Tham khảo tài liệu 'handbook of materials for product design part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Chapter 8 refractory materials themselves. Crowns are often self-supported refractory structures. The refractories must withstand or resist high temperatures heavy loads abrasion and corrosion. Types of oxide refractories used in glass melters are as follows 1. Clay refractories generally used for insulation Fireclay kaolinite Al2O3 2SiO2 2H2O plus minor components classified as low- medium- high- or super-duty 25 to 45 Al2O3 High alumina 50 to Al2O3 2. Nonclay refractories generally used for glass contact or furnace superstructure Magnesia MgO Silica cristobalite and trydimite Stabilized zirconia Extra-high alumina Mullite 3Al2O3 2SiO2 AZS alumina-zirconia-silica containing 30 to 42 zirconia Zircon ZrO2 SiO2 Chrome-magnesite and magnesite-chrome combinations of Cr2O3 and MgO Classifications based on methods of of refractory manufacture in order of increasing density are as follows Bonded Sintered sometimes densified by cold isostatic pressing before firing Fusion cast cast as blocks from arc-melted raw materials also referred to as fused or fused cast Many factors affect the choice of refractory for a particular application. These include melting temperature thermal conductivity mechanical strength creep resistance and resistance to corrosion and spalling to name a few. Generally different refractories are used in different regions of a glass-melting tank because the requirements are different. However the ultimate design consideration is resistance to corrosion by molten glass and by the hot gas atmosphere within the melter. Corrosion determines tank lifetimes and affects the rates at Inorganic Glasses which certain glass defects such as stones are generated. In selecting a refractory the considerations are in order 1. glass quality 2. tank lifetime 3. initial cost Many different corrosion mechanisms operate within a melter. The types and severity depend on the glass composition the composition and microstructure of the refractory and the .
