The current study shows the effect of various heat treatments on the cutting force and surface finishing of
machining for medium carbon steel (0.522C) with different cutting conditions have been investigated. In this research,
samples have been divided into two groups. Samples of the first group were heated to austenitizing temperature and
quenched in a polymer solution (Polyethylene glycol M. W.400), followed by tempering. Tempering process is to reduce
brittleness and relieve residual stresses. In this treatment, the samples were heated again to 450?C, held for one hour at
that temperature (soaking stage), then cooled in still air. Samples of the second group were heated to austenitizing
temperature and cooled by air (normalizing process). The cutting force and other properties were evaluated before and
after heat treatment. The results showed a direct effect of heat treatments on cutting force and machinability.
In other words, a correlation between the machinability and the heat treatment of specimens was established.

CONCLUSIONS
· The results obtained from this study can lead to the following conclusions;
· Normalizing has highest toughness compared to quenching and tempering processes , but has roughness values
close to quenching because almost the same cooling time.
· Built up edge (B. U. E) is less with the quenched samples in wet cutting and discontinuity of the chips leads to
decrease the cutting force and roughness despite the high hardness, but still not less than tempering and
normalizing processes.
· The best results of cutting force and roughness were for the tempered samples due to improvement of the
microstructure of medium carbon steel.
· The roughness is less with hardened material at low cutting speed, but the ductile tempered material needs high
speed for less roughness.
· The improvement of surface roughness was obtained in heat-treated samples more than those of the untreated
samples at all cutting conditions.