Determination of dynamic fracture toughness of heat affected zone of 9Cr-1Mo steel from instrumented drop weight tests

摘要

The dynamic fracture toughness (K{sub}1d) of the heat affected zone (HAZ) of 9Cr-1Mo steel at and below the nil ductility transition temperature has been estimated from instrumented drop weight test results. The presence of a significantmicrostructural gradient in the HAZ, comprising coarse, fine, and intercritical regions with sharp toughness differences, is reflected in the presence of distinctive load peaks in the load-time traces; the K{sub}1d estimates for the coarse, fine, andintercritical regions are 53, 85, and 128 MPa m{sup}1/2 respectively. The results from the 9Cr-1Mo steel were compared with those for AISI grade 403 martensitic stainless steel. The lack of distinctive multiple load peaks in the load-time traces for thelatter is attributed to the absence of a steep toughness gradient, owing to a more or less uniform martensitic microstructure in the HAZ.