Sumitomo Electric Industries, Limited

Fuminori Okada

Hiromu Izumida

Tetsuya Nakajima

Katsutoshi Iwamoto

Kazuaki Sugimura

A steel wire is formed of a steel containing: not less than 0.6 mass % and not more than 0.7 mass % carbon, not less than 1.2 mass % and not more than 2.1 mass % silicon, not less than 0.2 mass % and not more than 0.6 mass % manganese, not less than 1.4 mass % and not more than 2 mass % chromium, and not less than 0.15 mass % and not more than 0.3 mass % vanadium, with the balance being iron and unavoidable impurities. The steel includes a matrix made up of tempered martensite, and a non-metallic inclusion present in the matrix. When √area of the non-metallic inclusion is represented as Hand √area of a region including both the non-metallic inclusion and a decreased-hardness portion is represented as H, a ratio of Hto H, or, H/His at least 1 and less than 1.3.

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Osaka, Japan

Fuminori Okada