**4. Conclusions**

The e ffects of alloying elements (C and Mo) on the HAC properties of ASTM A516-65 grade steel use, as pressure vessel facilities, were investigated using a range of experimental and analytical methods. The main conclusions are as follows:


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

**Author Contributions:** Conceptualization, J.W.L., J.K.H., and S.J.K.; methodology, J.S.P., J.W.L., and S.J.K.; investigation, J.S.P. and S.J.K.; data curation, J.S.P. and S.J.K.; writing-original draft preparation, J.S.P. and S.J.K.; writing-review and editing; S.J.K.; Supervision. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported in part by the National Research Foundation of Korea (NRF) gran<sup>t</sup> funded by the Korea governmen<sup>t</sup> (MSIT), gran<sup>t</sup> number No. 2019R1C1C1005007. In addition, this work was partly funded and conducted under the Competency Development Program for Industry Specialists of the Korean Ministry of Trade, Industry and Energy (MOTIE), operated by the Korea Institute for Advancement of Technology (KIAT) (No. P0002019, HRD Program for High Value-Added Metallic Materials Expert).
