Abstract: 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.

Key words: Steel 60Mn,Φ450 nm Round Cast Billet,Reduction of Area at High Temperature

摘要： 用Gleeble-2000动态热/力模拟机,通过凝固法测定成分(%)为0.61C-0.74Mn-0.18Cr 60Mn钢的高温塑性(断面收缩率),得出60Mn钢存在>1 300℃和925~750℃两个高温脆性区。在925~750℃温度中,钢中AlN和NbN等氮化物在γ晶界析出,先共析α-相在γ+α区呈网膜状。通过优化工艺,钢中Als量由原来的≤0.015%降到≤0.010%,采用强化VD脱气和保护浇铸使[N]由60×10^-6降至40×10^-6,过热度由≤50℃降至≤35℃,比水量由0.40 L/kg降至0.30 L/kg,降低拉矫力并保持矫直前铸坯表面温度≥900℃,从而降低了铸坯疏松级别,等轴晶比由优化前的45.7%增至51.3%,内裂发生率由5.2%降至1.7%,铸坯质量显著提高。

关键词: 60Mn 钢, Φ450mm 圆铸坯, 高温断面收缩率