Search

Your search keyword '"大野, 宗一"' showing total 55 results
Start Over Author "大野, 宗一"
55 results on '"大野, 宗一"'

11. Solidification and Segregation in Continuously Cast Steel

Author

鈴木, 亮輔, 松浦, 清隆, 岩井, 一彦, 大野, 宗一, 大参, 達也, 藤村, 俊生, 鈴木, 亮輔, 松浦, 清隆, 岩井, 一彦, 大野, 宗一, 大参, 達也, and 藤村, 俊生

Abstract

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

Published
2018

18. Development and Characterization of Al-coated Mg Alloy

Author

松浦, 清隆, 中村, 孝, 三浦, 誠司, 大野, 宗一, Pietrzyk, Maciej, 德永, 透子, 松浦, 清隆, 中村, 孝, 三浦, 誠司, 大野, 宗一, Pietrzyk, Maciej, and 德永, 透子

Published
2015

19. Development and Characterization of Al-coated Mg Alloy [an abstract of entire text]

Author

松浦, 清隆, 中村, 孝, 三浦, 誠司, 大野, 宗一, Pietrzyk, Maciej, 德永, 透子, 松浦, 清隆, 中村, 孝, 三浦, 誠司, 大野, 宗一, Pietrzyk, Maciej, and 德永, 透子

Abstract

この博士論文全文の閲覧方法については、以下のサイトをご参照ください。, https://www.lib.hokudai.ac.jp/dissertations/copy-guides

Published
2015

23. Research on abnormal grain growth in reversely transformed austenite structure

Author

松浦, 清隆, 佐々木, 克彦, 三浦, 誠司, 大野, 宗一, 張, 献光, 松浦, 清隆, 佐々木, 克彦, 三浦, 誠司, 大野, 宗一, and 張, 献光

Abstract

Control of austenite grain structure is of great importance in heat treatment process, because the prior austenite grain structure entirely affects the size and morphology of the final microstructure, and thus to largely determine the final mechanical properties of steels. The present study mainly focuses on the abnormal grain growth (AGG) of reversely transformed austenite in 0.2 mass% carbon steel and attempts to control it. The AGG of austenite which leads to extraordinary coarse austenite grains and bimodal grain size distributions degrades final mechanical properties of steels, because an initial variation in prior austenite grain size can result in a coarse and inhomogeneous final grain structures. Hence, AGG in austenite grain structure during the heat treatment processes is very harmful, which is quite worth to be investigated.AGG has been extensively investigated because of both its technological relevance in the steel industry and scientific interest. In spite of the considerable research effort, there are still some important issues that remain to be resolved. For example, it is unclear whether the initial microstructure of steel, such as ferrite/pearlite (F/P) banded and non-banded structure affect the austenite abnormal grain coarsening or not. Since the banded structure with a great inhomogeneity in alloy elements distribution, it may have a great effect on the austenite abnormal grain coarsening behavior. On the other hand, it is unclear how to control the AGG of austenite during the heat treatment process. Therefore, the purpose of the present study is to investigate the abnormal grain coarsening behavior of reversely transformed austenite and attempts to control it.The contents of this thesis are described as follows. In Chapter 1, the research background is illustrated. By describing some steel manufacturing processes, the importance of refinement of austenite grains during reheating is emphasized. Moreover, it is explained that the occurrence of A

