The effect of austenite grain size and deformation(true strain 0.4) of gear steel 0.23C-0.74Mn-0.90Cr on continuous cooling transformation(CCT) structure and CCT curves have been studied by Gleeble 1500 hot simulator. Test results showed that as gear steel without deforming
the critical cooling rate to get complete polygonal ferrite + pearlite structure was 0.5~1 ℃/s
as cooling rate quicker
the products of medium temperature transformation consisted of bainite and acicular ferrite; as austenite deforming the polygonal ferrite initial transformation temperature went up
the cooling rate to get complete polygonal ferrite + pearlite structure up increased to 1~2 ℃/s
and the medium temperature transformation product was only acicular ferrite without bainite observed.