| 摘要 |
PROBLEM TO BE SOLVED: To provide a non-heat treated steel for a crank shaft which has adequate strength characteristics and machinability though containing no expensive V. SOLUTION: The non-heat treated steel for the crank shaft has a composition comprising, by wt.%, 0.35-0.55% C, 0.4-2% Si, 0.4-1.5% Mn, 0.01-0.1% P, 0.05-1% Cu, 0.05-1% Ni, 0.01-1% Cr, 0.005-0.05% s-Al, 0.005-0.030% N and the balance substantially Fe; has a structure of ferrite plus pearlite after having been hot-forged; and has a yield strength ratio of 0.50 or higher, which is the ratio of yield strength to tensile strength obtained from a tensile test at room temperature after having been hot-forged, and such a work hardening coefficient as to satisfy 0.1 to 0.4. COPYRIGHT: (C)2005,JPO&NCIPI
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