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문인형,백응율 대한금속재료학회(대한금속학회) 1985 대한금속·재료학회지 Vol.23 No.6
An investigation was carried out to develop the abrasion-and heat resistant P/M alloy steels for an application to valve seat of diesel engine. The alloy powder obtained by mixing the individual elemental powders was compacted and sintered by conventional P/M technique and the sintered specimen was subjected to the usual heat treatment for hardening. Under the optimal sintering-and heat treatment condition; (sintered at 1200℃ for 100 min., oil quenched from the austenitizing temperature of 850-900℃ and tempered at 550℃ for 60 min.) the ultimate tensile strength of the sintered alloy steel was more than 1300 N/㎟. It has also shown the appropriate hardness and elongation, as 40.5 HRC and 3%, respectively.
순동 용가재를 이용한 AA1050 알루미늄과 1180MPa 고강도강 GMAW 접합부의 미세조직 및 기계적 특성 연구
정주희,백응율 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5
전 세계적으로 탄소중립에 동의하고, 자동차 시장에서는 수소차, 전기차 등 친환경 자동차 개발에 힘을 쏟는 등 환경문제 해결에 적극적으로 참여하고 있는 추세이다. 그에 따라 자동차 온실가스 배출량을 2020년 2012년 대비 70% 저감을 목표로 규제하였고, 자동차 연비 기준 또한 2020년 국내 24.0km/l로 규제를 강화하였다. 자동차 연비를 향상시키기 위해 차체 및 부품의 ‘경량화’가 미래 자동차의 핵심 경쟁력이 되었다. 이를 위해 본 연구에서는 자동차 경량화를 위해 대표적인 경량화 소재인 알루미늄을 사용하여 스틸과의 이종 접합을 연구하였다. 알루미늄-스틸 용융 용접 시 가장 큰 문제점은 융점, 열전도도, 비열 등 물성 차이가 크고, 혼합엔탈피의 차이가 커 접합부에 Fe<sub>2</sub>Al<sub>5</sub>, FeAl<sub>3</sub>, Fe<sub>3</sub>Al<sub>4</sub> 등 금속간화합물(Intermetallic Compounds; IMC)이 쉽게 생성된다. 이렇게 형성된 금속간화합물 층(IMC layer)은 취성을 띄어 외부 충격에 취약하며 접합부 파단의 원인이 된다. 이를 해결하기 위해 IMC 생성을 최소화 시킬 수 있는 첨가 원소를 사용할 필요가 있다. 본 연구자는 순동이 알루미늄-스틸의 합금원소에 첨가 원소로 사용될 경우 구리 함량이 증가할수록 경도가 낮아지는 것을 발견하였다. 이러한 연구 결과를 바탕으로 본 연구에서 순동 용가재를 이용하여 순수 알루미늄계 AA1050과 1180MPa 고강도강을 GMAW 하여 접합을 시도하였다. 이번 발표를 통해, 알루미늄과 스틸의 이종용접을 통해 나타나는 미세조직의 변화와 그에 따른 기계적 성질의 변화에 대한 연구 결과를 공유하여 산업 적용 가능성에 대하여 살펴보고자 한다.
열피로에 의한 Fe-Cr-Ni-Cr 계 스테인리스강 피복층의 미세조직 변화
안상호,백응율,정재영 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.3
The thermal cycling fatigue behavior on the microstructure of hardfacing Fe-Cr-Ni-C stainless steels has been investigated using optical microscopy, scanning and transmission electron microscopy. x-ray diffractometry, differential scanning calorimeter, and high temperature tensile testing. The as-welded microstructures of Fe-Cr-Ni-C stainless steels exhibit a fully martensitic structure except for Fe-14%Cr-1Ni-0.11C alloy consisting of the small amount of δ-ferrite and the martensite. The thermal cycling fatigued microstructure varied as the distance of penetration increased from the top-surface to the inner region. A recrystallized ferrite structure of equiaxed grains followed by a lath-shaped ferrite structure and a tempered martensite structure were observed depending on C and Ni contents. The increase in the high thermal expansion coefficient due to low C and high Ni contents accelerated plastic deformation during thermal fatigue in hardfacing Fe-Cr-Ni-C stainless steel. In the case of alloys containing relatively high C and low Ni, the recrystallized ferrite region was not observed in thermally damaged region. This can be explained by low thermal expansion coefficient combined with the pinning effect of carbides.
