Optimization of microstructure and properties of high strength spring steel 고강도 스프링강의 미세조직 및 물성 최적화 Ph.D. thesis January, 2011 Sangwoo Choi ii The research in this thesis has been financially supported by POSCO Korea. Optimization of microstructure and properties of high strength spring steel Proefschrift ter verkrijging van de graad van doctor aan de Technische Universiteit Delft, op gezag van de Rector Magnificus prof.ir. K.C.A.M. Luyben, voorzitter van het College voor Promoties, in het openbaar te verdedigen op maandag 31 januari 2011 om 15.00 uur door Sangwoo CHOI Master of Science in Materials Science and Engineering Korea Advanced Institute of Science and Technology, Korea born at Gwangju, KOREA iv Dit proefschrift is goedgekeurd door de promotor: Prof. dr. ir. S. van der Zwaag Dit proefschrift is goedgekeurd door de promotor: Rector Magnificus, voorzitter Prof. dr. ir. S. van der Zwaag, TU Delft, promotor Prof. dr. ir. J. Sietsma, TU Delft Prof. dr. R. Boom, TU Delft Prof. dr. E.H. Brueck, TU Delft Prof. dr. Y. Houbaert, Ghent University, Belgium Prof. dr. ir. R. Benedictus, TU Delft Dr. P.E.J. Rivera Díaz del Castillo, University of Cambridge, United Kingdom The research in this thesis has been finacially supported by POSCO KOREA Keywords: Alloy design, Quenching and tempering, Spring steel, Ultra high strength, Reduction of area, Precipitation behavior, Step tempering, Dilatation, Modeling, Decarburization, Oxidation Cover designed by Inkyung You Copyright @2011 by Sangwoo Choi
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