Recent steel manufacturing produces 9 % Ni steels with high toughness through minimizing steel impurities and improving heat treatment. These 9 % Ni steels show ductile fracture and absorbed energy more than 20 kgfim in V-Charpy impact test at -196°C, which indicates V-Charpy impact test being insufficient for the material selection. It has become difficult to know the arrestability of these 9 % Ni steels through surface-notched double tension test using LN₂ (-196°C) as refrigerant. The method was developed to get brittle crack propagation-arrest toughness for high toughness material. In this paper crack arrestability of 9 %Ni steels which varies in toughness is examined by means of surface-notched double tension test and Charpy impact test of two specimen types. Surface-notched double tension test is conducted to check Kca values and Charpy impact test is conducted at temperature ranging -100-269°C in order to clarify the effect of specimen notch shape on ductile/brittle transition phenomenon of high toughness 9 %Ni steels and crack initiation and propagation energies. The following conclusions are obtained.
(1) 3-surfaces slitted Charpy impact test is available for the material selection of recent 9 %Ni steels because transition temperature of this method rises 4584°C higher than that of V-notched one.
(2) Crack arrestabilily of 9 %Ni steels can be estimated based on transition temperature and propagation energy of 3-surfaces slitted Charpy impact test.