Sintering process of zircon ramming material

Zircon ramming material is phosphoric acid or acidic aluminum phosphate as a binder, with zircon (or zircon plus corundum) as the aggregate (aggregate and powder), plus an appropriate amount of sinter aid preparation, using the ramming method of construction of semi-wet mixed material. The theoretical chemical composition of zircon is ZrO2 67.2% and SiO2 32.6%. Zircon used as ramming material requires no less than 63% ZrO2 content. Zircon will be decomposed into monocline ZrO2 and amorphous SiO2 in the high temperature heating process, zircon decomposition temperature is greatly affected by the impurity content, its decomposition temperature range is 1540~2000℃, pure zircon slowly began to decompose from about 1540℃, 1700℃ above the rapid decomposition, to 1870℃ decomposition rate can reach 95%.

Zircon sintering is based on the solid diffusion at high temperature, its speed is very slow, it is difficult to fully sintering, adding some oxides can promote sintering. The study shows that the oxides that promote zircon sintering at 1500℃ include Na2O3, K2O, MgO, CaO, ZnO, B2O3, MnO, Fe2O3, Co2O3 and NiO, etc. However, it must be noted that some oxides will significantly promote the decomposition of zirconite, a large number of zirconite decomposition will cause the volume stability of ramming material poor, so the appropriate sintering aid and its amount to be selected through the test.

The sintering property of zircon is very important for the prepared ramming material. In addition to the sintering aid, the particle size of zircon is also an important factor affecting sintering. For ramming materials, the composition of particle size must be considered to be reasonable, so as to ensure good sintering without excessive shrinkage.

Zirconite ramming material is mainly used as the bottom lining under the fused casting zirconium corundum mullite brick in the glass furnace, also as the filler for the expansion joints of silicon brick and the transition layer between silicon and high alumina refractory products, as well as the lining of some induction furnaces and melt flow tanks. Zircon - containing ramming materials have also been used as ladle lining, but due to the high cost and limited resources, they are no longer used.