Arc interruption phenomena and internal causes in narrow gap P-GMAW
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RESEARCH PAPER
Arc interruption phenomena and internal causes in narrow gap P-GMAW Wenji Liu 1
&
Zongbiao Jia 1 & Jianfeng Yue 1 & Haihua Liu 1 & Liangyu Li 1
Received: 7 April 2020 / Accepted: 3 July 2020 # International Institute of Welding 2020
Abstract Among the factors that influence welding defects, arc interruption is an important and unavoidable problem. When the welding torch swings during narrow gap pulsed gas metal arc welding (P-GMAW), arc interruption phenomenon always occurs at the same position along the torch trajectory and is therefore governed by some concrete conditions. Prior to arc interruption, the arc exhibits a distinct shape and the voltage signals fluctuate significantly. Internal causes of the distinct arc shape were investigated, and it was found that narrowness of the gap played an important role. As the metal vapor is easily ionized, the arc rises along with the rising vapor plume, expanding beyond the end of the wire and forming an approximately parabolic shape. The effect of narrow grooves on the droplets and weld beads, especially when the torch deviates from the groove center, will be beneficial for the generation and collection of metal vapor. Since the arc will always be prolonged prior to interruption and the voltage will fluctuate, the arc interruption of this kind can be predicted and eliminated, thus improving the welding quality of narrow gap. Keywords P-GMAW . Arc interruption . Narrow gap welding . Arc behavior
1 Introduction Narrow gap welding is preferred for manufacturing of thick plates because it can improve the welding efficiency while reducing the welding heat input and thermal deformation. Sidewall fusion difficulty is the key challenge of this technology, which contributes greatly to the welding defects. To improve the qualification rate of narrow gap welding, related technologies have been widely studied. In terms of narrow gap arc sensing, Li et al. [3] used support vector machine methods to predict torch deviation with the aim of designing better arc sensors to improve seam-tracking accuracy. Moreover, Baek et al. [1] proposed a method for measuring seam width with the arc sensor, which was used in the orbital welding system. In terms of welding arc behavior
Recommended for publication by Study Group 212 - The Physics of Welding * Wenji Liu [email protected] 1
Department of Mechanical Engineering, Tiangong University, Tianjin 300387, China
characteristics, high-speed cameras and signal acquisition systems have been used to study the corresponding arc shape, droplet transition, and arc signals. Liu et al. [4] discovered the “jump sidewall” behavior in the narrow gap P-GMAW process, which shows that narrow grooves have a critical effect on arc behavior. Lan et al. [2] investigated the effects of arc-sidewall distance on arc appearance in narrow gap MAG welding and established the relationship between the arcsidewall distance and arc stability. Zhang et al. [7] reported the arc climbing phenomenon and changes in the droplet transfer path and also revea
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