ATMOSPHERES FOR ALUMINUM ANNEALING

The use of non-cryogenic nitrogen as an annealing atmosphere for alumi nium-alloy coils has been explored in order to determine the maximum a llowable oxygen concentration in nitrogen that would produce an accept able surface finish. The effects of nitrogen purity on purge rates, fu rnace atmosphere profile, and coil surface were examined both in small - and industrial-scale practice. The results provide a basis for optim ising the economic benefits of latest nitrogen-generation technology w hile maintaining quality.