• 제목/요약/키워드: Alumina mold

검색결과 41건 처리시간 0.025초

석고 몰드에서 용출된 Ca이 주입성형 알루미나 소결체의 미세구조 및 파괴인성에 미치는 영향 (Effects of Dissolved Ca from Plaster Mold During Slip Casting on the Microstructure and Fracture Toughness of Sintered Alumina)

  • 박재관;임동기;김인태;김윤호
    • 한국세라믹학회지
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    • 제28권12호
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    • pp.1019-1025
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    • 1991
  • The effect of dissolved Ca ion from plaster mold during slip casting on the microstructure and fracture toughness of high-purity sintered alumina were investigated. When the alumina slip containing 1000 ppm MgO was casted on a calcined alumina mold, the sintered compact had a homogeneous microstructure with equiaxed grains. However, when the same slip was casted on a plaster mold, the sintered compact consisted of the mixture of equiaxed and elongated grains. This inhomogeneous microstructure was also observed in the sintered alumina doped with 100o ppm MgO and 100 ppm CaO whose compact was prepared on the calcined alumina mold indicating that the inhomogeneity was caused by CaO. It was found that the specimen containing both MgO and CaO had higher fracture toughness than that containing MgO only. The enhanced fracture toughness by CaO is probably due to the crack deflection along the boundaries of the elongated grains.

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알루미나몰드를 사용한 슬립캐스팅법에 의한 3Y-TZP/SUS316계 경사기능재료의 제조 (Fabrication of 3Y-TZP/SUS316 Functionally Graded Material by Slip Casting Method Using Alumina Mold)

  • 여정구;정연길;이세훈;최성철
    • 한국세라믹학회지
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    • 제34권1호
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    • pp.70-78
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    • 1997
  • 3Y TZP/SUS316계 경사기능재료를 슬립캐스팅법을 이용하여 제조하였다. 슬립캐스팅 공정에서 석고몰드를 대체하기 위해 알루미나몰드를 제조하였고, 3Y-TZP/SUS316 2상 슬러리의 최적 분산조건을 ESA, 점도계, 침전거동의 관찰 등을 통해 결정하였으며, 석고몰드와 알루미나몰드로 캐스팅한 시험편의 제반 특성을 소결수축율변화, 건조 및 소결거동, 미세구조 관찰 등으로 조사하였다. 그 결과 알루미나몰드를 사용하여 제조된 시험편에서는 석고몰드 사용시 나타나는 표면에서의 오염이 관찰되지 않았으며, 각 층의 두께조절이 쉬웠고 높은 재현성을 나타냄을 알 수 있었다. 특히 알루미나몰드를 사용하여 제조한 SUS316에서는 어떤 열화현상도 관찰되지 않았다. 결국 슬립캐스팅 공정으로 3Y-TZP/SUS316계 경사기능재료를 제조함에 있어서 기존의 석고몰드보다 다공질 알루미나몰드의 사용이 바람직하다는 것을 알 수 있었다.

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Fine Ceramics의 Casting공정을 위한 다공질 알루미나 몰드의 제조 (Fabrication of Porous Alumina Mold for the Casting Process of Fine Ceramics)

  • 박한수
    • 한국세라믹학회지
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    • 제36권1호
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    • pp.89-96
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    • 1999
  • 석고몰드의 단점을 극복할 수 있는 다공질 알루미나 몰드의 제조저건을 확립하였다. 다공질 알루미나 몰드의 제조를 위해 활성탄의 질량비에 따라 조성비를 달리하여 첨가한 후, ESA와 유동특성 등을 조하삼으로써 안정된 이상 슬러리를 제조하였으며, 이를 석고몰드에 캐스팅하여 얻은 원통형 알루미나 몰드를 사용하여 활성탄의 양과 소결온도에 따른 수축율 변화와 마모에 대한 저항성을 측정하였다. 다공질 알루미나 몰드의 소결에서는 비수축 소결구인 표면확산에 의해 입자간 넥 강도의 증진을 통한 몰드의 강도 증진을 도모하는 것이 바람직하며, 이를 위해 1,00$0^{\circ}C$이하에서 유지시간의 변화에 따른 열역학적 방법, 1,00$0^{\circ}C$이상의 온도에서 알루미나의 수축을 억제하면서 빠른 승온속도를 열처리온도에 따른 동역학적 방법과 이 두가지 방법을 혼합하는 방법 등으로 구분하여 다동질 알루미나 몰드의 소결조건을 분석하였다. 위 방법들에 대한 다공질 알루미나 몰드의 캐스팅 특성을 분석한 결과, 복합 소결법이 최적임을 알수 있었다. 제조된 다공질 알루미나 몰드의 비교적 높은 강도를 보였으며, 석고몰드레 비해 빠른 건조시간, 산, 염기에 대한 내식성 및 캐스팅 특성이 우수하였다.

