Y. LI et al.: RESEARCH STATUS AND PROSPECTS FOR TIG-MIG HYBRID-ARC-WELDING TECHNOLOGY
387–396
RESEARCH STATUS AND PROSPECTS FOR TIG-MIG
HYBRID-ARC-WELDING TECHNOLOGY
RAZISKAVA STANJA IN PERSPEKTIVE TEHNOLOGIJE TIG-MIG
HIBRIDNEGA OBLO^NEGA VARJENJA
Yinghao Li, Ran Zong
*
, Yujiao Zhang, Jingzhuo Yao
School of Mechanical Engineering, Shandong University of Technology, Zibo 255000, China
Prejem rokopisa – received: 2023-09-19; sprejem za objavo – accepted for publication: 2024-04-17
doi:10.17222/mit.2023.974
TIG-MIG hybrid welding integrates the merits of tungsten insert-gas welding (TIG) and metal inert-gas welding (MIG), and
achieves a new material-joining process with high quality, high efficiency and low cost. However, TIG-MIG hybrid welding also
had some shortcomings, such as a complex process, unstable arc, large heat input, limiting its application. To further improve
and promote TIG-MIG hybrid welding, numerous universities and research institutes have put forward a series of improvement
programs that achieve relatively good results. In this study TIG-MIG hybrid welding is discussed in three aspects: the weld-
ing-process improvement, welding-parameters optimization and numerical simulation of the welding process. It was found that
the stability of the hybrid arc welding process and the quality of the weld bead can be improved by improving the current polar-
ity, wire type and arc swing. The TIG current, the distance between the wire and tungsten, and the heat input had an important
impact on the weld quality and the formation of defects. A numerical simulation of the welding process analyzed the effects of
torch angle, the distance between the wire and tungsten, the welding speed and the temperature fields on the arc morphology,
molten-pool behavior, and droplet transfer. According to the above analysis, it summarized the current research status of
TIG-MIG hybrid welding, and then proposed future research directions based on the existing shortcomings and deficiencies.
Keywords: tungsten insert-gas welding; metal inert-gas welding; welding parameters; numerical simulation
TIG-MIG hibridno varjenje zdru`uje prednosti elektri~nega varjenja z volframovo fiksno elektrodo v za{~itnem plinu (TIG) in
oblo~nega varjenje s kontinuirano dodajalno kovinsko elektrodo v za{~itnem plinu (MIG). Za{~itni plin je v prvem primeru
obi~ajno Ar v drugem pa me{anica Ar in CO2. S tem hibridnim dokaj stro{kovno ugodnim postopkom se dose`e nov na~in
visoko kvalitetnega in u~inkovitega vezanja razli~nih materialov. Vendar pa ima hibridno TIG-MIG varjenje tudi nekaj slabosti.
To je kompliciran postopek z dokaj nestabilnim oblokom in velikim vnosom toplotne energije, ki omejuje njegovo splo{no
uporabo. [tevilne univerze in raziskovalni in{tituti so zato, da bi nadalje izbolj{ali in promovirali TIG-MIG hibridno varjenje,
za~eli s {tevilnimi raziskovalno-razvojnimi programi in projekti, ki so dali relativnodobre rezultate.V tem ~lanku avtorji
opisujejo in razpravljajo o TIG-MIG hibridnem varjenju s treh vidikov: izbolj{av procesa varjenja, optimizacije parametrov
varjenja in numeri~nih simulacij procesa varjenja. Avtorji ugotavljajo, da je mo`no stabilnost procesa hibridnega oblo~nega
varjenja in kvaliteto raztaljene kovine oziroma »posteljice« izbolj{ati z izbolj{anjem polarnosti elektri~nega toka, vrsto `ice in
nihanjem obloka. Elektri~ni TIG tok, razdalja med kovinsko `ico in volframovo `ico ter koli~ina vnesene toplotne energije
imajo pomemben vpliv na kvaliteto zvara in nastanek napak v zvaru. Z numeri~no simulacijo procesa varjenja so avtorji
analizirali vpliv kota med MIG in TIG gorilnikoma, razdalje med `ico in volframovo elektrodo, vpliv hitrosti varjenja in
temperaturnega polja na morfologijo obloka, obna{anja »bazen~ka« in prenosa kapljic raztaljenih kovin. V skladu z njihovo
analizo opisano v tem ~lanku avtorji povzemajo, da trenutno stanje raziskovanja TIG-MIG hibridnega varjenja in predlagane
smeri bodo~ih re{itev temeljijo na obstoje~ih slabostih in znanih te`avah tega postopka.
