PRELIMINARY-ANALYSIS OF HOT DUCTILITY CURVE IN SIMPLE C-MN STEELS

An attempt has been made to predict the tensile hot ductility curves f or simple C-Mn steels heated into the austenite phase to produce a coa rse grain size and cooled to test temperatures in the range 700-1100 d egrees C. The depth of the trough can be calculated from a knowledge o f the inclusion volume fraction and the volume fraction of the ferrite films surrounding the gamma grains. The temperature at which ductilit y recovers at the high temperature end can also be determined from the point at which the base of the trough intersects the curve of peak st rain v. temperature. This temperature is that at which dynamic recryst allisation becomes possible. Full recovery in ductility at the low tem perature end of the trough occurs when large amounts of ferrite are fo rmed; this is either 30-40 K below the Ar-3 (undeformed) or the Ae(3) depending on whether ferrite is present before or forms during deforma tion. The relevance of the hot ductility curve to the problem of trans verse cracking is also discussed.