Crankshaft and method of manufacturing forged material for crankshaft
AssigneeNippon Steel Corporation
InventorsManabu KUBOTA, Taketo MAEJIMA
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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%.
Claims8
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%.
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.
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.
Dependencies are inferred from the claim text.