INVESTIGATION ON PHASE TRANSFORMATION OF LOW CARBON MARTENSITIC STAINLESS STEEL ZG06Cr13Ni4Mo IN TEMPERING PROCESS WITH LOW HEATING RATE

In order to clarify martensite to austenite phase transformation mechanism of the steel ZG06Crl3Ni4Mo during tempering between As and A_f with low heating rate of 0.05℃/s,a systematic study by dilatometer,XRD,TEM and EDX was carried out.The experimental results indicated that the reversed austenite generated during tempering was rich in Ni and did not have high density dislocation,which demonstrated the martensite to austenite phase transformation with low heating rate proceeded by diffusion.The reversed austenite generated over 600℃would partially transform to martensite during subsequent cooling.One-stage tempering got the maximal amount of reversed austenite at 620℃.Two-stage tempering system(620—660)℃+600℃could dramatically increase the amount of reversed austenite,because the new martensite transformed from unstable reversed austenite at first-stage tempering at 620--660℃provided dispersive nucleation sites for the reversed austenite in the second-stage tempering at 600℃.