scholarly journals Globular-to-Spray Transition in Cold Wire Gas Metal Arc Welding

2021 ◽  
Vol 100 (4) ◽  
pp. 121-131
Author(s):  
R. A. RIBEIRO ◽  
◽  
P. D. C. ASSUNÇÃO ◽  
E. B. F. DOS SANTOS ◽  
E. M. BRAGA ◽  
...  
Keyword(s):  
Arc Welding ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Welding Current ◽  
Electrical Current ◽  
Feed Speed ◽  
High Speed Imaging ◽  
Transition Mechanism ◽  
Cold Wire ◽  
Metal Arc Welding

The electrical current required for a transition from globular to spray droplet transfer during gas metal arc welding (GMAW) is determined by the specified wire feed speed in the case of constant-voltage power supplies. Generally, in narrow groove welding, spray transfer is avoided, be-cause this transfer mode can severely erode the groove sidewalls. This work compared the globular-to-spray transition mechanism in cold wire gas metal arc welding (CW-GMAW) vs. standard GMAW. Synchronized high-speed imaging with current and voltage samplings were used to characterize the arc dynamics for different cold wire mass feed rates. Subsequently, the droplet frequency and diameter were estimated, and the parameters for a globular-to-spray transition were assessed. The results suggest that the transition to spray occurs in CW-GMAW at a lower current than in the standard GMAW process. The reason for this difference appears to be linked to an enhanced magnetic pinch force, which is mainly responsible for metal transfer in higher welding current conditions.

Arc Interruptions in Tandem Pulsed Gas Metal Arc Welding

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Ruham Pablo Reis ◽  
Daniel Souza ◽  
Demostenes Ferreira Filho
Keyword(s):  
Arc Welding ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Welding Process ◽  
Electrical Current ◽  
Gas Tungsten Arc ◽  
Metal Arc Welding ◽  
Two Factors ◽  
Single Arc ◽  
Mean Current

In addition to electromagnetic attraction between the arcs in Tandem Pulsed gas metal arc welding (GMAW), arc interruptions, mostly in the trailing arc at low mean current levels, may also occur, which is a phenomenon not widely discussed in the welding field. These arc interruptions must be avoided, since they also represent interruptions in metal fusion and deposition during the welding process, leading to lack of fusion/penetration and/or deposition flaws, adding cost for repairing operations. To improve the understanding on arc interruptions in Tandem Pulsed GMAW and how the current pulsing synchronism between the arcs relates to this phenomenon, this work proposes to evaluate the influence of parameters of adjacent arcs (Tandem Pulsed GMAW) and also of a single arc (GTAW—gas tungsten arc welding), but similarly subjected to magnetic deflection, on the occurrence of arc interruptions/extinctions. High-speed filming was used to help understand the interruption/extinction mechanism. In the case of Tandem Pulsed GMAW, the pulses of current of the leading and trailing arcs need to be almost-in-phase to prevent interruptions in the trailing arc. The distance of 10 mm between the adjacent arcs helped reduce the incidence of trailing arc interruptions, yet keeping a sound weld visual quality. In the case of GTAW, the higher the electrical current flowing through the arcs and the shorter their lengths, the more they resist to the extinction. The trailing arc interruptions in Tandem Pulsed GMAW seem to be determined by the deflection and heat in this arc, and their prevention can be achieved by a balance between these two factors, which is reached by synchronized pulsing currents.

scholarly journals Metal Transfer Mechanisms in Hot-Wire Gas Metal Arc Welding

2020 ◽  
Vol 99 (11) ◽  
pp. 281s-294s
Author(s):  
P. P. G. RIBEIRO ◽  
◽  
P. D. C. ASSUNÇÃO ◽  
E. M. BRAGA ◽  
R. A. RIBEIRO ◽  
...  
Keyword(s):  
Cross Sections ◽  
Arc Welding ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Melting Rate ◽  
Bead Geometry ◽  
Hot Wire ◽  
High Speed Imaging ◽  
Metal Arc Welding ◽  
Full Factorial

The hot-wire gas metal arc welding (HW-GMAW) process is widely used to increase the melting rate of a secondary wire through Joule heating without significantly increasing the total heat input to the substrate. Because there is limit-ed knowledge regarding the associated arc dynamics and its influence on bead geometry, the present study considers how these are affected by the hot-wire polarity (negative or positive), hot-wire feed rate, and hot-wire orientation using a two-factor full factorial experiment with three replicates. During welding, high-speed imaging synchronized with current and voltage acquisition to study the arc dynamics. After this, each replicated weld was cut into three cross sections, which were examined by standard metallography. The preliminary results suggest that the arc was stable within the range of process parameters studied. The arc polarity played a role on arc position relative to the hot wire, with a decrease in penetration depth observed when the arc was attracted to the hot wire.

