Invention Grant
- Patent Title: Low carbon composite free-cutting steel product excellent in roughness of finished surface and method for production thereof
- Patent Title (中): 成品表面粗糙度优异的低碳复合自由切削钢产品及其制造方法
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Application No.: US10579798Application Date: 2004-11-26
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Publication No.: US07666350B2Publication Date: 2010-02-23
- Inventor: Hiroshi Yaguchi , Koichi Sakamoto , Tomoko Sugimura , Goro Anan , Katsuhiko Ozaki
- Applicant: Hiroshi Yaguchi , Koichi Sakamoto , Tomoko Sugimura , Goro Anan , Katsuhiko Ozaki
- Applicant Address: JP Kobe-shi
- Assignee: Kabushiki Kaisha Kobe Seiko Sho
- Current Assignee: Kabushiki Kaisha Kobe Seiko Sho
- Current Assignee Address: JP Kobe-shi
- Agency: Oblon, Spivak, McClelland, Maier & Neustadt, L.L.P.
- Priority: JP2003-401831 20031201; JP2004-252798 20040831
- International Application: PCT/JP2004/017600 WO 20041126
- International Announcement: WO2005/054532 WO 20050616
- Main IPC: C22C38/60
- IPC: C22C38/60 ; C22C38/00

Abstract:
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≦Mn*S≦1.2 and Mn/S≧3.0, and contains a ferrite-pearlite structure as the metallographic structure, in which the average width (μm) 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° C. and 25° 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.
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