Title:
HOT-ROLLED STEEL SHEET, SQUARE STEEL TUBE, METHODS FOR PRODUCING SAME, AND BUILDING STRUCTURE
Document Type and Number:
WIPO Patent Application WO/2024/062686
Kind Code:
A1
Abstract:
Provided is a low-yield-ratio hot-rolled steel sheet having excellent strength and low-temperature toughness. The steel sheet has a predetermined component composition. The steel structure of the sheet thickness center part has a main phase, which is ferrite, and a second phase in which the total area ratio of pearlite and pseudopearlite is 6-25% and the area ratio of upper bainite is 5% or less. When a region surrounded by boundaries where the orientation difference between adjacent crystals is 15° or more is taken as a crystal grain, the average crystal grain size of the steel structure containing the main phase and the second phase in the sheet thickness center part is 10.0-30.0 μm, the area ratio of crystal grains having a crystal grain size within this average crystal grain size±5.0 μm is 35% or more, and the number of crystal grains in which the ratio (major axis)/(minor axis) of the major axis to the minor axis is 3.0 or more is 30/mm2 or fewer.
Inventors:
IWATA NAOMICHI (JP)
MATSUMOTO AKIHIDE (JP)
IDE SHINSUKE (JP)
MATSUMOTO AKIHIDE (JP)
IDE SHINSUKE (JP)
Application Number:
PCT/JP2023/020167
Publication Date:
March 28, 2024
Filing Date:
May 30, 2023
Export Citation:
Assignee:
JFE STEEL CORP (JP)
International Classes:
C22C38/00; B21B1/22; B21C37/08; B21C37/15; C21D8/02; C22C38/60; C21D9/08; C21D9/50
Domestic Patent References:
| WO2018110152A1 | 2018-06-21 | |||
| WO2020039980A1 | 2020-02-27 | |||
| WO2013153679A1 | 2013-10-17 |
Foreign References:
| JP2019196508A | 2019-11-14 | |||
| JP2020037734A | 2020-03-12 |
Attorney, Agent or Firm:
SUGIMURA Kenji (JP)
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