Title:
HIGH-STRENGTH THICK-WALLED ELECTRIC RESISTANCE WELDED STEEL PIPE FOR CONDUCTOR CASING FOR DEEP WELL, PRODUCTION METHOD THEREFOR, AND HIGH-STRENGTH THICK-WALLED CONDUCTOR CASING FOR DEEP WELL
Document Type and Number:
WIPO Patent Application WO/2016/103623
Kind Code:
A1
Abstract:
Provided is an electric resistance welded steel pipe that has high strength, high toughness, and excellent post-welding heat treatment resistance. A hot-rolled steel sheet comprising the following is used as a starting material: a composition containing 0.01-0.12% of C, 0.05-0.50% of Si, 1.0-2.2% of Mn, 0.03% or less of P, 0.005% or less of S, 0.001-0.10% of Al, 0.006% or less of N, 0.010-0.100% of Nb, and 0.001-0.050% of Ti; and a structure that comprises 90% or more by volume of a main phase that is a bainitic ferrite phase and 10% or less (including 0%) by volume of a second phase, in which the average particle size of the bainitic ferrite phase is 10 µm or less and extremely fine Nb deposits having a particle size of less than 20 nm are dispersed at a rate that, when calculated in terms of Nb, surpasses 75% by ratio (%) of the total amount of Nb. The starting material is formed to have a substantially circular cross section by roll forming and subsequently subjected to electric resistance welding in order to obtain an electric resistance welded pipe, the electric resistance welded section of the electric resistance welded pipe is subjected to inline heat treatment, and the result is subjected to diameter reduction rolling so that the deviation from roundness of a steel pipe end section is 0.6% or less.
Inventors:
GOTO SOTA (JP)
OKABE TAKATOSHI (JP)
OKAZAKI YUKIHIKO (JP)
OKABE TAKATOSHI (JP)
OKAZAKI YUKIHIKO (JP)
Application Number:
PCT/JP2015/006232
Publication Date:
June 30, 2016
Filing Date:
December 15, 2015
Export Citation:
Assignee:
JFE STEEL CORP (JP)
International Classes:
C22C38/00; B21C37/08; C21D8/02; C21D9/08; C21D9/50; C22C38/14; C22C38/58
Foreign References:
| JP2007138290A | 2007-06-07 | |||
| JP2007138289A | 2007-06-07 | |||
| JP2007254797A | 2007-10-04 | |||
| JP2010174343A | 2010-08-12 | |||
| JP2008274405A | 2008-11-13 | |||
| JP2004315957A | 2004-11-11 |
Other References:
HIROSHI NAKATA ET AL.: "API X80 Grade Electric Resistance Welded Pipe with Excellent Low Temperature Toughness", JFE GIHO, vol. 29, February 2012 (2012-02-01), pages 11 - 16
Attorney, Agent or Firm:
KUMASAKA, Akira et al. (JP)
Akira Kumasaka (JP)
Akira Kumasaka (JP)
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