Volume 19, Issue 4 (July 1991)
Warm Precracking at 295 K and Its Effects on the 4-K Toughness of Austenitic Steels
Experiments show that some austenitic steels at extreme cryogenic temperatures are toughened by warm prestress. We demonstrate this for Fe-17Cr-3Ni-13Mn-0.33N steel specimens that were warm precracked at 295 K and then fractured in liquid helium at 4 K where failure occurs by slip-plane cracking. On the other hand, Fe-13Cr-5Ni-22Mn-0.21N steel with higher toughness and a ductile fracture mechanism at 4 K was not affected by similar warm precracking. Austenitic and ferritic steel behaviors are compared, and precracking procedures for 4-K fracture tests are discussed.