近年各項基礎建設對結構用鋼的品質需求日漸提高，焊接厚鋼板所需入熱量的增加造成熱影響區晶粒粗大化，危害鋼材的機械性質。稀土元素鈰擁有優異的脫氧、脫硫能力，藉由在鋼液中添加鈰來控制鋼材中的介在物種類，進而改變鋼材的顯微結構，強化鋼材的機械性質。
本研究針對含鈰SS400鋼進行實驗，利用高溫雷射掃描共軛焦顯微鏡對試片進行熱處理，接著使用光學顯微鏡附設萊卡影像軟體分析沃斯田鐵晶粒尺寸，以探討鈰含量對沃斯田鐵晶粒之影響。接著，研究觀察含鈰介在物種類於高溫下對沃斯田鐵晶界遷移之影響。
實驗結果顯示，隨著鈰含量的增加，沃斯田鐵平均晶粒尺寸逐漸減小，當溫度從1200 oC升溫至1400 oC，鈰含量1476 ppm鋼材之沃斯田鐵晶粒尺寸縮小率由84 %提高至96 %。根據優勢相圖，隨著溫度升高，平衡氧活性及臨界硫活性皆增加，代表Ce2O3比CeO2及Ce2O2S更容易形成。當溫度大於1508 oC便不存在三種含鈰介在物同為優勢相之氧硫條件。被Ce2O2S釘扎的晶界其初始移動速率為9.06×10-2 μm/s，然而其平均移動速率為8.55×10-3 μm/s，證明Ce2O2S介在物擁有限制晶界遷移的作用。

In this study, SS400 steel with cerium was used to study the influence of the cerium content on the austenite grain coarsening at high temperature, using confocal laser scanning microscope for heat treatment of the specimens and optical microscope equipped with Leica application software for analysis of the austenite grain size. Then, the influence of types of cerium inclusions was investigated on the austenite grain boundary migration at high temperature. The results show that as the cerium content increases, the austenite grain size reduces gradually. When temperature increases from 1200 oC to 1400 oC, the austenite grain size of the steel material with 1476 ppm cerium reduces from 84 % to 96 %. The instantaneous velocity of the grain boundary contacted with inclusion at the initial position is 9.06×10-2 μm/s, but the average velocity is 8.55×10-3 μm/s. It proves that Ce2O2S can restrain the moving of grain boundary.

1. A. P. Gordon and D. L. McDowell, "Numerical Simulation of Time-dependent Fracture of Graded Bimaterial Metallic Interfaces." International Journal of Fracture, 2004. 126: pp. 321-344.
2. Y. Sahai and T. Emi, Tundish Technology for Clean Steel Production, World Scientific, 2008.
3. F. Pickering, "Non-metallic Inclusions in Steel," International Metals Reviews, 1978. 23: pp. 200-201.
4. Y. Smith, A. Coldren, and R. Cryderman, "Toward Improved Ductility and Toughness," Climax Molybdenum Company (Japan) Ltd., Tokyo, 1972. 119.
5. 黃文星 and付建勛, "鋼鐵冶煉之二次精煉與氧化物冶金," 合記圖書出版社, 2012.
6. E. M. Levin, C. R. Robbins, H. F. McMurdie, and American Ceramic Society, Phase Diagrams for Ceramists vol. Ⅰ-13: Columbus, Ohio: American Ceramic Society, 1964-2001.
7. S. Ogibayashi, "Advances in Technology of Oxide Metallurgy." Nippon Steel Technical Report, 1994. 61: pp. 70-76.
8. C. S. Smith, "Grains, Phases, and Interfaces: An Interpretation of Microstructure," Transactions of the Metallurgical Society of AIME, 1948. 175: pp. 15-51.
9. K. Huang and R. E. Logé, "Zener Pinning," Reference Module in Materials Science and Materials Engineering, 2016.
10. N. A. Haroun, "Theory of Inclusion Controlled Grain Growth," Journal of Materials Science, 1980. 15: pp. 2816-2822.
11. T. Nishizawa, I. Ohnuma, and K. Ishida, "Examination of the Zener Relationship Between Grain Size and Particle Dispersion," Materials Transactions, JIM, 1997. 38: pp.950-956.
12. P. A. Manohar, M. Ferry, and T. Chandra, "Five Decades of the Zener Equation," ISIJ International, 1998. 38: pp. 913-924.
13. C. H. Wörner and P. M. Hazzledine, "Grain Growth Stagnation by Inclusions or Pores," JOM, 1992. 44: pp. 16-20.
14. A. Kojima, A. Kiyose, R. Uemori, M. Minagawa, M. Hoshino, T. Nakashima, and H. Yasui, "Super High HAZ Toughness Technology with Fine Microstructure Imparted by Fine Particles." Nippon Steel Technical Report, 2004. 90: pp. 2-6.
