【摘要】 为了研究铸坯在连铸过程中所得铸态组织的偏析规律及其对材料性能的影响，采用分形理论和灰度分析方法对铸坯凝固组织和碳偏析形貌特征进行了定量分析。结果表明，灰度分析法得到的局部碳元素相对质量分数分布与真实铸坯对应良好，并且通过对比电子探针与灰度分析的结果，证明了该方法的有效性。由计盒维数法得到的分形维数可以定量表征凝固组织和碳偏析形貌的自相似复杂程度，凝固组织分形维数从铸坯的宽度边部到中心先减小再增大，从坯壳表面到厚度中心逐渐增大。碳偏析形貌分形维数在厚度方向上的变化更明显，从坯壳表面到厚度中心逐渐减小，两者的分形维数具有一定的负相关关系。在薄板坯连铸过程中选择较高的拉速有利于得到碳元素分布均匀、偏析点分布弥散、凝固组织更加稳定的铸坯。更多还原

【Abstract】 The as-casting microstructure obtained during the continuous casting process is a key factor due to its effect on the as-cast material properties. The objective of this work is focused on the casting microstructure of S50C steel thin slab in two different casting speeds, fractal theory and grayscale analysis method are introduced to have a quantitatively analysis in term of the solidification structure and morphology of carbon segregation. The results show that the C element relative content distribution calculated by grayscale analysis method can correspond well with the characteristics of the casting microstructure. At the same time, the effectiveness of the proposed method is verified by comparing the results of the electron probe and grayscale analysis method. In addition, the fractal dimension calculated by box-counting dimension method can be well used as a reliable parameter to quantitatively characterize the degree of self-similarity of solidification structures. The fractal dimension of solidification structure first decreases and then increases from the edge to the center of the broad surface width direction of the billet, and gradually increases from the surface of the billet to the thickness center. The fractal dimension of carbon segregation morphology changes more obviously in the direction of thickness and gradually decreases from the surface to the thickness center. The fractal dimension of solidification structure and carbon segregation morphology has a certain negative correlation. Based on the above results, in the process of thin slab casting and direct rolling, higher drawing speed is beneficial to obtain the billet with uniform distribution of carbon elements, dispersed segregation points and stable solidification structure.更多还原