Machinability of SAE 8620 with and without Machining Enhancers

Machinability of SAE 8620 hot rolled steel bare was evaluated. All samples were tested in the normalized condition. Machinability was determined using a CNC turning center with titanium nitride coated cutting inserts. Several heats from different steel suppliers were tested, some contained the machining enhancers calcium and tellurium as well as various sulphur levels. One heat did not contain enhancers for determination of a machinability baseline. Two machining parameters were used: 800 and 1200 c.s.f.m. (constant surface feet per minute), both at a feed rate of .015 i.p.r. (inches per revolution) and .075 in. d.o.c. (depth of cut). All the materials were chemically, mechanically, and metallurgically characterized.

This report will show that these machining enhancers can produce less insert damage (flank and crater) than the same grades without machining enhancers. Machinability will be evaluated with the aid of tool life charts, Taylor curves, and a new parameter involving both tool wear and tool forces.