Masters Theses

Keywords and Phrases

Cathodoluminescence; Continuous Casting; Crystallization; Cuspidine; Mold Flux; TTT Diagram

Abstract

"Mold flux plays a small but critical role in the continuous casting of steel. The carbon-coated powder is added at the top of the water-cooled copper mold, over time it melts and infiltrates the gap between the copper mold and the solidifying steel strand. Mold powders serve five primary functions: (1) chemical insulation, (2) thermal insulation, (3)lubrication between the steel strand and mold, (4) absorption of inclusions, and (5)promotion of even heat flux. All five functions are critical to slab casting, but surface defect prevention is primarily controlled through even heat flux. Glassy fluxes have high heat transfer and result in a thicker steel shell. Steels with large volumetric shrinkage on cooling must have a crystalline flux to reduce the radiative heat transfer and avoid the formation of cracks in the shell. Crystallinity plays a critical role in steel shell formation, therefore it is important to study the thermal conditions that promote each phase and its morphology.

Laboratory tests were performed to generate continuous cooling transformation(CCT) and time-temperature-transformation (TTT) diagrams. Continuous cooling transformation tests were performed in an instrumented eight cell step chill mold. Results showed that cuspidine was the only phase formed in conventional fluxes and all observed structures were dendritic. An isothermal tin bath quench method was also developed to isothermally age glassy samples. Isothermal tests yielded different microstructures and different phases than those observed by continuous cooling. Comparison of aged tests with industrial flux films indicates similar faceted structures along the mold wall, suggesting that mold flux first solidifies as a glass along the mold wall, but the elevated temperature devitrifies the glassy structure forming crystals that cannot form by continuous cooling"--Abstract, page iv.

Advisor(s)

O'Malley, Ronald J.
Smith, Jeffrey D.

Committee Member(s)

Brow, Richard K.

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Materials Science and Engineering

Sponsor(s)

Kent D. Peaslee Steel Manufacturing Research Center

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2017

Journal article titles appearing in thesis/dissertation

  • Application of cathodoluminescence in analyzing mold flux films
  • Investigation of mold flux crystallization by rapid quenching and isothermal aging in molten tin

Pagination

xii, 120 pages

Note about bibliography

Includes bibliographic references.

Rights

© 2017 Elizabeth Irene Peterson

Document Type

Thesis - Open Access

File Type

text

Language

English

Thesis Number

T 11112

Electronic OCLC #

992440406

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