THERMAL RELAXATION OF SHOT-PEENING-INDUCE D RESIDUAL-STRESS IN QUENCHED AND TEMPERED STEEL 42 CRMO 4

Thermal relaxation of shot-peening-induced macro and micro residual st ress in a quenched and tempered state of the 42 CrMo 4 steel is invest igated with X-rays and is described by the Avrami-approach. The parame ters of this relationship can now be determined more exactly using a n ew, iterative method. By means of the parameters determined, the relax ation of macro and micro residual stress is evaluated and compared. Th e influence of annealing time and temperature on the dependence of mac ro residual stress on distance to surface is modelled using the Avrami -approach. The transient relaxation of macro residual stress during he ating up to the temperature required can be determined by applying the stress-transient-method which will be presented here. It turns out th at not the elapsed heating time but rather the relaxation of residual stress during heating up determines the further relaxation of residual stress.