Abstract: A spring wire is subjected to a first shot peening process and a second shot peening process. In the first shot peening process, a first shot is projected on the spring wire at a first projectile speed. High kinetic energy of the first shot produces compressive residual stress in a region ranging from the surface of the spring wire to a deep position. In the second spring wire process, a second shot is projected at a second projectile speed lower than the speed of the first shot. The kinetic energy of the second shot is lower than that of the first shot. The low kinetic energy of the second shot increases the compressive residual stress in a region near the surface of the spring wire.

Abstract: A spring wire is subjected to a first shot peening process and a second shot peening process. In the first shot peening process, a first, shot is projected on the spring wire at a first projectile speed. High kinetic energy of the first shot produces compressive residual stress in a region ranging from the surface of the spring wire to a deep position. In the second spring wire process, a second shot is projected at a second projectile speed lower than the speed of the first shot. The kinetic energy of the second shot is lower than that of the first shot. The low kinetic energy of the second shot increases the compressive residual stress in a region near the surface of the spring wire.

Abstract: A high strength spring steel of this invention is characterized in containing, in percent of mass, of C: 0.36-0.48%; Si: 1.80-2.80%; Mn: 0.20-1.40%; P: 0.015% or less; S: 0.010% or less; Cu: 0.10-0.50%; Ni: 0.10-2.00%; Cr: 0.05-1.20%; s-Al: 0.005-0.040%; N: 0.002-0.012%; O: 0.002% or less, while the remainder is constituted of Fe and inevitable impurities and the quantity of inclusions of 10 ?m or larger in diameter per field of vision of 100 mm2 is 10 or less. A manufacturing method of high strength spring of this invention is characterized in that the high strength spring steel which is tempered to HRC52 or higher is formed into a spring shape by hot forming or cold forming and warm shot peening is carried out so as to produce a high strength spring of 1176 MPa or higher in maximum shearing stress.