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초고탄소강의 제어압연에 의한 세멘타이트의 구상화와 냉각중 마르텐사이트의 핵발생과 성장의 현상론적 고찰
최종술,윤진국 ( C . S . Choi,J . K . Yoon ) 한국열처리공학회 1993 熱處理工學會誌 Vol.6 No.2
Ultra high carbon steel(Fe-1.4%C) was prepared by means of a high frequency induction furnace. The preferred nucleation site of martensite was observed. The changes of hardness and impact thoughness due to tempering temperatures, and the spheroidization of cementite by controlled-rolling were also studied for the steel. The preferred nucleation site of martensite in the ultra high carbon steel is prior austenite grain boundary. The hardness of the steel is slightly increased up to about 300℃, and then decreased with further tempering temperature. However, the impact energy keeps a almost constant value, independent of the tempering temperature. The spheroidization of cementite is accelerated as the reduction in thickness per rolling pass is increased and the number of the rolling passes becomes greater.
Fe-Mn 이원계에서 비열탄성형 BCC 마르텐사이트와 HCP 마르텐사이트의 진동감쇠능
최종술,김준동,문인기,백승한 ( C . S . Choi,J . D . Kim,I . G . Moon,S . H . Baik ) 한국열처리공학회 1991 熱處理工學會誌 Vol.4 No.4
The damping capacities of the nonthermoelastic bcc type lath martensite and of the nonthermoelastic hcp type thin plate martensite in Fe-Mn alloys were studied. Fe-17%Mn alloy showing the hcp type thin plate martensite was superior to Fe-4%Mn alloy having the bcc type lath martensite in damping capacity. The damping capacity of the Fe-17%Mn alloy became greater with increasing the hcp martensite volume fraction. The damping mechanism of the Fe-4%Mn alloy was well explained by the dislocation model. However, the damping mechanism of the Fe-17%Mn alloy was explained on the basis of austenite/martensite interface moving model. The two alloys showed almost same levels of tensile strength. However, the elongation was greater in the Fe-17%Mn alloy than in the Fe-4%Mn alloy, showing lower yield strength in the former than in the latter. This result was considered to be attributed to formation of stress-induced martensite during tension test.
L12형 Ni3Fe 합금에서 규칙격자와 불규칙격자의 재결정거동
최종술,강석희 ( C . S . Choi,S . H . Kang ) 한국열처리공학회 1991 熱處理工學會誌 Vol.4 No.2
Recrystallization behaviors of ordered and disordered structures in L1₂type Ni₃Fe alloy were studied through hardness measurement and differential thermal analysis. When the disordered structure was isothermally aged at 480℃ below order-disorder transition temperature, the hardness of the structure was increased due to progressive ordering with increasing aging time. The hardness of the disordered structure was increased rapidly with increasing deformation degree up to 10%, and then gradually increased with further deformation degree, while the hardness of the ordered structure was increased rapidly with increasing deformation degree up to 10%, showing a constant hardness value up to 50% and gradually decreased with further deformation degree. The hardness of the ordered structure was higher than that of the disordered structure at all same deformation degrees. The recrystallization temperature of the ordered and disordered structures were decreased with increasing deformation degree. At the same deformation degrees, the recrystallization temperature of the ordered structure was lower than that of the desordered structure.
3. 6%C 회주철의 진동감쇠능 및 기계적 성질에 미치는 Sb 및 Ti 첨가의 영향
김정철(J . C . Kim),한동운(D . W . Han),백승한(S . H . Baik),최종술(C . S . Choi) 한국열처리공학회 2001 熱處理工學會誌 Vol.14 No.6
N/A Flake graphite cast irons with the high damping capacity have been used for the control of vibration and noise occurring in the members of various mechanical structures under vibrating conditions. However, the damping capacity which is morphological characteristics of graphite is one of the important factors in reducing the vibration and noise, but hardly any work has deal with this problem. Therefore, the authors have examined the damping capacity of various cast irons with alloying elements and studied the influences of the matrix structures, mechanical properties and morphological characteristics of graphite. The main results obtained are as follows: Effects of Sb on the damping capacities and mechanical properties have been investigated in 3.6%C-0.2%Ni gray cast iron. At 0.02%Sb, specific damping capacity showed the maximum value, and deceased with further increase in Sb content. Mechanical properties showed opposite trend with the damping capacity. And then, effects of Ti on the damping capacities and mechanical properties have been investigated in 3.6%C-0.2%Ni-0.02%Sb gray cast iron. Specific damping capacity increased with increase in Ti content. Graphite length also showed same behavior. Tensile strength increased with Ti content due to refinement of pearlite. In the case of 0.14%Ti addition in 3.6%C-0.2%Ni-0.02Sb cast iron, specific damping capacity and tensile strength was 36% and 25kgf/㎟ which are higher than 32% and 15kgf/㎟ at 3.6%C-0.2%Ni cast iron respectively.
