Weld cracking was observed in multiple heats of large-sized cast steel components. Fracture analysis, metallography, and mechanical testing indicated that the failure mechanism was aluminum nitride (AlN) embrittlement. Prevention of this type of embrittlement is achieved by controlling aluminum content, nitrogen content, and above all, cooling rate of the casting. A macro-etch procedure for evaluating large castings for AlN embrittlement has been available in ASTM A 703 for decades, and it was found to adequately predict embrittlement in this instance.

No abstract