Visualization of arc plasma and molten wire behavior in CO 2 arc welding process by three-dimensional numerical simulati
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RESEARCH PAPER
Visualization of arc plasma and molten wire behavior in CO2 arc welding process by three-dimensional numerical simulation Y. Ogino 1
&
S. Asai 1 & Y. Hirata 1
Received: 17 April 2020 / Accepted: 6 July 2020 # International Institute of Welding 2020
Abstract In the CO2 welding process, a consumable wire electrode is used and metal transfer phenomena are involved. However, when the arc current is high, the molten wire behavior becomes unstable, and it leads to a large degree of spattering. In this study, a threedimensional unified model comprising both the arc plasma and the molten wire was constructed, and the behavior of them was visualized using numerical simulations. The transfer mode is regarded as globular transfer in the numerical simulation with an arc current of 300 A. In addition, when the molten metal droplet becomes asymmetrical, the molten wire is pushed up by the arc plasma, and the transfer mode becomes repelled transfer. The temperature distribution and the metal vapor concentration distributions in the symmetrical and asymmetrical cases are significantly different. When the droplet shape is close to symmetrical, the metal vapor concentrates at the center of the arc plasma and the overall temperature of the arc plasma decreases. In contrast, when the droplet shape is asymmetrical, the high-temperature region and metal vapor region are separated. The numerical results showed that the properties of the arc plasma are significantly changed depending on the molten wire behavior. Keywords Numerical simulation . CO2 welding . Repelled transfer . Arc plasma . Metal vapor
1 Introduction The gas metal arc welding (GMAW) process is a highly productive welding process, and it is indispensable in various fields of industry. In the GMAW process, a consumable wire electrode melts, and molten metal droplets are transferred from the wire tip to the base metal. This phenomenon is called metal transfer, and its characteristics are closely related to the quality and stability of the overall process. Despite the need to control metal transfer phenomena, they are very complicated, not understood completely, and involve many different transfer modes [1]. The transfer mode strongly depends on the welding conditions, such as the arc current and voltage and the diameter of the wire electrode [2–6]. Especially at high currents, the behavior of the droplet becomes unstable. For Recommended for publication by Study Group 212 - The Physics of Welding * Y. Ogino [email protected] 1
Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka, Japan
example, in high-current metal inert gas welding, a rotating transfer in which the molten wire elongates and swings appears. In high-current CO2 welding, a repelled transfer, in which the molten wire is pushed up by the arc plasma, appears. In these unstable transfer modes, a large degree of spattering occurs. Then, in actual industrial practice, the welding parameters are limited because of the unstable droplet behavior. To control t
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