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

Patent metadata

Field	Value
Publication number	US-2019076902-A1
Application number	US-201716082894-A
Country	US
Kind code	A1
Filing date	Feb 14, 2017
Priority date	Mar 11, 2016
Publication date	Mar 14, 2019
Grant date	—

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.

First claim

1 . A method of manufacturing a variable wall thickness steel pipe with a hollow tubular raw pipe, the method comprising:
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.

2 . The method of manufacturing a variable wall thickness steel pipe according to claim 1 ,
wherein in the performing ironing, an unprocessed portion remains on the other end side of the raw pipe by stopping thrusting the plug in the middle.

3 . The method of manufacturing a variable wall thickness steel pipe according to claim 1 ,
wherein a thickness reduction rate of the thin portion in the performing ironing is within a range from 10% to 90%.

4 . The method of manufacturing a variable wall thickness steel pipe according to claim 1 ,
wherein the plug used in the locking and the performing ironing includes,
a tip end portion having an outer shape size smaller than an inner shape size of the raw pipe,
a base end portion having an outer shape size larger than the inner shape size of the raw pipe and smaller than an outer shape size of the raw pipe, and
a tapered portion being provided between the tip end portion and the base end portion so as to be tapered from the base end portion toward the tip end portion.

5 . The method of manufacturing a variable wall thickness steel pipe according to claim 1 ,
wherein the plug used in the locking and the performing ironing includes,
a base end portion having an outer shape size larger than an inner shape size of the raw pipe and smaller than an outer shape size of the raw pipe, and
a tip end portion leading to a tip end side of the base end portion and being tapered as being separated from the base end portion.

6 . The method of manufacturing a variable wall thickness steel pipe according to claim 4 ,
wherein the base end portion has a large-sized base end portion being disposed on the tip end portion side, and a small-sized base end portion having an outer shape size smaller than an outer shape size of the large-sized base end portion.

7 . A method of manufacturing a variable wall thickness steel pipe with a hollow tubular raw pipe, the method comprising:
locking the raw pipe in a die by thrusting a first plug into the raw pipe from an one end side, so as to expand an outer shape size 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; pulling the first plug from the raw pipe; and performing ironing in which an inner shape of the raw pipe is expanded while an outer shape of the raw pipe is maintained so that a thin portion is formed by thrusting a second plug, which has an outer shape different from the outer shape of the first plug, from the one end side of the raw pipe toward the other end side while the locked state of the raw pipe is maintained, whereas the restriction on the raw pipe is relaxed.

8 . The method of manufacturing a variable wall thickness steel pipe according to claim 7 ,
wherein the second plug used in the performing ironing includes,
a small-sized tip end portion smaller than an inner shape size of the raw pipe,
an intermediate-sized portion having an outer shape size larger than the inner shape size of the raw pipe,
a large-sized portion having an outer shape size larger than the outer shape size of the intermediate-sized portion and smaller than an outer shape size of the raw pipe,
a first tapered portion being provided between the small-sized tip end portion and the intermediate-sized portion, and
a second tapered portion being provided between the intermediate-sized portion and the large-sized portion.

9 . The method of manufacturing a variable wall thickness steel pipe according to claim 7 ,
wherein the second plug used in the performing ironing includes,
a base end portion having an outer shape size larger than the inner shape size of the raw pipe and smaller than an outer shape size of the raw pipe, and
a third tapered portion being tapered from the base end portion toward a tip end portion.

10 . The method of manufacturing a variable wall thickness steel pipe according to claim 1 ,
wherein the die includes,
a hollow small-sized portion having an inner shape size corresponding to the outer shape size of the raw pipe,
a hollow large-sized portion having an inner shape size larger than the outer shape size of the raw pipe, and
a hollow tapered portion being provided between the hollow small-sized portion and the hollow large-sized portion and being tapered from the hollow large-sized portion toward the hollow small-sized portion.

11 . The method of manufacturing a variable wall thickness steel pipe according to claim 10 ,
wherein the die further includes a hollow intermediate-diameter portion being provided in a part of the hollow small-sized portion in the longitudinal direction and having an inner shape size larger than the outer shape size of the raw pipe.

12 . The method of manufacturing a variable wall thickness steel pipe according to claim 1 , further comprising:
drawing the raw pipe after performing ironing.

13 . A method of manufacturing a variable wall thickness steel pipe with a hollow tubular raw pipe, the method comprising:
locking the raw pipe in a die by simultaneously or alternately thrusting plugs into the raw pipe respectively from an one end side and the other end side of the raw pipe, so as to expand an outer shape on the one end side and an outer shape on the other end side; pulling the plug on the other end side while the plug is inserted on the one end side; performing first ironing in which an inner shape of the raw pipe is expanded while the outer shape is maintained so that a first thin portion is formed by further thrusting the plug, which is inserted on the one end side, toward the other end side of the raw pipe while the one end side is locked in the die; inserting and pulling the plugs such that the plug is inserted on the other end side, whereas the plug on the one end side is pulled out; and performing second ironing in which the inner shape of the raw pipe is expanded while the outer shape is maintained so that a second thin portion is formed by further thrusting the plug on the other end side toward the one end side of the raw pipe while the other end side is locked in the die, wherein in the locking,
the raw pipe freely moves in a longitudinal direction of the raw pipe in a case where the plugs are simultaneously thrust, and
movement of the raw pipe in a thrusting direction of the plugs is restricted in a case where the plugs are alternately thrust.

14 . The method of manufacturing a variable wall thickness steel pipe according to claim 13 , further comprising:
drawing the raw pipe after performing second ironing.

15 . The method of manufacturing a variable wall thickness steel pipe according to claim 1 ,
wherein the raw pipe is a seamless steel pipe.

16 . A variable wall thickness steel pipe comprising:
an expanded portion that is provided on one side in a longitudinal direction and has a largest outer shape size in

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Mizumura Masaaki
• Iguchi Keinosuke
• Arita Hidehiro

Classifications

• B21K1/12

  of specially-shaped cross-section · CPC title

• B21C37/16 Primary

  Making tubes with varying diameter in longitudinal direction · CPC title

• B21C37/18

  conical tubes · CPC title

• B21C1/24

  by means of mandrels · CPC title

• B21K21/12

  Shaping end portions of hollow articles · CPC title