Klju~ne besede: oblo~no varjenje kovin in zlitin z volframovo elektrodo v za{~itnem plinu,parametri varjenja, numeri~ne
simulacije
1 INTRODUCTION
With the extensive application of metal materials,
welding technology has played an important role in
fields such as aerospace, mechanical manufacturing,
construction engineering, energy, and power.
1
Currently,
low-carbon manufacturing demands welding technology
that is both environmentally friendly and cost effective.
Traditional single-heat-source arc-welding processes
struggle to balance high-performance welded joints and
a high welding efficiency.
2
Hybrid-heat-source welding was a process that com-
bines two or more heat sources to obtain the advantages
of each. As shown in Figure 1, common methods of hy-
brid-heat-source welding included laser-friction hybrid
heat source,
3
laser-arc hybrid heat source,
4,5
ultra-
sonic-plasma hybrid heat source, and multi-arc hybrid
heat source.
6
As early as the 1970s, scholars proposed
the hybrid welding process of laser coupling with other
heat sources, but it failed to become popular due to its
high cost, low energy-utilization efficiency, and poor
adaptability.
7
Traditional TIG welding has the advan-
tages of simple equipment, low cost, and high quality.
However, its welding efficiency is relatively low because
the tungsten electrode did not melt. Traditional MIG
welding used wire as the electrode, which improved the
welding efficiency, but it was prone to splattering due to
unstable cathode spots.
8
To integrate the advantages of
TIG and MIG welding processes, scholars proposed
Materiali in tehnologije / Materials and technology 58 (2024) 3, 387–396 387
UDK 621.791.75:544.272 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 58(3)387(2024)
*Corresponding author's e-mail:
zongran@sdut.edu.cn (Ran Zong)

TIG-MIG hybrid welding. It coupled the TIG torch and
MIG torch together through the fixture to utilize the hy-
brid arc for melting the base material and the wire,
formed a molten pool, and achieved material joining un-
der the shield of inert gas. TIG-MIG hybrid welding im-
proved the weld quality and efficiency, presenting unpar-
alleled advantages compared to single-heat-source
welding. However, in practical applications, it still faced
drawbacks such as complex welding parameters, unsta-
ble arc, and high heat input.
9
To further promote
TIG-MIG hybrid welding, numerous experiments and
improvements have been conducted by universities and
research institutions. This paper provides an overview of
the research conducted by scholars to address the afore-
mentioned issues, including welding-process improve-
ments, optimization of the welding parameters, and a nu-
merical simulation of the welding process. Additionally,
it discussed and outlined the hot issues and future re-
search directions in TIG-MIG hybrid welding.
2 WELDING-PROCESS IMPROVEMENT
Numerous scholars had conducted research to further
improve the welding quality and adaptability by investi-
gating the hybrid-arc morphology and bead formation
from the perspectives of current polarity, welding-wire
type, and arc oscillation.
Gao
10
used alternating current TIG and direct current
MIG to form the TIG-MIG hybrid arc and conducted
welding experiments on low-carbon steel. It found that
DC MIG ensured the reliability of arc ignition when the
TIG arc polarity was converted. The polarity change of
the TIG arc caused the two arcs to attract and repel peri-
odically. When the two arcs repelled each other, the mol-
ten metal at the wire tip transferred to the rear of the
molten pool, which helped the molten metal reflux, thus
suppressing the formation of the humping bead. Zhang et
al.
