1.The results show that: the fillers of SiO2 based investment consist of SiO2, Al2O3 and MgO, and the binder is NH4H2PO4 for SiO2 based investment, the bulk density and the compression strength decrease, the apparent porosity and the thermal expansion increase, when the specimens are heated to 900℃; the fillers of Al2O3 based investment consist of Al2O3 and MgO, and the binder is NH4H2PO4; for Al2O3 based investment, the bulk density decreases and the apparent porosity increases when the specimens are heated to 900℃; the fillers of MgO based investment consist of MgO and Al2O3, and the binder is CA cement; for MgO based investment, the compression strength decreases and the thermal expansion increases greatly when the specimens are heated to 900℃.
结果表明：氧化硅系包埋料的骨料是氧化硅、氧化铝、氧化镁，结合剂为磷酸二氢铵，其900℃锻烧后显气孔率增加，体积密度下降，耐压强度降低，热膨胀增大；氧化铝系包埋料的骨料是氧化铝和氧化镁，结合剂为磷酸二氢铵，其900℃烧后显气孔率增加，体积密度下降，热膨胀变化不大；氧化镁系包埋料的骨料是氧化镁和氧化铝，结合剂是铝酸钙水泥，其900℃烧后耐压强度明显降低，热膨胀明显增大。
