Experimentally Based Study on the Effect of Initial Grain Size for Characterization of the Grain Coarsening Phenomenon During Hot Rolling of a Medium Carbon Steel

Laboratory experiments using a hot deformation simulator were carried out to clarify the effect of initial grain size on the grain coarsening phenomenon in hot metal working with light reduction. As an example of medium carbon steel AISI1045 was adopted and specimens of various grain sizes were prepared by changing the thermo-mechanical histories. They were subjected to a hot deformation testing by the simulator. The threshold grain size to cause the grain coarsening phenomenon was then determined and a criterion was presented to ensure a fine grain after hot rolling. The validity of the new criterion was checked through hot rolling of bars by a prototype mill in a laboratory.