The hot plasticity(reduction  of area)of steel  60Mn-0.61C

0.74Mn

0. 18Cr was  carried  out by  Gleeble-2000 dynanic themmo mechanical simulator using solidifying method. It was obtained that there were two low ductility regions  at high temperature - more than  1300 ℃ and 925~750 ℃.At temperature between 925 ℃ and 750 ℃

the nitride AlN and NbN precipitated at γ grainboundary and the procutectoid α- phase was distributed as net shaped in y+ a two phase region.With optimized process the Als in steel decreased to ≤0.010% from original ≤0.015%

by intensifying VD degas- sing  and  shielding  casting practice  the[N]  decreased to  40×10-⁶  from  60×10-⁶

and with  overheating  temperature  of molten  steel  decreasing  to  ≤35  ℃ from  ≤50  ℃

water ratio  decreasing  to  0.30 L/kg  from  0.40  L/kg

lowering  cast straightening force and keeping surface temperature of billet ≥900 ℃ before straightering

the rating of billet porosity decreased

the equiaxed zone ratio increased to 51.3% from 45.7% before optimized and internal crack ratio decreased to 1.7% from 5.2%

the quality of billet obviously improved.