Kobe Steel, Ltd.

Kabushiki Kaisha Kobe Seiko Sho

Goro Anan

Koichi Sakamoto

Hiroshi Yaguchi

Tomoko Sugimura

Atsuhiko Yoshida

Katsuhiko Ozaki

Yoshiteru Fukuoka

Keita Shiihashi

Akihiro Matsugasako

A low carbon resulfurized free-machining steel having a high machinability is provided. This steel comprises 0.02 to 0.15% by mass of C, up to 0.004% by mass (more than 0% by mass) of Si, 0.6 to 3% by mass of Mn, 0.02 to 0.2% by mass of P, 0.2 to 1% by mass of S, up to 0.005% by mass (more than 0%) of Al, 0.008 to 0.04% by mass of O, and 0.002 to 0.03% by mass of N; and the average oxygen concentration in the MnS in the steel is at least 0.4% by mass.

Low carbon resulfurized free-machining steel having high machinability

The present invention provides a low-carbon resulfurized free machining steel product excellent in machinability typified by finished surface roughness even though toxic Pb or special elements such as Bi or Te are not added, and a suitable production method thereof. A steel product has a specific composition, has contents of Mn and S satisfying the following conditions: 0.40&#x2266;Mn*S&#x2266;1.2 and Mn/S&#x2267;3.0, and contains a ferrite-pearlite structure as the metallographic structure, in which the average width (&#x3bc;m) of sulfide inclusions in the steel product is 2.8*(log d) or more, wherein d (mm) is the diameter of the steel product, and pro-eutectoid ferrite in the metallographic structure has a hardness HV of 133 to 150 or a difference in deformation resistance at a strain of 0.3 between 200&#xb0; C. and 25&#xb0; C. is 110 MPa or more and 200 MPa or less, the deformation resistances being determined in a compression test at a deformation rate of 0.3 mm/min.

Low carbon composite free-cutting steel product excellent in roughness of finished surface and method for production thereof

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Kobe, Japan

Goro Anan