Title Suggestion of a modified Ni equivalent and the ...
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Speaker Prof. Sung-Joon Kim Professor, Graduate Institute of Ferrous Technology Pohang University of Science and Technology(POSTECH) Korea Date & Time Tuesday, March 14, 2017 10:00 a.m. Place Abstract About the Speaker Host: Professor Setsuo Takaki For registration, please visit our website: http://i2cner.kyushu-u.ac.jp/ International Institute for Carbon-Neutral Energy Research Kyushu University I 2 CNER Hall, Ito campus, Kyushu University Title Suggestion of a modified Ni equivalent and the effect of carbon on hydrogen embrittlement of Cr-Ni austenitic stainless steels Contact: Research Support and International Affairs division International Institute for Carbon-Neutral Energy Research Tel:092-802-6934 Email:[email protected] For this presentation, two small subjects on the hydrogen embrittlement and stainless steels are prepared. Firstly, the Ni equivalent in Cr-Ni austenitic stainless steels, an important indicator of the resistance to hydrogen embrittlement is revisited. Although N is often added to Cr-Ni austenitic stainless steels as a strengthening element, its contribution to Ni equivalent has not been satisfactorily taken into account. Based on an up-to-date thermodynamic database, the existing Ni equivalents are reassessed, and a modified Ni equivalent is suggested to accurately consider the N effect on austenite stability. Secondly, the effect of C on hydrogen embrittlement in stable austenitic stainless steels is investigated. During deformation, planar slip is pronounced and fine dislocation structures develop, which is followed by mechanical twinning in both steels. After hydrogen pre-charging, the alloy with higher carbon is more susceptible to hydrogen embrittlement. Based on strain hardening behaviour, it is proposed that C enhances planar slip and refines mechanical twins. Therefore, a higher C concentration results in more sites available for stress concentration and hydrogen trapping, and accelerates the embrittlement. Professor Sung-Joon Kim has spent more than 20 years in Korea Institute of Materials Science (KIMS) after he got the Ph. D. from University of Illinois at Urbana-Champaign, USA. He joined the Graduate Institute of Ferrous Technology, POSTECH as a professor from Dec. 2011. Prof. Kim’s research interests are alloy design of high nitrogen austenitic stainless steels and advanced high strength steels for automotive application and microstructure-property relationship of alloys. He has published more than 200 papers in journals and 80 papers in conference proceedings. Prof. Kim received the best Scholar Award in 2007 from Korean Institute of Metals and Materials (KIMM), the Scientist of this month from the Korean Ministry of Sci. & Tech. in 2008, and the Presidential Medal of Korea in 2010. He served as the vice president of KIMS for 3 years from 2009 to 2011 and as a vice president of KIMM for 2 years from 2013 to 2014. He was selected as a member of National Academy of Engineering, Korea.
Transcript of Title Suggestion of a modified Ni equivalent and the ...
Speaker Prof. Sung-Joon Kim Professor, Graduate Institute of Ferrous Technology Pohang University of Science and Technology(POSTECH) Korea
Date & Time
Tuesday, March 14, 2017 10:00 a.m.
Place
Abstract
About the Speaker
Host: Professor Setsuo Takaki
For registration, please visit our website:http://i2cner.kyushu-u.ac.jp/
International Institute for Carbon-Neutral Energy ResearchKyushu University
I2CNER Hall, Ito campus, Kyushu University
Title Suggestion of a modified Ni equivalent and the effect of carbon on hydrogen embrittlement of Cr-Ni austenitic stainless steels
Contact: Research Support and International Affairs division International Institute for Carbon-Neutral Energy Research Tel:092-802-6934 Email:[email protected]
For this presentation, two small subjects on the hydrogen embrittlement and stainless steels are prepared. Firstly, the Ni equivalent in Cr-Ni austenitic stainless steels, an important indicator of the resistance to hydrogen embrittlement is revisited. Although N is often added to Cr-Ni austenitic stainless steels as a strengthening element, its contribution to Ni equivalent has not been satisfactorily taken into account. Based on an up-to-date thermodynamic database, the existing Ni equivalents are reassessed, and a modified Ni equivalent is suggested to accurately consider the N effect on austenite stability. Secondly, the effect of C on hydrogen embrittlement in stable austenitic stainless steels is investigated. During deformation, planar slip is pronounced and fine dislocation structures develop, which is followed by mechanical twinning in both steels. After hydrogen pre-charging, the alloy with higher carbon is more susceptible to hydrogen embrittlement. Based on strain hardening behaviour, it is proposed that C enhances planar slip and refines mechanical twins. Therefore, a higher C concentration results in more sites available for stress concentration and hydrogen trapping, and accelerates the embrittlement.
Professor Sung-Joon Kim has spent more than 20 years in Korea Institute of Materials Science (KIMS) after he got the Ph. D. from University of Illinois at Urbana-Champaign, USA. He joined the Graduate Institute of Ferrous Technology, POSTECH as a professor from Dec. 2011. Prof. Kim’s research interests are alloy design of high nitrogen austenitic stainless steels and advanced high strength steels for automotive application and microstructure-property relationship of alloys. He has published more than 200 papers in journals and 80 papers in conference proceedings. Prof. Kim received the best Scholar Award in 2007 from Korean Institute of Metals and Materials (KIMM), the Scientist of this month from the Korean Ministry of Sci. & Tech. in 2008, and the Presidential Medal of Korea in 2010. He served as the vice president of KIMS for 3 years from 2009 to 2011 and as a vice president of KIMM for 2 years from 2013 to 2014. He was selected as a member of National Academy of Engineering, Korea.
