	US 12,252,768 B2
	Steel for gear and method for manufacturing gear using the same
In Beom Lee, Goyang-si (KR); Min Woo Kang, Yongin-si (KR); Min Woo Kang, Incheon (KR); Dong Hwi Kim, Yongin-si (KR); Chang Won Kang, Hwaseong-si (KR); Myung Sik Kim, Daegu (KR); Sung Min Hong, Seoul (KR); Gung Seung Nam, Cheonan-si (KR); and Sang Won Lee, Asan-si (KR)
Assigned to HYUNDAI MOTOR COMPANY, Seoul (KR); KIA CORPORATION, Seoul (KR); and HYUNDAI STEEL COMPANY, Incheon (KR)
Filed by Hyundai Motor Company, Seoul (KR); Kia Corporation, Seoul (KR); and HYUNDAI STEEL COMPANY, Incheon (KR)
Filed on Dec. 26, 2023, as Appl. No. 18/396,165.
Application 18/396,165 is a division of application No. 17/234,428, filed on Apr. 19, 2021, granted, now 11,898,231.
Claims priority of application No. 10-2020-0121558 (KR), filed on Sep. 21, 2020.
Prior Publication US 2024/0124962 A1, Apr. 18, 2024
Int. Cl. C22C 38/48 (2006.01); C21D 7/13 (2006.01); C21D 8/00 (2006.01); C21D 9/32 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/44 (2006.01); C22C 38/46 (2006.01)

CPC C22C 38/48 (2013.01) [C21D 7/13 (2013.01); C21D 8/005 (2013.01); C21D 9/32 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/44 (2013.01); C22C 38/46 (2013.01)]

3 Claims

1. Steel for a gear, consisting of, based on a total weight of the steel:

C: 0.10-0.30 wt %;

Si: 0.60-0.80 wt %;

Mn: 0.25-0.75 wt %;

Cr: 1.80-2.20 wt %;

Ni: 0.50-1.50 wt %;

Mo: 0.20-0.40 wt %;

Nb: 0.025-0.050 wt %;

V: 0.030-0.050 wt %; and

a balance of Fe and inevitable impurities,

wherein contents of Nb and V satisfy the following <Relationship Formula 1>:

0.055<[Nb]+[V]<0.100 <Relationship Formula 1>,

wherein [Nb] represents a content of Nb and [V] represents a content of V,

wherein the steel has a metallic carbide or metallic nitride (MX) precipitate formed at a fraction of 0.03-0.07% therein,

wherein the MX precipitate is 150 nm or less in size, and

wherein the MX precipitate is formed at a density of 50 or more precipitates per 100 μm².