11
and Li
12
proposed the TIG-MIG alternating dou-
ble-arc welding process to solve the problems of exces-
sive heat input and an insufficient amount of filler metal
in traditional MIG. As shown in Figure 2a and 2b,an
auxiliary arc was used to heat the base metal in the base
value stage of the main arc pulse to change the shape of
the heat source and improve the weld quality. In the peak
stage of the main arc pulse, an auxiliary arc was used to
heat the welding wire to increase the deposition effi-
ciency. Tang et al.
13,14
studied the effect of electrode po-
larity on the arc-ignition performance of the TIG-MIG
hybrid welding. As shown in Figure 2c and 2d, MIG
could realize non-contact ignition by using a direct cur-
rent electrode positive (DCEP). The polarity connection
of the TIG and the distance between the wire and tung-
sten only affected the difficulty of non-contact ignition.
Wang et al.
15
studied the influence of polarity matching
and the distance between the wire and tungsten on the
TIG-MIG hybrid welding process for 5A06 aluminium
alloy. As shown in Figure 2e and 2f, the two arcs could
be completely coupled when the polarity of the TIG arc
and the MIG arc were the same. The two arcs repelled
each other and the coupling was difficult when the polar-
ity was opposite. With an increase of the distance be-
tween the wire and tungsten, the two arcs gradually
changed from coupling to mutual influence, until inde-
pendence.
Liang et al.
16
proposed a TIG-CMT hybrid-welding
process to solve the problem that Cold Metal Transfer
Y. LI et al.: RESEARCH STATUS AND PROSPECTS FOR TIG-MIG HYBRID-ARC-WELDING TECHNOLOGY
388 Materiali in tehnologije / Materials and technology 58 (2024) 3, 387–396
Figure 1: a) Laser-assisted friction-stir-welding schematic
3
, b) laser-arc hybrid-heat-source-welding schematic
5
, c) ultrasound-plasma hy-
brid-heat-source-welding schematic and d) TIG-MIG hybrid-welding schematic

(CMT) could not be applied to thick plates, as shown in
Figure 2g to 2i. The TIG arc was added to increase the
heat input on the workpiece to improve the penetration.
Jiang et al.
17
proposed a welding method for bypass hy-
brid variable polarity plasma arc, which offered a unique
advantage for adjusting the heat input of the wire and the
base metal freely. Similarly, to improve the stability of
the keyhole welding, Guo et al.
18
and Liu et al.
19
pro-
posed a hybrid-plasma-free arc-welding method based
on a plasma arc welding torch. The added free arc acted
in an assistant role to adjust the arc heat output without
affecting the arc pressure peak. Dong
20
and Zhang et al.
21
studied the droplet transfer of TIG-MIG hybrid welding
by using a cable-type wire. As shown in Figure 2j to
2m, the TIG arc force and the mechanical rotation force
of the cable-type wire changed the droplet shape, re-
duced the droplet diameter, and improved the stability of
the droplet transfer.
Zhu et al.
22
proposed a two-electrode TIG-MIG indi-
rect arc-welding method. As shown in Figure 3a,t h e
two tungsten electrodes were connected to the negative
electrode of the two TIG power supplies, and the weld-
ing wire was connected to the positive electrode of the
two TIG power supplies. The effect of wire feeding rate
and current on the process stability was studied. The re-
sults showed that there was an optimal wire feeding rate
for a certain welding current, which made the arc more
concentrated and the coupling degree higher. With the
increase of the welding current, the arc length increased
gradually. When the current exceeded the critical current,
the electromagnetic force and arc pressure acting on the
droplet increased obviously, which was manifested as a
projected transfer, and the process stability was excel-
lent.
Huang et al.
23
proposed a swing TIG-MIG hybrid
welding method to solve the problem of poor side-wall
fusion. As shown in Figure 3b and 3c, swing TIG-MIG
hybrid welding could increase the width of the TIG mol-
ten pool, effectively increase the spread of the weld, and
prevent the undercut defect. With the increase of the
swing frequency, the weld boundary becomes smoother.
Huang et al.
