TECHNOLOGICAL ASPECTS WHEN PERFORMING FRICTION WELDING OF HETEROGENOUS MATERIALS I. LUCACIU 1 ; M. BURCA 2 S. GLITA 2 ; D. TUNEA 2 ; A. MAGDA 2 1 University of Oradea 2 Polytechnic University Timisoara Keywords: roller, friction welding, heterogenous materials, diffusion, axial shortening, macrostructure, plastic flow, upsetting, cold-straining, crystalline modification. 1. ABSTRACT Compared with conventional procedures, friction welding is a non-electric joining procedure that has the following advantages: materials that are different both in their chemical composition and their melting points can be welded, as can materials having different dimensions and shapes; this is hygienic and highly productive procedure. The issue of welding heterogenous materials - aluminum with stainless steel – must also be approached from the point of view of the fact that the aluminum surface is covered by an oxide film with totally different properties than those of aluminum. The paper presents the results of applied research, results obtained when performing a continuous friction welding of aluminum alloy-6060 rollers, with two 1.4104 or 1.4305 stainless steel rolls or St 37 with 1.4305 stainless steel rolls, as seen in figure 1. a b Fig. 1. Friction welded rollers : a - St 37 with 1.4305 steel; b- AlMgSi 0,7 F27 aluminum with 1.4104 steel. When performing continuous friction welding, the necessary heat is obtained by converting the friction mechanical energy between the elements that are to be joined into thermal energy, under a certain pressure. The welding process takes place according to a work cycle specific to option a and option b in figure 1, respectively, cycles that include the following phases: fixing the components in the expander and the wedge grip of a special machine, pulling one of them into a rotation movement with constant or variable speed, pressing the other component with an axial force, heating up the contact surfaces until the plastic flow temperature is reached, braking and finally upsetting under zero speed. ANNALS of the ORADEA UNIVERSITY. Fascicle of Management and Technological Engineering, Volume IX (XIX), 2010, NR3 3.84