应力对U75V重轨钢珠光体转变的相变塑性影响

Stress influence on pearlite transition phase transformation plasticity of U75V heavy rail steel

基于Greenwood-Johnson理论,采用Gleeble-1500D热模拟实验机,对U75V重轨钢连续冷却转变过程中珠光体转变的相变塑性进行研究。通过测定不同加载应力下的膨胀曲线,对总变形中的组成应变,即热应变、相变应变、弹性应变、相变塑性应变进行分离,建立重轨钢相变塑性模型方程,通过数值模拟对热处理工艺进行优化。计算结果表明,重轨钢U75V在珠光体相变过程中,热应变在总应变中占80%以上;相变塑性应变在总应变中所占比例的最大值随应力而增加,当加载应力为-45MPa、相变在577.1℃结束时,相变塑性应变占总应变的比例最大可达到12.5%。

Phase transformation plasticity effect on residual stress and deformation cannot be ignored ,therefore ,the studies on the phase transformation plasticity is necessary .Based on Greenwood-Johnson theory ,using Gleeble-1500D thermal simulation ma-chine ,the transformation plasticity in the process of U 75V heavy rail steel continuous cooling transformation was studied .By measuring the expansion curve under different loading stresses ,the thermal strain ,phase transformation strain ,elastic strain and phase transformation plastic strain were separated ,and the phase transformation plasticity model of heavy rail steel was estab-lished .The results show that ：in the phase change process ,the thermal strain occupies the highest proportion and accounts for more than 80% ;the proportion of the maximum phase transformation plasticity strain in the total strain increases with the in-creasing of stress ;with the loading stress -45MPa and phase transition temperature at the end point 577.1℃ ,the phase trans-formation plasticity strain accounts for the biggest proportion in the total strain reaching 12.5% .