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US 2026/0275486 A1Published application
Steel product and method for modifying steel product
AssigneeSumitomo Heavy Industries, Ltd.
InventorTakashi MARUYAMA
Life of this patent
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Abstract
A steel product includes a compound layer in which iron and nitrogen are combined and a diffusion layer in which alloy nitrides are precipitated, on a surface, in which the compound layer includes, in an outer layer portion of the compound layer, a porous layer including a plurality of cavities, and in a cross section in a depth direction, an area ratio of the cavities in the compound layer is 3.0% or less.
Claims12
A steel product comprising:
- a compound layer in which iron and nitrogen are combined and a diffusion layer in which alloy nitrides are precipitated, on a surface,
- wherein the compound layer includes, in an outer layer portion of the compound layer, a porous layer including a plurality of cavities, and
- in a cross section in a depth direction, an area ratio of the cavities in the compound layer is 3.0% or less.
A steel product, comprising:
- a compound layer in which iron and nitrogen are combined and a diffusion layer in which alloy nitrides are precipitated, on a surface,
- wherein Expression (1) is satisfied in the diffusion layer:
- HV
- >
- 2
- /
- 3
- ×
- τ
- 0
- ∘
-
- max
- (
- 1
- )
- where
- τ0°max:
- maximum horizontal shear stress [MPa] generated inside when a load is applied to the surface;
- and
- HV:
- Vickers hardness at a depth position at which τ0°max occurs.
19 more elements
A method for modifying a steel product, comprising:
- a nitriding step of nitriding a steel material to form, on a surface of the steel material, a compound layer including a porous layer including a plurality of cavities;
- and
- a compression step of applying a compressive load to the surface of the nitrided steel material to close the cavities of the porous layer.
A method for modifying a steel product, comprising:
- a nitriding step of nitriding a steel material to form, on a surface of the steel material, a compound layer in which iron and nitrogen are combined and a diffusion layer in which alloy nitrides are precipitated;
- and
- a compression step of applying a compressive load to the surface of the nitrided steel material,
- wherein, in the compression step, the compressive load is applied such that Expression (1) is satisfied in the diffusion layer:
- HV
- >
- 2
- /
- 3
- ×
- τ
- 0
- ∘
-
- max
- (
- 1
- )
- where
- τ0°max:
- maximum horizontal shear stress [MPa] generated inside when a load is applied to the surface;
- and
- HV:
- Vickers hardness at a depth position at which τ0°max occurs.
21 more elements
Dependencies are inferred from the claim text.