ISSN   1004-0595

CN  62-1224/O4

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盾构机主轴承齿圈开裂失效研究

Cracking Failure of Gear Ring of TBM Base Bearing

  • 摘要: 盾构机主轴承常采用三排圆柱滚子结构,轴承内圈材质为42CrMo,其作为承受传动扭矩的齿圈,掘进过程中的扭矩一般在8 MN·m以上,长时间承受交变载荷,容易出现裂纹. 为了探究盾构机主轴承齿圈开裂失效机理,对华南地区某盾构项目Φ3.061 m的主轴承齿圈首先进行无损检测分析,齿轮根部出现多处趋于均布的齿根裂纹;其次对齿圈开裂的断口进行形貌分析,裂纹源处的脆性沿晶特征表明材料韧性不足;再次对齿圈齿根进行残余应力分析及工作应力校核,显示残余拉应力高达400 MPa,与外力叠加后超过材料的屈服强度;最后对齿圈进行材料分析发现基体Ni质量分数为0.13%偏低,从而降低了材料韧性及冲击强度,基体组织存在珠光体偏析带造成组织不均,非金属夹杂物等级为1.5级,偏高的夹杂物等级增大了开裂的风险. 因此,为减小裂纹产生的可能性、延长齿圈寿命,需优化齿轮感应淬火工艺,降低齿根残余应力;增加齿圈基体材料镍元素含量,提高材料韧性;优化原材料热处理工艺,提高基体组织均匀性;提高原材料纯净度,降低夹杂物等级.

     

    Abstract: The base bearing of TBM is usually of a three row cylindrical roller structure, the material of the base bearing inner ring is 42CrMo, as the gear ring that bears the transmission torque, usually has a torque of over 8 000 kN·m. During the excavation process, it can withstand alternating loads for a long time and is prone to cracking. In order to explore the mechanism of cracking on the base bearing gear ring of TBM, firstly, a non-destructive testing and analysis was conducted on aΦ3 061 mm base bearing gear ring of TBM project in South China, and it was found that there were multiple dedendum cracks that tended to be evenly distributed on the gear ring. Secondly, morphology analysis was conducted on the fracture surface of the gear ring cracking, and the brittle intergranular characteristics at the crack source indicated insufficient material toughness. Furthermore, after conducting residual stress analysis and working stress verification on the dedendum of the gear ring, it was found that the residual tensile stress was as high as 400 MPa, which exceeded the yield strength of the material after being combined with external forces. Finally, material analysis of the gear ring revealed that the content of nickel element in the matrix was relatively low at 0.13%, which reduced the material toughness and impact strength. Pearlite segregation bands were found in the matrix structure, resulting in uneven structure. The non-metallic inclusion level reached level 1.5, and higher inclusion levels increased the risk of cracking. Therefore, in order to reduce the possibility of cracks and extend the service life of the gear ring, it was necessary to optimize the gear induction quenching process and reduce the residual stress at the dedendum: increasing the content of nickel element in the matrix material of the gear ring to improve the toughness of the material; optimizing the heat treatment process of raw materials to improve the uniformity of the matrix structure; improving the purity of raw materials to reduce the level of non-metallic inclusions.

     

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