EXPANSION RING COMPRISING AT LEAST TWO CYLINDRICAL PORTIONS WITH DIFFERENT MECHANICAL PROPERTIES, METHOD OF MANUFACTURING SUCH EXPANSION RING, AND COLD EXPANSION METHOD USING SAID EXPANSION RING

摘要

The invention relates to an expansion ring for performing a cold expansion which is characterized in that it comprises at least two cylindrical portions (50a-50d) with different mechanical properties, determined according to the rate of expansion desired for the part (32a-32d) of the corresponding stack (30). Thus, it is possible to obtain a rate of expansion that varies from one room to another of a stack (30). The invention also relates to a cold expansion method which uses said expansion ring, a method of manufacturing an expansion ring and a tool for thermally treating an expansion ring.