楔横轧件螺旋痕产生原因研究

Study on the Cause of Spiral Groove in Cross Wedge Rolling

楔横轧的工艺特点决定,在轧制过程中经常会在轧件已轧表面产生带倾斜角的螺旋状凹痕缺陷。为探讨楔横轧轧件表面螺旋痕的起因问题,利用数值模拟质点跟踪技术找出楔横轧轧件表面螺旋痕开始出现的位置是在变形接触区外;通过分析轧件变形区应力分布及金属流动,发现在与轧辊斜楔尖部接触的轧件外层受轴向压应力,螺旋痕处与相邻区域的径向压应力差别不大,说明螺旋痕的产生不是直接受力所致;设计局部受力简化的塑性变形模型,表明金属受迫流动时可以带动相邻未受力区域部分金属产生同向流动;揭示出楔横轧螺旋痕的产生机理是由变形区金属带动附近已基本成形完毕的金属径向流动的结果;通过模拟和试验,发现螺旋痕的大小与成形角和断面收缩率成正比,展宽角影响较小;提出减轻和消除螺旋痕的措施。

Due to the process feature of cross wedge rolling,spiral dents with a tilt angle often appear on the rolling surface of the rolled piece in the rolling process.In order to explore the cause of spiral groove on the rolled piece by cross wedge rolling,by using point tracking technique,the place where spiral groove begins to appear is found outside the deforming contact zone.Through the analysis of stress distribution and metal flow in the deformation zone,it is found that the outer layer of the rolled piece contacted with wedge tip of the roll bears axial compressive stress,and the radial compressive stress in the place of spiral groove differs little from that of the adjacent area.This suggests that generation of spiral groove is not caused by direct force.A plastic deformation model of local force simplified is designed,and the simulation result shows when the metal is forced to flow,it can drive the metal in the adjacent unaffected area to flow in the same direction.It reveals that the generation of spiral groove results from the metal in the deformation area carrying the nearby basically formed metal to move radically.Based on the simulation and experimental results,it is indicated that the rank of spiral groove is directly proportional to the forming angle and area reduction,while the stretching angle has less effect on the rank of spiral groove.The measures to reduce or eliminate spiral grooves are proposed.