Abstract

Based on the principle of LC resonance, high-frequency sine wave pulse DC TIG welding (HFSWP DC TIG) was developed, and welding experiments were conducted on AISI444 ferritic stainless steel (FSS). The arc characteristics of HFSWP DC TIG and its effect on weld appearance and microstructure were studied theoretically and experimentally. The experimental results show that under the same conditions, compared with constant-current DC conventional arc welding (CAW), the arc pressure and arc thermal efficiency of HFSWP DC TIG are improved, and the weld penetration of the weld is increased by nearly two times. The weld microstructure is single-phase ferrite, and carbonitride, Laves phase, and phase are formed in the joint. In addition, according to the theoretical calculation of the pulse current waveform, the reason why the arc pressure of the high-frequency sine wave pulse current is increased compared with the constant-current DC and high-frequency square wave (triangular wave) pulse current is explained. The mechanism of arc shape and weld appearance change is described from the microscopic point of view, and the reason for the appearance of equiaxed grain in the weld is analyzed. HFSWP DC TIG provides a new idea for the improvement of high-frequency pulse technology.

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