Simultaneous Finishing of Inner and Outer Surfaces of Tube by Planetary Ball Rolling Process.

Abstract

Previously proposed "Planetary Conical Rolling" (PCR) is a new ironing process carried on between a cylinder die and rollers supported by inner race. Excellent features of PCR such as extremely high thickness reduction, mirror finishing of outer tube surface, no sliding between tool and material, supplement of high pressure in the radial direction were demonstrated. It was also reported that this process could be applied to pressure welding and thread forming. However, inner surface of tube after PCR was considerably rough because of indentation of roller edge on the material. In order to overcome this defect, "Planetary ball rolling", in which rollers in PCR tools were replaced with balls, is proposed. Performance of PBR was compared with PCR by the use of aluminum alloy tubes. As a result, roughness of inner surface of the tube was extremely improved by PBR. Influence of ball diameter on forming limit and surface finishing was investigated. It was found that forming limit was assumed with maximum contact angle and large ball. diameter was advantageous. Additionally, large ball was also effective to reduce surface roughness of both the inner and outer sides of tube. This was due to enlargement of deformation zone, which caused sufficient deformation on outer tube surface and reduced pilling up on the inner tube surface. Obtained tube had good quality and simultaneous finishing of inner and outer surfaces of a tube by PBR was demonstrated.