Nb微合金化高碳钢奥氏体晶粒长大原位观察

In-situ observation on austenite grain growth of a Nb microalloyed high-carbon steel

以往研究表明Nb析出相钉扎和固溶Nb溶质拖曳作用共同阻碍奥氏体晶粒长大。采用高温共聚焦显微镜研究了Nb对一种高碳含Nb钢奥氏体晶粒长大的影响,对含Nb钢加热过程组织演变进行原位观察。结果表明,Nb在没有钉扎作用下(即高温条件下)仍能起到阻碍奥氏体晶粒长大的作用,该阻碍效果主要是固溶Nb的溶质拖曳作用引起的。采用2种模型对奥氏体晶粒长大行为进行拟合,给出了不同加热温度下Nb微合金化高碳钢的Beck长大方程,同时考虑到加热温度和保温时间的共同影响,根据原位观察结果得到实验钢的奥氏体晶粒长大动力学模型,该模型能够较准确地预测Nb微合金化高碳钢奥氏体晶粒长大行为。

It was reported in previous studies that the growth of austenite was inhibited by the pinning effect of Nb-containing precipitates and the solute-dragging effect of solute Nb.The effect of Nb on austenite grain growth of high-carbon steel was investigated by laser scanning confocal microscope(LSCM).Microstructure evolution during heating process of the tested steel was observed by in-situ observation.The results show that even without the pinning effect of Nb-containing precipitates(at high temperatures),Nb can hinder the growth of austenite grains due to the solute-dragging effect of Nb.Two models were used to fit the austenite grain growth process,and the Beck growth models of Nb microalloyed high-carbon steels at different heating temperatures were established.The austenite grain growth kinetics model considering the influence of heating temperature and holding time can accurately predict the austenite grain growth process of Nb microalloyed high-carbon steels.