Study on Arc Characteristic of Flux-Cored Wire Pulse TIG Arc Additive Manufacturing
ZHAO Xiao-yan1, YANG Li-jun2*, HUANG Yi-ming1,2*, HUANG Shi-cheng1, LI Wang1
1. School of Materials Science and Engineering，Tianjin University，Tianjin 300350，China
2. Tianjin Key Laboratory of Advanced Joining Technology，Tianjin University，Tianjin 300350，China
Abstract：The arc characteristic of flux-cored wire pulsed TIG arc additive manufacturing was studied. The images of arc and droplet transition under different pulsed current were taken using high speed camera. High-speed camera images were analyzed. The results showed that the lagging melt phenomena in the wire melting process resulted in two contacting transition modes: slag bridge transition and liquid bridge transition, in addition, under the current parameters of 50/100 A, the frequency of slag bridge transition with intermittent droplets is the highest. Droplet transfer modes affected the arc temperature field and the distribution of flux composition in the arc. The characteristics of flux-cored wire pulsed TIG arc additive manufacturing were studied by spectral diagnosis, and the distribution of the arc temperature field under the conditions of different pulsed peak current and pulsed base current during additive manufacturing was analyzed. The spectral data of each point was measured by the lattice method, the temperature of each point was calculated according to the Boltzmann diagram method, finally the temperature of each point was fitted to obtain a complete arc temperature field. The result showed that the arc was disturbed and arc heat was absorbed by wire when the wire was fed from the front (left) side of the tungsten electrode axis. The temperature on the front side of the arc is lower than the back (right) side of the arc, and the size of the front side of the arc is slightly smaller than the back side. As the number of additive layers increased, the peak current was reduced, the arc shrunk. Also the proportion of the high- temperature region was relatively reduced, the proportion of low-temperature region is relatively enlarged. The highest temperature region of the arc appeared in the range of 1~2 mm below the tungsten electrode, which is about 13 000~15 000 K. The larger the pulse peak current, the larger the proportion of the highest temperature region. Due to the small current, the arc size was much smaller than the peak period in the pulse base current period, the interaction between the wire and the arc weakened, and the arc temperature field was basically symmetrical about the tungsten axis. The Na Ⅰ 589.5 nm spectrum line of the unique Na element in the basic flux-cored wire was selected to mark its distribution points, and the distribution of flux composition in the arc under different pulse peak currents and base currents was drawn by fitting. The results showed that the smaller the current, the lower the movement height of the powder. The flux composition was not contaminated on the tungsten electrode under different pulse peak currents, and the Na element was distributed in the back of the arc under different pulse peak currents and pulse base current. It showed that after the wire was fed into the molten pool from the front side of the arc, there was no strong spraying phenomenon of flux composition in the arc but it entered the molten pool for metallurgical reaction. The contact transition solves the problem of poor manufacturability of the flux-cored wire, the arc was relatively stable, and the tungsten electrode was prevented from being damaged by the spraying flux composition, the deposition process was stable.
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