Low carbon composite free-cutting steel product excellent in...

Details Low carbon composite free-cutting steel product excellent in... Low carbon composite free-cutting steel product excellent in...

2004-11-26

2010-02-23

King, Roy (Department: 1793)

Alloys or metallic compositions

Ferrous

Over 0.05 percent sulfur, over 0.04 percent phosphorus or...

C420S128000, C148S320000

Reexamination Certificate

active

07666350

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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