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WELDING RESEARCH
Classification of Metal Transfer Mode in
Underwater Wet Welding
Experiments were conducted to classify the metal transfer mode in
underwater wet welding at shallow water depth
BY N. GUO, Y. FU, J. FENG, Y. DU, Z. DENG, M. WANG, AND D. TANG
ABSTRACT
The metal transfer process of underwater flux­cored wet welding with a water depth
of 0.5 m is observed using an x­ray transmission method for arc voltages from 24 to 46 V
and a welding current from 237 to 440 A. Four fundamental metal transfer modes are
found: the globular repelled transfer mode, the surface tension transfer mode, the explo­
sive short­circuit transfer mode, and the “submerged arc transfer mode,” while the
explosive short­circuit transfer mode is rarely observed. In contrast to onshore welding,
the metal transfer mode of underwater wet welding is a mixed transfer mode rather than
a single transfer mode; this mode mainly consists of two or more fundamental metal
transfer modes, including the globular repelled transfer mode, the surface tension trans­
fer mode, and the “submerged arc transfer mode.” The proportion of the fundamental
transfer modes constituting the mixed transfer mode changes with variations in the
welding current and arc voltage. The mixed mode is divided into four types according to
the different categories of fundamental modes in the mixed mode, as represented by a
transfer mode map. The metal transfer process of underwater wet welding is unstable,
necessitating control by adjusting the composition of welding materials or improvement
in the properties of welding equipment.
KEYWORDS
• Underwater Wet Welding • Metal Transfer • Transfer Mode
• X­ray Transmission Method
Introduction
With the rapid development of marine engineering in recent years, the
underwater welding technology mainly containing wet and dry methods has
been widely used in the manufacture
and maintenance of offshore structures (Refs. 1, 2). Compared with the
dry and local cavity methods, the wet
method is used directly in the aqueous
environment and does not require any
mechanical protection measures between the water and welding arc. Due
to the simplicity of the welding
process, wet welding is considered the
most flexible method used to weld
even the most geometrically complex
constructions (Refs. 3, 4). However,
because there is no mechanical barrier
between water and the welding arc in
the underwater wet method, the ambient pressure leads to unstable burning
of the welding arc, resulting in an increased amount of welding spatter.
Due to the water dissociation and weld
material, the porosity content increases in the weld joint, which causes a reduction of its mechanical properties.
Because the cooling rate in the wet
method is accelerated by the effect of
the surrounding water, the quenching
of the structure increases, leading to a
decrease in the ductility of the welded
metal and the heat-affected zone
(HAZ). Furthermore, owing to the oxi-
dation of the weld pool, more alloy elements were oxidized and transferred
into the slag from the weld pool in wet
welding, compared with onshore welding (Refs. 4–7). The water depth is a
crucial factor influencing the welding
stability, and the maximum depth for
using wet welding with covered electrodes or flux-cored wire is 100 meters, because increasing water depth
makes the welding arc unstable and
the welding process more difficult and
complex (Refs. 3, 8). In recent years,
many works have been carried out to
reveal the welding mechanism and improve the welding quality in underwater wet welding. The joint quality of
underwater wet welding was affected
by the Ni content in weld metal, which
helps decrease the coarse strip PF in
the columnar grain zone. Through
suitable addition of Ni into the covering of electrodes, the mechanical properties of the joint, such as tensile
strength and impact toughness, would
be improved (Ref. 9).
