Two pieces of heat treated steel can have widely different properties, even if their composition and hardness is the same. If the steel was over-heated during austenitizing, it will have large grain size after quenching and tempering, and may even have tiny inter-granular cracks, which can drastically reduce toughness. When such parts break, the fractures look almost like cast iron.

All it takes is someone letting a process get out of control, or some genius decides that the process can go faster if they use more heat smirk

No, steel does not "soften" over time

Last edited by tex_n_cal; 06/14/14. Reason: last sentence
"...the designer of the .270 Ingwe cartridge!..."