Strain ageing in heavily drawn eutectoid steel wires

Differential scanning calorimetry (DSC) and thermopower measurements were used to study the mechanisms and kinetics of static strain aging in pearlitic steel wire. The starting material was Stemor cooled wire rod. The wire rod was pickled and drawn to semifinished wire in a dry drawing process, patented, further drawn in a wet drawing process at industrial drawing speeds, quenched in ice and stored under frozen conditions until performance of the DSC experiments. The DSC technique provided insight into the stages during which strain aging proceeds. The mechanism of strain aging below 250 deg C was found to be the migration of carbon atoms which are interstitially dissolved in the ferrite to dislocations. When the reservoir of C atoms in the ferrite is exhausted, partial decomposition of the cementite takes place to maintain the locking of ferrite dislocations.