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<p>Ratchet of S2 alloy tool steel is the key component of torque wrenches, requiring high strength, toughness, and performance stability. However, during mass production, torque wrench ratchet failed to meet the rated torque requirement of 1000&#xa0;N·m. The fracture morphology, microstructure, and mechanical properties were characterized and tested by stereo microscope (SM), optical microscope (OM), field emission electron microscope (SEM), Vickers hardness tester, and torque tester, respectively. The results showed that during batch heat treatment, severe decarburization layers were formed on both the inner and outer surfaces of the ratchet, resulting in a significant decrease in surface hardness, which greatly reduced the torsional strength of the ratchet. By increasing the spacing between the ratchet wheels in the heat-treated tray, improving the carbon potential of the protective atmosphere, and enhancing the circulation of the furnace atmosphere, the problem of decarburization layers on the outer and inner surfaces of ratchet has been successfully resolved. During mass production, the torsional strength of ratchet reached 1000 N·m, which fully meets its technical requirements.</p>

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Failure Analysis of Torque Wrench Ratchet Fracture

  • 期刊论文

  • 发表日期：

    2026年3月30日

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  • Jiahao Jin,
  • Jianming Zhai,
  • Yue Yu,
  • Lei Geng,
  • Jiaqi Liu,
  • Xi Chen,
  • Pin Tao,
  • Jinquan Sun

摘要

Ratchet of S2 alloy tool steel is the key component of torque wrenches, requiring high strength, toughness, and performance stability. However, during mass production, torque wrench ratchet failed to meet the rated torque requirement of 1000 N·m. The fracture morphology, microstructure, and mechanical properties were characterized and tested by stereo microscope (SM), optical microscope (OM), field emission electron microscope (SEM), Vickers hardness tester, and torque tester, respectively. The results showed that during batch heat treatment, severe decarburization layers were formed on both the inner and outer surfaces of the ratchet, resulting in a significant decrease in surface hardness, which greatly reduced the torsional strength of the ratchet. By increasing the spacing between the ratchet wheels in the heat-treated tray, improving the carbon potential of the protective atmosphere, and enhancing the circulation of the furnace atmosphere, the problem of decarburization layers on the outer and inner surfaces of ratchet has been successfully resolved. During mass production, the torsional strength of ratchet reached 1000 N·m, which fully meets its technical requirements.