Molten　aluminum　which　has　highly　chemical　activity　for　oxygen　is　formed　the　unique　oxide　called ”Obake” of the　Al-Si-O　system．The　Obake　was　generated　only　when　silicon　was　contained　in　alumimm　alloy and　silica　was contained　in　crucible．Comparing　chemical　composition　of　the　obake　formed　in　an　industrial　furnace　with　that　of the　molten　aluminum，Si　component　in　the　Obake　was　concentrated　both　from　the　castable　refractory　and　the molten　aluminum．The　ratios　of　Si　to　Al　in　the　molten　alumimm　and　the　Obake　were　expressed　by　Si：Al＝5：89 and　Si：Al=11：51，respectively．The　indispensable　condition　of　the　formation　of　Obake　was　that　SiO（g） was constantly　supplied．The　molten　aluminum　reacted　with　SiO2（s） according　to　the　reaction　of SiO2（s）＋2Al（l）＝SiO（g）＋Al2O(g） to　provide　SiO（g） and　A1、0（g）． Under　the　particular　oxygen　partial　pressure，Si（1）in　molten　aluminum　reacte〔1with　AIO（g）to　from　SiO（g）．The presence　of　SiO（g） was　revealed　by　the　result　ofthe　industrial　furnace　test，that　is，the　increase　of Si　component　in Obake，Furthemore，Obake　grew　when　its　surface　was　wetted　by　molten　aluminum，that　is，the　contact　angle between　Obake　and　molten　aluminum　was　reduced．

View full abstract