The invention relates to a process for producing an at least partly quenched and tempered sheet steel component, where the process comprises the following steps: providing a sheet steel, at least partly austenitizing the sheet steel at a temperature of at least Ac1, at least partly hardening the at least partly austenitized sheet steel to give an at least partly hardened sheet steel component, where the at least partly austenitized sheet steel is cooled to a temperature below Ms, at least partly annealing the at least partly hardened sheet steel component at a temperature of less than Ac1 for producing an at least partly quenched and tempered sheet steel component. A further subject of the invention is an at least partly quenched and tempered sheet steel component.

The invention relates to a process for producing an at least partly quenched and tempered sheet steel component, where the process comprises the following steps: providing a sheet steel, at least partly austenitizing the sheet steel at a temperature of at least Ac1, at least partly hardening the at least partly austenitized sheet steel to give an at least partly hardened sheet steel component, where the at least partly austenitized sheet steel is cooled to a temperature below Ms, at least partly annealing the at least partly hardened sheet steel component at a temperature of less than Ac1 for producing an at least partly quenched and tempered sheet steel component. A further subject of the invention is an at least partly quenched and tempered sheet steel component.

A high-strength cold-rolled steel sheet comprises: a chemical composition that contains C, Si, Mn, P, S, N, Al, Ti, Nb, and B with a balance consisting of Fe and inevitable impurities, and satisfies [mol % N]/[mol % Ti]<1; and a steel microstructure in which: an area fraction of ferrite is 30% or more and 60% or less; a total area fraction of tempered martensite and bainite is 35% or more and 65% or less; an area fraction of quenched martensite is 15% or less; an area fraction of retained austenite is 1% or more and 10% or less; an area fraction of low-Mn ferrite having a Mn concentration of 0.8×[% Mn] or less is 5% or more and 40% or less; a result of subtracting the area fraction of the low-Mn ferrite from the area fraction of the ferrite is 10% or more; an area fraction of a residual microstructure is less than 3%; and an average grain size of the low-Mn ferrite is 10 μm or less.

Disclosed in the present invention is a manufacturing method for a carbon steel and austenitic stainless-steel rolling clad plate, comprising the steps of: (1) obtaining a blank material of a carbon steel layer and a blank material of a stainless-steel layer; (2) assembling blank materials; (3) cladding and rolling; (4) cold rolling; (5) first annealing; and (6) second annealing. The carbon steel and austenitic stainless-steel rolling clad plate has two unique annealing processes, so that the clad plate has the performance advantages of the austenitic stainless-steel and the carbon steel. In addition, further disclosed in the present invention is a carbon steel and austenitic stainless-steel rolling clad plate manufactured by this method.

Provided are a high-strength wire rod having high hydrogen embrittlement resistance for cold heading, and a method for manufacturing the high-strength wire rod. The high-strength wire rod for cold heading has a chemical composition including, by weight %, C: 0.3% to 0.5%, Si: 0.01% to 0.3%, Mn: 0.3% to 1.0%, Cr: 0.5% to 1.5%, Mo: 0.5% to 1.5%, V: 0.01% to 0.4%, and a balance of Fe and other impurities, and the chemical composition satisfies the relational expression 1. The high-strength wire rod for cold heading has a microstructure including, by area %, 1% to 15% martensite, 0.1% to 5% pearlite, and a balance of bainite, and the fraction of martensite formed along grain boundaries of prior austenite in the martensite of the microstructure is 60% or more.

Provided is a steel sheet and a method for manufacturing same, the steel sheet, which can be used for automobile parts and the like, having superb bendability, and excellent balance of strength and ductility and of strength and hole expansion ratio. The steel sheet includes: by wt %, C: 0.25 to 0.75%, Si: 4.0% or less, Mn: 0.9 to 5.0%, Al: 5.0% or less, P: 0.15% or less, S: 0.03% or less, N: 0.03% or less, a balance of Fe, and unavoidable impurities; and as microstructures, ferrite which is a soft structure, and tempered martensite, bainite, and retained austenite which are hard structures.

Provided is a steel sheet which can be used for automobile parts and the like, and relates to a steel sheet having a superior balance of strength and ductility and strength and hole expansion ratio and superior bending formability, and a method for manufacturing same.

The present disclosure relates to a high-strength hot-dip galvanized steel sheet having excellent surface quality and electrical resistance spot weldability, and a method for manufacturing the same. A galvanized steel sheet according to an aspect of the present disclosure is a galvanized steel sheet including a base steel sheet and a zinc-based plating layer formed on a surface of the base steel sheet, wherein a ratio (a/b) of a hardness of a surface layer portion (a) to a hardness of an internal portion (b) of the base steel sheet may be less than 0.95.

Disclosed in the present disclosure is an ultrahigh-strength dual-phase steel. The matrix structure of the ultrahigh-strength dual-phase steel is ferrite and martensite, wherein the ferrite and the martensite are evenly distributed in an island shape. The ultrahigh-strength dual-phase steel contains the following chemical elements in percentage by mass: 0.12-0.2% of C, 0.5-1.0% of Si, 2.5-3.0% of Mn, 0.02-0.05% of Al, 0.02-0.05% of Nb, 0.02-0.05% of Ti, and 0.001-0.003% of B. Further disclosed in the present disclosure is a manufacturing method for the ultrahigh-strength dual-phase steel, comprising the steps of smelting and continuous casting, hot rolling, cold rolling, annealing, tempering, and leveling. The ultrahigh-strength dual-phase steel in the present disclosure has not only good mechanical properties but also excellent delayed cracking resistance and low initial hydrogen content, and can be suitable for manufacturing of vehicle safety structural parts.

The disclosed martensitic stainless steel is defined in its composition is by specified ranges of weight percentages of C; Mn; Si; ≤Mn+Si; ≤S; 10,000×Mn×S; P; Cr, with [Cr−10.3−80*(C+N).sup.2]≤(Mn+Ni); Ni; Mo; Mo+2W; Cu; Ti; V; Zr; Al; O; Ta; Nb; (Nb+Ta)/(C+N); Nb; N; Co; Cu+Co; Cu+Co+Ni; B; rare earths+Y; Ca; the remainder being iron and impurities resulting from processing. Its microstructure includes at least 75% martensite, at most 20% ferrite and at most 0.5% carbides, the size of the ferrite grains being between 4 and 80 μm, preferably between 5 and 40 μm. Also disclosed is a method of manufacturing such steel.