Disclosed is a steel composition including specified ranges of Ni; Mo; Co; Mo+Co+Si+Mn+Cu+W+V+Nb+Zr+Ta+Cr+C; Co+Mo; Ni+Co+Mo; and traces of Al; Ti; N; Si; Mn; C; S; P; B; H; O; Cr; Cu; W; Zr; Ca; Mg; Nb; V; and Ta in specified ranges; the remainder being iron and impurities. The inclusion population, as observed by image analysis over a polished surface measuring 650 mm.sup.2 if hot-formed or hot-rolled; and measuring 800 mm.sup.2 if cold-rolled, does not contain non-metallic inclusions of diameter >10 μm, and, in the case of a hot-rolled sheet, does not contain more than four non-metallic inclusions of diameter 5-10 μm over 100 mm.sup.2, the observation being performed by image analysis over a polished surface measuring 650 mm.sup.2.

Methods of strengthening surface regions of high-strength transformation induced plasticity (TRIP) steel are provided. The method may comprise shot peening at least one region of an exposed surface of a hot-formed press-hardened component comprising a high-strength steel. Prior to shot peening, the component has a microstructure comprising ≧about 5% by volume retained austenite in a matrix of martensite. The shot peening is conducted at a temperature of <about 150° C. and forms at least one hardened surface region comprising ≦about 2% by volume austenite. The TRIP steel may be zinc-coated and having a surface coating comprising zinc and substantially free of liquid metal embrittlement (LME). Zinc-coated hot-formed press-hardened components, including automotive components, formed from such methods are also provided.

Methods of strengthening surface regions of high-strength transformation induced plasticity (TRIP) steel are provided. The method may comprise shot peening at least one region of an exposed surface of a hot-formed press-hardened component comprising a high-strength steel. Prior to shot peening, the component has a microstructure comprising ≧about 5% by volume retained austenite in a matrix of martensite. The shot peening is conducted at a temperature of <about 150° C. and forms at least one hardened surface region comprising ≦about 2% by volume austenite. The TRIP steel may be zinc-coated and having a surface coating comprising zinc and substantially free of liquid metal embrittlement (LME). Zinc-coated hot-formed press-hardened components, including automotive components, formed from such methods are also provided.

A curvature retaining device (1) includes two support points (25a) that can abut against one surface of a plate-shaped workpiece W, one or more pressing points (40a) that can abut against a position of the other surface of the plate-shaped workpiece (W) between the support points (25a), and forward/backward drive means (support unit (23) and pressing unit (33)) for moving at least either the support points (25a) or the pressing points (40a) forward to and backward from the other. Preferably, the two support points (25a) abut against the one surface of the plate-shaped workpiece (W) at a first distance (Ls), the two pressing points (40a) abut against the other surface of the plate-shaped workpiece (W) at second distance (Lp) shorter than the first distance (Ls), and a middle point of the first distance (Ls) and a middle point of the second distance (Lp) match with each other.

A curvature retaining device (1) includes two support points (25a) that can abut against one surface of a plate-shaped workpiece W, one or more pressing points (40a) that can abut against a position of the other surface of the plate-shaped workpiece (W) between the support points (25a), and forward/backward drive means (support unit (23) and pressing unit (33)) for moving at least either the support points (25a) or the pressing points (40a) forward to and backward from the other. Preferably, the two support points (25a) abut against the one surface of the plate-shaped workpiece (W) at a first distance (Ls), the two pressing points (40a) abut against the other surface of the plate-shaped workpiece (W) at second distance (Lp) shorter than the first distance (Ls), and a middle point of the first distance (Ls) and a middle point of the second distance (Lp) match with each other.

In a WJP execution method for a reactor vessel lid, WJP is executed on the inner surface of the reactor vessel lid in a state in which an underwater environment is formed on the inner surface of the reactor vessel lid and an aerial environment is formed on the outer surface thereof. In addition, the reactor vessel lid with a waterproof jig attached thereto is arranged in water, the waterproof jig having a cylindrical shape extending to the side of the outer surface of the reactor vessel lid and constituting a vessel with the reactor vessel lid as the bottom portion thereof. Moreover, the reactor vessel lid is arranged on a base installed in the water.

In a WJP execution method for a reactor vessel lid, WJP is executed on the inner surface of the reactor vessel lid in a state in which an underwater environment is formed on the inner surface of the reactor vessel lid and an aerial environment is formed on the outer surface thereof. In addition, the reactor vessel lid with a waterproof jig attached thereto is arranged in water, the waterproof jig having a cylindrical shape extending to the side of the outer surface of the reactor vessel lid and constituting a vessel with the reactor vessel lid as the bottom portion thereof. Moreover, the reactor vessel lid is arranged on a base installed in the water.

A method and apparatus for forming an object by additive layer manufacturing. The method comprises: a) applying, by a heat source (4), heat to a portion of a surface of a workpiece (1) sufficient to melt said portion; b) adding material to the melted portion and moving the heat source (4) relative to the workpiece (1) whereby progressively to form a layer of material (10) on the workpiece (1); c) cooling the formed layer (10) to bring at least part of the layer (10) to a state of crystallisation, there producing a modified workpiece; d) peening, using a plurality of independently controllable impact treatment devices (7), the modified work-piece so as to plastically deform the cooled at least part of the layer (10); and repeating steps a) to d) as required whereby to form the object.

A method and apparatus for forming an object by additive layer manufacturing. The method comprises: a) applying, by a heat source (4), heat to a portion of a surface of a workpiece (1) sufficient to melt said portion; b) adding material to the melted portion and moving the heat source (4) relative to the workpiece (1) whereby progressively to form a layer of material (10) on the workpiece (1); c) cooling the formed layer (10) to bring at least part of the layer (10) to a state of crystallisation, there producing a modified workpiece; d) peening, using a plurality of independently controllable impact treatment devices (7), the modified work-piece so as to plastically deform the cooled at least part of the layer (10); and repeating steps a) to d) as required whereby to form the object.

A method for manufacturing a compressor scroll that appropriately impinges cavitation bubbles on target regions of a scroll. The method includes the step of water jet peening by jetting cavitation bubbles generated underwater by a water jet at a first side of an end plate (13A) of the scroll (13), with a center (P1, P2, P3) of the cavitation bubbles being offset from a center (O) of the spiral shape of a wall portion (13B) on the end plate (13A) and the step portion (13Aa) and the stepped portion (13Ba) positioned at an outer peripheral portion of the cavitation bubbles (C).