Abstract
Some metallurgical observation and discussion were made upon the machining behaviors of mild steel samples containing free-cutting additives: telluride, sulfide, selenide, lead and/or bismuth. A specially devised tool holder was employed in order to obtain the cutting part of work sample with built-up edge.
A part of free-machining mechanism of the tellurided steel samples at the cutting speeds around 60m/min was discussed based on the results from the observation with the optical- and electron-microscope as well as from the measurements of mechanical properties at various temperatures. Observed electron-microscopic substructure of a cut chip of a sample showed a peculiar subcell feature presumably caused by fast dynamic recovery of extremely strained ferrite.