An oxyrutile electrode used in wet
welding was developed to decrease the
diffusible hydrogen and improve the
mechanical properties of the weld
metal, while maintaining its great operability (Ref. 10). Through modification of the composition of electrode
coatings, for example, adding manganese, titanium, boron, as well as rare
earth metals (REM) to the electrode
coatings, it is possible to improve the
mechanical properties of welds by controlling the weld metal chemical composition and reducing the negative effects caused by increasing water depth
in underwater shielded metal arc weld-
N. GUO (gn21c@126.com) and J. FENG are with the State Key Laboratory of Advanced Welding and Joining and the Shandong Provincial Key Laboratory of Spe­
cial Welding Technology, Harbin Institute of Technology, Harbin and Weihai, China. Y. FU, Y. DU, and M. WANG are also at Shandong Provincial Key Laboratory
of Special Welding Technology, Harbin Institute of Technology at Weihai, Weihai, China. Z. DENG is with the School of Mechatronics Engineering, Harbin Insti­
tute of Technology, Harbin, China, and D. TANG is with the Department of Chemistry, Harbin Institute of Technology, Harbin, China.
APRIL 2016 / WELDING JOURNAL 133-s
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WELDING RESEARCH
ing (SMAW) (Ref. 7). A three-dimensional heat transfer simulation model
using the finite difference method of
wet welding was established, and, consequently, temperature profile, thermal history curves, and cooling time
of weldments were obtained (Ref. 11).
A heat-assisted method using realtime induction was employed in the
wet welding process in such a way as
to decrease the cooling rate of the
weldment in aqueous environments
(Ref. 12).
Problems mentioned previously in
wet welding are closely related to the
particular features of heat and mass
transfer that arise from the impact of
the water environment and the ambient pressure in underwater wet welding. Metal transfer is a major mass
transfer channel in the welding
process that plays a significant role in
determining the arc stability, welding
spatter, welding appearance, and welding quality (Refs. 13, 14). Hence, for
the development of underwater wet
welding technology, it is important to
observe the metal transfer behavior
and investigate its mechanism and
characteristics.
For onshore welding, many studies
have been performed to elucidate the
metal transfer mode used to define the
characteristic behavior of the droplet
transfer process (Refs. 15–20), and
those studies have generally used highspeed videography with laser backlighting, referred to as the visible light
method. A determinant contribution
to the classification of metal transfer
mode was established in 1976 by the
International Institute of Welding
(IIW), which was published by Prof.
Lancaster (Ref. 15). Three metal transfer modes of self-shielded flux-cored
arc welding were observed: bridging
transfer without arc interruption in explosive form or by surface tension,
globular repelled transfer, and droplet
transfer (Ref. 16). It was found that
the droplet transition modes of plasma-gas metal arc welding (GMAW) on
aluminum alloys included globular
transfer, short-circuiting transfer,
metastable spray transfer, and projected transfer (Ref. 17). In GMAW, controlled transfer modes were observed,
defined as the modes with transfers
forced by additional electrical signal or
mechanical control in contrast with the
natural transfer modes (Ref. 18); the
Fig. 1 — Schematic of the x­ray imaging system and electric signal detection system.
interchangeable GMAW modes were
found, which are composed of two or
more natural modes changing periodically according to certain rules (Ref.
19). By applying the bypass current,
the metal transfer mode changed from
the short-circuiting mode to the globular mode, and the metal transfer frequency increased by about 50% in
GMAW-GTAW (gas tungsten arc welding) double-sided arc welding (Ref. 20).
However, most of these investigations of metal transfer using the visible light method focused on the onshore welding; the metal transfer
process in underwater wet welding
cannot be examined by this method
due to the reflection and absorption of
visible light by the water and perturbation of the bubbles surrounding the
arc burning area. To monitor the
transfer process and investigate the
transfer characteristics in the underwater wet welding, the x-ray transmission method has been developed to
obtain the transfer images of wet
welding (Refs. 21–23). The non-shortcircuiting transfer mode of a rutile
covered electrode was observed during
underwater wet welding with x-ray
flash (Ref. 21). By using the x-ray
transmission method, clear, highspeed images of the droplet transfer
process in underwater flux-cored wire
wet welding were captured. Consequently, the transfer characteristics
and behavior were investigated (Ref.
