Overheat induced failure of a steel tube in an electric arc furnace (EAF) cooling system

A fractured steel tube component from the cooling system of an electric-arc-furnace (EAF) of a steelmaking plant was received with a request of a failure analysis investigation. The specific damage caused steam leakage and led to the furnace shut-down for maintenance resulting in significant steel production delays. Visual inspection, optical microscopy and microhardness testing were used as the principal investigation techniques in the present study. Prolonged overheating at high temperatures has led to decarburization and weakening of the surface of the tube. This resulted further in subsequent cracking due to the operating tensile stresses developed from steep thermal gradient and thermal cycling suggesting that the most probable failure mechanism is thermal fatigue.