Molten pool behaviour and weld forming mechanism of tandem narrow gap vertical GMAW

Cai, Xiaoyu; Lin, Sanbao; Fan, Chenglei; Yang, Chunli; Zhang, W.; Wang, Y. W.

doi:10.1179/1362171815y.0000000073

Cited by 23 publications

(9 citation statements)

References 6 publications

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“…Therefore, the velocity of the droplet at frame i in the Xand Y-directions can be expressed as Equations (7) and (8), where ∆T is the time interval between the previous frame and the next frame. Moreover, total velocity can be calculated using Equation (9). v i,X = K X i+1,0 − X i,0 ∆T .…”

Section: Extraction Of Droplet Kinematic Characteristicsmentioning

confidence: 99%

“…Under the periodic action of a pulse current, the droplets periodically transit to the molten pool, the speed of which has a great effect on the welding quality. As a result, a better adaptability of all-position welding can be obtained during the pulsed GMAW process [8,9]. Therefore, it is significant to observe and study the metal transfer process of pulsed GMAW.…”

Section: Introductionmentioning

confidence: 99%

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An Image-Processing Method for Extracting Kinematic Characteristics of Droplets during Pulsed GMAW

et al. 2019

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Featured Application: In this paper, the proposed monitoring system and image processing algorithm give a simple and feasible way to investigate kinematic characteristics, which can provide a new method for possible applications in studying mathematic descriptions of droplet flight trajectory and developing a precise automatic welding system. Abstract: Pulsed gas metal arc welding (GMAW) is widely applied in industrial manufacturing. The use of pulsed GMAW was found superior to the traditional direct-current (DC) welding method with respect to spatter, welding performance, and adaptability of all-position welding. These features are closely related to the special pulsed projected metal transfer process. In this paper, a monitoring system based on a high-speed camera and laser backlight is proposed. High-quality images with clear droplets and a translucent arc can be obtained at the same time. Furthermore, a novel image-processing algorithm is proposed in this paper, which was successfully applied to remove the interference of the arc. As a result, the edge and region of droplets were precisely extracted, which is not possible using only the threshold method. Based on the algorithm, centroid coordinates of undetached and detached droplets can be calculated, and more parameters of the kinematic characteristics of droplets can be derived, such as velocity, acceleration, external force, and momentum. The proposed monitoring system and image-processing algorithm give a simple and feasible way to investigate kinematic characteristics, which can provide a new method for possible applications in studying mathematic descriptions of droplet flight trajectory and developing a precise automatic welding system.

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Section: Extraction Of Droplet Kinematic Characteristicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An Image-Processing Method for Extracting Kinematic Characteristics of Droplets during Pulsed GMAW

et al. 2019

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“…The acceleration of the droplets due to the plasma drag force [6], combined with the weakened buffering effect of the weld puddle, made it easier for droplets to reach the bottom boundary of the weld pool, even with substantial redundant momentum. Moreover, because of the heat input before droplet impingement, the solid bottom was heat-softened [22]. Thus, when an accelerated and superheated droplet impinges on a thin fluid layer, it flows downward and crashes against the solid but already-softened bottom; creating a crater.…”

Section: Welding Torch Perpendicular To the Base Metalmentioning

confidence: 99%

Effect of Droplet Impingement on the Weld Profile and Grain Morphology in the Welding of Aluminum Alloys

et al. 2018

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To achieve a better understanding of the effect of droplet impingement on the weld profile and grain morphology, welding with vertical and inclined torches in the double pulsed-gas metal arc welding of aluminum alloy were compared. When using vertical welding, the grains along the wall of the finger-like penetration (FLP) were refined by a more violent flow driven by droplet impingement running in the confined space created by FLP. When using inclined welding, the sharp inflection point disappeared and the curved columnar grains emerged on the non-impact action side, which was attributed to the gradually weakened impingement at that location. Moreover, when the penetration became shallower due to a low mean current, the droplets impinged alternately along split trajectories, causing significant changes in the grain morphology, such as creating grains which were sharply shortened by the direct impact of droplet impingement at impact point. The change of trajectory was ascribed to the variation of the width/depth ratio of FLP, which changed the magnitude of the contradiction between the room required by the fluid flow driven by droplet impingement and the space supplied for that by FLP.

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“…Wei et al [7] developed non-axisymmetric tungsten narrow gap tungsten arc welding, in which the heating of the rotating arc and the stirring action of the molten pool make a good shape weld. Cai et al [8,9] combined the tandem technology to the narrow gap welding; a uniform fusion weld was obtained under appropriate welding parameters. In the above solutions, the motion path of the welding arc is changed mechanically, so the welding arc can heat the side wall directly, and the side wall penetration is increased significantly.…”

Section: Introductionmentioning

confidence: 99%

Influence of the Longitudinal Magnetic Field on the Formation of the Bead in Narrow Gap Gas Tungsten Arc Welding

Jian

2020

Metals

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The oscillation arc assisted by an extra alternating longitudinal magnetic field (LMF) in narrow gap tungsten arc welding is proved to be effective in avoiding welding defects due to insufficient fusion at the side walls in joining thick wall plates. The behavior of the welding arc and molten pool under the LMF is simulated to reveal the influence of the LMF on the formation of a uniform penetration weld bead. A unified mathematical model was developed for the narrow gap tungsten arc welding including the plasma arc, molten pool, electrode, and their interactions. Under the LMF, the whole welding arc is deflected and oscillates between the two side walls. When the magnetic-field strength is larger than 6 mT, the axis of the arc deflects to the side wall; the maximum value of heat flux at the bottom decreases by one-half, and the maximum value at the side wall is increased by a factor of ten. On the other hand, under the LMF, the forces acting on the molten pool are changed; the fluid flow pattern is helpful to increase the heat transferred to the side walls. The model is validated by experimental results. Both the percentage deviations of the simulation weld penetration at the side wall and at the bottom from the experimental results are lower than 10%.

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Molten pool behaviour and weld forming mechanism of tandem narrow gap vertical GMAW

Cited by 23 publications

References 6 publications

An Image-Processing Method for Extracting Kinematic Characteristics of Droplets during Pulsed GMAW

An Image-Processing Method for Extracting Kinematic Characteristics of Droplets during Pulsed GMAW

Effect of Droplet Impingement on the Weld Profile and Grain Morphology in the Welding of Aluminum Alloys

Influence of the Longitudinal Magnetic Field on the Formation of the Bead in Narrow Gap Gas Tungsten Arc Welding

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