STRUCTURAL MEMBER FOR AUTOMOBILE, TWO-WHEELED VEHICLE OR RAILWAY VEHICLE EXCELLING IN SHOCK ABSORPTION PERFORMANCE, SHAPE FIXABILITY AND FLANGE PORTION CUTTABILITY AND PROCESS FOR MANUFACTURING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a structural member for automobile, two-wheeled vehicle or railway vehicle excelling in shock absorption performance, shape fixability and flange portion cuttability, and to provide a process for manufacturing the same.

SOLUTION: The structural member for automobile, two-wheeled vehicle or railway vehicle excelling in shock absorption performance, shape fixability and flange portion cuttability has the following characteristics. The structural member has a hat-shaped cross section. The structural member has a free end portion at its flange portion. The free end portion contains an austenite phase at a ratio of 20 vol.% or more and has a sectional hardness of 150 to 350 in terms of Vickers hardness. On the same section, the central area of vertical wall portion contains a working-induced martensite phase at least 10 vol% or more than the free end portion at the flange portion. The sectional hardness of the central area of the vertical wall portion is at least 50 higher than that of the free end portion at the flange portion in terms of Vickers hardness. Further, there is disclosed a process for manufacturing the structural member.

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