本研究主要探討不同深冷條件與析出條件下對AISI 630不鏽鋼顯微結構與機械性質之影響，本實驗選用三種深冷條件(無深冷, -50℃持溫1小時, -196℃持溫1小時)搭配四種析出條件(H900:482℃持溫1小時, H925:496℃持溫4小時, H1025:552℃持溫4小時, H1150:620℃持溫4小時)。本實驗材料熱處理程序為：固溶熱處理→深冷處理→析出時效熱處理。
研究結果顯示析出條件H900至H1025之試件中，無論深冷條件，其組織皆已由沃斯田鐵相完全變態為麻田散鐵。析出條件H1150之試件含有微量沃斯田鐵相存在，經深冷處理，可降低逆變態沃斯田鐵之含量。透過金相觀察結果，析出條件H900與H925之試件顯微結構相似，於SEM觀察下，發現經-196℃超深冷處理可細化微細析出物，並使其數量增加，密集且均勻散佈於基地中，使材料硬度有所提升。析出條件H1150之試件中，經深冷處理，含有富銅析出物之肥粒鐵相於基地中所占面積比有下降之趨勢。機械性質方面，深冷處理對630不鏽鋼衝擊能影響不大，而時效熱處理前施以-50℃深冷處理對強度影響不大，-196℃超深冷處理可助於提升630不鏽鋼強度。

In this study, the effect of different sub-zero treatments and aging reactions on microstructure and mechanical properties of AISI 630 stainless steel have been investigated. Three sub-zero conditions (non-sub-zero treatment, -50℃ for 1 hr, -196℃ for 1 hr) and four precipitation conditions (H900 condition: 482℃ for 1 hr, condition H925: 496℃ for 4 hrs, condition H1025: 552℃ for 4 hrs, H1150 condition: 620℃ for 4 hrs). The sub-zero treatment implemented between solid solution and aging heat treatment.
The experimental results show that the structure of the specimens of H900 to H1025 conditions, regardless of the sub-zero conditions, are completely transformation from austenite phase to martensite phase. The specimen of the H1150 condition contains a small amount of austenite phase by the reverse martensitic transformation. After sub-zero treatment, the content of revesred austenite phase has been reduced. The microstructure of H900 and H925 conditions are similar. Observation with SEM, the sub-zero treatment at -196℃ can refines the short rod-like fine precipitate, increases their amount and desity, and results in a more uniform distribution. The spcimen of the H1150 condition had a white lamellar-like structure in the SEM observation, which is the ferrite phase containing Cu-rich precipitates. It was found that the area ratio of ferrite phase in the martensite matrix was decrease after sub-zero treatment. In terms of mechanical properties, the hardness of the specimens subjected to sub-zero treatment has been elevation. In this study, sub-zero treatment has little effect on the impact energy of 630 stainless steel, and the sub-zero treatment at -50 °C before aging heat treatment has little effect on the strength. The sub-zero treatment at -196 °C can help to improve the strength of 630 stainless steel.

[1] M. Durand-Charre, Microstructure of steels and cast irons. Springer Science & Business Media, 2013.
[2] K. C. Antony, "Aging reactions in precipitation hardenable stainless steel," JOM, vol. 15, no. 12, pp. 922-927, 1963.
[3] G. Yeli, M. A. Auger, K. Wilford, G. D. Smith, P. A. Bagot, and M. P. Moody, "Sequential nucleation of phases in a 17-4PH steel: Microstructural characterisation and mechanical properties," Acta Materialia, vol. 125, pp. 38-49, 2017.
[4] 侯文星, 邵慧昌, "析出硬化型630不鏽鋼之開發," 中國礦冶工程學會, vol. 42, pp. 77-85, 1998.
[5] 中國材料科學學會, "材料手冊Ⅰ鋼鐵材料," vol. 2, pp. 120-127, 1984.
[6] C. Hsiao, C. Chiou, and J. Yang, "Aging reactions in a 17-4 PH stainless steel," Materials Chemistry Physics, vol. 74, no. 2, pp. 134-142, 2002.
[7] U. Viswanathan, S. Banerjee, and R. Krishnan, "Effects of aging on the microstructure of 17-4 PH stainless steel," Materials Science Engineering: A, vol. 104, pp. 181-189, 1988.
[8] H. Rack and D. Kalish, "The strength, fracture toughness, and low cycle fatigue behavior of 17-4 PH stainless steel," Metallurgical Transactions, vol. 5, no. 7, pp. 1595-1605, 1974.
[9] R. L. Liu and M. F. Yan, "Improvement of wear and corrosion resistances of 17-4PH stainless steel by plasma nitrocarburizing," Materials Design, vol. 31, no. 5, pp. 2355-2359, 2010.
[10] H. Riazi, F. Ashrafizadeh, S. R. Hosseini, and R. Ghomashchi, "Influence of simultaneous aging and plasma nitriding on fatigue performance of 17-4 PH stainless steel," Materials Science Engineering: A, vol. 703, pp. 262-269, 2017.
[11] M. A. Jaswin and D. M. Lal, "Effect of cryogenic treatment on the tensile behaviour of En 52 and 21-4N valve steels at room and elevated temperatures," Materials Design, vol. 32, no. 4, pp. 2429-2437, 2011.