134-s WELDING JOURNAL / APRIL 2016, VOL. 95
Table 1 — Welding Parameters
Welding Parameters
Value
Arc voltage
Welding current
Contact tip­to­work distance
Travel speed
Water depth
24–46 V
237–440 A
20 mm
1.5 mm/s
0.5 m
22). As an example, for an arc voltage
of 24 V and a welding current of 240 A
in wet welding, the combination transfer mode that includes globular repelled transfer and short-circuit transfer is observed. In this transfer
process, repulsive forces, including the
electromagnetic force, vaporization
force, and gas flow drag force, act on
the droplet; the repelled transfer mode
is observed for 90% of the droplet
transfer (Ref. 23).
To date, the metal transfer modes
at different welding parameters in underwater wet welding have not been
adequately investigated. By using the
x-ray transmission method, the objective of this work was to classify the
metal transfer modes in underwater
wet welding and investigate transfer
mode characteristics, such as the
transfer frequency and droplet size.
The influence of the transfer modes
on welding spatter and welding appearance was also investigated to determine the optimal modes and con-
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WELDING RESEARCH
A
B
C
D
E
F
tigating the metal transfer mode comprehensively at wide ranges of welding
current and arc voltage in underwater
wet welding, in which the range of the
welding current was from 237 to 440
A, while that of the arc voltage was
from 24 to 47 V. Under different combinations of welding current and arc
voltage, four fundamental metal transfer modes could be observed during
the underwater wet welding: the globular repelled transfer mode, the surface tension transfer mode, the explosive short-circuit transfer mode, and
the “submerged arc transfer mode,”
while the explosive short-circuit transfer mode is rarely observed. In this paper, these four fundamental modes are
described below.
Fig. 2 — Metal transfer process of the globular repelled transfer mode.
Globular Repelled Transfer
Mode
Table 2 — Chemical Composition of Q235
Base Metal
C
Mn
Si
S
P
Q235
0.14­0.22
0.30­0.65
≤0.30
≤0.05
≤0.045
trol the droplet transfer behavior.
Experimental
Procedures
Bead-on-plate welding was carried
out on carbon structural steel (Q235)
with dimensions of 200 × 60 × 18 mm,
whose chemical composition is shown
in Table 2. The welding material was
TiO2-CaF2-CaO-SiO2 slag system selfshielded flux-cored wire with a diameter of 1.6 mm. To observe the metal
transfer modes in underwater wet
welding, a series of specimens was
welded at different combinations of
welding current (wire feed speed) and
arc voltage with direct current electrode positive (DCEP). A SAF-FRO
DIGI@WAVE500 welding power supply
was used as the constant voltage welding power source, with the specific
welding parameters shown in Table 1.
Figure 1 shows a schematic of the
x-ray imaging system and electric signal detection system for underwater
wet welding. The x-ray imaging system
consists of a microfocused x-ray tube,
an image intensifier transforming the
x-ray transmission images into visible
images, and a high-speed camera that
operates at a speed of 2000 frames per
second; the electric signal detection
system is used to collect arc voltage
and welding current signals synchronized with the film frames. Because
the wavelength of x-rays is considerably shorter than that of visible light,
x-rays have higher energy and can
therefore traverse relatively thick objects. When traversing the objects, xrays can also be absorbed by the material, and the ability of the material to
absorb the x-rays depends on its density and thickness. Due to their transmission and absorption properties,
the use of x-rays can overcome the effects of the water and bubble perturbation surrounding the arc burning
area and enable the capture of highcontrast images of the droplet transfer
process in underwater wet welding.
Using this x-ray imaging system, clear
images of metal transfer were successfully obtained from welding experiments in wet welding at different combinations of welding current (wire feed
speed) and arc voltage.
