Provided is a rubber article-reinforcing steel cord having improved shear fatigue resistance while reducing the weight of the steel cord by using a wire of high tensile strength. The rubber article-reinforcing steel cord 10 is a steel cord 10 having a two-layer twisted structure comprising a core filament 11 composed of a plurality of filaments and a sheath filament 12 composed of a plurality of filaments twisted around the core filament 11, wherein the tensile strength of the core filament 11 is higher than the tensile strength of the sheath filament 12, and the core filament 11 and the sheath filament 12 are twisted together in the same direction and the same pitch.

Provided is a rubber article-reinforcing steel cord having improved shear fatigue resistance while reducing the weight of the steel cord by using a wire of high tensile strength. The rubber article-reinforcing steel cord 10 is a steel cord 10 having a two-layer twisted structure comprising a core filament 11 composed of a plurality of filaments and a sheath filament 12 composed of a plurality of filaments twisted around the core filament 11, wherein the tensile strength of the core filament 11 is higher than the tensile strength of the sheath filament 12, and the core filament 11 and the sheath filament 12 are twisted together in the same direction and the same pitch.

A steel filament for twisting into a steel cord for the reinforcement of rubber articles, which contains a steel substrate that is coated with a coating comprising brass. The coating is different in that the amount of iron at the surface is distinctively higher than that prior steel filaments. The coating has an average iron content of 4 or more atomic percent compared to the total of iron, zinc and copper atoms in the layer extending from the surface to a depth of 3 nanometer below the surface. The steel filaments show an improved adhesion retention under hot and humid conditions and in organic cobalt compound containing rubbers as well as rubbers that are substantially free of cobalt. The lifetime of the rubber article is extended.

A steel filament for twisting into a steel cord for the reinforcement of rubber articles, which contains a steel substrate that is coated with a coating comprising brass. The coating is different in that the amount of iron at the surface is distinctively higher than that prior steel filaments. The coating has an average iron content of 4 or more atomic percent compared to the total of iron, zinc and copper atoms in the layer extending from the surface to a depth of 3 nanometer below the surface. The steel filaments show an improved adhesion retention under hot and humid conditions and in organic cobalt compound containing rubbers as well as rubbers that are substantially free of cobalt. The lifetime of the rubber article is extended.

A multi-strand cord (50) comprises an internal layer (CI) made up of K=1 internal strand (TI) having two layers (C1, C3), with the internal layer (C1) being made up of Q internal metallic threads (F1) and the external layer (C3) being made up of N external metallic threads (F3), and an external layer (CE) made up of L>1 external strands (TE) having two layers (C1′, C3′) wound around the internal layer (CI), with the internal layer (C1′) being made up of Q′ internal metallic threads (F1′) and the external layer (C3′) being made up of N′ external metallic threads (F3′). The cord (50) has an energy-to-break per unit area ES≥145 N.Math.mm.sup.−1 with ES=Σ.sub.i=1.sup.NcF.sub.mi×Σ.sub.i=1.sup.NcA.sub.ti/Nc×Cfrag/D where Σ.sub.i=1.sup.NcF.sub.mi is the sum of the forces at break, Σ.sub.i=1.sup.NcA.sub.ti is the sum of the total elongation, Cfrag is the coefficient of weakening, and D is the diameter.

A wire rope for face shovels or draglines, comprising: a core, said core is made from a plurality of core strands a plurality of outer strands laid on said core, a plurality of separator strands located in the interstices between said core strands and said outer strands, a plastic jacket around said plurality of outer strands, said plurality of separator strands and said core strands, wherein said plurality of separator strands extend from said core strands and in-between each pair of said plurality of outer strands so as to produce and maintain gaps between said pair of said plurality of outer strands; wherein said core strands are compacted, and the gap between said core strands is less than 0.4% of the diameter of the core strand.

A wire rope for face shovels or draglines, comprising: a core, said core is made from a plurality of core strands a plurality of outer strands laid on said core, a plurality of separator strands located in the interstices between said core strands and said outer strands, a plastic jacket around said plurality of outer strands, said plurality of separator strands and said core strands, wherein said plurality of separator strands extend from said core strands and in-between each pair of said plurality of outer strands so as to produce and maintain gaps between said pair of said plurality of outer strands; wherein said core strands are compacted, and the gap between said core strands is less than 0.4% of the diameter of the core strand.

Provided are a rubber article reinforcing steel wire that is superior in bending fatigue properties to the related art and has a flat cross-sectional shape, and a rubber article using the wire. In a rubber article reinforcing steel wire 10, a major diameter and a minor diameter are substantially perpendicular to each other. Assuming that the major diameter is W, the minor diameter is T, a straight line that passes through a center of the major diameter in a width direction and is parallel to a minor diameter direction is L1, a straight line that passes through a center of the minor diameter in a width direction and is parallel to a major diameter direction is L2, an intersection point of the L1 and the L2 is a center point C, a region within a half of a distance from the center point C to a surface is a central region Rc, and a region outside the central region Rc is a surface layer region Rs, a Vickers hardness Hvc of the central region Rc is more than a Vickers hardness Hvs of the surface layer region Rs; and assuming that a Vickers hardness on the L1 in the surface layer region Rs is Hv1, and a Vickers hardness on the L2 in the surface layer region Rs is Hv2, relationships represented by Hvc−Hv1≦150, Hvc−Hv2≦150, Hv1/Hvc×100≧85.11, and Hv2/Hvc×100≧79.84 are satisfied.

Provided are a rubber article reinforcing steel wire that is superior in bending fatigue properties to the related art and has a flat cross-sectional shape, and a rubber article using the wire. In a rubber article reinforcing steel wire 10, a major diameter and a minor diameter are substantially perpendicular to each other. Assuming that the major diameter is W, the minor diameter is T, a straight line that passes through a center of the major diameter in a width direction and is parallel to a minor diameter direction is L1, a straight line that passes through a center of the minor diameter in a width direction and is parallel to a major diameter direction is L2, an intersection point of the L1 and the L2 is a center point C, a region within a half of a distance from the center point C to a surface is a central region Rc, and a region outside the central region Rc is a surface layer region Rs, a Vickers hardness Hvc of the central region Rc is more than a Vickers hardness Hvs of the surface layer region Rs; and assuming that a Vickers hardness on the L1 in the surface layer region Rs is Hv1, and a Vickers hardness on the L2 in the surface layer region Rs is Hv2, relationships represented by Hvc−Hv1≦150, Hvc−Hv2≦150, Hv1/Hvc×100≧85.11, and Hv2/Hvc×100≧79.84 are satisfied.

Provided is a steel cord for rubber article reinforcement which has excellent corrosion resistance and productivity without deterioration of adhesion with rubber. A steel cord (1) for rubber article reinforcement, in which plural steel filaments (2) are twisted together, includes: a core having at least one core filament (2c); and a sheath having at least one sheath layer formed by twisting at least one sheath filament (2s) around the core. In this steel cord (1), brass plating is performed on the steel filaments (2) and zinc plating is further performed on the outer circumference of the brass plating of the core filament (2c), and the steel filaments (2) have a diameter d of 0.1 mm to 0.6 mm.