| 摘要 |
PROBLEM TO BE SOLVED: To provide a forging steel excellent in fatigue strength and hydrogen cracking resistance. SOLUTION: The forging steel contains, by mass, 0.15 to 0.75% C, 0.1 to 0.6% Si, 0.3 to 1.4% Mn, 0.1 to 2% Ni, 0.5 to 2.5% Cr, 0.1 to 0.5% Mo, 0.01 to 0.2% V, 0.015 to 0.04% Al, 0.0002% or below excluding 0% S, 0.003% or below excluding 0% Ti, and the balance of Fe and inevitable impurities. The respective number densities of S-containing inclusion particles having a S content of 20% by mass or above, and Ti-containing inclusion particles having a Ti content of 50% by mass or above among inclusion particles above 5μm in length present in an observation area in a cross section of the forging steel are 100 pieces/cm<SP>2</SP>or below, and 30 pieces/cm<SP>2</SP>or below, respectively. COPYRIGHT: (C)2009,JPO&INPIT |
