A method for manufacturing a part of nitrided steel includes a step of nitriding the part. After nitriding, laser shocking is carried out on a surface of the nitrided part.

A steel sheet has a predetermined chemical composition, in which a metallographic structure in a surface layer region ranging from a surface to a position of 20 μm from the surface in a sheet thickness direction consists of ferrite and a secondary phase having a volume fraction of 0.01% to 5.0%, a metallographic structure in an internal region ranging from a position of more than 20 μm from the surface in the sheet thickness direction to a ¼thickness position from the surface in the sheet thickness direction consists of ferrite and a secondary phase having a volume fraction of 2.0% to 10.0%, the volume fraction of the secondary phase in the surface layer region is less than the volume fraction of the secondary phase in the internal region, and in the surface layer region, an average grain size of the secondary phase is 0.01 μm to 4.0 μm, and a texture in which an X.sub.ODF{001}/{111} as the ratio of the intensity of {001} orientation to an intensity of {111} orientation in the ferrite is 0.60 or more and less than 2.00 is included.

A die steel which enables manufacturing a hot stamp die that has both high hardness and high thermal conductivity, a hot stamp die, and a manufacturing method thereof are provided. This steel for a hot stamp die has a component composition, in mass% of 0.45-0.65% C, 0.1-0.6% Si, 0.1-0.3% Mn, 2.5-6.0% Cr, 1.2-2.6% Mo, and 0.4-0.8% V, the remainder being Fe and unavoidable impurities. Further, this hot stamp die has the aforementioned component composition, and the manufacturing method is for manufacturing said hot stamp die.

A section steel according to an exemplary embodiment of the present invention is characterized in that it includes an amount of 0.08 to 0.17% by weight of carbon (C), an amount of 0.50 to 1.60% by weight of manganese (Mn), an amount of 0.10 to 0.50% by weight of silicon (Si), an amount of 0.10 to 0.70% by weight of chromium (Cr), an amount greater than 0 and 0.5% by weight or less of copper (Cu), an amount of 0.30 to 0.70% by weight of molybdenum (Mo), an amount greater than 0 and 0.02% by weight or less of phosphorus (P), an amount greater than 0 and 0.01% by weight or less of sulfur (S), an amount greater than 0 and 0.012% by weight or less of nitrogen (N), an amount greater than 0 and 0.003% by weight or less of boron (B), an amount of 0.01 to 0.5% by weight of the sum of at least one or more of nickel (Ni), vanadium (V), niobium (Nb), and titanium (Ti), and the remainder of iron (Fe) and other unavoidable impurities, and has a tensile strength of 490 to 620 MPa, a yield strength of 355 MPa or greater, and a yield ratio of 0.8 or less at room temperature, and a high-temperature yield strength of 273 MPa or greater at a temperature of 600° C.

The present invention has as its object the provision of a coated steel member and coated steel sheet excellent in hydrogen embrittlement resistance in a corrosive environment and methods for manufacturing the same. The coated steel member of the present invention is provided on its surface with an Al—Fe-based coating containing Cu and one or more of Mo, Ni, Mn, and Cr in a total by mass % of 0.12% or more by heating, cooling, and manufacturing a coated steel sheet having a layer containing Cu on its surface under predetermined conditions.

A method of manufacturing a hot-stamped part includes: inserting a blank into a heating furnace including a plurality of sections with different temperature ranges; step heating the blank in multiple stages; and soaking the blank at a temperature of about Ac3 to about 1,000° C., wherein in the step of heating the blank, a temperature condition in the heating furnace satisfies the following equation: 0 < (Tg - Ti) / Lt < 0.025° C./mm, where Tg denotes a soaking temperature (°C), Ti denotes an initial temperature (°C) of the heating furnace, and Lt denotes a length (mm) of step heating sections.

The invention provides a heat treatment method for a steel product. The steel product includes at least 0.5-0.7% of Si by weight; the method provides the following steps: step 1) putting the steel product under an Austenitizing temperature of 830-890° C. and lasting for a first time to Austenitize the steel product, step 2) immersing the Austenitized steel product in a salt bath at an isothermal temperature of 200-350° C. and lasting for the second time. The method of the invention improves the toughness and elongation of the steel product, keeps the wear resistance of the product, and can be well applied to the fields of thin section ring of bearings and the like. The invention also provides a steel product and a bearing ring.

A controlled thermal coefficient product manufacturing system and method is disclosed. The disclosed product relates to the manufacture of metallic material product (MMP) having a thermal expansion coefficient (TEC) in a predetermined range. The disclosed system and method provides for a first material deformation (FMD) of the MMP that comprises at least some of a first material phase (FMP) wherein the FMP comprises martensite randomly oriented and a first thermal expansion coefficient (FTC). In response to the FMD at least some of the FMP is oriented in at least one predetermined orientation. Subsequent to deformation, the MMP comprises a second thermal expansion coefficient (STC) that is within a predetermined range and wherein the thermal expansion of the MMP is in at least one predetermined direction. The MMP may be comprised of a second material phase (SMP) that may or may not transform to the FMP in response to the FMD.

The present invention relates to a manufacturing method of 800 MPa grade steel bar and the 800 MPa grade steel bar produced therefrom. The 800 MPa grade steel bar produced by the manufacturing method comprises, in weight percentages, the following composition: carbon, 0.10%-0.30%; manganese, 7.00%-11.00%; aluminum, 1.00%-3.00%; silicon, 0-1.00%; vanadium, 0.05%-0.30%; niobium; 0-0.10%; and the balance of Fe and inevitable impurities; the manufacturing method comprises the steps of smelting to obtain molten steel containing components of the steel bar; forming the molten steel into a billet by casting; heating the billet to a temperature T1 of 1050° C.≤T1≤1200° C. and thermally insulating for 1.5-2.5 hours; performing hot rolling on the thermally insulated billet, the finishing rolling temperature T2 being 500° C.≤T2≤800° C.; and naturally cooling the hot-rolled billet to ambient temperature. The hot-rolled steel bar of the present invention has a dual-phase microstructure of martensite and austenite. The hot rolled steel bar both has a high yield strength of 800-1000 MPa, an ultra-high tensile strength of 1300 MPa-1900 MPa, an ultra-high tensile to yield ratio of 1.6-2.2, and a high uniform elongation of 8%-20%.

There is provided an austenitic heat resistant steel including a chemical composition that consists of, in mass %, C: 0.04 to 0.12%, Si: 0.01 to 0.30%, Mn: 0.50 to 1.50%, P: 0.001 to 0.040%, S: less than 0.0050%, Cu: 2.2 to 3.8%, Ni: 8.0 to 11.0%, Cr: 17.7 to 19.3%, Mo: 0.01 to 0.55%, Nb: 0.400 to 0.650%, B: 0.0010 to 0.0060%, N: 0.050 to 0.160%, Al: 0.025% or less, and O: 0.020% or less, with the balance: Fe and impurities and that satisfies [0.170≤Nb−Nb.sub.ER≤0.480].