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양계조합을 중심으로 한 채난계 산업의 안정화와 발전방안
강의구 한국가금학회 1988 韓國家禽學會誌 Vol.15 No.4
우리나라 양계업도 기초단계에서 발전단계를 거쳐 완전한 한 개의 산업으로서 정립할 단계에 와있다. 모든 산업이 다 이런 과정을 거처 도약하고 있으니 양계산업도 예외는 될 수 없을 것이다. 다시 말하면 정비상완기에 돌입하였다는 말이요 만약 촌시라도 정비보완을 게을리 한다면 차기도약은 불가망일 것이며 아깝게도 우리의 땀과 열성으로 길러온 양계업은 빛도 못 본체 고사하고 마는 중대한 전환기라 하겠다. 보라!(중략)
강의구,이종철,남원종 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.5
The effect of prior microstructures on the behavior of cementite particles in conjunction with microstructural changes of the matrix during subcritical annealing was investigated by changing the initial microstructures into ferrite + coarse pearlite, ferrite + fine pearlite, bainite, and martensite, in medium carbon steels. While the coarsening of cementite particles in martensite proceeded rapidly with the growth of large cementite particles at boundaries with the dissolution of smaller particles within martensite laths, the coarsening rate of cementite particles in bainite was found to be much slower than that in martensite. This could be attributed to the thermal stability of cementite particles, the smaller amount of carbon in solution, and the lower driving force for solute diffusion due to the uniform size distribution of cementite particles in bainite. The controlling coarsening kinetics in medium carbon steels with ferrite-pearlite, bainite and martensite, were found as boundary diffusion, diffusion along dislocation, a combination of boundary diffusion and diffusion along dislocation, respectively. The effect of prior microstructures on the behavior of cementite particles in conjunction with microstructural changes of the matrix during subcritical annealing was investigated by changing the initial microstructures into ferrite + coarse pearlite, ferrite + fine pearlite, bainite, and martensite, in medium carbon steels. While the coarsening of cementite particles in martensite proceeded rapidly with the growth of large cementite particles at boundaries with the dissolution of smaller particles within martensite laths, the coarsening rate of cementite particles in bainite was found to be much slower than that in martensite. This could be attributed to the thermal stability of cementite particles, the smaller amount of carbon in solution, and the lower driving force for solute diffusion due to the uniform size distribution of cementite particles in bainite. The controlling coarsening kinetics in medium carbon steels with ferrite-pearlite, bainite and martensite, were found as boundary diffusion, diffusion along dislocation, a combination of boundary diffusion and diffusion along dislocation, respectively.
압연온도 및 어닐링 온도에 따른 5052합금의 미세조직 및 기계적 성질
강의구,남원종 대한금속·재료학회 2019 대한금속·재료학회지 Vol.57 No.10
The microstructural evolution and corresponding mechanical properties of 5052 Al alloys with different deformation temperatures and post-deformation annealing conditions were investigated. The warmrolled alloy showed higher strength and elongation than the cold-rolled and cryo-rolled alloys. The improved strength and ductility of warm rolled alloys is attributed to the formation of fine precipitates and a higher degree of recovery during rolling. The formation of precipitates and the occurrence of dynamic recovery during the warm-rolling process were confirmed by the absence of the first two peaks in DSC curves of warm-rolled alloys. In particular, it was found that the application of cryo-rolling combined with warm-rolling at 448K increased tensile strength and yield strength without a decrease of ductility. This notable increase of strength is attributed to the increased dislocation density during cryo-rolling and the subsequent formation of fine precipitates at dislocations during warm-rolling. The contribution of fine precipitates and fully recovered microstructures, during cryo-rolling, warm-rolling, and subsequent annealing enhances the effective combination of strength and elongation. The ultra-fine grained 5052 Al alloy with high strength (405 MPa) and ductility (11.4% elongation) could be achieved by a combination of cryo-rolling with warm-rolling (448 K) and subsequent static annealing at 448 K.
극저온과 온간 압연을 적용한 6061 Al 합금의 강도 향상에 대한 연구
강의구(U. G. Kang),이호진(H. J. Lee),남원종(W. J. Nam) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
Ultrafine-grained Al 6061 alloy which was fabricated by the combination of cryogenic rolling with warm rolling, exhibited high strength, ultimate tensile strength, 420㎫. The strengthening effect was compared with the results by other severe plastic deformation methods. This notable increase of tensile strength was achieved by the formation of fine precipitates during warm rolling. The presence fine precipitates of diameter below 100 ㎚, in ultrafine-grained matrix, were confirmed with TEM and STEM. Estimated precipitation-strengthening by the fine precipitates was approximately 100㎫. Based on the results, it was found that the cryogenic rolling combined with warm rolling would be effective in increasing strength and expanding application area in industries.
저탄소 마르텐사이트 강의 냉간압연과 온간압연을 통한 미세조직 개질
이종철,강의구,이중원,오창석,김성준,남원종 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
There have been a number of works on manufacturing ultrafine grained steels with average ferrite grain sizes of smaller than a few micrometers to develop beneficial high strength steels. Among microstructures in low carbon steels, lath martensite is known to be useful to produce an ultrafine grained ferrite matrix and finely globular cementite particle. Thus, severe plastic deformation and subsequent annealing at lower temperature of lath martensite would become an effective way to produce ultrafine grained steels. However, most ultrafine grained steels exhibited a total elongation of a few per cent in tensile tests. Such a defect is one of the primary factors restricting the potential applications of ultrafine grained steels. Therefore, the improvement of the strength-elongation balance is required for the application of ultrafine grained structural steels. In this study, the effect of deformation temperatures on microstructure, such as ferrite grain size and the distribution of cementite particles, and mechanical property of lath martensite steels, was investigated. Specimens were fabricated through cold rolling or warm rolling and subsequent annealing.
압력용기용 A516 강의 미세조직에 미치는 탄소 당량과 냉각 속도의 영향
이현욱,강의구,김민수,신상용,Lee, Hyun Wook,Kang, Ui Gu,Kim, Min Soo,Shin, Sang Yong 한국재료학회 2019 한국재료학회지 Vol.29 No.8
In this study, the effect of carbon equivalent and cooling rate on microstructure and hardness of A516 steels for pressure vessel is investigated. Six kinds of specimens are fabricated by varying carbon equivalent and cooling rate, and their microstructures and hardness levels are analyzed. Specimens with low carbon equivalent consist of ferrite and pearlite. As the cooling rate increases, the size of pearlite decreases slightly. The specimens with high carbon equivalent and rapid cooling rates of 10 and $20^{\circ}C/s$ consist of not only ferrite and pearlite but also bainite structure, such as granular bainite, acicular ferrite, and bainite ferrite. As the cooling rate increases, the volume fractions of bainite structure increase and the effective grain size decreases. The effective grain sizes of granular bainite, acicular ferrite, and bainitic ferrite are ~20, ~5, and ${\sim}10{{\mu}m$, respectively. In the specimens with bainite structure, the volume fractions of acicular ferrite and bainitic ferrite, with small effective grains, increase as cooling rate increases, and so the hardness increases significantly.