| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-strength martensitic steel which maintains sufficient strength even when used as springs and volts for automobiles and also excels in toughness, and a method for manufacturing the same. SOLUTION: The high-strength martensitic steel includes 0.1% by mass or more of C, and 80% or more of its metal structure consists of martensite. Characteristically 10% or less is the rate of the area occupied by former austenite grains of which former austenite crystal grain size number is 7 or greater in average and which differs by 3.0 or more in grain size number from the crystal grain number having the maximum frequency. COPYRIGHT: (C)2007,JPO&INPIT
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