24
developed a rotary pendulum TIG-MIG
Y. LI et al.: RESEARCH STATUS AND PROSPECTS FOR TIG-MIG HYBRID-ARC-WELDING TECHNOLOGY
Materiali in tehnologije / Materials and technology 58 (2024) 3, 387–396 389
Figure 2: a) Arc shape at the base value of the main arc, b) arc shape at the peak value of the main arc
12
, c) MIG DC reverse non-contact arc-ini-
tiation moment, d) MIG DC positive arc image
13
, e) TIG positive hybrid-arc morphology, f) TIG reverse-hybrid-arc morphology
15
, g) Schematic
diagram of melt-through formation during TIG-CMT welding, h) macrostructure of DC-CMT joint, i) TIG-CMT joint macrostructure15
16
,
j) 0-ms single-filament MIG droplet transfer, k) 10.5-ms single-filament MIG droplet transfer, l) 0 ms cable-type welding-wire droplet transfer
and m) 10.5-ms cable-type welding-wire droplet transfer
20

hybrid welding torch. It explored the influence of the
combination of transverse swinging TIG arc and MIG
arc on the bead formation. When the rotating pendulum
speed increased, the weld width decreased, the weld pen-
etration and residual height slightly increased, the ripple
spacing on the weld surface decreased, and the weld sur-
face gradually became smooth, as shown in Figure 3d.
The weld penetration gradually changed from asymme-
try to symmetry with the increase of the distance be-
tween the wire and tungsten, and the weld surface gradu-
ally became smooth from rough, as shown in Figure 3e.
According to the above analysis, the improvement of
the TIG-MIG hybrid welding process gave satisfactory
results. Changing the electrode polarity could improve
the stability of arc, suppress the formation of humping
defects, and increase the deposition efficiency. Changing
the type of welding wire and the relative position of the
electrode promoted the droplet transfer and improved the
weld quality. The mechanical swing of the TIG welding
torch integrated the advantages of manual arc welding,
which significantly increased the spread of the molten
metal, widened the molten pool and improved the weld
morphology and welding quality. The above hy-
brid-heat-source welding processes were improved for
specific materials and special working conditions. The
scope of the application urgently needed to be expanded.
A large number of experiments should be carried out for
the TIG-MIG hybrid welding process to develop a new
hybrid heat source welding process with strong adapt-
ability and high welding efficiency.
3 WELDING-PARAMETER OPTIMIZATION
Unreasonable parameter selection or excessive fluc-
tuation in the welding process would have a great impact
on welding quality, such as: weld size out-of-tolerance,
cracks, spatter, undercut, and humping.
25
To suppress the
welding defects and improve weld quality, researchers
studied arc shape, droplet transfer, molten-pool behavior
and bead formation from the aspects of shielding-gas
composition, welding current, voltage waveform and
heat input.
Tang et al.
13,14
studied the influence of shielding-gas
types on the arc-ignition performance of TIG-MIG hy-
brid welding. In Figure 4a to 4c, the reason for achiev-
ing non-contact ignition was that the outer electrons of
the TIG arc moved towards the wire tip and collided with
the shielding gas to partially ionize it. This led to a sig-
nificant increase in the conductivity of the gap, causing it
to breakdown at low voltage. It was easier to realize
non-contact ignition in a pure Ar atmosphere than in an
active atmosphere. Li
26
used Ar + N
2
double-layer shield-
ing gas for narrow-gap TIG-MIG hybrid welding of dis-
similar steel. As shown in Figure 4d and 4e, the welding
arc existed in the form of dual arc coupling under the
protection of inner Ar and outer N
2
, the arc shrank sig-
nificantly, changed from fasciculate to cone, which could
reduce the droplet size and increase the transfer fre-
quency.
Kaneemar et al.
27
studied the influence of torch angle
on the TIG-MIG hybrid welding, as shown in Figure 4f.
