Title:
ULTRA-THIN HOT ROLLED STEEL SHEET HAVING EXCELLENT ISOTROPY AND MANUFACTURING METHOD THEREOF
Document Type and Number:
WIPO Patent Application WO/2019/132408
Kind Code:
A1
Abstract:
An embodiment of the present invention provides an ultra-thin hot rolled steel sheet having excellent isotropy, and a manufacturing method thereof, the steel sheet comprising, 0.020 to 0.080 wt% of C; 0.05 to 0.50 wt% of Mn; 0.05 wt% or less of Al; 0.001 to 0.005 wt% of Ca; and the balance being Fe and other unavoidable impurities, wherein the C, Mn, Al, and Ca satisfy following relational expressions 1 to 4, the microstructure includes, by an area fraction, 80% or more of ferrite, and 20% or less of pearlite, and a ferrite grain size variation (∆G) according to rolling directions satisfies following relational expression 5: [Relational expression 1] 5 ≤ [Al/Ca] ≤ 40; [Relational expression 2] 20 ≤ 1000[C + 0.04Mn] ≤ 85; [Relational expression 3] 1 ≤ 1000[C + 0.04Mn]/[Al/Ca] ≤ 12; [Relational expression 4] 0.05 ≤ [C + 0.4Mn] ≤ 0.3; and [Relational expression 5] ∆G = [(GTD + GRD)/2] – G45°D ≤ 2.5 ㎛, wherein in relational expressions 1 to 4, the content of C, Mn, Al and Ca is by wt%, and in relational expression 5, ∆G indicates a variation of the average ferrite grain size (FGS), GTD indicates an FGS in the vertical direction of the rolling direction, GRD indicates an FGS in the horizontal direction of the rolling direction, and G45°D indicates an FGS in the 45° direction of the rolling direction.
Inventors:
KONG JONG-PAN (KR)
CHUNG JEA-SOOK (KR)
CHO YONG-SEOK (KR)
CHUNG JEA-SOOK (KR)
CHO YONG-SEOK (KR)
Application Number:
PCT/KR2018/016318
Publication Date:
July 04, 2019
Filing Date:
December 20, 2018
Export Citation:
Assignee:
POSCO (KR)
International Classes:
C22C38/00; B21B1/46; B21B3/00; B21B37/58; C21D8/02; C21D9/46; C22C38/04; C22C38/06
Foreign References:
JP2007009293A | 2007-01-18 | |||
JPH09327702A | 1997-12-22 | |||
JPH09296252A | 1997-11-18 | |||
JP2000054071A | 2000-02-22 | |||
KR20150004639A | 2015-01-13 |
Attorney, Agent or Firm:
C&S PATENT AND LAW OFFICE (KR)
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