A cold rolled and heat treated steel sheet having a composition with the following elements, expressed in percentage by weight: 0.10%≤Carbon≤0.5%,1%≤Manganese≤3.4%, 0.5%≤Silicon≤2.5%, 0.03%≤Aluminum≤1.5%, 0%≤Sulfur≤0.003% 0.002%≤Phosphorus≤0.02%, 0%≤Nitrogen≤0.01% and can contain one or more of the following optional elements 0.05%≤Chromium≤1%, 0.001%≤Molybdenum≤0.5%, 0.001%≤Niobium≤0.1%, 0.001%≤Titanium≤0.1%, 0.01%≤Copper≤2%, 0.01%≤Nickel≤3%, 0.0001%≤Calcium≤0.005%, 0%≤Vanadium≤0.1%, 0%≤Boron≤0.003%, 0%≤Cerium≤0.1%, 0%≤Magnesium≤0.010%, 0%≤Zirconium≤0.010% the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of the steel sheet having in area fraction, 10 to 30% Residual Austenite, 10 to 40% Bainite, 5% to 50% Annealed Martensite, 1% to 20% Quenched Martensite and less than 30% Tempered Martensite, wherein the cumulated amounts of Bainite and Residual Austenite is more than or equal to 25%.

The present invention relates to a cold-rolled steel sheet comprising: a base steel sheet; and a nickel or nickel alloy coating layer formed on the base steel sheet, wherein the adhesion amount of the nickel or nickel alloy is 50 mg/m.sup.2 or less.

According to the present invention, provided are a high-strength cold-rolled steel sheet and a manufacturing for manufacturing same. In the high-strength cold-rolled steel sheet, a metal layer is coated on a cold-rolled steel sheet to a thickness of nanometers, followed by annealing, thereby suppressing the formation of oxides of Si, Mn, and the like on the surface of the steel sheet to within a range in which the elution of Fe is not suppressed, and thus the high-strength cold-rolled steel sheet has improved phosphatability.

A cooling device for cooling a metallic item and a method for operating the cooling device. Such cooling devices having a plurality of cooling bars arranged in parallel in groups for applying a coolant to the metallic item are known in the prior art. In order to be able to set a desired distribution function of the coolant over the width of the metallic item as precisely as possible, the cooling device provides that similar application regions in at least two cooling bars within a group are each formed differently with respect to their contour and/or with respect to their surface area.

A steel sheet for a two-piece can, the steel sheet includes: by mass %, C: 0.010% or more and less than 0.030%; Si: 0.04% or less; Mn: 0.10% or more and less than 0.40%; P: 0.02% or less; S: 0.020% or less; Al: more than 0.030% and 0.100% or less; N: 0.0005% or more and less than 0.0030%; B: 0.0005% to 0.0030%; and balance Fe and inevitable impurities, wherein an amount of N that is present as BN and a whole amount of N satisfy the following expression (1):
[N as BN]/[N]>0.5   (1), where N as BN represents the amount of N that is present as BN, and N represents the whole amount of N, a yield point is 280 MPa or more and less than 420 MPa, yield elongation is 3% or less, and Δr is −0.30 to 0.20.

A cooling device with variable cooling rate for treating metal materials, in particular for cooling steel sheets in plate mills, hot strip mills or thermal treatment lines, by means of a spray nozzle cooling system. The cooling device consists of at least two cooling bars one of each two cooling bars being situated on the lower side and the other on the upper side transversely to the sheet travel direction of the sheet and centrally between two roller table rollers and includes a spray nozzle cooling system with which a plurality of full jet nozzles and a plurality of full cone nozzles are associated, the full jet nozzles being arranged symmetrically to the full cone nozzles. A method for operating the cooling device according to the disclosure.

A shock absorbing member which can increase impact absorption energy and also enables thinning of a steel sheet that is a starting material, a method for producing the shock absorbing member, and a method for producing a steel sheet for cold plastic working are provided. The shock absorbing member includes a ridge portion formed in a curved shape as viewed from a longitudinal direction, and a wall portion extending from the ridge portion. In the wall portion, a ratio σ.sub.5/τ.sub.5 between a tensile stress σ.sub.5 when an elongation in a tensile test is 5% and a shear stress τ.sub.5 when a shear strain in a shear test is 5√3% is 1.70 or less, or a ratio σ.sub.10/τ.sub.10 between a tensile stress σ.sub.10 when an elongation in a tensile test is 10% and a shear stress τ.sub.10 when a shear strain in a shear test is 10√3% is 1.70 or less.

The present invention provides a high-strength steel sheet, which can be used in various applications including automobile parts and exhibits excellent collision safety and excellent moldability, and a method for manufacturing the high-strength steel sheet. The high-strength steel sheet according to an aspect of the present invention satisfies a predetermined chemical composition and has a metallographic microstructure having ferrite fraction: 0% to 10%, MA fraction: 0% to 30%, hard phase other than ferrite and MA: 70% to 100% in terms of area proportion and retained austenite fraction: 5% to 30% in terms of volume proportion, and in the high-strength steel sheet, the skewness of IQ as analyzed by the EBRD method is −1.2 to −0.3 when the skewness is expressed by a predetermined relational expression in a case where crystal grains having a bcc structure and a bct structure are regarded as an aggregation of regions having an area of 0.05 μm.sup.2.

The present invention is to provide a steel plate with physical properties superior to existing steel plates used in fields such as industrial machinery, especially excellent low-temperature impact toughness along with high strength and high hardness, and a method for manufacturing same.

Provided are: steel for knives, having a higher hardness and better corrosion resistance than conventional steel for knives; a knife; steel for martensitic knives; and a production method for same. The steel for knives comprises a component composition containing, in mass %, 0.45%-1.00% C, 0.1%-1.5% Si, 0.1%-1.5% Mn, 7.5%-11.0% Cr, and 0.5%-3.0% of either Mo or W or a complex of both (Mo+W/2), with the remainder being Fe and unavoidable impurities. Also provided are steel for martensitic knives and a knife. A production method for steel for martensitic knives is also provided that includes a quenching temperature at quenching of 1,050-1,250° C., a processing temperature for subzero processing of no more than −50° C., and a tempering temperature at tempering of 100-400° C., and obtains steel for martensitic knives that has a hardness of at least 700 HV.

To obtain a high-strength hot-dip galvanized steel sheet having excellent surface appearance even in the case where a steel strip containing Mn at a predetermined ratio or more to Si is subjected to hot-dip galvanizing treatment, a method of producing a hot-dip galvanized steel sheet using a continuous hot-dip galvanizing apparatus comprises: subjecting a steel strip to annealing, by conveying it in an annealing furnace; and subjecting the steel strip discharged from a cooling zone to hot-dip galvanizing using a hot-dip galvanizing line, to obtain a hot-dip galvanized steel sheet. The steel strip has a chemical composition containing, in mass %, Mn: 1.7% or more and 3.5% or less and Si: 0.2% or more and 1.05% or less and satisfying [Si]/[Mn]≤0.30. The chemical composition, a dew point of an atmosphere in the soaking zone, and a delivery temperature of the heating zone satisfy Formula (1).