Estimation of fracture toughness of 20MnMoNi55 steel in the ductile to brittle transition region using master curve method

Fracture toughness is an important material property to assess the critical load for structural integrity of reactor pressure vessel steel. In this paper, master curve method proposed by Kim Wallin is used to estimate the fracture toughness of 20MnMoNi55 steel in the ductile to brittle transition regime. Reference temperature (T0)(T0) is evaluated using both single temperature and multi-temperature method for one inch thick compact tension (1T-CT) specimens. Reference temperature (T0)(T0) is also determined from Charpy V-notch test data and compared. Effect of selection of temperature range and number of test temperatures on the value of T0T0 is also studied. It is observed that Charpy test results yield lower values of unirradiated T0T0 compared to 1T-CT specimen tests. It is also observed that most of the fracture toughness values fall between 5% and 95% boundary of fracture toughness curves for all the evaluations.

► Master curve method is used in ductile to brittle transition regime.
► Fracture toughness of 20MnMoNi55 material is estimated.
► Reference temperature is evaluated using both single and multi-temperature test data.
► Effect of temperature range and number of test data is studied.
► Reference temperature is also determined from Charpy V-notch test for comparison.