Micro-welding of aluminium alloy by superposition of pulsed Nd:YAG laser and continuous diode laser
The combination of a pulsed Nd:YAG laser and a continuous diode laser could perform the high-performance micro-welding of
 aluminum alloy. A pulsed Nd:YAG laser was absorbed effectively from the beginning of laser scanning by pre-heating Nd:YAG
 laser pulse with the superposition of...
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Інститут електрозварювання ім. Є.О. Патона НАН України
2013
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| Cite this: | Micro-welding of aluminium alloy by superposition of pulsed Nd:YAG laser and continuous diode laser / Y. Okamoto, S. Nakashiba, T. Sakagawa and A. Okada // Автоматическая сварка. — 2013. — № 10-11 (726). — С. 101-106. — Бібліогр.: 6 назв. — англ. |
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| author | Okamoto, Y. Nakashiba, S. Sakagawa, T. Okada, A. |
| author_facet | Okamoto, Y. Nakashiba, S. Sakagawa, T. Okada, A. |
| citation_txt | Micro-welding of aluminium alloy by superposition of pulsed Nd:YAG laser and continuous diode laser / Y. Okamoto, S. Nakashiba, T. Sakagawa and A. Okada // Автоматическая сварка. — 2013. — № 10-11 (726). — С. 101-106. — Бібліогр.: 6 назв. — англ. |
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| description | The combination of a pulsed Nd:YAG laser and a continuous diode laser could perform the high-performance micro-welding of
aluminum alloy. A pulsed Nd:YAG laser was absorbed effectively from the beginning of laser scanning by pre-heating Nd:YAG
laser pulse with the superposition of continuous LD, and wide and deep weld bead could be obtained with better surface integrity.
|
| first_indexed | 2025-12-07T18:33:44Z |
| format | Article |
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10110-11/2013
UDC 621.791.947.2.03:621.375.826
MICRO-WELDING Of ALUMINUM ALLOY BY SUPERPOSITION
Of PULSED Nd:YAG LASER AND CONTINUOUS DIODE LASER
Y. OKAMOTO1, S. NAKASHIBA2, T. SAKAGAWA2 and A. OKADA1
1Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka,
Kita-ku, Okayama 700-8530, Japan. E-mail: okamoto@mech.akayama-u.ac.jp
2Advanced Laser Research Laboratory, Kataoka Corporation, 2-14-27 Shin-yokohama, Kohoku-ku, Yokohama 222-0033, Japan
The combination of a pulsed Nd:YAG laser and a continuous diode laser could perform the high-performance micro-welding of
aluminum alloy. A pulsed Nd:YAG laser was absorbed effectively from the beginning of laser scanning by pre-heating Nd:YAG
laser pulse with the superposition of continuous LD, and wide and deep weld bead could be obtained with better surface integrity.
6 Ref., 2 Tabls, 8 figures.
K e y w o r d s : pulsed Nd:YAG laser, aluminum alloy, micro-welding
Introduction
Mobile products such as PDA, Notebook PC and
mobile phone have been widely used in the fields of
information and communication technology. In the
automobile industry, hybrid vehicle and electric ve-
hicle attract customers because of their low energy
consumption, and they are expected as the key prod-
ucts of next generation. In order to accomplish highly
performance of these products, lightweight and high
specific strength materials are required. Aluminum
alloys have been widely used to achieve lightweight
and miniaturization in these fields, hence high-perfor-
mance welding has been required. A pulsed Nd:YAG
laser of 1064 nm in wavelength has been applied to
the micro-welding of aluminum alloy [1]. However,
the absorption rate of a Nd:YAG laser by aluminum
alloys is only 5 % at room temperature, as shown in
figure 1 [2, 3]. Since the absorbed laser energy is
very low, high peak power laser system must be used
to achieve sufficient penetration depth and acceptable
bead width. High peak power is useful to increase the
penetration depth and the bead width, but the exces-
sive heat input leads to the deterioration of surface
quality and integrity due to the spatter and the poros-
ity [4].
On the other hand, the aluminum alloy shows the
high absorption rate around 810 nm as shown in fig-
ure 1. The wavelength 808 nm of diode laser (here-
after LD) is useful to increase the absorption of la-
ser energy, and its absorption rate is 3 times higher
than that of Nd:YAG laser of 1064 nm. In addition,
low cost and high power LD is available by the re-
cent development of semiconductor technology, and
the high brightness LD is also expected. Therefore,
the micro-welding technology of aluminum alloy by
the combination of a pulsed Nd:YAG laser and a con-
tinuous LD was proposed, and efficient absorption of
Nd:YAG laser was expected [5, 6].
