Abstract
9Cr-2Mo steel developed for boiler tubes was considered to be applicable to LMFBR steam generators. Therefore, we investigated the basic characteristics which will be required when this steel is applied to LMFBR steam generators. The results obtained are as follows.
(1) Allowable stresses of 9Cr-2Mo steel on the base of ASME Case 1592 are reduced to be much higher at R.T. to 650°C than those of 2-1/4Cr-1Mo steel. High temperature fatigue properties are nearly equal with commercial 2-1/4Cr-1Mo and Type 304 steel, when the creep-fatigue interaction is considered.
(2) 9Cr-2Mo steel is more insensitive to the weld cracking than stabilized high Cr steels.
(3) This steel has almost the same carbon activity as Type 316 steel and the resistance to decarburization in sodium. The stress corrosion test in NaOH solution showed no cracking and better corrosion resistance than 2-1/4Cr-1Mo steel.
In conclusion 9Cr-2Mo steel is considered to be a promising material for LMFBR steam generators.
