Doctoral Dissertations

Keywords and Phrases

Nonmetallic inclusions; Steelmaking

Abstract

"The evolution of oxide inclusion size distribution and the shape of the distribution during steelmaking and casting and the process variables that influence the inclusion characteristics at different stages were investigated and documented. A statistical method for transforming the 2D size distribution to their actual 3D distributions and the application of a kinetic model to determine nucleation and growth mechanisms were tested. Finally, laboratory experiments were performed to study the effects of preexisting inclusions, steel active oxygen content, and supersaturation on the size and morphology of Al2O3 inclusions.

The inclusion size, composition, and morphology following steel deoxidation were found to depend on the steel conditions during deoxidation, and the method/sequence of deoxidant addition. The oxide size distribution evolved from lognormal to fractal and the distribution shape was quadratic or linear on a log-log plot. The distribution shape was preserved on both 2D and 3D analysis and used to identify new and aged inclusion populations. The Schwartz-Saltykov method for converting 2D data to 3D was found to be inadequate and the applied kinetic model could not explain certain observed trends. Finally, results from the laboratory study showed the oxide inclusion transformations from preexisting FeO and MnO'SiO2 inclusions to Al2O3 following Al-deoxidation. The reaction of Al with FeO was relatively fast compared to the sluggish reaction with MnO'SiO2. Al2O3 dendrites and clusters were observed after Al-deoxidation. The clusters consisted of spheres and dendrites and three possible sources of cluster formation were identified. The size of the spherical Al2O3 were larger with increased FeO size and results showed that increasing supersaturation had the strongest influence on the length of the dendrite"--Abstract, page iv.

Advisor(s)

O'Malley, Ronald J.

Committee Member(s)

Bartlett, Laura
Xu, Mingzhi
Smith, Jeffrey D.
Abraham, Sunday

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Metallurgical Engineering

Research Center/Lab(s)

Peaslee Steel Manufacturing Research Center

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2019

Journal article titles appearing in thesis/dissertation

  • Factors affecting the evolution of inclusion populations during steelmaking and casting processes
  • Three-dimensional study of inclusion morphology and size distribution in Mn-Si killed steel
  • Size distribution of inclusions in aluminum killed calcium treated steel during steelmaking, casting, and hotrolling
  • Effect of pre-existing inclusions on the size and morphology of Al2O3 inclusions-Part 1: Results from two-stage and fixed supersaturation deoxidation
  • Effect of pre-existing inclusions on the size and morphology of Al2O3 inclusions-Part 2: Single stage deoxidation with varying levels of supersaturation

Pagination

xv, 132 pages

Note about bibliography

Includes bibliographic references.

Rights

© 2019 Obinna Menyelum Adaba, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 11581

Electronic OCLC #

1119723901

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Included in

Metallurgy Commons

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