Study on the cause of spiral groove in cross wedge rolling

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. © 2011 Journal of Mechanical Engineering.