High strength, low carbon, dual phase steel rods and wires and process for making same

Claim 1

A process for making high strength, high ductility steel wire and rods comprising the steps of: heating a steel composition consisting essentially of iron, from about 0.05 to 0.15 wt. % carbon, and from about 1.0 to 3.0 wt. % silicon to a temperature T 1 for a period of time sufficient to substantially completely austenitized said steel; quenching the resulting austenitized steel composition to transform said austenite to 100% martensite; heating the resulting martensitic steel composition to a temperature T 2 in the two phase α+γ range for a period of time sufficient to transform said martensitic steel composition to a volume ratio of ferrite and austenite such that subsequent quenching results in a microstructure having about 10 to 40 volume percent martensite and about 60 to 90 volume percent ferrite; quenching the resulting ferrite-autenite steel composition to transform the austenite to martensite; and cold drawing the resulting steel composition, said steel composition characterized by a duplex ferrite-martensite microstructure having about 10 to 40 volume percent martensite and about 60 to 90 volume percent ferrite, said microstructure imparting to said steel composition cold formability properties permitting said steel composition to be cold drawn to a diameter representing up to about a 99.9% reduction in cross-sectional area and imparting to the resulting cold drawn steel product tensile strength properties of up to 400 ksi.