MnS凝固析出之后生长行为的实验研究及数值解析

The present MnS growth models, were established based on collisions, gatherings, and growths of the solute elements in the liquid phase, which are seriously different from those occurred in the mushy or solid-phase zone of end-solidification under actual conditions. Additionally, few reliable experiments and methods have been conducted to verify those models so that it is hard to accurately find a suitable model to describe its growth behavior. In the present proposal, the thermal-physical experiments of growth behavior of MnS in sulfur-bearing steels during solidification will be performed by utilizing a self-designed constrainted dendrite growth machine, where it is possible to quench the samples into Ga-In liquid metal. With this method one can obtain the features of in-situ morphology of MnS at solidification front and solidification zone, and further to explore the effects, including temperature gradient and soaking time, on the growth behaviors of MnS after solidification and precipitation. On the other hand, the growth behavior of sulfide will also be verified using various melting-solidification-heat preservation experiments with small sulfur-bearing steels. On the basis of our self-developed numerical model on segregation and coupled precipitation during solidification, the growth model of MnS will be established and finally to deduce the characteristics and laws of growth behavior of MnS after solidification and precipitation. The main scientific merit of this research is to lay theoretical foundation for establishing a process regulation of the sulfur-bearing special steel.

现有的MnS生长模型均为基于液相环境的溶质元素碰撞聚集长大模型，与MnS在凝固末期糊状区或固相区长大的实际环境存在较大差异，加之缺乏有效的实验验证手段，现有MnS生长模型、生长公式不能很好地诠释含硫钢中MnS的生长行为。本申请依托本中心自主研发的凝固枝晶生长仪和垂直定向凝固生长仪，开展含硫钢体系凝固过程MnS生长行为的热态实验，借助镓铟金属池对试样实时淬火，保留MnS在凝固前沿、已凝固区的原位形貌特征，探讨温度梯度、温度、保温时间、冷速等因素对MnS凝固析出之后生长行为的影响规律；借助含硫钢小钢锭不同热履历的熔炼-凝固-保温实验，对硫化物的生长行为进一步验证，用数据回归的方法得到MnS生长的经验公式；在本课题组开发的凝固过程偏析耦合析出数值模型基础上，采用数值解析的方法建立MnS的生长模型，总结MnS凝固析出之后生长行为的规律，为含硫特殊钢工艺规程的制定奠定理论基础。

本基金从MnS在含硫特殊钢的析出与长大行为研究入手，采用热态实验与数值解析相结合的方法进行了硫化物析出之后生长行为及溶质元素偏析行为的研究，解析MnS的长大机理及其影响因素。研究成果包括：（1）解析含硫特殊钢中MnS凝固析出之后的生长行为，以及温度、时间、温度梯度等因素对其生长行为的影响规律；（2）在数据回归基础上开发MnS生长模型，分析了含硫钢连铸坯中MnS在不同位置处、不同热履历下的生长行为、硫化物空间形态特征及分布规律；（3）用数值方法建立MnS生长模型，并编制为软件，诠释MnS的生长行为的规律；（4）基于MnS空间形貌及凝固析出时机，将MnS分为近球状、棒（枝）状、链状、团簇状、片状、多面体状、八面体状、聚集状、不规则状九类，解析了每类形成条件及析出时机，为硫化物的调控奠定理论基础。本基金共发表学术论文47篇，其中第一致谢30篇（SCI论文7篇，中文核心论文23篇），第二致谢发表论文：15篇（SCI论文6篇，中文核心论文9篇），第3、第4致谢各一篇；项目获软件著作权4项，培养博士后1名，博士3名，硕士生10名。