scholarly journals Effects of active gases on droplet transfer and weld morphology in pulsed-current NG-GMAW of mild steel

2020 ◽  
Author(s):  
Guoqiang Liu ◽  
Xinhua Tang ◽  
Qi Xu ◽  
Fenggui Lu ◽  
Haichao Cui
Keyword(s):  
Mild Steel ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Welding Process ◽  
Metal Transfer ◽  
Pulsed Current ◽  
Shielding Gas ◽  
Droplet Transfer ◽  
Spray Transfer ◽  
Pure Argon

Abstract Small amount of active gases CO 2 and O 2 were added into pure argon inert shielding gas to improve the weld formation of pulsed-current narrow-gap gas metal arc welding (NG-GMAW) of mild steel. Their effects on droplet transfer and arc behavior were investigated. A high-speed visual sensing system was utilized to observe the metal transfer process and arc morphology. When the proportion of CO 2 , being added into the pure argon shielding gas, changes from 5% to 5%, the metal transfer mode changes from pulsed spray streaming transfer to pulsed projected spray transfer, while it remains the pulsed spray streaming transfer when 2% to 10% O 2 is added. Both CO 2 and O 2 are favorable to stabilizing arc and welding process. O 2 is even more effective than CO 2 . However, O 2 is more likely to cause the inclusion defects in the weld, while CO 2 can improve the weld appearance in some sense. The weld surface concavity, which is sensitive to the formation of lack-of-fusion defect in NG-GMAW, is greatly influenced by the addition of active gas, but the weld width and weld penetration almost keep constant.

scholarly journals Effects of Active Gases on Droplet Transfer and Weld Morphology in Pulsed-Current NG-GMAW of Mild Steel

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Guoqiang Liu ◽  
Xinhua Tang ◽  
Qi Xu ◽  
Fenggui Lu ◽  
Haichao Cui
Keyword(s):  
Mild Steel ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Welding Process ◽  
Pulsed Current ◽  
Narrow Gap ◽  
Shielding Gas ◽  
Droplet Transfer ◽  
Pure Argon ◽  
Metal Arc Welding

AbstractThe current research of narrow-gap gas metal arc welding (NG-GMAW) primarily focuses on improving the sidewall fusion and avoiding the lack-of-fusion defect. However, the high cost and operation difficulty of the methods limit the industrial application. In this study, small amount of active gases CO2 and O2 were added into pure argon inert shielding gas to improve the weld formation of pulsed-current narrow-gap gas metal arc welding (NG-GMAW) of mild steel. Their effects on droplet transfer and arc behavior were investigated. A high-speed visual sensing system was utilized to observe the metal transfer process and arc morphology. When the proportion of CO2, being added into the pure argon shielding gas, changes from 5% to 25%, the metal transfer mode changes from pulsed spray streaming transfer to pulsed projected spray transfer, while it remains the pulsed spray streaming transfer when 2% to 10% O2 is added. Both CO2 and O2 are favorable to stabilizing arc and welding process. O2 is even more effective than CO2. However, O2 is more likely to cause slags on the weld surface, while CO2 can improve the weld appearance in some sense. The weld surface concavity in NG-GMAW is greatly influenced by the addition of active gas, but the weld width and weld penetration almost keep constant. This study proposes a new method which is beneficial to improving the weld bead formation and welding process stability.

scholarly journals Effects of active gases on droplet transfer and weld morphology in pulsed-current NG-GMAW of mild steel

2021 ◽  
Author(s):  
Guoqiang Liu ◽  
Xinhua Tang ◽  
Qi Xu ◽  
Fenggui Lu ◽  
Haichao Cui
Keyword(s):  
Mild Steel ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Welding Process ◽  
Pulsed Current ◽  
Narrow Gap ◽  
Shielding Gas ◽  
Droplet Transfer ◽  
Pure Argon ◽  
Metal Arc Welding

