| 摘要 |
A method for producing a martensitic stainless steel, which comprises heatin g a steel product having the chemical composition in mass %: C: 0.003 to 0.050 %, Si: 0.05 to 1.00 %, Mn: 0.10 to 1.50 %, Cr: 10.5 to 14.0 %, Ni: 1.5 to 7. 0, V: 0.02 to 0.20 %, N: 0.005 to 0.070 %, Ti: 0.0300 % or less and/or Zr: 0.58 0 % or less, balance: substantially Fe, P as a impurity: 0.035 % or less, and S as a impurity: 0.010 % or less, with the proviso that [C], [N], [Ti] and [Zr ] satisfy the formula: ([Ti] + 0.52 X [Zr] - 3.4 X [N])/ [C] > 4.5 wherein [C], [N], [Ti] and [Zr] represent the contents (mass %) of the above C, N, Ti and Zr, respectively, to 850 to 950~C, to thereby harden the steel product, and then tempering the hardened product at a tempering temperature (T) in the range of AC1 point of the above steel product .plusmn. 35~C and under a condition wherein the variation ( LMP1) of the following softening characteristic values (LMP1) is 0.5 or less: LMP1 = T X (20 + 1.7 X log(t)) X 10-3 wherein T and t represent a tempering temperature (K) and a tempering time (hour), respectively. The steel product may optionally further comprise 0.2 to 3.0 % of Mo. A martensitic stainless steel produced by the above meth od is reduced in the variation of offset yield strength.
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