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페라이트 상을 갖는 12Cr 내열강의 기계적성질 및 감쇠능에 미치는 시효처리의 영향
강창룡 ( C. Y. Kang ),최한글 ( H. G. Choi ),박형균 ( H. K. Park ),성장현 ( J. H. Sung ),이도훈 ( D. H. Lee ) 한국열처리공학회 2011 熱處理工學會誌 Vol.24 No.1
This study was carried out to investigate the effect of aging treatment on the mechanical properties and damping capacity of 12Cr heat resistant steel with ferrite phase. While hardness values in ferrite phase was not changed, that in martensite phase was dramatically dropped in early stage of aging treatment and then gradually decreased with increase of aging time. As aging treatment was carried out, the precipitation was not detected in ferrite phase, while carbides were precipitated in martensite phase. With increasing the aging time, tensile strength eventually decreased while impact toughness increased rapidly in the early stage of aging and then gradually increased. Besides, it was confirmed that damping capacity was not changed in the early stage of aging and then gradually increased with increase of aging time. (Received October 20, 2010; Revised November 9, 2010; Accepted December 7, 2010)
슈퍼 이상 스테인리스강의 내식성에 미치는 W첨가의 영향
김수천(S. C. Kim),최한글(H. G. Choi),김윤규(Y. K. Kim),강창룡(C. Y. Kang) 한국동력기계공학회 2009 한국동력기계공학회 학술대회 논문집 Vol.2009 No.6
Cr and Mo unwillingly precipitated sigma phase at temperature range of 600-900 °C, in DSS(duplex stainless steel) or SDSS(super duplex stainless steel) contained elements of Cr and Mo. Particularly, Mo is element that make sigma phase. These sigma phases have weak on impact toughness and corrosion resistance. But partial substition of W for Mo strengthen on impact toughness and corrosion resistance. So we studied for the effect of W addition in SDSS. In order to recognize the effect of W addition on corrosion resistance, we investgated electrochemical tests after aging treatments. We obtained that there are many sigma phases when aging temperature is at 750 °C And the longer aging time, the more amounts of sigma phases. Corrosion resistance is poor that aging treated at 750 °C and aging treated during long time than short time. But, specimen added W is good corrosion resistance as compared with specimen not added W.
원심주조된 B50A349A내열강의 미세조직 및 기계적성질에 미치는 단조조건의 영향
이상명 (S. M. Lee),김윤규 (Y. K. Kim),최한글 (H. G. Choi),강창롱 (C. Y. Kang) 한국동력기계공학회 2009 한국동력기계공학회 학술대회 논문집 Vol.2009 No.6
The aim of study is investigated to develop the optimum forging conditions on B50A349A heat resistance steel. The results obtained from this study are as follow: With increase the forging rate, the hardness and tensile strength wase increased, but impact value and elongation wase decreased. With increase the forging start temperature, the hardness and tensile strength wase increased, while, impact value and elongation wase decreased. With increase the forging finishing temperature, the tensile strength and hardness wase increased, but elongation and impect value was decreased..
슈퍼2상 스테인리스강의 기계적 성질에 미치는 W첨가의 영향
김수천(S. C. Kim),김윤규(Y. K. Kim),최한글(H. G. Choi),강창롱(C. Y. Kang) 한국동력기계공학회 2009 한국동력기계공학회 학술대회 논문집 Vol.2009 No.6
To recognize the effect of W addition on the mechanical properties in super duplex stainless steel, different W content is prepared. And we makes an experiment on different aging heat treatment conditions. At the result of, the effect of aging temperature is low precipitation of sigma phase at 475 °C, but precipitation of sigma phase at 600℃ and 750℃ is rapidly increased. But at 900 °C, precipitation of sigma phase is lower than former times, because precipitation region of sigma phase is missed. Therefore, hardness and strength are higher than former times, but impact values and elongation are decreased. At 600℃, the effect of aging time is low precipitation of sigma phase at the shortest time, but the longer time aging heat treatment, the more increase sigma phase increased. Therefore, hardness and strength are higher than the shortest time, but impact values and elongation are decreased. Specimen of W added decrease precipitation of sigma phase than specimen of W not added, because specimen's of W added sigma phase is decreased that Mo is substituted to W, relatively low diffusion coefficient. So, hardness and strength of specimen of W not added are higher than specimen of W added, but impact values and elongation of specimen of W not added are lower than specimen of W added.