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<p>The elements segregation and abnormal microstructure formation in the center of Mn-Cr alloyed steel thick slab and hot rolled sheet were investigated. The results showed that the abnormal microstructure bainite clusters appeared in the center of the thick slab, which were caused by severe enrichment of C, Mn and Cr elements with microsegregation index of 5.58, 2.43 and 5.21, respectively. The <i>WIRS-VB</i> microsegregation model indicates that the elements concentration in the interdendritic region increases sharply as the solid fraction exceeds 0.9. The severe enrichment of C, Mn and Cr elements promotes the transformation of undercooled austenite to bainite at a lower cooling rate of 0.42&#xa0;°C/s in the center of the thick slab based on the TTT curves and experimental results. After hot rolling, the microsegregation index of C, Mn and Cr elements in the center of the rolled sheet reduced to 2.24, 1.60 and 3.32, respectively. Meanwhile, the bainite clusters transformed into banded structures bainite with a microhardness of 483.64 HV, which is significantly higher than the matrix with a value of 164.42 HV. This study reveals the correlation between segregation and microstructure, providing a new perspective for quality control of thick steel slab and sheet.</p> Graphical Abstract <p></p>

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Mechanism of Mn-Cr Segregation Induced Abnormal Microstructure Formation in Thick Steel Slab and Hot-Rolled Sheet

  • 期刊论文

  • 发表日期：

    2025年9月12日

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  • Zichao Wang,
  • Jiang Du,
  • Jie Zeng,
  • Wanlin Wang,
  • Qin Gao,
  • Yan Yang,
  • Longyun Xu,
  • Xiong Xiao

摘要

The elements segregation and abnormal microstructure formation in the center of Mn-Cr alloyed steel thick slab and hot rolled sheet were investigated. The results showed that the abnormal microstructure bainite clusters appeared in the center of the thick slab, which were caused by severe enrichment of C, Mn and Cr elements with microsegregation index of 5.58, 2.43 and 5.21, respectively. The WIRS-VB microsegregation model indicates that the elements concentration in the interdendritic region increases sharply as the solid fraction exceeds 0.9. The severe enrichment of C, Mn and Cr elements promotes the transformation of undercooled austenite to bainite at a lower cooling rate of 0.42 °C/s in the center of the thick slab based on the TTT curves and experimental results. After hot rolling, the microsegregation index of C, Mn and Cr elements in the center of the rolled sheet reduced to 2.24, 1.60 and 3.32, respectively. Meanwhile, the bainite clusters transformed into banded structures bainite with a microhardness of 483.64 HV, which is significantly higher than the matrix with a value of 164.42 HV. This study reveals the correlation between segregation and microstructure, providing a new perspective for quality control of thick steel slab and sheet.

Graphical Abstract