Results and Discussion
Fundamental Metal
Transfer Modes
A series of welding experiments
were carried out with the aim of inves-
Figure 2 presents a typical example
of globular repelled transfer mode in
underwater wet welding. During the
globular repelled transfer, the droplet
formed from the molten metal on the
tip of the wire grew and spun around
the wire tip. From 2.0245 to 2.1665 s,
the droplet went through different
steps: an upward rise, a downward
drop and a rotation from the right side
of the wire to the left side. When the
droplet reached its maximum size at
2.1665 s, the droplet separated from
the wire tip under the action of its
own weight and transferred to the
weld pool, and the arc voltage increased from 43.4 to 65.3 V. Meanwhile, the welding current decreased
from 290.4 to 138.4 A, as shown in
Fig. 3.
A longer arc length is clearly beneficial for the formation of the globular
repelled transfer. Therefore, the proportion of the globular repelled transfer mode in the mixed mode will rise
with increasing arc voltage and/or decreasing welding current. Analysis of
the transfer frequency and the droplet
diameter of the globular repelled
transfer mode for an arc voltage of
24–46 V and a welding current of
237–440 A shows that the average
transfer frequency at different welding
parameters of the globular repelled
transfer mode varies from 5.6 to 18.8
droplets per second, whereas the average droplet diameter of the globular
repelled transfer mode varies from 2.8
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Fig. 3 — Arc voltage and welding current of the globular repelled transfer
mode.
A
B
Fig. 4 — Force condition schematic of the globular re­
pelled transfer mode.
C
Fig. 5 — Globular repelled spatters.
A
B
C
Fig. 7 — Force condition schematic of
the surface tension transfer mode.
D
E
F
Fig. 6 — Metal transfer process of the surface tension transfer mode.
to 3.54 mm.
Based on the metal transfer static
force balance theory, the metal transfer process is determined by forces acting on the droplet. In underwater wet
welding, before the molten droplet
contacts the weld pool, the droplet is
affected by gas flow drag force (FL),
136-s
gravitational force (G), plasma drag
force (F1), electromagnetic force (Fe),
surface tension (Fs), and vaporization
force (Fa) (Ref. 23), as shown in Fig. 4.
As the bubbles detached and rose
up in the water periodically, the gas
flow drag force (FL) generated and repelled the droplet when the droplet
WELDING JOURNAL / APRIL 2016, VOL. 95
came in contact with gas in the bubble,
causing the repulsive force of metal
transfer to increase obviously. The
droplets tended to be repelled toward
one side of the wire tip, as shown in
Fig. 2. Because the repulsive force increased obviously, the droplet deviated
from the wire axis after it detached
from the wire tip. Such strong deviations made it likely that the detached
droplet would fall outside the weld
pool, producing large-particle spatters,
as shown in Fig. 5.
Surface Tension Transfer Mode
In underwater wet welding, the surface tension transfer mode, characterized by the surface tension, is one of the
short-circuit transfer modes. Its representative process is shown in Fig. 6.
From 0.6420 to 0.7290 s, the
droplet formed on the tip of the wire,
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WELDING RESEARCH
Fig. 8 — Arc voltage and welding current of the surface
tension transfer mode.
A
B
C
D
E
F
Fig. 9 — Metal transfer process of the explosive short­circuit transfer mode.
A
B
C
D
E
F
Fig. 10 — Arc voltage and welding current of the explo­
sive short­circuit transfer mode.
grew, and spun around the wire axis,
similar to the globular repelled transfer mode. As the droplet grew, it
bridged the gap between the wire tip
and weld pool and finally contacted
the pool at 0.7290 s, creating a liquid
bridge. The surface tension (Fs) and
electromagnetic force (Fe) came into
being between the droplet and weld
pool, which accelerated the droplet
transfer from solid wire to weld pool,
as shown in Fig. 7.
The metal transfer process then entered the short-circuit stage. When the
droplet contacted the weld pool surface, the arc voltage descended from
35.9 to 12.6 V and the welding current
rose rapidly from 49.1 to 416.2 A, as
shown in Fig. 8.