Abstract The current research of narrow-gap gas metal arc welding (NG-GMAW) primarily focuses on improving the sidewall fusion and avoiding the lack-of-fusion defect. However, the high cost and operation difficulty of the methods limit the industrial application. In this study, small amount of active gases CO2 and O2 were added into pure argon inert shielding gas to improve the weld formation of pulsed-current narrow-gap gas metal arc welding (NG-GMAW) of mild steel. Their effects on droplet transfer and arc behavior were investigated. A high-speed visual sensing system was utilized to observe the metal transfer process and arc morphology. When the proportion of CO2, being added into the pure argon shielding gas, changes from 5% to 25%, the metal transfer mode changes from pulsed spray streaming transfer to pulsed projected spray transfer, while it remains the pulsed spray streaming transfer when 2% to 10% O2 is added. Both CO2 and O2 are favorable to stabilizing arc and welding process. O2 is even more effective than CO2. However, O2 is more likely to cause slags on the weld surface, while CO2 can improve the weld appearance in some sense. The weld surface concavity in NG-GMAW is greatly influenced by the addition of active gas, but the weld width and weld penetration almost keep constant. This study proposes a new method which is beneficial to improving the weld bead formation and welding process stability.

Mechanically assisted droplet transfer process in gas metal arc welding

2002 ◽  
Vol 216 (4) ◽  
pp. 555-564 ◽  
Author(s):  
Y Wu ◽  
R Kovacevic
Keyword(s):  
Transfer Process ◽  
Arc Welding ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Metal Transfer ◽  
Droplet Transfer ◽  
Macroscopic Appearance ◽  
Transfer Mode ◽  
Metal Arc Welding ◽  
Separate Control

Gas metal arc welding has been generally accepted as the preferred joining technique due to its advantages in high production and automated welding applications. Separate control of arc energy and arc force is an essential way to improve the welding quality and to obtain the projected metal transfer mode. One of the most effective methods for obtaining separate control is to exert an additional force on the metal transfer process. In this paper, the droplet transfer process with additional mechanical force is studied. The welding system is composed of an oscillating wire feeder. The images of molten metal droplets are captured by a high-speed digital camera, and both the macroscopic appearance and the cross-sectional profiles of the weld beads are analysed. It is shown that the droplet transfer process can be significantly improved by wire electrode oscillation, and a projected spray transfer mode can be established at much lower currents. By increasing the oscillation frequency, the droplet transfer rate increases while the droplet size decreases. In addition, the improvement in the droplet transfer process with wire oscillation leads to an enhancement of the surface quality and a modification of the geometry of the weld beads that could be of importance for overlay cladding and rapid prototyping based on deposition by welding.

Arc characteristics and metal transfer behavior of CMT+P process for Q235 steel of titanium-steel composite plate

2019 ◽  
Vol 33 (01n03) ◽  
pp. 1940040
Author(s):  
Yang Wang ◽  
Zhongyin Zhu ◽  
Guoqing Gou ◽  
Lin Peng ◽  
Yali Liu ◽  
...  
Keyword(s):  
High Speed ◽  
Short Circuit ◽  
Welding Process ◽  
Metal Transfer ◽  
Pulse Period ◽  
Cold Metal Transfer ◽  
Q235 Steel ◽  
Spray Transfer ◽  
Transfer Mode ◽  
Transfer Behavior

The cold metal transfer (CMT) with addition of pulses (CMT[Formula: see text]P) process is a new CMT welding method. This paper uses a high-speed camera and electrical signal synchronization acquisition system to perform a CMT[Formula: see text]P welding test on a 10 mm thick Q235 steel plate, and performs arc characteristic and droplet transfer behavior in the welding process. It has been founded that under relatively small currents and voltages, the CMT[Formula: see text]P transfer mode is a combination of a projected transfer mode with one droplet in the pulse period and a short circuit transfer mode during the CMT period. The process is stable with little spatter; at relatively large currents and voltages, the transition mode is the combination of pulse transfer, spray transfer and short circuit transfer. It results in one or more droplets that enter the pool both in pulse transfer in the spray transfer mode during the pulse period and in the short circuit transfer mode during the CMT period in a weld cycle.

scholarly journals Characteristics of Magnetic Field Assisting Plasma GMAW-P

2020 ◽  
Vol 99 (1) ◽  
pp. 25s-38s
Author(s):  
JIANG YU ◽  
◽  
BO WANG ◽  
HONGTAO ZHANG ◽  
PENG HE ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Welding Current ◽  
Plasma Welding ◽  
Droplet Transfer ◽  
Spray Transfer ◽  
The Wire ◽  
Indirect Arc ◽  
The Magnetic Field

