WELDED STEEL PIPE WITH EXCELLENT WELDING HEAT-AFFECTED ZONE TOUGHNESS, AND PROCESS FOR PRODUCING SAME

Title:

WELDED STEEL PIPE WITH EXCELLENT WELDING HEAT-AFFECTED ZONE TOUGHNESS, AND PROCESS FOR PRODUCING SAME

Document Type and Number:

WIPO Patent Application WO/2013/051249

Kind Code:

A1

Abstract:

The purpose of the present invention is to supply a welded steel pipe having excellent welding heat-affected zone toughness, while attaining excellent productivity and without sacrificing the quality of the inner part of the weld. The welded steel pipe having excellent welding heat-affected zone toughness has two butt-welded portions respectively for the inner and outer surfaces, the butt-welded portions having been formed in such a manner that either the inner or the outer surface is welded earlier than the other. The welded steel pipe is characterized in that the welding heat-affected zones have a metallographic structure which has an island martensite (MA) content of 4% or lower in terms of areal proportion and has an average prior austenite grain diameter of 400 µm or smaller, and that the following and others are taken into account: the average prior austenite grain diameters in the welding heat-affected zones formed by the preceding welding and the succeeding welding; the width of each of the weld beads formed by the preceding welding and the succeeding welding, the width being measured at the position 5 mm apart from the bead toe; and the inclination angles of the melt lines of the weld beads formed by the preceding welding and the succeeding welding.

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Inventors:

TANIZAWA AKIHIKO (JP)
OTA YOSHIAKI (JP)
UCHITOMI NORIAKI (JP)
OKATSU MITSUHIRO (JP)
NISHIMURA KIMIHIRO (JP)

Application Number:

PCT/JP2012/006332

Publication Date:

April 11, 2013

Filing Date:

October 03, 2012

Export Citation:

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Assignee:

JFE STEEL CORP (JP)

International Classes:

B23K9/025; B21C37/08; B23K9/18; B23K9/23; C22C38/00; C22C38/58; B23K101/06; B23K103/04

Domestic Patent References:

WO2010090349A1	2010-08-12
WO2006049036A1	2006-05-11

Foreign References:

JP2009202167A	2009-09-10
JP2006328523A	2006-12-07
JP2002194490A	2002-07-10
JPH06328255A	1994-11-29
JPH10277744A	1998-10-20
JPH0857642A	1996-03-05
JP2003136130A	2003-05-14
JP2001113374A	2001-04-24
JP2004099930A	2004-04-02
JP2006272377A	2006-10-12
JP2007268564A	2007-10-18
JP2009214127A	2009-09-24
JP2009233679A	2009-10-15
JP2009241128A	2009-10-22
JP2009202167A	2009-09-10

Other References: