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<p>This paper presents a systematic investigation of the chain-like CaO–Al<sub>2</sub>O<sub>3</sub>–SiO<sub>2</sub>–MgO inclusions found on the surface of crankshaft journals, elucidating their formation mechanism. The inclusions within the defects consist of numerous individual low-melting-point oxides and exhibit a strong correspondence with those observed in the hot-rolled bars. Thermodynamic calculations reveal that the introduction of trace amounts of SiO<sub>2</sub> broadens the liquid-phase region of CaO–Al<sub>2</sub>O<sub>3</sub>–SiO<sub>2</sub>–MgO inclusions at steelmaking temperatures to a notable extent, markedly enhancing the proportion of the liquid phase at the onset of melting. Conversely, a relatively high SiO<sub>2</sub> content elevates the melting point of these inclusions. Moreover, unlike their solid counterparts, liquid inclusions in molten steel are less prone to agglomeration and flotation. A substantial number of small liquid inclusions become entrapped in the interdendritic regions during the solidification of continuous casting billets. The pushing of secondary dendrite arms promotes the accumulation of these liquid inclusions during subsequent solidification stages, ultimately giving rise to chain-like, large-size CaO–Al<sub>2</sub>O<sub>3</sub>–SiO<sub>2</sub>–MgO inclusions following hot forging.</p>

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Formation Mechanism of Chain-Like CaO–Al2O3–SiO2–MgO Large-Size Inclusions on the Surface of Crankshaft

  • 期刊论文

  • 发表日期：

    2025年8月11日

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  • Jian Zhao,
  • Jinlong Lu,
  • Guoguang Cheng,
  • Tao Zhang,
  • Guanbo Wang,
  • Hu Long,
  • Zhongzhong Xun

摘要

This paper presents a systematic investigation of the chain-like CaO–Al2O3–SiO2–MgO inclusions found on the surface of crankshaft journals, elucidating their formation mechanism. The inclusions within the defects consist of numerous individual low-melting-point oxides and exhibit a strong correspondence with those observed in the hot-rolled bars. Thermodynamic calculations reveal that the introduction of trace amounts of SiO2 broadens the liquid-phase region of CaO–Al2O3–SiO2–MgO inclusions at steelmaking temperatures to a notable extent, markedly enhancing the proportion of the liquid phase at the onset of melting. Conversely, a relatively high SiO2 content elevates the melting point of these inclusions. Moreover, unlike their solid counterparts, liquid inclusions in molten steel are less prone to agglomeration and flotation. A substantial number of small liquid inclusions become entrapped in the interdendritic regions during the solidification of continuous casting billets. The pushing of secondary dendrite arms promotes the accumulation of these liquid inclusions during subsequent solidification stages, ultimately giving rise to chain-like, large-size CaO–Al2O3–SiO2–MgO inclusions following hot forging.