진원,최종술 ( W . Jin,C . S . Choi ) 한국열처리공학회 1991 熱處理工學會誌 Vol.4 No.3
Effect of thermal cycling on shape memory effect and stabilization of austenite was investigated in Fe-21%Mn alloy. The thermal cyclic treatment was carried out with two types, room temperature↔215℃ and room temperature↔260℃. In case of the room temperature↔215℃, the SME was rapidly increased up to 3 cycles and maintained nearly constant value regardless of further cycles. In case of the room temperature↔260℃, however, the SME was increased with increasing the thermal cycle up to 5 cycles and decreased gradually with further cycle. The variation of the ε martensite volume pct with the thermal cycle was in good agreement with the variation of the SME. Therefore, the change of the SME due to the cyclic treatment was explained with the change of the ε martensite content. As the thermal cycle was increased, the M_s temperature was decreased, and the A_s and A_f temperatures were increased, respectively.
Fe-17wt%Mn 합금의 진동감쇠능에 미치는 탄소와 티타늄 첨가의 영향
백승한,김정철,지과구,신명철,최종술 ( S . H . Baik,J . C . Kim,K . K . Jee,M . C . Shin,C . S . Choi ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.1
Effects of carbon and Ti on damping capacity are investigated in an Fe-17%Mn alloy. The suppressive force of carbon against γ→ε transformation increases linearly with an increase in its content, lowering Ms temperature and volume fraction of ε martensite. Carbon deteriorates damping capacity by reducing the interfacial area of damping sources and mobility of the boundaries contributing to anelastic deformation. The reduction in damping capacity is accelerated when carboncontaining alloy is aged at higher temperatures above room temperature. The effect of Ti on damping capacity is found to be benificial in carbon-containing alloy, which is attributed to the depletion of carbon solute due to the formation of TiC.
Fe-18wt%Mn 마르텐사이트 합금에서 주조상태와 열처리한 상태의 기계적 성질과 진동감쇠능에 관한 연구
백승한,김정철,지광구,신명철,최종술 ( S . H . Baik,J . C . Kim,K . K . Jee,M . C . Shin,C . S . Choi ) 한국열처리공학회 1995 熱處理工學會誌 Vol.8 No.3
In recent work, we reported that a hot-rolled Fe-18wt%Mn alloy exhibited high damping capacity as well as excellent mechanical properties. It was also proposed that damping capacity of the alloy was proportional to the γ/ε boundary area. In the present study, the effects of homogenization(12hrs at 1100℃) and solution treatment(1hr at 1050℃ before air cooling) on damping capacity and mechanical properties were investigated for as-cast and heat treated Fe-18wt%Mn alloy. The specimen subjected to both homogenization and solution treatment was found to show superior damping capacity and mechanical properties to the as-cast state due to removal of segregation and increase in γ/ε boundary area.
Fe-17wt%Mn 합금의 진동감쇠능 , 내후성 및 기계적 성질에 미치는 Cu 첨가의 영향
백승환,김정철,지광구,최종술 ( S . H . Baik,J . C . Kim,K . K . Jee,C . S . Choi ) 한국열처리공학회 1995 熱處理工學會誌 Vol.8 No.2
We have reported that an Fe-17wt%Mn alloy exhibits the highest damping capacity in the Fe-Mn binary system. In the present work, the effects of copper content on the damping capacity, atmospheric corrosion and mechanical properties were studied. The damping capacities were measured at room temperature for the air cooled Fe-17wt%Mn alloy having copper content from 0.1wt% to 1.1wt%. The damping capacity of the Fe-17wt%Mn alloy was decreased with increasing copper content. However, the addition of Copper was found to improve mechanical properties and atmospheric corrosion resistance. These mechanical properties were attributed to the formation of stress-induced martensite during tensile test.
논문 : 상변태 ; Fe-32Mn-6.5Si 합금에서 형상기억효과 및 변태거동에 미치는 미세조직의 영향
이지영 ( J. Y. Lee ),지광구 ( K. K. Jee ),최종술 ( C. S. Choi ),장우양 ( W. Y. Jang ),신명철 ( M. C. Shin ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.6
The objective of this study is to investigate the effect of microstructure and pre-strain on shape memory effect(SME) and transformation behavior in an Fe-32Mn-6.5Si alloy. The alloy was annealed at various temperatures from 600 to 1200℃ for 1 hour to vary microstructure after cold rolling. Shape memory effect and reverse transformation behavior were examined through bending test and TMA after deforming the alloy with various degrees of pre strain Austenite grain size increases with an increase in heat treatment temperature, except the specimen heat-treated at 600℃, which remains unrecrystallized. The specimen heat-treated at 600℃, retaining cold rolling effect, exhibits the best SME due to a high Md temperature. In the recrystallized specimens, the larger grain size, the better SME. As grain size increases, the reverse transformation range becomes shorter, indicating that reverse transformation takes place with less constraint. The better SME in a large grain size can be attributed to the easiness of the reverse transformation.