Theoretical and practical aspects of the production of thin-walled tubes by the KOBO method

The aim of the paper is to present the theoretical basis and to estimate the application in practice of the new, "cold" production method of thin-walled tubes from 3003 aluminum alloy, copper and CuSn8 bronze, which consists in extrusion on a press with reversibly rotating die (the KOBO method). The development of a new, knowledge-based technology of the manufacturing of thin-walled tubes from metals and alloys should satisfy the continuously increasing demand for these products. Experimental results obtained during metal forming operations with a change of the loading scheme (change of the deformation path) have shown the possibility of a great reduction of the plastic resistance of the deformed material. Moreover, they allow to state that the destabilization of the substructure preceding such a behavior, as well as localization of the plastic flow in the shear bands responsible for it, can take place in all operations of plastic straining independently of the applied temperature of the process. The present study addresses the problems directly connected with "cold" production of thin-walled (0.35, 0.45 and 0.60mm) tubes and discusses their quality aspects such as structure and mechanical properties of the final products. (c) 2005 Elsevier B.V. All rights reserved.