| 摘要 |
PROBLEM TO BE SOLVED: To provide a means for stably manufacturing a hot-forged member of a microalloyed steel, which has high strength and a high yield ratio of 0.8 or higher even when forged in a comparatively high temperature range. SOLUTION: A steel stock includes specified quantities of Si, P, S and Al in addition to 0.15-0.40% C, 0.5-2.0% Mn and 0.15-0.40% V, or further one or more of Cr, N, Ti and Nb with specified quantities. The method for manufacturing the hot-forged member of the microalloyed steel having the high strength and the high yield ratio comprises heating the above steel stock at 1,000°C or higher, hot-forging it, subsequently cooling it to a room temperature (preferably at a cooling rate of 0.5-5°C/s) to make a microstructure as a ferrite-pearlite structure, and further cold-working it at a working rate of 2-10%. COPYRIGHT: (C)2004,JPO
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