However, it is difficult to perform the sufficient
deep penetration depth with good surface integrity
at the beginning of laser scanning. The higher peak
power could become the penetration depth deeper,
while the deterioration of surface integrity might be
noticed. The deeper penetration depth from the begin-
ning of laser scanning with the better surface integri-
ty is very useful for the industrial application. from
the viewpoints mentioned above, the effects of super-
posed continuous LD on micro-welding of aluminum
alloy by a pulsed Nd:YAG laser were investigated,
and the pre-pulse method was discussed in order to
improve the penetration depth even at the beginning
of laser scanning by pre-heating Nd:YAG laser pulse.
Experimental procedures
figure 2 shows the schematic diagram of laser ir-
radiation system. Table 1 shows the specifications of
a pulsed Nd:YAG laser and a continuous LD used
in this study. A pulsed Nd:YAG laser of 1064 nm in
wavelength and continuous LD of 808 nm in wave-
length were superposed on the same beam axis by
a dichroic mirror, and the superposed laser beam of
two wavelengths were delivered to a processing head
through an optical fiber of 300 µm diameter with SI © Y. Okamoto, S. Nakashiba, T. Sakagawa, A. Okada, 2013
figure 1. Absorption rate of aluminum alloy A3003 at room
temperature
102 10-11/2013
type. These laser beams were collimated and focused
by lenses of 80 mm in the focal length. The welding
experiment was carried out by controlling a scanning
velocity of stage at the focusing point with N2 shield-
ing gas of flow rate 57 l/min. The aluminum alloy
A3003 of 0.5 mm thickness was used as a specimen
except for welding experiments of battery case, and
its physical properties are shown in Table 2.
The irradiation waveforms of Nd:YAG laser pulse
and continuous LD are shown in figure 3. The pow-
er of pulsed Nd:YAG laser can be controlled every
0.2 ms. In general, the sharp heating up and cool-
ing down might lead to the welding defects such as
blow holes and cracks. Therefore, the main pulse of
Nd:YAG laser for the processing was controlled with
a gradual increment and decrement of laser power
during the pulse duration 1.2 ms. In the case of su-
perposition of two laser beams, the irradiation of con-
tinuous LD started before the main Nd:YAG pulse as
shown in figure 3.
Effect of superposed continuous diode laser on
welding results
figure 4 shows the surfaces and cross sections
of weld bead for aluminum alloy A3003 of 0.5 mm
thickness with and without the superposition of con-
tinuous LD under the same peak power of Nd:YAG
laser. Although the power of continuous LD is ap-
proximately 1.2 % against the peak power of pulsed
Nd: YAG laser, the superposition of continuous LD
made it possible to increase the bead width by 15 %
and the weld depth by 150 % compared with welding
results without continuous LD. It means that the ener-
gy of pulsed Nd:YAG laser could be absorbed effec-
tively to the aluminum alloy by superposition of con-
figure 2. Schematic diagram of laser irradiation system with superposition of pulsed Nd:YAG laser and continuous diode laser
Ta b l e 1 . Specifications of pulsed Nd:YAG laser and continuous
diode laser
Nd:YAG laser Diode laser
Max. average power Pa 250 W 65 W
Max. peak power Pp 2.5 kW -
Wavelength λ 1064 nm 808 nm
Pulse repetition rate Rp 1 - 500 Hz CW
Pulse duration τ 0.08 - 1.2 ms CW
Ta b l e 2 . Physical properties of aluminum A3003
Specific heat 900 J/(kg⋅K)
Thermal conductivity 237 W/(m⋅K)
Density 2.73 g/cm2
Poisson’s ratio 0.33
Young’s modulus 70 kN/mm2
Coefficient of thermal expansion 2.4 × 10-6/K
figure 3. Irradiation waveform of pulsed Nd:YAG laser and con-
tinuous LD
10310-11/2013
tinuous LD. In general, the absorption rate increases
with increasing the temperature of material. Thus, it
is considered that the continuous LD could become
the surface temperature higher compared with the
case without continuous LD [5], hence the high ef-
ficient absorption of laser energy made it possible to
increase the penetration depth and bead width.
figure 5 shows the variations of bead width and
penetration depth at scanning speed 20 mm/s and 35
mm/s in welding experiments of aluminum alloy bat-
tery case. The size of battery case is 30 mm-width x
5 mm-length x 0.3 mm-thickness. The top cover plate
of 0.5 mm thickness was fitted and pressed into the
inside of battery case. The bead width and penetration
depth increased with increasing the continuous LD
power at both scanning speeds. The penetration depth
without continuous LD at scanning velocity 20 mm/s
is approximately 500 µm, and the equivalent penetra-
tion depth could be obtained even at higher scanning
velocity 35 mm/s by the superposition of continuous
LD 50 W. When the average power of continuous
LD is 60 W, the penetration depth was approximate-
ly 1.5 times larger than that without continuous LD.
