A treatment device is provided for single-stage treatment of a metal object, wherein the treatment comprises at least pickling and phosphating of the object. The treatment device comprises a treatment container for holding the object to be treated and for holding a flowable treatment substance, and a pumping apparatus for circulating at least a portion of the treatment substance. The treatment substance is flowable around at least part of the object to be treated, and the treatment substance is a phosphorus- or phosphate-containing solution. The phosphorus- or phosphate-containing solution consists of water and a reaction substance, and the reaction substance consists of phosphorus or of a phosphate and at least one additional substance that improves the treatment effect. The fraction of the phosphorous or the phosphate in the reaction substance is between 75 vol % to 94 vol %, and the reaction substance has no fractions of hydrochloric acid and sulfuric acid.

A high-strength steel sheet having a tensile strength of 1,180 MPa or more, and specified chemical composition. The steel sheet includes a steel structure in which an area fraction of martensite having a carbon concentration of more than 0.7?[% C] and less than 1.5?[% C] is 55% or more, an area fraction of tempered martensite having a carbon concentration of 0.7?[% C] or less is 5% or more and 40% or less, a ratio of a carbon concentration in retained austenite to a volume fraction of retained austenite is 0.05 or more and 0.40 or less, and the martensite and the tempered martensite each have an average grain size of 5.3 ?m or less, where [% C] represents the content, by mass %, of compositional element C in steel.

A high-strength steel sheet having a tensile strength of 1,180 MPa or more, and specified chemical composition. The steel sheet includes a steel structure in which an area fraction of martensite having a carbon concentration of more than 0.7?[% C] and less than 1.5?[% C] is 55% or more, an area fraction of tempered martensite having a carbon concentration of 0.7?[% C] or less is 5% or more and 40% or less, a ratio of a carbon concentration in retained austenite to a volume fraction of retained austenite is 0.05 or more and 0.40 or less, and the martensite and the tempered martensite each have an average grain size of 5.3 ?m or less, where [% C] represents the content, by mass %, of compositional element C in steel.

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.

A preferable aspect of the present invention provides: an ultra-high-strength hot-rolled steel sheet containing, by weight, one or two of 0.40-0.60% of C, 0.7-1.5% of Mn, 0.3% or less (excluding 0%) of Si, 0.03% or less (including 0%) of P, 0.004% or less (including 0%) of S, 0.04% or less (excluding 0%) of Al, 0.3% or less (excluding 0%) of Cr, 0.3% or less (excluding 0%) of Mo, 0.9-1.5% of Ni, and 0.9-1.5% of Cu, 1.1% or more of Cu+Ni, 0.04% or less (excluding 0%) of Ti, 0.005% or less (excluding 0%) of B, 0.006% or less (excluding 0%) of N, and the balance Fe and other impurities, the alloy elements satisfying relational formulas 1 and 2 below, wherein a microstructure of the hot-rolled steel sheet comprises, by volume, 7% or more of ferrite and 93% or less of perlite; a steel pipe and a member each using the same; and manufacturing methods therefor. [Relational formula 1] (Mn/Si) #3 (weight ratio) [Relational formula 2] (Ni/Si) #1 (weight ratio)

A preferable aspect of the present invention provides: an ultra-high-strength hot-rolled steel sheet containing, by weight, one or two of 0.40-0.60% of C, 0.7-1.5% of Mn, 0.3% or less (excluding 0%) of Si, 0.03% or less (including 0%) of P, 0.004% or less (including 0%) of S, 0.04% or less (excluding 0%) of Al, 0.3% or less (excluding 0%) of Cr, 0.3% or less (excluding 0%) of Mo, 0.9-1.5% of Ni, and 0.9-1.5% of Cu, 1.1% or more of Cu+Ni, 0.04% or less (excluding 0%) of Ti, 0.005% or less (excluding 0%) of B, 0.006% or less (excluding 0%) of N, and the balance Fe and other impurities, the alloy elements satisfying relational formulas 1 and 2 below, wherein a microstructure of the hot-rolled steel sheet comprises, by volume, 7% or more of ferrite and 93% or less of perlite; a steel pipe and a member each using the same; and manufacturing methods therefor. [Relational formula 1] (Mn/Si) #3 (weight ratio) [Relational formula 2] (Ni/Si) #1 (weight ratio)

A method of improving corrosion and mar resistance of steel components by creating a black magnetite finish, with a medium temperature process, prior to application of a phosphate layer coating.

Methods, compositions, and kit(s) for removing corrosion or scale from a metal or a non-metal article are disclosed. In a first stage of the method, an article exhibiting corrosion can be exposed to an acid wash composition including a first acid component having one or more of HCl, Phosphoric Acid, Oxalic Acid, a second acid inhibitor/surfactant component including ethoxylated alkyl mercaptan, and a third thixotropic gelling agent component including Talc or Fumed silica, sufficient to cause gelling of the acid wash composition. In a second stage of the method performed subsequent to the first stage, the article can be exposed to an acid neutralizing composition comprising bicarbonate, borax, isopropyl alcohol and water.

A near neutral pH pickling composition for the removal of oxides from metallic surfaces, including heat treated steel. The pickling composition comprises a) a water-soluble organic or inorganic nitro compound, wherein a central N atom has an oxidation state of 3+; b) a polarizing agent for the nitro compound, wherein the polarizing agent comprises at least one of a phosphonate and a carboxylate; c) a pH buffer, and d) at least one metal complexing agent. The composition is preferably maintained at a pH between about 4.5 and about 7.5. The near neutral pH pickle composition can be used on various metallic surfaces as well as composite surfaces comprising metallic and non-metallic portions.

A steel sheet that is welded and then cold rolled to a thickness between 0.5 mm and 3 mm, the deformation ratio created by cold rolling in the base metal is equal to ?.sub.MB, for which the deformation ratio created by the cold rolling in the welded joint is equal to ?.sub.S, where: $0.4?\frac{\mathrm{.Math.S}}{\mathrm{.Math.}MB}<0.7.$