculation value of the first laser beam,
wherein the laser generating unit is arranged so as to
radiate the first laser beam to a first radiation position of
the welding object through the wire such that an optical axis
of the first laser beam intersects a central axis of the wire,
the laser generating unit is arranged such that the
second laser beam is radiated to a second radiation position
of the welding object that is spaced a predetermined distance
from a target position where the central axis of the wire
intersects the welding object,
the first radiation position, the second radiation
position, and the target position are arranged so as to be
disposed on a welding line of the welding object,
. the calculating unit performs calculation using
parameters including an output set value set by the laser output
setting unit, a power density allowable value set by the maximum
power density setting unit, a focused beam diameter at a focal
point when the first laser beam is focused, a beam diameter
at an arbitrary coordinate value when the focal point of the
first laser beam is the origin and the optical axis of the first
laser beam in a propagation direction is a coordinate axis,
the amount of defocus when the first laser beam is radiated
to the first radiation point of the welding object, a laser-wire
distance from a first radiation point of the first laser beam
on the surface of the welding object to a target point of the
wire, a laser inclination angle of the optical axis of the first
laser beam with respect to the surface of the welding object,
and a wire inclination angle of the central axis of the wire
with respect to the surface of the welding object, and
when the power density calculation value at a laser
radiation point where the optical axis of the first laser beam
intersects the central axis of the wire, which is calculated
from the parameters, is greater than the power density
allowable value, the calculating unit calculates an output
calculation value using the power density allowable value and
the parameters and outputs the calculated value to the laser
generating unit, thereby performing welding such that the power
density of the first laser beam at an intersection point between
the optical axis of the first laser beam and the central axis
of the wire is equal to or less than the power density allowable
value.

A first laser beam (13) is radiated to a first radiation
position of a welding object (6) while intersecting a wire (7),
and a second laser beam (14) is radiated to a second radiation
position that is spaced a predetermined distance from a target
position of the wire (7) . Arc welding is performed between
the wire (7) and the welding object (6) while radiating the
first laser beam (13) and the second laser beam (14) such that
the first radiation position, the second radiation position,
and the target position are disposed on a welding line of the
welding object (6) . In this way, it is possible to prevent
the generation of spatter and perform welding at a high rate,
without increasing the size of a molten pool.