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

Patent metadata

Field	Value
Publication number	US-11969779-B2
Application number	US-202217590927-A
Country	US
Kind code	B2
Filing date	Feb 2, 2022
Priority date	Feb 21, 2017
Publication date	Apr 30, 2024
Grant date	Apr 30, 2024

Abstract

A mandrel 10 for 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 shank 14, a connection mechanism 15 and a mandrel ball 16. In a cross-section orthogonal to an axial direction of the mandrel ball 16 at a central position in the axial direction of the mandrel ball 16, the mandrel ball 16 has a first position 19 and a second position 20 at which a first straight line m that passes through a mandrel ball center 17 meets an outer periphery 21 of the mandrel ball. Further, a ratio (L 1 /L 2 ) between a dimension L 1 from the mandrel ball center 17 to the first position 19 and a dimension L 2 from the mandrel ball center 17 to the second position 20 is in a range of 0.915 to 0.976.

First claim

The invention claimed is:

1. A bent tube made of steel that comprises a bending portion that is two-dimensionally bent in a rotary draw bending operation and a straight tube portion, wherein:
when a wall thickness of the bending portion is represented by t 1 (mm), a wall thickness of the straight tube portion is represented by t 2 (mm), an outside diameter of the straight tube portion is represented by D 1 (mm), a bending radius of the bending portion is represented by R (mm), and a bending angle of the bending portion is represented by θ(°),
t 2 /D 1 : 0.005 to 0.3,
t 2 : 0.5 to 30,
D 1 : 15 to 700,
R: 1 D 1 to 6 D 1 ,
θ: 0 to 180,
a maximum thickness reduction ratio: 14.5% or less,
a maximum flattening ratio: 8.0% or less, and
a hardness ratio between straight tube portion and bending portion: 8 to 50%;
where,
the maximum thickness reduction ratio: a maximum value of {(t 2 −t 1 )/t 2 }×100(%),
the maximum flattening ratio: a maximum value of {(maximum value of outside diameter−minimum value of outside diameter)/D 1 } of the bending portion×100(%), and
the hardness ratio between straight tube portion and bending portion: {(average value of values obtained by measuring 5 points under conditions of a 1 mm pitch in a longitudinal direction of the tube with Hv (10 kg) at a center portion of an outside of bend in the longitudinal direction of the tube in an L cross-section of the tube)—(average value of values obtained by measuring 5 points under conditions of a 1 mm pitch in a longitudinal direction of the tube with Hv (10 kg) at the straight tube portion in the L cross-section of the tube)}/(average value of values obtained by measuring 5 points under conditions of a 1 mm pitch in a longitudinal direction of the tube with Hv (10 kg) at the straight tube portion in the L cross-section of the tube).

Assignees

• Nippon Steel Corp

Inventors

• Tamura Shohei
• Arita Hidehiro

Classifications

• B21D9/07 Primary

  with one or more swinging forming members engaging tube ends only · CPC title

• F16L43/001

  made of metal · CPC title

• B21D9/05

  co-operating with forming members · CPC title

• B21D7/025 Primary

  and pulling or pushing the ends of the work · CPC title

• B21D9/03 Primary

  and built-up from loose elements, e.g. series of balls · CPC title