Study on arc characteristics under high-frequency sine wave pulse current and effect of weld appearance and microstructure of AISI444 ferritic stainless steel

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 $\sigma$ 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.

Keywords:

• HFSWP DC TIG welding
• ferritic stainless steel
• arc characteristics
• weld appearance
• microstructures

Authors contributions

All co-authors participated in the writing or guidance of the paper and played an important role.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The datasets used or analyzed during the current study are available from the corresponding author on reasonable request.

Additional information

Funding

The present research work was financially supported by the Shenyang Collaborative Innovation Center Project for Multiple Energy Fields Composite Processing of Special Materials (Grant No. JG210027), Shenyang Key Technology Special Project of ‘The Open Competition Mechanism to Select the Best Solution’ (Grant Nos. 2022210101000827 and 2022-0-43-048), Shenyang Key Lab of High-tech Welding Power Source and Equipment (Grant No. S220058), and the National Natural Science Foundation of China (Grant No. 52175428).