| 摘要 |
The high strength steel plate according to the present invention contains 0.02 to 0.08% C, by mass, and has substantially a two phase microstructure of ferrite and bainite. The ferrite contains precipitates having particle size of 30 nm or smaller grain size. The steel plate has yield strength of 448 MPa or higher. The method for manufacturing the high strength steel plate comprises the steps of hot rolling, accelerated cooling, and reheating. The accelerated cooling is conducted down to the temperature of 300 to 600° C. at a cooling rate of 5° C./s or higher. The reheating is conducted up to temperature of 550 to 700° C. at a heating rate of 0.5° C./s or higher.
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