METHOD FOR MAKING TUBES WITH SHAPED OUTER ENDS Russian patent published in 2003 - IPC

FIELD: plastic metal working, possibly manufacture and repairing of tube bundles of heat exchange apparatuses. SUBSTANCE: method comprises steps of preliminarily forming calibrated portion by expanding tube end in order to receive its outer diameter exceeding diameter of opening of detachable die in closed state; realizing two-stage reduction of calibrated portion along length less than its initial length in order to form bearing portion and portion having first step arranged on tube end and second step; fixing tube against possible motion by reducing bearing portion due to applying radial effort to it; expanding tube along first step of bearing portion to diameter equal to that of second step; forming annular protrusion at applying axial compression effort to tube end. EFFECT: lowered deforming efforts. 5 dwg