X70HD管线钢形变诱导铁素体相变关键参数

Key parameters in the process of deformation induced ferrite transformation of X70HD pipeline steel

采用热膨胀法对X70HD(抗大变形)管线钢在特定条件下铁素体的静态相变点以及动态相变点进行测定。以测得的相变点为依据,制定两阶段累积变形量高达80%的热模拟实验。通过固定第一阶段变形参数,变化第二阶段变形过程中的变形温度以及应变速率,随后马上淬火,分析第二阶段变形温度与应变速率这2个因素对形变诱导铁素体生成量以及铁素体晶粒粒径的影响。研究结果表明:所获得的形变诱导铁素体为等轴铁素体,并且该等轴铁素体晶粒细小;第二阶段变形在奥氏体低温区时,应变速率越低越有利于形变诱导铁素体的生成;在奥氏体非再结晶区的较高温度范围内,应变速率越高越有利于形变诱导铁素体的生成。

X70HD pipeline steel＇s static phase transformation point and dynamic phase transition point were determined under certain conditions. Based on the measured phase transition points, a thermal simulation experiment of two stages large deformation whose accumulated deformation is as high as 80% was made. Deformation parameters in the first stage was fixed firstly, then the temperature and the strain rate of deformation in the second stage were changed before quenching, and then their influences on the generation of deformation induced ferrite and the grain size of ferrite were considered. The results show that the ferrite is deformation induced ferrite. The lower the strain rate is, the more deformation induced ferrite is found in the low temperature area of the austenite non-recrystallization region. And the higher the strain rate is, the more deformation induced ferrite is found in the high temperature area of the austenite non-recrystallization region.