A rolled steel sheet, for press hardening is provided, having a chemical composition where Ti/N>3.42, and the carbon, manganese, chromium and silicon contents satisfy: $2.6C+\frac{\mathrm{Mn}}{5.3}+\frac{\mathrm{Cr}}{13}+\frac{\mathrm{Si}}{15}\ge 1.1\%.$
The sheet has a nickel content Ni.sub.surf at any point of the steel in the vicinity of the surface over a depth Δ, such that: Ni.sub.surf >Ni.sub.nom, Ni.sub.nom denoting the nominal nickel content of the steel, and such that, Ni.sub.max denoting the maximum nickel content within Δ: $\frac{\left({\mathrm{Ni}}_{\max }+{\mathrm{Ni}}_{\mathrm{nom}}\right)}{2}\times \left(\Delta \right)\ge 0.6,$
and such that: $\frac{\left({\mathrm{Ni}}_{\max }-{\mathrm{Ni}}_{\mathrm{nom}}\right)}{\Delta }\ge 0.01$
and the surface density of all of the particles D.sub.i and the surface density of the particles D.sub.(>2 μm) larger than 2 micrometers satisfy, at least to a depth of 100 micrometers in the vicinity of the surface of said sheet:
D.sub.i+6.75 D.sub.(>2 μm) <270
D.sub.i and D.sub.(>2 μm) being expressed as number of particles per square millimeter, and said particles denoting all the oxides, sulfides, and nitrides, either pure or combined such as oxysulfides and carbonitrides, present in the steel matrix.

A method for producing a cold-rolled flat steel product coated with a metallic anticorrosion layer includes producing a steel melt containing in addition to iron and unavoidable impurities (in % by wt.): C: 0.01-0.35%, Mn: 1-4%, Si: 0.5-2.5%, Nb: to 0.1%, Ti: 0.015-0.1%, P: up to 0.1%, Al: to 0.15%, S: up to 0.01%, N: up to 0.1%, and optionally one or more elements from a group of rare earth metals. The method further includes casting the steel melt to give a preliminary product, hot-rolling the preliminary product to give a hot strip, coiling the hot strip to give a coil, annealing the hot strip, cold-rolling the annealed hot strip to give a cold-rolled flat steel product, finally annealing the cold-rolled flat steel product, and applying a metal anticorrosion layer based on zinc by electrolytic galvanization or hot dip galvanization of the cold-rolled and finally annealed flat steel product.

A method for producing a cold-rolled flat steel product coated with a metallic anticorrosion layer includes producing a steel melt containing in addition to iron and unavoidable impurities (in % by wt.): C: 0.01-0.35%, Mn: 1-4%, Si: 0.5-2.5%, Nb: to 0.1%, Ti: 0.015-0.1%, P: up to 0.1%, Al: to 0.15%, S: up to 0.01%, N: up to 0.1%, and optionally one or more elements from a group of rare earth metals. The method further includes casting the steel melt to give a preliminary product, hot-rolling the preliminary product to give a hot strip, coiling the hot strip to give a coil, annealing the hot strip, cold-rolling the annealed hot strip to give a cold-rolled flat steel product, finally annealing the cold-rolled flat steel product, and applying a metal anticorrosion layer based on zinc by electrolytic galvanization or hot dip galvanization of the cold-rolled and finally annealed flat steel product.

A high-strength galvanized steel sheet of the present invention includes a steel sheet having a chemical composition containing a predetermined component element, and a steel structure in which an average grain size of inclusions containing at least one of Al, Si, Mg, and Ca and existing in an area extending from a surface to a position of ⅓ of a sheet thickness is 50 μm or less, and an average nearest distance between ones of the inclusions is 20 μm or more; and a galvanized layer provided on a surface of the steel sheet and having a coating weight per one surface of 20 g/m.sup.2 or more and 120 g/m.sup.2 or less, in which an amount of diffusible hydrogen contained in the steel is less than 0.25 mass ppm, and a tensile strength is 1100 MPa or more.