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순수 티타늄 주조체의 주형온도에 따른 용탕반응성 및 표면거칠기 (Metal-Mold Reaction and Surface Roughness Measurement of Pure Titanium Casting Specimens with Mold Temperatures)

  • 차성수;송영주;박수철
    • 대한치과기공학회지
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    • 제32권4호
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    • pp.297-305
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    • 2010
  • Purpose: The purpose of this study was to observe the change of metal-mold reaction and surface roughness in titanium casting specimens for phosphate-silica alumina bonded investment with mold temperatures. Methods: The metal-phosphate silica alumina bonded mold interface reaction and surface roughness of titanium casting specimens according to mold temperatures were investigated. The Specimens were analysed by scanning electron microscopy and surface roughness tester. Results: The oxidation behavior indicated by the growth of oxide thickness. The titanium-oxide layer were consisted two layer of a porous external and a dense internal one. The reaction layer and surface roughness increased with increasing investment material temperature. Conclusion: In this work, The most suitable mold temperature in casting of pure titanium was $200^{\circ}C$.

슬립 캐스팅을 이용한 통기성 세라믹형의 쾌속 제작 (Rapid Tooling of Porous Ceramic Mold Using Slip Casting)

  • 정성일;정두수;임용관;정해도;조규갑
    • 한국정밀공학회지
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    • 제16권5호통권98호
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    • pp.98-103
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    • 1999
  • The application field of porous mold is more and more expended. A mixture of alumina and cast iron is used for making porous mold using slip and vacuum casting method in this study. Slip casting is a process that slurry is poured into silicon rubber mold, dried in vacuum oven, debinded and sintered in furnace, In this procedure, slurry is composed of powder, binder, dispersion agent, and water. Vacuum casting is a technique for removing air bubbles existed in the slurry under vacuum condition. Since ceramics has a tendency of over-shrinkage after sintering, cast iron is used to compensate dimensional change. The results shows that sintering temperature has a great effect on characteristics of alumina-cast iron composite sintered parts. Finally ceramic-metal composite sintered mold can be used for aluminum alloy casting of shoe mold using this process.

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금형온도와 탈지조건이 사출성형에 의한 알루미나 부품 제조에 미치는 영향 (EFfect of Molding Temperature and Debinding Conditions on Fabrication of Alumina Component by Injection Molding)

  • 임형택;임대순
    • 한국세라믹학회지
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    • 제32권5호
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    • pp.559-566
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    • 1995
  • Alumina powder was coated with stearic acid and then mixed with isotactic polypropylene, atactic polypropylene as binders at 15$0^{\circ}C$ for 2 hours. The mixture was then injection molded at various mold temperatures using injection molding machine to investigate the effect of the molding temperature and debinding parameters on the formation of the defects. The molded specimens were debinded in both air and nitrogen atmospheres. Wicking and solvent methods were also used to enhance debinding efficiency. The specimens were prefired at 120$0^{\circ}C$ and then sintered at 150$0^{\circ}C$ for 3 hours. Various defects were formed at mold temoperature of 3$0^{\circ}C$, 6$0^{\circ}C$ and 10$0^{\circ}C$ and any noticeable defect was not formed at 85$^{\circ}C$. The density of green body increased with mold temperature. Debinding in air atmosphere was more effective than in nitrogen atmosphere. Results also proved that wicking and solvent treatments helped minimize the number of defects.

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초합금 단결정 주조용 주형의 실리카 함량에 따른 고온강도 영향 (The Influence of the Silica Contents for High Temperature Strength for Single Crystal Casting Mold of Superalloys)

  • 안성욱;;;임옥동;진영훈;서동이;이재훈;김병호;오제명
    • 한국재료학회지
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    • 제8권10호
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    • pp.879-883
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    • 1998
  • 초합금의 진공정밀주조시에 진공하에서 용해한 합금을 $1000~1700^{\circ}C$로 가열한 세라믹 주형에 주입하고 난 후, 용탕이 장시간 주형안에 노출됨으로써, 주형의 고온강도가 높아야 하므로 고품위의 주형재를 사용하여 왔으나, 저품위의 값싼 소재를 사용하여 고품위의 주형과 동등한 효과를 갖게 하고자 주형내의 Silica 함량을 조절하였다. 그 결과 SiO2 첨가량이 7.7wt.%일 때, 다른 시험편에 비해 소성강도와 고온강도가 10-55%가량 증가 하였다. 따라서 일반적으로 정밀주조 주형으로 사용하는 용융알루미나와 colloidal silica의 혼합비를 제어하여 단결절 주조용 주형을 개발하였다.

