应变速率对中碳马氏体组织温变形流变应力的影响

Effect of Strain Rate on Flow Stress of Martensite in a Medium Carbon Steel Subjected to Warm Deformation

利用温压缩实验,在Gleeble-3500热力模拟试验机上测定了中碳钢马氏体(M)和铁素体+珠光体(F+P)两种组织的流变曲线。对比研究了应变速率对这两种组织流变行为的影响。结果表明:在相同温度下,M组织的应变速率敏感性指数(mM)和加工软化率(sM)都大于F+P组织的相应参数(mF+P)和(sF+P)。应变速率为0.001 s-1,变形温度为600℃、650℃、700℃,M组织的流变曲线均低于F+P组织的流变曲线;当应变速率从0.01 s-1增加到10 s-1,M组织和F+P组织的流变曲线相交,交点应变为临界应变,大于临界应变,M组织的流变应力低于F+P。这表明,对降低钢材温轧或零件温挤压的变形应力和成本来说,M组织可能比F+P更好。此外,对导致M组织上述流变行为的机理进行了初步探讨。

Flow curves of warm deformation performed on martensite structure（M） and ferrite plus pearlite structure（F＋P） in a medium carbon steel were determined on Gleeble-3500 machine.Comparison study was conducted on effect of strain rate on the warm low behavior of two starting microstructures of M and F＋P at various temperatures.It is found that the strain rate sensitive index（m^M） and working softening rate of s^M of M are larger than that of F＋P,（m^F＋P） and（s^ F＋P）.And the flow stress of M is lower than that of F＋P under the conditions of strain rate of 0.001s^-1 and deformation temperature at 600℃,650℃ and 700℃.When the strain rate ranges from 0.01s^-1 to 10.0s^-1,there are critical strain values at which the M flow curves intersect the F＋P curves under some conditions.In these cases,if the strain amount is larger than the critical strain,the martensitic flow stress is lower than that of F＋P.These results show that,M structure,compared with F＋P structure,may be a promising candidator for steel＇s warm working.Additional,the mechanism results in these characteristics of M flow behavior are also discussed.