From 0.7290 to 0.7515 s, a necking
emerged from the liquid bridge under
the combined action of the surface
tension and electromagnetic force between the droplet and weld pool; this
is the surface tension transfer stage,
which is characteristic of the surface
tension transfer mode. At 0.7515 s,
the liquid bridge was broken, and the
droplet
Fig. 11 — Metal transfer process of the “submerged arc transfer mode.”
was ultimately
from the wire axis. At 2.6050 s, the
transferred into the weld pool. Statisdroplet contacted the molten pool and
tical analysis of the transfer frequency
the transfer process entered the shortand droplet diameter shows that for
circuit transfer stage, in which a liquid
an arc voltage of 24–46 V and a weldbridge was created, and the surface
ing current of 237–440 A, the average
tension (Fs) and electromagnetic force
transfer frequency of this mode varies
(Fe) came into being consequently, as
from 5.18 to 17.5 droplets per second
shown in Fig. 7.
and the average droplet diameter
From 2.6050 to 2.6325 s, no neckvaries from 2.8 to 3.77 mm. In this
ing was present in the liquid bridge,
surface tension transfer mode, the
and the droplet was not directly transdroplet transferred smoothly and few
ferred into the molten pool under the
spatters were generated during the
combined effect of electromagnetic
transfer process; thus, this mode was
force and surface tension force. The
identified as the ideal mode.
electrical signal oscillogram of this
transfer process is shown in Fig. 10.
Explosive Short­Circuit Transfer Mode
When the droplet contacted the
weld pool at 2.6050 and 2.6325 s, the
The explosive short-circuit transfer
welding current increased from 35.6 to
mode, characterized by the explosive
339.1 A and from 39.4 to 377.6 A,
transfer process, is another short-circuit
respectively.
transfer mode, as shown in Fig. 9.
At 2.6450 s, the liquid bridge exFrom 2.5615 to 2.6050 s, the metal
ploded due to the soaring welding curtransfer process was similar to the
rent or internal metallurgical reaction,
globular repelled transfer mode, in
generating explosive spatters and
which the growing droplet is repelled
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WELDING RESEARCH
A
B
C
Fig. 13 — Explosive spatter.
Fig. 12 — Arc voltage and welding current of the “submerged
arc transfer mode.”
causing the droplet to be repelled violently into the weld pool at the same
time. Through analysis of the transfer
frequency and droplet diameter of the
explosive short-circuit transfer mode,
it is concluded the average transfer
frequency of this mode is approximately 10.04 droplets per second and
that the average droplet diameter is
approximately 3.03 mm. In underwater wet welding, the explosive shortcircuit transfer mode is seen less, and
the dominant short-circuit transfer
mode is surface tension transfer mode.
Submerged Arc Transfer Mode
Owing to the effect of arc force on
the molten pool surface, the liquid
metal is pushed aside and a depressed
cavity forms directly below the arc.
Consequently, when the arc length
gets shorter, the tip of the wire enters
into the depressed cavity. Thus, the
metal transfer process could not be observed clearly in the transfer images.
This transfer phenomenon is called
“submerged arc transfer mode.” The
transfer images of this process are
shown in Fig. 11.
At the beginning of the transfer
process (from 1.3865 to 1.3975 s), the
solid wire melted and entered into the
depressed cavity. From 1.3975 to
1.5125 s, the molten metal was directly transferred into the weld pool, leading to the appearance of the “submerged arc transfer mode.” Obviously,
a shorter arc length is favorable for the
appearance of the “submerged arc
transfer mode.” The electrical signal
oscillogram
of “submerged arc
transfer
mode” is
shown in Fig.