Y. LI et al.: RESEARCH STATUS AND PROSPECTS FOR TIG-MIG HYBRID-ARC-WELDING TECHNOLOGY
390 Materiali in tehnologije / Materials and technology 58 (2024) 3, 387–396
Figure 3: a) Schematic diagram of the relative positions of tungsten electrode and wire
22
, b) Schematic diagram of oscillating TIG-MIG hybrid
molten pool, c) comparison of weld bead at different oscillation frequencies
23
, d) shape and cross-section of weld bead at different oscillation
speeds and e) at different distance between wire and tungsten
24

When the angle of the TIG torch was 90° and the MIG
torch was 45°, the repulsive force between the two arcs
caused the MIG arc to shift from the wire axis by a small
angle, and the concentration of hybrid arc was higher, re-
sulting in wider spreading and better surface finish, as
shown in Figure 4g to 4i. Chen et al.
28
carried out a
low-current TIG arc-assisted MIG high-speed welding
process. It analysed the influence of various parameters
on bead formation from the aspects of heat and mass
transfer. The auxiliary TIG arc increased the MIG arc
length and reduced the arc pressure, as illustrated in Fig-
ure 4j to 4l. It reduced the tendency of molten metal to
gather behind the arc, and promoted the filling of the
weld toe, thereby suppressing the undercut defect. When
TIG arc was leading, MIG arc was stable and there were
no obvious spatters. When the TIG arc was trailing, the
current-voltage waveform of the hybrid arc fluctuates ir-
regularly, and a small amount of spatter was produced,
leading to poor weld quality.
Kaneemar et al.
29
used a symmetrical hybrid welding
torch to study the influence of TIG current on the bead
formation when the MIG current was fixed at 270 A. As
shown in Figure 5a to 5c, the MIG arc was stable, and
the weld was well formed, when the TIG current was
larger than the MIG current. The weld penetration in-
creased with the TIG current. As shown in Figure 5d
and 5e, the MIG arc was unstable, and there was a large
amount of splashing, when the TIG current was smaller
than the MIG current. The weld penetration was inde-
pendent of the TIG current. The experimental results
were compared with those obtained by traditional MIG
welding. The mechanical properties of the joint were
equivalent, and the welding efficiency was increased by
more than twice. Zong et al.
30
studied the influence of
the electrode’s relative position on arc stability and bead
formation in TIG-MIG hybrid welding. As shown in Fig-
ure 5f and 5g, the width of weld narrows to suppress the
occurrence of undercut defects, when TIG arc was lead-
ing. Even if the TIG current was as low as 50 A, the
Y. LI et al.: RESEARCH STATUS AND PROSPECTS FOR TIG-MIG HYBRID-ARC-WELDING TECHNOLOGY
Materiali in tehnologije / Materials and technology 58 (2024) 3, 387–396 391
Figure 4: Effect of shielding gas on non-contact arc initiation: a) Ar, b) Ar + 1% O
2
,c)Ar+15%O
2
14
; Effect of shielding gas on arc morphol-
ogy and droplet transfer d) Ar, e) Ar + N
2
26
; f) Schematic diagram of the hybrid welding experiment; Effect of torch angle on arc morphology
and weld-bead formation g) TIG 0°, MIG 35°, h) TIG 0°. MIG 45°, i) TIG 0°, MIG 55°
27
; Comparison of arc patterns of different welding meth-
ods, j) MIG, k) TIG + MIG and l) MIG + TIG
28

welding process exhibited good stability. As shown in
Figure 5h and 5i, TIG arc force caused reflux of molten
metal to suppress undercut, when TIG arc was trailing.
But the arc stability was poor when the TIG current was
smaller than 100 A. Roslan et al.
31
studied the influence
of the TIG current on the stability of TIG-MIG hybrid
arc. It found that the introduction of the TIG arc signifi-
cantly increased the stability of the MIG arc, even when
the TIG current was only 60 A. When the TIG current
increased to 120 A, the strong electromagnetic force in-
creased the length of MIG arc, resulting in a decrease in
droplet size and a significant increase in transfer fre-
quency.
Chen et al.
