[12] Patent
[11] Patent No.:GC0009409  
[45] Date of Publishing the Grant of the Patent: 31/Dec /2018                56/2018  
Number of the Decision to Grant the Patent:2018/141892
Date of the Decision to Grant the Patent:19/Dec/2018

[21] Application No.:GC 2014-27182

[22] Filing Date:18/5/2014

[30] Priority:

[33] State [32] Priority date [31] Priority No.

[72] Inventors:1- Toshihiro Miwa،2- Masayuki Horie

[73] Owner: JFE STEEL CORPORATION, 2-3, Uchisaiwai-cho 2-chome, Chiyoda-ku, 100-0011, Tokyo, Japan

[74] Agent: Saud M. A. Shawwaf Law Office




Int. Cl.: B21C 37/08; B21D 3/14, 39/20 (2006.01)

[56] Cited Documents:

-JP 8-300069 A (NKK Corp.) 19 November 1996
-JP 59-183943 A (Sumitomo Metal Industries, Ltd.) 19 October 1984
Examiner: Eng. Fahad M. AlBaker

[57] Abstract: A method for manufacturing a steel pipe includes a first pipe expanding step of expanding a steel pipe within a range of a pipe expanding ratio having a lower limit at a pipe expanding ratio at which a predetermined roundness is obtained and an upper limit at a maximum value of a pipe expanding ratio at which an equipment load of a pipe expanding machine falls in an allowable range when the steel pipe is expanded, and a second pipe expanding step of expanding the steel pipe after the first pipe expanding step at a pipe expanding ratio at which the pipe diameter of the steel pipe reaches a target value. This improves the roundness of the steel pipe without increasing the equipment load of the pipe expanding machine.
No. of claims: 3     No. of figures: 4


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