12; while the
wire tip enters into the
Fig. 14 — Arc voltage–welding current diagram illustrating the distri­
depressed
bution of mixed transfer modes: A — Globular repelled transfer
cavity, the
mode, surface tension transfer mode; B — globular repelled transfer
droplet conmode, surface tension transfer mode, and “submerged arc transfer
tacts the weld
mode”; C — “submerged arc transfer mode”; D — surface tension
pool easily
transfer mode and “submerged arc transfer mode”; E — the welding
and a succescould not be carried out.
sive short-circuit phenommode, surface tension transfer mode,
enon occurs, causing the arc voltage
and “submerged arc transfer mode.”
and welding current to fluctuate
The type of mixed transfer mode is
acutely.
related to the welding parameter valDuring the transfer process of this
ues and is typically represented
mode, the molten pool easily generthrough the transfer mode map. Figates explosions due to the rising curure 14 shows the distribution diagram
rent emerging frequently while the
of mixed transfer modes for different
wire tip enters the depressed cavity;
arc voltages and welding currents.
this gives rise to explosive spatter and
Based on the different categories of
makes the transfer process unstable,
the fundamental modes constituting
as shown in Fig. 13.
the mixed modes, Fig. 14 was divided
Mixed Transfer Mode
In underwater wet welding, the
metal transfer mode under certain
welding parameters is not the single
transfer mode but the mixed transfer
mode. As the explosive short-circuit
transfer mode is rarely observed, the
mixed transfer mode is mainly composed of three different fundamental
modes, i.e., globular repelled transfer
138-s WELDING JOURNAL / APRIL 2016, VOL. 95
into five regions, where every region
represents a type of mixed mode, except for region E, where the welding
could not be carried out. The relative
proportions of the fundamental
modes in mixed modes also change
with variations in the welding parameters, and their variations are shown in
Fig. 15.
Due to the large arc voltage or small
welding current, the arc length in the
region of Fig. 14A is longer, giving the
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A
B
C
D
Fig. 15 — Proportions of fundamental metal transfer modes in mixed transfer modes:
RP – globular repelled transfer mode; ST – surface tension transfer mode; S – “sub­
merged arc transfer mode.”
A
B
C
D
Fig. 16 — Weld appearance for different main fundamental transfer modes in the mixed
transfer mode: A — Globular repelled transfer mode; B — surface tension transfer mode;
C — surface tension transfer mode and “submerged arc transfer mode”; D — “sub­
merged arc transfer mode.”
droplet sufficient time to grow before
contacting the weld pool. Therefore,
the fundamental modes during this
type of mixed transfer mode are the
globular repelled transfer mode and
the surface tension transfer mode. For
an arc voltage of 42 V and a welding
current of 290 A, the percentage of the
globular repelled transfer mode in this
welding process is 68%, considerably
higher than that of the surface tension
transfer mode; therefore, the globular
repelled transfer mode is the main
fundamental mode.
As shown in Fig. 16A, when the
globular repelled transfer mode is the
main fundamental mode, large
droplets emerge frequently and the
welding appearance is nonuniform.
With the decrease in the arc voltage
and increase in the welding current,
the arc becomes shorter and the melting speed of the wire accelerates, making the droplet touch the weld pool
more easily so that the proportion of
the globular repelled transfer mode
decreases and that of the surface tension transfer mode increases, as
shown in Fig. 15A and B.
At an arc voltage of 34 V and a
welding current of 290 A, the surface
tension transfer mode is the main fundamental mode, comprising 77% of
the welding process, which is considerably higher than the contribution of
the globular repelled transfer mode.
During this welding process, the
droplets transfer steadily and few
spatters could be observed, causing
the smooth and uniform weld ripples
shown in Fig. 16C.
When the welding parameters enter
the region of Fig. 14B, the type of mixed
transfer mode changes and the mixed
mode includes all three fundamental
modes. For example, the “submerged
arc transfer mode” is also observed
when the arc voltage decreases from 46
to 42 V at a welding current of 368 A. At
an arc voltage of 34 V and a welding current of 368 A, the main fundamental
modes are the surface tension transfer
mode and the “submerged arc transfer
mode,” comprising 49 and 41% of the
welding process, respectively. The welding appearance under these welding
conditions is shown in Fig. 16C.
