Effect of the Amount of Austenite Precipitated on the Charpy Absorbed Energy for Ductile Fracture of 9% Ni Steel

An investigation was made on the effect of the amount of austenite precipitated on the Charpy absorbed energy for ductile fracture of high toughness 9% Ni steel. The main results obtained are as follows:(1) As slab reheating temperature and finish-rolling temperature are raised; the Charpy absorbed energy for ductile fracture increases.(2) As slab reheating temperature and finish-rolling temperature are raised, the amount of austenite precipitated decreases.(3) The Charpy absorbed energy for ductile fracture has a good relation with the amount of austenite precipitated.(4) The fraction of area of dimples smaller than one μm increases with an increase in the amount of austenite precipitated.(5) The Ni content measured at the bottom of dimples smaller than one μm by micro Auger analysis is as much as that of austenite.(6) The above results indicate that the austenite precipitated decreases the Charpy absorbed energy for ductile fracture through the formation of dimples smaller than one μm.