Effect of TIG arc characteristics on weld morphology and structure of AISI444 ferritic stainless steel under pulse current

Herein, we theoretically and experimentally examined the effects of current pulse frequency on arc characteristics, weld appearance, and weld microstructure of AISI444 ferritic stainless steel (FSS) welded by tungsten inert gas (TIG). The arc shape, pressure, and density distribution of TIG welding were measured using a high-speed camera and the sensor measurement and keyhole probe methods. Moreover, the arc characteristics, weld appearance, and weld microstructure under 0- to 500-Hz current pulse frequency were examined. The results show that the arc shape gradually compresses with increasing pulse frequency. When the pulse frequency is 500 Hz, the compression effect is the most obvious, the arc pressure and arc density are the largest, the weld penetration depth is the largest, and the melting width is the smallest. When the pulse frequency is 300 Hz, the finest equiaxed crystal microstructure is obtained. Furthermore, the mechanism of arc compression, arc pressure increase, weld morphology change, and grain refinement is analyzed.

Automated summary

This study examined the effects of current pulse frequency on TIG welding of AISI444 ferritic stainless steel, finding that as the pulse frequency increased, the arc shape gradually compressed and the weld penetration depth increased. The finest equiaxed crystal microstructure was obtained at 300 Hz.