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.

A cord including multifilament para-aramid yarn comprising filaments, wherein the filaments have a non-round cross section having a smaller and a larger dimension, where the cross-sectional aspect ratio between the larger and the smaller dimension is 1.5-10 and the smaller dimension of the cross section has a maximum of 50 m and wherein the para-aramid has at least 90% para bonds between the aromatic moieties. The cords have excellent fatigue properties.

A steel cord for tire belt ply reinforcement includes a cord formed by periodically twisting n wires, wherein the n wires are compressed by rolling, and at least one of the n wires is compressed into a non-circular shape, when n is an odd number, a cross-section of one wire from among the n wires is circular due to rolling, and cross-sections of n?1 wires from among the n wires are non-circular, and when n is an even number, cross-sections of two wires from among the n wires are circular due to rolling, and cross-sections of n?2 wires from among the n wires are non-circular due to rolling.

A cord including multifilament para-aramid yarn comprising filaments, wherein the filaments have a non-round cross section having a smaller and a larger dimension, where the cross-sectional aspect ratio between the larger and the smaller dimension is 1.5-10 and the smaller dimension of the cross section has a maximum of 50 m and wherein the para-aramid has at least 90% para bonds between the aromatic moieties. The cords have excellent fatigue properties.

Disclosed is a tire-reinforcing steel cord for a radial tire. The tire-reinforcing steel cord has a double layer structure including a first-layer core and a second-layer core provided on the surface of the first-layer core. The first-layer core has an elliptical or rectangular cross section. The tire-reinforcing steel cord can improve processability, fatigue characteristics, and rolling resistance performance of a tire, resulting in improved fuel efficiency. A radial tire using the tire-reinforcing steel cord is also disclosed.

Disclosed is a tire-reinforcing steel cord for a radial tire. The tire-reinforcing steel cord has a double layer structure including a first-layer core and a second-layer core provided on the surface of the first-layer core. The first-layer core has an elliptical or rectangular cross section. The tire-reinforcing steel cord can improve processability, fatigue characteristics, and rolling resistance performance of a tire, resulting in improved fuel efficiency. A radial tire using the tire-reinforcing steel cord is also disclosed.