MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF NEWLY DEVELOPED LOW-ACTIVATION MARTENSITIC STEELS

The reference ferritic-martensitic steel of the European Fusion Techno logy Program, the 10CrMoNbV MANET cast, has been modified by replacing the elements that result in long term residual radioactivity when irr adiated under a fusion neutron spectra by others which have shorter ac tivation periods. A base composition of a 9CrWVTa steel has been so de fined. Two different compositions of the base alloy have been cast fro m high purity components, in which the Mn and N contents have been var ied. The extracted carbide types and their size distribution have been studied under the electron microscope. The mechanical properties of b oth compositions have been determined. Both steel compositions have a ductile-brittle transition temperature (DBTT) well below room temperat ure while their tensile properties are comparable to those of the pare nt (MANET) steel.