Study on Electromagnetic Force in Arc Plasma With UHFP-GTAW of Ti-6Al-4V

Ti-6Al-4V titanium alloy is processed by ultrahigh-frequency pulsed gas tungsten arc welding (UHFP-GTAW), and the correlation between electromagnetic force and pulsed welding efficacy is studied. A mathematical model is formulated to analyze the macroscopic and internal electromagnetic forces. The axial and radial electromagnetic forces inside the arc plasma are evaluated with arc constriction. Meanwhile, the arc profile is also experimentally observed by a camera system to be the experimental evidence for the pinch effect. Owing to arc constriction during the UHFP-GTAW process, the axial component of the macroscopic electromagnetic force decreases, and the arc area diminishes, reducing the root radius. Therefore, larger axial pressure is found. The radial electromagnetic force inside the arc plasma is the most important factor for arc constriction. In addition, the reduced root radius makes the radial electromagnetic force to get reduced with increased pulsed frequency. The attenuation coefficient of magnetic force could be a key parameter for evaluating strength of the arc constriction. With decreased root radius with the UHFP-GTAW, the axial electromagnetic force inside the arc plasma can be maintained at a high level, which affects surface and mobility of the molten pool. The electromagnetic force is observed to have a close correlation with the root radius of the arc, which depends on the pulsed frequency.