Effect of Ce on the cleanliness, microstructure and mechanical properties of high strength low alloy steel Q690E in industrial production process

  • Hao Wang
  • Yan-ping BaoEmail author
  • Ming Zhao
  • Min Wang
  • Xiao-ming Yuan
  • Shuai Gao


In order to improve the strength and toughness of Q690E steel sheets, the effect of rare earth element Ce on the strength and toughness of Q690E steel was studied by means of transmission electron microscopy, scanning electron microscopy, and metallographic microscope. The results showed that the addition of Ce in steel limited the combination of S with Mn and Ca, transformed Al2O3 inclusion into spherical CeAlO3 inclusion, and modified the precipitate form of some composite inclusions of TiN and sulfide oxides into TiN precipitation alone. The inclusions were spheroidizing. The size of inclusions was decreased from 3–5 μm to 1–2 μm, and the distribution was dispersed. Ce played a role in purifying molten steel through desulphurization and deoxidization. Meanwhile, the addition of Ce in steel effectively increased the nucleation particles in the liquid phase, improved the nucleation rate, enlarged the equiaxed grain refinement area, and limited the development of columnar crystals. The average grain size of slab decreased from 45.76 to 35.25 μm, and the proportion of large grain size (> 50 μm) decreased from 40.41% to 23.74%. The macrostructural examination of slab was improved from B0.5 to C2.0, which realized the refinement of the solidified structure and reduced the banded structure of hot rolled plate. In addition, due to the inheritance of refined structure in the upstream, the recrystallization of deformed austenite and the growth of grain after recrystallization were restrained, and a refined tempered sorbite structure was obtained. When rare earth element Ce was added, the width of the martensite lath bundle was narrowed from about 500 nm to about 200 nm, which realized a remarkable grain refinement strengthening and toughening effect. Mechanical properties such as tensile, yield, and low-temperature impact toughness were significantly improved.


rare earth HSLA steel inclusion structure grain refinement strengthening 


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This research was financially supported by National Natural Science Foundation of China (No. 51774031) and Open Project of State Key Laboratory of Advanced Special Steel, Shanghai University (SKLASS 2017-12).


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Copyright information

© University of Science and Technology Beijing and Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Hao Wang
    • 1
    • 2
  • Yan-ping Bao
    • 1
    Email author
  • Ming Zhao
    • 3
  • Min Wang
    • 1
  • Xiao-ming Yuan
    • 2
  • Shuai Gao
    • 1
  1. 1.State Key Laboratory of Advanced MetallurgyUniversity of Science and Technology BeijingBeijingChina
  2. 2.Technical Center of Inner Mongolia Baotou Steel Union Co., Ltd.BaotouChina
  3. 3.The Rare Earth Steel Plates Plant of Baotou Iron and Steel Co., Ltd.BaotouChina

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