**4. Conclusions**

To clarify the formation mechanism and evolution of oxide inclusions in Ti-Ca-treated offshore structural steel, industrial sampling was conducted from LF, VD, and TD to final products. Continuous changes and correlations of various inclusions were explained by analysing the number density, morphology, and chemical composition using EPMA and FE-SEM. The primary findings are concluded as follows:


**Author Contributions:** Conceptualization, Z.R. and X.M.; methodology, Z.R., B.Z. and X.M.; software, Z.R.; validation, B.Z., X.M. and G.W.; formal analysis, Z.R.; investigation, Z.R. and X.M.; resources, H.L., P.Z. and F.W.; data curation, H.L., P.Z. and F.W.; writing—original draft preparation, Z.R.; writing—review and editing, Z.R, F.T.; visualization, Z.R.; supervision, X.M.; project administration, B.Z., X.M. and G.W.; funding acquisition, B.Z. and X.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Hebei Iron and Steel Group (HBIS), grant number ICSS2017-02.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** Financial support for this research provided by Hebei Iron and Steel Group (HBIS) is greatly appreciated. The authors also acknowledge the facilities and the scientific and technical assistance of the Australian Microscopy& Microanalysis Research Facility at the Centre of Microscopy and Microanalysis at the University of Queensland.

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