The precision forming of inner hole is one of technological bottlenecks in Cross-wedge Rolling (CWR) of hollow shaft with mandrel. The inner diameters show signs of characteristic fluctuation despite under the control of mandrel. The uniformity of inner diameter was investigated by finite element simulation and experiments in this study. The inner hole expands at the knifing stage and shrinks at the sizing stage. The dimensional fluctuation of inner diameter is mainly resulting from the improper metal flow. The radial and axial metal flows are insufficient at the knifing stage, which resulting in the hole expansion at knifing zone. The hole shrinkage is caused by the relatively adequate radial metal flow at sizing stage. The experiment results show that the hole expansion increases with the increasing stretching angle and mandrel diameter and decreases with the increasing forming angle and initial wall thickness. The hole expansion first increases and then decreases with the increasing reduction ratio. The hole shrinkage has positive correlations with forming angle, reduction ratio and initial wall thickness, and negatively correlates with stretching angle and relative mandrel diameter. A modified CWR roll with the curved-surface knife is proposed to get rid of the hole expansion. Based on experiments and simulations, the most suitable geometric parameters of the curved-surface knife are determined. Using mandrel diameter compensation can reduce the phenomenon of hole shrinkage. These methods were applied to the trial rolling of a half-shaft sleeve part, and the results show that the methods significantly restrain the inner diameter fluctuation.

内孔的精密成型是芯轴空心轴楔横轧（CWR）的技术瓶颈之一。尽管在心轴的控制下，内径仍显示出特征波动的迹象。本研究通过有限元模拟和实验研究了内径的均匀性。内孔在切削阶段扩大，在上浆阶段收缩。内径尺寸波动主要是由于金属流动不当造成的。切刀阶段径向和轴向金属流动不足，导致切刀区扩孔。孔收缩是由于在定径阶段相对足够的径向金属流动造成的。实验结果表明，扩孔量随着拉伸角度和芯棒直径的增大而增大，随着成形角度和初始壁厚的增大而减小。随着减速比的增大，扩孔量先增大后减小。孔收缩率与成形角、缩径比和初始壁厚呈正相关，与拉伸角和相对芯轴直径呈负相关。提出了一种改进的带有曲面刀的 CWR 辊，以消除扩孔问题。在实验和模拟的基础上，确定了最合适的曲面刀几何参数。使用芯棒直径补偿可以减少缩孔现象。这些方法应用于半轴套零件的试轧，