微细夹杂物弥散复合析出及晶内铁素体形核生长与形态控制研究

Using microinclusions to improve the comprehensive performance of steel is a hotspot research in ferrous metallurgy. The key problems of inclusion metallurgy are how to disperse microinclusions with suitable grain size and types, promoting the precipitation of composite inclusions in the process of solidification, based on this, intragranular ferrite nucleation, growth and morphology control are the key problems of inclusions metallurgy. This research revise the Stokes formula through the study on inclusions such as the shape coefficient, effect of wettability on the floating and removal process,in order to explore the wetting dispersing mechanism of microinclusoins. This research also build a theory based on two dimensional mismatch theory of crystal to reveal the nucleation and growth of sulfide, carbon nitride particle on oxide particles,also to reveal thermodynamic and kinetic mechanism of induction on intragranular ferrite. By serial section and 3D image reconstruction method, analyze the intragranular ferrite growth form under different cooling conditions, and explore the morphology control mechanism of acicular ferrite and lath ferrite. The results of this study can not only reveal the formation mechanism of intragranular ferrite, improve the metallurgical theory of inclusions,but also can affected zone refining of ship steel plate under welding in large line energy,and have important application value to develop high quality non tempered steel and pipeline steel.

利用微细夹杂物粒子改善钢材的综合性能是当前钢铁冶金领域研究的热点，如何在钢液中弥散分布适宜粒径与种类的微细夹杂物，凝固过程中促进复合夹杂物的析出，以此为基底诱导晶内铁素体形核、生长与形态控制是夹杂物冶金的关键问题。本课题通过研究夹杂物的形状系数、润湿性能对上浮与去除的影响，修正Stokes公式，探究微细夹杂物的润湿分散机理；建立基于晶格生长的二位错配度理论，揭示硫化物、碳氮化物粒子在氧化物粒子上形核、生长及诱导界内铁素体的热力学及动力学机理；采用连续切片与三维图像重构的方式，分析不同冷却条件下晶内铁素体的生长形态，探究针状铁素体与板条状铁素体的形态控制机理。本研究成果不仅可以揭示晶内铁素体的形成机理，完善夹杂物冶金理论，而且在大线能量焊接用船板钢热影响区组织细化，高品质非调制钢、管线钢的开发上具有重大的应用价值。

借助PIV测速装置与高速摄像仪，测定不同粒径、不同形状、不同润湿性能的固态（液态）粒子在溶液中上浮、聚集、去除特性，修正了stokes上浮公式，并结合施加电磁场的高温共聚焦显微镜原位观测，揭示了微细粒子在钢液中的弥散分布机理；基于晶格生长的二位错配度理论，分析了氧化物、硫化物、碳化物和氮化物等面心立方晶系（FCC）和六方晶系（HCP）为基底形核析出铁素体时的错配度，并建立了球形、三棱锥形夹杂物为基底诱导复合夹杂物析出的动力学模型，揭示了硫化物、碳氮化物粒子在氧化物粒子上形核、生长及诱导界内铁素体的热力学及动力学机理；借助高温真空感应炉冶炼、连续切片与三维图像重构的方式、高温共聚焦显微镜的原位观测，分析不同微细夹杂物在不同冷却条件下诱导出铁素体三维形态以及晶内铁素体与夹杂物之间的关系，系统揭示微细夹杂物诱导晶内铁素体形核生长机理及形态控制机理。通过这些研究，为大线能量焊接用钢、高品质非调质钢、管线钢的开发提供理论基础。