Forged product with a steel composition containing 0.15-0.75 of C, Si, Mn, Ni, Cr, Mo, V and Al and the crankshaft manufactured therewith

摘要

A column-shaped forged product obtained by hot forging a steel ingot containing: C: 0.15-0.75% (means% by weight, also hereinafter); Si: 0.1-0.6%; Mn: 0.3-1.4%; Ni: 0.1-2%; Cr: 0.5-2.5%, Mo: 0.1-0.5%; V: 0.01-0.20%; and Al: 0.015-0.04%, which satisfies: Ti: 0.002% or less; S: 0.0006% or less; N: 0.01% or less; and O: 0.002% or less, and the rest comprising iron with unavoidable impurities, where the density (OD) of the inclusions whose main axis exceeds 5 μm observed in the axial position of a section perpendicular to the axial direction of the forged product it is 70 nos / cm² or less, and, when the radius of the forged product is R, the ratio of the density (DR) of the inclusions whose main axis exceeds 5 μm observed in the R / 3 position with respect to the axial position towards the radial direction and the DO density satisfies the following inequality (1) on both sides of the forged product. 0.5 = DR / DO = 1.50 ... (1)