FRACTURE-TOUGHNESS OF FINE-GRAINED MICRO-ALLOYED STEELS AT NIL DUCTILITY TEMPERATURE AND TRANSITION RANGE

The conventional test methods combined with non-standard measuring of fracture toughness K-ic for the determination of low- temperature limit of exploitation was applied on nine different structural steels either fine-grained micro- alloyed steels or low-alloyed structural steels. These experiments confirmed that the results of low-temperature tests could be successfully used for the calculation of some fracture mechanics characteristics of the investigated steels as for instance the dynamics yield strenght sigma(yd), the dynamics fracture toughness K-id and, of course, the static fracture toughness K-ic.