The bead width at scanning velocity 35 mm/s with
continuous LD was also higher than that at scanning
velocity 20 mm/s without continuous LD. Moreover,
good quality weld beads could be obtained as shown
in figure 3.
It is confirmed that the effect of continuous LD
on the penetration depth was remarkable at the fast-
er processing speed. The high throughput and quality
micro-welding by using pulsed Nd:YAG laser could
be expected by superposition of continuous LD.
Effect of pre-Nd:YAG laser pulse on penetration
depth at the beginning of scanning
In order to achieve the high absorption of
Nd:YAG laser even at the beginning of laser scan-
ning, pre-heating Nd:YAG laser pulse was investi-
gated in the bead-on-plate experiment as shown in
figure 6. It was expected to keep the high surface
temperature before the irradiation of main Nd:YAG
laser pulse with the irradiation of continuous LD. As
shown in figure 6 (a), firstly, a continuous LD was
irradiated on the specimen surface. Secondly, the pre-
Nd:YAG laser pulse was irradiated as a rectangular
pulse waveform to increase the surface temperature
at the beginning of laser scanning. After the pre-
Nd:YAG laser pulse, the main Nd:YAG laser pulses
were irradiated.
Since the surface condition has greatly influ-
ence on the absorption state, the peak power of pre-
Nd:YAG laser pulse on the surface condition was
investigated. figure 6 (b) shows microphotographs
of irradiated surface for various peak powers by the
single laser shot. for more than peak power 500W,
the specimen surface was molten and became glossy,
and the glossiness of specimen surface might reflect
a main Nd:YAG laser pulse. On the other hand, the
specimen surface was not glossy in the case of peak
power 400 W, even the surface temperature increased.
Therefore, the peak power 400 W was used for the
pre-Nd:YAG laser pulse at pulse width 1.2 ms for
300 µm spot diameter.
figure 4. Surface and cross section of weld bead in bead-on-plate
irradiation at scanning velocity v = 30 mm/s, pulse duration of
Nd:YAG laser τ = 1.2 ms, pulse repetition rate of Nd:YAG laser
Rp = 120 Hz, peak power of Nd:YAG laser PYAG = 2375 W and
average power of LD PLD = 30 W
figure 5. Change of bead width and penetration depth for
power of continuous diode laser at scanning velocity v = 20
and 35 mm/s, pulse duration of Nd:YAG laser τp = 1.2 ms,
pulse repetition rate of Nd:YAG laser Rp = 120 Hz, peak pow-
er of Nd:YAG laser PYAG = 2375 W
104 10-11/2013
figure 7 shows the surfaces and cross sections of
weld bead at the beginning of laser scanning. Here,
the power density of pulsed Nd:YAG laser was set in
the transitional region between heat conduction weld-
ing and key-hole welding. In the case of only main
Nd: YAG laser pulse without the pre- Nd:YAG laser
pulse, the penetration depth gradually increased in the
scanning direction regardless of superposition of con-
tinuous LD (B, D). The penetration depth was unsta-
ble in the case of pre-Nd:YAG laser pulse without the
superposition of continuous LD (A). It is considered
that the absorption rate of pulsed Nd:YAG laser was
unstable at low specimen surface temperature, since
the power density is the transition condition between
the heat conduction welding and the key-hole weld-
ing. On the other hand, in the case of pre-Nd:YAG
laser pulse with the superposition of continuous LD
(C), it was obvious that the penetration depth became
larger from the beginning of laser scanning by stable
higher absorption of laser energy. Moreover, the sta-
ble welding process could be performed with steady
bead width and penetration depth. It indicated that
not only the use of pre-Nd:YAG laser pulse but also
the combination of pre-Nd:YAG laser pulse and the
superposition of continuous LD made it possible to
increase the molten volume at the beginning of laser
scanning.
