| 摘要 |
PROBLEM TO BE SOLVED: To provide a relatively inexpensive press formed member having high fatigue strength. SOLUTION: This press formed member is manufactured by using a steel sheet having a composition consisting of, by weight, <=0.01% C, <=1% Si, 0.05-0.5% Mn, <=0.1% P,η0.03% S, 0.02-0.1% sol.Al, 0.8-1.7% Cu, 0.02-0.1% Ti, and the balance Fe with inevitable elements, At this time, soft-nitriding treatment which doubles as artificial aging treatment is applied after solution heat treatment. This press formed part has a surface hardened layer of sufficiently large depth. Further, at the time of its manufacture, reduction in manufacturing costs as well as energy saving can be attained by combining artificial aging treatment with soft-nitriding treatment.
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