Effects of Alloying Elements on the Machinability of Low Carbon Steels

Abstract

Effects of alloying elements on the drillability of low carbon steels have beeninvestigated.
From the view point of the effects on the drillability of low carbon steels with normalized lamellar pear-lite structures, alloying elements are classified into two groups as follows.
(1) Elements represented by chromium which increase the pearlite fraction by lowering eutectoid carbon content and cause little solid solution hardening.
(2) Elements represented by phosphorus which have little effect on the pearlite fraction but increase the hardness by solid solution hardening of ferrite.
The first group elements largely increase the drillability and the second groupones have little effect on the drillability.
These effects of alloying elements on the drillability are understood mainly asthe net results of the benificial effect by decrease of the cutting force due to the contribution of pearlite on stress concentration and a negative effect by increase of the cutting force due to the increase of hardness.
The effects of alloying elements on the drillability with spheroidized structures of cold drawn low carbon steels are also discussed with the effects due to decreased stress concentrationby spheroidized pearlite and the effect due to hardness