On a precision forming criterion for groove-section profiled ring rolling process

For the groove-section profiled ring rolling (GSPRR) of difficult-to-deform materials, one of the most challenging issues is to ensure the precision forming of ring groove before the diameter reaches to the desired value. The deformation behavior and mechanism of the GSPRR has been clarified in this work. It is found that the pulling effect of the active deformation zone on the passive deformation zone, quantificationally described by a pulling coefficient introduced in this paper, plays a decisive role in the precision forming of ring groove. The smaller the pulling coefficient, the weaker the pulling effect. This leads to less metal flowing in the circumferential direction for diameter growth, thus more metal flowing into the main roll cavity for the groove forming. The influences of the dimensions of the target rolled ring, rectangular blank thickness and processing parameters on the pulling coefficient are revealed. And a regression model describing the relationship between the pulling coefficient and its key influencing factors is developed. Based on the pulling coefficient model, a precision forming criterion for the GSPRR is established, by which a critical value of the rectangular blank thickness ensuring the precision forming of ring groove can be determined. The critical value is related to the rectangular blank thickness and the structural dimensions of the target rolled ring such as the relative groove height, so the developed criterion can provide an important guidance to design the blank and the target rolled ring (forging drawing) for the GSPRR process.