增氢析氢法钢中夹杂物深度去除基理研究

Hydrogen absorbing followed by vacuum treatment is proposed as a new method in this project to meet an urgent need for advanced inclusion removal in high quality steels. Owing to the large diffusion coefficient of hydrogen in molten steel, advanced inclusion removal is achieved by generating fine dispersed hydrogen bubbles on inclusions which act as the nuclei of heterogeneous nucleation. However, there are few fundamental researches for the new method. Combining with the relevant researches on the formation of fine bubbles and new phases in the fields of mineral, metallurgy, materials and chemical engineering, the mechanism of advanced inclusion removal by hydrogen absorbing and releasing and its regulation mechanism is thoroughly studied by using water modeling, mathematical modeling, high temperature experiments and industrial tests. The studies will focus on: 1) nucleation thermodynamics and growth kinetics of a single hydrogen bubble in static molten steel, nucleation kinetics for bubble segregation in a micro unit molten steel; 2) characterization of size and density distribution of hydrogen bubbles and their behaviors, including nucleation, growth, collision, floatation and annihilation, in the macro-scale moving molten steel in vacuum refining reactors; 3) mechanism regulation, thermodynamics and kinetics of advanced inclusion removal by fine hydrogen bubbles in the molten steel. The project is aimed at providing theoretical basis for the research and development of advanced inclusion removal technology by fine hydrogen bubbles as well as other types of fine bubbles and enriching fundamental researches on bubble metallurgy and secondary refining.

面对我国优特钢夹杂物深度去除的迫切需求，本项目提出了将钢液增氢后再真空处理，利用氢扩散系数大特点，借助钢中夹杂物的异质形核作用，在钢中析出弥散微小氢气泡，利用微小气泡优异的夹杂物去除作用，实现夹杂物深度去除新方法，但相关基础研究缺乏。结合选矿、化工、材料和冶金领域微小气泡及新相生成研究相关理论和方法，综合采用水模、数模、高温实验室实验和工业实验，深入研究增氢析氢法钢中夹杂物深度去除机理和调控机制。主要研究目标：1）揭示静态钢液内部单个氢气泡形核热力学和长大动力学、单位体积钢液微元内氢气泡形核动力学；2）解析真空精炼反应器中大尺度运动钢液中氢气泡生成、碰撞、上浮、湮灭等析出相关行为与气泡尺寸和密度分布特征；3）阐明钢液中微小氢气泡去除夹杂物热力学和动力学及调控机制。为增氢析氢法钢中夹杂物深度去除技术及其他微小气泡去除夹杂物技术研发提供理论基础，丰富气泡冶金及炉外精炼基础研究。

增氢析氢法生成微小气泡深度去除钢中夹杂物技术，利用氢扩散系数大、钢液增氢和脱氢动力学良好的特点；首先向钢液快速增氢，然后再对增氢钢液进行真空析氢处理；借助钢中夹杂物的异质形核作用，在钢中析出弥散微小氢气泡；利用微小气泡优异的夹杂物去除作用，实现夹杂物深度去除。项目针对钢液中气泡形核析出、运动与演变、气泡尺寸和密度分布、气泡去除夹杂物关键基础问题进行系统深入研究。.分析了5个代表性钢种增氢热力学曲线，实验验证了热力学计算。测试了X17CrNi16-2不锈钢增氢析氢动力学曲线，分析表明高氢钢液析氢反应存在钢液表面向真空环境析氢和钢液内部析出细小氢气泡两种模式；钢液增氢析氢速度快，较增氮析氮法技术具有动力学优势。.建立了钢液/H2体系析气过程中气泡凸球面形核热力学模型；1873 K钢液中，溶气压力分别为0.05 MPa、0.1 MPa、0.2 MPa、真空处理压力均为100 Pa的条件下，气泡形核深度范围分别为0-0.375 m、0-1.035 m、0-2.444 m。.建立了钢液/H2饱和体系析气过程中气泡生长与上浮动力学模拟研究理想水模型，采用高速摄影仪观察了水溶液中过饱和CO2气泡形核与长大过程，构建了气泡长大和上浮动力学模型。建立了VD精炼钢中氢气泡析出水模型模拟研究系统，观察了气泡析出、运动及湮灭行为现象。.通过快速凝固试样方法，在真空悬浮炉增氮析氮实验和管式炉增氢析氢实验中，均分别观察到了形貌相近的氮气泡和氢气泡，气泡尺寸介于2-20μm。.应用水模型结合库尔特计数器进行了气泡去除夹杂物模拟研究，模拟研究了夹杂物数量、尺寸和润湿角对夹杂物去除动力学的影响，结果表明模拟粒子尺寸越大，气泡更容易生成，大尺寸粒子有更好的去除效果。.10㎏级实验研究和工业应用试验研究证实该技术能够有效去除钢中夹杂物，钢中10 μm以下的显微夹杂物去除效果显著，钢中全氧显著下降。.研究揭示了钢液中微小气泡析出、演变、去除夹杂物等行为特征，为溶气法生成微小气泡深度去除夹杂物技术研发提供了理论依据。