• 한국추진공학회지
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• 제1권1호
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• pp.104-110
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• 1997

고강도 알루미늄 합금 링롤재의 급냉, 링 팽창(expansion) 및 링 압축(compression) 응력제거처리 후 잔류응력을 예측하기 위하여 2차원 축대칭 열해석 및 탄소성 해석을 수행하였다. 급냉 및 응력제거처리 후 2단 과시효 처리(T73)된 링롤재에 대하여 3단계 절단법(Three step sectioning method)을 적용하여 링롤재의 두께에 따른 잔류응력 분포를 측정하였으며, 측정결과를 급냉 및 응력제거처리후 잔류응력 해석결과와 비교분석하였다. 링의 급냉후 원주 및 축방향의 잔류응력 해석값은 T73후 측정값과 비슷한 경향을 보였으며, 링의 내면과 외면에서 압축응력을 나타내었고 중심에서 인장응력을 나타내었다. 잔류응력은 링 팽창(T7351) 및 링 압축(T7352) 적용후 T73에 비해 현저히 감소하였으며, 축방향의 제거 효과가 원주방향보다 우수하게 나타났다. 또한 링 압축에 의한 제거효과가 링 팽창보다 크게 나타났다. 링롤재의 응력제거처리는 제거 효과 및 실용성 측면에서 링 압축 공정이 유리하며, 치수제어 및 장비용량 측면에서 링 팽창 공정이 유리하다는 결론을 얻었다.

• Journal of Advanced Marine Engineering and Technology
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• 제35권8호
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• pp.1048-1054
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• 2011

레이저 표면경화처리는 고밀도 에너지 열원에 의해 레이저 조사부위만 급속 가열한 후 표면의 열이 내부로 전도되어 급속히 자기냉각 됨으로써 표면을 경화시키는 방법이다. 이 표면처리 방법은 열처리에 의한 열변형이 거의 없고, 표면경화처리 이후 다른 공정을 수반하지 않는다. 또한 국부적인 가공이 가능하기 때문에 복잡한 형상을 가지는 금형에는 적합한 표면처리 방법이다. 본 연구에서는 열처리에 적합한 빔 프로파일을 가진 고출력 다이오드 레이저를 이용하여 금형재료용 주철의 표면처리를 실시하였다. 프레스 금형 공정에 따른 금형의 형상이 다르기 때문에 적용부위에 따라 시험편을 평면과 모서리부로 나누어 열처리를 실시하였다. 이때 모서리부의 열처리는 광학헤드를 $10^{\circ}$ 기울인 상태에서 진행하였다. 그 결과, 모서리부의 열처리는 평면부와 비교하여 형상에 따른 열전달 루트가 제한되므로, 입열이 집중되기 쉬워 평면 열처리보다 빠른 이송속도에서 경화가 이루어졌다.

• 대한기계학회논문집A
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• 제35권4호
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• pp.383-391
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• 2011

최근 차체 경량화를 위한 여러 가지 방법 가운데 고온에서 가공하여 성형성을 확보하고, 이후 열처리를 통하여 고강도를 가질 수 있는 프레스 열간 성형 및 핫스탬핑 기술이 각광을 받고 있으며, 이에 따라 핫스탬핑용 재료인 보론 첨가 강판의 수요도 늘어나고 있는 추세이다. 본 연구에서는 핫스탬핑용보론 첨가 강판의 우수한 경화능을 보이는 임계 최적 열처리 조건을 파악하고자, Al+Si 코팅이 된 보론강판을 각기 다른 온도로 열처리하여 수냉 조건에 따른 기계적 특성 및 조직을 관찰하였다. 또한, 이 결과를 토대로 선별된 기계적 특성이 우수한 보론강 시험편과 일반 냉연 강판인 SPRC 340과 SPRC 590 2종류의 상대재를 활용하여 특정 점용접 조건에서 용접을 실시하고, 보론강 및 상대재의 기계적 특성 변화에 따른 용접 후의 기계적 특성 및 조직, 그리고 코팅층 유무에 따른 특성 변화를 연구하였다.

