Provided is a steel component with excellent surface fatigue strength. The steel component has a nitride compound layer with a thickness of 5.0 μm to 30.0 μm and a hardened layer in an order from a component surface to a component inside, where a thickness of a porous layer on an outermost surface of the nitride compound layer is 3.0 μm or less and 40.0% or less of a thickness of the nitride compound layer, and the hardened layer has a hardness of HV600 or more at a position of 50 μm inward from the component surface, a hardness of HV400 or more at a position from the component surface to the component inside of 400 μm, and a hardness of HV250 or more at a position from the component surface to the component inside of 600 μm.

Alloy compositions for 3D metal printing procedures which provide metallic parts with high hardness, tensile strengths, yield strengths, and elongation. The alloys include Fe, Cr and Mo and at least three or more elements selected from C, Ni, Cu, Nb, Si and N. As built parts indicate a tensile strength of at least 1000 MPa, yield strength of at least 640 MPa, elongation of at least 3.0% and hardness (HV) of at least 375.

Alloy compositions for 3D metal printing procedures which provide metallic parts with high hardness, tensile strengths, yield strengths, and elongation. The alloys include Fe, Cr and Mo and at least three or more elements selected from C, Ni, Cu, Nb, Si and N. As built parts indicate a tensile strength of at least 1000 MPa, yield strength of at least 640 MPa, elongation of at least 3.0% and hardness (HV) of at least 375.

Provided is steel for nitrocarburizing with excellent surface fatigue strength. The steel has a nitride compound layer with a thickness of 5.0 μm to 30.0 μm and a hardened layer in an order from a steel surface to steel inside, where a thickness of a porous layer on an outermost surface of the compound layer is 3.0 μm or less and 40.0% or less of a compound layer's thickness, the hardened layer has hardness of HV600 or more, HV400 or more and HV250 or more at 50 μm inward from the steel surface, from the steel surface to the steel inside of 400 μm, and from the steel surface to the steel inside of 600 μm, respectively, an unhardened portion excluding the compound and hardened layers has a predetermined chemical composition, and the hardened layer has a chemical composition with a higher N content than the unhardened portion.

A hot-rolled steel sheet for nitriding or a cold-rolled steel sheet for nitriding, in which a dislocation density within 50 μm in the sheet thickness direction from the surface is not less than 2.0 times nor more than 10.0 times as compared to a dislocation density at the position of ¼ in the sheet thickness direction; and a method of manufacturing the same. The manufacturing method comprises, on a hot-rolled steel sheet or a cold-rolled steel sheet, performing pickling, and then performing skin pass rolling under the condition that a reduction ratio is 0.5 to 5.0% and FIT, defined as a ratio of a line load F (kg/mm) of a rolling mill load divided by a sheet width of the steel sheet and a load T (kg/mm.sup.2) per unit area to be applied in the longitudinal direction of the steel sheet, is 8000 or more.

A hot-rolled steel sheet for nitriding or a cold-rolled steel sheet for nitriding, in which a dislocation density within 50 μm in the sheet thickness direction from the surface is not less than 2.0 times nor more than 10.0 times as compared to a dislocation density at the position of ¼ in the sheet thickness direction; and a method of manufacturing the same. The manufacturing method comprises, on a hot-rolled steel sheet or a cold-rolled steel sheet, performing pickling, and then performing skin pass rolling under the condition that a reduction ratio is 0.5 to 5.0% and FIT, defined as a ratio of a line load F (kg/mm) of a rolling mill load divided by a sheet width of the steel sheet and a load T (kg/mm.sup.2) per unit area to be applied in the longitudinal direction of the steel sheet, is 8000 or more.

A valve is provided, in particular an injection valve, having a valve seat and a valve needle which extends along a closing direction for the most part, the valve seat having a valve-seat surface, and a valve-closing element is mounted on an end of the valve needle facing the valve seat, the valve-closing element being able to be moved between an open position and a closed position, and the valve-closing element together with the valve-seat surface forming a sealing seat in the closed position, the valve-closing element having a greater core hardness and/or surface hardness than the valve-seat surface.

Provided is a method for increasing magnetic induction intensity of soft magnetic metallic materials. The method includes carburizing or carbonitriding the soft magnetic metallic materials with carbon source or a carbonitriding agent by a heat treatment process, to increase the magnetic induction intensity of the soft magnetic metallic materials, wherein the soft magnetic metallic materials are amorphous materials, nanocrystals, silicon steel, or pure iron.

Provided is a method for increasing magnetic induction intensity of soft magnetic metallic materials. The method includes carburizing or carbonitriding the soft magnetic metallic materials with carbon source or a carbonitriding agent by a heat treatment process, to increase the magnetic induction intensity of the soft magnetic metallic materials, wherein the soft magnetic metallic materials are amorphous materials, nanocrystals, silicon steel, or pure iron.

Alloy compositions for 3D metal printing procedures which provide metallic parts with high hardness, tensile strengths, yield strengths, and elongation. The alloys include Fe, Cr and Mo and at least three or more elements selected from C, Ni, Cu, Nb, Si and N. As built parts indicate a tensile strength of at least 1000 MPa, yield strength of at least 640 MPa, elongation of at least 3.0% and hardness (HV) of at least 375.