Interaction between Precipitation and Deformation Induced Ferrite Transformation in a Nb Microalloyed Steel

摘要

Effect of the Nb on the deformation induced ferrite transformation (DIFT) was investigated. Hot compression tests were performed with varying at temperature from 1223K to 1103K with the true strain 0.51 using Gleeble 2000. After the hot deformation, the samples were held for 1～320s,and then cooled to 1053K at which deformation induced ferrite transformation occurred at a true strain 0.693 and a strain rate of 10s~(-1). After the heavy deformation, samples were water-quenched immediately to count the amount of deformation induced ferrite. The amount of ferrite increases with increasing holding time to a maximum then decreases at 1153K. Above this temperature the amount decreases, while below this temperature the amount increases with increasing holding time. After hot compression at different temperatures, the state of precipitation is different. The precipitation can affect DIFT when the deformation conditions are fixed. It was considered that the deformation induced ferrite transformation was accelerated by the strain induced precipitation of NbC under some temperature at which recrystallization is significantly retarded.