V(C,N)在V-N微合金非调质钢奥氏体中的析出动力学

Precipitation Kinetic of V(C,N)in Austenite of V-N Microalloyed Non-quenched and Tempered Steel

在Gleeble-3500热模拟试验机上采用应力松弛法,研究了38MnSiVS非调质钢在750~950℃、10%~40%变形量条件下的析出-时间-温度(precipitation-time-temperature,PTT)曲线。基于Dutta和Sellars提出的应变诱导析出模型(DS模型),建立了等温析出动力学模型,计算得到理论PTT曲线。通过与试验PTT曲线比较,得出模型对钢的析出鼻尖温度、析出开始时间和结束时间的预测较为精准。采用“时间补偿法”建立了连续冷却析出动力学模型,计算出连续冷却过程析出相的体积分数和平均尺寸,与透射电子显微镜和能谱分析结果基本一致,而且冷速的增大可抑制钒的析出,细化析出相,表明模型可以准确地预测钒微合金非调质钢的连续冷却析出过程。最后,通过析出强化增量计算得出,V(C,N)析出强化对38MnSiVS非调质钢强度的贡献较大。

Precipitation-time-temperature curve(PTT)of 38MnSiVS non-quenched and tempered steel deformed to 10%to 40%at 750 to 950℃was measured by stress relaxation method on the Gleeble-3500 thermal simulator.Based on the strain-induced precipitation model(DS model)proposed by Dutta and Sellars,the isothermal precipitation dynamics model was established,and then the theoretical PTT curve was calculated,by comparing with the experimental PTT curve,it was concluded that the model could accurately predict the precipitation nose top temperature,the precipitation start and end time of the steel.The continuous cooling precipitation kinetic model was established by using the“time compensation method”,and the volume fraction and average size of precipitates during continuous cooling were calculated,which were basically consistent with the results of transmission electron microscope and energy dispersive spectrometer analysis;moreover,the increase of cooling rate could inhibit the precipitation of vanadium and refine the precipitated phase,indicating that the model could accurately predict the continuous cooling precipitation process of vanadium microalloyed non-quenched and tempered steel.Finally,the calculation of precipitation strengthening increment showed that V(C,N)precipitation strengthening contributed greatly to the strength of 38MnSiVS non-quenched and tempered steel.