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<p>This study investigates the synchronous modification behavior and mechanisms of TiN and MnS inclusions in BT700L automotive beam steel through trace rare earth La alloying. The results demonstrate that without La addition, TiN and Al<sub>2</sub>O<sub>3</sub>-TiN inclusions exhibit sharp edges and large sizes. Upon La treatment, TiN transforms into LaAlO<sub>3</sub>-TiN composite phases with reduced dimensions. Sulfur-containing inclusions transition from MnS and Al<sub>2</sub>O<sub>3</sub>-MnS to LaAlO<sub>3</sub>-MnS and LaAlO<sub>3</sub>-TiN-MnS composites, maintaining a spherical shape but with significantly refined sizes. Quantitative analysis reveals that La addition reduces the average size of TiN inclusions from 3.41 to 2.72&#xa0;μm and MnS-type inclusions from 1.88 to 1.5&#xa0;μm. The proportion of MnS&#xa0;&gt;&#xa0;2&#xa0;μm decreases from 28 to 11&#xa0;pct, while fine MnS (0.5–1&#xa0;μm) increases from 16 to 43&#xa0;pct. Mechanistic studies indicate that LaAlO<sub>3</sub>, formed via La-Al complex deoxidation, serves as heterogeneous nucleation sites, effectively suppressing excessive aggregation of Ti, N, Mn, and S elements, thereby promoting finely dispersed LaAlO<sub>3</sub>-TiN and LaAlO<sub>3</sub>-MnS composite inclusions. This work elucidates the synergistic modification mechanism of La on TiN and MnS, providing both theoretical insights and technical solutions for industrial applications of trace rare earths to optimize inclusion control in automotive beam steels.</p>

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Study on the Synchronous Modification of TiN and MnS Inclusions in BT700L Automotive Beam Steel by Trace Rare Earth La

  • 期刊论文

  • 发表日期：

    2025年7月18日

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  • Fushuo Chen,
  • Shuang Liu,
  • Jun Peng,
  • Fan Yang,
  • Lixia Liu

摘要

This study investigates the synchronous modification behavior and mechanisms of TiN and MnS inclusions in BT700L automotive beam steel through trace rare earth La alloying. The results demonstrate that without La addition, TiN and Al2O3-TiN inclusions exhibit sharp edges and large sizes. Upon La treatment, TiN transforms into LaAlO3-TiN composite phases with reduced dimensions. Sulfur-containing inclusions transition from MnS and Al2O3-MnS to LaAlO3-MnS and LaAlO3-TiN-MnS composites, maintaining a spherical shape but with significantly refined sizes. Quantitative analysis reveals that La addition reduces the average size of TiN inclusions from 3.41 to 2.72 μm and MnS-type inclusions from 1.88 to 1.5 μm. The proportion of MnS > 2 μm decreases from 28 to 11 pct, while fine MnS (0.5–1 μm) increases from 16 to 43 pct. Mechanistic studies indicate that LaAlO3, formed via La-Al complex deoxidation, serves as heterogeneous nucleation sites, effectively suppressing excessive aggregation of Ti, N, Mn, and S elements, thereby promoting finely dispersed LaAlO3-TiN and LaAlO3-MnS composite inclusions. This work elucidates the synergistic modification mechanism of La on TiN and MnS, providing both theoretical insights and technical solutions for industrial applications of trace rare earths to optimize inclusion control in automotive beam steels.