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냉간 가공된 316LN 스테인리스강의 가공경화 거동과 크리프 특성
김우곤(Woo Gon Kim),이경용(Kyung Yong Lee),류우석(Woo Seog Ryu) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3
Strain-hardening behavior and creep properties of type 316LN stainless steels were investigated with the cold-worked(CW) reductions ; 0%(solution annealing), 20%, 30%, 40%, and 50%. An optimum CW level for creep properties was presented and discussed. A series of creep-rupture tests was conducted under 600℃ and 280㎫ using constant-load creep machines, and high-temperature tensile tests were conducted in 0~700℃ temperature range. The creep-rupture time increased gradually up to 30% reduction, but it decreased inversely over 30% reduction. The longest rupture time was exhibited at 30% reduction. The superior creep property at the 30% reduction is considered because fine carbides precipitate during creep and dislocations are pinned by them. So, the high dislocations may be sustained for a long time at high temperature. However, it is assumed that the higher CW reduction over 30% leads to excessive generation of deformation faults. Strain-hardening exponent, n value of type 316LN stainless steels decreased with increasing of the CW reductions, especially the n value in 200~400℃ temperature range showed a large decrease with the CW reductions.
STS 316L과 316LN 강의 고온 기계적 특성 및 가공 변질층에 관한 연구
오선세(Sun Sae Oh),이원(Won Yi) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.1
The deformed layers generated in face milling works were comparatively investigated to type 3l6L and nitrogen(N)-added type 3l6LN stainless steels. In order to characterize mechanical properties between type 3l6L and type 3l6LN, high-temperature tensile tests were conducted with different temperatures: R.T. to 700°C. The cutting forces of three components, Fx, Fy and Fz were measured using a tool dynamometer through the face milling cutting tests. The deformed layers were measured by micro-hardness tests along deformed layers. The results of mechanical properties showed that type 3l6LN was superior to type 3l6L. The deformed layers of two steels were generated in the 150㎛-300㎛ ranges, and type 316L was higher than type 316LN. The reason for this is due to the high strength properties by nitrogen effect. It was found that deformed structures were well observed for type 3l6L, but were minutely observed for type 3l6LN in this cutting conditions.
자동차 차체용 알루미늄 합금 판재의 기계적특성과 부식피로수명
박인덕(In-Duck Park),윤옥남(Ok-Nam Yoon),남기우(Ki-Woo Nam) 한국해양공학회 1997 韓國海洋工學會誌 Vol.11 No.2
The objective of this study is to compare the mechanical properties of 6000 series Al-Mg-Si aluminum alloy (AC120) with 5000 series Al-Mg aluminum alloy (TG25), and to investigate the influence of corrosion solution for fatigue life.<br/> Comparing of TG25 and AC120 alloy sheets, TG25 alloy sheets showing higher plastic strain ratio and total elongation have better formability than AC120 alloy sheets. The hardness of nugget area was a little higher than that of base metal area and the columnar structure and dendritic structure was observed in nugget area. Also, grain coarsening was observed in HAZ(Heat Affected Zone). In a corrosion fatigue experiment, the fatigue life decreased as concentration increased, when a dipping time was constant. The fatigue life decreased as dipping time increased, when a concentration was constant.
비파괴 신기술을 이용한 석유화학설비 경년손상의 새로운 평가변수 고찰
장재일(Jae-il Jang),최열(Yeol Choi),손동일(Dongil Son),이윤희(Yun-Hee Lee),권동일(Dongil Kwon),김정태(Jeoung Tae Kim) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8
Newly developed continuous indentation technique has made nondestructive assessment of tensile properties possible. The present study was undertaken to determine new parameters for indicating time-dependent material degradation of petro-chemical plant. Continuous indentation tests were performed at Cr-Ni steel and Cr-Mo steel which are widely used as facilities of petro-chemical plant. From the results, it was found that yield strength and tensile strength cannot be used as general degradation parameters because the change tendencies of the strengths with aging time are variable. On the other hand, work hardening exponent and yield ratio showed consistent tendency with increasing aging time. Therefore, main attention of this work was paid on them as new degradation parameters, and the in-field applicability of the parameters was evaluated and discussed.