公开(公告)号：EP2818260A4

公开(公告)日：2015-07-29

申请号：EP13772897

申请日：2013-04-02

申请人： JFE STEEL CORP

发明人： TAJIKA HISAKAZU ,  SAKIMOTO TAKAHIRO ,  IGI SATOSHI

IPC分类号： B21C37/08 ,  B21C37/30 ,  B21D5/01

CPC分类号： B21C37/16 ,  B21C37/08 ,  B21C37/0803 ,  B21C37/0815 ,  B21C37/30 ,  B21D3/14 ,  B21D5/015 ,  B23K11/0935 ,  B23K31/02 ,  B23K2201/06

公开(公告)号：EP3269465A4

公开(公告)日：2018-03-14

申请号：EP16761711

申请日：2016-03-07

申请人： JFE STEEL CORP

发明人： TAJIKA HISAKAZU ,  IGI SATOSHI

IPC分类号： B21C37/16 ,  B21C37/30 ,  F16L9/02

CPC分类号： B21C37/16 ,  B21C37/30 ,  F16L9/006 ,  F16L9/02

摘要： A steel pipe according to the present invention has a waveform shape formed on an outer diameter thereof by a pipe expansion process. The value "a/w" is 0.038% or smaller, where "a" and "w" denote the amplitude and the wavelength of the waveform shape, respectively. It is desirable to arrange the value "w/»" indicating a ratio of the wavelength "w" of the waveform shape to a Timoshenko's buckling wavelength "»" so as to be larger than 0.8. As a result, it is possible to provide a steel pipe of which deformability is improvable, while reducing labor and time required by the pipe expansion process.