Round-to-square section drawing through flat idle rolls

Cold drawn metal bars of regular polygonal section are industrially produce d by direct drawing from round stock using either a round-to-polygonal sect ion converging die or a drawing head comprising an adjustable set of symmet rically arranged flat idle rolls. In the present work a solution is obtaine d to determine the roll load and drawing force for steady state direct cold drawing of square section from round stock through flat idle rolls. The re sults obtained have shown that the drawing force in a case of fair lubricat ion condition amounts to about 40% of that required for drawing through con verging dies, which allows using a drawbench of lower load capacity. The dr awing stress is highly influenced by the friction conditions at the roll su rface and to a lesser extent by the area reduction ratio and roll diameter, indicating the need for good quality finish and adequate lubrication for t he rolls contact surface. The ratio of the drawing stress to the roll mean pressure is independent of friction and increases almost linearly with the increase of area reduction ratio. (C) 1999 Elsevier Science Ltd. All rights reserved.