Forged crankshaft
View Patent ↗To provide a forged crankshaft having an excellent wear resistance. The forged crankshaft according to the present embodiment includes a non-heat treated steel material. The non-heat treated steel material has a chemical composition which contains, by mass %, C: 0.45 to 0.70%, Si: 0.75 to 1.30%, Mn: 1.00 to 2.00%, S: 0.03 to 0.30%, Cr: 0.05 to 0.30%, Al: 0.005 to 0.050%, and N: 0.005 to 0.020%, the balance being Fe and impurities, and satisfies the following Formula (1): 1.1C+Mn+0.2Cr>2.0 (1) where a symbol of each element in Formula (1) is substituted by the content (mass %) of the each element. A matrix of the non-heat treated steel material is a ferrite-pearlite microstructure in which an area ratio of pro-eutectoid ferrite is less than 10% or a pearlite microstructure.
1. A forged crankshaft comprising a non-heat treated steel material, wherein
the non-heat treated steel material has a chemical composition which contains, by mass %, C: 0.45 to 0.70%, Si: 0.75 to 1.30%, Mn: 1.20 to 2.00%, S: 0.03 to 0.30%, Cr: 0.05 to 0.30%, Al: 0.005 to 0.050%, and N: 0.005 to 0.020%, the balance being Fe and impurities, and satisfies Formula (1), and wherein
a matrix of the non-heat treated steel material is one of a ferrite-pearlite microstructure in which an area ratio of pro-eutectoid ferrite is less than 10% or a pearlite microstructure:
1.1C+Mn+0.2Cr>2.0 (1)
where a symbol of each element in Formula (1) is substituted by the content (mass %) of the each element,
the forged crankshaft has a surface hardness obtained by Rockwell Hardness testing using the scale C of not less than 23.0, and
the forged crankshaft has a wear resistance where a difference in weight between before and after a pin-on-disk test is not more than 0.0100 g, the pin-on-disk test being conducted by preparing a specimen of 1.5 mm×2.0 mm×3.7 mm sampled from the forged crankshaft, and pressing a surface of 2.0 mm×3.7 mm of the specimen against an emery paper of grit 800 stuck on a surface of a rotary disk rotating at a circumferential speed of 39.6 m/min for 50 min at an interfacial pressure of 26 gf/mm 2 .
2. The forged crankshaft according to claim 1 , wherein
the chemical composition of the non-heat treated steel material contains Ti: no more than 0.03% in place of part of Fe.
3. The forged crankshaft according to claim 2 , wherein
the forged crankshaft includes a crank pin for which a surface hardening heat treatment is omitted.
4. The forged crankshaft according to claim 1 , wherein
the forged crankshaft includes a crank pin for which a surface hardening heat treatment is omitted.