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<p>In the present study, the influence of Zr content on the nano-sized precipitate, austenite grain and low-temperature impact toughness (LTIT) in the heat-affected zone (HAZ) of Mg–Ca–Zr deoxidized steel subjected to the high heat input welding (HHIW) at 400&#xa0;kJ/cm is investigated. Two steels with 0.008 wt pct (80Zr) and 0.035 wt pct (350Zr) Zr were compared. In 80Zr steel, the nano-sized precipitates are finer, with an average size of 209&#xa0;nm and a higher number density of 38.2/<i>μ</i>m<sup>2</sup>. These nano-sized precipitates are composed of (Mg,Ti,Zr)O–TiN–Zr(C,N). In contrast, the 350Zr steel contains coarser precipitates averaging 295&#xa0;nm in size and exhibiting a lower number density of 17.3/<i>μ</i>m<sup>2</sup>, which is attributed to the excessive Zr content. These precipitates are primarily composed of Zr(C,N). The finer and denser (Mg,Ti,Zr)O–TiN–Zr(C,N) precipitates in 80Zr steel can effectively pin austenite grain boundaries, limiting austenite grain growth to 320&#xa0;<i>μ</i>m compared to 571&#xa0;<i>μ</i>m in 350Zr steel. Consequently, the 80Zr steel exhibits better LTIT at −&#xa0;40&#xa0;°C, achieving the impact energy of 214&#xa0;J compared to merely 6&#xa0;J for the 350Zr steel. These improvements are primarily attributed to the refined grain size caused by the finer size and higher number density of nano-sized precipitates in the 80Zr steel.</p>

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Zr-Induced Deterioration of Impact Toughness in the HAZ of Mg–Ca–Zr Deoxidized Steel During HHIW: Role of Nano-sized Precipitate Coarsening and Austenite Grain Growth

  • 期刊论文

  • 发表日期：

    2026年5月22日

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  • Yanli Chen,
  • Jian Yang,
  • Yinhui Zhang,
  • Liang Wang,
  • Yuqi Zhang

摘要

In the present study, the influence of Zr content on the nano-sized precipitate, austenite grain and low-temperature impact toughness (LTIT) in the heat-affected zone (HAZ) of Mg–Ca–Zr deoxidized steel subjected to the high heat input welding (HHIW) at 400 kJ/cm is investigated. Two steels with 0.008 wt pct (80Zr) and 0.035 wt pct (350Zr) Zr were compared. In 80Zr steel, the nano-sized precipitates are finer, with an average size of 209 nm and a higher number density of 38.2/μm2. These nano-sized precipitates are composed of (Mg,Ti,Zr)O–TiN–Zr(C,N). In contrast, the 350Zr steel contains coarser precipitates averaging 295 nm in size and exhibiting a lower number density of 17.3/μm2, which is attributed to the excessive Zr content. These precipitates are primarily composed of Zr(C,N). The finer and denser (Mg,Ti,Zr)O–TiN–Zr(C,N) precipitates in 80Zr steel can effectively pin austenite grain boundaries, limiting austenite grain growth to 320 μm compared to 571 μm in 350Zr steel. Consequently, the 80Zr steel exhibits better LTIT at − 40 °C, achieving the impact energy of 214 J compared to merely 6 J for the 350Zr steel. These improvements are primarily attributed to the refined grain size caused by the finer size and higher number density of nano-sized precipitates in the 80Zr steel.