Clay/EAF dust계 시편의 소결과정 중 액상거동 제어
The control of liquid phase behavior during sintering of Clay/EAF dust bodies
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초록
지정 폐기물인 electrical arc furnace(EAF) 더스트에는 액상을 형성하는 flux 성분이 많이 포함되어있어, 점토와 혼합하면 시편의 소결온도를 낮춰주고 기계적 강도를 향상시키는 장점이 있다. 그러나 더스트-점토 계 벽돌 제조시 더스트 첨가량을 증가시키면 소결과정에서 과도한 액상이 생성되어 제품 불량률이 높이진다. 점토-더스트 계 시편의 소결공정 중에 발생하는 액상을 제어하기 하기위하여 Al2O3를 첨가하고 물리적 특성 변화를 분석하였다. Al2O3가 첨가된 더스트-점토 계 소결체는 기공크기가 감소되면서 미세구조가 균일해졌다. 이에 따라 기계적 강도가 증가되었고 동시에 최대강도가 나타나는 온도가 높아졌다. 또한 겉보기 밀도가 증가되었고 흡수율은 감소하였다. 첨가된 Al2O3는 mullite(3Al2O3·2SiO2)를 생성함으로서, 액상형성에 참여할 SiO2을 소모시키고 동시에 액상의 점도를 높여, 소결체의 내화도를 증진시키고 따라서 소결과정에서 시편 불량률을 낮출 것으로 분석되었다.
Abstract
The electrical arc furnace (EAF) classified as a special waste contains many flux components producing melts during a sintering process, so it decreases the sintering temperature and improves the mechanical properties of specimens. Increasing dust content in a clay-dust system brick, however, may cause the fraction defective higher due to the excessive liquid produced. To control the liquid behavior produced during sintering process for the clay-dust system specimens, the Al2O3 was added and the physical properties were analyzed. The microstructure for the clay-dust system body sintered with Al2O3 became homogeneous and the overall size of pores decreased. Adding Al2O3 to clay-dust system body increased the mechanical properties and the temperature of maximum strength increased as much as 50oC, and the apparent density increased and the absorption decreased. The mullite (3Al2O3?SiO2) was produced during sintering process by reaction of Al2O3 and SiO2 which could participate to liquid-producing-process and the viscosity of melts increased which was proved by measuring a critical viscosity temperature (Tcv) therefore, the refractoriness of specimens were improved to lower the fraction defective.
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