US 12,123,067 B2
Ferritic stainless steel having improved pipe-expanding workability and method for manufacturing same
Il Chan Jung, Pohang-si (KR); Young Min Seo, Pohang-si (KR); and Deok Chan Ahn, Seoul (KR)
Assigned to POSCO CO., LTD, Pohang-si (KR)
Appl. No. 16/767,206
Filed by POSCO, Pohang-si (KR)
PCT Filed Oct. 5, 2018, PCT No. PCT/KR2018/011764
§ 371(c)(1), (2) Date May 27, 2020,
PCT Pub. No. WO2019/124690, PCT Pub. Date Jun. 27, 2019.
Claims priority of application No. 10-2017-0176335 (KR), filed on Dec. 20, 2017.
Prior Publication US 2020/0385837 A1, Dec. 10, 2020
Int. Cl. C21D 9/46 (2006.01); C21D 6/00 (2006.01); C21D 8/02 (2006.01); C22C 38/00 (2006.01); C22C 38/06 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01)
CPC C21D 9/46 (2013.01) [C21D 6/004 (2013.01); C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 8/0247 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/06 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01); C21D 2211/005 (2013.01)] 5 Claims
OG exemplary drawing
 
1. A ferritic stainless steel, the ferritic stainless steel comprising, in percent (%) by weight of an entire composition, Cr: 10 to 25%, N: more than 0% and 0.015% or less, Al: 0.005 to 0.04%, Nb: 0.33 to 0.6%, Ti: 0.1 to 0.5%, Ca: 0.0004 to 0.002% and Mg: 0.0002 to 0.001%, a remainder of iron (Fe) and other inevitable impurities, and satisfying the following equation (1)
Z=X*Y≥17  equation(1)
wherein, based on a thickness (T) of ferritic stainless steel, X means [(111)//ND texture fraction]/[(100)//ND texture fraction] of a region from T/3 to 2T/3, and Y means 10*[(100)//ND texture fraction]/[(111)//ND texture fraction] of a region from a surface layer to T/3,
wherein the ferritic stainless steel comprises Al—Ca—Ti—Mg—O oxide having a maximum diameter of 0.05 to 5 mm and a distribution density of 9/mm2 or more,
wherein the Al—Ca—Ti—Mg—O oxide includes TiO2, CaO, Al2O3 and MgO, and
wherein a (111)//ND texture fraction in a center portion of the cold-rolled annealed ferritic stainless steel sheet is 70% or less, a (100)//ND texture fraction is 2% or more, the (100)//ND texture fraction in a surface layer portion is 30% or less, and the (111)//ND texture fraction is 10% or more.