Silica castable is typical acidic refractory castable which has excellent resistance to acidic slag corrosion, as well as to CaO, FeO, Fe2O3 and other oxides corrosion. Silica castable features in high refractoriness under load and high thermal conductivity. If working temperature is above 600℃, silica castable also has high thermal shock stability. Silica will have large volume change due to crystalline phases transformation, residual expansion of silica castable is beneficial to structural strength and air tightness of the masonry.
The crystalline phase types of SiO2 has great influence on the property of silica castable, reasonable ratio of tridymite and quartz is key point for the production of silica castable. During the production of silica castable, quartz can’t directly transform into tridymite, to get large as much tridymite as possible, appropriate mineralizer should be added into silica raw material to contribute to quartz transforming into tridymite and crystobalite, besides, it should not significantly decrease high temperature performances of silica castable.
The raw materials of silica castable are: 65%~75% of quartz aggregate, 20%~28% quartz powder, 2%~8% silica micro powder, 1%~3% calcium aluminate cement, and little amount of additives(sodium tripolyphosphate, sodium hexametaphosphate, organic fibers).
Silica micro powder is high efficient binders of refractory castable, it ensures certain mechanical strength during low temperature roasting, and it won’t decrease hot mechanical strength of silica castable during high temperature using. CaO in calcium is also a kind of mineralizer, which can contribute to quartz transforms into tridymite at high temperature. What’s more, silica powder can also reduce porosity of silica castable and increase its density.
|Bulk density g/cm3||>1.9||1.91||1.95||1.89|
|True density g/cm3||2.35||2.32||2.35||/|
|Apparent porosity %||<20||<20||<20||<20|
|Crushing strength MPa||50~80||80||56||51|
|Linear expansion rate %(1000℃)||/||1.18||/||/|
|Thermal conductivity W(m·K)||2.21||2.13||2.21||/|