摘要
钢中簇状非金属夹杂物由大量细小、分布均匀的固态夹杂物碰撞聚合而成,并且具有不规则分形的特征,因此,可以采用分形维数对其形貌进行定量描述。为了定量化描述钢中非金属夹杂物的形貌,系统整理了簇状夹杂物的分形维数研究。首先,总结了分形维数的定义、不同分形维数的计算方法、三维分形维数(D3)的测量方法以及三维和二维分形维数之间相互转化的计算模型。其次,分析了影响夹杂物分形维数大小的主要因素,包括夹杂物成分和计算误差。在计盒维数计算方法中,计算误差来源于覆盖盒子最大尺寸的选取,当0.25≤ε/d_(max)≤1(ε为覆盖盒子的尺寸,d_(max)为夹杂物最大直径)时,夹杂物分形维数计算误差较小。最后,总结了分形维数在夹杂物研究上的应用。不规则簇状夹杂物在钢液中的理论上浮速度可以通过分形维数进行计算,且夹杂物的分形维数越大,夹杂物的上浮速度越大。分形维数可以用于簇状夹杂物碰撞聚合形成的聚集体形貌研究。分形理论发展出的有限扩散凝聚模型(DLA模型)可用于钢中夹杂物聚合的模拟研究,结果表明,随着粒子释放点到种子之间距离的减小、粒子尺寸的增加以及种子尺寸的增加,夹杂物聚集度增加,解释了塞棒或水口结瘤的原因。研究结果为深入研究钢中簇状夹杂物的碰撞聚合过程对其从钢液中上浮去除和有效提升钢水的洁净度提供了一定参考。
Large clusters in steel are formed by collision and aggregation of fine and uniformly distributed solid inclusions,which have irregular fractal characteristics.Therefore,the fractal dimension can be used to quantitatively describe the morphology of inclusions.In order to describe the morphology of non-metallic inclusions in steel quantitatively,the research on the fractal dimension of clustered inclusions is organized.Firstly,the definition and different calculation methods of the fractal dimension,the measurement method of three-dimensional fractal dimension(D3),and the models for the transformation between the three-dimensional and two-dimensional fractal dimensions are summarized.Secondly,the main factors affecting the fractal dimension of inclusions are analyzed,including the composition of inclusions and the calculation error.The fractal dimension of large clusters is about 1.7-1.8.In the process of boxcounting dimension calculation,the calculation error comes from the selection of the maximum size of the covering box.When 0.25≤ε/d_(max)≤1,the calculation error of inclusion fractal dimension is avoided.Finally,the application of fractal dimension in the study of inclusions is summarized.The theoretical floating velocity of irregular clusters in molten steel can be calculated by fractal dimension.The floating velocity of inclusions increases with the increase of fractal dimension.The fractal dimension can be used to study the morphology of aggregates formed by inclusions after collision and aggregation.Based on the development of fractal theory,the diffusion-limited aggregation model(DLA model)is proposed to simulate the aggregation of inclusions in steel.As the distance between the release point of particles and seeds decreases,the particle size increases,and the seed size increases,the aggregation degree of inclusion increases.The stopper or nozzle can be considered as large seeds,and inclusions are easy to gather on its surface,which cause the nozzle clogging.The stopper or nozzle clogging can be reduced by improving the wettability between the stopper and inclusions.The aggregated clusters inclusions are in a chain or more dispersed branched structure with the increase of aggregation ratio between the basic particles.The result provides guidance for researching into the collision and aggregation process of clustered inclusions,which facilitates removal fraction by floating to the surface of the molten steel,enhancing the cleanliness of the steel.
作者
陈洁冰
周秋月
张立峰
CHEN Jiebing;ZHOU Qiuyue;ZHANG Lifeng(School of Mechanical and Materials Engineering,North China University of Technology,Beijing 100144,China;School of Metallurgy and Ecological Engineering,University of Science and Technology Beijing,Beijing 100083,China)
出处
《中国冶金》
CAS
CSCD
北大核心
2024年第10期1-15,共15页
China Metallurgy
基金
国家重点研发计划资助项目(2023YFB3709900)
国家自然科学基金资助项目(U22A20171)。
关键词
分形维数
簇状夹杂物
计盒维数法
夹杂物上浮
碰撞聚合
fractal dimension
cluster inclusion
box counting dimension method
inclusion floatation
collision and aggregation
