Journal Article

Three-Dimensional Characterization of Defects in Continuous Casting Blooms of Heavy Rail Steel Using X-ray Computed Tomography

Xunhui, Lei, Zhang Yuexin, Gao, Yuan, Yang, Wen, Liu, Nan, Zhang, Lifeng, Liu, Yubao, Cui Lingxiao

2021

Overview

Three-dimensional characterization of defects in continuous casting blooms of a heavy rail steel with different electromagnetic stirring intensities at the solidification end, also named final electromagnetic stirring, was performed employing a laboratory-based X-ray computed tomography to evaluate the effect of final electromagnetic stirring on the internal quality of blooms. The three-dimensional distribution and morphology of defects including porosities and oxide inclusions in blooms were characterized. The amount, size and shape complexity of defects increased gradually from the loose-side surface to the center of blooms. The total volume fraction of defects was 5265 and 3942 ppm when the current of final electromagnetic stirring was 200 and 300 A, respectively. The sphericity of defects varied from 0.1 to 0.75, and the equivalent spherical diameter varied between 20 and 450 μm. Most defects with a sphericity > 0.6 were nearly spherical and were assumed to be oxide inclusions. The volume fraction of both porosities and inclusions was small in the chilled layer and the columnar crystal zone and then increased rapidly toward the equiaxed zone. Increasing the current of F-EMS from 200 to 300 A significantly decreased the volume fraction of porosities in the center of the bloom from 2906 to 1873 ppm. It could also decrease the volume fraction and average diameter of oxide inclusions in the bloom by reducing the number of large inclusions.

• Publisher: Springer Nature B.V
• Subject: Blooms (metal) / Casting defects / Chill casting / Computed tomography / Continuous casting / Crystal defects / Diameters / Electromagnetic stirring / Levitation casting / Morphology / Nonmetallic inclusions / Rail steels / Shape / Solidification / Tomography