**4. Conclusions**

This study proposed a novel plasma arc welding process, named pulsed plasma gas variable polarity plasma arc welding process, and investigated the effect of pulsed plasma gas on the arc electrical signal, arc profile, and welding formation. The results can be summarized as follows:


**Author Contributions:** Z.L., S.C., and F.J. contributed to the project design; W.Z. and Z.Y. performed all experiments and data processing; F.J. wrote this manuscript; all authors participated in the discussion on the results and guided the writing of the article.

**Funding:** This work is Supported by National Natural Science Foundation of China (No.51875004), Beijing Natural Science Foundation (No.3172004), the China Scholarship Council (CSC) for one-year study in University of Alberta for Fan Jiang, International Research Cooperation Seed Fund of Beijing University of Technology (No.2018B16), the open project of Beijing Engineering Researching Center of Laser Technology (BG0046-2018-09) and start-up funding from Beijing University of Technology.

**Conflicts of Interest:** The authors declare no conflict of interest.
