Atypical Cases of Welded Structure Failures

摘要

First case describes hot temperature corrosion of 1.4841 heat resisting steel, which was caused by formation of the low melting nickel sulphide (LME effect). In the second case centrifugally cast tubes of Ø52.6 x 5.8 mm size made of 25/35 CrNi steel, which are exposed to high temperature and to severe reducing environment (carbon activity ac » 1), are concerned. In such condition a graphitization may start, that results in the disintegration of its structure, which is called „metal dusting". The third case is dealing with an attack of the 1.4301 steel pipe welds by microbiologically influenced corrosion. After short service time several leakages of water were revealed. It was proved, that failure was caused by microbiologically influenced corrosion of sulphate-reducing bacteria (SRB) and not by an improper welding technology.