Failure Analysis of Leakage in the Decomposition Tank of Bayer Process for Producing Alumina
摘要
A large batch of cracks appeared in and around the welds of alumina-decomposition tank used in production of alumina by Bayer process. The crack morphology and metallographic structure were analyzed by means of SEM, EDS and optical microscope. As a crack source, pores expanded along grain boundaries and pearlite under the promotion of stresses to form final cracks in alkaline environment, resulting in leakage. The multi-stress cracking mechanism in alkaline environment is strain induced-anodic dissolution. IGPSCC (intergranular pearlitic stress corrosion crack) electrochemical corrosion model for alkali embrittlement of thick wall tank welds is established, which provides a reference for the study of weld cracking in alumina-decomposition tank after long-term operation.