Title:
HIGH-STRENGTH ELECTRIC-RESISTANCE-WELDED STEEL PIPE OF EXCELLENT LONG-TERM SOFTENING RESISTANCE IN INTERMEDIATE TEMPERATURE RANGES, AND METHOD FOR PRODUCING SAME
Document Type and Number:
WIPO Patent Application WO/2014/002423
Kind Code:
A1
Abstract:
Provided are a high-strength electric-resistance-welded steel pipe of yield strength 450 MPa or higher and excellent long-term softening resistance in intermediate temperature ranges, and a method for producing the same. More specifically, an electric-resistance-welded steel pipe is made by a regular method for forming an electric-resistance-welded pipe where the material is a hot-rolled steel strip obtained by subjecting a steel material of a composition comprising, by mass, C: 0.026-0.084%, Si: 0.10-0.30%, Mn: 0.70-1.90%, Al: 0.01-0.10%, Nb: 0.001-0.070%, V: 0.001-0.065%, Ti: 0.001-0.033%, and Ca: 0.0001-0.0035%, and having a Pcm satisfying 0.20 or less, to the following steps: heat-soaking for 90 min or longer at a temperature ranging from greater than 1200°C to 1280°C; hot rolling at a rolling rate 20% or higher in an un-recrystallized temperature range; cooling, after conclusion of the rolling, at a mean cooling rate of 7-299°C/s at a temperature of 780-620°C in the thickness-wise middle part of the plate; and subsequently adjusting the cumulative residence time in the temperature range 480-350°C to 2-20 h. The entire thickness of the material of the plate near an electric resistance weld section is heated inline to a temperature in the range of 800-1150°C, the plate is cooled so that the mean cooling rate at 780-620°C in the thickness middle part temperature is in the range of 7-299°C is carried out, and the cumulative residence time at 500-360°C is adjusted to 2-200 s.
Inventors:
TOYODA SHUNSUKE (JP)
GOTO SOTA (JP)
OKABE TAKATOSHI (JP)
INOUE TOMOHIRO (JP)
GOTO SOTA (JP)
OKABE TAKATOSHI (JP)
INOUE TOMOHIRO (JP)
Application Number:
PCT/JP2013/003764
Publication Date:
January 03, 2014
Filing Date:
June 17, 2013
Export Citation:
Assignee:
JFE STEEL CORP (JP)
International Classes:
B21C37/08; C22C38/00; C21D8/10; C21D9/08; C21D9/50; C22C38/14; C22C38/58
Foreign References:
| JP2011094231A | 2011-05-12 | |||
| JP2010202976A | 2010-09-16 | |||
| JP2007254797A | 2007-10-04 | |||
| JP2004115871A | 2004-04-15 | |||
| JP4741528B2 | 2011-08-03 | |||
| JP2008195991A | 2008-08-28 | |||
| JP2006183133A | 2006-07-13 |
Other References:
F.R. LARSON; J. MILLER, TRANS. ASME, vol. 74, no. 99, 1952, pages 765 - 775
"Atlas for Bainitic Microstructures", vol. 1, 29 June 1992, THE IRON AND STEEL INSTITUTE OF JAPAN, pages: 4
"Atlas for Bainitic Microstructures", vol. 1, 29 June 1992, THE IRON AND STEEL INSTITUTE OF JAPAN, pages: 4
Attorney, Agent or Firm:
KUMASAKA, Akira et al. (JP)
Akira Kumasaka (JP)
Akira Kumasaka (JP)
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