Instrumented drop-weight test results for normalised and tempered 9Cr1Mo steel

Abstract

From instrumented drop-weight tests, the nil ductility transition temperature ( T NDT), and a conservative estimate of dynamic fracture toughness ( K Id), at T NDT for normalised and tempered 9Cr1Mo steel, are determined to be −25°C and 70 MPa√m, respectively. The latter value agrees well with that determined from pre-cracked Charpy tests. The K Id σ Yd ( σ Yd is the dynamic yield stress) ratio at T NDT is estimated to be 0·076 √m, in agreement with previous estimates. The uncertainties in crack profile measurement and effect of microstructural variation in the heat affected zone on fracture loads are also discussed.