Abstract: The invention concerns an assembly for fixing two thermally non-expansible thermoplastic tubular elements (1, 2) characterized in that it comprises a first thermally non-expansible thermoplastic tubular element (1) including a fixing zone (4) on the inner wall of one of its ends, a second thermally non-expansible thermoplastic tubular element including a fixing zone (6) on the outer wall of one of its ends, the diameter of the inner wall of said end of the first tubular element (1) being larger than the diameter of the outer wall of said end of the second tubular element (2) so as to define, when the two ends overlap, an annular space between said inner and outer walls, the assembly further comprising a thermoplastic sleeve (3) adapted to be housed in the annular space, said sleeve (3) containing a conductive element (5) capable of being induction-heated.