Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Njk Corporation

Hidehiro Arita

Masaaki Mizumura

Shohei Tamura

Atsushi Tomizawa

Keinosuke Iguchi

A mandrelfor producing a thin-walled bent tube having a bending portion with high strength and a small radius of curvature by rotary draw bending without either cracks in an outside of bend or wrinkles and buckling in an inside of bend occurring includes a shanka connection mechanismand a mandrel ballIn a cross-section orthogonal to an axial direction of the mandrel ballat a central position in the axial direction of the mandrel ballthe mandrel ballhas a first positionand a second positionat which a first straight line m that passes through a mandrel ball centermeets an outer peripheryof the mandrel ball. Further, a ratio (L/L) between a dimension Lfrom the mandrel ball centerto the first positionand a dimension Lfrom the mandrel ball centerto the second positionis in a range of 0.915 to 0.976.

Mandrel, bent tube, and method and apparatus for producing bent tube

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.

Method of manufacturing variable wall thickness steel pipe and variable wall thickness steel pipe

A mandrelfor producing a thin-walled bent tube having a bending portion with high strength and a small radius of curvature by rotary draw bending without either cracks in an outside of bend or winkles and buckling in an inside of bend occurring includes a shank, a connection mechanismand a mandrel ball. In a cross-section orthogonal to an axial direction of the mandrel ballat a central position in the axial direction of the mandrel ball, the mandrel ballhas a first positionand a second positionat which a first straight line m that passes through a mandrel ball centermeets an outer peripheryof the mandrel ball. Further, a ratio (L/L) between a dimension Lfrom the mandrel ball centerto the first positionand a dimension Lfrom the mandrel ball centerto the second positionis in a range of 0.915 to 0.976.

A camshaft-manufacturing method includes: a split die group preparation step; a processing preparation step of preparing a cam including a through-hole, a cam body which is smaller than each of the cam accommodation portions, and ribs which are provided on both sides in a thickness direction of the cam body and configured to be fitted into the rib accommodation portions, and a hollow shaft, accommodating the cam body in the cam accommodation portion and fitting the ribs in the rib accommodation portion, and inserting the hollow shaft into the through-hole of the cam; and a processing step of performing hydroform processing, and fixing the cam to the hollow shaft by expanding the hollow shaft.

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Tokyo, Japan

Hidehiro Arita