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Title:
STEEL MATERIAL FOR LINE PIPES, PRODUCTION METHOD FOR SAME, AND PRODUCTION METHOD FOR LINE PIPE
Document Type and Number:
WIPO Patent Application WO/2019/151046
Kind Code:
A1
Abstract:
The purpose of the present invention is to provide: a steel material for line pipes that has a sheet thickness of at least 30 mm, has high strength for use in submarine pipelines, and has excellent low-temperature toughness and DWTT performance; a production method for the steel material for line pipes; and a production method for a line pipe. A production method for a steel material for line pipes that has a tensile strength of at least 570 MPa, a compressive strength of at least 440 MPa, and a sheet thickness of at least 30 mm. According to this method, steel that has a specific component composition: is heated to 1,000°C–1,200°C; is hot rolled, the rolling end temperature being the average temperature of the steel sheet and being at or above the Ar3 transformation point but not above 790°C, the cumulative draft in a non-recrystallization temperature range being at least 60%, and the cumulative draft in a temperature range that is at or below 20°C above the rolling end temperature being at least 50%; is subjected to accelerated cooling at a cooling speed of at least 10°C/s from a temperature that is at or above the Ar3 transformation point to a cooling stop temperature that is the average temperature of the steel sheet and is 200°C–450°C; and then is reheated such that the surface temperature of the steel sheet is 350°C–550°C and the center temperature of the steel sheet is less than 550°C.

Inventors:
YASUDA Kyono (JFE STEEL CORPORATION 2-3, Uchisaiwai-cho 2-chome, Chiyoda-k, Tokyo 11, 〒1000011, JP)
YOKOTA Tomoyuki (JFE STEEL CORPORATION 2-3, Uchisaiwai-cho 2-chome, Chiyoda-k, Tokyo 11, 〒1000011, JP)
TANIZAWA Akihiko (JFE STEEL CORPORATION 2-3, Uchisaiwai-cho 2-chome, Chiyoda-k, Tokyo 11, 〒1000011, JP)
MURAOKA Ryuji (JFE STEEL CORPORATION 2-3, Uchisaiwai-cho 2-chome, Chiyoda-k, Tokyo 11, 〒1000011, JP)
HASE Kazukuni (JFE STEEL CORPORATION 2-3, Uchisaiwai-cho 2-chome, Chiyoda-k, Tokyo 11, 〒1000011, JP)
Application Number:
JP2019/001854
Publication Date:
August 08, 2019
Filing Date:
January 22, 2019
Export Citation:
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Assignee:
JFE STEEL CORPORATION (2-3 Uchisaiwai-cho 2-chome, Chiyoda-ku Tokyo, 11, 〒1000011, JP)
International Classes:
C21D8/02; B21B3/00; B21C37/08; C22C38/00; C22C38/58
Attorney, Agent or Firm:
KUMASAKA Akira et al. (JFE Techno-Research Corporation 7-1, Otemachi 2-chome, Chiyoda-k, Tokyo 04, 〒1000004, JP)
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