탄도충격을 받은 2층 육성용접 장갑판재의 균열생성 및 전파거동 연구
이성학,추성훈,백응율 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.7
The objective of this study is to investigate microstructural characteristics of a two-layer hardfaced armor plate after ballistic impact. In order to deaelop the newly-designed armor plate, high hardness, hypereutectic high Cr white iron and ductile SUS 309 stainless steel were hardfaced nn an HY l00 steel plate using self-shielding flux cored arc welding method. This hardfaced plate was ballistically impacted, and metallurgical observations of the area near the perforated region were conducted. The high Cr white iron hardfaced layer was obseved to block effectively a fast traveling prajectile, although microcracks were initiated at coarse primary carbides of the high Cr hardfaced layer, and propagated to form longer cracks However, very few cracks were found in the stainless steel hardfaced layer, which tended to hinder the propagating crack. These foundings suggest that ballistic performance of the multi-layered armor plates fabricated by hardfacing technique might be improved.
Fe-(12-17) %Cr-(0.19-0.32) %Cr 스테인레스 강으로 육성된 융접층의 미세조직과 기계적 특성에 미치는 C 및 Cr 함량의 영향
안상호,이성학,김낙준,추성훈,백응율,정재영 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.10
Fe-Cr-C hardfacing stainless steels were deposited on S45C carbon steel using a submerged arc welding process. The effects of C and Cr contents on the as-welded structures of Fe-(12-17)%Cr-(0.19-0.32)%C hardfacing stainless steels have been studied by microstructural observation and mechanical testing. The variation of as-welded structure as a function of C and Cr contents was compared with the microstructure predicted by the Schaeffler diagram. In Fe-12%Cr-(0.19-0.32)%C stainless steels, carbon solute atoms were primarily segregated in the interdendritic regions. And Cr-rich carbides tends to precipitate along the interdendritic regions in the stainless steels having C contents higher than 0.2%C. This explains why that the abrupt decreases of mechanical properties and the cleavage fracture surfaces appear in the stainless steels having C contents higher than 0.20%. The sliding wear mechanism varied from the adhesion to tribochemical reaction with increasing hardness of weld metal. However, the wear resistance tends to be affected by the introduction of abrasion. wear mode due to the hard carbide particles. This can be confirmed by the fact that its wear resistance increases with the increase of matrix hardness of weld metal.
고크롬 철계 합금 육성용접층의 파괴인성에 미치는 미세조직의 영향
안상호,이성학,김낙준,추성훈,백응율 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.7
This study aims at investigating the effect of matrix microstructure of high Cr white iron hardfacing alloys on fracture toughness and abrasion resistance. The hardfacing alloys were deposited twice on a mild steel plate using self-shielding flux cored arc welding method. In order to examine the matrix effect, different matrices such as pearlite, austenite, and mixture of pearlite and austenite were employed by changing the ratio of Mn/Si, while the total volume fraction of carbides was fixed. As the volume fraction of austenite in the matrix was increased, hardness and abrasion resistance were nearly constant, but fracture toughness was increased. In-situ observation of fracture process showed that cracks initiated at large primary M_7C₃ carbides tended to be blocked at the austenitic matrix, whereas they propagated through the pearlitic matrix. It could be concluded that abrasion resistance was controlled mainly by the volume fraction of primary carbides, while fracture toughness was controlled mainly by the amount of austenite in the matrix. Considering both abrasion resistance and fracture toughness, thus, the austenitic matrix was preferred for the high Cr white iron hardfacing alloys.