32
conducted a high-speed square-wave AC
TIG-MIG hybrid welding experiment to explore the in-
fluence of different polarity ratios (proportion of nega-
tive half-wave duration of AC TIG) on the stability of the
welding process and bead formation. When the polarity
ratio was 0, the hybrid arc had numerous breaks, and the
welding process was unstable, as shown in Figure 5j.
When the polarity ratio reached 10%, the shape of the
hybrid arc expanded and contracted periodically. The hy-
brid arc had fewer breaks, welding defects such as un-
dercut, humping and spatters were suppressed, and the
weld was well formed as a whole, as shown in Fig-
ure 5k.
Ogundimuy et al.
33
studied the effect of heat input on
the welding efficiency of 304 austenitic stainless steel
using a TIG-MIG hybrid arc. It found that obvious grain
coarsening appeared in the weld with an increase of heat
input. The elongation, tensile strength and mechanical
properties all showed a downward trend. Abima et al.
34
used the Taguchi method to optimize the parameter com-
bination for thr TIG-MIG hybrid welding of AISI 1008
mild steel. The results showed that the contribution rates
of gas flow rate, TIG current and MIG voltage to the ten-
sile strength and yield strength of the joint were 40 %,
27 % and 21 %, respectively. Increasing gas flow rate
and TIG current, while reducing MIG voltage, can im-
prove the tensile strength and yield strength of the joint.
The above researchers conducted experiments on pa-
rameters such as shielding gas, welding current, elec-
trode polarity, and relative position, respectively. Each
factor affected the welding process and bead quality to
varying degrees. The type of shielding gas not only af-
fected the difficulty of realizing non-contact arc initia-
tion, but also changed the arc shape and droplet transfer
mode. The arc stability was higher and there were fewer
spatters when the TIG current was greater than the MIG.
When the polarity of the two arcs was the same, the hy-
brid arc could be fully coupled, and the MIG could real-
ize non-contact arc initiation in DCEP mode. The MIG
arc was more stable when the TIG torch was leading,
Y. LI et al.: RESEARCH STATUS AND PROSPECTS FOR TIG-MIG HYBRID-ARC-WELDING TECHNOLOGY
392 Materiali in tehnologije / Materials and technology 58 (2024) 3, 387–396
Figure 5: Weld-bead shape and cross-section: a) I
TIG
= 500 A, I
MIG
= 270 A, b) I
TIG
= 400 A, I
MIG
= 270 A, c) I
TIG
= 300 A, I
MIG
= 270 A,
d) I
TIG
= 200 A, I
MIG
= 270 A, e) I
TIG
=0A,I
MIG
= 270 A
29
; Weld cross section f) TIG + MIG: I
TIG
=50A,I
MIG
= 250 A, g) TIG + MIG:
I
TIG
= 100 A, I
MIG
= 250 A, h) MIG + TIG: I
MIG
=50A,I
TIG
= 250 A, i) MIG + TIG: I
MIG
= 100 A, I
TIG
= 250 A
30
; Weld bead shape and volt-
age waveform (j) Polarity ratio 0; (k) Polarity ratio 10
32

which could effectively suppress the undercut defect. At
present, the welding parameters have been controlled
within a relatively good range, but there was still a lack
of in-depth exploration of the mechanism of the effects
of various welding parameters on the TIG-MIG mixed
heat source, which should be given attention in the fu-
ture.
4 NUMERICAL SIMULATION OF WELDING
PROCESS
The welding process involved heat transfer, mass
transfer, electromagnetism, and metallurgy. Various
physical fields interacted and coupled with each other,
with numerous influencing factors.
35
Numerical simula-
tion has become an important technical means to opti-
mize the welding process parameters, predict the weld-
ing quality and reveal the welding mechanism with the
rapid development of computer science and technology.
36
In recent years, scholars have studied the behaviour of
the molten pool and the arc from the perspectives of tem-
perature field, electromagnetic field and flow field.
Kaneemar et al.
37
analysed the effects of welding
torch angle and TIG current on the TIG-MIG hybrid arc.