Published
2014

25. 核融合用のBCC型高エントロピー合金に関する研究

Author

ZONG, Yun, 橋本, 直幸, 三浦, 誠司, 大野, 宗一, and 礒部, 繁人

Abstract

Nowadays, more and more researchers have paid attention to nuclear power because of its high production efficiency. With a performance target for the next 20 years, scientists start to work on controlling nuclear fusion to make a fusion reactor since the releasing energy of fusion is several times the amount produced from fission. As the important part of fusion reactor ITER, diverter, the materials designed for it require special properties that could survive at high temperatures, high corrosion, and high irradiation environment. After a few years of development, Carbon-fiber composite (CFC) and tungsten have become the candidate materials for the ITER divertor, but both kinds of materials have disadvantages. Considering this, high-entropy alloys with Ti, Zr, Hf, Ta, V, Nb, W, and Cr may be a good candidate which can replace pure tungsten in the future. In this research, MoNbTaTi, MoNbTaW, MoNbTaTiW, HfNbTaTiZr and HfNbTaTiV high-entropy alloy was investigated with a special focus on the irradiation hardening and microstructure.First of all, we developed body-centered cubic refractory high-entropy alloys, MoNbTaTi, MoNbTaW, and MoNbTaTiW, and explored their microstructure, and mechanical properties in order to develop a new high-irradiation resistance material suitable for fusion reactor components. Three HEAs were annealed at 1200°C for 48 hours to form single face BCC alloys, while MoNbTaW was also annealed at 1500°C. SEM inspection and EDS mapping have both validated this result. The Vickers hardness of three HEAs was investigated, and the stable results indicate that they are all stable at elevated temperatures. Three HEAs are ion irradiated with 6.4 MeV Fe3+ at a temperature of 500°C, and the irradiation hardening is examined using nanoindentation. In comparison to pure tungsten, the three HEAs exhibit increased resistance to irradiation.Secondly, based on Senkov alloy, which has been identified as BCC alloys with good ductility, this work developed the HfNbTaTiV, and explored its microstructure, and mechanical properties to make a comparison between F82H and Senkov alloy (HfNbTaTiZr). The phase diagram of HfNbTaTiV indicates that this alloy is stable with a single BCC matrix the temperature above 800°C. The mechanicapropertiesed including Vickers hardness and the tensile property has been conducted to HfNbTaTiV, Senkov alloy, and F82H. The results indicate that HfNbTaTiV has higher Vickers hardness than Senkov alloy, and the yield stress and tensile strength of HfNbTaTiV are larger than that of Senkov alloy and F82H, while elongation was found to be larger in the order of HfNbTaTiV, Senkov alloy, and F82H. Three HEAs are ion irradiated with 6.4 MeV Fe3+ at a temperature of 300°C, the irradiation hardening of Senkov alloy is larger than that of HfNbTaTiV and F82H. However, the TEM observation represents different results and the possibilities of this phenomenon will be discussed in this work, (主査) 教授 橋本 直幸, 教授 三浦 誠司, 教授 大野 宗一, 准教授 礒部 繁人, 工学院（材料科学専攻）

Published
2023

30. 高熱伝導率を有するF82H複合材料の開発

Author

Heo, Jeongwoo, 橋本, 直幸, 三浦, 誠司, 大野, 宗一, and 礒部, 繁人

Abstract

(主査) 教授 橋本 直幸, 教授 三浦 誠司, 教授 大野 宗一, 准教授 礒部 繁人, 工学院（材料科学専攻）

Published
2022

31. Al-Si合金を用いた高温潜熱蓄熱に関する研究 [全文の要約]

Author

能村, 貴宏, 大野, 宗一, 林, 重成, and 渡辺, 精一

Abstract

この博士論文全文の閲覧方法については、以下のサイトをご参照ください。, https://www.lib.hokudai.ac.jp/dissertations/copy-guides/, (主査) 准教授 能村 貴宏, 教授 大野 宗一, 教授 林 重成, 教授 渡辺 精一, 工学院（材料科学専攻）

Published
2022

41. 鋼の連続鋳造における凝固と偏析に関する研究

Author

鈴木, 亮輔, 松浦, 清隆, 岩井, 一彦, 大野, 宗一, and 大参, 達也

Abstract

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）

Published
2019

49. Mg/Alクラッド材の開発および特性調査に関する研究

Author

松浦, 清隆, 中村, 孝, 三浦, 誠司, 大野, 宗一, and Pietrzyk, Maciej

Abstract

(主査) 教授 松浦 清隆, 教授 中村 孝, 教授 三浦 誠司, 准教授 大野 宗一, 教授 Maciej Pietrzyk （AGH科学技術大学）, 工学院（材料科学専攻）

Published
2015

Catalog

Books, media, physical & digital resources
See catalog results