
196 Engineering Materials Technology
Free-cutting mild steel 100
Free-cutting a or ß brass 200 to 400
The machinability of a metal can be improved if its ductility is decreased.
Work hardening can make an improvement. Some multi-phase alloys have
good machinability as the insoluble phase can provide discontinuities within
the material and assist in breaking up a continuous chip to give small chips.
The addition of a small amount of lead to a mild steel improves its
machinability. For optimum machinability, the workpiece material must have
low ductility and also low hardness.
Problems
1 Distinguish between cold and hot working processes.
2 Describ ...