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.

An example component of a machine includes a core layer and an outer layer encasing the core layer. The outer layer has a greater carbon concentration and hardness than the core layer. The outer layer may also be compressively stressed, while the core layer may have tensile stress. The stress and/or hardness profile of the component may enhance its resistance to cracking, particularly in applications where the component is impacted by other object and/or operates at elevated temperatures. The component, such as parts of a fuel injector, may be formed by rough forming the component, carburizing the component, quenching the component, subzero processing the component, and then performing a tempering process. The components may have relatively sharp transition from the high carbon outer layer to the lower carbon core layer. Additionally, the components have a relatively high tempering resistance when used in relatively high temperature environments.

A method of processing ultra high hardness steel is provided to increase its usefulness in armor applications. The method involves slowly cooling the ultra high hardness steel to a cryogenic temperature, slowly returning the steel to an ambient temperature, slowly heating the steel, and again slowly returning it to an ambient temperature.

A method of processing ultra high hardness steel is provided to increase its usefulness in armor applications. The method involves slowly cooling the ultra high hardness steel to a cryogenic temperature, slowly returning the steel to an ambient temperature, slowly heating the steel, and again slowly returning it to an ambient temperature.

An armoring part for a vehicle includes a steel plate made of at least partially hot formed and press hardened armor steel and having a hardness of 380 to 760 Vickers (HV). Applied on at least one side of the steel plate is a coat which is made of a metal material which is softer than a metal material of the armor steel. The coat is a thermally applied layer and has a hardness of 10 to 230 Vickers (HV).

An armoring part for a vehicle includes a steel plate made of at least partially hot formed and press hardened armor steel and having a hardness of 380 to 760 Vickers (HV). Applied on at least one side of the steel plate is a coat which is made of a metal material which is softer than a metal material of the armor steel. The coat is a thermally applied layer and has a hardness of 10 to 230 Vickers (HV).

A composite armor plate is disclosed. The composite armor plate includes a first layer made from an ultra-high hardness, high strength alloy that is bonded to a second layer made from a high fracture toughness alloy that also may have high strength. The composite armor plate according to the present provides a gradient of strength, hardness, and toughness. The composite armor plate according to the invention may also include third and fourth layers of different alloys that provide combinations of hardness, strength, and fracture toughness that are intermediate of the hardness, strength, and fracture toughness provided by the first and second steel layers. A method of making the composite armor plate is also disclosed.

A composite armor plate is disclosed. The composite armor plate includes a first layer made from an ultra-high hardness, high strength alloy that is bonded to a second layer made from a high fracture toughness alloy that also may have high strength. The composite armor plate according to the present provides a gradient of strength, hardness, and toughness. The composite armor plate according to the invention may also include third and fourth layers of different alloys that provide combinations of hardness, strength, and fracture toughness that are intermediate of the hardness, strength, and fracture toughness provided by the first and second steel layers. A method of making the composite armor plate is also disclosed.

An example track shoe, cutting edge, or other component of a machine is formed in a heated process, such as hot-rolling followed by air-hardening. The air-hardening process involves cooling the component by flowing air over the component (e.g., air cooling), such that the component is cooled at a controlled rate. During the air-cooling process, such as in the range of about 250° C. to about 1100° C., the component may be machined, such as by shearing, punching, drilling, etc. The machining may form the final shape of the component. As the air-hardening process is completed, and the component approaches room temperature, the component may have at least 5% bainitic crystal composition, and as high as greater than 80% bainitic crystal composition, resulting in relatively high hardness and fracture toughness. The final track shoe may have a hardness between about 40 HRC and 55 HRC.