The droplet transfer and voltage-current characteristics of gas metal arc welding (GMAW) in single-pulsed GMAW (single GMAW-P), plasma pulsed GMAW (plasma GMAW-P), and plasma-GMAW-P with a magnetic field were studied using the synchronous acquisition system of high-speed camera and electric signals. The results showed the plasma arc and magnetic field had a significant effect on the droplet transfer process. The indirect arc of the plasma and gas metal arc emerged in the pulse peak phase causing a shunt phenomenon of the GMAW current. The period of the indirect arc was increased under the action of the magnetic field. In hybrid plasma GMAW-P, when the GMAW current did not exceed 140 A, several pulsed one-drop free transfers occurred and the droplet transfer period decreased with the increase in the plasma welding current; when the GMAW current exceeded 140 A, and the plasma welding current was less than 180 A, spray transfer was formed. The droplet transfer transformed into a projected transfer when the plasma welding current increased to 180 A. In plasma-GMAW-P hybrid welding with a magnetic field, the magnetic field had a slight effect on the transfer period. When the GMAW current did not exceed 140 A, the droplet transfer was mainly repelled transfer. The detaching location was on the right side of the wire when the magnetic field current was less than 3 A. When the magnetic field current exceeded 3 A, it was below or on the left side of the wire. When the GMAW current exceeded 140 A and the magnetic field current was less than 5 A, spray transfer was formed, but the droplet transfer mode transformed into a projected transfer with a magnetic field current of 5 A.

Dynamic Metal Transfer Behavior in Double-Wire DP-GMAW of Aluminum Alloy Under Different Pulse Phases

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Kaiyuan Wu ◽  
Jiatong Zhan ◽  
Xuanwei Cao ◽  
Xiaobin Hong ◽  
Peimin Xie
Keyword(s):  
High Speed ◽  
Droplet Diameter ◽  
Gas Metal Arc Welding ◽  
Metal Transfer ◽  
Double Pulse ◽  
Droplet Growth ◽  
Al Alloy ◽  
Spray Transfer ◽  
Pulse Phase ◽  
Transfer Behavior

Abstract The effects of pulse phase and pulse stage on the metal transfer characteristics in double-wire double pulse gas metal arc welding (DP-GMAW) of aluminum (Al) alloy were studied using high-speed camera images and current and voltage waveforms. In addition, the effects of various forces on dynamic metal transfer behavior were analyzed under different pulse phases and pulse stages. The results show that the spray transfer mode can be obtained in both the alternating pulse phase (APP) and synchronous pulse phase (SPP). The transfer pattern of the leading and trailing droplets is alternating in the APP, but changes to simultaneous metal transfer in the SPP, mainly owing to influence of the pulse phase on droplet growth. The transfer type is one drop double pulse (ODDP) during the strong pulse stage and one drop triple pulse (ODTP) during the weak pulse stage, regardless of the pulse phase. The pulse phase does, however, affect the Lorentz force between the leading and trailing droplets, causing droplet collision in the SPP, which results in a poorer weld bead appearance compared with in the APP. Finally, the droplet diameter was found to be similar during different pulse phases and pulse stages.

The effect of shielding gas composition in CO2 laser—gas metal arc hybrid welding

2008 ◽  
Vol 222 (11) ◽  
pp. 1315-1324 ◽  
Author(s):  
H-B Chae ◽  
C-H Kim ◽  
J-H Kim ◽  
S Rhee
Keyword(s):  
Molten Metal ◽  
High Speed ◽  
Dominant Role ◽  
Ambient Air ◽  
Metal Transfer ◽  
Video Observation ◽  
Hybrid Welding ◽  
Shielding Gas ◽  
Droplet Transfer ◽  
Laser Induced Plasma

In carbon dioxide (CO2) laser—gas metal arc hybrid welding, a shielding gas is supplied to isolate the molten metal from the ambient air, suppress the laser-induced plasma, remove the plume out of the keyhole, and stabilize the metal transfer. In this study, a shielding gas consisting of helium, argon, and CO2 was used, and its effects on the composition of the welding phenomena, such as behaviours of laser-induced plasma generation, molten pool flow, and droplet transfer in gas metal arc welding, were investigated. High-speed video observation was used to investigate the welding phenomena inside the arc regime. Consequently, helium was found to have a dominant role in suppressing laser-induced plasma; minimum helium content at a laser power of 8 kW was suggested for laser autogenous and hybrid welding. Argon and CO2 govern the droplet transfer and arc stability. A 12 per cent addition of CO2 stabilizes the metal transfer and eliminates undercut caused by insufficient wetting of molten metal.

