A method and apparatus for improving the fatigue and stress corrosion cracking performance of irregular surfaces, such as welds assemblies of components, using a positioning system, such as a robotic or CNC machine, to position a tool head for inducing compression along and into the surface of a workpiece to automatically follow the surface irregularities. The method and apparatus operates to follow a virtual control surface located below the actual surface of the workpiece thereby allowing the irregular topography surface to be uniformly processed with closed loop process control.

A method for manufacturing a metal plate, the metal plate including a first surface and a second surface positioned on the opposite side of the first surface, may include a step of rolling a base metal having an iron alloy containing nickel to produce the metal plate. The metal plate may include particles containing as a main component an element other than iron and nickel. In a sample including the first surface and the second surface of the metal plate, the following conditions (1) and (2) regarding the particles may be satisfied: (1) The number of the particles having an equivalent circle diameter of 1 μm or more is 50 or more and 3000 or less per 1 mm.sup.3 in the sample, and (2) The number of the particles having an equivalent circle diameter of 3 μm or more is 50 or less per 1 mm.sup.3 in the sample.

A method for manufacturing a metal plate, the metal plate including a first surface and a second surface positioned on the opposite side of the first surface, may include a step of rolling a base metal having an iron alloy containing nickel to produce the metal plate. The metal plate may include particles containing as a main component an element other than iron and nickel. In a sample including the first surface and the second surface of the metal plate, the following conditions (1) and (2) regarding the particles may be satisfied: (1) The number of the particles having an equivalent circle diameter of 1 μm or more is 50 or more and 3000 or less per 1 mm.sup.3 in the sample, and (2) The number of the particles having an equivalent circle diameter of 3 μm or more is 50 or less per 1 mm.sup.3 in the sample.

A component of a crawler type machine is hardened by explosive depth hardening. The component is typically a crawler track shoe (10), and the roller path surface (11) of the track shoe and immediate underlying metal portion are pre-hardened by placing explosive charge (15) on the surface of the track shoe (10), and detonating the explosive charge to impart a high force on the surface and underlying metal portion for a short duration. The resultant shock wave causes high-velocity deformation at a high stress level, which leads to intensive development of plastic displacement at microscopic size. This increases the hardness and the strength of the surface and underlying metal portion. The surface (11) may be hardened by repetitive explosive depth hardening. Grooves (20) may also be formed in the roller path (11) to accommodate any flow of material. Explosive depth hardening can be applied to other surfaces of the track shoe (10), such as the pin bore of a connection lug, or to other components such as a drive tumbler of the crawler.

A component of a crawler type machine is hardened by explosive depth hardening. The component is typically a crawler track shoe (10), and the roller path surface (11) of the track shoe and immediate underlying metal portion are pre-hardened by placing explosive charge (15) on the surface of the track shoe (10), and detonating the explosive charge to impart a high force on the surface and underlying metal portion for a short duration. The resultant shock wave causes high-velocity deformation at a high stress level, which leads to intensive development of plastic displacement at microscopic size. This increases the hardness and the strength of the surface and underlying metal portion. The surface (11) may be hardened by repetitive explosive depth hardening. Grooves (20) may also be formed in the roller path (11) to accommodate any flow of material. Explosive depth hardening can be applied to other surfaces of the track shoe (10), such as the pin bore of a connection lug, or to other components such as a drive tumbler of the crawler.

The invention is directed to a method for improving the fatigue behavior of the body (2) of a gas valve, the body comprising at least two bores (4, 10) and at least one bore intersection (20) defining an internal volume; wherein the method comprises the following step: subjecting the internal volume to an autofrettage by applying a pressure of comprised between 100 MPa and 500 MPa by means of a liquid. 10. The invention is also directed to a gas valve body (2) comprising at least two bores (4, 10) and at least one bore intersection (20) defining an internal volume with an internal wall; wherein the internal wall is treated by autofrettage resulting in compressive stresses at the intersection or at least one of the intersections.

The present invention relates to a method for manufacturing a component of austenitic TWIP or TRIP/TWIP steel. A flat product (1) is deformed by achieving at least one indentation (16) on at least one surface of the flat product (1) in order to have in the deformed product (5) areas of a high strength steel embedded in a matrix of a ductile material. The invention also relates to the use of the component where areas of a high strength steel embedded in a matrix of a ductile material are required in the same component.

The present invention relates to a method for manufacturing a component of austenitic TWIP or TRIP/TWIP steel. A flat product (1) is deformed by achieving at least one indentation (16) on at least one surface of the flat product (1) in order to have in the deformed product (5) areas of a high strength steel embedded in a matrix of a ductile material. The invention also relates to the use of the component where areas of a high strength steel embedded in a matrix of a ductile material are required in the same component.

A steel pipe for fuel injection pipe has a tensile strength of 500 to 900 MPa and a yield ratio of 0.50 to 0.85, and has a critical internal pressure (IP) satisfying [IP≥0.41×TS×α] (α=[(D/d).sup.2−1]/[0.776×(D/d).sup.2], where TS: tensile strength (MPa) of the steel pipe, D: steel pipe outer diameter (mm), and d: steel pipe inner diameter (mm)), wherein a circumferential-direction residual stress on an inner surface of the pipe is −20 MPa or lower after the steel pipe is split in half in a pipe axis direction.

A steel pipe for fuel injection pipe has a tensile strength of 500 to 900 MPa and a yield ratio of 0.50 to 0.85, and has a critical internal pressure (IP) satisfying [IP≥0.41×TS×α] (α=[(D/d).sup.2−1]/[0.776×(D/d).sup.2], where TS: tensile strength (MPa) of the steel pipe, D: steel pipe outer diameter (mm), and d: steel pipe inner diameter (mm)), wherein a circumferential-direction residual stress on an inner surface of the pipe is −20 MPa or lower after the steel pipe is split in half in a pipe axis direction.