Three-dimensional numerical model of short-circuiting transfer in GMAW
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RESEARCH PAPER
Three-dimensional numerical model of short-circuiting transfer in GMAW K. Hashimoto 1 & Y. Hirata 1 & K. Kadota 1 & Y. Ogino 1 Received: 30 April 2020 / Accepted: 13 August 2020 # International Institute of Welding 2020
Abstract Spatter generation is considered to be a practical problem in the industrial short-circuiting transfer process of gas metal arc welding. Extensive experimental research has been conducted, and some novel approaches have been developed to mitigate splatter generation. In this study, a three-dimensional numerical model of the short-circuiting transfer process was constructed, and the behavior of the liquid bridge was analyzed. The accuracy of the model was verified by comparing the calculation results with the results of an experiment on a water bridge. When short-circuiting transfer was performed with an inclined electrode wire, the liquid bridge was deformed in a manner similar to the deformation of an arch, and it subsequently broke up. Thereafter, the bridge droplet detached as a spatter from the wire tip. This behavior was caused by the difference in the magnetic flux density between the two sides of the liquid bridge. The balance between the surface tension and the electromagnetic force is important for the spatter generation. The inclination angle of the electrode wire, the short-circuiting current, and the surface tension of the molten metal are the most important factors that influence spatter generation. Keywords Gas metal arc welding . Short-circuiting transfer . Numerical simulation . Spatter generation . Electromagnetic force . Surface tension
1 Introduction In gas metal arc welding (GMAW), metal transfer occurs along with the melting of the electrode wire due to the arc heat. The mode of the metal transfer, which is closely related to the size and/or the shape of the molten droplet, is the primary factor that controls the features and stability of the welding arc plasma. In lower-voltage conditions, the arc length decreases. Then, the droplet contacts the weld pool and simultaneously generates an electrical short circuit. This short-circuiting transfer is suitable for the welding of a thin plate and/or position welding owing to the possibility of low-heat input welding. However, this method involves practical problems such as spatter generation and an unstable welding arc. Reducing the spattering 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
leads to improved weld quality and productivity. To mitigate spattering in short-circuiting transfer, several experimental studies have been conducted [1, 2], and various GMAW processes, such as cold metal transfer (CMT) [3–6], controlled short-circuiting (CSC) [7, 8], surface tension transfer (STT) [9], and controlled bridge transfer (CBT) [10, 11] have been developed. These processes can remarkably mitigate spattering by controlling various factors, such as the curren
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