Komatsu Corporation

Yuko Nagaki

Eiji Amada

Norimasa Tsunekage

Akihiro Ochiai

A steel constituting a chisel according to the present invention includes: 0.40-0.45% by mass of carbon, 0.50-0.80% by mass of silicon, 1.00-1.30% by mass of manganese, 0.001-0.005% by mass of sulfur, 2.90-3.80% by mass of chromium, and 0.20-0.40% by mass of molybdenum, with a balance consisting of iron and an unavoidable impurity, the steel has an ideal critical diameter DI defined by Equation (1) of 600 or more:DI=7&#xb7;(% C)&#xb7;(1+0.64&#xb7;% Si)&#xb7;(1+4.1&#xb7;% Mn)&#xb7;(1+2.83&#xb7;% P)&#xb7;(1&#x2212;0.62&#xb7;% S)&#xb7;(1+2.33&#xb7;% Cr)&#xb7;(1+3.14&#xb7;% Mo)&#x2003;&#x2003;(1).

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Himeji, Japan

Yuko Nagaki