**4. Conclusions**

In this study, the penetration shape of 9% nickel steel was confirmed by welding power and welding speed, which are the main laser-welding factors. The results of this study can be summarized as follows:

(1) The increase in bead height and bead width of 9% nickel steel was not uniform as the laser power increased. However, the penetration depth of the two materials was highly dependent on the laser power, despite the difference in properties of the two materials. In the case of A553-1, when the welding power increased from 3 to 5 kW, the average penetration depth increased from 4.3 to 5.7 mm, according to Figure 11.


**Author Contributions:** For research articles with several authors, a short paragraph specifying their individual contributions must be provided. The following statements should be used "Conceptualization, J.K. (Jaewoong Kim) and J.K. (Jisun Kim); methodology, J.K. (Jaewoong Kim); software, J.K. (Jisun Kim); validation, J.K. (Jaewoong Kim); formal analysis, S.K.; resources, K.C.; data curation, S.K.; writing—original draft preparation, J.K. (Jaewoong Kim); writing—review and editing, J.K. (Jaewoong Kim); visualization, S.K. and K.C.; project administration, J.K. (Jaewoong Kim); All authors have read and agreed to the published version of the manuscript.

**Funding:** This research has been conducted with the support of the Ministry of Trade, Industry and Energy, Republic of Korea as "Development of small and medium LNG fuel storage module for coastal ship" in the material parts technology development project.

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