基于热膨胀法与相体积计算模型研究连铸坯冷却过程中奥氏体相变行为  

Investigation on austenite transformation in continuously cast steel based on dilatometry and the phase fraction model

作　　者：龙木军[1] 董志华[1] 陈登福[1] 张星[1] 盛俊豪[1] 陈春梅[1] 

机构地区：[1]重庆大学材料科学与工程学院,重庆400044

出　　处：《工程科学学报》2015年第4期441-446,共6页Chinese Journal of Engineering

基　　金：中央高校基本科研业务费资助项目(CDJZR12130037)

摘　　要：采用热膨胀仪测试研究了Q450NQR1钢连铸坯5℃·min-1及20℃·min-1冷却速率下的线性热膨胀(ΔL/L0)和热膨胀系数随温度的变化规律.在此基础上,建立了一种基于平均原子体积的相体积计算模型,量化研究了奥氏体相变过程中各相体积分数的变化规律,并在将计算结果与显微组织观察结果对比分析基础上,讨论了连铸冷却速率对铸坯奥氏体相变过程的影响.结果表明:该计算模型可以较为准确地描述铸坯的奥氏体相变过程,适用于多相连续析出相变;随着冷却速率的增大,铸坯热膨胀曲线中对应于铁素体和珠光体析出的两个变化峰向低温区移动,峰值明显增大;冷却速率由5℃·min-1上升至20℃·min-1时,铁素体及珠光体起始析出温度分别降低约32℃和37℃,最终体积分数分别由0.894和0.106变为0.945和0.055.To understand the knowledge of liner thermal expansion and thermal expansion coefficient of Q450NQR1 casting steel, dilatometry experiments were performed at two different cooling rates of 5 ℃ ~ min 1 and 20 ℃ ~ min - 1. A mathematical model was de- veloped to quantitatively extract the kinetic information of austenite transformation based on the concept of average atomic volume. The model was verified by microstructure examinations, indicating that the model was appropriate to describe the behavior of austenite transformation and could be applied to multi-phase transformations during steel continuous casting. The influence of cooling rate on the austenite transformation was discussed with the model, it is found that, with increasing cooling rate, two peaks associated to the pre- cipitation of ferrite and pearlite on the thermal expansion coefficient curve shifted towards a lower temperature region with higher val- ues. As the cooling rate increases from 5 ℃ · min - 1 to 20 ℃ · min - l, the initial temperatures of ferrite and pearlite precipitation de- crease by 32 ℃ and 37 ℃, and the final volume fractions of ferrite and pearlite gradually change from 0. 894 and 0. 106 to 0. 945 and 0. 055, respectively.

关 键 词：连铸 奥氏体 相变 冷却速率 热膨胀 

分 类 号：TG142.1[一般工业技术—材料科学与工程]