| 摘要 |
A low carbon composite free-cutting steel product, which has a specific component composition with the proviso that the contents of Mn and S satisfy the relationships: Mn*S: 0. 40 to 1.2 and Mn/S >= 3.0, and has a metal structure comprising a ferrite pearlite structure, wherein when the steel product has a diameter of d (mm), sulfide based inclusions in the steel product have an average width (mum) of 2.8 log d or more, and wherein the initially precipitated ferrite in the above metal structure has a hardness of HV 133 to 150, or the difference in the deformation resistances at a strain of 0.3 at 200‹C and 25‹C, as measured by a compression test at a deformation rate of 0.3 mm/min, is 110 to 200 MPa; and a suitable method for producing the above steel product. The above steel product exhibits the machinability being excellent, in particular, in the roughness of a finished surface, even when it is not added with toxic Pb or a special element such as Bi or Te. ® KIPO & WIPO 2008
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