By reducing the angle of the welding torch, the electrode
tips were brought closer, the current from the wire to the
tungsten electrode disappeared and the repulsive force
between the two arcs increased, as shown in Figure 6a.
When the TIG current was low, the current flowed into
the base material was small and had no obvious effect on
the weld penetration. When the TIG current was higher
than 200 A, most of the TIG current flowed into the base
material, and the weld penetration increased with the in-
creased of TIG current.
Chen et al.
38
established adaptive plane and volumet-
ric heat source models for TIG and MIG respectively
based on experimental observations. It studied the effects
of welding torch angle on temperature distribution and
weld morphology, and compared them with experimental
results. As shown in Figure 6b, the heat-source algo-
rithm could accurately predict the welding process re-
gardless of whether the TIG torch was tilted backward or
forward. In subsequent research, Chen et al.
39
optimized
the arc heat and force model of TIG-MIG hybrid welding
by considering the influence of arc deflection and defor-
mation of the molten pool’s surface. The results showed
that the arc heat distribution of the TIG-MIG hybrid
welding was more uniform compared with single MIG,
and the peak of heat density was reduced by 5 %. The re-
distribution of arc force in TIG-MIG hybrid welding was
Y. LI et al.: RESEARCH STATUS AND PROSPECTS FOR TIG-MIG HYBRID-ARC-WELDING TECHNOLOGY
Materiali in tehnologije / Materials and technology 58 (2024) 3, 387–396 393
Figure 6: a) Temperature field distribution at different torch angles
37
, b) Comparison between experimental and simulated cross-sections at dif-
ferent TIG angles
38
and c) Droplet flow field distribution
41

beneficial to reduce the backward fluid flow and promote
the lateral flow of molten metal. A layer of 0.8-mm-thick
molten metal was formed under the hybrid arc, which ef-
fectively absorbed the impingement of droplet and fur-
ther decreased the backward fluid flow.
Lou et al.
40
simulated the temperature field of the
workpiece at different distances between the wire and
tungsten. When the distance was less than 8.5 mm, the
two molten pools formed by the TIG and MIG arcs can
be merged into a common molten pool. The two molten
pools formed an "8" shape when the distance was
10 mm. There was a low temperature region between the
two molten pools, and the tensile strength of the joint
was the strongest. The two molten pools became inde-
pendent of each other when the distance reached 12 mm.
Cui
41
and Han et al.
42
analysed the droplet transfer, as
shown in Figure 6c. When the distance between the wire
and tungsten was 7 mm, the interaction between the two
arcs was the strongest. The deflection angle between the
MIG arc and the droplet was the largest, and the back-
ward droplet momentum could promote the backward
fluid flow in the molten pool. The increase of backward
fluid-flow velocity of the molten metal promoted the
generation of undercutting. Zhao
43
analysed the effects
of metal vapor and distance between the wire and tung-
sten on the arc shape and droplet transfer. The metal va-
por could reduce the temperature in the MIG arc column,
expand the conductive path between the two arcs, and
enhance the coupling effect of the two arcs. The cou-
pling effect almost disappeared, and the two arcs showed
their own arc shape when the distance between the wire
and tungsten increased to 9 mm.
Wu et al.
44
proposed a self-adaptive arc heat and pres-
sure-distribution model for TIG-MIG hybrid welding to
study the influence of process parameters on the bead
formation. It found that the ratio of transverse outward
velocity to backward velocity of the molten metal de-
creased when the welding speed increased from 1.5 m/s
to 2.0 m/s. Molten metal was difficult to fill the weld
toes, resulting in undercut defects. Abima et al.
45
used a
Gaussian heat source model to simulate the temperature
field distribution of AISI 1008’s TIG, MIG and
TIG-MIG hybrid welding. It found that the temperature
distribution of the MIG molten pool was roughly the
Y. LI et al.: RESEARCH STATUS AND PROSPECTS FOR TIG-MIG HYBRID-ARC-WELDING TECHNOLOGY
394 Materiali in tehnologije / Materials and technology 58 (2024) 3, 387–396
Figure 7: Numerical analysis of the behavior of the molten pool and the suppression mechanism of undercut defect in TIG-MIG hybrid welding

same as that of TIG molten pool, but the peak tempera-
ture of the MIG was lower than that of TIG. The peak
temperature of TIG-MIG hybrid welding pool was lower
than that of single arc, and the temperature gradient was
smaller. As the joint of the TIG-MIG hybrid welding had
a higher heat input and slower cooling rate, the pearlite
structure of coarse dendritic crystal was formed, which
decreased the hardness.
