On the Temper-Brittleness of Steels (2nd Report)

On the temper-embrittlement of Ni-Cr structural steel, the author obtained the following results: (1) On the changes of absorbed energy and transition temperature of impact tests of specimens cooled rapidly or slowly after their tempering, that of transition temperatures has been most prominent, and the higher the tempering temperature, the larger their lowering in rapidly cooled condition. (2) In reheating specimens in tough condition, the shifts of transition temperatures have been most pronounced near 500°C and measured about 120°C by embrittling at 500°C for 100 hrs. (3) On the damping behaviours in torsional vibration, its maximum at about 40°C and minimum at about 100°C were higher in specimens cooled rapidly after tempering than in those that cooled slowly. (4) In isothermal embrittlement of specimens in the tough condition, the maximum and the minimum also lowered gradually with the advancement of embrittlement. (5) The extrapolated lattice constants in ferrite become smaller in isothermal embrittlement.