The effect of heat treatment process with a new cooling medium (nanofluid), which contains water with Cu, Ag, or Al2O3 particles, on the heat transfer characteristics and mechanical properties of an unsteady continuous moving cylinder in the presence of suction and ex- ternal forces is studied. The governing time-dependent boundary-layer equations are transformed into ordinary differential equations by using similarity transformation. These equations are solved numerically. The velocity and temperature profiles of the boundary layer for different parameter values are plotted and discussed in detail. The effect of the cooling medium and the external forces on the mechanical properties of the cylinder is investigated. According to the obtained results, using nanofuid as a cooling medium improves the hardness and strength of the surface by 10% to 40%, and using Al2O3 as nanoparticle in water-based fluid is effective. Results also show that un- steady motion has a direct effect on the mechanical properties of the surface.