Influences of feed and cross angle on rotary forging effects and redundant shear deformations in rotary piercing process

It was in 1967 that Sumitomo Metal Industries, Ltd. started its research and development efforts of an improved rotary piercing mill in full swing. In 1983, its first product was put into practice at the small-diameter seamless steel tube plant in the Wakayama Steel Works. Since then, the field operation at this plant has been successfully carried out. The rotary piercing mill employed at the above plant has the arrangement that cone-type rolls supported at both ends are used as the main rolls of which axes are inclined and crossed so that piercing may proceed at a high feed and cross (toe, cone) angle, with the disc rolls adopted instead of the plate guide shoes.Though several reports on this cone-type piercing mill have been published, they are rather fragmentary and leave something yet to be clarified. Furthermore, the recent progress in our research and development has resulted in the concept of "the new super piercer" which allows expansion piercing. This new super piercer will be employed as the core technology of a new medium-diameter seamless steel tube plant now under construction scheduled to operate in 1997. First of all, the influences of the feed and cross angle on the rotary forging effects and redundant shear deformations are summarized in this paper.