As the arc voltage decreases further
and the welding current increases further, the contributions of the globular
repelled transfer mode and the surface
tension transfer mode decrease,
whereas that of the “submerged arc
transfer mode” increase significantly,
as shown in Fig. 15C and D.
When the welding parameters enter
the region of Fig. 14C, the arc length decreases sharply and the mixed transfer
mode type changes such that only the
“submerged arc transfer mode” is observed in the transfer process. For example, when the arc voltage is 30 V and
the welding current is 440 A, the only
fundamental metal transfer mode is the
“submerged arc transfer mode.” During
this transfer mode, explosions of the
molten pool occur frequently, causing
small explosive spatters and a nonuniform weld appearance, as shown in Fig.
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16D. When the welding current ranges
from 237 to 368 A and the arc voltage
decreases to 28 V or less, the welding
parameters enter the region of Fig. 14D,
where the mixed transfer mode is composed of the surface tension transfer
mode and the “submerged arc transfer
mode.” Here, the surface tension transfer mode is the main fundamental
transfer mode, comprising 75% of the
welding process.
Conclusions
In the present study, the metal transfer mode and the transfer characteristics in underwater wet welding are investigated by the x-ray transmission
method. The following conclusions can
be drawn based on the obtained results:
1. Using the x-ray transmission
method, four of the fundamental metal transfer modes are found in underwater wet welding: the globular repelled transfer mode, the surface tension transfer mode, the explosive
short-circuit transfer mode, and the
“submerged arc transfer mode,” while
the explosive short-circuit transfer
mode is rarely observed.
2. Under the same welding parameters, the metal transfer mode is composed of different fundamental transfer modes, defined as the mixed transfer mode. For example, when the welding current is 368 A and the arc voltage is 42 V, the mixed transfer mode
consists of 26% globular repelled
transfer mode, 61% surface tension
transfer mode, and 13% “submerged
arc transfer mode.”
3. The mixed transfer modes are divided into four types according to the
different categories of fundamental
modes in the transfer process, and the
proportion of fundamental modes
changes with the variation of welding
parameters.
4. In the surface tension transfer
mode, the droplets transfer smoothly
and few spatters could be observed.
Therefore, increasing the proportion of
surface tension transfer mode in the
mixed transfer mode is favorable for the
improvement of the welding quality.
Acknowledgments
The authors are grateful for the financial support provided by the State
Key Development Program for Basic
Research of China (Grant No.
2013CB035502), the Shandong
Provincial Science and Technology Development Plan (Grant No.
2014GGX103033), and Postdoctoral
Science Foundation of China (Grant
No. 2014M561343).
References
1. Rowe, M., and Liu, S. 2001. Recent
developments in underwater wet welding.
Science and Technology of Welding & Joining
6(6): 387–396.
2. Labanowski, J. 2011. Development of
under-water welding techniques. Welding
International 25(12): 933–937.
3. Labanowski, J., Fydrych, D., and Rogalski, G. 2008. Underwater welding – A
review. Advances in Materials Sciences 8(3):
11–22.
4. Kononenko, V. Y. 2006. Technologies
of underwater wet welding and cutting. EO
Paton Electric Welding Institute.
5. Pessoa, E. C. P., Bracarense, A. Q.,
Zica, E. M., Liu, S., and Perez-Guerrero, F.
2006. Porosity variation along multipass
underwater wet welds and its influence on
mechanical properties. Journal of Materials
Processing Technology 179(1): 239–243.
6. Chigarev, V. V., and Ustinov, A. V.
2000. Design-experimental estimation of
the possibility of reduction of the HAZ
metal cooling rate in wet underwater welding. Avtomaticheskaya Svarka 5: 25–30.
7. Rowe, M. D., Liu, S., and Reynolds, T.
J. 2002. The effect of ferro-alloy additions
and depth on the quality of underwater
wet welds. Welding Journal 81(8): 156-s to
166-s.
