Failure Analysis of Continuous-annealing Furnace Radiant Tubes Exposed to Excessive Temperature at Mobarakeh Steel Company

Radiant tubes of a continuous-annealing furnace at Mobarakeh Steel Company failed after a fraction oftheir rated service life. The tubes were manufactured from INCONEL alloy 601 super alloy. In this study, a failure analysis oftheradiant tubes was performed by careful visual inspection of the failed tubes, scanning electron microscopy observation of crack region samples, energy dispersive X-ray spectroscopy and X-ray diffract meter analysis ofthetube metals and oxide scales. The experimental results showed that the mode of tube failure was a combination of creep damage and high-temperature oxidation attack which led to cracking. Significant growth of carbide precipitates was also observed in the failed zones; these precipitates result in both the drastic reduction of material ductility and the propagation of creep cracking. To avoid such overheating. precautions should be taken to improve the burning condition of the bottom burners and decrease the peak tube metal temperature. It is necessary to check the tube temperature periodically in critical positions; one should ensure that the temperature is lower than the design temperature.

Failure Analysis of Continuous-annealing Furnace Radiant Tubes Exposed to Excessive Temperature at Mobarakeh Steel Company Keywords:

failure , radiant tube , creep , oxidation , high temperature