Rolled material for high strength spring, and wire for high strength spring

Abstract

It is an object of the present invention to provide a rolled material, which is a material for high strength spring, and also can exhibit excellent corrosion fatigue properties after quenching and tempering even when suppressing the addition amount of an alloying element; and a wire for high strength spring obtained from such a rolled material. The rolled material for high strength spring of the present invention includes, in % by mass: C: 0.39 to 0.65%, Si: 1.5 to 2.5%, Mn: 0.15 to 1.2%, P: exceeding 0% and 0.015% or less, S: exceeding 0% and 0.015% or less, Al: 0.001 to 0.1%, Cu: 0.10 to 0.80%, Ni: 0.10 to 0.80%, and O: exceeding 0% and 0.0010% or less, with the balance being iron and inevitable impurities, wherein the number of oxide inclusions having an average diameter of 25 μm or more is 30 or less per 100 g of a steel material, and an amount of nondiffusible hydrogen is 0.40 ppm by mass or less.

1 . A rolled material for high strength spring, comprising, in % by mass:
 C: 0.39 to 0.65%,   Si: 1.5 to 2.5%,   Mn: 0.15 to 1.2%,   P: exceeding 0% and 0.015% or less,   S: exceeding 0% and 0.015% or less,   Al: 0.001 to 0.1%,   Cu: 0.10 to 0.80%,   Ni: 0.10 to 0.80%,   O: exceeding 0% and 0.0010% or less, and with the balance being iron and inevitable impurities,   wherein:   a number of oxide inclusions having an average diameter of 25 μm or more is 30 or less per 100 g of a steel material; and   an amount of nondiffusible hydrogen is 0.40 ppm by mass or less.   
     
     
         2 . The rolled material for high strength spring according to  claim 1 , further comprising, in % by mass, at least one of the following (a) to (d):
 (a) Cr: exceeding 0% and 1.2% or less,   (b) Ti: exceeding 0% and 0.13% or less,   (c) B: exceeding 0% and 0.01% or less, and   (d) at least one of Nb: exceeding 0% and 0.1% or less, and Mo: exceeding 0% and 0.5% or less.   
     
     
         3 . A wire for high strength spring, comprising in % by mass:
 C: 0.39 to 0.65%,   Si: 1.5 to 2.5%,   Mn: 0.15 to 1.2%,   P: exceeding 0% and 0.015% or less,   S: exceeding 0% and 0.015% or less,   Al: 0.001 to 0.1%,   Cu: 0.10 to 0.80%,   Ni: 0.10 to 0.80%,   O: exceeding 0% and 0.0010% or less, and   iron and inevitable impurities,   wherein:   a number of oxide inclusions having an average diameter of 25 μm or more is 30 or less per 100 g of a steel material; and   an amount of nondiffusible hydrogen is 0.40 ppm by mass or less;   an area ratio of tempered martensite is 80% or more; and   a tensile strength is 1,900 MPa or more.   
     
     
         4 . The wire for high strength spring according to  claim 3 , further comprising, in % by mass, at least one of the following (a) to (d):
 (a) Cr: exceeding 0% and 1.2% or less,   (b) Ti: exceeding 0% and 0.13% or less,   (c) B: exceeding 0% and 0.01% or less, and   (d) at least one of Nb: exceeding 0% and 0.1% or less, and Mo: exceeding 0% and 0.5% or less.