A method for setting conditions for a shaft diameter enlargement, a shaft diameter enlargement method, and a shaft diameter enlargement apparatus are provided. A controller of the shaft diameter enlargement apparatus controls a compressing section, a bending section, and a rotating section to enlarge an intermediate portion of a shaft workpiece to have a predetermined outer diameter by rotating the shaft workpiece about its axis with axial compressive force a bending angle being applied to the intermediate portion. The controller determines whether the shaft workpiece is acceptable, based on the number of rotations of die shaft workpiece required for enlarging the intermediate portion to have the predetermined outer diameter or based on an enlargement ratio of the intermediate portion.

There is provided a method of manufacturing a variable wall thickness steel pipe with a hollow tubular raw pipe. The method of manufacturing a variable wall thickness steel pipe includes locking the raw pipe in a die by thrusting a plug into the raw pipe from an one end side, so as to expand an outer shape on the one end side in a state, where the raw pipe is disposed inside the die and movement of the raw pipe in a longitudinal direction is restricted; and performing ironing in which an inner shape of the raw pipe is expanded while the outer shape is maintained so that a thin portion is formed by further thrusting the plug toward the other end side of the raw pipe while the locked state of the raw pipe is maintained, whereas the restriction on the raw pipe is relaxed.

There is provided a method of manufacturing a variable wall thickness steel pipe with a hollow tubular raw pipe. The method of manufacturing a variable wall thickness steel pipe includes locking the raw pipe in a die by thrusting a plug into the raw pipe from an one end side, so as to expand an outer shape on the one end side in a state, where the raw pipe is disposed inside the die and movement of the raw pipe in a longitudinal direction is restricted; and performing ironing in which an inner shape of the raw pipe is expanded while the outer shape is maintained so that a thin portion is formed by further thrusting the plug toward the other end side of the raw pipe while the locked state of the raw pipe is maintained, whereas the restriction on the raw pipe is relaxed.

Provided is a manufacturing method of a wire rod for forming a coil, the manufacturing method including the steps of: placing an element wire in a forming space surrounded by a plurality of split dies; and pressure-forming the element wire by moving the plurality of split dies in a direction of narrowing the forming space. In the step of pressure-forming the element wire, at least one of the plurality of split dies is moved, and the plurality of split dies each having a surface that changes in shape in a longitudinal direction of an element wire to pressure-form the element wire into the wire rod having a plurality of different cross-sectional shapes in the longitudinal direction.

Provided is a manufacturing method of a wire rod for forming a coil, the manufacturing method including the steps of: placing an element wire in a forming space surrounded by a plurality of split dies; and pressure-forming the element wire by moving the plurality of split dies in a direction of narrowing the forming space. In the step of pressure-forming the element wire, at least one of the plurality of split dies is moved, and the plurality of split dies each having a surface that changes in shape in a longitudinal direction of an element wire to pressure-form the element wire into the wire rod having a plurality of different cross-sectional shapes in the longitudinal direction.

A high-strength stainless steel rotor and a method for preparing the same, are provided. The high-strength stainless steel rotor, including the following element components by mass percentage: C: 0.03-0.050%, Cr: 14.90-15.80%, Ni: 5.00-5.70%, Cu: 2.20-2.80%, (Nb+Ta): 0.35-0.44%, Mo: 0.45-0.54%, V: 0.06-0.10%, Si: 0.20-0.60%, Mn: 0.40-0.80%, P≤0.010%, S≤0.010%, O≤0.003%, and the balance of iron and inevitable impurities.

A one-piece piston blank of near-net shape wherein the piston blank has a flange disposed opposite a skirt, the flange being spin-bendable to form a cooling channel with reduced preliminary removal of material relative to conventional forged piston blanks.

A one-piece piston blank of near-net shape wherein the piston blank has a flange disposed opposite a skirt, the flange being spin-bendable to form a cooling channel with reduced preliminary removal of material relative to conventional forged piston blanks.

Solid metal protrusions are formed by a method including: clamping and fixing the metal workpiece with a support die and a pressure die; pressing each cross section of an outer peripheral end parts of the metal workpiece fixed with the support die and the pressure die at a temperature lower than a softening point of a metal used as the metal workpiece from a direction perpendicular or oblique to an upright direction of the protrusions to be formed on one surface of the metal workpiece by press molding using a pressing die or a pressing jig; undergoing plastic flows of metal into through-holes formed as recessed parts that serve as female molds for forming the protrusions in at least one of the support die and the pressure die; and forming solid protrusions on the surface of the metal workpiece.

Solid metal protrusions are formed by the method including: clamping and fixing the metal workpiece between a support die and a pressure die; pressing end cross sections of two or more outer peripheral end parts of the metal workpiece fixed between the support die and the pressure die at a temperature lower than a softening point of a metal used as the metal workpiece from a direction perpendicular or oblique to an upright direction of the protrusions to be formed on one surface of the metal workpiece by press molding using a pressing die or a pressing jig; undergoing plastic flows of metal into through-holes formed as recessed parts that serve as female molds for forming the protrusions in at least one of the support die and the pressure die; and forming solid protrusions on the surface of the metal workpiece.