Method for producing a rifled tube

Patent metadata

Field	Value
Publication number	US-10632521-B2
Application number	US-201515528774-A
Country	US
Kind code	B2
Filing date	Nov 24, 2015
Priority date	Nov 25, 2014
Publication date	Apr 28, 2020
Grant date	Apr 28, 2020

Abstract

The production method for producing a rifled tube, which includes a plurality of first helical ribs on its inner surface, includes: a steps of:
preparing a steel tube; and producing a rifled tube by performing cold drawing on a steel tube by using a plug which includes a plurality of second helical ribs, the plug satisfying Formulae and:

0.08 < W ×( A−B )× N /(2π× A )<0.26  (1)

0.83< S ×( A−B )× N /(2× M )<2.0  (2)

where, W is a width of a groove bottom surface of the helical groove; A is a maximum diameter of the plug; B is a minimum diameter of the plug; N is a number of the second helical ribs; S is the width of the groove bottom surface; and M is a pitch of adjacent second helical ribs.

First claim

The invention claimed is:

1. A production method for producing a rifled tube for a thermal power generation boiler, comprising:
a step of preparing a steel tube having a chemical composition containing not more than 2.6% of Cr in mass % and having a tensile strength of not more than 600 MPa, and
a step of performing a chemical treatment and a cold drawing on the steel tube by using a plug to produce the rifled tube including a plurality of first helical ribs on the inner surface of the rifled tube and having an outer diameter of not more than 34 mm, wherein
the plug includes:
a plurality of helical grooves; and
a plurality of second helical ribs each located between adjacent helical grooves; wherein
in a cross section perpendicular to a central axis of the plug, the plug has a maximum diameter A (mm) and a minimum diameter B (mm),
in the cross section, the plug has N second helical ribs,
in the cross section, a groove bottom surface of the helical groove of the plug has a width W (mm),
in a longitudinal section parallel with the central axis of the plug, the groove bottom surface of the helical groove of the plug has a width S (mm), and
in the longitudinal section, adjacent second helical ribs are arranged by a pitch M (mm), wherein,
the maximum diameter A, the minimum diameter B, a number of the second helical groove N, and the width W satisfy Formula (1), and
the maximum diameter A, the minimum diameter B, a number of the second helical groove N, the width W and the pitch M satisfy Formula (2),
0.08< W ×( A−B )× N /(2π× A )<0.26  (1)

0.83< S ×( A−B )× N /(2× M )<2.0  (2).

2. The production method according to claim 1 , wherein
in the step of producing the rifled tube, the rifled tube in which a lead angle of the first helical rib is 20 to 43 deg is produced.

3. The production method according to claim 2 , wherein
in the step of preparing the steel tube, the steel tube having a tensile strength of not more than 500 MPa is prepared, and
in the step of producing the rifled tube, the rifled tube in which the lead angle is 30 to 43 deg is produced.

4. The production method according to claim 3 , wherein
in the step of preparing the steel tube, a two-stage heat treatment step is performed on a blank tube to produce the steel tube having a tensile strength of not more than 500 MPa, and wherein
the two-stage heat treatment step comprises:
a step of soaking the blank tube at a first heat treatment temperature of Ac 3 point to Ac 3 point +50° C., and
a step of reducing the first heat treatment temperature to a second heat treatment temperature of less than Ar 1 point to Ar 1 point−100° C. after the soaking, and soaking the blank tube at the second heat treatment temperature.

Assignees

• Nippon Steel & Sumitomo Metal Corp
• Mitsubishi Hitachi Power Sys
• Nippon Steel Corp

Inventors

• Nakashima Takashi
• Iseda Atsuro
• Miki Takeshi
• Otsuka Shunichi

Classifications

• F28F1/40

  the means being only inside the tubular element · CPC title

• B21C37/20 Primary

  Making helical or similar guides in or on tubes without removing material, e.g. by drawing same over mandrels, by pushing same through dies {; Making tubes with angled walls, ribbed tubes or tubes with decorated walls} · CPC title

• B21C37/207

  with helical guides · CPC title

• F28F2210/06

  having walls comprising obliquely extending corrugations, e.g. in the form of threads · CPC title

• B21C1/24

  by means of mandrels · CPC title