機械構造用炭素鋼の切りくず形態に及ぼす鉛の影響

抄録

The orthogonal cutting test was carried out on two structural steels, namely Fe-0.5%C-0.2%Si-0.8%Mn-0.1%Cr containing 0.16%Pb or non-Pb. The chip formation was transferred from shear type to flow type and the cutting force was reduced by the addition of Pb. The lead observed in the shear zone of the chip exhibited a thin string-like morphology, suggesting the ductile and very deformable characteristic of Pb. Those results indicate the major cause of the flow type chip formation. The shear angle can be maintained in the Pb-added steel because of the deformation concentrated on lead particles at the primary shear zone. In the case of low cutting speed conditions, the effect of Pb on machinability mainly reduces shear force in the primary shear zone. As for the lower friction coefficient between tool and chip, the effect of decreasing the cutting force is small.