Abstract: 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.

Abstract: This torsion beam manufacturing method is a method for manufacturing a torsion beam which is provided with a uniformly shaped closed cross-sectional portion in which a cross section orthogonal to a longitudinal direction is a closed cross section having a substantial V-shape or a substantial U-shape with a pair of ear portions, and a shape changing portion which leads to the uniformly shaped closed cross-sectional portion and in which a shape of the closed cross section changes progressively away from the uniformly shaped closed cross-sectional portion, the torsion beam manufacturing method comprising: thickening to form a pair of thickened portions in at least the shape changing portion by pressurizing each of the pair of ear portions from outside against swelling of the pair of ear portions in a slate where both outer surfaces of each of the pair of ear portions are supported.

Abstract: The present invention provides electric-resistance welded steel pipe optimal for applications such as production of shale gas which is comprised of steel having a chemical composition which contains, by mass %, respectively, C: 0.08 to 0.18%, Si: 0.01% to 0.50%, Mn: 1.30 to 2.1%, Al: 0.001 to 0.10%, Nb: 0.005 to 0.08%, and Ti: 0.005 to 0.03%, is limited to N 0.008% or less, P: 0.020% or less, and S: 0.010% or less, and has a balance of Fe and unavoidable impurities, wherein a structure at a center part of thickness is 40% to 70% by area of ferrite phase having a circle-equivalent diameter of 1.0 ?m to 10.0 ?m and a balance of a low temperature transformation phase comprising a bainite phase, and Ceq satisfies 0.32?Ceq?0.60.

Abstract: A method of manufacturing a flaring-processed metal pipe from a hollow shell including a plurality of portions having different deformation resistances in a circumferential direction is provided, the method includes: among the plurality of portions, specifying a portion having a relatively small deformation resistance as a low deformation resistance section, and a portion having a relatively large deformation resistance as a high deformation resistance section; and press-fitting a pipe expansion punch into the hollow shell such that a thickness reduction rate of the low deformation resistance section is smaller than a thickness reduction rate of the high deformation resistance section.

Abstract: This torsion beam manufacturing method is a method of manufacturing a torsion beam that includes a uniformly shaped closed cross-sectional portion of which a cross section orthogonal to a longitudinal direction is a closed cross section having a substantial V-shape or a substantial U-shape at any position in the longitudinal direction, and a shape changing portion which has a connection region leading to the uniformly shaped closed cross-sectional portion and including a closed cross section having a shape different from the shape of the closed cross section of the uniformly shaped closed cross-sectional portion. The torsion beam manufacturing method includes pulling process of applying a tensile force in the longitudinal direction to at least the connection region of a torsion beam material including the uniformly shaped closed cross-sectional portion and the shape changing portion, to obtain the torsion beam.

Abstract: This torsion beam manufacturing method is a method for manufacturing a torsion beam which is provided with a uniformly shaped closed cross-sectional portion in which a cross section orthogonal to a longitudinal direction is a closed cross section having a substantial V-shape or a substantial U-shape with a pair of ear portions, and a shape changing portion which leads to the uniformly shaped closed cross-sectional portion and in which a shape of the closed cross section changes progressively away from the uniformly shaped closed cross-sectional portion, the torsion beam manufacturing method comprising: thickening to form a pair of thickened portions in at least the shape changing portion by pressurizing each of the pair of ear portions from outside against swelling of the pair of ear portions in a slate where both outer surfaces of each of the pair of ear portions are supported.

Abstract: 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.

Abstract: This torsion beam manufacturing method is a method of manufacturing a torsion beam that includes a uniformly shaped closed cross-sectional portion of which a cross section orthogonal to a longitudinal direction is a closed cross section having a substantial V-shape or a substantial U-shape at any position in the longitudinal direction, and a shape changing portion which has a connection region leading to the uniformly shaped closed cross-sectional portion and including a closed cross section having a shape different from the shape of the closed cross section of the uniformly shaped closed cross-sectional portion. The torsion beam manufacturing method includes pulling process of applying a tensile force in the longitudinal direction to at least the connection region of a torsion beam material including the uniformly shaped closed cross-sectional portion and the shape changing portion, to obtain the torsion beam.

Abstract: A method of manufacturing a flaring-processed metal pipe from a hollow shell including a plurality of portions having different deformation resistances in a circumferential direction is provided, the method includes: among the plurality of portions, specifying a portion having a relatively small deformation resistance as a low deformation resistance section, and a portion having a relatively large deformation resistance as a high deformation resistance section; and press-fitting a pipe expansion punch into the hollow shell such that a thickness reduction rate of the low deformation resistance section is smaller than a thickness reduction rate of the high deformation resistance section.

Abstract: The present invention provides electric-resistance welded steel pipe optimal for applications such as production of shale gas which is comprised of steel having a chemical composition which contains, by mass %, respectively, C: 0.08 to 0.18%, Si: 0.01% to 0.50%, Mn: 1.30 to 2.1%, Al: 0.001 to 0.10%, Nb: 0.005 to 0.08%, and Ti: 0.005 to 0.03%, is limited to N 0.008% or less, P: 0.020% or less, and S: 0.010% or less, and has a balance of Fe and unavoidable impurities, wherein a structure at a center part of thickness is 40% to 70% by area of ferrite phase having a circle-equivalent diameter of 1.0 ?m to 10.0 ?m and a balance of a low temperature transformation phase comprising a bainite phase, and Ceq satisfies 0.32?Ceq?0.60.

Abstract: A roll former for steel plate (3) which enables edge corner deformation of steel plate edges (4) to be avoided, that is, a roll former for steel plate comprised of a top roll (1) and a bottom roll (2), the roll former for steel plate characterized by forming convex curved parts (5) having a bending direction opposite to a bending direction of the steel plate (3) in regions of the bottom roll (2), which forms the outer side of the steel plate (3), which contact the steel plate edges (4).

Abstract: A roll former for steel plate (3) which enables buckling of steel plate edges (4) to be avoided, that is, a roll former for steel plate comprised of a top roll (1) and a bottom roll (2), the roll former for steel plate characterized by forming convex curved parts (5) having a bending direction opposite to a bending direction of the steel plate (3) in regions of the bottom roll (2), which forms the outer side of the steel plate (3), which contact the steel plate edges (4).