目的 针对扭力轴花键冷打表面完整性规律不明的问题，研究冷打成形后花键表面的几何、力学和组织状态演变，为扭力轴花键抗疲劳制造工艺提供参考。方法 将扭力轴花键冷打成形，检测、表征冷打成形后花键的表面形貌及表面粗糙度、残余应力、表层硬化和表层微观组织状态，基于高应变率下的真实应力应变曲线，对表层等效塑性应变进行分析。结果 花键冷打起始与结束区域的表面存在“加工纹理不连续”、“起裂”缺陷。齿根表面形成残余压应力，达到–928.5 MPa。表层加工硬化效果明显，硬化层深度达1 mm，显微硬度和等效塑性应变沿层深呈梯度分布，显微硬度提升24.2%，等效塑性应变达到175%。表层组织发生严重塑性变形，呈“纤维状”，深度达500 μm。结论 扭力轴花键冷打表面质量不均匀，两端为薄弱区域，对齿根进行表面滚压处理是后续必不可少的工序。冷打成形引入的残余压应力、加工硬化和连续性的微观组织变形层对于表面完整性具有积极意义，其受后续工序的影响及演变需要进一步研究。

In order to solve the problem that the surface integrity of torque shaft spline during cold beating is not clear, the evolution of geometry, mechanics and microstructure of spline surface after cold beating is studied, which provides reference for anti-fatigue manufacturing process of torque shaft spline. The surface morphology, surface roughness, residual stress, surface hardening and microstructure of the spline were tested and characterized. Based on the true stress-strain curve at high strain rate, the equivalent plastic strain of the surface was analyzed. The surface of the beginning and end regions of spline cold beating had the defects of “processing texture discontinuity” and “crack initiation”. The residual compressive stress on the tooth root surface was –928.5 MPa. The effect of surface work hardening was obvious. The depth of hardened layer was 1 mm. The microhardness and equivalent plastic strain were distributed gradiently along the layer depth. The microhardness increased by 24.2% and the equivalent plastic strain reached 175%. Severe plastic deformation occurred in the surface layer, which was “fibrous” with a depth of 500 μm. The surface quality of torque shaft spline is uneven in cold beating, and the two ends are weak areas. Surface rolling treatment of tooth root is an essential process in the follow-up. The residual compressive stress, work hardening and continuous microstructure deformation layer introduced by cold beating are of positive significance to surface integrity, which needs further attention due to the influence and evolution of subsequent processes.