| 摘要 |
PROBLEM TO BE SOLVED: To provide an evaluation method of the delayed breaking resistance (hydrogen embrittlement) of a steel sheet, especially a TRIP steel sheet or the like which is processed in a region of high elongation not adapted heretofore to be formed into a press part not used heretofore from an aspect of a processing limit. SOLUTION: In the evaluation method of the delayed breaking resistance of the high-strength steel sheet with a tensile strength of 1,180 MPa or above, tensile processing of specific plastic strain quantity is applied to the test piece of the high-strength steel sheet and either one of U-bending processing of a specific bending radius and V-bending processing of a specific bending angle is subsequently applied to the high-strength steel sheet. Further, with specific compression stress loaded on both side parts of the test piece, the test piece is immersed in an electrolytic solution as a cathode and a constant current is passed through the cathode and an anode to perform hydrogen charge to evaluate the delayed breaking resistance of the high-strength steel sheet on the basis of the time until a crack is formed in the cathode test piece. COPYRIGHT: (C)2007,JPO&INPIT
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