TWI Frequently asked questions
The fracture toughness of ferritic steels is dependent on numerous factors, including the composition and processing route of the steel, the test temperature, and the thickness of specimen tested. Nevertheless, there is a lower limit of around 20MPa √m (632Nmm-3/2 ) implied by Annex J of BS7910:2005 ('Guide to methods for assessing the acceptability of flaws in metallic structures') which could be assumed for the purposes of carrying out preliminary fracture mechanics calculations.
Considerable benefit will be gained by carrying out Charpy testing and still more by determining fracture toughess directly.
