Fusion-cast AZS refractory was invented over 70 years ago. Until the early 1990s, there were only a handful of companies producing and delivering AZS refractories to the glass industry in N America and Europe. Due to the economic development in the BRIC region, today there are well over 20 companies worldwide that produce AZS refractories for use in the lining of glass melting furnaces. A large number of these companies are located in Asia. In the last decade, we have seen a greater willingness on part of the glass industry in N America ad, increasingly, in Europe to import lower-cost refractories from Asia. The basic manufacturing process for making fusion-cast AZS refractories consists of raw material selection, mould making, arc melting, casting, annealing, finishing, inspection and set-up. Though all AZS manufacturers use these process steps, there can be rather significant differences in the actual practice of each process step between different companies. This paper deals with several topics pertaining to the testing and selection of fusion-cast AZS refractories for use in glass melting furnaces. First, the impact of manufacturing process on AZS chemistry, microstructure, properties and performance is discussed. Next, the performance of lower-cost AZS refractories is compared with AZS produced in N America and Europe. Finally, some suggestions are provided for more reliable testing of AZS refractories.
