Patent ID: 7704338
Filing Date: 2010-04-27
Classification: C22C

Abstract:
1. A method of manufacturing a martensitic stainless steel characterized by comprising the following steps (a) to (d): (a) preparing steel materials 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 0.200%, 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: wherein [C], [N] and [Ti] mean the content (mass %) of C, N and Ti, respectively, (b) heating the steel materials at a temperature between 850 and 950° C., (c) quenching the steel materials, and (d) tempering the steel materials at a tempering temperature between about Ac1 and Ac1+35° C. and in a condition that the value of variation ΔLMP1 of the softening characteristics LMP1 in the steel material is not more than 0.5, so that a standard deviation in yield strength of the tempered steel in the steel material is 12 or less, wherein LMP1 is defined for a respective steel material by the following equation: wherein T is a respective actual tempering temperature (K), and t is a tempering time (hour), and LMP1 is controlled based on a difference between a respective actual LMP1 value and a designated LMP1 value.