Analysis of droplet explosion in pulsed GMAW with high strength austenitic filler wire

The droplet transfer behavior of the high strength nickel-chromium austenitic filler wires with different carbon and nitrogen content were investigated using high-speed photography technology to reveal the droplet explosion phenomenon in pulsed gas metal arc welding process. The results show that the explosion of the droplets was closely related to the nitrogen content in the wires, but has no corresponding relationship with the carbon content. The higher the nitrogen content in the wire, the more serious the droplet explosion. It was also found that the transfer efficiency of nitrogen in deposited metal was reduced with the increase of the content in the wires. The degree of nitrogen loss was consistent with the degree of droplet explosion. Calculations showed that the solubility of nitrogen in liquid droplet decreased with the increase of temperature. The direct cause of the droplet explosion is that the solid solution nitrogen in the droplet was supersaturated instantaneously and the gas quickly escaped due to the intense high temperature of the arc during the peak current period. The nitrogen content in the austenitic filler wire should be limited to less than 0.22% to avoid droplet explosion.