[12] N. M. Satish Kumar, Suresh. R and Nitin K Khedkar "Effect Of Cryogenic Treatment On Tool Steels," International Journal of Advanced Research, pp. 1035-1045, 2017.
[13] S. Kalia, "Cryogenic processing: a study of materials at low temperatures," Journal of Low Temperature Physics, vol. 158, no. 5-6, pp. 934-945, 2010.
[14] 羅苑齊, "超深冷處理對麻田散體不銹鋼顯微結構與機械性質影響之研究," 碩士論文,南台科技大學機械工程系,台南, 2012.
[15] P. Patil and R. Tated, "Comparison of effects of cryogenic treatment on different types of steels: A review," in International Conference in Computational Intelligence, 2012.
[16] L. E. Murr et al., "Microstructures and properties of 17-4 PH stainless steel fabricated by selective laser melting," Journal of Materials Research Technology, vol. 1, no. 3, pp. 167-177, 2012.
[17] T. LeBrun, T. Nakamoto, K. Horikawa, and H. Kobayashi, "Effect of retained austenite on subsequent thermal processing and resultant mechanical properties of selective laser melted 17–4 PH stainless steel," Materials Design, vol. 81, pp. 44-53, 2015.
[18] M. Mahmoudi, A. Elwany, A. Yadollahi, S. M. Thompson, L. Bian, and N. Shamsaei, "Mechanical properties and microstructural characterization of selective laser melted 17-4 PH stainless steel," Rapid Prototyping Journal, vol. 23, no. 2, pp. 280-294, 2017.
[19] J. C. Lippold and D. J. Kotecki, "Welding metallurgy and weldability of stainless steels," pp. 19-55, 2005.
[20] S. D. W. a. G. Aggen, "Specialty Steels and Heat-Resistant Alloys," ASM Handbook, vol. 1, pp. 1303-1408, 2005.
[21] H. M. Cobb, The history of stainless steel. ASM International, 2010.
[22] H. Mirzadeh, A. Najafizadeh, and M. Moazeny, "Flow curve analysis of 17-4 PH stainless steel under hot compression test," Metallurgical Materials Transactions A, vol. 40, no. 12, p. 2950, 2009.
[23] U. Viswanathan, G. Dey, and M. Asundi, "Precipitation hardening in 350 grade maraging steel," Metallurgical Transactions A, vol. 24, no. 11, pp. 2429-2442, 1993.
[24] 李驊登, "鋼鐵材料學," 國立成功大學課程講義, 2017.
[25] A. Padilha, R. Lesley, and P. Rios, Stainless steels heat treatment (Chapter 12). 2007, pp. 695-739.
[26] A. A. A564M-13e1, "Standard Specification for Hot-Rolled and Cold-Finished Age-Hardening Stainless Steel Bars and Shapes," ASTM International, 2013.
[27] D. Ludwigson and A. Hall, "The physical metallurgy of precipitation-hardenable stainless steels," BATTELLE MEMORIAL INST COLUMBUS OH DEFENSE METALS INFORMATION CENTER, 1959.
[28] G. F. Vander Voort, G. M. Lucas, and E. P. J. M. P. Manilova, OH: ASM International, . "Metallography and microstructures of stainless steels and maraging steels," pp. 670-700, 2004.
[29] W. D. Callister, Fundamentals of materials science and engineering. Wiley London, UK:, 2000.
[30] A. P. Mouritz, Introduction to aerospace materials. Strengthening of metal alloys: Elsevier, 2012.
[31] R. E. Smallman, Modern physical metallurgy (Precipitation Hardening). Elsevier, 2016, pp. 499-527.
[32] M. Murayama, K. Hono, and Y. Katayama, "Microstructural evolution in a 17-4 PH stainless steel after aging at 400 C," Metallurgical Materials Transactions A, vol. 30, no. 2, pp. 345-353, 1999.
[33] P. Othen, M. Jenkins, and G. Smith, "High-resolution electron microscopy studies of the structure of Cu precipitates in α-Fe," Philosophical magazine A, vol. 70, no. 1, pp. 1-24, 1994.
[34] T. B. Massalski, J. Murray, L. Bennett, and H. Baker, "Binary alloy phase diagrams. vol. i and ii," American Society for Metals, p. 1086, 1986.
[35] C. Roberts, "Effect of carbon on the volume fractions and lattice parameters of retained austenite and martensite," Trans. AIME, vol. 197, no. 2, pp. 203-204, 1953.
[36] J. D. Verhoeven, Steel metallurgy for the non-metallurgist. ASM International, 2007.
[37] Z. Nishiyama, Martensitic transformation. Elsevier, 2012.
[38] C. F. Jatczak, "Retained Austenite and its Measurement by X-ray Diffraction," SAE Transactions, pp. 1657-1676, 1980.
[39] H. Nakagawa and T. Miyazaki, "Effect of retained austenite on the microstructure and mechanical properties of martensitic precipitation hardening stainless steel," Journal of materials science, vol. 34, no. 16, pp. 3901-3908, 1999.
