Solidification and Segregation in Continuously Cast Steel

• Material Type: 博士論文
• Title: Solidification and Segregation in Continuously Cast Steel
• Author/Editor: 藤村, 俊生
• Author Heading: 藤村, 俊生
• Publication, Distribution, etc.: Hokkaido University
• Publication Date: 2019-03-25
• Publication Date (W3CDTF): 2019-03-25
• Alternative Title: 鋼の連続鋳造における凝固と偏析に関する研究
• Contributor: 鈴木, 亮輔; 松浦, 清隆; 岩井, 一彦; 大野, 宗一; 大参, 達也
• Degree grantor/type: 北海道大学
• Date Granted: 2019-03-25
• Date Granted (W3CDTF): 2019-03-25
• Dissertation Number: 乙第7078号
• Degree Type: 博士(工学)
• Conferring No. (Dissertation): 乙第7078号
• Text Language Code: eng
• NDC: 500
• Target Audience: 一般
• Note (General): In this study, the approximate analytical solutions for the solidus temperature which strongly depends on the steel composition were sought as the part of the solutions of the nonlinear heat- and solutes- transfer equations in the mushy zone of the continuously cast steel. Because the conventional theories of the solidification of the multicomponent steel were not well grounded due to the highly nonlinear phenomenon complicated by the time depending phase change interface. Neither analytic nor approximate solutions existed that describe the relation between the size of the mushy zone (the solid-liquid zone) and the volumetric energy generation. In addition, owing to the lack of the reliable measurements in the real casting process due to the difficulties of measurements, the significant discrepancies exist between the estimates of the solidus temperature and the thermo-analytical measurements by the small specimens of the various grades steel. This may cause the considerable errors in the accuracy of the numerical heat analysis to estimate the shell thickness and the solid fraction at the target point in the mushy zone of the continuously cast steel. The simultaneous solutions of the non-linear heat- and solutes equations were sought step by step through the three model, assuming the linear relation between solid fraction and temperature in the mushy zone. (1) Model Ⅰ: Develop the mathematical treatment to simultaneously solve the heat- and solutes- transfer equations, with the simple boundary conditions (Dirichlet conditions), adopting the measured solidification constants which represent the boundary positions with respect to time. (2) Model Ⅱ: Incorporate the Neumann’s boundary conditions (i.e., equal derivative values at the boundary front and back) which are generally used in the numerical analysis for the solid- liquid zone in the model. The solidification of the Fe-C binary steel was investigated to make the model as simple as possible. The model predictions were in good agreement with the numerical heat analysis and were also consistent with Neumann’s solution at the low carbon range. (3) Model Ⅲ: Obtain the solidus temperature of the multicomponent general steel by expanding the Model Ⅱ to the multicomponent steel. The predicted solidus temperatures of the various grades steel were in reasonable agreement with the measured zero ductility temperature of the high manganese steel and the thermo- analytical measurements. It was also shown that the conventional numerical heat analysis, such as the equivalent specific heat method, adopting the solidus temperature predicted by the model was in good agreement with that of Model Ⅲ. The model can reduce the extensive numerical computational load to seek the solidus temperature. The models and the predicted solidus temperature were, subsequently, used in the numerical heat analyses to estimate the solid fraction at which the electro magnetic stirring was applied in the continuously cast steel ii slabs. The industrial findings with these numerical heat analyses and the analog study with Pb-Sn alloy showed that the stirring at the low fraction solid was important to refine crystals and to improve the macrosegregations, in the continuously cast steel. The methods to transform the partial differential equations to ordinary equations and the boundary conditions adopted in the models were as shown in Table 1.; (主査) 教授 鈴木 亮輔, 特任教授 松浦 清隆, 教授 岩井 一彦, 准教授 大野 宗一, 准教授 大参 達也; 工学院（材料科学専攻）
• DOI: 10.14943/doctoral.r7078; https://doi.org/10.14943/doctoral.r7078
• Persistent ID (NDL): info:ndljp/pid/11479210; https://dl.ndl.go.jp/pid/11479210
• Collection: 障害者向け資料
• Collection (Materials For Handicapped People:1): テキストデータ
• Collection (particular): 国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文; https://dl.ndl.go.jp/collections/A00014
• Acquisition Basis: 博士論文（自動収集）
• Date Accepted (W3CDTF): 2020-04-06T03:04:11+09:00
• Date Created (W3CDTF): 2018-09
• Format (IMT): PDF
• Access Restrictions: 国立国会図書館内限定公開
• Service for the Digitized Contents Transmission Service: 図書館・個人送信対象外
• Availability of remote photoduplication service: 可
• Periodical Title (URI): http://dx.doi.org/10.14943/doctoral.r7078; http://hdl.handle.net/2115/77032
• Is Referenced By (URI): http://hdl.handle.net/2115/74156
• Data Provider (Database): 国立国会図書館 : 国立国会図書館デジタルコレクション; https://dl.ndl.go.jp