A steel sheet including a chemical composition satisfying an equivalent carbon content of 0.60% or more and less than 0.85%, and a steel microstructure with an area fraction of ferrite: less than 40%, tempered martensite and bainite: 40% or more in total, retained austenite: 3% to 15%, and ferrite, tempered martensite, bainite, and retained austenite: 93% or more in total. A 90-degree bending at a curvature radius/thickness ratio of 4.2 in a rolling (L) direction with respect to an axis extending in a width (C) direction causes a change of 0.40 or more in (a grain size in a thickness direction)/(a grain size in a direction perpendicular to the thickness) of the tempered martensite in an L cross section in a 0- to 50-μm region from a surface of the steel sheet on a compression side. The steel sheet has a tensile strength of 980 MPa or more.

A method of making a forged, martensitic, stainless steel alloy is provided. The alloy is a forged preform of martensitic, pitting corrosion resistant stainless steel alloy comprising, by weight: 12.0 to 16.0 percent chromium; greater than 16.0 to 20.0 percent cobalt, 6.0 to 8.0 percent molybdenum, 1.0 to 3.0 percent nickel, 0.02 to 0.04 percent carbon; and the balance iron and incidental impurities. The alloy has a microstructure that comprises a retained austenite phase less than or equal to 2 percent by volume of the microstructure. The method heats the preform to a solutionizing temperature to form a solutionized microstructure. The preform is cooled with a liquid to room temperature. The preform is immersed in a cryo-liquid to transform the retained austenite phase in the microstructure to martensite. The preform is heated to a temperature of less than 600° F. for a time sufficient to form a tempered forged preform.

Provided is a stainless steel sheet having a predetermined chemical composition, in which a total volume fraction of Cr-based carbides with a grain size of 2.0 μm or more is 10% or less.

A method is for manufacturing a high-strength steel sheet having a tensile strength of more than 1100 MPa and a yield strength of more than 700 MPa, a uniform elongation UE of at least 8.0% and a total elongation of at least 10%, made of a steel containing in percent by weight: 0.1%≤C≤0.25%, 4.5%≤Mn≤10%, 1%≤Si≤3%, 0.03%≤Al≤2.5%, the remainder being Fe and impurities resulting from the smelting, the composition being such that CMnIndex=C×(1+Mn/3.5)≤0.6. The method includes annealing a rolled sheet made of said steel by soaking it at an annealing temperature TA higher than the Ac.sub.1 transformation point of the steel but less than 1000° C., cooling the annealed sheet to a quenching temperature QT between 190° C. and 80° C. at a cooling speed sufficient to obtain a structure just after cooling containing martensite and retained austenite, maintaining the steel sheet at an overaging temperature PT between 350° C. and 500° C. for an overaging time Pt of more than 5 s cooling the sheet down to the ambient temperature.

The present invention describes a method of dynamical adjustment for manufacturing a thermally treated steel sheet. The method includes: A. a control step, wherein at least one sensor detects a deviation happening during the thermal treatment, B. a calculation step performed when the deviation is detected during the thermal treatment such that a new thermal path TP.sub.target is determined to reach m.sub.target taking the deviation into account, such calculation step including: 1) a calculation substep, wherein at least two thermal path, TP.sub.x corresponding to one microstructure m.sub.x obtained at the end of TP.sub.x, are calculated based on TT and the microstructure m.sub.i of the steel sheet to reach m.sub.target, 2) a selection substep wherein one new thermal path TP.sub.target to reach m.sub.target is selected, TP.sub.target being chosen from said TP.sub.x and being selected such that m.sub.x is the closest to m.sub.target, C. a new thermal treatment step, wherein TP.sub.target is performed online on the steel sheet.

High strength precipitation hardening stainless steel alloy is disclosed. The steel alloy has a composition by weight %, about: 30.0% max nickel (Ni), 0.0 to 15.0% cobalt (Co), 25.0% max chromium (Cr), 5.0% max molybdenum (Mo), 5.0% max titanium (Ti), 5.0% max vanadium (V), about 0.5% max lanthanum (La) and/or cerium (Ce), and in balance iron (Fe) and inevitable impurities. The steel alloy provides a unique combination of corrosion resistance, strength and toughness and is a material for aircraft landing gears and structures.

A rolling bearing is a tapered roller bearing, a cylindrical roller bearing, or a deep groove ball bearing including an inner ring, an outer ring, and a rolling element, each of the inner ring, the outer ring, and the rolling element being composed of a steel, the rolling bearing having a quench-hardened layer in at least one of an inner ring raceway surface of the inner ring, an outer ring raceway surface of the outer ring, and a rolling contact surface of the rolling element. A ratio of a total area of a plurality of martensite crystal grains in the quench-hardened layer is more than or equal to 70%. The plurality of martensite crystal grains are classified into a first group and a second group. An average grain size of the martensite crystal grains belonging to the first group is less than or equal to 0.97 μm.

Disclosed is a multi-layer rolled composite board, comprising a transition layer provided between two adjacent composite layers, wherein the transition layer is an anisotropic steel sheet. Also disclosed is a manufacturing method for the multi-layer rolled composite board, the method comprising the following steps: (1) providing a transition layer between adjacent composite layers to assemble a blank, and creating a vacuum between the layers; and (2) performing composite rolling, comprising: heating the blank to 1100-1260° C. and maintaining the temperature for 0.6 h or above, then performing hot rolling at a temperature of Ar3 or above, with the final rolling temperature being controlled to be higher than 820° C., cooling at a speed of 30-100° C./s after rolling, and then coiling, with the coiling temperature being controlled to be 20-750° C. The multi-layer rolled composite board of the present invention can be greatly transformed according to different compositions and processes so as to achieve different strength grades ranging from 150 MPa to 1700 MPa, thereby providing the basis for different specific mechanical properties for the whole steel sheet.

The invention relates to the use of a Q&P steel for production of a formed component (2) for high-wear applications, wherein the Q&P steel has a hardness of at least 230 HB, especially at least 300 HB, preferably at least 370 HB, and a bending angle α of at least 60°, especially at least 75°, preferably at least 85°, determined to VDA238-100, and/or a bending ratio of r/t<2.5, especially r/t<2.0, preferably r/t<1.5, where t corresponds to the material thickness of the steel and r to the (inner) bending radius of the steel.

Provided is a steel used for chassis parts, etc. of an automobile and, more specifically, to a hot rolled steel plate for an electric resistance welded steel pipe, which shows an excellent weldability in electric resistance welding, and a manufacturing method thereof.