• Title/Summary/Keyword: Spheroidization

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Development of Cast Iron Bonded Grinding Wheel by Using Spheroidization Mechanism of Graphite (흑연의 구상화기구를 이용한 주철본드 다이어몬드 숫돌의 개발)

  • 유기태;정해도;전형일
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1995.10a
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    • pp.61-64
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    • 1995
  • Grinding has been adapted as a finishing process,which can carry out form and surface integrity at the same time. Recently, high efficient and precise grinding technique is required bacause the needs for functional parts such as silicon wafer,ceramic,and electric materials are increasing. Accordingly, the development of grinding wheel appropriate to that purpose is very important. So, in this paper we newly developed a diamond grinding wheel by applying the superior characteristics of spheroidal graphite of the cast iron sintered product. Especially, a electric resistance sintering method was applied in which rapid heat treatment is possible. Finally, we have achieved successful results that the grinding wheel has high hardness,durability and grinding ability,and satisfies above conditions.

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The Effects of Si and Mo on the Structures and Mechanical Properties in High Si Spheroidal Graphite Cast Iron (고 Si 구상흑연주철의 조직과 기계적성질에 미치는 Si과 Mo의 영향)

  • Kim, Jong-Yeon;Ra, Hyung-Yong
    • Journal of Korea Foundry Society
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    • v.10 no.3
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    • pp.225-234
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    • 1990
  • Spheroidal graphite cast irons which are Fe-3%C-(4-6)%Si-(0-0.5)%Mo were studied to improve not only heat resistance but also mechanical properties. With increasing Mo content, the graphitization was decreased and carbide volume fraction was increased. The graphite spheroidization ratio was not decreased in Fe-3%C-6%Si-Mo system cast iron with increasing Mo content, but that was decreased in Fe-3%C-4%Si-Mo system and Fe-3%C-5%Si-Mo system cast irons. Hardness was increased with the Si and Mo contents. At constant Si content, tensile strength was increased with increasing Mo content, but that was decreased at 6%Si. In the experiment of oxidation, weight gain was decreased as the Si and/or Mo content increased, but increased at 1.5%Mo content.

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Condition and New Testing Method of Interfacial Oxide Films in Directly Bonded Silicon Wafer Pairs (직접 접합된 실리콘 기판쌍에 있어서 계면 산화막의 상태와 이의 새로운 평가 방법)

  • ;;;;D.B. Murfett;M.R.Haskard
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.3
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    • pp.134-142
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    • 1995
  • We discovered that each distinct shape of the roof-shaped peaks of (111) facets, which are generated on (110) cross-section of the directly bonded (100) silicon wafer pairs after KOH etching, can be mapped to one of three conditions of the interfacial oxide existing at the bonding interface as follows. That is, thick solid line can be mapped to stabilization, thin solid line to disintegration, and thin broken line to spheroidization. also we confirmed that most of the interfacial oxides of a well-aligned wafer pairs were disintegrated and spheroidized through high-temperature annealing process above 900$^{\circ}$C while the oxide was stabilized persistently when two wafers are bonded rotationally around their common axis perpendicular to the wafer planes.

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Studies on Grain Size Refinement for Rheocasting of Hypereutectic Al-18% Si by Using Sieve Type Mechanical Stirrer (과공정 Al-18% Si 합금의 레올로지 성형시 기계적 교반을 이용한 입자 미세화 연구)

  • 강용기;박진욱;강성수;강충길;문영훈
    • Transactions of Materials Processing
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    • v.9 no.4
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    • pp.389-394
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    • 2000
  • The studies on gram size refinement for rheocast processing of hypereutectic Al-18%Si alloys have been investigated in the present study. To increase the efficiency of mechanical stirring, sieve type stirrer are newly designed and implemented for rheocasting of hypereutectic Al-18%Si alloy. Mechanical stirring of semi-solid slurry by using sieve type mechanical stirrer results in morphological changes of the primary Si particles, from angular rod shape to near spherical shape and uniform distribution of proeutectic Si. The remarkable spheroidization of Primary Si Particles and distributional uniformity of proeutectic Si show well the efficiency of sieve type mechanical stirring method which can accelerate the coalescence-fracture-wear of the individual particles by strong turbulent flow between lattices during rotation of sieve type stirrer.

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A Study on the Graphitization and Scaling Resistance property of High Al-Cast Iron (고(高)알루미늄 내열주철(耐熱鑄鐵)에서의 흑연구상화(黑鉛球狀化)와 내산화성(耐酸化性)에 관한 연구(硏究))

  • Kim, D.K.;La, H.Y.
    • Journal of Korea Foundry Society
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    • v.1 no.2
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    • pp.2-9
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    • 1981
  • Graphite spheroidization and scaling resistance of cast iron containing 5-10% Al were investigated. It is impossible to obtain spheroidal graphite in cast iron containing Al with 8 % and over, but possible to obtain spheroidal graphite even in cast iron with an Al content of about 10 % by increasing Si content. In the scaling test carried out under the heating condition of $950^{\circ}C$ in air for total of 50 hours, the scaling resistance of cast iron containing Al with 8 % and over was remarkably superior, and also spheroidal graphite cast iron was superior to flake graphite cast iron. The scale became thinner more compacts and more protective with increasing Al content.