[40] G. Krauss and A. R. Marder, "The morphology of martensite in iron alloys," Metallurgical Transactions, vol. 2, no. 9, pp. 2343-2357, 1971.
[41] S. Morito, H. Tanaka, R. Konishi, T. Furuhara, and T. Maki, "The morphology and crystallography of lath martensite in Fe-C alloys," Acta materialia, vol. 51, no. 6, pp. 1789-1799, 2003.
[42] H. Bhadeshia and R. Honeycombe, Steels: microstructure and properties. Butterworth-Heinemann, 2017.
[43] M. Cohen, "Strengthening of steel," Trans. TMS-AIME, vol. 224, pp. 638-656, 1962.
[44] A. R. Marder, "The morphology of martensite in iron-carbon alloys," Trans. ASM, vol. 60, pp. 651-660, 1967.
[45] H. Kitahara, R. Ueji, N. Tsuji, and Y. Minamino, "Crystallographic features of lath martensite in low-carbon steel," Acta Materialia, vol. 54, no. 5, pp. 1279-1288, 2006.
[46] I. Mitelea, I. Bordeaşu, Ş.-E. Katona, and C. M. Crăciunescu, "Cavitation erosion of 17-4 PH stainless steels following sub-zero treatment," International Journal of Materials Research, vol. 108, no. 12, pp. 1099-1102, 2017.
[47] A. Akhbarizadeh, A. Shafyei, and M. Golozar, "Effects of cryogenic treatment on wear behavior of D6 tool steel," Materials Design, vol. 30, no. 8, pp. 3259-3264, 2009.
[48] D. Das, A. K. Dutta, and K. K. Ray, "Sub-zero treatments of AISI D2 steel: Part I. Microstructure and hardness," Materials Science Engineering: A, vol. 527, no. 9, pp. 2182-2193, 2010.
[49] F. Meng, K. Tagashira, R. Azuma, and H. Sohma, "Role of eta-carbide precipitations in the wear resistance improvements of Fe-12Cr-Mo-V-1.4 C tool steel by cryogenic treatment," ISIJ international, vol. 34, no. 2, pp. 205-210, 1994.
[50] A. Bensely, S. Venkatesh, D. M. Lal, G. Nagarajan, A. Rajadurai, and K. Junik, "Effect of cryogenic treatment on distribution of residual stress in case carburized En 353 steel," Materials Science Engineering: A, vol. 479, no. 1-2, pp. 229-235, 2008.
[51] L. Manjunatha, M. Lokesha, and B. Ajaykumar, "A review: Mechanical Properties of HSS Steel by deep Cryo-Treatment," in IOP Conference Series: Materials Science and Engineering, 2018, vol. 376, no. 1, p. 012098: IOP Publishing.
[52] D. Llewellyn and R. Hudd, Steels: metallurgy and applications. Elsevier, 1998.
[53] B. Leffler, "Stainless steels and their properties," AvestaPolarit AB, pp. 1-45, 1996.
[54] J. R. Davis, "ASM Metal Handbook: Desk Edition," ASM International, pp. 464-468, 1998.
[55] A. Handbook, "Properties and Selection: Irons, Steels, and High Performance Alloys," ASM International, vol. 1, p. 1397, 2005.
[56] A. Handbook, "Alloy phase diagrams," ASM international, vol. 3, p. 1.26, 1992.
[57] C. Kim, "X-ray method of measuring retained austenite in heat treated white cast irons," Journal of Heat Treating, vol. 1, no. 2, pp. 43-51, 1979.
[58] R. A. Abrahams, "The Development of High Strength Corrosion Resistant Precipitation Hardening Cast Steels," 2010.
[59] A. E975, "Standard practice for x-ray determination of retained austenite in steel with near random crystallographic orientation," ASTM International, 2007.
[60] M. Wang, Z.-Y. Liu, and C.-G. Li, "Correlations of Ni contents, formation of reversed austenite and toughness for Ni-containing cryogenic steels," Acta Metallurgica Sinica, vol. 30, no. 3, pp. 238-249, 2017.
[61] B. Fultz, J. Kim, Y. Kim, and J. Morris, "The chemical composition of precipitated austenite in 9Ni steel," Metallurgical Transactions A, vol. 17, no. 6, pp. 967-972, 1986.
[62] E. S. Park, D. K. Yoo, J. H. Sung, C. Y. Kang, J. H. Lee, and J. H. Sung, "Formation of reversed austenite during tempering of 14Cr− 7Ni− 0.3 Nb− 0.7 Mo− 0.03 C super martensitic stainless steel," Metals Materials International, vol. 10, no. 6, p. 521, 2004.
[63] R. Bhambroo, S. Roychowdhury, V. Kain, and V. Raja, "Effect of reverted austenite on mechanical properties of precipitation hardenable 17-4 stainlesssteel," Materials Science Engineering: A, vol. 568, pp. 127-133, 2013.
[64] J.-H. Wu and C.-K. Lin, "Influence of high temperature exposure on the mechanical behavior and microstructure of 17-4 PH stainless steel," Journal of materials science, vol. 38, no. 5, pp. 965-971, 2003.