Nippon Steel Corporation

Taketo Maejima

Manabu Kubota

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%.

Crankshaft and method of manufacturing forged material for crankshaft

Provided is a railway wheel which has excellent toughness even if the C content is as high as 0.80% or more. The chemical composition of the railway wheel of the present embodiment consists of: in mass %, C: 0.80 to 1.60%, Si: 1.00% or less, Mn: 0.10 to 1.25%, P: 0.050% or less, S: 0.030% or less, Al: 0.010 to 0.650%, and N: 0.0030 to 0.0200%, with the balance being Fe and impurities, and wherein, in a microstructure of the web part of the railway wheel, an area fraction of pearlite is 85.0% or more, an area fraction of pro-eutectoid cementite is 0.90 to 15.00%, and an average value of a width W of the pro-eutectoid cementite defined by Formula (3) is less than 0.70 μm:=½×(/2−((/2)−4))  (3)

Railway wheel

The railway wheel according to the present embodiment has a chemical composition consisting of: in mass %, C: 0.80 to 1.15%, Si: 0.45% or less, Mn: 0.10 to 0.85%, P: 0.050% or less, S: 0.030% or less, Al: 0.200 to 1.500%, N: 0.0200% or less, Nb: 0.005 to 0.050%, Cr: 0 to 0.25%, and V: 0 to 0.12%, with the balance being Fe and impurities, wherein at least in the microstructure of the rim part and the web part, the amount of pro-eutectoid cementite defined by Formula (1) is 2.00 pieces/100 μm or less:Amount of pro-eutectoid cementite(pieces/100 μm)=a total sum of the number of pieces of pro-eutectoid cementite which intersect with two diagonal lines in a square visual field of 200 μm×200 μm/(5.66×100 μm)×100  (1).

A railway wheel having, in mass %, C: 0.80 to 1.15%, Si: 1.00% or less, Mn: 0.10 to 1.25%, P: 0.050% or less, S: 0.030% or less, Al: 0.025 to 0.650%, N: 0.0030 to 0.0200%, Cr: 0 to 0.60%, and V: 0 to 0.12%, with the balance being Fe and impurities. The railway wheel has a hub part, a rim part including a tread and a flange, and a web part disposed between the hub part and the rim part. The area fraction of pearlite in the hub, web, and rim parts is 95% or more, and the amount of pro-eutectoid cementite is not more than 1.0 pieces/100 &#x3bc;m. The amount of pro-eutectoid cementite is calculated as (pieces/100 &#x3bc;m)=a total sum of the number of pieces of pro-eutectoid cementite which intersect with two diagonal lines in a square visual field of 200 &#x3bc;m&#xd7;200 &#x3bc;m/(5.66&#xd7;100 &#x3bc;m).

Method for producing railway wheel and railway wheel

A railway wheel is capable of suppressing formation of pro-eutectoid cementite even if the C content is high. The railway wheel has a chemical composition consisting of: in mass %, C: 0.80 to 1.15%; Si: 0.45% or less; Mn: 0.10 to 0.85%; P: 0.050% or less; S: 0.030% or less; Al: 0.120 to 0.650%; N: 0.0030 to 0.0200%; Cr: 0 to 0.25%; and V: 0 to 0.12%, with the balance being Fe and impurities, wherein an amount of pro-eutectoid cementite, which is defined by Formula (1), in a microstructure of the railway wheel is not more than 1.50 pieces/100 &#x3bc;m: Amount of pro-eutectoid cementite (pieces/100=a total sum of the number of pieces of pro-eutectoid cementite which intersect with two diagonal lines in a square visual field of 200 &#x3bc;m&#xd7;200 &#x3bc;m/(5.66&#xd7;100 &#x3bc;m) (1).

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Tokyo, Japan

Taketo Maejima