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석고몰드속에서 Boehmite의 Hydrosol-Gel로부터 제조된 알루미나의 미세구조에 미치는 M\ulcorner의 영향 (Effect of MgO on Microstructural Evolution of Alumina Prepared from Hydrosol-Gel Process of Boehmite in Plaster Mold)

  • 오경영;정창주
    • 한국세라믹학회지
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    • 제30권12호
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    • pp.1029-1038
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    • 1993
  • The microstructures of aluminas, included of dissolved CaO as $\alpha$-alumina seeded pseudo-boehmite hydrosol was gelled in plaster mold and doped of MgO as dipping of calcines(120$0^{\circ}C$-2h) into Mg-nitrate solution, were compared to the one of which additives are excluded during the gellation. It was formed the boundary layer of 300~350${\mu}{\textrm}{m}$ distance from surface to the inside, containing of approximately 500ppm CaO by dissolved Ca from plaster mold. As the MgO addition to the boundary layer with dissolved CaO, the microstructure of the layer was uniformed and inhibited the grian growth, compared to one of that additives be excluded specimen and of MgO doped-inside region. This result was considered as abnormal grain growth and effect of flat boundary formation be appeared by effects of dissolved CaO, were decreased by MgO co-doping.

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티타늄합금 주조용 치과매몰재의 조성에 따른 경화거동 및 용탕반응성에 관한 연구 (A Study on the Hardening Behavior and Metal-Mold Reaction in Dental Investment Materials for Titanium Castings)

  • 정국진;여인동;심광보
    • 한국주조공학회지
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    • 제19권5호
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    • pp.419-426
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    • 1999
  • Hardening behavior and metal-mold reaction of phosphate bonded investments for titanium and titanium alloys were investigated. Alumina and $Y_2O_3-stabilized$ zirconia, which are thermodynamically more stable than Titania, were used as major filler materials. $NH_4H_2PO_4$ was used as binder, and MgO was used as hardening acceleration material. A different composition ratio of binder and hardening acceleration material had effected on general hardening behavior and castings. And adding $YO_3-stabilized$ zirconia to alumina, metal-mold reaction characteristics for castings was evaluated. Considering working conditions and effects on castings, the best composition ratio conditions were both 10:10 and 12:8($NH_4H_2PO_4vs.\;MgO$). On the other hand, increasing the contents of $Y_2O_3-stabilized$ zirconia for filler material, metal-mold reaction layer of titanium castings was greatly decreased.

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가압-진공 하이브리드 주입성형에 의한 알루미나의 균질 성형 (Homogeneous Shape Forming of Alumina by Pressure-Vacuum Hybrid Slip Casting)

  • 조경식;송인범;김재
    • 한국세라믹학회지
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    • 제49권6호
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    • pp.592-600
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    • 2012
  • Conventional methods for preparing ceramic bodies, such as cold isostatic pressing, gypsum-mold slip casting, and filter pressing are not completely suitable for fabricating large and thick ceramic plates owing to disadvantages of these processes, such as the high cost of the equipment, the formation of density gradients, and differential shrinkage during drying. These problems can be avoided by employing a pressure-vacuum hybrid slip casting approach that considers not only by the compression of the aqueous slip in the casting room (pressure slip casting) but also the vacuum sucking of the dispersion medium (water) around the mold (vacuum slip casting). We prepared the alumina formed bodies by means of pressure-vacuum hybrid slip casting with stepwise pressure loading up to 0.5 MPa using a slip consisting of 40 vol% solid, 0.6 wt% APC, 1 wt% PEG, and 1 wt% PVA. After drying the green body at $30^{\circ}C$ and 80% RH, the green density of the alumina bodies was about 56% RD. The sintered density of an alumina plate created by means of sintering at $1650^{\circ}C$ for 4 h exceeded 99.8%.This method enabled us to fabricate a $110{\times}110{\times}20$ mm alumina plate without cracks and with a homogeneous density, thus demonstrating the possibility of extending the method to the fabrication of other ceramic products.