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급속응고된 Fe-6.5wt% Si 강판의 미세조직과 자기적 특성에 미치는 열처리의 영향
황돈하,이갑호,이태행,구자명 ( D . H . Hwang,K . H . Lee,T . H . Lee,J . M . Koo ) 한국열처리공학회 1995 熱處理工學會誌 Vol.8 No.2
The alloying of 6.5wt% Silicon in iron decreases the magnetization and the anisotropy and minimizes the iron loss noticeably. But it is very difficult to make thin sheets because of its poor ductility which is due to an ordering reaction (body centered cubic to CsCl type crystal structure). However the ordering reaction can be suppressed by rapid solidification method. The cooling rate of rapidly solidified Fe-6.5wt% Si alloy is about 10³K/s and rapidly solidified structure are fine structure, cellular structure, dendrite and equiaxed grain from surface. The precipitates of DO₃Phase emerges on B₂matrix and the coercive force was 0.51 Oe (50cycle, 15KGauss) in Fe-6.5wt% Si alloy which was processed by heat treatment of 1150℃ for 1hr in high vacuum.
코어금형용강 SKD11의 플라즈마 전해산화에 의한 피막 형성
김상무 ( S. M. Kim ),이태행 ( T. H. Lee ),강석조 ( S. J. Kang ),조영희 ( Y. H. Cho ),구자명 ( J. M. Koo ) 한국열처리공학회 2011 熱處理工學會誌 Vol.24 No.4
Surface coatings were prepared on SKD11 core mold steel by plasma electrolytic oxidation (PEO). The coatings were investigated about the formation condition of core mold steel. SKD11 were coated by PEO in a mix solution of Sodium Aluminate NaAlO2 (10g/l), Sodium Silicate powder Na2SiO3 (0.5g/l), Sodium tungstate dihydrate Na2WO42H2O (0.5g/l) at less than 30℃. The electrical condition were voltage : 500~600V ; Pulse : 600~1800Hz ; current density 15~20A/dm2 ; various time : 3min~40min. The coatings surface morphology, cross-section, friction coefficient, hardness were investigated. The coatings on SKD11 core mold steel by PEO indicated that the extension of service life.
철기(Fe Based) 나노결정질 합금 분말코어의 코팅제 및 입도가 연자기적 특성에 미치는 영향
장세종(S. J. Jang),최영진(Y. J. Choi),김상욱(S. W. Kim),전병서(B. S. Jeon),이태행(T. H. Lee),송창빈(C. B. Song),남궁정(J. Namkung) 한국자기학회 2015 韓國磁氣學會誌 Vol.25 No.3
This is a basic research for improving soft magnetic property of Fe based nano crystalline alloy powder core. The main study is done around characteristics of permeability, core loss, and DC bias depending on amount of insulation coating agent and particle size. First, Fe<SUB>73.5</SUB>Si<SUB>13.5</SUB>B<SUB>9</SUB>Nb₃Cu₁ amorphous alloy ribbon was fabricated by using the planar flow casting (PFC) device. Then, heat treatment and ball milling were done to obtain alloy powder. The amount of polyether imide (PEI) added to it was varied by 0.5, 1.0, 2.0, 2.5 wt% to have compression molding into 16 ton/㎠. After going through crystalline heat treatment, the made toroidal nano crystalline powder core (OD12.7 mm*ID7.62 mm*H4.75 mm) had smaller permeability as amount of insulation coating agent decreases. However, it was found out that core loss and DC bias characteristics have been improved. The reason for this results were expected to be because green density of power core decreases as amorphous alloy powder particles become smaller as amount of alloy powder insulation coating agent increases, it was determined that 1 wt% of insulation coating agent is appropriate. Also, for powder core made based on alloy powder size with amount of insulation coating agent fixed at 1 wt%, effective permeability and core loss were outstanding as particle size became bigger. However, characteristics of DC bias became worse as applied DC field increases. This is expected to be due to insulation effect, residual pores, or molding density of powder core resulting from thickness of coating on surface of alloy powder.
Co, Ni 로 개량되어 급속응고된 P/M 7075 알루미늄 합금의 조직 및 기계적 성질
조성석,이태행,조성길 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.3
The main objective aim of this study is to improve mechanical properties of a 7075 aluminum alloy. The alloy composition of a 7075 alloy was slightly modified. To enhance the precipitate hardening effect the content of zinc was increased by 2wt% also, 1wt% cobalt and 1wt% nickel were added to provide the dispersion hardening effect. These alloys were prepared by rapid soidification and hot extrusion. The experimental results suggest that newly developed P/M aluminum alloys exhibit much higher tensile strength than an I/M 7075 alloy. Especially, the alloys produced from fine powders show higher tensile strength and elongation compared to those from coarse powders. Improvements in tensile strength are attributed to suppression or elimination of coarse secondary phases, refinement of grain size and homogeneous distribution of fine precipitate particles, Co₂Al_9, Al₃Ni and oxide particles.
급속응고된 알루미늄합금 분말의 압출가공시 Cold compact 의 Preheating 에 관한 연구
조성석,이태행 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.3
Preheating processes before the extrusion of rapidly solidified Al-7.9wt%Zn-2.4wt% Mg-1.5wt%Co-0.92wt%Ni alloy powders were studied. Cellular dendrite structures of aluminum alloy powders are found to be decomposed when cold compacted powders are preheated at the temperatures above 490℃. In an aluminum alloy preheated at 490℃ and hot extruded, the density of pores is lower than 0.1% and the maximum diameter of pores is less than 1㎛. The grain size of the aluminum alloy is less than 1㎛ and fine oxide particles are dispersed uniformly within grains and at grain boundaries. After solution (490㎛/1hr) and aging (120㎛/1hr) treatments, the room temperature yield, strength tensile strength and elongation of the aluminum alloy are 71.9㎏/㎟, 76㎏/㎟ and 5.0%, respectively.