scholarly journals Influence of Pilot Gas Composition on Convective Pattern of Weld Pool Surface in Plasma Keyhole Arc Welding

2017 ◽  
Vol 35 (2) ◽  
pp. 98s-102s ◽  
Author(s):  
Van Anh Nguyen ◽  
Shinichi Tashiro ◽  
Bui Van Hanh ◽  
Manabu Tanaka
Keyword(s):  
Weld Pool ◽  
Arc Welding ◽  
Gas Composition ◽  
Pool Surface ◽  
Convective Pattern ◽  
Weld Pool Surface

scholarly journals Material Flow Behavior on Weld Pool Surface in Plasma Arc Welding Process Considering Dominant Driving Forces

2020 ◽  
Vol 10 (10) ◽  
pp. 3569 ◽  
Author(s):  
Manh Ngo Huu ◽  
Anh Nguyen Van ◽  
Tuan Nguyen Van ◽  
Dang Tran Hai ◽  
Thanh Nguyen Van ◽  
...  
Keyword(s):  
Weld Pool ◽  
Material Flow ◽  
Arc Welding ◽  
Shear Force ◽  
Driving Forces ◽  
Flow Behavior ◽  
Shielding Gas ◽  
Pool Surface ◽  
Marangoni Force ◽  
Weld Pool Surface

In this study, the effect of oxygen in the shielding gas on the material flow behavior of the weld pool surface was discussed to clarify the dominant driving weld pool force in keyhole plasma arc welding (KPAW). To address this issue, the convection flow on the top surface of weld pool was observed using a high-speed video camera. The temperature distribution on the surface along keyhole wall was measured using the two-color pyrometry method to confirm the Marangoni force activity on the weld pool. The results show that the inclination angle of the keyhole wall (keyhole shape) increased especially near the top surface due to the decrease in the surface tension of weld pool through surface oxidation when a shielding gas of Ar + 0.5% O2 was used. Due to the change in the keyhole shape, the upward and backward shear force compositions created a large inclination angle at the top surface of the keyhole. From the temperature measurement results, the Marangoni force was found to alter the direction when 0.5% O2 was mixed with the shielding gas. The shear force was found to be the strongest force among the four driving forces. The buoyant force and Lorentz force were very weak. The Marangoni force was stronger than the Lorentz force but was weaker than shear force. The interaction of shear force and Marangoni force controlled the behavior and speed of material flow on the weld pool surface. A strong upward and backward flow was observed in the case of mixture shielding gas, whereas a weak upward flow was observed for pure Ar. The heat transportation due to the weld pool convection significantly changed when only a small amount of oxygen was admixed in the shielding gas. The results can be applied to control the penetration ratio in KPAW.

scholarly journals Image Segmentation Approaches for Weld Pool Monitoring during Robotic Arc Welding

2018 ◽  
Vol 8 (12) ◽  
pp. 2445 ◽  
Author(s):  
Zhenzhou Wang ◽  
Cunshan Zhang ◽  
Zhen Pan ◽  
Zihao Wang ◽  
Lina Liu ◽  
...  
Keyword(s):  
Weld Pool ◽  
Arc Welding ◽  
Welding Parameters ◽  
Pool Surface ◽  
Spline Fitting ◽  
Robotic Arc Welding ◽  
Enhancement Method ◽  
Weld Pool Surface ◽  
The Difference ◽  
Occurrence Matrix

There is a strong correlation between the geometry of the weld pool surface and the degree of penetration in arc welding. To measure the geometry of the weld pool surface robustly, many structured light laser line based monitoring systems have been proposed in recent years. The geometry of the specular weld pool could be computed from the reflected laser lines based on different principles. The prerequisite of accurate computation of the weld pool surface is to segment the reflected laser lines robustly and efficiently. To find the most effective segmentation solutions for the images captured with different welding parameters, different image processing algorithms are combined to form eight approaches and these approaches are compared both qualitatively and quantitatively in this paper. In particular, the gradient detection filter, the difference method and the GLCM (grey level co-occurrence matrix) are used to remove the uneven background. The spline fitting enhancement method is used to remove the fuzziness. The slope difference distribution-based threshold selection method is used to segment the laser lines from the background. Both qualitative and quantitative experiments are conducted to evaluate the accuracy and the efficiency of the proposed approaches extensively.

scholarly journals Analysis of Eddy Formation and Heat Transfer Process in Weld Pool during Plasma Keyhole Arc Welding

2020 ◽  
Author(s):  
Nguyen Van Anh ◽  
Ngo Huu Manhh ◽  
Tam Thanh ◽  
Dang Tran ◽  
Hai T. Nguyen
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Heat Transport ◽  
Weld Pool ◽  
Arc Welding ◽  
Shear Force ◽  
Heat Transfer Process ◽  
Pool Surface ◽  
Eddy Formation ◽  
Weld Pool Surface

This investigation aims to discuss the formation process of eddies and the heat transportation in plasma keyhole arc welding. In order to clarify this issue, the measurement of the convection inside the weld pool, the convection on the weld pool surface, also the temperature distribution on the weld pool surface were carried out. The results showed that two eddies were found in the weld pool, which is controlled mainly through the shear force by the plasma flow acting on the weld pool surface. The magnitude, extent and direction of the shear force are thought to be determined primarily by the variation of keyhole profile. The relative shape and strength of each eddy is largely changed depending on the change of the keyhole profile when nozzle diameter changed. These relative strengths of each eddy are considered to decisively govern the heat transport in the weld pool coinciding with the direction of eddies. A larger eddy near the lower part of the keyhole inside the weld pool was found out in the case of 1.6 mm, meanwhile a upward larger eddy was found out near the upper part of the keyhole inside the weld pool in the case of 2.4 mm.

A stereo vision method for tracking particle flow on the weld pool surface

2009 ◽  
Vol 105 (12) ◽  
pp. 123104 ◽  
Author(s):  
C. X. Zhao ◽  
I. M. Richardson ◽  
S. Kenjeres ◽  
C. R. Kleijn ◽  
Z. Saldi
Keyword(s):  
Weld Pool ◽  
Stereo Vision ◽  
Particle Flow ◽  
Pool Surface ◽  
Weld Pool Surface

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.

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