15. S. Kanazawa, A. Nakashima, K. Okamoto, and K. Kanaya, "Improved Toughness of Weld Fussion Zone by Fine TiN Particles and Development of a Steel for Large Heat Input Welding." Tetsu-to-Hegane, 1975. 11: pp. 2589-2603.
16. S. Mukae, K. Nishio, and M. Katoh, "Solution of TiN and Toughness in Synthetic Weld Heat Affected Zone of Ti and N Bearing Mild Steels." 溶接学会论文集, 1985. 3: pp. 567-574.
17. J. Moon, C. Lee, and S. Uhm, "Coarsensing Kinetics of TiN Particle in a Low Alloyed Steel in Weld HAZ Considering Critical Particle Size." Acta Materialia, 2006. 54: pp. 1053-1061.
18. K. Yamamoto, T. Hasegaw, and J. Takamura, "Effect of Boron on Intra-granular Ferrite Transformation in Ti-Oxide Bearing Steels." ISIJ International, 1996. 36: pp. 80-86.
19. M. Hidesato, U. Ryuji, and F. Masaaki, "The Role of Mn Depletion in Intra-granular Ferrite Transformation in the Heat Affected Zone of Welded Joints with Large Heat Input in Structural Steels." ISIJ International, 1996. 36: pp. 1406-1412.
20. J. Yang, J. Shen, and K. Zhu, "Progress in the Technological Development of Oxide Metallurgy for Manufacturing Steel Plates with Excellet HAZ Toughness." Baosteel Technical Research, 2008. 2: pp. 1-16.
21. J. Yang, K. Zhu, and R. Wang, "Technology for Improving the Toughness of Heat Affected Zones with Strong Deoxidizers." Baosteel Technical Research, 2010. 4: pp. 1-6.
22. K. A. Gschneidner, Jr. "Physical Properties of the Rare Earth Metals." Bulletin of Alloy Phase Diagrams, 1990. 11: pp. 216-223.
23. S. B. Castor and J. B. Hedrick, "Rare Earth Elements." Industrial minerals volume, 7th edition: Society of mining, metallurgy, and exploration, Littleton, Colorado, 2006. pp. 769-792.
24. T. Du, "Physical-chemistry Effect of Rare Earth Elements on Metallic Materials." Acta Metallurgica Sinica, 1997. 33: pp. 69-77.
25. H. Chang, T. Du, and J. Yu, "Study of Thermodynamic Properties in Fe-Sn-Ce Liquid Solution and Action Mechanism of Cerium in 15MnV Steel Containing Tin." Journal of Iron and Steel Research, 1987.
26. F. Guo and L. Qin, "Mechanism of Rare Earth Elements on Impact Toughness of Extra Low Sulfur and Oxygen Structural Alloy Steel." Journal of the Chinese Rare Earth Society, 2008. 26: pp. 97-101.
27. L. Yue, L. Wang, and J. Han, "Effects of Rare Earth on Inclusions and Corrosion Resistance of 10PCuRE Weathering Steel." Journal of Rare Earths, 2010. 28: pp.952-956.
28. Z. Wen, D. Q. Yi, B. Wang, S. Q. Shi, and Y. K. Zhang, "Effect of Rare Earths on the Recrystallization Behavior of T91 Heat-resistant Steel." Journal of University of Science and Technology Beijing, 2013. 35: pp. 1000-1006.
29. S. Song, H. Sun, and M. Wang, "Effect of Rare Earth Cerium on Brittleness of Simulated Welding Heat-affected Zones in a Reactor Pressure Vessel Steel." Journal of Rare Earths, 2015. 33: pp. 1204-1211.
30. N. Yan, S.Yu, and Y.Chen, "In Situ Observation of Austenite Grain Growth and Transformation Temperature in Coarse Grain Heat Affected Zone of Ce-alloyed Weld Metal." Journal of Rare Earths, 2017. 35: pp. 203-210.
31. 方碩彥, "SS400鋼中鋁鈰脫氧脫硫之介在物預測模型與實驗驗證," 成功大學材料科學及工程學系碩士論文, 2017.
32. Y. Q. Liu, L. J. Wang, J. B. Guo, X. J. Hu, and K. C. Chou, "Thermodynamic Analysis of Cerium Inclusion Formed in Spring Steel Used in Fastener of High-speed Railway. " The Chinese Journal of Nonferrous Metals, 2013. 23: pp. 720-726.
33. S. Soeder, A. Kuhlmann, and T. Aigner, "Analysis of Protein Distribution in Cartilage Using Immunofluorescence and Laser Confocal Scanning Microscopy." Methods in Molecular Medicine, 2004. 101: pp. 107-125.