Jfe Steel Corporation

Yuta Imanami

Takashi Iwamoto

Kimihiro Nishimura

Kiyoshi Uwai

Kazuaki Fukuoka

A case hardening steel includes a chemical composition containing C: 0.10 mass % to 0.35 mass %, Si: 0.01 mass % to 0.13 mass %, Mn: 0.30 mass % to 0.80 mass %, P: 0.02 mass % or less, S: 0.03 mass % or less, Al: 0.01 mass % to 0.045 mass %, Cr: 0.5 mass % to 3.0 mass %, B: 0.0005 mass % to 0.0040 mass %, Nb: 0.003 mass % to 0.080 mass %, N: 0.0080 mass % or less, Ti as an impurity: 0.005 mass % or less, and the balance being Fe and incidental impurities, and satisfying Formulae (1) and (2):3.0[% Si]+9.2[% Cr]+10.3[% Mn]&#x2265;10.0&#x2003;&#x2003;(1)3.0[% Si]+1.0[% Mn]&#x3c;1.0&#x2003;&#x2003;(2)

Case hardening steel

Provided is a wire rod that has superior machinability by cutting regardless of the type of tool material and the type of lubricant and even in the case where no lubricant is used. A wire rod for cutting work comprises: a specific chemical composition; and Vickers hardness that satisfies the following expressions (1) and (2) in the case where an average aspect ratio of ferrite grains at a position of &#xbc; of a diameter from a surface of the wire rod for cutting work is more than 2.8, and satisfies the following expressions (3) and (4) in the case where the average aspect ratio is 2.8 or less,H&#x2264;350&#x2003;&#x2003;(1)H&#x2264;30&#x2003;&#x2003;(2)H&#x2264;250&#x2003;&#x2003;(3)H&#x2264;20&#x2003;&#x2003;(4).

Wire rod for cutting work

A mechanical structural component is a toothed component obtained by performing cold forging and carburizing treatment on a steel having a predetermined chemical composition, in prior austenite grains after the carburizing treatment, an area ratio of crystal grains of 50 &#x3bc;m or less is 80% or more, and an area ratio of crystal grains exceeding 300 &#x3bc;m is 10% or less, and a total helix deviation of teeth after the carburizing treatment satisfies Formula (1)()&#xd7;10&#x2264;5&#x2003;&#x2003;(1)where Bis a maximum total helix deviation in all teeth in mm, and L is a face width in mm.

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Tokyo, Japan

Yuta Imanami