An object comprising a chromium-based coating on a substrate is disclosed. The chromium is electroplated from an aqueous electroplating bath comprising trivalent chromium cations, wherein the chromium-based coating comprises at least one chromium-containing layer, the chromium-based coating does not contain macrocracks, wherein a macrocrack is a crack that extends from the outer surface of the chromium-based coating, through the chromium-based coating, to the substrate, the chromium-based coating has a Vickers microhardness value of 800-1100 HV, and the chromium-based coating exhibits a critical scratch load value (L.sub.C2) of at least 80 N in the adhesion test according to ASTM C1624-05 (2015; point 11.11.4.4). Further is disclosed a method for its production.

In a steel sheet according to the present embodiment, a Ti content and a N content satisfy Ti−3.5×N≥0.003, at a sheet thickness ¼ position, a metallographic structure includes 90% or more of martensite in terms of volume fraction, at the sheet thickness ¼ position, a number density of TiC having a circle equivalent diameter of 1 to 500 nm is 3.5×10.sup.4 particles/mm.sup.2 or more, at the sheet, thickness ¼ position, a value of a median value of a Mn concentration+3σ is 5.00% or less, and a hardness measured at the sheet thickness ¼ position is 1.30 times or more a hardness measured at a position 50 μm deep from a surface of the steel sheet.

In a steel sheet according to the present embodiment, a Ti content and a N content satisfy Ti−3.5×N≥0.003, at a sheet thickness ¼ position, a metallographic structure includes 90% or more of martensite in terms of volume fraction, at the sheet thickness ¼ position, a number density of TiC having a circle equivalent diameter of 1 to 500 nm is 3.5×10.sup.4 particles/mm.sup.2 or more, at the sheet, thickness ¼ position, a value of a median value of a Mn concentration+3σ is 5.00% or less, and a hardness measured at the sheet thickness ¼ position is 1.30 times or more a hardness measured at a position 50 μm deep from a surface of the steel sheet.

A combined oil control ring comprising a pair of annular side rails each having a gap, and an axially corrugated spacer expander arranged between the side rails; the corrugated spacer expander having on the inside seating tabs for pushing inner peripheral surfaces of the side rails; the side-rail-pushing surface of each seating tab being provided with a nitrided layer; an entire surface of each spacer expander except for those provided with the nitrided layer being coated with a plating film; and the plating film having Vickers hardness HV0.01 of 300 or less.

A method for creating oil-filled porous anodic oxide coatings for stainless steel is disclosed. The coating has anti-corrosion and omniphobic properties to resist both atmospheric conditions, or other conditions with exposure to vapor, and wet conditions, in which the coating is exposed to and/or immersed in liquid. The anodic oxide coating of the present invention can be made by the steps of cleaning and/or electropolishing a steel substrate, applying anodic oxidation to the steel substrate, washing the steel substrate in an organic solvent, and annealing the substrate at high temperature. To fill the porous coating with an oil, a solvent exchange method may be applied.

A method for creating oil-filled porous anodic oxide coatings for stainless steel is disclosed. The coating has anti-corrosion and omniphobic properties to resist both atmospheric conditions, or other conditions with exposure to vapor, and wet conditions, in which the coating is exposed to and/or immersed in liquid. The anodic oxide coating of the present invention can be made by the steps of cleaning and/or electropolishing a steel substrate, applying anodic oxidation to the steel substrate, washing the steel substrate in an organic solvent, and annealing the substrate at high temperature. To fill the porous coating with an oil, a solvent exchange method may be applied.

The chemical treatment steel sheet includes a steel sheet, a mat finished Sn plating layer that is provided as an upper layer of the steel sheet and is formed of a β-Sn, and a chemical treatment layer that is provided as an upper layer of the Sn plating layer. The Sn plating layer contains the β-Sn of 0.10 g/m.sup.2 to 20.0 g/m.sup.2 in terms of an amount of metal Sn. A crystal orientation index of a (100) plane group of the Sn plating layer is higher than crystal orientation indexes of other crystal orientation planes. The chemical treatment layer includes a Zr compound containing Zr of 0.50 mg/m.sup.2 to 50.0 mg/m.sup.2 in terms of an amount of metal Zr, and a phosphate compound.

A method for producing an alloy steel composition includes the following steps: performing a first heat treatment on an alloy steel composition and maintaining for a first time period to soften the alloy steel composition; performing a first cooling treatment on the softened alloy steel composition; performing a treatment on the softened the alloy steel composition to form a workpiece; performing a second heat treatment on the workpiece and maintaining for a second time period; and performing a second cooling treatment on the workpiece to make the workpiece become to be a Bainite structure, and a cooling rate of the second cooling treatment is high than the cooling rate of the first cooling treatment.

To provide a Sn-based plated steel sheet capable of exhibiting superior corrosion resistance, yellowing resistance, coating film adhesiveness, and sulphide stain resistance without using a chromate film. A Sn-based plated steel sheet of the present invention includes: a steel sheet; a Sn-based plating layer located on at least one surface of the steel sheet; and a coating layer located on the Sn-based plating layer, wherein the Sn-based plating layer contains 1.0 g/m.sup.2 to 15.0 g/m.sup.2 of Sn per side in terms of metal Sn, the coating layer contains zirconium oxide, and a content of the zirconium oxide is 1.0 mg/m.sup.2 to 10.0 mg/m.sup.2 per side in terms of metal Zr, the zirconium oxide includes zirconium oxide with an amorphous structure, and a crystalline layer whose main component is zirconium oxide with a crystalline structure is present on an upper layer of the zirconium oxide with the amorphous structure.

The present disclosure relates to an ultra-high-strength plated steel sheet and a method for molding the same, and more particularly, to an ultra-high-strength plated steel sheet having high tensile strength without the occurrence of plating peeling and hydrogen delayed fracture phenomenon during roll forming molding, and a method for molding the same.