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<p>To address the failure problem associated with carburized sulfur-containing 20MnCrS5 gears, this study conducted an engineering analysis of the coupled control of austenite grain stability and MnS inclusions in 20MnCrS5 gear steel produced <i>via</i> the electric arc furnace short process. The distribution, composition, and morphology of inclusions in the industrial slab were analyzed. The results indicated that the average ECD of MnS-type inclusions at the 1/4-thickness and core of the slab reached 3.65 and 2.81 <i>μ</i>m, respectively, which were significantly larger than the 1.18 <i>μ</i>m at the slab edge. MnS-type inclusions in the slab core also exhibited a stronger tendency toward irregular shapes, with a notably higher 2D aspect ratio compared with the other sampling positions. Composite MnS inclusions nucleated on oxide cores exhibited clearer spheroidization and dispersion behaviors across different slab locations, and only minor morphological variations were observed despite differences in local cooling conditions. These findings indicate that oxide inclusions can act as effective nucleation sites for promoting MnS dispersion and spheroidization during continuous casting. Isothermal heat treatment experiments identified the temperature sensitivity of grain growth in 20MnCrS5 steel bars within the range of 800&#xa0;°C to 1200&#xa0;°C. An empirical grain growth equation was established. The results showed that 950&#xa0;°C is the critical temperature for safe carburizing, above which controlling abnormal grain growth becomes necessary. <i>In situ</i> observation using high-temperature confocal microscopy directly revealed the strong pinning effect of MnS inclusions located at or near grain boundaries on boundary migration. This study contributes to the understanding of the coupled control of MnS inclusions and grain thermal stability in low-carbon, sulfur-containing Mn–Cr gear steels.</p>

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Synergistic Control Strategy for Sulfur-Containing Gear Steel Inclusions and Carburized Grain Stability: An Industrial Production Analysis

  • 期刊论文

  • 发表日期：

    2025年12月17日

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  • Jin Wang,
  • Yun Bai,
  • Ao Zhen,
  • Wei Liu,
  • Shulei Yang,
  • Shufeng Yang,
  • Jingshe Li

摘要

To address the failure problem associated with carburized sulfur-containing 20MnCrS5 gears, this study conducted an engineering analysis of the coupled control of austenite grain stability and MnS inclusions in 20MnCrS5 gear steel produced via the electric arc furnace short process. The distribution, composition, and morphology of inclusions in the industrial slab were analyzed. The results indicated that the average ECD of MnS-type inclusions at the 1/4-thickness and core of the slab reached 3.65 and 2.81 μm, respectively, which were significantly larger than the 1.18 μm at the slab edge. MnS-type inclusions in the slab core also exhibited a stronger tendency toward irregular shapes, with a notably higher 2D aspect ratio compared with the other sampling positions. Composite MnS inclusions nucleated on oxide cores exhibited clearer spheroidization and dispersion behaviors across different slab locations, and only minor morphological variations were observed despite differences in local cooling conditions. These findings indicate that oxide inclusions can act as effective nucleation sites for promoting MnS dispersion and spheroidization during continuous casting. Isothermal heat treatment experiments identified the temperature sensitivity of grain growth in 20MnCrS5 steel bars within the range of 800 °C to 1200 °C. An empirical grain growth equation was established. The results showed that 950 °C is the critical temperature for safe carburizing, above which controlling abnormal grain growth becomes necessary. In situ observation using high-temperature confocal microscopy directly revealed the strong pinning effect of MnS inclusions located at or near grain boundaries on boundary migration. This study contributes to the understanding of the coupled control of MnS inclusions and grain thermal stability in low-carbon, sulfur-containing Mn–Cr gear steels.