Abstract: Dual-phase steel, consisting essentially of a ferrite matrix containing islands of martensite, is produced by batch annealing of hot or cold rolled steel having carbon below 0.2% and manganese below 2% and at least critical contents of copper (0.4%) and nickel (0.6%), with heat to the alpha plus gamma region, followed by slow cooling. This procedure is effective and controllable, and yields a dual-phase steel product that has high tensile strength with excellent elongation properties and that develops good yield strength upon moderate deformation.

Abstract: A low alloy steel having a composition containing columbium, vanadium and silicon, advantageously in specified ranges of content, has demonstrated superior mechanical properties, comprising yield strength above 80 ksi, excellent toughness including good impact strength at low temperatures, and good formability evidenced by a suitably high percent elongation. The steel in its preferred embodiments includes a significant amount of manganese, and is economically producible in as-hot-rolled state to achieve the stated properties, subject to attainment of even higher strength by an aging treatment.