In the present study, coarse grain heat affected zone (CGHAZ) of the pearlite railway steel was thermally simulated at different cooling rates ranging from 1 to 4 °C/s to in–situ observe the austenite and pearlite formation by high temperature laser scanning confocal microscopy (HT–LSCM). During heating, austenite nucleation was started at 811 °C at fast heating rate of 9.1 °C/s. Pearlite was completely decomposed into austenite in 21 s at 1005 °C. At peak temperature of 1300 °C, austenite was composed of two microstructural compositions, i.e., high-carbon austenite and low-carbon austenite. Homogenization of austenite and formation of grain boundaries were continued even during cooling when the temperature was above the pearlite transformation. During cooling, Low-carbon austenite has increased the pearlite transformation by providing additional nucleation sites. By increasing the cooling rate from 1 to 4 °C/s, the pearlite transformation temperature was reducing, pearlite growth rate was increasing, and pearlite interlamellar spacing was becoming narrow, respectively. Mathematical interpretation of pearlite growth rate was developed that gives true changing behavior of pearlite growth rate with the varying cooling rate. Present study provides direct observation and unique quantitative information of austenite and pearlite formation in CGHAZ in pearlite railway steel.

在本研究中，以1至4°C / s的不同冷却速率对珠光体铁路钢的粗晶粒热影响区（CGHAZ）进行了热模拟，并通过高温激光扫描共聚焦原位观察奥氏体和珠光体的形成显微镜检查（HT–LSCM）。在加热过程中，奥氏体在811°C以9.1°C / s的快速加热速率开始形核。珠光体在1005°C下在21 s内完全分解为奥氏体。在1300℃的峰值温度下，奥氏体由两种显微组织组成，即高碳奥氏体和低碳奥氏体。即使在温度高于珠光体转变温度的冷却过程中，奥氏体的均质化和晶界的形成仍在继续。冷却期间 低碳奥氏体通过提供其他成核位置来增加珠光体的转变。通过将冷却速度从1°C / s增加到4°C / s，珠光体转变温度降低，珠光体生长速率提高，珠光体层间间距变窄。发展了对珠光体生长速率的数学解释，它给出了随着冷却速率的变化珠光体生长速率的真实变化行为。本研究为珠光体铁路钢中CGHAZ中的奥氏体和珠光体形成提供了直接观察和独特的定量信息。发展了对珠光体生长速率的数学解释，它给出了随着冷却速率的变化珠光体生长速率的真实变化行为。本研究为珠光体铁路钢中CGHAZ中的奥氏体和珠光体形成提供了直接观察和独特的定量信息。发展了对珠光体生长速率的数学解释，它给出了随着冷却速率的变化珠光体生长速率的真实变化行为。本研究为珠光体铁路钢中CGHAZ中的奥氏体和珠光体形成提供了直接观察和独特的定量信息。