**4. Conclusions**

In this paper, the behavior characteristics of S-GMAW weld pool were studied, and the differences of the pool behavior and weld microstructure were compared under different waveforms. The conclusions are as follows:

(1) In short-circuit period, the duration of destabilization and break-up of the liquid bridge is mainly related to the surface tension of the liquid metal, not the loop current. However, the rise rate of the loop current can effectively shorten the stability time of the liquid bridge and promote the

formation of the neck of the short-circuit liquid bridge. The liquid bridge explosion is related to the instantaneous power density of liquid bridge metal.


**Author Contributions:** Methodology, T.C.; Software, T.C.; Investigation, T.C., P.Z., Writing—Original Draft Preparation, T.C.; Writing—Review and Editing, S.X., T.C., B.W.; Supervision, S.X.; Project Administration, S.X., W.L.; Funding Acquisition, S.X.

**Funding:** This work was funded by the National Natural Science Foundation of China, grant No.51675269 and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).

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