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2 상조직강의 항복 및 변형거동에 미치는 퍼얼라이트의 영향
최병영,오상엽 대한금속재료학회(대한금속학회) 1987 대한금속·재료학회지 Vol.25 No.9
The dual phase steels of ferrite-martensite and ferrite-martensite-pearlite were prepared by two step cooling or isothermal holding after intercritical annealing. And this research investigated the effect of pearlite on the yielding and deformation behavior of these dual phase steels. It was observed that second phase particles with pearlite-martesite interfaces were distributed in the ferrite matrix. The structure of pearlite-martensite interface was also observed by using SEM. Continuous or discontinuous yielding apeared in the specimens of ferrite-martensite-pearlite. The lower yielding ratio and continuous yielding were shown in the specimens with more martensite content (≥5.8 vol%). The microstructure observed by TEM showed that the mobile dislocations causing continuous yielding and the pinned dislocations by solute atoms were distributed in the ferrite. The effect of pearlite on the variation of work hardening exponents during tensile deformation was also discussed in terms of the Modified Crussard-Jaoul analysis.
Double Hot Forging 에 의해 제조된 고주파 유도경화 베어링강의 특성에 관한 연구
최병영,장정석 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.1
Characterization of the microstructure and its effect on rolling contact fatigue of high frequency induction-hardened bearing steels produced by double hot forging have been studied using a 0.55 wt.% C-1.68 wt.% Mn steel. Rolling contact fatigue tests were conducted under a maximum Hertzian contact stress of 492 ㎏/㎟ with a rotating speed of 8,000 rev/min and a constant supply of lubricant. Very fine martensite which was superior resistance to rolling contact fatigue, was formed in the induction-hardened layer of double hot forged steels. It was also found that the less decrease of half value breadth of martensite peak in X-ray diffraction pattern during rolling contact fatigue, the longer rolling contact fatigue life of the specimens.
최병영,김익수,장병록,이용희 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.4
Wear of blades, buckets, plates and chisel occurred in operation of construction machinery, agricultural equipments, earthmoving equipments and offshore structures cause earlier failure of the components, resulting in the increased energy consumption, cost of maintenance and replacement. To solve the problems, advanced materials with higher resistance to abrasive wear have been attempted to make through alloy design and hot deformation followed by air cooling. 0.25C-1.4Mn-1.0Cr-0.7Ni-0.2Mo-0.08V-0.02Cu steels produced by hot forging were cooled in air to form bainite, showing higher resistance to wear than any other steels with different chemical composition in the sliding wear tests under the applied load of 74N. Higher strain hardening during sliding wear of 0.25C-1.4Mn-1.0Cr-0.7Ni-0.2Mo-0.08V-0.02Cu steels to cause microploughing wear mode seems to be one of the main reasons for showing higher resistance to wear than any other steels in this study.
