Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Relationship Among Welding Defects with Convection and Material Flow Dynamic Considering Principal Forces in Plasma Arc Welding

Version 1 : Received: 29 July 2021 / Approved: 30 July 2021 / Online: 30 July 2021 (12:34:53 CEST)

A peer-reviewed article of this Preprint also exists.

Nguyen, H.L.; Van Nguyen, A.; Duy, H.L.; Nguyen, T.-H.; Tashiro, S.; Tanaka, M. Relationship among Welding Defects with Convection and Material Flow Dynamic Considering Principal Forces in Plasma Arc Welding. Metals 2021, 11, 1444. Nguyen, H.L.; Van Nguyen, A.; Duy, H.L.; Nguyen, T.-H.; Tashiro, S.; Tanaka, M. Relationship among Welding Defects with Convection and Material Flow Dynamic Considering Principal Forces in Plasma Arc Welding. Metals 2021, 11, 1444.

Journal reference: Metals 2021, 11, 1444
DOI: 10.3390/met11091444

Abstract

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 surface was higher than that inside the molten weld pool due to the difference of the massive density between the air and the steel. Moreover, in the case of low welding current (80A) the convection speed of molten was faster than that of the high welding current case (160A) owing to the difference of main driving forces direction and strength, which leading to undercut and humping defects on the weld surface and excessive convex (burn-through) defect at the bottom weld side, respectively. The medium welding current (120A) had two convection patterns with the main flow in backward direction, which resulted in better welding quality without defect. 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.

Keywords

Plasma arc welding; thermodynamic; material flow; velocity distribution; welding current, Marangoni force; Shear force

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