US 11,952,647 B2
Method for manufacturing ferritic lightweight steel and ferritic lightweight steel using same
Jae Bok Seol, Jinju-si (KR); Hyo Ju Bae, Jinju-si (KR); Kwang Gyu Koh, Jinju-si (KR); Jung Gi Kim, Jinju-si (KR); Hyo Kyung Sung, Jinju-si (KR); and Young Kook Lee, Seoul (KR)
Assigned to INDUSTRY-ACADEMIC COOPERATION FOUNDATION GYEONGSANG NATIONAL UNIVERSITY, Jinju-si (KR)
Appl. No. 18/039,655
Filed by INDUSTRY-ACADEMIC COOPERATION FOUNDATION GYEONGSANG NATIONAL UNIVERSITY, Jinju-si (KR)
PCT Filed Nov. 11, 2021, PCT No. PCT/KR2021/016379
§ 371(c)(1), (2) Date May 31, 2023,
PCT Pub. No. WO2022/124601, PCT Pub. Date Jun. 16, 2022.
Claims priority of application No. 10-2020-0172118 (KR), filed on Dec. 10, 2020.
Prior Publication US 2023/0392238 A1, Dec. 7, 2023
Int. Cl. C22C 38/06 (2006.01); C21D 8/02 (2006.01); C22C 38/04 (2006.01)
CPC C22C 38/06 (2013.01) [C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 8/0263 (2013.01); C21D 8/0273 (2013.01); C22C 38/04 (2013.01); C21D 2211/001 (2013.01); C21D 2211/005 (2013.01)] 8 Claims
OG exemplary drawing
 
1. A method for producing a ferritic steel, the method comprising steps of:
(1) subjecting an alloy to solution treatment at 1,200° C. for 90 minutes;
(2) hot-rolling the alloy, subjected to solution treatment, at 900° C. to 1,100° C.;
(3) air-cooling the hot-rolled alloy to room temperature at a cooling rate of 10° C./s;
(4) cold-rolling the air-cooled alloy at room temperature until a thickness of the alloy is reduced by 70%;
(5) subjecting the cold-rolled alloy to intercritical annealing at 850° C. to 950° C. for 90 seconds;
(6) cooling the alloy, subjected to intercritical annealing, at a cooling rate of 10° C./s;
(7) isothermally annealing the cooled alloy at 430° C. for 50 seconds;
(8) air-cooling the isothermally annealed alloy; and
(9) subjecting the air-cooled alloy to low-temperature tempering-induced partitioning (LTP) at 300° C. for 10 minutes,
wherein a steel resulting from step (9) contains 2.0 to 3.0 wt % manganese (Mn), 5.0 to 6.0 wt % aluminum (Al) and 0.1 to 0.3 wt % carbon (C).