US 11,740,038 B2
Ferritic stainless steel having excellent sound absorption properties for exhaust system heat exchanger and method of manufacturing the same
Il Chan Jung, Pohang-si (KR); Jong Chul Kim, Daegu (KR); Jae Hong Shim, Seoul (KR); Deok Chan Ahn, Seoul (KR); and Jin Suk Kim, Pohang-si (KR)
Assigned to POSCO CO., LTD, Pohang-si (KR)
Appl. No. 16/337,695
Filed by POSCO, Pohang-si (KR)
PCT Filed Nov. 22, 2016, PCT No. PCT/KR2016/013478
§ 371(c)(1), (2) Date Mar. 28, 2019,
PCT Pub. No. WO2018/062618, PCT Pub. Date Apr. 5, 2018.
Claims priority of application No. 10-2016-0124985 (KR), filed on Sep. 28, 2016.
Prior Publication US 2020/0033077 A1, Jan. 30, 2020
Int. Cl. C22C 38/22 (2006.01); C22C 38/38 (2006.01); C22C 38/20 (2006.01); F28F 21/08 (2006.01); B22D 11/00 (2006.01); C21D 8/02 (2006.01); C21D 6/00 (2006.01); C22C 38/04 (2006.01)
CPC F28F 21/083 (2013.01) [B22D 11/002 (2013.01); C21D 6/002 (2013.01); C21D 8/0226 (2013.01); C22C 38/04 (2013.01); C22C 38/20 (2013.01); C22C 38/22 (2013.01); C22C 38/38 (2013.01)] 3 Claims
OG exemplary drawing
 
1. A ferritic stainless steel for an exhaust system heat exchanger, the ferritic stainless steel comprising, by weight percent, 0.001 to 0.01% of carbon (C), 0.001 to 0.01% of nitrogen (N), 0.2 to 1% of silicon (Si), 0.1 to 2% of manganese (Mn), 10 to 30% of chromium (Cr), 0.001 to 0.1% of titanium (Ti), 0.001 to 0.015% of aluminum (Al), 0.51 to 0.60% of niobium (Nb), 0.01 to 2.5% of molybdenum (Mo), and the balance of iron (Fe) and other unavoidable impurities, further comprising any one or more 0.01 to 0.15% of copper (Cu), 0.0002 to 0.001% of magnesium (Mg), and 0.0004 to 0.002% of calcium (Ca),
wherein the number of inclusions existing in a ferrite matrix in which a length of a longer side is greater than 2 μm and satisfying Formula 1 is 5 ea/mm2 or more, and the inclusions comprise two or more of Al2O3, MgO, SiO2 and CaO:
L/T≥3  Formula 1
wherein L is the length of the longer side of each inclusion and T is a length of a shorter side of the inclusion;
wherein a composition of the inclusions satisfies Formulae 3 and 4:
% (Al2O3)+% (MgO)+% (SiO2)+% (CaO)>90%  Formula 3%
(Al2O3)+% (MgO)<50%  Formula 4
wherein % (Al2O3), % (MgO), % (SiO2) and % (CaO) mean the content (% by weight) of each inclusion;
wherein a sound absorption index of the ferritic stainless steel is 7.0*10−4 or more.