A method for the manufacture of a cold-rolled steel sheet of thickness e.sub.f between 0.5 mm and 3 mm is provided. At least two hot-rolled sheets of thickness e.sub.i are supplied and butt welded, so as to create a welded joint (S1) with a direction perpendicular to the direction of hot rolling. The at least two hot-rolled sheets are pickled by continuous passage through a bath, then the assembly is cold rolled, in a step (L1), to an intermediate thickness e.sub.int, the direction of cold rolling (DL.sub.1) coinciding with the direction of hot rolling. The cold rolling is carried out with a reduction ratio ${\mathrm{.Math.}}_1=\mathrm{Ln}\left(\frac{e_i}{e_{\mathrm{int}}}\right)$
such that: $0.35\le \frac{\mathrm{Ln}\left(\frac{\mathrm{ei}}{e\mathrm{int}}\right)}{\mathrm{Ln}\left(\frac{ei}{ef}\right)}\le 0.65,$
then the welded joint (S1) is removed so as to obtain at least two intermediate cold-rolled sheets. Then the two intermediate cold-rolled sheets are butt welded, so as to create a welded joint (S2), the dire

A method for the manufacture of a cold-rolled steel sheet of thickness e.sub.f between 0.5 mm and 3 mm is provided. At least two hot-rolled sheets of thickness e.sub.i are supplied and butt welded, so as to create a welded joint (S1) with a direction perpendicular to the direction of hot rolling. The at least two hot-rolled sheets are pickled by continuous passage through a bath, then the assembly is cold rolled, in a step (L1), to an intermediate thickness e.sub.int, the direction of cold rolling (DL.sub.1) coinciding with the direction of hot rolling. The cold rolling is carried out with a reduction ratio ${\mathrm{.Math.}}_1=\mathrm{Ln}\left(\frac{e_i}{e_{\mathrm{int}}}\right)$
such that: $0.35\le \frac{\mathrm{Ln}\left(\frac{\mathrm{ei}}{e\mathrm{int}}\right)}{\mathrm{Ln}\left(\frac{ei}{ef}\right)}\le 0.65,$
then the welded joint (S1) is removed so as to obtain at least two intermediate cold-rolled sheets. Then the two intermediate cold-rolled sheets are butt welded, so as to create a welded joint (S2), the dire

A flat steel product consisting of (in wt %) 0.1-0.5% C, 1.0-3.0% Mn, 0.9-1.5% Si, ≤1.5% Al, ≤0.008% N, ≤0.020% P, ≤0.005% S, 0.01-1% Cr and optionally one or more of: ≤0.2% Mo, ≤0.01% B, ≤0.5% Cu, ≤0.5% Ni and optionally a total of 0.005-0.2% microalloying elements, the remainder iron and unavoidable impurities. The steel has a structure consisting of ≥80 area % martensite, where ≥75 area % is tempered and ≤25 area % is non-tempered, ≥5 volume % residual austenite, 0.5-10 area % ferrite, ≤5 area % bainite, and carbides with a length of ≤250 nm, wherein in the phase boundary between tempered martensite and residual austenite, there is a low-Mn ferrite seam having a width of 4.Math.12 nm and a Mn content of ≤50% of the average Mn content. Also, a method for producing the flat steel in which the structural characteristics of the flat steel product are set by suitable heat treatment.

A flat steel product consisting of (in wt %) 0.1-0.5% C, 1.0-3.0% Mn, 0.9-1.5% Si, ≤1.5% Al, ≤0.008% N, ≤0.020% P, ≤0.005% S, 0.01-1% Cr and optionally one or more of: ≤0.2% Mo, ≤0.01% B, ≤0.5% Cu, ≤0.5% Ni and optionally a total of 0.005-0.2% microalloying elements, the remainder iron and unavoidable impurities. The steel has a structure consisting of ≥80 area % martensite, where ≥75 area % is tempered and ≤25 area % is non-tempered, ≥5 volume % residual austenite, 0.5-10 area % ferrite, ≤5 area % bainite, and carbides with a length of ≤250 nm, wherein in the phase boundary between tempered martensite and residual austenite, there is a low-Mn ferrite seam having a width of 4.Math.12 nm and a Mn content of ≤50% of the average Mn content. Also, a method for producing the flat steel in which the structural characteristics of the flat steel product are set by suitable heat treatment.

