機械構造用炭素鋼の被削性に及ぼす介在物の影響

概要

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The plunge cutting test was carried out on several structural steels, Fe-0.4%C-0.2%Si-1.5%Mn and one containing 0.16%Pb and 0.06%S. The cutting force was reduced by the addition of Pb and the presence of MnS particles, and the former was found to be more effective to lower the cutting resistance. The lead observed in the primary shear zone of a chip exhibited a thin string-like morphology, suggesting the ductile and very deformable characteristic of Pb. The microhardness distribution inside the chip was lower for the Pb-bearing steel than for the MnS containing steel. Those results indicate that at the primary shear zone of the chip the deformation is mainly concentrated on lead particles and plastic shear strain accumulated in the chip remains lower. This lower plastic work is likely to be the outcome of the reduced shear stress, which might be the major origin of the lower cutting force observed in the Pb-bearing steel.