Effects of Heat-treated Structures and Cold Working on the Machinability of Case-hardening Low Chromium Steels Containing Different Sulfur Contents

Abstract

Effects of heat-treated structures and cold working on machinability and tool life with high speed steel tools in drilling case hardening Cr steels containing sulfur up to 0.1% have been investigated.
Lameller pearlite structures obtained by annealing or normalizing show the best drillability. As dispersion of cementite particles becomes uniform and spheridizing of carbide progresses drillability becomes worse remarkably. But machinability based on tool life is the best for spheroidized structures.
Drillability seems not to be improved by cold working. The effect of cold working on tool life with high speed steel tools is understood as the result of both a favorable effect by decrease of ductility and an unfavorable effect of work hardening.