• 한국재료학회지
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• 제30권5호
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• pp.231-238
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• 2020

The composition of martensite transformation in NiAl alloy is determined using pure nickel and aluminum powder by vacuum hot press powder metallurgy, which is a composition of martensitic transformation, and the characteristics of martensitic transformation and microstructure of sintered NiAl alloys are investigated. The produced sintered alloys are presintered and hot pressed in vacuum; after homogenizing heat treatment at 1,273 K for 86.4 ks, they are water-cooled to produce NiAl sintered alloys having relative density of 99 % or more. As a result of observations of the microstructure of the sintered NiAl alloy specimens quenched in ice water after homogenization treatment at 1,273 K, it is found that specimens of all compositions consisted of two phases and voids. In addition, it is found that martensite transformation did not occur because surface fluctuation shapes did not appear inside the crystal grains with quenching at 1,273 K. As a result of examining the relationship between the density and composition after martensitic transformation of the sintered alloys, the density after transformation is found to have increased by about 1 % compared to before the transformation. As a result of examining the relationship between the hardness (Hv) at room temperature and the composition of the matrix phase and the martensite phase, the hardness of the martensite phase is found to be smaller than that of the matrix phase. As a result of examining the relationship between the temperature at which the shape recovery is completed by heating and the composition, the shape recovery temperature is found to decrease almost linearly as the Al concentration increases, and the gradient is about -160 K/at% Al. After quenching the sintered NiAl alloys of the 37 at%Al into martensite, specimens fractured by three-point bending at room temperature are observed by SEM and, as a result, some grain boundary fractures are observed on the fracture surface, and mainly intergranular cleavage fractures.

• 한국전기전자재료학회논문지
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• 제14권6호
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• pp.475-480
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• 2001

Glasses in he system CuO-P$_2$O$_{5}$ -Nb$_2$O$_{5}$ -Nb$_2$O$_{5}$ -V$_2$O$_{5}$ were prepared by a press-quenching method on the copper plate. the glass-ceramics from these glasses were obtained by post-heat treatment, and the crystallization behavior and DC conductivities were determined. The conductivities of the glasses were range from 10$^{-6}$ s.$cm^{-1}$ / at room temperature ,but the conductivities of the glass-ceramics were 10$^{-3}$ s.$cm^{-1}$ / increased by 10$^3$ order. The crystalline product in the glass-ceramics was CuV$_2$O$_{6}$ . the crystal growth of CuV$_2$O$_{6}$ phase increased with heat-treatment conditions. The linear relationship between il($\sigma$T) and T$^{-1}$ suggested that the electrical conduction in the present glass-ceramics would be due to a small polaron hopping(SPH) mechanism.

• 한국응용과학기술학회지
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• 제20권4호
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• pp.283-288
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• 2003

Alkaline powder cleaning agents (APCAs) were prepared by blending of $Na_2CO_3$ tetrasodium pyrophosphate (TSPP). sodium orthosilicate (Na-OSi), Na-dioctyl sulfosuccinate (303C), Demol C, and MJU-100A (100A). The physical properties of APCAs tested with steel specimen showed the following results. The cleaning powers of APCA-6 ($Na_2CO_3$ 250g/TSPP 70g/Na-OSi 40g/303C 60g/Demol C 50g/100A 30g mixture) for press-rust preventing oil was 97% and 98% degreasing at 2wt%, $70^{\circ}C$ and $90^{\circ}C$, respectively; for Quenching oil, the cleaning power of APCA-6 was 95% degreasing at 2wt% and $70^{\circ}C$. From the results, it was ascertained that APCA-6 exhibited a good cleaning power. Also low foaming power tests proved that the APCA-6 maintained good defoaming effect.

