| 摘要 |
This invention relates to a method of manufacturing a martensitic stainless steel. The method comprises the following steps (a) to (c): (a) preparing a steel having a chemical composition consisting of, by 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: 0.003 to 0.070%, Ti: not more than 0.300% and the balance Fe and impurities, and P and S among impurities are not more than 0.035% and not more than 0.010% respectively, and that it also satisfies the following equation: ([Ti]−3.4×[N])/[C]>4.5 wherein [C], [N] and [Ti] mean the content (mass %) of C, N and Ti, respectively, (b) heating the steel at a temperature between 850 and 950° C., (c) quenching the steel, and (d) tempering the steel at a temperature between Ac1−35° C. and Ac1+35° C. and in a condition of not more than 0.5 of the value of variation &Dgr;LMP1 in the softening characteristics LMP1, which is defined by the following equation: LMP1=T×(20+1.7×log(t))×10−3 wherein T is a tempering temperature (K), and t is a tempering time (hour). The steel could further contain 0.2 to 0.3 % of Mo.
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