8. Ibarra, S., Grubbs, C. E., and Liu, S.
1994. State of the art and practice of underwater wet welding of steel. International workshop on underwater welding of marine structures. New Orleans, USA.
9. Guo, N., Liu, D., Guo, W., Li, H., and
Feng, J. 2015. Effect of Ni on microstructure and mechanical properties of underwater wet welding joint. Materials and Design 77: 25–31.
10. Santos, V. R., Monteiro, M. J., Rizzo,
F. C., Bracarense, A. Q., Pessoa, E. C. P.,
Marinho, R. R., and Vieira, L. A. 2012. Development of an oxyrutile electrode for wet
welding. Welding Journal 91(12): 319-s to
328-s.
11. Ghadimi, P., Ghassemi, H., Ghassabzadeh, M., and Kiaei, Z. 2013. Three-dimensional simulation of underwater welding and investigation of effective parameters. Welding Journal 92(8): 239-s to 249-s.
12. Zhang, H. T., Dai, X. Y., Feng, J. C.,
and Hu, L. L. 2015. Preliminary investigation on real-time induction heating-assist-
140-s WELDING JOURNAL / APRIL 2016, VOL. 95
ed underwater wet welding. Welding Journal 94(1): 8-s to 15-s.
13. de Meneses, V. A., Gomes, J. F. P.,
and Scotti, A. 2014. The effect of metal
transfer stability (spattering) on fume generation, morphology and composition in
short-circuit MAG welding. Journal of Materials Processing Technology 214(7):
1388–1397.
14. Pires, I., Quintino, L., and Miranda,
R. M. 2007. Analysis of the influence of
shielding gas mixtures on the gas metal arc
welding metal transfer modes and fume
formation rate. Materials and Design 28(5):
1623-s to 1631-s.
15. Iordachescu, D., and Quintino, L.
2008. Steps toward a new classification of
metal transfer in gas metal arc welding.
Journal of Materials Processing Technology
202(1): 391–397.
16. Liu, H. Y., Li, Z. X., Li, H., and Shi, Y.
W. 2008. Study on metal transfer modes
and welding spatter characteristics of selfshielded flux cored wire. Science and Technology of Welding and Joining 13(8):
777–780.
17. Yan, B., Gao, H. M., and Ling, Q. I.
U. 2010. Droplet transition for plasmaMIG welding on aluminium alloys. Transactions of Nonferrous Metals Society of China
20(12): 2234–2239.
18. Scotti, A., Ponomarev, V., and Lucas,
W. 2012. A scientific application oriented
classification for metal transfer modes in
GMA welding. Journal of Materials Processing Technology 212(6): 1406–1413.
19. Scotti, A., Ponomarev, V., and Lucas,
W. 2014. Interchangeable metal transfer
phenomenon in GMA welding: Features,
mechanisms, classification. Journal of Materials Processing Technology 214(11):
2488–2496.
20. Miao, Y., Xu, X., Wu, B., Han, D.,
Zeng, Y., and Wang, T. 2015. Effects of bypass current on arc characteristics and
metal transfer behaviour during MIG-TIG
double sided arc welding. Journal of Materials Processing Technology 224: 40–48.
21. Rehfeldt, D., Seyferth, J., and Uhlig,
W. 1980. A microprocessor-controlled system for monitoring and analyzing arc
welding process. International Conference on
Welding Research in the 1980’s, Session B,
Osaka, Japan.
22. Guo, N., Wang, M., Du, Y., Guo, W.,
and Feng, J. 2015. Metal transfer in underwater flux-cored wire wet welding at shallow water depth. Materials Letters 144:
90–92.
23. Guo, N., Guo, W., Du, Y., Fu, Y., and
Feng, J. 2015. Effect of boric acid on metal
transfer mode of underwater flux-cored
wire wet welding. Journal of Materials Processing Technology 223: 124–128.