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슈퍼 2상 스테인리스강의 기계적 성질에 미치는 σ상 및 N 첨가의 영향
김수천(S. C. Kim),조덕호(D. H. Jo),강창룡(C. Y. Kang) 한국동력기계공학회 2008 한국동력기계공학회 학술대회 논문집 Vol.2008 No.11
This study was carried out to investigate the influence of volume fraction of austenite phase, precipitation behavior and volume fraction of o phase, N addition on the volume fraction of austenite phase, o phase and mechanical properties in 25Cr-7Ni-4Mo-2W super duplex stainless steel. The results obtained from this study are as follows: With increasing the annealing temperature, the volume fraction of austenite increased and volume fraction of ferrite decreased, and volume fraction of austenite increased by N addition. Tensile strength decreased and elongation increased due to increasing the volume fraction of austenite by increasing annealing temperature. In the case of N addition specimens, tensile strength and elongation showed high value. The precipitation of o phase was precipitated at ferrite phase and interface of ferrite and austenite, and the more precipitation of o phase was stimulated by N addition. With increasing of volume fraction of precipitated o phase, tensile strength was increased, elongation and impact value decreased. In case of o phase precipitated, N addition specimen showed high value of tensile strength, elongation, hardness and impact value than no addition specimen, and impact value rapidly decreased by precipitated R phase in early stage of aging.
원심주조된 내열강의 미세조직 및 기계적성질에 미치는 단조 조건의 영향
강창룡(C. Y. Kang),이상명(S. M. Lee),조덕호(D. H. Jo),박영태(Y. T. Park),이도훈(D. H. Lee),김영철(Y. C. Kim) 한국동력기계공학회 2009 동력시스템공학회지 Vol.13 No.3
The effect of forging start temperature, forging ratio on the microstructure and mechanical properties of B7B4 steel ware investigated. Microstructure of centrifugal casted B7B4 steel consisted of martensite and ferrite phase. The volume fraction of ferrite increased with increase of forging start temperature and decreased with increase of forging ratio. Tensile strength and hardness decreased with higher of forging start temperature, while impact value and elongation increased with higher of forging start temperature. With increase of forging ratio, tensile strength rapidly increased up to the forging ratio of 30%, and then slowly increased, but elongation was decreased. Hardness and impact value rapidly increased with increase of forging ratio.