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Open AccessArticle

The Significance of Central Segregation of Continuously Cast Billet on Banded Microstructure and Mechanical Properties of Section Steel

1
Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China
2
Department of Metallurgical and Materials Engineering, University of Texas EI Paso, EI Paso, TX 799968, USA
3
State Key Laboratory of Metal Materials for Marine Equipment and Applications, Anshan 114021, China
*
Author to whom correspondence should be addressed.
Metals 2020, 10(1), 76; https://doi.org/10.3390/met10010076
Received: 11 December 2019 / Revised: 26 December 2019 / Accepted: 26 December 2019 / Published: 2 January 2020
(This article belongs to the Special Issue High-Strength Low-Alloy Steels)
The solidification structure and segregation of continuously cast billets produced by different continuous casting processes are investigated to elucidate their effect on segregated bands in hot-rolled section steel. It suggested that segregated spots are mainly observed in the equiaxed crystal zone of a billet. The solidification structure is directly related to superheating and the intensities of secondary cooling. To a certain extent, the ratio of the columnar crystal increases with the increase of superheating and secondary cooling. Moreover, the number of spot segregations decreases with the decrease of the equiaxed crystal ratio. After hot rolling, the segregation spots are deformed to form segregated bands in steels. The severe segregation of Mn in segregated bands corresponds with that in the segregation spots. The elongation ratio and low temperature toughness deteriorate significantly by a high fraction of degenerate pearlite caused by central segregation. With a decrease of central segregation, the total elongation is increased by 10% and the ductile–brittle transition temperature (DBTT) is also reduced from −10 to −40 °C. According to the experimental results, columnar crystal in billets is preferred to effectively reduce the degree of central segregation and further improve low temperature toughness and the elongation ratio. View Full-Text
Keywords: continuous casting process; solidification structure; central segregation; banded microstructure; mechanical properties continuous casting process; solidification structure; central segregation; banded microstructure; mechanical properties
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Guo, F.; Wang, X.; Wang, J.; Misra, R.D.K.; Shang, C. The Significance of Central Segregation of Continuously Cast Billet on Banded Microstructure and Mechanical Properties of Section Steel. Metals 2020, 10, 76.

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