| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a high-tension steel having excellent weldability and≥490 MPa tensile strength by efficiently improving the quenching property of a steel plate even in the case of adding extremely small amount of B which is conventionally considered to be insufficient to improve the quenching property. SOLUTION: In the steel containing extremely small amount of 0.0001 to 0.0003% B, in order to optimize Ti, N, and Al contents and to effectively segregate B into austenite grain boundary, the suitable holding of cooling is performed at the interval between hot-rolling and accelerated-cooling. Then, in a working and heat treatment process, the high-tension steel whose tension strength is 490 MPa or higher and has the excellent weldability is produced. COPYRIGHT: (C)2004,JPO
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