After 35 years of service, the steel shell of a continuous annealing furnace developed cracking problems, even after careful repairs. A metallurgical evaluation was performed on sections of the ASTM A36 steel furnace shell. Testing included chemical analysis, light metallography, mechanical testing, and hardness measurements. The evaluation found through-thickness decarburization of the 6 mm thick shell in the vicinity of open cracks. The strength of the shell decreased significantly in these areas. Laboratory decarburization tests performed on unaffected samples of ASTM A36 steel shell confirmed that field conditions existed that led to rapid through-thickness decarburization of the shell. High ambient humidity is believed to have contributed to rapid decarburization. ©Y 2012 Springer Science+Business Media, LLC and ASM International.
