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<p>Rack steel is a key material for constructing self-elevating offshore platforms, and as the thickness of steel plates continues to increase, increased requirements are placed on the steel’s hardenability. Boron is a key element in improving the hardenability of steels, but there are currently few reports on its role in rack steels. In this paper the influential mechanism of boron on the hardenability of A514Q Modified rack steel was investigated by conducting end quenching tests, establishing continuous cooling transformation (CCT) curves, and analyzing the grain boundary segregation behavior of boron. The results indicate that the 0.006 wt.% boron addition significantly improves the hardenability, reducing the critical cooling rate for martensitic transformation from 2 to 0.5&#xa0;°C·s<sup>-1</sup>. The boron is mainly enriched in the MA islands, especially those along prior austenite grain boundaries (PAGBs). Besides, the boron atoms are slightly segregated at matrix / MA islands interfaces. The PAGBs segregation of boron can be explained through non-equilibrium segregation mechanism. Analysis suggests that boron addition improves the hardenability of rack steels mainly because the segregation of boron at PAGBs decreases the grain boundary energy.</p>

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Influence of Boron on the Hardenability of Low Carbon Alloy Platform Steel

  • 期刊论文

  • 发表日期：

    2025年6月30日

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  • Guangdi Zhao,
  • Ximin Zang,
  • Bo Wang,
  • Jie Yang,
  • Lingzhong Kong,
  • Xue Li,
  • Xiaoyu Yao,
  • Zhenming Yu

摘要

Rack steel is a key material for constructing self-elevating offshore platforms, and as the thickness of steel plates continues to increase, increased requirements are placed on the steel’s hardenability. Boron is a key element in improving the hardenability of steels, but there are currently few reports on its role in rack steels. In this paper the influential mechanism of boron on the hardenability of A514Q Modified rack steel was investigated by conducting end quenching tests, establishing continuous cooling transformation (CCT) curves, and analyzing the grain boundary segregation behavior of boron. The results indicate that the 0.006 wt.% boron addition significantly improves the hardenability, reducing the critical cooling rate for martensitic transformation from 2 to 0.5 °C·s-1. The boron is mainly enriched in the MA islands, especially those along prior austenite grain boundaries (PAGBs). Besides, the boron atoms are slightly segregated at matrix / MA islands interfaces. The PAGBs segregation of boron can be explained through non-equilibrium segregation mechanism. Analysis suggests that boron addition improves the hardenability of rack steels mainly because the segregation of boron at PAGBs decreases the grain boundary energy.