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NTN TECHNICAL REVIEW No.742006 5. Conclusion NTN has performed a systematic series of experiments for carbonitriding with JIS-SUJ2 high carbon chromium bearing steel in an attempt to clarify the nitrogen penetration mechanism associated with this material. Also, assuming that the nitrogen penetration mechanism is similar to the carbon penetration mechanism, NTN has established a method for predicting nitrogen concentration distribution based on a series of experiments. The findings are summarized as follows: 1) The nitrogen penetration amount increases directly with an increases in the partial pressure of undecomposed NH3. 2) The nitrogen penetration amount increases directly with decreases in both carbon activity ac* and H2 partial pressure. 3) NTN has established a method for predicting the nitrogen concentration distribution of JIS- SUJ2 material. This method reflects considerations for the partial pressure of undecomposed NH3, the carbon activity ac*, H2 partial pressure and the diffusion coefficient that is dependent on nitrogen concentration. 4) NTN confirmed that, for various carbonitriding atmospheres, the predicted steel nitrogen concentration distribution (using NTN’s method for determining nitrogen concentration distribution) closely matches actual data obtained through EPMA analysis. References 1) N. Tsushima: SAE Technical Paper Series (1986) 860725 (in Japanese) 2) S. Narita and K. Yokose: “Effects of the nitriding potential caused by surface nitrogen concentration on various types of carbonitrided case hardening steel,” Japan Society for Heat Treatment 61st Lecture Series Preliminary draft (2005) 5 (in Japanese) 3) C. Ohki, M. Kawakita: “Effects of carbon activity from the carbonitriding process on high-carbon steel,” Japan Society for Heat Treatment 62nd Lecture Series Preliminary draft (2006) 5 (in Japanese) 4) C. Ohki, M. Kawakita: “Effects of base gas partial pressure from the carbonitriding process on high-carbon steel,” Japan Society for Heat Treatment 62nd Lecture Series Preliminary draft (2006) 17 (in Japanese) 5) Editorial Committee of the Society of Chemical Engineers Japan: Chemical Engineering Handbook, Maruzen (1950) 64 (in Japanese) 6) R.Collin, S.Gunnarson, and D.Thulin: "Influence of Reaction Rate on Gas Carburizing of Steel in a CO- H2-CO2-H2O-CH4-N2 Atmosphere, "Journal of The Iron and Steel Institute, (1972), 777 7) F. Neumann and U.Wyss: "Thermodynamische Grundlagen zum indirekten Messen des C-Pegels, " H.T.M., vol.49, No.4, (1994) 255 (in German) -52-
Atmospheric Control Method for JIS-SUJ2 Carbonitriding Processes Photo of author Chikara OHKI Elemental Technological R&D Center -53-
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88th Anniversary Special Issue; Pro
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R No.74 TECHNICAL REVIEW Special Is
Page 5 and 6: NTN TECHNICAL REVIEW No.742006 Pref
Page 7 and 8: Trends in Recent Machine Tool Techn
Page 13 and 14: Development of a New Grease Lubrica
Page 21 and 22: High-Speed Tapered Roller Bearing f
Page 29 and 30: Minimum Quantity and Cooling Jet Lu
Page 31 and 32: Minimum Quantity and Cooling Jet Lu
Page 33 and 34: dmn17010 4 Sealed High-speed Angula
Page 39 and 40: Development of Aerostatic Bearing S
Page 41 and 42: Development of Aerostatic Bearing S
Page 43 and 44: Introduction of New Products for Ma
Page 49 and 50: Atmospheric Control Method for JIS-
Page 55: Atmospheric Control Method for JIS-
Page 59 and 60: The Influence of Hydrogen on Tensio
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