双螺杆挤出机分配齿轮箱20CrMnTi渗碳齿轮断裂分析研究

Fracture analysis of 20CrMnTi carburizing gear used in torque distribution gear box of double screw extruder

解决双螺杆挤出机分配齿轮箱20CrMnTi渗碳齿轮的断裂问题,将断口宏观形貌分析、显微组织观察和硬度梯度检测技术应用到断裂齿轮的研究中。开展了结构设计和热处理工艺的分析,建立了渗碳齿轮失效机理与强度的内在联系。提出了齿轮在设计、工艺等方面的改进措施。结果表明,键槽底部与齿根圆距离小于2.5 mt是齿轮强度过低而断裂的主因,渗层大量残留奥氏体和心部网状铁素体降低了齿轮的疲劳强度,疲劳裂纹沿应力集中的线、面扩展迅速;降低奥氏体冷却过程的稳定性,渗碳正火≤950℃且保温<6 h,可改善齿轮的疲劳强度。

In order to solve the fracture problem of 20CrMnTi carburized gear used in the torque distribution gearbox of the twin screw extruder,the fracture morphology analysis,microstructure observation and hardness gradient test were investigated to the study of fracture gear.After the analysis of the structure design and heat treatment process,the internal relations between failure mechanisms and gear strength was established. A method was presented to the improvement measures in design and technology and other aspects of the gear. The experimental results show that the distance between the keyway bottom and the root circle less than 2. 5 mtis the main reason for the low strength and fracture of the gear; the large amount of residual austenite in the carburizing layer and the center network iron ferrite reduced the fatigue strength of the gear,fatigue crack is rapidly expanding along the line and plane of stress concentration; to reduce the stability of austenite cooling process,carburizing or quenching temperature not more than 950 ℃ and holding time less than 6 hours,can improve the fatigue strength of the gear.