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Dissertation
Crystallization and related phenomena in continuous casting mold powders
Doctor of Philosophy (Ph.D.), Drexel University
1992
DOI:
https://doi.org/10.17918/00008624
Abstract
Crystallization in mold powders has been associated with operational problems such as breakouts as well as defects in the cast product and it is necessary to control crystallization. However, factors influencing crystallization have not been clearly identified. A series of experimental powders were prepared with different levels of the lime to silica ratio, BaO, Li₂O and were evaluated in terms of crystallization temperature, crystallization tendency and fusion temperature. It was observed that powder chemistry influences fusion and crystallization temperature and that the addition of BaO facilitates glass formation. The laboratory studies were followed by plant study, on the casting of stainless steels, involving the pickup of TiO₂ by mold slag. It was seen that the TiO₂ content increases during casting, accompanied by decreasing SiO₂ content. The TiO₂ pickup was proportional to the Ti content in the melt. The crystallization temperature was found to decrease with increasing levels of TiO₂. A chemical parameter called "Depolymerization Index" (DI) was developed to account for the contributions from different oxide species to crystallization and defined as the ratio of total moles of oxygen in the various oxide species (in slag) to the total moles of network formers (in slag). Increasing values of DI distort the silicate chain and facilitate crystallization. It is proposed that the DI parameter be used as a design criterion. The compositional changes in mold slag due to pickup of Al₂O₃ and TiO₂ have been discussed in terms of the DI parameter. The model/analysis was then applied to some results from the casters to determine the applicability of DI parameter to real casting conditions.
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Details
- Title
- Crystallization and related phenomena in continuous casting mold powders
- Creators
- Sankararaman Sankaranarayanan
- Contributors
- Diran Apelian (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xvi, 169 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Materials (Science and) Engineering (Metallurgical Engineering) [Historical]; College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991021888817604721