Patent ID: 8444782
Filing Date: 2013-05-21
Classification: C21D

Abstract:
1. A method of manufacturing a ferritic/martensitic steel, the method comprising: melting a ferritic/martensitic steel having 9-12 wt % chromium; hot-working the melted ferritic/martensitic steel; normalizing the hot-worked ferritic/martensitic steel at a temperature of 1050° C. to 1200° C.; tempering the normalized ferritic/martensitic steel by thermal-treating the normalized ferritic/martensitic steel at a temperature of 600° C. or less for two hours, and leaving MX precipitates while avoiding the formation of M precipitating M wherein the tempered ferritic/martensitic steel is first cold-worked by cold-rolling at room temperature by a reduction ratio of 25%, and the first cold-worked ferritic/martensitic steel is first thermal-treated at a temperature of 730° C. to 780° C. for 10 minutes to obtain a first thermal-treated ferritic/martensitic steel, then the first thermal-treated ferritic/martensitic steel is second cold-worked by cold-rolling by a reduction ratio of 25%, and the second cold-worked ferritic/martensitic steel is second thermal-treated at a temperature of 750° C. for 10 minutes to obtain a second thermal-treated ferritic/martensitic steel, then the second thermal-treated ferritic/martensitic steel is third cold-worked by cold-rolling by a reduction ratio of 25%, and the third cold-worked ferritic/martensitic steel is third thermal-treated under a condition of 750° C. for 10 minutes to manufacture the ferritic/martensitic steel.