Effect of billet microstructure and deformation on austenite grain growth in forging heating of a medium-carbon microalloyed steel

We prepared samples with different ferrite-pearlite characteristics and deformation by heat treatment and Gleeble thermocompression respectively. Then, the different samples are rapidly heated to 1200 degrees C for 60 s to study the austenite grain growth. The study results show that the ferrite-pearlite characteristics has little effect on austenite grain growth. With the mean austenite grain size (MAGS) of billet microstructure increasing from 14 mu m to 56 mu m, the MAGS after heating only increases from 47 mu m to 56 mu m. With the cooling rate of billet samples increasing from 0.1 degrees C/s to 1.0 degrees C/s, the MAGS after heating has basically no change. However, the deformation of billet samples has significant effect on the austenite grain growth. With the deformation at 1150 degrees C increasing from 10% to 50%, the MAGS after heating decreases from 63 mu m to 31 mu m. In the meanwhile, the mean distance between element segregation bands decreases from 115 mu m to 33 mu m, and the mean width of element segregation bands decreases from 70 mu m to 20 mu m. Electron probe microanalysis shows that the segregation region has higher Si, Cr, Mn and V contents, which generate stronger solute drag effect on austenite grain boundaries. Deformation can crush the as-cast grains and make the segregation bands fine and dispersed, further refining the austenite grains after heating. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study found that the ferrite-pearlite characteristics have little effect on the growth of austenite grains, while deformation significantly impacts the growth of austenite grains. Deformation can crush the as-cast grains, make the segregation bands fine and dispersed, further refining the austenite grains.