ABSTRACT In this paper, the austenite grain growth behaviour of 12Cr ultra-super-critical (USC) rotor steel was investigated by a series of heat treatments. The heat treatments at heating temperatures of 900°C–1250°C and holding time of 1 h–20 h were conducted in an electric box-type heating furnace. Experimental results showed that the sizes of austenite grain were affected by heating temperatures and holding time, and heating temperature was the dominant factor. In addition, the grain growth rate changed significantly before and after the turning points of 1050°C and 1250°C. Meanwhile, an austenite grain growth mathematical model was established at different heating temperature stages, and possession of the capability to accurately predict austenite grain size was confirmed. Furthermore, the microstructure of austenite grain in the heating process was observed by optical microscope (OM) and transmission electron microscopy (TEM), which revealed the mechanism of austenite grain growth. Analysis indicated that the change of quantity of precipitate particles with increasing heating temperature was the main reason for the difference in austenite grain growth.

中文翻译：

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12Cr超超临界转子钢奥氏体晶粒长大动力学及晶粒长大机理

摘要 本文通过一系列热处理研究了 12Cr 超超临界 (USC) 转子钢的奥氏体晶粒长大行为。加热温度为 900°C~1250°C，保温时间为 1 h~20 h，在电箱式加热炉中进行热处理。实验结果表明，奥氏体晶粒尺寸受加热温度和保温时间的影响，加热温度是主导因素。此外，在1050°C和1250°C转折点前后，晶粒长大速率发生了显着变化。同时，建立了不同加热温度阶段的奥氏体晶粒长大数学模型，证实了其具有准确预测奥氏体晶粒尺寸的能力。此外，通过光学显微镜（OM）和透射电子显微镜（TEM）观察加热过程中奥氏体晶粒的显微组织，揭示了奥氏体晶粒长大的机理。分析表明，随着加热温度的升高，析出物颗粒数量的变化是奥氏体晶粒长大差异的主要原因。