Patent ID: 7438770

Claim:
A high strength steel spring having excellent hydrogen embrittlement resistance, which spring is made from a steel which comprises: 0.20 to 0.60% of C, 1.0 to 3.0% of Si, 1.0 to 3.5% of Mn, higher than 0% and not higher than 1.5% of Al, 0.15% or less of P, 0.02% or less of S, and balance of iron and inevitable impurities, wherein the structure includes: 1% or more residual austenite; 80% or more in total of bainitic ferrite and martensite; and 10% or less (may be 0%) in total content of ferrite and pearlite in the proportion of area to the entire structure, and wherein the mean axis ratio (major axis/minor axis) of the residual austenite grains is 5 or higher and the steel tensile strength is 1860 MPa or higher, and wherein the spring is made by a wire drawing operation.