Disclosed are a high-strength multiphase steel tinned raw plate and a manufacturing method therefor, wherein the mass percentages of the components of the multiphase steel tinned raw plate are: 0.081%-0.14% of C, 0.2%-0.8% of Mn, 0.01%-0.09% of Al, 0.01%-0.03% of P, 0.002%-0.015% of N, also containing one or more than one of 0.001%-0.005% of B, 0.005%-0.05% of Cr, 0.001%-0.1% of Ti, 0.001%-0.2% of Nb, 0.005%-0.03% of Cu, 0.001%-0.008% of Mo, and the balance of Fe and other inevitable impurities; and satisfy: 0.21% <Mn+1.3 Cr+3.2 Mo+0.5 Cu <0.91%. The tinned raw plate has a structure comprising ferrite grains, pearlite, martensite and cementite particles, wherein the total volume fraction of the pearlite, martensite and cementite particles is 5%-20%, the volume fraction of the martensite is 1%-5%, and the martensite has a solid solution content of carbon of 0.07%. The tinned raw plate has a high strength and better elongation, and can be used to produce a can body, a can bottom, an easy-open end and a twist-off cap, etc. of a three-piece can which has higher requirements for strength and elongation.

A cast steel shot media for performing a blasting treatment, including, at a weight ratio, 0.8% or more and 1.2% or less of C, 0.35% or more and 1.2% or less of Mn, and 0.4% or more and 1.5% or less of Si, in which a remainder has a hyper-eutectoid composition including Fe and inevitable impurities, and the cast steel shot media has a structure having a fine pearlite structure as a main constituent.

The present invention provides a hot-rolled steel sheet capable of preventing softening of the strength of a sheet-thickness central portion of the steel sheet in thermal treatment, even in the case where an amount of working performed on the steel sheet is small and a work hardening rate is low. A hot-rolled steel sheet of the present invention consists of chemical components of, in mass %, C: 0.040 to 0.150%, Si: 0 to 0.500%, Mn: 0.10 to 1.50%, P: 0 to 0.050%, S: 0 to 0.020%, Al: 0.010 to 0.050%, N: 0.0010 to 0.0060%, Nb: 0.008 to 0.035%, Cu: 0 to 0.10%, Ni: 0 to 0.10%, Cr: 0 to 0.02%, Mo: 0 to 0.020%, V: 0 to 0.020%, Ca: 0 to 0.0100%, B: 0 to 0.0050%, and the balance: Fe and impurities. The hot-rolled steel sheet contains 0.005 to 0.030% dissolved Nb. An area fraction of ferrite structure is 85% or more, the balance is cementite and/or pearlite structure, and an average crystal grain size of ferrite is equal to or more than 5 m and equal to or less than 20 m.

A steel sheet for hot pressing includes: a specific chemical composition; and a steel structure comprising ferrite and cementite and represented, in area %: a total area ratio of bainite and martensite: 0% to 10%; and an area ratio of cementite: 1% or more; and a concentration of Mn in the cementite is 5% or more.

A method of making a small diameter elongated steel article such as wire or strip is disclosed. The method includes the step of melting a steel alloy having the following weight percent composition TABLE-US-00001 C 0.88-1.00 Mn 0.20-0.80 Si 0.50 max. P 0.050 max. S 0.010-0.100 Cr 0.15-0.90 Ni 0.10-0.50 Mo 0.25 max. Cu 0.08-0.23 V 0.025-0.15 N 0.060 max. O 0.040 max.
and the balance is iron and usual impurities. The method includes melting the alloy, atomizing the molten alloy to make a pre-alloyed metal powder, consolidating the metal powder to substantially full density, and then hot working the consolidated metal powder to form an intermediate elongated article. The method further includes a multi-step heat treating process. A small diameter, elongated steel article having enhanced machinability is also disclosed.

Provided are a high-strength steel sheet and a method for manufacturing the steel sheet. The high-strength steel sheet has a specified chemical composition with the balance being Fe and inevitable impurities, a microstructure including, in terms of area ratio, 25% or less of a ferrite phase, 75% or more of a bainite phase and/or a martensite phase, and 5% or less of cementite, in which, in a surface layer that is a region within 50 m from the surface in the thickness direction, the area ratio of a ferrite phase is 5% to 20%, and a tensile strength is 1180 MPa or more.

A steel with high hardness and excellent toughness contains, in mass %, 0.55-1.10% C, 0.10-2.00% Si, 0.10-2.00% Mn, 0.030% or less P, 0.030% or less S, 1.10-2.50% Cr, and 0.010-0.10% Al, with the balance consisting of Fe and unavoidable impurities. The structure of the steel after quenching is a dual phase structure of martensitic structure and spheroidized carbide. Spheroidized cementite particles with an aspect ratio of 1.5 or less constitute at least 90% of all cementite particles. The proportion of the number of spheroidized cementite particles on the prior austenite grain boundaries to a total number of cementite particles is 20% or less.

Provided are a steel cord and a single steel wire having excellent straightness quality for reinforcing tire and a method of manufacturing the steel cord and single steel wire. The steel cord and the single steel wire include a wire undergoing through a drawing process, a heating process performed in a state in which tension is applied to the wire, and a cooling process; and a winding portion on which the wire is wound, the winding portion having a diameter greater than a diameter of the wire, wherein, when an end of the wire that has been wound on the winding portion for six months to one year is fixed on a point and the wire is pulled down vertically to 400 mm, a distance between a first axis that is perpendicular to the point and an opposite end of the wire is 30 mm or less. The method of manufacturing the steel cord and single steel wire having excellent straightness quality for reinforcing tire includes: a wire preparing process, a heating process, a cooling process, and a winding process.

According to an aspect of the present invention, there is provided a steel containing, by unit mass %, C: 0.08% to 0.12%, Si: 0.05% to 0.50%, Mn: 1.50% to 3.00%, P: 0.040% or less, S: 0.020% or less, V: 0.010% or less, Ti: 0.010% or less, Nb: 0.005% or less, Cr: 1.00% to 2.50%, Cu: 0.01% to 0.50%, Ni: 0.75% to 1.60%, Mo: 0.10% to 0.50%, Al: 0.025% to 0.050%, N: 0.0100% to 0.0200%, Ca: 0% to 0.0100%, Zr: 0% to 0.0100%, Mg: 0% to 0.0100%, and a remainder including Fe and impurities, in which a ratio of an Al content to a N content is 2.6 or less, a ratio of a Mn content to a Ni content is 1.5 or more and 3.0 or less.

A steel sheet for the manufacture of a press hardened part is provided, having a composition of: 0.15%C%0.22%, 3.5%Mn<4.2%, 0.001%Si%1.5%, 0.020%Al0.9%, 0.001%Cr1%, 0.001%Mo0.3%, 0.001%Ti0.040%, 0.0003%B0.004%, 0.001%Nb0.060%, 0.001%N0.009%, 0.0005%S0.003%, 0.001%P0.020%. A microstructure has less than 50% ferrite, 1% to 20% retained austenite, cementite, such that the surface density of cementite particles larger than 60 nm is lower than 107/mm.sup.2, and a complement of bainite and/or martensite, the retained austenite having an average Mn content of at least 1.1*Mn %. Press-hardened steel part obtained by hot forming the steel sheet, and manufacturing methods thereof.