Effect of an Annealing on the Mechanical Properties of Cold Rolled 9Cr-2W-NbV Steel

Ferritic/martensitic (F/M) steels are being considered as cladding materials for a sodium cooled fast reactor (SFR) which is one of the next generation nuclear powder reactors due to their high thermal conductivities, low expansion coefficients and excellent irradiation resistances to a void swelling compared to austenitic stainless steel. When this steel is applied as the fuel cladding in a SFR, its maximum temperature is expected to approach 650 .deg. C, and helium gas produced by transmutation of fissioning fuel will become the source of stress on the cladding. Such a cladding should thus have excellent mechanical properties at higher temperatures. In the fabrication processes of the F/M steel cladding, the extruded and heat treated steel tubes are usually subject to a cold working. The plastically deformed tubes should be annealed to relieve the stress from the cold working, and to recover their degraded mechanical properties from their working. The annealing conditions thus have become a subject of interest. This study was performed to evaluate the effects of an annealing on the mechanical properties of a cold rolled steel sheet