Nippon Steel Corporation

Yoko Sueyasu

Hiroaki Tahira

Kison Nishihara

Ken Yoshino

Tatsuhiko Abe

The steel shaft component consists of C: 0.40 to 0.60%, Si: 0.05 to 1.00%, Mn: 1.00 to 2.00%, P: 0.030% or less, S: 0.005 to 0.100%, Cr: 0.10 to 0.50%, V: 0.10 to 0.30%, Al: 0.005 to 0.050%, N: 0.0050 to 0.0200%, Ti: 0 to 0.050%, and the balance: Fe and impurities. A Vickers hardness Hs of the surface of the shaft part is 620 HV or more. A Vickers hardness Hb at an R/2 position satisfies Formula (1). A depth of the hardened layer Hr (mm) having a Vickers hardness of 620 HV or more satisfies Formula (2). The microstructure at the R/2 position is composed of ferrite and pearlite. Within the hardened layer, the number of density of V-containing precipitates having an equivalent circular diameter of more than 100 nm is 10 particles/276 μmor less./2.3≤≤350  (1)0.05≤≤0.40  (2)

Steel shaft component

A crankshaft with improved fatigue strength is provided. A crankshaftincludes journals, pins, and fillets, each fillethaving a residual stress distribution where the residual stresses are compressive residual stresses from the surface down to a depth of at least 300 μm, the maximum value of the compressive residual stress being not lower than 1000 MPa, the surface roughness Rz being lower than 3.00 μm.

Crankshaft and method of manufacturing the same

A hot forged steel material in the present embodiment includes a chemical composition that consists of, in mass %, C: 0.14 to 0.20%, Si: 0.20 to 1.00%, Mn: 1.00 to 1.90%, P: 0.030% or less, S: 0.030% or less, V: 0.16 to 0.30%, Al: 0.015 to 0.050%, N: 0.0050 to 0.0250%, Cr: 0.10 to 0.30%, Cu: 0 to 0.10%, and Nb: 0 to 0.10%, with the balance being Fe and impurities, and that satisfies Formula (1) and Formula (2), wherein a grain size number of ferrite in the steel is 9.0 or more, and an absorbed energy at &#x2212;30&#xb0; C. is 100 J or more in the Charpy impact test using a V notch specimen.0.36&#x2264;C+(Si+Mn)/6+(Cr+V)/5+Cu/15&#x3c;0.68&#x2003;&#x2003;(1)51/12&#xd7;C&#x2212;V&#x2264;0.52&#x2003;&#x2003;(2)

Growing community of inventors

Tokyo, Japan

Yoko Sueyasu