Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Improvement in the Long Term Creep Rupture Strength of SUS 316 Steel for Fast Breeder Reactors by Nitrogen Addition
Takanori NAKAZAWAHideo ABOMitsuru TANINOHazime KOMATSUMasanori TASHIMOTakashi NISHIDA
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JOURNAL FREE ACCESS

1989 Volume 75 Issue 8 Pages 1346-1353

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Abstract

Improvement of creep fatigue property of structural materials for fast breeder reactors. In order to im-prove the resistance to creep fatigue of SUS 316 steels, the effects of nitrogen, carbon, and molybdenum on creep properties have been investigated, under the concept that creep fatigue endurance is correspond to creep rupture ductility. Creep rupture tests and slow strain rate tensile tests were conducted at 550°C and extensive microstructural works were performed. The strengthening by nitrogen is much greater than carbon. Moreover, while carbon reduces rupture ductility, nitrogen does not change it. The addition of carbon results in coarse carbide formation on grain boundaries during creep, but with nitrogen very fine Fe2Mo particles precipitate on grain boundaries. The difference between the effects of nitrogen and carbon on creep properties is arise from the different morphology of precipitation. Strengthening by molybdenum brings about a slight decrease in rupture ductility. On the basis of these results, 0.01%C-0.07%N-11%Ni-16.5%Cr-2%Mo steel is selected as a promising material for fast breeder reactors. This steel has higher rupture ductility and strength than SUS 316 steel. It is also confirmed that this steel has a higher resistance to creep fatigue.

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© The Iron and Steel Institute of Japan
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