The steel sheet of the present invention has a steel microstructure containing, in area fraction, martensite: 20% to 100%, ferrite: 0% to 80%, and another metal phase: 5% or less, in which, on a surface of the steel sheet, a ratio of dislocation density in metal phases at a widthwise edge of the steel sheet to dislocation density in the metal phases at a widthwise center of the steel sheet is 100% to 140%, and, at a thicknesswise center of the steel sheet, a ratio of dislocation density in the metal phases at the widthwise edge of the steel sheet to dislocation density in the metal phases at the widthwise center of the steel sheet is 100% to 140%. The maximum amount of warpage of the steel sheet when the steel sheet is sheared to a length of 1 m in a rolling direction is 15 mm or less.

The steel sheet of the present invention has a steel microstructure containing, in area fraction, martensite: 20% to 100%, ferrite: 0% to 80%, and another metal phase: 5% or less, in which, on a surface of the steel sheet, a ratio of dislocation density in metal phases at a widthwise edge of the steel sheet to dislocation density in the metal phases at a widthwise center of the steel sheet is 100% to 140%, and, at a thicknesswise center of the steel sheet, a ratio of dislocation density in the metal phases at the widthwise edge of the steel sheet to dislocation density in the metal phases at the widthwise center of the steel sheet is 100% to 140%. The maximum amount of warpage of the steel sheet when the steel sheet is sheared to a length of 1 m in a rolling direction is 15 mm or less.

Described herein is a method of forming a heat-treated material includes positioning the heat-treated material between first and second susceptors. Each of the first and second susceptors includes a tool face shaped according to a desired shape of the heat-treated material. The method also includes applying a low-strength magnetic field to the first and second susceptors to heat the first and second susceptors. Further, the method includes compressing the heat-treated material between the first and second susceptors to form the heat-treated material into the desired shape. The method additionally includes applying a high-strength magnetic field to the heat-treated material before compressing the heat-treated material between the first and second susceptors.

Described herein is a method of forming a heat-treated material includes positioning the heat-treated material between first and second susceptors. Each of the first and second susceptors includes a tool face shaped according to a desired shape of the heat-treated material. The method also includes applying a low-strength magnetic field to the first and second susceptors to heat the first and second susceptors. Further, the method includes compressing the heat-treated material between the first and second susceptors to form the heat-treated material into the desired shape. The method additionally includes applying a high-strength magnetic field to the heat-treated material before compressing the heat-treated material between the first and second susceptors.

Disclosed is a chain mail constituted of a lattice of interlinked metal rings, in particular for personal protective equipment. The chain mail rings are made using a stainless steel wire whereof the mechanical tensile strength (Rm) is between 1,600 and 2,550 N/mm.sup.2, limits included.

An aspect of the present disclosure is directed to low-alloy steels exhibiting high hardness and an advantageous level of multi-hit ballistic resistance with low or no crack propagation imparting a level of ballistic performance suitable for military armor applications. Various embodiments of the steels according to the present disclosure have hardness in excess of 550 BHN and demonstrate a high level of ballistic penetration resistance relative to conventional military specifications.

An aspect of the present disclosure is directed to low-alloy steels exhibiting high hardness and an advantageous level of multi-hit ballistic resistance with low or no crack propagation imparting a level of ballistic performance suitable for military armor applications. Various embodiments of the steels according to the present disclosure have hardness in excess of 550 BHN and demonstrate a high level of ballistic penetration resistance relative to conventional military specifications.

A process for making steel armor products for use, for example as body armor. The steel armor product made has a compound curve and is made from a flat blank of armor steel by high-temperature annealing an armor steel blank to slightly above its austenitizing temperature, then followed by a slow, temperature-controlled cooling it, over-pressing the annealed blank to a first configuration so it springs back to a second configuration approximating the desired product shape when released from the press, and then heat-treating the product back to its austenitizing temperature, quenching it, and tempering it at a low temperature. The tool is conveniently made by lamination, using a series of thin plates of tool steel each cut to produce an approximation of the desired die.

A process for making steel armor products for use, for example as body armor. The steel armor product made has a compound curve and is made from a flat blank of armor steel by high-temperature annealing an armor steel blank to slightly above its austenitizing temperature, then followed by a slow, temperature-controlled cooling it, over-pressing the annealed blank to a first configuration so it springs back to a second configuration approximating the desired product shape when released from the press, and then heat-treating the product back to its austenitizing temperature, quenching it, and tempering it at a low temperature. The tool is conveniently made by lamination, using a series of thin plates of tool steel each cut to produce an approximation of the desired die.

An air hardenable steel alloy is disclosed comprising, in percent by weight: 0.18 to 0.26 carbon; 3.50 to 4.00 nickel; 1.60 to 2.00 chromium; 0 to 0.50 molybdenum; 0.80 to 1.20 manganese; 0.25 to 0.45 silicon; 0 to less than 0.005 titanium; 0 to less than 0.020 phosphorus; 0 up to 0.005 boron; 0 up to 0.003 sulfur; iron; and impurities. The air hardenable steel alloy has a Brinell hardness in a range of 352 HBW to 460 HBW. The air hardenable steel alloy combines high strength, medium hardness and toughness, as compared with certain known air hardenable steel alloys, and finds application in, for example, any of a steel armor, a blast-protective hull, a blast-protective V-shaped hull, a blast-protective vehicle underbelly, and a blast-protective enclosure.