• 제어로봇시스템학회논문지
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• 제3권1호
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• pp.89-93
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• 1997

This paper describes the automatic testing system developed for powder metallurgy process using the visual inspection, and its some internal algorithms. The system consists of one unit from each of the five types of units; feeding, slot, vision inspection, volumn counter, and inferior good extractor units. Some applications of the system to powder metallurgy process has shown the possibility of reducing the rework and increasing the efficiency of operation.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.129-130
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• 1999

The superplastic deformation characteristics is powder metallurgy(PM) Al-Li alloy has been studied within the framework of a recently proposed internal variable theory of superplasticity(SSP). The flow curves were obtained by performing a series of load relaxation tests at the temperature range from 45$0^{\circ}C$ to 52$0^{\circ}C$ It has been found that the overall flow curves were separated into the grain boundary sliding(GBS) and the accommodating dislocation glide processes/ The tensile curves were also obtained to clarify the superplastic deformation bahavior of PM Al-Li alloy. The microstructural features of PM AL-Li alloy have been examined through the transmission electron microscopy.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.231-235
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• 1990

Soft magnetic silicon steels containing up to 6.5wt% of silicon were prepared by powder metallurgical processing and their magnetic properties were evaluated. The magnetic properties of P/M silicon steels are similarly affected by the silicon addition as those of conventional ingot processed ones but are also significantly affected by density and interstitial impurities particularly oxygen content. Magnetic flux density, $B_{10}$ and coercivity, Hc, tends to decrease with silicon content whereas maximum permeability, ${\mu}m$, decreases first and then increases rapidly above 5 wt% silicon. Increasing density also increases magnetic flux density and maximum permeability but reduces coereivity. The latter two properties are, however, affected more strongly with oxygen content.

• 소성∙가공
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• 제16권4호
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• pp.244-249
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• 2007

The influence of powder compaction pressure on the hydraulic cylinder block fabricated by powder metallurgy is investigated in this study. The cylinder block is compacted with powder under various compaction pressures and then sintered, and its density and dimensions are measured to reveal the relationship of the powder compaction pressure with the product quality. Moreover, finite element analyses of the density distributions are carried out under the same conditions with the experiments and the predicted results are compared with the measured ones.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.308-311
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• 2002

Removal of gas in a mold has been a big problem in pressing mold or in injection mold. Air vent has been used to solve the problem, but it has weak points such as the Increased cost, the increased number of process. and vent marks on the surface of a product. In this study, the sintering method and rapid tooling method are used for making porous metal mold. Porous metal mold has many open pores, which are very small. When porous metal mold is used for pressing mold or injection mold, all process would be made short, produce cost would be down, and vent marks would be not leaved on the surface of a product. Characteristic of Porous material varies from sintering conditions, which are the length of sintering time, sintering temperature and sintering atmosphere etc. This study will find optimized sintering condition for the porous metal mold.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 춘계학술대회 논문요약집
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• pp.81-81
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• 2004

등통로각압축(ECAP, Equal Channel Angular Pressing)공정은 다결정의 재료 덩어리를 두 채널(channel)이 일정하게 교차하는 형태의 금형에 통과시켜 단면적과 단면 형상의 큰 변화 없이 압출하는 성형법으로 다른 공정에 비해 상대적으로 낮은 압력으로 재료에 소성변형을 발생시켜 입자를 미세화 시킬 수 있으며, 기존의 분말야금에 의한 방법에 비해 상용재료를 포함한 광범위한 금속 및 합금에 적용이 용이한 점과 재료 내부에 기포가 거의 잔류하지 않는 점등의 장점을 가지고 있다.(중략)

• 열처리공학회지
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• 제14권4호
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• pp.235-239
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• 2001

급속 표면가열과 기존의 전기로 열처리에서 얻어지는 경화의 가장 중요한 차이점은 전자가 불균질한 오스테나이트를 생성할 수도 있다는 것이다. 즉, 오스테나이트에 미용해 탄화물이 존재할 수도 있고 탄소와 합금원소의 농도 구배가 존재할 수도 있다. 합금강에서, 이러한 탄화물은 합금성분이 비교적 높기 때문에 철 탄화물에 비해서는 좀 더 천천히 기지에 용해된다. 또한 망간, 크롬, 니켈 및 몰리브덴과 같은 치환형 합금원소는 천천히 확산한다. 따라서, 균일한 오스테나이트를 생성하기 위해서는 더 많은 시간과 더 높은 온도가 요구된다. 그러나 표면 구역의 낮은 경화능에도 불구하고 냉각속도가 마르텐사이트의 체적분율이 큰 미세조직을 확보할 만큼 충분히 크기 때문에 경도는 높게 된다.

• 열처리공학회지
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• 제9권1호
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• pp.62-68
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• 1996

In order to establish making process of water atomized iron powder for powder metallurgy, effect of heat treatment condition on change of powder properties and impurities was investigated at each tempeature of $850{\sim}950^{\circ}C$. The results are as follows. Particle morphology of iron powder changed slightly from sphercial type to irregular type and the amount of fine particle decreased more and more with increasing of heat treatment time at each temperature. The flow rate and apparent desity of iron powder also decreased due to particle coalescence in order of $850^{\circ}C$, $950^{\circ}C$, $900^{\circ}C$. Those powder Properties became to decrease particularly at $900^{\circ}C$ in alpha iron region. On the other hand, residual carbon and oxygen contents in iron powder decreased extremely with increasing of heat treatment temperature and time.

• 오토저널
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• 제15권4호
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• pp.1-7
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• 1993

최근 엔진의 고성능, 고출력화, 저연비화 Maintenance Free화에 따라 엔진의 부하가 증대되었고, Valve Seat에 대해서도 내마모성, 내열성, 내식성 향상이 요구되고 있다. 특히 무연가솔린과 LPG사용으로 내구성을 갖는 High Performance의 Valve Seat 재질을 요구하게 되었고, 엔진의 높은 작동온도등 가혹한 조건하에서 'Recession'이라 일컬어지는 Seat마모가 생기게 된다. Valve Seat는 일반적으로 분말야금법에 따라 제조되고 있으며, 엔진조건에 따라 여러가지의 재질이 사용되며, 높은 온도에서 열전도성과 기공의 산화방지 및 Valve 내구성 향상의 효과를 얻기 위하여 동용침을 하여 사용하는 추세이다. 본 실험에서는 Valve Seat 기공부위의 산화와 마모특성을 조사하기로 한다.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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• pp.81-84
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• 2003

The effect of annealing condition on the texture and microstructure development in Ni tapes fabricated by cold-rolling including powder metallurgy was investigated. The Pole-figure results showed that the Ni tapes annealed at lower temperature than 50$0^{\circ}C$ were the mixture of brass deformation texture and cube texture. The specimens annealed at high temperatures had only well-developed cube texture and the FWHMs of in-plane and out-of-plane were in the range of 8-10$^{\circ}$. The degree of texture was not significantly depended on annealing temperatures. The grain morphologies of Ni tapes prepared at low temperatures showed serrated grain boundaries due to incomplete recrystallization, but the specimens prepared at high temperatures showed stabilized grain shape without serrated grain boundaries.