Abstract: This invention reveals steel alloys for use in manufacturing reinforcing wires for rubber products, such as tires. The steel filaments made with such steel alloys have an outstanding combination of strength and ductility. The steel alloys of this invention can be manufactured into filaments having a tensile strength in the range of 4000 MPa to 5000 MPa. Additionally, these can be patented in a low-cost process due to their having a very fast rate of isothermal transformation. This allows the steel in the steel wire being patented to transform from a face-centered cubic microstructure to an essentially body-centered cubic microstructure within a very short period. This invention more specifically discloses a steel alloy composition which is particularly suitable for use in manufacturing reinforcing wire for rubber products which consists essentially of (a) iron, (b) about 1.05 to about 1.7 weight percent carbon, (c) about 0.2 to about 0.8 weight percent manganese, (d) about 0.1 to about 0.