scholarly journals Application of Cold Wire Gas Metal Arc Welding for Narrow Gap Welding (NGW) of High Strength Low Alloy Steel

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 335 ◽  
Author(s):  
Rafael Ribeiro ◽  
Paulo Assunção ◽  
Emanuel Dos Santos ◽  
Ademir Filho ◽  
Eduardo Braga ◽  
...  
Keyword(s):  
Arc Welding ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Welding Parameters ◽  
Narrow Gap ◽  
Dynamic Features ◽  
Narrow Gap Welding ◽  
Cold Wire ◽  
Metal Arc Welding ◽  
Welding Processes

Narrow gap welding is a prevalent technique used to decrease the volume of molten metal and heat required to fill a joint. Consequently, deleterious effects such as distortion and residual stresses may be reduced. One of the fields where narrow groove welding is most employed is pipeline welding where misalignment, productivity and mechanical properties are critical to a successful final assemblage of pipes. This work reports the feasibility of joining pipe sections with 4 mm-wide narrow gaps machined from API X80 linepipe using cold wire gas metal arc welding. Joints were manufactured using the standard gas metal arc welding and the cold wire gas metal arc welding processes, where high speed imaging, and voltage and current monitoring were used to study the arc dynamic features. Standard metallographic procedures were used to study sidewall penetration, and the evolution of the heat affected zone during welding. It was found that cold wire injection stabilizes the arc wandering, decreasing sidewall penetration while almost doubling deposition. However, this also decreases penetration, and incomplete penetration was found in the cold wire specimens as a drawback. However, adjusting the groove geometry or changing the welding parameters would resolve this penetration issue.

Effect of Current Waveform on Metal Transfer in Controlled Short Circuiting Gas Metal Arc Welding

2013 ◽  
Vol 718-720 ◽  
pp. 202-208 ◽  
Author(s):  
Mao Ai Chen ◽  
Yuan Ning Jiang ◽  
Chuan Song Wu
Keyword(s):  
Transfer Process ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Welding Current ◽  
Metal Transfer ◽  
Arc Voltage ◽  
Metal Arc Welding ◽  
Maximum Stability ◽  
The Stability ◽  
Welding Inverter

With high-speed welding inverter and precisely controlling the welding current with arc-bridge state, advanced pulse current waveforms can be produced to optimize the transfer characteristics of short circuiting transfer welding. In this paper, the images of droplet/wire, and the transient data of welding current and arc voltage were simultaneously recorded to study the influence of peak arcing current, background arcing current and tail-out time on the stability of short circuiting transfer process. It was found that maximum short circuiting transfer stability is reached under specific welding conditions. Any deviation from these conditions will cause abnormal rises in arc voltage indicating instantaneous arc extinguishing and greater spatter. Optimal welding conditions were obtained to achieve the maximum stability of short circuiting metal transfer process.

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.

Application of a Front Tracking Method in Gas Metal Arc Welding (GMAW) Simulation

2004 ◽  
Vol 127 (3) ◽  
pp. 590-597 ◽  
Author(s):  
Guo Xu ◽  
William W. Schultz ◽  
Elijah Kannatey-Asibu
Keyword(s):  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Welding Current ◽  
Front Tracking ◽  
Front Tracking Method ◽  
Surface Method ◽  
Metal Arc Welding ◽  
Initial Drop ◽  
Velocity Pressure ◽  
First Time

A numerical model is developed to simulate the short-circuiting metal transfer process during gas metal arc welding (GMAW). The energy equation and the Marangoni convection are considered for the first time in analyzing the short-circuiting time. A front-tracking free surface method explicity tracks the profile of the liquid bridge. The electromagnetic field, distribution of velocity, pressure, and temperature are calculated using the developed model. Effects of welding current, surface tension temperature coefficient, and initial drop volume on short-circuiting duration time are examined. The results show that both the electromagnetic force and Marangoni shear stress play significant roles in short-circuiting transfer welding.

An overview on the cold wire pulsed gas metal arc welding

2019 ◽  
Vol 64 (1) ◽  
pp. 123-140 ◽  
Author(s):  
R. A. Ribeiro ◽  
P. D. C. Assunção ◽  
E. B. F. Dos Santos ◽  
E. M. Braga ◽  
A. P. Gerlich
Keyword(s):  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Cold Wire ◽  
Metal Arc Welding
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