Crankshaft and method of manufacturing forged material for crankshaft

Patent metadata

Field	Value
Publication number	US-2024091847-A1
Application number	US-202017754862-A
Country	US
Kind code	A1
Filing date	Nov 2, 2020
Priority date	Nov 7, 2019
Publication date	Mar 21, 2024
Grant date	—

Abstract

A crankshaft with improved fatigue strength and machinability is provided. The crankshaft includes a pin and journal, having a chemical composition of, in mass %: 0.40 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, the hardness measured at a position at a depth of ¼ of the diameter from the surface is higher than HV 245, the microstructure at that position is mainly composed of ferrite/pearlite, and the fraction of ferrite is not lower than 16%.

First claim

1 . A crankshaft including a pin and a journal, having a chemical composition of, in mass %:
0.40 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 higher than HV 245, a microstructure at that position is mainly composed of ferrite/pearlite, and a fraction of ferrite is not lower than 16%.

2 . The crankshaft according to claim 1 , wherein the chemical composition includes, in mass %:
0.005 to 0.060% Ti.

3 . A method of manufacturing a forged material for a crankshaft, comprising:
preparing a steel material having a chemical composition of, in mass %: 0.40 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; hot forging the steel material such that a temperature directly before finish forging is higher than 800° C. and lower than 1100° C.; and, after the hot forging, cooling the steel material such that an average cooling rate in a temperature range from 800 to 650° C. is not higher than 2.5° C./s.

4 . A method of manufacturing a forged material for a crankshaft, comprising:
preparing a steel material having a chemical composition of, in mass %: 0.40 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; 0.005 to 0.060% Ti; and balance Fe and impurities; hot forging the steel material such that a temperature directly before finish forging is higher than 800° C. and not higher than 1180° C.; and, after the hot forging, cooling the steel material such that an average cooling rate in a temperature range from 800 to 650° C. is not higher than 0.07° C./s.

5 . The method of manufacturing a forged material for a crankshaft according to claim 4 , wherein the temperature directly before finish forging is not lower than 1100° C. and not higher than 1180° C.

6 . The method of manufacturing a forged material for a crankshaft according to claim 3 , wherein, in the forged material for a crankshaft, a hardness is higher than HV 245, a microstructure is mainly composed of ferrite/pearlite, and a fraction of ferrite is not lower than 16%.

7 . The method of manufacturing a forged material for a crankshaft according to claim 4 , wherein, in the forged material for a crankshaft, a hardness is higher than HV 245, a microstructure is mainly composed of ferrite/pearlite, and a fraction of ferrite is not lower than 16%.

8 . The method of manufacturing a forged material for a crankshaft according to claim 5 , wherein, in the forged material for a crankshaft, a hardness is higher than HV 245, a microstructure is mainly composed of ferrite/pearlite, and a fraction of ferrite is not lower than 16%.

Assignees

• Nippon Steel Corp

Inventors

• Kubota Manabu
• Maejima Taketo

Classifications

• B21J1/04

  Shaping in the rough solely by forging or pressing · CPC title

• B21K1/08 Primary

  crankshafts · CPC title

• B21J1/06

  Heating or cooling methods or arrangements specially adapted for performing forging or pressing operations {(B21J5/063 takes precedence)} · CPC title

• C21D9/30 Primary

  for crankshafts; for camshafts · CPC title

• C22C38/00

  Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) · CPC title