• 환경생물
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• 제17권3호
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• pp.249-255
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• 1999

Poly(3-hydroxybutyrate)의 표면 형태가 생분해성에 미치는 영향을 조사하였다. 용융 상태의 PHB를 서냉 ($-0.5^{\circ}C$/min)시켰을 때 PHB의 결정화도는 액체질소 속으로 급냉한 후 $90^{\circ}C$에서 2시간 동안 숙성한 PHB의 결정화도보다 높게 나타났으나 전자의 PHB 시료는 미세 균열의 존재로 인하여 후자의 PHB 시료보다 더 빠르게 생분해되었다. 거친 표면을 가진 평판 위에서 hot press하여 표면을 거칠게 만든 PHB film의 생분해는 표면이 평활한 film보다 훨씬 더 빠르게 진행되었다.

• 한국응용과학기술학회지
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• 제20권2호
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• pp.81-86
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• 2003

To prepare alkaline degreasing agents(SADAs), tetrasodium pyrophosphate(TSPP), $Na_2CO_3$, Tetronix T-701 (T-701), Na-dioctyl sulfosuccinate(303C), Demol C, and MJU-100A were blended. The prepared degreasing agents were tested with steel specimens and the results were as follows. The degreasing powers of SADA-6($Na_2CO_3$ 50g/TSPP 25g/T-701 10g/303C 15g/Demol C 12g/MJU-100A 8g/water 130g mixture) for press-rust preventing oil were 98% and 99% degreasing at 4wt%, 70 $^{\circ}C$ and 90 $^{\circ}C$, respectively; for quenching oil, the degreasing power of SADA-6 was 92% degreasing at 4wt% and 70 $^{\circ}C$. From these results, it was proved that the SADA-6 exhibits a good degreasing power. Foam heights measured immediately after foaming by Ross & Miles method and Ross & Clark method at 6wt% and 60 $^{\circ}C$ were 16mm and 40mm, respectively. SADA-6 was proved a good low foaming degreasing agent.

• 한국응용과학기술학회지
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• 제10권2호
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• pp.35-40
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• 1993

Alkaline cleaning agent(ACA) was prepared by blending of POE(4)octadecylmine(S-204), $Na_2CO_3$, sodium orthosilicate(Na-OSi). Tetronix T-701(T-701), and MJU-100A. The physical properties of ACA tested with steel specimen showed the following results. The cleaning powers of ACA-6(S-204 80g/$Na_2CO_3$, 160g/Na-OSi, 80g/T-701, 60g/MJU-100A, 20g mixture) for press-rust preventing oil was 98% and 99% degreasing at 2wt%, $70^{\circ}C$ and $90^{\circ}C$, respectively : for quenching oil, the cleaning power of ACA-6 was 95% degreasing at 2wt% and $70^{\circ}C$. From these results, it was ascertained that ACA-6 exhibited a good cleaning power. Foam heights measured immediately after foaming by Ross & Miles method and Ross & Clark method at 3wt%. $60^{\circ}C$ were 17mm and 40mm, respectively. As the result, ACA-6 was proved a good low foaming cleaning agent.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.934-937
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• 2003

Glasses in the system $CuO-P_2O_5-V_2O_5$ were prepared by a press-quenching method on the copper plate. The glass-ceramics from these glasses were obtained by post-heat treatment, and the crystallization behavior and DC conductivities were determined. The conductivities of the glasses were range from $10^{-6}s.Cm^{-1}$ at room temperature, but the conductivities of the glass-ceramics were $10^{-3}s.Cm^{-1}$ increased by $10^3$ order. The crystalline product in the glass-ceramics was $CuV_2O_6$. Heat-treatment conditions influenced the crystal growth of $CuV_2O_6$ and conductivity. The linear relationship between in (${\sigma}T$) and $T^{-1}$ suggested that the electrical conduction in the present glass-ceramics would be due to a small polaron hopping(SPH) mechanism.