scholarly journals Droplet Transfer Induced Keyhole Fluctuation and Its Influence Regulation on Porosity Rate during Hybrid Laser Arc Welding of Aluminum Alloys

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1510
Author(s):  
Leilei Wang ◽  
Yanqiu Zhao ◽  
Yue Li ◽  
Xiaohong Zhan
Keyword(s):  
Aluminum Alloys ◽  
Weld Pool ◽  
Arc Welding ◽  
High Speed ◽  
Welding Current ◽  
Droplet Transfer ◽  
High Speed Imaging ◽  
Hybrid Laser Arc Welding ◽  
Globular Transfer ◽  
Weld Porosity

Hybrid laser arc welding (HLAW) features advantages such as higher welding speed and gap tolerance as well as smaller welding deformation and heat-affected zone than arc welding. Porosity in hybrid laser arc weld due to keyhole fluctuation tends to be the initial source of crack propagation, which will significantly diminish the weld performance. A high-speed imaging technique was adopted to record and analyze the droplet transfer and keyhole fluctuation behavior during hybrid laser arc welding of aluminum alloys. A heat transfer and fluid flow model of HLAW was established and validated for a perspective of the evolution process of droplet transfer and keyhole fluctuation. The relationship between keyhole fluctuation and weld porosity was also revealed. During the droplet transfer stage, liquid metal on the top surface of the weld pool flows toward the keyhole originated by globular transfer, and the keyhole fluctuates and decreases significantly, which has a higher tendency to form a bubble in the weld pool. The bubble evolves into porosity once trapped in the mush-zone near the trailing edge of the weld pool. Therefore, globular transfer during HLAW is the principal origin of keyhole fluctuation and weld porosity. Welding current has a significant influence on keyhole fluctuation and weld porosity rate. Droplet transfer frequency, keyhole fluctuation, and porosity rate increase with higher welding current under the globular transfer mode. The porosity rate shows a nearly positive correlation with the standard deviation of keyhole fluctuation.

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.

Study on the hybrid laser-arc welding of 3 mm thick high-strength steel with high speed

2018 ◽  
Vol 6 (2) ◽  
pp. 026546 ◽  
Author(s):  
Zhang Peilei ◽  
Gu Siyuan ◽  
Liu Zhengjun ◽  
Yu Zhishui
Keyword(s):  
High Strength Steel ◽  
Arc Welding ◽  
High Speed ◽  
High Strength ◽  
Hybrid Laser Arc Welding

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.

scholarly journals Relationship among Welding Defects with Convection and Material Flow Dynamic Considering Principal Forces in Plasma Arc Welding

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1444
Author(s):  
Huu Loc Nguyen ◽  
Anh Van Nguyen ◽  
Han Le Duy ◽  
Thanh-Hai Nguyen ◽  
Shinichi Tashiro ◽  
...  
Keyword(s):  
Weld Pool ◽  
Material Flow ◽  
Arc Welding ◽  
Welding Current ◽  
Plasma Arc Welding ◽  
Plasma Arc ◽  
Flow Dynamic ◽  
Pool Surface ◽  
Welding Defects ◽  
Marangoni Force

The material flow dynamic and velocity distribution on the melted domain surface play a crucial role on the joint quality and formation of welding defects. In this study, authors investigated the effects of the low and high currents of plasma arc welding on the material flow and thermodynamics of molten pool and its relationship to the welding defects. The high-speed video camera (HSVC) was used to observe the convection of the melted domain and welded-joint appearance. Furthermore, to consider the Marangoni force activation, the temperature on the melted domain was measured by a thermal HSVC. The results revealed that the velocity distribution on the weld pool surface was higher than that inside the molten weld pool. Moreover, in the case of 80 A welding current, the convection speed of molten was faster than that in other cases (120 A and 160 A). The serious undercut and humping could be seen on the top surface (upper side) and unstable weld bead was visualized on the back side (bottom surface). In the case of 160 A welding current, the convection on the weld pool surface was much more complex in comparison with 80 A and 120 A cases. The excessive convex defect at the bottom side and the concave defect at the top surface were observed. In the case of 120 A welding current, two convection patterns with the main flow in the backward direction were seen. Almost no welding defect could be found. The interaction between the shear force and Marangoni force played a solid state on the convection and heat transportation processes in the plasma arc welding process.