An aqueous composition for reducing corrosive removal of material in pickling of metallic surfaces comprising bare and/or galvanized steel. The composition includes a mixture of a compound of the formula R.sup.1O—(CH.sub.2).sub.x—C≡C—(CH.sub.2).sub.y—OR.sup.2 in which R.sup.1 and R.sup.2 are both H, and a compound of the formula R.sup.1O—(CH.sub.2).sub.x—C≡C—(CH.sub.2).sub.y—OR.sup.2 in which R.sup.1 and R.sup.2 are each, independently of one another, an HO—(CH.sub.2).sub.w— group with w≥2. X and y are each, independently of one another, from 1 to 4 in each of the two compounds of the formula R.sup.1O—(CH.sub.2).sub.x—C≡C—(CH.sub.2).sub.y—OR.sup.2. A process for pickling a metallic surface with reduced corrosive removal of material is disclosed.

An aqueous composition for reducing corrosive removal of material in pickling of metallic surfaces comprising bare and/or galvanized steel. The composition includes a mixture of a compound of the formula R.sup.1O—(CH.sub.2).sub.x—C≡C—(CH.sub.2).sub.y—OR.sup.2 in which R.sup.1 and R.sup.2 are both H, and a compound of the formula R.sup.1O—(CH.sub.2).sub.x—C≡C—(CH.sub.2).sub.y—OR.sup.2 in which R.sup.1 and R.sup.2 are each, independently of one another, an HO—(CH.sub.2).sub.w— group with w≥2. X and y are each, independently of one another, from 1 to 4 in each of the two compounds of the formula R.sup.1O—(CH.sub.2).sub.x—C≡C—(CH.sub.2).sub.y—OR.sup.2. A process for pickling a metallic surface with reduced corrosive removal of material is disclosed.

A high-strength hot-dip coated hot-rolled steel sheet excellent in terms of surface appearance quality and coating adhesiveness and a method for manufacturing. The method includes performing hot rolling followed by pickling on steel to form a pickled steel sheet, the steel having a chemical composition containing, by mass %, C: 0.02% or more and 0.30% or less, Si: 0.01% or more and 1.0% or less, Mn: 0.3% or more and 2.5% or less, P: 0.08% or less, S: 0.02% or less, Al: 0.001% or more and 0.20% or less, and Fe and inevitable impurities. The method further includes performing rolling with a rolling reduction ratio of 1% or more and 10% or less, and a hot-dip coating treatment. The obtained steel sheet has an arithmetic average roughness Ra of 2.0 μm or less on the surface of the steel sheet, and a tensile strength of 590 MPa or more.

A high-strength hot-dip coated hot-rolled steel sheet excellent in terms of surface appearance quality and coating adhesiveness and a method for manufacturing. The method includes performing hot rolling followed by pickling on steel to form a pickled steel sheet, the steel having a chemical composition containing, by mass %, C: 0.02% or more and 0.30% or less, Si: 0.01% or more and 1.0% or less, Mn: 0.3% or more and 2.5% or less, P: 0.08% or less, S: 0.02% or less, Al: 0.001% or more and 0.20% or less, and Fe and inevitable impurities. The method further includes performing rolling with a rolling reduction ratio of 1% or more and 10% or less, and a hot-dip coating treatment. The obtained steel sheet has an arithmetic average roughness Ra of 2.0 μm or less on the surface of the steel sheet, and a tensile strength of 590 MPa or more.

The invention provides metal members having liquid-repellent and corrosion-resistant surfaces, without the need for SAM surface treatment. A metal member of the disclosure has a porous surface, having the porous surface directly covered by a hydrocarbon-based oil comprising zinc dialkyldithiophosphate (ZnDTP). The porous surface may be an oxidized surface, and especially an anodized surface. The metal member may be a member of Al, Ti, Fe or Mg, or an alloy of any of these metals, or stainless steel. The concentration of the zinc dialkyldithiophosphate (ZnDTP) may be 0.1 mass % to 30.0 mass % with respect to the hydrocarbon-based oil.

A method for producing a hot-rolled steel sheet, a method for producing a cold-rolled full-hard steel sheet, and a method for producing a heat-treated sheet are provided herein. The methods comprising hot rolling a steel material of a composition comprising, in mass %, C: 0.05 to 0.12%, Si: 0.80% or less, Mn: 1.30 to 2.10%, P: 0.001 to 0.050%, S: 0.005% or less, Al: 0.01 to 0.10%, N: 0.010% or less, one or more selected from Cr in an amount of 0.05 to 0.50%, and Mo in an amount of 0.05 to 0.50%, one or more selected from Ti in an amount of 0.01 to 0.10%, Nb in an amount of 0.01 to 0.10%, and V in an amount of 0.01 to 0.10%, and the balance Fe and unavoidable impurities.