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: High strength, low alloy steel is produced, preferably as a hot rolled article (e.g. strip), to have a rimmed skin of essentially ferrite while having a main body or core which is aluminum-killed and comprises, for superior mechanical properties including yield strength, a suitable quantity of columbium and/or vanadium. The carbon, manganese and sulfur contents of the base metal, which provides the skin and plus the addition, the core, are preferably limited to provide special results as low alloy steel and also, by the same limitations, to provide auto sulfide shape control and thus to avoid unwanted directionality regarding toughness and bendability. The steel is made by pouring a mold 80-95% full of the base composition, then allowing the steel to rim for several minutes, and after a shell has solidified, continuing to pour while adding Al and Cb or V to the teemed stream, thereby providing an ingot with the above killed core, which can be hot reduced as desired.

Abstract: High strength low alloy steels, produced as strip or the like by hot rolling, permit unusual economy of alloying ingredients while achieving superior mechanical properties. With a composition containing specifically low carbon and low manganese, and moderate proportions of both columbium and vanadium, preferably with no requirement of silicon. Yield strengths in a range to and above 80 ksi are attainable depending on the total of columbium and vanadium, and excellent properties of toughness and formability are exhibited in transverse as well as longitudinal directions without adding special sulfide shape control agents. Processing conditions, for hot rolling and coiling, can be selected over wide temperature ranges, for convenience of control, e.g. to achieve product uniformity.

Abstract: High strength low alloy steels, produced as strip or the like by hot rolling, permit unusual economy of alloying ingredients while achieving superior mechanical properties, with a composition containing specifically low carbon and low manganese, and moderate proportions of both columbium and titanium, preferably with no requirement of silicon. Yield strengths in a range to and well above 80 ksi are attainable depending on the content of columbium and titanium, and good properties of formability are exhibited in the transverse direction. Processing conditions, for hot rolling and coiling, can be selected over reasonably convenient ranges of temperature conditions, while rolling load requirements are acceptable for products of various thicknesses. The steels are notably useful for thin strip, satisfying the usual mechanical property needs of such products with relatively low cost.