A Way to Weld Sheet Metal with Double-Electrode GMAW

2013 ◽  
Vol 651 ◽  
pp. 333-337 ◽  
Author(s):  
Guo Hong Ma ◽  
Yu Ming Zhang
Keyword(s):  
Arc Welding ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Metal Transfer ◽  
Constant Current ◽  
Spray Transfer ◽  
Metal Arc Welding ◽  
Globular Transfer ◽  
Double Electrode ◽  
Welding System

This paper designed a double-electrode GMAW(gas metal arc welding) system. This system includes main arc and bypass arc. Main arc (Base metal current: Ibm) is supplied with Constant Current power (CC mode) and bypass arc (bypass current: Ibp) is Constant Voltage power (CV mode). Main arc electrode used common carbon wire, bypass arc electrode used water cool copper. Welding experiment shows this DE-GMAW can change common metal transfer into spray transfer with lowest critical total current (Itotal) 200 amps. When Ibm decreases and bypass voltage increases, this critical current will increase and it is less than 230 amps when keeping spray transfer. High speed video proved that metal transfer is changed from spray transfer to globular transfer.

scholarly journals Influence of Gravity on Molten Pool Behavior and Analysis of Microstructure on Various Welding Positions in Pulsed Gas Metal Arc Welding

2019 ◽  
Vol 9 (21) ◽  
pp. 4626 ◽  
Author(s):  
Jin-Hyeong Park ◽  
Sung-Hwan Kim ◽  
Hyeong-Soon Moon ◽  
Myung-Hyun Kim
Keyword(s):  
Weld Metal ◽  
Arc Welding ◽  
Molten Pool ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Welding Process ◽  
High Speed Camera ◽  
Shielding Gas ◽  
Metal Arc Welding ◽  
The One

This study performed welding on various welding positions in the flat, overhead, and vertical down positions using a pulsed gas metal arc welding (P-GMAW) process. Despite the same amount of heat input on various welding positions, the welding characteristics varied depending on the welding positions. The effect of gravity on the welding process determined the different formation of the weld bead, and the influence of molten pool behavior on various welding positions changed the microstructure in the weld metal. The current and voltage signals were synchronized with a high-speed camera using a data acquisition (DAQ) system. To induce the one pulse one drop (OPOD) process of metal transfer, the shielding gas was used 95% Ar+5% CO2. The microstructure of the weld metal was analyzed in relation to molten pool behavior.

scholarly journals Influences of Weaving Parameters on Dynamic Characteristics and Stability Control of the Droplet Transfer in Arc-Weaving P-GMAW Process

2021 ◽  
Author(s):  
Di Wu ◽  
Yuxi Chen ◽  
Huabin CHEN ◽  
Shanben Chen
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Welding Process ◽  
Stability Control ◽  
Force Balance ◽  
Root Penetration ◽  
High Speed Photography ◽  
Force Model ◽  
Droplet Transfer

Abstract The dynamic characteristics of droplet transfer is extremely complicated with the combined effects of gravity force and weaving motion during the weaving vertical-up welding on thick plate. In this paper, we firstly observed the droplet transfer behavior under various weaving parameters with high-speed photography and electrical signals during pulsed gas metal arc welding (P-GMAW). Then we investigated the influences of different weaving parameters on the arc shape and molten pool as well as droplet characteristics. By establishing a novel weaving-force model based on static-force balance theory (SFBT), we further revealed the drop transfer mechanism in weaving P-GMAW process. Extensive experimental results demonstrated that the suitable weaving parameters could effectively improve the droplet transfer stability and suppress welding defects including incomplete root penetration and lack of sidewall fusion. The findings of this paper will provide a basis for enhancing the welding process stability and obtaining a high-quality weld joint.

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