不同温度下夹杂物特性的关联性研究

Control of inclusions in steel is the key to produce clean steel. So Scientific detection and analysis methods play important roles in the effective control of inclusions in steel. At present, detecting the inclusions directly in molten steel of high temperature can not be realized. It is a common way to detect inclusions of ingot which has cooled down to room temperature, however the characteristics of inclusions between room temperature and high-temperature molten steel are of difference considerably, causing deviation for analysis of inclusions. The project plans to adopt the means of thermodynamic model and mathematical simulation to study the relationship between inclusion composition and temperature, and to discuss the influences of inclusions precipitation, agggregation and grow up during colling and solidification process on the size, morphology, movement of inclusions. Then in order to observe different kinds of inclusions in entire processes consisting cooling, before and after solidification, CSLM will be employed. Finally the project will carry out some high-temperature experiments to research the formation mechanism of multiphase composite inclusions. Through the above research contents, the relationship between temperature and characteristics of inclusions can be revealed, meanwhile intrinsic relations of various inclusion characteristics under different temperatures can be established, which lay crucial theoretical foundation for further improving the accuracy of detection and analysis of non- metallic inclusions in steel.

钢中夹杂物的控制是洁净钢生产的关键，科学的夹杂物检测分析方法对钢中夹杂物的有效控制具有重要的作用。目前还不能直接对高温钢水中的夹杂物进行直接检测，通常用冷却到常温下钢锭中夹杂物的检测结果来代替，而常温下钢锭中夹杂物的特性与高温钢液中夹杂物的特性有较大的区别，给夹杂物的分析带来偏差。 本项目首先采用热力学模型和数学仿真模拟研究夹杂物的成分与温度的关系、钢液降温及凝固过程中夹杂物的聚集长大和析出对夹杂物尺寸的影响，然后利用高温共聚焦显微镜（CSLM）对降温、凝固过程以及凝固后冷却过程对不同种类夹杂物进行全程原位动态观察；最后通过高温试验研究多相复合夹杂物形成的机理。 通过上述研究获得温度对夹杂物特性影响的规律，建立不同温度下夹杂物特性之间的内在联系，为进一步提高钢中非金属夹杂物的分析和检测的准确性奠定理论基础。

常温下钢锭中夹杂物的特性与高温钢液中夹杂物的特性有较大的区别，给夹杂物的分析带来偏差，主要是因为在取样冷却过程试样中夹杂物尺寸、类型和形貌发生变化。本项目对钢液降温及凝固过程中夹杂物的聚集长大和析出对夹杂物尺寸的影响，由于温度和冷却条件的改变对单个的MnS夹杂物以及复合的MnS+Al2O3夹杂物特性变化影响较大，本项目重点研究了这两类夹杂物。.研究结果表明：（1）冷却速率从2.47K/s增至77.39K/s，MnS的尺寸从冷却速率从(8±0.5)μm降至(3±0.5)μm，随着冷却速率的增加，夹杂物析出长大的时间减少，硫化物的尺寸逐渐降低，单个的MnS逐渐变为球状，链状MnS密集程度显著减小，同时建立了冷却速率与MnS尺寸之间的关系，利于提高硫化物的检测效率；（2）通过捕获/推动的临界速率与Al2O3尺寸之间关系模型，得到当Al2O3夹杂物的尺寸小于临界尺寸时，Al2O3可以作为MnS析出的异质形核核心，研究表明小尺寸的Al2O3夹杂物可以被推至凝固前沿液相区，MnS以小尺寸Al2O3作为异质形核质点生成复合夹杂物。（3）S含量直接影响到MnS的析出量，对于包裹性夹杂物的包裹率影响较大，随着S含量的增加，包裹型夹杂物所占比例逐渐增加。（4）冷却速率对包裹型复合夹杂物的影响较小，然而，随着冷却速率的增加，钢样中Al2O3被MnS包裹形成的复合夹杂物的比例呈减少趋势。