Behavior of Exit Keyhole Diameter during Switch off Period in Plasma Keyhole Arc Welding

2018 ◽  
Vol 26 ◽  
pp. 87-92
Author(s):  
Anh Nguyen Van ◽  
Tashiro Shinichi ◽  
Huu Manh Ngo ◽  
Akihisa Murata ◽  
Tadasuke Murata ◽  
...  
Keyword(s):  
Weld Pool ◽  
Arc Welding ◽  
High Speed ◽  
Video Camera ◽  
High Speed Video ◽  
High Speed Video Camera

The purpose of this investigation is to clarify the behavior of exit keyhole diameter during switch off (cutting arc) period in case of Plasma keyhole arc welding (PKAW). During switch off period, the keyhole and weld pool are visualized from backside via a high speed video camera (HSVC). The result showed that keyhole diameter on the backside is unstable. The keyhole size is much changed in X-axis. Firstly, it is increased and then it is decreased to a stationary value at t = 0.05 s after cutting arc. Meanwhile, the size in Y-axis is not changed approximately from t = 0.01 s after cutting arc. The results can be considered to control this process more efficiency.

Transport Phenomena and Their Effect on Weld Quality in GMA Welding of Aluminum Alloys

Volume 3 ◽  
2004 ◽  
Author(s):  
H. Guo ◽  
H. L. Tsai ◽  
P. C. Wang
Keyword(s):  
Aluminum Alloys ◽  
Weld Pool ◽  
Gma Welding ◽  
Gas Metal Arc Welding ◽  
Welding Current ◽  
Weld Penetration ◽  
Three Dimensional Model ◽  
End Effects ◽  
Welding Arc ◽  
Micro Cracks

Gas metal arc welding (GMAW) of aluminum alloys has recently become popular in the auto industry to increase fuel efficiency of a vehicle. In many situations, the weld is short (say, less than two inches) and the “end effects” become very critical in determining the strength of the weld. At the beginning stage of the welding, when the metal is still “cold”, which is frequently called cold weld, limited weld penetration occurs. On the other hand, at the ending stage of the welding, a “crater” is formed involving micro-cracks and micro-pores. Both the cold weld and the crater can significantly decrease the strength of the weld and are more severe for aluminum alloys as compared to steels. Hence, there are strong needs to improve the GMAW process in order to reduce or eliminate the aforementioned end effects. In this paper, both mathematical modeling and experiments have been conducted to study the beginning stage, ending stage, as well as the quasi-steady-state stage of GMA welding of aluminum alloys. In the modeling, a three-dimensional model using the volume-of-fluid (VOF) method is employed to handle the free surfaces associated with the impingement of droplets into the weld pool and the weld pool dynamics. Transient weld pool shapes and the distributions of temperature and velocity in the weld pool are calculated. The predicted solidified weld bead shapes, including weld penetration and/or reinforcement, are in agreement with experimental results for welds in the aforementioned three stages. It was found that the thickness of the molten weld pool is smaller and there is no vortex developed, as compared to steel welding. The lack of penetration in cold weld is due to the lack of pre-heating by the welding arc. Three techniques are proposed and validated numerically to improve weld penetration by increasing the energy input at the beginning stage of the welding. The crater formation is caused by rapid solidification of the weld pool when the welding arc is terminated. By reducing welding current and reversing the welding direction before terminating the arc, the weld pool is maintained “hot” for a longer time allowing melt flow to fill-up the crater. This method is validated experimentally and numerically to be able to eliminate the formation of the crater and the associated micro-cracks.

scholarly journals Full penetration hybrid laser arc welding of up to 28 mm thick S355 plates using electromagnetic weld pool support

2018 ◽  
Vol 1109 ◽  
pp. 012015 ◽  
Author(s):  
Ömer Üstündag ◽  
Vjaceslav Avilov ◽  
Andrey Gumenyuk ◽  
Michael Rethmeier
Keyword(s):  
Weld Pool ◽  
Arc Welding ◽  
Hybrid Laser Arc Welding ◽  
Full Penetration

Study on Metal Transfer and Welding Spatter Characteristics of Basic Flux Cored Wire

2013 ◽  
Vol 477-478 ◽  
pp. 1369-1372 ◽  
Author(s):  
Yong Wang ◽  
Ying Qiao Zhang ◽  
Bao Wang ◽  
Zhi Jun Wang
Keyword(s):  
High Speed ◽  
Short Circuit ◽  
Welding Current ◽  
Metal Transfer ◽  
Welding Parameters ◽  
Droplet Transfer ◽  
Cored Wire ◽  
Basic Flux ◽  
Key Factor ◽  
Slag Column

The metal transfer behaviors of basic flux cored wire at different arc voltage and welding current and the resultant welding spatter were investigated by using a high speed camera. Two modes of metal transfer are found: globular repelled transfer (lower welding parameters) and small droplet transfer (higher welding parameters). The former is accompanied by large granular spatter, large droplet itself explosion spatter and electric explosive spatter of short-circuit, and spatter in the latter is reduced obviously. But if the slag column is found in the two models, spatter could be dropped evidently owing to its significant guiding role for metal transfer. Therefore the slag column is the key factor of reducing welding spatter.

Sign in / Sign up

Export Citation Format

Share Document