Doctoral Dissertations

Keywords and Phrases

Continuous casting; Low-Carbon steel; Reheating furnace; Scale formation; Scale morphology; Water jet descaling

Abstract

In modern steelmaking, cast slabs are exposed to high-temperature oxidizing environments during secondary cooling, reheating, and hot rolling, resulting in the formation of multilayer oxide scales on the steel surface. These scales interact with mold-flux residues originating from the casting process (CC). The morphology, chemistry, and adhesion of oxide scale strongly influence its removability during high-pressure hydraulic descaling and ultimately determine the surface quality of hot-rolled products. However, the mechanistic relationship between oxide scale evolution, scale-steel interfacial structure, and hydraulic descaling performance remains poorly understood.

This dissertation investigates oxide scale formation, modification, and removal in low-carbon thin-slab steels produced by the CC process. A laboratory methodology was developed to simulate reheating oxidation followed by controlled high-pressure water-jet descaling. Two industrial steels with different alloy compositions were examined under atmospheres representing conventional reheating conditions and hydrogen-rich environments. The influence of mold-flux residues was evaluated using representative flux compositions applied to different surface conditions. Oxide scale morphology, thickness, and interfacial structures were characterized using SEM/EDX and image-based analysis, supported by thermodynamic modeling of flux–oxide reactions.

Results show that optimal descaling was achieved using flat-jet nozzles with a lead angle of ~15° and impact pressures between 3000 and 4000 psi. Alloying elements and mold-flux residues significantly modified oxide scale structure and adhesion through flux–oxide reactions and partial liquid-phase formation during reheating.

Advisor(s)

Buchely, Mario F.

Committee Member(s)

Wen, Haiming
Osei, Richard
O'Malley, Ronald J.
Lekakh, S. N. (Semen Naumovich)

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Winter 2026

Journal article titles appearing in thesis/dissertation

Paper I, found on pages 33-48, has been published in the proceedings of the 2023 AISTech-Iron and Steel Technology Conference Proceedings.

Paper II, found on pages 49-86, has been published in the Journal of Steel Research International.

Paper III, found on pages 87-106, has been published in the proceedings of the AISTech 2024 Iron and Steel Technology Conference, 981-991.

Paper IV, found on pages 107-151, has been published in the Journal of Materials Science.

Paper V, found on pages 152-195, has been submitted to the Journal of Metallurgical and Materials Transactions B.

Paper VI, found on pages 196-235, is intended for submission to the journal of High Temperature Corrosion of Materials.

Pagination

xxvi, 255 pages

Note about bibliography

Includes_bibliographical_references_(pages 240-244)

Rights

© 2026 Tochukwu Princewill Ojiako, All Rights Reserved

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 12603

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