The author developed a 3D model, including droplets
and molten pool to investigate the phenomenon of
multi-coupling transport phenomena in TIG-MIG hybrid
arc welding, as shown in Figure 7a. The integrated dis-
tribution of "arc current density-arc pressure-electromag-
netic force-arc heat" was proposed, which could be
adapted to the evolution of the molten pool’s surface, as
illustrated in Figure 7b. The comparison between exper-
imental and simulated results on the bead cross-section
was shown in Figure 7c. The heat and force state of the
molten pool was analysed to investigate its influence on
the bead formation, as demonstrated in Figure 7d. Sensi-
tivity and dimensional analyses proved that the groove
sizes could be predicated based on the molten pool’s
characteristics, including the stress state of the liquid
metal, the morphology, and the fluid flow patterns, as il-
lustrated in Figure 7e and 7f. It revealed the quantitative
relationships among the welding parameters, the behav-
iour of molten pool, and the weld bead formation, pro-
moting the implementation of digital twinning technol-
ogy in the manufacturing industries.
The above scholars analysed the effects of welding
torch angle, between wire and tungsten, metal vapor,
welding speed and temperature field on the arc shape,
molten-pool behavior, droplet transfer and weld micro-
structure. The hypothesis and models were validated
through experiments, and good consistency was
achieved. The experimental verification process lacked
accurate and continuous physical quantity measurement,
which will result in some errors with the numerical sim-
ulation data. In the future, numerical simulation of
TIG-MIG hybrid welding, a multi-factor “arc-drop-
let-molten pool” integrate model considering metal va-
por should be established. Exploring the influence of the
attractive and repulsive forces between the two arcs and
the heat-force distribution of the arc on the workpiece,
reveal the hybrid welding mechanism, and provide a the-
oretical basis for optimizing welding parameters.
5 CONCLUSIONS AND PROSPECTS
This paper summarized the research progress of
TIG-MIG hybrid welding in recent years from three as-
pects: welding process improvement, welding parameter
optimization, and welding process numerical simulation.
The following conclusions can be drawn:
(1) The improvement of the TIG-MIG hybrid weld-
ing process enhanced the arc stability and optimized the
heat distribution, which increased welding quality and
efficiency.
(2) Shielding gas, electrical parameters and electrode
relative position all affected the welding process and
bead quality to varying degrees. The appropriate combi-
nation of welding parameters helped to achieve superior
and efficient welding.
(3) The combination of numerical simulation with a
small number of experiments could analyze the arc cou-
pling, droplet transfer and molten pool behavior from the
aspects of temperature field, electromagnetic field and
flow field.
At present, the research of TIG-MIG hybrid welding
has made a great breakthrough, but there are still unre-
solved problems. The author believed that future re-
search should focus on the following aspects:
(1) The external energy fields, such as ultrasound, vi-
bration, laser assisted and eddy current heating, could be
used to promote the thermal coupling of the two arcs to
develop a new hybrid-arc welding process with wider
adaptability and higher welding efficiency.
(2) Establish an integrated multi physical coupling
model of "arc-droplet-molten pool" to comprehensively
analyze the mechanism of bead formation through rea-
sonable simplifications and assumptions.
Acknowledgment
This work was supported by the Shandong Provincial
Natural Science Foundation [grant number
ZR2023ME139], National Natural Science Foundation
of China [grant numbers 51905321], Shandong Provin-
cial Natural Science Foundation [grant number
ZR2022ME210], and Shandong Provincial Key Labora-
tory of Precision Manufacturing and Non-traditional Ma-
chining.
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