US 12,403,526 B2
Crankshaft and method of manufacturing forged material for crankshaft
Manabu Kubota, Tokyo (JP); and Taketo Maejima, Tokyo (JP)
Assigned to NIPPON STEEL CORPORATION, Tokyo (JP)
Appl. No. 17/754,862
Filed by NIPPON STEEL CORPORATION, Tokyo (JP)
PCT Filed Nov. 2, 2020, PCT No. PCT/JP2020/041041
§ 371(c)(1), (2) Date Apr. 14, 2022,
PCT Pub. No. WO2021/090799, PCT Pub. Date May 14, 2021.
Claims priority of application No. 2019-202532 (JP), filed on Nov. 7, 2019.
Prior Publication US 2024/0091847 A1, Mar. 21, 2024
Int. Cl. B21K 1/08 (2006.01); C21D 9/30 (2006.01); C22C 38/00 (2006.01)
CPC B21K 1/08 (2013.01) [C21D 9/30 (2013.01); C22C 38/00 (2013.01)] 4 Claims
OG exemplary drawing
 
1. A crankshaft including a pin and a journal, having a chemical composition consisting of, in mass %:
0.48 to 0.60% C;
0.01 to 1.50% Si;
0.4 to 2.0% Mn;
0.01 to 0.50% Cr;
0.20 to 0.50% Al;
0.001 to 0.02% N;
up to 0.03% P;
0.005 to 0.20% S;
0.005 to 0.060% Nb;
0 to 0.060% Ti; and
balance Fe and impurities,
wherein, for each of the pin and journal, a hardness measured at a position at a depth of ¼ of a diameter from a surface is not lower than HV 250, a microstructure at that position is mainly composed of ferrite and pearlite, and a fraction of ferrite is not lower than 16%,
wherein the hardness is measured in accordance with JIS Z 2244 (2009) and the testing force is to be 300 gf (2.942 N).