Provided are a high-strength hot-rolled steel sheet and a method for manufacturing the steel sheet. The steel sheet includes C: 0.060% or more and 0.140% or less, Si: 1.00% or less, Mn: 1.30% or more and 2.50% or less, P: 0.030% or less, S: 0.0050% or less, Al: 0.070% or less, N: 0.010% or less, Ti: 0.060% or more and 0.140% or less, Cr: 0.10% or more and 0.50% or less, B: 0.0002% or more and 0.0020% or less, and the balance being Fe and inevitable impurities, in which the relationship 5.0≤18C+Mn+1.3Cr+1500B≤6.0 is obtained. The microstructure includes a bainite phase in an amount of more than 90% one, two, or all of a ferrite phase, a martensite phase, and a retained austenite phase in an amount of less than 10%.

Provided are a high-strength hot-rolled steel sheet and a method for manufacturing the steel sheet. The steel sheet includes C: 0.060% or more and 0.140% or less, Si: 1.00% or less, Mn: 1.30% or more and 2.50% or less, P: 0.030% or less, S: 0.0050% or less, Al: 0.070% or less, N: 0.010% or less, Ti: 0.060% or more and 0.140% or less, Cr: 0.10% or more and 0.50% or less, B: 0.0002% or more and 0.0020% or less, and the balance being Fe and inevitable impurities, in which the relationship 5.0≤18C+Mn+1.3Cr+1500B≤6.0 is obtained. The microstructure includes a bainite phase in an amount of more than 90% one, two, or all of a ferrite phase, a martensite phase, and a retained austenite phase in an amount of less than 10%.

A method of making high strength steel sheet with a tensile strength of 800 to 1000 MPa and a hole expansion ratio of at least 50%, comprising the steps of reheating a previously cast slab, or retaining the heat from a directly cast slab, above Ar3; hot rolling the slab to final desired thickness; cooling the steel sheet at a rate of 50° C. per second to a temperature less than 400° C.; and winding the steel sheet into a coil.

The device has a short production line, and all components are reasonably configured. A multifunctional cooling control device is adopted to integrate high-pressure water descaling and intermediate billet cooling functions, which is simpler and more efficient. Layout of a 4R+(3−4)F rolling mill, four thermos-detectors and short-distance underground coilers are use. The method includes the steps: carrying out continuous casting to manufacture a slab, high-pressure water rotating descaling, rough rolling by a four-stand high reduction rough rolling unit, machining by a drum shear, cooling after high-pressure water descaling in the multifunctional cooling control device, finish rolling by a three-stand or four-stand finish rolling unit, air cooling, dividing coils by a high-speed flying shear, and coiling by underground coilers, wherein temperature monitoring is respectively carried out after rough rolling, before finish rolling, after finish rolling, and before coiling by the underground coiler.

An object is to provide a steel plate having excellent deformability in the central portion in the thickness direction and a method for manufacturing the steel plate. A steel plate having a chemical composition containing, by mass %, C: 0.01% to 0.15%, Si: 0.01% to 1.00%, Mn: 0.10% to 2.00%, P: 0.010% or less, S: 0.0050% or less, Al: 0.002% to 0.100%, Ni: 5.0% to 10.0%, N: 0.0010% to 0.0080%, and with a balance being Fe and incidental impurities and a percentage reduction of area of 30% or more in a tensile test in the thickness direction performed on the central portion in the thickness direction.

Provided are a material for hot stamping, and the material includes: a steel sheet including carbon (C) in an amount of 0.28 wt% to 0.50 wt%, silicon (Si) in an amount of 0.15 wt% to 0.70 wt%, manganese (Mn) in an amount of 0.5 wt% to 2.0 wt%, phosphorus (P) in an amount less than or equal to 0.05 wt%, sulfur (S) in an amount less than or equal to 0.01 wt%, chromium (Cr) in an amount of 0.1 wt% to 0.5 wt%, boron (B) in an amount of 0.001 wt% to 0.005 wt%, an additive in an amount less than or equal to 0.1 wt%, balance iron (Fe), and other inevitable impurities; and fine precipitates distributed within the steel sheet. The additive includes at least one of titanium (Ti), niobium (Nb), and vanadium (V), and the fine precipitates include nitride or carbide of at least one of titanium (Ti), niobium (Nb), and vanadium (V) and trap hydrogen.

Provided is a hot rolled steel sheet having a tensile strength of 780 MPa or more, a sheet thickness of 1.2 to 4.0 mm, and a sheet width of 750 mm or more, and satisfying -15≤(λ.sub.W 1 +λ.sub.W.sub.2)/2-λ.sub.C ≤15 (where λ.sub.W.sub.1 and λ.sub.W.sub.2 respectively indicate hole expansion ratios (%) at ⅛ positions of the sheet width from one end of the hot rolled steel sheet in a sheet width direction perpendicular to a rolling direction and the other end at an opposite side, and λ.sub.C indicates a hole expansion ratio (%) of a sheet width center part).

The invention relates to a method for producing hot-rolled hot strip products in which a steel alloy is melted; the melted steel alloy is cast into slab ingots and after being heated to a temperature above Ac.sub.3, the slab ingots are hot rolled until they reach a desired degree of deformation and a desired strip thickness; the rolling is performed above the recrystallization temperature of the alloy; after the rolling, the strip is cooled to room temperature and for hardening purposes, is briefly heated to a temperature >Ac3 and cooled again, characterized in that the heating takes place with a temperature increase of more than 5 K/s, more than 10 K/s, more than 50 K/s, or more than 100 K/s and is kept at a desired target temperature for a period of 0.5 to 60 s before cooling to yield improved mechanical properties. and then a cooling takes place;

The invention relates to a method for producing hot-rolled hot strip products in which a steel alloy is melted; the melted steel alloy is cast into slab ingots and after being heated to a temperature above Ac.sub.3, the slab ingots are hot rolled until they reach a desired degree of deformation and a desired strip thickness; the rolling is performed above the recrystallization temperature of the alloy; after the rolling, the strip is cooled to room temperature and for hardening purposes, is briefly heated to a temperature >Ac3 and cooled again, characterized in that the heating takes place with a temperature increase of more than 5 K/s, more than 10 K/s, more than 50 K/s, or more than 100 K/s and is kept at a desired target temperature for a period of 0.5 to 60 s before cooling to yield improved mechanical properties. and then a cooling takes place;

Disclosed is a surface anti-corrosion treatment method for stainless steel. The method comprises the following steps: (1) performing chemical de-oiling and alkaline corrosion treatments on the surface of stainless steel by using a sodium hydroxide solution and a solution containing an alkaline corrosion active agent, and then washing with water; (2) performing, by using an oxidation solution, an oxidation treatment on the surface of the stainless steel treated in step (1), and then washing with water; (3) using the surface of the stainless steel treated in step (2) as a cathode and soaking same in an electrolyte for electrolysis, and then washing with water; and (4) placing the surface of the stainless steel treated in step (3) at a temperature of 50° C.-60° C. under a humidity of 60%-70%, and performing a hardening treatment. Also disclosed are the use of the treatment method in the treatment of a stainless steel part and a stainless steel part obtained after the treatment by means of the treatment method.