DEVELOPMENT OF WATER-BASED CORE TECHNOLOGY FOR LIGHT ALLOYS

ABSTRACT

This thesis describes, in a manufacturing context, the development of new waterbased core technology for light alloys. Cores used for steel casting are made from fused silica and are removed using hot sodium hydroxide under refluxing (pressurising hot acids). However, aluminium and other light alloys are attacked by sodium hydroxide. Currently there is no good core system for aluminium and other light alloys.

It is therefore desirable to find an alternative material/leaching agent combination for casting aluminium and other light alloys. The recent research review has shown that ceramic cores are mostly made by fused silica with different additives. The previous research has suggested using fused silica (different mesh size) as filling material and using magnesium oxide to control the slurry working life of core mixes.

Calcium silicate assists core leaching in dilute acid. The plaster (calcium sulphate) in the form of proprietary plasters (Crystcal R, Fine Casting Plaster) is used to create bond and gives strength to the core. Lithium carbonate acts has an accelerator, improving the strengthening effect of the plaster in the cores. The binder (Ludox® AM) and water act (as added materials) to bind the composition Core compositions were made with different core trials to produce a core, which records suitable strength and quick leaching properties for light alloys.

Core trials were individually mixed and poured into a wooden core box. Cores were pre-dried for by two hours cooling. The cores were subjected to computerised three-point bend test to record the Modulus of rupture (MOR). The plain strain fracture toughness and Weibull parameters were calculated. The Weibull parameter was plotted using Minitab analysis software. Using the cores, gravity die casting process were carried out.

The subsequent castings was dipped in diluted nitric, citric and acetic acid to leach out the core. Using different core compositions, core trials were mixed, poured, dried, tested and leached. The high amount of plaster in core trials records high MOR when cores were fired between 200°- 400° C and the opposite result when fired between 600°- 800° C. The different grade of plasters(CRP,FCP) do not influence the strength. One percent of magnesium oxide gives a very short working life.

High amount of binder(Ludox® Workable MOR results can be obtained depending on composition allowing manual handling or a waxing process. The fracture toughness is typical of a brittle material, with matching Weibull parameters. The casting process suggests that the new materials are sufficiently refractory.

The cores are leached out using diluted nitric, acetic and citric acid at rates compatible with commercial manufacture. This methodology has successfully produced a core using fused silica with plaster and magnesium oxide for aluminium and possibly for light alloys. Different core trials can be used depending on the specific industrial application relating to strength and removal with acid attacking the metal.

Further work is needed to fine tune optimum leaching conditions. AM) in core produce strong cores. twenty-four hours. Cores were fired to different temperatures for two hours, followed

Korea Abstract

이 논문은 제조 맥락에서 경합금을 위한 새로운 수성 핵심 기술의 개발을 설명합니다. 강철 주조에 사용되는 코어는 용융 실리카로 만들어지며 환류(고온 산 가압) 하에 뜨거운 수산화나트륨을 사용하여 제거됩니다.

그러나 알루미늄 및 기타 경합금은 수산화나트륨의 공격을 받습니다. 현재 알루미늄 및 기타 경합금을 위한 좋은 코어 시스템은 없습니다. 따라서 알루미늄 및 기타 경합금 주조를 위한 대체 재료/침출제 조합을 찾는 것이 바람직합니다. 최근 연구 검토에 따르면 세라믹 코어는 대부분 다른 첨가제를 사용하여 용융 실리카로 만들어집니다.

이전 연구에서는 용융 실리카(다른 메쉬 크기)를 충전재로 사용하고 산화마그네슘을 사용하여 코어 믹스의 슬러리 작업 수명을 제어할 것을 제안했습니다. 규산칼슘은 묽은 산에서 코어 침출을 돕습니다. 전용 플라스터(Crystcal R, Fine Casting Plaster) 형태의 플라스터(황산칼슘)는 결합을 생성하고 코어에 강도를 부여하는 데 사용됩니다.

탄산리튬은 촉진제를 가지고 있어 코어의 석고 강화 효과를 향상시킵니다. 결합제(Ludox® AM)와 물은 조성을 결합하기 위해 작용합니다(추가된 재료로서) 코어 조성은 경합금에 적합한 강도와 빠른 침출 특성을 기록하는 코어를 생산하기 위해 다양한 코어 시도로 만들어졌습니다.

코어 시험을 개별적으로 혼합하고 나무 코어 상자에 부었습니다. 코어는 2시간 냉각 동안 사전 건조되었습니다. 코어는 파열 계수(MOR)를 기록하기 위해 컴퓨터화된 3점 굽힘 테스트를 거쳤습니다. 일반 변형 파괴 인성 및 Weibull 매개변수가 계산되었습니다. Minitab 분석 소프트웨어를 사용하여 Weibull 매개변수를 플로팅했습니다.

코어를 이용하여 중력 다이캐스팅 공정을 진행하였다. 후속 주조물을 희석된 질산, 시트르산 및 아세트산에 담그어 코어를 침출시켰다. 다양한 코어 조성을 사용하여 코어 시험을 혼합, 붓고, 건조하고, 시험하고, 침출했습니다. 코어 시험에서 많은 양의 석고는 코어가 200°-400°C 사이에서 소성될 때 높은 MOR을 기록하고 600°-800°C 사이에서 소성될 때 반대 결과를 기록합니다.

다른 등급의 석고(CRP,FCP)는 영향을 미치지 않습니다. 힘. 산화마그네슘의 1%는 작업 수명이 매우 짧습니다. 많은 양의 결합제(Ludox® Workable MOR 결과는 수동 취급 또는 왁스 처리가 가능한 조성에 따라 얻을 수 있습니다. 파괴 인성은 Weibull 매개변수와 일치하는 취성 재료의 전형입니다.

주조 공정은 새로운 재료가 충분히 내화성이 있음을 시사합니다. 코어는 상용 제조와 호환되는 속도로 희석된 질산, 아세트산 및 시트르산을 사용하여 침출됩니다. 이 방법은 알루미늄 및 가능한 경합금용 석고 및 산화마그네슘과 용융 실리카를 사용하여 코어를 성공적으로 생성했습니다.

다양한 코어 시험을 사용할 수 있습니다. 강도 및 금속을 공격하는 산 제거와 관련된 특정 산업 적용에 따라 최적의 침출 조건을 미세 조정하려면 추가 작업이 필요합니다. 코어의 AM)은 강한 코어를 생성합니다. 24시간. 코어는 2시간 동안 다른 온도로 소성되었습니다.

Figure 7. Sand casting with sand cores (59)
Figure 7. Sand casting with sand cores (59)
Figure 12. Cast iron split moulds with core
Figure 12. Cast iron split moulds with core
Figure 13. Pouring process to assembled mould
Figure 13. Pouring process to assembled mould

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