| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a workpiece (a strength-gradient member) having a higher strength part compared with the other part in the longitudinal direction, and the strength-gradient steel member manufactured with it. SOLUTION: The workpiece is made by pressing in which a blank holder is applied to a part in the longitudinal direction of a material to be worked. By this, a part, which has a larger induced strain amount compared with the other part, can be formed in the longitudinal direction. A steel plate having strain age hardening characteristics, in which the tensile strength, when heat treatment of heating to the temperature of≤300°C after imparting the tensile strain of 5 % or more is applied, is increased by≥40 MPa as compared with the tensile strength when the same heat treatment as the above is applied without imparting the tensile strain, is used as the material to be worked. Alternatively, further, the heat treatment at a temperature of≤300°C is executed after the pressing. By this, the strength-gradient steel member, in which a higher strength part compared with the other part is formed in the longitudinal direction of the workpiece, can be formed. COPYRIGHT: (C)2005,JPO&NCIPI
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