METHOD FOR FASTENING TUBES IN TUBE OPENINGS Russian patent published in 2001 - IPC

FIELD: plastic metal working, namely processes for fastening tubes in tube openings of heat exchanging apparatuses. SUBSTANCE: method is realized with use of effect of localized oriented plastic deformation of tube material. Method comprises steps of preliminarily reducing tube end portions for forming transition cone portion; making annular protrusion on outer surface of each end portion; placing one end of tube in tube opening having outer and inner annular grooves, inner annular groove has triangular cross section; placing tube in such a way that to arrange its transition portion in zone of width of said inner annular groove; fixing tube against its possible motion and fastening it in tube opening by expanding; performing expanding operation by two stages at applying compression effort to inner surface of tube; at first stage of tube expanding forming second protrusion in order to provide out-of-contact deformation of tube material that fills inner annular groove of tube opening. First annular protrusion of tube has trapezoidal cross section. Compression effort is applied to tube surface by mechanical expanding. EFFECT: enhanced efficiency of fixation of tube in tube opening. 3 cl, 7 dwg