The temperature change of specimen surface was
investigated by the numerical calculation in order
to discuss the welding phenomenon with and with-
out the pre-heating pulse. The general finite element
program ‘ANSYS Rev.11.0’, in which the unsteady
calculation is possible, was used for the numerical
analysis by using the analytical model as shown in
figure 8 (a). In the case of superposition of contin-
uous LD, the key-hole effect was assumed. Inter-
nal heat generation by the heating element of shape
mixed column and hemisphere was considered as a
figure 6. Irradiation waveform and irradiated surface state at pulse duration of Nd:YAG laser τ = 1.2ms without continuous LD in pre-
heating method: (a) Irradiation waveform of pre-heating and main Nd:YAG lase pulse; (b) Irradiated surface for various peak powers
of pre-heating pulse by single shot
figure 7. Welding results at the beginning of laser scanning with
and without pre-Nd:YAG laser pulse at scanning velocity v =
= 30 mm/s, pulse duration of Nd:YAG laser τ = 1.2 ms, pulse
repetition rate of Nd:YAG laser Rp = 120 Hz, peak power of
Nd:YAG laser PYAG = 2375 W, peak power of pre-Nd:YAG laser
pulse Ppre = 400 W and average power of LD PLD = 0, 30 W. (a)
PLD = 0 W; (b) PLD = 30 W
10510-11/2013
heat source as shown in figure 8 (b). The total power
of a pulsed Nd:YAG laser and a continuous LD was
irradiated as an internal heat generation. A continu-
ous LD was irradiated on the specimen surface ex-
cept for pulsed Nd:YAG laser shot. The absorption
rate of pulsed Nd:YAG laser was defined as 15 % for
a heat flux and 30 % for an internal heat generation,
and 30 W continuous LD was given by temperature
dependent absorption rate, which were determined by
the former investigation [5, 6]. The pulse waveform
of main Nd:YAG laser was the same as shown figure
6 (a). Pre-Nd:YAG laser pulse and a main Nd:YAG
laser pulse without the superposition of continuous
LD were given as a heat flux of absorption rate 15 %
as shown in figure 8 (c). A pulse of Nd:YAG laser of
300 µm spot diameter was irradiated at the pulse rep-
etition rate 120 Hz and the scanning speed 30 mm/s.
The convective heat transfer condition of air was con-
sidered after the set time of laser irradiation. Except
for the laser beam irradiated area, the convective heat
transfer condition of air was also considered. The
pure aluminum thermo physical properties of speci-
men were used for this analysis. Coefficient of heat
transfer and the initial temperature were 35 W/(m2⋅K)
and 296 K, respectively.
figure 8 (d) shows the calculated surface tem-
perature of spot center before the irradiation of main
Nd:YAG laser pulse. In the case of only Nd:YAG la-
ser pulse, the surface temperature was the same as an
initial temperature before the first main Nd:YAG laser
pulse, since there was no energy input. Only continu-
ous LD irradiation increased the surface temperature
by 40 K. By using both pre-heating pulse and contin-
uous LD, the surface temperature increased approxi-
mately 200 K higher than that of main Nd:YAG laser
pulse without pre-heating pulse. The absorption rate
of Nd:YAG laser to aluminum alloy increases dras-
tically more than 900 K, melting point of aluminum
figure 8. Analytical model and calculated surface temperatures of spot center before irradiation of main Nd:YAG laser pulse with and
without pre-Nd:YAG laser pulse at scanning velocity v = 30 mm/s, pulse duration of Nd:YAG laser τ = 1.2 ms, pulse repetition rate of
Nd:YAG laser Rp = 120 Hz, peak power of Nd:YAG laser PYAG = 2375 W, peak power of pre-Nd:YAG laser pulse Ppre = 400 W and
average power of LD PLD = 0, 30 W
106 10-11/2013
alloy. Without pre-heating pulse and continuous LD,
a pulsed Nd:YAG laser was irradiated on the speci-
men surface at low temperature firstly, which led to
the unstable absorption of a pulsed Nd:YAG laser
beam. On the other hand, it is easy to reach the melt-
ing point in the case with pre-heating pulse and con-
tinuous LD compared with the case of only Nd:YAG
laser irradiation. Therefore, it was considered that the
energy of pulsed Nd:YAG laser could be absorbed ef-
fectively and stably to the specimen surface because
of its higher surface temperature even at the begin-
ning of laser scanning with pre-heating pulse and
continuous LD.
Conclusions
The effects of superposed continuous LD on mi-
cro-welding of aluminum alloy by a pulsed Nd:YAG
laser were investigated, and the pre-pulse method
was also discussed in order to improve the penetra-
tion depth even at the beginning of laser scanning by
pre-heating Nd:YAG laser pulse. Main conclusions
obtained in this study are as follows.
(1) The energy of pulsed Nd:YAG laser could be
absorbed to the aluminum alloy effectively, since the
surface temperature of specimen was kept higher by
the superposition of continuous LD during the inter-
val time of Nd:YAG laser pulse.
(2) The high-efficiency and high-quality welding
for aluminum battery case could be performed by the
superposition of pulsed Nd:YAG laser and continuous
diode laser. 15 % increase in bead width and 150 %
increase in penetration depth were obtained by the su-
perposition of continuous LD.
