MICROSTRUCTURE EVOLUTION AND MECHANICAL PROPERTIES OF COLD DRAWN HYPEREUTECTOID STEEL WIRE

Microstructure evolution of hypereutectoid steel wire during the drawing process was studied by SEM, TEM, XRD and VSM, respectively. The results show the cementite in the hypereutectoid steel shows good deform ability. With the drawing strain increased, the pearlitic colonies gradually aligned to the drawing direction. Moreover, partial dissolution of cementite caused by cold deformation was observed, and the quantitative tests show that dissolution of cementite increased in correspondence with the increase in strain. The increase of lattice constant in ferrite matrix, a slight left shift in the ferrite diffraction peaks ware due to carbon atoms dissolved into ferrite crystal. Mechanical properties of steel wire with different strain was measured, and the main strengthening mechanism was discussed. In the initial stages of drawing, the strengthening of pearlite steel may be accorded with Hall-Petch relationship.