	US 12,188,109 B2
	Steel material for brake disc of motor vehicle having excellent wear resistance and high temperature strength and method of manufacturing the same
Seng-Ho Yu, Pohang-si (KR); Young-Jin Jung, Pohang-si (KR); and Kyung-Keun Um, Pohang-si (KR)
Assigned to POSCO CO., LTD, Pohang-si (KR)
Appl. No. 17/415,389
Filed by POSCO, Pohang-si (KR)
PCT Filed Dec. 18, 2019, PCT No. PCT/KR2019/017987 § 371(c)(1), (2) Date Jun. 17, 2021, PCT Pub. No. WO2020/130619, PCT Pub. Date Jun. 25, 2020.
Claims priority of application No. 10-2018-0165447 (KR), filed on Dec. 19, 2018.
Prior Publication US 2022/0064769 A1, Mar. 3, 2022
Int. Cl. C22C 38/54 (2006.01); C21D 8/02 (2006.01); C21D 9/46 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/42 (2006.01); C22C 38/44 (2006.01); C22C 38/46 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01); F16D 65/12 (2006.01)

CPC C22C 38/54 (2013.01) [C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 9/46 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/46 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01); F16D 65/125 (2013.01)]

3 Claims

1. A steel material for a brake disc of a motor vehicle, the steel material comprising, by weight: 0.02 to 0.07% of carbon (C), 0.1 to 0.5% of silicon (Si), 0.2 to 0.7% of manganese (Mn), 0.05% or less (excluding 0) of phosphorus (P), 0.02% or less (excluding 0) of sulfur(S), 0.07% or less (excluding 0) of aluminum (Al), 0.1 to 0.5% of chromium (Cr), 0.3 to 1.0% of molybdenum (Mo), 0.05% or less (excluding 0) of vanadium (V), 50 ppm or less (excluding 0) of boron (B), 0.01 to 0.5% of nickel (Ni), 0.5% or less (excluding 0) of copper (Cu), 0.02% or less (excluding 0) of titanium (Ti), 0.05% or less (excluding 0) of niobium (Nb), and 2 to 100 ppm of calcium (Ca), with a balance of Fe and unavoidable impurities,

wherein the steel material has a Brinell hardness of 260 to 340 HB, the steel material satisfies the following Relational Expressions 1 and 2, and a microstructure includes, by area, 90% or more martensite and 10% or less of bainite:

260≤1589×[C]+228≤340 [Relational Expression 1]

[C]/[Mo]≤0.250 [Relational Expression 2]

wherein [C] and [Mo] are in % by weight.