(3)A pulsed Nd:YAG laser was absorbed ef-
fectively from the beginning of laser scanning by
pre-heating Nd:YAG laser pulse with the superposi-
tion of continuous LD due to the high surface tem-
perature of specimen. The combination of pre-heat-
ing Nd:YAG laser pulse and continuous LD made it
possible to perform the stable welding state from the
beginning of laser scanning by stable absorption of
pulsed Nd:YAG laser.
1. zhang, J., Weckman, D.C., zhou, Y. (2008) Effects of tempo-
ral pulse shaping on cracking susceptibility of 6061-T6 alu-
minum Nd:YAG laser welds. Welding J., 87, 18–30.
2. (2001) Chronological Scientific Tables 2001. Maruzen: Na-
tional Astronomical Observatory Institute, 523.
3. Abe, N. (2003) Trend of direct materials processing with
high power diode lasers. The Review of Laser Engineering,
31(5), 318-325.
4. Sakurai, T., Nakagawa, Y. (2004) Development of LD + YAG
hybrid laser. In: Proc. of 62nd Laser Materials Processing
Conf., 102–110.
5. Sakagawa, T., Okamoto, Y., Uno, Y. et al. (2009) High-ef-
ficiency welding of aluminum alloy by hybrid system com-
bined pulsed Nd:YAG laser and diode laser. In: Proc. of 26th
Int. Congress on Applications of Lasers & Electro-Optics,
1008–1014.
6. Haraguchi, S., Okamoto, Y., Uno, Y. et al. (2010) Investiga-
tion on welding phenomenon for aluminum alloy by super-
position of pulsed YAG laser and diode laser. J. of Advanced
Mechanical Design, Systems, and Manufacturing, 4(5), 875–
882.
Received 01.03.2013
|
| id | nasplib_isofts_kiev_ua-123456789-103235 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| language | English |
| last_indexed | 2025-12-07T18:33:44Z |
| publishDate | 2013 |
| publisher | Інститут електрозварювання ім. Є.О. Патона НАН України |
| record_format | dspace |
| spelling | Okamoto, Y. Nakashiba, S. Sakagawa, T. Okada, A. 2016-06-15T06:17:23Z 2016-06-15T06:17:23Z 2013 Micro-welding of aluminium alloy by superposition of pulsed Nd:YAG laser and continuous diode laser / Y. Okamoto, S. Nakashiba, T. Sakagawa and A. Okada // Автоматическая сварка. — 2013. — № 10-11 (726). — С. 101-106. — Бібліогр.: 6 назв. — англ. https://nasplib.isofts.kiev.ua/handle/123456789/103235 621.791.947.2.03:621.375.826 The combination of a pulsed Nd:YAG laser and a continuous diode laser could perform the high-performance micro-welding of
 aluminum alloy. A pulsed Nd:YAG laser was absorbed effectively from the beginning of laser scanning by pre-heating Nd:YAG
 laser pulse with the superposition of continuous LD, and wide and deep weld bead could be obtained with better surface integrity. en Інститут електрозварювання ім. Є.О. Патона НАН України Автоматическая сварка Пленарные доклады Международной конференции Micro-welding of aluminium alloy by superposition of pulsed Nd:YAG laser and continuous diode laser Микросварка алюминиевых сплавов пульсирующим лазером NdYAG и непрерывным диодным лазером Article published earlier |
| spellingShingle | Micro-welding of aluminium alloy by superposition of pulsed Nd:YAG laser and continuous diode laser Okamoto, Y. Nakashiba, S. Sakagawa, T. Okada, A. Пленарные доклады Международной конференции |
| title | Micro-welding of aluminium alloy by superposition of pulsed Nd:YAG laser and continuous diode laser |
| title_alt | Микросварка алюминиевых сплавов пульсирующим лазером NdYAG и непрерывным диодным лазером |
| title_full | Micro-welding of aluminium alloy by superposition of pulsed Nd:YAG laser and continuous diode laser |
| title_fullStr | Micro-welding of aluminium alloy by superposition of pulsed Nd:YAG laser and continuous diode laser |
| title_full_unstemmed | Micro-welding of aluminium alloy by superposition of pulsed Nd:YAG laser and continuous diode laser |
| title_short | Micro-welding of aluminium alloy by superposition of pulsed Nd:YAG laser and continuous diode laser |
| title_sort | micro-welding of aluminium alloy by superposition of pulsed nd:yag laser and continuous diode laser |
| topic | Пленарные доклады Международной конференции |
| topic_facet | Пленарные доклады Международной конференции |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/103235 |
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