Patent ID: 11892048
Assignee: SUMITOMO ELECTRIC INDUSTRIES, LTD.
Field: Materials, metallurgy (Chemistry)
Classification: CPC F  C | IPC C  F

Claim 6:
7. A spring steel wire comprising:
a main body made of a steel and having a line shape; and
an oxidized layer covering an outer peripheral surface of the main body;
the steel constituting the main body containing not less than 0.5 mass % and not more than 0.7 mass % C, not less than 1 mass % and not more than 2.5 mass % Si, not less than 0.2 mass % and not more than 1 mass % Mn, and not less than 0.5 mass % and not more than 2 mass % Cr, with the balance being Fe and unavoidable impurities,
the steel constituting the main body having a pearlite structure,
the oxidized layer having a thickness of not less than 2 μm and not more than 5 μm,
the oxidized layer containing not less than 60 mass % Fe3O4, wherein
the oxidized layer includes
a first Fe3O4 layer,
a second Fe3O4 layer covering an outer peripheral surface of the first Fe3O4 layer, and
a FeO layer between the first Fe3O4 layer and the main body, wherein

the first Fe3O4 layer has a Si concentration higher than a Si concentration of the second Fe3O4 layer and a Si concentration of the main body,
the FeO layer partially covers the outer peripheral surface of the main body,
in a portion of the main body where the outer peripheral surface thereof is not covered with the FeO layer, the main body and the first Fe3O4 layer are in contact with each other,
the first Fe3O4 layer has a Si concentration of not less than 2.5 mass % and not more than 6 mass % and a Cr concentration of not less than 1.5 mass % and not more than 3 mass %, and
the first Fe3O4 layer has a thickness of not less than 0.3 μm and not more than 1.5 μm.