Comparison of Ductile-Brittle Transition Temperature Testing of 3Cr1MoV Steel with Small Punch Specimens of Different Notch Forms

Small punch tests at -196-25℃ were carried out on linear-type U-notched and V-notched specimens, which were machined from 3Cr1MoV steel test blocks in a hydrogenation reactor. The load-displacement curves, fracture morphology and E_sp/F_m (E_sp is fracture energy, F_m is maximum load) vs temperature curves of two notched specimens were compared. The results show that the load-displacement curves of V-notched specimens indicated a pop-in phenomenon below -140℃ while those of U-notched specimens were smooth. With the decrease of temperature, the maximum load of U-notched specimen increased and then decreased, and the maximum displacement decreased. The fracture morphology of two notched specimens had small difference at the same test temperatures. The E_sp/F_m vs temperature curve of U-notched specimen had obvious up and down platforms, and the correlation coefficient was higher than that of V-notched specimen, therefore the U-notched specimen is more suitable to evaluate the ductile-brittle transition temperature by small punch test than the V-notched specimen.