Precipitation hardened martensitic stainless steel, manufacturing method therefor, and turbine moving blade and steam turbine using the same
AssigneeMitsubishi Hitachi Power Systems, Ltd.
InventorsYuichi HIRAKAWA, Yoshikuni KADOYA, Hiroharu OOYAMA, Tatsuya FURUKAWA, Naoto TOCHITANI
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Abstract
The precipitation hardened martensitic stainless steel is characterized by containing, in percent by weight, 12.25 to 14.25% Cr, 7.5 to 8.5% Ni, 1.0 to 2.5% Mo, 0.05% or less C, 0.2% or less Si, 0.4% or less Mn, 0.03% or less P, 0.005% or less S, 0.008% or less N, 0.90 to 2.25% Al, the balance substantially being Fe, and the total content of Cr and Mo being 14.25 to 16.75%. A turbine moving blade and a steam turbine are manufactured by using this martensitic stainless steel.
Claims14
1-10. (canceled)
A precipitation hardened martensitic stainless steel containing, in percent by weight, 12.25 to 14.25% Cr, 7.5 to 8.5% Ni, 1.0 to 2.5% Mo, 0.05% or less C, 0.2% or less Si, 0.4% or less Mn, 0.03% or less P, 0.005% or less S, 0.003% to 0.008% N, higher than 1.35% and not lower than 2.25% Al, optionally Nb or Ta, the balance substantially being Fe, and the total content of Cr and Mo being 14.25 to 16.75%, the total content of Nb and Ta being up to 0.01%.
A manufacturing method for a precipitation hardened martensitic stainless steel, comprising subjecting a steel billet, which has a chemical composition, in percent by weight, of 12.25 to 14.25% Cr, 7.5 to 8.5% Ni, 1.0 to 2.5% Mo, 0.05% or less C, 0.2% or less Si, 0.4% or less Mn, 0.03% or less P, 0.005% or less S, 0.003% to 0.008% N, higher than 1.35% and not lower than 2.25% Al, optionally Nb or Ta, the balance substantially being Fe, and the total content of Cr and Mo being 14.25 to 16.75%, the total content of Nb and Ta being up to 0.01%, to aging treatment at 550 to 600° C. after being subjected to solution heat treatment at 910 to 940° C.
Dependencies are inferred from the claim text.