US Patent 7615186 Spring steel excellent in sag resistance and fatigue property

The spring steel according to the present invention is a spring steel excellent in sag resistance and fatigue property containing: C: 0.5 to 0.8% by mass (hereinafter, referred to as %), Si: 1.2 to 2.5%, Mn: 0.2 to 1.5%, Cr: 1.0 to 4.0%, V: 0.5% or less (including 0%), P: 0.02% or less (excluding 0%), S: 0.02% or less (excluding 0%), Al: 0.05% or less (excluding 0%), and Fe and inevitable impurities as the balance, wherein the Si content and the Cr content satisfy the following formula (1):0.8×[Si]+[Cr]≧2.6  (1)(wherein, [Si] and [Cr] respectively represent the Si content (%) and the Cr content (%)).