Patent ID: 8557061

Claim:
A spring steel, having a composition consisting essentially of: C: 0.35-0.65%, Si: 1.5-2.5%, Mn: 0.05-1%, Cr: 0.05-1.9%, P: 0.015% or less (exclusive of 0%), S: 0.015% or less (exclusive of 0%), Ti: 0.0250.1%, Al: 0.05% or less (exclusive of 0%), N: 0.01% or less (exclusive of 0%), Nb : 0.1% or less (exclusive of 0%); optionally one or more of Cu, Ni, and V; and a balance being Fe and inevitable impurities, wherein said spring steel has a tensile strength of 2000 MPa or higher and a hydrogen embrittlement fatigue crack life of 712 sec. or higher, and an amount of Ti in Ti nitride, an amount of Ti in Ti sulfide, and an amount of Ti in Ti carbide satisfy following formulas (1), (2), and (3); [Ti with N ]≧3.42×[N]−0.354×[Al]−0.103×[Nb] (1) [Ti with S ]≧1.49×[S] (2) [Ti with C ]≧0.015 (3), in which [Ti with N ] represents the amount of Ti (mass %) forming Ti nitride, [Ti with S ] represents the amount of Ti (mass %) forming Ti sulfide, [Ti with C ] represents the amount of Ti (mass %) forming Ti carbide, and [N], [Al], [Nb], and [S] represent an amount (mass %) of each element in the steel; and the percentages above are mass percentages and wherein the steel is produced by a process comprising: cooling a steel having the composition within the range from 1,500° C. to 1,400° C. at a rate of 0.8° C./sec or less; setting the heating temperature of the steel to at least 1,200° C. but no more that 1,300° C.; spraying water on the hot steel before carrying out a hot-rolling process until the steel reaches a temperature of 950° C. or below; rolling the steel at a starting temperature of 850° C. or above, and cooling the steel after hot rolling at a starting temperature of 950° C. or less to a temperature of 700° C., at a rate of 20° C/sec or less.