• 제목/요약/키워드: hard metal

검색결과 281건 처리시간 0.026초

Slot Grinding시 전해 인프로세스 드레싱의 영향에 관한 연구 (Effect of Electrolytic In-process Dressing in Slot Grinding)

  • 유정봉;정해도;최헌종
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 1995년도 추계학술대회 논문집
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    • pp.48-52
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    • 1995
  • Chipping is an unavidable phenomean in the slot grinding process of hard and brittle materials. However,it should be reduced for the improvement of surface integrity in the manufacture of optical and semiconductor components. Electrolytic In-process Dressing (ELID) technique for metal bonded superabrasive grinding wheel has been developed for mirror surface grinding of hard and brittle materials. Electrically dressed wheel surface has sharply exposed abrasives and results in lower grinding force, higher grinding efficiency in grinding. The paper deals with a newly developed method for slot grinding using ELID and was implemented to improve grooved surface quality and decreases chipping size on the edge of the groove. As a result, we accomplished shipping-free grooves and obtained the clear ground sufaces on glass and tungsten carbide.

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HDD 스핀들용 빗살무늬 저널베어링의 최적설계 (An Optimum Design of Herringbone Grooved Journal Bearings for Spindle Motor of Hard Disk Drive System)

  • 유진규
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2002년도 춘계학술대회논문집
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    • pp.530-532
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    • 2002
  • This paper presents an optimum design of herringbone grooved journal bearing for spindle motor of hard disk drive (HDD) system. In addition to the conventional “rectangular” groove, various groove profiles are designed. The stiffness and damping coefficients of the oil film and frictional torque are calculated and compared for tile various groove profiles. The “circular”, “valley”, and “reversed saw tooth” grooves do not produce high direct stiffness, since they partly increase the groove depths in the direction of lubricant flow, causing to reduce the pumping action of the bearing. The maximum direct stiffness can be obtained by the “rectangular”, “saw tooth”, and “step” grooves. With the same cross sectional area of the grooves, these three grooves have the same maximum stiffness, damping coefficients, and frictional torque. Among these recommendable grooves, the saw tooth groove may keep its original profile for long, enduring metal-to-metal contact during startup and shutdown.

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Shearing Properties of Hard Metal Powder and Iron Powder in the Low Density Range

  • Jonsen, P.;Haggblad, H.A.
    • 한국분말야금학회:학술대회논문집
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    • 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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    • pp.1296-1297
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    • 2006
  • Both plastic and elastic properties change dramatically from the beginning to the end of the compaction phase. Previous investigations have shown that powder transfer and high powder flow during initial compaction at low density affects the strength of the final component significantly. Investigated here are shear failure and elastic shear modulus in the low density range for hard metal powder and for pre-alloyed water atomized iron powder. Direct shear test equipment for sand and clay has been modified to measure the shearing properties of powder for an axial loading between 1 kPa and 500 kPa.

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알루미늄 합금의 표면경화 (Formation of Thicker Hard Alloy Layer on Surface of Aluminum Alloy by PTA Overlaying with Metal Powder)

  • Lee, Young-Ho
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 1996년도 특별강연 및 추계학술발표 개요집
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    • pp.3-15
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    • 1996
  • The formation of a thicker hard alloyed layer have been investigated on the surface of aluminum cast alloy (AC2B) by PTA overlaying process with Cr, Cu and Ni motel powders under the condition of overlaying current 125-200A. overlaying speed 150 mm/min and different powder feeding rate 5-20 g/min. In addition the characteristics of hardening and wear resistance of alloyed layer here been examined in relation to the microstructure of alloyed layer. Main results obtained were summarized as follows: 1) There was an optimum overlaying condition to get a good alloyed layer with smooth surface. This good layer became easy to be formed as increasing overlaying current and decreasing powder feeding rate under a constant overlaying speed. 2) Cu powder was the most superior one in metal powders used due to a wide optimum overlaying condition range, uniform hardness distribution of Hv250-350, good oar resistance and freedom from cracking in alloyed layer with fine hyper-eutectic structure. 3) On the contrary, irregular hardness distribution was usually obtained in Cr ar Ni alloyed layers of which hardness was increased as Cr or Ni contents and reached to maximum hardness of about Hv400-850 at about 60wt%cr or 40wt%Ni in alloyed layer. 4) Cracking occurred in Cr or Ni alloyed layers with higher hardness than Hv250-300 at mere than 20-25wt% of Cr or Ni contents in alloyed layer. Porosity was observed in all alloyed layers but decreased by usage of spherical powder with smooth surface.

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금속/비금속 복합센서기반 위험물 탐지기술 개발 (Development of Hazardous Objects Detection Technology based on Metal/Non-Metal Detector)

  • 유동수;김석환;이정엽;이석재
    • 제어로봇시스템학회논문지
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    • 제20권2호
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    • pp.120-125
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    • 2014
  • Conventional handheld metal detectors use a single induction coil to detect the metallic parts of explosive objects, and the detector generates an acoustic signal from its magnetic response to a metallic object so that an operator can confirm the existence of mines. Though metal detectors have very useful detection mechanisms to find mines, it is easy to cause a high false alarm ratio due to the detection of non-explosive metallic items such as cans, nails and other pieces of metal, etc. Also, because of the physical characteristic of a metal detector it is hard to detect non-metallic objects such as mines made of wood or plastic. Furthermore, the operator must move it to the left and right slowly and repeatedly to attain enough sensor signals to confirm the existence of mines using only a monotonous acoustic signal. To resolve the disadvantages of handheld detectors, many new approaches have been attempted, such as an arrayed detector and a visualization algorithm based on metal/non-metal sensor. In this paper, we introduce a visualization algorithm with a metal/non-metal complex sensor, an arrayed metal/non-metal sensor and the their testing and evaluation.

경금속에 대한 노출력이 없는 거대세포 간질성 폐렴(Giant Cell Interstitial Pneumonia) 1예 (A Case of Giant Cell Interstitial Pneumonia without History of Exposure to Hard Metal)

  • 홍지현;이재명;강민종;김동규;정기석;장기택;박혜림;이인재
    • Tuberculosis and Respiratory Diseases
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    • 제52권4호
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    • pp.419-424
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    • 2002
  • 경금속 진폐증에 속하는 거대세포 간질성 폐렴은 경금속을 사용한 절삭, 연마의 과정 중 발생하는 분진을 흡입하여 발생하는 것으로 알려져 있으나 이러한 직업력이 불분명한 증례를 개흉생검술을 통해 진단하였기에 보고하는 바이다.

단결정 실리콘 태양전지를 위한 screen printing 전극과 photo lithography 다층전극의 적용에 대한 연구 (Application of Screen Printing and Photo Lithography Multi-layer Metal Contact for Single Crystalline Silicon Solar Cells)

  • 김도완;최준영;이은주;이수홍
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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    • pp.109-109
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    • 2006
  • Screen printing (SP) metal contact is typically applied to the solar cells for mass production. However, SP metal contact has low aspect ratio, low accuracy, hard control of the substrate penetration and unclean process. On the other hand, photo lithograpy (PL) metal contact can reduce defects by metal contact. In this investigation, PL metal contact was obtained the multi-layer structure of Ti/Pd/Ag by e-beam process. We applied SP metal contact and PL metal contact to single crystalline silicon solar cells, and demonstrated the difference of conversion efficiency. Because PL metal contact silicon solar cell has Jsc (short circuit current density) better than silicon solar cell applied SP metal contact.

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