Effect of temperature and heating time on embrittlement and changes in content and shape of ferrite in steel 02Cr22Ni11Nb

Requirements are discussed for the properties (intergranular corrosion resistance, weldability, radiation purity) of an overlaying band of two-phase corrosion-resistant austenitic-ferritic steel 02Cr22Ni11Nb (22/11 Nb) used for the manufacture of austenitic linings of the primary circuit components for a WWER-1000 nuclear power plant. Also discussed are the causes of embrittlement of CrNi steels at low temperatures and the practical determination of ferrite in the two-phase CrNi steel structure. The experiments performed are described and the effects of temperature and heating time are assessed on the shape and level of ferrite in the structure of cast and formed steel 22/11 Nb. The results are also reported of research of embrittlement of fully formed steel 22/11 Nb in the temperature range 500 to 1050 degC. (B.S.)