Wang Jun, Liu Man, Wang Lifan, He Ping, Hu Haijiang, Xu Guang
The State Key Laboratory of Refractories and Metallurgy, Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081, China.
Materials (Basel). 2024 Jul 1;17(13):3236. doi: 10.3390/ma17133236.
Previous studies on the austenite grain growth were mostly based on a fixed temperature, and the relationship between the austenite grain and austenitizing parameters was fitted according to the results. However, there is a lack of quantitative research on the austenite grain growth during the heating process. In the present work, based on the diffusion principle of the controlled Ti microalloying element, the diffusion process of carbonitrides containing Ti during the heating process was analyzed. Combined with the precipitation model and the austenite growth model, the prediction model of austenite grain growth of Ti microalloyed steel during different heat treatment processes was established. The austenite grain size versus the temperature at four different heating rates of 0.5, 1, 10, 100 °C/s was calculated. The grain growth behavior of austenite during the heating process of Ti microalloyed steel was studied by optical microscope, scanning electron microscope and transmission electron microscope. The experimental data of the austenite grain size was in good agreement with the calculation by the proposed model, which provides a new idea for the prediction of austenite grain size in non-equilibrium state during the heating process. In addition, for Ti-containing microalloyed steels, the austenite grain size increased with the increasing heating temperature, while it changed little by further prolonging isothermal time after certain heating time, which was related to the equilibrium degree of the precipitation and the dissolution of Ti element. The austenite grain coarsening temperature of the tested Ti microalloyed steel was estimated within 1100~1200 °C.
以往关于奥氏体晶粒长大的研究大多基于固定温度，并根据结果拟合奥氏体晶粒与奥氏体化参数之间的关系。然而，对于加热过程中奥氏体晶粒长大缺乏定量研究。在本工作中，基于可控钛微合金化元素的扩散原理，分析了含钛碳氮化物在加热过程中的扩散过程。结合析出模型和奥氏体长大模型，建立了钛微合金钢在不同热处理工艺下奥氏体晶粒长大的预测模型。计算了在0.5、1、10、100℃/s四种不同加热速率下奥氏体晶粒尺寸与温度的关系。通过光学显微镜、扫描电子显微镜和透射电子显微镜研究了钛微合金钢加热过程中奥氏体的晶粒长大行为。奥氏体晶粒尺寸的实验数据与所提出模型的计算结果吻合良好，为预测加热过程中非平衡态奥氏体晶粒尺寸提供了新思路。此外，对于含钛微合金钢，奥氏体晶粒尺寸随加热温度的升高而增大，而在一定加热时间后进一步延长等温时间变化不大，这与钛元素析出和溶解的平衡程度有关。所测试的钛微合金钢的奥氏体晶粒粗化温度估计在1100~1200℃范围内。