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Study on the Spheroidizing Mechanism of Graphite in Cast Iron (II) (鑄鐵에 있어서의 黑鉛球狀化 機構에 關한 硏究 (Ⅱ))

  • Choi, Hyung-Sup;Park, Won-Koo
    • Journal of the Korean Chemical Society
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    • v.8 no.2
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    • pp.57-61
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    • 1964
  • It was verified at Part Ⅰ of this investigation that there is a minimum wettability between molten iron and graphite, which was preliminarily coated with magnesium, and thus the spheroidization of graphite might have resulted from the lack of wettability between magnesium-adsorbed graphite and iron matrix. Being continued from the last work, the wettability between pure iron and graphite, coated with the various thickness of cerium, are measured at melting point of pure iron in vacuum and 200 mmHg argon gas atmosphere. The result indicates the presence of a minimum wettability at a critical thickness of cerium film as was proved in the case of magnesium. The experimental analysis shows that, the minimum wettability could be attributed entirely to a minimum work of adhesion between liquid iron and graphite at a critical concentration of cerium in the iron-graphite interface.

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열 cycle 재현법을 이용한 원자로압력용기(RPV)강 용접열영향부(HAZ) 해석

  • 김주학;문종걸;변택상;이창희;홍준화
    • Proceedings of the Korean Nuclear Society Conference
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    • 1997.05b
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    • pp.17-22
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    • 1997
  • ASME SA508 Class 3 원자로압력용기강을 대상으로, 용접열영향부(heat affected zone, HAZ)의 최고온도(peak temperature) 등온분포도(isothermal diagram)를 작성 및 해석하였고, 재현(simulated) 열영향부 시험편을 제작하여 미세조직검사 및 기계적특성 시험을 실시하였다. 그 결과, 최고온도 등온분포도를 이용하여, 미소열영향부(subzone of HAZ)의 미세조직(microstructure)에 미치는 예열(preheat)온도와 용접입열량(weld heat input)의 크기 효과를 예측할 수 있었다. 또한, 재현 HAZ 의 기계적특성 시험결과, 용접용융선(fusion line) + 1 mm 이내의 위치로 대표되는 열 cycle 조건에서는 모재보다 양호한 강도와 인성을 보였고, 용접용융선 + 2~3mm부근에서 가장 미세한 조직(fine tempered lower bainite)과 우수한 충격인성을 나타냈다. 한편, 용접용융선 + 약 5mm 위치에서의 열 cycle 을 재현한 시험편에서는 미세조직의 변화(spheroidization of carbides)와 함께 인성 및 기계적 특성이 저하하여 모재보다 낮은 값을 보이는 것을 발견할 수 있었다.

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The Effects of Drawing Strain and Annealing Condition on Mechanical Properties of High Strength Steel Wires (고강도강선의 신선 가공할 및 열처리 조건이 기계적 성질에 미치는 영향)

  • Lee, J.W.;Lee, Y.S.;Park, K.T.;Nam, W.J.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.10a
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    • pp.138-141
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    • 2008
  • The effects of annealing temperature and time on mechanical properties and microstructures were investigated in cold drawn pearlitic steel wires. During annealing, the increment of the tensile strength at low temperatures found to be due to age hardening, while the decrease in the tensile strength at high temperatures was attributed to age softening, involving the spheroidization of lamellar cementite and recovery of lamellar ferrite. Since tensile strength and the occurrence of the delamination would be closely related to the dissolution of cementite, the lower annealing temperature and the increase of drawing strain caused the higher tensile strength and the easier occurrence of the delamination in cold drawn pearlitic steel wires.

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Characterization of Microstructures of Variously Heat Treated Hypoeutectoid and Eutectoid Steel by Magnetic Coercivity Measurement (보자력 측정에 의한 아공석강 및 공석강의 열처리에 따른 미세조직 평가)

  • Byeon Jai Won;Kim C. S.;Kwun S. I.
    • Korean Journal of Materials Research
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    • v.14 no.8
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    • pp.565-572
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    • 2004
  • The microstructures of variously heat treated hypoeutectoid($0.45\%$ carbon) and eutectoid($0.85\%$ carbon) steel were characterized by magnetic coercivity measurement. The effect of spheroidization of cementites on the coercivity was investigated for $0.45\%$ carbon steel. In case of $0.85\%$ carbon steel, microstructural parameters such as prior austenite grain size, phase and pearlite interlamellar spacing were measured along with coercivity to investigate the relationships between them. Prior austenite grain size had little effect on the measured coercivity. Coercivity was observed to be high in order of martensite, pearlite and ferrite phases. The linear decrease of coercivity with increasing pearlite interlamellar spacing was found. The effect of each microstructural factor on the coercivity and the potential of coercivity as a nondestructive evaluation parameter for assessing microstructures of steel products are discussed.

Plasma Engineering for Nano-Materials

  • Kim, Seong-In;Shin, Myoung-Sun;Son, Byung-Koo;Song, Seok-Kyun;Choi, Sun-Yong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.08a
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    • pp.79-79
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    • 2012
  • A high temperature and a low temperature plasma process technologies were developed and demonstrated for synthesis, hybrid formation, surface treatment and CVD engineering of nano powder. RF thermal plasma is used for synthesis of spherical nano particles in a diameter ranged from 10 nm to 100 nm. A variety of nano particules such as Si, Ni, has been synthesized. The diameter of the nano-particles can be controlled by RF plasma power, pressure, gas flow rate and raw material feed rate. A modified RF thermal plasma also produces nano hybrid materials with graphene. Hemispherical nano-materials such as Ag, Ni, Si, SiO2, Al2O3, size ranged from 30 to 100 nm, has been grown on graphene nanoplatelet surface. The coverage ranged from 0.1 to 0.7 has been achieved uniformly over the graphene surface. Low temperature AC plasma is developed for surface modification of nano-powder. In order to have a three dimensional and lengthy plasma treatment, a spiral type of reactor has been developed. A similar plasma reactor has been modfied for nano plasma CVD process. The reactor can be heated with halogen lamp.

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