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이종금속 용접에 사용되는 ER309L 용접금속의 기계적 성질에 미치는 후열처리의 영향
최한글 한국산업기술융합학회 2023 산업기술연구논문지 (JITR) Vol.28 No.3
STS309(L) is widely used as a welding material for dissimilar welding of carbon steel and stainless steel. In general, austenitic stainless steel does not perform post-weld heat treatment (PWHT) to relieve thermal stress even after welding due to a sensitization. However, in the case of dissimilar joints between carbon steel and stainless steel, PWHT is often performed to relieve the thermal stress resulting from welding in carbon steel. Nevertheless, the stainless steel side may be subjected to heat treatment during PWH, leading to a deterioration in the mechanical properties of the stainless steel. Therefore, in this study, we investigated the effects of PWHT duration on the ferrite volume fraction, ferrite number, and mechanical properties. Through this, we aimed to determine the maximum post-heat treatment duration. The chemical composition did not change with an increase in the post-heat treatment time; however, the elongation and ferrite number decreased, and the tensile strength increased.
텅스텐이 첨가된 슈퍼 2상 스테인리스강의 내부식성에 관한 연구
최한글(Han-Gul Choi),박형균(Hyung-Gyun Park),정병호(Byung-Ho Jung),한현성(Hyun-Sung Han),배동수(Dong-Su Bae),강창룡(Chang-Yong Kang) 한국해양공학회 2010 韓國海洋工學會誌 Vol.24 No.5
The effect of aging on the precipitation if the σ phase and corrosion resistance in W-substituted, super-duplex stainless steel was investigated. The volume fraction of the σ phase and the current density increased as the aging temperature increased up to 750℃, and, then, they decreased. As aging time increased, the volume fraction if the σ phase and the current density also increased. The σ phase considerably influenced to corrosion resistance. When Mo was substituted for W in super-duplex stainless steel, the volume fraction of the σ phase and the current density both decreased markedly.
해양 및 건축용 항복강도 420MPa급 강재 접합부 및 신뢰성 평가
정승진,최한글,김인찬 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5
해양구조용 또는 건축구조용으로 사용되는 특수 형강은 우리나라에서는 매년 약 60-100만톤 가량을 일본, 베트남 등으로부터 수입하고 있으며, 특히 해양구조용 H형강과 같은 고급 특수 형강의 경우, 거의 전량 수입에 의존하고 있는 실정이다. 본 연구에서는 해외 의존도가 높은 특수형강 중, 저온인성 보증 해양구조용 H형강과 반복화재·지진 대응 건축구조용 내화·내진 H형강의 실제 상용화를 위해서 개발강재의 접합을 위한 용접재료 개발 및 접합부 평가를 진행하였다. 해양구조용 H형강용 접합기술 개발 연구에서는 –40℃에서 우수한 저온 충격특성을 요구하는 해양구조용 형강(EN10025 규격)을 접합할 고인성의 용접재료 개발을 진행하였고, 이를 위해서는 합금설계, 미세조직 제어기술, 용접 조건 제어, CTOD를 통하여 접합부 및 신뢰성 평가를 진행하였다. 건축구조용 H형강용 접합 기술 개발 연구에서는 반복화재·지진 상황 하에서도 건축물의 붕괴를 방지하여 국민들의 생활안전을 확보할 수 있는 반복화재·지진 대응 건축구조용 내화·내진 H형강 접합 기술 개발을 목표로 하고 있으며, 이를 위해서는 고강도와 함께 고인성 및 높은 고온강도(내화 특성)을 동시에 확보하는 용접재료를 개발하였고, 기존에 많이 사용하는 FCAW, SMAW 외에 SAW 개발은 진행하였고, 우수한 SAW 용접재료 개발 및 접합부 평가를 완료하였다.
선박·해양 구조물용 YS 460MPa 강재 FCAW 용접금속의 강도와 인성에 미치는 C의 영향
정상훈,엄정호,최한글,정병호,허성화,강창룡,Jeong, Sang-Hoon,Eom, Jeong-Ho,Choi, Han-Geul,Jeong, Byung-Ho,Hur, Sung-Hwa,Kang, Chang-Yong 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.6
This paper has an purpose to study the effect of C on the toughness of YS 460 MPa FCAW weld metal. These effects were evaluated by charpy impact and CTOD test about 4 FCAW weld metal containing various C and Si content in relation to microstructure. Increase of C content was helpful to increase AF volume fraction and reduce PF(G) and FS volume fraction by increasing super cooling rate for ferrite transformation. Also, Increase of C content up to 0.045wt% made the strength and impact toughness higher by increasing AF volume fraction. The weld metal containing higher C content indicated higher CTOD value. It is because the volume fraction of PF(G) and FS, can play a role as crack initiation site, was reduced. Effect of C on the strength and elongation of weld metal was higher with an increase of Si contents.
페라이트상을 갖는 마르텐사이트계 내열강의 미세조직 및 감쇠능에 미치는 열처리의 영향
김윤규(Y. K. Kim),최한글(H. G. Chio),성장현(J. H. Sung),강창룡(C. Y. Kang) 한국동력기계공학회 2009 한국동력기계공학회 학술대회 논문집 Vol.2009 No.11
This study was carried out to investigate the effect of microstructure on the damping capacity of martensite heat-resistant steel with ferrite phase. In case of the specimen with martensite plus ferrite phase, the volume faction of ferrite phases was under 5%. The damping capacity was decreased with the increase of solution treatment temperature and time. With the increase of tempering temperature and time damping capacity was increased. The damping capacity was higher in case of specimen with martensite single phase than the specimen with martensite phase contained the ferrite phases.
선박 및 해양구조물용 항복강도 460 MPa급 강재의 FCA 다층 용접금속부 특성에 미치는 규소의 영향
김종식,이명수,정종민,최한글,정상훈,강창룡 대한금속·재료학회 2018 대한금속·재료학회지 Vol.56 No.7
This study investigated the effect of Si on the characteristics of FCA multi-layer weld metal with 460 MPa yield strength grade steels for ships and marine structures. The effect on microstructure was evaluated by tensile, charpy impact and CTOD testing of 4 FCAW welds containing various C and Si contents. C content affected weld metal properties depending on Si content, microstructure, strength and impact value. With lower C content, strength and impact value increased when Si content was reduced, because of higher AF volume fraction. With higher C content, those properties were little affected by Si content. These phenomena indicate that C affects phase transformation more than Si. The CTOD value was higher with lower Si and higher C content. This was interpreted to mean that a lower volume fraction of not only PF, FS but also the M-A phase, can affect crack initiation sites, due to higher C and lower Si contents.
텅스텐이 첨가된 슈퍼 2상 스테인리스강의 내식성에 미치는 시효처리의 영향
김수천(Soo-Chun Kim),최한글(Han-Gul Choi),김윤규(Yun-Kyu Kim),이종문(Jong-Mun Lee),박진환(Jin-Hwan Park),강창룡(Chang-Yong Kang) 한국해양공학회 2009 韓國海洋工學會誌 Vol.23 No.6
The effect of aging on the precipitation of the a phase and the corrosion resistance in tungsten substituted super duplex stainless steels was investigated. The volume fraction of the σ phase and the current density increased with aging at temperatures up to 75℃ and then decreased. Wth an increase in aging time, the volume fraction of the σ phase and the current density also increased. The σ phase hardly influenced the corrosion resistance. With the substitution of tungsten for molybdenum in super duplex stainless steel, the volume fraction of the σ phase and the current density decreased remarkably.
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.
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.