| 摘要 |
PURPOSE:To improve tensile strength under relatively low-temp. steam conditions and also to improve creep rupture strength and to reduce embrittlement under high-temp. conditions, by constituting a turbine rotor of an Fe-base alloy having a specific composition in which W is incorporated to an Ni-Cr-Mo steel. CONSTITUTION:The turbine rotor is constituted of the Fe-base alloy containing, by weight, 0.10-0.35% C, <=0.35% Si, <=1% Mn, 1.1-2.5% Ni, 1.5-3.5% Cr, 0.3-1.5% Mo, and 0.1-2.0% W. In this Fe-base alloy, W is an element necessary for improving strength at high temp. by solid solution strengthening, but the effect is insufficient when W content is below 0.1% and, when it exceeds 2.0%, creep rupture strength and toughness are deteriorated. Moreover, Ni is effective in increasing the hardenability of the steel and improving tensile strength and toughness and it is necessary to be added by 1.0% and more, but, when Ni content exceeds 2.5%, there is a tendency that deterioration in creep rupture strength and embrittlement under high-temp. conditions are accelerated.
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