The present invention relates to a flat steel product which has good deep-drawing ability, low edge-crack sensitivity and good bending behaviour. To this end, the flat steel product contains a steel which consists of (in wt %) 0.1-0.5% C, 1.0-3.0% Mn, 0.9-1.5% Si, up to 1.5% Al, up to 0.008% N, up to 0.020% P, up to 0.005% S, 0.01-1% Cr and optionally one or more of the following elements: up to 0.2% Mo, up to 0.01% B, up to 0.5% Cu, up to 0.5% Ni and optionally a total of 0.005-0.2% microalloying elements, the remainder being iron and unavoidable impurities, wherein 75<(Mn2+55*Cr)/Cr<3000 where Mn is the Mn content of the steel in wt % and Cr is the Cr content of the steel in wt %. The steel has a structure which consists of at least 80 area % martensite, of which at least 75 area % is tempered martensite and at most 25 area % is non-tempered martensite, at least 5 volume % residual austenite, 0.5 to 10 area % ferrite and at most 5 area % bainite, wherein in the region of the phase boundary between tempered martensite and residual austenite there is a low-Mn ferrite seam which has a width of at least 4 nm and at most 12 nm and the Mn content of which is at most 50% of the average Mn content of the flat steel product. The flat steel product contains carbides with a length of less than or equal to 250 nm. The invention also relates to a method for producing a flat steel product according to the invention, in which method the structural characteristics of the flat steel product according to the invention are set by suitable heat treatment.

The present invention relates to a flat steel product which has good deep-drawing ability, low edge-crack sensitivity and good bending behaviour. To this end, the flat steel product contains a steel which consists of (in wt %) 0.1-0.5% C, 1.0-3.0% Mn, 0.9-1.5% Si, up to 1.5% Al, up to 0.008% N, up to 0.020% P, up to 0.005% S, 0.01-1% Cr and optionally one or more of the following elements: up to 0.2% Mo, up to 0.01% B, up to 0.5% Cu, up to 0.5% Ni and optionally a total of 0.005-0.2% microalloying elements, the remainder being iron and unavoidable impurities, wherein 75<(Mn2+55*Cr)/Cr<3000 where Mn is the Mn content of the steel in wt % and Cr is the Cr content of the steel in wt %. The steel has a structure which consists of at least 80 area % martensite, of which at least 75 area % is tempered martensite and at most 25 area % is non-tempered martensite, at least 5 volume % residual austenite, 0.5 to 10 area % ferrite and at most 5 area % bainite, wherein in the region of the phase boundary between tempered martensite and residual austenite there is a low-Mn ferrite seam which has a width of at least 4 nm and at most 12 nm and the Mn content of which is at most 50% of the average Mn content of the flat steel product. The flat steel product contains carbides with a length of less than or equal to 250 nm. The invention also relates to a method for producing a flat steel product according to the invention, in which method the structural characteristics of the flat steel product according to the invention are set by suitable heat treatment.

A multi-layered metal sheet is disclosed formed of a laminate of a plurality of metal sheets fixed to each other by a clinch formed in a concave shape from one main surface toward another main surface, the clinch has an schematic pillar shape, the clinch being defined by an open top, a pair of cut surfaces which are respectively formed from the open top toward a bottom, a pair of inclined surfaces respectively inclined from the open top toward the bottom, transitional surfaces which connect the cut surfaces and the inclined surfaces to each other, and the bottom having overlapping parts which extend over the main surface of the multi-layered metal sheet on a lower side immediately below the cut surfaces, and lengthwise end portions of a cut formed in each of upper edge portions of the cut surfaces are disposed on upper edge portions of the transitional surfaces.

A bearing component such as a bearing ring includes a metallic base body and at least one alloy steel coating on the base body, the coating being applied to the base body by deposition welding. The base body is preferably non-alloy steel or cast iron, and the alloy includes at least one carbide-forming transition metal such as niobium, tantalum, zirconium, titanium, hafnium, tungsten, molybdenum, vanadium, or manganese. The coating can form a raceway of the bearing component or a structural element such as a flange. Also a method of forming such a bearing component is provided.

A bearing component such as a bearing ring includes a metallic base body and at least one alloy steel coating on the base body, the coating being applied to the base body by deposition welding. The base body is preferably non-alloy steel or cast iron, and the alloy includes at least one carbide-forming transition metal such as niobium, tantalum, zirconium, titanium, hafnium, tungsten, molybdenum, vanadium, or manganese. The coating can form a raceway of the bearing component or a structural element such as a flange. Also a method of forming such a bearing component is provided.

The application provides in an aspect a process for producing urea in a urea plant comprising a high pressure synthesis section comprising a reactor, wherein the process comprises reacting NH.sub.3 feed and CO.sub.2 feed under urea formation conditions in said reactor to form a urea synthesis solution comprising urea, water, carbamate and ammonia, wherein the process further comprises contacting a carbamate-containing liquid stream with an equipment part of said high pressure synthesis section that is made of a ferritic steel alloy.