| 摘要 |
PROBLEM TO BE SOLVED: To provide a martensitic stainless steel sheet for a flapper valve, which has corrosion resistance and high fatigue characteristics, and generates little burr after stamped due to high hardness. SOLUTION: The martensitic stainless steel sheet for the flapper valve includes, by mass%, 0.15% or less C, 2.0% or less Si, 2.0% or less Mn, 0.060% or less P, 0.020% or less S, 2.0-6.0% Ni, 12.0-20.0% Cr, 2.0% or less Mo, 0.10% or less N, and 0.02% or less O, has Md(N) of 125 or more, which is defined in the expression (1): Md(N)=580-520C-2Si-16Mn-16Cr-23Ni-26Cu-300 N-10Mo...(1), includes the balance substantially Fe, consists of martensitic single-phase, and has Vickers hardness of 400 or more. The method for manufacturing the steel sheet is characterized by solution treating the steel material of the above composition, cold rolling it at a rolling rate of 5%, and further aging it at 550 deg.C or lower, as needed.
|