VIM에 의해 제조된 고주파 유도경화 베어링강의 특성에 관한 연구
최병영,장정석,Choe, Byeong-Yeong,Jang, Jeong-Seok 한국재료학회 1998 한국재료학회지 Vol.8 No.12
VIM에 의해 제조된 0.55wt.% C-1.68wt.% Mn강을 사용하여 고주파 유도경화 베어링강의 특성을 조사하였다. 시편의 청정도는 DIN 50602에 의한 K4값이 6.41로 측정되어 높게 나타났다. 고주파 유도경화된 시편은 약 2.7mm의 유효경화층 깊이를 가진 표면경화층이 형성되었으며 불균질한 submicron크기의 lath 마르텐사이트가 표면경화층에 형성되었다. 회전접촉 피로 시험은 최대 헤르쯔 응력 492 kgmm$^{-2}$ 을 가하며 탄성유체 윤활조건에서 실시되었다. 회전접촉 피로시험 후 시편의 궤도면 직하에서 측정된 미소경도는 유도경화한 경우에 비해 표면직하 약 $500\mu\textrm{m}$ 깊이까지 증가하였다. 그 경도증가량의 최대치를 나타내는 위치는 표면에서부터 약 100$\mu\textrm{m}$ 깊이로 밝혀졌으며 백색부식영역 (white etching area)을 나타내었다 회전접촉 피로시험 후 시편의 궤도면 직하, 이 백색 부식영역에서 균열이 생성되고 전파하였다. Characteristics of high frequency induction- hardened bearing steel have been investigated using 0.55wt.% C-1.68wt.% Mn specimens produced by vacuum induction melting (VIM). The K4 value in DIN 57602 of the specimens was assessed to be 6.41, high level of cleanliness. The specimens were high frequency induction-hardened to form heterogeneous submicron- lath martensite in the surface hardened layer with about 2.5mm in effective depth. Rolling contact fatigue tests were conducted in elasto-hydrodynamic lubricating conditions under a maximum Hertzian contact stress of$ 492kgmm^{-2}$ . It was found that microhardness in the subsurface, up to about $500\mu\textrm{m}$ in depth, below the raceway of rolling contact fatigued specimens was increased in comparison with that of induction-hardened layers. The depth of maximum microhardness- increased region was about $100\mu\textrm{m}$ from surface, showing white etching area. Crack initiation and propagation in the white etching area below the raceway of rolling contact fatigued specimens were observed.
사회적 경제 교육을 위한 ‘통합사회’ 교육과정 재구성에 관한 연구
최병영 한국사회교과교육학회 2016 사회과교육연구 Vol.23 No.3
The objective of this research is to examine the expandability of education of social economy. The details and the results of the research are as follows. First, as the size of education of social economy expands, there is an increase in demand for related education, but there is a lack of education contents for students. Second, the middle school textbook 『The Citizen that Lives Together, the Democratic Citizen』, which was published by the Gyeonggi Provincial Office of Education, is one of the only social economy textbooks released by an official education organization. The analysis of the textbook showed that democracy, community and solidarity etc., which are important values of social economy, were further emphasized when the term ‘social economy’ was directly mentioned in the textbook title or units chapter titles of the textbook. Third, it was shown that when including education on social economy related concepts in the curriculum, it was more appropriate to include this as part of the ‘integrated social studies’ subject matter rather than as part of ‘economics’. Themes such as market failure, government failure, corporate social responsibility(CSR) and ethical consumption coincide with the core values and contents of social economy. Fourth, there is a need to present the concepts of social economy as a medium unit in the textbooks, and they can be presented together with the concepts of economic phenomenon according to market failure, the role of each of the stakeholders in the economy and CSR etc. In the case this is difficult, there is a need to explicitly describe the values of social economy proposed by the achievement standards of the curriculum. 본 연구의 목적은 사회적 경제 교육의 확장성을 탐구하는 것이다. 이를 위해 진행한 연구내용과 결과는 다음과 같다. 첫째, 사회적 경제의 규모가 확대됨에 따라 교육수요가 늘어나고 있지만, 학생들을 위한 교육은 미미하다. 둘째, 공식적인 교육기관이 발행한 사회적 경제 교재는 경기도 교육청의 『더불어 사는 민주시민』 중학교용 교과서가 거의 유일하다. 교재분석 결과 사회적 경제의 주요가치인 민주주의, 공동체, 연대 등은 교재나 단원 명칭에 사회적 경제를 명시했을 때 더욱 강조된다. 셋째, 사회적 경제를 교육과정에 포함시킨다면 적합한 과목은 ‘경제’보다 ‘통합사회’다. 시장실패, 정부실패, 기업의 사회적 책임, 윤리적 소비 같은 주제는 사회적 경제의 주요 가치와 내용요소에 부합된다. 넷째, 사회적 경제는 중단원 정도의 단원 제시가 필요하며, 시장실패에 따른 경제현상과 경제주체별 역할, 기업의 사회적 책임 등을 함께 제시할 수 있다. 여의치 않다면 교육과정에 제시된 성취기준에 따라 사회적 경제의 가치요소를 명시적으로 기술할 필요가 있다.